Code for Welding of Steel Structures

Transcription

1 Translated English of Chinese Standard: GB NATIONAL STANDARD OF THE GB UDC PEOPLE S REPUBLIC OF CHINA P GB Code for Welding of Steel Structures 钢结构焊接规范 Issued on: December 5, 2011 Implemented on: August 1, 2012 Issued by: Ministry of Housing and Urban-Rural Development; General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) and the Standardization Administration (SAC) of the People's Republic of China. Page 1 of 121

2 Table of Contents Foreword General Provisions Terms and Symbols Terms Symbols Basic Requirement Materials Design of Welding Connections General Requirements Form and Size of Weld Groove Theoretical Throat of Weld Welding Nodal Points of Combined Welding Member Technics for Avoiding the Nodal Point of Lamellar Tearing Welding Connection Design of Member Production and Field Installation Design of Welding Connections Bearing Dynamic Load and Anti-earthquake Welding Procedure Qualification General Requirement Substitute Principles of Welding Procedure Qualification Requalification Preparation of Test Pieces and Samples Testing Prequalification of WPS Welding Procedures Preparation of Base Metal Requirement of Welding Consumables Assemble Requirement of Welding Joint Tack Weld Welding Environment Preheat and Interpass Temperature Control Post-weld Hydrogen Relief Heat Treatment Post-weld Stress Relief Treatment Weld Tab and Backing Technic Requirement of Welding Procedure Control of Welding Deformation Repairs Correction Back Gouging Temporary Welds Page 4 of 121

3 7.16 Striking and Extinguish of Arc ESW and EGW Inspection General Requirement Weld Inspection of Structure Bearing Static Load Weld Inspection of Structure Requiring Fatigue Assessment Weld Strengthening and Reinforcement Appendix A Form, Size and Marking Method for Welding Joint Groove of Steel Structure Appendix B Format of WPQR Appendix C Testing of ESW Weld of Box Members Explanation of Wording in This Code List of Quoted Standards Page 5 of 121

4 Foreword This code was jointly prepared by the Central Research Institute of Building and Construction of MCC Group Co., Ltd. and organizations concerned according to the requirements of the Ministry of Construction "Notice on Printing and Publishing 'Development and Revision Plan of National Engineering Construction Standards and Codes (second batch) in 2005' " (Jianbiao [2007] No.126). This code provides the technical requirements on design of welding connections, manufacture, materials, procedure and quality control of steel structures as well as staffing. Meanwhile, in order to implement technical and economic policies of the nation and reflect the sustainable development concept in the steel structure construction field, this code not only controls the welding quality of steel structures, but also strengthen the requirements on energy conservation, material saving and environmental protection, etc. During the preparation process this code, we summarized the practical experience and research achievements on steel structure welding in China in recent years, the drafting group conducted multiple monographic studies, sufficiently adopted the new technology, new procedure and new materials practically used in works, and used the international and foreign advanced standards for reference, solicited opinions from all sides, discussed and modified the specific contents repeatedly and finalizes it upon review. The main contents of this code are: General Provisions, Terms and Symbols, Basic Requirement, Materials, Design of Welding Connections, Welding Procedure Qualification, Welding Procedures, Inspection, Weld Strengthening and Reinforcement, etc. Provisions printed in bold type in this code are compulsory ones, and must be enforced strictly. The Ministry of Housing and Urban-Rural Development is in charge of the administration of this standard and the explanation of the compulsory provisions of this code, and Central Research Institute of Building and Construction of MCC Group Co., Ltd. is in charge of the explanation of specific technical contents. All relevant organizations are kindly requested to sum up and accumulate your experiences in actual practice during the process of implementing this code. The relevant opinions and advice, whenever necessary, can be fed back to "Code for Construction of Concrete Structures" Administrative Group of Central Research Institute of Building and Construction of MCC Group Co., Ltd. (Address: No.33, Xitucheng Road, Haidian District, Beijing, ; for future reference. Chief development organizations of this code: Central Research Institute of Building and Construction of MCC Group Co., Ltd. and China Second Metallurgy Group Corporation Limited Participating development organizations: National Engineering Research Center for Steel Structures, China Jingye Engineering Corporation Limited, China Page 6 of 121

5 1 General Provisions This code is formulated with view to implementing national technical and economic policies in the steel structure welding, to achieving technical advancement, economic rationality, safety and usability, and to ensuring quality and energy conservation and environmental protection This code is applicable to the welding of structures bearing static load or dynamic load and with steel thickness not less than 3mm in industrial and civil steel structure engineering. The applicable welding methods in this code include shielded metal arc welding, gas-shielded arc welding, flux cored wire self-shield arc welding, submerged-arc welding, ESW, EGW, stud welding and their combination Steel structure welding must comply with the current relevant provisions of the nation on safety technology and labor protection, etc Steel structure welding shall not only comply with this code, but also shall comply with those specified in the in the current relevant standards of the nation. Page 8 of 121

