Steel structure welding specification Century Weiye tells you-Shenyang Century Weiye Steel Structure Co., Ltd

Steel structure welding specification Century Weiye tells you

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2016-09-12

Steel structure welding specification

Steel structure from the process of blanking, grouping, welding, inspection, etc.

Steel structure manual arc welding construction technology standard

According to the standard:

"Uniform Standard for Construction Quality Acceptance of Construction Engineering" GB50300-2001

"Code for acceptance of construction quality of steel structure engineering" GB50205-2001

"Manual ultrasonic flaw detection method for steel welds and classification method for flaw detection results" GB11345

"Steel fusion welding butt joint radiography and quality classification" GB3323

Ultrasonic flaw detection method and quality classification method for welded ball joint steel grid welds JBJ/T3034.1

"Ultrasonic flaw detection method and quality classification method for bolt-and-steel joint steel grid welds" JBJ/T3034.2

"Technical Regulations for Welding of Building Steel Structures" JGJ81

1. Scope

This process standard is applicable to the manufacture and installation of manual arc welding of steel structures in general industrial and civil construction projects.

2. Construction preparation

2.1 Materials and main equipment

2.1.1 Welding electrode: The model is selected according to the design requirements and must have a quality certificate. Bake before applying welding as required. It is strictly forbidden to use the electrode with the peel off and the rust of the core. When the design is not specified, E43 series carbon steel structure welding rod should be used when welding Q235 steel; E50 series low alloy structural steel welding rod should be used when welding 16Mn steel; low hydrogen type welding rod (alkaline welding rod) should be used when welding important structure. After baking according to the instructions, put it in a heat preservation bucket and take it with you. Acidic electrodes and alkaline electrodes are not allowed to be mixed.

2.1.2 Arc striking plate: Arc plate is required when connecting with groove. The arc plate material and groove type should be the same as the weldment.

2.1.3 Main equipment: electric welding machine (AC, DC), welding wire, welding tongs, mask, small hammer, welding rod oven, welding rod insulation barrel, wire brush, asbestos strip, thermometer and so on.

2.2 Working conditions

2.2.1 Familiar with the drawings and do the welding technology.

2.2.2 Before the welding, the validity period of the welder's certificate shall be checked, and the welding work that the welder can bear shall be proved.

2.2.3 On-site power supply should meet the welding power requirements.

2.2.4 The ambient temperature is lower than 0 °C. For preheating, the postheating temperature should be determined according to the process test.

3. Operating process

3.1 Process:

Job preparation → arc welding (flat welding, vertical welding, horizontal welding, overhead welding) → weld inspection.

3.2 Steel structure arc welding:

3.2.1 Flat welding

3.2.1.1 Select qualified welding process, welding rod diameter, welding current, welding speed, welding arc length, etc., verified by welding process test.

3.2.1.2 Cleaning the welding joint: Check whether the groove and assembly clearance meet the requirements before welding, whether the positioning welding is firm, and there shall be no oil or rust around the weld.

3.2.1.3 The baking electrode should meet the specified temperature and time. The electrode removed from the oven should be placed in the electrode barrel and used as needed.

3.2.1.4 Welding current: According to the welding thickness, welding level, welding rod type, diameter, welder proficiency and other factors, select the appropriate welding current.

3.2.1.5 Arc starting: The arcing point of the fillet weld should be at the end of the weld, preferably greater than 10mm. It should not be arced casually. After the arc is triggered, the electrode should be pulled away from the weld zone immediately, so that the electrode and the component are An arc is generated by keeping a gap of 2 to 4 mm. Butt weld joints are connected in time and corner joints. Pilot plates and lead plates are provided at both ends of the weld. They must be welded to the weld zone after arcing on the arc runner plate. The joint in the middle should be in front of the weld joint. Fire at 15 to 20 mm, and preheat the weldment before returning the electrode to the beginning of the weld. Fill the weld pool to the required thickness before welding.

