Views:5 Author:Site Editor Publish Time: 2018-06-29 Origin:Site
Small diameter seamless steel pipes refer to seamless steel pipes with a diameter of ≤ 159 mm. According to the different production equipments, it is divided into three grades: diameter Φ76 mm, Φ76~114 mm and Φ114~159 mm. Small-diameter seamless steel tubes are widely used, including general-purpose fluid pipes and structural pipes of general carbon steel and low-alloy steel with large capacity in the market, and a large number of oil well pipes with high added value and complex steel types for energy and other industries. High-pressure boiler tubes, etc., as well as special alloy tubes used in high-end industries such as nuclear power, aviation, and aerospace.
The billet used in the production of small-diameter seamless steel tubes by the cold-drawing process is of a small specification and cannot be used for continuous casting. Before cold drawing, it needs to be heated and perforated, and it must be multi-pass heat-treated, pickled, and cut.
Therefore, the process of cold-drawing small-diameter seamless steel tubes is a backward process with high energy consumption, high metal consumption and serious pollution. When foreign developed countries produce general small-diameter seamless steel pipes, the cold-drawing process has basically been eliminated.
In recent years, the proportion of hot-rolled seamless steel pipes in China has dropped from 85% to about 70%. The proportion of cold-drawn (rolled) steel pipes has increased from 15% to 30% in the same period. In cold-drawn (rolled) steel pipes, cold-drawn steel pipes account for about 80%. 85%, cold rolled tubes account for about 15% to 20%. This shows that in recent years, the production of seamless steel pipes in China has not been transformed in a more rational direction due to the increase in output, but rather it has deteriorated, the proportion of hot-rolled pipes has decreased, and the proportion of cold-drawn pipes has continuously increased.
According to market research, the market share of small-diameter cold-drawn steel pipes of special-purpose pipe varieties is about 500,000 tons, mainly low- and medium-pressure boiler tubes and structural pipes; the small-diameter cold-drawn pipes in ordinary fluid pipes are about 4.5 million tons. At present, the market share of small-diameter cold-drawn tubes in China is about 5 million tons, which is mainly the smallest size tube with a diameter of ∧Φ76 mm.
The main process: continuous casting billet → sawing → heating → perforation → hollow reduction → (full floating mandrel) rolling tube → reheat → reduce diameter → cooling → sawing → finishing → finished product. Process Features: A single continuous casting billet to produce all specifications of products, continuous casting billet and ignited billet; Circular furnace with regenerative combustion technology has a certain degree of difficulty; Vertical rolling technology; The fastest rolling cadence, 4 tubes per minute, the most Suitable for the production of Φ21.3~60.0 mm ultra-small diameter seamless steel tubes.
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