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The manufacturing method shall be as follows:
Tubes shall be manufactured by a combination of the tube manufacturing method and the finishing method shown in table 1. If necessary, appropriate heat treatment may be applied to the tube.
Tubes may be made using coated steel sheet or coated steel strip if so, requested by the purchaser.
Bevel end finishing may be applied under the purchaser’s specification, in which case the shape shall be based on the agreement between the manufacturer and the purchaser.
| Symbol of Grade | Symbol of Manufacturing Method | Marking of Symbol of Manufacturing Method | |
| Tube manufacturing | Finishing method | ||
| STK540 |
Seamless: S
Electric resistance
Butt welded: B
Automatic arc welded: A
|
Hot finished: H
Cold finished: C
As electric resistance
welded: G
|
As given in clause 11 b) |
| Symbol of Grade | C | Si | Mn | P | S |
| STK540 | 0.23 max. | 0.55 max. | 1.50 max. | 0.040 max. | 0.040 max. |
|
Notes a) If necessary, alloying elements other than specified in this table may be added. b) For the tube of grade STK540 exceeding 12.5 mm in wall thickness, the chemical composition may be subject to the agreement between the purchaser and the manufacturer. |
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| Symbol of Grade |
Tensile Strength
N/mm²
|
Yield Point of Proof Stress
N/mm²
|
Tensile Strength in Weld Zone
N/mm²
|
Flattening | Bendability | |
|
Distance between Plates
(H)
|
Bend Angle | Inside Radius | ||||
| Applied outside diameter | ||||||
| All outside diameters | All outside diameters | All outside diameters | All outside diameters | 50 mm max. | ||
| STK540 | 540 min. | 390 min. | 540 min. | 7/8 D | 90° | 6 D |
|
NOTE 1 D of this table is the outside diameter of the tubes. NOTE 2 1 N/mm²—1 MPa Note a) Standard of bend angle shall be the start point of bending. |
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| Symbol of grade | Tube Manufacturing Method | ||||
| Seamless and butt welded | Electric resistance welded and automatic arc welded | All manufacturing methods | |||
| Applied outside diameter | |||||
| All outside diameters | 350 mm | Over 350 mm | All outside diameters | ||
| Test Piece and Direction of Test Piece | |||||
|
No. 11 test piece
No. 12 test piece
|
No. 11 test piece
No. 12 test piece
|
No.5 test piece | No.4 test piece | ||
| Tube axis direction | Tube axis direction | Perpendicular to the tube axis direction | Tube axis direction | Perpendicular to the tube axis direction | |
| STK540 | 23 | 23 | 18 | 21 | 17 |
| For the tubes of outside diameter 40 mm or under, the elongation value in this table shall not be applied. However, the test result for these tubes shall be recorded. Further, the elongation may be specified by agreement between the manufacturer and the purchaser. | |||||
- Outside Diameter Tolerance a)
| Classification | Outside Diameter b) |
Tolerances on
Outside Diameter c)
|
Applicable Division |
| Class 1 | Under 50mm | ± 0.5mm |
Applied when there is no specification.
Applicable to hot-finished seamless steel tubes.
|
| 50mm or Over | ± 1% | ||
| Class 2 | Under 50mm | ± 0.25mm |
Applied when there is a specification.
Not applicable to hot-finished seamless steel tubes.
|
| 50mm or Over | ± 0.5% | ||
| Notes |
a) For the local parts such as repaired parts if the wall thickness can be confirmed to be within the tolerance in the table below, the outside diameter tolerance of this table need not be applied. |
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|
b) The method for measuring the outside diameter of tubes exceeding 350mm in outside diameter may be determined by the circumferential length. The mutual conversion of outside diameter D and the circumferential length l shall be by the following formula: D = l / π Where D: outside diameter (mm) l: circumferential length (mm) π：3.1416 |
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|
c) The tolerances on the outside diameter of ends of electric resistance welded and automatic arc welded steel tubes exceeding 350mm in outside diameter shall be ±0.5%。 |
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- Wall Thickness Tolerance a)
| Classification | For Seamless Steel Tube | For Other than Seamless Steel Tube | Applicable Division | ||
| Wall Thickness | Tolerance of Wall Thickness | Wall Thickness | Tolerance of Wall Thickness | ||
| Class 1 | Under 4mm | +0.6mm, -0.5mm | Under 4mm | +0.6mm, -0.5mm |
Applied when there is no specification.
Applicable to hot-finished seamless steel tubes.
|
| 4mm or Over | +15%, -12.5% | 4mm or Over to and excl. 12mm | +15%, -12.5% | ||
| 12mm or Over | +15%, -1.5mm | ||||
| Class 2 | Under 3mm | ±0.3mm | Under 3mm | ± 0.3mm |
Applied when there is a specification.
Not applicable to hot-finished seamless steel tubes.
|
| 3mm or Over | ±10% | 3mm or Over to and excl. 12mm | ±10% | ||
| 12mm or Over | +10%，-1.2mm | ||||
| Notes | a) The tolerances on the wall thickness of tubes exceeding 1016.0 mm in outside diameter may be agreed upon between the manufacturer and the purchaser. | ||||
Each tube having passed the inspection shall be marked with the following items on each STK540 tube. For tubes of smaller outside diameter or when there is a special request by the purchaser, marking may be applied on a bundle. The order of arrangement of the markings is not specified. When approved by the purchaser, part of the items may be omitted.
• Grade symbol• Symbol representing the manufacturing process. The following symbol should be used to indicate the production technique. However, a space may be used in place of the dash.
1. As welded steel tube with electric resistance: -E-G
2. Hot finished electric resistance welded steel tube: -E-H
