The influence of retained austenite (RA) stability on the impact abrasive wear and underlying mechanisms in bainitic steel remains insufficiently understood. In this work, the impact abrasive wear behavior of a bainitic steel was systematically investigated, with a focus on the RA stability. The tempering-induced microstructural evolution was characterized by SEM, TEM and EBSD, while RA stability was quantified via interrupted tensile tests combined with XRD-based determination of the strain-dependent RA volume fraction. The results indicated that under high impact loads, material loss was dominated by micro-fatigue induced spalling. During wear, RA underwent strain-induced phase transformation, which simultaneously provided transformation-assisted surface hardening and induced local volume expansion that alleviated stress concentration and retarded crack initiation and propagation. In contrast, excessively stable RA suppressed transformation-induced strengthening, thus providing limited improvement in the wear resistance. In addition, subsurface work hardening associated with ultrafine-grained layers and the blunting of abrasive particles by cementite further contributed to improved wear resistance after tempering. These findings provide new insights into the role of retained austenite in controlling the impact wear mechanisms of bainitic steels and offer reference for microstructural design of wear-resistant materials.

Silicon significantly affects the formation of carbide and nano-bainite structure, thus affecting the wear resistance of the alloys. To clarify the effect of silicon content on the microstructure and wear resistance of high vanadium wear-resistant alloys (HVWA), three silicon contents (0.66 wt%, 2.14 wt%, 5.17 wt%) were designed in HVWAs, and nano-bainite matrix was obtain through isothermal quenching process at low temperature. The vanadium carbides(VC) are distributed in nano-bainite matrix. The number of pellet/agglomerate VC in HVWAs increased and the number of strip/chrysanthemum VC decreased with increasing silicon content. The thickness of bainite ferrite strip and thin film retained austenite gradually decreases with the increase of silicon in the alloy, and the thickness of bainite ferrite strips in three alloys is 100-600 nm, 50-450 nm and 50-350 nm, respectively. When the silicon content is 2.14 wt%, the alloy has excellent comprehensive mechanical properties and wear resistance. Compared with other two alloys, the impact toughness of alloy with 2.14 wt% Si was improved by 10.2 % and 151.8 % respectively, and the wear weight loss was decreased by 35.4 % and 60.1 % under the conditions of 2.387 MPa wear load and 48 mu m abrasive size. Due to a larger amount of high hardness pellet/agglomerate VC and significantly refined nano-bainite matrix which can efficiently resist abrasive scratches, the alloy with 2.14 wt% Si obtains superior toughness and wear resistance.

Isothermal hot compression experiments were conducted on 12Cr2Mo1V steel to investigate the hot deformation behavior at the temperature range of 900-1200 degrees C and the strain rate range of 0.01-5 s-1 by using a Gleeble-1500D thermo-mechanical simulator. Microstructural evolution was characterized using optical microscope, electron backscatter diffraction, and transmission electron microscope analysis. Results demonstrate that increasing temperature and decreasing strain rate generally promote dynamic recrystallization (DRX) while reducing geometrically necessary dislocation (GND) densities. However, at 1200 degrees C with a constant strain rate of 0.1 s-1, as well as at 1150 degrees C with strain rates of 0.1-0.01 s-1, GND densities exhibited an anomalous increase due to the formation of subgrains evolved from dislocation cells. According to the measured true stress-strain data, the hot processing maps were constructed, identifying the optimal workability window at 1170-1200 degrees C and 0.01-0.1 s-1. The constitutive model was constructed based on Hansel-Spittel model and incorporated into FORGE (R) software to perform the finite element simulations on the hot deformation process of 12Cr2Mo1V steel. The predicted force-displacement curve results agree well with the measured curves, verifying the dependability of the Hansel-Spittel constitutive model for describing the rheological behavior of 12Cr2Mo1V steel during hot compression. With the increase of temperature, the variation of equivalent strain within the sample reduced, which is beneficial to obtain homogenous microstructure.

In order to get the heavy section ductile iron gear casting, segmented manufacturing was carried out during production. With the help of the numerical simulation software, high-quality pig iron, pure scrap steel and strengthen inoculation were used to obtain qualified castings, which has accumulated valuable experience for the production of ductile iron gears of the same specification.

