X90管线钢的抗氢致开裂性能

目前有关X90管线钢抗H2S性能的研究报道较少.为此,采用NACE TM 0284-2003方法对X90和X80管线钢进行氢致开裂(HIC)试验以对比研究其抗HIC性能,论述了氢致开裂的机理,并分析了X90管线钢的微观组织和化学成分对氢致开裂的影响.结果表明:X90管线钢的抗HIC性能较X80管线钢差,X90钢的热影响区与焊缝区的抗HIC性能比母材好;X90钢易产生Mn的偏析,且C会加剧其偏析,同时Cr的碳化物析出使氢鼓泡易在此处产生,2种因素均导致X90钢的抗HIC性能降低;适当控制微观组织比例,降低C含量,在保证提高X90管线钢强度的同时,严格控制Mn和Cr的含量,可以提高其抗HIC性能.     

小直径薄壁钢管HIC腐蚀评价方法探讨

对管线钢10(HSC)在NACE A溶液中进行氢致开裂试验,通过形貌观察、裂纹统计与评价等方法研究了试样形式、裂纹测量和氢致开裂(HIC)裂纹认定对小直径薄壁管线钢氢致开裂性能的影响。结果表明:舟形或整管试样应以中性层的弧长和试样的壁厚作为试样裂纹率的计算依据;钢管中的HIC裂纹可能呈现为不规则状,平行于试样中性层的方向为裂纹的长度方向,垂直于试样中性层的方向为裂纹的厚度方向;小直径薄壁管对裂纹厚度率非常敏感,相关标准中“位于内壁或外壁1 mm以内的裂纹不算作HIC裂纹”的规定不适用于小直径薄壁管,对于小直径薄壁管的HIC腐蚀应建立新的评价方法。     

超快冷工艺对高铌X80管线钢抗腐蚀性能的影响

依据NACE标准,研究了采用新型超快速冷却工艺生产的X80管线钢抗硫化物应力腐蚀开裂(SSCC)、抗氢致开裂(HIC)和抗CO2等腐蚀的情况.SSCC腐蚀实验表明,产生开裂的临界应力值在65 ％σs (390MPa)左右,超过此临界值,试样的腐蚀敏感性较高,抗腐蚀能力较差,在95％σs加载水平下,应力敏感性极高.HIC腐蚀实验表明,裂纹敏感百分比、裂纹长度百分比和裂纹厚度百分比均为零.抗CO2腐蚀实验表明,在CO2压力为0.1MPa条件下,平均腐蚀速率为0.6843mm/a.研究表明采用新型超快冷工艺生产的X80管线钢具有优良的抗SSCC腐蚀性能、抗HIC腐蚀性能和抗CO2腐蚀性能.     

API X52管线钢在饱和硫化氢气田水溶液中的氢渗透与氢致开裂行为

天然气输送管道氢致开裂问题日益突出,而API X52管线钢在气田模拟水溶液中氢渗透和氢致开裂的研究较少。模拟了饱和硫化氢某气田水溶液,采用电化学和恒载荷拉伸试验方法,测定了API X52管线钢在不同充氢电流密度下的氢扩散系数、可扩散氢浓度(ω0)及管线钢氢致开裂临界可扩散氢浓度(ωHIC)。结果表明:API X52管线钢可扩散氢浓度(ω0)与充氢电流密度呈线性关系,即ω0=0.99+0.07J;其恒载荷下开裂临界可扩散氢浓度的对数值(lnωHIC)随拉应力(σ)呈线性下降,即σ=475-450lnωHIC。     

连铸坯偏析对钢板氢致开裂的影响

按照YB/T 4003-1997《连铸钢板坯低倍组织缺陷评级图》对连铸坯进行了宏观低倍检验,并利用OPA-100型原位分析仪对连铸坯偏析进行了定量检测,然后按照NACE 0284-2003《管道、压力容器抗氢致开裂钢性能评价的试验方法》对经热机械控制工艺(TMCP)轧制成的钢板取样进行氢致开裂(HIC)腐蚀试验。结果表明:连铸坯中心偏析是钢板发生HIC的主要原因,偏析元素主要有硫、磷、碳、锰等;通过合理的成分设计和工艺控制,实现了连铸坯偏析的良好控制,所生产的连铸坯可满足抗HIC管线钢工业生产需求。     

