摘要:
采用光学显微镜、拉伸试验机和低温冲击韧性试验机研究了热处理工艺对80 kg水电站用钢组织性能的影响,分析了试验钢在不同淬火温度和回火温度下微观组织的变化规律,讨论了试验钢在不同热处理状态下力学性能变化规律。结果表明:试验钢在较低温度下淬火得到粒状贝氏体组织,随着淬火温度的提高,逐渐转变为板条贝氏体组织。试验钢淬火后采用不同温度高温回火,淬火时形成的位错出现合并、重组并消失,淬火内应力得到释放,随着回火温度的升高,板条状组织出现了合并长大,铁素体数量增加,逐渐向多边形铁素体转变。同时,屈服强度呈现先升高后降低的现象,在630℃达到最大值;抗拉强度则是单边下降,当回火温度达到650℃时,抗拉强度出现了不合格现象,延伸率和-40℃低温冲击韧性值在回火阶段显著提高,综合对比认为较好的淬火温度可以选择900~930℃,回火温度可以选择600~630℃。
关键词:
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水电钢 /
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调质 /
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板条贝氏体 /
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碳化物
Abstract:
The influence of heat treatment process on the microstructure and properties of 80 kg hydropower station steel was studied by optical microscope,tensile testing machine and low-temperature impact toughness testing machine.The microstructure changes of steel at different quenching and tempering temperature were analyzed.The mechanical properties changes of test steel under different heat treatment conditions wer also discussed.The results show that test steels under the low temperature quenching produces granular bainite and under high temperature quenching forms lath bainite.The dislocations formed during quenching merge and recombine and disappear,and the stress in quenching is released when the test steel is tempered at different tempering temperatures.With the increase of tempering temperature,the lamellar structure appeared merging and growing,and the ferrite volume fraction increased,and gradually transformed into polygonal ferrite.The yield strength firstly increases and then decreases and reaching its maximum value at 630 ℃ tempering temperature.Tensile strength decreases unilaterally and fails to meet requirement when the tempering temperature reaches 650 ℃.The percentage elongation and-40 ℃ low temperature impact toughness increases significantly at tempering stage.Thus quenching temperature has been proposed at 900～930 ℃ and tempering temperature at 600～630 ℃ for the best performance.
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