1. Type
The rolling techniques are divided into hot rolling, hot extrusion and cold drawing (rolling) stainless steel tubes. According to the difference of stainless steel metallographic structure, it can be divided into semi-ferritic and semi-martensitic stainless steel pipes, martensitic stainless steel pipes, austenitic stainless steel pipes, austenitic-ferritic iron stainless steel pipes, etc.
2. Specifications and appearance
(1) According to GB14975-94 "Stainless Steel Seamless Steel Tube", the normal length of the steel pipe (indefinite length) is 1.5-10m for hot-rolled steel pipe, and the hot-extruded steel pipe is equal to and greater than 1m. For cold drawn (rolled) steel pipes with a wall thickness of 0.5～1.0mm, 1.0～7m; for those with a wall thickness greater than 1.0mm, 1.5～8m. Stainless steel pipe processing
(2) There are 45 kinds of hot-rolled (hot-extruded) steel pipes with a diameter of 54-480mm; a total of 36 kinds with a wall thickness of 4.5-45mm.
There are 65 kinds of cold drawn (rolled) steel pipes with a diameter of 6～200mm and 39 kinds with a wall thickness of 0.5～21mm.
(3) There must be no cracks, folds, cracks, cracks, folds, delamination and scarring on the surface and back of the steel pipe. These defects should be completely removed (except for pipes for mechanical processing). And the outer diameter exceeds the negative deviation.
Other minor surface defects that do not exceed the allowable negative deviation can not be removed. Stainless steel pipe processing
(4) Allowable depth of straights. Hot-rolled and hot-extruded steel pipes with a diameter less than and equal to 140mm are not more than 5% of the nominal wall thickness, and the large depth is not more than 0.5mm; cold drawn (rolled) steel pipes are not more than 4% of the nominal wall thickness, and the large depth is not more than 4%. More than 0.3mm.
(5) Both ends of the steel pipe should be cut at right angles and burrs should be removed.
3. Chemical composition inspection
(1) According to GB14975-94, the steel pipe should be made of stainless steel. Its chemical composition should be in accordance with GB1220-92 "Stainless Steel Rods" and GB1221-92 "Technical Conditions for Heat-Resistant Steels" respectively.
(2) The sample preparation of chemical composition is carried out according to GB222-84, and the chemical analysis is carried out according to the relevant section in GB223.
(3) The chemical composition index inspection of imported stainless steel pipes shall be conducted in accordance with the relevant standards stipulated in the treaty.
4. Physical performance inspection
(1) Defined according to GB14975-94. Austenitic, austenite-ferrite type steel pipes must be tested for intergranular corrosion.
(2) The tensile test is in accordance with GB228-87, the intergranular corrosion test is in accordance with GB4334.5-90, the flattening test is in accordance with GB246-97, the flaring test is in accordance with GB242-97, the non-metallic inclusions is in accordance with GB10561-89, and the water pressure test is in accordance with GB. /T241-90 is delineated and implemented.
(3) The physical performance index test of the imported pipe is held in accordance with the relevant standards stipulated in the treaty.
5. Main import and export situation
(1) The specifications of stainless steel pipe imported from Japan are 323.9×18mm; 18×3mm×5～8m, etc.
(2) The hot-rolled stainless steel pipe imported from Italy has specifications of 273×10mm×6m, steel grade TP321, and implements ASTMA312 standard, and the intergranular corrosion test is in accordance with ASTMA262E method.
