C.S. Li

Simulation on temperature field of 50CrV4 automobile gear bar steel in continuous rolling by FEM

Abstract The temperature field of 50CrV4 automobile gear bar steel in continuous rolling is simulated by FEM. The temperature variations of the bar during continuous rolling are obtained. The cross-sectional temperature field for some passes has been solved simultaneously. It is clear that the surface temperature of a bar calculated by FEM accords well with the temperature found in practice. The simulated results in this paper describe the temperature pattern of rolling in great detail. Especially, this paper offers reference data for the TMCP treatment of bar steel.

Formation and control of strip scale pores in hot rolling

Abstract In order to solve the problem of strip surface pores generated by the combination of the tertiary scale on strip surface with black oxide layers produced on the roll surface, the mechanism of strip scale pores formation was analyzed using several instruments such as the SEM, the AHM-2-HL optical microscope and the Oxford ISIS EDAX energy spectrometer. A method of control is advanced to reduce strip scale pores, which is effective and clearly beneficial for enhancing the strip surface quality in practice.

FEM Analysis of Stress on Roll Surface Black Oxide Layers Exfoliation in Hot Strip Rolling

To understand the mechanism of formation and exfoliation, black oxide layers were investigated, and the effects of stress on the exfoliation were analyzed by finite element method (FEM). The roll surface on which black oxide layers form is composed mainly of Fe3O4, which is caused by the oxidation of the roll material itself. Cracks form and are easily propagated along M3C- and M7C3-type carbides, which leads to further cracking along M3C and M7C3 carbides as a result of contact stress fatigue produced by cyclic mechanical stresses that normally occur during the rolling process. Thermal fatigue of the roll surface is produced by the thermal cycles created alternately by contact with the hot strip and the cooling water on the roll. The generation and propagation of cracks in the black oxide layers during rolling is promoted by circumference compressive stress at roll surface. Under this stress, the exfoliation of the black oxide layers happens on the roll surface.

INFLUENCES OF EDGING ROLL SHAPE ON THE PLASTIC STRAIN DISTRIBUTION OF SLAB DURING MULTI-PASS V-H ROLLING PROCESS

Multi-pass slab vertical-horizontal (V-H) rolling process with variable edging roll shape have been simulated with explicit dynamic finite element method and updating geometric method. The distributions of plastic strain contour in slab during rolling process with different edging roll and under different rolling stage have been obtained. The results show that there exist two thin strain assembling zones in slab when the flat edging roll is used, and there just exist one strain assembling zone in slab when the edging roll with groove is used. And compared the deformation equality between flat edging roll and edging roll with groove, the later is better than the former, which supplies the theory prove to the slab deformation distribution during V-H rolling process and is helpful for predicting the slab texture.