交流干扰下不同组织X100钢在格尔木土壤模拟溶液中的腐蚀行为

目的 使用不同组织X100钢模拟焊接接头,探究在格尔木土壤模拟环境下,交流干扰对X100管线钢焊接接头腐蚀行为的影响规律。方法 采用动电位极化曲线、恒电位极化曲线、浸泡实验及表面分析技术,对X100管线钢焊接接头的腐蚀行为进行系统研究。结果 动电位极化曲线表明,随着交流电流密度的增加,不同组织X100钢腐蚀电流密度呈增加的趋势,阴极由耗氧反应控制转变为由析氢反应主导。在交流干扰下,腐蚀速率V退火>V热轧>V正火,恒电位极化测试中,退火组织受到交流干扰的影响更为明显。不同组织X100钢腐蚀形态以局部腐蚀为主,且有不同程度的点蚀发生。退火组织的腐蚀坑数量多,尺寸大而深,点蚀多分布在珠光体与铁素体的晶界处,少数分布在珠光体内部;正火组织点蚀数量最少,尺寸最小;热轧组织中粒状贝氏体较多且呈弥散分布,有较多的小点蚀分布在粒状贝氏体聚集的区域。结论 不同组织X100管线钢因微观结构不同而导致其耐蚀性有所差异。交流干扰下,由于珠光体与铁素体组织形成的微电偶腐蚀较为严重,从而导致退火组织的耐腐蚀性最差;正火组织中M/A岛呈针状分布,粒状贝氏体相对较少,耐腐蚀性最好;热轧组织的耐蚀性居于退火组织与正火组织两者之间。     

微观组织对X52钢抗H2S腐蚀和开裂性能的影响

通过对X52钢进行热处理获得三种不同组织。SEM观察发现三种组织分别为铁素体/带状珠光体、马氏体/贝氏体和针状铁素体/回火马氏体。通过动电位极化、线性极化电阻、氢致开裂（HIC）实验和硫化物应力腐蚀开裂（SSC）实验,研究了不同热处理对X52钢在H₂S环境中的腐蚀与开裂行为的影响。结果表明马氏体/贝氏体显微组织由于位错密度很高且脆性大,因而腐蚀速率及HIC和SSC敏感性很高。铁素体/带状珠光体组织和针状铁素体/回火马氏体组织腐蚀速率及HIC和SSC敏感性很低。针状铁素体/回火马氏体组织由于不含带状组织且晶粒细小以及碳化物的析出,因此其HIC和SSC抗性优于铁素体/带状珠光体组织。     

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 采用三点弯曲法研究了不同组织类型的X70级管线钢的硫化物应力腐蚀开裂(SSCC)行为。结果表明：均匀细小的针状铁素体为主的显微组织具有优良的抗SSCC性能;针状铁素体内高密度缠结的位错和碳氮化物在位错网络上的沉淀析出是针状铁素体钢具有优良的抗SSCC性能的主要原因。     

Microstructure evolution and corrosion resistance in simulated CGHAZ of X80 high-deformability pipeline steel

In this study, the microstructure evolution and corrosion resistance in 0.5M Na₂CO₃-1 M NaHCO₃ solution of X80 high-deformability (X80HD) pipeline steel coarse-grained heat-affected zone (CGHAZ) with several heat input levels were investigated. It is shown that the microstructure of CGHAZ changes from bainite ferrite to granular bainite as the heat input increasing. In addition, the corrosion resistance and the stability of passive film of base material are better than those of CGHAZ with several heat input levels. Too small or too big heat input is inadvisable and better corrosion resistance of CGHAZ is attained when heat input is 30kJ/cm.     

热处理工艺对7%Cr钢显微组织及耐蚀性能的影响

利用质量损失法和电化学方法测试了3种不同组织类型的7%Cr钢在CO₂环境中的腐蚀行为,并通过EBSD和SKPM手段从晶界和表面电势角度分析了组织类型引起的耐蚀性能差异原因。结果显示:7%Cr钢轧态组织为贝氏体+铁素体,淬火态组织为淬火马氏体,正火态组织为铁素体+少量珠光体。试验钢的耐蚀性能排序为淬火态＞正火态＞轧态,试验钢产物膜中Cr元素的富集程度及其极化曲线自腐蚀电位均与此规律相符,试样表面最大电势差与此规律相反。轧制试样两相间存在电势差,易于形成原电池;淬火试样中Cr元素可通过晶界快速扩散至腐蚀位置形成产物膜;正火试样游离态Cr元素较少且高比例的大角度晶界不利于其扩散至腐蚀界面。     

