Stainless Steel 440 A

General Characteristics of Stainless Steel 440 A

Type 440A is a martensitic stainless steel that may be heat treated to Rc56 and shows good toughness when heat treated. It has moderate corrosion resistance as annealed so is suitable for mild environments. It is not recommended for elevated temperatures.

Applications of Stainless Steel 440 A

This grade of stainless steel finds applications as forged pivot pins, dental and surgical instruments, cutlery and valve parts etc.

Forging Stainless Steel 440 A

This steel hot works like a high-speed tool steel. Preheat to 1400/1500ºF (760/815ºC) then slowly to 1900/2200ºF (1040/1205ºC.) Do not forge below 1700ºF (925ºC) and reheat as necessary. Furnace cool if possible, or cool in warm lime or ashes. Anneal after forging.

Great care must be taken with this alloy to avoid cracking.

Heat Treatment

Annealing

For maximum softness heat uniformly to 1550/1600ºF (840/870ºC) and soak, then cool very slowly in furnace.

For an intermediate or process anneal, heat uniformly to 1350/1400ºF (730/760ºC) and furnace or air cool.

Hardening

Preheat to 1400/1500ºF (760/815ºC) – then heat to 1850/1950ºF (1010/1065ºC) – soak and quench in warm oil, or air cool.

Tempering

To remove peak stresses and retain maximum hardness, Rc 56/57, temper one hour at 300/350ºF (150/175ºC.)

Machinability

For best machinability a dead-soft annealed condition is optimum, together with the use of carbide or ceramic tools and chip curlers and breakers.

Weldability

This alloy is seldom welded, but if it were great care would be needed with pre and post heating and actual heat input. A typical welding process involves a preheat, to be maintained at 500ºF (260ºC), then welding followed by a six hour anneal at 1350/1400ºF (730/760ºC) – with a slow furnace cool to below 500ºF (260ºC) between welding and annealing.

 

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