为研究Nb含量对焊接热影响区微观组织和性能的影响,采用熔化极气体保护焊(gas metal arc welding,GMAW)和手工焊条电弧焊(shielded metal arc welding,SMAW)对0.055%Nb和0.075%Nb含量的X80钢管进行环焊.采用夏比冲击试验和金相分析方法...为研究Nb含量对焊接热影响区微观组织和性能的影响,采用熔化极气体保护焊(gas metal arc welding,GMAW)和手工焊条电弧焊(shielded metal arc welding,SMAW)对0.055%Nb和0.075%Nb含量的X80钢管进行环焊.采用夏比冲击试验和金相分析方法,研究热影响区的微观组织差异和夏比冲击韧性.并借助扫描电镜和超高温激光共聚焦显微镜分析不同Nb含量X80管体的微观组织对热影响区性能的影响.结果表明,在0℃和-20℃时,0.075%Nb和0.055%Nb的X80钢管GMAW环焊接头热影响区均具有较高的冲击韧性,其平均冲击吸收能量均高于150 J.其中0.055%Nb略高于0.075%Nb的GMAW环焊接头热影响区夏比冲击吸收能量;焊接热输入较低时,0.055%Nb低于0.075%Nb的X80环焊接头粗晶区的韧脆转变温度,具有更好的低温韧性.焊接热输入较高时,0.075%Nb的X80环焊接头粗晶区具有更高的上平台冲击吸收能量,且上平台温度和韧脆转变温度也更低,其低温韧性也更优异;还发现了X80环焊接头热影响区的冲击韧性不仅与热输入量和热影响区马氏体-奥氏体组织(M-A)的形状、大小、分布有关,而且还受管体中Nb含量、原始的强度与韧性、微观组织状态的遗传影响.展开更多
High-strength pipeline steel and large diameter line pipes are often used to increase the capacity of transportation and reduce the cost associated with the construction and operation of long-distance gas pipeline pro...High-strength pipeline steel and large diameter line pipes are often used to increase the capacity of transportation and reduce the cost associated with the construction and operation of long-distance gas pipeline projects. China＇ s initiatives to construct long-distance natural gas pipelines has brought in new opportunities for the development of X80 line pipes. Baosteel has designed the optimum chemical composition of X80 with high niobium and low molybdenum content. In addition, a welding experimental platform and a finite element model （FEM） have supported the development of X80 UOE pipes in an efficient and economical way. The application and recent development of X80 UOE pipes were introduced in this paper. To comply with the requirements of the Second West-East Gas Pipeline Project （2^nd WEPP ）, X80 pipeline steel with low carbon bainite microstructure was developed by utilizing the optimized composition and TMCP process. The matching welding material, welding procedure and UOE forming processes for 1 219mm outside diameter X80 UOE pipes were also developed. More than 340 000 t of X80 UOE pipes were produced and applied in the 2^nd WEPP. Furthermore, to meet the prospective demand for long-distance gas pipelines with an annual transportation capacity of over 40 billion m3 ,larger size X80 UOE pipes with 1 422 mm OD × 30. 8 mm WT were trial produced recently. DWTT performance, the main technical challenge for heavier wall pipes, was improved by using optimized microstructural design. The newly developed X80 pipes can be potentially used for larger transportation capacity pipelines in China.展开更多
Hot-rolled wide strip for production of large diameter,heavy gauged(up to 19 mm) helical line pipe grade X80 was a priority development over the last three years.Microstructure,texture and mechanical properties of str...Hot-rolled wide strip for production of large diameter,heavy gauged(up to 19 mm) helical line pipe grade X80 was a priority development over the last three years.Microstructure,texture and mechanical properties of strips have been characterised.Also the welding conditions have been simulated.The favourable microstructure is achieved by the proper selection of an appropriate chemical composition of low carbon content and increased niobium micro alloying in combination with suitable strictly controlled hot-rolling parameters.The addition of niobium in combination with the adjustment of other alloying elements increases the recrystallisation stop temperature and thus makes it possible to apply a high temperature processing(HTP) concept.The homogeneous bainitic microstructure across the strip gauge is then formed during accelerated cooling on the run-out table of the hot-rolling mill.All results indicated excellent properties of these hot strips which make it suitable for spiral pipes of grade X80 for example 18.9mm×Φ1 220 mm at dimension.展开更多
Strain capacity is an important performance indicator for designing and evaluating high-grade steel pipelines.Due to the inhomogeneity of material properties in welded structures,girth welds are one of the main factor...Strain capacity is an important performance indicator for designing and evaluating high-grade steel pipelines.Due to the inhomogeneity of material properties in welded structures,girth welds are one of the main factors that restrict the strain capacity of pipelines.In this paper,girth-welded pipes with cracks in the inner surface of the weld have been studied,and the ductile crack initiation and propagation behavior have been simulated using the Gurson model.The corresponding nominal strain at the onset of crack initiation was defined as the characteristic value of strain capacity.The influencing factors on the strain concentration area,strain concentration factor,and strain capacity of girth-welded pipes were quantitatively analyzed.A semiempirical calculation formula for the strain capacity of typical girthwelded X80 grade pipes has been proposed as a function of the crack size,mismatch coefficient of the weld,and softening degree of the heat affected zone(HAZ).This study can facilitate the defect assessment of girth-welded pipes.展开更多
