What is Cold Work Tool Steel?  & What is Hot Work Tool Steel?

Cold Work Tool Steel
Cold work tool steel basically is high carbon steel, the alloy content contains tungsten, manganese, chromium and molybdenum relatively low alloy steel. These alloys added to improve hardenability, allowing less distortion than the W series of quenching oil. These are relatively cheap steel, high carbon content they will produce sufficient wear resistance, used for short-term operation. It is used for all types of blanking and forming dies, gauges, fixtures, etc.

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 Steel

Hot working tool steel to make iron and nonferrous metals as well as hot forming of the workpiece at high temperature of the alloy derivative. They are used in the manufacture of pressure die casting, extrusion and forging, as well as in the process of pipe and glass manufacturing.
By heat as tool steel tool not only by the use of continuous high temperature, also occurs in the heat load fluctuation in the tool is in contact with the materials to be processed.

In ASTM Steel Standard Hot Work Tool Steel include the “H” Hot Work Tool Steel Series from H. Like H10,H11, H12, H13, H14,H19,H21 H22,H23,H24,H25,H26, H42 Steel.

As the Chemical Composition different, Classified as:

Chromium Hot Work Tool 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。

Tungsten Hot Work Tool Steels

Steel Grade from H21 to H26. normal working hardness is 450-600HV.

Molybdenum Tungsten Hot Work Tool 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.

Table 1: Classification and approximate compositions of principal types of tool steels

AISI UNS Wt. %
C Cr V W Mo Co
Cr-steels
H10 T20810 0.4 3.25 0.4 – 2.5 –
H11 T20811 0.35 5 0.4 – 1.5 –
H12 T20812 0.35 5 0.4 1.5 1.5 –
H13 T20813 0.35 5 1 – 1.5 –
H14 T20814 0.4 5 – 5 – –
H19 T20819 0.4 4.25 2 4.25 – 4.25
W-steels
H21 T20821 0.35 3.5 – 9 – –
H22 T20822 0.35 2 – 11 – –
H23 T20823 0.3 12 – 12 – –
H24 T20824 0.45 3 – 15 – –
H25 T20825 0.25 4 – 15 – –
H26 T20826 0.5 4 1 18 – –
Mo-steels
H42 T20842 0.6 4 2 6 5 –
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