Preparation before installation welding
The steel plates for high-rise building structures used in this project are not widely used in China, and the process qualification test of the corresponding welding methods is carried out for a large number of representative joint forms. The test steels include Q345GJC-Z15 (wall thickness 70mm), Q345GJC-Z15 (wall thickness 40mm), Q345C (flange thickness 28mm), and the welding position is column-column horizontal welding, column-beam flat welding (including upper and lower flanges of truss beam) Welding), T-angle vertical welding. The groove form and size are as designed. After the post-weld appearance and ultrasonic inspection, samples were taken for mechanical and physical tests. Test results The tensile strength of the joint reached the standard value of the tensile strength of the base metal, and the joint was bent at 180° without cracks. The welding materials and welding equipment technical conditions used should conform to national standards and have excellent performance. Cleaning slag, gouging, electrode drying and insulation equipment should be complete and effective.
Manual arc welding and CO2 gas shielded welding consumables and equipment
(1) The welding rod should be dried in a high temperature drying box, and the number of drying of the welding rod must not exceed two.
(2) The welding wire package should be in good condition. If there is damage, the welding wire will be contaminated or bent, and it should be partially discarded when it is disordered.
(3) The purity of CO2 gas should not be lower than 99.9% (volume ratio), the water content should be less than 0.05% (weight ratio), and the high pressure inside the bottle should be stopped when it is lower than 1MPa.
(4) The voltage of the welding Machine should be normal, the ground wire should be firmly pressed, the contact should be reliable, the cable and the welding tongs should be damaged, and the wire feeder should be able to feed the wire evenly. The gas pipe should be free of air leakage or blockage.
Installation welding procedure and general regulations
The general order of welding is: pre-weld inspection → preheating and descaling → welding pad and arcing plate → welding → inspection 1. Check the groove angle, blunt edge, gap and misalignment before welding, inside and outside the groove The rust spots, oil stains, iron oxide scales, etc. should be removed.
2. Preheat. Before welding, use gas welding or special baking gun to uniformly heat the base material within 100mm of the groove and its sides, and measure the temperature with a surface thermometer to prevent the temperature from meeting the requirements or local oxidation of the surface and preheating temperature.
3. Re-check the preheating temperature. If the temperature is not enough, reheat it to meet the requirements.
4. Mounting pad and arc-striking plate, the surface cleaning degree is the same as that of the groove surface, the pad and the base material should be tightly attached, and the arc-striking plate and the base metal should be welded firmly.
5. Welding: The weld bead of the first layer should seal the joint between the base metal and the backing plate in the groove, and then weld it layer by layer to fill the groove. After welding each weld, the welding slag must be removed. And spatter, welding defects should be ground and repaired in time.
6. An interface must be continuously welded. If it is necessary to stop welding in the middle, it should be insulated and slow-cooled. Before welding, it should be reheated according to the regulations.
7. In case of rain or snow, stop welding. There should be windshield and canopy around and above the welding joint. When the wind speed is greater than 5m/s, the welding should be stopped. When the ambient temperature is below zero, the preheating and post-heating measures shall be taken as required.
8. The 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 finished 24 hours after completion.
9. Welders and inspectors should fill in the operation record form carefully.
Welding sequence and process parameters of typical nodes
(1) When the upper and lower columns are not welded to the side of the plate by two welders on both sides, the ear plates are cut off.
(2) Then, on the side of the cut ear plate, two welders are symmetrically welded to the 1/3 of the plate thickness on both sides.
(3) The two welders respectively undertake the welding of the adjacent two sides.
(4) The joints of the weld bead between each two layers shall be staggered from each other. The weld bead joints of the two welders shall also pay attention to the staggering of each layer. During the welding process, the temperature between the layers shall be checked.
(5) Welding process parameters CO2 gas shielded welding: wire diameter Φ1.2mm, current 280 ~ 320A, welding speed 350 ~ 450mm / min
Wire extension length: about 20mm, gas flow rate 25 ~ 80L / min,
Voltage 29～34V, interlayer temperature 120～150°C
Column-beam, beam-beam joint
(1) Firstly weld the lower flange of the beam, the flange weld bead on both sides of the beam web should be symmetrically welded.
(2) After the lower flange is welded, the upper flange is welded.
(3) If the flange thickness is greater than 30mm, the upper and lower flanges should be alternately welded.
(4) Welding process parameters CO2 gas shielded welding: wire diameter φ1.2mm, current 280～360A, welding speed 300～500mm/min
The wire has a length of about 20 mm and a gas flow rate of 20 to 80 L/mm.
Voltage 30 ~ 38V, interlayer temperature 120 ~ 150 ° C
Experience
High-rise building steel structure installation welding quality control is a comprehensive technology, welding quality is affected by material properties, process methods, equipment, process parameters, climate and welder technology and mood. Before the construction, the operation instructions are compiled according to the process evaluation, so that each welding personnel can clearly understand the operation essentials, the use of materials and the quality requirements. During the construction process, the welder records the welding and welding, and the welding engineer checks and accepts the welds one by one and makes a record.
The project has been completed and a total of 10,100 welds have been welded, of which 8,990 grade I welds have been tested. The pass rate of flaw detection has reached 98%, and all of them have passed the repair.
