Bhushan Power & Steel Limited, a fully integrated 2.3 Million TPA Steel making

Company with turnover of INR 4217 Crores (USD 937 Million) and 7 World Class

ISO 9000 Certified State of the Art Plants at Chandigarh, Derabassi, Kolkata and

Orissa in India.

A leading manufacturer of flat, rounds and long products including value added

products with total steel value chain right from Coal Mining, Billets, HR Coils, Pig

Iron, CR Coils, GP/GC, Precision Tubes, Black Pipe/GI Pipe, Cable Tapes, Tor

Steel, Wire Rod and Special Alloy Steel.

Successfully commissioned 2.3 Million TPA Greenfield Steel and Power Plant in

Orissa with HR Coil making facility

—First in Private Sector in the State of Orissa. For the Orissa plant, technology

and equipments are procured from world-renowned companies like Lurgi from

Germany, ABB Ltd., SMS Siemag etc. Bhushan is selling its Value added range of

products in Secondary Steel through a large distribution network in India

(comprising more than 35 sales offices) and Abroad.

A rock-solid foundation combined with continuous upgradation and innovation has

ensured that we have constantly surpassed our goals. Our end-to-end portfolio

offers a wide spectrum of products with consistently superior quality. In addition to

our export thrust, we supply to fast-growing sectors like automotive, white goods,

construction, furniture, fasteners, telecommunication, etc.

Growing from strength to strength

1970 - Started with very small initial outlay for manufacturing Door Hinges & later on, Rail Track

Fasteners.

1973 - Manufacturing facilities set up for Tor Steel and Wire Rod in Chandigarh.

1981 - Rolling Mill Project commissioned at Chandigarh for Round and Narrow Strips.

1985 - Backward Integration Project for Steel Melting facilities.

1986 - Upgrading of Mini Steel Plant with continuous casting and ladle furnace facilities. 1997 -

Commissioning of Narrow Width Cold Rolling Project at Chandigarh.

1998 - Commissioning of Precision Pipe Project at Chandigarh.

2001 - Commissioning of Cold Rolling & Galvanizing Complex at Kolkata.

2002 - Addition of narrow width Cold Rolling facilities at Kolkata.

2003 - Expansion of wide width Cold Rolling facilities, ERW Water Pipes & Tubes down stream

facilities at Kolkata.

2004 - Further expansion of Cold Rolling facilities at Kolkata.

2005 - Commissioning of Orissa Project consisting of 4 DRI Kilns, Steel Making Facilities, Coal

Washery and 100 MW Power Plant.

2007 - Commissioning of further expansion of Orissa Project consisting of HR Coil Mill, Steel

making, Blast Furnance, Sinter plant, Coke oven plant, Oxygen plant and Lime & Calcining Plant.

2009 - Commissioning of 3.5 million tpa Coal Washery, 146 MW Power Plant and 0.3 million tpa

Sponge Iron under Phase III of Orissa Project.

2010 - Commissioning of 130 MW Power Plant and Electric Arc Furnace under Phase III of Orissa

Project and further expansion of Orissa Project under Phase IV consisting of 6 DRI Kilns, 130 MW

Power Plant, Steel Making Facilities, 6th strand, 2nd CSP Caster & Tunnel Furnace, Oxygen Plant,

Lime Calcining with downstream facilities - Cold Rolling, Galvanizing, Galvalume, Colour Coating,

Precision Tube & Black Pipe/GI Pipe.

Our Mission is to achieve clear identity and leadership globally in Steel production and distribution by

integration of complete chain of production starting from captive iron ore to end user Steel products.

Our revolution in Steel production has helped us to carve a niche unique only to a market leader.

Every year passes by with new value additions and more accolades from our customers - Locally

and Globally. Our rising chart in respect of all-important parameters of production and finance is a

testimony to our claim.

In pursuing our mission, we at Bhushan Power & Steel Ltd. are guided by the following values -

Quality - To be the best in quality. We aim and achieve excellence.

Technology - State of the art technology and product enrichment by continuous Research and

Development.

Customer Friendly - Our products are world class and more and more clients are appreciating and

using our products. We also undertake customized products with values addition and enhancement.

Corporate Governance - We comply with all applicable laws and regulations. We believe in

maintaining clean environment and conservation of natural resources. We contribute towards

betterment of our staff and provide them with best of facilities.

Environment Protection and Practice - We are adopting and implementing pollution control

measures as a matter of policy. Please read our thrust and directions on this subject by Clicking

here (All our efforts are in accordance with the laid down norms of Central Pollution Control Board

for Industrial and Mixed use areas).

Our Commitments

To improve the quality of our products and complete integration of various stages of

production.

To be conscious towards quality and pricing of our products. We strive by continuous

research and development to make our products world class, having distinct identity and

uniqueness. Our customers get best value for their money.

To run the company profitably year after year.

A workforce motivated, skilled and well looked after.

A workplace safe, secure and hygienic.

To make our Environment Clean, Healthy and Hospitable.

Bhushan Power & Steel Ltd., produces a number of steel products for domestic users, Industrial

concerns etc. for infrastructure development at its manufacturing bases at Chandigarh,

Derabassi (Punjab), Kolkata and Orissa.

ALL OUR PRODUCTS CONFORM TO INDIAN AND INTERNATIONAL SPECIFICATION.

HR COIL STEEL BILLETS ALLOY STEEL ROUNDS

TOR STEEL

WIRE RODS PIG IRON SPONGE IRON POWER

CR COILS NARROW CR COILS CR SHEETS PRECISION TUBES (ERW and CEW)

CABLE TAPES BLACK PIPE GI PIPES GP COILS / SHEETS

GP CORRUGATED SHEETS

     

 

 

ELECTRIC ARC FURNACE

An electric arc furnace (EAF) is a furnace that heats charged material by means of an electric arc.

Arc furnaces range in size from small units of approximately one ton capacity (used in foundries for producing cast iron products) up to about 400 ton units used for secondary steelmaking. Arc furnaces used in research laboratories and by dentists may have a capacity of only a few dozen grams. Industrial electric arc furnace temperatures can be up to 1,800 degrees Celsius, while laboratory units can exceed 3000 °C. Arc furnaces differ from induction furnaces in that the charge material is directly exposed to an electric arc, and the current in the furnace terminals passes through the charged material

Construction

A schematic cross-section through an EAF. Three electrodes (black), molten bath (red), tapping spout at left, refractory brick movable roof, brick shell, and a refractory-lined bowl-shaped hearth.

An electric arc furnace used for steelmaking consists of a refractory-lined vessel, usually water-cooled in larger sizes, covered with a retractable roof, and through which one or more graphite electrodes enter the furnace. The furnace is primarily split into three sections:

the shell, which consists of the sidewalls and lower steel 'bowl'; the hearth, which consists of the refractory that lines the lower bowl; the roof, which may be refractory-lined or water-cooled, and can be shaped as a section

of a sphere, or as a frustum (conical section). The roof also supports the refractory delta in its centre, through which one or more graphite electrodes enter.