6 2 Terms and Symbols 2.1 Terms Hydrogen relief heat treatment The post-weld heat treatment method in which the welding joints of the structural steel, which is likely to have cold crack, are heated to certain temperature (250 ~350 ) after welding and held for a while so as to accelerate the diffusion of hydrogen in the welding joints and delayed crack due to the accumulation of diffusible hydrogen Stress relief heat treatment The post-weld heat treatment method in which the welding joints are heated to the certain temperature (550 ~650 ) below the base metal A c1 line after welding and held for a while so as to reduce welding residual stress and improve joint structure property Weld access hole The weld penetrating hole which is set at the corresponding position at the cross of member welds in order to guarantee continuity of main weld and facilitate to welding operation Prequalification of WPS The welding procedures that the provisions in this code may be adopted without passing welding procedure qualification test, under the conditions of meeting some specific welding methods, parameters, steels, joint form and welding consumable combination correspondingly specified in this code Temperature of welding circumstance The temperature of the surrounding environment of weldment during welding Flux cored wire self-shield arc welding The method that the weld zone is protected by the slag and gas formed by the reaction of welding wire flux core at high temperature, without additionally adding gas or welding flux for protection Testing The technical operation composed of testing of one or several properties of a given product, test treatment or services providing according to specified procedures Inspection The checking of materials, staff, procedures, process or results and the determination of its compliance to the specific requirement or that to general requirement on the basis of professional judgment. α - Weld groove angle; h - Weld groove depth; b - Weld groove root clearance; P - Weld groove root face height; 2.2 Symbols Page 9 of 121

7 h e - Theoretical throat of weld; z - Reduction of theoretical throat of weld; h f - Weld leg size; h k - Size of reinforced weld leg; L - Weld length; B - Weld width; C - Weld reinforcement; - Butt weld misalignment; D(d) - Main (branch) pipe diameter; Φ - Diameter; Ψ - Dihedral; δ - Sample thickness; t - Plate and wall thickness; a - Spacing; W - Width of section steel rod piece; f - Nominal stress of fillet weld; T f - Nominal shear stress of fillet weld; η - Reduction coefficient of weld strength; f w f - Design value for the shear strength of fillet weld; HV10 - Vickers hardness where the test force is 98.07N (10kgf) and the load is maintained for (10~15)s; R eh - Upper yield strength; R el - Lower yield strength; R m - Tensile strength; A - Percentage elongation after fracture; Z - Percentage reduction of area. Page 10 of 121

8 meet the following requirements: 1 Welding technicians shall receive specific welding technology training and have welding engineering or practical construction experiences of more than one year; 2 Welding technical leaders shall not only meet the requirements of Clause 1 in this article, but also shall have the technical titles above the intermediate level. As for the construction units undertaking the welding engineering Level C and Level D in term of difficulty, their welding technical leaders shall have senior technical titles; 3 Welding inspection personnel shall have received specific technical training and have certain welding practical experience and technical level as well as inspection personnel post certificate; 4 Non-destructive testing personnel must pass the assessment by professional organization, and the certificate shall be within the period of validity. They shall be engaged in non-destructive testing and examination and verification according to the qualified assessment items and authority. As for the non-destructive testing examiners undertaking the welding engineering Level C and Level D in term of difficulty, they shall meet the requirements of Level 3 qualification specified in the current national standard "Non-destructive Testing- Qualification and Certification of Personnel" (GB/T 9445); 5 Welders shall take technical qualification examination according to the requirements of the steel type, welding nodal point form, welding method and welding position of the steel structure that they are engaged in, and shall obtain corresponding qualification certificate, their welding scope shall not be beyond the requirements of the qualification certificate. 6 Welding heat treatment personnel shall have corresponding profession skill. When using electrical heater for heating, operation personnel shall have received professional training The responsibilities of relevant personnel for steel structure welding engineering shall meet the following requirements: 1 Welding technicians are responsible for conducting welding procedure qualification, preparing welding process scheme and technical measures and instructions for welding operation or welding procedure sheet, as well as handling the welding technology problems during construction; 2 Welding inspection personnel are responsible for the inspection and control of the butt weld operation during the whole process and issuing inspection report; 3 Non-destructive testing personnel shall conduct flaw detection on the tested positions according to the detection method and specified in the design document or corresponding specifications, and shall issue testing report; 4 Welders shall weld according to the requirements of welding procedure document; 5 Welding heat treatment personnel shall operate according to the heat treatment instruction and corresponding operation specifications The safety, health and operating environment of relevant personnel for steel structure welding engineering shall comply with those specified in the current relevant safety and health standards of the nation. Page 12 of 121

