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According to the welding deformation theory, the main factors affecting the welding deformation are: the larger the weld size, the more deposited metal, and the larger the deformation; When the weld size is equal, the greater the heat input of the weld, the greater the deformation formed; When welding large and long welds, the deformation of section welding is smaller than that of straight welding; The welds are arranged asymmetrically or symmetrically but asymmetrically. The more serious the deviation of the welds, the greater the deformation; The smaller the rigidity of the component, the greater the deformation. Welding standard After process experiment and process analysis, it is confirmed that the square tube butt weld adopts double-layer CO2 gas maintenance welding. H08Mn2SiA, 1.2mm welding wire is used for welding data; The maintenance gas is pure CO2. The welding current of the first layer of weld is 200~250A, and that of the second layer is 240~320A; The arc voltage is 24~26V. The process requirements are: one layer of weld must be fully welded to ensure the reverse side is well formed; Welding current, arc voltage, wire feeding speed and welding speed can be adjusted according to the equipment model
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Rectangular tube is a kind of light thin-walled steel tube with hollow square section, also known as steel cold-formed section. It is a shape steel with square section and overall dimension made of Q235 hot-rolled or cold-rolled strip or coil as the base material after cold bending and forming and then high-frequency welding. Hot rolled extra thick wall square tubes, except for the thickening of wall thickness, have corner dimensions and edge straightness to the extent that they exceed the resistance welded cold formed square tubes.
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Square alloy tube with ferrite structure in service. Chromium content is 11%~30%, with body centered cubic crystal structure. This kind of steel generally does not contain nickel, and sometimes contains a small amount of elements such as Mo, Ti, Nb, etc. This kind of steel has the characteristics of high thermal conductivity, small shrinkage coefficient, good oxidation resistance, stress corrosion resistance, etc. It is mostly used to manufacture parts and components resistant to atmospheric, steam, water and oxidizing acid corrosion. The application of this kind of alloy square tube is limited because of its poor plasticity, significantly reduced plasticity and corrosion resistance after welding. The application of secondary refining technology (AOD or VOD) can greatly reduce the interstitial elements such as carbon and nitrogen, thus making this kind of steel widely used.
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1. Performance index analysis of rectangular tube - plasticity: plasticity refers to the ability of metal materials to produce plastic deformation (permanent deformation) without destruction under load. 2. Analysis of performance index of rectangular tube - hardness: hardness is a pointer to weigh the soft and hard level of metal data. At present, the commonly used method for measuring hardness in consumption is the indentation hardness method, which uses an indenter of geometric shape to press into the surface of the metal data to be tested under load, and determines the hardness value according to the indentation level. 3. Performance index analysis of rectangular tube - fatigue: the strength, plasticity and hardness discussed above are all mechanical performance indicators of metal under static load.
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The manufacturing technology of fine steel pipes is very strict. Only a few steel pipe factories can meet the conditions for consumption of fine steel pipes, which leads to the appearance of fine steel pipes in the market, some of which are not really fine steel pipes. Therefore, when we purchase steel pipes, we should know some skills to distinguish fine steel pipes. But for ordinary steel pipes, it is indicated that they are not lubricated enough, and their toughness and torsional strength are not good enough. Once this steel pipe stops flaring or flattening, it is easy to show cracks. When these cracked steel pipes are used in machinery and equipment, they will present falling and broken residues. These residues will enter more and more delicate parts with the use of the equipment, which will affect the speed and progress of the equipment for a long time, presenting various equipment problems. If fine steel pipes are used, this phenomenon will be reduced in greater layers. Fine seamless steel pipe is a kind of high-precision steel pipe material after cold drawing or hot rolling. This allows the pipeline to be free from leakage under high pressure. Even after flaring, flattening and other operations, the pipeline will not show cracks. This ensures the normal operation of the equipment, speeds up the consumption efficiency and improves the overall interests. With the change of time, the supply and demand relationship of the market is also changing from time to time. This is why there are always some new products in the market. Because every industry hopes to have higher quality and higher performance products. In the steel pipe market, the speed of change will be even higher. Especially in recent years, the renewal rate of steel pipes has reached a peak. Under such a background, there are many steel pipes whose quality cannot keep up with this change, which have slowly disappeared. However, there are also some steel pipes that, depending on their quality and application performance, have opened up a larger market space, and fine steel pipes are one of them.
Directly supplied by Xingtai medium thick wall square tube manufacturer
1. Cooling curve of heat treatment. The heat treatment processing process generally includes three whole processes: heating, thermal insulation and refrigeration, in which heating is to change the ferrite to austenitic stainless steel, thermal insulation and insulation is to stainless steel the austenite, and the seamless square tube refrigeration method is different due to different processing technologies. The current situation of rectangular tube market products is mainly to dominate the refrigeration rate, Due to different cooling rates, they change into ferrite, martensite, austenite or mixed structure. 2. Ideal heat treatment mode. According to the regularity of steel refrigeration change, when waiting for the temperature in the critical value area, the refrigeration rate is high. According to the nose area of the C curve as soon as possible to prevent the transformation into ferrite or martensite mechanism. In the risk area where the austenite change is just beginning, the refrigeration rate must become slower to reduce the deformation or crack caused by the stress of the mechanism due to the mechanism change. 3. Cooling curve of quenching oil. The heat treatment quenching oil must have the said refrigeration characteristics. The seamless square tube has a faster refrigeration speed for parts at the temperature of the critical value area, and a slower refrigeration speed for parts at the temperature of the risk area. 4. Strength rules and deformation hazards. The critical value of different raw materials is different in the cooling rate, and the strength rules of the parts are also different when they are applied. The fineness of the current parts in the square tube market is also different in the rules governing deformation. Therefore, it is necessary to select quenching oil with moderate cooling rate according to the details of the strength rules and the consumption process rules governing deformation. 5. Selection of quenching oil for heat treatment of seamless square tube. The selection specification of quenching oil was mentioned from the consideration of heat treatment and heat treatment process: the cooling characteristics of quenching oil must meet the requirements of regular strength and no cracks are allowed to form, and the deformation governing heat treatment should find a very good blend between each other within the effective small range, and this divergent cooling rate rule is a rule clearly proposed for different temperature sections, This shows an orientation for the research and development of heat treatment quenching oil.
