Available Shapes
AISI 4340 Alloy Steel
4340 is a 1.8% nickel – chromium – molybdenum high hardenability high tensile steel – generally supplied hardened and tempered in the tensile range of 930 – 1080 Mpa (condition U) – (Rc 28 – 36).. Characterized by high strength and toughness in relatively large sections. Prehardened and tempered 4340 can be further surface hardened by flame or induction hardening and by nitriding.
Applications
Analysis
Forging
Annealing
Stress Relieving
Hardening
Hardening
Applications
Heavy Duty Shafts, Gears, Axles, Spindles, Couplings, Pins etc
Analysis
Carbon | 0.38-0.43% | Chromium | 0.70-0.90% |
Manganese | 0.60-0.80% | Molybdenum | 0.20-0.30% |
Silicon | 0.15-0.35% | Nickel | 1.65-2.00% |
Phosphorous | 0.025% max | Sulphur | 0.025% max |
Forging
Preheat the steel carefully, then raise the temperature to 1150-1210°C for forging. Do not forge below 850°C. It has good forging characteristics but care must be taken when cooling as the steel shows susceptibility to cracking. Cooling in ash or lime after forging is recommended.
Annealing
Heat the steel slowly to 800-860°C and allow enough time for the steel to be thoroughly heated. Cool slowly in the furnace.
Stress Relieving
When components are heavily machined, ground or otherwise subject to cold work, stress relieving will be beneficial prior to hardening.
Hardening
4340 steel is usually supplied ready heat treated. If further heat treatment is required annealed 4340 should be heated slowly to 830-865°C and after adequate soaking at this temperature quench in oil. Temper as soon as the steel reaches room temperature.
Hardening
Heat the steel carefully to a suitable temperature selected by reference to a tempering chart or table, soak at the temperature for 2 hours per 25mm of section, then allow to cool in air.