API SPEC 5L-2007 (line pipe specification), compiled and issued by the American Petroleum Institute, is commonly used all over the world. Line pipe: The oil, gas, or water that is output from the ground is transported to the petroleum and natural gas industrial enterprises through the line pipe. Line pipes include seamless pipes and welded pipes. The pipe ends have flat ends, threaded ends, and socket end; the connection methods are end welding, coupling connection, socket connection, etc. The main material of the tube is B, X42, X46, X56, X65, X70, and other steel grades.

Steel line pipe standard:

API SPEC 5L-American Petroleum Institute Standard

GB/T9711-China National Standard

Steel line pipe use:

Oxygen, water, and oil conveying pipes used in petroleum and natural gas industries

Mainly produce steel pipe grades:

B, X42, X52, X60, X65, X70 L245 L290 L320 L360 L390 L450 L485

Steel line pipe size tolerance:

1.【Separate fire for steel line pipes】Low temperature tempering (150-250 degrees)

The structure obtained by low-temperature tempering is tempered martensite. Its purpose is to reduce the internal stress and brittleness of quenched steel under the premise of maintaining high hardness and high wear resistance, so as to avoid cracking or premature damage during use. It is mainly used for various high-carbon cutting tools, measuring tools, GB/T9711.1 pipeline steel pipes, rolling bearings, and carburized parts, etc. The hardness after tempering is generally HRC58-64.

2.【Separate fire for steel line pipes】Medium temperature tempering (250-500 degrees)

The structure obtained by tempering at medium temperature is tempered troostite. The purpose is to obtain high yield strength, elastic limit, and high toughness. Therefore, it is mainly used for the treatment of various GB/T9711.1 pipeline steel pipes and hot work molds, and the hardness after tempering is generally HRC35-50.

3. 【Separate fire for steel line pipes】High temperature tempering (500-650 degrees)

The structure obtained by high-temperature tempering is tempered sorbate. Traditionally, the heat treatment combining quenching and high-temperature tempering is called quenching and tempering treatment, and its purpose is to obtain comprehensive mechanical properties with good strength, hardness, plasticity, and toughness. Therefore, it is widely used in automobiles, GB/T9711.1 pipeline steel pipes, machine tools, and other important structural parts, such as connecting rods, bolts, gears, and shafts. The hardness after tempering is generally HB200-330.