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By certification 
BS4659 BS1is a high duty shock resisting alloy tool steel. In the hardened conditionS1 heat resisting toolsteelcombines great hardness with good toughness and shock resisting properties.Â
| Â | C. | Si. | Mn. | Cr. | V. | W |
| Min.% | 0.45 | 0.25 | 0.2 | 1.25 | 0.15 | 1.00 |
| Max.% | 0.55 | 0.45 | 0.4 | 1.75 | 0.30 | 3.00 |
Forging:
Heat slowly and uniformly to 1000°C. Forge within a range of 1000/800°C, reheating if necessary. Cool slowly (preferably in a furnace) to avoid setting up stresses.
Annealing:
Heat uniformly to 770°C, equalise, then furnace cool.
Stress Relieving:
If machining operations have been heavy or if the tool has an unbalanced section, remove stresses before hardening by heating up to 700°C, equalise, then cool slowly.
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Hardening:
Pre heat the S1 tool steel to 650°C and thoroughly soak. Continue heating to the final hardening temperature of 900/950°C. Allow sufficient time for the component to be heated through. Quench in oil.
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Martempering:
Martempering is an alternative hardening procedure which may be used when suitable salt bath equipment is available.
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Tempering:
Heat uniformly and thoroughly at the selected tempering temperature and hold for at least one hour per inch of total thickness.
