How to perform steel structure welding?

Dear brothers, I have just registered and am in the second grade of elementary school. I am now responsible for supervising the production of pipe supports and other structural parts. I work with fear every day, for fear that one day something will happen to the part I am responsible for, and I will be doomed. Our director always tells us in a serious tone that the first responsibility of the supervisor is quality, and the progress is second. But, God, due to the shortage of supervisors, I was transferred by the owner to be the supervisor. I don’t even have a certificate. I’m so scared. Please give me more valuable advice.

For details, please refer to GB50205-2001 "Construction Quality Acceptance Code for Steel Structure Engineering" 1 Construction method 1.1 Main construction method 1.1.1 First cut the columns according to the drawing and weld the corbels, ribs, etc. of each node. After welding, check and process to ensure that the straightness, warping and other process parameters of the column meet the requirements of the specification. 1.1.2 Assemble the columns and beams into pieces on the prefabricated platform to form a door-shaped structure, and then assemble it into a well-shaped three-dimensional structure and hoist it as appropriate. 1.1.3 Use segmented installation, lift with truck crane, or single beams such as contact beams. 1.1.4 After aligning the steel structure in place using the relative elevation method, install the connecting beams, first the main beam, then the auxiliary beam, and then lay the platform. 1.2 Construction technical preparation 3.2.1 Organize the construction team members to familiarize themselves with the drawings and ancillary design documents or related information, conduct technical briefings to the construction team, so that they can clarify the installation procedures, installation quality control points and requirements and safety education, and ensure quality first and civilized construction. 3.2.2 In order to ensure the quality of welding assembly, the prefabricated steel platform of the steel structure is laid at the construction site according to the specific installation position of the steel structure. 3.2.3 In accordance with Article 8 of this measure, check the preparation of construction machinery, testing tools and means of materials and construction water and electricity. ； Prepare the construction record form in accordance with Article 9 of this plan. 1.3 Inspection and acceptance of materials The inspection and acceptance of materials shall be organized by the owner and the supervision unit, and shall be carried out together with relevant personnel of the construction unit. 1.3.1 The steel materials and welding materials used in steel structure projects must have factory certificates and quality certificates, and comply with design and specification requirements. 1.3.2 The surface quality of steel should meet the requirements of relevant standards and specifications. The depth of surface corrosion, pitting or scratches should not be greater than 1/2 of the negative deviation of the thickness of the steel, and there should be no delamination and other defects at the fracture. 1.3.3 Welding consumables used for welding steel structures must have factory quality certificates, comply with design and specification requirements, and must not have peeling coatings or rust marks on the welding consumables. 1.4. Sizing and cutting of raw materials 1.4.1 Before sizing and cutting the materials, the appearance dimensions of the steel should be inspected. If any defects are found, they should be corrected before cutting. In this project, profiles and steel plates are mainly cut using oxygen-acetylene. 1.4.2 When steel flame heating is used for correction, the heating temperature shall be selected according to the properties of the steel, but shall not exceed 900°C. The allowable deviation after material correction should comply with the following regulations: a) The local flatness of the steel plate is less than 1.5mm, and when the plate thickness is greater than 14mm, it should be less than 1.0mm ； b) The bending height of the section steel is less than 1/1000 of the length of the section steel and does not exceed 5.0mm ； c) The distortion of section steel or H-section steel shall not exceed h/250 and shall not be greater than 5.0mm, (h represents the cross-sectional height of the section steel) ； d) The verticality of the angle steel limb is less than b/100 (b represents the width of the angle steel limb) ； The perpendicularity of the channel steel flange to the web is less than b/80, and the perpendicularity of the I-beam and H-shaped steel flange to the web is less than b/100 and not more than 2.0mm. ； e) There is no obvious concavity or damage on the steel surface after correction, and the scratch depth is less than 0.5mm. ； 1.4.3 Strictly follow the dimensions of the construction drawings, and only after the on-site setting out is verified to be correct can material numbering and cutting be carried out. Especially the overall dimensions of frame 1, each equipment base beam, and each facade diagonal brace angle must be carefully checked before cutting and blanking. 1.4.4 Before cutting, rust, dirt, etc. in the cutting area should be removed, and there should be no cracks or gaps in the section after cutting. ； Slag and spatter on the cutting surface must be removed. 3.4.5 Paint marks (marking) should be applied to the components after cutting.: Drawing number—part number or length, specification). 1.5 Prefabrication of components 1.5.1 According to the drawing requirements, the columns, connecting beams, connecting plates, corbels, etc. of the steel structure are prefabricated and numbered and stacked separately. The connection of the columns and beams is carried out on the platform. 1.5.2 When welding, the requirements of the welding process card should be strictly followed, welding should be carried out as required, and welding should not be done randomly. 1.5.3 Qualified prefabricated columns should meet the following requirements: a) The curvature height of the column body is less than 1/1000 of the column body and does not exceed 12mm ； b) The column body is twisted: ≤8mm ； 1.6 Ground assembly of steel components 1.6.1 During assembly, the prefabricated platform should be laid and firmly supported to fully bear the weight of the components. 