GB18248 Seamless Steel Tubes For Gas Cylinder
GB 18248——Seamless steel tubes for gas cylinder
Scope
This standard specifies the dimensions, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality certificates of seamless steel tubes for gas cylinders and accumulator housings.
This standard applies to the production of seamless steel tubes for gas cylinders and accumulator housings.
Steel grade:
37Mn, 34Mn2V, 30CrMo, 35CrMo, 34CrMo4, 30CrMoSiA
Steel pipe production process: hot rolling, cold drawing
Dimensions, shape, weight and tolerance
Outer diameter and wall thickness
Unless otherwise specified in the contract, the steel pipe is delivered at nominal outer diameter (D) and nominal wall thickness (S).
According to the requirements of the purchaser, the steel pipe can be delivered according to the nominal outer diameter and the minimum wall thickness (5 .
The outer diameter and thickness of the steel pipe shall comply with the provisions of GB / T 17395.
According to the requirements of the purchaser, the steel pipe of GB / T 17395 can be supplied through negotiation between the supplier and the buyer.
The allowable deviation of the nominal outer diameter and nominal wall thickness of the steel pipe shall be in accordance with Table 1. When the nominal outer diameter and the minimum wall thickness are used, the allowable deviation shall comply with the requirements of Table 2.
Unless otherwise specified in the contract, the allowable deviation of the wall thickness of the steel pipe shall be delivered in accordance with normal grade accuracy. According to the requirements of the purchaser, the steel wall thickness tolerance can be delivered according to the advanced precision after negotiation between the supplier and the buyer.
Table 1
| Manufacturing process | Size range | Outer diameter tolerance % | Wall thickness tolerance % | |
| Ordinary level | Advanced | |||
| Hot rolling | D＜339.7mm | ±1 |
+12.5 -10 |
±10 |
| D≥339.7mm |
+15 -12.5 |
+12.5 -10 |
||
| Cold drawing | All | ±0.75 | ±10 | ±7.5 |
Table 2
| Manufacturing process | Size range | Outer diameter tolerance % | Minimum wall thickness tolerance % | |
| Ordinary level | Advanced | |||
| Hot rolling | D＜339.7mm | ±1 |
+25 0 |
+22.5 0 |
| D≥339.7mm |
+30 0 |
+25 0 |
||
| Cold drawing | All | ±0.75 |
+22.5 0 |
+15 0 |
According to the requirements of the purchaser, after consultation between the supplier and the buyer, and in the contract, the steel pipes with the allowable deviation of the dimensions specified in Tables 1 and 2 may be supplied.
Length
The usual length of normal length steel pipe is 4000mm - 12000mm.
After consultation between the supply and demand sides. 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.
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
Bending
5.3.1 The bending degree per metre of steel pipes shall comply with the following provisions;
a) When the wall thickness is ≤ 15 mm, the bending degree is not more than 1.5mm / m,
b) When 15mm <wall thickness ≤ 30mm, the bending degree is not more than 2.0 mm / m;
c) When the wall thickness is > 30 mm, the bending is not more than 3.0 mm / m.
The full-length bending of the steel pipe shall not exceed 0.15 % of the length of the steel pipe.
Out of roundness and uneven wall thickness according to the requirements of the purchaser, negotiated by the supplier and the buyer, and specified in the contract. The out-of-roundness and wall thickness of the steel pipe shall not exceed 80% of the outer diameter tolerance and the wall thickness tolerance, respectively.
The end faces of the steel pipe at the end of the end shall be perpendicular to the axis of the steel pipe, and the burrs of the cut shall be removed.
Weight
Delivery weight,
Steel pipes shall be delivered in actual weight. According to the requirements of the purchaser, the supplier and the buyer shall negotiate and indicate in the contract, and may also deliver according to the theoretical weight.
Calculation of theoretical weight
The theoretical weight of the steel pipe is calculated in accordance with GB/T 17395. The steel pipe delivered according to the nominal outer diameter and the minimum wall thickness (ie the lower deviation is 0) shall be calculated by the average wall thickness. The average wall thickness is the maximum and minimum wall thickness calculated according to the wall thickness and its allowable deviation. The average of the values.
Weight tolerance
According to the requirements of the purchaser, the supplier and the buyer shall negotiate and indicate in the contract that the deviation between the actual weight of the delivered steel pipe and the theoretical weight shall comply with the following provisions:
a) single steel pipe: 10%;
b) Steel pipes of at least 10t per batch: 7.5 %.
Technical requirements
Steel grades and chemical composition
The grade and chemical composition of the steel shall comply with the requirements of Table 3. Appendix A lists the comparison of this standard steel grade with other similar steel grades.
Table 3
| Grade | Chemical composition | ||||||||||
| C | Si | Mn | P | S | P+S | Cr | Mo | V | Ni | Cu | |
| 37Mn | 0.34~0.40 | 0.10~0.30 | 1.35~1.75 | ≤0.020 | ≤0.020 | ≤0.030 | ≤0.30 | - | - | ≤0.30 | ≤0.20 |
| 34Mn2V | 0.30~0.37 | 0.17~0.37 | 1.40~1.75 | ≤0.020 | ≤0.020 | ≤0.030 | ≤0.30 | - | 0.07-0.12 | ≤0.30 | ≤0.20 |
| 30CrMo | 0.26~0.34 | 0.17~0.37 | 0.40~0.70 | ≤0.020 | ≤0.020 | ≤0.030 | 0.80~1.10 | 0.15~0.25 | - | ≤0.30 | ≤0.20 |
| 35CrMo | 0.32~0.40 | 0.17~0.37 | 0.40~0.70 | ≤0.020 | ≤0.020 | ≤0.030 | 0.80~1.10 | 0.15~0.25 | - | ≤0.30 | ≤0.20 |
| 34CrMo4 | 0.30~0.37 | ≤0.40 | 0.60~0.90 | ≤0.020 | ≤0.020 | ≤0.030 | 0.90~1.20 | 0.15~0.30 | - | ≤0.30 | ≤0.20 |
| 30CrMoSiA | 0.28~0.34 | 0.90~1.20 | 0.80~1.10 | ≤0.020 | ≤0.020 | ≤0.030 | 0.80~1.10 | ≤0.10 | - | ≤0.30 | ≤0.20 |
|
a: should satisfy w(V+Nb+Ti+B+Zr)≤0.15%
b: According to the requirements of the purchaser, after consultation between the supplier and the buyer, and stated in the contract, S ≤ 0.010%, S + P ≤ 0.025%
c: This grade is based on the chemical composition of 34CrMo4 in EN 10297-1 2003, and the composition of P, S, Ni and Cu is adjusted.
