| Through the test of mechanical properties,such as impact toughness,fracture toughness,Vickers hardness and tensile properties,combined with the fractographic analysis,the insensitivity of four types Fe-Mn-C TWIP steels and 20 Mn Si V on defects were studied.The results are as follows:1)It is found that there are many shrinkage cavities and inclusions in the cast TWIP steels,the grain is coarse and uneven,and a large amount of carbides precipitate at grain boundaries,which all means the highest degree of defects;the amount of precipitates and inclusions decrease after water toughing,and thus lower the degree of defects;the grain get refined and become uniform after hot rolling,the shrinkage cavities disappeare and the inclusions decrease further in the hot-rolled TWIP steels,resulting in the lowest degree of defects.2)The impact toughness of the TWIP steel made under different defect levels is excellent.Even in the as-cast state with many defects,the impact energy can reach more than 100 J.The impact toughness fluctuation of the four TWIP steels is much smaller than that of ordinary carbon steel under different defect levels.With the increase of Mn content in TWIP steel,the fluctuation range of impact toughness decreases.3)The fracture toughness of the refined TWIP steel has been greatly improved compared with ordinary carbon steel.As the degree of defects in each experimental steel decreases,the fracture toughness increases,especially after hot rolling.At the same time,the fracture toughness gradually increased with the increase of Mn content.4)After hot rolling with different cumulative reduction ratios,all three TWIP steels show good strong plasticity,especially 30 Mn is the best.In addition,the experimental plastic steels with different cumulative reduction ratios have little difference in the measured strong plastic product after stretching.They have better performance at different defect levels,reflecting their insensitivity to defects.Figure 43;Table 14;Reference 53... |
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