风电齿轮轴渗碳淬火工艺研究

研究了渗碳淬火工艺对18CrNiMo7-6钢制风电齿轮箱中、小模数齿轮轴性能的影响,得出齿轮轴的热处理工艺:920℃渗碳,650℃出炉;825℃盐水淬火;170℃回火。经此工艺热处理的齿轮轴不仅各项性能指标均满足要求,还缩短了渗碳时间,降低了生产成本。     

变速器中间齿轮轴渗碳淬火畸变的控制

针对汽车变速器中间齿轮轴在渗碳淬火热处理后齿型、齿向的畸变问题,分析了其产生原因。通过热处理工艺改进,调整了渗碳淬火工艺参数并改变了装炉方式,提高了齿轮轴接触精度和使用寿命。     

齿轮泵主动齿轮轴裂纹原因分析

<正>零件渗碳后一般采用直接淬火及空冷后重新加热淬火两种工艺。渗碳后直接淬火工艺简单,生产效率高,但淬火后晶粒容易粗大,影响零件性能。渗碳后重新加热淬火的工艺可以细化晶粒,提高渗碳件的性能~([1])。齿轮泵主动齿轮轴采用的是渗碳空冷后重新加热淬火的工艺,但渗碳空冷后发现轴表面有纵向裂纹齿轮轴共49件,有8件发现裂纹。常见热处理纵向裂纹厂般是在冷速快,零件完全淬透的情况下,由于组织应力作用而产生。高合金钢零件由于淬透性高,在     

渗碳淬火工艺对12Cr2Ni4钢内氧化级别的影响

对12Cr2Ni4钢进行渗碳淬火工艺试验,研究了预备热处理、渗碳保温时间、渗碳后淬火方式对12Cr2Ni4钢内氧化级别的影响。采用金相法检验表层内氧化层的深度,并按照国家标准对内氧化评级。结果表明:预备热处理采用调质的抗内氧化能力是明显好于正回火的;一次淬火的抗内氧化能力明显好于二次淬火的;随着渗碳保温时间的延长,表层内氧化层的深度增加。因此,预备热处理后采用调质、渗碳后采用一次淬火、渗碳保温时间缩短可以明显减小表层内氧化的层深。     

真空低压渗碳热处理在重载齿轮上的应用

研究了20CrMnTiH钢同步器齿毂经真空低压渗碳热处理后组织和性能的变化,并与气氛渗碳热处理工艺进行对比。结果表明,真空渗碳热处理后齿面位置处几乎无晶间氧化和非马氏体组织,在晶间氧化的控制上较大幅度优于气氛渗碳热处理工艺;高压气淬在齿毂类零件的热处理畸变控制方面优于油液淬火。     

20CrMnMo钢重载齿轮轴磨削裂纹控制与

重载齿轮轴工作承载大、冲击力强、要求安全性高,使用时除应具有优良的耐磨性能还应具有较高的接触疲劳强度和弯曲疲劳强度,同时具有较高的抗冲击和抗过载能力.因此,齿轮轴的渗碳热处理工艺是满足这些性能要求的关键.近几年,本公司20CrMnMo齿轮轴深层渗碳在后序磨削加工中经常出现磨削裂纹,导致齿轮轴在工作中沿裂纹开裂或剥落,从而降低齿轮轴的使用寿命.通过改进热处理工艺能有效控制20CrMnMo钢齿轮轴深层渗碳磨削裂纹的产生.     

17CrNiMo6钢花键齿轮轴渗碳淬火畸变控制

针对生产中17CrNiMo6钢花键齿轮轴在渗碳淬火后花键精度等级低的问题,分析了其原因,并通过改进热处理工艺和热处理工装,有效控制了花键齿轮轴在热处理中的轴向畸变,从而保证了花键的精度要求,解决了生产中的重要问题。     

大模数人字齿轮轴深层渗碳工艺参数优化

通过优化大模数齿轮轴深层渗碳淬火工艺参数,使渗碳淬火后表层脱碳深度、内氧化深度、碳化物形态、硬度梯度分布曲线得到极大的改善,减少了齿轮轴在磨削过程中产生裂纹的倾向,提高了齿轮轴使用寿命。     

大齿轮轴热处理畸变的控制

分析了大齿轮轴渗碳淬火后齿面产生较大畸变的原因,找出了适合预留收缩余量和等温淬火工艺．解决了大齿轮轴的热处理畸变。     

18Cr2Ni4WA钢制渗碳齿轮轴纵裂原因分析

某厂生产了一批采煤掘进机用 1 8Cr2Ni4WA钢制齿轮轴 ,齿顶圆直径为1 75mm ,轴径为1 2 5mm ,齿轮轴长为 340mm。该齿轮轴经渗碳直接油冷淬火+低温回火后 (渗碳及淬回火工艺参数不详 ) ,所有的轴全部在平行于轴向发生开裂 ,裂纹产生于表面并裂向心部 ,长度贯穿全轴长 ,见图 1。图 1　开裂齿轮轴实物Fig .1　Crackedgearshaft　　纵裂是常见的淬裂类型之一 ,其产生的力学条件是 :在切向残余应力呈表面受拉、心部受压的情况下 ,作用于零件表面的最大拉应力超过材料的断裂强度。国内外的热处理实践证明[1] ,渗碳淬火零件的残余应力分布与…     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.