tool steels(brief guide)

7/31/2019 Tool Steels(Brief Guide)

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Tool Steels


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Tool Steels


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Tool Steels

Technically any steel used as a

component part of a tool could

be called a tool steel. This is avague definition, as almost any

steel could be used for certainparts of a tool.


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Tool Steels

To be more specific, a steel

containing alloying elements that

enable it to be heat-treated toobtain desirable characteristics

such as strength, hardness,strength, hardness,

toughness, and wear resistancetoughness, and wear resistance

could be referred to as a tool steel

.


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Tool Steels

The term tool steel as used in

present-day industry refers to a

group of high-quality, carefullymanufactured steels that are

characterized by high hardness a

resistance to abrasion.


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Tool Steels

Certain groups of tool steels also

have a high resistance to softening

at high temperatures. They areseparated from alloyed and heat-

treatable constructional steels by

precise production and quality

control methods.


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Tool SteelsThe high price ofalloying elementsand precise production requirementsand quality control are the reasons for

the high cost of tool steels. However,when we stop to consider that toolsteels are made into a complicated

tool or die which has requiredhundreds of man-hours in itsmanufacture and will produce

thousands or even millions of parts, it


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Tool Steels Classification

In the past tool steels have beenclassified in several ways. One

common method has been to classify

them according to the method of

quenching, such as water-hardening

steels, oil-hardening steels, and air-hardening steels.


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Another method is to classify themaccording to alloys, such as carbon

tool steels and alloy tool steels. Still

another method has been toclassify them according to

applications such as shock-

resisting steels, cold-work steels,

hot-work steels, die-casting die

steels, drill steels, tool and die


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Tool Steels

Classification


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The American Iron and SteelInstitute (AISI) and

The Society of AutomotiveEngineers (SAE) have developeda system of classifying tool steels

which groups grades of similarproperties as shown


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W- Water-hardening Tool Steels.

O- Oil hardening Tool Steels.

A- Air hardening Die Steels

D- High carbon High chromium Die Steels

S- Shock resisting Tool SteelsT and M- Tungsten and Molybdenum High-speed Steels.

L-Low Alloy (Special Purpose)

H- Hot Working Steels.

P- Pre hardened Steels


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W- Water-hardening Tool Steels.

W1 and W2 are both readily available and of

low cost. W2 contains vanadium and is more

uniform in response to heat treatment; it is of a

finer grain size with a higher toughness. Both

are shallow-hardening and, when hardened

with a hard case and a softer internal core,have high toughness. They are quenched in

water or brine


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W-Water hardening

AISISTEEL

TYPE

C Mn Si W Cr Mo Ni Co

W1 1.05 0.25 0.20 - 0.20 - 0.05

W2 1.00 0.25 0.20 - - - 0.20


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O- Oil hardening Tool Steels.Steels O1 and O2 have, for many years, beenthe workhorses of the die-steel industry and are

known familiarly as manganese oil-hardeningtool steel. Readily available and of low cost,these steels, which are hardened in oil, haveless movement than the water-hardening steels

and are of equal toughness when the water-hardening steels are hardened throughout. Forspecial applications, type O6, which containsfree carbon in the form of graphite, has been

used successfully.


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O-Oil hardening

AISISTEEL

TYPE

C Mn Si W Cr Mo V others

O1 0.90 1.25 0.30 0.50 0.50 - 0.05

O2 0.90 1.60 - - - - -

O3 1.45. 0.80. 1.10 - - 0.25 -


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A- Air hardening Die Steels.The principal air-hardening die steel employed is steel

A2- This steel has a minimum movement in hardening

and has higher toughness than the oil-hardening diesteels, with equal or greater wear resistance. It has a

slightly higher hardening temperature than the

manganese types. The availability of the popular A2

steel is excellent- Type A8 is the toughest steel in thisgroup, but its low carbon content makes it less wear-

resistant than A2.


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A-Air hardening

AISISTEEL

TYPE


A2 1.00 0.60 0.30 - 5.25 1.10 0.25

A8 0.55 - 1.00 1.25 5.00 1.25 -

A9 0.50 - 1.00 - 5.20 1.40 1.00 1.40

Ni


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Tool Steels ClassificationD- High carbon High chromium Die Steels.

The principal steels of wide application for long-run dies are steels in this group. Grade D2containing 1.50% carbon is of moderatetoughness and intermediate wear resistance,whereas steels D3, D4, and D7, containingadditional carbon, are of very high wearresistance and somewhat lower toughness.

Selection between these is based on the lengthof run desired and machining and grindingproblems. D2 and D4, containing molybdenum,are air-hardening and have minimum

movement in hardening.


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D-High Carbon High

Chromium Die SteelAISISTEEL

TYPE


D

2 1.55 0.30 0.40 - 11.5 0.80 0.90

D3 2.10 0.40 0.90 0.80 11.70 - -

D4 2.25 0.35 0.5 - 11.5 0.80 0.20

D7 2.30 0.40 0.40 - 12.5 1.10 4.00


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S- Shock resisting Tool Steels.These steels contain less carbon and have

higher toughness. They are employed

where heavy cutting or forming operations

are required and where breakage is a

serious problem with higher-carbon

materials that might have longer life

through higher wear resistance alone.

