GB3087-2008 is applied to the seamless steel tubes that are made of quality carbon structural steels and used for manufacturing various low and medium pressure boilers.
1 Scope
This standard specifies the dimensions, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality specifications of seamless steel tubes for low and medium pressure boilers.
This 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.
2 Reference standard
The provisions contained in the following standards constitute provisions of this standard by reference in this standard. At the time of publication, the editions indicated were valid. All standards will be revised and parties using this standard should explore the possibility of using the latest version of the following standards.
- GB/T222—1984 Sample sampling method for chemical analysis of steel and chemical composition tolerance of finished products
- GB/T223.5-1997 Methods for chemical analysis of steels and alloys - Determination of acid-soluble silicon content by molybdate spectrophotometry
- GB/T 223.12—1991 Methods for chemical analysis of steels and alloys - Sodium carbonate - Diphenylcarbonyl hydrazide photometric method
- GB/T 223.19—1989 Chemical analysis methods for steel and alloys Xinyatongling-trichloromethane extraction
- GB/T 223.23—1994 Methods for chemical analysis of steels and alloys - Determination of nickel content by succinimide spectrophotometry
- GB/T 223.62—1988 Methods for chemical analysis of steels and alloys - Determination of phosphorus content by butyl acetate extraction spectrophotometry
- GB/T 223.63—1988 Methods for chemical analysis of steels and alloys - Determination of manganese content by sodium periodate (potassium) photometric method
- GB/T 223.69—1997 Method for chemical analysis of steel and alloys. Determination of carbon content by gas volume method after combustion in tubular boilers
- GB/T 223.72—1991 Methods for chemical analysis of steels and alloys - Aluminium chromatographic separation - Barium sulfate gravimetric method
- GB/T 226—1991 Low-fold structure of steel and defect acid etching test
- GB/T 228—1987 Metal tensile test method
- GB/T 241—1990 Metal pipe hydraulic test method
- GB/T 242—1997 Metal pipe flaring test method
- GB/T 244—1997 Metal tube bending test method
- GB/T 245—1997 Metal tube crimping test method
- GB/T 246—1997 Metal tube flattening test method
- GB/T 699—1999 high quality carbon structural steel
- GB/T 2102—1988 Acceptance, packaging, marking and quality instructions for steel pipes
- GB/T 5777-1996 Ultrasonic flaw detection test method for seamless steel tubes
- GB/T 7735-1995 Steel pipe eddy current testing method
- GB/T 12606—1999 Steel pipe leakage magnetic flaw detection method
- GB/T 17395—1998 Seamless steel pipe size, shape, weight and tolerance
- YB/T 5222-1993 high quality carbon round billet
3 size, shape, weight
3.1 Outer diameter and wall thickness
3.1.1 The outer diameter, wall thickness and theoretical weight of the steel pipe shall comply with the provisions of Table 1 of GB/T 17395-1998.
Steel pipes of different specifications as specified in Table 1 of GB/T 17395-1998 may be supplied through negotiation between the supplier and the buyer.
3.1.2 The allowable deviation of the outer diameter and wall thickness shall comply with the requirements of Table 1.
When the purchaser requests to supply according to advanced precision, it should be indicated in the contract.
After consultation between the supplier and the buyer, and in the contract, it can produce steel pipes with deviations from those specified in Table 1.
Table 1 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% | ||
Chemical Composition(%)
| Standard | Steel Grade | C | Si | Mn | S | P | Cr |
| GB 3087 | 10 | 0.07-0.13 | 0.17-0.37 | 0.35-0.65 | 0.020 | 0.025 | ≤0.15 |
| 20 | 0.17-0.23 | 0.17-0.37 | 0.35-0.65 | 0.020 | 0.025 | ≤0.25 |
3.2 length
Table 3 Longitudinal mechanical properties of steel tubes
| Standard | Steel pipe | Wall thickness (mm) | Tensile strength (MPa) | Yield Strength (MPa) | Elongation % |
| ≥ | |||||
| GB3087 | 10 | / | 335-475 | 195 | 24 |
| 20 | ＜15 | 410-550 | 245 | 20 | |
| ≥15 | 225 | ||||
4.4.2 The high-temperature transient performance of the steel pipe used for medium-pressure boiler superheated steam pipe shall comply with the provisions of Table 4. The purchaser shall indicate the purpose of the steel pipe in the contract.
According to the requirements of the purchaser, the supplier and the buyer shall negotiate and indicate the test temperature in the contract, and the supplier shall provide the actual high-temperature transient performance data of the steel pipe.
Table 4 Minimum yield strength of steel pipe at high temperature
| Steel grade | Sample status | Temperature，℃ | |||||
| 200 | 250 | 300 | 350 | 400 | 450 | ||
| 10 | Delivery status | 165 | 145 | 122 | 111 | 109 | 107 |
| 20 | 188 | 170 | 149 | 137 | 134 | 132 | |
4.5 Process test
4.5.1 Hydraulic test
The steel pipe should be hydraulically tested one by one.
The supplier can replace the hydraulic test with eddy current testing. Ultrasonic testing or magnetic flux leakage testing can also be used instead of hydraulic testing after consultation between the supplier and the buyer. When using eddy current flaw detection, the grade A hole of GB/T 7735-1994 should be used; when ultrasonic flaw detection, the depth grade of the longitudinal notch groove on the outer surface of the comparison sample tube should meet the requirements of C8 in GB/T5777-1996; The longitudinal notch groove on the outer surface of the comparative sample tube shall comply with the provisions of N12.5 in GB/T 12606-1999, with a minimum depth of 0.5 mm and a maximum depth of 1.5 mm.
