The Hardness Analysis of the Martensitic Stainless Steels after Hardening with Variations of Carbon Equivalent and Cooling

Abstract

Stainless steels are some types of Austenitic, Ferritic and Martensitic. Martensitic types are several types and are one which can be hardened by hardening process, so it can be used for cutting tool or components that require high hardness and corrosion resistance.The purpose of this study was to obtain information about the hardness of martensitic stainless steel type after hardening with variations of carbon equivalent and cooling.The experimental method used was hardening by heating the material up to 1100 ^oC temperature, held for 30 minutes, then cooled rapidly/quenching to water, oil and air, then heated to 400 ^oC, cooled slowly, the materials before and after heat treatment were tested the hardness of Rockwell C method.The results showed all types of martensitic stainless steels have hardness increased significantly after hardening process ie from about 20 HRC to about 44.7 – 48.9 HRC, based on the carbon equivalent the difference in hardness value was not significant i.e type 410, Ceq = 1.537% (46.9-48.5) HRC, type 420, Ceq = 1.717% (44.5-48.9) HRC, and type 431, Ceq = 2.025% (46.9-47.4) HRC, based on variations of cooling water and oil there is no significant difference, but for air tend to be low ie type 410 (water = 48.5 HRC, oil = 48.8 HRC, air 46.9 HRC), type 420 (water = 48.9 HRC, oil = 47.2 HRC , air = 44.5 HRC) and type 431 (water = 47.4 HRC, oil = 47.7 HRC, air = 46.9 HRC), hardness after tempering down ranges from about 3-7 HRC on all types of martensitic stainless steels .

Keywords: Hardness, Stainless Steel, Hardening, Cooling .