Straight seam welded steel pipe, according to the welding process is divided into high frequency resistance welding and submerged arc welding, straight seam submerged arc welding referred to as UOE, straight seam high frequency resistance welding referred to as ERW.
High-frequency electric resistance welded steel pipe (ERW steel pipe) Because the welding process is compared with submerged arc welding, the ERW process does not add any welding material during the welding process, and the weld bead is not subjected to thermal melting, but the weld metal undergoes a recrystallization process. Therefore, the welds formed are exactly the same as the chemical composition of the base metal. After the steel pipe is annealed after welding, the internal stress of the cold working is formed, and the internal stress of the weld is improved. Therefore, the comprehensive mechanical properties of the ERW steel pipe are better.
Straight seam submerged arc welding (UOE steel pipe) because it uses the post-weld cold expansion process to increase the pipe, so the UOE steel pipe geometry is relatively accurate, the UOE steel pipe butt joint quality is good to ensure the welding quality, through the pipe expansion process to a certain extent Partial internal stress is eliminated. In addition, UOE steel pipe is welded with multi-wire (three wire, four wire). The welding process produces a small amount of wire energy and a small influence on the heat affected zone of the base metal.
After the multi-wire welding, the welding wire to the front wire can eliminate the stress generated during welding, thereby improving the mechanical properties of the steel pipe. The base metal can achieve 100% ultrasonic flaw detection on the steel sheet one by one, meeting the requirements of the high pressure pipeline for the base metal. However, although the overall performance of UOE steel pipes is superior to other steel pipes, its high price has discouraged users with financial constraints.
First, the difference between raw materials and production capacity
The raw material of the ERW steel pipe is a hot rolled steel coil, and the raw material of the UOE steel pipe is a hot rolled steel plate. Therefore, the ERW steel pipe can realize continuous line operation, and the production efficiency is high, and the production cost is low; while the UOE steel pipe is processed by the steel plate, the continuous assembly line operation cannot be realized, the production efficiency is low, and the production cost is high.
The ERW steel pipe is limited by the thickness of the steel coil. The maximum thickness that can be produced is 25mm, and the maximum diameter that can be produced is 660mm. The maximum thickness that can be produced by UOE steel pipe is 40mm. The maximum diameter can be produced only by the width of the steel plate. The maximum diameter of production is 1422mm.
Second, the difference between welding
ERW steel pipe welding does not need to add welding wire; UOE steel pipe needs to add welding wire.
Third, the difference in appearance
The inner and outer welds of the ERW steel pipe need to be removed, so it is beneficial to the anti-corrosion; the inner and outer wall welds of the UOE steel pipe have a high residual height, which is unfavorable for anti-corrosion.
Fourth, the difference between procurement costs and difficulties
ERW steel pipe purchase cost is low, UOE steel pipe cost is very high, the general price difference is 15%-25%. There are fewer manufacturers of UOE steel pipes in China, and the procurement is difficult. When the diameter is < φ 406 mm, the difference in procurement costs is greater. There are many manufacturers of ERW steel pipes, and the procurement difficulty is low. When the diameter is <Φ406mm, the procurement cost will be reduced greatly.
Fifth, the application difference
ERW steel pipes are mainly used in long-distance pipelines such as natural gas, refined oil, crude oil and pulp. UOE steel pipes are mainly used in high-pressure submarine long-distance pipelines, alpine regions, and onshore second, third and fourth regions.