3.2.1.6 Welding speed: Constant speed welding is required to ensure uniform thickness and width of the weld. It is advisable to keep the distance between molten iron and molten slag (2~3mm) from the inside of the mask.

3.2.1.7 Welding arc length: It is determined according to the type of welding rod. Generally, the arc length is stable, the acid electrode is generally 3~4mm, and the alkaline electrode is generally 2~3mm.

3.2.1.8 Welding angle: According to the thickness of the two weldments, the welding angle has two aspects. One is that the angle between the welding rod and the welding advancing direction is 60-75°; the other is that there are two cases in the angle between the welding rod and the welding. When the thickness of the weldment is equal, the angle between the electrode and the weldment is 45°; when the thickness of the weldment is not equal, the angle between the electrode and the side of the thicker weldment is greater than the angle between the electrode and the side of the thinner weldment.

3.2.1.9 Arcing: When each weld is welded to the end, the arc should be filled and arced in the opposite direction of the welding direction so that the arc pit is inside the weld bead to prevent the arc pit from biting. After the welding is completed, the arc cutting plate should be cut by gas cutting, and the grinding should be smoothed, and it is not allowed to hit with a hammer.

3.2.1.10 Cleaning slag: After the whole weld is welded, the slag is removed. After the welder self-test (including the appearance and weld size), there is no problem before the welding can be continued.

3.2.2 Vertical welding: The basic operation process is the same as that of flat welding, but the following problems should be noted:

3.2.2.1 Under the same conditions, the welding power source is 10% to 15% smaller than the flat welding current.

3.2.2.2 Short arc welding is used, and the arc length is generally 2 to 3 mm.

3.2.2.3 The angle of the electrode is determined according to the thickness of the weldment. The thickness of the two weldments is equal, and the angle between the electrode and the left and right sides of the electrode is 450. When the thickness of the two weldments is not equal, the angle between the electrode and the side of the thicker weldment should be larger than the angle of the thinner side. The electrode should form a 600-800 angle with the vertical surface so that the corner arc is slightly upward and blows toward the center of the bath.

3.2.2.4 Arcing: When welding to the end, the arc pit is filled by the arc-discharging method, and the arc is moved to the center of the molten pool to stop the arc. It is strictly forbidden to make the arc pit aside. In order to prevent biting, the arc should be lowered to change the angle of the electrode so that the electrode is perpendicular to the weldment or slightly blown downward by the arc.

3.2.3 Horizontal welding: Basically the same as flat welding, the welding current is 10% to 15% smaller than the current with the same condition, and the arc length is 2 to 4 mm. The angle of the electrode, the welding rod should be inclined downward when the horizontal welding, the angle is 700 ~ 800, to prevent the iron from falling. According to the thickness of the two weldments, the angle of the electrode can be adjusted appropriately, and the advance direction of the welding rod and the welding is 700 to 900.

3.2.4 Overhead welding: Basically the same as vertical welding and horizontal welding. The angle between the welding rod and the welding piece is related to the thickness of the welding piece. The welding rod and the welding direction are between 700 and 800 degrees. It is recommended to use small current and short arc welding.

3.3 Winter low temperature welding:

3.3.1 When performing arc welding under the condition that the ambient temperature is lower than 0 °C, in addition to complying with the relevant regulations of normal temperature welding, the welding process parameters should be adjusted to make the weld and heat affected zone slowly cool. If the wind exceeds 4, windshield measures should be taken; joints that are not cooled after welding should avoid snow and ice.

3.3.2 Steel structure To prevent welding cracks, it should be preheated and preheated to control the interlayer temperature. When the working temperature is below 0 °C, a process test shall be carried out to determine the appropriate preheating and postheating temperatures.

4, quality standards

4.1 General provisions

4.1.1 This chapter is applicable to the engineering quality acceptance of steel component welding and welding of nails in the manufacture and installation of steel structures.

4.1.2 Steel structure welding engineering can be divided into one or several inspection batches according to the division principle of the corresponding steel structure fabrication or installation engineering inspection lot.

