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通过观察试样保温不同时间后立即快速淬火后的金相组织,测定布氏硬度及不同组织的显微硬度,研究了一种低碳低合金铸钢在970℃正火时的组织演变规律。结果表明,低碳低合金铸钢试样在970℃保温2 min淬火开始生成板条马氏体,保温2~10 min时得到铁素体、珠光体和马氏体3种组织;随保温时间延长,铁素体含量降低;保温时间大于10 min后,得到的组织均为板条马氏体。保温25 min和40 min时,试样表面硬度低于心部,初步分析认为是表面氧化脱碳和晶粒粗化所致。
The microstructure of the low carbon and low alloyed cast steel during normalizing at 970 ℃ was investigated by observing the microstructure of the quenched steel immediately after quenching at different time after the sample was kept warm and measuring the Brinell hardness and the microhardness of different tissues. The results show that the low carbon and low alloyed cast steel samples begin to form lath martensite after quenching at 970 ℃ for 2 min and get ferrite, pearlite and martensite at the temperature of 2 ~ 10 min. With the holding time Prolonged ferrite content decreased; holding time is greater than 10 min, the resulting tissue lath martensite. Insulation 25 min and 40 min, the sample surface hardness lower than the heart, the initial analysis that the surface oxide decarbonization and grain coarsening caused.