Available Shapes
709M40 Alloy Steel
709M40 is a 1% Cr-Mo medium hardenability general purpose high tensile steel. It is generally supplied in the Hardened and Tempered condition in the tensile range of 850 – 1000Mpa (T Condition) but can be heat treated to 700 – 1200Mpa dependent on section size (R – W Condition). This alloy is used in most industry sectors for a wide variety of applications. Typical uses include Drive shafts, couplings, bolts and gears, together with many surface and sub-surface components in the oil and gas industries. This grade also has reasonably good impact properties at low temperatures and can be good for some elevated temperature uses. 709M40 can be further surface hardened by either flame or induction hardening methods, giving case hardnesses in excess of 50 HRc.
Applications
Analysis
Forging
Annealing
Hardening
Tampering
Typical Mechanical Properties*
Applications
Axels shafts, crankshafts, connecting rods, gears, high tensile bolts and studs, propeller shafts joints, rifle barrels and breech mechanisms for small arms parts, induction hardened trackpins.
Analysis
Carbon | 0.36-0.44% | Chromium | 0.90-1.50% |
Manganese | 0.70-1.00% | Molybdenum | 0.25-0.35% |
Silicon | 0.10-0.35% | Sulphur | 0.040% max |
Phosphorous | 0.035% max |
Forging
Preheat the steel carefully, then raise temperature to 850-1200°C for forging. Do not forge below 850°C. After forging 709M40, cool slowly in still air.
Annealing
Heat the steel slowly to 680-700°C. Cool in air.
Hardening
709M40 is commonly supplied ready heat treated at ‘T’ condition. If further heat treatment is required annealed 709M40 should be heated slowly to 860-890°C and after adequate soaking at this temperature quench in oil. Temper as soon as tools reach room temperature.
Tampering
Heat the component carefully to a suitable temperature selected by reference to a tempering chart or table, soak at the temperature for two hours per 25mm of ruling section, then allow to cool in air. Tempering between 250-375°C is not advised as tempering within this range will seriously reduce the impact value.
Typical Mechanical Properties*
Heat the component carefully to a suitable temperature selected by reference to a tempering chart or table, soak at the temperature for two hours per 25mm of ruling section, then allow to cool in air. Tempering between 250-375°C is not advised as tempering within this range will seriously reduce the impact value.