CO32--HCO3-溶液中X80管线钢焊接接头的应力腐蚀开裂分析

采用慢应变速率试验(SSRT)、扫描电镜(SEM)观察研究了国产X80管线钢焊接接头在 0.5 mol/L Na2CO3 1 mol/L NaHCO3 溶液中的应力腐蚀开裂(SCC)敏感性.结果表明,拉伸试样全部断裂在焊缝或热影响区.在所研究的电位区间,拉伸试样随着外加电位正向增加,断面收缩率、断裂时间和断后伸长率增加,而断口部位的裂纹平均扩展速率减小,SCC敏感性降低.试样断口形貌在阴极电位条件下呈准解理断裂,在自腐蚀电位和阳极电位条件下,焊缝试样断口主要是韧性断裂.应力腐蚀机理可以用阳极溶解理论和氢致破裂来解释.     

X70管线钢焊缝应力腐蚀破裂的研究

采用慢应变速率试验、扫描电镜试验研究了X70管线钢焊缝拉伸试样在通5％CO2 95％N2的NS4溶液中的应力腐蚀破裂(SCC)敏感性。结果表明断口和柱面SCC裂纹均发生在热影响区(HAZ)。施加阴极电位时，在试样断口观察到明显的准解理断裂特征，断口和柱面有穿晶SCC裂纹。在自腐蚀电位和阳极电位条件下，SCC敏感性很低。在所研究的电位区间，总体趋势是随电位正向增加，断面收缩率、断裂时间和延伸率增加，而断口部位SCC裂纹平均扩展速率减少、即SCC敏感性降低。并利用显微组织变化和电化学理论分析了焊缝试样HAZ的SCC机理。     

库尔勒土壤模拟溶液中X80钢焊接接头的应力腐蚀开裂行为

利用动电位扫描技术和慢应变速率拉伸试验(SSRT)以及扫描电子显微镜(SEM)研究了库尔勒土壤模拟溶液中不同外加阴极电位下X80管线钢焊接接头的应力腐蚀开裂(SCC)行为。结果表明:阴极电位对X80钢焊接接头处的SCC敏感性影响较为明显。拉伸试样全部断裂在焊缝或热影响区。在Ecorr下,金属表面裂纹萌生于点蚀坑,试样开裂为阳极溶解机制。当外加电位为-800 m V至-900 m V时,金属处于阴极保护电位区,此时金属的SCC敏感性较低,其开裂机制为阳极溶解和氢致开裂混合机制。当外加电位小于等于-950 m V时,外加电位越低,材料的SCC敏感性越大,此时金属SCC行为表现为氢脆机制。     

LC4铝合金的应力腐蚀研究

用Ⅱ型试样以慢拉伸方法研究了拉伸速度和极化电位对LC4铝合金应力腐蚀开裂行为的影响。采用应力腐蚀开裂面积A_(SCC)、应力腐蚀最大抗拉强度σ_(SCC)及其所对应的应变ε_(SCC)作为衡量应力腐蚀开裂敏感性的参数。结果表明,随拉伸速度降低,应力腐蚀开裂敏感性升高,但用σ_(SCC)来表现应力腐蚀开裂的敏感性不如A_(SCC)明显。阳极极化使抗拉强度下降;阴极极化时。若极化电位较小,则抗拉强度略有升高,强阴极极化抗拉强度则又会降低,说明应力腐蚀包含氢脆和阳极溶解两种机制。断口形貌观察发现,开路、阴极极化和充氢时的断口形貌相同,阳极极化则与其不同,表明开路时的应力腐蚀开裂是以氢脆为主的。     

外加电位对X90钢及其焊缝在近中性土壤模拟溶液中应力腐蚀行为的影响

采用慢应变速率拉伸(SSRT)实验、动电位极化技术和SEM观察等方法,研究了X90钢基体和焊缝在近中性土壤模拟溶液中不同阴极保护电位下的应力腐蚀行为。结果表明,X90管线钢及其焊缝组织在近中性土壤模拟溶液中均具有一定的应力腐蚀敏感性,裂纹扩展为穿晶腐蚀裂纹;应力腐蚀开裂(SCC)的裂纹萌生与扩展与外加保护电位有关。在开路电位(OCP)~-1000 m V的电位范围内,X90钢的SCC机制均为阳极溶解(AD)+氢脆(HE)的混合机制;在OCP下,由于AD作用较强,SCC敏感性较明显;在-800 m V下,由于AD和HE作用均较弱,导致SCC敏感性最低;而在-900 m V时,由于HE作用明显增强,具有最高的SCC敏感性;在相同电位条件下,焊缝的SCC敏感性高于母材。     

