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对影响大型风机塔顶法兰设计的因素进行了分析。模拟结果显示,塔顶法兰的设计受其他零部件尺寸的影响也比较大,不容忽视。对塔顶法兰进行设计时必须考虑到这一点,为以后塔顶法兰的设计提供了有利的依据。 相似文献
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《理化检验(物理分册)》2017,(10)
某福建沿海地区用于电流互感器的铝合金法兰发生多处开裂,采用宏观检验、化学成分分析、金相分析、扫描电镜以及能谱分析等方法对该法兰开裂原因进行了分析。结果表明:法兰开裂均起始于螺栓孔处,为在腐蚀介质和应力共同作用下发生的应力腐蚀开裂;法兰螺栓扭紧力高、服役环境氯离子含量高以及法兰所用铝合金材料应力腐蚀开裂敏感性高等是造成该法兰开裂的主要原因。最后针对法兰开裂原因提出了预防措施。 相似文献
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方法兰加工简单、节约材料,因而在制冷装置中一直得到广泛使用,并沿用至今。《固定式压力容器安全技术监察规程》实施后,限制了方法兰在氨制冷装置中的使用。本文叙述了方法兰在制冷装置中的使用情况,并对方法兰的安全性进行分析、探讨。 相似文献
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运用LS-DYNA非线性有限元软件,建立了法兰连接结构的三维有限元模型,使用罚函数法实现了法兰盘-螺栓连接-法兰垫的非线性耦合作用,利用温度荷载法实现了螺栓连接结构的预紧力加载,采用ALE多物质流-固耦合算法研究了法兰连接结构在爆炸冲击荷载作用下的动力响应特性,分别研究了法兰连接在爆炸冲击荷载作用下冲击波入射角、螺栓连接预紧力、法兰垫厚度对其结构的影响,并考虑了垫片为金属材料(合金钢)以及非金属材料(橡胶)时的情况。结果表明,法兰盘为法兰连接的主要耗能构件。合金钢法兰垫片受冲击波入射角的影响较小,而螺栓连接则主要受冲击波入射角的影响。法兰盘在高压压缩波的作用下会产生相对于螺栓连接的不均匀压缩变形。厚垫片并非比薄垫片好,适当减小法兰垫片厚度,可以提高法兰结构的抗冲击能力。 相似文献
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采用化学成分分析、低倍检验、金相检验、能谱分析以及显微硬度测试等方法对某42CrMoA钢锻件内部裂纹产生的原因进行了分析。结果表明:42CrMoA钢锻件的内部裂纹属氢致白点裂纹;由于该锻件锻造后去氢处理不及时,加上锻造不良产生的枝晶组织促进了氢分子在锻件内部的扩散,导致了微裂纹的萌生和扩展。建议42CrMoA钢锻件在锻造后及时进行去氢热处理,锻造时适当增加锻造比,改善材料的组织。 相似文献
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34Mn2V钢的热加工缺陷 总被引:1,自引:0,他引:1
34Mn2V钢坯经火焰切割下料,再经热冲压制成氧气瓶,因氧气瓶底凹面出现热撕裂而造成大量废品。通过试验跟踪和解剖分析,研究了下料坯端面裂纹和半成品瓶底部相应缺陷的本质。结果表明,切割下料时在切割面热影响层发生部分奥氏体化;当切割热消失后,奥氏体化的金属即受到周围冷金属的冷却作用形成马氏体组织。因此,瓶底的局部热撕裂是由下料坯切割时产生的温度梯度和相变引起的。采用预热切割、切割后缓冷和下料坯温度降至环境温度前立即入炉退火都能避免热影响层的开裂。 相似文献
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Carbon steel axle forgings were rejected due to internal cracks observed during final machining. To determine the cause of
the cracks, the preforms of the forging were analyzed in detail at each stage of the forging. The analysis revealed a large
central burst in the intermediate stage of the forging preform, which subsequently increased in the final stage. A high upset
strain during forging, especially in the final stage, accentuated the center burst by high lateral flow of the metal. It was
concluded that the center burst of the axle forging resulted from a high concentration of nonmetallic inclusions in the central
portion of the raw bar stock rather than the usual problem of improper forging temperature. Strict control over the inclusion
content in the raw material by changing the vendor eliminated the problem. 相似文献
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Experimental evidence to support Johnson's [6] analysis of the residual surface stress distribution produced in a flat surface by a spherical indenter is presented. The theory suggests that high residual stresses develop just outside the contact area as a result of the superposition of elastic unloading stresses onto the stresses at maximum load when the specimen has deformed plastically. The experiments involved the use of a semi-brittle steel, sufficiently hardened so that, while tensile stresses in the surface produced cracks, the substrate deformed plastically under the triaxial stress system beneath the indenter. Radial cracks produced by the indenter frequently extended after load removal, implying the presence of the high tensile circumferential residual stresses predicted by the theory. This work and recent studies of indentation loading of glasses show that there are important situations where residual stresses can contribute to their failure and wear. 相似文献
