Improved Nonlinear Equation Method for Numerical Prediction of Jominy End-Quench Curves

Without considering the effects of alloying interaction on the Jominy end-quench curves, the prediction resuits obtained by YU Bai-hai＇s nonlinear equation method for multi-alloying steels were different from those experimental ones reported in literature. Some alloying elements have marked influence on Jominy end-quench curves of steels. An improved mathematical model for simulating the Jominy end-quench curves is proposed by introducing a parameter named alloying interactions equivalent （Le）. With the improved model, the Jominy end-quench curves of steels so obtained agree very well with the experimental ones.

Experimental and CFD investigations on cooling process of end-quench test

The microstructure of an alloy is affected intensively by the cooling process.To figure out the inherent relation between the cooling rate and microstructure of an advanced nickel-based superalloy,experimental and numerical studies on the cooling process were conducted.Specifically,the measurement was performed concerning both the temperature of the specimen during the end-quench test and the size of the secondaryγ′phase of the specimen after that.The heat transfer coefficient of the quenched surface was determined by the inverse heat transfer method for simulation.The results show that the cooling rate of the quenched surface exceeds 1574 K/min.Based on the averaged cooling rate obtained from the simulation and the measured size of the secondaryγ′phase,an empirical correlation in a double logarithmic relationship between them is proposed.The relationship is verified by the experiment with specified cooling rates.

Effect of Mn on hardenability of 25CrMo axle steel by an improved end-quench test

With the sixth large-scale railway speed-up,the quality of the axles is essential to the safety of the locomotive.According to the high-speed axle technical standard for the control of alloy elements in axle steel,optimization experiments of 25CrMo steel composition were performed by vacuum inductive melting.In order to study the hardenability of high-speed rail axles,an improved end-quench test was put forward.The advantage is that it enables the heat to transfer along the axial direction,thus avoiding edge effects.The hardenability of 25CrMo axle steels with Mn content of 0.60wt.% and 0.80wt.% was investigated mainly by means of optical microscopy and hardness tests.The experimental results indicate that the Mn has a pronounced effect on the hardenability of the steel.With an increase in Mn content from 0.60wt.% and 0.80wt.%,the hardenability of 25CrMo axle steel increases and the hard microstructure is maintained at an increasing distance from the quenched end.From the surface of the water quenched end to the center of the sample,the microstructure is martensite,martensite with bainite,and bainite.

Research on Optimizing the Hidden Layer Structure of ANN-Based Model and Its Application in Predicting End-Quench Curves of Steels

In this paper, a method of optimizing the number of hidden layer neurons has been put forward. This optimizing method is suitable for three layers B-p network. The purpose of this optimizing method is to reduce the predicting errors when the model is used as predicting model. As an example of application, a predicting model of steel end-quench curves has been designed by using this optimizing method. The result shows that the optimization of ANN hidden layer architecture has an effect on reducing predicting errors.

Feasibility of Prototyping the Jominy Test Device: Corroborating for Studies and Preliminary Results of the Heating and Data Acquisition Subsystems

This work contributed to a detailed study on a better understanding of the Jominy test, adopted a proportion of study to create the Jominy test device, exhibited favorable conceptions for the development of a prototype of the device, covering the four aspects of the project, being they: test device, test body heating system, test automation and instrumentation using embedded electronics and financial analysis for the elaboration of this project in Brazil. It was possible to observe in the results that the system is efficient, simple and functional, it was possible to obtain the first test carried out in the controlled environment the temperature data in degrees centigrade, the recorded data were automatically launched in Microsoft Excel by the PLX DAQ software, making the acquisition of the data. In the matter of preparing the test device, the drawings are presented in the 3D modeling software, cost tables of the materials used for assembly in Brazil. In terms of the heating system, a heating system was adopted that uses electromagnetic induction, the cost of materials related to the heating system design was also presented. Another relevant factor that contributes to the research and improvement of the prototype is the municipality, located in the Paraiba Valley region, located in the state of São Paulo, consisting of a fertile and relevant scenario of regional, national, international and multinational statistics, thus concluding the effectiveness for the mainly metallurgical industries. The results obtained were satisfactory and consistent, when they were created for the Jominy test device with the ability to submit small pieces for testing and mainly essential in the didactic point of view for a higher education institution of engineering and technology.

