Stainless Steel 440 C

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 60) and wear resistance.

General Characteristics

This alloy shows good stainless properties with maximum hardness, and is used primarily as a bearing steel. It is used in the hardened and tempered condition and may attain Rc 60 as heat treated.

Chemical Analysis

C% Mn% P% S% Si% Cr%
0.95/1.20 1.00 max 0.040 max 0.030 max 1.00 max 16.0/18.0

Mo%

0.75 max

Applications

Alloy 440C is used in bearing assemblies, ball and races – cutlery, needle valves, ball check valves, valve seats, pump parts, ball studs, bushings and wear-resistant textile components. The alloy is not good for use at elevated temperatures, but is good in normal domestic and mild industrial environments.

Forging

This steel hot works like a high speed tool steel. Preheat to 1400/1500ºF (760/815ºC) then slowly to 1900/2100ºF (1040/1150ºC.) Do not forge below 1700ºF (925ºC) and reheat as necessary. Furnace cool if possible or in warm lime or ashes. Anneal after forging, but cool to room temperature before annealing.

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 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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