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通过落球冲击和滑动磨损试验探讨了站击对高铬铸铁和奥氏体不锈钢耐磨性的影响。结果表明:当基体同为马氏体时,金属型高铬铸铁的耐磨性在冲击前,后都比砂型高铬铸铁好,站击作用使金属型高铬铸铁的耐磨性略有降低而对砂型高铬铸铁的耐磨性影响较大;基体中含有30.8%残余奥氏体对高铬铸铁的耐磨性有利,站击后残余奥氏体的形变和相变对高铬铸殊的耐磨性更有利; 相似文献
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利用自行开发研制的高温滑动磨损与热接触疲劳材料试验机,并运用表面覆膜技术、金相分析和扫描电镜,研究了用于精轧机的高铬镍无限冷硬铸铁轧辊材料在热轧状态下的耐磨特性,分析了这种轧辊材料的表面形貌、表层组织的变化情况。结果表明,当轧制公里数达到88km时,高铬镍无限冷硬铸铁轧辊表面产生了碳化物的浮凸和剥落。 相似文献
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我厂φ280复二重线材轧机,使用轧辊材质低铬钼无限冷硬铸铁,图纸尺寸:辊长1213毫米,辊身直径φ285毫米,辊颈直径φ150_(-0.10)~(0.05)毫米。辊颈装配为单体轴水滑动配合。在轧制中轧辊处于比较恶劣的条件,特别是K_6二扁处,辊颈常受严重磨损,磨损超差一 相似文献
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采用自制的板带高温摩擦试验机模拟实际固溶–冲压–淬火一体化热成形工艺下7075铝合金的高温摩擦过程,分别对上下摩擦头进行冷却和加热以模拟实际热冲压过程对模具和压边圈的冷却和加热,分析了下模加热温度、法向载荷和滑动速度对7075铝合金摩擦行为及磨损机理的影响。结果表明:铝合金摩擦系数随着下模加热温度的升高而增大,磨损机制由300 ℃时的黏着磨损转变为500 ℃时的黏着磨损、氧化磨损和磨粒磨损;施加法向载荷越大,摩擦系数越大,不同载荷下磨损机制均为黏着磨损及轻微的磨粒磨损,且随着载荷增大,黏着磨损程度有所加深;高滑动速度导致了磨损表面局部氧化物的生成,使摩擦系数随着滑动速度增大而减小,滑动速度为30 mm·s?1时,磨损机制主要是氧化磨损、磨粒磨损和黏着磨损。 相似文献
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利用分子动力学模拟研究了WC–Co硬质合金在不同条件下的摩擦过程,分析了晶粒尺寸、摩擦载荷和滑动速率等因素对硬质合金摩擦磨损行为的影响,从原子尺度揭示了硬质合金发生摩擦磨损的微观机制。结果表明,随晶粒尺寸增大,相比于晶粒转动,Co相和WC中的位错滑移逐渐在摩擦引起的塑性变形机制中起主导作用。摩擦载荷增大会导致易变形的Co粘结相被挤出表面而首先去除,通过减小晶粒尺寸可以抑制Co相的挤出–磨损机制,进而提高硬质合金的抗滑动磨损性能。滑动速率升高会降低磨损速率,主要原因是在高速滑动过程中,亚表层各相中位错的形核扩展缺乏持续的驱动应力,位错密度较低,WC不易发生断裂,Co相被挤出表面造成的磨损程度明显减轻。 相似文献
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本文对比研究了烧结、铸造亚共晶高铬铸铁和TM52钢结硬质合金在不同冲击功条件下的抗冲击磨粒磨损性能,利用扫描电子显微镜(SEM)观察分析磨损表面磨损形式及亚表层的微裂纹发展,开展磨损机制的分析探讨。结果表明,采用液相烧结技术制备的高铬铸铁具有优异的抗冲击磨粒磨损性能。烧结高铬铸铁在中、低冲击功条件下耐磨性能均明显优于TM52(4~10倍),在中、高冲击功工况下的耐磨性能相比铸造高铬铸铁提高10倍以上。烧结高铬铸铁的磨损机制主要是显微切削,当冲击功高时还会发生疲劳剥落磨损和脆性碎裂。烧结高铬铸铁中的短杆状M_7C_3型碳化物对金属基体的割裂和应力集中较小,而马氏体为主的基体具有高强韧性,能够有力地支撑和保持其中的碳化物均匀分散,阻滞微裂纹的萌生和扩展。 相似文献
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针对轧钢厂GCr15轴承钢240 mm × 240 mm方坯粗轧阶段轧辊磨损较严重的情况,采用Archard磨损数学模型模拟分析了轧件压下量、轧辊硬度、热传导系数及摩擦因子在一道次成形后对轧辊磨损规律的影响。模拟结果表明,轧辊硬度越高,轧辊抗磨损能力越强;热传导系数对轧辊磨损的影响较小;当摩擦因子f>0.25时,其摩擦因子对轧辊磨损量变化明显;当轧件压下量在△h<50 mm 时,轧件压下量对轧辊的磨损量影响显著。根据所得结果,结合现场轧制工艺和轧辊材质,将使用的球墨铸铁Ⅰ轧辊[抗拉强度≥400 MPa,硬度HRC值40,热传导系数18 kW/(m2·℃),摩擦因子0.3]改成球墨铸铁Ⅱ轧辊[抗拉强度≥500 MPa,硬度HRC值45,热传导系数17kW,/(m2·℃),摩擦因子0.2],并将压下量由70 mm降至50 mm,使轧辊单槽过钢量由优化前10000 t提高至优化后的18000~20000 t。 相似文献
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Sunghak Lee Do Hyung Kim Jae Hwa Ryu Keesam Shin 《Metallurgical and Materials Transactions A》1997,28(12):2595-2608
This is a study of the thermal fatigue property in three centrifugally cast work rolls, i.e., a nickel-grain cast-iron roll (Ni-grain roll), a high-chromium cast-iron roll (Hi-Cr roll), and a high-speed steel roll
(HSS roll). The thermal fatigue mechanism was investigated with a focus on the roll microstructure and the increase in tensile
stress which led the specimen to fracture when it reached the tensile strength. The thermal fatigue test results indicated
