1 Overview:
(1) Production and manufacturing methods: Stainless steel is a general term for stainless acid-resistant steel. It is divided into stainless steel and acid-resistant steel and can resist weak and strong corrosive media. Steel pipes made of this type of steel are resistant to corrosion. The method of manufacturing a seamless steel pipe with basically the same, the steel press GB14975-94 "stainless steel seamless pipe" specified by 0Cr13,1Cr13,2Cr13,3Cr13,1Cr17Ni2,1Cr25Ti, 1Cr21Ni5Ti, 00Cr18Ni10,1Cr18Ni9,1Cr18Ni9Ti, 00Cr17Ni14Mo2,0Cr18Ni12Mo2Ti, 1Cr18Ni12Mo3Ti use, 1Cr23Ni18,1Cr18Ni11Nb other steel manufacturing.
(2) Uses: stainless acid-resistant stainless seamless steel tubes are widely used, acid-resistant steel parts petroleum, chemicals, pipes for various purposes, and should ensure that the chemical composition and physical properties of the steel.
2. Type:
Rolling method then rolled, hot extrusion and cold drawn (rolled) stainless steel tube. A different stainless steel microstructure by a half ferrite half martensitic stainless steel pipe, martensitic stainless steel, austenitic stainless steel, austenitic - ferritic stainless steels tubes.
Graphic stainless steel tube
3. Specifications and appearance quality:
(1) According to the provisions of GB14975-94 "Stainless Steel Seamless Steel Pipe", the normal length of steel pipe (indefinite) hot-rolled steel pipe is 1.5 ~ 10m, and the hot extruded steel pipe is equal to or greater than 1m. Cold drawn (rolled) steel pipe wall thickness of 0.5 ~ 1.0mm, 1.0 ~ 7m; wall thickness greater than 1.0mm, 1.5 ~ 8m.
(2) There are 45 kinds of hot-rolled (hot-extruded) steel pipes with a diameter of 54 to 480 mm, and a total of 36 kinds of wall thicknesses of 4.5 to 45 mm. There are 65 kinds of cold drawn (rolled) steel pipes with a diameter of 6 to 200 mm, and 39 kinds of wall thicknesses of 0.5 to 21 mm.
(3) There shall be no cracks, folds, cracks, cracks, rolling, separation and crusting defects on the inner and outer surfaces of the steel pipe. These defects shall be completely removed (except for mechanical processing pipes), and the wall thickness shall not be The outer diameter exceeds the negative deviation. Other minor surface defects that do not exceed the allowable negative deviation may not be removed.
(4) Straight road allowed depth. Hot-rolled and hot-extruded steel pipes, not less than or equal to 140mm in diameter and not more than 5% of the nominal wall thickness, the maximum depth is not more than 0.5mm; cold-drawn (rolled) steel pipes are not more than 4% of the nominal wall thickness, and the maximum depth is not more than 0.3 Mm.
(5) Both ends of the steel pipe should be cut at right angles and the burrs should be removed.
4. Chemical composition test:
(1) According to the provisions of GB14975-94, the steel pipe shall be made of stainless steel. Its chemical composition should meet GB1220-92 "stainless steel rod" and GB1221-92 "heat-resistant steel technical conditions".
(2) The chemical composition is prepared according to GB222-84, and the chemical analysis is carried out according to the relevant part of GB223.
(3) The chemical composition index inspection of imported stainless steel pipes shall be carried out in accordance with the relevant standards stipulated in the contract.
5. Physical property test:
(1) According to the provisions of GB14975-94. Austenitic, austenitic-ferritic steel pipes shall be tested for intergranular corrosion.
(2) Tensile test according to GB228-87, intergranular corrosion test according to GB4334.5-90, flattening test according to GB246-97, flare test according to GB242-97, non-metallic inclusion according to GB10561-89, hydraulic test according to GB /T241-90 specifies implementation.
(3) The physical property index inspection of the inlet pipe shall be carried out in accordance with the relevant standards stipulated in the contract.
