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研究了缓慢冷却速度和缓慢冷却终止温度对C-Mn-Cr系冷轧双相钢的显微组织和力学性能的影响。结果表明,随缓慢冷却速度的增加,试验钢的强度增加,伸长率则减小,屈强比变化不大,均在0.46左右。在不同缓慢冷却速度下,试验钢的显微组织均由铁素体和马氏体组成,随着缓慢冷却速度的增加,晶粒尺寸逐渐减小,马氏体体积分数明显增多。铁素体中存在非连续的碳化物沉淀相,能谱分析表明,该沉淀相为(Fe,Cr,Mn)3C,并且在较慢的缓慢冷却速度下,这种非连续的碳化物沉淀相数量少、尺寸大。缓慢冷却终止温度从590℃增加到680℃,试验钢的强度略有降低,而缓慢冷却终止温度超过700℃后,强度迅速降低,伸长率呈上升趋势,屈强比基本不变。在低缓慢冷却终止温度下,试验钢的显微组织由铁素体和马氏体组成,并且马氏体中存在微细孪晶,而在高缓慢冷却终止温度下的马氏体则为板条状。
The effects of slow cooling rate and slow cooling stop temperature on the microstructure and mechanical properties of C-Mn-Cr cold-rolled duplex steel were investigated. The results show that with the slow cooling rate increases, the strength of the test steel increases, the elongation decreases, and the yield ratio changes little, both at about 0.46. At different slow cooling rates, the microstructure of the test steel consists of ferrite and martensite. With the slow cooling rate increasing, the grain size decreases and the volume fraction of martensite increases obviously. The presence of a discontinuous carbide precipitation phase in the ferrite and energy spectrum analysis revealed that the precipitated phase was (Fe, Cr, Mn) 3C and that at a slower slow cooling rate this discontinuous carbide precipitation phase A small number of large size. When the slow cooling stop temperature increased from 590 ℃ to 680 ℃, the strength of the test steel decreased slightly. However, when the temperature was slowly cooled down to 700 ℃, the strength decreased rapidly, the elongation increased and the yield ratio remained almost unchanged. At the slow cooling stop temperature, the microstructure of the test steel consists of ferrite and martensite and fine twins exist in the martensite, whereas the martensite at the high and slow cooling end temperature is the slab shape.