The hearth may be hemispherical in shape, or in an eccentric bottom tapping furnace (see below), the hearth has the shape of a halved egg. In modern meltshops, the furnace is often raised off the ground floor, so that ladles and slag pots can easily be maneuvered under either end of the furnace. Separate from the furnace structure is the electrode support and electrical system, and the tilting platform on which the furnace rests. Two configurations are possible: the electrode supports and the roof tilt with the furnace, or are fixed to the raised platform.

A typical alternating current furnace has three electrodes. Electrodes are round in section, and typically in segments with threaded couplings, so that as the electrodes wear, new segments can be added. The arc forms between the charged material and the electrode, the charge is heated both by current passing through the charge and by the radiant energy evolved by the arc. The electrodes are automatically raised and lowered by a positioning system, which may use either electric winch hoists or hydraulic cylinders. The regulating system maintains approximately constant current and power input during the melting of the charge, even though scrap may move

under the electrodes as it melts. The mast arms holding the electrodes carry heavy busbars, which may be hollow water-cooled copper pipes carrying current to the electrode holders. Modern systems use 'hot arms', where the whole arm carries the current, increasing efficiency. These can be made from copper-clad steel or aluminium. Since the electrodes move up and down automatically for regulation of the arc, and are raised to allow removal of the furnace roof, heavy water-cooled cables connect the bus tubes/arms with the transformer located adjacent to the furnace. To protect the transformer from heat, it is installed in a vault.

The furnace is built on a tilting platform so that the liquid steel can be poured into another vessel for transport. The operation of tilting the furnace to pour molten steel is called "tapping". Originally, all steelmaking furnaces had a tapping spout closed with refractory that washed out when the furnace was tilted, but often modern furnaces have an eccentric bottom tap-hole (EBT) to reduce inclusion of nitrogen and slag in the liquid steel. These furnaces have a taphole that passes vertically through the hearth and shell, and is set off-centre in the narrow 'nose' of the egg-shaped hearth. It is filled with refractory sand, such as olivine, when it is closed off. Modern plants may have two shells with a single set of electrodes that can be transferred between the two; one shell preheats scrap while the other shell is utilised for meltdown. Other DC-based furnaces have a similar arrangement, but have electrodes for each shell and one set of electronics.

A mid-sized modern steelmaking furnace would have a transformer rated about 60,000,000 volt-amperes (60 MVA), with a secondary voltage between 400 and 900 volts and a secondary current in excess of 44,000 amperes. In a modern shop such a furnace would be expected to produce a quantity of 80 metric tonnes of liquid steel in approximately 60 minutes from charging with cold scrap to tapping the furnace. In comparison, basic oxygen furnaces can have a capacity of 150-300 tonnes per batch, or 'heat', and can produce a heat in 30–40 minutes. Enormous variations exist in furnace design details and operation, depending on the end product and local conditions, as well as ongoing research to improve furnace efficiency - the largest scrap-only furnace (in terms of tapping weight and transformer rating) is in Turkey, with a tap weight of 300 metric tonnes and a transformer of 300 MVA.

To produce a ton of steel in an electric arc furnace requires approximately 400 kilowatt-hours per short ton of electricity, or about 440kWh per metric tonne; the theoretical minimum amount of energy required to melt a tonne of scrap steel is 300kWh (melting point 1520°C/2768°F). Therefore, the 300-tonne, 300 MVA EAF mentioned above will require approximately 132 MWh of energy to melt the steel, and a 'power-on time' (the time that steel is being melted with an arc) of approximately 37 minutes, allowing for the power factor. Electric arc steelmaking is only economical where there is plentiful electricity, with a well-developed electrical grid.

Working of Electric arc furnace

An arc furnace pouring out steel into a small ladle car. The transformer vault can be seen at the right side of the picture. For scale, note the operator standing on the platform at upper left. This is a 1941-era photograph and so does not have the extensive dust collection system that a modern installation would have, nor is the operator wearing a hard hat nor dust mask.

Scrap metal is delivered to a scrap bay, located next to the melt shop. Scrap generally comes in two main grades: shred (whitegoods, cars and other objects made of similar light-gauge steel) and heavy melt (large slabs and beams), along with some direct reduced iron (DRI) or pig iron for chemical balance. Some furnaces melt almost 100% DRI.

The scrap is loaded into large buckets called baskets, with 'clamshell' doors for a base. Care is taken to layer the scrap in the basket to ensure good furnace operation; heavy melt is placed on top of a light layer of protective shred, on top of which is placed more shred. These layers should be present in the furnace after charging. After loading, the basket may pass to a scrap pre-heater, which uses hot furnace off-gases to heat the scrap and recover energy, increasing plant efficiency.

The scrap basket is then taken to the melt shop, the roof is swung off the furnace, and the furnace is charged with scrap from the basket. Charging is one of the more dangerous operations for the EAF operators. There is a lot of energy generated by multiple tonnes of falling metal; any liquid metal in the furnace is often displaced upwards and outwards by the solid scrap, and the grease and dust on the scrap is ignited if the furnace is hot, resulting in a fireball erupting. In some twin-shell furnaces, the scrap is charged into the second shell while the first is being melted down, and pre-heated with off-gas from the active shell. Other operations are continuous charging - pre-heating scrap on a conveyor belt, which then discharges the scrap into the furnace proper, or charging the scrap from a shaft set above the furnace, with off-gases directed through the shaft. Other furnaces can be charged with hot (molten) metal from other operations.

After charging, the roof is swung back over the furnace and meltdown commences. The electrodes are lowered onto the scrap, an arc is struck and the electrodes are then set to bore into the layer of shred at the top of the furnace. Lower voltages are selected for this first part of the operation to protect the roof and walls from excessive heat and damage from the arcs. Once the electrodes have reached the heavy melt at the base of the furnace and the arcs are shielded by the scrap, the voltage can be increased and the electrodes raised slightly, lengthening the arcs and increasing power to the melt. This enables a molten pool to form more rapidly, reducing tap-to-tap times. Oxygen is also supersonically blown into the scrap, combusting or cutting the steel, and extra chemical

heat is provided by wall-mounted oxygen-fuel burners. Both processes accelerate scrap meltdown.