1.6.2 Before the steel structure is assembled into a portal-shaped steel structure on the platform, a physical stakeout should be carried out on the platform, the names of the connecting parts should be marked, and the construction drawings should be carefully checked. It should also be ensured that the center line of each column and the center axis of the beam are in the same horizontal plane and perpendicular to each other. They can only be assembled after they are confirmed to be correct. 1.6.3 All components on the frame must be assembled and inspected before welding can be carried out. At the same time, welding shall be carried out in the following order. a) First weld the nodes at the intersection of beams and columns in the same section. Welding in the same section should be done symmetrically in diagonal order or at the same time. b) For the welding of each node, the welding seam between the column and the connecting plate should be welded first, and then the beam and column or the beam and the connecting plate should be welded. The welding seam of each node should be symmetrical, and segmented backward welding should be used according to the different lengths of the welding seams. c) Finally weld the secondary nodes and the welds between secondary beams and diagonal braces. d) When there is a diagonal brace at the bottom of the column, the support on the side of the column foot should be welded after being installed in place to avoid serious deformation. 1.6.4 After the frame is welded, each parameter should be retested to compare the difference between the two and analyze the reasons, which can be used as a reference for the next step of assembly. 1.7 Welding and inspection of steel structures 1.7.1 Welding of steel structures must be performed by welders who have passed the welder examination and obtained the relevant project certificates. 1.7.2 The electrodes used for welding must be baked and placed in the electrode barrel. It is strictly prohibited to use electrodes with peeling coatings or rusty cores, flux that is damp and agglomerated, and slag shells that have been melted. 1.7 3 When welding, the welding process should be followed. Free welding and arc ignition on the base metal outside the weld bead are not allowed. Welding should be done in strict accordance with the required sequence. 1.7.4 After welding, the welder should promptly clean the slag on the surface of the weld and the spatter on both sides, and check the appearance quality of the weld. The metal surface of the weld should be uniform and free of defects such as cracks, slag inclusions, weld nodules, burn-throughs, arc craters, and pores. 3.8 Re-testing and inspection of the foundation 3.8.1 Before installing the steel structure, re-test the foundation axis, foundation top level, elevation, bolt hole position, center distance, etc., and go through the handover procedures. 1.8.2 Steel column feet are installed with shims. Inclined pad irons should be installed under the column foot stiffening plate or column limb close to the anchor bolts. The superimposed length of each group of inclined pad irons should not be less than 2/3 of the pad length. The layers of the pad iron groups should be spot welded and fixed before secondary grouting. 1.9 Steel structure installation 1.9.1 After the foundation is accepted, place the pads as required, use the pads to adjust the top elevation and levelness of the column foot plates, and tighten the anchor bolts in time when the requirements of the specification are met. Measure the centerline of each row of foundations and mark it on the column base plate with a sample punch. 1.9.2 After the components are hoisted in pieces, they are first tightened and fixed with four traction ropes. Then, the steel structure can be aligned by using the relative elevation method by using inverted chains on the traction ropes and fine-tuning the pads under the column foot plates. 1.9.3 When installing contact beams and platform beams, scaffolding can be erected according to site conditions to ensure construction safety. 1.9.4 Various parameters should be controlled during the installation of steel structures: a) The offset of the center line of the column base plate from the positioning axis is less than 5.0mm ； b) The allowable deviation of the column elevation datum point is between -8.0 and 5.0mm ； c) The column axis verticality deviation shall not be greater than L/1000 and shall not be greater than 35mm ； d) The mid-span verticality of the beam is less than 1/500 of the beam cross-section height, and the offset of the center of the corbel is less than 5.0mm ； e) The height difference between the top surfaces of beams between the same spans is less than 1/1500 of the total length, and the verticality of the beam mid-span is less than the deviation h/500 (h represents the beam cross-section height). 1.10 Installation of ladders, platforms and railings a.) In order to reduce aerial operations, the cantilever beams or diagonal braces and outer ring beams on the platform columns should be installed when the span is assembled on the ground. b) Welding can only be done after all the platform beams on the frame are hoisted and in place. When welding, start with the main beam first and then the auxiliary beam. After the platform beams have been installed and passed the inspection, patterned steel plates can be laid and welded strictly in accordance with the requirements of the construction drawings. Missing or missing welding is strictly prohibited. d) When installing platform railings, attention should be paid to the verticality, height and railing spacing of the railings, and smooth transitions at the corners. e) When installing the ladder, ensure that it is firmly and reliably connected to the platform or column. f) After the platform, railings and ladders are installed, welding slag and burrs should be removed and polished in time. The allowable deviations of each size are shown in the table below. Allowable deviations in the installation of ladders, platforms and railing steel structures (mm) Items allowable deviations Notes 1 Platform length and width ±4 2 Platform diagonals 6.0 3 Platform unevenness 3.0 4 Ladder longitudinal deflection height ≤ Lt/1000 Lt - total length of ladder 5 Ladder step unevenness ≤ l/100 6 Inclined ladder step spacing ± 5 7 Railing height ± 10 8 Spacing between railing posts ±10

