Seamless steel pipe with small outer diameter can be called as small-diameter seamless steel pipe. Small-diameter seamless steel pipe can also be divided into: seamless small-diameter steel pipe and straight seam (also called welding) small-diameter seamless steel pipe. In the outer diameter, steel pipe of 89 mm or less, 4 mm or more, can be collectively referred to as a small-diameter seamless steel pipe.
The small-diameter cold-drawn seamless steel pipe is a circular, square, rectangular steel with a hollow section and no seam at the periphery. It's formed by perforating a steel ingot or a solid tube blank, and then hot rolled, cold rolled or cold drawn. The seamless steel pipe has a hollow section and is used as a pipe for conveying fluid. Compared with a solid steel such as round steel, the steel pipe is light in weight when it has the same bending and torsional strength, and is an economical section steel, which is widely used in manufacturing structures, parts and mechanical parts, such as oil drill pipes, automotive drive shafts, bicycle frames, and steel scaffolding used in construction.
The solid tube blank is inspected and the surface defects are cut to the required length, centered on the end face of the perforated end of the tube blank and then sent to the heating furnace for heating. Perforation on the punching machine While rotating and advancing at the same time. Under the action of the roll and the head, the cavity is gradually formed into a hollow tube inside the tube blank, and then sent to the automatic tube rolling machine to continue rolling. The final wall is thickened by the homogenizing machine, and the sizing machine is sized to meet the specification requirements. The continuous rolling tube unit is used to produce hot rolling seamlessly. Steel pipes are a more advanced method. If you want to obtain seamless pipes with smaller size and better quality, you must use cold rolling or cold drawing or a combination of the two. Cold rolling is usually carried out on a two-roll mill. The annular groove formed by the slot and the fixed conical head is rolled, and the cold drawing is usually performed on a single-chain or double-chain cold drawing machine. The extruded tube blank is placed in a closed extrusion circle. The perforated rod in the barrel moves together with the extrusion rod to extrude the extrusion from the smaller die hole, which produces a steel tube of smaller diameter.
Small-diameter hot-rolled seamless steel pipe: hot rolling is relative to cold rolling, cold rolling is rolling below the recrystallization temperature, and hot rolling is rolling above the recrystallization temperature.
The delivery state of hot-rolled seamless steel pipes is generally delivered after heat treatment in the hot-rolled state. After passing the quality inspection, the hot-rolled seamless steel pipe must be strictly hand-selected by the staff. After the quality inspection, the surface must be oiled, followed by multiple cold-drawing experiments, and the perforation experiment must be carried out after the hot-rolling treatment. , If the perforation diameter is too large, it will be straightened and corrected. After straightening, it is sent to the flaw detector by the transmission device for flaw detection test, and finally it is labeled, arranged in specifications and placed in the warehouse.
