CONSTITUTE EQUATIONS OF 40Cr STEEL UNDER SUPERPLASTIC COMPRESSIVE DEFORMATION

The microstructure of 40Cr steel sample and its surface is ultra-fined through salt-bath cyclic quenching and high frequency hardening, then the superplasticity is studied under isothermal superplastic compressive deformation condition. The experimental results indicate that the stress-strain curves are shown to take place obvious superplastic flow characteristic at the temperature of 750-770℃ and at the initial strain rate of (1.7-5.0)×10-4 s-1. Its strain rate sensitivity is 0.30-0.38, the steady superplastic flow stress is 60-70MPa, the superplastic flow activation energy is 198-217kJ/mol, and it is close to α-Fe grain boundary self-diffusion activation energy. The super-plastic compressive constitute equations of this steel are correspondingly set up. Due to the finer microstructure of high frequency hardening, it appears bigger strain rate sensitivity value, smaller the steady superplastic flow stress and the superplastic flow activation energy, so it has better superplastic deformation capability.

Vacuum brazing of TiAl to 40Cr steel with Ti-Zr-Cu-Ni-Sn amorphous foils

Vacuum brazing of TiAl alloy to 40Cr steel was carried out in a vacuum furnace using Ti40 Zr10 CU34. 95 Ni11. 2Sn3.85 , Ti51Zr8.7 Cu24. 5 Ni11.8 Sn4 and pure copper foils, and the mierostructure and microhardness of the resultant joints were investigated. The experimental results reveal that FeTi compounds formed in the brazing seam made with pure copper foil. However, the FeTi compounds were not detected when using Ti-Zr-Cu-Ni-Sn foils and the brazing seams were composed of two layers, one layer mixed Ti（ Ni, Cu）Al and Ti-Al compounds, and the other mixed the filler metal matrix with Ti-Sn and Ti （Ni, Cu ） compounds. The microhardness test results show that the brazing seams have higher microhardness values than the TiAl alloy and 40Cr steel base metals. Moreover, the microhardness in the brazing seam. made with Ti51 Zr8 7 Cu24 5N i11.8Sn4 is higher than those made with Ti 40 Zr , o Cu34. 95 Ni l12 Sn3 a5 and pure copper.

FEM simulation on residual stress distribution during diffusion bonding between Ti （ C, N） metallic ceramic/interlayer/40Cr steel

Based on ANSYS FEM software, the distribution of residual stress in the diffusion bonding joints between Ti（ C,N） metallic ceramic/interlayer/4OCr steel was calculated and experimentally ver^ed. The results showed that the trend on the distribution of residual stress field in the joints was not changed with the use of interlayer. The maximum residual stress was always located in metallic ceramic with area ranging from 1 mm to 4 mm to the interlayer. The maximum residual stress in the joints was also affected by diffusion temperature. The satellite pulse current during the initial stage on diffusion bonding can promote the formation of liquid film at the interface, by which diffusion temperature and loading pressure can be greatly decreased. The crack initiation was easily produced at the corner of Ti （ C, N） metallic ceramic close to the interlayer. If a higher residual stress produced in the joints, the crack was propagated into the whole ceramic.

BEHAVIOUR OF BUFFER LAYER IN JOINING OF SIALON CERAMICS TO STEEL 40Cr

The buffer layer material itself may be influential to the bond strength between active brazing filler and ceramics.For Ag_(57)Cu_(38)Ti_5 filler metal,Cu or Ta is excellent buffer layer material, but Kovar or Ni-15Cr-15Co is worse.It was important to design a layer of soft buffer,such as Cu,to relax interfacial stress rather than hard buffer layer,such as Mo,to avoid stress. There is an optimum thickness range of soft buffer layer,saying h/L=0.02—0.1. It was a good solution to the interfacial stress problem to use soft/hard buffer layer to increase metal/ceramics joint strength.Finally,an idea of designing gradual materials as buffer layer between metal and ceramics was suggested.

SUPERPLASTICITY OF A WATER-QUENCHED AND TEMPERED 40Cr STEEL

The superplastic deformation characteristics, of commercial 40Cr (i.e., 5140) steel that was water-quenched only 1 times and subsequent high-temperature tempered, were investigated. The results showed that the 40Cr steel has a fine grain of 10-15μm at room temperature, and exhibits a tensile elongation of 304%, a true flow stress of 89.3MPa and a strain rate sensitivity m-value of 0.227 at the initial strain rate of 1.0×10-3s-1and at the temperature of 750°C. The final fracture is caused by the development of neck. The experimental result of elongation is in good agreement with the theoretically predicated value according to the analytical expression (where ef, m, f, nv and ε is respectively elongation, average strain rate sensitivity, initial geometric defect, average strain hardening sensitivity at constant deformation velocity and average true strain). The fracture surface is intergraular, and superplastic deformation induces an equiaxed and grown grain. Decreasing strain rate increases tensile elongation and strain rate sensitivity m-value. The primary superplastic deformation mechanism is thought to be atom-diffusion-controlled grain boundary sliding.

