齿轮的淬火冷却和变形控制

淬火冷却是齿轮生产中的重要工艺，它对齿轮精度和质量有着显著影响，从装夹方式、淬火介质状态以及淬火设备等方面进行改进，力求做到齿轮的均匀冷却，可以大幅度减小齿轮的变形量，并提高其变形规律性。     

第一届淬火及变形控制国际会议介绍

美国金属学会(ASM)于92年9月22日～25日在芝加哥举办了“第一届淬火与变形控制国际会议”,来自世界各地的300名代表参加了会议。会议由ASM热处理技术分会的淬火冷却委员会发起组织,由ASM热处理小组、国际热处理联合会(IFHT)淬火及冷却委员会及ASM欧洲分部协办。     

淬火的冷却技术

冷却是淬火工艺中最重要的工序之一，为使工件得到马氏体或（和）贝氏作组织，同时不开裂和变形尽量小，须有理想的冷却介质，热处理工作者根据淬火冷却机理，通过控制或改变冷却的方法，以达到近似的理想状态。本文从冷却介质、设备和操作方法等角度讨论淬火冷却技术。     

淬火剂SST101冷却机制的探讨

本文对淬火剂ＳＳＴ１０１在其不同浓度、温度下冷却曲线及４０Ｃｒ钢在该介 淬火后的淬透性、变形开裂性的测定,探讨了其冷却机制。结果表明,该淬火剂在冷却金属时,在钨表面形成一层聚合物隔离膜,此膜能降低金属淬火时产生的热应力和组织应力,避免了冷却不均现象,减小了工件变形与开裂。     

聚合物淬火剂的冷却机制及在热处理中的应用

对淬火剂SST101在其不同浓度下冷却曲线及40CrMn钢在该介质中淬火后的淬透性，变形开裂性及力学性能进行了测定，并探讨了其冷却机制，所得结果对淬火剂SST101的应用，具有重要的指导意义。     

大规格铝合金型材挤压在线淬火变形原理

分析并总结出大规格铝合金型材挤压在线淬火变形的过程和原理,对型材淬火变形造成的形位尺寸缺陷进行具体分析并提出解决方案。淬火变形是冷却过程中型材热胀冷缩以及内部应力综合作用的结果,其过程分为"正变形-恢复-反变形"三个步骤,型材最终向冷却速度慢的部位变形。通过变形情况来判断并调整型材不同部位的淬火冷却强度,同时采用局部提前冷却技术,可以在保证型材力学性能的前提下有效减少或避免大规格型材由于淬火引起的弯曲、开口尺寸变化、平(弧)面变化、波浪和扭拧等缺陷。     

略谈模具淬火变形与开裂

模具热处理时,淬火变形与开裂是最常见的缺陷,特别是淬火开裂,多半难以挽救。一、模具淬火变形的分析模具在淬火时,一方面要求有足够的冷却速度,以获得马氏体组织,保证所需要的机械性能;另一方面又要求尽量降低冷却速度,避免产生因内应力过大而造成的变形和开裂。这就是热处理淬火时所面临的基本矛盾。 1.热处理变形的形式淬火变形按其发生的时间可分为淬火变形和时效变形两类,在淬火时发生的变形称为淬     

工件的淬火变形机理及预防和矫直措施

由于淬火过程中的快速冷却而在工件内部产生的内应力是导致淬火变形的根本原因．在较详细探讨影响工件淬火变形的主要因素的基础上，提出了相应的预防和矫直措施．对降低生产成本具有一定的实用价值．     

低温碱浴淬火剂的再生方法

碳工具钢和低合金工具钢在工模具和零件制造上得到广泛应用。但由于其淬透性差，淬硬度低，淬火变形大等不足之处，应用上受到一定限制。目前中、小型厂矿在制造精度高，形状复杂、壁厚相差悬殊的工模具时，为获得较高硬度、强度、韧性和减少变形开裂时，常采用低温碱浴淬火剂，并有明显效果。但因使用时间短即老化变质而废弃，造成碱浴的大量浪费。表1为常用低温碱浴——硝盐淬火剂和盐浴加热介质。低温碱浴淬火剂特点；淬火时在高温区＞M哨冷却速度接近水，低温区＞M哨的冷却速度接近油，淬火能力强，是较理想的淬火冷却介质；淬火后可获…     

NQ—A型聚合物水溶性淬火介质的应用

综合论述了ＮＱ—Ａ聚合物淬火介质的冷却性能和工艺性能，通过典型钢件淬火硬度、变形和开裂倾向的研究，证明以一定浓度的ＮＱ—Ａ聚合物水溶性介质取代水和淬火油，可使钢件获得满意的淬火效果。     

