The production process of ssaw steel pipe is more complicated than that of lsaw steel pipe. The proportion in steel pipe is stable at 42%~45% in recent years, and the welded pipe has a rising trend. Compared with welded steel pipes, spiral steel pipes are highly reliable in material reliability and variety, especially for the production of thick-walled and alloy steels. The main problems are high investment, high cost, complicated manufacturing process, and large wall thickness and ellipticity tolerance.
The welded pipe is actually a deep-processed product of the plate. Under the similar conditions, the market competitiveness of the spiral steel pipe is improved due to its high reliability. With the continuous improvement of the quality of the steel plate and the improvement of the technical level of the welded pipe, some spiral steel pipes The market occupied has the possibility of being replaced by welded pipes, but this is only a very limited area.
The hot rolling process is the main manufacturing method of spiral steel pipe, accounting for 80% of the production of seamless pipe. The variety and quality level of the hot strip mill unit are limited by the technical level of the rolling mill itself, and are largely restricted by smelting and continuous casting.
Therefore, the advanced process should refer to the complete process of smelting to pipe processing. Internationally renowned spiral steel pipe enterprises are mostly complete professional steel pipe factories or steel joint enterprises. It is difficult for enterprises that manufacture spiral steel pipes by purchasing blanks to occupy a stable position in the fierce market competition.
Using electric arc furnace or converter smelting, LF furnace refining, VD vacuum treatment, full protection casting, continuous casting, round tube blank, hot strip mill (NPN, PQF), processing, is the international advanced spiral steel pipe production process, using the above. The process can produce special pipes such as oil, high pressure boiler tubes, medium and low alloy tubes, and the like.
For smelting equipment, the capacity of electric arc furnace or converter should not be less than 70-100 tons, which creates conditions for ladle refining. It should pay full attention to the on-line detection means and automatic control system of continuous rolling mills, equipped with advanced flaw detection system, positioning for oil pipes and high pressure boilers. T
he production line of the pipe shall be equipped with a high-level heat treatment and processing system to gradually realize the hot charging and hot feeding of the steel billet and the on-line normalization, controlled rolling and air cooling.