An important part of steelmaking is the formation of slag, which floats on the surface of the molten steel. Slag usually consists of metal oxides, and acts as a destination for oxidised impurities, as a thermal blanket (stopping excessive heat loss) and helping to reduce erosion of the refractory lining. For a furnace with basic refractories, which includes most carbon steel-producing furnaces, the usual slag formers are calcium oxide (CaO, in the form of burnt lime) and magnesium oxide (MgO, in the form of dolomite and magnesite). These slag formers are either charged with the scrap, or blown into the furnace during meltdown. Another major component of EAF slag is iron oxide from steel combusting with the injected oxygen. Later in the heat, carbon (in the form of coke or coal) is injected into this slag layer, reacting with the iron oxide to form metallic iron and carbon monoxide gas, which then causes the slag to foam, allowing greater thermal efficiency, and better arc stability and electrical efficiency. The slag blanket also covers the arcs, preventing damage to the furnace roof and sidewalls from radiant heat.

Once flat bath conditions are reached, i.e. the scrap has been completely melted down, another bucket of scrap can be charged into the furnace and melted down, although EAF development is moving towards single-charge designs. After the second charge is completely melted, refining operations take place to check and correct the steel chemistry and superheat the melt above its freezing temperature in preparation for tapping. More slag formers are introduced and more oxygen is blown into the bath, burning out impurities such as silicon, sulfur, phosphorus, aluminium, manganese and calcium and removing their oxides to the slag. Removal of carbon takes place after these elements have burnt out first, as they have a greater affinity for oxygen. Metals that have a poorer affinity for oxygen than iron, such as nickel and copper, cannot be removed through oxidation and must be controlled through scrap chemistry alone, such as introducing the direct reduced iron and pig iron mentioned earlier. A foaming slag is maintained throughout, and often overflows the furnace to pour out of the slag door into the slag pit. Temperature sampling and chemical sampling take place via automatic lances. Oxygen and carbon can be automatically measured via special probes that dip into the steel, but for all other elements, a 'chill' sample - a small, solidified sample of the steel - is analysed on an arc-emission spectrometer.

Once the temperature and chemistry are correct, the steel is tapped out into a preheated ladle through tilting the furnace. For plain-carbon steel furnaces, as soon as slag is detected during tapping the furnace is rapidly tilted back towards the deslagging side, minimising slag carryover into the ladle. For some special steel grades, including stainless steel, the slag is poured into the ladle as well, to be treated at the ladle furnace to recover valuable alloying elements. During tapping some alloy additions are introduced into the metal stream, and some more lime is added on top of the ladle to begin building a new slag layer. Often, a few tonnes of liquid steel and slag is left in the furnace in order to form a 'hot heel', which helps preheat the next charge of scrap and accelerate its meltdown. During and after tapping, the furnace is 'turned around': the slag door is cleaned of solidified slag, repairs may take place, and electrodes are inspected for

damage or lengthened through the addition of new segments; the taphole is filled with sand at the completion of tapping.

Ladle (metallurgy)

A ladle of molten iron is poured into an open hearth furnace for conversion into steel at Allegheny Ludlum Steel Corp., 1941

In foundry work a ladle is a container used to transport and pour out molten metals. It needs to be:

Strong enough to contain a heavy load of metal. Heat-resistant like a furnace. Heat-insulated as much as can be managed, to avoid losing heat and overheating its

surroundings.

For foundries making small castings, a hand-held ladle somewhat resembling a kitchen ladle for

soup is enough, with a long handle to keep the heat of the metal away from the person holding it.

For bigger castings and in steel mills, it can run on wheels, a purpose-built carrying car or be slung

from an overhead crane.

Ladles are most commonly made of fabricated steel. The most common shape is a vertical cylinder,

but other shapes are possible: the most common of these is known as a 'torpedo' ladle, is shaped as

a horizontal cylinder suspended between two bogies, and is commonly used to transport liquid iron

from a blast furnace. Between the molten metal and the steel shape is a refractory material that may

be from 1 mm (0.04") to 150 mm (6") thick or more. The refractory material protects the steel shell

and acts as a thermal barrier to contain the heat.

Ladles can be "lip pour" design or "bottom pour" design:

For lip pour design the ladle is tilted and the molten metal pours out of the ladle like water from a pitcher.

For bottom pour ladles, a stopper rod is inserted into a tapping hole in the bottom of the ladle. To pour metal the stopper is raised vertically to allow the metal to flow out the bottom of the ladle. To stop pouring the stopper rod is inserted back into the drain hole. Large ladles in the steelmaking industry may use slide gates below the taphole.

Ladles can be either open-topped or covered. Covered ladles have a (sometimes removable) dome-

shaped lid to contain radiant heat; they lose heat slower than open-topped ladles. Small ladles do

not commonly have covers, although a ceramic blanket may be used instead (where available).

Medium and large ladles which are suspended from a crane have a bale which holds the ladle on

bearings, called trunnions. To tilt the ladle a worm gear mechanism is used, which tilts the cylindrical

shell while the bale carries the weight. The gear mechanism may be hand operated with a large

wheel or may be operated by an electric motor or pneumatic motor. Internal friction brakes are used

to regulate the tilting speed of the ladle. The largest ladles are poured using a special, two-winch

crane, where the main winch carries the ladle while the second winch engages a lug at the bottom of

the ladle. Raising the second winch then rotates the ladle on its trunnions.

Some ladles are designed for special purposes such as adding alloys to the molten metal. Ladles

may also have porous plugs inserted into the base, so gases can be bubbled through the ladle to

enhance alloying or metallic treatment practices.

CONTINUOS CASTING MACHINE.

Continuous casting, also called strand casting, is the process whereby molten metal is solidified

into a "semifinished" billet, bloom, or slab for subsequent rolling in the finishing mills. Prior to the

introduction of continuous casting in the 1950s, steel was poured into stationary molds to form

ingots. Since then, "continuous casting" has evolved to achieve improved yield, quality, productivity

and cost efficiency. It allows lower-cost production of metal sections with better quality, due to the

inherently lower costs of continuous, standardised production of a product, as well as providing

increased control over the process through automation. This process is used most frequently to cast

steel (in terms of tonnage cast). Aluminium and copper are also continuously cast.

Sir Henry Bessemer, of Bessemer converter fame, received a patent in 1857 for casting metal

between two contra-rotating rollers. The basic outline of this system has recently been implemented

today in the casting of steel strip.

Equipment and process

1. Ladle 2. Stopper 3. Tundish 4. Shroud 5. Mold 6. Roll support 7. Turning zone 8. Shroud 9. Bath level 10. Meniscus 11. Withdrawal unit 12. Slab

A. Liquid metal B. Solidified metal C. Slag D. Water-cooled copper plates E. Refractory material

A 3D schematic

Molten metal (known as hot metal in industry) is tapped into the ladle from furnaces. After

undergoing any ladle treatments, such as alloying and degassing, and arriving at the correct

temperature, the ladle is transported to the top of the casting machine. Usually, the ladle sits in a slot

on a rotating turret at the casting machine; one ladle is 'on cast' (feeding the casting machine) while

the other is made ready, and is switched to the casting position once the first ladle is empty.

