Seamless steel pipe is a hollow cross section, no seams round, square, rectangular steel. Seamless steel ingot is made of perforated or solid tube capillary tube, and then by hot-rolled, cold-rolled or cold- call is made. Seamless hollow sections, a large number of channels for transporting fluids, steel pipe and solid steel bar, etc. compared to the same torsional strength in bending, lighter, which is an economic cross-section steel and widely used in the manufacture of structural parts and mechanical parts, such as drill pipe, automotive drive shafts, bicycle frames and construction using steel scaffolding. Seamless pipe in chemical oil health food machinery and other industrial use is relatively wide, thanks to seamless pipe stainless steel properties of corrosion resistance and structure itself. The cast ingot can damage tissue, grain refining of steel, and eliminate defects in the microstructure, so the steel dense tissue, improve the mechanical properties. This improvement is mainly reflected in the rolling direction, so that the steel is no longer certain extent isotropic; pouring bubbles formed cracks and porosity, but also in under the action of high temperature and pressure welding. By cross-sectional shape of the pipe can be divided into tube and shaped tubes. Since the perimeter of equal conditions, the maximum area of a circle with a circular tube can carry more fluid. In addition, the circular cross section to withstand internal or external radial pressure, the force is uniform, so the vast majority of the pipe is pipe. Besides, seamless tube divided into carbon steel seamless pipe and alloy seamless pipe according to the difference of material.
Seamless steel pipe production process in general can be divided into two kinds of cold-drawn and hot-rolled, cold-rolled seamless pipe production processes generally more complicated than hot-rolled, tube must first conduct a three-roll rolling, extrusion to be sizing test, if the surface does not respond after cracking tube to be cut through the cutting machine, cut to a length of about one meter blank. Then enter the annealing process, the annealing pickling use acidic liquids, pickling should pay attention to whether there is a lot of surface blistering generated, if a large number of bubbles generated illustrate the quality of steel reach the appropriate standards. Appearance is shorter than hot rolled seamless steel tube, cold-rolled seamless steel pipe wall thickness generally smaller than it, but the surface looks brighter than the thick-walled seamless pipe, the surface is not too more rough, not too many glitches caliber. Hot-rolled seamless delivery status after the state is generally rolled after heat treatment delivery. After hot-rolled seamless quality control staff after going through a strict hand-selected, after the inspection to be coated with oil, then followed by repeated drawing experiments after handling hot piercing experiments If the perforation is too large will be expanded diameter straightening corrected. After straightening by the transfer device to the testing machine for testing experiments, the final label for specifications choreography and placed them into the warehouse.
