Straight seam steel pipe is the longitudinal parallel steel pipe of weld and steel pipe. It is usually divided into metric welded steel tube, welding thin-walled tube, transformer cooling oil pipe and so on. The production process of straight seam welding tube is simple, high production efficiency, low cost and fast development. The strength of spiral welded pipe is generally higher than that of straight seam welded pipe, which can be used to produce pipe diameter of large pipe diameter with a narrow billet, and the pipe diameter can be different with the same width of billet. However, compared with the same length of straight pipe, the weld length increases by 30~100 %, and the production speed is low.

The material of the straight pipe is introduced:

Straight seam steel tubes are made with Q195, Q215A, Q235A steel and Q235B pu carbon. It can also be made by welding 0317 standard model 6012 and steel mother 755 soft steel.

Welding process of straight seam pipe:

Straight seam steel tube is divided into high frequency straight seam steel tube and submerged arc welded steel pipe by production process. It is divided into UOE, RBE and JCOE steel tube according to its different forming way. Hebei chengyuan pipe group co., LTD. Introduces the forming process of common high frequency straight pipe and submerged arc welded steel pipe.

1, the high frequency welded steel pipe is the use of alternating current (ac) skin effect and proximity effect, steel (strip) after rolling forming, the formation of a cross section of broken circular tube billet, within the tube billet near the center of induction coil rotating one or a set of impedance (magnet) and impedance and pipe opening form a electromagnetic induction loop, under the action of skin effect and proximity effect, the pipe opening edges produce powerful and concentrated heat effect, make the weld edge rapidly heated to required after roller extrusion temperature, welding metal molten state to realize the joint between the crystal, after cooling to form a firm butt weld.

High frequency welding is charge according to the principle of electromagnetic induction and communication in the conductor skin effect and proximity effect and eddy current heating effect, make the edge of the weld steel locally heated to a molten state, the squeezing roller, to realize the joint between the crystal butt weld, so as to achieve the purpose of the welding seam welding. High frequency welding is a kind of induction (or contact pressure welding) welding, it need to weld filler, no welding spatter, narrow welding heat affected zone, weld moulding beauty, weld the advantages of good mechanical performance, thus is widely used in steel production.

2. Submerged arc welding process

1. Board: after entering the production line, the steel plate used to make the large-caliber submerged arc welded steel pipe shall first carry out the full-plate ultrasonic inspection.

2. Milling side: double-side milling of the edge of the steel plate by milling edge machine to achieve the required plate width, edge parallelism and groove shape;

3. Precurving edge: using the prebender to prebend the edge of the plate to make the edge of the plate meet the required curvature;

4, molding: on the JCO forming machine bending of the plate after half after many step punching, pressure into a "J" shape, and the other half of the steel plate bending, same pressure into a "C" shape, open after the formation of the "O" shape

5. Pre-welding: weld steel pipe with straight seam after molding and gas shielded welding (MAG) for continuous welding;

6. Internal welding: the welding of the inside of the straight pipe is made by using the longitudinal column multi-wire submerged arc welding (more than four wires).

7. External welding: welding on the outside of straight seam welding steel tube with longitudinal and multi-wire submerged arc welding;

8, ultrasonic inspection Ⅰ: inside and outside of straight seam welded steel pipe weld and weld on both sides of the base of 100% of the check;

9, X-ray inspection Ⅰ: 100% of inside and outside weld X-ray industrial TV inspection, using image processing system to ensure the sensitivity of detection;

10. Expanding diameter: the length of the submerged arc welded steel pipe is expanded to improve the size accuracy of the steel tube and improve the distribution state of the inner stress in the steel tube.