2 Quality Assurance Measures 2.1 The construction process must be operated in strict accordance with the ISO9000 quality system, and all construction personnel should clarify their respective quality responsibilities. 2.2 Conduct technical briefings for construction personnel before construction to familiarize them with the installation points and quality requirements of each process. During the steel structure construction process, a system of combining self-inspection, mutual inspection and special inspection must be adhered to ； Strict process inspection is carried out, and those who are not qualified are not allowed to proceed to the next process. 2.3 Construction personnel must strictly follow the construction deployment and relevant construction technical measures. During the construction process, original construction records must be made and signed by inspection personnel. 2.4 Carry out basic intermediate handover in a timely manner, and conduct joint inspections by the supervisor and construction unit in a timely manner for project quality inspection points and hidden projects, and go through acceptance confirmation procedures. 2.5 In windy weather, a windproof shed should be erected for outdoor welding. ； When the outdoor ambient temperature is below 0°C, measures such as preheating before welding and postheating should be taken. 2.6 During the hoisting process of columns and steel frame beams, Φ89×5 steel pipes or shaped steel should be fixed at the easy-to-deform locations depending on the specific structural form. Cut off after the steel structure is securely installed. 3 HSE Guarantee Measures 3.1 Strictly implement the safety operating procedures of various types of work and the relevant production safety regulations and systems formulated by the company, project department and construction unit. 3.2 All necessary labor protection supplies must be worn during construction. The scaffolding erected for high-altitude operations such as the installation of columns, beams, and connecting beams must be reliable and must be confirmed by safety personnel before use. Probe boards are prohibited from scaffolding installation. 3.3 When working at heights such as installing columns, beams, and tie beams, construction workers must wear safety belts and carry their work tools in bags to avoid falling and injuring people. 3.4 Various construction machinery and equipment should be operated only after confirmation by the safety officer, and should be operated correctly in accordance with operating procedures. 3.5 During hoisting, unrelated personnel are strictly prohibited from entering the working environment. The crane must obey the arrangements of the hoisting engineer. No one is allowed to stand under the boom and within the rotation range of the crane. 3.6 During the hoisting process of the steel structure, it is strictly prohibited to cut the connecting parts or temporary reinforcements on the components. 3.7 Garbage and waste materials generated during construction should be piled up at designated points and cleaned regularly. The processing of welding rod heads shall be carried out in accordance with the requirements of the company's "Health, Safety and Environmental Management Procedure Documents". 3.8 Garbage generated by high-altitude construction shall not be thrown down directly. It shall be packed in woven bags or other containers in a sealed manner and lowered with ropes or cranes. 3.9 The construction site should be carried out in a civilized manner, and materials or semi-finished products should be stacked neatly. Clean up the place promptly before leaving get off work and make it tidy and orderly. 4 Main construction machinery and tools and materials 4.1 Main construction machinery serial number Machine name Model specification Unit quantity Remarks 1 Automobile crane 12t unit 2 SCR welding machine ZX5-400D unit 3 AC welding machine BX-500 unit 4 Angle grinder Ф100 unit Ф150 unit 5 Reverse chain 1t unit 2t unit 5t unit 6 Oxygen acetylene meter cover 7 Welding rod drying box thermostat 8 Welding rod insulation cylinders 9 Screw jacks 5t~10t 10 Aluminum alloy straight ladder 8 m handle 11 Semi-automatic cutting machine SP-100 set 12 Magnetic drill Ф30 set 13 Adding and subtracting wire Ф48 set 14 Hand hammer 2~4kg handle 15 Sleigh bar hex head L=1500 Article 4.2 Main inspection tools serial number machine name model specification unit quantity remarks 1 level D-2 set 2 steel ring ruler 5m 3 steel ring ruler 30m 4 straight edge 1 m 5 squares 900 L=500 6 squares 450 7 levels 2mm/1000mm 8 magnetic line hammer 9 weld inspection ruler 10 transparent hose Ф10 m