抗H_2S腐蚀性能试验中的一种慢速通气方法

在依据NACE TM0177-2005中的A法进行硫化物应力腐蚀(SSC-A)试验和NACE TM0284-2011进行氢致开裂(HIC)试验时,提出了一种慢速通气方法,并采用碘量滴定法测定了溶液中H2S的质量浓度,同时对H2S在溶液中达到饱和的时间和H2S达到饱和时溶液的pH值进行了研究。结果表明:采用慢速通气法进行SSC-A试验和HIC试验分别比标准要求的快速通气方法每次试验可节约800 mL和1 695 mL H2S气体,大大降低了试验成本,减少了有毒气体H2S的排放,同时还可保证试验结果的可靠性和真实性。     

管线用钢显微组织对氢致裂纹影响的研究

选用了四种不同显微组织的国产同牌号管线用钢,根据美国腐蚀工程师协会标准NACETM0284-2003,对其进行氢致开裂实验,并用光学显微镜和扫描电镜对其断面组织进行了观察,分析其显微组织对抗氢致裂纹性能的影响。认为,带状组织以及组织不均匀性是引起材料抗氢致裂纹性能下降的主要因素,但这两种因素引起开裂的方式和机理不同。同时发现晶粒度大小对该材料抗氢致裂纹性能没有明显影响。     

显微组织对X80钢氢致裂纹敏感性和氢捕获效率的影响

对以针状铁素体为主的X80管线钢进行不同工艺的热处理,分别得到具有多边形铁素体组织或板条马氏体组织的试样。研究了显微组织对不同试样在饱和H_2S环境中的氢致裂纹(HIC)敏感性和氢渗透行为的影响。结果表明:具有不同显微组织的X80钢其HIC敏感性从大到小的排序为:1水淬处理的板条马氏体组织试样,2空冷处理的多边形铁素体组织试样,3原始针状铁素体组织试样;氢在材料中的捕获效率是影响材料HIC敏感性的主要因素之一,渗氢通量J_∞、氢扩散系数D_(eff)越低,氢捕获效率越高,管线钢的氢致裂纹敏感性越高。     

抗酸钢中产生氢致裂纹与氢鼓包的原因分析

将生产的抗酸管线钢按照NACE TM0284-2003标准进行硫化氢腐蚀试验,通过光学显微镜、扫描电镜对酸性腐蚀后试样中的氢致裂纹进行宏观与微观观察,发现氢致裂纹呈现多种形态,有阶梯状氢致裂纹、单个裂纹、Y字形裂纹等;对试样表面氢鼓包进行微观观察,发现鼓包心部实际也是氢致裂纹。观察发现:不论是氢致裂纹还是氢鼓包,裂纹均起源于偏析带状、氧化物夹杂以及粗大晶粒的晶界处。最终通过工艺控制,得到了良好的带状组织,保证了抗酸管线的批量生产。     

不同热处理对V150钻杆材料性能的影响

随着酸性油气田的陆续出现,钻杆在酸性环境下腐蚀性能的研究显得尤为重要。采用金相显微镜、万能试验机、冲击试验机、扫描电镜、能谱仪等对不同热处理后V150钻杆材料的性能进行了研究。结果表明:热处理可以提高V150钻杆材料的抗硫化氢应力腐蚀(SSC)性能及氢致开裂(HIC)性能;二次回火对V150钻杆材料的力学性能及腐蚀性能影响不大。夹杂和缺陷是导致V150钻杆材料抗SSC性能降低的主要原因。HIC试验后试样的主要腐蚀产物为Fe和Mn的硫化物,Cu,Ni等元素有利于提高G105钻杆材料的抗HIC敏感性。     

