Martensitic stainless steel AISI 431
Grade 431 stainless steels are martensitic, heat-treatable grades with excellent corrosion resistance,
torque strength, high toughness and tensile properties.
All these properties make them ideal for bolt and shaft applications.
These steels, however, cannot be cold-worked owing to their high yield strength, hence they are suitable for
operations such as spinning, deep drawing, bending or cold heading.
Fabrication of martensitic steels is generally carried out using techniques that allow hardening and tempering
treatments and poor weldability.
The corrosion resistance properties of grade 431 steels are lower than that of austenitic grades.
The operations of grade 431 are limited by their loss of strength at high temperatures, due to over-tempering,
and loss of ductility at negative temperatures.
Chemical composition ( by weight % )
Full anneal — Full annealing cannot be performed on grade 431 steels.
This grade gets hardened even during slow cooling.
Process anneal — Grade 431 steels are heated to 620 to 660°c and then air-cooled.
Grade 431 steels are generally hardened by heating at temperatures from 980 to 1065°c, holding for nearly ½ h,
followed by oil or air quenching. Complex or hardened parts of grade 431 steels can be pre-heated to temperatures from
760 to 790°c and tempered, to improve their mechanical properties. Tempering of these steels at 425 to 600°c should
be avoided, owing to the loss of impact toughness at this temperature range.
Typical applications of grade 431 stainless steels include the following:
* Pump and propeller shafts
* bolts and nues
* beater parts
* marine systems
* laboratory equipments
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