The Difference Between the Hot-Rolling and Cold-Drawing Seamless Steel Pipe

Seamless steel pipe, according to the differences of manufacturing process., is divided into hot-rolling seamless steel pipe and cold-drawing seamless steel pipe.

Hot-rolling seamless pipe is generally produced in the automatic rolling machine. After inspection and removal of surface defects, the solid tube is cut into required length, end to end in the perforated tube surface centering, and then sent to the furnace heating, piercing the piercer. While continuing to rotate the perforation and forward, under the action of the roll and the head of the tube gradually formed an internal cavity, said capillary. Continue rolling and then sent to the automatic rolling machine. Finally, after all the Leveling machine leveling the wall thickness and the sizing mill sizing, to meet the specifications.

The solid tube into a hollow capillary; we can understand stereotypes, both the rolling section as an annular; their equipment is called puncher. Perforation process requirements are: First, to ensure uniformity of the capillary wall thickness piercing, small oval, high precision geometry; followed by capillary inner and outer surfaces to be smooth, without scarring, folding, cracks and other defects; Section Third is to have the appropriate speed and rolling cycle perforated to fit the rhythm of the entire production crew, so that the capillary finishing temperature can meet the requirements of rolling machines. The thick hair becomes thin-walled tubes (nearly finished wall thickness) of the blank pipe; we can set them as a wall, the wall thickness is determined that the value of the process according to the subsequent shortage of tube process and reducing the amount of empirical formula; the device is called rolling machine. On the rolling process requirements are: first, the thick hair become thin-walled tube blank pipe (minus wall extends) to ensure that when the first blank pipe wall thickness with high uniformity; secondly shortage tube inner and outer surfaces with good quality.

Cold drawing is usually carried out on 0.5 ~ 100T single chain or double chain drawing machine. Cold rolling is performed below the recrystallization temperature, and hot rolling is rolling at a temperature above the recrystallization conducted. Cold-drawing seamless steel pipe is often small diameter while hot-rolling seamless steel pipe is often a large diameter. Generally speaking, for cold-drawing seamless steel pipe, accuracy and price both higher than hot-rolling seamless steel pipe. Mainly because of,poor control of the thickness and width of the edge in this respect. We are familiar with thermal expansion and contraction, since the beginning of the hot rolling out even the length, thickness are standard, and finally cooled or there will be some negative difference, this negative difference edge width wider, thicker the more obvious manifestations. So for large steel for steel edge width, thickness, length, angle, and no law requires very precise edges.

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