1. Welding preparation?
Cleaning the joint before welding requires that burrs, oil stains, rust scales and oxide scales affecting the weld quality within 30mm on both sides of the groove must be cleaned up.
2. When the construction environment temperature is below zero or the carbon equivalent of steel is more than 0.4 1%, and the structural stiffness is too large and the object is thick, preheating measures should be taken before welding. The preheating temperature is 80℃~ 100℃, and the preheating range is 5 times of the plate thickness, but not less than100 mm.
3. When the thickness of the workpiece is greater than 6mm, in order to ensure the penetration strength, a V-shaped or X-shaped groove should be cut at the butting edge of the plate, the groove angle is 60, the blunt edge P is 0~ 1mm, and the assembly clearance B is 0 ~1mm; When the thickness difference is greater than or equal to 4 mm, the butt edges of thicker plates shall be chamfered.
4. Before welding, carefully check the smooth wire feeding and gas flow of CO2 welder. ?
5. If bottled gas is used, it should be discharged and purified, and the gas pressure should be checked. If it is 9.8×10.5pq (10kgf/mm2), it should be stopped.
6. Adjust the specifications according to different welding workpieces and welding positions. The following formula can be used in common welding specifications: V=0.04I+ 16 (allowable error 1.5V).
2. Welding materials?
The purity of CO2 gas should be 99.5%; The water content shall not exceed 0.65438 0%; The carbon content shall not exceed 0. 1%.
2. Welding wire brand low-carbon steel and high-strength low-alloy steel are important ... CO2 semi-automatic gas shielded welding process is suitable for welding various large steel structures of low-carbon steel and low-alloy high-strength steel. High welding productivity, good crack resistance, small welding deformation and wide deformation range, which can be used to weld thin and medium plate parts.
Three. Operating point
1. Joints with grooves in vertical or inclined positions must be welded from bottom to top, and downward welding can be used for thin plate butt joint and vertical fillet welding without grooves; Horizontal, horizontal and vertical butt joints can be welded to the left. ?
2. For outdoor operation, when the wind speed is greater than 1m/s, windproof measures should be taken. ?
3. Reasonable welding sequence must be selected according to the structure of the workpiece to be welded. ?
4. The butt end shall be equipped with arc striking and arc extinguishing plates of appropriate size. ?
5. Please be sure to clean the dirt and nozzle splash in the hose. ?
6. For plate joints with grooves, especially thick plate multi-pass welding, the welding wire should stay on both sides of the groove for a short time when swinging, and the thickness of each layer of sawtooth strip should not be greater than 4mm, so as to make the weld fusion good. ?
7. Select the contact tip of welding wire correctly according to the diameter of welding wire, and the extension length of welding wire should generally be controlled within the range of 10 times of the diameter of welding wire. ?
8. When welding, the wire feeding hose must be pulled smoothly and cannot be bent. The radius of the wire feeding hose should not be less than150 mm. Before welding, the residual impure gas in the gas supply hose should be discharged. ?
9. After the contact nozzle is worn, the aperture increases, which leads to unstable welding, so it is necessary to replace the contact nozzle. ?
4. Welding procedure?
Welding plate seam, with vertical and horizontal cross welds, should first weld the end weld, then weld the edge weld.
2. If the joint length exceeds 1 m, symmetrical welding method or step-by-step welding method should be adopted. ?
3. When the butt weld and fillet weld on the shelf exist at the same time, the butt weld of the plate should be welded first, then the butt weld of the shelf, and finally the fillet weld of the shelf and the plate. ?
4. All symmetrical objects should be welded from the center to the front and back, and be symmetrical left and right. ?
5. When vertical, horizontal, vertical and fillet welding of objects exist at the same time, vertical fillet welding should be carried out first, and then fillet welding should be carried out; Welding short weld first, then welding long weld. ?
6. The weld legs of all lifting frames shall be the weld corners around the thickness of lifting frames. After welding, carefully check the weld quality. ?
7. If the weld quality of the parts is not good, it should be modified when the parts are qualified, and it cannot be left in the whole installation and welding.
Welding quality requirements:
1. Butt welds of important structures shall be inspected internally by a certain number of X-ray or ultrasonic joints according to various technical requirements specified in the design, and evaluated according to the design grade.
2. Check the external welds, so check all structural welds. The external quality requirements of welds are as follows:
(1) Weld flatness, and the flatness of any part within ≤ 100mm shall be ≤2mm.
(2) The weld shall be smooth transition, and the sudden transition angle shall not be less than 90.
(3) The height difference of weld length is 25mm, and the height difference shall be ≤1.5mm. ..
④ When the thickness of the object is less than or equal to 4 mm, the tolerance of K value of fillet weld is 0.9K0 ≤ K0+1; When the thickness of the object is greater than 4 mm, 0.9K0 ≤ K ≤ K0+2. (K0 is the design leg size) ⑤ Weld undercut: when the thickness of the plate is less than or equal to 6 ≤6mm d≤0.3mm, D < 0.5mm；; When the thickness of the plate is greater than 6mm, D is less than or equal to 0.5mm (D is undercut depth).
⑥ The weld shall not be lower than the surface of the workpiece, and there shall be no cracks and unfused defects.
⑦ The depression depth at the intersection of multi-pass weld surface accumulation should be ≤1mm..
⑧ All welding defects are allowed to be repaired, and should be polished and smooth after repair.
Pet-name ruby component material for steel casting, after welding must be annealed at 550℃, in order to eliminate stress.
3. The welding structure allows pyrotechnic correction.
4. Then take it out.