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一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．     

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．     

人工神经网络在硼钢淬透性预测中的应用

根据收集和整理的实验数据，建立了硼钢的化学成分与其淬透性之间的非线性人工神经网络模型，用这种方法预测了一些硼钢的端淬值和淬透性曲线，并与用其它经验公式计算的结果进行了比较。结果表明：所建网络能较准确预测硼钢淬透性，这为研究硼钢淬透性提供了一种有效的方法。     

Calculated hardenability for improved consistency of properties in heat treatable engineering steels

Hardenability is one of the most important parameters controlling the heat treated properties of engineering steels. It affects the consistency of response for microstructure, hardness, strength, toughness, and dimensional change (distortion). This study illustrates that a major benefit of controlling hardenability is improving the consistency of dimensional distortion resulting from heat treatment. To facilitate the supply of steels to hardenability limits, especially restricted hardenability, a new technique was developed for the prediction of Jominy hardenability from chemical composition. The technique, termed the “Database Method,” uses measured Jominy hardenability and chemical composition data, contained in a database, to calculate the hardenability for a query composition. Using up to ten known steels, selected from the database with compositions closely matching that of the query steel, a small adjustment is made to the measured hardenability of each known steel allowing for the small difference in composition between the query and chosen steel. The final calculated result for the query steel is taken as the average of the various estimates. The basis of the Database Method is explained, and the advantages are illustrated for selecting engineering grades.     

Case hardenability at high carbon levels

Loss of hardenability in the case was thought to be responsible for a lower than specified hardness found on a large carburized bushing. Pseudo Jominy testing on several high hardenability carburizing grades confirmed that hardenability fade was present at carbon levels above 0.65% and particularly for those steels containing molybdenum. Analysis of previous work provided a formula for calculating Jominy hardenability at various carbon levels. Again the results confirmed that the loss of hardenability was more severe in steels containing molybdenum.     

基于人工神经网络的结构钢端淬曲线预测系统模型的研究

利用人工神经网络技术建立了结构钢端淬曲线预测系统的数学模型,该模型覆盖了较大范围的钢种,系统除了能对已训练过的钢种的端淬曲线准确描述外,还能在一定精度范围内对新钢种的端淬曲线进行预测.本文还研究了训练步数、训练数据量对模型预测精度的影响.     

Hardenability testing of steels when gas quenching is applied

Abstract

The common test for assessing hardenability is the standardised Jominy end-quench test according to ASTM-A255 or DIN-EN 50191. This test is applied essentially for non-alloyed and low alloyed structural steels, when quenched in liquid quenchants, but it is not applicable for high alloyed (air hardening) steels, because the cooling rate at the opposite end of the Jominy specimen is higher than the critical cooling rate of those steels. Today there is no a standardised method to test and evaluate the hardenability of high alloyed steels. Nowadays, not only high alloyed steels, but also some low alloyed structural steels are quenched by high pressure gas quenching (HPGQ) in vacuum furnaces. Obviously there is need from one side to develop a standardised method for testing and evaluation of hardenability for high alloyed steels when they are gas quenched, and from the other side to establish a database for hardenability of low-alloyed structural steels when they are quenched in vacuum furnaces by HPGQ, i.e. at different high pressures and different flow velocities. Corresponding equipment that can be used to satisfy both requirements is discussed.     

Estimation of Hardness During Heat Treatment of Steels

Metal Science and Heat Treatment - A hardness model employing the end quench Jominy method is developed for steels C25, EN8, EN19, EN31 and EN24. The time-temperature data are obtained from four...     

