Girth weldability and welding process of Baosteel X80 UOE linepipes

Baosteel Technical ResearchVolume 4, Number 3, September 2010, Page 15Girth weldability and welding process of Baosteel X80 UOE linepipesLU ShuoWelding & Surface Technology Division, Research Institute ,Baoshan Iron & Steel Co, Ltd, Shanghai 201900 ,ChinaAbstract: An analysis of the ginth weldability of Baosteel X80 UOE (U-ing-O ing Expanding ) linepipes was conductedusing manual shielded metal arc welding ( SMAW ) and semiautomatic self-shielded flux cored wire arc welding( FCAW). A technical specification for the optimum quality of a girth welding joint was obtained through a large amountof testing. According to the requirements of America Ptroleum Institute( API) standard I 104 and the standards of the 2ndWest - East natural gas transmission pipeline project ,the mechanical properties of a gith welding joint were estimated. Inaddition ,the effect of the girth welding procedure specifications and the consumable ' s suitability on the impact toughnessof the girth welding joint was discussed.Key words: X80; UOE linepipe; gith weld; SMAW; FCAW; mechanical performancedoi: 10. 3969/j. ssn. 1674 - 3458.2010.03.002welding is a systematic type of engineering , which isaffected by many intermal and extermal factors,i. e. the1 Introductionmaterials and specifications of the linepipes . the trans-The demand for energy resources is becomingmission pressure ,the characteristics of the medium, theincreasingly urgent following the rapid development inconstruction environment , the hardware and softwarethe industrialized world. More attention is being paid toconfiguration of the construction team . and the require-clean energy resources, and natural gas will play anments of the business owner, etc. When a pipelineimportant role from this perspective. However , naturalproject is designed and programmed, all the abovegas resources are mostly distributed a long way fromfactors should be taken into consideration to select theareas of consumption，and the transport of it to thesewelding method , consumable , girth welding techniqueareas is a tough task. As an economical, safe andand construction procedurepractical transmission method, long distance and largeIn general, before the construction and field girthdiameter linepipes have been widely used in the trans-welding of linepipe projects，the owner should commi-mission of natural gas , petroleum and liquid mines " .ssion a qualified institution to set the girth weldingBased on the above, the construction of largeprocess specifications. ,as well as develop girth weldingdiameter long distance linepipes has recently madetechnique analysis tests based on these specifications.some important developments. in China ,the first West-After that , the girth welding process specifications canEast natural gas transmission pipeline project wasbe established and used to supervise the welding in thecompleted in 2004 . and the 2nd West- East natural gafield.transmission pipeline project will be completed inAs a UOE( U-ing-O ing Expanding) linepipe mill ,2012. Overseasincreasing number of gas and oilBaosteel has not only paid attention to the quality of itstransmission pipeline projects will be built in theUOE linepipe. ,but also to the related technologies thatcoming years and some of them will commence cons-its customers use. This has mainly been the girthwelding technology of UOE linepipe. Therefore . Bao-truction in the near future-'For the first time in 1926, the American Petroleumsteel has developed girth weldability evaluations andInstitute ( API) issued the API standard 5L and it haswelding technique tests for X80 UOE linepipe. Thisbeen widely used to supervise the production ofwork allows Baosteel to guarantee customers of thepipeline steel and linepipes. Currently, pipeline steelUOE linepipe products ’girth weldability,as well ashas evolved from low strength carbon steel to X42 ,giving Baosteel an understanding of technological proX46,X52,X60,X65,X70 and X80 . and in some trialblems that may occur during the linepipe girth weldinglinepipe sections, even ultra-high strength