Square and rectangular pipe is a name for square pipe and rectangular pipe, that is, steel pipes with equal and unequal side lengths. It is made of strip steel that has been processed and rolled. Generally, the strip is unpacked, flattened, coiled, welded to form a round tube, and then rolled into a square tube from the round tube and then cut to the required length. Widely used in machinery manufacturing, construction, metallurgical industry, agricultural vehicles, agricultural greenhouses, automobile industry, railways, highway guardrails, container skeletons, furniture, decoration and steel structure fields. So, why does brittle fracture occur in square and rectangular tubes?
Causes of brittle fracture of square and rectangular tubes
The pickling solution used in the pickling process of square and rectangular tubes is generally a mixture of various acids, mainly sulfuric acid, nitric acid and hydrofluoric acid. These mixed acids are highly corrosive and oxidizing, and the temperature of the corrosive medium It is also relatively high, which puts forward high requirements for the corrosion resistance of anti-corrosion materials.
There are many anti-corrosion materials suitable for square and rectangular pipes, and the best ones for seamless square and rectangular pipes are epoxy resin and its modified resin. The principle of pickling of square tube is to use acidic liquid to remove the oxide skin on the surface of the square tube after pretreatment, and remove the metal ions on the surface, so that it has a beautiful finish. The material forms of pickling include belt washing, tube washing, plate washing, line washing, etc. Due to defects such as cracks in the hot-rolled tube blank or after the high-precision cold-drawn tube is made into an oil cylinder, there is almost no fracture during use. Plastic deformation occurs, generally brittle fracture.
Brittle fracture is caused by a variety of reasons. For example, when there are precipitates on the grain boundary, no matter their strength is stronger or weaker than that of the matrix, it is the cause of cracks; the segregation of inclusions on the grain boundary is also the cause of fracture; in addition, even at the intersection far less than the yield limit Under the action of variable load, fatigue fracture will also occur. During the low-stress brittle fracture that occurs in high-strength metallic materials, the material structure is far from homogeneous and isotropic. The rational use of square and rectangular pipes to clean rusted pipe fittings ensures that the pipe fittings can serve the production for a long time and create more production benefits.
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