9 than 40mm, the steel plates with through-thickness characteristic requirements should be adopted in the design. The through-thickness characteristic grade of steels shall be selected based on the engineering structure type, nodal point form, plate thickness and stress state according to the relevant requirements of the current national standard "Steel Plate with Through-thickness Characteristics"(GB/T 5313) Welding electrodes shall meet the requirements of the current national standards "Carbon Steel Covered Electrodes" (GB/T 5117) and "Low Alloy Steel Covered Electrodes" (GB/T 5118) Welding wires shall meet the relevant requirements of the current national standards "Steel Wires for Melt Welding" (GB/T 14957), "Welding Electrodes and Rods for Gas Shielding Arc Welding of Carbon and Low Alloy Steel" (GB/T 8110), "Carbon Steel Flux Cored Electrodes for Arc Welding " (GB/T 10045) and "Low Alloy Steel Flux Cored Electrodes for Arc Welding" (GB/T 17493) The welding wires and welding flux used for submerged arc welding shall meet the relevant requirements of the current national standards "Carbon Steel Electrodes and Fluxs for Submerged Arc Welding" (GB/T 5293) and "Low-alloy Steel Electrodes and Fluxs for Submerged Arc Welding" (GB/T 12470) Argon used in gas-shielded arc welding shall meet the relevant requirements of the current national standard "Argon" (GB/T 4842) and its purity shall not be less than 99.95% The carbon dioxide used in gas-shielded arc welding shall meet the relevant requirements of the current professional standard "Carbon Dioxide for Welding Use" (HG/T 2537). As for the important welding nodal points of primary members used in special steel structural engineering with the welding difficulty of Level C and Level D, the quality of the carbon dioxide used shall meet the requirements for high-grade products in the standard The stud and welding porcelain ring used for stud welding shall meet the relevant requirements of the current national standard "Cheese Head Studs for Arc Stud Welding" (GB/T 10433). Page 14 of 121

10 5 Design of Welding Connections 5.1 General Requirements The design of welding connections of steel structure shall meet the following requirements: 1 Number and size of welds should be reduced; 2 The arrangement of welds should symmetrical with the neutral axis of component section; 3 The space of nodal point area shall be convenient for welding operation and post-welding inspection; 4 Nodal point form of smaller stiffness should be adopted and intensive and two-way or three-way intersection of welds should be avoided; 5 Weld position shall be kept clear from the area of high stress; 6 Groove form and size shall be selected according to different welding procedure methods The identified weld symbol in the design drawing and detailed production drawing shall meet the relevant requirements of the current national standards "Weld Symbolic Representation on Drawings" (GB/T 324) and "Standard for Structural Drawings" (GB/T 50105) In the construction drawing of steel structure design, the following welding technology requirements shall be specified clearly: 1 The steel designation of members and the model and performance requirements of welding materials as well as corresponding current national standards; 2 The welded part of the intersection nodal point of steel structure member, valid weld length, weld leg size and the depth of partial penetration weld; 3 As for weld quality grade, where non-destructive testing is required, non-destructive testing method and inspection proportion shall be indicated; 4 Within the allowable range of plant-made unit and member assembly nodal points, and structure design stress diagram shall be proposed according to engineering needs In the detailed production drawing of steel structure, the following welding technology requirements shall be indicated: 1 All the welding technology requirements in the design drawing shall be marked in detailed, and the welded part of the intersection nodal points of steel structure member, welding method, valid weld length, weld groove form, weld leg size, depth of partial penetration weld and post-weld heat treatment requirements shall be specified clearly; 2 The detailed size of weld groove shall be marked clearly, if there is steel backing, its size shall be marked; 3 As for heavy and large-scare steel structures, the positions for plant-made unit and field assembly welding shall be specified clearly and plant made or field installed welds shall be marked; 4 Member segment positions and splicing nodal points shall be determined according to transportation condition, installation capacity, welding operability and allowable design Page 15 of 121

11 range, and weld design shall be conducted according to the relevant requirements of design specifications and submitted to the original design organization for structure safety examination and verification According to steel structure importance, load bearing characteristic, weld form, working environment and stress state, weld quality grade shall be selected in accordance with the following principles: 1 In the members which bear the dynamic load and shall be carried out with fatigue calculation, all the welds in equal strength connection with the base metal shall be fully penetrated, and their quality grade shall meet the following requirements: 1) As for the butt weld in the horizontal position or T-shaped composite butt and fillet weld with the acting force vertical to weld length direction, it shall be Grade 1 in tension and shall not be lower than Grade 2 under compression; 2) As for the longitudinal butt weld with acting force parallel to weld length direction, it shall not be lower than Grade 2; 3) The joint plate and chord member fillet welds of transverse beams of railways and highway bridges shall be of Grade 1; bridge deck and chord member fillet welds as well as bridge deck and U-shaped rib angle welds (bridge deck side) shall not be lower than Grade 2; 4) As for the T-shaped joint welds between web plate of crane beam of heavy duty system (A6~A8) and intermediate duty system (A4 and A5) with hoisting capacity Q larger than or equal to 50t and the upper flange as well as between the upper cord of crane truss and node plate shall be fully penetrated, the weld form shall be of composite butt and fillet weld, its quality grade shall not be lower than Grade 2. 2 In the member requiring no fatigue calculation, the butt weld required to be of the equal strength with the base metal should be fully penetrated. Under tension, its quality grade shall not be lower than Grade 2, and should not be lower than Grade 2 under compression. 3 As for the butt weld in partial penetration, the T-shaped joints of composite butt and fillet weld adopting fillet weld or partial penetration and fillet welds in lapping connection, their quality grade shall meet the following requirements: 1) It shall not be lower than Grade 2 for the structures directly bearing dynamic load and requiring fatigue calculation, the intermediate duty system crane beam with the crane load equal to or larger than 50t as well as the important nodal points such as beam & column and bracket. 2) It may be Grade 3 for other structures. 5.2 Form and Size of Weld Groove Welding position, joint form, groove form, weld type pipe structure nodal point form (Figure 5.2.1)code shall be in accordance with those specified in Tables ~ Table Welding Position Codes Code F H V O Welding position Flat welding Horizontal welding Vertical welding Extending welding Page 16 of 121

