Types Of Welded Joints

Introduction To Welding Technology

Welding is a fabrication process used to join materials, usually metals or thermoplastics, together. During welding, the pieces to be joined (the workpieces) are melted at the joining interface and usually a filler material is added to form a pool of molten material (the weld pool) that solidifies to become a strong joint.

In contrast, Soldering and Brazing do not involve melting the workpiece but rather a lower-melting-point material is melted between the workpieces to bond them togetherIn most welding procedures metal is melted to bridge the parts to be joined so that on solidification of the weld metal the parts become united. The common processes of this type are grouped as fusion welding. Heat must be supplied to cause the melting of the filler metal and the way in which this is achieved is the major point of distinction between the different processes.

The method of protecting the hot metal from the attack by the atmosphere and the cleaning or fluxing away of contaminating surface films and oxides provide the second important distinguishing feature. For example, welding can be carried out under a shield comprising of a mixture of metal oxides and silicates which produce a glass-like flux, or the whole weld area may be swept clear of air by a stream of gas such as argon, helium or carbon dioxide which is harmless to the hot metals.

 The weld joint is where two or more metal parts are joined by welding.

The five basic types of weld joints are the butt, corner, tee, lap, and edge.

Butt Joint: it is used to join two members aligned in the same plane. This joint is frequently used in plate, sheet metal, and pipe work.

 

Corner and Tee Joints: these joints are used to join two members located at right angles to each other. In cross section, the corner joint forms an L-shape, and the tee joint has the shape of the letter T.

 

Lap Joint: this joint is made by lapping one piece of metal over another. This is one of the strongest types of joints available; however, for maximum joint efficiency, the overlap should be atleast three times the thickness of the thinnest member of the joint.

 

Edge Joint: it is used to join the edges of two or more members lying in the same plane. In most cases, one of the members is flanged, as seen in the figure. This type is frequently used in sheet metal work for joining metals 1/4 inch or less in thickness that are not subjected to heavy loads.

Types Of Welds

There are many types of welds. The most common types are the bead, surfacing, plug, slot, fillet, and groove.

1. A weld Bead is a weld deposit produced by a single pass with one of the welding processes. A weld bead may be either narrow or wide, depending on the amount of transverse oscillation (side-to-side movement) used by the welder. A weld bead made without much weaving motion is often referred to as a stringer bead. On the other hand, a weld bead made with side-to-side oscillation is called a weave bead.

2. Several weld beads applied side-by-side are usually used in Surfacing which is a welding process used to apply a hard, wear-resistant layer of metal to surfaces or edges of worn- out parts.

3. A Fillet weld is triangular in shape and this weld is used to join two surfaces that are at approximately right angles to each other in a lap, tee, or comer joint.

4. Plug and Slot welds are welds made through holes or slots in one member of a lap joint. These welds are used to join that member to the surface of another member that has been exposed through the hole.

5. Groove welds (also may be referred to as Butt welds) are simply welds made in the groove between two members to be joined. The weld is adaptable to a variety of butt joints, as seen in the figure.

=> Groove welds may be joined with one or more weld beads, depending

on the thickness of the metal. If two or more beads are deposited in the groove, the weld is made with multiple-pass layers, as shown in the figure. As a rule, a multiple-pass layer is made with stringer beads in manual operations.

=> The buildup sequence refers to the order in which the beads of a multiple-pass weld are deposited in the joint. Usually, before adding the next pass, the previous pass needs to cool down to a certain temperature which is called the inter-pass temperature. Also, before adding the next pass, the surface of the previous pass needs to be cleaned from slag, especially with SMAW, using a wire brush or other appropriate method.

Welding TerminologyA+A-

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Defective Weld - A weld with one or more of the following defects: Porosity, undercut, slag inclusion and improper weld size.

Direct Current (DC) - Or "continuous current," is considered as the constant flow of electrons in the single direction from low to high potential.

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Down Hand Weld - A vertical weld where the welder starts at the top and works downward.

Edge Weld - A weld where the edges of two pieces come together.

*Electrode (Arc Welding) - A rod made up of filler metal with a coating on it designedto aid and protect the bead during the welding process.

Electrode Holder - The "handle" portion of the arc welder that holds the electrode in place.

Face Shield (Helmet) - A safety device worn over the face to protect the eyes and face from the arc, sparks and molten metal. Arc welding without proper eye protection can lead (quickly) to permanent damage to the eyes.

Ferrous - Containing or relating to iron.

Fillet Weld - A weld joining two pieces of metal that are more or less perpendicular to each other.

Filler metal - Is a metal added in the making of a joint through welding, brazingor soldering. Various types of filler metals exist.

Fixture - A tool or device used to hold pieces in place for welding.

Flat Weld - A weld where the pieces being joined come together horizontally in front of and below the welder.

Flux - A substance that facilitates soldering, brazing and welding by chemically cleaning the metals to be joined.

