this presentation is only about the cold work tool steel and its types includes oil hardened air hardened , high carbon high chromium steels

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2. M.Ahsan (MM-34) Qamar Shafiq (MM-41)
Usama Tahir (MM-10)
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3. A TOOL STEEL is any steel used to make tools for cutting, forming, or otherwise
shaping a material into a part or component for a definite use. The earliest tool
steels were simple, plain carbon steels.
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4. Tool Steel can classified it into following types.
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5. These steels are used for making tools for cold work applications, when
the tool surface temperature does not rise more than 205 to 260 °C (400 to
500 °F).
These are characterized by high abrasion & wear resistance , average
toughness and heat softening resistance.
They are used in production of larger parts or parts that require minimal
distortion during hardening.
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7. These are hardened by Oil –quenching & contain high
carbon with Manganese , Chromium & Molybdenum.
These are characterized by high machinability ,wear
resistance and non –distorting properties.
Tempering temperature for these steels varies from 100-
425˚C.
 Taps
 Blanking & forging dies
 Threading dies
 Expansion reamers.
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10. It is one of the most well respected oil-hardening tool and die steels. It is
easy to machine. Normal care in treatment gives good results in
hardening and produces small dimensional changes. It has good
abrasion-resistance, and sufficient toughness for normal tool-and-die
applications.
AISI 01:
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11. The machinability of O1 steels is very good with a rating of 90% that of water
hardening low alloy steels.
O1 steels should be heated uniformly to 780-820°C (1436-1508°F) until completely
heated through. If needed, the steels can be preheated at 300-500°C (572-932°F).
About 30 min/per 25 mm of ruling section is to be provided and then the steels
should be immediately quenched in oil.
When quenched from the proper hardening temperature this grade normally
expands .0015 in./in. plus. In many instances a slight scaling will occur during
heat treatment which tends to counteract this expansion. Like all tool steels,
hardening of 01 to insure minimum size change careful study of the die or tool
and the furnace equipment used for heat treatment.
O1 steels can be easily cold-worked in the annealed condition .
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12. The heat treatment requires O1 steels to be slowly preheated to 649°C (1200°F)
and then heated at 788-816°C (1450-1500°F). Then these steels should be held at
the same temperature for 10 to 30 minutes and finally oil quenched.
Annealing should be performed at 788°C (1450°F) followed by slow furnace cool at
a temperature less than 4°C (40°F) per hour.
Tempering of O1 steels is performed at 177-260°C (350-500°F) to realize Rockwell
C hardness of 62 to 57.
Forging of O1 steels can be performed at 1038°C (1900°F) down to 857°C (1575°F)
but not below 816°C (1550°F).
Martempering is a substitute hardening procedure which can be used along with
suitable salt bath equipment.
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13. Typical applications for O1 tool steel include medium run dies, press
tools, drawing punches, broaches, bushings,chuck jaws, paper cutting
machine knives, plug gauges, thread gauges and precision measuring
tools.
Also commonly used in applications such as cams, cloth cutting knives,
cold taps, reamers, collets, cutting hobs, strip slitting cutters, trimmer
dies, tube expander rolls, plastic moulds and woodworking knives.
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17. These are hardened by air – quenching and contain Carbon
(1.0%) with Manganese , Chromium & Molybdenum and
Tungsten.
These are characterized by wear resistance and high
hardenability , fair red hardness , good toughness &
resistance to decarburization..
Tempering temperature for these steels varies from 150-
425˚C.
Applications:
 Knives
 Blanking & Trimming dies.
 Coining dies.
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19. A2 tool steels are cold worked in the annealed condition.
 AISI A2:
A2 tool steels are forged between 1093 to 913°C (2000 to 1675°F). These tool
steels should not be forged below 899°C (1650°F).
Forming of A2 tool steels is carried out by machining or hot forging.
A2 tool steels have medium machinability.
The data below will provide an overview of A2 air-hardening, medium-
alloy, cold-work tool steels.
