离子渗钨钼手用锯条齿部合金层含碳量的研究

经理论分析及试验研究，提出了双层辉光离子渗钨钼手用锯条齿部合金化层含碳量的确定方法，导出渗碳时计算齿部合金化层含碳量的经验公式，通过淬火，回火及切削试验选了了离子渗钨钼手用锯条齿部的最佳含碳量。     

Al-Zn-Mg-Cu合金淬透性研究进展

Al-Zn-Mg-Cu合金密度小,比强度高,具有良好的加工性能,是现代航空航天武器装备等领域发展的关键结构材料.但是对于大型结构件,该系铝合金表现出一定的淬火敏感性.综述了Al-Zn-Mg-Cu合金淬透性研究方法和影响该系铝合金淬透性的因素.其中淬透性研究方法包括:端淬-硬度试验法测定铝合金淬透层深度、TTP曲线、CCT曲线、TTT曲线、理论计算法以及计算机数值模拟法.并且从合金的化学成分、轧制制度、均匀化制度、淬火制度、时效制度和几何尺寸等方面分析了影响淬透性的因素.     

等离子表面Mo-Cr低合金高速钢的摩擦学特性

为了研究Q235钢表面冶金形成Mo-Cr低合金高速钢的摩擦学特性,利用双层辉光离子渗金属技术,在Q235钢表面进行Mo-Cr共渗,随后进行超饱和渗碳、淬火及回火复合处理.研究结果表明:Mo-Cr共渗层厚度在100 μm以上,表面Mo含量可达20%,Cr含量达到10%,超饱和渗碳表面含碳量超过2.0%,表面成分接近钼系高速钢.淬火及回火后表面硬度达到1300HV,超过一般冶金高速钢.磨损试验表明,摩擦系数随着接触应力的增加而增大,平均相对耐磨性是GCr15渗碳淬火钢的2.2倍.     

咨询与服务

贵刊1996年第6期第37页施友方同志撰写的“钢件渗碳淬火有效硬化层深度测定”一文,在介绍GB9450—88时,认定标准规定“有效硬化层深度测定方法为两种,即:一、显微硬度梯度曲线法;二、校核法.”我理解GB9450—88第四条有效硬化层深度的校核是对显微硬度梯度曲线新确定的DC值的校核,不能理解为两种测量方法.应如何正确解释,望明示.     

55DTi钢复合热处理后的接触疲劳性能及其失效形式

低淬透性钢是把含碳量为0.55—0.7%的优质碳素钢中的 Mn、Si 含量降低,改变脱氧工艺,并加入少量 Ti 作为变质剂以细化晶粒、提高强度、降低淬透性的一种钢材。由于不含 Cr,Ni,Mo 等合金元素,所以成本比20CrMnTi 钢低15%左右,可用于制作拖拉机齿轮,取得了良好的效果。目前我国对低淬钢采用的是高频淬火工艺,它虽能获得一定的硬度,但磨损性能及其它性能低于渗碳钢。本文研究目的是使55DTi 低淬透性钢的性能接近或达到20CrMnTi 的水平。     

20CrNiMo钢零件渗碳表层淬火开裂原因分析

20CrNiMo钢零件经气体渗碳淬火后,在其渗碳区域表面发现裂纹。借助化学成分分析、硬度测试和金相检验对其开裂的原因进行了分析。结果表明:淬火裂纹仅存在于渗碳层中,渗碳表层碳含量过高,渗碳表层存在的大量块状、网状碳化物是零件表层产生淬火裂纹的主要原因。     

20CrMo钢渗碳渗硼再淬火复合处理后的机械性能

本文通过20CrMo钢的渗碳渗硼再淬火复合处理,讨论了渗层的硬度分布和耐磨性能;对渗层的接触疲劳性能进行了对比试验.试验表明,经过渗碳渗硼的复合处理,接触疲劳寿命有显著提高,为牙轮钻头渗碳渗硼新工艺提供了机械性能方面的重要依据.用上述工艺试制了一批牙轮钻头,现场试验表明,钻头使用寿命可提高40～60%.     

