Low alloy steel

 Introduction of varieties

Welding high strength steel welding high strength steel, also known as weldable low alloy high strength structural steel, is the main body of low alloy high strength steel. It has three basic properties: first, lower carbon content and good weldability. Second, the yield strength is higher than that of ordinary carbon steel. When used as structural material, the yield strength of steel is involved in the strength design of the structure. Third. On the basis of high strength, according to the different requirements of use, it has different characteristics, such as anti aging, impact resistance, resistance to toughness, notch sensitivity, fire resistance and so on. The main steel grades of high strength steel in our country have been included in GB/T1591 - 94, the classification and standard of low alloy special steel derived from it: steel BG713 - 86, YBG741 - 87 pressure vessel for boiler, GB5681 - 85, GB6653 - 86, GB6654 - 86GB6655 - 86, GB6479 - 86, GB3513 shipbuilding steel for GB712 to 88 automotive steel GB3273 - 82 bridge steel YB (T) 60 - 81 bicycle steel GB3647 - 83, GB3696 - 83 to guarantee the thickness of the directional performance steel GB5313 pipe for steel GB479 - 86, GB8162 - 87GB8163 - 87, YB231 - 70 nuclear steel, steel, steel, steel, and other steel. The design of alloy for high strength steel is the first to consider the strength of the steel. The strengthening mechanism includes solid solution strengthening, precipitation strengthening, fine grain strengthening, dislocation and substructure strengthening, and the microstructure enhancement of phase transition. The combination of these 5 intensification mechanisms can produce high strength welded steel with different levels of yield strength from 295MPa to 880Mpa, as well as the strength and toughness of different strength and toughness. Weldability is the basic attribute of welding high strength steel. It is required that under certain welding conditions, it is easy to get good weld and heat affected zone, which has the equivalent mechanical properties and processing properties. The effect of chemical composition of steel on weldability is shown in Table 2. Effective measures to improve welding performance are to reduce carbon content, reduce P and S content, and select suitable alloy elements.

The basic method to evaluate the weldability of welded high strength steel is usually the welding carbon equivalent Ceq and the welding crack sensitivity index Pcm.