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20. 1.Annealing—Heating slowly and uniformly to 845~870℃, furnace cooling to
540℃ at a rate 8~15℃/h. Hardness max. HB 248
2.Stress Relieving —Heat to 650~675℃, furnace cooling.
3.Hardening—
Preheating: Heat to 790℃, holding 20 minutes per 25 mm.
Austenitizing: Heating to 925~980℃, holding 20 minutes per 25 mm.
Quenchant: By air.
4.Tempering— Heating to175~540℃, holding 30 minutes per 25 mm. Air-
cooling. Hardness HRC 63 to HRC 54
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21. A2 MicroSturcture 1000x
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24. Group A tool steels exhibit minimum distortion and the highest safety
(least tendency to crack) in hardening
chromium, and molybdenum are the principal alloying elements used to
provide this deep hardening moderate resistance to softening at elevated
temperatures.
A2, A3, A7, A8, and A9 contain a high percentage of chromium (5%), which
provides moderate resistance to softening at elevated temperatures.
Types A4, A6, and A10 are lower in chromium content (1%) and higher in
manganese content (2%). They can be hardened from temperatures about
110 °C (200 °F) lower than those required for the high-chromium types,
further reducing distortion and undesirable surface reactions during heat
treatment. 24

25. Silicon is added to type A8 To improve toughness, both silicon and nickel
are added to types A9 and A10 Because of the high carbon and silicon
contents of type A10, graphite is formed in the microstructure; as a result,
A10 has much better machinability when in the annealed condition, and
somewhat better resistance to galling and seizing when in the fully
hardened condition, than other group A tool steels.
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26. These are hardened by Oil –or – Air Hardening & contain carbon(1.4-2.3%)
& Chromium (12-14%) , with molybdenum, cobalt, Vanadium.
Vanadium prevents these steels from showing Grain coarsening (upto
1040˚C).
Chromium imparts non-deforming properties.
Tempering of these steels results in high hardness, wear & abrasion
resistance.
Tempering temperature for these steels varies from 150-375˚C.
Applications:
 Mandrel for tube rolling by Pilger rolls.
 Blanking & piercing dies, Coining dies, Drawing dies.
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29. D2 has a machinability rating of 65, as compared with a rating of 100 for a 1 pct
carbon tool steel.
Tests on this grade normally show a slight amount of contraction after hardening
with the part in the as-quenched condition or tempered below 900F. Tempering at
approximately 925F usually eliminates this contraction and brings the part
virtually back to its original size. D2 has the minimum distortion in heat-treatment
as compared with other tool steels.
D2 is a high carbon, high chromium alloy tool steel. It is a tool steel with
high dimensional stability in heat treatment. A microstructure with coarse
complex carbides provide a steel with high wear resistance and good
toughness.
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30. Use a controlled-atmospheric furnace or pack in some inert material in a sealed
container to prevent decarburization. To anneal, heat slowly to approximately
1600°F to 1650°F and hold at temperature for 1-1/2 hours for each inch of greatest
thickness. Cool slowly at a rate of 20 degrees per hour to 900°F, after which the
steel may be allowed to cool down with the furnace. Resulting hardness will be
Brinell 217 max.
Hardening should be done in neutral salt bath, fluidised bed or other controlled
atmosphere furnaces. Preheat slowly to 300-800°C then raise to 980-1020°C,
followed by air cooling. It is essential to soak at hardening temperature for 10-20
minutes. Obtainable hardness 63 – 65 HRC.
Tempering should be carried out immediately on completion of quenching. For
maximum hardness and abrasion resistance heat to 150-250°C holding at
temperature 1 hour for each 25mm of section. Tempering curve given indicates
typical values obtained from air cooling from 1010°C. Nitriding treatment for
improved retention of hardness is recommended for certain applications.
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34. High duty cutting tools (dies and punches), long run form rolls, tube mill rolls, deep
drawing tools for sheet and strip, shear blades, circular shears, thread rolling dies,
small moulds for plastic industries and pressing tools for ceramic industries.
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