Code for welding of steel structures
Steel structure consists of blanking, assembly, welding and inspection.
Technical standard for manual arc welding construction of steel structure
According to the standard:
Unified standard for construction quality acceptance of building engineering (GB50300-200 1)
Code for Acceptance of Construction Quality of Steel Structure Engineering (GB50205-200 1)
Manual ultrasonic flaw detection method and grading method of flaw detection results for steel welds GB 1 1345.
Radiography and quality classification of butt joint of steel fusion welding GB3323
Ultrasonic flaw detection method and quality grading method of welded ball joint steel grid structure jbj/t3038+0
Ultrasonic flaw detection method and quality grading method for welded joints of steel grid structures with bolted ball joints JBJ/T3034.2
Technical specification for welding of building steel structures JGJ8 1
1 and range
This process standard is applicable to manual arc welding engineering of steel structure fabrication and installation in general industrial and civil construction engineering.
2, construction preparation
2. 1 Materials and main machines and tools
2. 1. 1 covered electrode: to select the model according to the design requirements, a quality certificate is required. Bake before welding as required. It is forbidden to use covered electrode whose coating falls off and the welding core rusts. When there are no regulations in the design, covered electrode with E43 series carbon steel structure shall be selected for welding Q235 steel. When welding 16Mn steel, E50 series low alloy structural steel covered electrode should be selected. When welding important structures, low hydrogen covered electrode (alkaline covered electrode) should be used. After baking according to the instructions, put it in a heat preservation bucket and carry it with you. Acid covered electrode and alkaline covered electrode are not allowed to be mixed.
2. 1.2 Arc striking plate: Arc striking plate is used for groove connection, and the material and groove type of arc striking plate are the same as those of weldment.
2. 1.3 main machines and tools: welding machine (AC/DC), electrode holder wire, electrode holder, mask, hammer, covered electrode oven, covered electrode insulation barrel, wire brush, asbestos strip, thermometer, etc.
2.2 Operating conditions
2.2. 1 Be familiar with drawings and make technical disclosure of welding process.
2.2.2 Before welding, the validity of the welder's certificate shall be checked to prove that the welder can undertake the welding work.
2.2.3 The field power supply shall meet the requirements of welding power consumption.
2.2.4 When the ambient temperature is lower than 0℃, the preheating and post-heating temperatures shall be determined according to the process test.
3, the operation process
3. 1 process flow:
Operation preparation → arc welding (flat welding, vertical welding, horizontal welding and overhead welding) → weld inspection.
3.2 Arc welding of steel structure:
3.2. 1 flat welding
3.2. 1. 1 Select qualified welding process, such as covered electrode diameter, welding current, welding speed, welding arc length, etc. And verified by welding process test.
3.2. 1.2 Cleaning weld: Before welding, check whether the groove and assembly gap meet the requirements, whether the tack welding is firm, and there shall be no oil stain and rust around the weld.
3.2. 1.3 covered electrode should be baked at the specified temperature and time, and the covered electrode taken out of the oven should be put in a covered covered electrode heat preservation barrel for later use.
3.2. 1.4 welding current: according to the thickness of weldment, welding grade, covered electrode model, diameter, welder's proficiency and other factors, select the appropriate welding current.
3.2. 1.5 arc initiation: the arc point of fillet weld should be at the end of weld, which should be greater than 10mm, and arc initiation is not allowed casually. After arcing, the covered electrode should be removed from the weld zone immediately, so that a gap of 2 ~ 4 mm can be kept between the covered electrode and the components to generate an arc. Butt welds shall be connected and fillet welded in time. Arc striking plates and lead-out plates shall be set at both ends of the weld. Before welding to the welding area, the arc striking plate must be used. The intermediate joint should be placed at the position 15 ~ 20 mm before the weld. After the weldment is preheated, the coated covered electrode should be put back at the beginning of the weld, and the molten pool can be filled to the required thickness before welding.
3.2. 1.6 welding speed: constant speed welding is required to ensure uniform weld thickness and width, and it is appropriate to keep the same distance (2 ~ 3 mm) between molten iron and slag and the inside of the mask.