Forge - A device used to heat metal for forming and bending.

(Blacksmithing)

Fuel Gases - Gases mixed with oxygen in heating and cutting operations.

Gas Tungsten Arc Welding (GTAW) or (TIG) - Commonly known as tungsten inert gas (TIG) welding; an arc welding process that uses a non-consumabletungsten electrode to produce the weld.

Hand Shield - Similar to a Face Shield or Helmet, but held in front of the face rather than worn.

Iron - A base element that is the primary substance in the makeup of steel, cast iron and wrought iron.

Inert gas/Shielding gas - A gas that does not normally combine chemically with materials. Their purpose is to protect the weld area from atmospheric gases, such as oxygen, nitrogen, carbon dioxide and water vapor.

Lap Joint - A joint where two pieces of metal lap over each other, allowing a bead to be placed between the edge of one piece and the face of the other.

*MIG Welding (Metal Inert Gas) - Also known as wire-feed welding, althoughit is possible to do wire-feed welding without the inert gas. Metals that are difficult to arc weld may be MIG welded.

Mild Steel - Steel with less than 0.15% carbon. (Also called low carbon steel). Most steel in common use is mild steel.

Out-Of-Position Weld - Any weld where the work is not flat in front of the welder.

Overhead Weld - An inverted weld where the pieces being joined are above the welder.

Oxyfuel - Pure oxygen combined with gas

Plasma - A gas that has been heated to the point where it will conduct electricity.

Plasma Cutting - A cutting process where the metal is heated to the melting point by an arc through the plasma and then removed by the pressure of the gas as directed by the nozzle. CNC (computer numeric control) plasma cutters are used for precise cutting of complex patterns in metal.

Polarity - The polarity of a machine refers to direction of current flow. Polarity can only be obtained on a DC machine.

Radiation - Energy from heat or light that you cannot see.

Shielding Gas - --See Inert gas.

Slag Inclusion - Non-metallic material trapped in a weld.

Soldering - A method of joining metal parts using a filler material (solder) that has a melting temperature below 450°C (842°F).

Spot Weld - A weld between two overlapping pieces of material; normally used for sheet metal.

Tack Weld - A small weld used to hold pieces of an assembly in place prior to the final (continuous) welding.

TIG Welding (Tungsten Inert Gas) - A welding process where an inert gas protects the molten metal from the atmosphere to produce a high quality weld.

Tungsten - A non-consumable material used in TIG welding to carry current to the weld puddle. (very hard, heavy, steel-grey-to-white transition metal; W in the periodic table.)

Up Hand Weld - A vertical weld where the welder starts at the bottom and works upward.

Ventilate - To cause fresh air to enter and move around an enclosed space

Weave Bead - A welding pattern often used in butt welds where the welder moves the arc back and forth across the joint while also moving along it.

Weld - To join two pieces of metal together permanently by melting the parts that touch.

Welder (noun) - A person whose job is welding.

Welding Power Supply - A device that provides an electrical current to perform welding.

Welding Rod - A means of delivering filler metal to the weld. In arc welding, the rod is called an electrode.

Voltage (V) - Is the pressure required to move the electric current.

ypes Of Welding

There are many different types of welding processes and in general they can be categorized as:-

 1. Arc Welding: A welding power supply is used to create and maintain an electric arc between an electrode and the base material to melt metals at the welding point. In such welding processes the power supply could be AC or DC, the electrode could be consumable or non-consumable and a filler material may or may not be added. The most common types of arc welding are:

  => A. Shielded Metal Arc Welding (SMAW): A process that uses a coated consumable electrode to lay the weld. As the electrode melts, the (flux)

coating disintegrates, giving off shielding gases that protect the weld area from atmospheric gases and provides molten slag which covers the filler metal as it travels from the electrode to the weld pool. Once part of the weld pool, the slag floats to the surface and protects the weld from contamination as it solidifies. Once hardened, the slag must be chipped away to reveal the finished weld.

 =>B. Gas Metal Arc Welding (GMAW): A process in which a continuous and consumable wire electrode and a shielding gas (usually an argon and carbon dioxide mixture) are fed through a welding gun.

 => C. Gas Tungsten Arc Welding (GTAW): A process that uses a nonconsumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by a shielding gas, and a filler metal that is fed manually is usually used.

 

2. Gas Welding: In this method a focused high temperature flame generated by gas combustion is used to melt the workpieces (and filler) together. The most common type of gas welding is Oxy-fuel welding where acetylene is combusted in oxygen.  

 

3. Resistance Welding: Resistance welding involves the generation of heat by passing a high current (1000–100,000 A) through the resistance caused by the contact between two or more metal surfaces where that causes pools of molten metal to be formed at the weld area. The most common types of resistance welding are Spot-welding (using pointed electrodes) and Seam-welding (using wheel-shaped electrodes).  