pipelineprocess. Baosteel is working on measures to effectivelysteels , such as X100 and X120 have been used. In fact,solve these problems and therefore can provide tech-X80 is an important direction in the development ofnological support regarding linepipe girth welding to itslinepipes中国煤化工For customers of large diameter linepipes , field githwelding is the main technology which is used during21 FTYRCNMHGconstruction and installation and can determine thequality and efficiency of linepipe projects. Field girthIn order to evaluate the girth weldability of BaosteelCorresponding author: LIU Shuo; E-mail: liushuo@ baoseel. .com.l6Baosteel Technical Research, Vol.4, No.3, Sep. 2010X80 UOE linepipe and achieve the optimal girt!equivalent (Cg) ,cold crack sensitivity index (Pm) ofwelding procedure . manual shielded metal arc weldingthe X80 UOE linepipe. Table 2 shows the dimensions( SMAW) and semiautomatic self- shielded flux coredand mechanical properties of the X80 UOE linepipe.wire arc welding ( FCAW ) were used to conductThe above target indexes all meet the relevant require-testing.ments of the API standard 5L and the technologicalstandards of the second West- East natural gas trans-2.1 Linepipe materialsmission pipeline project.Table 1 shows the chemical composition and carbonTable 1 Chemical composition.Co and Pem of X80 UOE linepipeChemical composition/%Steel gradebc“WynPcmX800.0420. 21.830. 160.0050.160.4360.170Table 2 Dimensions and mechanical properties of X80 UOE linepipeYield strength/ Tensile strength/Impact toughnessDWTT shear areaSteel grade Thickness mm Diameter/mmMPa( - I0C)/J( -5C)/%X80 .221219568293/337/34089/902.2 Selection of consumablessemi-automatic FCAW , were used in this experiment.Linepipe girth welding belongs to multilayer andIn the manual SMAW process , cellulose electrodesmulti-pass welding. The entire girth weld consists ofwere applied to the root weld, while ferrite lowthe root weld (hot weld) , the fllr weld and the caphydrogen basic electrodes were applied to the fller andweld. In the field grith welding construction , productioncap weld. In the semi-automatic FCAW process , solidlines are often used. Therefore ,different welding passeswire surface tension transfer ( STT) welding with aof the same girth welding are usually completed byCO2 shield was applied to the root weld, while self-different welding teams. In fact, different weldingshielded flux cored wires were applied to the fller andmethods are usually used on the same girth weld-cap welding. Table 3 shows the manual and semi-auto-ing:+-matic girth welding experiments of welding consum-Two different welding methods , manual SMAW andable selections for X80 UOE linepipe.Table 3 Consumable selections for X80 UOE linepipe girth weldingMethodNo.WeldType( AWS)BrandDiameter/ mmFlux typeTE6010BOHLER FOX CEL中3.2.CelluloseF&C _E9018-GBOHLER FOX BVD 90φ4.0BasicSMAWRφ3.2F&C，E10018-G .BOHLER FOX BVD 100ER70S-GJintai JM-58φ1.2Solid wireF &CE81T8-Ni2JHOBART FABSHIELD X80φ2.0.Flux cored wireFCAWE81T8-GLINCOLN Primacore sw 88Pφ2.0Flux cored wirER7OS-GF&CELGASHIELD BFS 464Ni2中2.0Note:R stands for root weld and F & C sand for fller and cap welding.2.3 Welding procedure specificationsso that welding defects do not appear during theTable 4 shows the girth welding process specifica-welding process. Furthermore, the longitudinal sub-tions of X80 UOE linepipe. In order to understand themerged arc welded (SAW ) weld should be staggeredeffect that the welding process has on the mechanicalmore than 100 mm. Secondly , two linepipe sectionsproperties of girth welding, two different weldingshoul中国煤化工; assembly, thprocess specifications were used in the SMAW andassemhown in Fig. 1. InFCAW combinations.YHCN M H G and post-heatingIn the X80 UOE linepipe girth welding experiment ,treatment shoula be used , whule the Inter-pass tempera-the hybrid V groove shown in Fig. I should be used.ture should be maintained at less than 150C. AFirstly ,the part 25 mm from the bevel of the linepipeLINCOLN INVERTEC V350 一PIPE pulsed weldingend should be cleaned by brushing and grinding lightlypower source should be used in the SMAW process ,LIU Shuo. Girth weldability and welding process of Baosteel X80 UOE linepipes17while a LINCOLN STT- I should be used for rootfiller and cap welding in the FCAW process.welding and a LINCOLN DC-400 should be used forTable 4 Girth welding process secifications of X80 UOE linepipeMethod No._WeldPolarityCurren/AVoltage/VWeld speed/(cm . min)RemarksRDCEN75-9020-2620-35T1F &CDCEP180-21020-288-20.SMAW-In Tl and T4 ,the great285-9520-2520 -35heat input welding pro-I320 -2612-20cess was used throughincreasing current and120-15020 -2215 -35decreasing weld speed,FCAWF&C230 -27018-2010-20while in other groupsdecreased heat input120- 15020-22was used.[6180 -22018 -2014-263 Results and discussion3.1 ResultsTest specimens were taken from the joint after thegirth welding was completed. From Fig.2,it can beseen that the girth weld bead is very uniform andT.6+0.4continuous , and no weld defect can be found aroundthe girth welding joint. Figs. 2 and 3 are the examples2.0+0.5of the girth weld macrograph and microstructure ofTI,Fig.1 A hybrid V-groove in X80 UOE linepipe girthrespectively , and the others are almost the same as thewelding (x=13-15°,β=35 +5° )appearance of TI.(a) Girth weld on the front(b) Girth weld on the backig.2 Macrography of T1 girth weld joints10u(2) Weld (AF+Bu)(b) CGHAZ (PF+B+P)(c) FGHAZ (F+P)Note: AP - aciculaer ferie:; Bu - under binite; CGHAZ - carse grain heat aft zone;中国煤化工HAZ - fme gain heataffected zoneFig3 Microstructures of three T1MHCNMHGTable 5 shows some of the mechanical properties forbend test. Fig. 4 shows the impact toughness of thethe girth weld joints TI - T7 , including a joint trans-girth weld joint. Fig. 5 shows the examples of Vickersverse tensile test,a nick break test and a guided sidehardness for TI and T4 , and the others are almost the18Basteel Technical Research, Vol.4, No.3, Sep. 2010same as above these two. Fig. 6 is a sketch of theVickers hardness measurement points.Table 5 A selection of mechanical properties for the girth weld joints T1 -17No.Tensile strength/ MPaFracture positionSide bend(d =4a,a = 180°)Nick-break670/670/675/570Base linepipe0k)kT2665/675/670/670OkDk670/665/665/575T4645/640/640/645Girth weld645/640/640/640630/625/630/635650/650/655/650- Girth weld+ Girth weldFusion line1400t;120|140- .. 100120 Fof冒.8080 t6(50 LT3TT5T6(a) SMAW girth weld joint(b) FCAW girh weld jointFig.4 Impact toughness of the girth weld joint T1 -17 (Impact testing temperature: -10C)260r + TI230r + -T425巨240230210蒋220重2102009019002468101214 160246810121416oint NoPoint No.(a) Vickers hardnessof TI(b) Vickers hardness ofT4Flg.5 Vickers hardness of T1 and T4indicating that the above girth welding process com-bination can meet the relevant requirements of the test.In addition, the girth welding quality is not only........determined by the design of the welding process-....specifications , but also by the ability and experience of1 1.5士0.5 mmthe welders, especially for the manual SMAW andsemi-automatic FCAW. Therefore，before the field girth..welding of a pipeline project , the welders should betrained and their qualifications should be certified toensure that they are capable of doing field girth1.5土0.5 mmweldih中国煤化工was found that theFig.6 Vickers hardness measurement pointspropeconformed to theAPI拉HCNMHG" East natural gas3.2 Discussiontransmission pipeline project standard for the tensileAs known from the above testing results， thestrength , guided bend and nick-break tests. The tensileappearance of the girth welds are fairly good,strength of the girth weld joint was comparatively low.LIU Shuo. Girth weldability and welding process of Baosteel X80 UOE linepipes19in only T6 joint , which was mostly due to the matchingof the consumable. In other words . the strength of the4 Conclusionsflux cored wire from LINCOLN was relatively low.During the Vickers hardness testing, no abnormity(1) The field girth weldability of Baosteel's X80appeared in any of the joint positions.UOE linepipe is excellent under the conditions ofAs indicated in Fig. 4, the impact toughness of themanual SMAW and semi- automatic FCA W welding . asTI and T7 girth welding joints cannot satisfy