锻轧机辊环的研究与应用

1.辊环化学成分设计 (1)碳 碳是提高材质硬度和耐磨性的重要元素。碳能较多地溶于奥氏体(A)中,增大奥氏体向马氏体转变后的硬度,形成高碳马氏体,以提高基体的硬度和抗磨性。碳含量对共晶碳化物(K)的体积百分数有很大影响,提高碳量,K量也相应增加,从而可进一     

一种析出强化型Fe-C-Mn-Ni奥氏体合金钢的微观组织和力学性能

对Fe-C-Mn-Ni-X(X为铬、钒等元素)奥氏体合金钢锻材进行固溶和时效处理,研究了时效温度(650,700,750℃)和时效时间(0～25h)对合金钢显微组织与力学性能的影响。结果表明:固溶态和时效态合金钢显微组织形态相差不大,时效处理后,合金钢中析出大量与奥氏体基体呈共格或半共格位向关系的纳米VC相;固溶态合金钢表现出很强的时效硬化能力,随时效温度升高,硬度达到峰值的时间缩短,峰值硬度降低;时效处理后,合金钢的屈服强度和抗拉强度显著增加,断后伸长率和加工硬化指数则明显下降,拉伸失效模式由韧性断裂转变为韧脆混合断裂;随时效温度升高和时效时间延长,合金钢的强度有所降低,但加工硬化能力增强。     

残余奥氏体量对高钒高速钢滚动磨损性能的影响

对不同热处理下的高钒高速钢，采用X射线衍射仪测量其残余奥氏体量，利用滚动磨损试验机测量其耐磨性，分析了残余奥氏体量对其力学性能及滚动磨损性能的影响。研究结果表明：高钒高速钢成分为3.04C，8．80V，3．87Cr，2．98Mo时，热处理对基体的显微组织的影响主要表现为马氏体和残余奥氏体的相对变化量上；残余奥氏体量增加，其滚动耐磨性升高，并呈开口向上的二次曲线关系，但耐磨性数据波动范围明显加大；残余奥氏体量与硬度呈开口向下的二次曲线关系，与冲击韧性近似呈直线关系。在本试验条件下，综合考虑残余奥氏体量对其滚动耐磨性、耐磨性数据波动范围及力学性能的影响，残余奥氏体量以45％～55％（体积分数）为宜，其相应的淬火温度为950～1050℃，回火温度为450～550℃。     

复层化学成分和显微组织对瓦楞辊性能的影响

研究了C、Cr、W、Mo、V和Nb等合金元素和显微组织对堆焊瓦楞辊力学性能的影响。结果表明：随共晶体种类和体积百分数的增多，堆焊层的硬度增高，但抗生降低；决定准焊层硬度的首要因素是基体组织，特别是奥氏体的数量，其次是碳化物的数量。高合金堆焊条可使瓦楞辊的齿面硬主高于60HRC，耐磨性提高4和8倍以上。     

含钒耐磨堆焊合金的组织与性能

通过在Fe-Cr-C自保护金属芯堆焊焊丝中加入不同含量的钒（钒的质量分数分别为0.73%,2.3%,3.1%,4.1%）,研究了钒对Fe-Cr-C堆焊合金微观组织、硬度及耐磨性的影响。试验结果表明,随钒含量的增加,堆焊合金组织的基体由奥氏体向奥氏体＋马氏体转变,当钒的质量分数超过4%时,基体组织全部转变为马氏体;随钒含量的增加,堆焊合金组织中的初生碳化物由长条状、粗大直边六角状转变为球状或不规则形状,基体中析出大量弥散分布的二次碳化物;随钒含量的增加,堆焊合金的硬度和耐磨性亦相应提高。     

深冷处理对W4Mo3Cr4VSi钻头性能影响的实验研究

研究深冷处理对高速钢钻头硬度、耐磨性的影响,结果表明,深冷处理可以改变高速钢钻头的显微组织结构.通过显微图(SEM)观察发现,深冷处理促使残余奥氏体向马氏体转变,并在马氏体基体上析出弥散分布的微细碳化物,从而提高了钻头的硬度和耐磨性,钻头使用寿命提高2～4倍.     

