Construction Steel Structure Welding

Installation preparation before welding
The project uses high-rise building structure with steel in the country are not many applications for which a larger number and a representative of the welding joint form of the corresponding procedure qualification test methods. Test of steel including Q345GJC-Z15 (thickness 70mm), Q345GJC-Z15 (thickness 40mm), Q345C (flange thickness of 28mm), welding position for a column - column horizontal position, column - Liangping welding (including the upper and lower flange flat truss welding), T-type corner vertical welding. Groove in the form and size according to design requirements. Appearance and ultrasound  examination after welding, after passing a sample in the mechanical and physical tests. Joint tensile strength test results of base metal tensile strength of the standard value, the joint bent 180 ° without cracking. Use of welding materials and welding equipment technical requirements should be consistent with national standards, excellent performance. Slag, gas gouging, electrode drying insulation and other devices should be complete and effective.
5.2.2 manual arc welding and CO2 welding consumables and equipment for gas shielded arc
(1) The electrode should be dried at high temperature drying box, no more than two electrode drying.
(2) wire packaging should be intact, if any, pollution or damage caused by bending wire, disorders should be part of the discarded.
(3) CO2 gas purity should be not less than 99.9% (by volume), water content should be less than 0.05% (by weight), the bottle pressure is lower    than 1MPa should stop using it.
(4) welding voltage should be normal, ground compaction solid, reliable contact, no broken cable and electrode holder, wire feeder wire should be uniform, there should be no leakage or blockage of the trachea.
5.3 Installation of welding procedures and general requirements
General welding sequence: preheating before welding rust → Check → Welding arc plate and inspection plate → Welding →
5.3.1 Check before welding bevel angle, blunt edge, the wrong port clearance and volume of the groove and on both sides of the rust, oil, iron oxide and other skin should be cleaned.
5.3.2 preheating. Before welding gun with a gas welding or special grilled on both sides of the groove and the base material within 100mm uniform heating and temperature measuring of surface temperature, to prevent the surface temperature does not meet the requirements or partial oxidation, the preheating temperature.
5.3.3 re-examine the preheating temperature, such   as the temperature is not enough to be re-heated to conform to requirements.
5.3.4 Welding arc plate and the plate, the surface cleanliness requirements and groove surface of the same plate to be closely aligns with the base metal, base metal arc welding plate and should be solid.
5.3.5 Welding: weld the first layer should be sealed within the base metal groove connection with the pad, and then by road to the fill layer tired welding groove, after each weld, all welding must be removed slag and spatter, weld defects occur in time wore off and repair.
5.3.6 End of an interface must be continuous welding, as they had to stop over in welding, the insulation should be the slow cooling treatment, and then before welding, should be required to re-heating.
5.3.7 case of rain, snow should stop welding, welded joint components should wind around and above, canopy, wind speed greater than 5m / s welding should be stopped. Ambient temperature is below zero, should be required to take measures to pre-and post-construction heat.
5.3.8 Weld carbon steel should be cooled to ambient temperature, low-alloy structural steel should be completed after 24h, for weld inspection test.
5.3.9 welders and inspection personnel to fill job record sheet.
5.4 Code-shaped nodes welding sequence and process parameters
(1) no ear plate side of the column up and down by two welders to weld on both sides of the symmetric thickness of 1 / 3 of the time, cut the ear plate.
(2) and then cut out the side lug of symmetry by two welders in welding to the thickness of 1 / 3.
cable tray suppliers, cable management system, cable tray fittings
(3) and then take the two welders were welding the adjacent sides.
(4) between each two layers of weld joints should be staggered, two welders weld welded joints staggered each layer should also pay attention, pay attention to detect the welding process temperature between layers.
(5) Welding process parameters
CO2 Gas Shielded Welding: Wire diameter Φ1.2mm, Current 280 ~ 320A, welding speed 350 ~ 450mm/min
Extended length of wire: about 20mm, the gas flow rate 25 ~ 80L/min,
Voltage 29 ~ 34V, interpass temperature 120 ~ 150 ℃
5.4.2 Column - beam, beam - beam node
(1) first welding beam bottom flange, beam web  weld on both sides of the flange welded to maintain symmetry.