Dry and clean age hardening of aluminum alloys by high-pressure gas quenching

When precipitation-hardenable aluminum parts are water quenched, distortion occurs due to thermal stresses. Thereby, a costly reworking is necessary, and for this reason polymer quenchants are often used to reduce distortion, with the disadvantage that the quenched parts have to be cleaned after quenching. In opposition to liquid quenchants, gas quenching may decrease distortion due to the better temperature uniformity during quenching. Furthermore, cleaning of the quenched parts can be avoided because it is a dry process. For this purpose, a heat-treating process was evaluated that included a high-pressure gasquenching step. Gas quenching was applied to different aluminum alloys (i.e., 2024, 6013, 7075, and A357.0), and tensile tests have been carried out to determine the mechanical properties after solution annealing, gas quenching, and aging. Besides high-pressure gas quenching, alloy 2024 was quenched at ambient pressure in a gas nozzle field. The high velocity at the gas outlet leads to an accelerated cooling of the aluminum alloy in this case. Aluminum castings and forgings can be classified as an interesting field of application of these quenching methods due to their near-net shape before the heat treatment. Cost savings would be possible due to the reduced distortion, and therefore, less reworking after the precipitation hardening.     

Optimum design of the heat-transfer coefficient during gas quenching using the response surface method

The heat-transfer coefficient during gas quenching is optimized to obtain minimum distortion with stress and hardness distribution requirements satisfied. During the gas-quenching process, the heat-transfer coefficient has a significant influence on the properties of the final product, such as the hardness, strength, residual stress and distortion. Significant distortions after quenching will increase the cost due to post-manufacturing processes such as grinding and hot straightening. Therefore, minimizing the distortion will benefit in most gas-quenching cases. A step function is used to represent the heat-transfer coefficient in terms of the quenching time. Five coefficients of the step function are used as the design variables to minimize the distortion. Two design constraints are used to satisfy the maximum principal stress and the average surface hardness requirements of the final product. The finite element package DEFORM is used to predict the material responses during the quenching process. Phase transformations, deformation and heat transfer are integrated during the simulation process. The response surface method is used to obtain the analytical models of the objective function and constraints in terms of the design variables. Once the closed-form equations of the objective and constraints are obtained, a design optimization tool is used to search the optimum design point. This paper summarizes the methodology that is used to optimize a plane strain example.     

超高强度钢300M在真空炉中的高压气体淬火

用真空高压气淬炉对低合金超高强度钢３００Ｍ进行热处理的试验结果表明，不仅其力学性能完全达到了相应技术条件规定的要求，而且还有比真空油淬的变形小，不需清洗等优点。     

Gas Quenching during Age Hardening of the Aluminium Casting Alloy Al-7Si-0.3Mg

For quenching of age hardenable aluminium alloys today predominantly aqueous quenching media are used,which can lead due to the Leidenfrost phenomenon to a non-uniform cooling of the parts and thus to thermal stresses.Particularly at thin-walled or complex shaped parts local plastic deformations can occur by the uneven thermal stresses. In relation to the conventional quenching procedures in aqueous media, gas quenching exhibits a number of technological,ecological and economical advantages. In comparison to liquid quenching media, gas does not change its phase during quenching. Moreover, the cleaning problem of the parts can be avoided. The quenching intensity can be adjusted by the variable parameters gas pressure and gas speed as well as the kind of gas and thus can be adapted to the requirements of the alloy. By the higher uniformity and the better reproducibility, gas quenching offers a high potential to reduce distortion. The goal of these investigations is to clarify, if the cooling rate during gas quenching is sufficient to obtain the specific required strength after age hardening of the alloy Al-7Si-0.3Mg. For this purpose different tests in high-pressure gas quenching facilities, gas nozzle fields and water quenching baths were performed.     

Gas Quenching during Age Hardening of the Aluminium Casting Alloy AI-7Si-0.3Mg

For quenching of age hardenable aluminium alloys today predominantly aqueous quenching media are used.which can lead due to the Leidenfrost phenomenon to a non-uniform cooling of the parts and thus to thermal stresses.Particularly at thin-walled or complex shaped parts local plastic deformations can occur by the uneven thermal stresses. In relation to the conventional quenching procedures in aqueous media, gas quenching exhibits a number of technological.ecological and economical advantages. In comparison to liquid quenching media, gas does not change its phase during quenching. Moreover, the cleaning problem of the parts can be avoided. The quenching intensity can be adjusted by the variable parameters gas pressure and gas speed as well as the kind of gas and thus can be adapted to the requirements of the alloy. By the higher uniformity and the better reproducibility, gas quenching offers a high potential to reduce distortion. The goal of these investigations is to clarify, if the cooling rate during gas quenching is sufficient to obtain the specific required strength after age hardening of the alloy A1-7Si-0.3Mg. For this purpose different tests in high-pressure gas quenching facilities, gas nozzle fields and water quenching baths were performed.     

