酸性服役条件下石油天然气输送用管L245NCS的开发

通过合理的化学成分设计,对原材料成分的合理控制,对每工序特别是热处理工序的研究,获得所需要的组织和性能,最终达到满足力学性能要求及抗氢致开裂和抗硫化物应力开裂的目的.     

车轮钢中的白点(一)

研究了车轮钢中白点形成的机理以及白点对断口形貌的影响.结果表明,氢和空位聚集导致鼓泡形核和长大,随着鼓泡内氢气压力的升高,裂纹从鼓泡核壁形核、扩展导致白点形成.白点的断口为准解理,和氢致滞后开裂断口相同,含白点试样的断口形貌依赖于断裂方式和试样厚度.钢中的白点除了产生二次裂纹和局部准解理断面外,对各种断口形貌均没有明显的影响.     

高强度管线钢微观组织对氢致裂纹的影响

 通过扫描电镜（SEM）和电子背散射衍射（EBSD）等方法,从组织结构和晶界2个方面,研究了微观组织对高强度管线钢氢致裂纹（HIC）的影响。结果表明：高强度管线钢组织结构中存在数量较多的、大块状的M/A岛时,会显著增加HIC的敏感性,而增加AF组织数量及其均匀性有利于降低HIC的敏感性;高强度管线钢的HIC裂纹沿着大角度晶界的边界扩展,而小角度晶界具有一定的止裂作用。     

低合金板探伤缺陷的原因分析和探讨

应用低倍试验、金相检验、扫描电镜等分析方法,对Q345、16MnR轧制钢板探伤不合格的原因进行了探讨。结果表明：MnS夹杂引起聚集氢,导致氢致裂纹的产生,以及碳在板材心部的偏析,钢板中心出现了贝氏体组织,使探伤不合格。     

铁素体晶界结构对管线钢HIC敏感性的影响

摘要：铁素体作为酸性环境用管线钢的主要组织类型之一,探究其晶界结构与管线钢氢致开裂（HIC）敏感性之间关系,可为进一步优化管线钢的抗HIC性能提供指导。对热轧态管线钢进行不同工艺热处理,采用扫描电子显微镜（SEM）、电子背散射衍射（EBSD）、透射电子显微镜（TEM）观察了试样的晶界、位错结构及氢鼓泡、氢致裂纹形貌,用电化学充氢及动态充氢方法对试样的HIC敏感性及氢致塑性损失进行了测试,用电化学氢渗透及氢微印实验对试样的氢捕获效率及氢原子分布进行了观察与分析,探索了铁素体晶界结构与HIC敏感性之间内在关联。其结果表明：当材料中以小角度晶界占主导或大小角度晶界比例约为1∶1时,对氢原子的捕获效率较高,HIC敏感性也相对较大;大小角度晶界均能捕获氢原子,但与氢的作用机制不同,大角度晶界主要促进氢致裂纹萌生,而小角度晶界主要促进氢致裂纹扩展。     

Resistance of Trip 800 Steels in a Sour Environment Containing H2S

We have evaluated the resistance of two samples of TRIP 800 steel prepared under laboratory conditions at the Faculty of Metallurgy and Materials Engineering (FMME) V?B (Technical University of Ostrava, Czech Republic) in a sour environment containing H₂S. The first steel investigated had a C–Mn–Si composition, and the second steel had a C–Mn–Si–Al composition. Both TRIP steels were characterized using the yield strength in the range 420 to 450 MPa and tensile strength in the range 880 to 900 MPa. The TRIP steel samples were in the form of sheets with a thickness of 1.5 mm. The residual austenite content was 11% and 13%, respectively, in the two steels studied. The resistance to hydrogen embrittlement was evaluated in a sour environment that contained hydrogen sulphide using hydrogen‐induced cracking (HIC) and sulphide stress cracking (SSC) tests performed in accordance with NACE standards. Both TRIP 800 steels showed a high resistance to hydrogen embrittlement, and no SSC cracks were observed. Some cracking arising from HIC was observed in both steels. The measured parameters showed some variation; in some cases they were lower than recommended limits, but in other cases the measured parameters were higher (e.g., the crack length ratio was up to 70%). The cracks initiated preferentially at non‐metallic inclusions, either at elongated manganese sulphide particles, or at oxide stringers that were rich in Al.     

