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利用温压缩实验,在Gleeble-3500热力模拟试验机上测定了中碳钢马氏体(M)和铁素体+珠光体(F+P)两种组织的流变曲线。对比研究了应变速率对这两种组织流变行为的影响。结果表明:在相同温度下,M组织的应变速率敏感性指数(mM)和加工软化率(sM)都大于F+P组织的相应参数(mF+P)和(sF+P)。应变速率为0.001 s-1,变形温度为600℃、650℃、700℃,M组织的流变曲线均低于F+P组织的流变曲线;当应变速率从0.01 s-1增加到10 s-1,M组织和F+P组织的流变曲线相交,交点应变为临界应变,大于临界应变,M组织的流变应力低于F+P。这表明,对降低钢材温轧或零件温挤压的变形应力和成本来说,M组织可能比F+P更好。此外,对导致M组织上述流变行为的机理进行了初步探讨。
The rheological curves of martensite (M) and ferrite + pearlite (F + P) in medium carbon steel were measured on a Gleeble-3500 thermal simulator using a warm compression test. The effect of strain rate on the rheological behavior of these two microstructures was compared. The results showed that the strain rate sensitivity index (mM) and processing softening rate (sM) of M tissue were all higher than those of F + P (mF + P) and (sF + P) at the same temperature. The rheological curves of M tissue at strain rate of 0.001 s-1, deformation temperature of 600 ℃, 650 ℃, 700 ℃ are lower than that of F + P microstructure. When the strain rate increases from 0.01 s-1 to 10 s -1, M and F + P, the critical point of strain is larger than the critical strain, and the flow stress of M is lower than that of F + P. This shows that the M-structure may be better than F + P for reducing the deformation stress and cost of warm rolling of steel or warm extrusion of the part. In addition, the mechanism that led to the above rheological behavior of M organizations was discussed.