6. Main import and export situation:
(1) The specifications of stainless steel pipes imported from Japan are 323.9×18mm; 18×3mm×5～8m.
(2) Italy imported hot-rolled stainless steel pipe with 273×10mm×6m, steel grade TP321, ASTM 312 standard, and intergranular corrosion test according to ASTM A262E.
7. Packaging:
According to GB2102-88 "General requirements of steel pipe acceptance, packaging, marking and quality certificate".
8. Other:
(1) Refer to GB3089-82 "Stainless steel-corrugated steel thin-wall seamless steel pipe";
(2) Refer to GB3092-93 "Stainless Steel Small Diameter Steel Pipe";
(3) Refer to GB222-84 "Sample sampling method for chemical analysis of steel and allowable deviation of chemical composition of finished products".
9. Classification of stainless steel pipes:
(1) Classified by production method:
(1) Seamless pipe - cold drawn pipe, extruded pipe, cold rolled pipe.
(2) Welded pipe:
(a) Classification by process - gas shielded pipe, arc welded pipe, electric resistance welded pipe (high frequency, low frequency).
(b) According to the weld seam - straight seam welded pipe, spiral welded pipe.
(2) Classification according to the shape of the section: (1) round steel pipe; (2) rectangular pipe.
(3) Classification by wall thickness - thin-walled steel pipe and thick-walled steel pipe.
(4) Classification by use:
(1) Civilian pipes are divided into round pipes, rectangular pipes and flower pipes, which are generally used for decoration, construction and structure;
(2) Industrial pipes: steel pipes for industrial piping, steel pipes for general piping (drinking water pipes), mechanical structures/fluid conveying pipes, boiler heat exchange pipes, food sanitary pipes, etc. Generally used in various fields of industry such as: petrochemical, paper, nuclear, food, beverage, pharmaceutical and other industries have higher requirements for fluid media.
10. Identification of stainless steel pipes:
(1) Magnetic test: The magnetic test is the simplest method to distinguish between annealed austenitic stainless steel and ferritic stainless steel. Austenitic stainless steel is non-magnetic steel, but will have mild magnetic properties after cold working under large pressure; while pure chrome steel and low alloy steel are strong magnetic steel.
(2), nitric acid point test: A remarkable feature of stainless steel tubes is the inherent corrosion resistance to concentrated nitric acid and dilute nitric acid. This property makes it easy to distinguish from most other metals or alloys. However, the high carbon type 420 and 440 steels are slightly corroded when subjected to the nitric acid point test, and the non-ferrous metals are immediately corroded when they encounter concentrated nitric acid. Dilute nitric acid is highly corrosive to carbon steel.
(3) Copper sulfate point test: The copper sulfate point test is the easiest way to quickly distinguish ordinary carbon steel from all types of stainless steel. The concentration of the copper sulfate solution used is 5 to 10%.
Before the point test, the test area should be thoroughly cleaned of grease or various impurities, and a small area is polished with a soft cloth, and then the copper sulfate solution is dripped into the cleaned area with a drop bottle. Ordinary carbon steel or iron forms a layer of surface metallic copper in a few seconds, while stainless steel surfaces do not produce copper deposits or show copper color.
(4) Sulfuric acid test: The sulfuric acid immersed stainless steel tube test can distinguish 302 and 304 from 316 and 317. The trimming of the sample shall be finely ground and then cleaned and passivated for half an hour in nitric acid (specific gravity 1.42) at a concentration of 20 to 30% and a temperature of 60 to 66 °C.
The sulfuric acid test solution has a volume concentration of 10% and is heated to 71 ° C. When the .302 and 304 steels are immersed in this hot solution, they are rapidly corroded and generate a large amount of bubbles, and the sample turns black in a few minutes; and 316 and 317 steel The sample is not corroded or the reaction is very slow (no bubbles are generated), and the sample does not change color within 10 to 15 minutes. The test can be made more accurate if the samples with known compositions are simultaneously tested for approximate comparison.
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