Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Processing Properties
Other Designations
Introduction
Hot work tool steels are known as Group H steels. These are divided into three sub-groups such as molybdenum hot-work steels, tungsten hot-work steels, and chromium hot-work steels. Molybdenum is a carbide former and a silvery white metal, which can be alloyed with other elements. It has good weldability and secondary hardening characteristics. It promotes formation of fine grain and increases temper brittleness. The molybdenum hot-work steels include types H42 and H43.
The H42 steels are considered as a principal alloy of the molybdenum hot-work steel category. The composition of the molybdenum hot-work steels is similar to that of molybdenum high-speed steels. Applications and characteristics of the molybdenum hot-work steels are similar to that of tungsten hot-work steels.
Chemical Composition
The following table shows the chemical composition of H42 tools steels.
| Element | Content (%) |
|---|---|
| C | 0.55-0.70 |
| Mn | 0.15-0.40 |
| Cr | 3.75-4.50 |
| Ni | 0.3 |
| Mo | 4.50-5.50 |
| W | 5.50-6.75 |
| V | 1.75-2.20 |
| Cu | 0.25 |
| P | 0.03 |
| S | 0.03 |
Physical Properties
The physical properties of H42 tool steels are outlined in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Density | 8.15 g/cc | 0.294 lb/in3 |
Mechanical Properties
The mechanical properties of H42 steels are tabulated below.
| Properties | Metric | Imperial |
|---|---|---|
| Hardness, Rockwell C | 50.0 – 60.0 | 50.0 – 60.0 |
| Poisson’s ratio (25°C) | 0.27-0.30 | 0.27-0.30 |
| Elastic modulus | 190-210 GPa | 27557-30458 ksi |
Thermal Properties
The table below shows the thermal properties of H42 tool steels.
| Properties | Conditions | ||
|---|---|---|---|
| T (°C) | Treatment | ||
| Thermal expansion | 11.9 x 10-6/ºC | 20-540 | – |
Processing Properties
The following table provides the processing properties of H42 tool steels.
| Properties | Metric | Imperial |
|---|---|---|
| Processing temperature (tempering) | 565 – 650°C | 1050 – 1200°F |
| Processing temperature (tempering) | 1120 – 1220°C | 2050 – 2230°F |
| Annealing temperature (hardening) | 845 – 900°C | 1550 – 1650°F |
Other Designations
Other designations that are equivalent to H42 tool steels include:
- ASTM A681
- UNS T20842
- FED QQ-T-570
