What Does S2 Mean on Tools' Steel Bits?
S2 alloy steel is a shock-resisting tool steel type. It retains good ductility even in hardened conditions, which allows it to perform in applications where shock impact is transmitted to the alloy. Shock-resisting tool steels like this are designated as group S steels.
Chemical Composition
The following table shows the chemical composition of S2 tool steels.
| Element | Content (%) |
|---|---|
| Iron, Fe | 97.0 |
| Silicon | 1.05 |
| Carbon, C | 0.4-0.55 |
| Molybdenum, Mo | 0.4 |
| Manganese, Mn | 0.4 |
| Vanadium, V | ≤0.5 |
| Phosphorus, P | ≤0.03 |
| Sulfur, S | ≤0.03 |
How strong is S2 alloy steel?
| Physical Properties | Metric | English | Comments |
|---|---|---|---|
| Density | 7.83g/cc | 0.283lb/in³ | |
| Mechanical Properties | Metric | English | Comments |
| Hardness, Knoop | 624 | 624 | Converted from Rockwell C Hardness. |
| Hardness, Rockwell C | 55 | 55 | |
| Hardness, Vickers | 602 | 602 | Converted from Rockwell C Hardness. |
| Tensile Strength, Ultimate | 2150MPa | 312000psi | |
| Tensile Strength, Yield | 2000MPa | 290000psi | |
| Elongation at Break | 7.0 % | 7.0 % | in 50 mm |
| Bulk Modulus | 160GPa | 23200ksi | Typical for steel |
| Shear Modulus | 80.0GPa | 11600ksi | Typical for steel |
| Thermal Properties | Metric | English | Comments |
| CTE, linear | 10.9µm/m-°C @Temperature 20.0 - 100 °C | 6.06µin/in-°F @Temperature 68.0 - 212 °F | |
| 13.0µm/m-°C @Temperature 0.000 - 300 °C | 7.22µin/in-°F @Temperature 32.0 - 572 °F | ||
| 14.1µm/m-°C @Temperature 0.000 - 500 °C | 7.83µin/in-°F @Temperature 32.0 - 932 °F | ||
| Processing Properties | Metric | English | Comments |
| Processing Temperature | 175- 425°C | 347- 797°F | Tempering Temperature |
| 845- 900°C | 1550- 1650°F | Hardening Temperature | |
| Annealing Temperature | 760- 790°C | 1400- 1450°F | |
| Component Elements Properties | Metric | English | Comments |
| Carbon, C | 0.40 - 0.55 % | 0.40 - 0.55 % | |
| Iron, Fe | 97 % | 97 % | As Balance |
| Manganese, Mn | 0.40 % | 0.40 % | |
| Molybdenum, Mo | 0.40 % | 0.40 % | |
| Phosphorus, P | <= 0.030 % | <= 0.030 % | |
| Silicon, Si | 1.05 % | 1.05 % | |
| Sulfur, S | <= 0.030 % | <= 0.030 % | |
| Vanadium, V | <= 0.50 % | <= 0.50 % |
Physical Properties
The physical properties of S2 tool steels are given in the following table.
| Properties | Metric | Imperial |
|---|---|---|
Density | 7.79 g/cc | 0.281 lb/in3 |
Melting point | 1421°C | 2590°F |
Mechanical Properties
The mechanical properties of S2 tool steels are tabulated below.
Properties | Conditions | ||
T (°C) | Treatment | ||
Poisson's ratio | 0.27-0.30 | 25 | - |
Elastic modulus | 190-210 GPa | 25 | - |
Thermal Properties
The following table shows the thermal properties of S2 tool steels.
Properties | Conditions | ||
T (°C) | Treatment | ||
Thermal expansion | 10.9 x 10-6/ºC | 20-100 | - |
Other Designations
Other designations that are equivalent to S2 tool steels include:
ASTM A681
FED QQ-T-570
SAE J437
SAE J438
UNS T41902
Fabrication and Heat Treatment
Machinability
The machinability rating of S2 tool steels is 85% of that of the W group steels.
Forming
S2 tool steels are formed using conventional procedures under annealed conditions.
Welding
S2 tool steels are readily weldable using standard methods.
Heat Treatment
S2 tool steels are slowly preheated to 649ºC (1200ºF) and then directly heated by increasing the temperature to 871ºC (1600ºF). This is followed by holding the steels for 10 to 20 mins and quenching in brine or water.
Forging
Forging is carried out in S2 tool steels at temperatures ranging from 899 to 1093ºC (1650 to 2000ºF). Forging below 871ºC (1600ºF) is not preferred.
Cold Working
S2 tool steels can be cold-worked under annealed conditions.
Annealing
Annealing is performed on S2 tool steels at 788ºC (1450ºF) followed by cooling in the furnace at a rate of not more than 4ºC per hour.
Tempering
S2 tool steels are tempered at 177 to 427ºC (350 to 800ºF) to obtain Rockwell C hardness of 60 to 50.
Related Issues
How strong is S2 alloy steel? Applications for shock-resisting steels include springs, as well as chisels, dies for forging, and punches. S2 steel is also used to make Ball bearings for the mining industry. They are also used for screwdrivers and driver bits.
What is S2 tool steel used for?
【DURABLE S2 Material】: The bit socket head is made of S2 alloy steel, which is strong and has good toughness, not easy to break. It is the best material for making a bit set.
Is S2 steel hardened?
AISI Type S2 is a water-hardening tool steel with extreme toughness and resistance to shock loading. Even at a hardness of Rockwell C 59-60, it will bend before it breaks.
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