H2 S-CO2环境下低铬钢的硫化物应力腐蚀开裂行为

目的评价90SS和90SS-3Cr油管钢在H_2S-CO_2环境下的硫化物应力腐蚀开裂(SSCC)行为,并分析其断裂机理。方法利用四点弯曲实验和慢应变速率拉伸实验,结合显微组织分析、扫描电子显微镜分析技术,研究90SS和90SS-3Cr两种钢材在H_2S-CO_2环境下的应力腐蚀开裂行为和断口形貌特征。结果 90SS-3Cr钢的显微组织中存在更多的非金属夹杂物。经过720 h四点弯曲实验后,90SS和90SS-3Cr试样表面均未出现宏观及微观裂纹,表现出良好的抗硫化物应力腐蚀开裂能力。在慢应变速率拉伸实验中,当H_2S浓度由0增加至6 mol/L时,90SS-3Cr试样的断后伸长率δ、断面收缩率φ及断裂时间t分别下降了71.6%,69.6%,61.4%,远高于90SS钢的塑性损失(分别下降2.9%,52.5%,10.3%)。断口形貌分析表明,90SS-3Cr钢在较低浓度H_2S时就由塑性断裂向脆性断裂转变。结论随着H_2S浓度的升高,90SS和90SS-3Cr钢的塑性损失增加,抗SSCC能力均下降。相比90SS钢,90SS-3Cr钢对应力腐蚀开裂更为敏感。     

Electrochemical and XPS surface analytical study on the reactivity of Ni‐free stainless steel in artificial saliva

Nowadays, there is a strong demand to replace CrNi stainless steels used for biomedical applications such as brackets in orthodontics with a new generation of more biocompatible austenitic, nickel‐free alloys. The aim of this work is the investigation of the growth and stability of the surface films formed on DIN 1.4456 Ni‐free stainless steel (18% Cr, 18% Mn, 2% Mo) in artificial saliva (pH 7.9) at 37 °C by electrochemistry and XPS surface analyses and the assessment of the ions that leach from the steel. These results show that the open circuit potential asymptotically increases and the corrosion current density decreases from 1 to 24 h exposure time to the artificial saliva. XPS provides evidence that the surface film present on the surface after mechanical polishing transforms into a passive film that becomes progressively enriched in Cr (III) oxy‐hydroxides whereas iron and manga­nese oxides are depleted. It is found that the instantaneous corrosion rate decreases exponentially with the amount of Cr (III) in the passive film. The results are discussed regarding the biocompatibility, thus the release of ions into solution, of the new nickel‐free stainless steel. Based on the results presented in this paper and literature evidence, a comprehensive model is proposed that substantiates the biocompatibility of these alloys.     

Special features of welding equipment and pipelines in nuclear power stations made of pearlitic and austenitic steels

In long-term service of dissimilar welded joints (DWJ) in sections connecting equipment and pipelines made of pearlitic and austenitic steels, corrosion damage was observed in the material associated with the intercrystalline corrosion of the metal of the type 10Kh16N24AM6, deposited with UA 395/9 electrodes. The deposited metal of the type 02Kh23N15 is characterized by high corrosion resistance, is not susceptible to hot cracking and can be recommended for the first layer of the load-carrying edges of DWJ.     

Effect of Cooling Rates in Coiling Process on Microstructures and Mechanical Properties in Al-Bearing Hot-Rolled TRIP Steel

In this study, the effect of cooling rates on microstructures and mechanical properties in a Al-bearing hot-rolled transformation-induced plasticity steel was investigated. The experiments were carried out using hot simulation machine and hot rolling mill, where the samples were cooled at different cooling rates. The results showed that with the increase in cooling rates, film-like retained austenite gradually disappeared and only blocky retained austenite was retained at higher cooling rates. The volume fraction of retained austenite was 9–11% at cooling rates of 0.05–1°C/s and 4–6% at cooling rates of 5–10 °C/s. In addition, martensite/austenite island was observed because of the heterogeneous carbon distribution. The samples cooled at 0.05 °C/s and 0.5 °C/s exhibited excellent mechanical properties, with tensile strengths of 712 MPa and 726 MPa, total elongations of 42% and 36% and strength and ductility balances of 29.91 GPa% and 26.15 GPa%, respectively. During plastic deformation, the instantaneous work hardening exponent of the sample cooled at 0.05 °C/s increased continuously until it reached the maximum value, while the instantaneous work hardening exponent of the sample cooled at 0.5 °C/s remained stable.     

含裂纹型缺陷压力容器用钢失效评定曲线研究

在力学性能测试的基础上．应用CEGB R6-Revison 4方法中的选择1和选择3曲线，对16MnR，20R和Q235B三种吉裂纹型缺陷压力容器用钢的失效评定曲线进行研究。结果表明．三种材料的失效评定曲线基本上均在Lr〈0.4后因试样结构不同而发生分散。而且均以是以Lr=0.7为分界线，在两侧分别出现不同的最为保守和最不保守曲线。给出了符合三种材料特性的失效评定曲线拟合方程，以便为工程应用提供依据。     

焊接热输入对近焊缝区组织性能的影响

采用焊接热模拟技术模拟不同焊接热输入条件下,峰值温度为1 350℃时对应近焊缝区的组织和性能,并对母材进行宏观力学特性测试;对比分析不同焊接热输入条件下所得近焊缝区的组织和性能。结果表明:经过3种不同焊接热输入所得近焊缝区的组织均由板条状贝氏体和少量碳化物组成;随着焊接热输入的增加,近焊缝区组织晶粒变大,贝氏体板条束变粗变厚,析出的碳化物数量增多,并且强度降低、韧性增强,但总体上跟母材的性能基本一致;当焊接线能量为12 kJ/cm时近焊缝区达到最佳的强韧性匹配。