Although the quality of manual tungsten argon arc welding joints is high, the production efficiency is low. It is only used for welding thin parts and is rarely used for welding thick parts. Manual tungsten argon arc welding is usually used as base welding in production. This is only described below. The key points of operation for manual tungsten arc welding of large diameter pipe butt joints, filling and cover layer welding shall be carried out in accordance with the process regulations.
There are 3 tack welds, each 10~15mm long. The pipe is placed horizontally, with one tack weld on the right side, ensuring that the gap above is 3mm and the gap below is 4mm. The tilt angle of the welding gun, the wire filling position and the arc centering position are shown in Figure-Small diameter pipe horizontal rotation butt welding gun tilt angle and arc centering position.
Ignite the arc on the right tack weld, preheat it in place, and do not add wire for the time being. After the tack weld and both sides of the groove melt to form a molten pool, move the arc to the left to the left end of the tack weld, and press the arc downward. , after you hear the breakdown sound and see the welding hole, add wire while welding to the left for a certain distance, extinguish the arc, turn the weldment, turn the arc crater to the right, and start the arc to continue welding. Repeat this until the bottom bead is welded.
There are 3 tack welds, each 10~15mm long. The pipe is fixed vertically. One tack weld is on the right side, ensuring that the gap in the front is 3mm and the gap in the back is 4mm. The tube axis is fixed in a vertical position. The angle of the welding gun is shown in Figure-The tilt angle of the welding gun and the arc centering position for welding the bottom bead.
Ignite the arc on the tack weld on the right side without adding welding wire at first. After the left side of the tack weld melts and forms a molten pool and a molten hole, add wire from the front edge of the molten pool and swing the welding gun slightly laterally. Stop for a moment on the side to ensure that the root of the weld is well fused. The heat of the arc should be slightly biased towards the pipe below to prevent undercutting on the uphill surface. Weld in this way from right to left until the filler bead is welded.
In order to facilitate welding, the large-diameter pipe weld seam is divided into left and right half circles according to the clock position for welding. There are 3 tack welds evenly distributed, 1 is at the 7 o’clock position, ensuring that the gap at the 6 o’clock position is 3 mm, and the gap at the 0 o’clock position is 4 mm.
Bevel both ends of all tack welds so that the axis is in a horizontal position after the pipe is fixed. The tilt angle of the welding gun and the arc centering position are shown in Figure-Welding gun tilt angle and arc centering position for all-position welding of small diameter pipes. First weld the first half turn in a counterclockwise direction. Ignite the arc on the tack weld at the 7 o’clock position of the clock. No welding wire is added first. After the right end of the tack weld melts and a hole in the molten pool is formed, feed the welding wire from left to right from the rear edge of the molten pool. When the end of the welding wire Melts to form small droplets, which are immediately sent to the molten pool.
When welding reaches the 4:30 position of the clock, the welding gun angle and wire feeding position can be changed, and the welding wire is fed from the front edge of the molten pool.
During the welding process, the arc should swing laterally in a zigzag shape with the groove gap as the center, and stay on both sides of the groove for a while to ensure good fusion on both sides of the groove and avoid protruding in the middle of the base weld bead. Weld until the arc is extinguished 10 ~ 20mm to the left of 0 o’clock on the clock. After welding for half a circle in a clockwise direction, ignite the arc on the tack weld at the 7 o’clock position of the clock. No welding wire is added at first. After the left end of the tack weld melts and a hole in the molten pool is formed, add the welding wire from the front edge of the molten pool, and then Weld in a clockwise direction, the welding gun makes a small zigzag swing, and stops on both sides of the groove. Stop adding wire when welding to the seal. After the end of the original weld is melted, add wire and finish welding the last joint. Fill in the welding wire. The arc is extinguished after the crater is full.
In order to facilitate welding, the welding seam is also divided into two half circles according to the clock position, and the welding positioning welding seam is evenly distributed in 3 places, each 10~15mm long, one is at the 7 o’clock position, and the gap at the 6 o’clock position is ensured. 3mm, the gap at the 0 o’clock position of the clock is 4mm.
The axis of the pipe is fixed at an angle of 45° to the horizontal plane, and the base bead is welded in two half circles, left and right. The relative relationship between the welding gun tilt angle, wire adding position, and arc centering position is shown in Figure-Welding gun tilt angle and arc centering position for all-position welding of small diameter pipes. Note: The inclination angle of the welding gun, wire adding position and arc centering position must follow the centerline of the groove and move horizontally. The welding steps are the same as those for all-position welding of horizontally fixed large-diameter pipes. The welding gun swings in the horizontal direction, so the scale pattern of the weld is at a 45° angle to the axis of the pipe.