Study On Hot Ductility And Static Recrystallization Behavior Of8%Cr Roller Steel

In order to inhibit the deflection, breakage and peeling of roller steels which usuallyserve at high compressive conditions, high strength, excellent wear resistance andhardenability are required. The improvement of Cr-content in roll steels has become oneof the main development direction for the reason that the effective increase ofhardenability and the significant promotion of wear and corrosion resistance can beachieved by Cr alloying.During the heat processing, it is prone to appear mixed crystals and surface crackingdue to high deformation resistance resulting from high content of alloying element in8%Cr roll steel. According to the research of thermal plasticity and static recrystallization,the optimal forging process can be determined and the grain size satisfying the heattreatment requirements can be controlled. In this paper, thermoplastic and staticrecrystallization behavior of8%Cr roller steel under different deformation conditionswere studied by hot tensile and compression experiment, the main research results are asfollows:The peak stress of the steel decreased with the increase of deformation temperatureand the decrease of strain rate. Elongation under the condition of high strain rate is betterthan that of the low strain rate condition, and the highest elongation can be obtained at1050℃when the strain rate is0.1s-1and at1100℃when the strain rate is1s-1.The reduction of area of8%Cr roller steel increased and then decreased with theincrease of deformation temperature. When the strain rate is0.1s-1, the highest reductionof area can be obtained at1050℃, while it would be obtained at1050~1150℃whenthe strain rate is1s-1.The analysis of hot tensile fracture morphology of8%Cr roller steel under theconditions of different deformation temperature and strain rate showed that the fracturemechanism transforms from intergranular brittle fracture to dimple fracture, and thenumber of dimple on fracture increases and the toughness improves with the increase ofstrain rate. The dynamic recrystallization is conducive to prevent the nucleation andextension of cracks which first nucleate in grain boundary and then extend along the grainboundary during the hot deformation process.The analysis of static recrystallization microstructure of8%Cr roller steel in the temperature range of900~1100℃and strain rate of0.01~1s-1manifested that the rate ofstatic recrystallization was improved with the increase of temperature, strain rate anddeformation. The activation energy is246.2kJ/mol and n is0.38.