 

4. Energy Beam Welding: In this method a focused high-energy beam (Laser beam or electron beam) is used to melt the workpieces and thus join them together.

 

 5. Solid-State Welding: In contrast to other welding methods, solid-state welding processes do not involve the melting of the materials being joined. Common types of solid-state welding include; ultrasonic welding, explosion welding, electromagnetic pulse welding, roll welding, friction welding (including friction-stir-welding), etc.  

Welding Terminology- Part 2

Defective Weld - A weld with one or more of the following defects: Porosity, undercut, slag inclusion and improper weld size.

Direct Current (DC) - Or "continuous current," is considered as the constant flow of electrons in the single direction from low to high potential.

Down Hand Weld - A vertical weld where the welder starts at the top and works downward.

Edge Weld - A weld where the edges of two pieces come together.

*Electrode (Arc Welding) - A rod made up of filler metal with a coating on it designedto aid and protect the bead during the welding process.

Electrode Holder - The "handle" portion of the arc welder that holds the electrode in place.

Face Shield (Helmet) - A safety device worn over the face to protect the eyes and face from the arc, sparks and molten metal. Arc welding without proper eye protection can lead (quickly) to permanent damage to the eyes.

Ferrous - Containing or relating to iron.

Fillet Weld - A weld joining two pieces of metal that are more or less perpendicular to each other.

Filler metal - Is a metal added in the making of a joint through welding, brazingor soldering. Various types of filler metals exist.

Fixture - A tool or device used to hold pieces in place for welding.

Flat Weld - A weld where the pieces being joined come together horizontally in front of and below the welder.

Flux - A substance that facilitates soldering, brazing and welding by chemically cleaning the metals to be joined.

Forge - A device used to heat metal for forming and bending.

(Blacksmithing)

Fuel Gases - Gases mixed with oxygen in heating and cutting operations.

Gas Tungsten Arc Welding (GTAW) or (TIG) - Commonly known as tungsten inert gas (TIG) welding; an arc welding process that uses a non-consumabletungsten electrode to produce the weld.

Hand Shield - Similar to a Face Shield or Helmet, but held in front of the face rather than worn.

Iron - A base element that is the primary substance in the makeup of steel, cast iron and wrought iron.

Inert gas/Shielding gas - A gas that does not normally combine chemically with materials. Their purpose is to protect the weld area from atmospheric gases, such as oxygen, nitrogen, carbon dioxide and water vapor.

Lap Joint - A joint where two pieces of metal lap over each other, allowing a bead to be placed between the edge of one piece and the face of the other.

*MIG Welding (Metal Inert Gas) - Also known as wire-feed welding, althoughit is possible to do wire-feed welding without the inert gas. Metals that are difficult to arc weld may be MIG welded.

Mild Steel - Steel with less than 0.15% carbon. (Also called low carbon steel). Most steel in common use is mild steel.

Out-Of-Position Weld - Any weld where the work is not flat in front of the welder.

Overhead Weld - An inverted weld where the pieces being joined are above the welder.

Oxyfuel - Pure oxygen combined with gas

Plasma - A gas that has been heated to the point where it will conduct electricity.

Plasma Cutting - A cutting process where the metal is heated to the melting point by an arc through the plasma and then removed by the pressure of the gas as directed by the nozzle. CNC (computer numeric control) plasma cutters are used for precise cutting of complex patterns in metal.

Polarity - The polarity of a machine refers to direction of current flow. Polarity can only be obtained on a DC machine.

Radiation - Energy from heat or light that you cannot see.

Shielding Gas - --See Inert gas.

Slag Inclusion - Non-metallic material trapped in a weld.

Soldering - A method of joining metal parts using a filler material (solder) that has a melting temperature below 450°C (842°F).

Spot Weld - A weld between two overlapping pieces of material; normally used for sheet metal.

Tack Weld - A small weld used to hold pieces of an assembly in place prior to the final (continuous) welding.

TIG Welding (Tungsten Inert Gas) - A welding process where an inert gas protects the molten metal from the atmosphere to produce a high quality weld.

Tungsten - A non-consumable material used in TIG welding to carry current to the weld puddle. (very hard, heavy, steel-grey-to-white transition metal; W in the periodic table.)

Up Hand Weld - A vertical weld where the welder starts at the bottom and works upward.

Ventilate - To cause fresh air to enter and move around an enclosed space

Weave Bead - A welding pattern often used in butt welds where the welder moves the arc back and forth across the joint while also moving along it.

Weld - To join two pieces of metal together permanently by melting the parts that touch.

Welder (noun) - A person whose job is welding.

Welding Power Supply - A device that provides an electrical current to perform welding.

Welding Rod - A means of delivering filler metal to the weld. In arc welding, the rod is called an electrode.

Voltage (V) - Is the pressure required to move the electric current.