GB 28884 Seamless Steel Tubes For Large Volume Gas Cylinder
GB 28884-2012 Seamless steel tubes for large volume gas cylinder
Scope
This standard specifies the size, shape, weight and allowable deviation of seamless steel tubes for large volume gas cylinders; technical requirements; test methods; inspection rules; packaging, marking and quality certificates.
This standard is applicable to the production of seamless steel tubes with a volume of 300L to 3000L.
Steel Grade:30CrMoE, 42CrMoE
Order content
Contracts or orders for ordering steel pipes in accordance with this standard shall include but are limited to the following:
a) standard number;
b) Product Name:
c) steel grades and groups;
Example: When ordering according to grade 30 CrMoE group 2, the grades and groups are indicated as adding 30CrMoE-2.
d) the quantity ordered (total weight or total count);
e) Dimensions (nominal outer diameter X minimum wall thickness or nominal outer diameter X nominal wall thickness);
f) length (length or length);
R) Special requirements.
Sze, shape and weight
Outer diameter and wall thickness
Unless otherwise specified in the contract. Steel pipes are delivered in nominal outer diameter (D) and minimum wall thickness (Smin). Very according to the demand side. After consultation between the supply and demand sides. The well is indicated in the contract. Steel pipes can be delivered in nominal outer diameter (D) and nominal wall thickness (S).
The nominal outer diameter and wall thickness of the steel pipe shall comply with the regulations, and the nominal outer diameter shall be greater than 356 mm. According to the requirements of the purchaser. After consultation between the supply and demand sides. And noted in the contract. Steel pipes of specifications other than GB / T 17395 can be supplied.
Note: Unless otherwise stated. The "wall thickness" as stated in this standard includes the minimum wall thickness and the nominal wall thickness.
The allowable deviation of the outer diameter and wall thickness of the steel pipe shall comply with the requirements of Table l.
According to the requirements of the purchaser, the supplier and the buyer will negotiate and indicate in the contract. Steel pipes with tolerances outside the dimensions specified in Table 1 may be supplied.
Table 1 Allowable deviation of outer diameter and wall thickness of steel pipe
| Category | Steel pipe size(mm) | Allowable Tolerance |
| Outer diameter（D） | - | ±1%D |
| Minimum wall thickness | D≤559 |
+25%Smin 0 |
| D≤559 |
+27.5%Smin 0 |
|
| Tolerance wall thickness | D≤559 |
+12.5%S -10%S |
| D≤559 | ±12.5%S |
Length
The steel pipe is delivered in a fixed length or multiple length.
The allowable deviation of the length of the steel pipe shall comply with the following provisions:
a) when the length is ≤6000mm, +10mm;
b) When the length is > 6000mm, + 20mm.
The full-length allowable deviation of the length of the steel tube is +20mm, and the length of each double-length should be left with a margin of 10 mm~15 mm.
Straightness
The maximum deviation distance from the straight line of the steel pipe over the entire length of the steel pipe shall not exceed 0.15 % of the total length of the steel pipe. The maximum deviation distance between the steel pipe and the straight line (foot) of the steel pipe within a meter range shall not exceed 3.0 mm/m.
Unroundness and uneven wall thickness
The unevenness of the steel pipe and the uneven wall thickness of the cross section shall not exceed 80% of the outer diameter tolerance and the wall thickness tolerance, respectively.
Tip shape
The end face of the inner end of the steel pipe shall be perpendicular to the axis of the steel pipe, and the burr of the cut shall be removed.
Weight
When the steel pipe is delivered according to the nominal outer diameter and the minimum wall thickness, the steel pipe is delivered according to the actual heavy star.
When the steel pipe is delivered according to the nominal outer diameter and the nominal wall thickness, the steel pipe is delivered according to the actual weight. It can also be delivered according to the theoretical weight. The theoretical weight of the steel tube is calculated according to the provisions of GB / T 17395 (the density of the steel is 7.85 kg / dm3).
According to the requirements of the purchaser. After consultation between the supply and demand sides. And stated in the contract, the allowable deviation of the actual weight of the single steel pipe from the theoretical weight is ±10%, and the allowable deviation of the actual weight of the whole batch of steel pipe from the theoretical weight is (-10%, +5%).
Technical requirements
Steel grade and chemical composition
The grade and chemical composition of the steel (melting analysis) shall be in accordance with Table 2.
When the demand side requests the analysis of the finished product. It should be stated in the contract. The chemical composition tolerance of the finished steel pipe shall comply with the provisions of GB/T 222.
Table 2 Steel grades and chemical composition
| Grade | Category | chemical composition | ||||||||
| C | Si | Mn | P | S | Cr | Mo | Ni | Cu | ||
| 30CrMoE | 1 | 0.25-0.35 | 0.15-0.35 | 0.40-0.90 | ≤0.02 | ≤0.01 | 0.80-1.10 | 0.15-0.25 | ≤0.30 | ≤0.20 |
| 2 | 026-0.34 | 0.17-0.37 | 0.40-0.70 | ≤0.02 | ≤0.01 | 0.80-1.10 | 0.15-0.25 | ≤0.30 | ≤0.20 | |
| 42CrMoE | 1 | 0.40-0.45 | 0.15-0.35 | 0.75-1.00 | ≤0.02 | ≤0.01 | 0.80-1.10 | 0.15-0.25 | ≤0.30 | ≤0.20 |
| 2 | 0.38-0.45 | 0.17-0.37 | 0.50-0.80 | ≤0.02 | ≤0.01 | 0.90-1.20 | 0.15-0.25 | ≤0.30 | ≤0.20 | |
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a:Grade 30CrMoE group l is equivalent to 4130X . The purchaser specifies. Groups ordered according to this standard l steel pipe. You can press 4130X grade.
b:Grade 42CrMoE Group l is equivalent to Ding 4142. The purchaser specifies. Groups ordered according to this standard l steel pipe, can be used according to 4142 brand Ting goods.
