伞齿轮淬火变形的有限元模拟

针对伞齿轮渗碳后模压淬火过程,对伞齿轮进行了一定的简化,确定了材料的各项热物性参数和力学性能参数,考虑了马氏体转变的相变潜热,测定了淬火过程中的热膨胀系数,最终建立了伞齿轮淬火的有限元模型。利用ABAQUS/Standard计算了伞齿轮工件的温度场和应力场,分析了淬火过程中伞齿轮工件各个位置的温度变化规律和淬火变形规律。     

大棒材在线淬火及自回火过程的数值模拟

棒材在线淬火-自回火是大棒材生产中先进的生产工艺。考虑相变潜热和材料热物性随温度的变化,利用有限元软件MSC.Marc,对不同直径的45号钢及42CrMo钢大直径棒材(50mm以上)轧后在线淬火及空冷过程的温度场进行了模拟,对淬火临界冷却速度进行了计算,获取不同直径棒材的最大淬硬层深度及形成最大淬硬层深度所需的淬火时间;研究了不同淬火时间后棒材的温度场,分析了棒材自回火的可能性。     

火车车轮淬火过程中的温度场

 为分析火车车轮淬火过程中车轮内部温度变化情况,利用MSC/MARC商用有限元软件结合用户子程序开发对车轮淬火过程中的温度场进行了模拟计算。温度的模拟结果与实测结果吻合较好。研究结果对车轮淬火工艺的制订和车轮的生产工艺的制定具有指导意义和应用价值。     

22CrMo钢渗碳淬火过程组织与应力变化的数值模拟

 根据描述渗碳过程的数学模型,利用有限差分法,对22CrMo钢圆柱体试样渗碳过程进行了数值模拟,得出渗碳层中碳浓度分布。基于渗碳模拟结果,根据描述淬火过程的数学模型,利用有限元法对试样淬火过程的温度场、组织场及应力场进行了数值模拟,分析了淬火过程中组织和内应力变化,及渗碳过程对淬火过程组织及应力变化的影响。对渗碳淬火后试样的组织进行了金相分析,并测量了表面和内部各点残余应力,计算值和测量值相吻合。     

液固相铝-不锈钢板复合轧制温度场的模拟计算

根据液固相轧制的实际情况,对模型的边界条件进行了简化,同时考虑了速度场对温度场的影响,利用等效比热法处理了凝固问题,在此条例上利用ＡＮＳＹＳ软件对液固相轧制过程的温度和速度场进行了耦合计算,得到了温度场分布,计算结果与实测值基本吻合,计算结果表明瞬态分析方法可解决稳态问题。     

齿轮钢淬火过程多场耦合分析

利用有限元分析软件MSC.Marc,结合热弹塑性模型和编写的用户子程序,对(%)0.21C-1.03Cr- 0.20Mo0.03Nb齿轮钢圆柱体淬火过程的温度、组织和应力场进行了多场耦合分析。结果表明,淬火过程产生的内 应力促进马氏体相变,在马氏体相变的情况下,组织应力强于热应力,使淬火后工件的残余应力呈组织应力分布。 测量值和计算值对比表明,淬火过程应力场数值模拟中,考虑应力与相变的相互作用,使计算结果更为精确。     

冷却速率对T91钢相变过程及组织的影响

利用DIL805A/D高精度差分膨胀仪,通过线膨胀行为测量获得相关动力学信息,结合冷却后的组织特征,研究了T91钢不同冷却速度(2～6000℃/min)下过冷奥氏体的相变过程和产物,确定了该钢组织转变的临界冷却速度以及淬火速率对马氏体转变点及组织的影响,绘制了连续冷却转变曲线。研究表明:T91钢的连续冷却过程中只存在铁素体和马氏体转变区,10℃/min为马氏体转变的临界冷却速度。不同淬火速率对T91钢马氏体开始转变温度有较大的影响,它不同于随冷速增加而相变点升高的经典理论。淬火速率通过碳原子气团、内应力的形成来影响过冷奥氏体状态,从而影响相变点;随淬火速度的增加,过冷奥氏体转变后的组织呈细化趋势。     

