Microstructure and mechanical properties of Hadfield steel matrix composite reinforced with oriented high-chromium cast iron bars

To obtain a compatible material of high hardness and high toughness, Hadfield steel matrix was reinforced by oriented high-chromium cast iron bars. The mechanical behaviors of the as-cast and water-quenched composites were comparatively studied with a Hadfield steel substrate. The experimental results showed that the alloy powders inside the flux-cored welding wires could be melted by the heat capacity of Hadfield steel melt and became high-chromium cast iron bars. The impact toughness of the water-quenched composite was higher than that of the as-cast composite and lower than that of the Hadfield steel. The wear rate of the water-quenched composite was 1.23 mg/h m² at 0.3 kg and 2.93 mg/h m² at 1.2 kg, which was lower compared with those of the as-cast composite and Hadfield steel. The impact toughness and wear resistance of the water-quenched composite were related not only to the combining actions of the Hadfield steel matrix and high-chromium cast iron bars but also to the effect of heat treatment. The wear behavior of the water-quenched composite was industrially tested as pulverizer plate.     

Effect of welding wire and groove angle on mechanical properties of high strength steel welded joints

Mechanical properties of high strength steel welded joints strictly depend on the welding process, the filler material composition and the welding geometry. This study investigates the effects of using cored and solid welding wires and implementing various groove angles on the mechanical performance of weld joints which were fabricated employing the gas metal arc welding process. It was found that weld joints of low alloy, high strength steels using low alloy steel cored welding wires exhibited higher tensile strength than that of low alloy steel solid wire and chromium‐nickel steel bare welding wire when the method of gas metal arc welding is employed. The effect of groove angle on the strength and toughness of V‐groove and double V‐groove butt‐joints was investigated. V‐groove joints, with higher tensile strength than double V‐groove joints in the whole range of groove angles, were superior in toughness for small groove angles, but impact toughness values of both joints were comparable for large angles. The effect of heat input and cooling rate on the weld microstructure and weld strength was also investigated by performing thermal analysis employing the commercial software ANSYS. It was concluded that cooling rate and solidification growth rate determined the microstructure of the weld zone which had great consequences in regard to mechanical properties.     

双液金属复合耐磨板厚度对复合层组织和性能的影响

利用双液铸造液膜连接工艺制备大平面的低碳钢/高铬铸铁耐磨板。采用SEM,EDS对复合层进行组织观察及成分分析。结果表明:不同厚度的复合板从低碳钢侧至高铬铸铁侧可以分为低碳钢→珠光体过渡层→复合层→高铬铸铁过渡层,双金属复合层完全实现了冶金结合。通过对复合层区域进行显微硬度分析,从低碳钢至高铬铸铁侧的显微硬度在345~1260HV范围梯度分布。复合层的显微组织主要为γ-Fe+粒状碳化物。高铬铸铁过渡层奥氏体组织呈现垂直复合层方向的树枝状生长,并随着耐磨板厚度的增加,奥氏体生长的方向性逐渐消失。根据低碳钢的温度变化初步建立了相关的温度场数学模型。     

Investigations on the Cast Boron Steel Guide Roller and Its Application in Steel Wire-Rod Mill

A new type of abrasion-resistant cast boron steel was developed based on the service conditions of the guide roller in the high-speed steel wire-rod mill. The lath martensite was its matrix and the broken Fe₂B and dispersive distributed TiB₂ were its wear resistant skeleton. The tensile strength, hardness, and impact toughness of cast boron steel quenched at 1000°C excel 750 MPa, 54 HRC, 14 J/cm², respectively. The guide roller made of this steel has high strength and wear resistance and excellent thermal fatigue resistance and it is reliable to use in the high-speed steel wire-rod mill. Its service life is 1.133 times longer than that of cast high chromium nickel alloy steel and corresponding to that of the sintered-carbide.     

