Characteristics and application of 420 stainless steel

420 stainless steel is a hardenable stainless steel with better applicability, which has higher strength, hardness and wear resistance than 410 stainless steel.

When forging 420 stainless steel, the material should be preheated to 760-815°C first, and then heated to 1100-1205°C and forged. Ideal forgings should be cooled in a furnace at 845°C, but not in warm dry lime or ash. Air cooling after forging may cause cracking of the material. The forging temperature of this material cannot be lower than 900°C.
During heat treatment and annealing, in order to achieve maximum softness, it should be heated to 840-900°C and slowly cooled in a furnace to obtain an approximate hardness of 179 BHN.
If used as an intermediate or process anneal, the material should be heated to 730-790°C, then furnace or air cooled, and an approximate hardness of 196 BHN can be obtained.
During hardening, the material should be heated to 1010-1065°C and quenched in warm oil.
For maximum hardness and corrosion resistance, tempering should be performed between 150-205°C followed by air cooling. This will yield a hardness of approximately Rc 52. To ensure maximum corrosion resistance, the grade should not be tempered at temperatures exceeding 430°C.
In terms of machinability, 420 stainless steel is somewhat similar to high carbon tool steel because of its higher carbon content. If machinability is paramount, easier machining will be gained from free machining of 420 stainless steel, but may compromise other properties.
In terms of weldability, this material is rarely welded. Satisfactory welds can be obtained by preheating to 150-205°C, followed by annealing at 730-790°C and air cooling for 6-8 hours. If weldability is important, 420 filler rods should be used.