3.2. 1.7 welding arc length: it depends on different models of covered electrode. Generally, the arc length is required to be stable, and the acidic covered electrode is generally 3 ~ 4 mm, and the alkaline covered electrode is generally 2 ~ 3 mm.
3.2. 1.8 welding angle: according to the thickness of two weldments, the welding angle has two aspects: first, the included angle between the covered electrode and the welding direction is 60 ~ 75; Second, there are two angles between covered electrode and welding. When the thickness of weldments is equal, the included angle between covered electrode and weldments is 45; When the weldments are not equal in thickness, the included angle between covered electrode and thicker weldments should be greater than that between covered electrode and thinner weldments.
3.2. 1.9 arc closing: when each weld is welded to the bottom, the arc pit shall be filled, and the arc shall be started in the direction opposite to the welding direction, so that the arc pit can be thrown into the weld bead to prevent the arc pit from biting meat. Arc plates shall be cut off by gas cutting after welding, and polished flat. It is not allowed to shoot them down with a hammer.
3.2. 1. 10 slag removal: after the whole weld is welded, slag removal and welder's self-inspection (including appearance and weld size, etc.). ) prove that there is no problem, you can move the welding to another place to continue.
3.2.2 Vertical welding: The basic operation process is the same as flat welding, but the following issues should be noted:
3.2.2. 1 Under the same conditions, the welding power supply is smaller than the flat welding current 10% ~ 15%.
3.2.2.2 adopts short arc welding, and the arc length is generally 2 ~ 3mm.
The angle of 3.2.2.3 covered electrode is determined according to the thickness of weldment. The thickness of the two weldments is equal, and the included angle between covered electrode and covered electrode is 450; When the thickness of two weldments is different, the included angle between covered electrode and the thicker weldment should be greater than that of the thinner weldment. Covered electrode should form an angle of 600 ~ 800 with the vertical plane, so that the angle arc is slightly upward and blows to the center of the molten pool.
3.2.2.4 arc closing: When the welding reaches the end point, fill the arc pit with arc opening method, and move the arc to the center of the molten pool to close the arc. It is forbidden to throw the arc pit aside. In order to prevent meat biting, the angle of covered electrode should be changed by lowering the arc, so that the covered electrode is perpendicular to the weldment or slightly blown down by the arc.
3.2.3 Horizontal welding: basically the same as horizontal welding, the welding current is less than 10% ~ 15% under the same conditions, and the arc length is 2 ~ 4 mm The angle of covered electrode. During horizontal welding, the covered electrode should be inclined downward at an angle of 700 ~ 800 to prevent molten iron from falling. According to the different thicknesses of two weldments, the covered electrode angle can be adjusted appropriately, and the covered electrode and welding direction are 700 ~ 900.
3.2.4 Overhead welding: basically the same as vertical welding and horizontal welding. The included angle between covered electrode and weldment is related to the thickness of weldment, and the included angle between covered electrode and welding direction is 700 ~ 800, so short arc welding with low current should be adopted.
3.3 Low temperature welding in winter:
3.3. 1 When conducting arc welding at ambient temperature below 0℃, in addition to observing the relevant provisions of normal temperature welding, the welding process parameters should also be adjusted to make the weld and heat affected zone cool slowly. If the wind force exceeds 4, windproof measures should be taken; Joints that are not cooled after welding should avoid contact with ice and snow.
3.3.2 In order to prevent welding cracks, the steel structure should be preheated and preheated to control the interlayer temperature. When the workplace temperature is lower than 0℃, process tests should be conducted to determine the appropriate preheating and post-heating temperatures.
4, quality standards
4. 1 General provisions
4. 1. 1 This chapter is applicable to the engineering quality acceptance of welding and nail welding of steel members in steel structure fabrication and installation.
4. 1.2 steel structure welding engineering can be divided into one or several inspection lots according to the inspection lot division principle of corresponding steel structure manufacturing or installation engineering.
4. 1.3 carbon structural steel shall be inspected for weld flaw detection after the weld is cooled to ambient temperature, and low alloy structural steel shall be welded for 24h.
