GB/T18984 Seamless Steel Pipe For Low Temperature Pipe
GB/T18984-2003 seamless steel pipe for low temperature pipeline
Scope
This standard applies to -45 ° C ~ -100 ° C grade low temperature pressure vessel pipelines and seamless steel tubes for low temperature heat exchanger pipelines
The seamless steel pipes produced by this standard are divided into two categories according to the processing methods of products.
Hot rolled steel pipe: WH
Cold drawn steel pipe: WC
The letter "DG" after the grade of the steel listed in this standard is the first letter of the "low temperature" and "pipe" Chinese pinyin.
Size, shape and weight
Outer diameter and wall thickness
The outer diameter and wall thickness of the steel pipe (not more than 25mm) shall comply with the provisions of GB/T17395-1998. According to the requirements of the purchaser, steel pipes of different specifications can be produced through negotiation between the supplier and the buyer.
Tolerances of outer diameter (D) and wall thickness (S) of steel pipe
| Process | Size(mm) | Tolerance | |
| Hot-rolled | O.D. | <351 | +/-1.0% D(+/-0.50min) |
| >=351 | +/-1.25% D | ||
| W.T. | <=25 | +/-12.5% S(+/-0.40 min) | |
| Cold drawn | O.D. | <=30 | +/-0.20 |
| 30-50 | +/-0.30 | ||
| >50 | +/-0.75% D | ||
| W.T. | <=3 | +12.5% S, -10% S | |
| >3 | +/-10% S | ||
Note: Outside diameter greater than or equal to 351 thermal Flaring wall thickness allowable deviation: Guests 15 write S
Length
Normal length: The normal length of steel pipe is 400omm - 1200omm.
After consultation between the supplier and the buyer, a short-length pipe of not less than 3 000 mm in length and not less than 3 000 mm of the total weight of the delivery of the steel pipe may be delivered.
Length and length of the length: The length of the steel pipe and the total length of the double length should be within the normal length, and the total length tolerance is +20 mm. The length of each double ruler should be left as shown below:
Outer diameter: ≤159mm................................................ ...... 5mm - 10mm;
Outer diameter: >159mm................................................ .....10mm - 15mm.
Curvature
The bending degree of the bending steel pipe should not exceed the following:
Wall thickness ≤ 15 mm ............................................. .....1.5 mm / m ;
Wall thickness >15 mm ............................................. .....2.0mm / m;
Thermal expansion tube with outer diameter ≥ 351 mm........................................... .........3.0mm / m.
Tip 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.
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 non-roundness and wall thickness of the steel pipe shall not exceed 80% of the outer diameter and wall thickness tolerance respectively.
Delivery weight
Steel pipes are delivered according to actual weight and can also be delivered according to theoretical weight. The theoretical weight of the steel tube is in accordance with the provisions of GB / T 17395 - 1998 (the density of steel is 7. 85 kg / dm, ).
Weight tolerance:
According to the requirements of the purchaser, the actual weight of the delivered steel pipe and the theoretical weight allowable deviation are negotiated between the supplier and the buyer and indicated in the contract:
Single steel pipe: 10%;
A minimum of 10 tons of steel pipe per batch: 7.5%.