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Grade 30CrMoE group l is equivalent to 4130X . The purchaser specifies. Groups ordered according to this standard l steel pipe. You can press 4130X grade.
Grade 42CrMoE Group l is equivalent to Ding 4142. The purchaser specifies. Groups ordered according to this standard l steel pipe, can be used according to 4142 brand Ting goods.
Production method
Steel smelting method
Steel should be refined by electric arc furnace and vacuum refining. Or the oxygen converter is refined outside the furnace and vacuum refined. According to the requirements of the purchaser, after consultation between the supplier and the buyer, and in the contract, the steel can adopt other smelting methods with higher requirements.
Steel pipe manufacturing method
The steel pipe shall be manufactured by hot rolling or hot rolling and cold drawing.
Delivery status
The steel pipe is delivered in a hot rolled (expanded) state, a cold drawn state, or a cold drawn heat treatment state. The state of thermal expansion refers to the deformation state of the billet steel tube after being integrally heated and expanded to form a larger diameter steel tube.
Mechanical properties
The longitudinal mechanical properties of the steel tube specimens after quenching and tempering heat treatment shall be in accordance with Table 3. The size of the test bar blank should ensure that the mechanical properties are normally reflected after heat treatment.
Table 3 Longitudinal mechanical properties
| Grade | Tensile strength | Yield Strength | Elongation | hardness |
| 30CrMoE | ≥720 | ≥485 | ≥20 | ≤269 |
| 42CrMoE | ≥930 | ≥760 | ≥16 | ≤330 |
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a: The tensile specimen shall be the specimen No. R4 specified in GB / T228.1: when the steel pipe is not large enough to intercept the sample No. R4. A larger circular section specimen of 8 mm or 5 mm diameter may be used. The gauge length of the specimen is 5 times the diameter of the cross section of the specimen.
b: The mechanical properties of 30CrMoE are equivalent to 4130X.
The mechanical properties of C 42CrMoE are equivalent to 4142 .
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a: The tensile specimen shall be the specimen No. R4 specified in GB / T228.1: when the steel pipe is not large enough to intercept the sample No. R4. A larger circular section specimen of 8 mm or 5 mm diameter may be used. The gauge length of the specimen is 5 times the diameter of the cross section of the specimen.
b: The mechanical properties of 30CrMoE are equivalent to 4130X.
The mechanical properties of C 42CrMoE are equivalent to 4142 .
Non-metallic inclusions
Steel pipes shall be inspected for non-metallic inclusions. The non-metallic inclusions of steel pipes are rated according to the A method of GB/T 10561-2005. The fine and coarse grades of the inclusions of A, B, C and D shall not exceed 2.5 respectively. The total number of fine grades and the total number of coarse grades of all types of inclusions A, B, C, and D should be no more than 6.0.
Grain size
According to the requirements of the purchaser, the supplier and the buyer will negotiate. And in the contract, the steel pipe sample blank is prepared according to quenching and tempering heat treatment. Its grain size should be 6.5 or finer
Surface Quality
The inner and outer flesh of steel pipes are not allowed to crack, fold, fold, separate layers and crusting. This defect should be completely removed, and the removal site should be smooth and the depth of removal should not exceed 10% of the wall thickness. The actual wall thickness of the removal site should not be less than the minimum allowable wall thickness.
The scale of the inner and outer surfaces of the steel pipe should be removed.
Full length automatic thickness measurement
The steel pipe should be fully rooted (except for the blind end zone of the automatic flaw detection tube). The surface area covered by the automatic thickness measurement system should be 100%. The wall thickness of the automatic measurement shall comply with the allowable deviation of the wall thickness specified in Table l.
Nondestructive testing
The steel pipe shall be subjected to ultrasonic longitudinal and transverse flaw detection inspection in accordance with the acceptance level L2 of GB/T5777-2008.
experiment method
The size and shape of the steel pipe shall be measured one by one using gauges that meet the accuracy requirements.
The inner and outer surfaces of the steel pipe shall be inspected visually under full lighting conditions.
Testing regulations
Inspection and acceptance
The inspection and acceptance of steel pipes shall be carried out by the supplier's quality and technical supervision department.
Group rule
Steel pipes are inspected and accepted in batches. Each batch of steel pipes shall be composed of steel pipes of the same grade, the same heat number, the same specification and the same delivery state, and the number of steel pipes per batch shall not exceed 50.
Re-inspection and decision rules
The re-inspection and determination rules of steel pipes shall comply with the provisions of GB/T 2102.
Packaging, sign and quality certificate
The packaging, marking and quality certificate of steel pipes shall comply with the provisions of GB/T 2102.