How to weld the weld of the pipe welds well
1. Pre welding preparation
Welding equipment: root welding using ZX7-400-3 welder; filling and cover face using Xiong Valley ZD-500 multi-function semi-automatic welder.
Welding material: the root welding is made of Bole 3.2 E6010 cellulose electrode, and the linen E81T8-G 2 core self shielded welding wire is used for filling and covering.
Guchi Kiyori: first of all, we need to clean up the groove. Use angle grinder or electric wire brush to remove oil, rust, water and other dirt within 25mm range of groove and positive and negative edges until all metallic luster is exposed.
Pipe mouth group: the pipe mouth group directly affects the quality of root welding, must be strictly controlled by welding parameters, control the blunt edge of the slope in the range of 0.5 ~ 2.0mm; the groove clearance is strictly controlled at 2.5 ~ 3.5mm, the top of the pipe mouth is 2.5mm, and the bottom of the pipe mouth is 3.5mm. As shown in Figure 1.
Nozzle positioning welding: the location of the nozzle is fixed inside the card, and it can be used in 8~10 U cards. It is distributed evenly in the pipe mouth and is firmly welded. The weldment is then fixed on the welding rack at a slanting 45 degree position.
1. Selection of welding parameters
Welding process parameters are the important basis for guiding the welding operation. From root welding to filling and cover welding, welding process regulations must be kept and welding process parameters are strictly controlled.
2. Root welding
Preheating before welding: high grade X70 steel, strong crack tendency, before root welding must be preheated, the groove and the surrounding heating to 80~120 degrees, can be root welding.
Root welding: E6010 cellulose downward welding and double combination welding from the top of pipe. The welding point is welded from the point above the center line 5mm to 8mm, and the arc is drawn from the surface of the bevel. Then the arc is drawn to the root of the groove, and then it is dragged down the weld seam after the blunt edge is melted.
Short arc operation is used to prevent the formation of air holes, help to melt the root of the slope, prevent the non - penetration and non fusion, and prevent the inner concave and collapse, and the joints are full when the electrode is replaced.
After the root welding is finished, the surface slag and spatter should be completely removed, especially the junction of the weld and the groove surface should be cleaned up to avoid the slag inclusion in the welding of the lower welds.
3. Fill welding
The filling layer is made of Lincoln E81T8-G 2 core self shielded welding wire and semi-automatic welding by hand.
X70 grade steel has a certain tendency of crack. In order to prevent cracks, the temperature of interlayer must be ensured above 80 degrees C, and proper heating measures must be taken in winter welding construction.
After the root welding is completed, the welding layer should be cleaned immediately, followed by the welding of the hot welding layer and the filling layer, and the welding defects of the filling layer are mainly the pores, the slag and the non fusion. During welding, short arc welding should be maintained; straight line bars or a little swing should be adopted; the inclination angle of the welding gun should be adjusted continuously from top to bottom.
Welding gun dip angle
The welding wire remains as shown in Figure 2. After each layer of welding, it is necessary to clean the slag with a grinder or electric wire brush first, and then weld the next layer; when the filling layer is wide, it is possible to discharge welding, first row down the road and then on the road. As shown in Figure 3, the welding path is uniform and full, and the two sides are in good fusion.
In particular, it should be noted that the edge of the groove can not be damaged when the final layer is filled with welding, and the contour of the slope of the cover layer is clear (as shown in Figure 3), which provides reference for the control of the weld width of the cover welding.
4. Cover surface
The surface welding should be qualified for weld appearance size, no welding defects and beautiful appearance. It is the last working procedure and the key process.
There is a prominent difficulty in welding the cover of the pipe mouth at 45 degrees centigrade. It is easy to appear the defects of the edge of the bite and the super high weld seam. The groove is easy to appear between the welds. It is necessary to adopt appropriate technological methods.
In strict accordance with the requirements of process parameters, it is appropriate to swing the strip in a straight line with a slight swing of the wobble strip, and it is appropriate to melt the edge of the slope at both sides 1.5mm to 2mm, and the wobble strip is adopted, which is beneficial to the precipitation of gas and the floatation of the slag, and the gas hole and slag can be prevented.
As shown in Figure 4, it can not only reduce the number of exhaust welds, but also easily control the edge of the weld, the super high track and the groove between the welds and so on. The transition between the welds is slow and the forming is beautiful, and it is good for improving the quality and efficiency of the weld.