4. 1.4 After the weld is welded, the welder's steel seal shall be affixed to the weld and the parts specified in the process.
4.2 Welding engineering of steel members
I. Main control items
4.2. 1 covered electrode, welding wire, flux, electroslag welding nozzle and other welding materials should be matched with the parent material, and meet the design requirements and the current national industry standard "Technical Specification for Welding of Building Steel Structures" JGJ8 1. Covered electrode, flux, flux-cored wire, melting nozzle, etc. Before use, it should be baked and stored according to the provisions of its product manual and welding process documents.
Inspection quantity: all inspections.
Inspection method: check the quality certificate and baking record.
4.2.2 Welders must pass the examination and obtain the certificate. Licensed welders must carry out welding in the projects that have passed the examination and within the approved scope.
Inspection quantity: all inspections.
Inspection method: check the welder's certificate, its approved scope and validity period.
4.2.3 The construction unit shall evaluate the welding process, welding materials, welding methods and post-weld heat treatment of the steel used for the first time, and determine the welding process according to the evaluation report.
Inspection quantity: all inspections.
Inspection method: check the welding procedure qualification report.
4.2.4 Ultrasonic flaw detection shall be used to check the internal defects of the primary and secondary welds with full penetration according to the design requirements. When ultrasonic flaw detection can't judge the defects, radiographic flaw detection should be adopted, and the classification and flaw detection methods of internal defects should conform to the current national standard "Manual ultrasonic flaw detection method and classification method of flaw detection results for steel welds" GB 1 1345 or "Radiography and quality classification of butt welded joints of steel" GB3323.
Classification and flaw detection methods for internal defects of welded spherical joint grid welds, bolted spherical joint grid welds and T-joints, K-joints and Y-joints of circular tubes shall conform to the current national standards, namely, ultrasonic flaw detection method and quality grading method of welded spherical joint steel grid welds JBJ/T3034. 1, ultrasonic flaw detection method and quality grading method of bolted spherical joint steel grid welds JBJ/T3034.2 and welding technology of building steel structures.
The quality grade and defect classification of primary and secondary welds shall comply with the provisions in Table 4.2.4.
Inspection quantity: all inspections.
Inspection method: check the ultrasonic or radiographic inspection records.
Table 4.2.4 Quality Grade and Defect Classification of Primary Weld and Secondary Weld
Welding quality grade I and II.
Internal defects ultrasonic flaw detection evaluation grade Ⅱ-Ⅲ
Inspection grade b, grade b
Inspection ratio 100% 20%
X-ray flaw detection evaluation grade II-III for internal defects
Inspection level AB level AB level
Inspection ratio 100% 20%
Note: The calculation method of flaw detection ratio shall be determined according to the following principles: (1) The percentage of welds manufactured by the factory shall be calculated for each weld, and the flaw detection length shall not be less than 200mm. When the weld length is less than 200mm, the whole weld shall be inspected; (2) The percentage of welds installed on site shall be calculated according to the number of welds of the same type and welding conditions, and the flaw detection length shall be no less than 200mm and no less than 1 weld.
4.2.5 For the combined welds of butt joint and fillet joint that need penetration, such as T-joint, cross joint and fillet joint, the weld leg size should not be less than t/4 (Figure 4.2.5a, B, C); The weld leg size of the connection weld between the web and the upper flange of a crane beam or similar member that requires fatigue inspection is t/2 (Figure 4.2.5d) and should not be greater than 10 mm ... The allowable deviation of the weld leg size is 0 ~ 4mm.
Check quantity: check all data; Spot check of similar welds 10%, and there should be no less than 3 places.
Inspection method: observation and inspection, and spot-check measurement with weld gauge.
Figure 4.2.5 Weld leg dimensions
4.2.6 There shall be no defects such as cracks and flash on the weld surface. The primary weld and the secondary weld should not have defects such as surface porosity, slag inclusion, arc pit crack and arc scratch. In addition, there should be no defects such as undercut, incomplete penetration and root shrinkage in the primary weld.
Inspection quantity: each batch of similar components 10%, and not less than 3 pieces; 5% of each type of weld shall be spot-checked according to the number of welded joints in the spot-checked components, and it shall not be less than1; Each inspection has 1 quota, and the total number of spot checks should not be less than1quota.
