不锈钢热轧板材焊接接头的晶间腐蚀试验

利用常规方法和电化学方法分别测定了304奥氏体不锈钢和410S铁素体不锈钢热轧板材钨极氩弧焊(TIG)焊接接头的晶间腐蚀倾向。结果表明:采用硫酸+硫酸铜法和双环动电位再活化法(DL-EPR)都能很好地评价304不锈钢焊接接头的晶间腐蚀倾向,且两者吻合较好。由于410S母材的抗蚀性较差,采用硫酸+硫酸铜法无法评价其焊接接头的晶间腐蚀倾向,而双环动电位再活化法可以定量、快速测定其晶间腐蚀敏感性,试验发现410S的热影响区和母材有晶间腐蚀倾向,其中靠近熔合线的热影响区晶间腐蚀最严重。     

双环电化学动电位再活化法评价11Cr铁素体不锈钢晶间腐蚀敏感性

利用TEM,EDS和SAED等分析方法,研究了11Cr铁素体不锈钢409L在600℃敏化下析出物特性,并将双环电化学动电位再活化法(DL-EPR)用于评价409L钢的晶间腐蚀敏感性,通过研究DL-EPR的扫描速率、介质成分、介质温度对测试结果的影响,对该方法进行了优化,并用该优化法研究了敏化处理对409L钢晶间腐蚀敏感性的影响.结果表明,敏化的409L钢发生晶间腐蚀是由于M_(23)C_6沿晶界析出.在最优化条件下,DL-EPR法能定量评价409L钢的晶间腐蚀敏感性且具有良好的重复性.随敏化处理时间延长,沿晶界析出的M_(23)C_6增多,晶间腐蚀敏感性也随之增强.     

DL-EPR法评价2205双相不锈钢晶间腐蚀敏感性

利用Thermo-Calc软件并结合金相显微镜,定性研究了2205双相不锈钢在800℃下敏化不同时间后的微观组织演变过程.通过研究扫描速率、介质成分、介质温度和试样表面状态优化了双环电化学动电位再活化法(DL-EPR),并用该优化方法研究了2205双相不锈钢晶间腐蚀敏感性.结果表明:DL-EPR法能定量评价σ相对2205双相不锈钢晶间腐蚀敏感性的影响,随敏化时间延长,σ相含量增多,晶间腐蚀敏感性也随之增加.腐蚀形貌的观测验证了这一规律.     

304不锈钢在RCC-M 1310标准下的耐蚀性

不锈钢材料虽然有良好的抗腐蚀性能,但是对晶间腐蚀比较敏感。选取3种不同的304不锈钢材料在RCC-M 1310标准下采用H2SO4-CuSO4方法对304不锈钢进行晶间腐蚀试验,观察碳含量和晶粒大小对耐晶间腐蚀性能的影响,并且利用DL-EPR技术对晶间腐蚀程度做了定量分析。结果表明,RCC-M 1310标准下,304不锈钢的碳含量越高、晶粒越大,晶间腐蚀越严重,晶界更加宽且深。     

电化学动电位再活化法评价热处理对430不锈钢晶间腐蚀敏感性的影响

利用电化学动电位再活化(EPR)并结合金相分析研究了热处理温度、冷却方式和保温时间对430不锈钢晶间腐蚀敏感性的影响。结果表明:430不锈钢开始敏化温度区间为700~750℃,随着热处理温度的升高,晶粒逐渐长大,敏化程度的变化以及碳氮化物析出位置受随后的冷却方式影响;热处理温度为900℃时,430不锈钢在短时间内发生敏化,随着保温时间的延长,敏化程度并没有明显降低; 700℃下短时间保温并空冷能够有效降低已敏化430不锈钢的晶间腐蚀敏感性。     

预应变对304不锈钢薄板晶间腐蚀敏感性的影响

利用硫酸-硫酸铜腐蚀试验方法和双环电化学动电位再活化法(DL-EPR),对304不锈钢薄板在预应变和敏化之后的晶间腐蚀敏感性进行了研究。采用金相显微镜对经过硫酸-硫酸铜试验后的试样进行观察,利用电化学测试方法进行试样敏化度(DOS)的测量。结果表明:304不锈钢薄板经过预应变-敏化处理后的晶间腐蚀程度较经单一敏化处理后的更加严重,随着预应变的加大,晶间腐蚀加重,敏化度也提高。     

典型不锈钢晶间腐蚀敏化温度的研究

用电化学动电位再活化（EPR）法、硫酸—硫酸铜法及扫描电镜研究了典型的202、304奥氏体不锈钢与409、430铁素体不锈钢在不同敏化温度下晶间腐蚀的敏感性。结果表明,奥氏体与铁素体不锈钢敏感温度区间不同,奥氏体不锈钢诱发晶间腐蚀的敏感温度约为650℃,铁素体不锈钢诱发晶间腐蚀的敏感温度约为950℃。研究结果为正确地评判不锈钢晶间腐蚀敏感性及优化生产工艺提供了科学依据。     

铁素体不锈钢的晶间腐蚀性能研究

    分别采用Cu-CuSO₄-16% H₂SO₄沸腾试验和电化学再活化方法研究了八种400系列铁素体不锈钢的晶间腐蚀性能.结果表明：C含量及稳定化元素是影响铁素体不锈钢晶间腐蚀性能的关键因素;电化学测量方法评价铁素体不锈钢的晶间腐蚀性能时易受晶粒再活化的影响,可结合电镜观察表面提高测量的准确性.     