From the ladle, the hot metal is transferred via a refractory shroud (pipe) to a holding bath called a

tundish. The tundish allows a reservoir of metal to feed the casting machine while ladles are

switched, thus acting as a buffer of hot metal, as well as smoothing out flow, regulating metal feed to

the molds and cleaning the metal (see below).

Metal is drained from the tundish through another shroud into the top of an open-base copper mold.

The depth of the mold can range from 0.5 to 2 metres (20 to 79 in), depending on the casting speed

and section size. The mold is water-cooled to solidify the hot metal directly in contact with it; this is

the primary cooling process. It also oscillates vertically (or in a near vertical curved path) to prevent

the metal sticking to the mold walls. A lubricant can also be added to the metal in the mold to

prevent sticking, and to trap any slag particles—including oxide particles or scale—that may still be

present in the metal and bring them to the top of the pool to form a floating layer of slag. Often, the

shroud is set so the hot metal exits it below the surface of the slag layer in the mold and is thus

called a submerged entry nozzle (SEN). In some cases, shrouds may not be used between tundish

and mold; in this case, interchangeable metering nozzles in the base of the tundish direct the metal

into the moulds. Some continuous casting layouts feed several molds from the same tundish.

In the mold, a thin shell of metal next to the mold walls solidifies before the middle section, now

called a strand, exits the base of the mold into a spray-chamber; the bulk of metal within the walls of

the strand is still molten. The strand is immediately supported by closely spaced, water cooled

rollers; these act to support the walls of the strand against the ferrostatic pressure (compare

hydrostatic pressure) of the still-solidifying liquid within the strand. To increase the rate of

solidification, the strand is also sprayed with large amounts of water as it passes through the spray-

chamber; this is the secondary cooling process. Final solidification of the strand may take place after

the strand has exited the spray-chamber.

It is here that the design of continuous casting machines may vary. This describes a 'curved apron'

casting machine; vertical configurations are also used. In a curved apron casting machine, the

strand exits the mold vertically (or on a near vertical curved path) and as it travels through the spray-

chamber, the rollers gradually curve the strand towards the horizontal. In a vertical casting machine,

the strand stays vertical as it passes through the spray-chamber. Molds in a curved apron casting

machine can be straight or curved, depending on the basic design of the machine.

In a true "Horizontal Casting Machine", the mold axis is horizontal and the flow of steel is horizontal

from liquid to thin shell to solid (no bending). In this type of machine, either strand oscillation or mold

oscillation is used to prevent sticking in the mold.

After exiting the spray-chamber, the strand passes through straightening rolls (if cast on other than a

vertical machine) and withdrawal rolls. There may be a hot rolling stand after withdrawal, in order to

take advantage of the metal's hot condition to pre-shape the final strand. Finally, the strand is cut

into predetermined lengths by mechanical shears or by travelling oxyacetylene torches, is marked

for identification and either taken to a stockpile or the next forming process.

In many cases the strand may continue through additional rollers and other mechanisms which

might flatten, roll or extrude the metal into its final shape.

Aluminium and copper can be cast horizontally and can be more easily cast into near net shape,

especially strip, due to their lower melting temperatures.

Range of continuously cast sections

Casting machines are designated to be billet, bloom or slab casters. Slab casters tend to cast sections with an aspect ratio that is much wider than it is thick:

o Conventional slabs lie in the range 100–1600 mm wide by 180–250 mm thick and up to 12 m long with conventional casting speeds of up to 1.4 m/minute, (however slab widths and casting speeds are currently increasing).

o Wider slabs are available up to 3250×150 mm, for example at Nanjing Iron & Steel in China.

o Thin slabs: 1680×50 mm Conventional bloom casters cast sections above 200×200 mm e.g. the Aldwarke Bloom caster in

Rotherham, UK, casts sections of 560×400 mm. The bloom length can vary from 4 to 10 m Billet casters cast smaller section sizes, such as below 200 mm square, with lengths up to 12 m

long. Cast speeds can reach up to 4 m/minute. Rounds: either 500 mm or 140 mm in diameter Conventional beam blanks: look similar to I-beams in cross-section; 1048×450 mm or

438×381 mm overall Near net shape beam blanks: 850×250 mm overall Strip: 2–5 mm thick by 760–1330 mm wide

Startup, control of the process and problems

Starting a continuous casting machine involves placing a dummy bar (essentially a curved metal

beam) up through the spray chamber to close off the base of the mould. Metal is poured into the

mould and withdrawn with the dummy bar once it solidifies. It is extremely important that the metal

supply afterwards be guaranteed to avoid unnecessary shutdowns and restarts, known as

'turnarounds'. Each time the caster stops and restarts, a new tundish is required, as any uncast

metal in the tundish cannot be drained and instead freezes into a 'skull'. Avoiding turnarounds

requires the meltshop, including ladle furnaces (if any) to keep tight control on the temperature of the

metal, which can vary dramatically with alloying additions, slag cover and deslagging, and the

preheating of the ladle before it accepts metal, among other parameters. However, the cast rate may

be lowered by reducing the amount of metal in the tundish (although this can increase wear on the

tundish), or if the caster has multiple strands, one or more strands may be shut down to

accommodate upstream delays. Turnarounds may be scheduled into a production sequence if the

tundish temperature becomes too high after a certain number of heats.

Many continuous casting operations are now fully computer-controlled. Several electromagnetic and

thermal sensors in the ladle shroud, tundish and mould sense the metal level or weight, flow rate

and temperature of the hot metal, and the programmable logic controller (PLC) can set the rate of

strand withdrawal via speed control of the withdrawal rolls. The flow of metal into the moulds can be

controlled via two methods:

By slide gates or stopper rods at the top of the mould shrouds If the metal is open-poured, then the metal flow into the moulds is controlled solely by the

internal diameter of the metering nozzles. These nozzles are usually interchangeable.

Overall casting speed can be adjusted by altering the amount of metal in the tundish, via the ladle

slide gate. The PLC can also set the mould oscillation rate and the rate of mould powder feed, as

well as the spray water flow. Computer control also allows vital casting data to be repeated to other

manufacturing centres (particularly the steelmaking furnaces), allowing their work rates to be

adjusted to avoid 'overflow' or 'underrun' of product.

While the large amount of automation helps produce castings with no shrinkage and little

segregation, continuous casting is of no use if the metal is not clean beforehand, or becomes 'dirty'

during the casting process. One of the main methods through which hot metal may become dirty is

by oxidation, which occurs rapidly at molten metal temperatures (up to 1700 °C); inclusions of gas,

slag or undissolved alloys may also be present. To prevent oxidation, the metal is isolated from the

atmosphere as much as possible. To achieve this, exposed metal surfaces are covered – by the

shrouds, or in the case of the ladle, tundish and mould, by synthetic slag. In the tundish, any

inclusions – gas bubbles, other slag or oxides, or undissolved alloys – may also be trapped in the

slag layer.

