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《热加工工艺》2016,(15)
为了改善球墨铸铁的低温冲击性能,研究了不同镍含量对铸态球墨铸铁组织性能的影响和镍含量为0.6%退火态球墨铸铁的组织和低温冲击性能。结果表明:不同镍含量下球墨铸铁铸态显微组织均为铁素体+石墨球+少量珠光体组成,随着镍含量在0.0%~0.6%之间的增加,铁素体晶粒逐渐细小,石墨球亦逐渐细小圆整,且数量增多,镍含量为0.8%时,石墨球化率和均匀性下降。随着镍含量的增加,珠光体的含量增加,球墨铸铁的硬度和抗拉强度逐渐提高,屈服强度先升高后下降,而伸长率却总体呈下降趋势。镍含量为0.6%的球墨铸铁经760℃加热,零保温,随即以5℃/min冷却速度降温到620℃后出炉空冷后,得到了铁素体+石墨球组织,冲击试样在-60℃下仍然属于韧性断裂,冲击功仍高达13.2 J,能够满足工程机械零部件在较低温下工作冲击韧性的需求。 相似文献
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研究了Sb和热处理工艺对厚大断面球墨铸铁组织和性能的影响。试验结果表明,适量的稀土元素可以降低Sb的反球化作用,改善石墨形态,增加石墨球数量。Sb和热处理可促进珠光体的生成,提高强度。通过这种常规的方法,使70 mm厚的附铸试块的性能达到了QT900-2的要求,500 mm×500 mm×700 mm厚的试块硬度达到HB310以上,硬度偏差小于HB20。 相似文献
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研究了Sb对厚大断面球墨铸铁组织和力学性能的影响,详细阐述了该试验采用的炉料、化学成分、球化处理、孕育处理以及热处理等试验方法。试验结果表明:(1)合理的RE加入量可以中和Sb的反球化作用,改善石墨形态,增加石墨球数量;(2)Sb强烈细化珠光体,但是含量太高会导致碳化物的生成;(3)采用940℃(3 h)+460℃(4 h)的热处理工艺,合金含量为w(Cu)1.0%、w(Sn)0.15%和w(Sb)0.025%时,70 mm厚的附铸试块性能可以达到QT800-2的要求。 相似文献
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介绍了覆砂铁型铸造工艺的优点;通过采用含Sb的专用球化剂、覆砂铁型铸造工艺,试制了铸态高强度、高伸长率球铁曲轴.结果表明:曲轴本体金相组织为球化等级2级、石墨大小6级、珠光体体积分数达到85%~95%,本体抗拉强度870~940 MPa、伸长率4.4%-6.0%,完全达到客户要求. 相似文献
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AbstractThe effect of up to 0.15% phosphorus on the microstructure and mechanical properties of step-block castings made from compacted- graphite iron has been examined. There was no major effect on the microstructure, but two minor effects were observed. First, the higher-phosphorus irons showed a small increase in the amount of carbides and pearlite within the microstructure, but there was no effect on the depth of surface chill. Second, at low magnesium contents the higher-phosphorus irons demonstrated a marked increase in the amount of flake graphite. Phosphorus had no adverse effect on tensile strength, and a reported lowering of tensile elongation at elevated phosphorus content was not found in this work. There was, however, a decrease in Charpy impact toughness at higher phosphorus levels. 相似文献
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To improve the mechanical properties of heavy section ductile cast iron, bismuth (Bi) was introduced into the iron. Five castings with different Bi content from 0 to 0.014 wt.% were prepared; and four positions in the casting from the edge to the center, with different solidification cooling rates, were chosen for microstructure observation and mechanical properties test. The effect of the Bi content on the graphite morphology and mechanical properties of heavy section ductile cast iron were investigated. Results show that the tensile strength, elongation and impact toughness at different positions in the five castings decrease with a decrease in cooling rate. With an increase in Bi content, the graphite morphology and the mechanical properties at the same position are improved, and the improvement of mechanical properties is obvious when the Bi content is no higher than 0.011wt.%. But when the Bi content is further increased to 0.014wt.%, the improvement of mechanical properties is not obvious due to the increase of chunky graphite number and the aggregation of chunky graphite. With an increase in Bi content, the tensile fracture mechanism is changed from brittle to mixture ductile-brittle fracture. 相似文献
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ER7车轮钢经不同工艺热处理后,可获得珠光体片层间距以及铁素体含量不同的显微组织,并对不同工艺处理试样的拉伸性能及-20 ℃冲击性能进行了测试。结果表明,随冷却速度的增大,车轮钢铁素体含量增加,珠光体片间距和珠光体球团尺寸减小。增大冷却速率,会使车轮钢的屈服强度、抗拉强度、伸长率和断面收缩率都随之增加。随着珠光体片间距和晶粒尺寸减小,车轮钢的断裂韧性也相应增大。在850 ℃加热并通过水雾冷却后的车轮钢试样强韧匹配最好,综合力学性能最好。 相似文献
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