4.1.3 Carbon structural steel shall be tested for weld flaw detection after the weld is cooled to ambient temperature and the low alloy structural steel shall be welded 24 hours after the completion of welding.

4.1.4 After the weld is welded, the welder's seal shall be marked on the weld and the part specified in the process.

4.2 Steel component welding engineering

I master project

4.2.1 Welding rod, welding wire, flux, electroslag welding fracturing and other welding materials and the parent metal should be matched with the design requirements and the current national industry standard "Technical Regulations for Welding of Building Steel Structures" JGJ81. Welding rods, fluxes, flux cored wires, and fuses are to be baked and stored in accordance with the product specifications and welding procedure documents before use.

Number of inspections: full inspection.

Inspection method: Check the quality certificate and baking record.

4.2.2 The welder must pass the examination and obtain a certificate of conformity. A certified welder must be welded within the scope of its qualifying program and its approval.

Number of inspections: full inspection.

Inspection method: Check the welder certificate and its scope of approval and validity.

4.2.3 The construction unit shall carry out the welding procedure qualification for the steel, welding materials, welding methods and post-weld heat treatment adopted for the first time, and the welding process shall be determined according to the assessment report.

Number of inspections: full inspection.

Inspection method: Check the welding procedure assessment report.

4.2.4 Design requirements Full-welded first- and second-level welds shall be inspected by ultrasonic flaw detection for internal defects. When ultrasonic flaw detection cannot judge the defects, radiographic inspection shall be used. The internal defect classification and flaw detection method shall conform to the current state. Standard "Steel Weld Manual Ultrasonic Flaw Detection Method and Flawing Result Grading Method" GB11345 or "Steel Fusion Welded Butt Joint Radiographing and Quality Grading" GB3323.

Welded ball joint grid weld, bolt ball joint grid weld and round pipe T, K, Y joint related wire weld, its internal defect grading and flaw detection method should be in line with the current national standard "welding ball node steel grid Weld seam ultrasonic flaw detection method and quality classification method" JBJ/T3034.1, "Bolt ball joint steel grid weld seam ultrasonic flaw detection method and quality classification method" JBJ/T3034.2, "Building Steel Structure Welding Technical Regulations" JGJ81 .

The quality grade and defect classification of the primary and secondary welds shall comply with the requirements of Table 4.2.4.

Number of inspections: full inspection.

Inspection method: Check the ultrasonic or radiographic inspection record.

Table 4.2.4 First and second grade weld quality grades and defect classification

Weld quality grade Level 1 Level 2

Internal defect ultrasonic flaw detection rating II III

Inspection level B level B level

Detection rate 100% 20%

Internal defect radiographic inspection rating II III

Inspection level AB level AB level

Detection rate 100% 20%

Note: The method of counting the proportion of flaw detection should be determined according to the following principles: (1) For the welds made in the factory, the percentage should be calculated according to each weld, and the length of the flaw should be no less than 200mm. When the length of the weld is less than 200mm, the whole strip should be Weld seams are tested; (2) For the installation of welds on site, the percentage shall be calculated according to the number of welds of the same type and the same welding conditions. The length of the flaw detection shall be not less than 200 mm and shall be not less than 1 weld.

4.2.5 T-joints, cross-joints, corner joints, etc., which require penetration and angle butt joint welds, the size of the weld feet shall not be less than t/4 (Fig. 4.2.5a, b, c); The required weld feet of the web of the required crane beam or similar member and the upper flange are t/2 (Fig. 4.2.5d) and should not be greater than 10 mm. The allowable deviation of the solder fillet size is 0 to 4 mm.

Inspection quantity: all data inspection; 10% of similar welds are checked, and should not be less than 3.

Inspection method: observation inspection, spot check with weld gauge.

Figure 4.2.5 Solder Foot Size

4.2.6 There shall be no defects such as cracks or welds on the surface of the weld. The primary and secondary welds shall not have defects such as surface pores, slag inclusions, crater cracks, and arc scratches. And the first-stage welds shall not have defects such as undercut, unwelded, and root shrinkage.

