GB 9948 Seamless Steel Tubes For Petroleum Cracking
GB 9948 Seamless steel tubes for petroleum cracking
1.Scope
This standard specifies the classification, code, size, shape, weight, technical requirements, test methods, inspection rules, packaging, marking, and quality certificates for seamless steel pipes for petroleum cracking.
This standard applies to the use of seamless tubes for furnace tubes, heat exchanger tubes and pressure pipes.
3 classification, code
Steel Grade: 10, 20, 12CrMo, 15CrMo, 1Cr5Mo, 1Cr19Ni9, 1Cr19Ni11Nb.
Steel Grade: 10, 20, 12CrMo, 15CrMo, 1Cr5Mo, 1Cr19Ni9, 1Cr19Ni11Nb.
The seamless steel pipes of this standard are divided into two categories according to the manufacturing methods of the products. The categories and codes are:
a) hot rolling (extrusion, expansion) steel pipe WH;
b) cold drawn (rolled) steel pipe WC
4.Order content
Contracts or orders for ordering steel pipes in accordance with this standard shall include the following:
a) standard number;
b) product name;
c) grade; d) quantity ordered (total weight or total length);
e) Dimensions (outer diameter x wall thickness in mm) and accuracy class:
f) manufacturing method;
g) Special requirements.
5 Dimensions, shape, weight and tolerance
5.1 outer diameter and wall thickness
5.1.1 The outer diameter and wall thickness of the steel pipe shall comply with the requirements of Table 1. According to the requirements of the purchaser, other steel pipes with outer diameter and wall thickness can be supplied through negotiation between the supplier and the buyer.
5.1.2 When the purchaser fails to indicate the allowable deviation level of the steel pipe in the contract, the allowable deviation of the outer diameter and wall thickness of the steel pipe shall comply with the general level.
According to the requirements of the purchaser. After consultation between the supplier and the buyer, and indicate in the contract. It is possible to produce steel pipes with different tolerances than those specified in Table 1.
Table 1 Allowable deviation of outer diameter and wall thickness of steel pipe
| Classification | Manufacturing method | Size | Allowable deviation | ||
| PA | PC | ||||
| W-H | Hot rolled steel pipe | OD | ≤50 | ±0.50 | ±0.30 |
| ＞50~159 | ±1% OD | ±0.75% OD | |||
| ＞159 | ±1% OD | ±0.9% OD | |||
| WT | ≤20 |
+15% WT -10% WT |
±10% WT | ||
| ＞20 |
+12.5% WT -10% WT |
±10% WT | |||
| Thermal expansion steel pipe | OD | All | ±1% OD | ||
| WT | All | ±15% WT | |||
| W-C | Cold drawn steel pipe | OD | 13~30 | ±0.20 | ±0.15 |
| ＞30~50 | ±0.30 | ±0.25 | |||
| ＞50 | ±0.75% OD | ±0.6% OD | |||
| WT | ≤3.0 |
+12.5% WT -10% WT |
±10% WT | ||
| ＞3.0 | ±10% WT | ±7.5% WT | |||
5.2Length
The usual length of normal length steel pipe is 4000mm - 12000mm.
After consulting between the supply and demand. It is also stated in the contract that steel pipes with a length greater than 12000 mm or shorter than 4000 mm but not shorter than 3000 mm can be delivered, but the number of steel pipes with a length Shorter than 4000 mm should not exceed 5% of the total delivered quantity of the batch of steel pipes.
5.3Fixed length and multiple length
The length of the fixed length and the multiple length are negotiated by the supplier and the buyer according to the requirements of the purchaser, and the steel pipe can be delivered according to the length of the fixed length or the length of the double.
The length of the steel pipe shall be within the normal length, and the allowable deviation of the length shall comply with the following provisions:
a) When the length is ≤ 6000mm. +10mm
b) + 20mm when the length is > 6000 mm
The length of each double ruler should be left as shown below:
When the outer diameter is ≤ 159 rnm, 5mm - 10mm
When the outer diameter is >159 mm, 10mm - 15mm
5.4 Out of roundness 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 non-roundness and wall thickness of the steel pipe shall not exceed 80% of the outer diameter and wall thickness tolerance respectively.