A study of self‐hardening bainitic cast steel

Bainitic cast steel is a kind of wear resistant material which has high strength and toughness, and can usually be obtained by isothermal quenching or molybdenum alloying. However, isothermal quenching has lower production efficiency and molybdenum alloying has higher production cost. In this paper, according to the characteristics that manganese and boron elements delayed the pearlitic transformation, the authors developed a new type of self‐hardening bainitic cast steel in which manganese and boron were main alloy elements and a small amount of titanium, nitrogen, calcium, barium and yttrium elements were also added in the steel that could refine and purify the solidification structure of steel. On this basis, the author studied the effect of tempering treatment on microstructures, mechanical properties and wear resistance of bainitic cast steel. The results showed that impact toughness of bainitic cast steel increased ceaselessly with the increase of tempering temperature, and there was tempering brittleness while tempering from 450°C–500°C. Moreover, the hardness of bainitic cast steel decreased with the increase of tempering temperature, and hardness decreased slowly and maintained at 55HRC or above when tempering temperature was lower than 300°C. Under the condition of two‐body pin‐on‐disc wear, the wear resistance of bainitic cast steel decreased with the increase of tempering temperature, but bainitic cast steel tempering at 300°C had excellent wear resistance in the condition of impact wear. In the practical use, the bucket teeth of excavator and the hammer of crusher making from self‐hardening bainitic cast steel were safe and reliable, and their service life were increased by 120–150% than Hadfield manganese steel.     

铸造C12A耐热钢的焊接及组织与性能的研究

本文对铸造C12A高强耐热钢进行了组织与性能、可焊性、焊缝组织变化厦性能特点等方面进行了研究分析。试验结果表明：淬火组织为板务马氏体＋部分针状马氏体＋少量残余奥氏体，其硬度比较高，塑性和韧性不是很好；淬火＋回火组织为保留马氏体形态的回火索氏体，其硬度不是很高，塑性和韧性比较好，具有盘好的综合性能；退火组织为铁素体，其硬度低，塑性和韧性高；焊接后的全相组织中，没有焊接裂纹等焊接缺陷存在，具有良好可焊性。对于淬火＋回火后的铸造C12A耐热钢，经过焊接，基体组织和性能没有明显发生变化，过渡区的金相组织为板条马氏体＋奥氏体组织，其硬度有所降低；熔化区的金相组织为针状马氏体＋奥氏体＋板条马氏体，硬度很高；焊后经过回火处理的基体佥相组织与性能没有变化。过度区的金相组织为保留板条马氏体形态的回火索氏体组织，较基体组织要粗大，其硬度要比基体有所下降；熔化区的金相组织转变为保留板每马氏体的回火索氏体，但组织较为基体组织要细小，其性能表现为硬度要比基体的有所升高。铸造C12A焊接后再经回火处理，可使焊接后的组织差别消除；性能变化趋于平缓，有利于材料的使用。     

A Study of Modification of M2 Cast High Speed Steel

M2 cast high speed steel was inoculated by addition of rare earth(RE)‐Al‐N, network eutectic carbides were eliminated, matrix structures were refined and the segregation of tungsten and molybdenum elements were relieved. In the condition that the hardness did not decrease, impact toughness obviously increased. Quenching at 1180 °C and three‐times tempering at 560 °C, the hardness of M2 cast high speed steel kept 65~66HRC, impact toughness reached 21.3J/cm². Modified M2 cast high speed steel had excellent thermal fatigue resistance and high temperature wear resistance. Roll made in modified M2 cast high speed steel had excellent service effect using in slit rolling mill stand of hot rolling bar mill.     