A major problem that may occur in continuous casting is breakout. This is when the thin shell of the

strand breaks, allowing the still-molten metal inside the strand to spill out and foul the machine,

requiring a turnaround. Often, breakout is due to too high a withdrawal rate, as the shell has not had

the time to solidify to the required thickness, or the metal is too hot, which means that final

solidification takes place well below the straightening rolls and the strand breaks due to stresses

applied during straightening. A breakout can also occur if solidifying steel sticks to the mould

surface, causing a tear in the shell of the strand. If the incoming metal is overheated, it is preferable

to stop the caster than to risk a breakout. Additionally, lead contamination of the metal (caused by

counterweights or lead-acid batteries in the initial steel charge) can form a thin film between the

mould wall and the steel, inhibiting heat removal and shell growth and increasing the risk of

breakouts.

Another problem that may occur is a carbon boil – oxygen dissolved in the steel reacts with also-

present carbon to generate bubbles of carbon monoxide. As the term boil suggests, this reaction is

extremely fast and violent, generating large amounts of hot gas, and is especially dangerous if it

occurs in the confined spaces of a casting machine. Oxygen can be removed through the addition of

silicon or aluminium to the steel, which reacts to form silicon oxide (silica) or aluminium oxide

(alumina). However, too much alumina in the steel will clog the casting nozzles and cause the steel

to 'choke off'.

Computational fluid dynamics and other fluid flow techniques are being used extensively in the

design of new continuous casting operations, especially in the tundish, to ensure that inclusions and

turbulence are removed from the hot metal, yet ensure that all the metal reaches the mould before it

cools too much. Slight adjustments to the flow conditions within the tundish or the mould can mean

the difference between high and low rejection rates of the product.

Starter bar

The starter bar has a free end portion which is flexible for storage and a substantially rigid portion at

the end which plugs the mold. The starter bar is constructed in discrete blocks secured to one side

of a planar spine provided in segments and arranged end to end. Adjustable spacers in the form of

tapered blocks are disposed between the blocks of the bar to allow the starter bar to be self-

supporting in a curved configuration corresponding to the casting path. A more flexible spine in the

end portion of the starter bar allows the starter bar to be curved to a tighter radius than that of the

casting path while the blocks fan out in an unsupported configuration. A storage ramp is provided to

support the flexible end in the stored position.

Direct strip casting

Direct strip casting is a continuous casting process for producing metallic sheet directly from the

molten state that minimises the need for substantial secondary processing

ROLLING(Metal Working)

In metalworking, rolling is a metal forming process in which metal stock is passed through a pair of

rolls. Rolling is classified according to the temperature of the metal rolled. If the temperature of the

metal is above its recrystallization temperature, then the process is termed as hot rolling. If the

temperature of the metal is below its recrystallization temperature, the process is termed as cold

rolling. In terms of usage, hot rolling processes more tonnage than any other manufacturing

process and cold rolling processes the most tonnage out of all cold working processes.[1][2]

There are many types of rolling processes, including flat rolling, foil rolling, ring rolling, roll bending,

roll forming, profile rolling, and controlled rolling.

There are two types of rolling processes:

Hot rolling Cold rolling

HOT ROLLING

Hot rolling is a metalworking process that occurs above the recrystallization temperature of the

material. After the grains deform during processing, they recrystallize, which maintains an equiaxed

microstructure and prevents the metal from work hardening. The starting material is usually large

pieces of metal, like semi-finished casting products, such as slabs, blooms, and billets. If these

products came from a continuous casting operation the products are usually fed directly into the

rolling mills at the proper temperature. In smaller operations the material starts at room temperature

and must be heated. This is done in a gas- or oil-fired soaking pit for larger workpieces and for

smaller workpieces induction heating is used. As the material is worked the temperature must be

monitored to make sure it remains above the recrystallization temperature. To maintain a safety

factor a finishing temperature is defined above the recrystallization temperature; this is usually 50 to

100 °C (122 to 212 °F) above the recrystallization temperature. If the temperature does drop below

this temperature the material must be re-heated before more hot rolling.[3]

Hot rolled metals generally have little directionality in their mechanical properties and deformation

induced residual stresses. However, in certain instances non-metallic inclusions will impart some

directionality and workpieces less than 20 mm (0.79 in) thick often have some directional properties.

Also, non-uniformed cooling will induce a lot of residual stresses, which usually occurs in shapes

that have a non-uniform cross-section, such as I-beams and H-beams. While the finished product is

of good quality, the surface is covered in mill scale, which is an oxide that forms at high-

temperatures. It is usually removed via pickling or the smooth clean surface process, which reveals

a smooth surface.[4] Dimensional tolerances are usually 2 to 5% of the overall dimension.[5]

Hot rolling is used mainly to produce sheet metal or simple cross sections, such as rail tracks.

COLD ROLLING

Cold rolling occurs with the metal below its recrystallization temperature (usually at room

temperature), which increases the strength via strain hardening up to 20%. It also improves the

surface finish and holds tighter tolerances. Commonly cold-rolled products include sheets, strips,

bars, and rods; these products are usually smaller than the same products that are hot rolled.

Because of the smaller size of the workpieces and their greater strength, as compared to hot rolled

stock, four-high or cluster mills are used.[2] Cold rolling cannot reduce the thickness of a workpiece

as much as hot rolling in a single pass.

Cold-rolled sheets and strips come in various conditions: full-hard, half-hard, quarter-hard, and skin-

rolled. Full-hard rolling reduces the thickness by 50%, while the others involve less of a reduction.

Quarter-hard is defined by its ability to be bent back onto itself along the grain boundary without

breaking. Half-hard can be bent 90°, while full-hard can only be bent 45°, with the bend radius

approximately equal to the material thickness. Skin-rolling, also known as a skin-pass, involves the

least amount of reduction: 0.5-1%. It is used to produce a smooth surface, a uniform thickness, and

reduce the yield-point phenomenon (by preventing Luder bands from forming in later processing).[6] It

is also used to breakup the spangles in galvanized steel.[citation needed] Skin-rolled stock is usually used

in subsequent cold-working processes where good ductility is required.[2]

Other shapes can be cold-rolled if the uniform is relatively uniform and the transverse dimension is

relatively small; approximately less than 50 mm (2.0 in). This may be a cost-effective alternative to

extruding or machining the profile if the volume is in the several tons or more. Cold rolling shapes

requires a series of shaping operations, usually along the lines of: sizing, breakdown, roughing,

semi-roughing, semi-finishing, and finishing.[2]

OXYGEN PLANT

Oxygen absorption plants is the modern non-cryogenic gas separation system. Plants based on

absorption and sometimes membrane technology.