内燃机车连杆断裂原因分析及改进

热处理过程中,被加热工件受热一定要均匀,这关系到热处理的效果,直接决定了被处理工件的力学性能。柴油机连杆加热时段温度场温度梯度越小,所处的温度场温度越均匀,机械性能就越均匀。由于每个批次的连杆化学成分略有差别,在试验过程中依据不同的马氏体相变温度,调整热处理工艺。马氏体相变温度升高10℃,淬火温度相应调整降低10℃,回火温度提高10-20℃,连杆的显微组织中贝氏体组织明显减少,硬度和强度匹配合理,有效的避免的裂纹的出现。     

相变对无约束淬火控冷工艺参数的影响

以高密集射流冷却时钢板表面的对流换热边界为基础,采用有限元分析对不锈钢1Cr18Ni9Ti和合金钢20CrMnTi常压无约束淬火过程的温度场、应力应变场进行数值模拟,分析对比了2种钢板的温度及X向应力变化规律,且对不同上下水量比下2种钢板的厚度方向的变形量进行了比较,分析了淬火过程马氏体相变对钢板变形的影响,为优化控冷工艺更好控制板形提供了依据.     

中厚板淬火冷却过程温度场热应力场数值模拟

建立了中厚板淬火冷却过程温度场、热应力场数学模型,通过有限元数值模拟方法,研究了中厚板无约束淬火过程温度场、热应力场变化情况,为优化中厚板淬火工艺,保证淬火质量提供依据.     

热处理工艺对车轮残余应力的影响

运用有限元法,综合考虑了温度、相变及应力的耦合作用,对车轮热处理残余应力及热处理工艺对它的影响规律进行了分析.模拟分析表明,马钢生产的HDSA车轮踏面的最大周向残余压应力为140MPa左右,压应力区深度达到38.2 mm.得到了淬火温度、淬火时间、回火温度和回火时间对踏面上周向残余压应力和踏面下压应力区深度的影响规律,其中回火温度对踏面上的残余应力影响最大.     

高强耐磨钢板直接淬火板型控制工艺研究

通过控制轧制后在线直接淬火的工艺研究,揭示耐磨钢板淬火时组织转变、热胀冷缩产生的应力应变与板型控制的关系,通过确定钢板终轧温度、入水温度、钢板上下水比、冷速等参数,确保钢板组织转变均匀、板型良好。大量实验表明,采用在线淬火工艺流程简单、效率高、节约能源。     

Comparison of Austenite Decomposition Models During Finite Element Simulation of Water Quenching and Air Cooling of AISI 4140 Steel

An indigenous, non-linear, and coupled finite element (FE) program has been developed to predict the temperature field and phase evolution during heat treatment of steels. The diffusional transformations during continuous cooling of steels were modeled using Johnson–Mehl–Avrami–Komogorov equation, and the non-diffusion transformation was modeled using Koistinen–Marburger equation. Cylindrical quench probes made of AISI 4140 steel of 20-mm diameter and 50-mm long were heated to 1123 K (850 °C), quenched in water, and cooled in air. The temperature history during continuous cooling was recorded at the selected interior locations of the quench probes. The probes were then sectioned at the mid plane and resultant microstructures were observed. The process of water quenching and air cooling of AISI 4140 steel probes was simulated with the heat flux boundary condition in the FE program. The heat flux for air cooling process was calculated through the inverse heat conduction method using the cooling curve measured during air cooling of a stainless steel 304L probe as an input. The heat flux for the water quenching process was calculated from a surface heat flux model proposed for quenching simulations. The isothermal transformation start and finish times of different phases were taken from the published TTT data and were also calculated using Kirkaldy model and Li model and used in the FE program. The simulated cooling curves and phases using the published TTT data had a good agreement with the experimentally measured values. The computation results revealed that the use of published TTT data was more reliable in predicting the phase transformation during heat treatment of low alloy steels than the use of the Kirkaldy or Li model.     

