The Study Of Bake-hardening Property And Fatigue Property For Hot-rolled Low Carbon Steel

Advanced steels are no doubt the basis for automobiles to be of high performance, light weight and safety. Under the condition that both keeping automotive safety performance and moderately reducing vehicle weight, how to achieve the purpose of high performance, energy conservation and environmental protection, naturally becomes the goal that all people pursuits. The developed hot-rolled bake-hardening steel in this paper can satisfy the above-mentioned requirements, so it is significant for the development of automobile steel.The paper had studied experimental steel, which smelted in the laboratory. The hot rolling experiment was carried on laboratory rolling mill, the microstructure of steel was observed, the mechanical properties and baking hardening properties of the test steel was determinated, and the bake hardening mechanism was analyzed. The main studied contents and results are as follows:1. Through fatigue tests on the MST810, measuring mechanical properties and bake-hardening of the test steel under the different steel rolling technology, measuring the values of BHT, BH, n, r.2. Observating the typical organization of the experimental steel by optical microscopy (OM) and scanning electron microscopy (SEM), such as ferrite organization, ferrite and slice layer pearlite organization, ferrite and degradation pearlite organization, ferrite and bainite organization. Studying the relationship between the microstructure and BH value, it is found that in the ferrite and degradation pearlite organization, the degradation pearlite organization is good for improving the value BHT and BH.3. Studying the bake hardenability mechanism of experimental steel by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), it is found that bake hardening is composited by Cottrell atmosphere, dislocation strengthening, precipitation strengthening, etc.4. Measuring the S-N curve of experimental steel E14 before and after baking, analyzing the fatigue properties, determining the fatigue limit. After baking the fatigue limit of experimental steel E14 slightly increased.