Big adsorption oxygen plant

Application

Oxygen finds broad application in various technological processes and in almost all industry

branches. The primary oxygen application is associated with its capability of sustaining burning

process, and the powerful oxidant properties.

Due to that, oxygen has become widely used in the metal processing, welding, cutting and brazing

processes. In the chemical and petrochemical industries, as well as in the oil and gas sector oxygen

is used in commercial volumes as an oxidizer in chemical reactions.

Metal gas welding, cutting and brazing

The use of oxygen in gas-flame operations, such as metal welding, cutting and brazing is one of the

most significant and common applications of this gas. Oxygen allows generating high-temperature

flame in welding torches thus ensuring high quality and speed of work performance.

Metal industry

Oxygen is heavily used in the metal industry where it helps to increase burning temperature by the

production of ferrous and non-ferrous metals and significantly improve the overall process efficiency.

Another important oxygen application in the metal industry is connected with its use for carbon

fixation with the yield of carbon dioxide.

Chemical and petrochemical industries

In the chemical and petrochemical industries, oxygen is widely used for oxidation of raw chemicals

for recovery of nitric acid, ethylene oxide, propylene oxide, vinyl chloride and other important

chemical compounds.

Oil and gas industry

In the oil and gas industry, oxygen finds application as a means for viscosity improvement and

enhancement of oil-and-gas flow properties. Oxygen is also used for boosting production capacity of

oil cracking plants, efficiency of high-octane components processing, as well as for the reduction of

sulfuric deposits in refineries.

Fish farming

The use of oxygen in the fish farming helps increase the survival and fertility ratios and reduce the

incubation period. Along with fish culture, oxygen is applied for shrimps, crabs and mussels rearing.

Glass industry

In glass furnaces oxygen is effectively used for burning temperature increase and burning processes

improvement.

Waste management

The use of oxygen in incinerators allows to significantly increase flame temperature and eventually

ensure enhanced cost efficiency and incinerators production capacity

Oxy-fuel welding and cutting.

Side of metal, cut by oxygen - propane cutting torch

A cutting torch is used to cut a steel pipe.

Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the

U.S.) and oxy-fuel cutting are processes that use fuel gases and oxygen to weld and cut metals,

respectively. French engineers Edmond Fouché and Charles Picard became the first to develop an

oxygen-acetylene welding set-up in 1903.[1] Pure oxygen, instead of air (20% oxygen/80% nitrogen),

is used to increase the flame temperature to allow localized melting of the workpiece material (e.g.

steel) in a room environment. A common propane/air flame burns at about 2,000 °C (3,630 °F), a

propane/oxygen flame burns at about 2,500 °C (4,530 °F), and an acetylene/oxygen flame burns at

about 3,500 °C (6,330 °F).

Oxy-fuel is one of the oldest welding processes, though in recent years it has become less popular

in industrial applications. However, it is still widely used for welding pipes and tubes, as well as

repair work. It is also frequently well-suited, and favored, for fabricating some types of metal-based

artwork.

In oxy-fuel welding, a welding torch is used to weld metals. Welding metal results when two pieces

are heated to a temperature that produces a shared pool of molten metal. The molten pool is

generally supplied with additional metal called filler. Filler material depends upon the metals to be

welded.

In oxy-fuel cutting, a cutting torch is used to heat metal to kindling temperature. A stream of oxygen

is then trained on the metal, and metal burns in that oxygen and then flows out of the cut (kerf) as an

oxide slag.[2]

Torches that do not mix fuel with oxygen (combining, instead, atmospheric air) are not considered

oxy-fuel torches and can typically be identified by a single tank (Oxy-fuel welding/cutting generally

requires two tanks, fuel and oxygen). Most metals cannot be melted with a single-tank torch. As

such, single-tank torches are typically used only for soldering and brazing, rather than welding.

Uses

Oxy-gas torches are used for or have been used for:

Welding metal: see below. Cutting metal: see below. Also, oxy-hydrogen flames are used:

o In Stone Work for "flaming" where the stone is heated and a top layer crackles and breaks. A steel circular brush is attached to an angle grinder and used to remove the first layer leaving behind a bumpy surface similar to hammered bronze.

o In the glass industry for "fire polishing". o In jewelry production for "water welding" using a water torch. o Formerly, to heat lumps of quicklime to obtain a bright white light called limelight, in

theatres or optical ("magic") lanterns. o Formerly, in platinum works, as platinum is only fusible in the oxy-hydrogen flame and

in an electric furnace.

In short, oxy-fuel equipment is quite versatile – not only because it is preferred for some sorts of iron

or steel welding but also because it lends itself to brazing, braze-welding, metal heating (for

annealing or tempering, bending or forming), the loosening of corroded nuts and bolts, and also is

the ubiquitous means for oxy-fuel cutting of ferrous metals.

Apparatus

The apparatus used in gas welding consists basically of an oxygen source and a fuel gas source

(usually cylinders), two pressure regulators and two flexible hoses (one of each for each cylinder),

and a torch. This sort of torch can also be used for soldering and brazing. The cylinders are often

carried in a special wheeled trolley.

There have been examples of oxyhydrogen cutting sets with small (scuba-sized) gas cylinders worn

on the user's back in a backpack harness, for rescue work and similar.

There are also examples of pressurized liquid fuel cutting torches, usually using gasoline. These are

used for their increased portability.

Regulator

The regulator is used to control pressure from the tanks to the required pressure in the hose. The

flow rate is then adjusted by the operator using needle valves on the torch. Accurate flow control

with a needle valve relies on a constant inlet pressure to it.

Most regulators have two stages: the first stage of the regulator is a fixed-pressure regulator whose

function is to release the gas from the cylinder at a constant intermediate pressure, despite the

pressure in the cylinder falling as the gas in the cylinder is used. This is similar to the first stage of a

scuba-diving regulator. The adjustable second stage of the regulator controls the pressure reduction

from the intermediate pressure to the low outlet pressure. The regulator has two pressure gauges,

one indicating cylinder pressure, the other indicating hose pressure. The adjustment knob of the

regulator is sometimes roughly calibrated for pressure, but an accurate setting requires observation

of the gauge.

Some simpler or cheaper oxygen-fuel regulators have only a single stage regulator, or only a single

gauge. A single-stage regulator will tend to reduce its outlet pressure as the cylinder is emptied,

requiring manual readjustment. For low-volume users, this is an acceptable simplification. Welding

regulators, unlike simpler LPG heating regulators, retain their outlet (hose) pressure gauge and do

not rely on the calibration of the adjustment knob. The cheaper single-stage regulators may

sometimes omit the cylinder contents gauge, or replace the accurate dial gauge with a cheaper and

less precise "rising button" gauge.