针对国家西气东输二线管道建设需要,介绍了φ1 219 mm×18.4 mm X80钢级螺旋埋弧焊管的"一步法"和"两步法"生产工艺技术。采用SEM,TEM等方法研究分析了X80钢的组织与性能特点,设计开发出了Mn-Mo-B-Ti合金系BSG-...针对国家西气东输二线管道建设需要,介绍了φ1 219 mm×18.4 mm X80钢级螺旋埋弧焊管的"一步法"和"两步法"生产工艺技术。采用SEM,TEM等方法研究分析了X80钢的组织与性能特点,设计开发出了Mn-Mo-B-Ti合金系BSG-H06H1焊丝和BSG-SJ101H1焊剂,实现了焊缝以针状铁素体为主的组织控制和较高的强韧性匹配,焊接速度高达1.7 n/min。热模拟试验和焊接工艺试验研究表明,X80钢的焊接热输入在20～25 kJ/cm时,焊缝的冲击韧性最佳;同时研究表明,X80钢在制管前后屈服强度没有发生太大的变化。对试制的φ1 219 mm×18.4 mm X80螺旋埋弧焊管分析表明,性能完全符合标准要求。展开更多
文摘为研究Nb含量对焊接热影响区微观组织和性能的影响,采用熔化极气体保护焊(gas metal arc welding,GMAW)和手工焊条电弧焊(shielded metal arc welding,SMAW)对0.055%Nb和0.075%Nb含量的X80钢管进行环焊.采用夏比冲击试验和金相分析方法,研究热影响区的微观组织差异和夏比冲击韧性.并借助扫描电镜和超高温激光共聚焦显微镜分析不同Nb含量X80管体的微观组织对热影响区性能的影响.结果表明,在0℃和-20℃时,0.075%Nb和0.055%Nb的X80钢管GMAW环焊接头热影响区均具有较高的冲击韧性,其平均冲击吸收能量均高于150 J.其中0.055%Nb略高于0.075%Nb的GMAW环焊接头热影响区夏比冲击吸收能量;焊接热输入较低时,0.055%Nb低于0.075%Nb的X80环焊接头粗晶区的韧脆转变温度,具有更好的低温韧性.焊接热输入较高时,0.075%Nb的X80环焊接头粗晶区具有更高的上平台冲击吸收能量,且上平台温度和韧脆转变温度也更低,其低温韧性也更优异;还发现了X80环焊接头热影响区的冲击韧性不仅与热输入量和热影响区马氏体-奥氏体组织(M-A)的形状、大小、分布有关,而且还受管体中Nb含量、原始的强度与韧性、微观组织状态的遗传影响.
文摘High-strength pipeline steel and large diameter line pipes are often used to increase the capacity of transportation and reduce the cost associated with the construction and operation of long-distance gas pipeline projects. China＇ s initiatives to construct long-distance natural gas pipelines has brought in new opportunities for the development of X80 line pipes. Baosteel has designed the optimum chemical composition of X80 with high niobium and low molybdenum content. In addition, a welding experimental platform and a finite element model （FEM） have supported the development of X80 UOE pipes in an efficient and economical way. The application and recent development of X80 UOE pipes were introduced in this paper. To comply with the requirements of the Second West-East Gas Pipeline Project （2^nd WEPP ）, X80 pipeline steel with low carbon bainite microstructure was developed by utilizing the optimized composition and TMCP process. The matching welding material, welding procedure and UOE forming processes for 1 219mm outside diameter X80 UOE pipes were also developed. More than 340 000 t of X80 UOE pipes were produced and applied in the 2^nd WEPP. Furthermore, to meet the prospective demand for long-distance gas pipelines with an annual transportation capacity of over 40 billion m3 ,larger size X80 UOE pipes with 1 422 mm OD × 30. 8 mm WT were trial produced recently. DWTT performance, the main technical challenge for heavier wall pipes, was improved by using optimized microstructural design. The newly developed X80 pipes can be potentially used for larger transportation capacity pipelines in China.
文摘Hot-rolled wide strip for production of large diameter,heavy gauged(up to 19 mm) helical line pipe grade X80 was a priority development over the last three years.Microstructure,texture and mechanical properties of strips have been characterised.Also the welding conditions have been simulated.The favourable microstructure is achieved by the proper selection of an appropriate chemical composition of low carbon content and increased niobium micro alloying in combination with suitable strictly controlled hot-rolling parameters.The addition of niobium in combination with the adjustment of other alloying elements increases the recrystallisation stop temperature and thus makes it possible to apply a high temperature processing(HTP) concept.The homogeneous bainitic microstructure across the strip gauge is then formed during accelerated cooling on the run-out table of the hot-rolling mill.All results indicated excellent properties of these hot strips which make it suitable for spiral pipes of grade X80 for example 18.9mm×Φ1 220 mm at dimension.
基金supported by the grants from the National Natural Science Foundation of China(Grant No.51874324)the Chinese Scholarship Council(CSC)for the financial support。
文摘Strain capacity is an important performance indicator for designing and evaluating high-grade steel pipelines.Due to the inhomogeneity of material properties in welded structures,girth welds are one of the main factors that restrict the strain capacity of pipelines.In this paper,girth-welded pipes with cracks in the inner surface of the weld have been studied,and the ductile crack initiation and propagation behavior have been simulated using the Gurson model.The corresponding nominal strain at the onset of crack initiation was defined as the characteristic value of strain capacity.The influencing factors on the strain concentration area,strain concentration factor,and strain capacity of girth-welded pipes were quantitatively analyzed.A semiempirical calculation formula for the strain capacity of typical girthwelded X80 grade pipes has been proposed as a function of the crack size,mismatch coefficient of the weld,and softening degree of the heat affected zone(HAZ).This study can facilitate the defect assessment of girth-welded pipes.