Influence of carbon diffusion on microstructure and wear behaviour of duplex stainless steel surface layers on lamellar grey cast iron

Surface welding with duplex stainless steel was performed to enhance the wear and corrosion properties of grey cast iron, which is used as material for applications as pump components in maritime and chemical environments. The method used for surface welding and the corresponding process parameters determine the chemical composition and microstructure, which both determine the corrosion and wear properties of the surface layer. High heat input leads to high chemical dilution and thus, reduced corrosion resistance. Slow cooling rates, which are recommended for welding of grey cast iron components, facilitate the formation of carbides in the fusion zone of the chromium‐rich duplex stainless steel surface layer. On the one hand, carbides lead to increased hardness and thus, improved wear resistance of the surface layers. On the other hand, carbides and high chemical dilution rates reduce the corrosion resistance and therefore should be avoided. Under high cooling rates, the risk of cracking in the heat affected zone of the grey cast iron increases due to martensitic phase transformations. The paper describes the correlation of process parameters, microstructure and chemical composition with a focus on carbon diffusion and carbide formation, ever considering the effect on the wear behaviour in an oscillation tribometer and under erosion‐corrosion conditions.     

冲击磨损工况下铁基耐磨材料的现状及发展

在破碎、研磨、挖掘等机械设备上,因其常常受物料的冲击磨损,导致耐磨件快速失效,每年耐磨件消耗量很大,如何实现耐磨性和经济效益的有机统一是人们关注的问题。而耐磨材料也在不断地发展,从第一代钢铁耐磨材料Mn13到第三代钢铁耐磨材料高铬铸铁,再到陶瓷颗粒增强复合材料,以应对不同磨损工况。冲击磨料磨损是一种较为复杂的磨损工况,要求材料具有较高的硬度,同时材料还要保持一定的韧性以抵抗冲击力。针对冲击磨损工况下铁基耐磨材料,介绍了国内外耐磨材料的发展现状,概述了从高锰钢到复合材料,再到复合结构的发展过程,总结了复合材料从基体的选择到增强颗粒的选择,及多种颗粒混合增强的研究进展,重点对陶瓷颗粒增强铁基复合材料及复合结构进行了较为全面的介绍,从软质基体包嵌硬质单元和硬质基体包嵌强韧网络单元两种复合方式进行分析,并对未来复合结构技术的发展进行展望。     

WC_p/高锰钢基复合材料及复合结构的冲击磨损性能

采用挤压铸造法制备出WC_p/高锰钢基复合材料和复合材料-钢复合结构,研究复合材料和复合结构的冲击磨料磨损性能。在复合结构的WC预制体中及周围添加还原Fe粉,以控制复合结构中复合材料-钢的界面结构。结果表明:复合结构中复合材料-钢的界面在还原Fe粉吸热熔化的作用下,并没有出现复合材料中WC的熔解和形成过渡层的现象。复合材料磨损表面发生材料的崩落,耐磨性低于高锰钢,而复合结构耐磨性比高锰钢提高了1.34倍。通过对磨损形貌及组织的分析,讨论了复合材料崩落的原因及复合结构对冲击磨料磨损改善的机理。     

无压渗透法制备铸造表面复合材料

提出用无压渗透法制备铸造表面复合材料的新方法。通过预先制备带有孔隙的硼铁合金 预制块, 用普通浇注的方法, 获得以灰铸铁为基的铸造表面复合材料。复合层从化合物层到亚共晶 层的厚度达8 mm , 其组织和硬度由表层向基体呈梯度分布, 表面化合物及过共晶层的耐磨性优于 Cr12 型高铬铸铁。      

Microstructure,mechanical properties and high stress abrasive wear behavior of air-cooled MnCrB cast steels

Three medium carbon low alloyed MnCrB cast steels containing different Cr contents (0.3%, 0.6%, and 1.2%) were designed and the effect of Cr contents on the microstructure, mechanical properties and high stress abrasive wear behavior of the cast steels after 850 °C air-cooling and 220 °C tempering was studied. The results show that the hardenability of the MnCrB cast steels was excellent. The microstructure of the cast steels with low Cr contents (0.3% or 0.6%) consists of granular bainite and lower bainite/martensite multiphase. With increasing of Cr content, the formability of martensite was improved, the hardness and wear-resistance increased, but the impact toughness decreased in that more bainite was replaced by martensite. The air-cooled MnCrB cast steel containing 0.6% Cr, with granular bainite and lower bainite/martensite multiphase, exhibited excellent combination of strength, hardness, ductility, and impact toughness. In addition, its abrasive wear-resistance was 30% more than that of Hadfield cast steel in the high stress abrasive wear condition. This air-cooled MnCrB cast steel by simple alloying scheme and heat treatment has the advantages of high-performance, low cost, and environmentally friendly. It is a potential advanced wear-resistant cast steel for low- or even medium-impact abrasive conditions.     