Threshold Stress Intensity of Hydrogen-Induced Cracking and Stress Corrosion Cracking of High Strength Steel

Stress corrosion cracking (SCC) of highstrength steels in an aqueous solution has been wide-ly investigated[1— 8] .It has long been accepted thatSCC of high strength steel in water is one kind ofhydrogen- induced cracking (HIC) [1— 5] .Because ofhydrolysis of the metal ions,the value p H of the lo-cal environment within a pit,crevice or crack on asteel surface can be decreased to about 3.5 [1] .Be-cause of crack- tip acidification,local conditions arealways favorable for release of hydro…     

镁处理对海底管线钢氢致开裂敏感性和氢捕获效率影响

摘要：通过NACE TM 0284 2016标准试验和Davanathan Stachurski双电解池氢渗透试验,评估和分析了不同镁添加量X70级别海底管线试验钢的氢致开裂（HIC）敏感性和氢捕获效率。结果表明,镁处理可以细化钢中夹杂物,形成以Ti2O3为主要成分的复合夹杂物。随着镁添加量的增加,试验钢的晶粒依次细化,虽然钢中夹杂物总数增多,但大尺寸夹杂物数量减少。镁处理是通过改变夹杂物数量、成分和尺寸分布从而改善其抗HIC敏感性的。在本试验范围内,镁添加量为0.003%（质量分数）的试验钢抗HIC性能最佳。     

Cracking simulation for strained linepipes exposed to different heavy corrosion and pulsating load

Susceptibility of steel to cracking ‐either by contact with gas in wet H₂S environments or near neutral solutions‐ is a dominant factor for residual life of gas‐line pipes. Three different phenomena are concerned with cracking, namely hydrogen induced cracking (HIC), sulphide stress cracking (SSC) and stress orientated hydrogen induced cracking (SOHIC). Whereas laboratory test methods for HIC are established the situation is different in combination with stress. If the coating is damaged and a near neutral liquid medium is penetrating the pipe surface a strain induced crack might occur. This type of corrosion is named near neutral SCC (NNSCC). A qualified test method with simulated cyclic loading conditions was not available. A test stand including pulsating tension on a high level qualified for high strength steels, wet environments with pH‐values between 2.7 (sour gas) and 8,3 (synthetic seawater) and bubbling several gases such as H₂S, CO₂ or N₂ through the test solution with controlled room temperature was developed. The test‐method enables to qualify steels and pipes for line pipes in tests of short duration compared to lifecycles of line pipes.     

Mechanisms of Hydrogen Induced Stress Crack Initiation and Propagation in Super Duplex Stainless Steels

Austenitic and ferritic duplex stainless steels, DSS, have recently suffered from hydrogen stress induced cracking, HISC, in subsea components with a cathodic protection. This paper provides discussions on possible HISC mechanisms. HISC initiation can occur at the ferritic grain boundaries and phase boundaries at a stress lower than the yield strength, but dominantly at phase boundaries at a stress higher than the yield strength. EBSD analysis shows that HISC in DSS results from the interaction between the dynamic plasticity by creep and hydrogen diffusion. A model on the formation of microstresses in these two phases under creep conditions is proposed, which explains why HISC occurs mainly in the ferritic phase. Discontinuous two‐dimensional HISC paths were observed. The austenitic phase acts as obstacles for crack propagation. The fracture covers “valleys” and “peaks” with the cleavage ferrite and the austenite with microfacets or striations due to the hydrogen‐enhanced localized‐plasticity.     

乏燃料运输罐体旋转凹槽开裂原因分析

某乏燃料运输容器壳体的旋转凹槽在制造过程中发生开裂,为了确定失效原因,防止此类失效事件再次发生,实验对该旋转凹槽的化学成分、力学性能、金相组织和断口形貌进行了分析,确定了断裂原因。结果表明,旋转凹槽的失效模式为氢致延迟开裂,材料中H含量偏高和材料脆化是导致旋转凹槽发生氢致开裂的主要原因。     

某镍基粉末高温合金盘坯的热处理开裂分析

针对某镍基粉末高温合金盘坯在热处理后开裂的问题进行了分析。结果表明:盘坯组织中存在热诱导孔隙缺陷,热诱导孔隙缺陷在盘坯表面形成了微裂纹,降低了材料的抗拉强度。盘坯在热处理过程中,受到残余应力共同作用,其数值超过了材料的抗拉强度导致开裂。该盘坯中的孔隙是由于包套在热等静压过程中漏气造成的,提高包套质量是消除盘坯热诱导孔隙缺陷的关键。     

The extension of hydrogen blister-crack array in linepipe steels

Hydrogen induced fracture in linepipe steels is characterized by the formation of internal blisters caused by hydrogen precipitation at an inclusion-matrix interface, followed by the formation of blister-crack array by cracking the region connecting the blisters through the action of internal hydrogen pressure and external stress. The manner of extension of the hydrogen induced fracture of this type is considerably influenced by the presence of external stress: in the absence of the external stress fracture develops by linking the blisters which are formed in stacked arrays out of a plane approximately perpendicular to the external stress axis. Shear stress distribution induced around the blister is sensi-tively influenced by the external stress applied parallel to the blister plane; therefore, it is expected that the manner of extension of the blister-crack array should be influenced by the external stress. In the present paper the above mentioned influence of the external stress on the manner of extension of the hydrogen induced fracture is explained based on stress analysis around a hydrogen gas pressurized crack-like cavity under stress.     

