409L铁素体不锈钢的热变形行为

采用热/力模拟实验研究409L铁素体不锈钢在950、1 000、1 050、1 100、1 150℃、应变速率为0.01、0.1、1.0 s-1,压下量为50%时的热变形行为,讨论热变形参数对流变应力的影响.结果表明,409L铁素体不锈钢的表观应力指数为4.06,热变形表观激活能为212 kJ/mol;409L铁素体不锈钢的热变形方程.ε=3.017.109[sinh(α.pσ)]4.06exp(-212 000/RT).其软化机制与Zener-Hollomon(Z)参数有关,随着Z值从6.11×105增加到1.15×109,热变形峰值应力相应从11.71 MPa增加到66.94 MPa.     

Corrosion behavior of cold-rolled and post heat-treated 316L stainless steel in 0.9wt% NaCl solution

The effect of cold rolling and post-rolling heat treatment on the microstructural and electrochemical properties of the 316 L stainless steel was investigated. Two-pass and four-pass cold-rolled stainless steel specimens were heat-treated by annealing at 900°C followed by quenching in water. During the cold rolling, the microstructure of the as-received specimen transformed from austenite to strain-induced α′-martensite due to significant plastic deformation that also resulted in significant grain elongation(i.e., ～33% and 223% increases in the grain elongation after two and four rolling passes, respectively). The hardness of the heat-treated as-received specimen decreased from HV 190 to146 due to the recovery and recrystallization of the austenite grain structure. The cyclic polarization scans of the as-rolled and heat-treated specimens were obtained in 0.9 wt% Na Cl solution. The pitting potential of the four-pass rolled specimen was significantly increased from 322.3 to 930.5 m V after post-rolling heat treatment. The beneficial effect of the heat treatment process was evident from ～10-times-lower corrosion current density and two-orders-of-magnitude-lower passive current density of the heat-treated specimens compared with those of the as-rolled specimens. Similarly, appreciably lower corrosion rate(3.302 × 10~(-4) mm/a) and higher pitting resistance(1115.5 m V) were exhibited by the postrolled heat-treated specimens compared with the as-rolled 316 L stainless steel specimens.     

铁素体不锈钢热轧板材的拉伸行为和断裂特征

用金相显微镜、X射线衍射仪、SEM手段研究2种铁素体不锈钢热轧板材0.04C-16Cr、0.02C-12Cr在室温下的拉伸行为和断裂特征.结果表明,这2种铁素体不锈钢的强度高,但塑性较差;C、Cr含量较低的0.02C-12Cr钢的强度、硬度均较0.04C-16Cr的高,这是由于0.02C-12Cr在空冷过程中产生了大量的马氏体;2种钢室温下都为韧性断裂,其断口微观形貌主要为细小韧窝聚集,沿轧制方向分布的条带组织中存在细小的碳化物颗粒,成为韧窝的发源地;部分断口出现了分层和侧向开裂现象.分析其断口形貌、断裂过程和组织特征,可知沿着轧制方向分布的条带组织致使材料表现出上述力学行为和断裂特征.     

Nb在现代铁素体不锈钢中的应用研究进展

Nb元素越来越多地被应用于铁素体不锈钢中以提高其性能。本文综述了Nb对铁素体不锈钢强度、韧性、耐腐蚀、抗高温氧化等性能影响的研究进展,以及国内外含Nb铁素体不锈钢在汽车、建筑、家用电器等领域中的应用现状。分析了目前我国含Nb高性能铁素体不锈钢研发中存在的主要问题,认为我国未来应重点研究新型超临界温度的含Nb耐热不锈钢等高端装备制造材料,以促进含Nb高性能铁素体不锈钢的研发和生产,改善我国不锈钢的品种结构。     

409L铁素体不锈钢热轧板材焊接接头的电化学腐蚀行为

采用电子探针(EPMA)和金相显微镜对409L铁素体不锈钢热轧板材焊接接头的3个区域(母材区(BM)、热影响区(HAZ)和焊缝区(WM))的成分和组织进行分析,并且运用电化学的方法测试其3个区域在10％ H2SO4溶液中的极化曲线特征参数,并对其进行室温(25℃)、24 h的浸泡腐蚀试验.结果表明:409L铁素体不锈钢...     