Evaluation of effect of chromium on wear performance of high manganese steel

Abstract

The effects of elements such as Ni, Mo, Cr, Cu, and V on the wear behaviour of high manganese steels have been reported extensively. Most researchers agree on the influence of many of the elements but disagree on the effect of Cr. A study has been conducted to evaluate the effect of 1.7 and 2.3 wt-Cr on high manganese steel when subjected to various wear conditions: impact loading, abrasion, combined impact-abrasion, and combined abrasion-corrosion. The study has revealed that adding Cr to high manganese steel resulted in an increase in hardness and hardenability, and a decrease in toughness. The effect on wear resistance was found to depend on the wear conditions. Chromium alloyed high manganese steels showed superior wear resistance compared with plain Hadfield steels where corrosion, abrasion, and combined impact-abrasion conditions prevailed. Such conditions required a high surface hardness. Plain Hadfield steel showed superior wear resistance in conditions where pure impact wear is encountered. Such conditions required an increase in toughness rather than surface hardness.     

热处理对高铬铸铁基蜂窝陶瓷复合材料耐磨性的影响

通过传统重力浇注工艺,用高铬铸铁金属溶液铸渗ZrO2增韧Al2O3(ZTA)陶瓷颗粒蜂窝状预制体,从而获得高铬铸铁基蜂窝陶瓷复合材料。将复合材料在930℃、980℃、1 030℃、1 080℃温度下淬火,并分别在230℃、330℃、430℃、530℃时回火,研究了热处理条件对高铬铸铁基蜂窝陶瓷复合材料组织及三体磨料磨损性能的影响。研究结果表明:在相同回火温度条件下,随着淬火温度的升高,复合材料硬度升高,其耐磨性也随之升高;在相同淬火温度条件下,随着回火温度的升高,材料的硬度及耐磨性能也随之升高,两者达到一定温度后其硬度及耐磨性都下降,材料耐磨性与材料的硬度变化趋势一致。最终得到复合材料的最佳热处理工艺为:1 030℃×2h,空冷+530℃×0.5h。     

Improvement of toughness of high chromium white cast iron: duplex ferritic-austenitic matrix

It is attempted to enhance the impact toughness of industrially used high chromium white cast iron (WCI) without sacrificing wear resistance. The microstructure is engineered by cyclic annealing to obtain features such as duplex grain matrix, where austenite envelops ferrite grain, refined M₇C₃ carbide. The newly cast and heat-treated alloy shows remarkable impact toughness i.e. 13J with improved wear resistance. The fracture micro-mechanism is studied through extensive scanning electron microscopy and it is ascertained that enhanced impact toughness results from crack arrest at duplex grain boundaries. A few other toughness enhancing features are also discussed. The results are compared with standard ASTM grade Class-III high chromium WCI and are found to be encouraging.     

粉末烧结法和铸造法制备ZrO2增韧Al2O3陶瓷颗粒增强高铬铸铁基复合材料及其耐磨性能

将粒径为1~2 mm的ZrO₂增韧Al₂O₃陶瓷颗粒(ZTA_p)、高铬合金粉末和黏结剂混合真空烧结制备蜂窝状预制体,再浇注高铬铸铁液制备出ZTA_p增强高铬铸铁基复合材料。采用SEM、EDS、XRD分析复合材料的界面微观结构和物相组成,通过三体磨损试验评价复合材料的耐磨性能。结果表明,烧结高铬铸铁基体在铸造过程中发生重熔,与铸造高铬铸铁基体呈冶金结合,ZTA_p与金属基体界面结合致密,无裂纹、气孔等缺陷。复合材料三体耐磨性能达到高铬铸铁的3倍以上。将该复合材料应用于制备磨辊件,经过5 000 h服役,柱状区和复合区在磨辊半径方向上的磨损量分别为8.2 mm、5.9 mm,预计寿命可达到高铬铸铁磨辊的2倍以上。      

