The production technology and equipment of seamless steel pipe factory are introduced. Seamless steel pipe is a kind of steel pipe or other metal pipe or alloy pipe with seamless periphery produced by perforation and other methods. What is the outer diameter range of seamless pipe? 0. 1 ~ 1425mm, with a wall thickness of 0.0 1 ~ 200mm. In addition to circular tubes, there are various tubes with special cross-section and variable cross-section.
Keywords: production technology, equipment, pipe rolling, piercer ....
How to make it? There are many ways to produce seamless pipes. According to the delivery requirements, seamless steel pipes can be produced by hot rolling (about 80 ~ 90%) or cold drawing (about 10 ~ 20%). There are round, square or polygonal steel ingots, rolled billets or continuous casting billets in hot tube, and the quality of billets directly affects the quality of steel pipes.
Heat pipes have three basic processes:
(1) threading the ingot or blank into the hollow thick-walled capillary on the piercer;
(2) the capillary tube is rolled thin on an extension machine and extended into a hollow tube close to the wall thickness;
(3) rolling on a finishing mill to obtain the required finished pipe. The series of pipe rolling mill is expressed by the maximum outer diameter of the produced steel pipe (see pipe rolling mill).
The production method of seamless steel pipe is shown in table:
(1) Automatic pipe rolling is one of the methods to produce seamless steel pipes. Production equipment includes piercing mill, automatic pipe mill, homogenizer, sizing mill and reducing mill. Its production process flow is shown in the figure.
(2) Continuous pipe rolling production? Production equipment includes piercer, continuous pipe mill and tension reducing mill. The round billet is inserted into the mandrel after passing through the capillary tube, and is continuously rolled by 7-9 two-high rolling mills with rollers arranged at 90 degrees to each other. After rolling, the core-pulling rod is reheated to reduce the tension, and the steel pipe with the length of 165m can be rolled. The annual output of 140mm continuous pipe mill is 400,000-600,000 tons, which is 2-4 times that of automatic pipe mill. The characteristics of this unit are that it is suitable for producing steel pipes with outer diameter less than168m, with large equipment investment, large installed capacity, 30m mandrel length and complicated processing and manufacturing. MPM, which appeared at the end of 1970s, forced the mandrel to move at a lower speed than the steel pipe by external force in the rolling process, which can improve the metal flow conditions and roll long pipes and large-diameter steel pipes with short mandrel.
(3) The periodic tube rolling production takes polygonal and circular steel ingots or continuous casting billets as raw materials, which are heated and perforated by water pressure to form a cup-shaped billet, and then rolled into a capillary by a two-roll skew rolling extension machine, and then a section of steel tube is rolled into a circle by a roller on a periodic tube rolling machine with a reducing hole groove. Periodic pipe mill is also called periodic pipe mill. Circulating pipe rolling takes steel ingot as raw material, which is suitable for rolling large diameter thick-walled steel pipes and variable cross-section pipes.
(4) Three-roll tube rolling production is mainly used to produce thick-walled tubes with high dimensional accuracy. The accuracy of pipe wall thickness produced by this method is 5%, which is about twice as high as that produced by other methods. The process is shown in Figure 4. In 1960s, due to the invention of a new three-high skew rolling mill (Transval mill), this method developed rapidly. The new type of rolling mill is characterized by rapidly rotating the inlet turret to change the rolling angle when rolling to the tail, preventing the tail from forming a triangle, and expanding the ratio of the outer diameter to the wall thickness of the produced varieties from 12 to 35, which not only can produce thin-walled pipes, but also improves the production capacity.
(5) Pipe jacking production? The traditional method is to extend the billet into a cup-shaped capillary by hydraulic punching and skew rolling, insert the long mandrel into the bottom of the capillary cup with a push rod, then pass through a series of roller die sets with gradually reduced holes and grooves, and finally roll it into a tube. This production mode requires less equipment investment, can be used for continuous casting billets, and can produce extra-large and extra-thick-walled pipes with a diameter of 1070mm and a wall thickness of 200mm, but the production efficiency is low, the wall thickness is relatively thick, and the pipe length ratio is short. After the emergence of the new CPE process, the tube blank is perforated by oblique rolling, closed and then extended into a tube by top rolling, which overcomes some shortcomings of the traditional method and becomes a method with better economic benefits in the production of seamless tubes.