Gas hoses

The hoses are specifically designed for welding and cutting. The hose is usually a double-hose

design, meaning that there are two hoses joined together. These hoses are colour-coded for visual

identification and their threaded connectors are handed to avoid accidental mis-connection: oxygen

is right-handed as normal, fuel gases use a left-handed thread.[3] These left-handed threads also

have an identifying groove cut into their nuts.

Colour coding of hoses varies between countries. In the USA, oxygen is green, and the fuel hose is

red.[3] In the UK, the oxygen hose is blue (black hoses may still be found on old equipment), and the

acetylene fuel hose is red.[4] Where LPG fuel such as propane is used, the fuel hose should be

orange, indicating that it is compatible with LPG. LPG will damage an incompatible hose, including

most acetylene hoses.

Connections between flexible hoses and rigid fittings are made by a crimped hose clip over a barbed

spigot. The use of worm-drive or Jubilee clips is specifically forbidden in the UK. The hoses should

also be clipped together at intervals approximately 3 feet apart.

Non-return valve

Between the regulator and hose, and ideally between hose and torch on both oxygen and fuel lines,

a flashback arrestor and/or non-return valve (check valve) should be installed to prevent flame or

oxygen-fuel mixture being pushed back into either cylinder and damaging the equipment or making a

cylinder explode.

European practice is to fit flashback arrestors at the regulator and check valves at the torch. US

practice is to fit both at the regulator.

The flashback arrestor (not to be confused with a check valve) prevents the shock waves from

downstream coming back up the hoses and entering the cylinder (possibly rupturing it), as there are

quantities of fuel/oxygen mixtures inside parts of the equipment (specifically within the mixer and

blowpipe/nozzle) that may explode if the equipment is incorrectly shut down; and acetylene

decomposes at excessive pressures or temperatures. The flashback arrestor will remain switched off

until someone resets it, in case the pressure wave created a leak downstream of the arrestor.

Check valve

A check valve lets gas flow in one direction only. Not to be confused with a flashback arrestor, a

check valve is not designed to block a shock wave. The pressure wave could occur while the ball is

so far from the inlet that the pressure wave gets past before the ball reaches its off position. A check

valve is usually a chamber containing a ball that is pressed against one end by a spring: gas flow

one way pushes the ball out of the way, and no flow or flow the other way lets the spring push the

ball into the inlet, blocking it.

Torches

The torch is the part that the welder holds and manipulates to make the weld. It has a connection

and valve for the fuel gas and a connection and valve for the oxygen, a handle for the welder to

grasp, a mixing chamber (set at an angle) where the fuel gas and oxygen mix, with a tip where the

flame forms.

The top torch is a welding torch and the bottom is a cutting torch

Welding torch

A welding torch head is used to weld metals. It can be identified by having only one or two pipes

running to the nozzle and no oxygen-blast trigger and two valve knobs at the bottom of the handle

letting the operator adjust the oxygen flow and fuel flow.

Cutting torch

A cutting torch head is used to cut materials. It is similar to a welding torch, but can be identified by

the oxygen blow out trigger or lever.

The metal is first heated by the flame until it is cherry red. Once this temperature is attained, oxygen

is supplied to the heated parts by pressing the "oxygen-blast trigger". This oxygen reacts with the

metal, forming iron oxide and producing heat. It is this heat which continues the cutting process. The

cutting torch only heats the metal to start the process; further heat is provided by the burning metal.

The melting point of the iron oxide is around half of that of the metal; as the metal burns, it

immediately turns to liquid iron oxide and flows away from the cutting zone. However, some of the

iron oxide remains on the work piece, forming a hard "slag" which can be removed by gentle

tapping, and/or a grinder.

The role of oxygen

Oxygen is not the fuel. It is what chemically combines with the fuel to produce the heat for welding.

This is called 'oxidation', but the more specific and more commonly used term in this context is

'combustion'. In the case of hydrogen, the product of combustion is simply water. For the other

hydrocarbon fuels, water and carbon dioxide are produced. The heat is released because the

molecules of the products of combustion have a lower energy state than the molecules of the fuel

and oxygen. In oxy-fuel cutting, oxidation of the metal being cut (typically iron) produces nearly all of

the heat required to "burn" through the workpiece.

The word "oxygen" is often shortened to 'oxy', as in the term 'oxy-acetylene torch'.

Oxygen is usually produced elsewhere by distillation of liquified air and shipped to the welding site in

high pressure vessels (commonly called "tanks" or "cylinders") at a pressure of about 21,000 kPa

(3,000 lbf/in² = 200 atmospheres). It is also shipped as a liquid in Dewar type vessels (like a large

Thermos jar) to places that use large amounts of oxygen.

It is also possible to separate oxygen from air by passing the air, while under pressure, through a

zeolite sieve which selectively absorbs the nitrogen and lets the oxygen (and argon) pass. This gives

a purity of oxygen of about 93%. This works well for brazing.

Types of flame

Oxidising and reducing flame

The welder can adjust the oxy-acetylene flame to be carbonizing (aka reducing), neutral, or

oxidizing. Adjustment is made by adding more or less oxygen to the acetylene flame. The neutral

flame is the flame most generally used when welding or cutting. The welder uses the neutral flame

as the starting point for all other flame adjustments because it is so easily defined. This flame is

attained when welders, as they slowly open the oxygen valve on the torch body, first see only two

flame zones. At that point, the acetylene is being completely burned in the welding oxygen and

surrounding air [2]. The flame is chemically neutral. The two parts of this flame are the light blue inner

cone and the darker blue to colorless outer cone. The inner cone is where the acetylene and the

oxygen combine. The tip of this inner cone is the hottest part of the flame. It is approximately

6,000 °F (3,300 °C) and provides enough heat to easily melt steel [2]. In the inner cone the acetylene

breaks down and partly burns to hydrogen and carbon monoxide, which in the outer cone combine

with more oxygen from the surrounding air and burn.

An excess of acetylene creates a carbonizing flame. This flame is characterized by three flame

zones; the hot inner cone, a white-hot "acetylene feather", and the blue-colored outer cone. This is

the type of flame observed when oxygen is first added to the burning acetylene. The feather is

adjusted and made ever smaller by adding increasing amounts of oxygen to the flame. A welding

feather is measured as 2X or 3X, with X being the length of the inner flame cone. The unburned

carbon insulates the flame and drops the temperature to approximately 5,000 °F (2,800 °C). The

reducing flame is typically used for hardfacing operations or backhand pipe welding techniques. The

feather is caused by incomplete combustion of the acetylene to cause an excess of carbon in the

flame. Some of this carbon is dissolved by the molten metal to carbonize it. The carbonizing flame

will tend to remove the oxygen from iron oxides which may be present, a fact which has caused the

flame to be known as a "reducing flame" [2].

