Several Manufacturing Processes of Seamless Tubing
Hot-rolled Seamless tubing is generally produced on automatic rolling mills. After inspection and removal of surface defects, the solid tube blank is cut into required lengths, centered on the end face of the perforated end of the tube blank, and then sent to a heating furnace for heating and perforated on a punching machine. During the continuous rotation and advancement of the perforation at the same time, under the action of the roll and the plug, a cavity is gradually formed inside the tube blank, which is called a capillary tube. And then sent to the automatic rolling mill to continue rolling. Finally, the wall thickness of the whole machine is averaged, and the diameter is sizing by a sizing machine to meet the specification requirements. It is a relatively advanced method to produce hot-rolled seamless steel pipes with continuous pipe rolling mills.
To obtain seamless tubing with smaller size and better quality, cold rolling, cold drawing, or a combination of the two must be used. Cold rolling is usually carried out on a two-roll mill, and the steel pipe is rolled in an annular pass composed of a variable-section circular hole groove and a stationary conical head. Cold drawing is usually carried out on a single-chain or double-chain cold drawing machine of 0.5 to 100T.
In the extrusion method, the heated Seamless tubing blank is placed in a closed extrusion cylinder, and the perforated rod moves together with the extrusion rod to extrude the extrusion part from the smaller die hole. This method can produce steel pipes with smaller diameters.