Domestic Production of US Standard Low-Temperature Seamless Steel Pipes

Literature Overview

The paper by Zhang Qinglian, Wang Chaofeng, and Zhai Guoli (2017), published in Steel Pipe (Vol. 46, No. 5), discusses the domestic production status, quality, and application of US standard low-temperature seamless steel pipes based on ASTM A333/A333M. The research was conducted at Baoshan Iron & Steel Co., Ltd. (BAOSTEEL). The paper provides a comprehensive overview of the domestic production capabilities for Grades 1, 3, 6, and 8 low-temperature seamless pipes, covering the full range of service temperatures from -29°C down to -195°C, and recommends the transition from ASTM A333/A333M to ASTM A334/A334M to expand the application scope from cryogenic piping to cryogenic heat exchanger tubes.

Core Technical Content

ASTM A333/A333M Standard Requirements

ASTM A333/A333M specifies the requirements for seamless carbon steel and low-alloy steel pipes for low-temperature service. The standard covers five grades, each with specific chemical composition, mechanical property, and impact test requirements:

Domestic Production Status and Quality Analysis

BAOSTEEL has achieved domestic production of Grades 1, 3, 6, and 8, establishing a complete supply system for low-temperature seamless steel pipes down to -195°C. The key production challenges include:

1. Chemical composition control: The carbon and manganese content must be tightly controlled to ensure adequate low-temperature toughness. For Grades 6 and 8, the carbon equivalent (CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) should be limited to 0.40% or below to prevent cold cracking during welding and to ensure ductile fracture behavior at cryogenic temperatures.
2. Heat treatment: All grades require normalizing or normalizing-tempering treatment to achieve the required impact energy. For Grades 6 and 8, the normalizing temperature should be in the range of 880–950°C with furnace cooling or air cooling, followed by tempering at 600–650°C for Grade 8 to further improve toughness. The grain size after normalizing should be ASTM No. 6 or finer.
3. Impact testing: The Charpy V-notch impact test is the primary acceptance criterion for low-temperature grades. The test specimens should be taken from the HAZ of a weld or from the pipe body, depending on the application. For ASTM A333 pipes, the impact test is performed on specimens taken from the pipe body at the specified test temperature. The minimum energy values are as listed in the table above.

Welding Considerations for Low-Temperature Pipes

The welding of low-temperature seamless steel pipes presents unique challenges due to the risk of cold cracking and the need to maintain low-temperature toughness in the weld metal and HAZ:

• Preheat temperature: For Grade 1 and Grade 3, a minimum preheat of 50°C is recommended. For Grade 6, the preheat should be increased to 100°C. For Grade 8, a preheat of 150°C is required to prevent hydrogen-induced cracking.
• Welding consumables: Low-hydrogen consumables (hydrogen content ≤ 5 mL/100g) must be used for all grades. The weld metal composition should match or slightly exceed the base metal composition in terms of carbon and manganese content. For Grade 8, a nickel-manganese alloy consumable may be required to ensure adequate toughness at -165°C.
• Interpass temperature: The interpass temperature should be limited to 250°C for Grades 1 and 3, 200°C for Grade 6, and 150°C for Grade 8 to prevent excessive grain growth in the HAZ.
• Post-weld heat treatment (PWHT): PWHT is required for all grades with wall thickness exceeding 20 mm. The PWHT temperature should be 580–650°C for Grades 1 and 3, and 600–650°C for Grades 6 and 8, with a minimum holding time of 1 hour per 25 mm of wall thickness.

Quality Control and NDT Requirements

The quality control program for low-temperature seamless steel pipes should include the following NDT methods:

Key Insights and Strategic Recommendations

The paper's recommendation to transition from ASTM A333/A333M to ASTM A334/A334M is strategically significant. ASTM A334/A334M covers seamless steel tubes for low-temperature service in heat exchangers, which have more stringent dimensional tolerances and tighter chemical composition requirements compared to ASTM A333 pipes. This transition would enable BAOSTEEL to enter the cryogenic heat exchanger tube market, which is currently dominated by imported products from Japan, Korea, and Europe.

From a metallurgical perspective, the key to achieving consistent low-temperature toughness in Grades 6 and 8 lies in the microstructure control during the normalizing-tempering cycle. The desired microstructure is a fine-grained ferrite-pearlite matrix with a grain size of ASTM No. 7 or finer. Any presence of retained austenite or coarse grain boundaries can significantly reduce the impact energy at cryogenic temperatures. The use of thermomechanical controlled processing (TMCP) during rolling can further refine the grain structure and improve the low-temperature toughness.

The domestic production of ASTM A333 Grades 1, 3, 6, and 8 represents a significant achievement for the Chinese steel industry, as these grades are widely used in LNG (Liquefied Natural Gas) facilities, ethylene plants, and cryogenic storage tanks. The ability to supply these pipes domestically reduces project costs by 30–40% compared to imported products and eliminates supply chain risks associated with international trade.

Reference Value

This paper serves as a comprehensive reference for engineers involved in the specification, procurement, and quality control of low-temperature seamless steel pipes. The welding procedure recommendations and NDT requirements outlined in the paper should be incorporated into the project-specific quality assurance plan for any cryogenic piping system. The strategic recommendation to transition to ASTM A334/A334M provides a roadmap for the expansion of domestic production capabilities into higher-value cryogenic applications.