3Cr低合金钢焊接接头腐蚀膜对基体的保护作用

利用扫描电镜分析3Cr低合金管线钢高频电阻焊接头微观组织,采用高温高压反应釜和电化学阻抗测试技术对焊接接头的CO₂腐蚀行为进行研究. 3Cr低合金钢高频电阻焊焊缝和母材的化学成分一致,组织均为铁素体+珠光体,且焊缝组织更加细小、均匀. 失重试验结果表明,焊接接头的腐蚀速率比母材小0.28 mm/年. 电化学阻抗测试结果表明,浸泡时间48和168 h后,焊缝表面腐蚀膜电阻均大于母材,焊缝腐蚀膜对基体的保护性均好于母材. 这是由于焊缝组织分布均匀细小,表面腐蚀膜均比母材均匀和致密. 浸泡48 h时焊缝表面为双层膜结构,母材为单层膜;浸泡168 h时焊缝和母材表面均为单层膜结构.     

X70级管线钢抗硫化物应力腐蚀开裂实验研究

用三点弯曲方法及SEM?TEM等手段研究了不同组织类型的X70级管线钢硫化物应力腐蚀开裂(SSCC)行为?结果表明,显微组织以均匀细小的针状铁素体为主的管线钢具有优良的抗SSCC性能;这主要是源于针状铁素体内高密度缠结的位错和碳氮化物在位错网络上的沉淀析出起到了强烈的氢陷阱作用?     

影响鞍钢X70管线钢CO2腐蚀行为的环境因素和材料因素

利用失重法、扫描电镜等,研究了X70管线钢在CO2分压为2MPa的NACE溶液中高温高压环境下的腐蚀行为,结果表明,温度和Cl-是影响X70钢腐蚀的主要环境因素,随温度的升高均匀腐蚀速率增大。钢中珠光体、粒状贝氏体组织及非金属夹杂物MnS、CaS等在腐蚀环境中促进了管线钢的腐蚀。因此在材料方面要降低珠光体及粒状贝氏体含量,细化夹杂物,并降低夹杂物级别。     

Effect of Strain Aging on Tensile Behavior and Properties of API X60, X70, and X80 Pipeline Steels

The effect of strain aging on tensile behavior and properties of API X60, X70, and X80 pipeline steels was investigated in this study. The API X60, X70, and X80 pipeline steels were fabricated by varying alloying elements and thermomechanical processing conditions. Although all the steels exhibited complex microstructure consisting of polygonal ferrite (PF), acicular ferrite, granular bainite (GB), bainitic ferrite (BF), and secondary phases, they had different fractions of microstructures depending on the alloying elements and thermomechanical processing conditions. The tensile test results revealed that yielding behavior steadily changed from continuous-type to discontinuous-type as aging temperature increases after 1% pre-strain. After pre-strain and thermal aging treatment in all the steels, the yield and tensile strengths, and yield ratio were increased, while the uniform elongation and work hardening exponent were decreased. In the case of the X80 steel, particularly, the decrease in uniform elongation was relatively small due to many mobile dislocations in PF, and the increase in yield ratio was the lowest because a large amount of harder microstructures such as GB, BF, and coarse secondary phases effectively enhanced work hardening.     

太钢X70高级别管线钢的开发

介绍了太钢X70高级别管线钢的成分设计,冶炼和TMCP工艺。X70管线钢的显微组织由针状铁素体、多边形铁素体和少量粒状贝氏体组成,该钢种具有高强度、高低温冲击韧性和优异的落锤撕裂性能,其钢质纯净,带状组织级别低。     

X52钢的CO2腐蚀行为

通过扫描电镜观察及X射线衍射分析,研究X52钢在模 拟输送管腐蚀环境条件下的腐蚀行为.结果表明,X52钢的平均腐蚀速率为06289 mm/a ,其表面形成三层形貌及成分各异的腐蚀产物,三层膜中主要的腐蚀产物均是FeCO3和Fe 2O3,宏观腐蚀形态基本为均匀腐蚀,但是在扫描电镜下观察到金属遭受的破坏以局部 腐蚀为主.     

Effect of heat treatment on H2S corrosion of a micro-alloyed C–Mn steel

The H₂S corrosion resistance of a C–Mn pipeline steel with three different microstructures has been evaluated using electrochemical techniques with a 3% wt. NaCl solution at 50 °C. Microstructures included martensite, ferrite, and ferrite + bainite. Electrochemical techniques included potenthiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and electrochemical noise (EN) measurements. Most of the tests lasted 24 h. All techniques showed that the highest corrosion rate corresponded to the steel with a martensitic microstructure; up to one order of magnitude higher than the corrosion rate for steels with a ferritic + bainitiic microstructure, whereas the steel with the ferritic microstructure showed the lowest corrosion rate. EIS tests showed that the corrosion process was under charge transfer control, whereas EN results indicated that the three steels exhibited a clear tendency towards a localized type of corrosion. However, for longer immersion times, the steel with a martensitic microstructure tended to exhibit a mixture of uniform and localized attack. Results were discussed in terms of grain size, grain boundary energy, amount and distribution of particles found in each steel.     

