Hot dip galvanized pipe is to make molten metal react with iron matrix to produce alloy layer, so as to combine the matrix and coating. Hot dip galvanizing is to pickle the steel pipe first. In order to remove iron oxide on the surface of the steel pipe, after pickling, it is cleaned in ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution tank, and then sent to the hot dip galvanizing tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. The matrix of hot-dip galvanized steel pipe has complex physical and chemical reactions with the molten plating solution to form a corrosion-resistant zinc ferroalloy layer with compact structure. The alloy layer is integrated with pure zinc layer and steel pipe matrix, so it has strong corrosion resistance.
(I) cracking of rolling groove weld
1. Grind the inner wall welding rib of the pipe orifice pressure groove part to reduce the rolling groove resistance.
2. Adjust the axis of steel pipe and grooving equipment, and require the steel pipe and grooving equipment to be horizontal.
3. Adjust the pressing groove speed. The forming time of pressing groove shall not exceed the specified length, and apply force evenly and slowly.
(II) fracture of grooved steel pipe
1. Grind the welding reinforcement on the inner wall of the groove pressing part of the steel pipe orifice to reduce the groove rolling resistance.
2. Adjust the axis of steel pipe and grooving equipment, and the steel pipe and grooving equipment shall be horizontal.
3. Adjust the groove pressing speed. The groove pressing speed shall not exceed the regulations, and apply force evenly and slowly.
4. Check the width and model of the support roll and pressure roll of the grooving equipment, and whether there is bite caused by the mismatch of the two roll sizes.
5. Check whether the groove of steel pipe is specified with vernier caliper.
(III) the groove rolled and formed by the groove rolling machine shall meet the following requirements
1. The surface from the pipe end to the groove section shall be flat without concave convex and rolling mark.
2. The groove center shall be concentric with the pipe wall, the groove width and depth shall meet the requirements, and check whether the clamp model is correct.
3. Apply lubricant on the rubber sealing ring and check whether the rubber sealing ring is damaged. Oil lubricant shall not be used as the lubricant.
1. The galvanized steel pipe nozzle is not in a straight line with the steel pipe after butt joint. It is recommended to cut off a small section of the steel pipe head before processing.
2. After the nozzle of galvanized steel pipe is butt jointed, the butt joint of two nozzles is not tight, resulting in uneven thickness of welded junction; As well as the ellipse of the pipe orifice caused by the steel pipe itself or transportation collision, it is recommended to cut off a small section of the steel pipe head before processing.
3. After the nozzle of galvanized steel pipe is butted, sand holes appear at the nozzle:
4. Due to technical reasons during welding.
5. There are zinc nodules at the pipe orifice, resulting in welding difficulties and sand holes. Simple zinc nodules removal shall be carried out for too large and too many pipes.
1. Disordered screw thread: the pipe hoop and the screw thread cannot be completely contacted and loosened. Cut off the disordered screw thread and re thread it for installation.
2. The steel pipe screw thread is not consistent with the pipe hoop screw thread and cannot be connected. The pipe hoop shall be replaced or the equipment shall be adjusted for re threading.
3. Missing marks after steel pipe threading: measure whether the wall thickness of steel pipe can meet the standard thickness requirements of steel pipe threading