THE EFFECT OF BORON AS A FUNCTION OF AUSTENITISING TEMPERATURE

奥氏体化温度对硼钢淬透性的影响,从实验结果得到,在各种热处理条件下均随温度的提高逐渐降低。氧化及氮化的因素对硼钢淬透性的下降是有一定的影响,但硼原子本身在奥氏体中的分布情况对淬透性的影响是更重要的一个因素。 在渗硼试样中观察硼化合物的形成,指出,从高奥氏体化温度直接淬火后,硼的沉淀物是在奥氏体晶界上及晶粒内均匀分布的,但在等温处理、正火处理或慢冷试样中,硼化合物大部份沉淀在奥氏体晶界上。因此,硼钢在高温奥氏体化后失去良好淬透性的原因,可能是由于硼原子从奥氏体晶界上的回扩散作用,使晶界上得不到足够的硼原子降低晶界能,引起硼的效能暂时的消失。     

Development of microalloyed high-carbon steels for plough disks

Plough disks are often made of high-carbon steels with small additions of chromium (0.40 to 0.60%), in the as-quenched and tempered condition. As a consequence, they combine wear resistance with the tensile, fatigue, and impact strength necessary to withstand extremely adverse work conditions. In an effort to produce steels for this use with improved mechanical properties, four different steel compositions, all microalloyed with niobium, were produced for the present work. Two steels kept the basic chromium content of the commercial alloy (0.40 to 0.60%), while this element was replaced with manganese in the other two steels. The chromium and manganese steels were produced with two levels of niobium. The Jominy hardenability, tensile properties, and impact and wear resistance of these materials were evaluated. A microstructural characterization was also performed. The results show that the developed steels can have the required hardness and strength levels. The high-niobium steels showed the best wear resistance but the poorest impact toughness. The wear resistance of the low-niobium steels was slightly higher and the impact toughness slightly lower than in the commercial alloy. The low-niobium steels show potential for commercial use.     

The optimum content of boron in steel

Boron microalloying of steel allows the manufacturer to increase its hardenability or decrease the content of alloying elements. Boron steels have a wide application range, but the optimum boron content that would ensure maximum hardenability of boron steels has not been strictly determined. In this paper, the effect of the boron content (0.000005 – 0.005%) on the hardenability of low-carbon and low-alloy steels is investigated.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 24–26, January, 1995.     

Experimental studies on bulk tempering of 34CrNiMo6 steel

The class of steels for hardening and tempering, alloyed with chrome, nickel and molybdenum, standardized in Europe (four steel grades), USA (10 grades) and Russia (9 grades) is highly diversified and is especially interesting in the production of machine parts having an extremely large range of dimensions. The heat treatment features of these steels are particularly attractive: high bainitic hardenability and a good temperability etc. The correlation between the hardness achieved after high tempering on products made from these steels, their equivalent diameter and the heat and time parameters of tempering can be explained by means or Jominy samples test for products with equivalent diameters equal to or less than 100 mm, or by the results obtained through the method of simulation of oil cooling (Pavaras-Gheller method) for products with equivalent diameters higher than 100 mm. In this paper, based on experimental results, these correlations are customized for a steel group representative as is 34CrNiMo6.     

Promising Sparingly Alloyed Boron-Bearing Steels for the Production of High-Strength Fasteners

The main advantages of boron-bearing steels used for production of rolled sections at cold upset shops of Russian automotive plants are considered. A thermodynamic model for the majority of boron-bearing steels for high-strength fasteners is used to plot nomograms characterizing the effect of titanium, aluminum, nitrogen, and boron on the amount of nitrides and oxides segregated in crystallization and on the content of effective boron. The effect of effective boron on the characteristics of hardenability is estimated. The studies conducted are used for determining the range of permissible contents of titanium and aluminum ensuring through hardenability of rolled bars from steels 12G1R, 20G2R, and 30G1R up to 25 mm in diameter. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 51 – 55, May, 2005.     

Calculation of the hardenability of boron steels

Boron is a chemical element that affects astrongly the hardenability of structural steel The property of boron to increase hardenability has led to the creation of numerous boron-containing steels. At present, the main difficulties in their production have been overcome and the necessary experimental material for calculating the mechanical properties, including hardenability, has been accumulated. The standard J-406SAE describing a method for calculating the hardenability of boron steels has been issued in the U. S. The present work concerns the possibility of applying the method to domestic steels.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 19–22, March 1995.     

The Jominy end quench for light-weight alloy development

The Jominy end quench test is well known as a method of measuring hardenability in steels. In nonferrous alloys, there is a desire to determine the effect of quenching on final properties after heat treating. The Jominy end quench test offers a method for studying many quenching conditions with a minimum of samples. The potential for developing a new understanding of the complex response of nonferrous alloys to processing conditions, especially quenching, will be presented. Examples of the properties measured on Jominy end quench specimens of aluminum and titanium alloys will be presented.     