the APIlong as the girth welding process and the selection ofstandard 1104 or the 2nd West - East natural gas trans-consumable is optimal. The mechanical properties 0mission pipeline project standard ，while the other jointsthe welding joint can satisfy the requirements of bothhave a fairly high low-termperature impact toughness. Inthe API standard 1104 and the second West - Eastgeneral ,the fusion line is the weakest position in all thenatural gas transmission pipeline project standard.girth weld joints,but for T2 -T6 ,they all have a high(2) For the manual SMAW girth welding，the heatinput has a great influence on the impact toughness oflevel of toughness.In the above girth weld joint mechanical propertythe girth welding, and an increased heat input couldtests , there is no doubt that the field girth weldability ofresult in a decrease in the impact toughness of the girthBaosteel's X80 UOE linepipe is excellent, and the lowwelding joint. Both the basic electrodes used can meettensile strength and impact toughness in certain girththis requirement.(3) For the semi-automatic FCAW girth welding,weld joints only occurred because of the girth weldingthe heat input has no important impact on the me-process design and the suitability of the consumable.From Fig.4(a), it is evident that the impactchanical properties of the girth weld joint, while thematching welding materials have a great influence ontoughness of the SMAW girth weld decreases greatlyfollowing an increase in the welding heat input. As aresult,a fairly low heat input is recommended whenReferencesusing SMAW field girth welding on linepipes through[1] Liu Shuo. High strength pipeline automatic girth weldingdecreasing the welding current or increasing thetechnology and its development at Baosteel [ J]. Baosteelwelding speed. In practice ，the welding torch movingTechnology ,2009(3) :31-35. .method of straight drawing and no swing is often used[2] Graef M and Hillenbrand H G. Grade X80 line pipe andin the linepipe construction field. Furthermore , the T2pipeline construction [ C/OL] // 9th Intermaional Con-ference and Exhibition of EUROPIPE. Dusseldorf:and T3 girth welding joints have excellent mechanicalEUROPIPE GmbH, 1997:1-5[ 1997-11-5]. http: // www.properties , which suggest either low strength matchingeuropipe. com/ 72-1-1990- 1999. html.or high strength matching of the consumable is accep-[3] Biermann K, Brihl F ,Zschau M,et al. Experiences withtable，and the selection of the two kinds of consumablesite erection and field welding of the pipeline steel X80is determined by other factors in linepipe production.[J]. Oi1l & Gas Journal , 1997(9):1-11Through Fig.4(b),it is apparent that the impact[4] Booth G F,Howse D s and Howard R D. A new tech-nique for girth welds in land pipelines: hybrid laser-arctoughness of the FCAW girth weld increases slightlywelding[C] // Proceedings of the Second Internationalfollowing an increase in the welding heat input , whichWLT-Conference Lasers in Manufacturing, Lasers incould be considered as a natural measurement fluctua-manufacturing 2003. ed. by Poprawe R. Munich: Thetion. Therefore, for semi -automatic FCAW field girthGerman Scientific Laser Society (WLT) ,2003:1-8.welding, the welding heat input has no important[5] Graf M K and Niederhoff K A. Overmatching criterionand manual welding of line pipe in grades more than X70impact on the mechanical properties of the girth weld[ C/OL ]// Pipeline Technology Conference. Ostende:joint. In addition, with the change in the matchingEUROPIPE GmbH，1995: 1-11[ 1995-9-14]. http: //consumable , the girth weld impact toughness decreaseswww. europipe. com/ 72-1-1990-1999. html.prominently, and the property of the T7 specimencouldn't meet the requirements of the correspondingstandard. Based on this experiment, the self-shieldedflux cored wire of ELGASHIELD BFS 464Ni2couldn 't adapt to the semi automatic girth welding ofthe X80 UOE linepipe. The influencing mechanism ofthe flux cored wire on the impact toughness of the girthwelding joint is very complicated , relating not only tothe inner flux ,but also to the outer metal sheath.LIU Shuo中国煤化工MHCNMHG