(6) Extruded pipe production? Firstly, the peeled round blank is perforated or reamed, then heated by induction or salt bath, coated with lubricant on the inner surface, and sent to an extruder. The metal is extruded into a tube through the annular gap between the die hole and the mandrel (Figure 5). Mainly used for producing low-plasticity high-temperature alloy pipes, special-shaped pipes, composite pipes and non-ferrous metal pipes. This method has a wide production range, but the output is low. In recent years, due to the improvement of die materials, lubricants and extrusion speed, the production of extruded pipes has also developed.
(7) Rolling production of guide plate and tube? Also known as the Dissel Act. Perforated capillary with long mandrel is rolled into thin-walled tube on guide plate mill. This mill is similar to the two-high cross-rolling piercer, except that the fixed guide plate is changed to the movable guide plate. Due to the production of long mandrel, the inner wall of the pipe is smooth and scratch-free; But the tool cost is high and the adjustment is complicated. It is mainly used to produce general carbon steel pipes with the outer diameter below150 mm. At present, it is used less and has no great development prospect.
(8) Spinning tube production? The flat plate or hollow blank is spun one or more times on a spinning machine to form a thin-walled tube. The pipe has high precision, good mechanical properties and wide size range, but the production efficiency is low. Mainly used in the production of non-ferrous metal pipes, but also increasingly used in the production of steel pipes. Besides producing household appliances, chemical containers and machine parts, spinning tubes are mostly used in military industry.
In the 1970s, large-diameter ultra-thin circular tubes and special-shaped pipe fittings with a diameter of 6000mm and a diameter-wall ratio of 10000 were produced by powerful spinning.
(9) Cold-rolled and cold-drawn pipe production? It is used to produce thin-walled, precision and special-shaped pipes with small caliber. Production is characterized by multi-process circulation process. Cold-rolled with a periodic cold-rolling mill, its elongation can reach 6 ~ 8 (Figure 6). In 1960s, it began to develop in the direction of high speed, multi-line, long stroke and long tube blank. In addition, the small-roll cold rolling mill has also been developed. It is mainly used to produce ultra-thin precision tubes with wall thickness less than 1mm, with complicated cold rolling equipment, difficult tool processing and inflexible variety specification conversion. Usually, the process of combining cold rolling and cold drawing is adopted, that is, large deformation is obtained by cold rolling and wall reduction, and then various specifications are obtained by cold drawing. ?
Seamless steel pipe production equipment: piercer? The commonly used two-roll cross-rolling piercing process is shown in the figure. The round tube blank is rolled into a hollow thick-walled tube (capillary tube), and the axes of the two rollers form an inclination angle with the rolling line. In recent years, the angle of inclination increased from 6 ~12 to13 ~17, which accelerated the perforating speed. In the production of steel pipes with a diameter of more than 250 mm, secondary perforation is used to reduce the wall thickness of capillaries. New technologies, such as active rotating guide plate perforation, reverse ejection hole, axial discharge and cyclic top welding, were also developed, which strengthened perforation technology and improved capillary quality.
Automatic pipe mill? Roll thick-walled capillary into thin-walled hollow tube. Generally, it is rolled to the wall thickness of finished products after 2-3 passes, and the total elongation is about1.8-2.2. Since 1970s, technologies such as single-hole grooved roll, double-stand tandem mill, double-groove tracking rolling and spherical plug have all improved production efficiency and realized the mechanization of pipe rolling.
Homogenizer? The structure is similar to that of the drill. The purpose of leveling is to eliminate the defects and ovality of the inner and outer surfaces of the hollow tube and reduce the uneven transverse wall thickness. In recent years, a three-roll homogenizer has been adopted, which improves the deformation and homogenization efficiency of the homogenizer.
Sizing machine It is composed of 3 ~ 12, and the reducer is composed of 12 ~ 24, and the reducing rate is about 3 ~ 28%. The tension reducing mill that appeared in 1950s controlled the wall thickness with proper tension while adjusting the roll speed and reducing the diameter. The new tension reducing mill is generally three rollers, 18 ~ 28 stands, with the maximum reduction rate of 80%, the wall thickness reduction rate of 44% and the outlet speed of18 mm/s. Tension reducing mill has the disadvantage of thickening at both ends, which can be eliminated by "sudden electric control at the head and tail" or micro-tension reducing.
Automatic pipe rolling unit? Commonly used series have four kinds of external diameters: 100mm, 140mm, 250mm and 400mm, and produce steel pipes with external diameters of17 ~ 426 mm. The characteristics of the unit are that the main deformation is realized on the piercer, the specification changes flexibly and the production range is wide. Due to the development of continuous pipe rolling technology, units below 140mm will no longer be built.