How much temperature can 20# steel withstand

The maximum heat-resistant temperature of 20# steel seamless steel pipe in the national standard GB/8163-2018 is 425℃. Many people say that the lowest temperature that 20# steel in GB/T8163-2018 can withstand is -20℃, and the maximum heat-resistant temperature is 425℃. Because the operating temperature range of 20# steel seamless steel pipe in GB/T 8163-2018 is -20℃~425℃, the maximum heat-resistant temperature is 425℃. At present, according to the relevant specifications of "pressure steel pipeline", the lower limit of the allowable use temperature of 20# steel is -20℃, but according to relevant data and literature, some people have tried to do low-temperature impact tests at different temperatures. Referring to "The Effect of Heat Treatment on the Tough-Brittle Transition Temperature of 20 Steel", according to the test data, it can be seen that the pressure steel pipeline (normalizing) delivered in accordance with the specification has a cold-brittle transition temperature of about -40℃, below 0℃. As the temperature drops, the impact energy continues to decrease, and there is no strict transition point. However, the seamless steel pipe of GB/T8163-2018 standard is recommended to be used for fluid transportation at room temperature and is not recommended for use in high-temperature environments. For seamless steel pipes with temperature requirements, it is recommended to use the 20G steel grade in the national standard GB/T5310 standard, and its use temperature does not exceed 450℃, and it is recommended not to exceed 350℃.

Seamless steel pipes have hollow cross-sections and are widely used as steel pipelines for conveying fluids, such as steel pipelines for conveying oil, natural gas, coal gas, water, and certain solid materials. Compared with solid steel such as round steel, steel pipe is lighter in weight when the bending and torsional strength are the same. It is an economical cross-section steel and is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, bicycle frames, and steel scaffolding used in construction. The use of steel pipes to manufacture annular parts can improve material utilization, simplify the manufacturing process, save materials and processing time, and has been widely used in steel pipes.

The 20 in No. 20 steel refers to the carbon content, which is 0.2%, belonging to low carbon steel. Steel can be divided into low-carbon steel, medium-carbon steel, and high-carbon steel. Carbon content: low carbon steel is generally less than 0.25%; medium carbon steel is generally between 0.25 and 0.60%; high carbon steel is generally greater than 0.60%.

In addition to carbon (C) and a certain amount of silicon (Si) (generally not more than 0.40%) and manganese (Mn) (generally not more than 0.80%, up to 1.20%) alloy elements for deoxidation, the steel does not contain other alloy elements (except residual elements).

General boiler steel tube use temperature:

①General boiler steel tube use temperature is below 350℃. Domestic steel tubes are mainly made of 10# steel, 20# steel carbon steel hot rolled steel tubes, or cold-drawn steel tubes. The implementation standard is GB/T3087 standard.

②High-pressure boiler steel tubes are often in high temperature and high-pressure conditions during use. Under the action of high-temperature flue gas and water vapor, the steel tubes will oxidize and corrode. Steel tubes are required to have high lasting strength, high oxidation and corrosion resistance, and good organizational stability.

Common materials and maximum allowable temperatures (maximum operating temperature) of high-pressure boiler steel tubes: Common national standard high-pressure boiler steel tube steel grades and their maximum allowable temperatures. The working conditions of high-pressure boiler steel tubes are very harsh. They must work safely for 10 to 20 years, or even longer, under high pressure and high temperature, and under the erosion and corrosion of high-speed airflow, water flow, and gas. The working temperatures of high-pressure boiler steel tubes of different steel grades are also different. In general, the working temperature of alloy boiler steel tubes is higher than that of ordinary carbon steel boiler tubes. The following are the commonly used national standard high-pressure boiler steel tube steel grades and their parameters:

Common steel tube use temperature range: below 600℃, the thermal conductivity of various stainless steels is basically in the range of 10~30W/(m•℃), and the thermal conductivity tends to increase with the increase of temperature. At 100℃, the order of thermal conductivity of stainless steel from large to small is 1Cr17, 00Cr12, 2Cr25N, 0Cr18Ni11Ti, 0Cr18Ni9, 0Cr1Ti, 0Cr18Ni9, 0Cr17Ni12Mο2, 2Cr25Ni20. At 500℃, the order of thermal conductivity from large to small is 1Cr13, 1Cr17, 2Cr25N, 0Cr17Ni12Mο2, 0Cr10Cr17Ni12Mο2, 0Cr18Ni9Ti and 2Cr25Ni20. The thermal conductivity of austenitic stainless steel is slightly lower than that of other stainless steels. Compared with ordinary carbon steel, the thermal conductivity of austenitic stainless steel at 100℃ is about 1/4 of that of ordinary carbon steel.