外加电位对X80管线钢在轮南土壤模拟溶液中应力腐蚀行为的影响

采用慢应变速率拉伸(SSRT)实验、SEM观察和动电位极化曲线测量等方法,研究了外加电位对X80管线钢母材及焊缝在轮南土壤模拟溶液中的应力腐蚀开裂(SCC)行为。结果表明,X80钢母材及焊缝在轮南土壤模拟溶液中均具有一定的应力腐蚀敏感性。在同一外加电位下,X80钢焊缝的SCC敏感性高于母材的;X80钢SCC敏感性及开裂机理受外加电位影响显著,在-500 mV外加阳极电位下,X80钢的SCC机理为裂尖阳极溶解-膜破裂机制,在-800 mV阴极电位以下(-850,-1000和-1500 mV),氢脆作用在SCC过程中的影响明显增强,阴极析氢反应促进了钢的氢致开裂,导致X80钢SCC敏感性显著增加。     

外加电位对316L不锈钢在硼酸溶液中应力腐蚀行为的影响

采用慢应变速率拉伸 (SSRT) 实验,结合不同扫描速率下的动电位极化曲线,对316L不锈钢在动电位极化曲线不同区下的应力腐蚀开裂 (SCC) 敏感性以及腐蚀机理进行了研究。通过断口的SEM形貌进一步分析了316L不锈钢在硼酸溶液中的应力腐蚀开裂机理。结果表明,在近中性硼酸溶液环境下,外加电位对应力腐蚀开裂敏感性具有一定影响;当外加电位处于钝化区和过钝化区时,其SCC机制是由阳极溶解控制,且随着电位的升高其SCC敏感性增大;外加电位为-600 mV时,开裂机制为氢致开裂,此时316L不锈钢有最大SCC敏感性。     

力学与电化学作用下X80钢焊接接头SCC行为分析

采用动电位扫描技术及慢应变速率拉伸试验(slow strain rate test, SSRT)研究了X80钢焊接接头在库尔勒模拟溶液中应力腐蚀开裂(stress corrosion cracking, SCC)行为,并利用扫描电镜(scanning electron microscope, SEM)对不同应变速率下试样断口形貌进行表征.结果表明,随着应变速率的增加,X80钢焊接接头的腐蚀速率则呈现持续增大的趋势.当应变速率为1×10-5/s时,试样的腐蚀情况最为严重. X80钢焊接接头在不同应变速率下的腐蚀机制是由电化学-力学交互作用共同决定的.试样发生应力腐蚀后断裂于焊缝处,这是由于焊接过程导致焊缝晶格存在大量的缺陷,使得晶格活性较高所致.     

外加电位对X70管线钢在库尔勒土壤模拟溶液中应力腐蚀开裂敏感性的影响

采用慢应变速率拉仲试验(SSRT)研究了不同外加电位下X70管线钢在库尔勒土壤模拟溶液中的应力腐蚀开裂(SCC)行为,并用扫描电镜分析了不同电位下的断面形貌.结果表明,X70管线钢在库尔勒土壤模拟溶液中具有SCC敏感性;在Ecorr附近施加弱极化时,应力腐蚀开裂敏感性增加;施加强阳极电位时,发生强烈阳极溶解,导致阳极溶解断裂;施加强阴极电位时,析氢过程加强,导致氢致应力腐蚀断裂.     

X70钢焊接接头在近中性溶液中应力腐蚀行为研究

采用慢应变速率试验(SSRT)、扫描电镜以及电化学测量技术研究了X70管线钢焊接接头在近中性模拟土壤溶液中的应力腐蚀开裂(SCC)行为。结果表明,断口和柱面SCC裂纹均发生在热影响区(HAZ)。在试验溶液中,随着外加极化电位降低管线钢SCC敏感性增强,电位负移到一定电位值后,SCC敏感性减弱;随着溶液pH值降低,腐蚀速率增大,敏感电位区间负移。施加阴极电位时,在试样断口观察到明显的准解理脆断特征,断口和柱面有穿晶SCC裂纹。分析了焊接接头试样HAZ的SCC机理,在试验介质中,管线钢应力腐蚀开裂主要受阳极溶解和氢致开裂两种机理的联合作用,适当的电位可以使阳极溶解和氢致开裂的联合作用达到最大,从而造成较严重的应力腐蚀开裂。     

X70管线钢在近中性及高pH值溶液中的电化学行为和SCC敏感性

采用动电位极化曲线测试法研究了温度、通气条件和pH值对X70管线钢在NS4溶液和0.5 mol/LNa2CO3 1 mol/L NaHCO3溶液中的电化学极化行为的影响,并用慢应变速率试验(SSRT)研究了X70管线钢在这些溶液中的应力腐蚀破裂(SCC)敏感性。结果表明,X70管线钢在NS4溶液中不出现活化—钝化转变区,随外加电位负移,SCC敏感性增加,表现出氢致破裂(HIC)的特征;在0.5 mol/L Na2CO3 1 mol/L NaHCO3高pH值溶液中出现活化—钝化转变区,在阴极极化区,也表现出氢致破裂(HIC)的特征,但在阳极极化区,发生的是阳极溶解型应力腐蚀破裂(ADSCC)。     