Effect of interlayer on the mechanical properties of YG8 hard carbide/40Cr steel brazed joints

The effects of Cu foil and Ni foil on the mechanical properties of YG8 hard carbide/4OCr steel brazed joints were investigated. The results show that both Cu foil and Ni foil were beneficial to decrease the residual stress and enhance the joint strength. Moreover, Ni foil exhibited the better impact on enhancing the joint strength relative to Cu foil. When Cu foil was used as interlayer material, the key factor to restrain the joint strength was the massive and quick dissolution of Cu. Therefore, in order to prevent the excessive dissolution of Cu foil, the process parameter should be controlled strictly in the brazing process.

Vacuum Brazing of TiAl Based Alloy with 40Cr Steel

The vacuum brazing of TiAl based alloy with 40Cr steel was investigated using Ag-Cu-Ti filler metal. The experimental results show that the Ag, Cu, Ti atoms in the filler metal and the base metal inter-diffuse toward each other during brazing and react at the interface to form an inter-metallic AlCu 2Ti compound which joins two parts to produce a brazing joint with higher strength.

40Cr钢高效深磨磨削力试验研究

通过对40Cr钢在高效深磨条件下磨削力的试验研究,分析了不同工况对磨削力变化的影响,提出了40Cr钢高效深磨工艺参数的优化方案。试验结果表明:40Cr钢在高效深磨条件下,磨削力随磨削深度的变化呈波浪式起伏的非线性关系,随砂轮线速度的提高而明显减小,同时能获得比普通磨削大得多的比材料磨除率,以及较好的工件表面质量。

球铁、45钢及40Cr基体镀铁工艺最佳活化规范的研究

在其他条件一定的情况下 ,采用二次旋转正交组合试验设计方法 ,以活化电流密度、活化时间为因素开展试验 ,探索球墨铸铁、45钢及 40 Cr最佳活化规范。通过研究分析了活化电流密度及活化时间对结合强度的影响规律 ,指出 3种材质最佳活化规范差异 ,并在金相。

40Cr钢紧固螺钉整体淬火介质的应用

研究了 40 Cr钢聚乙烯醇水溶液整体淬火的新工艺。试验结果表明 :该工艺可使仅用喷射状态下的表面淬火介质聚乙烯醇水溶液的使用范围进一步扩大到整体淬火中 。

40Cr钢的钻削力仿真与实验研究

通过单因素试验,研究了在40Cr钢的钻削加工过程中,不同切削参数对钻削力和扭矩的影响.通过大型金属塑性成形有限元软件Deform-3D对钻削过程进行仿真研究,并将仿真结果和实验结果作了对比.结果表明,在进给量不变的情况下,随着切削速度的增加,钻头所受轴向力和扭矩先变大后减小;在相同的切削速度条件下,随着进给量的不断增大,轴向力和扭矩几乎线性增大;钻削力和扭矩的仿真结果比实验结果略小,说明仿真结果具备比较高的可靠性,可以对实验结果起到近似的预测作用.

40Cr合金结构钢热轧圆钢生产实践

为开发高品质40Cr热轧圆钢,对首钢长钢公司的40 Cr合金结构钢热轧圆钢生产工艺进行详细介绍,确定了冶炼、精炼和连铸浇注等关键参数,优化了轧制温度和冷却工艺控制。通过产品质量分析及应用实践证明,40 Cr热轧圆钢的拉拔和顶锻性能良好,可满足用户加工使用要求。

40Cr钢空心阴极辅助离子渗氮

利用空心阴极辅助离子渗氮技术,在低压（100-150Pa）、中低温（400-550℃）条件下对40Cr钢进行离子渗氮处理。试验结果表明在500℃×6h的条件下离子渗氮,可在40Cr钢表面形成高硬度、化合物层约为2μm、厚度约为200μm的渗层,表层硬度比基体硬度提高两倍。

Research into Grinding Hardening of Microalloyed Non-quenched and Tempered Steel

Grinding hardening is a new technology of hardening steel piece surfaces with grinding heat generated in the grinding process instead of with a high or medium frequency induction heating method,which can effectively integrate grinding and surface hardening. Experimental studies were carried out on grinding hardening of non-quenched and tempered steel. Through grinding experiments with variable depths of cut and feeding rate,the variation in the depth of the hardening layer was studied and the microstructure of the hardening zone of the test pieces was subsequently ana-lyzed. In the end,the hardening effect of non-quenched and tempered steel was compared with that of 40Cr steel,which revealed the superiority of non-quenched and tempered steel in grinding hardening technology.