渗碳淬火件硬度对淬硬层深度测定的影响

硬度法测定渗碳淬火件的淬硬层深度时,如果硬度不同的零件一律按550HV1的界限硬度测定,测定结果误差較大。应根据渗碳淬火件的表面硬度和基体硬度的高低,对550HV1的界限硬度进行修正,用特定值的界限硬度测定的淬硬深层度才是正确的。     

衬底偏压对CrN／Si3N4纳米多层膜结构和力学性能的影响

采用磁控溅射法在不同基底偏压条件下制备了CrN／Si3N4纳米多层膜,用x射线衍射仪、原子力显微镜及纳米压痕仪表征,结果表明,衬底偏压对CrN／Si3N4纳米多层膜微观结构、界面结构、硬度和磨损性能有重要影响;漂浮电位时,导致多层膜界面粗糙,CrN呈（200）、（111）共同生长,硬度和弹性模量低;当偏压变化时,界面宽度和粗糙度变化不大,硬度和模量变化的主要原因是不同衬底偏压下的晶格畸变导致两层材料弹性模量变化和晶粒尺寸变化。与漂浮电位相比,涂层的屈服应力和断裂韧性有所增强。     

偏压对CrN/Si3N4纳米多层膜结构、硬度和断裂韧性的影响

利用磁控溅射法在不同基底偏压条件下制备了CrN/Si3N4纳米多层膜,分别用X射线衍射仪、原子力显微镜及纳米压痕仪表征多层膜的微观结构及力学性能,结果表明,衬底偏压对CrN/Si3N4纳米多层膜微观结构、界面结构、硬度和磨损性能有重要影响。漂浮电位时多层膜界面粗糙,CrN呈(200)、(111)共同生长,硬度和弹性模量低,有偏压且变化时界面宽度和粗糙度变化不大,硬度和模量变化的主要原因是不同衬底偏压下的晶格畸变导致两层材料弹性模量变化和晶粒尺寸变化。基底偏压的优化有助于改善涂层的屈服应力和断裂韧性。     

Über den Zusammenhang zwischen dem Kohlenstoffgehalt in Stählen und der Härte des Martensits

About the interrelation between carbon content in steels and the martensite hardness The hardenability of steels, identified by the interrelation between carbon content and available maximum hardness in a full martensitic microstructure is important for decision in case of steel selection and optimal construction of components. In the industrial practice formulas for calculation were used, deduced from the classic statements of Hodge/Orehoski and Burns/Moore/Archer. But the calculated results are significantly different. For a more exactly view datas of the “Atlas zur Wärmebehandlung der Stähle” were used. The better results are to expect by using the formula of Just. The application is also important for case hardening. It can be concluded that a lower carbon content than 0,35 mass‐%, the value usual is used, is sufficient to arrive a limit hardness of 52.5 HRC or 550 HV for determination of the case hardening depth. This confirms with the investigations of the AWT‐Fachausschuß 5/AK4. There has been found a formula of interrelation between carbon content and martensite hardness that gives a curve identical with the curve from Burns/Moore/Archer.     

Enhancement of the steel quenching process by an electric field

An electric field is known to be able to increase considerably the heat flux during the boiling process by suppressing the occurrence of film boiling. This field enhancement technique can be applied to the steel quenching process to accelerate the cooling rate and thus increase the effective hardenability of the steel. This report describes a quench experiment performed with an electric field. The effective hardenability (depth of high hardness) of the samples quenched with the field was measured to be significantly higher than those quenched without the field. Examination of the microstructures showed that the application of the electric field increased the depth to which martensite formed in the sample.     

硬度法测定渗氮层深度结果的测量不确定评定及分析

主要以综合评定法对硬度法测定渗氮层深度结果的测量不确定度来源进行了分析,分别讨论了硬度法测定总渗氮层和有效渗氮层深度由于界限硬度值要求不同,导致引入的标准不确定度分量不同,并对每个标准不确定度分量进行了评定。结果表明：在相同试验条件和方法下,硬度法测定总渗氮层深度结果测量不确定度明显小于硬度法测定有效渗氮层深度结果测量不确定度。其原因在于试验测定结果重复性引入的标准不确定度分量是硬度法测定总渗氮层深度结果测量不确定度主要来源;而硬度法测定有效渗氮层深度结果测量不确定度主要来源却是由计算模型中插入的界限硬度值引入的。另外,采用硬度法测定深度,应注意硬度计工作台移动的分度值和垂直度偏差对测量结果的影响。     