Tag example
Example 1 : A hot rolled (expanded) steel pipe made of steel with a grade of 10MnDG and having an outer diameter of 1 59 mm, a wall thickness of 7 mm and a length of 600 ohms is marked as:
10MnDC Bu 159X7X6 00 Small GB / T 18984 A 2003
Example 2: A cold drawn (rolled) steel pipe manufactured by steel of the grade 10MnDG with an outer diameter of 159 mm and a wall thickness of 7 mm and delivered in the usual length is marked as:
WC 1 OMnDG159X7 one GB / T 18984 one 2003
Chemical properties of GB/T18984 seamless steel pipe
| Standard | Grade | C | Si | Mn | P(max) | S | Ni | Mo | V |
|
GB/T18984-2003 |
16MnDG | 0.12-0.20 | 0.20-0.55 | 1.20-1.60 | 0.025 | 0.025 | - | - | - |
| 10MnDG | <=0.13 | 0.17-0.37 | <=1.35 | 0.025 | 0.025 | - | - | <=0.07 | |
| 09DG | <=0.12 | 0.17-0.37 | <=0.95 | 0.025 | 0.025 | - | - | <=0.07 | |
| 09Mn2VDG | <=0.12 | 0.17-0.37 | <=1.85 | 0.025 | 0.025 | - | - | <=0.12 | |
| 06Ni3MoDG | <=0.08 | 0.17-0.37 | <=0.85 | 0.025 | 0.025 | 2.5-3.7 | 0.15-0.30 | <=0.05 |
Production method
Steel should be smelted in an oxygen converter or an electric furnace and refined outside the furnace. According to the requirements of the purchaser, it is negotiated between the supplier and the buyer and indicated in the contract. It can also be manufactured by other methods.
Steel pipes shall be manufactured by hot rolling (expansion) or cold drawing (rolling).
Delivery status
The steel pipe is delivered in a normalized state. When the finish rolling temperature is not lower than the phase transition critical temperature (Ar3), it can be regarded as normalizing treatment.
Longitudinal Mechanical Properties of GB/T18984 seamless steel pipe
|
Standard |
Grade |
Tensile strength | Lower yield strength（Rcl/Mpa） | Elongation | |
| Rm/Mpa | W.T.<=16mm | W.T.>16mm | A/% | ||
|
GB/T18984-2003 |
16MnDG | 490-665 | >=325 | >=315 | >=30 |
| 10MnDG | >=400 | >=240 | >=35 | ||
| 09DG | >=385 | >=210 | >=35 | ||
| 09Mn2VDG | >=450 | >=300 | >=30 | ||
| 06Ni3MoDG | >=455 | >=250 | >=30 | ||
Minimum impact test temperature of steel pipe
|
Grade
|
Minimum impact test temperature
|
|
|
℉
|
℃ | |
|
16MnDG
|
--
|
-45
|
|
10MnDG
|
--
|
-45
|
|
09DG
|
--
|
-45
|
|
09Mn2VDG
|
--
|
-70
|
|
06Ni3MoDG
|
--
|
-100
|
Performance Testing:
Hydraulic test
Flattening test
Bending test
Flaring test
Low-order tissue test
Use the grade 09Mn2VDG and . Steel pipes made of 6Ni3MoDG steel shall be inspected at low magnification. There shall be no visible white spots, inclusions, subcutaneous bubbles, tumbling and delamination on the cross-section acid immersion test piece.
Non-metallic inclusion inspection
Steel pipes made of grades 09Mn2VDG and 06Ni3MoDG steel shall be inspected for non-metallic inclusions.
The inspection of non-metallic inclusions in steel shall be assessed by the medium A method and the JK standard rating chart of GB / T 10561. The inclusion levels of A, B, C and D shall not exceed 2. 5 respectively, according to the most serious ones. determination.
Nondestructive testing
Steel pipes made of grades 09MnZvL and 06Ni3MoDG steel shall be ultrasonically tested one by one. The longitudinal notch groove depth of the outer surface of the comparative sample tube of cold drawn (rolled) steel pipe shall comply with the provisions of C8 of GB / T 5777, and the depth of the longitudinal notch groove of the outer surface of the comparative sample tube of hot rolled (expanded) steel pipe shall comply with GB / T 5777 C10 regulations.
According to the requirements of the purchaser, the supply and demand sides negotiate and indicate in the contract that the steel pipes of grades 09Mn2VDG and 06Ni3MoDG can be added to other non-destructive tests, and the steel pipes of 16MnDG, 09DG and 10MnDG can also be added for non-destructive testing.
Surface Quality
The inner and outer surfaces of steel pipes shall not be folded, rolled, separated, cracked and crusted. These defects shall be completely removed and the actual wall thickness at the clearing shall not be less than the minimum allowable wall thickness.
Other local defects where the depth does not exceed the negative deviation of the wall thickness of the steel tube are allowed to exist.