BEHAVIOUR OF Ti IN AS-CAST MEDIUM MANGANESE AUSTENITIC STEEL

The majority of Ti is found to be preferentially precipitated in the form of TiC from medium manganese steel melt.The TiC may contribute to the heterogeneous nuclei of fine austenite crystallization,to the retardation of dislocation movement as well as to pile-up and proliferate the dislocations,thus,the matrix of the as-cast steel will be effectively strength- ened.It was also found that the TiC can be acted as the heterogeneous nuclei of the nodular eutectic carbide formation and caused the dispersion o fan abundance of the carbide in the interstices between austenite dendrite arms.

Effects of Rare Earths on Toughness of 31Mn2SiRE Wear- Resistance Cast Steel

The toughness of 31Mn2SiRE wear-resistance cast steel were increased by means of RE compound modification and high temperature austenitizing. The results show that the microstructures can be refined, needle and network ferrite are eliminated, the dislocation density and the quantity of dislocated martensite are increased remarkably, and the shape and distribution of inclusions are improved by the addition of RE. Therefore, the mechanical properties of the modified steel can be greatly increased, especially the toughness (αK) by 44%, yield strength (σs) by 10%, and elongation (δ5) by 42%.

Influence of carbon content on wear resistance and wear mechanism of Mn13Cr2 and Mn18Cr2 cast steels

By means of impact abrasion tests, micro-hardness tests, and worn surface morphology observation via SEM, a comparison research based upon different impact abrasive wear conditions was conducted in this research to study the influence of different carbon contents(1.25 wt.%, 1.35 wt.%, and 1.45 wt.%) on the wear resistance and wear mechanism of water-quenched Mn13Cr2 and Mn18Cr2 cast steels. The research results show that the wear resistance of the Mn18Cr2 cast steel is superior to that of the Mn13Cr2 cast steel under the condition of the same carbon content and different impact abrasive wear conditions because the Mn18Cr2 cast steel possesses higher worn work hardening capacity as well as a more desirable combination of high hardness and impact toughness than that of the Mn13Cr2 cast steel. When a 4.5 J impact abrasive load is applied, the wear mechanism of both steels is that plastic deformation fatigue spalling and micro-cutting coexist, and the former dominates. When the carbon content is increased, the worn work hardening effect becomes increasingly dramatic, while the wear resistance of both steels decreases, which implies that an increase in impact toughness is beneficial to improving the wear resistance under severe impact abrasive wear conditions. Under the condition of a 1.0 J impact abrasive load, the wear mechanism of both steels is that plastic deformation fatigue spalling and micro-cutting coexist, and the latter plays a leading role. The worn work hardening effect and wear resistance intensify when the carbon content is increased, which implies that a higher hardness can be conducive to better wear resistance under low impact abrasive condition.

Influence of carbon content on microstructure and mechanical properties of Mn13Cr2 and Mn18Cr2 cast steels

In this paper, a comparison study was carried out to investigate the influence of carbon content on the microstructure, hardness, and impact toughness of water-quenched Mn13Cr2 and Mn18Cr2 cast steels. The study results indicate that both steels' water-quenched microstructures are composed of austenite and a small amount of carbide. The study also found that, when the carbon contents are the same, there is less carbide in Mn18Cr2 steel than in Mn13Cr2 steel. Therefore, the hardness of Mn18Cr2 steel is lower than that of Mn13Cr2 steel but the impact toughness of Mn18Cr2 steel is higher than that of Mn13Cr2 steel. With increasing the carbon content, the hardness increases and the impact toughness decreases in these two kinds of steels, and the impact toughness of Mn18Cr2 steel substantially exceeds that of Mn13Cr2 steel. Therefore, the water-quenched Mn18Cr2 steel with high carbon content could be applied to relatively high impact abrasive working conditions, while the as-cast Mn18Cr2 steel could be only used under working conditions of relatively low impact abrasive load due to lower impact toughness.

As-cast Medium Mn Steel with Nodular Carbide Modified by Y-base Heavy RE Compound

1.IntroductionMedium Mn steel was developed be-cause the wear resistance of Hadfield steel(Mn13)is poor under low or medium im-pact and extrusion abrasion[1-4].In theforegoing investigations[2-4]we found thatwith the increase of C content,theneedle-like and network carbide in mediumMn steel increased(as shown in Fig.1(a)and(c)).Although its wear resistance was largelyimproved,its impact toughness was greatlydecreased.In order to increase toughness,along-term high temperature heat-treatmentwas needed.But the treatment caused cracks