12 requirements: 1 Weld tab and backing shall be removed; 2 Arc transition shall be made at corner of column and beam junction during removing, and cut surface shall be free from damage edge with size greater than 1mm; 3 After lower flange backing is removed along the length, the defects such as welding slag of weld at the back side of joint must be polished and removed, and repair welding to weld shall be conducted for gentle transition The weld access hole of beam web at junction of beam and column shall meet the following requirements: 1 Process of weld access hole on web plate should be conducted together with weld tab removing after longitudinal composite weld of web plate and flange plate is completed; smooth transition of processed weld access hole shall be guaranteed; 2 The weld access hole height of web plate at lower flange shall be the same as the web plate thickness and not be less than 20mm; the spacing between junction of weld access hole edge and lower flange plate and weld fusion line of column and beam flange shall be greater than 10mm. the longitudinal composite weld of web plate and flange plate shall not skirt the weld all around with a web thickness at weld access hole; 3 Where web thickness is greater than 40mm, the preheating temperature for weld access hole thermal cutting shall be above 65, and magnetic powder inspection or penetrating inspection may be conducted for polished cut surface (where necessary); 4 Surfacing welding shall not be adopted for blocking weld access hole. Page 40 of 121

13 6 Welding Procedure Qualification 6.1 General Requirement As for the steels, welding consumables, welding method, joint type, welding position, post-weld heat treatment (PWHT) system as well as various parametrical composition conditions (welding parameter, preheating and afterheat measures) adopted by constructor for the first time, they shall complying with the principle of prequalification specified in Section 6.6 in this code, and welding procedure qualification shall be conducted before steel structure member manufacture, installation and construction The constructor shall make a scheme for welding procedure qualification according to the design nodal point form of steel structure, steel type and specification, adopted welding method and welding position, protocol corresponding guide book for welding procedure qualification, weld test piece and cut sample according to those specified in this code (which shall be inspected and tested by testing organization with corresponding qualification), determine whether welding joint has required service performances and issue test report; relevant organizations shall witness the welding process of welding procedure qualification conducted by constructor; inspection organization with corresponding qualification shall assess the protocol welding process according to inspection results and the relevant requirements of this code and issue welding procedure qualification report (WPQR) Environment of welding procedure qualification shall reflect the conditions engineering construction site As for the welding procedure qualification, such welding parameters as weld heat input, preheat and afterheat shall be determined according to the weldability of material to be welded The performance of equipment and instrument used for welding procedure qualification shall be in normal operating condition; steels, stud and welding consumables used for welding procedure qualification must be able to cover the materials used in practical engineering, shall meet the requirements of relevant standard and be provided with quality proof documents by manufacturer Test piece used for welding procedure qualification shall be welded by licensed welding personnel of the enterprise conducting the engineering The welding method, welding position and classification code adopted for welding procedure qualification shall be in accordance with those specified in Table , Table and Figures ~ ; the steels type shall be in accordance with those specified in Table 4.0.5; the joint type of test piece shall be in accordance with those specified in Table Page 41 of 121

14 fillet weld of complete penetration/partial penetration T-shaped/cross joints may substitute that of fillet weld The applicable thickness scope of thickness of acceptable test piece in engineering shall be in accordance with those specified in Table Table Thickness of Acceptable Test Piece and Applicable Thickness Scope in Engineering Applicable thickness scope in engineering Type code of welding method Thickness of acceptable test piece (t) (mm) Minimum value of plate thickness Maximum value of plate thickness 25 3mm 2t 1, 2, 3, 4, 5, 8 25<t t 2t > t unlimited t minimum 18mm 1.1t t minimum 10mm 1.1t 9 2t, and equal to or less than 1/3φ t<12 t 16mm 12 t< t 2t Note: φ refers to the diameter of stud. t t 1.5t As for the joint of acceptable pipe material, the coverage of wall thickness shall meet those specified in Article in this code, and coverage principle of diameter shall meet the following requirements: 1 As for pipe material with outside diameter less than 600mm, the diameter coverage shall not be less than the outside diameter of pipe material used for procedure qualification test; 2 As for pipe material with outside diameter not less than 600mm, the diameter coverage shall not be less than 600mm As for butt joint of sheets and butt joint of pipe material with outside diameter not less than 600mm at corresponding position, their welding procedure qualification results may substitute each other Except for stud welding, assessment results of horizontal position welding may substitute that of flat position welding, while assessment results of flat position welding cannot substitute that of horizontal position welding. As for vertical/overhead position welding and other position welding, their assessment results cannot substitute each other As for complete penetration joints welded on single side with backing and those without backing, their assessment results cannot substitute each other; as for complete penetration joints welded on single side with backing and complete penetration joints welded on both sides with back gouging on reverse side, their assessment results may substitute each other; as for joints with backing made of different materials, their assessment results cannot substitute each other Where stud material is unchanged, the welded steel adopting stud welding shall meet the following substitute principles: 1 The stud welding procedure qualification test for steels of Types III and IV may Page 45 of 121

