Carbon steel and low-alloy steel plates for boilers and pressure vessels
Carbon steel and low-alloy steel plates for boilers and pressure vessels (GB 713-86) are mainly used to make the shell, head, steam drum and pipe per boiler. These plates are applicable to steam-water fire-tube boilers, hot water boilers, and capacity boilers below 1.25MPa.
Carbon steel and low-alloy steel plates for boilers and pressure vessels are mainly divided into several categories, including national standards, industrial standards, and domestic and foreign standards. The national standard mainly refers to the Chinese National Standard. Specifically, steel plates for boilers and pressure vessels refer to the steel plate with minus 20 Celsius material strength and impact value requirements of no less than 275J. The industrial standards refer to the technical conditions stipulated by enterprises, including batch, size, steel grade and performance. The domestic and foreign standards refer to the standard conditions stipulated by other countries and regions, such as American ASTM standard and German DIN standard.
Carbon steel and low-alloy steel plates for boilers and pressure vessels (GB 713-86) are made of carbon steel by heating, cutting, and rolling. Generally, the thickness of the steel plates ranges from 6mm to 50mm. The processing temperature of carbon steel is usually lower than the casting temperature of low-alloy steel, so the processing of carbon steel is relatively simple. Carbon steel has resistance to corrosion, but poor in hardness and strength. Low-alloy steel has good properties on strength, hardness, wear resistance, and corrosion resistance. Being expensive in cost, it is mainly used in high-end industries such as ships and petroleum exploration.
Carbon steel and low-alloy steel plates for boilers and pressure vessels must have the good process performance, certain mechanical properties and the suitable chemical composition. According to the mechanical properties requirements of small, medium and large thickness of plates, there are over 140 kind of steel grades and their series. The most used steel grade for making boiler is Q245R, Q345R, 16Mn. The steel plate for pressure vessels and boilers must pass a series of tests such as tensile strength test, hardness test, flattening test, eddy current test and hydrostatic test. The test standards are clearly stipulated in international and national standards.
Finally, we should also make a note on welding techniques. Only qualified welding is allowed when welding carbon steel and low-alloy steel plates for boilers and pressure vessels. It is advised to adopt higher grade welding materials. Usually, quenching and tempering are necessary for welding structure with large plate thickness and importance; for welding the common thin plate structures, preheating beforehand is enough. It is recommended to use two-layer welding (one welding wire and one welding rod) for welding low-alloy steel when the plate thickness is over 10mm. The welding products should pass the test after the welding.
In short, carbon steel and low-alloy steel plates for boilers and pressure vessels (GB 713-86) are materials that can withstand high temperature and pressure. They are used mainly in the construction of boilers and pressure vessels. The steel classified according to different standards and the production and inspection should be conform to related rules or regulations. Additionally, appropriate welding methods should be applied to guarantee the safety and reliability.
