?? ????? ???? ?????????? ????? ????? ???? ?????????? ????? ?? ???????? ???? ?? ?????? ??? ????? ???? ?????? 5% ?? ?? ??? ?? ??? ?? ????? ?? ?????? ??????? ????? ?????? ????? ?? ???? ??, ?? ?? ????? ??? ?? ??????? ?? ???????????? ??? ????? ???? ?? ??? ????? ???? ?????? ?? ?? ???? ?????? ?? ????? ???? ??? ???? ???? ??? ?????? ????? ?? ????? ??? ???? ???? ??? ?????? ??? ?? ???? ????????, ???????? ?????, ?????, ???, ????, ?????? ?? ???? ?????? ???????? ??? ????? ???? ???? ??? ???????, ??????? ?? ?????????? ???? ????? ???? ???? ?????? ?? ????? ???? ???? ???????? ?? ???????? ???? ?? ???????? ?? ???? ??? ?? ??????? ??? ????? ?? ???? ???? ?????????? ??????, ????? ?????? ?? ????? ???? ??? ????? ?? ???? ???

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Low alloy structural steel grades and their expression: there are five grades of low alloy structural steel in China, and the main elements are manganese, silicon, vanadium, titanium, sharp, chromium, nickel and rare earth elements. Its trademark is composed of yield point letter Q, yield point value and quality grade (Grade A, B, C, D, e). It is divided into five grades, which are expressed as follows: yield point grade – quality grade. Yield point grade: q295, Q345, Q390, Q420, Q460.

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1. ????? ?????? ???????? ?????? ?????? ?? ????? ???? ?????????? ?????? ?? ???? ??? ???? ??? ???? ???? ?????, ????? ???? ??? ???? ?? ?????? ?? ?????? ?? ????, ????? ????? ?????? ???????? ???? ??? ?? ???? ?????? ?????? ?? ???, ?? ????? ??? ??? ???? ??????? ?????? ?? ?????? ?? ??? ?? ???? ?? (???? ?? ?????? ??? ???? ????, ???????? ???? ??? ?????? ??????? ????, ???), ?? ?????????? ??????????? ???? ?? ??? ?????, ??? ?????, ????????, ??? ?? ????? ?? ???? ??? ????????? ?????????, ??? ?? ???? ????? ?? ??????? ?? ?? ???? ??????? ?? ???? ???

2. ????? ????????? ????????? ?? ?????? ?? ?? ?????? ?? ????? ???? ???? ????? ??? ????? ?????????? ?? ???????? ???? ?????, ?? ????? ???????? ?? ??? ????? ???????? ?? ??????? ?? ??? ?????, ?????????, ???? ????? ?? ???????? ???? ??????? ?????? ?? ????? ???? ?????? ?????, ???? ???, ?????? ?????? ?? ???? ??, ???????? ???? ?? ?? ??? ?? ?????? ???? ??, ????? ????? ??? ????? ?? ????? ?? ???????? ?? ???????? ???????? ????, ????? ??????? ?? ??? ????? ???????? ??????? ?? ???????? ???????? ???? ??, ????? ??????? ?? ???? ????? ??????? ?????? ???? ???? ?????, ?? ??????? ??????? ?? ?????? ???????? ???????? ???? ???? ?? ?? (?? ???? ?? ??? ??) ???? ????? ???? ?????, ????? ?? ????? ??? ????????? ?? ???????? ???? ???

3. ????? ???????? ????????? ??????? ?????? ????? ????? ???? ?????? ?? ???? ???? ?????? ????? ?? ????? ??? ???? ???? ??, ?? ???? ??? ?? ????? ?? ?????? ?? ????? ?? ????? ?????? ????? ?? ????? ??? ???? ?? ??, ?????????? ??? (????? ??? ?? ??????? ?????????? ???) ?? ???? ?????? ?? ??????? ?????? ???? ?????, ???? ??????? ?????????? ???????????? ??? ??? ?? ???????? ???? ?? ????? ?????? ?? .. ?????, ? ???? ?????????? ???, ????? ??????? ??? ?? ????? ?? ???????? ???????? ??????? ???? ???? ?????? ????, ?????? ?????, ?? ????? ???? ?????? ?? ???? ?????????? ?? ??? ??????? ????? ??? ???????????? ?? ?????? ?????? ???

????? ???? ?????? ?? ??????

