GB 3087—1999
Seamless steel pipe for low and medium pressure boilers

Standard name: seamless steel pipe for low and medium pressure boilers
Standard number: GB 3087—1999 neq ISO 9329-1:1989 Replacement GB 3087—1982
Standard type: National Standard of the People's Republic
Standard issuing unit: National Quality and Technical Supervision Bureau approved 1999-11-01
Implementation date: 2000-08-01 implementation

 
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%

 
 
3.2 length
3.2.1 Normal length
The usual length of steel pipes is specified as follows:
Hot-rolled (extruded, expanded) steel pipe............................................................4000~12000mm;
 Cold drawn (rolled) steel pipe.................................................................. 4000~10500mm.
 
After consultation between the supplier and the buyer, the steel pipe with a length of not less than 3000mm can be delivered, but the weight must not exceed 5% of the total delivery weight of the batch of steel pipes.
 
3.2.2 Length and length of the ruler
The length of the fixed length and the length of the double scale should be within the normal length range, and the full length tolerance is mm.
The length of each double ruler is set as follows:
OD ≤ 159mm..................................................................5~10mm;
Outside diameter>159mm..................................................................10~15mm.
 
3.2.3 Range length
The length of the range should be within the usual length range.

3.3 Bending
The bending of the steel pipe shall not be greater than the following:
Wall thickness ≤ 15mm..................................................................1.5mm/m;
Wall thickness >15mm..................................................................2.0mm/m;
Thermal expansion tube with an outer diameter of ≥ ............................................................ 3.0mm/m.
 
3.4 tip shape
The end faces of the steel pipe should be perpendicular to the axis of the steel pipe, and the burrs of the cut should be removed.
3.5 Unroundness and uneven wall thickness
According to the requirements of the purchaser, the supplier and the buyer shall negotiate and indicate in the contract that the out-of-roundness and wall thickness of the same section of steel shall not exceed 80% of the outer diameter and wall thickness, respectively.
 
3.6 Delivery weight
The delivery weight of steel pipes shall comply with the provisions of GB/T 19395. The density of the steel is calculated as 7.85 kg/dm3.
 
3.7 Tag example
A steel pipe with an outer diameter of 76 mm and a wall thickness of 3.5 mm made of steel No. 10:
a) Hot-rolled steel pipe, the outer diameter and wall thickness are of ordinary grade accuracy, and the length is 3000mm.
10-76×3.5×3000 times—GB 3087—1999
 
b) Cold drawn (rolled) steel pipe, the outer diameter is advanced precision, the wall thickness is ordinary precision, and the length is 5000mm
Cold 10-76 high × 3.5 × 5000 times - GB 3087-1999


4 Technical requirements
4.1 Steel grades and chemical composition
Table 2 Chemical composition of steel pipes

Standard	Grade	Chemical Composition(%)
		C	Si	Mn	P	S	Cr	Cu	Ni
GB3087	10	0.07～0.13	0.17～0.37	0.38～0.65	≤0.030	≤0.030	0.3～0.65	≤0.25	≤0.30
	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

4.1.1 The steel pipe is made of steel No. 10 and No. 20, and the chemical composition (melting analysis) shall comply with the provisions of GB/T 699. The steel pipe is inspected according to the olefinic components.
4.1.2 When the requester requests the analysis of the finished product, it should be indicated in the contract.
The chemical composition allowable deviation of the finished steel pipe shall comply with the provisions of GB/T222.
 
4.2 Manufacturing methods
4.2.1 Method of manufacturing steel
Steel shall be manufactured by electric furnace, oxygen converter or open hearth method. When the manufacturer specifies a certain manufacturing method, it shall be indicated in the contract; the steel directly used for continuous casting billet must be refined outside the furnace.
4.2.2 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. Hot rolled tube blanks shall comply with the provisions of YB/T 5222.
4.2.3 Manufacturing method of steel pipe
The steel pipe can be manufactured by a hot rolling (extrusion, expansion) or cold drawing (rolling) seamless method. When the purchaser specifies a certain manufacturing method, it should be indicated in the contract.
 
4.3 Delivery status
Steel pipes shall be delivered in hot rolled or heat treated condition. The finishing temperature of the steel pipe delivered in the hot rolled state shall not be less than Ar3.
 
4.4 Mechanical properties
4.4.1 Delivery conditions The longitudinal mechanical properties of steel pipes are to comply with the requirements of Table 3.
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
 
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.