In the United States, it is AWS D1.1

First, pre-welding preparations are carried out, including groove preparation, pre-welding part cleaning, electrode drying, preheating, pre-deformation and flaw detection on the cutting surface of high-strength steel, etc. Welding rods and flux must be dried before use. Generally, the baking temperature of acidic electrodes is 75~150℃ and the time is 1~2h. ； The baking temperature of alkaline low-hydrogen welding rod is 350~400℃ and the baking time is 1~2h. The dried electrodes should be placed in an insulating cylinder (box) at 100~150℃. Low-hydrogen electrodes should be re-baked at room temperature for more than 4 hours. The number of repeated baking should not exceed two times. When baking the welding rod, attention should be paid to the gradual temperature rise in the box. Welding construction includes the following steps: 1． Arc ignition and arc extinguishing There are two types of arc ignition: impact method and scratch method. The impact method is to impact the welding rod perpendicularly to the workpiece, and then quickly maintain a certain distance. ； The scratching method is to lightly scratch the end of the welding rod across the workpiece and then maintain a certain distance. During construction, it is strictly prohibited to spark arcs on the base metal outside the weld area. The local area where the arc is struck within the groove should be welded once, and no arc crater should be left. 2. After the arc is ignited by the bar transport method, the normal welding process begins. During the welding process, the welding rod moves in three directions at the same time: ①Feed down along its center line ； ②Move along the direction of the weld ； ③Lateral swing. Since the welding rod is gradually shortened by arc melting, in order to maintain a certain arc length, the welding rod must be fed downward along its center line, otherwise arc breakage will occur. The speed at which the welding rod moves along the direction of the weld depends on the diameter of the welding rod, the welding current, the thickness of the workpiece, and the assembly and location of the seam. The moving speed is too fast and the weld penetration is too small, which can easily lead to incomplete welding.: If the moving speed is too slow, the weld seam is too high, and the workpiece is overheated, it will cause increased deformation or burn-through. In order to obtain a weld of a certain width, the welding rod must be oscillated laterally. When doing lateral swing, the width of the weld is generally about 1.5 times the diameter of the electrode. The movements in the above three directions are closely coordinated. According to different seam positions, joint forms, electrode diameter and performance, welding current, workpiece thickness, etc., by adopting appropriate rod transport methods, high-quality welds can be obtained in various welding positions. 3． Treatment after completion: After welding, the weld seam and both sides should be thoroughly cleaned of spatter, welding slag and welding flash. If there are no special requirements, the need for post-weld heat treatment should be determined based on the residual stress, structural state, hydrogen content and mechanical properties of the deposited metal of the welded joint.

Lifting---Positioning---Spot welding----Welding

What is said above is too complicated, let me explain briefly: 1. Choose the right welding method for welding. Manual welding, automatic welding and gas welding have different advantages and disadvantages. 2. Pay attention to the welding conditions, such as welding position, welding temperature, and welding surrounding environment. 3. Welding groove form and weld size. 4. Welding parameter selection. 5. Weld defect inspection

For details, please refer to GB50205-2001 "Steel Structure Engineering Construction Quality Acceptance Code" 0. Construction technical preparation 1. Technical briefing to construction personnel before construction 2. Inspection and acceptance of materials 3. Numbering and cutting of raw materials 4. Prefabrication of components 5. Ground assembly of steel components to the frame 6. Welding and inspection of steel structures 7. Retesting and inspection of foundation 8. Installation of steel structure 9. Installation of ladders, platforms, and railings 10. Completion of completion documents