共查询到20条相似文献,搜索用时 13 毫秒
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采用温楔横轧方法制备出表层具有超微细复相组织的高碳珠光体钢棒件,研究了珠光体组织在温变形过程中的演变.结果表明,珠光体组织中的渗碳体片层主要以弯曲扭折的形式协调塑性变形,表现出较强的塑性变形能力;剧烈塑性变形促进了渗碳体片层的球化,表层球化完全的渗碳体颗粒粒径均小于0.2μm;温楔横轧后铁素体基体发生了动态连续再结晶,等轴铁素体平均晶粒尺寸为0.3~0.4 μm,0.5R处和心部的渗碳体球化不完全,铁素体再结晶也不完全;铁素体晶粒的超细化和渗碳体片层的球化明显改善高碳珠光体钢棒件的塑性,温变形过程中应变、应变速率及温度分布的不均匀是引起组织性能差异的根本原因. 相似文献
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利用光学显微镜、电子背散射衍射(EBSD)、落锤试验机等检测方法,对5种轧制工艺试制的大壁厚大口径高强韧X80M管线钢进行了金相组织、有效晶粒度、晶界特性、相分析及落锤撕裂试验(DWTT)性能的对比分析。结果表明,粗轧采用低温轧制,并保证道次压下率及轧后充分再结晶,可以减小奥氏体再结晶晶粒尺寸、提高奥氏体再结晶晶粒均匀性;精轧采用较小道次变形并充分回复后再变形的“回复-变形”的轧制方式,可以提高{112}取向晶粒数量、细化有效晶粒尺寸、增加大角度晶界比例、减少粗大马奥岛的数量和尺寸。采用该粗轧和精轧工艺,壁厚为30.8 mm、管径为1 422 mm的X80M管线钢-20 ℃温度下的全厚度DWTT性能达到94%,高于85%的工程应用验收要求。 相似文献
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Dae Jin Ha Chang-Young Son Joon Wook Park Jong Seog Lee Yong Deuk Lee Sunghak Lee 《Materials Science and Engineering: A》2008,492(1-2):49-59
Effects of high-temperature hardness and oxidation on sticking phenomena occurring during hot rolling of two STS 430J1L ferritic stainless steels were investigated in this study. Hot-rolling simulation test was conducted using a high-temperature wear tester. The sticking started from the initial nucleation stage in which the rolled materials were stuck onto the roll specimen surface, proceeded to the growth stage in which stuck fragments grew further, and reached the saturation stage. The modified 430J1L steel had a smaller number of sticking nucleation sites and slower growth rate than the conventional 430J1L steel because of higher high-temperature hardness, thereby leading to less serious sticking. When the simulation test was conducted at 1070 °C, Cr oxides were formed on the surface of the rolled materials, and thus the sticking was drastically reduced because of the increased surface hardness of the rolled materials. In order to prevent or minimize the sticking, thus, it was suggested to improve high-temperature properties of stainless steels in the case of hot rolling at 900–1000 °C, and to promote the formation of oxides in the case of hot rolling at temperatures higher than 1000 °C. 相似文献
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为研究GH4169合金楔横轧加工过程中动态再结晶及织构演变规律,采用金相显微镜(OM)和电子背散射衍射(EBSD)对30%,50%两种断面收缩率下GH4169合金楔横轧件表层与心部的微观组织、晶体取向及织构进行分析。结果表明:GH4169合金楔横轧加工过程中,随着动态再结晶的发生,晶体取向逐渐变得随机化分布;轧制表层大角度晶界数量较轧件心部多,轧件表层织构强度变化不大,心部织构强度明显增强;经过楔横轧变形后织构发生转动,原始态织构类型为{001}〈110〉,{111}〈110〉,{111}〈011〉,轧制后主要织构类型为{001}〈010〉,{112}〈110〉,{110}〈111〉,{110}〈112〉;GH4169合金楔横轧件动态再结晶及织构演变规律是由楔横轧特殊变形特点决定的。 相似文献
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楔横轧非对称轴类件时由于存在较大不平衡的轴向力,会产生轴向窜动并导致台阶缺损和表面重皮等质量缺陷.为了减小不平衡的轴向力,目前一般采取的方法是结合工艺参数对楔横轧力能参数的影响规律,利用数值模拟手段,通过多次预设计工艺参数并反复试算以获得能使左右两端轴向力相等或近似相等的最佳工艺参数.该试算方法计算量大、繁琐、不直观,且需逐个零件进行,通用性差.本文通过利用中心组合实验设计并结合响应面法获得轴向力的响应曲面图,利用轴向力等值线选取工艺参数以保证非对称轴类件楔横轧的轴向平衡,本方法简单、直观,极大地节省了工艺参数选择所需时间,缩短了非对称轴类件楔横轧的模具设计周期. 相似文献
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Development of bainitic rail steels with potential resistance to rolling contact fatigue 总被引:1,自引:0,他引:1
K. SAWLEY J. KRISTAN 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(10):1019-1029
