Modeling of numerical simulation and experimental verification for carburizing-nitriding quenching process

A model considering quantitative effects of diffused carbon and nitrogen gradients and kinetics of phase transformation is presented to examine metallo-thermo-mechanical behavior during carburized and nitrided quenching. Coupled simulation of diffusion, phase transformation and stress/strain provides the final distribution of carbon and nitrogen contents as well as residual stress and distortion. Effects of both transformation and lattice expansion induced by carbon and nitrogen absorption were introduced into calculating the evolution of the internal stress and strain. In order to verify the method and the results, the simulated distributions of carbon and nitrogen content and residual stress/strain of a ring model during carburized and nitrided quenching were compared with the measured data.

Numerical simulation research of dimension variation in heavy plate during quenching and tempering process

The dimension variation of B610E steel during the quenching and tempering process was simulated by ABAQUS,the coefficient of heat transfer during quenching was verified by the buried thermocouple test and the trend of the dimension variation during the quenching process was also calculated by ABAQUS. It was shown by the comparison of simulated results and industrially measured results that only the simulation of thickness and width variation was accurate, while length variation needed further simulation. Besides, the dimension variation trend was identical with the measured results.

Simulation on flow, heat transfer and stress characteristics of large-diameter thick-walled gas cylinders in quenching process under different water spray volumes

Cooling strength is one of the important factors affecting microstructure and properties of gas cylinders during quenching process,and reasonable water spray volume can effectively improve the quality of gas cylinders and reduce production costs.To find the optimal water spray parameters,a fluid-solid coupling model with three-phase flow was established in consideration of water-vapor conversion.The inner and outer walls of gas cylinder with the dimensions of d914 mm×38 mm×12000 mm were quenched using multi-nozzle water spray system.The internal pressure,average heat transfer coefficient(have)and stress of the gas cylinder under different water spray volumes during quenching process were studied.Finally,the mathematical model was experimentally verified.The results show that both the internal pressure and have increase along with the increase of spray volume.The internal pressure increases slowly first and then rapidly,but have increases rapidly first and then slowly.To satisfy hardenability of gas cylinders,the minimum spray volume should not be less than 40 m^3/(h·m).The results of stress indicate that water spray quenching will not cause deformation of bottle body in the range of water volume from 40 to 290 m^3/(h·m).

Numerical and experimental analysis of quenching process for cam manufacturing

In order to obtain satisfactory mechanical properties for the cam used in high-power ship diesel engines, a new quenching technology was proposed by designing a two-stage quenching process with an alkaline bath as the quenching medium. To demonstrate the effectiveness of the proposed new quenching technology, both numerical analysis and experimental study were performed. The new quenching technology was analyzed using finite element method. The combined effects of the temperature, stress and microstructure fields were investigated considering nonlinear material properties. Finally, an experimental study was performed to verify the effectiveness of the proposed new quenching technology. The numerical results show that internal stress is affected by both thermal stress and transformation stress. In addition, the direction of the internal stress is changed several times due to thermal interaction and microstructure evolution during the quenching process. The experimental results show that the proposed new quenching technology significantly improves the mechanical properties and microstructures of the cam. The tensile strength, the impact resistance and the hardness value of the cam by the proposed new quenching technology are improved by 4.3%, 8.9% and 3.5% compared with those by the traditional quenching technology. Moreover, the residual stress and cam shape deformation are reduced by 40.0% and 48.9% respectively for the cam manufactured by the new quenching technology.

Numerical Simulation of Thermal Stress Fields in the Magnetic Quenching Process of 45 Steel

Based on a transient temperature distribution of a 45 steel cylinder workpiece during magnetic quenching, which was obtainedby solving the governing equations with nonlinear boundary on the condition of coupling effects of heat-magnetism. Accordingto the theory of thermal non-elasticity, computational mechanics, ferromagnetism and phase transformation, a new constitutiveequation considering effects of phase transformation is proposed and solved by means of finite element method. The transientthermal stress and residual stress are obtained and the influencing factors on the thermal stress of magnetic field are analyzedand discussed.

