Tianjin Tianyingtai Steel Pipe Co., Ltd. is one of the most credible manufacturers and suppliers of spiral carbon steel pipe in China. Welcome to consult the quotation and import cheap spiral carbon steel pipe made in China here from our factory.
Product Info
The spiral steel pipe is a spiral seam steel pipe which is made of steel coiled coil as raw material, which is often heated and extruded, and welded by automatic double wire double-sided submerged arc welding process.
Weld processing
1. If the gap is too large, the proximity effect is reduced, the eddy current heat is insufficient, and the weld intergranular joint is poor and unfused or cracked.
2. If the gap is too small, the proximity effect will increase, the welding heat will be too large, and the weld will be burnt; or the weld will be pressed and rolled to form a deep pit, which will affect the surface quality of the weld.
After the two edges of the tube blank are heated to the soldering temperature, under the extrusion of the pressing roller, a common metal grain is formed to infiltrate and crystallize, thereby finally forming a firm weld bead. If the pressing force of the spiral steel pipe is too small, the number of common crystals will be small, the strength of the weld metal will decrease, and cracking will occur after the force is applied; if the pressing force is too large, the molten metal will be extruded out of the weld. Not only the weld strength is reduced, but also a large number of internal and external burrs are generated, and even defects such as weld seams are caused.
Quality Inspection
The spiral steel pipe shall be subjected to mechanical performance test, flattening test and flare test before leaving the factory, and shall meet the requirements specified in the standard. The quality inspection method of straight seam steel pipe is as follows:
1. Judging from the surface, that is, in appearance inspection. The appearance inspection of welded joints is a simple and widely used inspection method, which is an important part of the inspection of finished products, mainly to find defects and dimensional deviations on the surface of the weld. It is generally inspected by the naked eye and by means of tools such as standard templates, gauges and magnifiers. If there is a defect on the surface of the weld, there is a possibility of defects inside the weld.
2. Physical method inspection: The physical inspection method is a method of measuring or testing using some physical phenomena. Inspection of the internal defects of materials or workpieces is generally carried out by means of non-destructive testing. Non-destructive testing includes ultrasonic flaw detection, radiographic inspection, penetrant inspection, and magnetic flaw detection.
3. Strength test of pressure vessel: In addition to the sealing test, the pressure vessel shall be subjected to a strength test. There are two types of hydraulic pressure test and air pressure test. They both verify the weld density of containers and pipes that work under pressure. The air pressure test is more sensitive and speedy than the water pressure test, and the tested product does not need to be drained, which is especially suitable for products with difficult drainage. However, the risk of the test is greater than the hydraulic test. When conducting tests, the corresponding safety technical measures must be observed to prevent accidents during the test.
4. Density test: For welding containers that store liquid or gas, the welds are not dense, such as penetrating cracks, pores, slag inclusions, incomplete penetration and loose structures, which can be found by compactness test. The methods of compactness test include: kerosene test, water carrying test, water flushing test, etc.
5. Hydrostatic test Each steel pipe shall be subjected to hydrostatic test without leakage. The test pressure shall be calculated according to the test stress Mpa of the S-hydrostatic test in P=2ST/D, and the test stress of the hydrostatic test shall be corresponding. The steel strip standard specifies 60% of the minimum yield (Q235 is 235Mpa). Regulating time: D<508 test pressure holding time is not less than 5 seconds; D≥508 test pressure holding time is not less than 10 seconds 4 Non-destructive testing steel pipe repair welding seam, steel belt butt weld and hoop seam X-ray or ultrasonic inspection. For the spiral weld of the steel direction for the transportation of combustible ordinary fluids, 100% SX ray or ultrasonic inspection shall be carried out. X-rays shall be applied to the spiral welds of steel pipes used for the transportation of common fluids such as water, sewage, air and heating steam. Ultrasonic inspection spot check (20%).
According to the quality inspection results of spiral steel pipes, spiral steel pipes are generally divided into three categories: qualified products, repaired products and waste products. Qualified products refer to spiral steel pipes whose appearance quality and intrinsic quality meet the relevant standard or delivery acceptance technical conditions; the repaired products refer to the appearance quality and internal quality which are not completely in compliance with the standard and acceptance strips, but are allowed to be repaired, and the standard and acceptance conditions can be met after rework. Spiral steel pipe; scrap refers to spiral steel pipe that is unqualified in appearance quality and internal quality, and does not require standard or acceptance conditions after repair or repair.
Waste products are divided into internal waste and external waste. Internal waste refers to the scrap spiral steel pipe found in the foundry or in the foundry; the waste refers to the scrap found after the delivery of the spiral steel pipe, which is usually revealed during mechanical processing, heat treatment or use, and the economic loss caused by it is far away. It is more waste than inside. In order to reduce external waste, the spiral steel pipes produced in batches are best sampled for experimental heat treatment and roughing before leaving the factory. Potential spiral steel pipe defects are found in the spiral steel pipe plant as much as possible in order to take necessary remedial measures as soon as possible.
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