Influence of Rewetting Behavior on the Distortion of Bearing Races

Immersion quenching in evaporable fluids like oil, polymer solutions, or water is a widely used technique in heat treatment shops because this technique provides higher heat transfer coefficients than the most alternative gas quenching techniques. The disadvantages of immersion quenching in evaporating fluids are the complex heat transfer mechanisms which consist of the three phases, film boiling, nucleate boiling, and convection. Especially the transition from film to nucleate boiling—the rewetting of the sample surface—is a complex process which leads to a strong position dependence of the heat transfer coefficient of the cooled work pieces. In particular, immersion quenching of thin-walled rings can result in large changes of ovality with comparable high scattering. To understand these results, two series of experiments were performed. Rings were quenched in oil in a special quenching tank and the rewetting behavior was documented. Furthermore, bearing races were quenched in a standard tank. Before and after heat treatment, these rings were measured by a coordinate measuring system and the distortion was determined. The investigations have clearly shown that the vapor film can have an important influence on distortion generation during oil quenching. The resulting distortion can principally be explained by the observed rewetting behavior.     

低碳贝氏体钢渗碳工艺及在轿车齿轮上的应用

对低碳帐房底体钢的渗碳工艺、显微组织、力学性能、液火变形进行了研究。结果表明,此钢渗碳工艺性能良好,渗碳层组织理想,力学性能优良,采用渗碳气冷淬火 ,使轿车齿轮淬火变形比２０ＣｒＭｎＴｉ钢的明显减小。     

W18Cr4V钢真空气淬和普通油淬的组织与性能比较

采用真空气淬法和普通空气加热油淬法分别对W18Cr4V钢进行热处理。利用金相显微镜和洛氏硬度计对热处理后W18Cr4V高速钢的组织和硬度进行了比较观察和测试分析。结果表明,两种淬火工艺处理的试样组织基本一致,均为隐晶形的淬火马氏体基体组织、大颗粒状的共晶碳化物和细小点粒状的二次碳化物及残留奥氏体,气淬后的组织更均匀;回火后的组织也很相似,为回火马氏体及未溶解的共晶碳化物和二次碳化物。经真空气淬的试样硬度（65HRC）仅比普通空气加热油淬的（66HRC）略有降低,但能满足工模具的硬度要求,而且试样表面光洁,呈银灰色,变形微小,对于要求精度不太高的零件,无需进行后续加工,对环境也无污染。     

Optimization of Process Parameters for the Axial Distortion and Distortion Range During Die Quenching of a Spiral Bevel Gear

The strength of high-duty gears can be improved by carburizing and quenching processes. Quenching distortion is inevitable during the process, and it has direct effects on the precision of the gear. For spiral bevel gear with big diameter and small thickness, die quenching process is applied in the manufacturing to control the distortion in axial direction. Die quenching parameters must be optimized to minimize the distortion while considering non-uniformity of chemical compositions and loads. In this paper, material models of gear material (22CrMoH) built based on the phase transformation kinetics, static mechanical properties and phase transformation plasticity equations. Finite element analysis (FEA) models are conducted to study the whole die quenching process based on the production process. Die quenching experiments and testing of microstructures and distortions are conducted to verify the accuracy of the FEA models. The effects of loads and bottom die obliquity on the final distortion are studied to set the appropriate range and control distortion. The distortion was very sensitive to the bottom die obliquity and some part of load ranges. The distortion changes little when the load of inner die was in the range of 1.38-2.07 MPa and the load of outer die was in the range of 2.07-2.76 MPa. The distortion range is fitted the production requirements by setting the inclination angle of bottom die between 0.12° and 0.29°.     

工业机器人精密减速器输入轴的真空低压渗碳高压气淬工艺

针对轴齿类零件高温渗碳淬火热处理畸变问题,研究了工业机器人减速器精密轴齿类零件真空低压渗碳和高压气淬工艺。结果表明,在升温阶段采用阶梯式升温保温方式,强渗阶段以乙炔-氮气交替脉冲进行强渗和扩散,淬火冷却阶段精确控制氮气压力1.8 MPa(18 bar)并使之稳定,可使轴齿类零件的总畸变量控制在0.005~0.015 mm。实际生产结果表明,轴齿类零件采用真空低压渗碳和高压气淬技术,渗碳层中的马氏体为1级,残留奥氏体和碳化物为1~2级,心部组织为1~2级。批量生产的减速器精密轴齿表面硬度、心部硬度和有效硬化层深度均值分别为59.7 HRC、38.6 HRC和0.681 mm,全部满足技术要求。