模具修复梯度耐磨堆焊层组织性能研究

提出了采用“母材 过渡层 耐磨层”的复合堆焊修复方法。工艺试验表明,通过打底焊过渡层的方法可以有效防止堆焊出现的裂纹。金相显微分析表明,采用Cr-Mo-W-Nb系耐磨堆焊焊条的堆焊合金组织为马氏体基体 残余奥氏体 碳化物,基体上分布的碳化物使堆焊层具有强的耐磨性。性能测试结果表明,堆焊表面平均硬度达到HRC60.1,完全满足模具材料硬度要求,硬度梯度分布合适,堆焊层耐磨性为母材的7.58倍。     

高铬铸钢轧辊的热处理工艺及其组织和硬度

通过SEM、EDS、XRD分析及硬度测试,研究了高铬铸钢轧辊热处理奥氏体化温度和保温时间对轧辊组织和硬度的影响规律,并确定了轧辊的热处理工艺。结果表明:随着奥氏体化温度升高和时间延长,轧辊基体中的铬含量增加,硬度先升后降;随温度升高和时间缩短,残余奥氏体增多;1 030℃奥氏体化保温1.5 h空冷淬火,520℃回火保温时间10～30 min热处理后,轧辊的组织均匀、硬化效果好,硬度达到了740～760 HV。     

石墨钢的热处理及其耐磨性能

本文研究了一定成分(1.2%C,1.55%Si,0.6%Mn,0.04%S,0.03%P)的石墨钢在铸态及不同规范热处理后的耐磨粒磨损性能。结果指出,铸态的耐磨性最低;正火和780℃退火后870℃加热再150℃等温淬火的最耐磨.超过了经淬火及200℃回火的常用犁铧钢65Mn。150℃及200℃等温淬火后,具有最高的硬度(HRC62～63);而综合机械性能以300℃等温淬火为最好。根据金相组织和硬度值,论述了基体组织及硬度对钢的耐磨性的影响。证实了组织中有一定量残余奥氏体存在时,虽然降低了硬度,却提高了钢的耐磨性。     

20钢的奥氏体氮碳共渗及稀土对共渗的作用

本文介绍20低碳钢经不同温度氮碳共渗后渗层的组织、硬度及耐磨性能,并探讨了渗剂中添加稀土的工艺。结果表明:经650℃奥氏体氮碳共渗的20钢,表面具有良好的抗咬合性和耐磨性,心部又具有较好的强度及韧性;稀土在奥氏体氮碳共渗中具有催渗作用,使渗层增厚,耐磨性略有改善.     

RESEARCH AND APPLICATION OF AS-CAST WEAR RESISTANCE HIGH CHROMIUM CAST IRON

ＲＥＳＥＡＲＣＨＡＮＤＡＰＰＬＩＣＡＴＩＯＮＯＦＡＳＣＡＳＴＷＥＡＲＲＥＳＩＳＴＡＮＣＥＨＩＧＨＣＨＲＯＭＩＵＭＣＡＳＴＩＲＯＮＬｉｕＪｉｎｈａｉＬｉｕＧｅｎｓｈｅｎｇＬｉＧｕｏｌｕＨｅｂｅｉＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙＷａｎｇＫｕ...     

含碳量对20%Cr合金氧化和高温磨损性能的影响

对不同含碳量的20%Cr合金进行了900℃大气气氛下的抗氧化性试验,测定了在此温度下的氧化动力学曲线,并在自制的高温磨损试验机上进行了800℃的高温磨粒磨损试验。用扫描电镜及电子探针分析和测定了氧化、磨损面的形貌及其亚表层的组织及成分分布。试验表明,随含碳量增加,氧化过程由良性的外部氧化转向恶性的内部氧化,从而使合金的抗氧化性下降。合金中共晶碳化物（Cr,Fe）7C3在高温下有较高的硬度和稳定性,因此,合金含碳量的增加,提高了800℃时的抗磨性。在高温磨损过程中由于基体组织的变形而使碳化物折断。因此,基体抵抗变形的能力将对利用碳化物来提高合金的抗高温磨损性能起到重要的作用。     

介稳奥氏体锰钢耐冲击磨粒磨损性能及磨面组织

利用冲击磨粒磨损试验结合扫描电镜、透射电镜和穆斯堡尔谱等分析手段研究了介稳奥氏体锰钢的耐磨性和磨损机制。结果表明,介稳奥氏体锰钢在某一冲击功下具有最佳耐磨性。在磨损过程中磨面诱发生产两类马氏体,无碳马氏体和合金马氏体。最耐磨时的磨面组织为合金奥氏体和无碳马氏体的混合组织。     

The Role of Reversible Martensitic Transformation in the Wear Process of TiNi Shape Memory Alloy

It has been established that the superelastic effect of TiNi alloy is related to a reversible martensitic transformation; that is, stress-induced transformation. The high elastic recovery of TiNi alloy has made it a potential candidate for high wear resistance applications. In the present study the tribological behavior of superelastic TiNi alloy was studied and compared to Ni, Ti, and AISI 304 stainless steel using dry sliding wear and friction tests. The effect of normal load and testing temperature on superelasticity has been investigated. It has been found that although AISI 304 stainless steel and superelastic TiNi alloy have similar hardness, TiNi exhibits superior wear resistance. The wear rate of AISI 304 stainless steel is over four times higher than TiNi. The superior wear resistance of TiNi and the effect of load and temperature on wear were discussed and related to the reversible martensitic phase transformation, as well as self-accommodation and stabilization of martensite.     