The steel plates for high-rise building structures used in this project are not widely used in China, and the process qualification test of the corresponding welding methods is carried out for a large number of representative joint forms. The test steels include Q345GJC-Z15 (wall thickness 70mm), Q345GJC-Z15 (wall thickness 40mm), Q345C (flange thickness 28mm), and the welding position is column-column horizontal welding, column-beam flat welding (including upper and lower flanges of truss beam) Welding), T-angle vertical welding. The groove form and size are as designed. After the post-weld appearance and ultrasonic inspection, samples were taken for mechanical and physical tests. Test results The tensile strength of the joint reached the standard value of the tensile strength of the base metal, and the joint was bent at 180° without cracks. The welding materials and welding equipment technical conditions used should conform to national standards and have excellent performance. Cleaning slag, gouging, electrode drying and insulation equipment should be complete and effective.
Manual arc welding and CO2 gas shielded welding consumables and equipment
(1) The welding rod should be dried in a high temperature drying box, and the number of drying of the welding rod must not exceed two.
(2) The welding wire package should be in good condition. If there is damage, the welding wire will be contaminated or bent, and it should be partially discarded when it is disordered.
(3) The purity of CO2 gas should not be lower than 99.9% (volume ratio), the water content should be less than 0.05% (weight ratio), and the high pressure inside the bottle should be stopped when it is lower than 1MPa.
(4) The voltage of the welding Machine should be normal, the ground wire should be firmly pressed, the contact should be reliable, the cable and the welding tongs should be damaged, and the wire feeder should be able to feed the wire evenly. The gas pipe should be free of air leakage or blockage.
Installation welding procedure and general regulations
The general order of welding is: pre-weld inspection → preheating and descaling → welding pad and arcing plate → welding → inspection 1. Check the groove angle, blunt edge, gap and misalignment before welding, inside and outside the groove The rust spots, oil stains, iron oxide scales, etc. should be removed.
2. Preheat. Before welding, use gas welding or special baking gun to uniformly heat the base material within 100mm of the groove and its sides, and measure the temperature with a surface thermometer to prevent the temperature from meeting the requirements or local oxidation of the surface and preheating temperature.
3. Re-check the preheating temperature. If the temperature is not enough, reheat it to meet the requirements.
4. Mounting pad and arc-striking plate, the surface cleaning degree is the same as that of the groove surface, the pad and the base material should be tightly attached, and the arc-striking plate and the base metal should be welded firmly.
5. Welding: The weld bead of the first layer should seal the joint between the base metal and the backing plate in the groove, and then weld it layer by layer to fill the groove. After welding each weld, the welding slag must be removed. And spatter, welding defects should be ground and repaired in time.
6. An interface must be continuously welded. If it is necessary to stop welding in the middle, it should be insulated and slow-cooled. Before welding, it should be reheated according to the regulations.
7. In case of rain or snow, stop welding. There should be windshield and canopy around and above the welding joint. When the wind speed is greater than 5m/s, the welding should be stopped. When the ambient temperature is below zero, the preheating and post-heating measures shall be taken as required.
8. The 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 finished 24 hours after completion.
9. Welders and inspectors should fill in the operation record form carefully.
Welding sequence and process parameters of typical nodes
(1) When the upper and lower columns are not welded to the side of the plate by two welders on both sides, the ear plates are cut off.
(2) Then, on the side of the cut ear plate, two welders are symmetrically welded to the 1/3 of the plate thickness on both sides.
(3) The two welders respectively undertake the welding of the adjacent two sides.
(4) The joints of the weld bead between each two layers shall be staggered from each other. The weld bead joints of the two welders shall also pay attention to the staggering of each layer. During the welding process, the temperature between the layers shall be checked.
(5) Welding process parameters CO2 gas shielded welding: wire diameter Φ1.2mm, current 280 ~ 320A, welding speed 350 ~ 450mm / min
Wire extension length: about 20mm, gas flow rate 25 ~ 80L / min,
Voltage 29～34V, interlayer temperature 120～150°C
Column-beam, beam-beam joint
(1) Firstly weld the lower flange of the beam, the flange weld bead on both sides of the beam web should be symmetrically welded.
(2) After the lower flange is welded, the upper flange is welded.
(3) If the flange thickness is greater than 30mm, the upper and lower flanges should be alternately welded.
(4) Welding process parameters CO2 gas shielded welding: wire diameter φ1.2mm, current 280～360A, welding speed 300～500mm/min
The wire has a length of about 20 mm and a gas flow rate of 20 to 80 L/mm.
Voltage 30 ~ 38V, interlayer temperature 120 ~ 150 ° C
Experience
High-rise building steel structure installation welding quality control is a comprehensive technology, welding quality is affected by material properties, process methods, equipment, process parameters, climate and welder technology and mood. Before the construction, the operation instructions are compiled according to the process evaluation, so that each welding personnel can clearly understand the operation essentials, the use of materials and the quality requirements. During the construction process, the welder records the welding and welding, and the welding engineer checks and accepts the welds one by one and makes a record.
The project has been completed and a total of 10,100 welds have been welded, of which 8,990 grade I welds have been tested. The pass rate of flaw detection has reached 98%, and all of them have passed the repair.
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