共查询到19条相似文献,搜索用时 983 毫秒
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本文根据开裂氢浓度理论,针对不同的堆焊方法的不锈钢堆焊试块进行了氢剥离试验,并运用计算机对试块在试验中堆焊层中氢扩散过程进行了计算。从而得出了剥离试块的开裂氢浓度C_(dc),发现开裂氢浓度与试样的几何尺寸、堆焊层的厚度及堆焊的方法等都有很大的关系。其中自动氩弧焊堆焊及CO_2气体保护焊堆焊的试块抗剥离性能明显优于其它方法,而相同几何尺寸及堆焊层厚度的手工堆焊试样和带极堆焊试样则抗剥离性能相当。 相似文献
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《机械工程材料》2017,(5)
通过C110钢的硫化物应力开裂试验和氢渗透试验,研究了外加电位对C110钢抗硫化物应力开裂及氢渗透行为的影响,并对其开裂机制进行了探讨。结果表明:当加载应力为C110钢屈服强度的85%、未外加电位时,C110钢通过了NACE TM 0177-2016标准A法检测,具有良好的抗硫化物应力开裂性能,而外加-100mV和+100mV电位(相对于开路电位)时,C110钢试样发生了断裂,硫化物应力开裂敏感性增强;外加阳极电位时,开裂机制与阳极溶解有关;外加阴极电位时,开裂机制与阴极析氢有关;随着外加阴极电位的增大,稳态氢渗透电流密度增大,次表面氢浓度增大,硫化物应力开裂的敏感性增强。 相似文献
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分析了波形膨胀节爆炸失效的原因,发现304不锈钢冷加工成形时(液压)发生马氏体相变,在湿硫化氢环境下含形变马氏体的304奥氏体不锈钢发生了湿硫化氢引起的氢致开裂(HIC)或应力导向氢致开裂(SOCHIC),当裂纹扩展到某一临界尺寸时便发生了低应力脆断型的爆炸事故。 相似文献
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X90管线钢在石油天然气管道中具有广泛应用前景,其焊接接头在服役过程中存在氢致开裂(Hydrogen induced cracking,HIC)倾向。采用电化学氢渗透试验和预充氢慢应变速率拉伸试验(Slow strain rate tensile test,SSRT),对X90管线钢焊接接头的氢捕获效率和氢致开裂敏感性进行了研究。利用场发射扫描电子显微镜(Field emission scanning electronic microscope,FE-SEM)对试样断口形貌及裂纹处夹杂物进行观察和分析,采用氢微印技术(Hydrogen microprint technique,HMT)对显微组织中氢的局部分布和聚集进行分析。结果表明,不同充氢电流密度下,X90管线钢焊接接头SSRT试样的断裂位置均为焊缝,其氢致开裂敏感性明显高于母材。与X90管线钢母材相比,焊缝中氢扩散系数较小,氢浓度、可逆和不可逆氢陷阱密度均较高。焊缝中的针状铁素体、贝氏体组织晶界及其亚晶界和夹杂均是有效的氢捕获陷阱,具有较高的氢捕获效率;焊缝中尺寸大于2μm夹杂物的数量多于母材,氢致裂纹易在富Al、富S、富Si夹杂... 相似文献
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对开裂的天然气集气末站汇管进行了宏观形貌、显微组织、化学成分分析和力学性能测试、断口形貌观察以及腐蚀产物相组成确定,对其开裂原因进行了分析。结果表明:集气末站汇管开裂裂纹位于汇管的焊缝区,裂纹分为表面裂纹与隐藏裂纹,裂纹性质属氢致开裂和应力导向氢致开裂;设备内壁防腐涂层质量低劣是导致开裂的主要原因,焊接工艺不当对开裂有明显的促进作用。 相似文献
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对SPV490Q钢焊接接头的楔形张开加载(WOL)预裂纹试样在不同浓度硫化氢溶液中进行了应力腐蚀试验,测定了焊缝的应力腐蚀临界应力强度因子KISCC和应力腐蚀裂纹扩展速率da/dt。结果表明:随着H2S浓度的升高,SPV490Q钢焊缝的应力腐蚀临界应力强度因子KISCC下降,应力腐蚀裂纹扩展速率da/dt增大,焊接接头的应力腐蚀抗力降低。 相似文献
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以车载压缩天然气气瓶用钢34CrMo4为材料,试样为紧凑拉伸(CT)试样,采用多功能动态应力腐蚀试验机进行恒位移速率拉伸试验,实测了在20,63,200,630和2000 ppm的硫化氢水溶液中的应力腐蚀临界应力强度因子KISCC和裂纹扩展速率da/dt。结果表明,应力腐蚀临界应力强度因子KISCC随硫化氢浓度的增大而减小,但当硫化氢浓度达到一定量时,溶液的浓度对KISCC值的影响并不大;裂纹扩展速率da/dt随硫化氢浓度的增大而增大,但在630~2000 ppm范围内,硫化氢浓度对裂纹扩展速率影响很小。 相似文献
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Jun-Seok Choi Hyun-Chul Lee Yong-Taek Im 《Journal of Mechanical Science and Technology》2010,24(9):1885-1890
A numerical algorithm based on the element deletion method and rigid-viscoplastic finite element approach depending on Cockcroft-Latham
and specific plastic work fracture criteria was applied to predict formation and evolution of possible cracking in a cold
extrusion of aluminum and steel alloys. The Cockcroft-Latham fracture criterion induced an internal crack while an external
crack occurred owing to the specific plastic work criterion in simulations. As a result, the Cockcroft-Latham criterion was
found to be valid for predicting chevron cracking in comparison with the experimental observation available in the literature.
Using the Cockcroft-Latham criterion, cracking was carefully investigated in terms of the size of the crack and gap distance
between cracks depending on the number of elements and boundary condition at the punch interface. The critical damage values
for the Cockcroft-Latham fracture criterion were also calculated based on the tensile instability and fracture conditions
to investigate their effect on possible cracking. Finally, a processing map based on the Cockcroft-Latham fracture criterion
for preventing chevron cracking in the cold extrusion of commercially available steel alloy was developed by considering processing
parameters such as reduction in area and semicone angle. According to this investigation, the developed element deletion method
with the Cockcroft-Latham fracture criterion was reasonably accurate for carrying out chevron cracking analyses in the cold
extrusion with proper selection of a critical damage value. 相似文献
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S. Manimozhi S. Suresh V. Muthupandi 《The International Journal of Advanced Manufacturing Technology》2010,51(1-4):217-223
Advanced creep-resistant steels have been developed to meet the demanding requirements of fossil power plants that strive to improve the generation efficiency by enhancing the steam temperature and pressure. These are ferritic steels with nominal chromium content ranging from 2% to 12% with significant addition of tungsten besides Nb, V, and N in small level. One of the candidate materials is 9Cr-0.5Mo-1.7W steel, developed for steam circuit components of tubes, and pipes of power plants for an operating temperature of 600°C. Hydrogen cracking is a major issue in welding of this steel, due to solid-state metallurgical transformations that lead to untempered martensite in the HAZ of weld joint. The hydrogen cracking does not occur below a threshold stress level called critical cracking stress. The critical stress for cracking in this steel was determined by carrying out implant weldability tests using shielded metal arc welding process for various levels of diffusible hydrogen in the weld metal and an empirical model relating levels of diffusible hydrogen and time taken for cooling from 800°C to 500°C to the critical stress has been developed. Results of current study also showed that residual diffusible hydrogen plays a major role in deciding hydrogen cracking than the initial diffusible hydrogen in the weld metal. 相似文献