Details of L360 straight seam steel pipes commonly used in industrial projects

The production process of straight seam welded steel pipes is relatively simple. The main production processes are high-frequency welding thick-walled straight seam steel pipes and submerged arc welding thick-walled straight seam steel pipes. Thick-walled straight seam steel pipes have high production efficiency, low cost and rapid development. The strength of spiral welded steel pipes is generally higher than that of straight seam welded steel pipes. The main production process is submerged arc welding. Spiral steel pipes can use the same width of billets to produce welded steel pipes with different diameters, and can also use narrower billets to produce welded steel pipes with larger diameters. However, compared with thick-walled straight seam steel pipes of the same length, the weld length increases by 30~100%, and the production speed is lower. Therefore, smaller-diameter welded steel pipes are mostly welded by straight seam welding, while large-diameter welded steel pipes are mostly welded by spiral welding. When producing large-caliber thick-walled straight seam steel pipes in the industry, T-welding technology is used, that is, short sections of thick-walled straight seam steel pipes are butt-jointed to meet the length required by the project. The probability of defects in T-welded thick-walled straight seam steel pipes is also greatly increased, and the welding residual stress at the T-weld is large. The weld metal is often in a triaxial stress state, which increases the possibility of cracks.

First, the chemical composition of the L360 straight seam steel pipe

Main element content: carbon (C) content does not exceed 0.22%, silicon (Si) does not exceed 0.45%, manganese (Mn) is between 1.20%-1.60%, phosphorus (P) and sulfur (S) do not exceed 0.025% and 0.015% respectively.

Alloy elements: It also contains a small amount of alloy elements such as copper (Cu), nickel (Ni), chromium (Cr), molybdenum (Mo), etc. The addition of these elements helps to improve the strength, toughness, and corrosion resistance of the steel pipe.

Second, the mechanical properties of L360 straight seam steel pipe

Strength: yield strength ≥360MPa, tensile strength ≥460MPa, weld tensile strength ≥460MPa.

Plasticity: elongation ≥20%, with good plastic deformation ability, not easy to break when subjected to external force.

Toughness: Charpy impact energy ≥100J is usually required, indicating that it has high toughness, can withstand a certain impact load, and is not easy to brittle fracture in low temperatures and other environments.

Third, the process performance of L360 straight seam steel pipe

Welding performance: The welding heat-affected zone is narrow, the welding performance is good, and a variety of welding methods can be used for connection, such as high-frequency resistance welding, submerged arc welding, etc.

Forming performance: During the forming process, it has good processability and dimensional stability and can meet the processing requirements of different shapes and sizes.

Fourth, the production process of L360 straight seam steel pipe

Raw material preparation: Hot-rolled steel plates or steel strips are usually used as raw materials. Strict inspection and acceptance are required before storage to ensure that their chemical composition and mechanical properties meet the requirements.

Forming: The raw materials are formed by a forming unit to form a tube blank with a round or square cross-section. The forming methods include UOE forming, JCO forming, RBE forming, etc. Different forming methods are suitable for the production of steel pipes with different specifications and requirements.

Welding: The formed tube blank enters the welding process. High-frequency resistance welding uses the skin effect and proximity effect of alternating current to quickly heat the edge of the weld to the welding temperature and then achieves intercrystalline bonding through roller extrusion; submerged arc welding melts metal to the weld under the flux layer through the welding wire to form a weld, which has the advantages of stable welding quality and high production efficiency.

Heat treatment: The steel pipe after welding needs to be heat treated to eliminate welding stress and improve the organization and performance of the steel pipe. Heat treatment methods include normalizing, tempering, quenching, etc.

Inspection: During the production process, the steel pipe must be 100% inspected, including appearance inspection, non-destructive testing, mechanical property testing, chemical composition analysis, etc. Non-destructive testing methods include ultrasonic testing, X-ray testing, magnetic particle testing, etc.

Fifth, the implementation standards of L360 straight seam steel pipe

Common implementation standards include GB/T9711-2017 "Steel pipes for pipeline transportation systems in the petroleum and natural gas industry", API 5L-2018 "Pipeline Steel Pipe Specifications", SY/T5257-2012 "Steel elbows for oil and gas transportation", etc.

Sixth, the application field of L360 straight seam steel pipe

It is mainly used for long-distance transmission pipelines in the fields of petroleum, natural gas, chemical industry, electricity, water supply, and drainage, as well as urban pipeline construction such as urban gas and urban water supply. It can also be used as pile foundation pipes, bridge pipes, building structure pipes, etc.

Seventh: Specification range of L360 straight seam steel pipe

Outer diameter: usually between 219mm and 1220mm, common specifications are 273mm, 325mm, 377mm, 426mm, 508mm, 559mm, 610mm, 711mm, 762mm, 813mm, 914mm, 1016mm, 1219mm, etc.

Wall thickness: generally between 6mm and 30mm, the wall thickness range that can be produced for steel pipes of different outer diameters is different.

Among them, materials such as X42, X46, X56, and X80 are API standard materials, which are not commonly used materials for pipes in my country. Among them, according to different uses, there are different post-production processes. (It can be roughly divided into scaffolding pipes, fluid pipes, wire casings, bracket pipes, guardrail pipes, etc.). Straight seam welded steel pipe standard GB/T3091-2008 and low-pressure fluid welded steel pipe is a kind of straight seam welded steel pipe, generally used for water and gas transportation,

Straight seam welded steel pipe, steel pipe made of hot rolled or cold rolled steel plate, or steel strip coil welding on welding equipment is called straight seam welded steel pipe. (Since the welding part of the steel pipe is in a straight line, it is named so). Commonly used materials in China are generally Q235A, Q235B, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, 16Mn, 20#, Q345, L245, L290, X42, X46, X70, X80, etc.