COUPLED NUMERICAL SIMULATION ON COLD ROLLER'S TEMPERATURE FIFLD-PHASE TRANSFORMATION - STRESS FIELD DURING ITS QUENCHING PSOCESS

Complicated changns occur inside the steel parts during quenching process. The abruptly changed boundary conditions make the temperature field,micro - structure and stress field change dramatically in very short time, and these variables take a contact interactions in the whole process. In this paper, a three dimensional non - linear mathematical model for queeching process has been founded and the numerical simulation on temperature field,microstructre and stress field has been realized.In the FEM analysis, the incremental iteration method is used to deal with such complicated nonlinear as boundary nonlinear, physical property nonlinear,transformation nonlinear etc.The effect of stress on transformation kinetics has been considered in the calculation of microstructure. In the stress field anal- ysis,a thermo- elasto - plastic model has been founded, which considers such factors as transforma- tion strain,transformation plastic strain, themal strain and the effect of temperature and transforma- tion on mechanical propertier etc. The transient temperature field, microstructure distribution and stress field of the roller on any time can be displayed vividly,and the cooling curve and the changes of stress on any position can also be given.

Transformation Plasticity─The Effect on Metallo-Thermo-Mechanical Simulation of Carburized Quenching Process

Theory of metallo-thermo-mechamics and the developed CAE code offer a powerful tool to simulate residual stresses and distortion during heat treatment processes, in which the transformation plasticity is one of factors to be considered being coupled with stress/strain and metallic structure. It is pointed out in this paper that, especially in the case of carburized quenching, transformation plasticity plays very important role on the distortion, which is verified by axisymmetric finite element, employing heat treatment simulation code "HEARTS". Simulated results with the careful consideration on the effect of transformation plasticity reveal to improve remarkably the accuracy of prediction of the displacement and the mode of distortion, compensating the discrepancy between experimental and calculated results. Attention is also paid on the difference in transformation plasticity and conventional plasticity in simulating the volume fraction, stress and strain in ring-shaped specimen during quenching. Moreover some discussions are made on practical use of the effect, and recent experimental results on the coefficient of transformation plasticity are presented.

Numerical simulation of circular jet impinging on hot steel plate

Flow structure and heat transfer characteristics of an axisymmetric circularjet impinging on a hot 1Cr18Ni9Ti medium plate have been simulated numerically using computationalfluid dynamic (CFD) code. The relation between flow field of jet impingement and its heat transfercapability is analyzed, and the phenomenon that heat transfer at stagnation point is smaller thanthat of points directly around is discussed. The simulation result provides boundary conditions forthermal analysis of medium plate quenching.

Quenching Simulation of PM Coated Tools

HIP cladding is a powder metallurgical coating technique used in the production of wear parts and tools. In many cases the composite components consist of carbide-free hot-work steel as base material and wear resistant carbide-rich PM cold-work steel as coating material. To ensure operativeness a heat treatment matched to the substrate and coating material is required. Dissimilar phase transformation behaviour and different thermal expansion coefficients of layer and substrate entail inner stresses affecting the transformation kinetics in turn. In order to get a deeper insight into these effects Finite Element simulation tools are used. On the one hand, the transient heat conduction problem of the quenching process has to be solved. Non-linear boundary conditions and phase transformation of both, substrate and layer are considered. On the other hand, the mechanical response is calculated. The overall aim of the investigation is an improvement of common heat treatment techniques used for HIP cladded wear parts.

42CrMo汽车转向节热处理裂纹形成机理

针对锻件热处理后出现的单枝上表面裂纹问题,基于宏微观热处理有限元数值仿真模拟对裂纹进行了分析,并探究了裂纹的形成机理。通过光学显微镜和能谱仪分析可知该裂纹与典型淬火裂纹形貌相似,且裂纹附近没有脱碳现象,但是存在明显氧化现象,确定该裂纹在淬火阶段产生,在回火阶段发生氧化。结合应力模拟结果可以判定前期单枝表面急速冷却收缩,主要是由于产生了表面x方向拉应力而导致的裂纹。由此分析了单枝表面在该时期的最大x方向拉应力的分布情况,发现其与实际裂纹出现区域基本重合,进一步证明了该裂纹产生机理的正确性。