40拖拉机驱动轴结构及热处理工艺优化

通过对40拖拉机驱动轴疲劳断裂断口形貌进行分类分析,结果表明,结构设计和热处理工艺不合理是驱动轴断裂的主要原因,并提出了相应的改进措施,解决了生产企业产品质量问题。

Influence of yttrium on laser surface alloying organization of 40Cr steel

In order to improve the performance of the metal rollers, Mo＋Y2O3 alloy powders were used to coat uniformly on the surface of 40Cr steel roller substrates for the laser surface alloying treatment by a CO2 laser, The results showed that many good consequences were ob- tained after adding the rare earth oxide Y2O3. The crystal grains of the alloy layer were significantly refined. The boundary of crystal grains was strengthened. The unifomaity and density of the microstructure were increased. The hardness and wearing resistance of the alloy layer were considerably improved. The valence electron structure analysis of the alloy layer was made by the empirical electron theory of solids and molecules （EET）. The calculated results demonstrated that Y should be mixed in the first stage and Fe should be in the eighteenth hybrid bands. The analyzed outcomes illustrated that the electron theory of the solid solution shows the strengthening effect on the alloying layer, which has enhanced bond and confirrned the experimental results.

转向架牵引拉杆局部电弧增材修复工艺研究

采用ER80S-G焊丝在焊前不预热的条件下对调质态40Cr钢进行电弧增材修复,模拟转向架牵引拉杆局部缺陷的挖补,对比分析了脉冲冷焊和常规TIG焊两种工艺在堆焊结合强度、微观组织、硬度分布以及对热影响区性能的影响程度等方面差异。结果表明:脉冲冷焊和TIG焊的堆焊层都结合良好,热影响区均未发现冷裂纹。脉冲冷焊的热输入较低,焊后冷却速度快,热影响区窄,试件焊后的角变形量仅为TIG焊的1/6,堆焊层和热影响区的晶粒比TIG焊细小,强度和硬度都高于TIG焊。虽然脉冲冷焊的熔覆效率低,但补焊的连接强度高、变形小、对母材性能的影响小,比TIG焊更适合于转向架牵引拉杆的局部增材修复。

Deformation and phase transformation mechanisms of 40Cr10Si2Mo steel during hot compression

Thermo-mechanical experiments on martensitic heat-resistant 40Cr10Si2Mo steel were conducted using a Gleeble simulator in temperature and strain rate ranges of 1073–1373 K and 0.1–20 s^(-1),respectively.Processing maps were developed and correlated with deformed microstructures based on the dynamic material model theory.The analysis of the maps revealed that both applied temperature and strain rate had significant effects on the power dissipation efficiency and flow instability of the steel alloy.Electron backscatter diffraction analysis was also implemented to study the effect of deformation conditions on martensitic morphology.The results showed that higher temperatures and strain rates led to a fine martensitic packet,and the martensite lath increased in width at high temperatures.Two deformation domains,which exhibit different recrystallization processes,were recognized.The discontinuous dynamic recrystallization(DRX)mechanism in the low strain rate domain was characterized by the migration and growth of high-angle grains during straining.In contrast,in the high strain rate domain,the development of new grain boundaries is primarily associated with the deformation microbands in the low-temperature deformation domain.As the temperature increased,the high dislocation density accelerated the migration of the grain boundaries.Furthermore,the DRX mechanism changed from continuous DRX to post-DRX.This change in the DRX mechanism type was attributed to the time during which the sample remained high temperature after deformation.

The effect of composition and thickness of buffer on joining strength of brazing

ZrO 2 and 40Cr steel were brazed by inserting buffer Ni,4J33,Ti and Cu separately. The chemical composition of 4J33 and Ni will damage the wetting property of Ag 66 Cu 30 Ti 4 filler metal to ceramic and hinder the interface reaction between the active filler metal and ZrO 2, so ZrO 2/40Cr steel can not be bonded. Cu and Ti can efficiently release the residual stresses in the ceramic without injuring the wettabilty of filler metal, so the high joining strength can be obtained by inserting Cu and Ti.

方坯连铸凝固传热的数值仿真及实践

对重特方坯连铸二次冷却进行数值仿真获得的40Cr钢适宜的二次冷却制度,经实验室热态模型实验和生产使用验证,与原有二冷制度相比,喷水量大幅度降低,钢坯质量显著改善。