that the thermal fatigue property was best in the HSS roll, followed by the Hi-Cr roll and the Ni-grain roll, respectively,
and that the thermal fatigue life of each roll decreased with the increase of the mean temperature or of the temperature range
of the thermal fatigue cycle. The results were then interpreted based on the amount of primary carbides and the cyclic softening
phenomenon associated with the exposed time to elevated temperatures. The coarse primary carbides on the specimen surface
acted as fatigue crack initiation sites, as they cleaved at a low stress level to form cracks. The HSS roll, having the highest
tensile strength and the smallest amount of primary carbides, thus showed better thermal fatigue property than the other rolls.
For the improvement of the thermal fatigue property of the rolls, this study suggests a homogeneous distribution of primary
carbides by reducing the carbide segregation formed along the solidification cell boundary and by optimizing of the roll-casting
process. 相似文献
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试验研究出一种高硫钢自润滑新材料,利用金属硫化物的自润滑减摩作用来提高轧机导辊的使用寿命.从对试验钢的金相结构分析和磨损试验,以及经生产实践,结果表明当硫含量在1.5%时的导辊耐磨性最佳,使用寿命达到了不含硫导辊的2.4倍. 相似文献
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导辊磨损原因分析及改善方法 总被引:2,自引:0,他引:2
通过对导辊工作条件和温度场的分析,找出了导辊磨损过快的原因在于工作时导辊温度过高,提出了以改善冷却条件为导辊磨损过快问题的解决方法。 相似文献
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With a focus on the backup roll,a rolling-contact-fatigue experiment was performed on samples of 5% Cr forged steel.The P-S-N fatigue curves were determined and the fatigue strength was calculated.The emergence of cracks on the test-sample surfaces was observed at different fatigue cycles.A micro-hardness tester was used to measure the hardness of the subsurface fatigue layer.The microstructures were analyzed at various magnifications with an optical microscope,scanning electron microscope,and transmission electron microscope.Based on these tests,the rolling-contact-fatigue mechanism of the large forged steel backup roll was also considered.The results showed that the contact-fatigue strength of the tested backup roll steel was 1 249 MPa;the surface fatigue crack lengthened continuously as the number of cycles increased and followed an S-shaped curve;the subsurface fatigue hardness reached its highest value at about 90 (HV) increment from the matrix hardness of 540 (HV) in the backup roll;the subsurface martensite/bainite microstructure was crushed and the dislocation density was greatly increased.Under alternating contact stresses,the surface/subsurface material was damaged and exhibited many microdefects.At the least,the surface fatigue layer on backup rolls should be fully removed before the microcracks enter a period of rapid propagation. 相似文献