双相区加速冷却处理对X80管线钢组织与性能的影响

采用双相区加速冷却法(加速冷却始冷温度为700 ℃)对X80管线钢进行热处理,获得了贝氏体和铁素体(B+F)双相组织。然后通过组织表征、力学性能测试以及在3.5wt%NaCl溶液中的耐蚀性进行研究。结果表明:热处理后获得的管线钢组织由板条状贝氏体、多边形铁素体及少量马氏体/奥氏体岛组成。与热处理前相比,(B+F)双相管线钢屈强比较低,为0.65,初始加工硬化指数为0.31,均匀伸长率达8.3%,塑性显著提升;双相组织中含有52.4%的铁素体,因而耐腐蚀性明显提高。通过双相区加速冷却法获得的(B+F)两相组织在塑变过程中发生协调变形,可以适应大变形的需求,同时耐蚀性优异,为大变形管线钢实际生产提供一定的借鉴。     

X80管线钢及其接头的低温韧性和显微组织

分别利用示波冲击韧性试验、硬度试验和光学显微镜、透射电镜研究了X80管线钢及其焊管接头的力学性能和显微组织。试验结果表明，X80钢及其焊管接头具有良好的韧性，其中焊缝的韧性最高，焊接热影响区粗晶区因受焊接热效应引起晶粒粗化和形成脆性组织，故韧性最低。试验钢由针状铁素体和少量块状铁素体组成，焊缝为典型的针状铁素体组织，焊接热影响区粗晶区以粒状贝氏体为主。焊接热影响区熔合线附近的硬度值最高，越远离熔合线硬度值越低，并逐渐接近母材的硬度值。     

Effects of Microstructure on Corrosion of X70 Pipe Steel in an Alkaline Soil

Corrosion of X70 steel with different heat treatments (quenching, air cooling, and furnace cooling) in an alkaline soil was investigated by weight-loss, surface characterization and electrochemical measurements. The cathodic/anodic reactions of X70 steel in alkaline soil are dominated by the oxygen reduction and formation of iron oxides that deposit on the steel surface. The protection of the oxide deposit is through a physical block effect. The deposit layer formed on as-received steel has a compact, complete structure and thus, provides an effective protection over the underneath steel. However, the deposit layers on the heat-treated steels are generally loose, porous and defective, and provide minor protectiveness. Corrosion of steel is affected by its microstructure. Generally, steels with heat treatments have a higher corrosion rate than the as-received steel. The presence of more pearlite enhances the corrosion rate of ferrite by a galvanic effect. When the steel contains bainite and martenite phases, the activity of the steel is further increased.     

显微组织对25CrMo48V超高强度钢在NaCl溶液中腐蚀行为的影响

采用动电位极化法和电化学阻抗法等研究了不同冷却方式对25CrMo48V超高强度钢在NaCl溶液中的腐蚀行为的影响。结果表明,25CrMo48V超高强度钢炉冷后的显微组织为多边形铁素体和珠光体,空冷后为下贝氏体和多边形铁素体,水淬后为板条马氏体。由电化学分析可知,不同显微组织的试样在NaCl溶液中具有相似的电化学腐蚀过程;在质量分数为1%、3%、5%、7%的NaCl溶液中,不同显微组织的试样具有相同的腐蚀速率变化规律,下贝氏体组织的空冷试样腐蚀速率最低,而板条马氏体组织的水淬试样腐蚀速率最高。通过观察不同显微组织的试样在NaCl溶液中浸泡后的宏观腐蚀形貌,可知下贝氏体组织的耐腐蚀性最好,板条马氏体组织的耐腐蚀性最差,与电化学测试结果一致。     

