Chemical Composition
The following table shows the chemical composition of S1 tool steels.
| Element | Content (%) |
|---|---|
| C | 0.40-0.55 |
| Mn | 0.10-0.40 |
| Si | 0.15-1.20 |
| Cr | 1.00-1.80 |
| Ni | 0.3 |
| Mo | 0.5 |
| V | 0.15-0.30 |
| Cu | 0.25 |
| P | 0.03 |
| S | 0.03 |
| W | 1.50-3.00 |
Physical Properties
The physical properties of S1 tool steels are given in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Density (@20°C/68°F) | 7.89 g/cc | 0.285 lb/in3 |
Mechanical Properties
The mechanical properties of S1 tool steels are tabulated below.
| Properties | Metric | Imperial |
|---|---|---|
| Hardness, Rockwell C (air cooled from 899°C, 30 mins) | 54.5 | 54.5 |
| Hardness, Rockwell C (air cooled from 927°C, 30 mins) | 56 | 56 |
| Hardness, Rockwell C (air cooled from 982°C, 30 mins) | 56.5 | 56.5 |
| Modulus of elasticity | 207 GPa | 30000 ksi |
| Charpy impact (V-notch; oil quenched from 954°C; 149°C temper temperature) | 10.8 J | 8.00 ft-lb |
| Charpy impact (V-notch; oil quenched from 954°C; 625°C temper temperature) | 29.8 J | 22.0 ft-lb |
| Machinability (1% carbon steel) | 70.0 – 75.0% | 70.0 – 75.0% |
| Poisson’s ratio | 0.27-0.30 | 0.27-0.30 |
Thermal Properties
The following table shows the thermal properties of S1 tool steels.
| Properties | Conditions | ||
|---|---|---|---|
| T (°C) | Treatment | ||
| Thermal expansion | 12.4 x 10-6/ºC | 20-100 | – |
Fabrication and Heat Treatment
Forging
S1 tool steels are uniformly preheated at 1000°C (1832°F). These steels are then forged at temperatures ranging from 800 to 1000°C (1472 to 1832°F). This process is followed by cooling in a furnace to avoid stress.
Annealing
Annealing is carried out in S1 tool steels by uniformly heating the steels to 770°C (1418°F) followed by equalization. These steels are then cooled in the furnace.
Stress Relieving
S1 tools steels are heated up to 700°C (1292°F) before hardening, equalized, and then slowly cooled in order to remove stresses during heavy machining operations.
Hardening
S1 tools steels are preheated to 650°C (1202°F) and soaked. They are then continuously heated to the final temperature that ranges from 900 to 950°C (1652 to 1742°F). Finally, the steels are quenched in oil.
Martempering
Martempering is performed in the case of S1 tool steels as an alternative procedure for hardening. This is carried out in a salt bath equipment.
Tempering
S1 tool steels are tempered by uniformly heating the steels at the preferred tempering temperature followed by holding for an hour.
