Correlation of microstructure and surface roughness of disc drums fabricated by hot forging of an AISI 430F stainless steel

Abstract

The surface roughness of disc drums fabricated by hot forging of an AISI 430F stainless steel was investigated. Emphasis was placed on the role of microstructural changes, which depend on postforging annealing conditions. In the forged drum specimens, MnS inclusions were heavily elongated, and a large amount of martensite was found. Three different annealing conditions were used on the forged drum specimens to completely or partially decompose martensite. The surface roughness tests were conducted on these specimens, and then the test data were compared via hardness and microstructures. The top plane of disc drums. where MnS inclusions were elongated perpendicular to the machined surface, showed a good surface toughness because of the free-machining effect of MnS. However, the side plane, where MnS inclusions were aligned parallel to the machined surface, showed an increased surface roughness due to reduction of the MnS effect. These findings suggested that a proper amount of martensite formed during forging and annealing would be beneficial for cost efficiency, as well as machinability of the 430F stainless steel products.