共查询到19条相似文献,搜索用时 109 毫秒
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The corrosion behavior of a rusted 550 MPa grade offshore platform steel in Cl- containing environment was investigated. The results revealed that the corrosion process can be divided into initial stage in which corrosion rate increased with accumulation of corrosion products and later stage in which homogeneous and compact rust layer started to protect steel substrate out of corrosion mediums. On the contrary, structural analysis of rust layers by X-ray diffraction showed that α-FeOOH increased from 1. 3% to 3. 6% and the Fe3O4 increased from 1. 0% to 1. 5% while γ-FeOOH reduced slightly according to corrosion time increased from 30 cycles to 73 cycles. The results of electron probe microanalysis indicated that Cr concentrated mainly in the inner region of the rust, inner/outer interface especially, whereas Ni and Cu were uniformly distributed all over the rust after 73 corrosion cycles. According to electrochemical measurements, it was found that the corrosion rate of rusted steel reduced from 0. 61 mm/a after 45 cycles to 0. 34 mm/a after 85 cycles, 44. 3% reduction approximately, and Rrust values increased with increment of corrosion time. Therefore, formation of compact inner rust layer and enrichment of Cr are important to improve corrosion resistance of offshore platform steel. 相似文献
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Effect of Niobium on Isothermal Transformation of Austenite to Ferrite in HSLA Low-Carbon Steel 总被引:2,自引:1,他引:1
CAO Jian-chun LIU Qing-you YONG Qi-long SUN Xin-jun 《钢铁研究学报(英文版)》2007,14(3):51-55
Using thermomechanical simulation experiment,the kinetics of the isothermal transformation of austenite to ferrite in two HSLA low-carbon steels containing different amounts of niobium was investigated under the conditions of both deformation and undeformation.The results of optical microstructure observation and quantitative metallography analysis showed that the kinetics of the isothermal transformation of austenite to ferrite in lower niobium steel with and without deformation suggests a stage mechanism,wherein there exists a linear relationship between the logarithms of holding time and ferrite volume fraction according to Avrami equation,whereas the isothermal transformation of austenite to ferrite in high niobium steel proceeds via a two stage mechanism according to micrographs,wherein,the nucleation rate of ferrite in the initial stage of transformation is low,and in the second stage,the rate of transformation is high and the transformation of residual austenite to ferrite is rapidly complete.Using carbon extraction replica TEM,niobium carbide precipitation for different holding time was investigated and the results suggested that NbC precipitation and the presence of solute niobium would influence the transformation of austenite to ferrite.The mechanism of the effect of niobium on the isothermal transformation was discussed. 相似文献
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通过金相、扫描电镜,相变临界点和过冷奥氏体等温转变的分析,研究了Nb对共析钢(质量分数:C 075%,C 0.78%)珠光体相变微观组织和等温转变动力学的影响。结果表明:微量Nb(质量分数为0.04%、0064%)的加入使钢中先共析铁素体的量较未含铌钢有所增加,这很可能是Nb的加入使得共析碳含量明显升高的结果,同时使珠光体相变产物的形貌发生明显变化,珠光体中渗碳体的展弦比显著降低。此外Nb提高了先共析铁素体和珠光体的开始转变温度,即Nb的加入在一定程度上降低了过冷奥氏体的热力学稳定性;相变动力学表明加入Nb 0.04%可使珠光体相变的鼻子点温度升高约50℃,且最快开始相变时间比不含铌钢推迟一个数量级以上,即Nb的加入推迟了鼻子点和较低温度下的珠光体相变,提高了钢的淬透性。 相似文献
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《钢铁研究学报(英文版)》2011,(Z1):983-986
590 MPa automobile beam steel strips are used mainly to manufacture the longitudinal beam of trucks.It’s welding properties are critical to the safety of truck.The microstructure and mechanical properties of welding joints processed by CO 2 arc welding with different welding parameters were studied.The results showed that the welding joints were weak when welding heat input were small and the non metal inclusions were found in the weld joints when welding heat input are big.The quality of the welding joints is good enough at 170A of the arc current and 24V of the arc voltage.Keeping the other welding parameters fixed,the incomplete fusion defect occurred in the welding joint with backward welding,but the quality of the welding joint is good with forward welding. 相似文献
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车轮钢摩擦热影响区的相变及其损伤机理 总被引:2,自引:0,他引:2
将有限元热力耦合一温度场分析与材料相变特征的实验研究相结合,研究了高速度(200kin/h)、大载荷(10^5N)条件下车轮摩擦热影响区的相变过程,探讨了材料对该过程的影响。结果表明,轮一轨摩擦导致的车轮踏面局部升温可超过材料的奥氏体相变的临界点,碳含量为0.5%时,完全奥氏体化层的深度可达0.6mm;过冷奥氏体高速冷却,几乎全部形成脆硬的马氏体薄层,造成踏面剥离。通过降碳来降低车轮钢奥氏体相变的临界点,可以显著抑制踏面马氏体层的形成。随着碳含量从0.7%降至0.4%,材料的Ae3提高45℃,马氏体层的厚度减小30%,有助于减少车轮踏面的热疲劳损伤。 相似文献
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基于合金设计制备出2种低合金试验热轧板钢,在采用水淬+盐浴回火的淬火-分配-回火(Q-P-T)工艺处理后,达到了屈服强度900MPa和伸长率15%的设计指标,为后期自行设计的单道次穿水淬火冷却装置用于热轧板的Q-P-T工艺工程可行性的研究奠定了基础。X射线衍射、扫描电镜和透射电镜的微观组织分析表明:与传统的淬火回火(Q&T)工艺相比,Q-P-T先进高强度钢中位错型板条马氏体基体及其内弥散分布的合金碳化物贡献于高的强度,板条马氏体间的薄片状奥氏体贡献于优良的塑性。此外,还进一步探讨了Q-P-T工艺中残余奥氏体的作用和多道次穿水淬火冷却装置用于不同厚度热轧板在线Q-P-T处理的可行性。 相似文献