Tool very high impact toughness and relatively

Tool steels are similar carbon and alloy steels with
different properties such as hardness, abrasion resistance, toughness and
resistance to softening at high temperatures. Tin steels contain carbide
forming elements such as chromium, 
molybdenum and tungsten in different combinations. They also contain
cobalt or nickel, which improves high temperature performance. They are usually heat-treated to improve the hardness and used
for stamping, forming, shearing and cutting metals and forming of plastics. .There
are six catagories of tool steel:
water-hardening, cold-work tool steels, shock-resisting, high-speed, hot-work,
and special purpose/plastic mold tools steel.

1.   
Water-hardening group

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W-group steel is actually high-carbon flat carbon
steel. This set of steel is the most used tool steel due to its low cost
compared to other steel steels.

2. Cold-work group

Cold-work group has three groups: oil-hardening, air-hardening,
and high carbon-chromium. This steels group have high hardenability and wear
resistance, with average toughness. Characteristical they are in the production
of larger parts or parts that have a minimum flection requirement when being
hardened.

2.1. Oil-hardening

A very useful oil hardening steel is O1 steel. It is a
very good cold work steel.Making very good knives and forks via oil hardening
steel.

2.2. Air-hardening

Air hardening steels are qualified by low deformation during heat treatment thanks to their high chromium content. They have good machinability so wear resistance and stiffness balance.

 

3. Shock-resisting group

Shock-resisting group has high shock resistance and good hardenability. This group
designed to resist shock at both low and high temperatures. Also
Shock-resisting group has a very high impact toughness and relatively low
abrasion resistance.

4. High speed group

T-type and M-type tool steels are used to cut tools in situations where
strength and hardness must be maintained at high temperatures.
High
speed steel is a subset of tool steel and is often used on tool tips and
cutting tools. It is usually used in electric saw blades and drill bits. It can
withstand higher temperatures without losing its hardness. This feature allows
the HSS to cut faster than the high carbon steel, so it is called high speed
steel. HSS grades have high hardness and abrasion resistance compared to carbon
and tool alloys in general.

 

5. Hot-working group

Hot working steels are a group of steels used to cut or shape the material at high temperatures. H-group tool steels were developed for strength and stiffness during prolonged exposure to high temperatures. These tool steels are low carbon and medium to high alloyed and provide good hot stiffness and toughness and fair wear resistance due to the significant amount of carbide.

6. Special purpose group /
Plastic Mold Steel
(P)Mold
steels are used to make molds for molding plastics and rubber.

(L)Low-alloy  type tool
steels are usually reserved for Machine parts – Arbors, chucks, cams, and
collets and Special applications needing dependable strength and toughness.

 

1.8.Specialty
Steels

Special steels include a wide range of ferrous alloys with special handling properties that stand out in terms of corrosion resistance, abrasion resistance and toughness, high strength or magnetic properties.

 

Maraging Steels

Maraging steels are low carbon
alloys containing high amounts of nickel (15% to 25%) and lesser proportions of
cobalt, molybdenum, and titanium. Chromium is also sometimes added for
corrosion resistance. They suitable heat treatment. Heat treatment results in
very high strength together with good toughness. Tensile strengths of 2000
MPa  and 10% elongation are not unusual.
Applications include parts for missiles, machinery, dies, and other situations
where these properties are required andjustify the high cost of the alloy.

Free-machining steels

These steels have extremely low carbon levels (0.005% C),
which result from the use of alloying elements such as niobium and titanium
that combine with C and leave the steel virtually free of interstitial atoms.
The result is excellent ductility, even greater than low-C steels. Applications
include deep-drawing operations in the automotive industry.