Inspection quantity: 10% of each batch of similar components shall be inspected, and shall not be less than 3 pieces; in the sampled parts, each type of weld shall be checked 5% according to the number of strips, and shall not be less than 1; one inspection per inspection, The total number of random checks should not be less than 10.

Inspection method: Observe or check with magnifying glass, weld gauge and steel rule. When there is doubt, use infiltration or magnetic particle inspection.

II general project

4.2.7 For welds requiring pre-weld preheating or post-weld heat treatment, the preheating temperature or post-heating temperature shall be in accordance with the relevant national standards or determined by process tests. The preheating zone shall be on both sides of the bead, and the width of each side shall be more than 1.5 times of the thickness of the weldment, and shall not be less than 100 mm; the post-heat treatment shall be carried out immediately after the welding, and the holding time shall be 1 h per 25 mm of the plate thickness according to the thickness of the plate. determine.

Number of inspections: full inspection.

Inspection method: Check pre- and post-heat construction records and process test reports.

4.2.8 The quality standards for secondary and tertiary welds shall comply with the requirements of Table A.0.1 of Appendix A of this code. The third-grade butt welds shall be inspected for appearance quality in accordance with the secondary weld standard.

Inspection method: observation inspection or inspection using a magnifying glass, weld gauge and steel ruler.

4.2.9 Allowable deviation of weld size shall comply with the provisions of Table A.0.2 of Appendix A of this code.

Inspection quantity: 10% of each batch of similar components shall be inspected, and shall not be less than 3 pieces; in the sampled parts, each weld shall be checked 5% according to the number of strips, but not less than one; each inspection shall be carried out, The total number of random checks should not be less than 10.

Inspection method: Check with weld gauge.

4.2.10 Welded into a concave fillet weld, the weld metal and the base metal shall be smoothly transitioned; the fillet welds processed into a concave shape shall not leave a mark on the surface.

Inspection quantity: 10% of each batch of similar components, and not less than 3 pieces.

Inspection method: observation inspection.

4.2.11 Weld feel should be achieved: uniform shape, good forming, smooth transition between weld bead and weld bead, weld bead and basic metal, and weld slag and spatter are basically removed.

Inspection quantity: 10% of each batch of similar components should be checked, and should not be less than 3 pieces; in the sampled parts, each weld should be checked 5% by quantity, and the total number of inspections should not be less than 5.

Inspection method: observation inspection.

Steel structure manufacturing (installation) welding engineering quality inspection standard

Item No. Item Allowable deviation (mm) Inspection method

Main control item 1 Types and specifications of welding materials Section 4.3.1 Inspection of product qualification documents, Chinese signs and inspection reports (full inspection)

2 Re-inspection of welding materials Section 4.3.2 Inspection re-examination report (full inspection)

3 Material matching Article 5.2.1 Inspection quality certificate and baking record (full inspection)

4 Welder certificate Article 5.2.2 Check welder certificate and its scope of approval and validity (all welders)

5 Welding procedure qualification Article 5.2.3 Inspection welding procedure assessment report (full inspection)

6 Internal defects Article 5.2.4 Inspection of weld flaw detection records (full inspection)

7 Combination weld size Article 5.2.5 Observation and inspection, weld gauge inspection and measurement (full inspection of data, 10% of similar welds, and ≥ 3)

8 Weld surface defects Article 5.2.6 Observe inspection or use magnifying glass, weld gauge and steel rule inspection, if necessary, use penetration or magnetic particle inspection

General items 1 Appearance quality of welding consumables Article 4.3.4 Observation and inspection (1% by quantity, and ≥10 packs)

2 Preheating and post-heat treatment Article 5.2.7 Inspection test report (full inspection)

3 Quality of weld appearance Article 5.2.8 Observing inspection or inspection using 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)

5 Concave fillet welds Section 5.2.10 Observation and inspection (10% of the same type of components, and ≥ 3 pieces)

6 Weld senses Article 5.2.21 Observation and inspection (Article 5.2.21)

5, finished product protection

5.1 After welding, it is not allowed to hit the joint, and it is not allowed to water the steel that has just been welded. Slow cooling measures should be taken at low temperatures.

