不同钢制造LPG球罐在湿H2S环境下失效行为的对比研究

对16MnR钢和SPV50Q钢液化石油气(LPG)球罐在湿H2S环境下的失效行为进行了对比研究.通过观察从16MnR钢球罐上所取下的严重腐蚀球壳板的裂纹特 征和SPV50Q球罐内壁所作金相复膜照片的裂纹形貌,以及分析现场所测试的硬度和残余应力,表明：16MnR钢球罐的失效是由氢诱导开裂(HIC)所引起,损伤部位发生在母材上,而SPV50Q钢球罐则是由硫化物应力腐蚀开裂(SSCC)所造成,裂纹主要出现在焊接接头附近的热影响区(HAZ).     

Q125级1% Cr套管钢焊接接头CO_2腐蚀行为

采用高温高压反应釜和电化学测试手段对含Cr质量分数为1%的Q125级套管钢焊接接头的CO2腐蚀行为进行了研究。结果表明:焊接接头的母材和热影响区的耐CO2腐蚀性能相近,母材为回火马氏体,热影响区为回火索氏体,组织对实验钢的耐CO2腐蚀性能影响不明显。焊缝区的Cr含量较高,腐蚀产物中的Cr富集加剧,且结构致密,其更能有效的阻止阴离子的通过,从而保护金属基体免受腐蚀介质的腐蚀。电化学分析可得,焊缝区的自腐蚀电位最正,自腐蚀电流最小,不易发生腐蚀;母材区的自腐蚀电位最负,自腐蚀电流最大,母材金属将作为阳极首先发生腐蚀,焊缝作为阴极得到保护。     

细晶Q420低合金高强钢焊接接头组织性能研究

采用CO2气体保护焊对细晶Q420低合金高强钢进行焊接,用光学显微镜、扫描电镜分析了焊接接头显微组织及断口形貌,试验测试了焊接接头拉伸、弯曲及冲击性能.结果表明,细晶Q420钢母材由晶粒细小的铁素体和珠光体构成,选用ER55-G焊丝所得焊接接头焊缝金属具有比母材更高的抗拉强度,焊缝及热影响区均具有良好的冲击性能,断口为典型韧窝状延性断裂形态.在所选焊接工艺参数下,其热影响区表现出比焊缝金属更好的冲击性能.     

经济型铁素体不锈钢与耐候钢异种金属接头的耐蚀性能

采用ER-309焊丝焊接了T4003与Q450NQR1耐候钢、Nirosta4003与Q450NQR1耐候钢两种异质接头,用金相方法分析了母材和接头的显微组织,通过盐雾腐蚀试验及电化学极化曲线测量对异种金属焊接接头的耐蚀性能进行了评价。结果表明,对T4003和Nirosta4003铁素体不锈钢同种金属所形成的焊接接头而言,焊缝的耐蚀性能均优于对应的母材,但热影响区的耐蚀性能变差。对T4003和Nirosta4003铁素体不锈钢与Q450NQR1耐候钢焊接形成的异质接头而言,焊缝的耐蚀性能下降。在盐雾状态下,同种金属焊接所形成的焊缝与母材的耐盐雾腐蚀性能水平相当,耐蚀性能较好;T4003和Nirosta4003不锈钢与Q450NQR1耐候钢焊接而成的异质接头腐蚀较为明显,尤其是耐候钢一侧的腐蚀较为严重,出现了大量的腐蚀坑。在异种金属所形成的焊接接头中,不锈钢母材、热影响区、焊缝以及耐候钢母材由于腐蚀电位差的不同形成原电池,致使耐候钢母材的腐蚀加剧。     

湿H2S环境下低合金钢焊接接头氢扩散数值模拟

利用电化学渗透法测定了氢在16MnR低合金钢焊接接头处的焊缝金属、热影响区金属以及母材中的扩散系数.利用有限元软件ABAQUS,对16MnR钢焊接接头氢扩散进行数值模拟,考虑焊接残余应力、不同组织对氢扩散的影响,得到焊接接头扩散氢的浓度随时间的分布.结果表明,在焊缝和热影响区,氢的扩散系数和焊接残余应力较大,使氢在焊缝和热影响区聚集,降低材料的力学性能,使得焊接接头部位成为最薄弱环节,在湿H2S环境下很容易发生与氢有关的损伤和破坏.     