Ⅲ代高锰钢组合辙叉研发

针对普通整铸型高锰钢辙叉存在铸造缺陷、使用寿命低等问题,设计研发了高质量、高使用寿命、低维护成本、维护便捷的新型Ⅲ代高锰钢辙叉。通过优化冶炼工艺,突破了传统铸造技术瓶颈,大幅提升了铸造钢坯的力学性能;引入组合辙叉制造理念,创新了铸造辙叉产品结构,提高了使用寿命,同时也满足了在线更换需求。验证结果表明,Ⅲ代高锰钢组合辙叉养护维修成本较前代产品降低50%以上,最高使用寿命(通过总重)达8.0亿t,提高了2~3倍以上。

SILICON EFFECTS ON THE NODULIZING OF CARBIDES IN AS-CAST MEDIUM MANGANESE STEELS

Water toughening is generally required for the widely used manganese-system wear-resistant cast steels (0.9-1.4 % C, 5.5-14.0% Mn). The purpose of the treatment is to get rid of the needle-like carbides and carbide networks in the as-cast state,

重载铁路75 kg/m钢轨12号单开道岔铸锻式高锰钢组合辙叉研制

设计速度160 km/h及以下铁路道岔大多采用固定型辙叉,固定型辙叉分为高锰钢辙叉、合金钢组合辙叉2大类。辙叉用高锰钢按成型工艺划分为铸造和锻造2种方式:铸造高锰钢可能存在缩孔、缩松、夹杂物等缺陷,辙叉使用寿命相对较短;锻造高锰钢通过锻压工艺弥合了缩松、缩孔等缺陷,其组织致密,能更好地发挥高锰钢材料韧性强的优良特性,辙叉使用寿命远超铸造高锰钢。锻造高锰钢辙叉使用效果良好,但造价过高,为了兼顾使用寿命与成本,从结构设计、焊接工艺等方面开展研究,以铸造高锰钢辙叉为基体,在心轨小断面上焊接锻造高锰钢材料,通过铸造和锻造的有机结合延长辙叉寿命,为相关应用提供参考。

镶嵌翼轨锻造合金高锰钢组合辙叉研制

时速160 km/h及以下铁路道岔大多数采用固定型辙叉,固定型辙叉分高锰钢辙叉和合金钢组合辙叉两大类。辙叉用高锰钢从成型工艺分铸造和锻造两种方式,铸造高锰钢基体有时存在缩孔、缩松和夹杂物缺陷,产品寿命相对较短。基于合金化锻造高锰钢辙叉制造技术,兼顾制造成本和工艺,对组合辙叉结构进行创新研究,研制60 kg/m钢轨18号单开道岔镶嵌翼轨锻造合金高锰钢组合辙叉,具有较好的市场价值。

含氮高锰钢铸造过程快速凝固方法研究

从两方面提出了高锰钢铸造过程快速凝固方法以提高钢中氮含量。通过计算钢水开始凝固温度、降低过热度,建立了高锰钢从浇铸到凝固释放热量公式模型;提出了采用热导率更高的型砂、在砂模中添加冷却装置、浇铸过程中添加冷钢等加速钢水冷却的方法,并分析了影响铸件凝固时间的因素。结果表明:铸造砂热导率对铸件凝固时间的影响最大,其次是强化冷却,而过热度的影响最小。通过改善铸型冷却性能和悬浮铸造的方法可以显著缩短钢液凝固时间,有效抑制凝固过程氮的逸出,显著提高高锰钢中氮含量。

Microstructure and Impact Wear Resistance of TiN Reinforced High Manganese Steel Matrix

A high-manganese austenitic steel matrix （Mn13） composite reinforced with TiN ceramic particles was synthesized by means of Vacuum-Evaporation Pattern Casting （V-EPC）. The composite microstructure and interface bonding of TiN/matrix were analyzed utilizing optical microscope （OM） and X-ray diffraction （XRD）. The effects of different volume fraction of TiN on impact wear resistance were evaluated by MLD-10 impact wear test. The results showed that TiN was evenly distributed in composite layer and had a good interface bonding with matrix when the volume fractions of TiN were 27% and 36% respectively. However, cast defects and TiN agglomeration occurred when the TiN volume fraction increased to 48~. Compared with high-manganese austenitic steel （Mnl3）, the im- pact wear resistance of the TiN-reinforced composite is better. In small impact load conditions, composite layer can effectively resist abrasives wear and TiN particles played an important role in determining impact wear resistance of composite layer. In large impact load, the synergistic roles of spalling of TiN particles and the increase of work hardening of Mn13 based material are responsible for impact wear resistance.