Rails are a major capital and maintenance cost for railways in North America. While manufacturers produce clean steels with high quality, most rails made today retain the basic carbon–manganese chemistry of traditional pearlitic rails. This paper describes the development of a bainitic rail steel with potential additional resistance to rolling contact fatigue damage. It is shown that rails can be produced in bainitic steel without the need for complex heat treatments after rolling, and that bainitic rails can have higher hardness and fracture toughness than pearlitic rails. Although small‐ and full‐scale tests indicate that the wear performance of bainitic steel depends considerably on test conditions, the indication is that bainitic steel rails can have significantly better rolling contact fatigue performance compared to pearlitic rails. Reasons for the superior fatigue performance are not fully understood, although a number of hypotheses exist. A conclusion is that continued research would be useful to understand quantitatively the physics and metallurgy of wheel/rail contact. 相似文献
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不同厚度的10CrN iMnMo低合金高强钢连铸连轧并热处理后,强度变化不大,但冲击韧性值却相差较大.采用金相显微镜和透射电子显微镜等手段对低合金钢10CrN iMnMo轧制态及热处理后的组织和性能进行研究.结果表明,轧制态的低合金钢板材上有大量的纳米级碳化物弥散分布于铁素体基体上,但其组织由于板厚的不同而不同.厚板≥12 mm其组织为铁素体+贝氏体;而薄板的组织为铁素体+贝氏体+马氏体+残余奥氏体.在后续热处理中,厚板的强度降低,而冲击韧性变化很大.薄板的强度变化较厚板小,并且冲击韧性变化不明显,这主要是由于马氏体的存在和碳化物析出强化的作用. 相似文献
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《Materials at High Temperatures》2013,30(2):287-292
AbstractStudies have been made to investigate what effect different factors have on oxide formation on stainless steels at 600–1,000°C in air. The factors include the effect of microstructure, airflow rate, surface preparations, residual oxides and variations of the dew point of the air. Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES) and light optical microscope (LOM) were used to characterise the oxides. 相似文献
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Gyoko Oh 《Fatigue & Fracture of Engineering Materials & Structures》2022,45(1):40-54
Probabilistic assessments are important for weldments due to large scatters in the fatigue strength. Using thin-walled cone-pipe welded joints of stainless steels, fatigue tests under bending loads were carried out. The test data were statistically analyzed with the Benard's approximation, Gaussian, 2P-Weibull, and 3P-Weibull distributions. Stress–life curves at different failure probabilities by a uniform scatter band model were obtained. The metallographic structures were investigated, and the stress concentration states were analyzed to elucidate the causes of the strengths and scatters. In the high-cycle fatigue regime, the 3P-Weibull distribution was most matched with the Benard's approximation, and the coefficient of determination was 0.9817. The microstructure of the weld metal with a high weld opening angle was mainly ferrite phase with 20% austenite distribution, which had the high strength. The stress concentration factors depended on the weld opening angle, indicating the main factor that affected strengths and scatters. 相似文献
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采用润滑滚动磨损实验测试Fe-0.03Te-0.3Pb-0.9Mn易切削不锈钢的表面摩擦磨损特性。比较不同磨损时间球珠作用下合金表面磨损形貌、体系硬度、摩擦因数和磨损体积的差异,并对其润滑滚动磨损机理进行深入研究。结果表明:磨损启动期,合金表面磨损性能相对稳定,在MnS和Pb等易切削相交互作用下,合金表面犁削底部开始产生裂纹;磨损稳定期,合金表面性能逐渐变化,犁削底部裂纹持续生长,交织的裂纹开始产生片状或块状凸起物;磨损失效期,合金表面润滑膜和剥落物大量脱落,剥落物形成磨料磨损,犁削逐渐贯通消失,合金表面体系相结构快速瓦解。 相似文献
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对于滚动轴承寿命及可靠性试验,在不进行国家规定的寿命试验时,为节约样品成本与试验成本,一般所选的样本量较小.然而使用方或生产方希望能在样本数量与失效数量均较少的情况下,在一定精度下能定量客观地给出被试轴承的形状参数及可靠度、平均寿命等可靠性指标.为此,利用Bayes方法,依据滚动轴承寿命服从二参数Weibull分布的特点,选用无信息先验分布,根据试验数据,给出被试轴承形状参数与可靠度的点估计及形状参数、可靠度、可靠寿命与平均寿命的区间估计.为小样本少失效条件下滚动轴承可靠性的定量评价提供了有效方法. 相似文献
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滚压加工螺纹可以获得更高的螺纹强度、精度,其在加工效率和环保性方面的优越性不容忽视.同时,滚压加工可以解决某些工艺方法不能解决的问题,如对特大型缸体的加工,可以达到减少机床和夹具、提高工件加工精度、缩短加工周期和节约作业面积的效果.为此,本文采用一种四滚丝轮车床滚压加工得到了304不锈钢管圆锥外螺纹.通过金相分析、扫描电镜、显微硬度计和万能试验机等手段,研究了304不锈钢管滚压成形圆锥外螺纹的组织及性能,并与传统的套丝管螺纹进行对比.研究结果表明,套丝加工的管螺纹,齿表层出现孔洞、金属组织被切断,其内部显微组织仍是原有的等轴晶,齿形不完整;而滚压加工使得螺纹表层组织细化,形成了沿螺纹齿形连续分布的纤维组织.套丝加工后304钢管螺纹硬度有所提高,但幅度不大;与套丝加工相比,滚压加工后304钢管螺纹的抗剪拉力和硬度均有大幅提高. 相似文献