AF1410钢电子束焊接接头的腐蚀行为

针对AF1410钢电子束焊接接头,分析焊缝区、热影响区、母材区的微观组织,测试并研究各微区的电化学性能以及接头在3.5％(质量分数)NaCl溶液中的腐蚀行为.研究表明:焊缝区、热影响区、母材区的微观组织及电化学性能互相之间均存在明显差异,热影响区的自腐蚀电位最低,母材区的自腐蚀电位最高;未经热处理的AF1410钢电子束...     

Q125级套管钢高频电阻焊接头耐CO2/H2S腐蚀行为

采用SEM,EBSD和电化学等手段研究了Q125级石油套管钢高频电阻焊接头的耐CO₂/H2S腐蚀行为.结果表明,Q125级套管钢高频电阻焊接头处母材的耐腐蚀性能最好,热影响区次之,而焊缝的耐腐蚀性能最差,导致高频电阻焊接头在CO₂/H₂S腐蚀环境中产生了沟槽腐蚀.试验钢焊缝处的大角晶界比例高于母材和热影响区,从而使焊缝区反应速度常数高于母材和热影响区,这是焊缝区腐蚀速率最高的一个重要原因.通过电化学分析表明,焊缝处的电极反应的极化阻力最小,腐蚀反应易于发生;而母材的电极反应的极化电阻最大,腐蚀反应不易进行,这与腐蚀试验所得结果及极化曲线分析结果一致.     

H_2S浓度和pH值对X65海管钢焊接接头腐蚀行为的影响

采用高压釜模拟海底集输环境,通过电化学测试技术、浸泡实验、SEM和XRD技术研究了H2S浓度和pH值对X65钢焊接接头腐蚀行为的影响。结果表明,X65钢焊接接头中热影响区的开路电位最负,焊缝最正,母材介于两者之间,腐蚀电流密度从大到小的顺序为:热影响区母材焊缝;焊接接头平均腐蚀速率在0.1~0.25 mm/a之间,硫化物浓度增加、pH值降低均可导致腐蚀速率增加;X65钢海管焊接接头在模拟现场工况条件下以均匀腐蚀为主,焊缝区腐蚀程度低于热影响区。     

S450EW焊接接头在NaHSO_3溶液中的腐蚀行为研究

采用熔化极富氩气体保护焊进行S450EW同种金属焊接,并利用电化学测试研究了焊接接头不同区域的耐蚀性能。结果表明,S450EW焊接接头母材区和焊缝区显微组织均为粒状贝氏体,热影响区为铁素体和珠光体的混合组织。焊缝区主要发生均匀腐蚀,但母材区和热影响区以局部腐蚀为主,而且热影响区腐蚀程度更深。焊丝中较高的Ni含量使得焊缝区抗大气腐蚀性能较好,而热影响区铁素体和珠光体两相组织导致其腐蚀速率较高。     

Q690贝氏体桥梁钢焊接接头在模拟乡村大气中耐蚀性能研究

采用干、湿周期浸润法、电化学方法,结合X射线衍射仪(XRD)、场发射原子探针显微镜(FE-EPMA)等现代表面分析技术,研究了Q690贝氏体桥梁钢及其焊接接头在模拟乡村大气环境中的腐蚀动力学规律及机理。结果表明,在整个腐蚀周期内,Q690钢及其焊接接头腐蚀动力学过程可以分为两个阶段,即n>1的加速腐蚀阶段和n<1的减速腐蚀阶段。腐蚀前期,因Q690钢焊接接头母材、热影响区和焊缝区存在明显显微组织差异,形成了以焊缝、热影响区为阳极、母材为阴极的电偶腐蚀对,导致其耐蚀性比母材要差;腐蚀后期,稳定锈层的形成缩小了Q690钢及焊接接头之间的耐蚀性差异。     

Probing the nonuniform corrosion of pipeline weldments under stepwise increasing solution temperature using a coupled multielement electrical resistance sensor

A coupled multielement electrical resistance sensor (MERS) was designed to probe the nonuniform corrosion of an X65 pipeline weldment under a stepwise increasing solution temperature. In conjunction with electrochemical impedance spectroscopy (EIS) measurements, the initiation and propagation of the nonuniform corrosion on different welding areas, that is, base metal (BM), heat-affected zone (HAZ), and welding metal (WM) were well understood. The results show that the contributions of galvanic current (current flowing across the three different welding areas) and internal current (current flowing in a certain welding area) for the steel loss of BM, HAZ, and WM were significantly different under each solution temperature. The main contributor to the steel loss of HAZ gradually transformed from internal current to galvanic current with the solution temperature increasing. The WM would change from anodes to cathodes due to the preprecipitation of the FeCO₃ crystals on WM when the solution temperature increased over 40°C. The BM would transform from cathodes to anodes at 40°C and the steel loss of BM was mainly induced by the internal current in BM over the whole test duration.     

