Field girth weldability evaluation of X70 UOE pipeline

Based on API STD 1104-2005 and CSA Z662-2007,field girth welding tests and girth weldability evaluations were executed for three types of wall thickness X70 UOE pipeline,in which the most popular main line girth welding method,single-wire automatic gas metal arc welding(GMAW),was used. The welding procedure specification was optimized to achieve a good quality and cold-crack-free girth weld joint without preheating or post-weld heat treatment. In addition,porosities,inclusions,and incomplete fusion defects were avoided. The tensile strength,bending,Vickers hardness,Charpy V-notch impact toughness,and crack tip opening displacement fracture toughness of the girth weld joint were evaluated,and the joint exhibited good mechanical performance. Thus,the field girth weldability of Baosteel's X70 UOE pipeline is excellent for automatic GMAW.     

Development and application of Baosteel X80 large diameter UOE longitudinal submerged arc welded pipes

With the increase in energy demand,the demand for oil and gas transmission pipes,particularly high-grade longitudinal submerged arc welded pipes (LSAWs),have been growing in recent years.The construction of the 2nd West-East natural gas transmission pipeline project shows that the oil and gas pipeline construction has entered a new phase of development with X80 pipes being applied in large scales for the first time in China.This paper briefly introduces the 2nd West-East natural gas transmission pipeline project and its main technical requirements with the focus on the features of API standard 5L X80 grade  1219 mm series of U-ing-O-ing-Expanding (UOE) LSAW pipes,which Baosteel developed with the integrated technology for the 2nd West-East natural gas transmission pipeline project.The analysis shows the extra-low carbon content,the high contents of manganese and niobium,the fine microstructure,the high strength,the toughness and the good weldability of X80 pipes meet the requirements of "the technical specification of LSAW linepipes for the 2nd West-East natural gas transmission pipeline project in China".By the end of June 2010,Baosteel had totally produced 322000 t of  1219 mm X80 UOE steel pipes,which have been successfully used in the 2nd West-East natural gas transmission pipeline project,thus filling the gap of the production of large diameter X80 UOE LSAW pipes in China.     

Research and development of deepwater offshore linepipe of Baosteel UOE SAWL X70 of heavy wall thickness and large diameter

Baoshan Iron & Steel Co.,Ltd.,(referred to as Baosteel) in China first succeeded in developing the U-ing-O-ing -Expanding(UOE) longitudinal submerged arc welded pipes(SAWLs) offshore linepipe of a maximum thickness/ outside diameter(T/D) 0.042 in 2011.Described in this paper is the research and development of the X70 UOE SAWL pipes by the company.The result shows that the said X70 linepipe has been in compliance with relevant requirements as specified in Specifications DNV-OS-F101,and has been successfully used in the South China Sea deepwater gas pipeline project.     

Investigation of the impact toughness of self-shielded flux-cored wire girth welds for X80 pipelines

Self-shielded flux-cored wire is a convenient and efficient consumable for pipeline field girth welding because of its self-protection characteristic and high deposition rate,especially for remote construction sites in rugged terrain. From the perspective of pipeline safety,the impact toughness of the girth welds is an important factor in pipeline integrity,which determines the crack arrest behavior in the girth welds. Therefore,improving the girth weld impact toughness is of primary importance in the field of pipeline girth welding. Three self-shielded flux-cored wires comprising different chemical composition systems have been applied to large diameter X80 UOE( U-ing-O-ingExpanding) pipeline semi-automatic girth welding,and the impact toughness of the welds has been evaluated by girth weld chemical composition analysis and microstructural analysis using scanning electron microscopy( SEM) and energy dispersive spectrometry( EDS) to investigate pipeline girth weld impact toughness and find ways to improve it.This helps in determining the main factors that influence girth weld impact toughness. Pipeline girth weld impact toughness is mainly determined by the final microstructure produced in the solid-state phase transition. In the as-weld state,acicular ferrite( AF) and fine bainite( FB) are a benefit to the impact toughness. For multilayer semiautomatic self-shielded flux-cored wire welding,the normalizing and tempering function of the latter beads to the initial beads plays an important role in the transition of girth weld microstructure,which affects the impact toughness. The original AF and FB and the corresponding heat treatment microstructure of the fine and uniform block ferrite and pearlite result in very good impact toughness. The following two mechanisms are found to promote the production of AF and FB in the girth weld. First,elements promoting the broadening of the austenitic region,such as Ni,C,Cu,and Mn,induce low temperature phase transitions and restrain the opposing function of Al,which is a benefit to the production of AF and FB. Second,dispersed high-melting-point inclusions,especially Al2O3,induce the nucleated production of AF. The advantageous function of inclusions is determined by their shape,distribution,and dimension. Dispersed spherical inclusions of small dimension are a benefit to the production of AF,and result in good impact toughness.     

