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| Brand Name: | TORICH |
| Model Number: | GB/T 20409 |
| MOQ: | 0.5 TON |
| Price: | negotiable |
| Payment Terms: | L/C, D/A, D/P, T/T, Western Union, MoneyGram |
| Supply Ability: | 60000 Tons per Year |
GB/T 20409 Multi-rifled Seamless Steel Tubes for High-pressure Boiler
Application:High-quality carbon structural steel, alloy structural steel cold-drawing or cold-rolled internal thread tube for boilers suitable for producing high pressure and above pressure
Size:Length--8-12m
OD--28.6-66.7mm
WT--6.38-18.33mm
Curvature--≤1.0mm/m
Surface Quality:
1.The internal and external surfaces of female threaded tubes are not allowed to have cracks, folds, knots, folds, and delaminations. These defects should be completely removed. The depth of defect removal should not exceed 10% of the wall thickness, and the actual wall thickness at the filling removal site should not be less than the wall thickness. The minimum allowable thickness deviation, the clearance should be rounded off
2.The shape of the thread should be kept intact. There must be no drawing, curling or collapse.
3.The inner and outer straight surfaces of internally threaded tubes (including non-sharpened core rods) shall be allowed to have a depth of not more than 4% of the minimum wall thickness and a maximum of 0.2 mm.
4.Other local imperfections that do not exceed the wall thickness to allow negative deviations are allowed to exist.
5.Oxide scales on the inner and outer surfaces of the internally threaded tube should be removed so that the thin oxide layer does not interfere with the inspection.
The grade and chemical composition of steel
| Number | Brand | chemical composition(mass fraction)/ % | ||||||
| C | Mn | Si | Cr | Mo | S | P | ||
| 1 | 20G | 0.17~0.23 | 0.35~0.65 | 0.17~0.37 | -- | -- | ≤0.020 | ≤0.025 |
| 2 | 20MnG | 0.17~0.23 | 0.70~1.00 | 0.17~0.37 | -- | -- | ≤0.020 | ≤0.025 |
| 3 | 25MnG | 0.22~0.29 | 0.7~1.00 | 0.17~0.37 | -- | -- | ≤0.020 | ≤0.025 |
| 4 | 12CrMoG | 0.08~0.15 | 0.40~0.70 | 0.17~0.37 | 0.40~0.70 | 0.40~0.55 | ≤0.020 | ≤0.025 |
| 5 | 15CrMoG | 0.12~0.18 | 0.40~0.70 | 0.17~0.37 | 0.80~1.10 | 0.40~0.55 | ≤0.020 | ≤0.025 |
Note1:Residual element content of 20G,20MnG,25MnG should satisfy: Cu≤0.20%,Cr≤0.25%,Ni≤0.25%,V≤0.08%,Mo≤0.15%；The remaining elements of other brands should satisfy: Cu≤0.20%,Ni≤0.30%. | ||||||||
The size of the internal screw tubes and the allowable deviation of the thread parameters
| Code | Project | “A” teeth types allowable deviation | “B” teeth types allowable deviation |
| A | O.D≤38.1mm | ±0.15mm | -- |
| B | O.D≤38.1mm | -- | ±0.15mm |
| C | I.D of the root of the screw Thread: | ±0.15mm | ±0.15mm |
| E | Minimum I.D | Negative deviation to zero | Negative deviation to zero |
| F | Minimum W.T | +22% | +22% |
| G | Thread tips | -- | -- |
| I | Thread top width | -- | -- |
 | Height of thread: | ±0.3mm | ±0.18mm |
| K | Side Angle of thread. | ±15° | ±15° |
| O | radius of rounded corner at the root of thread | -- | -- |
| M | Thread pitch | ±3.2mm | ±3.2mm |
| N | Thread lead | ±3.2mm×thread tips | ±3.2mm×thread tips |
| Helix angle | Rating | Rating |
| T | Thread top width (axial) | ±1.3mm | ±1.3mm |
| U | Thread top (axial) groove width | -- | -- |
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