The performance of ERW steel pipe can well meet the requirements of long-distance pipeline transportation of oil and gas, so it is widely used in the field of transportation.At present, the maximum diameter of ERW steel pipes designed according to API standards in the world can reach 630mm-660mm, the wall thickness is 8-20mm, and the hot coil used can reach 2000mm.
ERW steel pipe is different from other types of welded pipe, the weld has no added metal, and the edge of the steel strip is rapidly heated through the skin effect and proximity effect characteristics of high-frequency current.Then through an effective extrusion process, the edges of the steel strip are forged and welded together to form a weld, and the bright line of dissolution is only 0.15~0.2mm wide.At the same time, the welding speed is fast (generally greater than 15m/min), the heat-affected zone is narrow, and the subsequent annealing treatment eliminates the welding residual stress, and then the normalizing heat treatment improves the structure of the welding zone.
Therefore, the microstructure, composition and hardness of the weld zone are close to those of the base metal, and the microstructure of the weld zone is in the hot-rolled state rather than the as-cast state. Due to the process.characteristics of ERW, the deformation of the steel pipe is relatively sufficient during the forming process, and cold sizing is required after extrusion and welding.Through the alternation and reduction of the vertical and horizontal directions of the steel pipe, the residual stress of the steel pipe during cold forming is reduced. The axial incision test shows that the opening displacement of the ERW steel pipe is indeed small.
ERW steel pipe has no high welding seam reinforcement, and the inner and outer burrs are basically flush with the outline of the steel pipe, so there is basically no stress concentration phenomenon in use. The existence of residual stress makes the steel pipe stress superimposed during the working process. In the conveying medium with hydrogen sulfide, hydrogen sulfide stress corrosion is very sensitive to the stress. However, ERW steel pipe does not have the weakest area at the root of the weld.
At the same time, the surface of ERW steel pipe is smooth and flat, with uniform wall thickness and good roundness, which can make the anti-corrosion coating uniform. In the field construction, the counterpart is easy and the construction speed is fast.
Features of Large Diameter ERW Steel Pipe
The ERW production unit has a large investment and many processes, so the processing cost of the steel pipe is relatively high. Since the large-diameter ERW steel pipe has no repair welding and is not allowed to face the head pipe, the relative yield is lower. Therefore, the direct price of large-diameter ERW steel pipes is relatively high, but from the overall perspective of pipeline construction, the cost does not increase.
(1) The large-diameter ERW steel pipe has good quality and long service life.
(2) The surface quality of large-diameter ERW steel pipes is good, the coating is uniform, a lot of coating materials are saved, and the anti-corrosion cost of steel pipes is low.
(3) The large-diameter ERW steel pipe has high geometrical dimensional accuracy, good roundness, fast butt welding speed, and high on-site construction efficiency, which greatly reduces the construction cost.
(4) The welding speed of large-diameter ERW steel pipe is much higher than that of SSAW steel pipe, and the production efficiency is high. It can ensure the timely and necessary construction.
ERW steel pipe is different from other types of welded pipe, the weld has no added metal, and the edge of the steel strip is rapidly heated through the skin effect and proximity effect characteristics of high-frequency current.Then through an effective extrusion process, the edges of the steel strip are forged and welded together to form a weld, and the bright line of dissolution is only 0.15~0.2mm wide.At the same time, the welding speed is fast (generally greater than 15m/min), the heat-affected zone is narrow, and the subsequent annealing treatment eliminates the welding residual stress, and then the normalizing heat treatment improves the structure of the welding zone.
Therefore, the microstructure, composition and hardness of the weld zone are close to those of the base metal, and the microstructure of the weld zone is in the hot-rolled state rather than the as-cast state. Due to the process.characteristics of ERW, the deformation of the steel pipe is relatively sufficient during the forming process, and cold sizing is required after extrusion and welding.Through the alternation and reduction of the vertical and horizontal directions of the steel pipe, the residual stress of the steel pipe during cold forming is reduced. The axial incision test shows that the opening displacement of the ERW steel pipe is indeed small.
ERW steel pipe has no high welding seam reinforcement, and the inner and outer burrs are basically flush with the outline of the steel pipe, so there is basically no stress concentration phenomenon in use. The existence of residual stress makes the steel pipe stress superimposed during the working process. In the conveying medium with hydrogen sulfide, hydrogen sulfide stress corrosion is very sensitive to the stress. However, ERW steel pipe does not have the weakest area at the root of the weld.
At the same time, the surface of ERW steel pipe is smooth and flat, with uniform wall thickness and good roundness, which can make the anti-corrosion coating uniform. In the field construction, the counterpart is easy and the construction speed is fast.
Features of Large Diameter ERW Steel Pipe
The ERW production unit has a large investment and many processes, so the processing cost of the steel pipe is relatively high. Since the large-diameter ERW steel pipe has no repair welding and is not allowed to face the head pipe, the relative yield is lower. Therefore, the direct price of large-diameter ERW steel pipes is relatively high, but from the overall perspective of pipeline construction, the cost does not increase.
(1) The large-diameter ERW steel pipe has good quality and long service life.
(2) The surface quality of large-diameter ERW steel pipes is good, the coating is uniform, a lot of coating materials are saved, and the anti-corrosion cost of steel pipes is low.
(3) The large-diameter ERW steel pipe has high geometrical dimensional accuracy, good roundness, fast butt welding speed, and high on-site construction efficiency, which greatly reduces the construction cost.
(4) The welding speed of large-diameter ERW steel pipe is much higher than that of SSAW steel pipe, and the production efficiency is high. It can ensure the timely and necessary construction.