X80管线钢在近中性pH溶液中腐蚀行为研究

目的研究X80管线钢在近中性p H溶液中的腐蚀与应力腐蚀裂纹萌生行为。方法采用电化学实验和浸泡实验研究X80管线钢在近中性p H溶液中的腐蚀行为,采用慢应变速率拉伸实验研究X80管线钢在近中性p H溶液中,在自腐蚀电位和外加电位下的应力腐蚀裂纹萌生行为。结果 X80管线钢在近中性p H溶液中的极化曲线只有活化区,没有钝化区,其自腐蚀电位约为-750 m V,浸泡195天后,试样表面没有氧化膜出现,但是观察到点蚀坑。在自腐蚀电位下,X80管线钢试验表面有大量的应力腐蚀裂纹;在-500 m V阳极外加电位下,X80管线钢试验表面几乎没有观察到应力腐蚀裂纹;在-850 m V阴极外加电位下,X80管线钢试验表面的应力腐蚀裂纹很少,但是随着外加阴极电位负移到-1300 m V时,X80管线钢试验表面的应力腐蚀裂纹增多。结论 X80管线钢在近中性p H溶液中发生均匀腐蚀,但是夹杂物剥落能在X80管线钢表面形成点蚀坑。在近中性p H溶液中,在自腐蚀电位下,X80管线钢应力腐蚀裂纹萌生敏感性最强;外加阴极电位抑制应力腐蚀裂纹萌生,但是随着外加阴极电位的负移,应力腐蚀裂纹萌生敏感性增强;外加阳极电位下,由于均匀腐蚀的作用,应力腐蚀裂纹萌生敏感性较弱。     

Stress corrosion cracking behavior of X70 pipe steel in an acidic soil environment

Stress corrosion cracking (SCC) behavior of X70 pipe steel was investigated in an extracted acidic soil solution by slow strain rate test (SSRT), potentiodynamic polarization curve measurements and surface analysis technique. The SCC process and mechanism of X70 steel in the acidic soil solution is mixed-controlled by both anodic dissolution and the hydrogen involvement. With the different applied potentials, the dominance of SCC process changes. At a relatively less negative potential, the steel SCC is based primarily on the anodic dissolution mechanism. When the applied potential is shifted negatively, hydrogen is involved in the cracking process, resulting in a transgranular cracking mode. With the further negative shift of applied potential, the SCC of the steel follows completely a hydrogen-based mechanism, with a river-bed shaped brittle feature of the fracture surface. Heat treatment alters the microstructure of the steel, resulting in a change of SCC susceptibility. In particular, the quenched steel with a bainite microstructure has a high susceptibility to SCC in the acidic soil, while the as-received steel with a ferrite matrix have a low SCC susceptibility.     

Corrosion Behavior of Low-Alloy Pipeline Steel with 1% Cr Under CO2 Condition

Carbon dioxide corrosion behavior of low-alloy pipeline steel with 1% Cr exposed to CO₂-saturated solution was investigated by immersion experiment. SEM, EDX, TEM, EPMA and XRD were utilized to investigate the microstructure, corrosion morphologies, corrosion phases and elements distribution of corrosion scale. The results demonstrate that the microstructure of tested steel consists of ferrite and carbides. During the corrosion process, ferrite dissolves preferentially, leaving carbide particles behind. The residual carbide particles may promote the nucleation of FeCO₃ crystal. The phase comprising of the inner layer is Cr compound, and the one of the outer layer is FeCO₃. The formation process of corrosion scale can be illustrated as follows: Firstly, a thin scale consisting of thin inner layer and outer layer is formed, which represents poor corrosion resistance; then, the inner layer changes little, once it has been formed, and the outer layer becomes thick and compact, which demonstrates that a fine corrosion resistance is obtained. The chemical elements of chromium and molybdenum accumulate in the inner layer of corrosion scale. The corrosion behavior of low-alloy steel based on microstructure and morphology characterization is also discussed.     

X80钢在干湿交替与水饱和哈密土壤环境下的腐蚀行为

目的揭示X80钢在干湿交替与水饱和哈密土壤环境下的腐蚀行为与规律。方法采用失重实验和电化学测试分析腐蚀速率与阴阳极电化学过程的变化规律,利用金相分析观察母材和焊缝的组织特征,通过SEM、EDS、XRD等微观分析手段观察腐蚀产物形貌、元素含量与物相组成,从而研究干湿交替与水饱和土壤环境对X80钢腐蚀行为的影响。结果 X80钢在干湿交替环境下的腐蚀速率是水饱和下的2～3倍,其在干湿交替与水饱和哈密土壤环境下的腐蚀产物物相均由Fe3O4、FeOOH、FeS所构成。X80钢在干湿交替环境下,表面的腐蚀产物膜出现大量凹坑与裂隙,使O2在试样表面分布不均,形成氧浓差电池,并且该凹坑与裂隙有利于腐蚀性离子进入,加剧局部腐蚀。在同一环境下,由于焊接接头各区域组织差异引起的微电偶腐蚀,X80钢焊缝的腐蚀速率明显高于母材。结论干湿交替环境与土壤中大量存在的Cl-显著加速了X80钢母材及焊缝的局部腐蚀,且X80焊缝耐蚀性明显低于母材,其腐蚀机理均为氧浓差电池和局部腐蚀自催化效应共同作用,腐蚀形态也由以全面腐蚀为主(水饱和环境)转变为以点蚀+溃疡状腐蚀为主(干湿交替环境)。