The effect of hydrogen induced cracking on the integrity of steel components

The occurrence of hydrogen embrittlement is a much researched phenomenon, known to cause mechanical property degradation and catastrophic failures. The ductility loss brought about by hydrogen ingress is encountered even in unstressed bodies where such cracking is termed hydrogen induced cracking (HIC) and is in phenomenological contrast to catastrophic failures encountered by stressed bodies subjected to hydrogen producing environments. This article will discuss HIC in some detail. This form of cracking is especially detrimental and often observed in oil country tubular goods (OCTG) which are subjected to sour gas. Consequently, the significance of HIC is most appreciated by oil companies at various stages of oil extraction, transportation and storage. In this article the chemical and metallurgical genesis of HIC, its harmful impact on material and component integrity are discussed. It has been noted that MnS inclusions are extremely harmful to this form of cracking. Similarly, centreline segregation in the ingot stage and deoxidation practices during steelmaking were found to affect HIC. Some case studies of HIC obtained from literature are presented. The variables affecting the propensity to HIC are provided in brief. Suitable measures to reduce or eliminate HIC in steels are also discussed.     

Experimental Investigation on the Performance of Armour Grade Q&T Steel Joints Fabricated by Flux Cored Arc Welding with Low Hydrogen Ferritic Consumables

Quenched and Tempered(Q&T)steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness.These steels are prone to hydrogen induced cracking(HIC) and softening in the heat affected zone(HAZ)after welding.The use of austenitic stainless steel(ASS) consumables to weld the above steel was the only available remedy to avoid HIC because of higher solubility for hydrogen in austenitic phase.Recent studies revealed that low hydrogen ferritic(LHF)steel con...     

Wet hydrogen sulfide cracking of steel monitoring by acoustic emission: discrimination of AE sources

In the petroleum industry, it is known that equipments which operate in wet hydrogen sulfide (H₂S) media can be subjected to damages like Hydrogen Induced Cracking (HIC) and Sulfide Stress Cracking (SSC). In this study, Acoustic Emission (AE) technique is used to monitor the cracking of steels immersed in sour media. The aim is to establish a methodology for HIC and SSC detection by AE and therefore to get more detailed information on the cracking mechanisms in steels during standard tests. The main focus of this article is the preliminary identification of the different AE sources involved during the tests performed in sour media. The methodology of identification of the different AE signals and the monitoring of HIC and SSC tests performed on different steel grades are described. The results indicate that AE can provide an early detection of cracking (HIC and SSC) when the various AE sources are identified.     

Effect of bainitic microstructure on the susceptibility of pipeline steels to hydrogen induced cracking

Hydrogen induced cracking (HIC) of API X80 and API X100 pipeline steels have been investigated in high pH carbonate-bicarbonate environment using slow strain rate testing (SSRT) method. It has been found that while both steels are highly susceptible to HIC, and diffusible hydrogen content is higher in API X80 than in API X100, the later steel is more vulnerable than the former at high (more negative) cathodic potential. This higher susceptibility can be primarily attributed to the combined effect of (1) separation of bainitic lath boundaries due to hydrogen trapping in these locations, (2) mobile hydrogen, and (3) stress. The charging-discharging experiments followed by SSRT experiments in air suggest that, the cracks that appeared due to lath boundary separation did not cause the reduction of ductility by themselves, rather it was the diffusible hydrogen that forced these cracks to propagate and, ruptured the steel with very low percent reduction of area (%RA). Despite the fact that the mobile hydrogen content plays a key role in causing the embrittlement, the large number of cracks in API X100 steel, resulting from the bainitic lath boundary separation at high cathodic potential, superseded the effect of higher diffusible hydrogen content in API X80 steel. The general conclusion is that bainitic lath type microstructure is more vulnerable to HIC at high cathodic potential than the ferritic/granular bainitic ones. It has been also found that applying cathodic protection can lead to excessive hydrogen embrittlement in both of the abovementioned steels in high pH carbonate-bicarbonate environment and, therefore, efforts need to be invested in developing nobler (more positive corrosion potential) and better HIC resistant steels.     

