GB 3087 Grade 20 Seamless Boiler Tubes
Standard:GB 3087——Seamless steel pipe for low and medium pressure boilers
GB 3087 standard is applicable to the manufacture of high-quality carbon structural steel hot-rolled (extruded, expanded) and cold drawn (rolled) seamless steel tubes for various structural low-pressure and medium-pressure boilers and locomotive boilers.
GB 3087 Grade 20 Seamless Boiler Tubes Quick Details
Manufacture:Seamless process ,Hot-finished or Cold-finished
Wall thickness(WT): 3.2 mm——21 mm.
Outer diameter (OD): 33 mm——323 mm
Length: 6M or specified length as required.
Ends: Plain End, Beveled End, Treaded
Manufacturing methods of GB 3087 Grade 20 Seamless Boiler Tubes
(1)Method of manufacturing steel
Steel are manufactured by electric furnace, oxygen converter or open hearth method.
(2)Manufacturing method of tube blank
The tube blank can be produced by a hot rolling method, and a continuous casting billet or a steel ingot can also be used.
(3)Manufacturing method of steel pipe
The steel pipe can be manufactured by a hot rolling (extrusion, expansion) or cold drawing (rolling) seamless method.
Chemical composition of GB 3087 Grade 20 Seamless Boiler Tubes
|
Grade |
Chemical Composition(%) |
|||||||
|
C |
Si | Mn | P | S | Cr | Cu |
Ni |
|
|
20 |
0.17～0.23 | 0.17～0.37 | 0.38～0.65 | ≤0.030 | ≤0.030 | 0.3～0.65 | ≤0.25 |
≤0.30 |
Mechanical properties of GB 3087 Grade 20 Seamless Boiler Tubes
|
Grade |
Wall thickness (mm) |
Tensile strength (MPa) |
Yield Strength (MPa) |
Elongation % |
|
≥ |
||||
|
20 |
＜15 | 410～550 | 245 | 20 |
| ≥15 |
225 |
|||
Allowable deviation of outer diameter and wall thickness
|
Type of steel pipe |
Outer diameter(mm) |
Tolerance |
||
| ordinary |
advanced |
|||
|
Hot rolled tube |
OD |
≤159 | ±10%（min±0.50mm） | ±0.75%(min±0.40mm) |
| ＞159 | ±1.0% |
±0.90% |
||
|
WT |
≤20 | ＋15.0%(min＋0.45mm) －12.5% －0.35mm) |
±10%（min±0.30mm) | |
|
＞20 |
±12.5% |
±10% |
||
| OD≥351 |
±15% |
|||
|
Cold drawn tube |
OD |
10～30 | ±0.40mm | ±0.20mm |
|
＞30～50 |
±0.45mm | ±0.25mm | ||
| ＞50 | ±1.0% |
±0.75% |
||
|
WT |
1.5～3.0 |
+15% -10% |
±10% |
|
| ＞3.0 | +12.5% -10% |
±10% |
||
Testings
(1)Hydraulic test
The steel pipe should be hydraulically tested one by one.
(2)Flattening test
Steel pipes with an outer diameter of more than 22mm to 400mm and a wall thickness of not more than 10mm shall be subjected to a flattening test.
(3)Flaring test
The steel pipe with a wall thickness of not more than 8 mm can be subjected to a flare test with a top taper of 30°, 45° or 60°.
(4) Bending test
Steel pipes with an outer diameter of not more than 22 mm will be subjected to a bending test
(5)Non-destructive testing
According to the requirements of the purchaser, the steel pipe will be ultrasonically tested one by one.
Surface quality of GB 3087 Grade 20 Seamless Boiler Tubes
The inner and outer surfaces of the steel pipe do not have cracks, folds, creases, crusting or separation, and these defects should be completely removed. The clearance depth shall not exceed the negative deviation of the nominal wall thickness, and the actual wall thickness at the cleaning site shall not be less than the minimum allowed by the wall.
