SV30轴承钢奥氏体化时第二相的溶解及淬火相变特性

利用DIL805A型相变仪对SV30轴承钢进行了990~1 070℃保温10min和1 030℃保温0~100min的淬火处理,研究了淬火前后试验钢的显微组织、硬度和残余奥氏体含量,分析了第二相溶解行为和淬火相变特性。结果表明:当淬火温度由990℃升高到1 070℃时,钢中的M23C6型碳化物溶解速率变快,但M_2N型氮化物在1 050℃或以上温度时才能大量溶解;当在1 070℃保温10min时碳化物能够完全溶入奥氏体中,但仍有质量分数约为6.3%氮化物未溶入;在1 010~1 030℃保温10~30min淬火后,试验钢的硬度达到58HRC以上,在1 030~1 070℃淬火后,试验钢中含有体积分数为30%~50%的残余奥氏体。

Nb对锆合金LOCA淬火相变及力学性能影响的分子动力学研究

失水事故(loss of coolant accident, LOCA)下锆合金中原β-Zr层的力学性能对核安全具有重大意义,Nb作为锆合金中重要的合金元素对其有重要影响。运用分子动力学方法研究了Zr-x Nb(x=0, 0.5, 1, 2.5,质量分数,%)合金在淬火过程中的相变行为和淬火后的拉伸行为,分析了Nb对其力学性能的作用机制。结果表明,Nb淬火相变模拟过程产生了类似原β-Zr组织的层片状多晶,这种层片状多晶主要由fcc和hcp结构原子组成;多晶的bcc→fcc相变路径遵从Brain位相关系,bcc→hcp相变路径遵从P-S位相关系;在降温过程中,添加的Nb会通过增大锆合金hcp与bcc结构的自由能之差来增加β→α的相变阻力,从而稳定锆合金的β相;Zr、Zr-0.5Nb和Zr-1Nb合金模型中Nb促进了晶界处bcc相的生成,使得变形集中于晶界,导致晶界易发生断裂;而Zr-2.5Nb中,晶粒内部的Nb含量较高,易形成bcc相,从而协调变形,提高其塑性;此外Zr-2.5Nb中团簇呈弥散分布,这使得其整体强度得到提高。

20钢奥氏体逆相变淬火

采用正交回归设计实验方法,分析了20钢一次淬火温度和二次淬火温度对奥氏体逆相变淬火后硬度的影响,建立了硬度回归方程。结果表明,随二次淬火温度的升高,硬度逐渐降低:20钢奥氏体逆相变淬火后的硬度最大可达49 HRC。

T8钢奥氏体逆相变淬火

采用正交回归设计实验方法,分析了T8钢二次淬火温度和二次淬火保温时间对奥氏体逆相变淬火后硬度的影响,建立了硬度回归方程。结果表明,随二次淬火温度的升高,硬度逐渐升高。在820℃和850℃时,随二次淬火保温时间的延长,其硬度增加;而在880℃时,随二次淬火保温时间延长,其硬度却逐渐降低。与常规淬火硬度相比,T8钢奥氏体逆相变淬火后硬度提高6HRC,硬度最大可达68HRC。

3Cr2W8V模具钢表面激光相变淬火的显微组织及耐磨性能研究

采用高功率CO2激光束对3Cr2W8V模具钢表面进行相变淬火，研究了相变强化层的显微组织与耐磨性能。结果表明：激光表面强化处理后的显微组织由品粒细小的码氏体和残余奥氏体组成，显微硬度比处理前提高了1．5倍，耐磨性能提高了1倍，同时变形小，可用于模具的表面处理。

激光相变硬化在CrMo铸铁汽车模具中的应用

利用不同的激光工艺参数对CrMo铸铁汽车模具表面进行了激光相变硬化试验,探讨了激光工艺参数对激光相变硬化层的深度、显微硬度的分布及组织结构变化的影响。结果表明,适当的工艺参数可使试样的表面硬度得到不同程度地提高,同时可以消除表面裂纹,显著提高汽车模具的使用寿命。

汽车模具材料表面强化中的激光相变硬化技术的研究与应用

使用不同的激光工艺参数对汽车模具CrMo铸铁、Cr12两种材料表面进行激光相变硬化试验,研究了激光硬化层沿横向和深度方向显微硬度的分布情况以及硬化层的组织结构的变化。结果表明,材料经激光强化处理,表面硬度可大幅提高,同时可以消除表面裂纹,从而有效地提高汽车模具的使用寿命。

CrMo铸铁汽车模具材料的激光表面处理

利用不同的激光工艺参数对汽车模具CrMo铸铁材料表面进行激光相变硬化试验,探讨了激光工艺参数对激光相变硬化层深度的影响,研究了横向和沿深度方向显微硬度的分布情况以及硬化层的组织结构的变化。研究表明,采取适当的工艺措施,表面硬度在不同程度上都得到了提高,同时可以消除表面裂纹,从而成倍的提高了汽车模具的使用寿命。