SPV50Q钢在含H2S酸性环境下的腐蚀特性

利用动电位极化和交流阻抗技术，研究了SPV50Q钢在含H2S酸性环境下的腐蚀特性。结果表明，H2S对钢腐蚀过程影响很大，腐蚀速度随H2S含量的增加而增大，随pH降低和溶液温度的升高，钢的腐蚀亦不断增强；尽管随浸泡时间的延长，容抗弧半径不断增大，但其变化幅度不大，并在一定时间后减小，表明钢表面所形成的硫化物膜保护性较差，不能有效抑制钢的腐蚀。     

Corrosion Behavior of Metal Active Gas Welded Joints of a High-Strength Steel for Automotive Application

In this work, the corrosion behavior of metal active gas-welded joints of a high-strength steel with tensile yield strength of 900 MPa was investigated. The welded joints were obtained using two different heat inputs. The corrosion behavior has been studied in a 3.5 wt.% NaCl aqueous solution using electrochemical impedance spectroscopy and potentiodynamic polarization tests. Optical microscopy images, scanning electron microscopy and transmission electron microscopy with energy-dispersive x-ray revealed different microstructural features in the heat-affected zone (HAZ) and the weld metal (WM). Before and after the corrosion process, the sample was evaluated by confocal laser scanning microscopy to measure the depth difference between HAZ and WM. The results showed that the heat input did not play an important role on corrosion behavior of HSLA steel. The anodic and cathodic areas of the welded joints could be associated with depth differences. The HAZ was found to be the anodic area, while the WM was cathodic with respect to the HAZ. The corrosion behavior was related to the amount and orientation nature of carbides in the HAZ. The microstructure of the HAZ consisted of martensite and bainite, whereas acicular ferrite was observed in the weld metal.     

Intergranular corrosion susceptibility in supermartensitic stainless steel weldments

The intergranular corrosion susceptibility in supermartensitic stainless steel (SMSS) weldments was investigated by the double loop – electrochemical potentiokinetic reactivation (DL-EPR) technique through the degree of sensitization (DOS). The results showed that the DOS decreased from the base metal (BM) to the weld metal (WM). The heat affected zone (HAZ) presented lower levels of DOS, despite of its complex precipitation mechanism along the HAZ length. Chromium carbide precipitate redissolution is likely to occur due to the attained temperature at certain regions of the HAZ during the electron beam welding (EBW). Scanning electron microscopy (SEM) images showed preferential oxidation sites in the BM microstructure.     

130mm铝合金扫描激光填丝焊接头微区组织和性能

针对船用130 mm 5A06铝合金厚壁结构件的扫描激光填丝焊接头,对其焊缝（weld metal,WM）、热影响区（heat affected zone,HAZ）及母材（base metal,BM）的显微组织进行研究,并通过维氏硬度和微型剪切试验研究了接头各区力学性能差异.结果表明,5A06铝合金单激光焊缝以等轴晶为主,填丝焊焊缝以柱状晶为主,HAZ和BM晶粒比WM粗,母材及热影响区为轧制的纤维状组织;由于焊接热循环作用,接头热影响区硬度略高于母材,抗剪强度二者差别不大,单激光焊缝硬度和抗剪强度略高于填丝层.总体而言,焊缝区强度低塑性好,母材及热影响区强度高塑性低.     

On the microstructure-polarization behavior correlation of a 9Cr-1Mo steel weld joint