基于凝固相转变影响的结晶器内热力耦合分析

 为了研究凝固相转变对结晶器内坯壳生长过程的影响,结合高温相转变试验结果建立数学模型,考虑铸坯与结晶器的接触状态,利用有限元软件ANSYS建立结晶器内三维瞬态热力耦合有限元模型,采用生死单元技术模拟温度场,采用热弹塑性接触有限元方法模拟应力场分布。模拟了[δ]铁素体转变量分别为0%、50%和100% 3种情况下结晶器内坯壳的温度场和应力场变化规律。结果表明,沿拉坯方向坯壳表面温度和厚度在距离弯月面以下120 mm左右开始周期性波动,且随[δ]铁素体转变量的增加,波动增加,同时铸坯沿拉坯方向累积位移总量和应力值均减小,沿拉坯方向上位移和应力波动水平增加。     

Microstructural Evolution and Properties of a High Strength Steel with Different Direct Quenching Processes

A high strength low alloy steel with low carbon equivalent was selected for simulating online direct quenching and coiling(DQ-C)process.The influence of stop quenching temperature on mechanical properties and microstructures was studied and compared with normal direct quenching and tempering(DQ-T)process.The study confirmed that required mechanical properties were obtained for both the processes.Properties of the experimental steel with DQ-C process could reach the same level as that of DQ-T process in general.In the DQ-C process,strength decreased with increase in stop quenching temperature.Martensite was obtained and experienced an aging process at stop quenching temperature below Mf.On fast cooling below Ms,martensite was partially transformed and carbon partitioning occurred during slow cooling.The reduction in solid solution carbon and increased amount of retained austenite led to lower strength compared with the DQ-T process.DQ-C process was more favorable for microalloy carbide precipitation.However,impact toughness under different cooling conditions was adequate because of low carbon equivalent and refined microstructure.     

淬火-贝氏体区配分工艺及钢的组织性能

 Q&P（Quenching and Partitioning, 淬火配分）工艺在CCE条件下,通过采用[Ms]和[Mf]点之间的最佳淬火温度和低于[Ms]点的配分温度,避免配分阶段的贝氏体形成最终可以得到最高含量的残余奥氏体组织。但试验中得到不足体积分数8%的残余奥氏体含量限制了钢塑性的提高。通过提出淬火-贝氏体区配分工艺,并应用在(0.21～0.29)C-(1.5~2.0)Si-(1.5～2.1)Mn成分钢,得到了体积分数12%左右的残余奥氏体含量和25%左右的伸长率,同时强度保持在1 000～1 100 MPa,强塑积最高达到36.6 GPa·%。不同的淬火温度和配分温度试验结果表明,工艺变化对强度影响较低,伸长率和强塑积随着配分温度的提高而提高,其中270 ℃的淬火温度试样的提高幅度高于245 ℃淬火试样,采用Q&PB工艺得到了无碳贝氏体＋马氏体＋残余奥氏体的三相组织。淬火和贝氏体区配分得到了优异的强度和塑性的结合,为新一代汽车用钢的发展提供新的思路。     

车轮热处理过程中的变形分析

在考虑了温度、相变及应力的耦合作用的基础上,运用有限元法分析了车轮热处理过程的变形。车轮热处理变形主要发生在淬火阶段,且集中在辐板两端的圆弧处。辐板的变形导致轮毂沉降,并在淬火结束时达到峰值,在随后的回火和冷却过程中沉降减小,热处理结束后HDSA840车轮沉降达1.3 mm。     

Mathematical Modeling of Surface Heat Flux During Quenching

In this article, a method to model the heat flux during quenching has been developed to bring out the effect of initial soaking temperature. Quench probes with a diameter of 20 mm and a length of 50 mm were prepared from 304 L stainless steel. These probes were quenched from different initial soaking temperatures ranging from 400 °C to 950 °C in water. Time-temperature data were recorded during the quenching. The heat flux and temperature at the quenched surface were estimated based on the inverse heat-conduction method. The computation results showed that the peak in the heat flux increased with an increase in the initial soaking temperature of the probes. The heat flux was dependent on the initial soaking temperature. A model for the surface heat flux was proposed as a function of dimensionless parameters. The model could be used to compute the heat flux at different surface temperatures and was specified as a boundary condition to simulate the quenching for the particular material-quenchant combination. The model was verified by running a direct quenching simulation with heat fluxes computed at different surface temperatures using the proposed model as a boundary condition in ANSYS, a commercial finite element program.