431 Steel

431 with the added chromium and nickel alloys gives this stainless steel its better toughness as well as a better corrosion resistance compared to straight up chromium stainless steels. This makes this steel grade ideal for operations like deep drawing, compressor parts and construction. This steel grade is also often used in processing chemically aggressive plastics, like PVC for instance.

Corrosion resistance

431 stainless steel has excellent resistance in a variety of corrosive media. The condition of the surface plays an important role for this steel grade, the better the finish e.g. polished, the better the corrosion resistance compared to rougher finishes. Intergranular corrosion is a high possibility due to the formation of chromium carbides, which lead to chromium depleted sections.

Heat resistance

Stainless steel 431 should not be used at temperatures above the standard tempering temperature, due to the loss of mechanical properties. With occasional operations at 1697°F (925°C) and continuous operations at a temperature of 1598°F (870°C) this steel grade is resistant to scaling.

Annealing

Heat parts to a temperature range of 1256-1472°F (680-800°C) and hold, then cool slowly and controlled in the furnace.

Hardening

Heat uniformly to a temperature of 1742-1922°F (950-1050°C) followed by cooling the material in oil or air. This steel grade tends to harden by cooling in air.

Tempering

Heat the work piece uniformly to a temperature of 1112-1202°F (600-650°C) and hold for a minimum of 1 hour and then cool in air.

For our tempering diagram, please click here.

Hot working

Heat the work piece to 2100-2200°F (1149-1204°C), then cool smaller work pieces in air and larger ones in dry lime or ashes. When the work piece has reached an ambient temperature, it should be annealed. Hot working at a temperature below 1650°F (900°C) should be avoided.

Cold working

In its annealed condition, 431 can be die cut, molded and cold headed.

Quenched 431 may be poorly magnetizable. With increased cold working, the magnetizability increases.

Machinability

In its annealed condition 431 is to some extend easily machined. In its hardened condition, above 277 BHN (30HRC), it is more difficult to machine.

Forging

Carefully and slowly heat the work piece to a temperature of about 1562°F (850°C) and then rapidly increase heat to a temperature of 2102-2156°F (1150-1180°C). The forging temperature is 2156-1742°F (1180-950°C) followed by a slow cooling in the furnace, dry ash or other materials which support a slow cooling.

Welding

Preheat the parts to about 212-572°F (100-300°C), welding temperature under 392°F (200°C) should be avoided. After welding is finished and the work piece has reached an ambient temperature, heat for a post-weld heat treatment to 1202°F (650°C). Without the additional post-weld heat treatment, the mechanical properties in the heat affected areas and in the weld seam may be very different to those in the base metal. To prevent contamination, welding with gas containing hydrogen or nitrogen should be avoided as it effects the mechanical properties negatively. In order to ensure the best possible corrosion resistance in the weld, tempering colors have to be removed either mechanically or chemically.