The continuous rolling process of straight seam steel pipe: the continuous rolling process of straight seam steel pipe, continuous rolling process is used in the continuous rolling and fixed diameter reduction process of steel pipe. Continuous steel pipe rolling is a process in which steel pipes and mandrels move together in multiple racks. The deformation and movement of steel pipes are simultaneously affected by the joint action of rolls and mandrels. The mandrel can be free-floating, that is, it is driven forward by the metal; it can also be limited, that is, the mandrel is given a movement speed to limit its free movement. During the movement, the mandrel, the roll, and the steel pipe are connected as a whole, and the change of any one of them will cause a change in the state of the whole system. The continuous rolling theory is the theory of studying the relationship between them.
The kinematic phenomenon of steel pipe continuous rolling:
1. Kinematic phenomenon;
2. Slip phenomenon;
3. Tension coefficient.
Analysis of the Motion State of Continuously Rolled Tube
1. The displacement relationship between the rolled piece and the mandrel;
2. Rack and its determination;
3. Intermittent rolling analysis;
4. Movement characteristics of the single rolling mandrel.
Deformation and stress in continuous rolling of steel pipes:
1. Internal stress analysis of continuous rolling pipe;
2. Analysis of side wall deformation and stress.
Welded pipes are classified by use:
According to the purpose, it is divided into general welded pipe, galvanized welded pipe, oxygen-blown welded pipe, wire casing, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welded thin-walled pipe, electric welded special-shaped pipe and spiral welded pipe.
General welded pipe: General welded pipe is used to convey low-pressure fluid. Made of Q195A, Q215A, Q235A steel. It can also be manufactured from other mild steels that are easy to weld. Steel pipes are subject to water pressure, bending, flattening, and other tests, and there are requirements for the surface. Usually, the delivery length is 4-10m, and it is often required to be delivered in fixed length (or double length). The specification of the welded pipe is represented by the nominal diameter (mm or inch). The nominal diameter is different from the actual one. The welded pipe has two types of ordinary steel pipe and thickened steel pipe according to the specified wall thickness. The steel pipe is divided into two types: threaded and unthreaded according to the pipe end form.
1) Galvanized steel pipe: To improve the performance of the steel pipe, the general steel pipe (black pipe) is galvanized. There are two types of galvanized steel pipes: hot-dip galvanizing and electric steel zinc. The hot-dip galvanizing layer is thicker and the cost of electric galvanizing is low.
2) Oxygen-blowing welded pipe: used for steelmaking oxygen-blowing pipe, generally small diameter welded steel pipe, with eight types of specifications from 3/8 inch to 2 inches. Made of 08, 10, 15, 20, or Q195-Q235 steel strip. To prevent corrosion, some are aluminized.
3) Wire casing: It is also an ordinary carbon steel electric-welded steel pipe, which is used in concrete and various structural power distribution projects. The commonly used nominal diameter is from 13-76mm. The wall of the wire casing is relatively thin, and it is mostly used after coating or galvanizing, and a cold bending test is required.
4) Metric welded pipe: the specification is in the form of seamless pipe, and the welded steel pipe expressed by outer diameter * wall thickness in millimeters is welded with ordinary carbon steel, carbon steel, or ordinary low-alloy steel with the hot or cold band, or with hot band welding Then it is made by cold drawing method. Metric welded pipes are divided into ordinary energy and thin-walled pipes, which are generally used as structural parts, such as transmission shafts, or conveying fluids, and thin-walled pipes are used to produce furniture, lamps, etc., to ensure the strength and bending test of steel pipes. Made of Q215, Q235A, B steel, and 20 steel, diameter 63.5-219.0mm. There are requirements for the bending degree of the pipe, the end surface should be perpendicular to the center line, and the ellipticity and the hydraulic pressure and flattening tests are generally carried out.
6) Transformer tube: It is used to manufacture transformer cooling tubes and other heat exchangers. It is made of ordinary carbon steel and requires flattening, flaring, bending, and hydraulic tests. Steel pipes are delivered in fixed lengths or multiple lengths, and there are requirements for the bending degree of steel pipes.
7) Special-shaped pipes: square pipes, rectangular pipes, hat-shaped pipes, hollow plastic steel doors, and windows steel pipes welded by ordinary carbon-bonded structural steel and 16Mn steel strips, mainly used as agricultural machinery components, steel windows, doors, etc.
8) Welded thin-walled tube: mainly used to make furniture, toys, lamps, etc. In recent years, thin-walled tubes made of stainless steel strips have been widely used in furniture, decoration, fences, etc.
9) Spiral welded pipe: It is made by rolling the low-carbon carbon structural steel or low-alloy structural steel strip into a tube blank according to the angle of the helix (called the forming angle), and then welding the pipe seam. It can be made with narrower The strip steel produces large diameter steel pipes. Spiral welded pipes are mainly used for oil and gas pipelines, and their specifications are expressed by outer diameter * wall thickness. Spiral welded pipes are single-sided welded and double-sided welded. The welded pipes should ensure that the hydraulic test, the tensile strength of the weld, and the cold bending performance must meet the regulations.