超纯铁素体不锈钢中TiN析出的动力学分析

采用动力学的方法研究超纯铁素体不锈钢凝固过程中Ti、N的偏析及冷却速率对TiN夹杂析出的影响。结果表明,超纯铁素体不锈钢凝固过程中,Ti的富集程度稍低于N;凝固末期残余液相中[Ti]和[N]的浓度分别提高至其初始浓度的2.5倍和3.2倍;随着钢液的逐渐凝固,析出的TiN颗粒尺寸增大;随着冷却速率的增大,析出的TiN颗粒尺寸减小,但析出时间几乎不受影响,冷却速率分别为10、20、30K/s时,TiN颗粒尺寸分别为7.1、4.8、3.9μm;其他条件相同时,随着钢中初始Ti含量或N含量的减少,凝固析出的TiN颗粒尺寸减小且析出时间推迟;相比Ti含量对TiN夹杂尺寸的影响,N含量的影响更为显著。     

不锈钢的腐蚀与防腐

一般情况下不锈钢具有较好的耐腐蚀性，但在特殊的操作工况下，此材料不但不能有效的抵抗腐蚀，而且还会出现诸如点蚀、应力腐蚀、晶间腐蚀等现象，而应力腐蚀、晶间腐蚀会给工程带来重大的安全隐患．结合工程实际，分别介绍了以上各种腐蚀的机理及不锈钢在化学介质中的抗腐蚀性，并重点介绍晶间腐蚀产生的原因和防腐措施．     

304不锈钢在西沙海洋大气环境中的腐蚀行为

采用扫描电镜、能谱、电化学阻抗谱和拉曼光谱等分析测试手段,研究了西沙群岛苛刻海洋大气环境下,经过不同时间暴露后304不锈钢的腐蚀行为和机理.304不锈钢在西沙大气暴露后的腐蚀类型主要是以局部腐蚀的点蚀为主,腐蚀产物主要由β-FeOOH、γ-Fe₂O₃和Fe₃O₄组成.随暴露时间的延长,不锈钢表面钝化膜的稳定性变差,点蚀数目增加、点蚀坑深度增大日.表面腐蚀产物覆盖率也逐渐增多.与其他部位相比,点蚀更容易在表面划痕处产生.提高表面加工精度,有助于提高其耐腐蚀性能.     

2507双相不锈钢在SO2污染模拟海水中的腐蚀行为

采用开路电位、电化学阻抗谱(EIS)、Mott-Schottky曲线和浸泡腐蚀实验研究了2507双相不锈钢在含不同浓度(0,0.001和0.01 mol·L-1)NaHSO3模拟海水中的腐蚀行为.研究表明:开路电位随NaHSO3浓度的增加而负移,腐蚀倾向增大;电荷转移电阻Rt随浓度的增加而减小,耐蚀性降低;2507不锈钢的腐蚀形态为局部腐蚀,点蚀程度随浓度升高有所加剧,腐蚀速率随浓度的增加而增大;Mott-Schottky曲线和成膜后电化学阻抗谱测试表明,NaHSO3的加入增加了2507不锈钢表面钝化膜的点缺陷浓度,降低了钝化膜的稳定性,电荷转移阻力减小,腐蚀更容易发生.这可能归因于NaHSO3的加入增加了模拟海水的酸度,并随NaHSO3浓度的增加促进了不锈钢表面钝化膜的破坏.     

Reduction of chromium oxides in stainless steel dust

The recovery of metal oxides from stainless steel dust using C (graphite), SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr (L'_Crm/s) in the recovered metal and residual slag phases was defined as the major performance metric. The results show that the recovery ratio of metals increases as the ratio of CaO:SiO₂ by mass in the residual slag increases to 1.17. The residual content of metals in the slag decreases as the Al₂O₃ content of the slag is increased from approximately 8wt% to 10wt%. The recovery ratio of Cr increases with increasing L'_Crm/s, and a linear relationship between L'_Crm/s and the activity coefficient ratio of CrO in the slag and the recovered metal phase is observed. The combination of C and SiFe or Al as the reducing agents reveals that Si is the more effective coreductant.     

