Alloy steel pipe used for high pressure boiler

4140 steel is an ultra-high strength steel, with high strength and toughness, hardenability is also good, no obvious temper brittleness, small deformation during quenching, high fatigue limit after quenching and tempering and resistance to multiple impact, Low temperature impact toughness, high creep strength and durability at high temperatures. The steel is usually quenched and tempered as a heat treatment solution.
The two numbers at the beginning of a steel number indicate the carbon content of the steel, expressed in parts per million of the average carbon content, such as 40Cr, 4140 steel alloy steel, the main alloying elements in the steel, in addition to individual microalloying elements, generally a few percent Indicated. When the average alloy content is less than 1.5%, only the symbol of the element is generally marked in the steel number, and the content is not marked, but in special circumstances, it is easy to cause confusion. After the element symbol, the number “1” may also be marked, for example, the steel number. "12CrMoV" and "12Cr1MoV", the former chromium content of 0.4-0.6%, the latter is 0.9-1.2%, the remaining components are the same. When the average content of alloying elements is ≥ 1.5%, ≥ 2.5%, ≥ 3.5%, etc., the content shall be indicated after the element symbol, which may be expressed as 2, 3, 4...etc. For example 18Cr2Ni4WA.
(3) Alloying elements such as vanadium V, titanium Ti, aluminum AL, boron B, and rare earth RE in steel are microalloying elements. Although the content is very low, they should be marked in the steel number. For example, in 20MnVB steel. Vanadium is 0.07-0.12% and boron is 0.001-0.005%.
4 High-grade steel should be added "A" at the end of the steel to distinguish it from ordinary high-grade steel.
5 special purpose alloy structural steel, steel crown (or suffix) represents the symbol of the steel use. For example, special 30CrMnSi steel for rivets, the steel number is ML30CrMnSi.
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