In the long-distance pipeline construction, the pipeline accounts for a large proportion, generally 35% to 40% of the total investment pipeline project management. How to choose a reasonable price, excellent performance of the pipeline is particularly important, a reasonable choice of pipeline construction investment savings, the construction of the pipeline system and safe operation has a very important impact. Natural gas pipe straight seam high-frequency resistance welded steel pipe, spiral submerged arc welded pipe, LSAW steel pipe.

The main difference between seamless steel pipe and welded pipe is the molding process. Generally welded steel pipe, such as water pipes, are usually bent and welded together by a flat plate, after which you can find a seam; the diameter is usually a spiral weld.

In the pipe from the top of the arc, from top to bottom all-position welding technology, welding speed method, weld appearance, good welding quality, welding materials can be saved, reducing labor intensity is a common hand can not be more widely than now Applied to large-diameter long-distance pipe welding in the lower welding of large-diameter thin-walled tube construction of all power status has a certain promotional value.

Welding method is under the conditions of welding materials, according to the design requirements of the welding components, and can meet the requirements of the scheduled service. The four factors are affected by the welding material, welding, the type of part and the usage requirements.

Steel pipe hardness and tensile strength

Effect of remanence on welding quality and its influence Gas pipeline construction and repair welding operations, sometimes appear blowing phenomenon, affecting the welding process. The formation of a magnetic strike is due to the presence of metal residual magnetism in the pipe. Usually, the magnetic induction and remanence are divided into two processes. Magnetically-induced plants tend to produce tube links such as metal smelting, handling using electromagnetic cranes, tube parking in a strong magnetic field, non-destructive testing after magnetization, and placing the tube close to the power cord and so strongly. Magneto-electric welding often occurs during the process. When assembling and using the magnetic retainer, the fixture and the DC welding pipe are connected to each other. For example, a long contact is connected to a DC power cable, a bare wire section or a short-circuit pipe welding fixture.

3PE corrosion-resistant steel pipe buried pipe life is crucial, the same material, pipe buried in the ground for decades and some non-corrosive, leaks in a few years. Because they use different outer coating.

Classification and Production Methods of Welded Steel Pipe

Eddy current testing features are as follows: Advantages of eddy current testing 1, When test, the coil does not require contact with the workpiece, but also without the coupling medium, so the detection speed.

The following hs code apply to all kinds of steel pipe products, such as seamless pipe, welded pipe(erw pipe, ssaw pipe, lsaw pipe), stainless steel pipe, pipe fittings, etc.

Steel pipes are ubiquitous and can be found in underground and residential walls, laboratories, and commercial and industrial structures. Pipes transport fluids, including water, natural gas, waste and air. There are three manufacturing methods for the production of steel pipes. The seamless steel pipe is produced by extrusion die. The welded steel pipe is produced by rolling the steel plate into the pipe and welding.

Due to the strong bending ability of carbon steel pipe factory, so in recent years, the stadium building roof truss, beam, column, the steel structure housing, with the development of steel structure manufacturing industry in the construction of more and more use of steel structure, household appliances, furniture, plumbing, HVAC, gas, transportation and agriculture equipment the manufacturing industry, coal, oil and gas exploitation of underground resources, gun, air and space rockets, artillery, missile etc.. Iron and steel can not be separated, so the development of the national economy on the pipeline is closely related to the living standard of the people.

Galvanized steel surface coated with a layer of zinc is generally low carbon steel, galvanized layer is generally 20um thick. At 419 ° C, the melting point of zinc is about 908 ° C. During welding, zinc is melted into the liquid that floats on the surface of the cell or the root of the weld. Zinc is more soluble in iron and the zinc corrosion solution will enter the weld metal along the grain boundaries, forming a "low melting point of liquid metal embrittlement." At the same time, brittle intermetallics of zinc and iron may form, and these brittle phases, Tensile stress cracks in the weld metal plasticity decreased. If the weld, fillet weld is the most easy to penetrate the crack. When welding galvanized steel, the zinc layer oxidizes, melts, evaporates and even volatilizes white smoke and steam at the bevel surface and edges at the arc heat, easily causing the weld pores.