400系铁素体不锈钢中夹杂物的检测及分析

利用普通金相识别技术和电子探针成分分析对410S、430、409L铁素体不锈钢热轧板夹杂物的类型、形貌特征、来源及其对钢的性能影响作综合检测和分析.结果表明:410S和430不锈钢板材所含夹杂物主要为CaO-Si O2-Al2O3-MgO系复合夹杂物;409L不锈钢板材中夹杂物主要为Ti(C、N)和Al N.夹杂物主要来源于AOD脱氧产物、钢液的二次氧化、炉衬材料和耐火材料的腐蚀剥离等.3种不锈钢的纵向和横向的力学性能相差不大;但若夹杂物较多且分布不均匀时会形成明显的点蚀和分层剥蚀.     

Effect of tin addition on the microstructure and properties of ferritic stainless steel

This article reports the effects of Sn on the inclusions as well as the mechanical properties and hot workability of ferritic stainless steel. Precipitation phases and inclusions in Sn-bearing ferritic stainless steel were observed, and the relationship between the workability and the microstructure of the steel was established. Energy-dispersive X-ray spectroscopic analysis of the steel reveals that an almost pure Sn phase forms and MnS-Sn compound inclusions appear in the steel with a higher Sn content. Little Sn segregation was observed in grain boundaries and in the areas around sulfide inclusions; however, the presence of Sn does not adversely affect the workability of the steel containing 0.4wt% Sn. When the Sn content is 0.1wt%-0.4wt%, Sn improves the tensile strength and the plastic strain ratio and also improves the plasticity with increasing temperature. A mechanism of improving the workability of ferritic stainless steel induced by Sn addition was discussed:the presence of Sn lowers the defect concentration in the ultra-pure ferritic lattice and the good distribution of tin in the lattice overcomes the problem of hot brittleness that occurs in low-carbon steel as a result of Sn segregation.     

不锈钢中磷和铬的联合测定

提出一种快速分析不锈钢中磷和铬的联合测定的方法,针对不锈钢中高铬含量的情况,采用王水和高氯酸溶解后,准确控制发烟时间可使磷和铬全部氧化完全.试样溶解后磷的测定采用酸性介质中用抗坏血酸为还原剂的铋磷钼蓝光度法,在波长660 nm处测定其吸光度,铬的测定采用高氯酸氧化亚铁容量法,实现了磷和铬的联合测定.通过研究与应用认为,此法对磷含量在0.005%～0.050%之间,铬含量在10%～35%的之间合金钢、不锈钢皆适用,试验结果满意.     

复合脱氧剂对430不锈钢脱氧行为的影响

在MoSi2炉和MgO坩埚内用复合脱氧剂对430不锈钢液进行了脱氧实验研究.以Al和FeSi作为对比脱氧剂,考察了SiCaBa、SiCaBaAl、SiCaBaMg、SiCaBaAlSr四种复合脱氧剂对430不锈钢中的全氧含量及脱氧产物的分布、尺寸和形貌的影响.实验表明,用SiCaBa对430不锈钢液脱氧,可获得较低的氧含量,其脱氧产物易于上浮,钢中的夹杂物尺寸明显减小且形态发生改善呈球形.     

Corrosion behavior of cold-rolled and post heat-treated 316L stainless steel in 0.9wt%NaCl solution

