Spiral welded pipe VS straight seam welded pipe
The difference between Spiral welded pipe and straight seam welded pipe
Spiral welded pipe: It is made by rolling a low carbon carbon structural steel or a low alloy structural steel strip into a tube blank at a certain angle of a helix (called a forming angle), and then welding the pipe joint to make it narrower. Strip steel produces large diameter steel pipes.
Spiral welded pipe is mainly used for oil and natural gas transmission pipelines, and its specifications are expressed by outer diameter * wall thickness.
Spiral welded pipes are single-sided welded and double-sided welded. The welded pipe shall ensure that the hydraulic test and the tensile strength and cold bending performance of the weld are in compliance with the regulations.
Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development.
The strength of the spiral welded pipe is generally higher than that of the straight welded pipe. It is possible to produce a welded pipe with a large diameter by using a narrow blank, and it is also possible to produce a welded pipe having a different pipe diameter by using a blank of the same width. However, compared with the straight pipe of the same length, the weld length is increased by 30 to 100%, and the production speed is low.
From the welding process, the welding method of spiral welded pipe and straight seam steel pipe is the same, but the straight seam welded pipe will inevitably have many T-weld joints, so the probability of welding defects is greatly improved, and the welding residual at the T-weld joint The stress is large, and the weld metal tends to be in a three-direction stress state, increasing the possibility of cracking.
Moreover, according to the submerged arc welding process regulations, each weld should have an arc starting point and an arc extinction point, but each straight seam welded pipe cannot meet this condition when welding the circumferential joint, and thus there may be More welding defects.
Generally, the diameter of the pipe can be divided into an outer diameter, an inner diameter, and a nominal diameter. The outer diameter of the tube in which the pipe is a spiral steel pipe is indicated by the letter OD, and then the size and wall thickness of the outer diameter are added.
Straight seam welded pipe, where the production of straight seam welded pipe, hot expansion pipe, etc., with strip steel as raw material for production, the pipe obtained by straight seam welding on high frequency welding equipment is called straight seam welded pipe. (Because the welded portion of the steel pipe is in a straight line, it is named). Among them, according to different uses, and different post-production processes, (substantially can be divided into scaffolding tubes, fluid tubes, wire casings, bracket tubes, guardrail tubes, etc.). Straight seam welded pipe standard GB/T3091-2008 and low pressure fluid welded pipe is a kind of straight seam welded pipe. Generally, water and gas are transported. After welding, a hydraulic pressure test is added to the common welded pipe. Therefore, the low pressure fluid pipe is more straight than the ordinary straight seam. The price of welded pipe is generally higher (according to the current market price, it is about 80 yuan higher). For example: welded pipe fluid pipe 1 inch (DN25) (that is, Φ33.5*3.25) price is about 4300 per ton, and ordinary Straight seam welded pipe is around 4350RMB.
1, The definition
The main raw materials of spiral welded pipe and straight seam welded pipe are low carbon steel hot rolled coil and hot rolled strip. They are widely used in petroleum, metallurgy, construction, coal mine, port, machinery and other industries for oil and gas transportation, low pressure water gas transportation and mining fluid transportation. , belt conveyor rollers, car drive shafts, etc.
Spiral welded pipe is made by rolling a low carbon carbon structural steel or a low alloy structural steel strip into a tube blank at a certain angle of a helix (also called a forming angle), and then welding the pipe joint to make it narrower. Strip steel produces large diameter steel pipes. Spiral welded pipe is mainly spiral submerged arc welded pipe (SSAW), which is widely used in the construction of various gas pipelines in China. Its specifications are expressed by the outer diameter * wall thickness. Spiral welded pipes are single-sided welded and double-sided welded. The welded pipe shall ensure that the hydraulic test and the tensile strength and cold bending performance of the weld are in compliance with the regulations.
The straight seam welded pipe is formed by forming a hot rolled coil through a molding machine to deform the steel coil into a smooth cylindrical shape, and welding by using the skin effect of the high frequency current and the adjacent effect or the arc under the solder layer to make the blank The edge is heated and melted, and is fused under a certain pressing force, and finally cooled to form. The high-frequency straight seam welded pipe (ERW) in which the edge of the pipe blank is melted by high-frequency current is called a straight seam submerged arc welded pipe (LSAW).
2, The difference in technology
Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development. The strength of the spiral welded pipe is generally higher than that of the straight welded pipe. It is possible to produce a welded pipe with a large diameter by using a narrow blank, and it is also possible to produce a welded pipe having a different pipe diameter by using a blank of the same width. However, compared with the straight pipe of the same length, the weld length is increased by 30 to 100%, and the production speed is low.
Therefore, most of the smaller diameter welded pipes are straight seam welded, while the large diameter welded pipes are mostly spiral welded.
Spiral welded pipe is made by rolling a low carbon carbon structural steel or a low alloy structural steel strip into a tube blank at a certain angle of a helix (also called a forming angle), and then welding the pipe joint to make it narrower. Strip steel produces large diameter steel pipes.
The straight seam welded pipe is formed by forming a hot rolled coil through a molding machine to deform the steel coil into a smooth cylindrical shape, and welding by using the skin effect of the high frequency current and the adjacent effect or the arc under the solder layer to make the blank The edge is heated and melted, and is fused under a certain pressing force, and finally cooled to form.