How can we weld the steel pipe well

Then, taking the more typical φ1016×21mm X70 steel pipe inclined at 45° as an example, let's talk about the welding techniques of the steel pipe inclined weld.

First, the steel pipe is prepared before welding.

1. Welding equipment: ZX7-400-3 welding machine is used for root welding; Xionggu ZD-500 multi-function semi-automatic welding machine is used for filling and capping.

2. Welding materials: Bo Le φ3.2 E6010 cellulose welding rod is used for root welding; E81T8-G φ2.0 flux-cored self-shielded welding wire is used for filling and capping.

3. Groove cleaning: Before assembly, the groove should be cleaned first. Use an angle grinder or an electric wire brush to remove oil, rust, water, and other dirt within 25mm of the groove and the front and back edges until all the metallic luster is exposed.

4. Steel pipe mouth pairing: Steel pipe mouth pairing directly affects the quality of root welding, and must be carried out strictly according to the welding process parameters, and the blunt edge of the groove is controlled within the range of 0.5-2.0mm; the groove gap is strictly controlled within 2.5-3.5mm, the top of the steel pipe mouth is 2.5mm, and the bottom of the steel pipe mouth is 3.5mm.

5. Steel pipe mouth positioning welding: The steel pipe mouth is positioned using internal card point fixation, and 8-10 U-shaped cards can be used, evenly and symmetrically distributed in the steel pipe mouth, and firmly welded. Then fix the weldment on the welding frame at an inclined 45° position.

Second, the operation of steel pipes during welding

1. Select steel pipe welding process parameters: Welding process parameters are an important basis for guiding welding operations. From root welding to filling and capping welding, welding process regulations must be followed and welding process parameters must be strictly controlled.

2. Root welding of steel pipes

- Preheating before welding: X70 steel grade is higher and has a stronger tendency to crack. It must be preheated before root welding. The groove and the surrounding area must be heated to 80-120℃ before root welding can be carried out.

- Root welding: E6010 cellulose downward welding is used, and two people start welding from the top of the pipe. The starting point is 5mm-8mm beyond the center line from the vertex, and the arc is drawn from the groove surface, and then the arc is drawn to the root of the groove. After the blunt edge is melted through, it is dragged straight down along the weld.

Short arc operation is used to prevent the formation of pores, which is conducive to the melting of the root of the groove, and to prevent the formation of incomplete penetration and incomplete fusion. At the same time, it is necessary to prevent the formation of concavities and collapse, and to ensure that the joint is full when the electrode is replaced. After the root welding is completed, the surface slag and spatter should be thoroughly removed, especially the junction between the weld and the groove surface should be cleaned to avoid slag inclusions when welding the lower layer of the weld.

3. Filling welding of steel pipe: The filling layer uses E81T8-G φ2.0 flux-cored self-shielded welding wire and adopts manual semi-automatic welding. X70 grade steel has a certain tendency to crack. In order to prevent cracks, the interlayer temperature must be guaranteed to reach above 80℃. Appropriate heating measures must be taken for 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; the welding defects of the filling layer are mainly pores, slag inclusions, and unfusion. Maintain short arc welding during filling welding; use straight line feeding or slight swing; constantly adjust the inclination of the welding gun from top to bottom to keep the welding wire; after each layer of welding is completed, the slag must be cleaned with a grinder or electric wire brush before welding the next layer; when the filling layer is wide, row welding can be used, first the lower row and then the upper row, and then the upper row, and the welds are required to be uniform and full, with good fusion on both sides. It should be noted that when filling the last layer of welding, the groove edge should not be damaged to ensure that the groove contour of the cover layer is clear, which provides a reference for controlling the weld width of the cover welding.

4. Covering of steel pipe: The cover welding of steel pipe should ensure that the weld appearance size is qualified, there are no welding defects, and the shape is beautiful. It is the last process of the weld and also the key process. There are prominent difficulties in the 45° inclined steel pipe cover welding. The appearance is prone to defects such as undercuts and super-high welds, and grooves are prone to appearing between welds. Appropriate process methods must be adopted: strictly follow the process parameter requirements, use a straight line with a slight swing to transport the weld, the swing amplitude should be appropriate, and the melting of the groove edges on both sides should be 1.5mm to 2mm. The use of swinging transport is conducive to gas precipitation and slag floating, and can prevent the formation of pores and slag inclusions; when welding, it is advisable to arrange the upper pass first, and then the lower pass. This cannot only appropriately reduce the number of weld passes, but also can easily control weld undercut, super-high weld, and grooves between welds. The transition between welds is smooth and the shaping is beautiful, which is conducive to improving weld quality and efficiency.