Tools Steels

Deependra Kumar Singh

Assistant Professor
Metallurgical and Materials Engineering
Introduction
• Tool steels are high quality steels made by controlled
chemical composition, and processed to develop
properties useful for working and shaping of other
materials
• The carbon content in them is between 0.1-1.6%
• Tool steels also contain alloying elements like,
chromium, molybdenum and vanadium
• Their suitability comes from their
distinctive hardness, resistance to abrasion and
deformation, and their ability to hold a cutting edge
at elevated temperatures
• Tool steel offers better durability, strength, corrosion
resistance and temperature stability, as compared
to the construction & engineering steel 2
Classification of Tool Steels
Oil-hardened
COLD-WORKED
TOOL STEELS Air-hardened

High Carbon, High Chromium

SHOCK-RESISTING
TOOL STEELS
Chromium-based
HOT-WORKED
Tungsten-based
TOOL STEELS
Molybdenum-based
WATER-HARDENED
TOOL STEELS

Tungsten-based
HIGH-SPEED
TOOL STEELS Molybdenum-based
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Cold-Worked Tool Steels
• These steels are used for making tools for cold work
applications, when the tool surface temperature does
not rise more than 200 °C
• These are characterized by high abrasion & wear
resistance, higher toughness and high impact
resistance
• These steels are also called “non-distorting steels”, as
they show little change in dimension during heat
treatment
• These are divided into 3 groups:
➢ Oil hardening Steels [GRADE ‘O’]
➢ Air hardening Steels [GRADE ‘A’]
➢ High Carbon, High Chromium Steels [GRADE
‘D’]
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Cold-Worked Tool Steels
• Oil Hardening Steels
➢ Hardened by oil-quenching & contain high carbon with
manganese, chromium & molybdenum
➢ Characterized by high machinability, wear resistance & non-
distorting properties
• Air Hardening Steels
➢ Hardened by air-quenching and contain carbon (1.0%) with
manganese, chromium & molybdenum & tungsten
➢ Characterized by high wear resistance & high hardenability,
fair red hardness, good toughness & resistance to
decarburization
• High Carbon, High Chromium Steels
➢ 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 form showing Grain
coarsening (upto 1040°C). Chromium imparts non-deforming
properties. Tempering of these steels results in high
hardness, wear & abrasion resistance
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Shock-Resisting Steels
• Shock-resisting steels are designed to have high
impact resistance (toughness), along with other
properties such as strength, hardness
• Are also known as S-grade steel
• Silicon (0.1 to 2.5%) is a common addition to this
class of steels, as it provides tempering resistance
and increases toughness
• Applications for shock-resisting steels includes
springs, as well as chisels, dies for forging, and
punches
• These steels are also used to make ball bearings for
the mining industry
• They are also used for screwdrivers and driver bits
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Shock-Resisting Steels
• Carbon content = 0.5-0.6%. Alloying elements – Cr,
W, Mo, Si
• These are characterized by good toughness,
hardness and improved hardenability
• These steels are generally oil-hardened
• “Low temperature tempering” is carried out where
toughness and hardness of the tool steel are of
prime importance, otherwise “high temperature
tempering” is preferred
• Silicon-manganese steels (0.55% C, 2.0% Si, 1.0 %
Mn) are included in this group. Due to their high Si-
content, decarburization and grain coarsening takes
place in these type of steels
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General Heat Treatment Procedure
• Annealing: Slow & uniform heating in the range of
790-800 °C followed by furnace cooling at rate of 8-
15 °C/hour
• Stress relieving: Heat to 650-675 °C and furnace
cooling
• Hardening: Preheating – warming to about 650 °C &
holding for 20 minutes
• Austenitizing: heating to 900-950 °C & holding
again for 20minutes
• Tempering: Heating to 205-650 °C, holding for 30
minutes and then, air cooling

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Some Common Types
• S1 (Tungsten Alloyed)
➢ Contains tungsten for enhanced hardness and wear resistance
➢ Common in heavy-duty applications where both shock and
wear are important
• S2 (Chromium-Vanadium Alloyed)
➢ Often used for tools subjected to high impacts
➢ Has good toughness and ductility but lower wear resistance
than S1
• S5 (Silicon-Molybdenum Alloyed)
➢ Known for excellent toughness and shock resistance
➢ Commonly used for shear blades and chisels
• S7 (Silicon-Molybdenum Alloyed)
➢ One of the most widely used shock-resistant tool steels
➢ Offers high impact strength, toughness, and moderate wear
resistance, making it suitable for punches and dies
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Applications
• Chisels
• Pneumatic chisels
• Punches
• Shear blades
• Scarring Tools
• River sets
• Driver bits

