The production of LSAW Steel Pipes for use in deep-sea environments requires the following special materials and processes:

Special materials

High strength alloy steel: pipeline steel of steel grades such as X70 and X80. Adding alloying elements such as chromium (Cr), molybdenum (Mo), and nickel (Ni) can improve the strength, toughness, and corrosion resistance of steel. Molybdenum can enhance the high-temperature creep resistance of steel and help maintain the structural stability of steel pipes in deep-sea high-pressure environments with possible temperature changes; Nickel can improve the low-temperature toughness of steel, making it less prone to brittle fracture in deep-sea low-temperature environments.

Corrosion resistant alloys: For deep-sea areas with severe corrosion environments, corrosion-resistant alloys or corrosion-resistant coatings are used on the surface of steel pipes. Nickel based alloys have excellent resistance to seawater corrosion, pitting corrosion, and crevice corrosion, and can be used to manufacture the inner corrosion-resistant layer of bimetallic composite pipes.

Special welding materials: Match corresponding welding materials based on the composition and properties of the base material, such as welding wire and flux containing appropriate amounts of alloying elements, to ensure that the weld has the same strength, toughness, and corrosion resistance as the base material.

Special craftsmanship

Advanced rolling technology

Multi stage rolling: Through multi-stage rolling such as rough rolling and finishing rolling, the rolling temperature, reduction amount, and pass deformation rate are controlled at different stages to refine the internal grain size and uniform structure of the steel plate, and improve the comprehensive performance of the steel plate.

High penetration rolling technology: using the rapid cooling process of the casting billet during the rolling stage to increase the temperature gradient in the thickness direction of the casting billet, improve the deformation penetration effect of rolling, and solve the problems of difficult grain refinement in the thickness center of thick walled pipeline steel and poor uniformity of the thickness section structure.

Accurate heat treatment process

Quenching and tempering: Quenching can enhance the strength and hardness of steel by obtaining martensitic and other strengthening structures; Tempering can eliminate quenching stress, improve toughness and plasticity. By precisely controlling the temperature, time and other parameters of quenching and tempering, the steel pipe can achieve ideal performance.

Controlled cooling process: The uniform cooling technology based on the difference in cooling rate and cooling temperature drop is adopted to achieve ideal temperature changes at different positions of the steel plate during accelerated cooling, achieving effective control of microstructure and properties.

High precision molding process

UOE forming: After pre bending at the edge, a single steel plate undergoes processes such as U-forming, O-forming, internal welding, external welding, and mechanical cold expansion to ensure the roundness and dimensional accuracy of the steel pipe, giving it good compressive strength.

JCOE Forming: Following the "J-C-O-E" pre welding, forming, and cold expansion processes after welding, LSAW steel pipes with large diameters and thick walls can be produced. By precisely controlling the mold size, pressure, and other parameters during the forming process, the quality of the steel pipes is ensured.

High quality welding process

Double sided submerged arc welding: Adopting the double-sided submerged arc welding method, the welding process is stable, the weld quality is high, and the toughness, plasticity, uniformity, and density of the weld can be effectively guaranteed.

Welding parameter optimization: Accurately adjust welding current, voltage, welding speed and other parameters based on the material and thickness of the steel pipe, control the heat input of the weld seam, avoid welding defects, and ensure the performance of the weld seam.

Strict testing process

Non destructive testing: Ultrasonic testing, radiographic testing and other non-destructive testing methods are used to comprehensively inspect the welds and body of steel pipes, and timely detect internal defects such as cracks, pores, slag inclusions, etc.

Physical and chemical performance testing: Conduct mechanical performance tests on steel pipes, including tensile tests, impact tests, hardness tests, as well as corrosion resistance tests such as hydrogen induced cracking (HIC) tests, sulfide stress corrosion (SSC) tests, etc., to ensure that the performance of steel pipes meets the requirements for use in deep-sea environments.

The cost of producing LSAW steel pipes for use in deep-sea environments

The cost of producing LSAW steel pipes for use in deep-sea environments is influenced by various factors, and the following is a rough estimate:

Raw material cost

High strength alloy steel: Taking X70 steel grade as an example, the price of X70 straight seam welded pipe DN800 on the market is approximately 3260-3301 yuan/ton. If it is a higher performance X80 steel grade, the API 5L PSL2 X80 thick walled straight seam steel pipe from Hebei Jincheng Pipeline is priced at 6000 yuan/ton for 1-99 tons and 5500 yuan/ton for 100 tons and above.

Corrosion resistant alloy: Nickel based alloys have high prices due to their excellent performance. For example, steel pipes containing nickel based alloys have only a partial cost of nickel based alloys. Calculated at a unit price of over 200 yuan per kilogram for 0Cr20Ni65Mo10Nb4, if nickel based alloys account for a large proportion in steel pipes, the cost of alloy materials alone may reach over 200000 yuan per ton.

Production process cost

Rolling process: multi-stage rolling and high penetration rolling require advanced equipment and precise control. The cost of equipment procurement, maintenance, and energy consumption is relatively high, which may increase the cost of steel pipes by 500-1000 yuan per ton.

Heat treatment process: precise heat treatment such as quenching, tempering, and controlled cooling requires professional heat treatment equipment and energy consumption. Technical personnel also need to strictly control parameters, which increases costs by about 800-1500 yuan/ton.

Molding process: UOE molding equipment has high costs, while JCOE molding requires multiple processes. The mold loss, equipment operation, and labor costs during the molding process increase the cost of forming each ton of steel pipe by 1000-2000 yuan.

Welding process: Welding materials, welding equipment losses, and welding quality control for double-sided submerged arc welding, combined with the cost of optimizing welding parameters, increase the welding cost by approximately 800-1200 yuan per ton.

Testing process: Non destructive testing and physical and chemical performance testing require professional testing equipment, personnel, and materials. The testing cost may account for 10% -15% of the total cost. Calculated at 5000 yuan per ton of steel pipe, the testing cost is approximately 500-750 yuan.

Other costs

Transportation and logistics costs: If the production site is far away from the usage site and transportation methods such as sea and land are used, the transportation cost may be between 300-800 yuan per ton.

Tax cost: Tax policies vary in different regions, and value-added tax and other taxes are generally around 13%. Assuming the production cost of steel pipes is 5000 yuan/ton, the tax cost is about 650 yuan/ton.

In summary, the cost of LSAW steel pipes with ordinary strength and general corrosion resistance requirements used in deep-sea environments may be between 5000-8000 yuan/ton; For LSAW steel pipes with special requirements such as high steel grade and high corrosion resistance, the cost may exceed 10000 yuan/ton, or even higher.