Hot galvanized is the addition of some auxiliary material to the molten zinc at a high temperature, and then attaching the zinc-dip bath metal structure to the metal member on the zinc layer. Hot-dip galvanizing with anti-corrosion ability, coating adhesion, good hardness and so on. Cold galvanized is the use of the degreased workpiece electrolysis device, the pickling component is zinc salt solution, and connected to the cathode electrolysis device; zinc electrolysis device placed on the front of the connecting plate, the power supply is reversed, moving from the positive to negative direction current The use of it to deposit a layer of zinc on the workpiece.

galvanized zinc sheet appears on the surface, that is, those rough small particles do not polish, which not only affect the appearance of small particles, but also affect the use. This is because the bottom of the dregs is too agitated and the surface temperature of the galvanized sheet is too high because of the good affinity with the aluminum, aluminum and zinc in the zinc solution, except for the bottom ash float process Together, attached to the galvanized sheet surface. For example, the bottom ash is often treated to maintain the cleanliness of the galvanized steel. The temperature of the zinc-plating solution is not too high and is maintained at a suitable temperature of 440 to 450 degrees Celsius. Liquid zinc aluminum content is not high, maintained at about 0.1% is appropriate, but also pay attention to inventory will increase oxidation, etc. In short, as long as the strict production of zinc, or can be eliminated.

The advantages of galvanized pipe are as follows: 1, Galvanized pipe can be protected by hot galvanized surface, and the inner cavity of the tube or any other coating angle difficult to enter, deepen the zinc easily covered to the top, so that the entire galvanized pipe is protected.

Low-carbon steel pipe generally rolled into angle, channel, I-beam, steel, steel or steel. It is widely used in various building components, containers, huts, stoves and agricultural machinery. Low-carbon high-quality steel rolled into thin-sheet production car cab, hood and other deep wahsed products. It can also be rolled into strips for dmanding production of machine parts. Mild steel is generally not used after heat treatment, when the carbon content by carburizing or cyanindation of 0.15% or more, can be used for shafts, bushings, sprockets and other parts of the surface temperature requirements, wear-resistant.

Livable cities generally have two pipeline systems that supply water pipes and sewage sewer system, also known as the third set of piping systems in the pipeline system, is a water supply system, sewage together, after purification treatment, continue to apply as a living miscellaneous water supply system. United States, Japan, India, Russia have established a municipal wastewater reuse system.

The welded pipe is called the welded pipe for short, and the commonly used steel or steel strip is welded by the curled forming of the unit and the mold. The production process of welded steel pipe is simple, the production efficiency is high, the specifications are many, the equipment is less, but the general strength is lower than that of the seamless steel pipe. Since 1930s, with the rapid development of high-quality strip rolling production and progress of welding and testing technology, and constantly improve the weld quality, varieties and specifications of welded steel pipe is increasing, and in more and more fields especially in the heat pipe, who spare decorative tube, tube for low-pressure fluid etc. instead of the seamless steel tube. The production process of the straight welded pipe is simple, the production efficiency is high, the cost is low, and the development is fast. The strength of the spiral welded pipe is generally higher than that of the longitudinal welded pipe. The welded pipe with larger diameter can be produced with a narrow billet, and the welded pipes with different diameters can also be produced with the same width blank. But compared with the same length, the length of the weld increases by 30~100%, and the production speed is low.

According to the manufacturing process of steel pipe, seamless steel pipe can be divided into (SML), as the main oil gathering pipe and the small caliber high pressure natural gas pipeline, the number for the long oil pipeline is very few, most of the pipeline is the use of high-frequency welded pipes (ERW), spiral submerged arc welding pipe (SSAW) and LSAW (LSAW) three. The following table for several technological characteristics of the steel pipe and the quality of performance comparison: high-frequency welded pipes (ERW) according to the different welding modes are divided into induction welding and contact welding in two forms, the hot-rolled steel coil as raw material, after pre bending, continuous molding, welding, heat treatment, sizing, straightening, cutting and other processes. Compared with the spiral welded seam with short, high dimensional accuracy, uniform thickness, good surface quality, high pressure, but the drawback is the production of small diameter thin-walled tube only, weld is easy to produce gray spot and lack of fusion, groove corrosion defects.

ERW is the first letter of resistance welding Electric resistance welding abbreviation ERW pipe and submerged arc welding pipe welding methods are significantly different, the use of unfilled metal pressure welding, the weld is not filled with other components, by high-frequency current The skin effect and the proximity effect, so that the instant plate edge heated to the welding temperature, squeezed by the extrusion roller forging the formation of the weld.