Stainless Steel 440 A

General Characteristics

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.

Principal Design Features

This is a high carbon martensitic stainless with moderate corrosion resistance good strength and the ability to obtain and keep excellent hardness (Rc 56) and wear resistance.

Chemical Analysis

C% Mn% P% S% Si% Cr%
0.60/0.75 1.00 max 0.040 max 0.030 max 1.00 max 16.0/18.0

Mo% 0.75 max

Applications

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

Forging

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.

Harden:

preheat to 1400/1500ºF (760/815ºC) – then to 1850/1950ºF (1010/1065ºC) – soak and quench in warm oil or air cool. For better carbide solution, heat to 2000ºF (1090ºC.)

Temper:

This alloy will attain Rc 60. To remove peak stresses and retain maximum hardness temper at least 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 not commonly welded due to its tendency to air harden, 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.

Hot Working

Pre-heat to 1400 F (760 C), then bring slowly up to 1900-2200 F (1038-1204 C) before proceeding. Do not work this material below 1700 F (927 C). Cool material slowly after working and once at room temperature, anneal fully.****Pre-heat to 1400 F (760 C), t

Cold Working

This alloy is considered only slightly cold workable by common practices.

Hardening

Bring the material slowly up to 1400 F (760 C), then on to a soak temperature of 1850 F (1010 C), air or oil cool. Density: 0.28 Specific Gravity: 7.7 Specific Heat: 0.11 Electrical Resistivity: 360 Melting Point: 2700 MoETensile: 29

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