Inspection method: visual inspection or inspection with magnifying glass, weld gauge and steel rule. In case of doubt, penetrant inspection or magnetic particle inspection shall be adopted.
Second, the general project
4.2.7 For welds requiring pre-welding or post-welding heat treatment, the preheating temperature or post-heating temperature shall meet the current national standards or be determined through process tests. The preheating zone is on both sides of the weld, and the width of each side should be greater than 1.5 times of the thickness of the weldment, and should not be less than100 mm; ; Post-heat treatment shall be carried out immediately after welding, and the holding time shall be determined according to the thickness of every 25mm1h..
Inspection quantity: all inspections.
Inspection method: Check the construction records and process test reports before and after heating.
4.2.8 The appearance quality standard of secondary and tertiary welds shall conform to the provisions of Table A.0. 1 in Appendix A of this specification. The appearance quality inspection of the tertiary butt weld shall be carried out according to the secondary weld standard.
Inspection quantity: each batch of similar components 10%, and not less than 3 pieces; 5% of each type of weld shall be spot-checked according to the number of welded joints in the spot-checked components, and it shall not be less than1; Each inspection has 1 quota, and the total number of spot checks should not be less than1quota.
Inspection method: observation or inspection with magnifying glass, weld gauge and steel rule.
4.2.9 The allowable deviation of weld size shall comply with the provisions of Table A.0.2 in Appendix A of this specification.
Inspection quantity: each batch of similar components 10%, and not less than 3 pieces; The number of components randomly selected for each weld shall be 5%, but it shall not be less than1; Each inspection has 1 quota, and the total number of spot checks should not be less than1quota.
Inspection method: check with weld gauge.
4.2. 10 is welded into a concave fillet weld, and the transition between the weld metal and the parent metal should be smooth; The fillet weld processed into a concave shape should not leave cutting marks on its surface.
Inspection quantity: each batch of similar components is randomly selected 10%, and should not be less than 3 pieces.
Inspection method: observation and inspection.
4.2. 1 1 The welding induction is uniform in appearance and well formed, and the transition from weld bead to weld bead and from weld bead to base metal is smooth, and the welding slag and splash are basically clean.
Inspection quantity: each batch of similar components 10%, and not less than 3 pieces; 5% of each weld is spot-checked according to the number of components to be spot-checked, and the total number is not less than 5.
Inspection method: observation and inspection.
Standard for quality inspection of steel structure manufacturing (installation) welding engineering
Inspection method of allowable deviation (mm) of project serial number
Main control items 1 welding material varieties and specifications Article 4.3. 1 Inspection of product qualification documents, Chinese marks and inspection reports (full inspection)
2 Re-inspection of welding materials Article 4.3.2 Check the re-inspection report (full inspection)
3 Material matching 5.2. 1 Inspection quality certificate and baking record (full inspection)
Article 5.2.2 of the welder certificate shall check the welder certificate, its approved scope and validity period (applicable to all welders).
Article 5.2.3 Inspection of Welding Procedure Qualification Report (Full Inspection)
6 Internal Defects Article 5.2.4 Inspection of weld flaw detection records (full inspection)
7. Article 5.2.5 Observation and inspection of combined weld size and spot-check measurement of weld thickness (check all data and spot-check similar welds 10% and ≥3 places).
8 Weld surface defects Article 5.2.6: Observe and inspect, or inspect with magnifying glass, weld gauge and steel rule. If necessary, use penetrant or magnetic particle inspection.
—Observe and check the appearance quality of welding materials for the general item 1 in Article 4.3.4 (by quantity 1% and ≥ 10 package).
2 Pre-heating and Post-heat Treatment Article 5.2.7 Inspection Test Report (Full Inspection)
3 Article 5.2.8 Inspection of weld appearance quality or inspection with magnifying glass, weld gauge and steel rule (Article 5.2.8).
4 Weld size deviation Article 5.2.9 Observation and inspection Article 5.2.9.
Observation and inspection of concave fillet weld in Article 5.2. 10 (random sampling of similar components 10%, and ≥3 pieces).