X80钢气保焊焊缝金属的韧化

采用优化的WER70焊丝,在管线环焊缝常用焊接线能量条件下,对X80钢进行了气保焊试验.焊缝-20℃冲击功平均达到181 J,焊接接头具有较理想的组织,对接焊缝与焊丝熔敷金属的力学性能基本相当.     

X80钢焊缝再热后的组织与性能

针对西气东输二线X80高强度高韧性厚壁管线钢管双面埋弧焊接工艺特点,采用Gleeble1500热模拟试验和实物焊接试验,研究分析了内焊缝(一次焊缝)受到外焊(二次焊接)热循环后组织与性能变化情况。通过SEM、光学显微镜等进行了微观组织分析并做力学性能测试。结果表明,一次焊缝受到二次焊接热循环峰值温度在(α+γ)两相区范围时发生脆化,韧性降低22%;而一次焊缝在外焊二次热输入为20 kJ/cm时,冲击韧性最好;二次焊接在一次焊缝中形成了焊接临界粗晶区(WICHAZ),呈现粗大的条状铁素体,板条间为排列成行M-A组元或渗碳体,硬度由212HV5迅速增加到261HV5,韧性也随之变差。     

Practice and reflection of Baosteel longitudinal UOE submerged arc welding technologies self-reliance integrated innovation

The capability of self-reliance integrated innovation is one of the key factors that influence steel enterprise’ s core competitiveness.The main equipments of Baoteel UOE unit are from abroad,but the key consistent pipe manufacturing technologies including iron making,steel making,heavy plates are self-reliance integrated.The self-reliance integrated innovation of Baosteel UOE unit has the features of high challenge, high efficiency,high starting point,consistent technologies etc.The independent innovation capacity achieved by adjusting measures to local conditions and periods in introducing projects is the key to the development of continuing robust.Baosteel longitudinal UOE submerged arc welding tube project practice also offer beneficial reference for independent of integration innovation.     

基于应变设计用X80大应变UOE钢管的研发

在地质灾害多发地区,基于应变的管道设计对管线管提出了大应变的性能要求。通过实验室研究了不同组织类型对管线钢大应变性能的影响,发现多边形铁素体+贝氏体的组织具有很好的大应变性能和其他性能的匹配。更进一步研究了双相比例、组织形态等对大应变性能的具体影响,以及轧钢工艺参数对双相组织的影响。基于该组织设计及实验室研究,宝钢进行了Ф 1 219×26.4 mm厚壁X80大应变UOE管线管的试生产。试制钢管性能良好,能够满足西三线X80大应变管线管的技术要求。     

Analysis of inclusions and precipitates in tough weld metal of X80 steel

Submerged arc welding(SAW)and gas metal arc welding(GMAW)experiments of Nb-bearing X80 steel were conducted with high-toughness wires.The inclusions in weld metals were analyzed in terms of their types and sizes.In GMAW,the inclusions are primarily Ti,Ca,Si,Al,and Mg compounds with no Nb and are generally less than 0.8 pm in size,whereas,in SAW weld,the inclusions are larger,mostly approximately 2-5 μm in size,and are cored with Ca and Ti,exhibiting obvious oxidation metallurgical features.The SAW joint was hot-deformed,and Nb-bearing nano precipitates were newly found in the weld metal through transmission electron microscopy,and Nb-free core-shell inclusion was found through scanning electron microscopy.The inclusions and precipitates were dispersed in or on the boundaries of acicular ferrite,contributing to acicular ferrite nucleation and grain refinement.     

X80级管线钢热影响区的局部脆化

研究了国产X80级管线钢热影响区的冲击韧性和组织的局部脆化.结果表明,该钢的焊接热影响区的冲击韧性较母材降低50%以上;在所研究的20～-40 ℃温度区间内,其断口的宏观形貌特征从部分脆性特征转变为完全的脆性断口;20 ℃放射区断口呈现韧性断裂和解理断裂共存的混合型断口,并且试验温度为20 ℃和0 ℃时,分别在放射区和纤维区可观察到微观裂纹;热影响区断口表层剖面组织为粒状贝氏体,显示出粗晶区的特征.裂纹扩展方向为沿晶界扩展,粒状贝氏体中M/A岛尺寸增大,并存在裂纹穿过岛状物的现象,这是晶界严重脆化的结果.     

高强度高韧性X80管线钢的研制与应用

由于长距离高压油气输送的需要,高强度高韧性管线用钢得到迅速发展.宝钢在完成"西气东输"工程用X70管线钢后,进行了更高强度级别X80管线钢的研制.现就宝钢X80管线铜的研制和应用情况,X80管线钢的成分、工艺、组织、性能和制成φ1 016×15.3 mm螺旋焊管性能进行论述.合理的成分配合最佳的控轧控冷工艺,是X80管线钢获得具有针状铁素体微观组织和高的冲击韧性、优良的低温抗动态撕裂能力的关键.     