The common low alloy steel widely used in pressure vessel is mostly ferrite pearlite structure. The final properties are obtained by hot rolling or normalizing, and its structure is accepted by the equilibrium structure of steel. The main alloy element in steel is carbon. Increasing the carbon content can increase the quantity of pearlite and increase the yield limit and strength limit. However, there is a certain limit to increase the carbon content, because the increase of carbon content will affect the welding performance and other properties of steel (such as stamping performance, etc.), so that the brittleness transition temperature increases and the cold brittleness goes bad. Therefore, the carbon content of low alloy structural steel for pressure vessels is generally limited to less than 0.20%. When the carbon content is limited, the increase of the strength of this kind of steel mainly depends on the addition of a small amount of various alloy elements (the total addition is less than 5%, generally less than 3%, mostly 1% – 2%). For the low alloy structural steel with ferrite pearlite structure, the effects of adding alloy elements on its strength are as follows:

Ite ?????? ?? ???? ?????? ?? ????? ????;

② ??????? ?? ??????? ?????? ??? ??????;

③ ???? ?? ???? ?? ????????? ????;

④ ??????? ?? ????? ?? ???????? ????;

Ening ????? ?????

??????? ?? ??????? ????? ?????? ??? ??????? ???? ???, ????? ?????????? ??? ?????? ?? ????? ???? ??? ???? ?????? ??? ????????, ????, ?????, ??????? ??? ????? ???? ???? ?? ??? ?? ?????? ?? ??? ?? ????????? ?? ????? ??? ???? ???, ??????? ?? ??????? ?? ????? ????? ?? ??? ??? ?? ????? ???? ?????? ??? ???? ???? ??? ?? ?????? ?? ?????? ?? ???, ?? ??????? ?? ??????? 1.8% ?? ?? ??, ?? ? ???? ????? ?? ???? ??? ????? ???? ?? ???? ??, ????? ???????????? ?? ??????? ?? ?? ???? ??? ?? ???? ??? ???? ?????, ??????? ????????? ???? ?? ???? ?? ???? ?? ?? ????? ???? ?? ?????????? ????? ?? ???? ?? ???? ?? ???? ??, ????? ????? ???? ?????? ?? ??? ???? ??????? ?????? ???? ?? ?? ??????? ????? ?? ???? ??? ???? ???

The silicon content in low alloy structural steel is generally in the range of 0.2% – 1.7%, which will reduce the toughness. Chromium and nickel are also solid solution strengthening elements of ferrite, and nickel has a good effect on improving low temperature toughness; phosphorus strengthening ferrite has a significant effect, but due to the increase of cold brittleness, the maximum content should be limited to 0.15%, and the total content of phosphorus and carbon should be limited to less than 0.25%.

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????????? ???? (?? ????? ???? ???? ????? ?????????? ??????) (???? 1591) ?? ??????, ????? ????? ???? ???? ????? ?????????? ?????? ?? ???????? ????? ?? ???????? ?????? ?? ???????? ??? ????????? ???? ????? ???? ?????? ?? ????? ?????? ?? ????, ?? ????? ???? ?????????? ????? ??? ? ???? ???? ????? ???? ??, ????? ????? ????????????, ??????? ?? ???????????? ?? ???? ??? Q345 ????? ??? ????? ?????? ???????? ?? ?? ?? ????? ?????? ?? ?? ??????? ?????? ??? ????? Q390 ?? ?? ???????? ?????? ??? ?????? ?????????? ????? Q235 ?? ????? ???, ?? ????? ???? ???? ????? ???? ?????????? ????? ????? 20% ~ 30% ??? ???? ??, ?? ????? ????? ?????? ??? ?? ???? ???????? ??? ?? ????? ???? ?????????? ????? ?? ????? ????? ??? ?? ??????? ??????, ????? ?????, ????? ???? ?? ????? ??? ?? ??? ???? ?? ??? ???? ???? ??? ?? ????? ???????? ?? ??????? ??????? ???????? ??? ?????? ??? ?? ????? ???? ???? ??, ????? ??? ?? ??????? ????-????? ???????? ???, ???? ???? ?? ????????, ????-?????? ???????? ?? ??? ??????????, ?????? ?? ?????? ??? ??? ?????????

?? ???? ?????????? ????? ?? ??? ?? ??-?????? ?????????? ????? ??? ????? ???? ?????? ?? ??????? 3% ?? ?? ??, ????? ????? ????? ??? ?? ???? ?? ???????? ???? ?? ???? ??? ????? ???? ?? ??? ???? ???? ??? ?? ??? ?? ????? ?? ???? ?????? ????? ?? ????? ??? ?????? ??????? ?? ????? ??? ???? ???? ??, ????? ??? ????? ?? ????? ???? ???? ????? ????? ??? ???? ??? ????? ????? ???????, ????????????, ???????????? ?? ??? ???????? ?? ??? ??? ??? ?? ?????, ??????, ?????? ?? ???? ???????? ??? ????? ???? ???? ??, ???? ????? ??????? ?????, ???? ???? ???? ??????, ??? ??????, ???? ?????? ????????, ?????????, ????????, ?????? ?? ???? ???? ?????? ?? ???? ???????? ?? ????????? ???? ??? ???