WEAR AND SEALING CHARACTERISTICS OF ENGINE VALVE GUIDE

0 INTRODUCTIONWith the increment in requirements for diesel engine reliabiity and particle emissions standards, reducing valve guide wealowering particle numbers and decreasing the SLC become important issues in engine design. All these factors are affect…     

Study on relative wear resistance and wear stability of high-speed steel with high vanadium content

In this work, a new concept of wear stability was put forward by authors, and it was quantitatively expressed by factor of wear stability. Different hardness, impact toughness and retained austenite content high-speed steel with high vanadium content samples were obtained by varying heat treatment conditions. The effects of hardness, impact toughness and retained austenite content on relatively wear resistance and wear stability were studied under abrasive wear condition. Results show that relative wear resistance increases with increasing hardness or decreasing impact toughness, whereas the wear stability rises with the increasing of hardness or impact toughness. The analyzing results reveal that mechanical behaviors are only apparent factors to influence wear behaviors. Relative wear resistance substantially depends on retained austenite content (Ar). At retained austenite content of about 30 vol.%, the relative wear resistance is optimal. However, wear stability is scarcely influenced by retained austenite content, which depends on the maximum changing amount of retained austenite under certain condition (ΔAr) in essence. With increasing ΔAr, wear stability linearly decreases.     

Effect of retained austenite on rolling element fatigue and its mechanism

Experiments were carried out on a rolling contact fatigue testing machine with two rollers as specimens which were made of the commercial steel 18Cr2Ni4WA. Various treatments are conducted to obtain rollers with different amounts of retained austenite. The experimental results show that the contact fatigue resistance of the specimen with the largest amount of retained austenite is much better than that of the specimen with the smaller amount of retained austenite. It is considered that the precipitation particles from austenite, the deformation-induced martensite, the beneficial alteration of the residual stresses and the toughness of the austenite are the main reasons for the high contact fatigue resistance of this steel.     

Effect of microstructure and properties on the high temperature wear characteristics of 3Cr2W8V (H21) steel

The effects of microstructure on the high temperature wear characteristics of 3Cr2W8V steel, the high temperature wear mechanisms and the features of the worn surface have been investigated by means of a resistance-heating high temperature wear-testing device of our own design. It has been shown that the primary parameters affecting the high temperature wear behaviour of the material seem to be the precipitated carbides and austenite grain size in the microstructure, high temperature hardness and oxidation resistance of the material. The optimum high temperature wear resistance of the steel can be obtained by employing suitable quenching and tempering temperatures. The wear test temperature vs. wear value curves for this steel, heat treated using different heat treatment regimes, are similar in shape and different from each other in wear value. However, the wear mechanisms of this steel vary with temperature ranging from room temperature to 700 °C. Although in the range 400–700 °C all the scars are primarily composed of a number of grooves and varying degrees of built-up layered areas, the presence of these layered areas reduces the high temperature wear.     

Simulation of roller guide wear in a high temperature test rig

Simulation of roller guide wear in rod or wire rolling mills has been performed in a high temperature test rig where the specimen rollers are in intermittent contact with the periphery of a heated rotating steel disc.By varying the time in contact during each cycle and deliberately superimposing a sliding component on the rolling contact, three components of guide roller wear were separated and quantified. The dominant component is wear due to sliding at the contact surface during rolling, followed by the isolated contribution from absolute rolling, while wear during roller acceleration is of less importance.Surface studies and the observed linear increase in wear vs. number of test cycles together with the linear increase in wear rate with normal force clearly show that abrasion by disc oxides is the dominant wear mechanism at elevated temperatures. The influence of disc temperature on the operating wear mechanisms as well as the resulting wear are also evaluated.A quantitative classification of four guide roller materials, a high chromium tool steel, two grades of high chromium cast iron and a cermet, has also been made. The hard cermet, containing about 50 vol.% titanium carbides, proved to be the outstanding material in roller guide applications.     

钴基合金-碳化钨复合涂层材料耐磨性能的研究

采用真空熔烧法制得钴基合金—碳化钨复合涂层材料,借助扫描电子显微镜、X射线衍射仪等先进的测试手段对涂层的组织结构和表面形貌进行观察分析。应用盘销式摩擦磨损试验机对不同碳化钨质量分数的复合涂层材料和淬火态45钢进行了磨损试验。结果表明:在相同试验条件下,复合涂层的耐磨性显著高于淬火钢,且其耐磨性随碳化钨质量分数的增加而提高:淬火钢的耐磨性随着载荷的增加迅速降低,而复合涂层的耐磨性则变化不大。