大口径油气管道环焊技术的进展及在宝钢的应用

介绍了当前管道工业的发展及管道焊接技术的进展情况,并阐明了管道全位置下向焊接技术的特性.管道环焊缝是由根焊、热焊、填充焊、盖面焊等不同焊道组成.对常用的手工焊、半自动焊和自动焊接方法在管道环焊缝不同焊道焊接时的应用以及各自特点做了介绍,还对焊接材料的选用、焊接设备的选型作了描述.宝钢铜管厂大口径直缝埋弧焊管(UOE)项目即将投产,投产后大口径焊管产品使用技术的研究势在必行,宝钢应尽快开展大口径UOE焊管的环缝焊接技术的研究,为将来的推广应用提供必要的技术支撑.     

马钢2250热连轧生产厚壁X80管线钢

 对马钢2250热连轧生产的X80管线钢的力学性能、显微组织、析出物及制作的螺旋焊管质量进行了分析研究。结果表明：马钢生产的厚18.4 mm X80管线钢力学性能优良,平均屈服、抗拉强度分别为575 MPa和660 MPa,-20 ℃平均冲击功为295 J,-15 ℃DWTT平均剪切面积为98%。马钢X80管线钢为针状铁素体组织,晶粒细小,析出物呈弥散分布。制造的管体满足西气东输二线标准对X80管线钢的质量要求,产品质量优良。     

Evaluation of automatic girth weldability of pipeline in special conditions

To meet the requirements of pipeline consumers abroad, in this study, an automatic gas metal arc welding type of girth welding was performed with a heat input of no more than 0.25 kJ/mm and high-strength solid-wire matching for an X70 M large-diameter UOE pipeline.An integral evaluation of the X70 M pipeline girth weldability was performed with respect to the girth-weld cold-cracking sensitivity during the welding process and the strengthening, hardening, and embrittlement of the girth weld joint after girth welding in especially rigorous welding conditions with accelerated failure characteristics.The performance of the above girth weld joint with joints welded using the main construction-field girth welding procedure was compared to ensure the good girth weldability of the X70 M pipeline.The results of this study have important supervisory significance for field-construction girth welding.Finally, the girth weldability of the X70 M pipeline was found to satisfy the field construction requirements even when the welding conditions are especially rigorous.     

Engineering critical assessment on welding flaws of the X65 UOE girth weld based on CRACKWISE

Focused on the girth weld of a Φ762 × 28. 6 mm( X65) offshore UOE pipe,the fracture toughness properties at different weld joint positions were tested. Meanwhile,the largest size of different cracks under service condition was calculated by using CRACKWISE. The service life of the UOE pipe with postulated crack-like flaws was calculated by considering various fatigue factors,such as vibrations caused by ocean current and fluctuations of inner pressure. The assessment process and results can be used to direct the repair of weld flaws laid in pipes or to assess the reliability of in-serving pipes.     

高级别管线钢X80～X120的研发与应用

通过管线长距离运输天然气、石油是能源运输的主要方式之一。出于降低成本的需要，天然气输送管线的工作压力不断提高，这就要求应用X80-X120更高级别管线钢。根据有关的文献资料，系统整理并介绍了高级别管线钢的性能指标、成分设计以及生产应用中的热点问题，并讨论了未来中国天然气管线所采用高级别钢的可能选择。     

X80管线钢板的开发研究

利用MMS-200热模拟机研究了X80管线钢的相变规律,采用热膨胀法及金相组织分析手段,建立了连续冷却转变曲线,分析了工艺参数对组织的影响规律。试验结果表明,当冷却速率在5～20℃/s时,可以获得需要的针状铁素体组织。根据相变规律,在济钢4 300 mm宽厚板轧机成功开发了壁厚22 mm高强度、高韧性X80管线钢板。检验结果表明,试验钢板的各项性能指标均满足西气东输二线的技术要求。     

工艺制度对X80级抗大变形管线钢组织和性能的影响

利用扫描电镜,研究了工艺制度对X80级抗大变形管线钢组织和性能的影响。研究结果表明,随开始冷却温度的降低,先共析铁素体含量逐渐增加,贝氏体组织含量逐渐降低,钢板抗大变形性能参数提高。当开始冷却温度为720～740℃时,钢板具有最佳的综合力学性能,屈服强度Rt0.5为565 MPa,抗拉强度Rm为730 MPa,伸长率为42.7%,屈强比Rt0.5/Rm为0.75,Rt1.5/Rt0.5为1.161、Rt2.0/Rt1.0为1.116,均匀变形伸长率达到12.33%。