高压锅炉用水冷壁管失效开裂分析

应用扫描电镜、光学显微镜及X射线能谱仪等实验分析方法，对高压锅炉用水冷壁管失效开裂原因进行分析研究，结果表明．高压锅炉用水冷壁管开裂为应力腐蚀开裂，同时还有氢脆的作用。     

Influence of Microstructures on Polarization Resistance and Hydrogen-Induced Cracking of a Micro-Alloyed Steel Submitted to Different Cooling Rates

The effect of different microstructures on the polarization resistance (Rp) and the hydrogen-induced cracking (HIC) of a micro-alloyed steel austenitized and submitted to different cooling rates was studied.Samples 19.1 x 6 x 2 mm,containing the whole thickness of the plate were extracted from a 20 mm plate and heat treated on a quenching dilatometer,were submitted to Rp and HIC corrosion tests.Both Rp and HIC tests followed as close as possible ASTM G59 and NACE standard TM0284-2003,in this case,modified only with regard to the size of the samples.Steel samples transformed from austenite by a slow cooling (cooling rate of 0.5℃.s-1) showed higher susceptibility to hydrogen-induced cracking,with large cracks in the middle of the sample propagating along segregation bands,corresponding to the centerline of the plate thickness.For cooling rates of 10℃.s-1,only small cracks were found in the matrix and micro cracks nucleated at non-metallic inclusions.For higher cooling rates (40℃.s-1) very few small cracks were detected,linked to non-metallic inclusions.This result suggests that structures formed by polygonal structures and segregation bands (were eutectoid microconstituents predominate) have higher susceptibility to HIC.Structures predominantly formed by acicular ferrite make it difficult to propagate the cracks among non-oriented and interlaced acicular ferrite crystals.Smaller segregation bands containing eutectoid products also help inhibit cracking and crack propagation;segregation bands can function as pipelines for hydrogen diffusion and offer a path of stress concentration for the propagation of cracks,frequently associated to non-metallic inclusions.Polarization resistance essays performed on the steel in theas received condition,prior to any heat treatment,showed larger differences between the regions of the plate,with a considerably lower Rp in the centerline.The austenitization heat treatments followed by cooling rates of 0.5 e 10℃.s-1 made more uniform the corrosion resistance along the thickne     

0Cr17Ni4Cu4Nb传感器断裂原因分析

某力学传感器在出厂检验流程中发生断裂失效,为了确定失效原因,防止此类失效事件再次发生,实验对该传感器的力学性能、金相组织和断口形貌进行了分析,确定了断裂原因。结果表明,传感器的失效模式为氢致延迟开裂,材料中氢含量偏高和开裂位置机加工质量较差是导致传感器发生氢致开裂的主要原因。结合失效原因,提出了改进措施。     

C-Mn-Cr-Nb系低合金钢抗氢致开裂性能

 研究了一种低C、低Mn、高Cr和高Nb低合金钢经控轧控冷及轧后回火处理后性能与组织的变化,并对试验钢进行了抗氢致开裂(HIC)试验。结果表明：与轧态相比,回火处理后试验钢的力学性能有较大提高,600℃左右回火后屈服强度由轧态519MPa增加到626MPa,抗拉强度由653MPa增加到705MPa,且韧性基本未降低,回火处理后组织仍以针状铁素体为主,回火后M/A岛尺寸减少。此外,轧态与回火态钢均能满足抗HIC试验衡量标准,回火处理后抗HIC性能优异。降低Mn质量分数能显著提高低合金钢抗HIC性能,提高Cr质量分数和Nb质量分数能有效强化低Mn钢的强度。     

车轮钢中的白点(二)

研究了车轮钢中白点对力学性能的影响.结果表明,当白点含量少且尺寸较小时,对拉伸性能没有影响,但使冲击韧性明显下降;当白点含量较多或尺寸较大时,使拉伸性能下降,但对断裂韧性没有影响.钢中的白点能增加疲劳扩展速率并使扩展速率发生波动.氢致滞后开裂与白点无关,而与氢原子有关.     

汽车用AISI 347不锈钢在酸性溶液环境的诱发破裂

研究了汽车用AISI 347不锈钢在酸性氯化钠水溶液中的环境诱发破裂性能。结果显示,经过650℃保温后AISI 347不锈钢具有抵抗敏化的能力;其腐蚀电位钝态区范围随650℃保温时间的延长而缩小;在25℃、pH=2的3.5%(质量分数)NaCl水溶液或90℃、pH=2的1%NaCl水溶液中,主要以延性韧窝状的模式断裂,应力腐蚀破裂仅局限在试棒断面的边缘,其抵抗环境诱发破裂性能良好,具有优良的抗应力腐蚀破裂的性能。     

焊接接头微区氢行为的研究Ⅱ）──焊接接头近缝区受载缺口前端氢浓度再分布

用离子探针研究了１０ＳｉＭｎＮｉＣｒ钢不同焊接条件下氢在焊接接头负载缺口顶端的再分布，发现近缝区开裂方向有两个氮浓度富集峰。并探讨了双氢峰的形成机理。