The oxidizing flame is the third possible flame adjustment. It occurs when the ratio of oxygen to

acetylene required for a neutral flame has been changed to give an excess of oxygen. This flame

type is observed when welders add more oxygen to the neutral flame. This flame is hotter than the

other two flames because the combustible gases will not have to search so far to find the necessary

amount of oxygen, nor heat up as much thermally inert carbon.[2] It is called an oxidizing flame

because of its effect on metal. This flame adjustment is generally not preferred. The oxidizing flame

creates undesirable oxides to the structural and mechanical detriment of most metals. In an oxidizing

flame, the inner cone acquires a purplish tinge, gets pinched and smaller at the tip, and the sound of

the flame gets harsh. A slightly oxidizing flame is used in braze-welding and bronze-surfacing while

a more strongly oxidizing flame is used in fusion welding certain brasses and bronzes [2]

The size of the flame can be adjusted to a limited extent by the valves on the torch and by the

regulator settings, but in the main it depends on the size of the orifice in the tip. In fact, the tip should

be chosen first according to the job at hand, and then the regulators set accordingly.

Welding

The flame is applied to the base metal and held until a small puddle of molten metal is formed. The

puddle is moved along the path where the weld bead is desired. Usually, more metal is added to the

puddle as it is moved along by means of dipping metal from a welding rod or filler rod into the molten

metal puddle. The metal puddle will travel towards where the metal is the hottest. This is

accomplished through torch manipulation by the welder.

The amount of heat applied to the metal is a function of the welding tip size, the speed of travel, and

the welding position. The flame size is determined by the welding tip size. The proper tip size is

determined by the metal thickness and the joint design.

Welding gas pressures using oxy-acetylene are set in accordance with the manufacturer's

recommendations. The welder will modify the speed of welding travel to maintain a uniform bead

width. Uniformity is a quality attribute indicating good workmanship. Trained welders are taught to

keep the bead the same size at the beginning of the weld as at the end. If the bead gets too wide,

the welder increases the speed of welding travel. If the bead gets too narrow or if the weld puddle is

lost, the welder slows down the speed of travel. Welding in the vertical or overhead positions is

typically slower than welding in the flat or horizontal positions.

The welder must add the filler rod to the molten puddle. The welder must also keep the filler metal in

the hot outer flame zone when not adding it to the puddle to protect filler metal from oxidation. Do

not let the welding flame burn off the filler metal. The metal will not wet into the base metal and will

look like a series of cold dots on the base metal. There is very little strength in a cold weld. When the

filler metal is properly added to the molten puddle, the resulting weld will be stronger than the

original base metal.

Cutting

For cutting, the set-up is a little different. A cutting torch has a 60- or 90-degree angled head with

orifices placed around a central jet. The outer jets are for preheat flames of oxygen and acetylene.

The central jet carries only oxygen for cutting. The use of a number of preheating flames, rather than

a single flame makes it possible to change the direction of the cut as desired without changing the

position of the nozzle or the angle which the torch makes with the direction of the cut, as well as

giving a better preheat balance [2]. Manufacturers have developed custom tips for Mapp, propane,

and polypropylene gases to optimize the flames from these alternate fuel gases.

The flame is not intended to melt the metal, but to bring it to its ignition temperature.

The torch's trigger blows extra oxygen at higher pressures down the torch's third tube out of the

central jet into the workpiece, causing the metal to burn and blowing the resulting molten oxide

through to the other side. The ideal kerf is a narrow gap with a sharp edge on either side of the

workpiece; overheating the workpiece and thus melting through it causes a rounded edge.

Oxygen Rich Butane Torch Flame

Fuel Rich Butane Torch Flame

Cutting is initiated by heating the edge or leading face (as in cutting shapes such as round rod) of

the steel to the ignition temperature (approximately bright cherry red heat) using the pre-heat jets

only, then using the separate cutting oxygen valve to release the oxygen from the central jet [2]. The

oxygen chemically combines with the iron in the ferrous material to instantly oxidize the iron into

molten iron oxide, producing the cut. Initiating a cut in the middle of a workpiece is known as

piercing.

It is worth noting several things at this point:

The oxygen flowrate is critical — too little will make a slow ragged cut; too much will waste oxygen and produce a wide concave cut. Oxygen Lances and other custom made torches do not have a separate pressure control for the cutting oxygen, so the cutting oxygen pressure must be controlled using the oxygen regulator. The oxygen cutting pressure should match the cutting tip oxygen orifice. Consult the tip manufacturer's equipment data for the proper cutting oxygen pressures for the specific cutting tip [2].

The oxidation of iron by this method is highly exothermic. Once started, steel can be cut at a surprising rate, far faster than if it was merely melted through. At this point, the pre-heat jets are there purely for assistance. The rise in temperature will be obvious by the intense glare from the ejected material, even through proper goggles. (A thermic lance is a tool which also uses rapid oxidation of iron to cut through almost any material.)

Since the melted metal flows out of the workpiece, there must be room on the opposite side of the workpiece for the spray to exit. When possible, pieces of metal are cut on a grate that lets the melted metal fall freely to the ground. The same equipment can be used for oxyacetylene blowtorches and welding torches, by exchanging the part of the torch in front of the torch valves.

For a basic oxy-acetylene rig, the cutting speed in light steel section will usually be nearly twice as

fast as a petrol-driven cut-off grinder. The advantages when cutting large sections are obvious - an

oxy-fuel torch is light, small and quiet and needs very little effort to use, whereas a cut-off grinder is

heavy and noisy and needs considerable operator exertion and may vibrate severely, leading to stiff

hands and possible long-term repetitive strain injury. Oxy-acetylene torches can easily cut through

ferrous materials in excess of 50 mm (2 inches). Oxygen Lances are used in scrapping operations

and cut sections thicker than 200 mm (8 inches). Cut-off grinders are useless for these kinds of

application.

Robotic oxy-fuel cutters sometimes use a high-speed divergent nozzle. This uses an oxygen jet that

opens slightly along its passage. This allows the compressed oxygen to expand as it leaves, forming

a high-velocity jet that spreads less than a parallel-bore nozzle, allowing a cleaner cut. These are not

used for cutting by hand since they need very accurate positioning above the work. Their ability to

produce almost any shape from large steel plates gives them a secure future in shipbuilding and in

many other industries.

Oxy-propane torches are usually used for cutting up scrap to save money, as LPG is far cheaper

joule-for-joule than acetylene, although propane does not produce acetylene's very neat cut profile.

Propane also finds a place in production, for cutting very large sections.

Oxy-acetylene can only cut low to medium carbon steels and wrought iron. High carbon steels

cannot be cut because the melting point is very close to the temperature of the flame, and so the

slag from the cutting action does not eject as sparks, but rather mixes with the clean melt near the

cut. This keeps the oxygen from reaching the clean metal and burning it. In the case of cast iron,

graphite between the grains and the shape of the grains themselves interfere with cutting action of

torch.[8]