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Hot-Worked Tool Steels
• Hot-worked tool steels, often categorized as H-grade
tool steels, are designed to perform well at elevated
temperatures while maintaining their strength,
hardness, and wear resistance
• These steels are primarily used for tools that shape
or cut materials at high temperatures, such as dies
for forging, extrusion, and die-casting

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Hot-Worked Tool Steels
The key characteristics of hot-worked tool steels include:
• High toughness to resist cracking or chipping under
thermal stress
• Good thermal conductivity to dissipate heat
effectively
• Resistance to softening at elevated temperatures,
allowing them to maintain hardness and strength
• Resistance to thermal fatigue and wear, ensuring
durability during prolonged exposure to heat

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Hot-Worked Tool Steels
• Carbon content = 0.3-0.5% . These steels are used
for high temperature metal forming operation (except
cutting), where the temperature is around 200-800°C.
• These are characterized by high yield strength, high
red hardness, wear resistance, toughness, erosion
resistance, resistance to softening at elevated
temperatures, good thermal conductivity
• These are divided into 3 groups depending on the
principle alloying elements:
➢ Chromium based [H11- H19]
➢ Tungsten based [H20- H26]
➢ Molybdenum based [H41- H43]

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Applications of Hot-Worked Tool Steels
• Die-casting dies for metals such as aluminum,
magnesium, and zinc
• Forging dies that shape metal at high temperatures
• Extrusion dies for hot extrusion processes
• Hot shear blades used to cut heated metals
• Plastic injection molds that deal with high
temperatures during the molding process.

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Common Types
• H10 (Chromium-Molybdenum Steel)
➢ Offers excellent toughness and resistance to
cracking under thermal cycling
➢ Commonly used in forging dies and die-casting tools
• H11 (Chromium-Molybdenum-Vanadium Steel)
➢ Known for its balance between toughness, wear
resistance, and ability to withstand high
temperatures
➢ Often used for dies in aluminum die-casting and
extrusion operations
• H12 (Chromium-Molybdenum-Vanadium Steel)
➢ Offers better wear resistance but slightly less
toughness than H11
➢ Suitable for hot forging and die-casting applications 15
Common Types
• H13 (Chromium-Molybdenum-Vanadium Steel)
➢ The most commonly used hot-work tool steel, with a
good balance of toughness, hardness, and heat
resistance
➢ It is widely used in aluminum, zinc, and magnesium
die-casting, as well as extrusion dies and forging
tools
• H19 (Tungsten-Based Tool Steel)
➢ Contains tungsten to enhance its ability to retain
hardness at high temperatures
➢ Used in specialized applications where heat
resistance is critical, such as in high-speed forging
dies

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Water-Hardened Tool Steels
• These steels contain carbon in the range of 0.9-1.0%
along with Cr, V, Mo
• These are characterized by high tensile strength &
hardness levels but low ductility & toughness values
• In order to improve machinability, these steels are
given “Spheroidizing annealing treatment”
• Presence of Cr improves both hardness & hardenability
and Vanadium checks the tendency of grain
coarsening.
• Tempering temperatures are in the range 170-220°C

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Applications
• Heavy forging hammers, hand hammers
• Forging dies, bending dies, cutting dies
• Large blanking tools, boring tools
• Chisels, scissors, knife blades
• Milling cutters, lathe centre
• Watch maker’s tools
• Engraving tools

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High Speed Tool Steels
• These are high alloyed tool steels developed initially to
do high speed metal cutting. Now, they used in a wide
variety of machining operation
• These are characterized by high hardness (60-65 HRC
at 600-650°C), high red hardness, wear resistance,
reasonable toughness and good hardenability
• They contain 0.6 % carbon, 4% Chromium, 5-12%
Cobalt
• Carbon imparts hardness of at-least 60 HRC of
martensite formed. Chromium increase hardenability &
corrosion resistance. Cobalt increases the thermal
conductivity, melting point, red hardness & wear
resistance of high-speed steels

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High Speed Tool Steels
• These are divided into two groups depending upon the
principal alloying elements & the composition:
➢ Molybdenum High speed steel [GRADE ‘M’]
(contains molybdenum, tungsten, chromium, vanadium
& sometimes cobalt)
➢ Tungsten High Speed steels [GRADE ‘T’]
(contain high amount of tungsten with chromium,
vanadium and some cobalt)

• Applications:
➢ End mills, drills, lathe tools, planar tools
➢ Punches, reamers
➢ Routers, taps, saws
➢ Broaches, chasers, and hobs
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Heat Treatment - High Speed Tool Steels

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Thank You!