Phase composition of 30 CrMnSi tempered steel

Abstract

Influence of heat treatment on the phase-structural condition of 30 CrMnSi steel was investigated. It was found that the main morphological component of the steel is the α-phase which consists of a mixture of lath (0.7) and platе tempered martensite (0.3). One half of the lath martensite is grained substructure. There is no grain substructure in the platе martensite. Residual austenite in the lath and plate low-temperature martensiteis located on boundaries of martensite crystals in the form of long thin interlayers. The volume ratio of residual austenite equals to~3 %. The biggest part of the γ-phase is located in the platе martensite, and the smallest part is located in the grained substructure lath component of the martensite. The average scalar dislocations density in the material equals to ρ = 7·1010 cm-2, at that, the biggest part of dislocations is located in the form of dislocation charges (excess dislocations density ρ ± = 6.3·1010 cm-2). The carbide phase is represented by М6С-type primary carbides. Carbide particles have a spherical shape, the average particle diameter equals to 0.5 µm, the volume ratio is ~1%. Cementite and secondary special carbides are not found. Carbons may be found in the γ-solid solution (0.005wt.-%); the γ-solid solution is the second place of carbons localization (0.015wt.-%); in particles of carbide phases (0.14wt.-%). Apparently, almost half of the carbon is accumulated on defects of the crystalline lattice.