welded steel pipe

The production methods of seamless steel pipes can be roughly divided into oblique rolling method (Menesmann method) and extrusion method. The oblique rolling method (Menesmann method) is to first pierce the tube blank with oblique rolling rolls, and then extend it with a rolling mill. This method has a fast production speed, but requires high machinability of the pipe blank, and is mainly suitable for producing carbon steel and low alloy steel pipes. The extrusion method is to use a piercing machine to pierce the pipe blank or steel ingot, and then use an extrusion machine to extrude it into a steel pipe. This method is less efficient than the oblique rolling method and is suitable for producing high-strength alloy steel pipes. Both the oblique rolling method and the extrusion method must first heat the billet or ingot, and the steel pipe produced is called hot-rolled pipe. Steel pipes produced by hot working methods can sometimes be further cold worked as needed. There are two methods for cold working: one is the cold drawing method, which involves pulling steel pipes through a drawing die to gradually thin and elongate them; Another method is the cold rolling method, which applies the hot rolling machine invented by the Menesmann brothers to cold working. The cold processing of seamless steel pipes can improve the dimensional accuracy and processing smoothness of the pipes, and improve the mechanical properties of the materials.

Materials of alloy steel pipes Alloy steel pipes have good hardness, which are widely used for pipelines for transporting oil, natural gas, gas, water and certain solid materials. The common alloys are ferroalloys, ferro-chromium alloys, iron-nickel alloys, aluminum alloys(light weights) and copper alloys(good thermal conductivity). The main materials include 16-50Mn, 27SiMn, 20-40Cr, 12-42CrMo, 16Mn, 12Cr1MoV, T91, 27SiMn, 30CrMo, 15CrMo, 20G, Cr9Mo, 10CrMo910, etc. Alloy steel pipes made from 16Mn belong to low alloy steel pipes. Applications of alloy steel pipesAlloy steel pipes are mainly used for high-pressure and high temperature pipelines and equipment such as power plants, nuclear power, high-pressure boilers, high temperature superheaters and reheaters. Three expressions of alloy steel pipe specifications 1. The first one is the outer diameter plus wall thickness. For example, an alloy steel pipe with an outer diameter of 57mm can be indicated by 57x3. 2. The second one is using the inner diameter, that is, the nominal inner diameter. For example, an alloy steel pipe with an outer diameter of 57mm is indicated by DN50. 3. The third one is the inch. For example, an alloy steel pipe with an outer diameter of 57mm can be indicated by 2 inches (1 inch equals to 25.4mm.)  Specific welding steps of alloy steel pipesWelding processes of alloy steel pipes are heating before welding, quenching and tempering after welding. HeatingBefore welding the alloy steel pipe, it should be heated, and weld it after the temperature is controlled for 30 minutes. The heating and virtual beam temperature tempering of welding are actively operated by the temperature control cabinet for temperature adjustment. Adopt far infrared tracking heat treatment furnace plates. Intelligently and actively set the graph and record the graph, and use the thermal resistance to accurately measure the temperature. The thermal resistance measuring point is from 15mm to 20mm away from the edge of the weld during heating. Welding methods1. In order to prevent welding deformation of the alloy steel pipe, each column joint is welded symmetrically by two people, and the welding direction is from the middle to the two sides. After welding one to three layers, reverse planing should be carried out. After the carbon arc gouging is used, the welding equipment needs to be polished. The welding surface should be nitridation treated to show the metal texture and prevent the surface carbonization from causing cracks. The outer hole is welded once, and the remaining inner holes are welded once. 2. When welding alloy steel pipes with two layers, the welding direction should be opposite to that of the layer of alloy steel pipes. The butt welds of each layer are separated by 15 to 20mm.3. The welding current, welding speed and number of overlapping layers of multiple welding machines should be maintained.4. In welding, you must start welding from the pilot arc board and finish welding on the pilot arc board. Cut, polish and clean after welding.  Quenching and tempering after weldingAfter the seam are welded, it should be tempered within 12 hours. If the alloy steel pipe cannot be quenched and tempered immediately, heat preservation and slow cooling should be adopted. When the alloy steel pipe is tempered, temperatures of the two thermal resistances should be measured and the thermal resistance should be welded on both sides of the seam.

Hot dip galvanized steel pipe is widely used in construction, machinery, coal mine, chemical industry, electric power, railway vehicles, automobile industry, highway, bridge, container, sports facilities, agricultural machinery, petroleum machinery, prospecting machinery and other manufacturing industries. ASTM A53 Galvanized Steel Pipe is a welded steel pipe with hot-dip or electro galvanized surface.  Galvanizing can increase the corrosion resistance of steel pipe and prolong its service life.  The galvanized pipe is widely used, not only as the pipeline for water delivery, gas, oil and other general low-pressure fluid, but also as the oil well pipe and oil pipe of the petroleum industry, especially the offshore oil field, the oil heater, condensate cooler, coal distillate wash oil exchanger pipe of the chemical coking equipment, as well as the trestle pipe pile, the support frame pipe of the mine tunnel, etc.   ASTM A53 Galvanized Steel Pipe is to make molten metal react with iron matrix to produce alloy layer, so that the matrix and coating are combined.  Hot dip galvanizing is to pickle the steel pipe first, in order to remove the iron oxide on the surface of the steel pipe, after pickling, it is cleaned by ammonium chloride or zinc chloride aqueous solution or the mixture of ammonium chloride and zinc chloride aqueous solution tank, and then it is sent into the hot dip galvanizing tank.  Hot dip galvanizing has the advantages of uniform coating, strong adhesion and long service life.  

1. Using the three-dimensional space simulation module, the three-dimensional coordinate system of the curved surface is established according to the relationship between the curved surface and the building axis provided by the original design drawings, and the three-dimensional structure diagram of the hyperbolic arc roof is drawn. Three dimensional structural drawing of arc roof.  2. According to the load calculation, the vertical pole spacing and horizontal pole step distance of steel pipe scaffold for roof construction are determined, and the steel pipe scaffold is simulated and positioned in the three-dimensional structure diagram. Pre positioning of steel pipe scaffold.  3. The intersection of the vertical pole of the steel pipe scaffold and the horizontal pole of the steel pipe scaffold is generated into a plane projection grid line on the hyperboloid. Generate the steel pipe grid projection line.  4. Calculate the elevation of the corresponding point on the spatial hyperboloid at each grid node in the horizontal projection plane coordinate system.  5. Record the three-dimensional coordinates, grid point spacing and other parameters of all intersections.