Phase change materials as quenching media for heat treatment of 42CrMo4 steels

In the present work,paraffin phase change material is used as quenchant for the heat treatment of 42CrMo4 alloy and compared with water,air,and CuO doped paraffin.The samples were prepared based on ASTM E 8M-98 standard for tensile test and then heated up to 830°C,kept for 4 h in an electric resistance furnace and then quenched in the mentioned media.Elastic modulus,yield strength,ultimate tensile strength,elongation,and modulus of toughness were determined according to the obtained stress?strain curves.Moreover,the hardness and microstructural evolution were investigated after the heat treatment at different media.The samples quenched in paraffin and CuO-doped paraffin are higher in ultimate tensile strength(1439 and 1306 MPa,respectively)than those quenched in water(1190 MPa)and air(1010 MPa).The highest hardness,with a value of HV 552,belonged to the sample quenched in CuO-doped paraffin.The microstructural studies revealed that the non-tempered steel had a ferrite/pearlite microstructure,while by quenching in water,paraffin and CuO-doped paraffin,ferrite/martensite microstructures were achieved.It is also observed that using the air as quenchant resulted in a three-phase bainite/martensite/ferrite microstructure.

船用汽轮机末级叶片抗蚀技术试验研究

通过 4种抗蚀方法的热态冲蚀试验 ,获得了一种符合船用汽轮机末级叶片特殊要求的极具前景的表面抗蚀方法 。

Numerical analysis of 3D spot continual induction hardening on curved surface of AISI 1045 steel

In order to investigate and predict the material properties of curved surface AISI 1045 steel component during spot continual induction hardening(SCIH),a 3D model for curved surface workpieces which coupled electromagnetic,temperature and phase transformation fields was built by finite element software ANSYS.A small size inductor and magnetizer were used in this model,which can move along the top surface of workpiece flexibly.The effect of inductor moving velocity and workpiece radius on temperature field was analyzed and the heating delay phenomenon was found through comparing the simulated results.The temperature field results indicate that the heating delay phenomenon is more obvious under high inductor moving velocity condition.This trend becomes more obvious if the workpiece radius becomes larger.The predictions of microstructure and micro-hardness distribution were also carried out via this model.The predicted results show that the inductor moving velocity is the dominated factor for the distribution of 100% martensite region and phase transformation region.The influencing factor of workpiece radius on 100% martensite region and phase transformation region distribution is obvious under relatively high inductor moving velocity but inconspicuous under relatively low inductor moving velocity.

固溶温度对17Cr-1Ni-3Mn-0.12N经济型不锈钢组织及力学性能影响

针对一种新成分体系17Cr经济型不锈钢,通过室温拉伸试验、显微组织观察、X射线衍射等手段,研究了不同固溶温度对17Cr不锈钢显微组织和力学性能的影响,遴选出最佳的热处理温度区间,同时明确了固溶温度对该类型不锈钢奥氏体稳定性的影响。结果表明,17Cr不锈钢在900~1000℃固溶处理会发生上下屈服,1200℃固溶处理不发生相变诱导塑性(TRIP)效应,其最佳的固溶处理温度区间为1050~1150℃。不同固溶温度处理后试验钢均呈现铁素体、奥氏体和马氏体三相并存的组织;随着固溶温度升高,淬火马氏体相变发生率先降后增,奥氏体的热力学稳定性先升高后下降,同时TRIP效应减弱、抗拉强度降低、断后伸长率提高,奥氏体力学稳定性升高。分析拉伸试样断口可知,试样由马氏体处起裂呈解理断裂,而铁素体在断裂过程中阻碍了裂纹扩展。本研究为经济型双相不锈钢成分及显微组织设计提供了新的思路和理论基础。

Austenite/martensite structure and corresponding ultrahigh strength and high ductility of steels processed by Q&P techniques

The microstructure of steels treated by Q&P(quenching and partitioning) process was characterized,a method of controlling retained austenite fraction based on inhomogeneous martensitic transformation was proposed,and the mechanical properties of steels treated by Q&P process were measured.The results show that the microstructure of the studied steels is mainly composed of initial martensite,fresh martensite and retained austenite.The initial marteniste formed at the first quenching step is easily etched;the fresh martensite formed at the final quenching step looks like 'blocky' type phase,and the retained austenite is mainly located on the packet boundary and initial austenite grain boundary.The inhomogeneous microstructure causes the experimental optimum quenching temperature corresponding to maximum retained austenite fraction to be higher than the calculation based on CPE(constrained paraequilibrium) model.The product of tensile strength and total tensile elongation is 47.5 GPa%,and tensile strength of 1760 MPa was obtained for the steel with carbon content of 0.51 wt%.The TRIP(transformation induced plasticity) effects of the large fractioned metastable austenite make a main contribution to the high ductility improvement,and the martensitic matrix provides high strength.