采用原位法制备出(W&Ti)C复相颗粒增强高铬铸铁基复合材料,研究了增强颗粒对材料显微组织和磨损行为的影响规律.结果表明:与高铬铸铁相比,复合材料显微组织中WC和TiC颗粒的存在使其洛氏硬度(HRC)从55提高到70.在磨损过程中,高铬铸铁靠近磨损表面的M7C3型碳化物在磨料的反复作用下会产生裂纹并向基体内部扩展.破碎的碳化物更容易脱落,无法抵抗磨料对材料表面的犁削作用,从而加速材料的磨损.复合材料中相对较软的基体相在磨损时会逐渐被去除,磨损表面会暴露出大量WC和TiC颗粒.表面凸起的增强颗粒会承受来自磨料的主要破坏作用,进而有效地保护周边的基体材料.对比发现,在相同磨损条件下复合材料的磨损性能提高了 1倍以上.

半自磨机内部钢球的运行轨迹和抛落点受到磨机转速、衬板高度、提升面角等因素影响,部分钢球会直接冲击筒体衬板.半自磨机大型化使衬板的服役条件急剧恶化,对衬板的结构强度、材料强韧性和耐磨性提出了更高的要求.依据大型半自磨机衬板设计经验,结合衬板专业设计软件及三维扫描分析技术,对提升条排数等结构设计参数进行了系统分析;对比了几种广泛使用的耐磨材料在大型半自磨机高频次、高能量冲击条件下的匹配性,提出了合理的选材建议.

尾架是高压压铸机的重要部件之一,重16.8 t、最大壁厚大于400 mm.通过数值模拟软件优化铸造工艺,采用喂线法球化处理,多级孕育处理,试制了厚大断面球墨铸铁尾架铸件.结果表明,尾架铸件各项力学性能均达到了QT500-7材料标准的要求,铸件质量完全满足无损检测技术要求.

由于矿石性质和磨机工艺参数存在较大差异,衬板的磨损受到多方面因素的影响,磨机内不同仓位衬板的磨损速率也存在较大差异.为了掌握衬板磨损规律从而指导衬板更换和衬板优化设计,通过 3D 激光扫描分析技术,将磨机衬板的磨损状态转化为云点数据,对处理后的云点数据与标准模型进行对比,获取较为准确的磨损系数和规律.依据磨损规律对不同仓位衬板的结构进行合理优化,在节约金属用量、提高衬板使用寿命的同时,实现寿命匹配.

通过真空实型铸造工艺(V-EPC)在ZG45钢表面制备不同含钒量的高铬合金复合层,采用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分析了含钒量对铸渗层组织的影响,使用洛氏硬度计和冲击磨损试验机研究了钒含量对硬度和耐磨性的影响.研究表明,铸渗层组织主要由α-Fe与α-Fe+M7 C3+VC共晶组织组成,过渡层内各合金元素成梯度分布,C、Cr、V元素自铸渗层向基体发生了扩散,且C、Cr、V元素的分布与碳化物的分布高度重合.随着钒含量的增加,晶粒逐渐细化,共晶碳化物数量逐渐增多,VC也增多,铸渗层硬度和耐磨性显著提高.热处理后有大量二次碳化物析出,随着铸渗层中钒含量增加,热处理后二次硬化效果显著提高.

随着技术进步和工业发展,支承件的需求量逐渐增多,装备制造业的大型化、重型化促使其组成部件逐渐向大型化方向发展,加上球墨铸铁自身的成本优势和性能特点,机床、平台、横梁等支承件越来越多地采用球墨铸铁材料.列举了厚大断面球墨铸铁在机床、平台、装备领域中的应用实例,指出了厚大断面球墨铸铁在这些领域的发展要结合产品的结构特点和要求,充分挖掘厚大断面球墨铸铁自身优势,强力推进厚大断面球墨铸铁支承件的发展.

针对铜矿湿磨工况下,半自磨机衬板顶端提升条早期断裂的失效行为进行了研究.采用X射线衍射仪(XRD)、光学显微镜(OM)、扫描电镜(SEM)及显微硬度计等分析了衬板提升条和底端处材料的相组成和组织形貌特征,讨论了上述两处材料的磨损机理和裂纹的萌生、扩展行为.结果表明:衬板的冲击磨损机理为疲劳剥落和显微切削,其中顶端提升条处疲劳剥落和显微切削都较明显,而底端则以显微切削磨损为主.衬板使用过程中,顶端提升条长期受到较大的冲击磨损作用,亚表层发生形变而硬化.受形变和夹杂物共同影响,裂纹在形变层内夹杂物周围萌生,随后向基体内部扩展,最终导致衬板断裂.提高衬板用钢熔炼质量,减少衬板夹杂物,并在保证衬板高硬韧性前提下,进一步提高衬板用钢的韧性,将是提高半自磨机衬板使用寿命的必要条件和主要路径.