敏化态00Cr12Ti的动电位电化学阻抗谱特征研究

采用双环电化学动电位再活化(DL-EPR)法和动电位电化学阻抗(DEIS)研究了敏化态铁素体不锈钢00Cr12Ti在0.1 mol/L H_2SO_4+0.0001 mol/L KSCN溶液中正反向扫描过程中的电化学行为,并用等效电路图对阻抗数据进行拟合。结果表明:DEIS的变化与DL-EPR曲线上的区域相对应,都呈现出活化区、活化-钝化过渡区、钝化区和再活化区。正向扫描过程中电位0.2 V左右开始出现容抗弧变小,且低频区实部减小出现负阻抗,这主要是由于形成的钝化膜还不完整,有局部新鲜表面存在;而反向扫描过程中在0.2 V左右阻抗急剧降低,而后逐渐升高,在这个过程中低频一直存在着负阻抗,这主要是由于晶界贫铬钝化膜不稳定,发生局部溶解和修复。发生晶间腐蚀后,低频又出现了负阻抗。由于腐蚀的中间产物吸附在电极表面,低频区出现感抗弧,生成的中间产物的扩散过程为控制步骤;而且DEIS中活化区和再活化区由R_(ct)的最小值的倒数的比值得到的敏化度(DOS)和DL-EPR曲线得到的敏化度存在着一致性。     

铸造SAF2906超级双相不锈钢耐晶间腐蚀性能评价

研究了铸造SAF2906超级双相不锈钢在850℃敏化不同时间的微观组织,通过研究扫描速率、介质成分和介质温度优化了双环电化学动电位再活化法(DL-EPR),得出DL-EPR评价SAF2906钢晶间腐蚀敏感性的最优条件为:溶液介质1. 0 mol/L HCl+2. 0 mol/L H2SO4,溶液温度为30℃,扫描速率为1 m V/s。并用该优化方法,研究了SAF2906双相不锈钢的耐晶间腐蚀性能。结果表明:随敏化时间延长,σ相含量增多,晶间腐蚀敏感性也随之增加。通过对比不同敏化温度下SAF2906钢的腐蚀形貌,验证了DLEPR评价铸造SAF2906钢耐晶间腐蚀性能的可靠性。     

用慢应变速率试验方法研究Cr18Mo2铁素体不锈钢的应力腐蚀开裂敏感性

用慢应变速率试验方法在143℃沸腾MgCl_2溶液中研究了不同碳含量、钛的加入量及热处理对Cr18Mo2铁素体不锈钢SCC敏感性的影响。随着碳含量的降低,钢的晶间腐蚀和点腐蚀程度减小,SCC敏感性相应减小。加入适量的钛可以明显减小其SCC敏感性,当Ti/(C+N)比在9.1～13.0时最显著。加入过量的钛引起σ相在晶界附近沉淀,致使SCC敏感性明显增大。 经1100℃处理的Cr18Mo2钢,晶间腐蚀程度显著增大,成为SCC敏感性的控制因素,断口呈沿晶开裂,SCC敏感性明显增大。经850℃处理后,晶间腐蚀明显减轻,点腐蚀成为SCC敏感性的主要的影响因素,断口呈穿晶开裂,SCC敏感性显著减小。 Cr18Mo2钢开裂敏感的应变速率为9×10~(*7)s~(-1)。断裂时间、断裂时延伸率ε_f和断面收缩车RA等参数可适用于评价铁素体不锈钢的SCC敏感性。     

超低碳不锈钢的铸态局部腐蚀行为研究

通过晶间腐蚀和点蚀等多种腐蚀试验方法,研究了含碳量对304型不锈钢局部腐蚀行为的影响。试验结果表明,超低碳不锈钢具有更好的抗晶间腐蚀与抗点蚀性能。     

Study for corrosion characteristics of ferritic stainless steel weld metal with respect to added contents of Ti and Nb

This paper identified the effects of Ti and Nb on pitting and intergranular corrosion resistance in a ferritic stainless steel weld metal of the automobile exhaust system. We fabricated 4 flux cored wires designed with 0–0.2 wt% Ti and 0–1.0 wt% Nb and performed Flux Cored Arc Welding. Through the potentiodynamic polarization test in 0.5M NaCl, we evaluated pitting resistance. And in order to evaluate the intergranular corrosion resistance, we observed microstructure after we performed DL-EPR test in 0.5M H₂SO₄+0.01M KSCN. As a result of the test, the specimen added with 0.2%Ti+1.0%Nb showed the highest pitting resistance. From observing the degree of sensitization and microstructure, the intergranular corrosion resistance was higher as the contents of Ti and Nb increased. And through EBSD we observed Cr carbide which affects the corrosion resistance.     