5 . 5 End shape
The end faces of the steel pipe should be perpendicular to the axis of the steel pipe, and the incision burrs should be removed.
5 . 6 Weight
Steel pipes are delivered according to actual weight. It can also be delivered according to the theoretical weight. The theoretical weight of high-quality carbon structural steel (10, 20), alloy structural steel (12CrMo, 15CrMo) and heat-resistant steel (1Cr5Mo) steel pipe according to GB / T 17395-1998 (the density of steel is 7.55 kg / dm3). The theoretical weight of the stainless steel (1Cr19Ni9, 1Cr19Ni11 Nb) steel pipe is 1.015 times the theoretical weight calculated according to GB / T 17395-1998.
According to the requirements of the purchaser. After consultation between the supplier and the buyer, and indicating in the contract, the deviation of the theoretical weight of the delivered steel pipe from the actual weight shall comply with the following provisions:
a) Single steel pipe: ±10%:
b) Steel pipes with a minimum of 10t per batch: ±7%.
6 Technical requirements
6.1 Steel grades and chemical composition
6.1.1 The grade and chemical composition (melting composition) of steel shall comply with the requirements of Table 2.
Table 2 Chemical Composition
Table 2 Chemical Composition
| Grade | Chemical Composition % | ||||||||
| C | Si | Mn | Cr | Mo | Ni | Nb | Pmax | Smax | |
| 10 | 0.07~0.13 | 0.17~0.37 | 0.35~0.65 | - | - | - | - | 0.030 | 0.020 |
| 20 | 0.17~0.23 | 0.17~0.37 | 0.35~0.65 | - | - | - | - | 0.030 | 0.020 |
| 12CrMo | 0.08~0.15 | 0.17~0.37 | 0.40~0.70 | 0.40~0.70 | 0.40~0.55 | - | - | 0.030 | 0.020 |
| 15CrMo | 0.12~0.18 | 0.17~0.37 | 0.40~0.70 | 0.80~1.10 | 0.40~0.55 | - | - | 0.030 | 0.020 |
| 1Cr5Mo | ≤0.15 | ≤0.50 | ≤0.60 | 4.00~6.00 | 0.45~0.60 | ≤0.60 | - | 0.030 | 0.020 |
| 1Cr19Ni9 | 0.04~0.10 | ≤1.00 | ≤2.00 | 18.0~20.0 | - | 8.0~11.0 | - | 0.030 | 0.020 |
| 1Cr19Ni11Nb | 0.04~0.10 | ≤1.00 | ≤2.00 | 17.0~20.0 | - | 9.0~13.0 | 0.8~1.0 | 0.030 | 0.020 |
6.1.2The content of residual elements in steel should meet the requirements of Table 3.
Table 3
| Grade | Residual elements % | ||||
| Ni max | Cr max | Cu max | Mo max | V max | |
| 10 | 0.25 | 0.15 | 0.20 | - | - |
| 20 | 0.25 | 0.25 | 0.20 | 0.15 | 0.08 |
| Other | 0.30 | 0.30 | 0.20 | - | - |
6.1.3 The nitrogen content of steel smelted in an oxygen converter shall not exceed 0.008%.
6.1.4 When the demand side requests to do a finished product analysis, it should be indicated in the contract. The chemical composition tolerance of the finished steel pipe shall comply with the provisions of GB / T 222 1984.
6. 2 Manufacturing methods
6.2.2. Smelting method of steel
High-quality carbon structural steel and alloy structural steel shall be smelted by electric protection, oxygen transfer and external refining or electroslag remelting.
Stainless steel and heat-resistant steel shall be smelted by electric furnace plus furnace external refining or electroslag remelting.
After consultation between the supply and demand sides. Other smelting methods can also be used. When the buyer specifies a certain smelting method, it should be indicated in the contract.