TiCp/Cr15高铬铸铁复合材料的制备与性能

以TiC_p粉末和水雾化Cr15高铬铸铁粉末为原料,采用粉末冶金液相烧结技术制备TiC_p增强高铬铸铁复合材料。研究了TiC_p含量对高铬铸铁的物相组成、显微组织和力学性能的影响。研究结果表明,全致密的TiC_p增强高铬铸铁基体复合材料的构成相为TiC、M₇C₃型碳化物、马氏体和少量奥氏体;随着TiC_p添加量增大,金属基体逐步呈孤岛状,并在其中析出越来越多的M₇C₃型碳化物,同时TiC_p逐步呈连续网状分布;同时,其硬度稳步提升,而抗弯强度和冲击韧性降低。当TiC_p添加量为20wt%时烧结态复合材料具有最佳综合力学性能。此时硬度为HRC 66.8 ,冲击韧性为6.86 J/cm2,抗弯强度为1 343.10 MPa。当TiC_p添加量为25wt%时硬度达到最大值HRC 67.20 。      

稀土变质处理对耐磨高铬铸铁组织性能的影响

本文采用稀土变质荆对高铬铸铁进行变质处理,通过OM和SEM测试观察高铬铸铁变质处理前后及热处理前后的形貌及微观组织,并通过硬度、冲击韧性及磨损量测试研究变质和热处理对其力学性能的影响。结果表明：高铬铸铁在经过稀土变质处理后组织细化,网状碳化物破碎成孤立块状,硬度、冲击韧性及耐磨性提高;经过950℃-1000℃正火处理后,碳化物进一步破碎,在奥氏体基体上析出弥散的二次碳化物,进一步提高了高铬铸铁的硬度、韧性和耐磨性能。     

Investigation of wear resistance and microstructure of a newly developed chromium and vanadium containing iron‐based hardfacing alloy

Plasma transferred arc (PTA) welded Ni and Co‐based alloys have gained high acceptance in many industrial applications for the wear protection of components. Recently, the cost of nickel and cobalt is rising drastically. This paper presents the development of a cost‐effective high chromium and vanadium containing iron‐based hardfacing alloy with high hardness and wear resistance. The welding processing of the alloy is carried out by PTA welding of atomized powders. Investigations on powder production as well as on weldability are presented. The coatings are metallographically studied by optical microscopy, SEM, EDX and micro‐hardness measurements. The wear resistance properties of the coatings are examined using pin on disk, dry sand rubber wheel and Miller testing, the corrosion properties are determined by immersion corrosion tests. The newly developed iron‐based alloy has nearly the same wear resistance as Ni‐based alloys with fused tungsten carbides at a higher level of corrosion resistance and much lower cost.     

高铬白口铸铁干滑动摩擦磨损特性的研究

研究了两种碳化物 ((Fe,Cr) 2 3 C6型碳化物和 (Fe,Cr) 7C3 型碳化物 )和 3种基体组织 (共析组织、马氏体组织和奥氏体组织 )的高铬白口铸铁与淬火 4 0Cr钢对磨时的干滑动摩擦磨损特性。试验结果表明 ,与(Fe,Cr) 2 3 C6型碳化物相比 ,(Fe,Cr) 7C3 型碳化物有利于提高高铬白口铸铁的耐磨性 ,降低其摩擦系数 ;在高接触应力情况下 ,与马氏体和奥氏体基体的合金相比 ,共析组织基体的合金具有更大的摩擦系数 ,其耐磨性也更好。