15 substitute welding procedure qualification test for steels of Types I and II; 2 The stud welding procedure qualification tests for steels of Types I and II may substitute each other; 3 The stud welding procedure qualification tests for steels of Types III and IV cannot substitute each other. 6.3 Requalification As for shielded metal arc welding, requalification shall be conducted where one of the following conditions changes: 1 The tensile strength grade of electrode deposited metal changes; 2 Low hydrogen type electrode is changed into non-low hydrogen type electrode; 3 Welding electrode specification changes; 4 The current polarity of direct current welding electrode changes; 5 Multipass welding and single pass welding change; 6 Back-gouging is no longer adopted; 7 The direction of vertical position welding changes; 8 The changes of current value and voltage value actually adopted for welding exceed the recommended scope specified in product description for welding electrode As for consumable gas shielded arc welding, requalification shall be conducted where one of the following conditions changes: 1 Transformation between solid welding wire and flux cored wire; 2 The type of single shielding gas changes; the type and mixture ratio of multiple shielding gases change; 3 Shielding gas flow rate increases by above 25% or decreases by above 10%; 4 Swing amplitude of welding torch exceeds ±20% the acceptance value; 5 The change of current value, voltage value and welding speed actually adopted for welding exceed 10%, 7% and 10% the acceptance values respectively; 6 During solid wire gas-shielded arc welding, droplet transfer and short circuit transfer change; 7 Welding wire model changes; 8 Welding wire diameter changes; 9 Multipass welding and single pass welding change; 10 That back gouging is adopted is changed into it is not adopted; As for non-consumable gas shielded arc welding, requalification shall be conducted where one of the following conditions changes: 1 Shielding gas type changes; 2 Shielding gas flow rate increases by above 25% or decreases by above 10%; 3 Welding wire addition changes; wire feed in cold state and thermal state changes; welding wire type, strength grade and model change; 4 Swing amplitude of welding torch exceeds ±20% the acceptance value; 5 The change of current value and welding speed actually adopted for welding exceed 25% and 50% the acceptance values respectively; 6 Welding current polarity changes As for submerged arc welding, requalification shall be conducted where one of the following conditions changes: Page 46 of 121

16 1 Welding wire specification changes; welding wire and flux models change; 2 Multi-wire welding and single-wire welding change; 3 The condition whether cold wire is added changes; 4 The type and polarity of welding current change; 5 The change of current value, voltage value and welding speed actually adopted for welding exceed 10%, 7% and 15% the acceptance values respectively; 6 That back gouging is adopted is changed into it is not adopted; As for ESW, requalification shall be conducted where one of the following conditions changes: 1 Single-wire and multi-wire change; plate electrode and filament change; the condition whether consumable nozzle exists or not changes; 2 The change of consumable nozzle section area is greater than 30%; consumable nozzle designation changes; welding wire diameter change; single/multiple consumable nozzle change; flux model changes; 3 Single-side groove and double-side groove change; 4 Type and polarity of welding current change; 5 The condition that current voltage characteristic of welding source being constant voltage or constant current changes; 6 The change of current value, voltage value, wire feed speed and steep-lifting speed actually adopted for welding exceed 20%, 10%, 40% and 20% the acceptance values respectively; 7 Deviation from vertical position exceeds 10 ; 8 Transformation between forming water cooling sliding block and baffle; 9 Change of flux charge weight exceeds 30% As for EGW, requalification shall be conducted where one of the following conditions changes: 1 Model and diameter of welding wire change; 2 Type or mixture ratio of shielding gases change; 3 Shielding gas flow rate increases by above 25% or decreases by above 10%; 4 Welding current polarity changes; 5 The change of current value, wire feed speed and voltage value actually adopted for welding exceed 15%, 30% and 10% the acceptance values respectively; 6 Change of deviation from vertical position exceeds 10 ; 7 Transformation between forming water cooling sliding block and baffle As for stud welding, requalification shall be conducted where one of the following conditions changes: 1 Stud material changes; 2 Stud nominal diameter changes; 3 Porcelain ring material changes; 4 Non-penetration welding and penetrate welding change; 5 During penetrate welding, the plate thickness and coating amount of penetrated sheets increase, and the type of coating changes; 6 Stud welding position deflects position of flat welding by above 25, or positions of flat welding, horizontal welding and overhead welding change; Page 47 of 121

