What is the difference between the two forming processes of straight seam submerged arc welded steel pipe

UOE ( U -O -Expanding ）

The UOE forming process first needs to process grooves, flattening, and bending of the steel plate edge, and then press it into a U shape by a forming machine, and then bend it into an O shape. Submerged arc welding is used for internal and external final welding, and finally the segmental mechanical expansion process is used for cold expansion of the whole pipe body. After the steel pipe is formed and welded, a series of inspections are carried out. This process is currently the most widely used, mature, and quality-recognized production process for large-diameter longitudinal submerged arc welded pipes in the world.

Main Features of UOE Welded Steel Pipe

1) The forming process is separated from the welding process, which belongs to discontinuous single production.
2) It can produce thick-walled steel pipes, and the maximum wall thickness can reach about 4Omm.
3) The length of the weld seam of the steel pipe is only half of that of the spiral weld seam at the same length, and the probability of defects in the weld seam is less.
4) High output, the output of one UOE unit is generally equivalent to the total output of 2~4 spiral welded pipe units.
5) The strength and dimensional accuracy of the steel pipe are improved by adopting the diameter expanding process.
6) UOE steel pipe is straight seam, which makes pipe laying and maintenance more convenient.
7) The equipment is larger than the spiral welded pipe unit, and the investment cost is high.
JCOE ( J -C -O -Expanding）

Compared with the UOE molding method, the cost of the JCOE molding process is relatively low, the process adaptability is strong, the wear of the molding die is small, and the molding die is light, and its technology and products are widely used. The JCOE pipe-making process is to form the steel plate in the order of J forming-C forming-O forming. After the steel pipes are joined, gas shielded welding is used for pre-welding, and then submerged arc welding is used for internal and external final welding, and finally the segmental mechanical diameter expansion process is adopted. Carry out cold expansion of the whole pipe body, and finally carry out a series of inspections.

Main features of the JCOE process

Each forming process of JCOE is completed on a large press, and the technical requirements for the steel pipe adjustment operation are high, and the forming unit takes a long time. Compared with the UOE process, due to multiple moldings, the processing efficiency is low, but there are fewer molds and equipment investment is lower. Therefore, the number of domestic JCOE units is more than that of UOE units; since JCO is multi-step pressing, the dimensional accuracy of steel pipes is lower than that of UOE, so UOE steel pipes are mostly used in marine pipelines.

JCO Molding Quality Control

During the JCO forming process, the steel plate is gradually fed into the forming mold by the steel pusher, and needs to be re-aligned before each side is formed, and finally processed into a straight open-seam steel pipe, and finally the joint pre-welding and final welding . JCO forming machine generally adopts automatic control, and the forming machine is designed as a short stroke, and the maximum pressure can reach 9000t. Before replacing the mold with different pipe diameters, clean up the sundries of the lower die pad to ensure that the lower die pad is flat after loading, so as not to affect the accuracy in the thickness direction.