It is worth mentioning that the number of cold stretching and cold rolling may not correspond to each other. It can be several times of cold drawing, several times of cold rolling, even cold drawing without cold rolling, or cold rolling without cold drawing. The process is formulated according to the product situation and operated according to the process requirements. Furthermore, the commonality between cold drawing and cold rolling of manufacturers is that they can both make the wall thickness of semi-finished stainless steel seamless pipe thinner and the length longer. The difference is that the former operates faster, but the one-time growth is less; The latter operation is time-consuming, but the one-time growth can be more. The cold drawing and cold rolling of this enterprise are all carried out on automatic equipment, and the operator only needs to install the workpiece and control the button after debugging, so the work efficiency is relatively high. The heat treatment is also automatic. The workpiece goes in from one end of the furnace and comes out from the other end, and runs continuously. The time depends on the requirements of the user, the size of the wall thickness and the material. The fast time is less than 4~5 min, and the slow time is over 7~8 min.
Stainless steel seamless pipes processed by cold drawing and cold rolling as described above can only be regarded as semi-finished products, and the accuracy level is very low, which often fails to meet the requirements put forward by users, such as uneven wall thickness, bumps, scratches on internal and external surfaces, spots or pits, and so on, so it is necessary to repair and grind them. The specific operation procedure is: firstly, the cold-drawn and cold-rolled stainless steel seamless pipes are inspected, and the defective parts are grinded according to the inspection situation. In the form of grinding, mechanical integral grinding is usually used for small-diameter thin-walled seamless pipes. For medium and large caliber thick-walled seamless pipes, mechanical grinding is adopted if there is an integral defect problem; If it is a defect problem in a local area, manual grinding is used (which is more common), and the manual tools are portable electric grinder and upside-down grinder.
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