【作者】 匡毅；

【导师】 袁子洲；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2005， 硕士

【摘要】 本文第一章研究了ZGMn18Cr2Mo超高锰钢的在压缩变形时的加工硬化能力;同时,研究了时效处理工艺对超高锰钢的组织及小变形轴向压缩情况下的形变硬化能力的影响。结果表明,适当的时效处理可以提高超高锰钢的形变硬化能力,硬化速率与起始硬度无关。经时效处理的超高锰钢,其真应力—真应变分段符合Hollomon方程,具有双n力学行为,小变形即可获得较高形变硬化。在小压缩变形情况下,有高密度的位错、少量层错和大量的形变孪晶形成,并有一定数量的交叉孪晶和纳米尺寸的超微细碳化物。薄膜透射电镜观察和X射线衍射结构分析未发现形变诱发马氏体存在。说明超高锰钢加工硬化是位错强化、孪晶强化、层错强化及弥散析出的超微细碳化物颗粒强化综合作用的结果。 本文第二章研究了淬火工艺(包括奥氏体化温度、保温时间及冷却速度)对KmTBCr26高铬铸铁的硬度和冲击韧性的影响;回火温度对KmTBCr26高铬铸铁的显微组织和力学性能的影响。结果表明,淬火工艺对试样硬度有显著地规律性地影响,得到最高硬度的最佳奥氏体化温度为980～1020℃,最佳保温时间与试样的原始组织有关;不同淬火工艺的试样冲击韧性数据无明确规律性。随回火温度升高,淬火后显微组织由马氏体与奥氏体的混合组织向铁素体-碳化物组织转变;回火温度对试样硬度和韧性有显著地规律性地影响,回火温度达到460℃时,此种材料综和力学性能最好。 本文第三章论述了大型耐热铸钢坩埚与ZG20SiMn钢制水泵叶轮的消失模铸造生产技术及控制要点。对于大型薄壁铸件,要选用密度较高的泡沫塑料,这样一方面可以防止变形,另一方面可以防止塌箱。适当降低涂层的透气性也有助于避免垮塌缺陷。另外,对于半封闭腔体,设置辅助抽气筒是非常必要的。对于水泵叶轮这种薄壁复杂铸件来说,消失模铸造能够充分发挥其许多独特工艺优势。合理设计浇注系统、正确更多还原

【Abstract】 The effect of ageing treatment on microstructure and strain hardening ability during the process of uniaxial small compressive deformation of Super—high manganese steel was investigated. The results showed that the strain hardening ability of super—high manganese steel could be enhanced by appropriate ageing treatment meanwhile the strain hardening ability was not relevant to initiative hardness. For the Super—high manganese steel treated by various ageing techniques , the relation between true stress and true strain accorded with Hollomon equation in sections, behaving as double n, getting excellent hardening under small compressive deformation. the microstructure of the dense dislocations, some stacking faults, the great amount of deformation twins, some intersecting twins and ultrafine carbides in a nano-scale has been observed under the condition of the uniaxial small scale compressive deformation. By thin film TEM observed and X-ray structure analysis no deformation-inducing martensite has been observed, and it is shown that the work hardening mechanism of Super-high manganese steel can be attributed to composite strengthening of dislocation , twin, stacking and precipitation of ultrafine carbides.The effects of quenching process (including austenitizing temperature, austenization holding time and quenching rate) and temper temperature on mechanical properties of KmTBCr26 high chromium cast iron have been investigated by measuring hardness and impact toughness. The results show that the quenching process has prominent well-regulated influence on the hardness of the samples, and the optimal austenitizing temperature which produce the highest hardness is 980~1020°C and the optimal austenization holding time is related to the original microstructure of samples, while the data of impact toughness of samples in various quenching process treatments is ruleless. The results also show the transformation of martensite and austenite after quenching to ferrite-carbides with temper temperature increasing, and that the temper temperature hasprominent well-regulated effect on hardness and impact toughness, the results also indicated that the synthetic mechanical properties of the material became excellent when temper temperature was 460℃.In this paper, the technique and essentials of process control of ZG20SiMn water pump impeller and heat-resistant cast steel crucible in lost foam casting were discussed, it was pointed that a lot of superiority of LFC were exerted sufficiently for water pump impeller of the thin wall and the complicated shape. The relevant casting defects were relieved or eliminated through designing the casting system in reason, selecting conectly refractory coating and molding sand and increasing the filling density of molding sand, at the same time the quality of the complex and near net shape casting in LFC was improved. For the large thin wall casting, higher density foam was adopted to prevent the deformation as well as collapse. It is helpful to prevent collapse by decreasing appropriately permeability of coating. In addition, it is very necessary to adopt the assistant abstraction barrel for semi-closed cavity.更多还原