Intergranular corrosion of Ti-stabilized 11 wt% Cr ferritic stainless steel for automotive exhaust systems

Intergranular corrosion (IGC) of type 409L ferritic stainless steel (FSS) was investigated. A free-exposure corrosion and a double loop electrochemical potentiokinetic reactivation (DL-EPR) tests were conducted to examine IGC of the FSS. IGC occurred in the specimens aged at the temperature range of 400–600 °C that has the sensitization nose located around 600 °C. The critical I_r/I_a value was determined to be about 0.03 above which IGC occurred. Based on the analysis of the intergranular precipitates by an energy dispersive spectroscopy (EDS) and a transmission electron microscopy (TEM), IGC was induced by the Cr depletion zone formation due to Cr segregation around intergranular TiC.     

Interkristalline Korrosion ferritischer Chromstähle mit rd. 17 Gew.-% Chrom nach Glühen im Temperaturbereich um 500 °C

Intergranular corrosion of ferritic 17% chromium stainless steels after heat-treatment in the 500 °C temperature range After stabilizing heat-treatment at 750°C, the non-stabilized, ferritic 17% chromium stainless steel Mat.-Nr. 1.4016 (X8Cr17) still contains a sufficient high concentration of carbon dissolved in solid solution, that after heat-treatment in the 500 °C temperature range carbides rich in chromium of the M₂₃C₆-type are precipitated, causing a relatively weak pronounced susceptibility of the steel to intergranular attack. The susceptibility to this type of attack can be detected by testing specimens in the sulfuric acid-copper sulfate-test with increased concentration of sulfuric acid as compared with the DIN standard 50914, followed by metallografic examination of the specimens. The susceptibility to intergranular corrosion of the material investigated occurring after heat-treatment in the low temperature range, which until now is unknown, is described in terms of a Rollason-diagram as it is commonly used for austenitic chromium-nickel stainless steels. As it is to be expected, the stabilized 17% chromium steels Mat. No. 1.4510 (X8CrTi17), 1.4511 (X8CrNb17) and 1.4523 (X8CrMoTi17) are resistant to intergranular corrosion after heat-treatment at low temperatures.     

Microstructure and intergranular corrosion resistance of UNS S17400 (17-4PH) stainless steel

UNS S17400 or 17-4PH is a precipitation hardening martensitic stainless steel with many industrial applications. Quite different mechanical properties can be produced in this material by varying the aging temperature. In this work, the influence of aging temperature on the intergranular corrosion susceptibility was evaluated by electrochemical and metallographic tests. The microstructural features were investigated by X-ray diffraction, optical and scanning electron microscopy. Intergranular chromium carbide precipitation occurs in specimens aged at high temperatures, although NbC carbides were also observed. The results obtained by double loop electrochemical potentiodynamic reactivation tests (DL-EPR) show that the susceptibility to intergranular corrosion resistance increases with the increase of aging temperature. Healing due to Cr diffusion in the 600-650 °C range was not observed by DL-EPR tests.     

超纯铁素体不锈钢研制和生产

超纯铁素体不锈钢因碳、氮含量极低,较普通铁素体不锈钢以及马氏体不锈钢拥有更优越的耐腐蚀性、韧性及焊接性。介绍了超纯铁素体不锈钢的应用范围和发展趋势,阐述了超纯铁素体不锈钢铸件的生产工艺,并对其进行了市场预测和经济效益分析。     

Evolution of intergranular corrosion resistance for HR3C heat-resistant austenitic stainless steel at elevated temperature

An attempt has been made to investigate the evolution of intergranular corrosion (IGC) resistance of HR3C heat-resistant austenitic stainless steel. The double-loop electrochemical potentiokinetic reactivation (DL-EPR) tests were conducted to evaluate the IGC resistance of HR3C steel. The results show that the side peaks can be observed in active–passive region of DL-EPR curves due to inhomogeneous distribution of the chromium dissolved in matrix. The variation of the degree of sensitisation (DOS) during sensitising at 800°C can be divided into three regions (sensitisation dominant region, desensitisation dominant region and equilibrium region). When HR3C steel is sensitised at 800°C for over 24?h, the equilibrium state in DOS can be reached. Simultaneously, the IGC morphologies after DL-EPR tests can correlate well with the DOS. On the basis of the equilibrium state in DOS, proper heat treatments and corrosion protection measures can be taken to avoid IGC of HR3C steel.