Qianxi large diameter square and rectangular tube production
Square pipe is a kind of name for square pipe and rectangular pipe, that is, steel pipes with equal and unequal side lengths. It is rolled from strip steel after processing. Generally, the strip steel is unpacked, leveled, curled and welded to form a round pipe, which is then rolled into a square pipe and cut to the required length. Square and rectangular tubes are also called square and rectangular cold-formed hollow steel sections, which are called square and rectangular tubes for short, and their codes are F and J.
Qianxi large diameter square and rectangular tube production
1. Seamless square tube electrochemical coloring method: refers to the color of the film formed by electrochemical oxidation in a specific solution. 2. High temperature oxidation coloring method: immerse the workpiece in a specific molten salt and adhere to the corresponding process parameters, so that the profiled tube can form a certain thickness of oxide film and show various colors. 3. Chemical oxidation coloring method: refers to the color of the film formed by chemical oxidation in a specific solution, including salt method, mixed sodium salt method, sulfuration method, acid oxidation method and alkaline oxidation method. The common bacteriological method is widely used, but to ensure the color difference of a batch of products, reference electrodes must be used for control. 4. Gas phase cracking coloring method: it is relatively complex, and is rarely used in the industrial consumption of seamless square tubes. 5. Chemical method of ion stacking oxide coloring method: put the stainless steel seamless square tube in the vacuum coating machine to stop vacuum evaporation coating. This method is suitable for processing large quantities of products because of its large investment and high cost.
Qianxi large diameter square and rectangular tube production
Under the action of bending moment, during the transition from elastic deformation to plastic deformation of the full section of the cross section at the bending part of the rectangular tube, the outside of the strip steel is pulled, the inside is pressed, and at the same time, it is also affected by the radial pressure. In addition, the rigidity of the roll tool ring angle limits, on the one hand, the neutral layer of the rectangular tube strip steel moves inward, and on the other hand, the thickness of imperial steel is reduced at the bending part. In the process of bending from the outside to the inside to move the neutral layer inward, the circumferential stress is far greater than the radial stress, and the radial strain mainly occurs outside the neutral layer. Therefore, the radial displacement velocity of each layer of fiber outside the rectangular tube is different. At the inner side, due to the small radial strain, the radial displacement velocity of each layer of fiber has little difference, which is almost a constant. Here, the radial displacement velocity inside the neutral layer is treated as a constant.
Qianxi large diameter square and rectangular tube production
(1) Alloy composition For seamless square tubes, elements 0, 10 and F are the main alloy elements that make the alloy have good pitting corrosion resistance. Other elements may also have corresponding effects. K and other elements will reduce the pitting corrosion resistance of seamless square tubes. It is certain that the effect of alloying elements on the pitting corrosion resistance of data can be summarized briefly into favorable effects. 13. The impact of 0 is variable. 3 is beneficial in solid solution, but it is harmful when it is precipitated as intermediate metal phase, 0 is good in solid solution, and it is harmful when it is precipitated as carbide, but it has slightly adverse effects. (2) The study on cold working of austenitic seamless square tubes shows that the number of etch pits on the surface of the specimen increases and the size of the etch pits decreases after cold working. This is due to the increase of dislocation density during cold processing. Dislocation exposed on the surface is easy to cause corrosion pits. Cold processing tends to increase pitting corrosion. (3) For a given alloy environment system, the element that determines the corrosion potential of alloy spots is the brightness of the data surface. In fact, it is meaningless to compare the corrosion tendency of stop points of alloys with different surface brightness. The influence of surface brightness on the pitting corrosion performance of seamless square tubes is shown in the figure. It indicates that in the same data environment system, if the surface brightness is different, the difference of pitting corrosion potential can be more than 14. (4) The oxide formed by heating of the seamless square tube in the air may have a serious impact on the pitting corrosion performance. The microstructure of hot-dip galvanized square tubes plays an important role in the pitting corrosion resistance of alloys. Various phases, such as sulfide inclusion and 3-ferrite. Phase, sensitized grain boundary and weld may have a decisive impact on the pitting corrosion resistance of steel, and they are all sensitive parts to pitting corrosion. For cast seamless square tubes with complex microstructure and martensite seamless square tubes with microstructure sensitive to heat treatment process, the relationship between pitting corrosion and constituent phases is closer. It is pointed out that the complex manganese sulfide inclusions are more sensitive to pitting corrosion. Therefore, the use of aluminum deoxidizer should be prevented when smelting seamless square tubes. (5) The oxide film produced by welding may be detrimental to the pitting corrosion resistance of the alloy in strong chloride solution. (6) The main function of passivation treatment is to dissolve the inclusions and infections on the surface of the seamless square tube to make it clean. It can also remove the manganese sulfide inclusions on the surface, which may become the source of pitting corrosion, thus improving the pitting corrosion resistance of the seamless square tube. It should be noted that the seamless square tube should be cleaned with sodium hydroxide solution after passivation treatment.