Effect of Travel Speed on the Stress Corrosion Behavior of Friction Stir Welded 2024-T4 Aluminum Alloy

The effect of travel speed on stress corrosion cracking (SCC) behavior of friction stir welded 2024-T4 aluminum alloy was investigated by slow strain rate tensile test. Microstructure and microhardness of the welded joint were studied. The results showed that the size of second phase particles increased with increasing travel speed, and the distribution of second phase particles was much more homogeneous at lower travel speed. The minimum microhardness was located at the boundary of nugget zone and thermomechanically affected zone. In addition, the SCC susceptibility of the friction stir welded joint increased with the increase of travel speed, owing to the size and distribution of second phase particles in the welds. The anodic applied potentials of ?700, ?650, ?600 mV, and cathodic applied potential of ?1200 mV facilitated SCC while the cathodic applied potential of ?1000 mV improved the SCC resistance. The SCC behavior was mainly controlled by the metal anodic dissolution at the open circuit potential, and hydrogen accelerated metal embrittlement.     

堆内构件304L焊接件在除氧和氯离子环境中的应力腐蚀开裂研究

采用高温高压慢应变速率拉伸试验方法(SSRT),研究了在除氧环境下不同浓度氯离子对304L焊接件在模拟一回路高温高压硼锂水介质中氯致应力腐蚀开裂的影响。结果表明:当氯离子浓度为1 mg/L时,其各项力学性能指标与惰性氮气空白样一致,表明在低浓度氯离子除氧条件下,304L焊接件没有应力腐蚀敏感性。随着氯离子含量(1~50mg/L)的增加,304L焊接件应力腐蚀敏感指数变化呈增加趋势。断口侧面没有观察到明显的裂纹,氯离子浓度越低,断口缩颈现象越明显,表明主要是机械断裂。氯离子浓度较高时,棱角部分出现微裂纹源,可能与棱角部分应力更为集中相关。所有样品的断裂位置都在焊缝和热影响区,在焊缝和热影响区发生了巨大的形变,离断口越近,变形越严重。焊接部位是304L堆内构件中薄弱环节,应该成为应力腐蚀开裂和其他性能检测的重点部位。     

Stress corrosion cracking study of microalloyed pipeline steels in dilute NaHCO3 solutions

Studies were carried out to evaluate the stress corrosion cracking (SCC) behavior of a X-70 microalloyed pipeline steel, with different microstructures by using the slow strain rate testing (SSRT) technique at 50 °C, in NaHCO₃ solutions. Both anodic and cathodic potentials were applied. Additionally, experiments using the SSRT technique but with pre-charged hydrogen samples and potentiodynamic polarization curves at different sweep rates were also carried out to elucidate hydrogen effects. The results showed that the different microstructures in conjunction with the anodic applied potentials shift the cracking susceptibility of the steel. In diluted NaHCO₃ solutions cathodic potentials close to their rest potential values decreased the SCC susceptibility regardless the microstructure, whereas higher cathodic potentials promote SCC in all steel conditions. Certain microstructures are more susceptible to present anodic dissolution corrosion mechanism. Meanwhile concentrated solution did not promotes brittle fracture.     

低碳钢在“乙醇胺+CO_2”水溶液中的应力腐蚀开裂

<正> 一、引言 我国炼油工业中的脱硫装置溶剂再生塔通常应用乙醇胺水溶液脱除进料中的酸性气体CO_2和H_2S。温度较低时,乙醇胺吸收酸性气体;温度升高时又重新放出所吸收的酸性气体,其可逆反应如下[1]: 2RNH_2+CO_2+H_2O(?)[(RNH_2)H]_2CO_3 2RNH_2+H_2S(?)[(RNH_2)H]_2S 反应式中R代表-OHCH_2CH_2。关于应用乙醇胺脱除酸性气体的详细工艺过程参看文献。 由于乙醇胺和酸性气体构成的复杂环境和应力(包括焊缝残余应力)的联合作用,经常使再生塔高温塔段(塔内环境的温度为90～120℃,pH值为9～11)发生应力腐蚀开裂     

Study on H2S stress corrosion test of welded joint for X65pipeline steel and numerical analysis

The susceptibility of welded joint for the X65 pipeline steel to H2S stress corrosion cracking (SCC) is investigated.SCC tests on the steel are carded out in the environment based on NACE TM-O1-77 solution with saturated gaseous H2S. The threshold stress intensity factor and crack propagation velocity are calculated according to wedge-opening loading (WOL)specimens. The three-dimensional elastic-plastic finite element analysis of WOL specimens is pesformed by using the FEM programming package ANSYS. Stress field and concentration of hydrogen distribution property ahead of the crack tip are obtained. This paper surveyed the microstructure of welded joint and studied on the mechanical properties of X65 pipeline steel.It provides experimental basis for studying stress corrosion. The results of numerical analysis are consistent with conclusions of stress corrosion test.