17 Table Acceptance Criteria for Appearance Inspection of Stud Welding Joint Appearance inspection item Acceptance criteria Test methods Overall size of weld Full weld within the range of 360 Arc discharge stud welding: weld height K 1 1mm; weld width K 2 0.5mm Electric arc welding: the minimum weld leg size shall be in accordance with those specified in Table Visual inspection, steel ruler and weld gauge Weld defect Free from defects like pore, slag inclusion and crack Visual inspection and magnifier (5 times) Weld undercut Height of stud welding Back rake of Stud Welding Undercut depth 0.5mm; the maximum length shall not be larger than the diameter of stud. Height deviation ±2mm Inclination angle deviation θ 5 Steel ruler and weld gauge Steel ruler Steel ruler and protractor Table Minimum Weld Leg Size for Stud Welding Joint by Electric Arc Welding Method Diameter of stud (mm) Minimum weld leg size for fillet weld (mm) 10, , 19, The non-destructive testing for test piece shall be carried out after passing the appearance inspection and the non-destructive testing method shall be determined according to the design requirements. The radiographic inspection shall meet the requirements of the current national standard "Radiographic Examination of Fusion Welded Joints in Metallic Materials" (GB/T 3323); the weld quality shall not be less than Grade BII; the ultrasonic testing shall meet the requirements of the current national standard "Method for Manual Ultrasonic Testing and Classification of Testing Results for Ferritic Steel Welds" (GB 11345); the weld quality shall not be less than Grade BII The mechanical performance, hardness and macroscopic acid etching test method of the sample shall meet the following requirements: 1 The tensile test method shall meet the following requirements: 1) Tensile test for butt joint shall meet shall meet the relevant requirements of the current national standard "Tensile Test Method on Welded Joints" (GB/T 2651); 2) Tensile test for stud welding joint shall meet the requirements of Figure The bend test method shall meet the following requirements: 1) The bend test for butt joint shall meet the requirements of the current national standard "Bend Test Methods on Welded Joints" (GB/T 2603); the bend center diameter is 4δ (δ is the thickness of the bending sample), and the bending angle is 180. The sample thickness for face bend and back bend shall be the whole thickness of test piece (δ<14mm) while that for the side bend δ=10mm. Where the thickness of test piece is not greater than 40mm, the width of test piece shall be the whole thickness of test piece; where the thickness Page 57 of 121

18 The electrode E5015 and E5016 shall not be greater than 6mL/100g; The flux-cored wire shall not be greater than 6mL/100g. 4 Where the plate thickness of welded joint is different, the preheat temperature shall be determined according to the maximum plate thickness; where the materials of welding joint are different, the preheat temperature shall be determined according to the steel with high strength and high carbon content; 5 The environment temperature shall not be less than 0. 4 The weld size shall meet the design requirements; the minimum weld leg size shall be in accordance with those specified in Table 5.4.2; the maximum weld size of single pass welding shall be in accordance with those specified in Table The welding procedure parameters shall meet the following requirements: 1) The parameter of prequalified welding procedure shall be in accordance with those specified in Table ; 2) As for the weld requiring for complete penetration, backing shall be added during single welding while back gouging shall be carried out during double welding; 3) The maximum width of weld pass during shielded metal arc welding shall not be greater than 4 times the nominal diameter of electrode; the maximum width of weld pass during solid wire gas shielded arc welding and flux cored wire gas shielded arc welding shall not be greater than 20mm; 4) Distance from the electrode nozzle and workpiece: union melt welding: 40±10mm; gas shielded arc welding: 20±7mm; 5) Category of shielding gas: CO 2 and rich argon gas with mixture ratio as 80% argon + 20% CO 2 ; 6) Flow of shielding gas: 20~50L/min. 6 The structure type of various prequalified welding nodal point welding nodal points and the form and size of the welding grooves must meet the requirements of Chapter 5 in this code: 1) Dihedral angle of oblique-angle fillet weld ψ>30 ; 2) Local dihedral angle of pipe material intersecting joint ψ>30. 7 The characteristic of prequalified structural load shall be static load. 8 Where the welding wire diameter is not conforming to Table , it shall not be prequalified. 9 Where the variation range of welding procedure parameters exceeds the requirements of Section 6.3 in this code according to Table and Table , it shall not be prequalified. Page 62 of 121

19 7 Welding Procedures 7.1 Preparation of Base Metal The surface to be welded and both sides of the abase metal shall be uniform, smooth, clean and free from burr, crack and other defects unfavorable for weld quality. The range within 30mm from the surface to be welded to the edge of the weld groove shall be free from oxide skin, rust, grease and water which may affect the normal weld and weld quality Machine processing, thermal cutting, carbon arc air gouging, gouging and polishing may be adopted for the processing or defect removal of welded joint groove The surface quality of groove processed by thermal cutting shall meet the requirements of the current professional standard "Thermal Cutting - Quality and Dimensional Deviation in the Gas Cutting" (JB/T ); where the thickness of steels is not greater than 100mm, the cut depth shall not be greater than 0.2mm; where the thickness of steels is greater than 100mm, the cut depth shall not be greater than 0.3mm The cut with depth greater than that specified in Article of this code as well as the gap and flute on the groove surface shall be polished and removed by mechanical processing Where the cutting defect on the groove surface of base metal need to be repaired, the repair process shall be established according to the requirements of this code, and shall be recorded and filed; as for hardened and tempered steel or structure which shall be subject to fatigue assessment where bearing dynamic load, the repair for the cutting defect on the groove surface of base metal shall be reported to the supervision engineer before implementation The testing and repair of steel rolling defect (Figure 7.1.6) shall meet the following requirements: 1 Where the defect length of steel interlayer on the edge of welding groove is greater than 25mm, the depth shall be tested by non-destructive testing. Where the defect depth is not greater than 6mm, it shall be removed by mechanical method; where the defect depth is greater than 6mm but not greater than 25mm, it shall be removed by mechanical method and then filled by welding; where the defect depth is greater than 25mm, its size shall be determined by ultrasonic. Where the area (a d) of single defect or the total area of aggregated defects is not greater than 4% the total area (B L) of the cut steel, it is deemed as acceptable, otherwise it shall not be used; 2 The size of internal interlayer of steels shall not exceed that specified in Article 1 of this Section; where the distance b from its position to the groove surface of base metal is not less than 25mm, no repair welding is needed; where the distance b is less than 25mm, repair shall be carried out; 3 Where the interlayer is a crack with length a and depth d not greater than 50mm, it shall be repaired; where the crack depth d is greater than 50mm or the accumulative length is greater than 20% of the plate width, is shall not be used; 4 The repair welding shall meet those specified in Section 7.11 of this code. Page 64 of 121