Hydrogen-induced cracking in two linepipe steels

Linepipe steels are susceptible to hydrogen-induced cracking (HIC) in wet, sour gas environments. Two commercially produced linepipe steels were investigated with regard to HIC on cathodic charging. Both steels, B and C, showed a high banded microstructure consisting of alternative layers of polygonal ferrite and a mixture of non-ferritic constituents (pearlite, bainite, and martensite-austenite). The degree of banding was higher in Steel B than in Steel C. Also present were elongated inclusions in Steel B, while in Steel C they were more or less equiaxed. On cathodically hydrogen-charging in the absence of external stress, microvoids formed at low current densities at or around inclusions. On prolonged charging, these voids grew and propagated parallel to the bands, running along the interface between ferrite/non-ferrite constituents, along inclusions lodged in the non-ferritic consitituents, and at places through the non-ferritic constituents. Steel B, not unexpectedly, showed more severe permanent microstructural damage than Steel C, leading to the conclusion that a high banded structure and/or the presence of elongated inclusions is deleterious to resistance against HIC.     

Relationship between microstructure and hydrogen induced cracking behavior in a low alloy pipeline steel

Hydrogen induced cracking(HIC) behaviors of a high strength pipeline steel with three different microstructures, granular bainite lath bainite(GB + LB), granular bainite acicular ferrite(GB + AF), and quasi-polygonal ferrite(QF), were studied by using corrosion experiment based on standard NACE TM0284. The HIC experiment was conducted in hydrogen sulfide(H_2S)-saturated solution. The experimental results show that the steel with GB + AF and QF microstructure present excellent corrosion resistance to HIC, whereas the phases of bainite lath and martensite/austenite in LB + GB microstructure are responsible for poor corrosion resistance. Compared with ferrite phase, the bainite microstructure exhibits higher strength and crack susceptibility of HIC. The AF + GB microstructure is believed to have the best combination of mechanical properties and resistance to HIC among the designed steels.     

Critical Assessment 17: Mechanisms of hydrogen induced cracking in pipeline steels

Hydrogen induced cracking (HIC) remains a prominent issue for oil and gas exploration in challenging environments. This assessment discusses HIC in light of hydrogen transport through pipeline steel microstructures and crack initiation and propagation processes. While there has been significant research in hydrogen permeation through steel alloys, additional understanding is necessary in microstructures specific to pipeline steels. Furthermore, a standard model for crack initiation and propagation processes needs to be established; a fracture mechanics based model, which has been used by some researchers, is presented in the present paper to predict crack propagation. Advanced characterisation techniques can help elucidate mechanisms of hydrogen induced crack growth. Ultimately, linking hydrogen transport and cracking processes during HIC will enable optimised alloy and microstructure design.     

Hydrogen—induced Cracking of Weld Metal of Austenitic Stainless Steels

For 308L and 347L weld metals of austenitc stainless steels(ASS) ,hydrogen induced cracking(HIC) occurred during dynamically charging under costant load.The threshold stress intensity for HIC,KIH,decreased linearly with the logarithm of the concentration of diffusible hydrogen Co in the weld metals and the rolled plate of type 304L ASS.i,e ,KIH=85.2-10.7ln Co(308L),KIH=76.1-9.3ln Co(347L) ,and KIH=91.7-10.0lnCo(304L).The fracture mode for HIC in the three type of ASS changed from ductile to brittle with the decrease in the applied stress intensity Ki or /and the increase in Co .The boundary line between ductile and brittle fracture surfaces was KI-54 25ep(-Co/153)=0.     

Influence of the Hydrogen Sulfide Concentration on the Corrosion and Hydrogenation of Pipe Steels (A Survey)

Materials Science - We consider the process of corrosion of steels in hydrogen-sulfide media of different concentrations with regard for the specific features of the formation of sulfides of...