ASTM A672 B70 CL22 is a straight seam welded steel pipe that is a pressure pipeline material widely used in petroleum, chemical, power, and other industries. Its excellent performance and strict production standards make it an ideal choice for high-pressure and high temperature environments. This article will explore the characteristics, production process, application fields, and market prospects of this material in depth to help readers fully understand this important industrial material.
First, the material characteristics and standard analysis of ASTM A672 B70 CL22 straight seam welded steel pipe
ASTMA672B70CL22 belongs to electric fusion welding (EFW) steel pipe, which implements the American ASTM standard system. The material has the following core characteristics:
1. Chemical composition: It is based on carbon manganese steel, with trace alloy elements added, and the carbon content is controlled below 0.30%, ensuring good welding performance and low-temperature toughness. The specific composition must meet the B70 level requirements in the ASTM A672 standard, and the content of impurity elements such as phosphorus and sulfur is strictly limited to below 0.025%.
2. Mechanical properties:
- Minimum yield strength ≥380MPa (55ksi)
- Tensile strength ≥485-660MPa
- Elongation ≥18% (gauge length 50mm)
- Special requirement -46℃ Charpy V-notch impact energy ≥27J
3. Special requirements: CL22 means that the steel pipe is suitable for the low-temperature environment of -30℃ to -20℃ and needs to pass a strict low-temperature impact test. Compared with ordinary B70 grade, CL22 has higher requirements in the welding process and heat treatment.
Second, the production process of ASTM A672 B70 CL22 straight seam welded steel pipe
The production of high-quality ASTMA672B70CL22 straight seam steel pipe requires 12 key processes:
1. Plate pretreatment: Special steel plate produced by controlled rolling and controlled cooling process, with thickness tolerance controlled at ±0.1mm. Large domestic steel mills such as Baosteel and Anshan Iron and Steel have stable supply capabilities, and some high-end products still rely on imports.
2. Forming welding:
- JCOE forming process: Through multiple step-by-step pressing and forming, it is more suitable for small and medium-caliber steel pipes than the traditional UOE process
- Multi-wire submerged arc welding: Using a DC+AC dual power supply system, the welding speed can reach 1.2-1.8m/min
- Online ultrasonic detection: 100% weld automatic flaw detection, sensitivity up to Φ1.6mm flat bottom hole
3. Heat treatment process: Normalizing treatment must be carried out (900-930℃ insulation and air cooling), eliminate welding residual stress, and refine grains. A leading enterprise uses a roller bottom continuous furnace with a temperature control accuracy of ±5℃.
4. Testing technology:
- Hydrostatic test: The test pressure is calculated according to the standard formula and the holding time is ≥10 seconds
- Eddy current test: Cover the entire length of the pipe body
- Third-party certification: Bureau Veritas, SGS, and other institutions conduct factory audits and product certification
Third, typical application scenarios of ASTM A672 B70 CL22 straight seam welded steel pipes
1. Energy field: A Central Asian natural gas pipeline project adopts Φ813×20.6mm specifications, with a design pressure of 10MPa and a service temperature of -25℃. Compared with seamless steel pipes, it can save 15-20% of costs.
2. Chemical equipment: The heat exchanger tube bundle in a PTA unit in Zhejiang uses Φ508×16mm steel pipes, which are resistant to H2S corrosion environment. Special attention should be paid to the implementation of the post-weld heat treatment system.
3. Power industry: High-pressure water supply pipelines for supercritical units, with an operating temperature of 300-350℃. Actual cases show that the hardness of the weld area remains in the range of 180-220HV after 10 years of service.
Fourth, the market status and development of ASTM A672 B70 CL22 straight seam welded steel pipes
1. Supply and demand pattern: In 2024, my country’s EFW steel pipe production capacity will be about 8 million tons, of which high-end products that meet the ASTM A672 standard account for less than 30%. Major production enterprises.
2. Technology trends:
- Intelligent production: A demonstration factory introduced the MES system to achieve process parameter traceability
- Green manufacturing: The pickling process is gradually replaced by mechanical shot blasting
- Material upgrade: Develop high-strength grades such as B80 and B90
3. Procurement suggestions:
- Verify whether the factory has dual certification of API 5L and ASTM
- Require complete MTC material certification and heat treatment records
- Focus on checking the weld excess height (should be ≤3mm) and ovality (≤0.5%D)
Fifth, quality control points of ASTM A672 B70 CL22 straight seam welded steel pipe
1. Welding defect prevention and control: Statistics of a certain project show that the proportion of unfused steel pipes is as high as 52%, and the welding line energy needs to be monitored (18-22kJ/cm is appropriate).
2. Dimension accuracy control: In a customer feedback case, the angle deviation of the pipe end groove caused difficulties in on-site assembly welding. It is recommended to increase the 3D scanning detection of the pipe end.
3. Anti-corrosion support: It is recommended to use FBE coating (thickness ≥ 350μm) or 3PE anti-corrosion, which extended the life of steel pipes to 40 years in a Saudi Arabian project.
With the advancement of the “Belt and Road” energy infrastructure projects, the market demand for ASTM A672 B70 CL22 straight seam welded steel pipes will continue to grow. In the next five years, it is expected that the application of this product in LNG receiving stations, refining and chemical integration, and other fields will maintain an annual growth rate of 8-10%. At the same time, the application of new technologies such as digital twins and intelligent monitoring will further improve the quality reliability, and service performance of this product.
Post time: Jun-26-2025