5.2 It is not allowed to arbitrarily arc on the outer base metal of the weld.

5.3 All components can be welded after being calibrated, and the horn and fixture should not be moved at will to prevent component dimensional deviation. The seams of the concealed parts must be subjected to the concealed acceptance procedure before the next concealment process can be carried out.

5.4 Low temperature welding is not allowed to clear the slag immediately, and should be carried out after the weld is cooled.

6, should pay attention to the quality of the problem

6.1 Dimensions exceed the allowable deviation: For the weld length, width, thickness, centerline offset, bending and other deviations, the relative position and size of the welded part should be strictly controlled, and the qualified rear welding should be carried out carefully.

6.2 Weld cracks: In order to prevent cracks, suitable welding process parameters and welding procedures should be selected to avoid large currents. Do not suddenly extinguish flames. Weld joints should be overlapped by 10~15mm. No welding or tapping is allowed during welding. Weldment.

6.3 Surface porosity: The electrode is baked according to the specified temperature and time. The welding area must be cleaned. The proper welding current is selected during the welding process to reduce the welding speed and completely escape the gas in the molten pool.

6.4 Welded slag: Multi-layer welding should be layered to remove the slag. The operation should be carried out correctly and the arc length is appropriate. Pay attention to the flow direction of the slag. When using the alkaline electrode, the slag must be left behind the slag.

7, quality record

7.1 Welding material quality certificate.

7.2 Welder certificate and number.

7.3 Welding process test report.

7.4 Welding quality inspection report, ultrasonic and radiographic inspection records.

7.5 Design changes, negotiation records.

7.6 Concealed project acceptance record.

7.7 Other technical documents.

8. Safety and environmental protection measures

8.1 The outer casing of the welding machine must be well grounded, and the installation and disassembly of the power supply should be carried out by an electrician.

8.2 The welding machine shall be provided with a separate switch. The switch should be placed in a rain-proof lock box, and gloves should be operated sideways when pulling.

8.3 The welding tongs must be well insulated from the wire. The connection is firm and gloves should be worn when replacing the electrode. Work in wet locations and stand on insulating sheets or boards.

8.4 It is strictly forbidden to weld on pressurized containers or pipes. The equipment that is charged and charged must be cut off first.

8.5 Welding containers or pipes containing flammable, explosive and toxic materials must be cleaned. And open all the holes.

8.6 When welding in a closed metal container, the container must be reliably grounded, well ventilated, and should be monitored. Do not enter oxygen into the container.

8.7 When welding the preheated workpiece, there should be insulation measures such as asbestos cloth or baffle.

8.8 It is forbidden to contact the wire rope and the ground wire, and it is not necessary to replace the zero wire with wire rope or electromechanical equipment. All ground connections must be securely connected.

8.9 When the site is changed and the wire is turned, the power should be cut off and the ladder must not be lifted by hand.

8.10 When removing welding slag and using arc gouging to clear the root, wear protective glasses or a mask to prevent the iron slag from splashing and injuring people.

8.11 When multiple welders are used together for centralized welding, the welding platform or weldment must be grounded. There should be a light barrier.

8.12 Tungsten tungsten should be placed in a sealed lead box. When grinding the tungsten electrode, gloves and masks must be worn and the dust should be removed in time.

8.13 The upper shell of the carbon dioxide gas preheater shall be insulated and the terminal voltage shall not exceed 36 volts.

8.14 When thunderstorms occur, open-air welding operations should be stopped.

8.15 Inflammable and explosive materials should be cleared around the welding site, or covered or isolated.

8.16 When welding in a flammable flammable gas or liquid diffusion zone, it shall be subject to the approval of the relevant department. Can be welded.

8.17 At the end of the work, the welder should be cut off and the operation site checked to confirm that there is no risk of fire before leaving.