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本文研究了轧制工艺参数(奥氏体化温度、道次压下率及终轧温度)对低碳钢板(4C船板)轧后铁素体晶粒平均直径和脆性转化温度的影响及后二者之间的相互关系。实验结果表明:这些轧制工艺参数中终轧温度起主要作用,它决定了轧后铁素体晶粒平均直径、脆性转化温度及-40℃时的冲击韧性;在约800℃终轧,效果最好。 本文也研究了轧后快冷时间及冷却速度对低碳钢板的组织和脆性转化温度的影响。实验结果表明,延长快冷时间及加快冷却对轧后组织产生复杂影响:使魏氏组织级别增加;使伪共析珠光体量增加;使珠光体退化及细化。这样复杂的组织变化,对脆性转化温度带来复杂的影响。结果表明,快冷时间及冷却速度都有一定限度。本文对低碳钢中珠光体的退化及珠光体形态作了一些研究。根据所得到的实验结果,关于控制轧制及控制冷却对低碳钢板的组织和冷脆性的影响,得出七点结论。
In this paper, the influence of rolling process parameters (austenitizing temperature, pass reduction rate and finishing temperature) on average ferrite grain diameter and brittle transition temperature after rolling of low carbon steel plate (4C ship plate) The relationship between the two. The experimental results show that the final rolling temperature plays a major role in these rolling parameters, which determines the average ferrite grain diameter after rolling, the brittle transition temperature and the impact toughness at -40 ℃, and the final rolling at about 800 ℃. the best. This paper also studies the effect of rapid cooling time and cooling rate on microstructure and brittle transition temperature of low carbon steel. The experimental results show that prolonging the cooling time and speeding up the cooling have a complex effect on the microstructure after rolling: increasing the organization level of Pseudosteloid, increasing the amount of pseudo-eutectoid pearlite, degenerating and refining pearlite. Such complex organizational changes have a complex effect on the temperature of brittle transformation. The results show that the fast cooling time and cooling rate has a certain limit. In this paper, some studies on the degeneration of pearlite and pearlite morphology in mild steel have been done. Based on the experimental results obtained, seven conclusions are drawn concerning the effects of controlled rolling and controlled cooling on microstructure and cold embrittlement of mild steel.