Calculation of phase transformation latent heat based on cooling curves in end-quench test and its application in nickel-based superalloy

To obtain the phase transformation latent heat corresponding to different cooling rates with low test workload and cost,the Newton thermal analysis method and the improved Newtonian thermal analysis method were discussed based on the cooling curve obtained in the end-quench test.The validity of two methods was given by the latent heat calculation of 45^(#) steel.The results show that the relative error of latent heat is 5.20%through the improved Newtonian thermal analysis method,which is more accurate than the Newtonian thermal analysis method.Furthermore,the latent heat release of phase transformation of the self-designed CSU-A1 powder metallurgy nickel-based superalloy increases from 4.3 to 12.29 J/g when the cooling rate decreases from 50.15 to 33.40℃/min,because there is more sufficient time for the alloy microstructure to complete the phase transformation process when the cooling rate is smaller.

Quench sensitivity and microstructure character of high strength AA7050

The effect of quenching rate on the electrical conductivity and microstructure of thick plates of incumbent AA7050 was investigated by employing Jominy end quench test. The electrical conductivity measurement and microstructural observation were conducted at different distances from the quenched end. The results indicate that the average cooling rates decrease with increasing the distance from the quenched end of the bar in the quench sensitive temperature range. However, the electrical conductivity increases with the increase of distance from the quenched end. The surface parts of the plate were fully recrystallized, while partial recrystallization took place at the quarter and center parts of the plate. The quench induced grain boundary precipitates became remarkably coarser and discontinuously distributed with increasing distance from the quenched end of the bar. Plenty of heterogeneous precipitates were observed to nucleate on A13Zr dispersoids when the distance from the quenched end was greater than 38mm.

淬火介质对7050铝合金末端淬特性的影响

采用室温水和浓度为20%的PAG水溶液(聚烷撑二醇聚合物)作为淬火介质进行Jominy末端淬火实验,用于评价7050铝合金淬透性;监测合金固溶和淬火过程中的升温速率和冷却速率,测定距淬火端不同距离的合金的淬火态电导率和时效态硬度,观察室温水淬火试样不同位置晶内淬火析出相。结果表明:采用室温水和20%PAG进行末端淬火时,合金的淬透深度分别约为65和40 mm;采用PAG淬火可使合金温度快速通过淬火敏感区间,同时在淬火敏感区间外降低合金的冷却速率,使试样淬火端和中间部位合金的温度差减小。随着距淬火端距离的增加,淬火诱发析出的η平衡相的尺寸和体积分数增加,无析出区宽化。

利用JMatPro软件对低合金耐磨钢热处理参数的计算

利用材料性能模拟软件JMat Pro对新型耐磨钢ZG30Si Mn Cr2Mo VRE进行热力学和相转变的计算,得到合金钢的平衡相组成、等温转变曲线(TTT)、连续转变曲线(CCT)和Jominy淬透性曲线。以此制定合金的热处理工艺方案。结果表明,合金经930℃水淬+230℃回火处理,合金的硬度和韧性达到最佳匹配。

描述钢淬透性的一个新数学模型

提出了一个新的描述钢淬透性的数学模型及淬透性表征参数．根据端淬实验数据和实验曲线导数变化规律,用线性试探法建立了端淬曲线微分方程,然后解得硬度分布函数．硬度分布函数将端淬曲线描述为直线段和曲线段构成的分段函数:直线段描述试样端部获得全部马氏体区域的硬度,在此区域硬度保持恒定最高值;在曲线段硬度递减,最后趋近恒定最低值．钢的淬透性值用数学参数来表示,它数值上等于从原点到硬度分布曲线拐点的距离．用非线性模拟程序代入实验值获得了淬透性值．模拟结果表明,所获得的模型与实验值吻合很好．