20 the requirements of base metal; adopted; 2 Where the plate thickness of welding joint is not less than 25mm, the low-hydrogen welding consumables should be 3 X in this Table shall be corresponding to relevant requirements of welding consumable standard; a than 16mm; It is only applicable to Q3459 steel with thickness not greater than 35mm and Q3709 steel with thickness not greater b It is only applicable to Q4209 steel with thickness not greater than 16mm. 7.3 Assemble Requirement of Welding Joint The size of welding groove should meet the requirements of Appendix A in this code, and the permissible size deviation for groove after assembling shall meet the requirements of Table Table Permissible Size Deviation for Groove during Assembling No. Item Non-back-gouging Back gouging 1 Root face of joint ±2mm 2 Root clearance of joint without backing ±2mm +2mm -3mm 3 Root clearance of joint with backing 4 Joint groove angle +6mm -2mm Root radius of U-shaped and J-shaped groove The joint clearance must not be filled with foreign bodies like electrode grips and iron blocks Where the assembling clearance deviation for groove is greater than that specified in Table but not greater than 2 times the thickness of the thinner plate or 20mm (the smaller one of above two values shall prevail), surfacing may be carried out on one side or both sides of the groove The misalignment of butt joint shall not be greater than the requirements of Table in this code. Where the misalignment of butt joint with different thickness is greater than 3mm, the thicker component shall be smoothly transited according to a gradient not greater than 1: Where T-shaped joint connected by fillet weld and partial penetration weld is adopted, the two components shall be closely against each other with root clearance not greater than 5mm; where the clearance is greater than 5mm, the plate end to be welded shall be subject to surfacing and grinded to be flat and smooth, and the clearance shall meet relevant requirements Where the root clearance of fillet joint components of T-shaped joint is greater than 1.5mm and less than 5mm, the size of fillet weld leg shall be increased according to the value of root clearance As for lap joints and connection joints of plug welding, slot welding and between the steel backing and base metal, the clearance between contact surfaces shall not be greater than 1.5mm. +3mm -0mm Page 67 of 121

21 7.4 Tack Weld The tack weld must be carried out by welder provided with corresponding qualification certificate; the adopted welding consumables shall be equivalent to that of the normal weld The surface quality of base metal near the tack weld shall meet those specified in Section 7.1 of this code The thickness of tack weld shall not be less than 3mm, the length shall not be less than 40mm while the spacing should be 300~600mm As for welding joint with steel backing, the tack weld should be carried out within the joint groove; the preheat temperature of tack weld should be greater than that of the normal welding by 20~50 ; the tack weld and normal weld shall be provided with the same welding procedures and welding quality requirements; the crack, pore and slag inclusion (if any) in the tack weld shall be completely removed As for dynamic load structure requiring for fatigue assessment, the tack weld process document shall be formulated according to the structure characteristics and the requirements in this Section. 7.5 Welding Environment As for shielded metal arc welding and self-shield flux-cored wire electric arc welding, the maximum wind speed in the welding operation area should not exceed 8m/s while that of the gas shielded arc welding should not exceed 2m/s; where the above range is exceeded, effective measures shall be taken to protect the welding arc area from wind effect The welding is strictly forbidden under any of the following conditions: 1 The relative humidity in welding operation area is greater than 90%; 2 The surface of welded piece is wet or exposed to rain, ice and snow; 3 The welding conditions are not consistent with relevant requirements of the current national standard "Safety in Welding and Cutting" (GB 9448) Where the temperature of welding circumstance is less than 0 but not less than -10, heating or protective measures shall be taken. It shall be ensured that temperature of base metal of the joint welding not less than twice the plate thickness in any direction and not less than 100mm is not less than 20 or the specified minimum preheat temperature (the higher one of the above two values shall prevail); the temperature shall not below this temperature in the welding process Where the temperature of welding circumstance is less than -10, procedure qualification test under corresponding welding environment must be conducted, and welding shall be conducted after passing such assessment. If it is not consistent with above requirements, the welding is strictly forbidden. 7.6 Preheat and Interpass Temperature Control The preheat temperature and interpass temperature shall be determined or subject to welding test according to comprehensive factors like the chemical composition of steel, restraint state of joint, amount of heat input, hydrogen content level of deposited metal deposited metal and the adopted welding method Where the common steels is welded by medium heat input, the minimum preheat temperature should meet the requirements of Table Page 68 of 121