|
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The chemical composition allowable deviation of the finished steel pipe shall comply with the provisions of GB / T 222.
Manufacturing methods
Steel smelting method Steel should be killed in electric furnace or oxygen converter smelting steel.
Manufacturing method of steel pipe
The steel pipe shall be manufactured by hot rolling (expansion) or cold rolling (drawing). If the purchaser does not specify otherwise, the manufacturing method is determined by the supplier.
Delivery conditions Hot-rolled (expanded) steel pipes shall be delivered in hot-rolled (expanded) condition, and cold-rolled (drawn) steel pipes shall be delivered in cold-rolled (drawn), normalized or annealed condition.
Mechanical properties
The supplier shall provide the measured values of the mechanical properties of the specimens made by heat treatment of the steel tubes, but not as the conditions for the goods. The reference values of the mechanical properties measured by the steel tube heat-treated blanks are listed in Appendix B (informative).
Appendix B
| Grade | Heat treatment | Mechanical properties | |||||||
| Quenching | Normalizing | Tensile strength | Yield Strength | Elongation | Impact energy | ||||
| Temperature ℃ | Coolant | Temperature ℃ | Coolant | ≥ | Temperature ℃ | Joule | |||
| 37Mn | 820~860 | water | 550~650 | air | 750 | 630 | 16 | -50 | 27 |
| 34Mn2V | 850~890 | air | - | - | 745 | 530 | 16 | -20 | 27 |
| 30CrMo | 860~900 | water,oil | 490~590 | water,oil | 930 | 785 | 12 | -50 | 27 |
| 35CrMo | 830~870 | oil | 500~600 | water,oil | 980 | 835 | 12 | -50 | 27 |
| 34CrMo4 | 830~870 | oil | 530~630 | water,oil | 980 | 835 | 12 | -50 | 27 |
| 30CrMoSiA | 860~900 | oil | 470~570 | water,oil | 1080 | 885 | 10 | room temperature | 27 |
| Except for impact work, the test temperature is room temperature | |||||||||
Inspection and test methods
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 visually inspected under full lighting conditions.
Other inspections of steel pipes shall comply with the requirements of Table 4.
Inspection rules
Inspection and acceptance
The inspection and acceptance of steel pipes shall be carried out by the technical quality supervision department of the supplier.
Group batch rules
If the steel pipe is not heat treated after being cut into individual pieces, all pipe sections cut from a steel pipe rolled by one tube shall be regarded as one.
Steel pipes shall be 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, the same heat treatment system (where applicable) and the same delivery state. The number of steel pipes per batch shall not exceed 200.
Number of samples
The sampling quantity of each batch of steel pipe inspection shall comply with the requirements of Table 4.
Table 4
| Test items | Sampling method | Number of samples | experiment method |
| chemical composition | GB/T 20066 | Take 1 sample per furnace |
GB/T 223 GB/T 4336 GB/T 20123 GB/T 20125 GB/T 20126 |
| Stretching test | GB/T 2975 | Take 1 sample for each batch on each of the two steel pipes | GB/T 228—2002 |
| Impact test | GB/T 2975 | Take 1 set of 3 samples on each of the two steel pipes in each batch | GB/T 229—1994 |
| Hydraulic test | - | Root by root | GB/T 241—2007 |
| Eddy current testing | - | Root by root | GB/T 7735—2004 |
| Magnetic flux leakage test | - | Root by root | GB/T 12606—1999 |
| Non-metallic clip impurity detection | GB/T 10561 | Take one sample for each batch on each of the two steel pipes | GB/T 10561—2005 |
| Ultrasonic flaw detection | - | Root by root | GB/T 5777—1996 |
Re-inspection and decision rules
The re-inspection and determination rules of steel pipes shall comply with the provisions of GB / T 2102 - 2006.
Packaging, marking and quality certificate
The packaging, marking and quality certificate of steel pipes shall comply with the provisions of GB / T 2102 - 2006
Appendix A, GB 18248 Equivalent
The comparison of this standard steel grade with other similar steel grades.
The comparison of this standard steel grade with other similar steel grades.
| GB 18248 | JIS G 3429-2006 | ISO 11120-1999 | EN 10297-1 2003 | ASTM A372/A372M-03 | DOT 49CFR 178.37-2006 |
| 37Mn |
STH11 STH12 |
- | 38Mn6 | Grade C | Inter-mediate mangan |
| 34Mn2V |
STH11 STH12 |
- | - | - | - |
| 30CrMo | STH21 | Group Ⅱ | 34CrMo4 | Grade E | 4130 X |
| 35CrMo | STH22 | Group Ⅱ | 34CrMo4 | - | - |
| 34CrMo4 | STH22 | Group Ⅱ | 34CrMo4 | - | - |
| 30CrMoSiA | - | - | - | - | - |