20MnCrS5真空低压渗碳气淬多场耦合模拟分析

目的采用试验研究、模拟计算和理论分析相结合的手段,对20MnCrS5齿轮钢真空低压渗碳过程的组织性能演变机理进行研究。方法引入符合真空渗碳强渗、扩散交替进行的扩散边界条件,并修正硬度计算方程,开发真空低压渗碳高压气淬过程仿真模型。分别建立ϕ15mm×100mm圆棒试样二维轴对称和三维实体有限元模型,对20MnCrS5圆棒试样不同工艺参数下真空渗碳过程进行模拟仿真,开展真空渗碳试验与仿真分析化研究。结果二维轴对称模型和三维实体模型计算精度接近,可以代替三维模型,提高计算效率。不同工艺参数真空渗碳过程得到的模拟和试验结果吻合较好,验证了改进模型和方程的可用性,并对不同工艺条件下碳浓度、组织和性能演变规律进行了研究。而后将模型应用到德国FZG(Forschungsstelle für Zahnräder und Getriebebau)标准齿轮样件,对其真空渗碳过程进行了模拟,结果可较好地反映齿轮不同位置碳浓度分布的特点,进一步验证了模型的准确性。结论通过本研究,揭示了20MnCrS5齿轮钢真空低压渗碳过程的组织性能演变机理,并为复杂零部件真空渗碳过程工艺开发提供了新的思路。

旋流法熔渣水淬余热回收数值模拟研究

热炉渣及其余热的利用是钢铁工业面临的巨大挑战。如何回收熔渣中的余热,进行余热发电是节能减排、环保的重要内容。熔渣余热回收包括机械破碎法、鼓风法和离心法等,但热回收技术不成熟,均有缺点。为提高水淬法的热能回收利用、降低回收装置的占地面积、提高熔渣的冷却效率,本文通过Fluent数值模拟的方法,对旋流法熔渣余热回收装置进行研究,主要探究熔渣的放热情况、流动情况以及装置蒸汽产出。模拟结果显示,熔渣在旋流法反应器内停留时间可达约15 s,换热时间充分。捕渣网的设计可以加速熔渣在反应器内的沉降。同时由于水的比热和潜热巨大,对熔渣的降温速率可以达到水泥生产的玻璃态炉渣产品的需求。通过使用旋流法对50 t/h、1550℃熔渣余热进行回收利用,可以产生高达40 t/h、209.9℃过热蒸汽用以发电,产生的年收益可达51082万元,具有非常大的应用潜力。

高温铜渣风淬造粒实验研究及铜渣液滴冷凝过程的数值模拟

为了探究高温铜渣风淬造粒的可行性和分析液体黏度对风淬造粒效果的影响,搭建了风淬造粒实验台,对水、机油和液态石蜡的风淬造粒效果进行对比,得出随着液体黏度的升高,液滴形状更加接近球形且尺寸分布更加均匀;冷凝后的石蜡颗粒粒径分布较窄,有利于对高温颗粒进行二次余热回收。使用流体体积函数模型(VOF)和凝固熔化模型和辐射模型(DO)对单个铜渣液滴的冷凝过程进行了数值模拟。结果表明,初始温度为1355 K,直径为2 mm的铜渣液滴被300 K室温空气冷却时,液滴表面能够快速凝固形成坯壳,经过1.62 s后铜渣液滴完全凝固。冷却过程中迎风面冷却速度较快而背风面较慢,导致液滴凝固不均匀。气流速度越大,对铜渣液滴的冷却能力越强,液滴的冷凝越快;液滴初始粒径越小,换热效率越高,凝固时间越短。

基于材料成分波动的22CrMo锥齿轮渗碳淬火性能评估

以22CrMo材料锥齿轮为研究对象,通过有限元方法,研究了材料成分波动对锥齿轮渗碳淬火性能的影响。利用材料数据库软件,基于22CrMo材料元素范围的上、下限建立2组材料性能数据库;利用热处理仿真软件建立模型,并对2组材料成分的被动锥齿轮进行渗碳淬火仿真,对比分析了锥齿轮渗碳淬火后表层碳浓度、微观组织演化及齿轮变形等数据。结果表明,材料成分波动对22CrMo锥齿轮淬火后的相组织分布以及齿轮变形量影响较大,对渗碳层影响较小。

