Tool steels comprise carbide-forming elements such as chromium, vanadium, molybdenum and tungsten in different combinations. They also contain cobalt or nickel which improves their high-temperature performance. They are generally heat-treated to improve the hardness and used for stamping, forming, shearing and cutting metals and forming of plastics. They are classified according to their composition and properties into various categories.
Cold work tool steels
It is used for all types of blanking and forming dies, gauges, fixtures, etc.
2. Medium-alloy cold-work steels
3. High-carbon, high-chromium cold-work steels
4. Oil-hardening cold-work steels
In ASTM Steel standard Cold Work Tool Steel main include the “W” (Water Hardening), “O”(Oil Hardening), “A” (Medium Alloy Air Hardening), “D” (High Carbon, High Chromium) Tool Steel Series. Typical Steel Grade like: W1, W2, W5 tool Steel; O1, O2, O6, O7 Oil Steel; A2, A4, A6,A7,A8, A9,A10, A11 Cold work Steel; D2,D3, D4,D5,D7 Steel; etc.
Hot work tool steels
They are used in the manufacture of pressure die casting, extrusion and forging, as well as in the process of pipe and glass manufacturing.
1. Chromium hot-work steels – Steel Grade Number From H10 to H19. their carbon composition about 0.34-0.40, Normal Working Hardness 400~600 HV. Normal Working Temperature Below: 540°C。
2. Tungsten hot-work steels – Steel Grade from H21 to H26. normal working hardness is 450-600HV.
3. Molybdenum hot-work steels – Steel Grade Number from H41 to H43. These are low carbon, High Molybdenum , Tungsten series High Speed Tool Steel. Its usage is similar with Tungsten Series High Speed Tool Steel.
High-speed tool steels
3. Intermediate high-speed steels
M2 is a high speed steel in tungsten-molybdenum series. It is usually used to manufacture a variety of tools, such as drill bits, taps and reamers.
M35 is similar to M2, but with 5% cobalt added. The addition of cobalt increases heat resistance.
M42 is a molybdenum-chromium-vanadium-tungsten high speed steel alloy with an additional 8% cobalt. It is widely used in metal manufacturing because of its superior red-hardness as compared to more conventional high speed steels, allowing for shorter cycle times in production environments due to higher cutting speeds or from the increase in time between tool changes. M42 is also less prone to chipping when used for interrupted cuts and cost less when compared to the same tool made of carbide. Tools made from cobalt-bearing high speed steels can often be identified by the letters HSS-Co.
To increase the life of high speed steel, tools are sometimes coated. One such coating is TiN (titanium nitride). Most coatings generally increase a tool’s hardness and/or lubricity. A coating allows the cutting edge of a tool to cleanly pass through the material without having the material gall (stick) to it. The coating also helps to decrease the temperature associated with the cutting process and increase the life of the tool.
Other high speed tool steel
Tungsten high-speed steels T1 – T15
Intermediate high-speed steels M50, M52
Other tool steels
1. Water-hardening tool steels
2. Shock-resistant tool steels
3. Low-carbon tool steels
4. Low-alloy special purpose tool steels.
Shock-resisting steels S1 – S7
Low-alloy special-purpose tool steels L2 – L6
Low-carbon mold steels P2 – P21