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目的分析非调质钢曲轴感应淬火时出现裂纹的原因。方法首先统计了裂纹的分布规律,并确定了裂纹源位置,之后通过金相检验、低倍检验,从锻打工艺、材料偏析等角度对裂纹进行了原因分析。结果产生在分模面位置的裂纹,是因产品结构造成该区域材料在锻打过程中发生流速不均,当材料的框型偏析位置在锻造挤压下流动到此处时,偏析的材料产生了微细空洞,该微细空洞在后续感应淬火时成为裂纹源而引起开裂。结论该裂纹的产生与材料框型偏析有直接关系。研究对控制非调质钢曲轴生产中的裂纹缺陷,提高曲轴生产质量,具有重要应用价值。 相似文献
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The influence of ausforming on the methods of tensile and impact fracture in a low alloy steel, has been studied.The ausforming produced austenite grains elongated parallel to the rolling direction and on subsequent quenching and tempering between 400 and 600° C, extensive networks of cementite particles formed along their boundaries. In this condition tensile failure occurred by the formation of longitudinal cracks along the prior austenite boundaries and these cracks joined together by transverse ductile tearing. On tempering above 600° C the boundary carbides coalesced and the matrix softened, and in this condition the steel possessed considerable resistance to transverse crack propagation. 相似文献
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AISI 1024 steel was severely deformed by using warm (500 °C) multiaxial forging (MAF) technique using up to nine forging passes
in order obtain a composite ultrafine grained (UFG) microstructure consisting of fragmented cementite particles. Microstructural
evolution is studied using optical and electron microscopy. After warm MAF, the hardness and strength properties improved
significantly, although total elongation values decreased. The tribological properties of UFG low carbon steel produced by
MAF have been investigated. Dry sliding was carried out using constant sliding speed. The wear test results showed that the
strengthening of AISI 1024 steel by warm MAF processing did not lead to improvement of wear resistance. The results are explained
on the basis of its microstructural features and lower pull-off work. Higher grain boundary density, presence of submicron-sized
cementite particles, and lower pull-off work are found to be responsible for lower sliding wear resistance of UFG steel. 相似文献
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经常规锻造、近β锻造和β锻造的Tell(Ti—6.5Al—3.5Mo—1.5Zr—0.3Si)钛合金盘获不同的显微组织,对应了不同的断裂韧性。在常规锻造的等轴组织中,虽然可以观察到穿过等轴α相的二次裂纹,但裂纹扩展路径平直,分枝少,断裂表面光滑平整,因而断裂韧性低。近β锻造得到双态组织,由于等轴α相含量的减少,魏氏α相比例增多和形态的改变,二次裂纹增加,断裂韧性显著提高。在β锻造的网篮组织中,α条上的疲劳条带和二次裂纹明显增加,裂纹扩展路径曲折,分枝多,故断裂韧性最高。可见,显微组织影响盘件断裂韧性的主要因素在于,裂纹扩展过程中产生的裂纹分枝、疲劳条纹和二次裂纹的密度以及裂纹扩展路径的曲折程度。 相似文献
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采用外观观察、电镜分析、金相检验等方法,对弹簧扁钢在热卷耳过程中发生的开裂原因进行了分析。结果表明热加工过程中温度控制不当,引起扁钢局部过烧进而导致卷耳变形时发生严重开裂现象。 相似文献
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00Cr14Ni14Si4奥氏体不锈钢中微量铝硫与锻造裂纹 总被引:3,自引:0,他引:3
00Cr14Ni14Si14钢的锻造裂纹与钢中Al,S以及由之形成的氧化物和硫化物含量过高有关。钢在模铸凝固和冷却过程中形成夹杂物年,呈点链状的氧化物和晶界析出的薄片Y相在热加工时弱化了晶界降低了钢的导热性和高温塑性,从而在夹杂偏析区显示出宏观的热加工裂纹。 相似文献