22 Table Minimum Preheat Temperature Requirements for Common Steels ( ) Category of steel Plate thickness of the thickest component of joint t (mm) t 20 20<t 40 40<t 60 60<t 80 t>80 I a II III IV b Notes: 1 The weld heat input is about 15~25kJ/cm; the preheat temperature may be reduced by 20 from that specified in this Table for any 5kJ/cm increase of heat input. 2 Where non-low-hydrogen welding consumables or welding method is adopted for welding, the preheat temperature shall be 20 above that specified in this Table; 3 Where the temperature at the welding position of base metal is less than 0, the preheat temperature in this Table shall be properly increased according to the welding environment as well as designation and plate thickness of steel, and the minimum interpass temperature shall be maintained in the welding process; 4 Where the plate thickness of welding joints is different, the minimum preheat temperature and Interpass temperature shall be selected according to the plate thickness of the thicker plate; 5 Where the material of welding joints is different, the minimum preheat temperature shall be selected according to the steel with higher strength and higher carbon equivalent; 6 This Table is not applicable to steels with supply state as hardened and tempered the preheat temperature of TMCP steel may be determined by test; 7 " " refers to that where the welding environment is above 0, preheating measures may not be taken; a Cast steel is not included; the preheat temperature of cast steel for Category I steel should be determined by reference to the requirements of Category II steel; b It is only applicable to Q460 and Q460GJ steels of Category IV steels Preheating may not be carried out where the ESW and EGW is carried out with environment temperature above 0 ; where the plate thickness is greater than 60mm, the base metal in arc striking area shall be preheated and the preheat temperature shall not be less than In the welding process, the minimum interpass temperature shall not be less than the preheat temperature; where the static load structure is welded, the maximum interpass temperature should not exceed 250 ; where the dynamic load structure requiring for fatigue assessment and the hardened and tempered steel are welded, the maximum interpass temperature should not exceed The preheat and interpass temperature control shall meet the following requirements: 1 The preheat and interpass temperature before welding should be maintained by electrical heating method and flame heating method and shall be measured by special thermodetector; 2 The hot area for preheating shall be on both sides of the weld groove; the width shall be greater than the 1.5 times the plate thickness at the welding position and shall not be less than 100mm; the preheat temperature should be measured on the rear surface of the heating surface of welded piece, and the measuring point shall be not less than 75mm away from the welding point before electric arc passing in any direction; where fired heater is adopted for preheating, the temperature measurement on the front face shall be carried out after removing Page 69 of 121

23 the fired heater The determination of preheat temperature and interpass temperature for Category III and Category IV steels and hardened and tempered steels shall meet the instructive parameter requirements provided by the steel plant. 7.7 Post-weld Hydrogen Relief Heat Treatment Where hydrogen relief heat treatment after welding is required, it shall meet the following requirements: 1 The heating temperature of hydrogen relief heat treatment shall be 250~350, the holding time shall be determined according to the plate thickness of workpiece (not less than 0.5h per 25mm plate thickness), and the whole holding time shall not be less than 1h. It shall be slowly cooled to normal temperature after the holding time; 2 The heating and temperature measurement method for hydrogen relief heat treatment shall meet the requirements of Article in this code. 7.8 Post-weld Stress Relief Treatment Where the post-weld stress relief after welding is required by the design or contract document, for the butt joint that bear the tensile stress in the dynamic load structure subject to the fatigue assessment or nodes or members with dense welds, electric heater for local annealing and heating furnace for integral annealing should be adopted for the post-weld stress relief treatment; where they are only dimensions of the stable structure, vibration method may be adopted to relieve the stress The post-weld heat treatment shall meet the relevant requirements of the current professional standard "Welding Assembly for Carbon Steel and Low Alloy Steel - Post-welding Heat Treatment Method" (JB/T 6046). Where the electric heater is adopted for the local stress relief heat treatment, it shall meet the following requirements: 1 Heating equipment equipped with automatic temperature controller is used and its heating, temperature measurement and temperature control performances shall meet the service requirements; 2 The width of heating plate (strip) on each side surface of the member weld shall be at least 3 times of the steel plate thickness and shall not be less than 200mm; 3 Both sides of the member except the heating plate (strip) should be properly covered with insulation materials Where the stress of the intermediate welding layer is relieved by hammering method, a ball peen hammer or small-sized vibrating tool shall be adopted and the base metal at the edge of the root weld, cap weld or weld groove shall not be hammered Where the stress is relieved by vibration method, it shall meet the relevant requirements of the current professional standard "Recommended practice for Vibration Stress Relief on Welding Structure" (JB/T 10375). 7.9 Weld Tab and Backing The steels of starting weld tab, runoff weld tab and steel backing plate shall meet those specified in Chapter 4 of this code; such steels shall be provided with strength not greater than that of the welded steel and weldability close to that of the welded steel Starting weld tab and runoff weld tab shall be arranged at the end of welding joint, and the arc striking and termination of weld shall be within the provided extension section. The length of starting weld tab and runoff weld tab for shielded metal arc welding and gas Page 70 of 121