There are three common methods for joining plastic-coated composite steel pipes, which are screw connection, flange connection, and groove connection. The thread connection is a traditional form, which is mostly used between DN15-100. The connection technology is divided into multiple steps such as threading, deburring, plastic pipe chamfering, cutting, screw corrosion protection, and connection. The length of the bushing is different according to the use of the pipe fittings, but one thing is the same, that is, it must be ensured that the end face of the pipe touches the silicone rubber at the root and conforms to the shape of the secondary seal. The pipeline device with working pressure ≥1.6MPa can be applied. The trend of screw connection is that the cost is low, the operation is simple and convenient, but it is easy to be restricted by the caliber. The plastic composite steel pipe with screw connection is in the aspects of comprehensive performance, cost performance, and application fields. Composite pipes are mainly divided into two categories, plastic-coated steel pipes and plastic-lined steel pipes. These two kinds of pipes are now popular green environmental protection pipes, which are people's favorite pipes***. They haven't risen in China for a long time, they are a new type of composite materials, but their scope of application involves various major engineering fields. What is the difference between plastic coated and plastic lined composite steel pipes? Plastic-coated pipe fittings are extruded and coated with a hot-melt adhesive layer through a co-extrusion method, and then put into a zinc pipe together, heated and pressurized in a plastic lining unit and cooled and shaped, then the plastic pipe is compounded on the inner wall of the steel pipe . The connection method of fire-fighting plastic pipe fittings is the same as that of hot-dip galvanized pipe. The two ends of the pipe are tapped. The connecting pipe fittings are made of inner wall composite plastic layer and galvanized ma steel pipe fittings. When connecting, apply sealant to the joints and threads. Large-diameter pipes Use snap ring or flange connection. The connection method of the steel-plastic composite pressure pipe is similar to that of the aluminum-plastic pipe. The pipe can be bent at a small angle in one direction, so it is not necessary to use pipe fittings for small-angle steering, mechanical flaring crimping for large-angle steering, and internal seals for connecting pipes deal with. The inner rib embedded plastic-lined pipe is connected by a special snap ring, without tapping on the steel pipe, the installation is more convenient, and the pipe can be used for surface and concealed installation. The surface of plastic coated steel pipe is smooth, beautiful, and the color of external light can be selected at will. Because the inner wall is smooth, it can prevent the growth of microorganisms, the resistance of the transport fluid is small, it can increase the flow rate, save energy, and is used in various water supply and drainage projects. The use of plastic coated steel pipes is very common in our construction industry, mainly because these types of steel pipe materials have certain characteristics. First of all, it is mainly produced by using steel pipe as the basic body, and it is produced by technical development by specialized personnel.
Introduction to the connection method of plastic-coated composite steel pipe; First, the connection method of plastic-coated steel pipe connection method such as threaded flange and groove. The composite pipe has passed the industry test of the building materials testing center, the sanitary standard test of the provincial and municipal BING prevention and control center, the sanitation of the municipal health bureau, ISO9001 quality system certification, etc. The plastic coated power cable threading steel pipe is black, and the surface of the coating is smooth and beautiful. The steel-plastic composite pipes such as PE, internal and external plastic coated PE, external anticorrosion and thermal insulation pipes have internal and external coated PE and internal and external cold spray epoxy resin. Second, the wall of plastic-coated steel pipe is smooth, good drainage performance, small fluid resistance, and no scaling is a big point compared to other pipelines, which can greatly reduce losses. At the same time, the linear expansion coefficient of large-diameter plastic-coated pipes is very small, which makes it very beneficial as a main water delivery pipe. Epoxy resin greatly overcomes the defects of large linear expansion coefficients of other plastics and ordinary pipes. Large-diameter plastic-coated steel pipe is a cost-effective product upgraded from traditional steel-plastic pipe and galvanized pipe. It has comprehensive characteristics, that is, it has high strength, high extensibility, low temperature brittleness, small expansion coefficient, and corrosion resistance, wear resistance, and small fluid resistance of plastic pipes. It belongs to a new type of water supply and drainage, anti-corrosion green Large-diameter pipes are increasingly used by various domestic industries. The internal and external plastic-coated composite steel pipe is a new type of pipeline material newly developed in China. It has a plastic protective layer both inside and outside, with a composite structure of reinforced welded steel pipe or seamless pressure-bearing steel pipe in the middle, which overcomes the easy rust, Corrosion, high pollution, and the defects of low strength and easy deformation of plastic pipes, which integrate the common points of steel pipes and plastic products, are environmentally friendly products that are widely used. Plastic-coated composite steel pipe is a steel composed of a layer of polyethylene resin, ethylene-acrylic acid copolymer, epoxy (EP) powder, polypropylene (PP), or polyvinyl chloride (PVC) and other organic materials with a thickness of the inner wall of the steel pipe. Plastic composite pipe, which not only has the advantages of high strength, easy connection, and resistance to water flow impact of steel pipe, but also overcomes the shortcomings of steel pipe corrosion, pollution, scaling, low strength of plastic pipe, poor fire performance, etc., design life Up to year. Whether it is in engineering construction or machinery manufacturing, it is inseparable from steel pipes. That is to say, steel pipes play a very important role in people's lives. If there are no various pipes, then in construction, various engineering construction awards are difficult to carry out.