Choice among the grades is a matter of

ex erience.


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S-Shock Resisting

AISISTEEL

TYPE


S1 0.50 - 0.50 2.25 1.30 - 0.25

S5 0.60 0.85 1.9 - 0.20 0.50 0.20

S7 0.50 0.75 0.30 - 3.25 1.40 -


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T and M. Tungsten and Molybdenum High-speed Steels.Steels T1 and M2 are equivalent inperformance and represent standard high-speed steels which have excellent properties

for cold-working dies. They have highertoughness than many of the other die steels,combined with excellent wear resistance. Whilethey are expensive, they are readily available.

T15 and M4 are hardened by the standardmethod rather than carburizing, because theyalready have a very high carbon contentcombined with a high vanadium content.


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T-Tungsten base High Speed

steel

AISISTEEL

TYPE


T1 0.75 - - 18.00 4.00 - 1.10

T15 1.55 - - 12.25 4.00 - 5.00 5.00

Co


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Tool Steels ClassificationT and M. Tungsten and Molybdenum High-speed Steels.

Type Ml may occasionally be used in place ofT1 and M2, but it is more susceptible to

decarburization. Steel T15 is the most wear-

resistant of all steels in the list, and steel M4 isslightly greater in wear resistance than a steel

such as D4. These steels are more difficult to

machine and grind than the other high-speed

steels, but the improved performanceobtainable very often justifies the extra

machining expense.


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M-Molybdenum base High

Speed steelAISISTEEL

TYPE


M1 0.80 - - 1.50 3.75 8.50 1.05

M2 0,85 - - 6.25 4.15 5.00 1.90

M4 1.30 - - 5.50 4.00 4.50 4.00

M7 1.00 - - 1.70 3.75 8.75 2.00

M42 1.08 - - 1.50 3.75 9.50 1.10 8.00

Co


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L- Low alloy Tool Steels.Of the many low-alloy steels effective as

die materials, steel L6 is a chromium-

nickel steel. In large sizes it is water-quenched and has a hard case and a soft

core, with an attendant high overall

toughness. In small sizes it may be oil-quenched


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L-Low Alloy

(Special Purpose)

AISISTEEL

TYPE


L6 0.75 0.70 - - 0.80 0.30 - 1.50

Ni


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H- Hot Working Steels.

Die casting dies. extrusion dies, hot

forming dies, and hot drawingmandrels are typical hot-work

applications.


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H-Hot Working

AISISTEEL

TYPE


H12 0.35 - 1.00 1.25 5.00 1.35 0.30

H13 0.38 - 1.00 - 5.20 1.25 1.00

H21 0.30 0.25 0.30 9.00 3.25 - 0.25

H26 0.53 - - 18.00 4.00 - 1.00


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P- Pre hardened Steels.

Steels which are pre hardened from arange of 28-33 HRc is available for

plastic components.


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P-Pre hardened

AISISTEEL

TYPE


P4 0.07 - - - 5.00 - -

P5 0.10 - - -- 2.25 - -

P6 0.10 - - - 1.50 - 0.20 3.50Ni

P20 0.30 - - - 0.75 0.25 -


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Effects of alloying elements

NICKEL (Ni)It is added to steel generally with

Chromium.It helps to produce fine grain in

the steel.This leads to lesser distortionduring quenching.Nickel improves

resistance to corrosion.An alloy called invar

having 35 to 36% Nickel has nearly zeroco-efficient of thermal expansion. This alloy

is used to manufacture measuring

instruments.


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NICKEL (Ni)It is added to steel generally with

Chromium.It helps to produce fine grain in

the steel.This leads to lesser distortionduring quenching.Nickel improves

resistance to corrosion.An alloy called invar

having 35 to 36% Nickel has nearly zeroco-efficient of thermal expansion. This alloy

is used to manufacture measuring

instruments.


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CHROMIUM(Cr)

Small quantities of Chromium is added to

Carbon Steel to increase its hardness.However ductility is reduced. Chromium

promotes grain growth in steel.Two of the

most important properties of Steelscontaining chromium are wear resistance

and cutting ability. Chromium also increases

the corrosion resistance of steel.


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MOLYBDENUM(Mo)It is often used in conjunction with

Chromium. It is used in tool steels because

it increases the hot hardness. Within the

temperature range where it is effective it is

twice as strong and much cheaper than

Tungsten. It is commonly used in forging

dies that must resist impact and abrasion at

elevated temperature


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VANADIUM (V)It acts as a deoxidizer and also

removes Nitrogen from steel. It forms

complex carbides with Carbon. These

carbides together with chromium and

nickel greatly strengthen the steel. A0.3 to 0.25% Vanadium increases the

elastic limit, yield point and impact

strength, with almost no loss in ductility


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MANGANESE (Mn)It is usually present in all commercial

steels. It reduces the harmful effect of

Sulphur by forming Manganese

Sulphide. 11 to 14% Manganese and 1

to 1.4 Carbon Alloy is resistant to wearand abrasion under high impact stress.