The effect of cold rolling and post-rolling heat treatment on the microstructural and electrochemical properties of the 316L stainless steel was investigated.Two-pass and four-pass cold-rolled stainless steel specimens were heat-treated by annealing at 900℃followed by quenching in water.During the cold rolling,the microstructure of the as-received specimen transformed from austenite to strain-inducedα′-martensite due to significant plastic deformation that also resulted in significant grain elongation(i.e.,~33%and 223%increases in the grain elongation after two and four rolling passes,respectively).The hardness of the heat-treated as-received specimen decreased from HV 190 to 146 due to the recovery and recrystallization of the austenite grain structure.The cyclic polarization scans of the as-rolled and heat-treated specimens were obtained in 0.9wt%NaCl solution.The pitting potential of the four-pass rolled specimen was significantly increased from 322.3 to 930.5 mV after post-rolling heat treatment.The beneficial effect of the heat treatment process was evident from~10-times-lower corrosion current density and two-orders-of-magnitude-lower passive current density of the heat-treated specimens compared with those of the as-rolled specimens.Similarly,appreciably lower corrosion rate(3.302×10^?4mm/a)and higher pitting resistance(1115.5 mV)were exhibited by the postrolled heat-treated specimens compared with the as-rolled 316L stainless steel specimens.     

Effect of welding parameters on the heat-affected zone of AISI409 ferritic stainless steel

One of the main problems during the welding of ferritic stainless steels is severe grain growth within the heat-affected zone (HAZ). In the present study, the microstructural characteristics of tungsten inert gas (TIG) welded AISI409 ferritic stainless steel were investigated by electron backscattered diffraction (EBSD), and the effects of welding parameters on the grain size, local misorientation, and low-angle grain boundaries were studied. A 3-D finite element model (FEM) was developed to predict the effects of welding parameters on the holding time of the HAZ above the critical temperature of grain growth. It is found that the base metal is not fully recrystallized. During the welding, complete recrystallization is followed by severe grain growth. A decrease in the number of low-angle grain boundaries is observed within the HAZ. FEM results show that the final state of residual strains is caused by competition between welding plastic strains and their release by recrystallization. Still, the decisive factor for grain growth is heat input.     

Nb、Ti单稳定高纯铁素体不锈钢铸坯的凝固组织和夹杂物

采用金相显微镜和扫描电镜,研究并讨论了铌、钛单稳定条件下,高纯铁素体不锈钢的凝固组织及夹杂物的状态.结果表明:单钛稳定相对单铌稳定能显著提高铁素体不锈钢的等轴晶比例,铌更能起到细化晶粒的作用.铌、钛单稳定条件下铁素体不锈钢中夹杂物的分布和类型存在较大的差异.     

Effects of TiC on the microstructure and formation of acicular ferrite in ferritic stainless steel

The formation mechanism of acicular ferrite and its microstructural characteristics in 430 ferrite stainless steel with TiC additions were studied by theory and experiment. Using an edge-to-edge matching model, a 5.25 mismatch between TiC (FCC structure) and ferritic stainless steel (BCC structure) was identified, which met the mismatch requirement for the heterogeneous nucleation of 430 ferritic stainless steel. TiC was found to be an effective nucleation site for the formation of acicular ferrite in a smelting experiment, as analyzed by metallographic examination, Image-Pro Plus 6.0 analysis software, and SEM-EDS. Furthermore, small inclusions in the size of 2-4 μm increased the probability of acicular ferrite nucleation, and the secondary acicular ferrite would grow sympathetically from the initial acicular ferrite to produce multi-dimensional acicular ferrites. Moreover, the addition of TiC can increase the average microstrain and dislocation density of 430 ferrite stainless steel, as calculated by Williamson-Hall (WH) method, which could play some role in strengthening the dislocation.     

Corrosion behavior of high-strength spring steel for high-speed railway

The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray (5wt% NaCl solution). A formation model of γ-FeOOH and a transformation model describing the conversion of γ-FeOOH to α-FeOOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-FeOOH into α-FeOOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products.     

304奥氏体不锈钢晶界贫Cr的数值模拟

应用基于铬扩散的半经验-半理论公式模型模拟304不锈钢的晶界贫Cr现象。运用该模型不但可以预测不同的热处理温度和时间下304不锈钢热处理过程中晶界上最小Cr的质量分数,而且还可以分析晶界附近Cr的质量分数分布,由模拟结果可进一步得到更宽范围内的温度-时间-质量分数图(TTC)。模拟结果表明:贫Cr区的宽度随敏化时间和温度的增加逐渐变宽;表征材料晶间(应力)腐蚀敏感性的TTC图与参考文献的模拟与实验结果基本一致。