Article 5.2. 1 1 Observation and inspection of welds (Article 5.2. 1 1)
5, finished product protection
5. 1 After welding, joints are not allowed, and the newly welded steel bars are not allowed to be watered. Slow cooling measures should be taken at low temperature.
5.2 It is not allowed to strike an arc on the external parent metal of the weld at will.
5.3 All parts can be welded only after calibration, and the shim and fixture shall not be moved at will to prevent the size deviation of the parts. The hidden parts of the weld must go through the concealment acceptance procedures before the next concealment process can be carried out.
5.4 Low-temperature welding is not allowed to remove slag immediately, but should be carried out after the weld is cooled.
6. Quality problems that should be paid attention to
6. The dimension of1exceeds the allowable deviation: for the deviation of weld length, width and thickness, centerline deviation and bending, the relative position dimension of the welding part should be strictly controlled, and welding is allowed only after it is qualified, and care should be taken when welding.
6.2 Weld cracks: In order to prevent cracks, appropriate welding process parameters and welding procedures should be selected to avoid large current and sudden flameout. The weld should overlap 10 ~ 15 mm, and it is not allowed to move or knock the weldment during welding.
6.3 Surface porosity: covered electrode is baked at the specified temperature and time, and the welding area must be cleaned. In the welding process, appropriate welding current should be selected to reduce the welding speed and make the gas in the molten pool escape completely.
6.4 Welding slag inclusion: Multi-layer welding should remove welding slag layer by layer, with correct operation and proper arc length. Pay attention to the flow direction of slag. When using alkaline covered electrode, the slag must stay behind the slag.
7, quality records
7. 1 welding material quality certificate.
7.2 Welder certificate and number.
7.3 Welding procedure test report.
7.4 Welding quality inspection report, ultrasonic and radiographic inspection records.
7.5 Design change and negotiation records.
7.6 concealed engineering acceptance record.
7.7 Other technical documents.
8, safety and environmental protection measures
8. 1 The shell of the welding machine must be well grounded, and the installation and disassembly of its power supply must be carried out by an electrician.
8.2 The electric welding machine shall have a separate switch. The switch should be placed in the rain brake box, and gloves should be worn for lateral operation when it is closed.
8.3 Electrode holder and welding wire must be well insulated. The connection is firm, and gloves should be worn when replacing covered electrode. When working in a wet place, you should stand on an insulated rubber board or wooden board.
8.4 It is forbidden to weld containers or pipelines under pressure, and the power supply must be cut off before welding live equipment.
8.5 Welded containers or pipes that have stored flammable, explosive and toxic substances must be cleaned and all orifices must be opened.
8.6 When welding in a closed metal container, the container must be reliably grounded, well ventilated and supervised. It is forbidden to input oxygen into the container.
8.7 When welding preheating workpieces, insulation measures such as asbestos cloth or baffle should be taken.
8.8 Wires and grounding wires are strictly forbidden to contact with wire ropes, and it is even more impossible to replace the zero line with wire ropes or electromechanical equipment. All grounding connectors must be firmly connected.
8.9 When replacing the rotating handle on site, cut off the power supply and do not climb the ladder with the handle.
8. 10 When cleaning welding slag and cleaning roots with arc gouging, you should wear protective glasses or masks to prevent iron slag from splashing and hurting people.
8. 1 1 When several welders are welding together, the welding platform or weldment must be grounded. And there should be a light shield.
8. 12 thorium tungsten electrode should be placed in a closed lead box. When grinding thorium tungsten electrode, gloves and masks must be worn, and dust should be removed in time.
8. The upper shell of13 carbon dioxide gas preheater should be insulated, and the terminal voltage should not be greater than 36V.
8. 14 During the thunderstorm, the open-air welding operation should be stopped.
8. 15 Around the welding site, inflammable and explosive articles should be removed, or covered and isolated.
8. When16 must be welded in the diffusion area of flammable gas or liquid, it shall be approved by the relevant departments. Before welding.
8. 17 After the work, cut off the power supply of the welder, check the operation site and confirm that there is no fire danger before leaving.