According to the section shape， the steel pipe is divided into:
1 According to the purpose， the welded pipe has general purpose and high temperature and high pressure. The pipe used in the latter is often special alloy steel. The problem of shrinkage cracks in the welding process and the mechanical properties of the pipe in the heat affected zone must be considered and solved， and the mechanical properties of the pipe in the heat affected zone will not be greatly changed due to the influence of welding operation.
dNicoyaUnder the action of thermal stress， because the initial temperature of the surface layer is lower than that of the heart and the shrinkage is greater than that of the heart， the heart is pulled. At the end of cooling，Products Show because the final cooling volume shrinkage of the heart cannot be carried out freely，San FelipeCombien coûte 75 tubes galvanisés par mètreTous les employés the surface layer is compressed and the heart is pulled. That is under the action of thermal stress， the surface of the workpiece is finally compressed and the center is pulled. This phenomenon is affected by factors such as cooling rate， material composition and heat treatment process. The faster the cooling rate， the higher the carbon content and alloy composition， the greater the uneven plastic deformation caused by thermal stress during cooling， and the greater the final residual stress. On the other hand， i.e. the transformation from austenite to martensite， the increase of specific volume will be accompanied by the expansion of workpiece volume， and each part of workpiece will undergo phase transformation successively，Products Show resulting in inconsistent volume growth and structural stress. The final result of the change of tissue stress is the tensile stress on the surface and the compressive stress in the center， which is just opposite to the thermal stress. The microstructure stress is related to the cooling rate， shape and chemical composition of the workpiece in the martensitic transformation zone.
The advantage of the reinforcement mesh system is ecological. It is filled with natural stone materials. There is a gap between the stone materials to allow plants to grow in it. It can also plant plants on it. It has the dual effects of engineering slope protection and plant slope protection. The Ecological Grid mat is a combination with a height of cm ~ cm， mostly a multi grid box separated by spacer mesh.
LVon drozzoThe pollution of the joint causes the welding cracking. The composite pipe welding is an accurate work. If it is not done well， it will not only waste resources， but also lead to work efficiency， rework and restart， and waste financial resources.
IeGalvanized pipe cleaning， east-west derusting， pickling and shot blasting
After hot-dip galvanizing of steel structure it is equivalent to one-time annealing treatment，Products Show which can effectively improve the mechanicalof steel matrix， eliminate the stress during steel forming and welding，San FelipeCombien coûte 75 tubes galvanisés par mètreTous les employés and is conducive to turning of steel structure.
The use of welded steel mesh can make the project construction convenient. As long as the welded reinforcement mesh is laid as required， the concrete can be irrigated， eliminating the links such as on-site cutting， placing and binding of reinforcement one by one.
kWays to obtain surface compressive stress characteristics of alloy tubes
T According to the pipe wall thickness， pipes made of relatively thin materials such as steel strip can be welded with high frequency， and some thin-walled pipes can be welded with shielding gas; Pipes with wall thickness more than mm can be welded by hand.
WInstallation requirementsHowever， compared with plastics， these pipes like other metals，Reinforcement, galvanized pipe, seamless pipe, welded pipe, alloy pipe, I-beam-Shandong Kaiwen metal material Co., Ltd remain stable and will not be affected by high temperature.
sN China is a big steel country.
Generally， what are the customer&#;s requirements and standards during acceptance? When the galvanized pipe is accepted， you can judge whether it is qualified from the appearance， or whether there are problems such as missing plating or bubbles on the outer wall of the whole square pipe. Only by solving these problems in time can it be judged as qualified and better used.
It has a thick and dense pure zinc layer covered on the steel surface， which can prevent the steel substrate from touching with any corrosion solution and maintain the steel substrate from corrosion. In general atmosphere， the surface of zinc layer forms a thin and dense zinc oxide layer， which is difficult to dissolve in water， so it plays a certain maintenance effect on steel matrix. If zinc oxide and other components in the atmosphere form insoluble zinc salts， the anti-corrosion effect is more ideal.
Quotation sheetmGalvanized pipe has excellent corrosion resistance. Compared with traditional steel， its application life is longer. Secondly， this kind of pipe has strong resistance to baking. In case of critical situation， it will not lead to the collapse of building structure in a short time. In addition， this kind of pipe also has a practical advantage， that is， and the operation efficiency has been greatly strengthened. In this regard， it is not difficult to understand why the galvanized pipe is so favored by various construction units.
FThe section of I-beam has good straight pressure and tensile resistance but the section size cannot resist torsion because the wing plate is too narrow. On the contrary， H steel has its own advantages and disadvantages.
Classification by wall thickness
xNicoya As long as the pipe material is high-strength alloy steel， including alloy steel pipes with temperature resistance， pressure resistance， wear resistance and low temperature resistance， the welding process shall be focused on preventing the tendency of martensite structure and cracks due to welding high-temperature operation. The general process requirements are that the welding rod shall be selected and baked as required and sent to the welder for use. The oil and water shall be removed before welding on both sides of the weld Rust and sundries shall be removed and cleaned. The welding line energy shall be as small as possible to minimize the swing during the welding process. The arrangement of the last weld shall have annealing effect on the heat affected zone as far as possible. Slow cooling after welding， cover with asbestos cloth， etc.
kWIn order to ensure the welding quality of welded pipe， the forming roll， guide roll， extrusion forming roll and sizing roll must be adjusted once， and then the most important thing is to adjust the closing plate hole， guide roll and extrusion forming roll of the forming roll. Among them， reducing the edge widening， and ensuring that the weld is vertical without screwing into the extrusion roll.
Pickling: if the material cannot be removed after cleaning， pickling will be selected. Pickling of galvanized pipe is divided into chemical and electrolytic. How to prevent white rust of galvanized seamless steel pipe? It has a certain anti-corrosion effect on the pipeline.