4.5.2 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.
No cracks or cracks shall appear on the specimen after the flattening test.
4.5.3 crimping test
According to the requirements of the purchaser, the supply and demand sides negotiate and indicate in the contract that the steel pipe made of No. 10 steel can be subjected to the crimping test.
The curling width (measured by the inner wall) shall not be less than 12% of the nominal inner diameter, nor less than 1.5 times the nominal wall thickness, and the curling angle shall be 90°. No cracks or cracks shall occur outside the sample curl after crimping.
4.5.4 Flaring test
According to the requirements of the purchaser, the supply and demand sides negotiate and indicate in the contract that 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°. No cracks or cracks shall appear on the specimen after flaring.
The flaring ratio of the outer diameter of the sample after flaring shall comply with the requirements of Table 5.
Table 5 steel pipe outer diameter expansion rate
| Standard | Steel grade | steel pipe outer diameter expansion rate，% | ||
| Inside diameter / outer diameter | ||||
| ≤0.6 | ＞0.6-0.8 | ＞0.8 | ||
| GB3087 | 10 | 12 | 15 | 19 |
| 20 | 10 | 12 | 17 | |
4.5.5 Bending test
Steel pipes with an outer diameter of not more than 22 mm shall be subjected to a bending test with a bending angle of 90° and a radius of curvature of six times the outer diameter of the steel pipe. There must be no cracks or cracks in the bend.
According to the requirements of the purchaser, the supply and demand sides negotiate and indicate in the contract that the steel pipe for the locomotive boiler can be bent. The bending angle and the radius of the core are negotiated by both the supplier and the buyer.
4.6 Low-power test
For steel pipes directly manufactured by continuous casting billet or steel ingot, the supplier shall ensure that there are no white spots, inclusions, slag inclusions, skin turning, delamination and subcutaneous air bubbles on the cross-section acid-leaching low-strength test piece of the steel pipe or the blank.
4.7 Surface quality
The inner and outer surfaces of the steel pipe are not allowed to 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.
Straight road allowed depth:
Cold drawn (rolled) steel pipe: not more than 4% of the wall thickness, the maximum depth is 0.3mm;
Hot-rolled (extruded, expanded) steel pipe: not more than 5% of the wall thickness, the maximum depth is 0.5mm.
Other defects where the depth does not exceed the wall thickness negative deviation and the remaining wall thickness is not less than the minimum allowed by the wall thickness are allowed to exist.
4.8 Non-destructive testing
According to the requirements of the purchaser, after consultation between the supplier and the buyer, and in the contract, the steel pipe can be ultrasonically tested one by one. The depth of the longitudinal notch groove on the outer surface of the sample pipe should meet the requirements of C8 in GB/T 5777-1996.
5 Test methods
5.1 The size of the steel pipe shall be measured one by one using gauges that meet the accuracy requirements.
5.2 The inner and outer surfaces of steel pipes shall be visually inspected one by one.
5.3 Other inspection items for steel pipes shall comply with the requirements of Table 6.
Table 6 Inspection items, sampling quantities and test methods for steel pipes
| Number | Test items | Experiment method | Number of samples |
| 1 | Chemical composition | GB/T 222 GB/T 223 | Take one sample per furnace (tank) |
| 2 | Stretching test | GB/T 228 | Take one sample for each batch on each of the two steel pipes |
| 3 | Hydraulic test | GB/T 241 | Each |
| 4 | Flattening test | GB/T 246 | Take one sample for each batch on each of the two steel pipes |
| 5 | Crimping test | GB/T 245 | Take one sample for each batch on each of the two steel pipes |
| 6 | Flaring test | GB/T 242 | Take one sample for each batch on each of the two steel pipes |
| 7 | Bending test | GB/T 244 | Take one sample for each batch on each of the two steel pipes |
| 8 | Low magnification test | GB/T 226 | Take one sample for each batch on each of the two steel pipes |
| 9 | Ultrasonic flaw detection | GB/T 5777 | Each |
| 10 | Eddy current testing | GB/T 7735 | Each |
| 11 | Magnetic flux leakage test | GB/T 12606 | Each |
6 Inspection rules
6.1 Inspection and acceptance
The inspection and acceptance of steel pipes shall comply with the provisions of GB/T 2102.
6.2 Batch rule
The steel pipes are inspected and accepted in batches. Each batch shall consist of steel pipes of the same grade, the same furnace (tank) number, the same specification and the same heat treatment system (heating).
All pipe sections taken from double-length long seamless steel pipes shall be considered as one.
The number of roots of each batch of steel pipes does not exceed the following:
The outer diameter is not more than 76mm, and the wall thickness is not more than 3mm......................................................400 PCS;
Outer diameter is greater than 351mm....................................................................................50 PCS;
Other sizes of steel pipes..........................................................................................200 PCS.
When the number of remaining steel pipes is not less than 50% as specified above, it shall be listed as a batch; if it is less than 50% of the above, it may be incorporated into the same grade, the same furnace (can) number, the same specification and the same heat treatment system (furnace) Next) in the adjacent batch.
6.3 Number of samples
The sampling quantity of each inspection item of each batch of steel pipe shall be as specified in Table 6.
6.4 Re-inspection and decision rules
The re-inspection and determination rules of steel pipes shall comply with the provisions of GB/T 2102.
7 Packaging, marking and quality instructions
The packaging, marking and quality specifications of steel pipes shall comply with the provisions of GB/T 2102.
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