根据国内某铜矿大型半自磨机实际运行状况,针对磨机运行期间筒体衬板开裂、磨矿效率低及运营成本较高等问题,基于Milltraj半自磨机介质抛落轨迹计算技术,结合实际设计经验,对半自磨机筒体衬板结构进行了改进和优化.生产应用结果表明,磨矿处理量大幅提升,综合运营成本显著降低,取得了较好的应用效果.

本文针对低碳贝氏体钢在服役过程中存在的化学成分和热处理工艺系统尚不完善的问题,从化学成分和热处理工艺两方面出发,通过控制材料C质量分数分别为:0.38％、0.43％、0.48％,Si质量分数分别为:1.0％、1.5％、2.0％,等温淬火温度分别为270℃、310℃和340℃,研究了成分和工艺对低碳合金贝氏体钢组织和性能的影响规律.结果 表明:随着碳含量升高,低碳合金贝氏体钢的冲击韧性不断下降,硬度不断上升;随着Si含量的升高,实验钢的冲击韧性呈上升的趋势,而硬度则呈下降的趋势;实验钢经过等温淬火处理后,碳质量分数为0.43％硅质量分数为1.5％,等温温度为310℃时,其综合力学性能最优.

介绍了厚大断面球铁托轮的铸造工艺及其生产实践.采用数值模拟预测铸造缺陷,依据模拟结果调整冒口、冷铁布局;采用优质生铁、纯净的废钢及合理的球化温度和浇注温度,获得了无缺陷、组织良好、力学性能优异的托轮铸件.

立式搅拌磨是一种高效、节能的超细磨设备.作为立式搅拌磨的重要组成部分,螺旋衬板的使用性能和寿命直接影响立式搅拌磨的磨矿效率和能耗.通过合理选材、细化生产工艺,获得了质量优异的螺旋衬板铸件.

分析了矿山耐磨材料的一般性选材原则,如工艺流程、碎磨设备、磨损规律、衬板结构、材料性能和生产成本等,介绍了国内耐磨材料的研究及应用现状,重点分析了其在自磨机、半自磨机等矿山设备的应用局限性,并对矿山耐磨材料的未来发展方向进行了展望.

随着磨机大型化,衬板使用寿命问题变得愈加突出.介绍了影响磨机衬板使用寿命的各种因素,包括磨机类型及规格、磨机转速、物料和磨球填充率、矿石属性、衬板结构及衬板材料等.分析发现,只有综合考虑各种影响因素,才能有效提高大型磨机衬板的使用寿命.

对国内某大型铁矿湿式工况条件下大型半自磨机筒体衬板进行磨损失效分析.采用化学分析法,对试样进行成分分析、硬度测试、微观组织分析、磨损面及亚表层显微硬度及磨损形貌分析,讨论了该工况条件下衬板的磨损失效机理.结果表明,长时间在钢球、磨料冲击和摩擦的共同作用下,大型半自磨机合金钢衬板的失效是由冲击和磨料磨损的交互作用造成的,且主要磨损失效机制为显微切削和疲劳剥落.

介绍了大型耐磨合金钢衬板的工艺优化实践.通过调整化学成分、合理设计热处理工艺,获得了各项指标优异的衬板铸件.结果表明,在整个寿命周期内,1#材质衬板的平均磨损率 0.528mm/万 t,4#材质衬板的平均磨损率0.496mm/万 t.经估算,4#材质衬板处理矿量可提高 6.38％.

重100 t、最大壁厚>165 mm的Z字形球墨铸铁平台结构复杂、技术指标要求高,铸造难度大.通过合理设计铸件生产工艺,利用模拟软件进行铸造工艺模拟,合理使用冷铁和保温冒口,选用优质原辅材料、喂线法球化处理和适度强化孕育处理,获得了质量合格的Z字形球墨铸铁平台铸件.铸件检测结果表明:各项力学性能均达到了QT400-18AR材料标准要求,铸件质量满足无损检测技术要求.