改善中碳Cr-Mn-Si钢淬透性的合金化研究

借助于传统的末端淬火试验方法研究了添加Mo、Mo+B和Mo+Ni对改善中碳Cr-Mn-Si钢淬透性的有效性。结果表明,中碳Cr-Mn-Si钢及分别添加Mo、Mo+B和Mo+Ni时形成粒状贝氏体相变倾向较大,端淬试样空冷端即形成粒状贝氏体,因此端淬曲线上无法得到符合SAE J406标准的理想临界直径(D_I)等淬透性定量信息。然而,端淬曲线的硬度与微观组织对应关系证明添加Mo、Mo+B和Mo+Ni均可降低粒状贝氏体相变倾向,增大马氏体形成能力,从而改善淬透性。虽然添加Mo+B时抑制粒状贝氏体相变、改善淬透性的效果明显,但易受钢中的冶炼残留Al和N的影响,而添加Mo+Ni复合改善淬透性的作用更具优势,且不受钢中的冶炼残留Al和N的影响,因此添加Mo+Ni成为改善中碳Cr-Mn-Si钢淬透性优选的合金化方向。     

人工神经网络在金属热处理中的应用

人工神经网络是一种能获得输入和输出之间相互关系的信息处理技术。在金属热处理中，人工神经网络已用于预测钢的ＴＴＴ曲线、ＣＣＴ曲线、Ｍｓ点、淬透性曲线等方面。     

The Effect of Hardenability Variation on Phase Transformation of Spiral Bevel Gear in Quenching Process

The hardenability of gear steel is dependent on the composition of alloying elements and is one of important criteria to assess process of phase transformation. The variation of hardenability has to be considered in control of the microstructures and distortion during gear quenching. In this paper, the quantitative effect of hardenability has been investigated on phase transformations of spiral bevel gears in die quenching. The hardenability deviation of 22CrMoH steel was assessed by using Jominy test. The dilatometry experiments were conducted to build phase transformation kinetic models for steels with low and high hardenability, respectively. The complete die quenching process of spiral bevel gear was modeled to reveal the significant difference on microstructures and temperature history with variation of hardenability. The final microstructures of the gear are martensite in surface layer after quenching process. There are bainite inside the gear tooth and the mixture of bainite and ferrite inside gear for the gear with low hardenability. The microstructure is bainite inside the gear with high hardenability.     

Calculation of hardenability of structural steels from their chemical composition

Although there are a few methods for calculating hardenability of steels, only two or three of the Russian production plants use them. Other plants find them inapplicable, because of the substantial differences between calculated and experimental results. A data bank on hardenability compiled from 5000 heats of various structural steels and five years of tests on the mathematical model created from the data allowed specialists from the USA to create a J-406 SAE standard for calculating the hardenability of steels. Within an accuracy of ± 10%, the method gives an ideal critical diameter of the structural steels included in the standard. This paper presents a method for calculating hardenability of Russian structural steels, which has been developed on the basis of the American J-406 SAE.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 19–24, January, 1995.     

中碳结构钢淬透性的两种预报方法的比较研究

采用三层反向传播(BP)人工神经网络(ANN)技术建立钢淬透性预测预报的数学模型,基于Visual Basic编程语言建立了中碳结构钢淬透性的BP-ANN预测预报系统.将其对45、35Mn2、48CrMnMo、30CrMnNiMo钢的预报结果与近年来发展的改进型非线性数学模型所得结果以及对应的试验数据进行了比较研究,发现BP-ANN预测预报系统可以根据钢的化学成分较准确地预测钢的端淬试验各个距离点处的硬度值,但是各点处预报结果之间相不关联,且难以与钢的端淬显微组织建立有机联系;而改进型非线性数学模型可以较好地预报整条端淬曲线,辅以梅尼尔(Maynier)模型还可对各点处对应的显微组织进行预测预报.将两种模型结合使用来对钢材的淬透性进行预测预报,则有望进一步提高预测预报结果的可靠性.