6 . 2 . 2 manufacturing method of tube blank
The tube blank shall be manufactured by hot rolling (forging) method, and the hot rolled (forged) tube blank shall comply with the provisions of YB / T5137: continuous casting billet or steel ingot may also be used.
6 . 2 . 3 manufacturing method of steel pipe
Steel pipes shall be manufactured by hot rolling (extrusion, expansion) or cold drawing (rolling).
6 . 3 delivery status
The steel pipe shall be delivered after heat treatment according to the heat treatment system (method) specified in Table 4. The heat treatment system (method) shall be filled in the quality certificate.
Table 4 Heat treatment system for steel pipes (method)
| Grade | Heat treatment |
| 10 | Normalizing |
| 20 | Temper |
| 12CrMo | 900 ° C ~ 930 ° C normalizing, 670 ° C ~ 720 ° C tempering. Holding time: The period furnace is more than 2 hours, and the continuous furnace is more than 1 hour. |
| 15CrMo | 930 ° C ~ 960 ° C normalizing, 680 ° C ~ 720 ° C tempering. Holding time: The period furnace is more than 2 hours, and the continuous furnace is more than 1 hour. |
| 1Cr5Mo | Annealing |
| 1Cr19Ni9 | Solution treatment: solution temperature ≥ 1040 ° C |
| 1Cr19Ni11Nb | Solution treatment: hot-rolled steel tube solid solution temperature ≥ 1050 ° C, cold drawn steel tube solid solution temperature ≥ 1095 ° C. |
| When the finishing temperature of the hot-rolled steel pipe meets the normalizing temperature, it can replace the normalizing. | |
6.4 Mechanical properties
The room temperature longitudinal mechanical properties of the steel pipe in the delivery state shall comply with the requirements of Table 5.
Steel pipes with an outer diameter of not less than 76 mm and a wall thickness of not less than 14 mm shall be subjected to a longitudinal standard specimen V-notch impact test. The impact test results are evaluated in accordance with 6B / T 17505.
Table 5. Mechanical properties
| Grade | Tensile strength (MPa) | Yield Strength (MPa) | Elongation % | Impact energy ( j) | Hardness (HB) | ||
| Wall thickness | |||||||
| ≤16 | ＞16~30 | ＞30 | |||||
| 10 | 335~475 | ≥205 | ≥195 | ≥185 | 25 | 35 | - |
| 20 | 410~550 | ≥245 | ≥235 | ≥225 | 24 | 35 | - |
| 12CrMo | 410~560 | ≥205 | ≥195 | ≥185 | 21 | 35 | ≤156 |
| 15CrMo | 440~640 | ≥235 | ≥225 | ≥215 | 21 | 35 | ≤170 |
| 1Cr5Mo | 390~590 | ≥195 | ≥185 | ≥175 | 22 | 35 | ≤187 |
| 1Cr19Ni9 | ≥520 | ≥205 | ≥195 | ≥185 | 35 | - | - |
| 1Cr19Ni11Nb | ≥520 | ≥205 | ≥195 | ≥185 | 35 | - | - |
6.5 Hydraulic test
The steel pipe shall be hydraulically tested one by one, and the maximum test pressure is 20 MPa. Under the test pressure, the voltage regulation time is not less than 10S, and the steel pipe shall not leak.
6.6 Process performance
Flattening test
Steel pipes with an outer diameter greater than 22mm to 400mm shall be tested for flattening. After the flattening test. There must be no cracks or cracks in the specimen.
6 . 6 . 2 flaring test
High-quality carbon structural steel and stainless steel pipes with an outer diameter of not more than 76 mm and a wall thickness of not more than 8 mm shall be tested for flare. According to the requirements of the purchaser, the supplier and the buyer will negotiate. 4. Alloy structural steel tubes and heat - resistant steel tubes can also be used for flare test.
6.7 Low-test
Steel pipes directly rolled with steel ingots should be tested at low magnification. There should be no visible white spots, inclusions, subcutaneous bubbles, tumbling and delamination on the cross-section acid immersion test piece.
