X70和16Mn钢土壤腐蚀行为比较I电位和平均腐蚀速度

通过研究国内常用的X70和16Mn 2种管道钢在土壤浸出液中的电位-时间曲线，并根据失重试验和极化曲线，比较它们的平均腐蚀速度.结果表明，16Mn钢腐蚀电位比X70钢稍负约20 mV，其平均腐蚀速度明显高于X70钢；X70钢的腐蚀产物膜具有短期保护性.     

钢筋混凝土结构设计与施工中的钢材节约

从构造设计和施工两方面介绍在钢筋混凝土施工中,节约钢材的一些措施。     

超临界水冷堆燃料包壳管用低活性F/M钢的优化设计

应用热力学计算与实验验证,系统研究了Cr、W、C、Mn对高Cr低活性F/M（铁素体/马氏体）钢基体相及显微组织的影响规律,并在此基础上,对钢的组织和成分进行设计与优化,以适应超临界水系统对包壳材料的性能要求。研究表明：Cr是决定高Cr低活性实验钢中奥氏体Cr固溶量以及钢中是否出现铁素体的最重要影响因素;W和C对实验钢铁素体相的出现有显著影响,而Mn的影响相对较小;W对实验钢中Laves相出现的温度范围及数量具有显著影响,Laves相消失的临界温度随W量降低而降低;在不采用Co、Ni等奥氏体形成元素且不增加Mn量的情况下,通过调控W、C等含量,Cr含量≥11%的Cr-W-C-Mn系低活性F/M钢即可获得全马氏体组织。     

稀土元素La对碳锰纯净钢组织和冷却转变的影响

通过显微组织观察和对临界转变温度的测定,研究了稀土元素La对碳锰纯净钢组织和冷却转变过程的影响。结果表明,当镧含量较高时,纯净钢冷却转变组织粗化,形成魏氏组织的趋势增加,珠光体片层间距不均匀;在碳锰纯净钢的冷却转变过程中,随La含量的增加,先共析铁素体开始析出温度降低,析出速度加快,共析转变开始温度降低。镧在晶界的偏聚是造成碳锰纯净钢组织和相变过程变化的主要原因。     

EH36高强度船板钢奥氏体连续冷却的转变行为

利用Gleeble2000型热模拟试验机对EH36船板钢连续冷却相变行为以及在增速冷却和减速冷却条件下的相变行为进行了研究。结果表明：在连续冷却条件下,在400-650℃范围内,冷却速率在4～16℃／s时,相变组织以贝氏体组织为主且随着冷速的增大贝氏体的体积分数增加;在冷却速率≥1℃／s时,先以一定速率冷却至600℃,然后将冷速减半时,其显微组织与半速恒速冷却组织相近;而先以一定速率冷却至600℃,然后将冷速加倍时,其显微组织与两倍速恒速冷却的显微组织相近。     

Introduction of creep-rupture testing capability and proficiency at Baosteel

To characterize the long-term service performance and predict the lifetime of heat-resistant steel applications,more than 300 test pieces can be loaded simultaneously at Baosteel to determine the relationship between stress and rupture duration at specific temperatures. In addition,versatile testing methods have been established that evaluate creep-rupture,stress-relaxation,and creep-fatigue,as well as state-of-the-art tensile testing at hyper-high temperatures exceeding 2 100 ℃. Based on the Larson-M iller method,according to API 530,the accumulation of large volumes of data with respect to stress,temperature,and rupture time of actually tested steels ensures the reliability of predicting the allowable working stress over 100 000 h at any given temperature. For examples,the stress tendencies against rupture time of T/P91 and T/P92 steel tubes,as obtained by Baosteel,are consistent with those from NIMS and ECCC. As an accredited provider of the Proficiency Testing schemes in ISO/IEC 17025 and ISO/IEC 17043,Baosteel has periodically organized national proficiency testing with respect to creep and rupture,thereby providing an efficient way for all parties to assess their technical competence when performing uniaxial creep testing by the methods in ISO 204 and ASTM E139.     

Prediction of fracture in a dual-phase steel subjected to non-linear straining

In this work, selected fracture criteria are applied to predict the fracture of dual-phase steel subjected to non-linear strain paths. Furthermore, the effects of manufacturing history are studied. Four fracture criteria were calibrated in three tests using standard specimens. The fracture criteria were first validated in the circular Nakajima test. A second validation test case was included in order to validate fracture prediction for non-linear strain paths. In this test a sheet metal component was manufactured and subsequently stretched until it fractured. All fracture criteria included in this study predict fracture during the Nakajima test with reasonable accuracy. In the second validation test however, the different fracture criteria show considerable diversity in accumulated damage during manufacturing which caused substantial scatter of the fracture prediction in the subsequent stretching. This shows that manufacturing history influences the prediction of fracture.     

Failure Investigation of a Furnace Tube Support

A furnace tube support failed after 6 months service at 850 °C. The support was an HK alloy, a member of the heat-resistant cast alloy family (H-Series) steels. The H-series steels are widely used in the petrochemical industry for components requiring enhanced high-temperature properties. Microstructural changes occurring at high temperature clearly affect the mechanical properties. The property degradation in HK-40 steel furnace tube support subjected to high temperature was caused by the formation of sigma phase. The investigation included metallurgical analysis, materials characterization, and mechanical analysis.     

Influence of case hardening on wear resistance of a sintered low alloy steel

PM technique has been applied for some products in the autoindustries due to unique functions and cost saving. The wear resistance of PM steel parts is one of the most significant surface properties. Nitriding and carburizing processes consist of exposing metallic materials to nitrogen and carbon to improve their surface hardness and wear resistance. In this research, the partially diffusion prealloyed powders, Ultrapac LE, containing Fe-4Ni-1.5Cu-0.5Mo with 0.2% graphite and two different densities were sintered at 1120 °C for 30 min. Depending on the applied pressures during cold pressing, two different porosities of 14.11 and 10.26 vol.% were obtained. Some specimens were carburized and some others were nitrided in cyanate liquid salt bath. The pin-on-disc wear test and hardness test were used to evaluate the surface behavior of specimens. The results showed that the wear resistance increased by nitriding and carburizing processes and the effect of nitriding is more than carburizing on wear resistance. In the case of materials studied, except for 4 h nitrided specimens, other specimens with higher porosity level showed better wear resistance. In these specimens, large pores entrapped the wear debris and created a densified layer. It prevented the formation of large abrasive agglomerates. For the carburized specimens, wear mechanisms were affected by the brittle fracture caused by abrasive wear. So, wear resistance did not increase significantly. In this investigation, abrasive, plastic deformation and oxidation wear were observed as wear mechanisms.