高温烟气水冷换热管的数值模拟及结构优化

由于烟气水冷热交换器烟气侧温度很高,能快速提升换热管的温度,如果此时冷却水吸收的热量不足以冷却换热管则会造成换热管超温爆管。采用FLUENT软件对某新型烟气急冷器换热管进行数值模拟,并进行结构优化。结果显示,由于烟气入口侧的温度较高,流速较快,造成换热管壁面温度也较高,从而导致换热管外的冷却水形成膜状沸腾。对异形换热管进行数值模拟,发现与圆形换热管相比冷却水侧产生的水蒸气分布更均匀,在壁面处不会形成局部水蒸气含量过多的情况,同时能使换热管壁面最高温度降低约265 K,使换热管壁面平均温度降低4.8%~8.3%。并且研究了烟气处理量对换热管的影响,发现随着烟气处理量的增加,烟气出口温度和换热管壁面温度也随之升高;在相同的烟气处理量下,异形管外冷却水吸收的热量多于圆形管外冷却水吸收的热量。

核电用钢淬火过程温度场-组织场数值模拟及试验研究

为获得SA508Gr.4N钢末端淬火过程中温度场及组织场的变化规律,通过对非线性有限元模拟软件进行二次开发,建立SA508Gr.4N钢末端淬火过程中的温度-组织耦合的有限元模型,并通过实验对数值模拟结果进行验证。研究结果表明:所建立的温度-组织耦合模型计算结果与实验结果吻合良好,温度场的变化主要受综合换热系数影响;组织场模型适用于扩散型和非扩散型相变组织与维氏硬度的预测。随淬火端面的距离增大,试样组织呈现出由完全马氏体相到马氏体+贝氏体混合相的变化,维氏硬度逐渐降低,与温度-组织耦合模型计算得到的组织、硬度变化规律一致,因此,本文所提模型可以用于预测SA508Gr.4N钢末端淬火过程中温度场及组织场变化规律。

40Cr轴类件淬火过程的数值模拟与分析

充分考虑40Cr轴类件淬火瞬态问题、相变问题、变热系数问题,以及淬火过程中的温度场、组织场和内应力场耦合问题。通过DEFORM有限元软件建立40Cr轴类件淬火过程的计算模型,并对模型进行试验验证,证明有限元计算模型的可靠性。

Numerical Simulation of Steel Tube Induction Heating During Quenching Process

Induction heating process of steel tube using of intermediate frequency is characterized by short time,precise temperature control and environment friendly.It has been widely applied to the quenched steel,bent pipe,etc.In this paper,induction heating process for a typical variety of seamless steel tube,in particular the heating section different frequency combination is studied by numerical stimulation.The temperature field has been calculated during the entire heating process of tube.The optimum operating parameters of induction heating has been suggested which in turn provides an important reference data to the research of seamless steel tube induction quenching.

基于改进集中热容法的Mg-Gd-Y-Zr-Ag变形镁合金表面换热系数求解方法

表面换热系数作为淬火数值模拟过程的重要边界条件,其求解精度直接影响温度场、热应力场的演变规律。实验通过设计矩形淬火探头并进行单面水浴淬火,根据热电偶记录的温降数据,采用改进的集中热容法对Mg-Gd-Y-Zr-Ag变形镁合金进行表面换热系数的求解。研究结果表明:表面换热系数呈现先增大后减小的趋势且水浴淬火过程存在蒸汽膜沸腾阶段、二次形核阶段以及对流换热阶段3个阶段,在第27秒时表面换热系数达到峰值2496.31 W/(m^(2)·℃),此时淬火面温度为211℃。用此方法计算得到的随温度变化的换热系数以列表的形式代入Abaqus有限元模型的相互作用模块,同一深度处仿真温度与实测温度最大相对误差为15%,平均相对误差仅为6%;采用K-S双样本分布检验对仿真与实验的温度曲线进行分布检验,在合适的显著性水平下4个样本的统计量均不在拒绝域内,验证了改进的集中热容法用来求解水浴淬火过程中表面换热系数的正确性。