L415 high-frequency straight seam welded pipe (named because the welded pipe is in a straight line). According to different uses and different post-production processes (which can be roughly divided into scaffold tubes, fluid tubes, epoxy wire sleeves, bracket tubes, guardrail tubes, etc.). There is no difference between producing straight seam welded pipe (excluding pipe processing) and producing other spiral steel pipes. Deformation heat treatment is widely used in the production of straight seam welded pipes today. This is an important feature and an important way to improve the mechanical properties of Q345B straight seam welded pipes. The so-called deformation heat treatment is to make the steel and alloy undergo plastic deformation in the austenite state, and then perform quenching without recrystallization of the deformed austenite. For hot-rolled petroleum pipes, epoxy resin should control the deformation and the temperature of the final rolling. The temperature of the straight reducer of the straight welded pipe is generally above 850℃ (at this time, the steel structure is still in the austenitic state). Quenching can complete the deformation heat treatment process. At different impact temperatures, the value of the impact is also different. The welding current in swing welding of straight seam steel pipes is slightly larger than that of traditional welding methods; secondly, the elongation of tungsten pole in swing welding of straight seam steel pipes is determined according to the wall thickness of the pipe, which is usually 4-5mm; the flow rate of argon gas is slightly larger than that of traditional welding methods , About 8-10l/min; * is the oscillating amplitude of the straight seam steel pipe swing is 2mm at the blunt edge of the two sides of the fusion; the left and right hand flexible cooperation, uniform swing, uniform wire feeding straight seam welded pipe transportation development direction Rotate the tube several times when developing the mating direction in the direction of large diameter and high pressure, so that the offset value is reduced and the gap is kept uniform. What are the main uses of straight seam steel pipes? Generally, chemical and electrolytic methods are used for pickling. Pipeline corrosion protection only uses chemical pickling, which can remove oxide scale, rust, and old coatings. Sometimes it can be used as sandblasting. Reprocessing after descaling is approved by the purchaser. Hot-rolled seamless straight seam steel tubes can be batch-sampled according to the rolling root array. Descaling of hand tools can reach Sa2 level, and descaling of power tools can reach Sa3 level. If the steel surface is firmly attached Iron oxide scale, the tool's rust removal effect is not ideal, and the rust removal speed of the straight welded pipe with the anchor depth required for anti-corrosion construction cannot be achieved: it is used to transport, distribute, control or stop fluid flow.
The design pressure of L415 high frequency straight seam welded pipe shall not be lower than the set pressure of the safety pressure relief device. The production process of straight seam steel pipe belongs to the elastoplastic large deformation and contact nonlinear multiple nonlinear coupling problem, which makes the theoretical research and experimental research far behind the engineering theory. Even if the finite element method is used, there are still many difficulties. At present, there is no perfect numerical simulation research. jobs. In engineering theory, the design of the forming process and forming unit of the straight seam welded pipe still uses the experience design method. The main drawback of the experience design method is that the rationality of the process and roll design must be tested by consumption theory. The cost is high and the cycle is long, which is not suitable for market economy. Unfolding needs. The application of elastoplastic large deformation and contact nonlinear finite element method, and the application of large-scale multiphysics finite element software-ANSYS, established a more practical three-dimensional finite element model of the welded pipe forming process, and discussed the small diameter welded pipe blank in a single pass , The forming process in multiple passes, obtained the distribution law of the change of stress and strain and the change law of curvature and pressing force of the tube blank during the forming process, and made the plane distribution diagram of stress and strain on the half tube blank . The main stress of the straight seam pipe for water supply and drainage is just perpendicular to the direction of the low impact resistance of the pipe, while the spiral pipe is staggered in the direction of the low impact resistance of the pipe, so that the disadvantage of the long weld seam of the spiral pipe has become a trend. Both spiral steel pipes and straight seam steel pipes belong to the series of welded steel pipes, and the number of applications is very large, but in terms of price, spiral steel pipes have a greater tendency than straight seam steel pipes. It can be said that the price of spiral steel pipe is lower, and the specific specifications used in the project mainly depend on the design requirements. Below we will compare spiral steel pipe and straight seam steel pipe. The left side of the above two products is a spiral steel pipe, and the right side is a straight seam steel pipe. The weld seam of the spiral steel pipe is a spiral shape, and the weld seam of the straight seam steel pipe is a straight line. Straight seam steel pipes are formed by hot-rolled coils formed by a forming machine, using the skin effect and proximity effect of high-frequency current to heat and melt the edges of the tube blanks, and pressure welding under the action of squeeze rollers to achieve the production of steel pipes.