processing and welding: Before welding, thoroughly remove the rust, oil, water, paint, etc. that are harmful to welding, and select the electrode suitable for the steel type. The spot welding time interval is shorter than the carbon steel spot welding distance, and the spiral pipe brush should be used when removing the welding slag. After welding, the surface should be ground or cleaned to prevent local corrosion or strength degradation.
Cutting and stamping: Since the spiral tube is stronger than normal materials, punching and shearing require higher pressure, and the gap between the knife and the knife is accurate and does not cause shearing and work hardening. Preference is given to using plasma or laser cutting. When gas cutting or arc cutting is to be used, the heat affected zone is ground and heat treatment is required.
Spiral tube bending: The sheet can be bent 180°, but in order to reduce the crack of the curved surface, the radius is twice the thickness, and the thick plate gives twice the thickness radius in the rolling direction and is bent perpendicular to the rolling direction. It is necessary to give a radius of 4 times the thickness of the plate, especially in the case of welding, in order to prevent cracking of the machining, the surface of the weld zone should be ground.
Welding repair method for spiral tube crack
It is one of heat resistant stainless steel. It has excellent oxidation resistance and corrosion resistance and is widely used in alkali tubes for ion membrane electrolysis. Due to the high technical requirements of the material, once the alloying elements and filling materials of the substrate are incomplete, the welding process is not suitable, the working conditions are not good, the medium in the pipe is corroded, the working stress and the serious defects that like to cause cracks in the pipe will bring produce. Serious hidden dangers. Then, the repair of the crack is an important maintenance method.
1. Prepare for welding. A φ6 mm bore 10 mm was drilled from both ends of the crack to prevent crack propagation during the grinding process. Then, the groove of the groove angle α = 60°, the gap b = 3.2 mm, and the blunt edge p = 1.5 mm were ground by an angle grinder. The distance between the cracks is the length of the grooves, the transition surfaces of the weld and the substrate are ground through the crack holes, and the oil, rust and other debris on both sides of the grooves are cleaned.
2, using ZX7-400A welding machine, DC reverse connection, welding material is A402, φ3.2mm for bottoming, filling and covering, welding current is 110A.
3, using arc-extinguishing welding base, uniform arc welding filling and covering, single channel bottom, double channel filling, 3 cover plates. Each room was thoroughly cleaned and each joint was staggered approximately 15mm to ensure no defects. The welding direction is from left to right, and the welding sequence is performed layer by layer from bottom to top.
4. After repair welding, the appearance of the weld should be flat, the weld height h h1mm, width ≤ 4mm, normal use after coloring inspection.