2D70铝合金淬透性研究

采用16,30℃自然水末端淬火试验方法,并通过对材料硬度和电导率指标的测试分析,研究了不同温度对2D70铝合金材料淬透性的影响,描绘出不同温度下该合金的端淬曲线,对比分析了相同条件下2D70和2124合金的端淬曲线。研究结果表明,2D70合金的淬火敏感性很小,16和30℃水温对该合金端淬效果差别不大,该合金自由端淬淬透深度至少大于150mm。

低碳钒微合金钢的淬透性研究

利用钢-淬透性的末端淬火实验,结合碳化钒的析出热力学计算,研究V对低碳钢淬透性的影响。结果表明:随着V含量的增加,实验钢的淬透性提高。VC的热力学计算结果表明,在880℃淬火温度下,0.22C钢中固溶V含量随着钢中添加的V含量增加而增加。当钢中添加V含量大于0.137%(质量分数)时,VC将在奥氏体中析出,固溶C含量开始减少。综合考虑固溶C含量、固溶V含量及原始奥氏体晶粒尺寸等因素,对实验钢理想临界直径进行计算,发现理想临界直径的变化趋势与末端淬火实验结果相吻合。

结构钢端淬曲线预测新方法

端淬试样硬度分布模型采用了含有待定参数-淬透性系数的解析函数,本文定义的钢的淬透性系数与现有合金元素的淬透性系数不同,其大小直接决定端淬曲线的递减速率．端淬曲线的计算预测问题转化成淬透性系数的求解．在端淬实验标准状态下,淬透性系数取决于钢的化学成分．用分部逼近法建立了结构钢淬透性系数与化学成分之间的关系式．将计算获得的淬透性系数代入到硬度分布模型对端淬曲线进行了预测,结果表明预测曲线与实验值吻合很好．

基于梅尼尔模型端淬试样组织分布的预报预测

以梅尼尔组织预报预测模型为基础,通过函数拟合,得到端淬试样不同位置的冷却速度,利用自编的计算机数值模拟预报程序,实现了对端淬试样淬火后组织及其含量分布的预报预测,通过试验对其结果进行了验证,表明预测结果与试验结果吻合,具有一定的可靠性。

铝合金的淬透性及其研究方法

简介钢材的淬透性,以便于我们研究铝合金淬透性时拓宽思路。对铝合金材料的淬透性及其研究成果和研究方法进行了论述。

非线性方程法模型中合金元素交互作用因子的确定

采用试错法及数理统计分析,获得了改进非线性方程法模拟模型中合金元素交互作用因子的数值,并给出其适用范围。通过对国内外文献中给出的300多种结构钢端淬曲线模拟效果的比较,表明这两种方法得到的交互作用因子均可满足工程要求,同时现场试验结果也证明了这一点。

端淬曲线非线性方程法模拟模型中合金化当量公式的修正

采用试错法、数理统计分析及理论分析相结合的方法,对余柏海非线性方程法模拟模型中锰、硼和铬等合金元素的合金化当量公式进行了修正。利用修正后的模型对国内外文献给出的80余种碳素结构钢和单合金结构钢端淬曲线进行了数值模拟,研究表明,模拟曲线与文献给出的曲线吻合的较好。修正后的模型具有较高的可靠性。

ZG30SiMnCr2MoVRE耐磨钢热处理参数的仿真

本文利用材料相图及性能模拟软件JMatPro对新型耐磨钢ZG30SiMnCr2MoVRE进行热力学和相转变的计算，得到合金钢的平衡相组成、等温转变曲线（TTT）、连续转变曲线（CCT）和Jominy淬透性曲线。以此制定合金的热处理工艺方案，结果表明合金在930℃水淬，230℃回火处理，合金的硬度和韧性达到最佳匹配。

钢的端淬曲线优化拟合研究

By using Modified Simplex Method,this paper optimizes the parameters J 0\,E \-s and \%C\-\%f in a mathematical model of the Jominy Curves of Steels.The precision of the model is improved and the residual error is reduced.