6. 8 non-metallic inclusions
Steel pipes that are directly rolled by continuous casting or ingots shall be inspected for non-metallic inclusions. The non-metallic inclusions of steel pipes are rated according to the A method and the JK standard rating chart in GB/T 10561-1989. The inclusion levels of A, B, C and D should not exceed 2. 5, according to the most serious Determined.
6. 9 Surface quality
The inner and outer surfaces of the steel pipe are not allowed to have cracks, folds, crusting, rolling and separation. These defects should be completely removed and the depth of removal should not exceed the negative deviation of the nominal wall thickness. The actual wall thickness at the cleaning site should not be less than the minimum allowed by the wall thickness.
The allowable depth or height of the straight on the inner and outer surfaces of the steel pipe shall comply with the following requirements:
a) Cold drawn (rolled) steel pipe: not more than 4% of the nominal wall thickness, and the maximum is 0.2mm.
b) Hot-rolled (extruded, expanded) steel pipe: not more than 5 % of the nominal wall thickness, and the maximum is 0. 4mm.
Other local defects that do not exceed the wall thickness allow for negative deviations are allowed to exist.
6. 10 Nondestructive testing
The steel pipe shall be ultrasonically inspected and tested in accordance with the provisions of GB/T 5777. The longitudinal groove depth grade of the outer surface of the comparative sample tube is: cold drawn (rolled) steel pipe C5, hot rolled (extruded, expanded) steel pipe C8.
After consultation between the supply and demand sides. Additional non-destructive testing can be added.
7 Test methods
The size and shape of the steel pipe shall be measured by the gage which meets the accuracy requirements.
The inner and outer surfaces of the steel pipe shall be visually inspected under full lighting conditions.
Other inspections of steel pipes shall comply with the requirements of Table 6.
Table 6 Inspection items, sampling quantities, sampling methods and test methods for steel pipes
| Test items | experiment method | Sampling method | Number of samples |
| Chemical composition |
GB/T 223 GB/T 4336 GB/T 11170 |
GB/T 222 | Take one sample per furnace |
| Tensile test | GB/T 228 | GB/T2975 | Take one sample for each batch on each of the two steel pipes |
| Hardness test | GB/T 231.1 | GB/T2975 | Take one sample for each batch on each of the two steel pipes |
| Impact test | GB/T 229 | GB/T2975 |
Each batch takes three sets of three specimens on each of the two steel pipes
|
| Hydraulic test | GB/T 241 | - | Root by root |
| Flattening test | GB/T 246 | GB/T 246 | Take one sample for each batch on each of the two steel pipes |
| Flaring test | GB/T 242 | GB/T 242 | Take one sample for each batch on each of the two steel pipes |
| Low magnification test | GB/T 1979 | GB/T 226 | Take one sample for each batch on each of the two steel pipes |
| Non-metallic inclusions | GB/T 10561 | GB/T 10561 | Take one sample for each batch on each of the two steel pipes |
| Eddy current flaw detection | JB/ T 7735 | - | Root by root |
| Magnetic particle inspection | GB/T 12606 | - | Root by root |
| Ultrasonic flaw detection | GB/T 5777-2008 | - | Root by root |
8 Inspection rules
8 . Inspection and acceptance
2. The inspection and acceptance of steel pipes shall be carried out by the technical supervision department of the supplier.
8 . 2 group batch rules
Steel pipes are inspected and accepted in batches. Each batch shall consist of steel pipes of the same grade, the same heat number, the same specification and the same heat treatment system (heating). The quantity of each batch of steel pipes shall not exceed the following provisions:
a) outer diameter ≤ 76mm, and wall thickness ≤ 3mm: 400;
b) outer diameter > 351mm: 50 pieces;
c) Other sizes; 200 roots.
8.3 Re-inspection and decision rules
The re-inspection and determination rules for steel pipes shall comply with the provisions of G8 / T 2102 and GB / T 17505.
8 . 4 numerical repair
The numerical rounding shall comply with the provisions of YB / T 081.
9 Packaging, marking and quality certificate
The packaging, marking and quality certificate of steel pipes shall comply with the provisions of GB / T 2102.