高锰钢辙叉模型跟趾端一体化设计与应用

高锰钢辙叉是铁路轨道中的关键部件,国内采用砂型铸造组芯造型的方法获得锰叉铸件,而组芯造型经常会产生许多铸造问题。本论文通过将锰叉木模跟趾端模型设计成一体化结构,直接取消模型跟趾端芯盒,成功实现了锰叉铸造生产线自带芯一体成形,并进行了生产验证。

铸造孔洞对辙叉应力应变场的影响

利用同步辐射三维断层扫描技术获取了铸造辙叉心轨内部的孔洞形貌信息,建立了无孔洞辙叉、含有规则椭球形孔洞辙叉以及复杂形貌铸造孔洞辙叉的有限元模型,对比研究了孔洞形貌以及孔洞深度对辙叉最大VON Mises应力和塑性应变的影响。结果表明,尺寸为Φ220μm的微小孔洞虽然对辙叉的应力、塑性应变分布形式不造成显著影响,但孔洞附近产生严重的应力、应变集中;并且与规则椭球形孔洞模型对比,含铸造孔洞模型由于缺陷形貌的不规则变化,将引起更加严重的应力、应变集中现象;随铸造孔洞所处深度增加,辙叉模型的最大应力、塑性应变集中值逐渐减小;当孔洞处于8 mm深度处,辙叉最大应力、塑性应变值与无孔洞模型相近。

厚大高锰钢铸件微裂纹形成机理研究

以高锰钢组合辙叉心轨铸件为研究对象,分析了厚大(厚度大于120mm)高锰钢铸件微观裂纹形成机理。通过金相显微镜和扫描电镜(SEM)观察,发现微观裂纹沿晶界分布,并且在裂纹周围富集大量的氧化物、碳化物和低熔点磷共晶。铸件凝固过程中的拉应力使得微观裂纹在这些氧化物、碳化物和低熔点磷共晶处萌生。因此,凝固过程中的拉应力及这些夹杂物的存在是厚大高锰钢铸件形成微观裂纹的主要原因。

Ti在铸态奥氏体锰钢中的作用

Ti在铸态奥氏体中锰钢中主要以TiC的形式存在。由热力学计算和透射、扫描电镜观察及相结构分析与微区成分分析证实:TiC可以在液态中锰钢中优先生成,做为奥氏体结晶的非均质核心,细化奥氏体晶粒,阻碍位错运动,造成了位错的塞积与增殖,有效地强化了基体。并发现TiC做为团球状共晶渗碳体的非均质核心,使团球状共晶渗碳体大量弥散地分布于奥氏体晶间。

新型抗磨锰钢的研究

通过优化成分、适当的合金化及炉前变质等措施，得到了一种成本低、韧性好、加工硬化能力强，进而在非强烈冲击工况下具有高抗磨性的铸态奥氏体锰钢．

铸造复合变质及表面合金化中锰奥氏体钢的强韧化

通过铸造表面合金化和复合变质处理 ,使中锰奥氏体钢的强度、韧性和表面硬度显著提高。结果表明 ,复合变质剂使钢的力学性能σb、σs、αk、HV分别提高了 45 %、43%、2 63%和 1 1 %;氧化物总量从原来的 0 .0 35 %降到 0 .0 0 7%,硫化物总量从原来的 0 .0 2 9%降到 0 .0 1 %,夹杂物圆度从 1 .43变为 1 .0 4 ;Nb N和 Nb2 C可作为奥氏体锰钢的异质结晶核心。经铸造表面合金化 ,钢的表面可形成厚度为 7.2 mm、硬度为

变质中锰耐磨钢与铸态水韧节能热处理

对中锰耐磨钢首先通过变质处理，获得了晶粒细小、缺陷较少、成分偏析较小的优良一次结晶组织，然后再采用铸态水韧热处理工艺，不仅节能效果显著，而且获得了较高的冲击韧度和耐磨性能，其综合经济技术效益十分显著。

铸态锰钢中的碳化物

对铸态锰钢中的碳化物作了研究 .铸态锰钢中有两类碳化物 :一类是凝固时生成的弥散分布在基体上的团球状碳化物 .另一类是在塑性变形时 ,在应变马氏体形成以前 ,优先析出的呈弥散分布的细小颗粒 .这两类碳化物一起构成了铸态锰钢组织中的第二相硬质点 .这些硬质点和细化的奥氏体晶粒的界面都是位错运动的障碍 ,造成了位错密度的提高 。

高锰钢铁路辙叉内部铸造缺陷对使用性能的影响

高锰钢铁路辙叉是铁路钢轨的关键部件,在使用过程中承受强烈的冲击和摩擦作用,其表面发生龟裂剥落而失效。通过对辙叉断口的电子扫描、内部裂纹和铸造缺陷的光学观察分析表明,高锰钢铁路辙叉表面的龟裂是由组织中存在的铸造缺陷引起的;裂纹在铸造缺陷处萌生,并且沿着这些缺陷密集处和辙叉表层加工硬化产生的滑移带的方向扩展;辙叉内部的铸造缺陷主要是沿晶界析出的非金属夹杂物和缩松。提出了设计合理的冒口、通入惰性气体或能产生这类气体的盐类、采取有效的脱氧工艺等措施,减少高锰钢铁路辙叉中的铸造缺陷,从而延长其使用寿命。