热轧对7055铝合金淬透性的影响

为研究热轧对7055铝合金淬透性的影响,采用末端淬火实验、硬度测试、光学显微镜和透射电镜研究了不同冷却速率处合金的组织和性能.实验结果表明:合金热轧后淬透性大大降低,淬透深度由约100 mm降至约45 mm,这主要与慢速淬火时析出的η平衡相的数量和尺寸的改变有关;热轧增加了η平衡相的形核位置,并引入大量的位错,增加了η平衡相的长大速率.因此,热轧合金固溶后慢速淬火时,析出的η平衡相的数量和尺寸都大大增加,时效后形成的η’沉淀强化相数量减少,硬度随冷却速率减小而下降的程度增加,合金的淬透性降低.     

10CrNi3MoV 30C对称双球扁钢淬透性试验研究

通过球扁钢淬透性的测定以及对中频淬火态横截面硬度分布、金相组织与晶粒度的观察评定 ,研究了 10CrNi3MoV 30C双球扁钢的淬透性。结果表明 ,10CrNi3MoV 30C球扁钢的淬透性良好 ,用端淬试验来研究 10CrNi3MoV 30C球扁钢的中频淬火是可行的。     

钢末端淬透性测定的影响因素

通过总结实践得出影响钢末端淬透性测定的因素有试样坯料的制取、热处理操作的准确性、末端淬透性试样的制备、洛氏硬度值的测量和人为因素,并提出操作的方法和技巧,以提高末端淬透性测定的准确性。     

Failure Analysis of a Threaded Pipe Ruptured During Hydraulic Testing

In the present case study, failure analysis of a piping system that ruptured during hydraulic testing has been carried out to find the root cause and determine the mode and mechanism of failure. Chemical composition of the pipe was found to be in compliance with the standard composition of AISI4130. The failure cause of the pipe has been investigated through visual examination, microstructural observation, hardenability analysis, and fractography. Threaded grooves were produced through machining after heat treatment. Variation in hardness and strength through thickness (from case to core) was evaluated using standard hardenability graph. Hardenability analysis showed that the strength of the pipe after machining was still well above the calculated maximum stress at any point of piping system. This finding was further supported by the microstructural study. The actual cause of pipe failure during hydraulic test was found to be due to the stress concentration factor being developed by some notch from improper thread machining which lead brittle failure and was also revealed by fractography analysis.     

Effect of carbon content and microalloying on martensitic hardenability of austenite of dual-phase steel

Abstract

Microstructure maps were constructed for a C–Mn steel and microalloyed steels of the same base composition, after intercritical annealing to produce 23 and 50% of austenite. The critical cooling rates for the transformation to martensite of 90 and 50% of the austenite present were thus determined as functions of the carbon content of the austenite. At the 90% martensite level, the hardenability of the austenite was very similar to that of fully austenitized steel of the same composition, and varied identically with carbon content. At the 50% martensite level, the hardenability of the austenite was considerably greater than that of fully austenitized steel of the same composition. The presence of niobium and vanadium had no effect on the martensitic hardenability of the austenites: by forming carbides they simply altered the carbon content of the austenite at a fixed volume fraction of austenite. It is proposed that the martensitic hardenability of austenite of dual-phase steel depends on the size of the austenite volumes as well as on their carbon content. In the present study, the size of the austenite volumes was large enough to make them more hardenable than would be predicted on the basis of standard hardenability data for fully austenitized steels.

MST/548     

Comparison of hardenability and over-aging precipitation behaviour of three 7xxx aluminium alloys

The purpose of the paper is to compare hardenability and aging precipitation behaviour of three 7xxx aluminium alloys (7150, 7055 and 7056). The hardenability has been studied by Jominy test. The aging precipitation behaviour has been investigated according to their hardness and electrical conductivity after over-aging treatment. The micro-structural characterisation has been observed by scanning electron microscope and transmission electron microscope. These results show that AA7056 has the highest hardenability and sensitivity to over-aging treatment compared with AA7150 and AA7055. The highest w(Zn)/w(Mg) ratio and the lowest Cu content of AA7056 are beneficial for inhibiting quench precipitates and decreasing the stability of meta-stable η′ phase.