The use of 9Cr-1Mo ferritic steel necessitates its fabrication by the process of welding. The heat-affected zone (HAZ) of 9Cr-1Mo ferritic steel is a combination of many microstructures. In the present study, the corrosion properties of the base metal, weld metal, and the various regions of the HAZ are assessed with respect to their microstructures. The various microstructures in the HAZ were simulated by heat treatment of the normalized and tempered base metal at 1463, 1200, and 1138 K for 5 min followed by oil quenching. The microstructure of the base metal in the normalized and tempered condition revealed martensite laths with M₂₃C₆ carbides at lath boundaries, and uniform dispersion of fine, acicular M₂C. The weld metal showed predominantly martensitic structure with dispersion of carbides. Simulation of the microstructures of the HAZ by heat treatment resulted in the following microstructures: coarse-grained martensite of 75 μm size at 1463 K, fine-grained martensite at 1200 K, and martensite + proeutectoid α-ferrite at 1138 K. In all cases, carbide precipitation was observed in the martensitic matrix. Microhardness measurements of HAZ-simulated base metal showed increasing hardness with increasing heat treatment temperature. The hardness values obtained corresponded very well with the regions of the actual HAZ in the weld joint. Electrochemical polarization studies were carried out on the base metal, weld metal, weldment (base metal + weld metal + HAZ), and the simulated HAZ structures in 0.5 M sulfuric acid solution. Critical current densities (i _crit1 and i _crit2), passive current densities (i _pass and i _sec-pass), and transpassive potential (E _tp) were the parameters considered for evaluating the corrosion resistance. The HAZ structures simulated at 1463 and 1200 K, corresponding to coarse- and fine-grained martensitic regions of an actual HAZ, had corrosion properties as good as the normalized and tempered base metal. Of the various simulated HAZ structures, the intercritical region, which was simulated at 1138 K, possessed the worst corrosion resistance. The weld metal possessed the worst corrosion resistance of the various microstructural regions in the weld joint. The weldment adopted the degraded corrosion properties of the weld metal.     

Analysis of the Creep Behavior of P92 Steel Welded Joint

Different regions of heat-affected zone (HAZ) were simulated by heat treatment to investigate the mechanisms of the Type IV fracture of P92 (9Cr-2W) steel weldments. Creep deformation of simulated HAZ specimens with uniform microstructures was investigated and compared with those of the base metal (BM) and the weld metal (WM) specimens. The results show that the creep strain rate of the fine-grained HAZ (FGHAZ) is much higher than that of the BM, WM, the coarse-grained HAZ (CGHAZ), and the inter-critical HAZ (ICHAZ). According to the metallurgical investigation of stress-rupture, the FGHAZ and the ICHAZ have the most severely cavitated zones. During creep process, carbides become coarser, and form on grain boundaries again, leading to the deterioration of creep property and the decline of creep strength. In addition, the crack grows along the FGHAZ adjacent to the BM in the creep crack growth test (CCG) of HAZ.     

时效处理对铝锂合金电子束焊接头耐蚀性能的影响

对铝锂合金电子束焊接头进行焊后热处理,研究了时效处理前后接头各区域的晶间腐蚀、剥蚀和电化学腐蚀行为。结果表明,接头经过时效处理后,焊缝晶界析出的T1(Al_2CuLi)相数量增加,并且形成了明显的晶界无沉淀带(Precipitate Free Zone,PFZ)。焊态下接头未出现晶间腐蚀,热影响区和母材区均出现了孔蚀;焊后时效处理增大了接头的晶间腐蚀倾向,热影响区同时发生了孔蚀和晶间腐蚀,母材区出现了严重的晶间腐蚀。焊态下焊缝和热影响区均具有优异的抗剥蚀能力,母材区对剥蚀的敏感性较高;焊后时效处理可提高接头母材区的抗剥蚀能力,但会增大热影响区的剥蚀敏感性。电化学腐蚀测试表明,与时效后的接头焊缝相比,焊态下焊缝的自腐蚀电位较高,腐蚀电流密度小,具有相对较好的耐蚀性。     

High-Temperature Corrosion Behavior in Different Regions of 9 Cr-1 Mo Steel Weldment in SO2 + O2 Atmosphere

This paper investigates the high-temperature corrosion behavior of microstructurally different regions of the weldment of 9 Cr-1 Mo steel used in thermal power plant boiler in SO₂ + O₂ environment. The weldment is produced by tungsten inert gas welding method, and the different regions of the weldment (weld metal, heat-affected zone, and base metal) are exposed in SO₂ + O₂ (ratio 2:1) environment at 973 K for 120 h. The reaction kinetics and corrosion growth rate of different regions of weldment in isothermal condition are evaluated. The post corroded scales of the different specimens are studied in SEM, EDS, and XRD. The results indicate that the weld metal shows higher corrosion rate followed by HAZ and base metal. The higher rate of corrosion of weldmetal is mainly attributed to the least protective inner scale of Cr₂O₃ with minimum Cr Content. This is due to the formation of delta ferrite, which leads to the precipitation of the Cr-based secondary phases and depletes the free Cr from the matrix. The thermal cycles during welding at high temperature are favorable for the formation of delta ferrite. On the other hand, in absence of delta ferrite, the base metal and HAZ regions of the weldment show lower corrosion rate than weld metal. The difference in corrosion rate in the three regions of the weldment is supplemented by post-corroded scale characterizations.