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SILICON (Si)

When added to Steel it is a more

efficient deoxidiser than Manganese.Addition of small percentage of Silicon

increases the strength with little loss in

Ductility, ill is used in spring steels

which contain about 2% Silicon, 0.8%

Manganese and 0.6% Carbon.


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TUNGSTEN (W)

It is more effective than molybdenum in

retaining hardness at very hightemperatures. It is a primary alloying

element in tool steels, that must

maintain their hardness at high

operating temperatures.


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SILICON (Si)

When added to Steel it is a more

efficient deoxidiser than Manganese.Addition of small percentage of Silicon

increases the strength with little loss in

Ductility, ill is used in spring steels

which contain about 2% Silicon, 0.8%

Manganese and 0.6% Carbon.


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COBALT (Co)

Cobalt is added to high speed steel from 1to 12% for the purpose of obtaining a

cutting tool with a sharp edge. It is also

used for making magnet steels containingabout 35% Cobalt.


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TITANIUM (Ti)

It is the strongest carbide former. It is

added to fix carbon in stainless


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COPPER (Cu)

Copper imparts atmospheric corrosionresistance to Steel. About 0.1 to 0.4% is

only added


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SULPHUR (S)

Sulphur is harmful to steel as it makes the

steel brittle at higher temperatures aproperty called "hot shortness". However

about 0,3% Sulphur is added to free cutting

steels to increase machinability


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PHOSPHOROUS (P)

Phosphorous, when dissolved in ferrite,

increases strength, hardness andresistance to corrosion. It is added to low

carbon steels upto 0.12%. It is undesirable

to have phosphorous in high strength andhigh carbon steels, because it makes steel

brittle at low temperatures, a property called

"cold shortness.


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TITANIUM (Ti)




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TYPICALANALYSIS

OF EN

STEELS


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EN STEELSMaterial

C Si Mn Cr Ni VHardening

TempoC

EN-8 0.35-0.45

0.05-

0.35

0.60-

1.00- - - 830-

860

EN-9 0.50-

0.60

0.05-

0.35

0.50-

0.80

- - - 810-

940

EN-16 0.30-0.40

0.10-

0.35

1.30-

1.80- - - 830-

860

EN-24 0.35-0.45

0.10-

0.35

0.45-

0.70

0.90-

1.40

1.30-

1.80

0.20-

0.35

820-

850

EN-31 0.95-1.10

0.15-

0.35

0.50 1.30-

1.60- - 800-

840

EN-36 0.12-0.18

0.30-

0.60

0.30-

0.60

0.60-

1.10

3.00-

3.75- 750-

820


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Steels for blanking and

forming tools

tee s or an ng an


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tee s or an ng an

forming toolsIn selecting steel for blanking and forming tools, anumber of factors must be taken into account.

The tool-user and the toolmaker have differentdemands. A good steel must meet the demands

of both. Steel manufactures has therefore

developed steel grades in close cooperation with

toolmakers and users in order to find the optimum

solutions for various areas of application for

blanking and forming tools.

St l f bl ki d


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forming toolsFor the tool-user

Hardness/Compressive strength

Wear resistance

Toughness

St l f bl ki d


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forming toolsFor the toolmaker:Machinability

Grindability

Stock standard sizes

Heat treatment properties

Surface treatment properties


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Good resistance to thermal shockand thermal fatigue

Good high-temperature strength

Good toughness and ductility Good machinability, Good polishability

Good through-hardening properties Good dimensional stability duringhardening

Hot work tool steel-H13


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Application Tools for die casting

Tools for hot pressing

Tools for extrusion

Tools for drawing

Plastic moulds

Hot shearing


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AISI H13

Hot work tool steel-H13

W302

8407/QRD-90 Supreme

C

0.37

Si

1.0

Mn

0.40

Cr

5.3

Mo

1.4

V

1.0


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Good resistance to thermal shockand thermal fatigue

Good high-temperature strength

Good toughness and ductility Good machinability, Good polishability

Good through-hardening properties Good dimensional stability duringhardening

Cold work steel-D3


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AISI P20

Pre-hardened tool steel

~M200

718

C

0.35

Si

0.3

Mn

0.7

Cr

1.8

Ni

0.7

Mo

0.3


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AISI P20


~M200

718

C

0.35

Si

0.3

Mn

0.7

Cr

1.8

Ni

0.7

Mo

0.3


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AISI P20


~M200

718

C

0.35

Si

0.3

Mn

0.7

Cr

1.8

Ni

0.7

Mo

0.3


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forming tools

TITANIUM (Ti)




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forming tools

TITANIUM (Ti)



tool steels(brief guide)

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