1, electrode force
Projection welding electrode pressure depends on the performance of the welded metal, the size of the bump and bump the number of a welded. Electrode pressure should be enough to bump reaches the welding temperature will completely pressure-fed, and two of the workpiece tight fit. Electrode force-fed over the General Assembly prematurely pressure bump, lost the role of projection welding, the current density decreases to reduce the joint strength. The pressure is too small will cause serious splash.
2, the welding time
For a given workpiece material and thickness, the welding time is determined by the welding current and bump stiffness. Projection welding of low carbon and low alloy steel, compared with the electrode force and welding current, welding time when the secondary. Determine the appropriate electrode force and Mig Welding Wires, welding time adjustment to get the solder joints. If you want to shorten the welding time, it is necessary to correspondingly increase the welding current, but the excessive increase of the welding current may cause metal overheat and splash, usually projection welding the welding time is longer than the spot, while the current is smaller than the spot.
3, the welding current
Of each solder joint for projection welding current required is the same than the spot when a solder joint. But must enable the bump completely crushing current bump melting current should be recommended in the use of appropriate electrode under pressure Buzhi Yu extrusion maximum current of the excess metal. For some bump size, the amount of metal extrusion increases with increasing current. Incremental amplitude modulation current can reduce the extrusion of metal. And Welding Electrode Suppliers and thickness of the weld metal is still the main basis to select the welding current.

Installing the preparatory work before welding
The project to use the high-rise building structure in the domestic steel plate is not much corresponding welding procedure qualification test methods, for which a large number of representative joint form. Test steel including Q345GJC-Z15 (wall thickness 70mm), the Q345GJC-Z15 (wall thickness 40mm) of Q345C (flange thickness 28mm), welding position column - the column cross welding column - Liangping welding (including truss girder upper and lower flange level welding), T-angle vertical welding. The form and dimensions of the groove design requirements. Sampling for mechanical and physical test appearance after welding and ultrasonic inspection and approval. Joint tensile strength of the test results to the standard value of the tensile strength of the base material, fittings 180 ° bend without cracks. Welding materials and welding equipment technical conditions should be consistent with the national standards, excellent performance. Cleaning residue, gouging, the electrode drying insulation and other devices should be complete and effective.
5.2.2 manual metal arc welding and CO2 gas shielded welding consumables and equipment
(1) welding rod should be in the high-temperature drying oven drying, the electrode drying no more than two.
(2) wire packaging should be in good condition, if it is damaged and lead wire contamination or bent, the disorder should be part discarded.
(3) CO2 gas purity should be not less than 99.9% (volume ratio), the water content should be less than 0.05% (weight ratio), is less than 1MPa should stop using the bottle hypertension.
(4) The welder voltage should be normal, pressed firmly ground reliable contact, no damage cables and welding tongs, wire feeder wire feed should be uniform, trachea should be no leakage or blockage.
5.3 Installation of welding procedures and general provisions
Welding of general order: Preheat rust before welding inspection → → assembly and welding pad and arc board → welding → test
5.3.1 groove angle before welding inspection, blunt edge, gap, and the amount of the wrong mouth, groove and on both sides of the rust, oil, iron skin, etc. should be cleaned.
5.3.2 preheating. Before welding gas welding or specially roasted gun uniform heating of the groove and the base metal on both sides of each of the 100mm range and surface temperature measurement temperature, to prevent the temperature does not meet the requirements or the surface of the partial oxidation, preheat temperature.
5.3.3 Recheck the preheat temperature, if the temperature is not enough should be re-heated to make it meet the requirements.
5.3.4 assembly and Types Of Welding Electrodesand arc plate, surface cleanliness requirements the same as the surface of the groove, pad and base metal snapping, should be solid arc plate and base metal welding.
5.3.5 Welding: the first layer of weld bead should seal the junction of the the groove base metal pad, then by trace layer tired solder to fill the groove, After everyNickel Electrodesmust be removed before welding slag and spatter, weld defects should be promptly rubbed off and repair.
5.3.6 an interface must be continuous welding finished, as a last resort midway stop welding, insulation slow cooling process, the regulations should be re-heated again before welding.
5.3.7 in case of rain, the snow should stop welding, the component weld around and above should have windshield, canopy, wind speed greater than 5m / s should stop welding. Ambient temperature is below zero, should be required to take the measures of preheat and post-heat construction.
5.3.8 carbon structural steel in the weld cooling to ambient temperature, low-alloy structural steel weld inspection test completed 24h.
5.3.9 welders and inspection personnel to fill in the job log table.
5.4 of typical welding sequence of nodes and process parameters
(1) up and down the column ear plate side by two welders in bilaterally symmetrical weld to a thickness of 1/3, cut ear board.
(2) and then cut off the ear plate side symmetrical on both sides by two welders welding to thickness of 1/3.
(3) borne by two welders were welding adjacent sides.
(4) each between the two layers of weld joints should be staggered, and the two welder weld joints should also pay attention to each layer staggered welding process should pay attention to the temperature detection layer.
(5) welding process parameters
CO2 arc welding: wire diameter Φ1.2mm, current 280 ~ 320A, welding speed 350 ~ 450mm/min
Wire extension length: about 20mm, the gas flow 25 to 80L/min
Voltage 29 ~ 34V, interpass temperature 120 to 150 ° C
5.4.2 Column - beam, the beam - beam joint
(1) first welding of the bottom flange of the beam flange weld both sides of the beam web to maintain symmetry welding.
(2) Subject to the bottom flange welding finished, and then welded to the top flange.
(3), should the rotation of the upper and lower flange welding flange plate thickness greater than 30mm.
(4) welding process parameters
CO2 arc welding: wire diameter φ1.2mm, current 280 ~ 360A, welding speed 300 ~ 500mm/min
Wire extension length of about 20 mm, the gas flow 20 to 80L/mm
Voltage 30 ~ 38V, interpass temperature of 120 ~ 150 ℃
6 Experience
The high-rise building steel structure installation welding quality control is an integrated technology, welding quality by the material properties, process methods, equipment, process parameters, climate and welder technical and emotional impact. Assessed according to the process before the construction of the preparation of the operating instructions, to facilitate each welding explicitly operating essentials, the use of the material and quality requirements. Well before welding and welding welders record in the construction process, the welding engineer check one by one weld inspection and acceptance, and make a record.
The project construction has been completed, a total of 10,100 weld welding, including 8990 grade â…  weld, testing pass rate of 98% reached the required rework all.