304 stainless steel welded pipe identification method Steel numbering and representation method ① Use international chemical element symbols and national symbols to represent chemical composition, and Arabic letters to represent component content: such as: China, Russia 12CrNi3A ② Use fixed digits to represent steel Series or numbers; for example: United States, Japan, 300 series, 400 series, 200 series; ③ The serial number is composed of Latin letters and order, and only indicates the purpose. China's numbering rules ① The use of element symbols ② Purpose, Chinese pinyin, open hearth steel: P, boiling steel: F, calming steel: B, class A steel: A, T8: special 8, GCr15: ball ◆ combined steel, spring steel , Such as: 20CrMnTi 60SiMn, (C content is expressed in parts per thousand) ◆ Stainless steel, alloy tool steel (C content expressed in parts per thousand), such as: 1Cr18Ni9 per thousand (ie 0.1% C), stainless C≤ 0.08% such as 0Cr18Ni9, ultra-low carbon C≤0.03% such as 0Cr17Ni13Mo International stainless steel marking method The American Iron and Steel Institute uses three digits to mark various standard grades of malleable stainless steel. Among them: ① Austenitic stainless steel is marked with 200 and 300 series numbers, ② Ferrite and martensitic stainless steel is marked with 400 series numbers. For example, some more common austenitic stainless steels are marked with 201, 304, 316 and 310, ③ ferritic stainless steels are marked with 430 and 446, martensitic stainless steels are marked with 410, 420 and 440C, Duplex (Austenite-Ferrite), ④Stainless steel, precipitation hardening stainless steel, and high alloys with less than 50% iron are usually named after patent names or trademarks. Classification and classification of 304 stainless steel pipe standards 4-1 Classification: ①National Standard GB ②Industry Standard YB ③Local Standard ④Enterprise Standard Q / CB 4-2 Classification: ①Product Standard ②Packing Standard ③Method Standard ④Basic Standard 4- 3 Standard level (divided into three levels): Y level: international advanced level I level: international general level H level: domestic advanced level 4-4 national standard GB1220-84 stainless steel bar (level I) GB4241-84 stainless welding plate garden (Grade H) GB4356-84 Stainless Welding Plate (Grade I) GB1270-80 Stainless Steel Pipe (Grade I) GB12771-91 Stainless Steel Welded Pipe (Grade Y) GB3280-84 Stainless Steel Cold Plate (Grade I) GB4237-84 Stainless Hot Plate (Class I) GB4239-91 Stainless Cold Strip (Class I)