GB/T 6653-2017 Certified | Steel for Welded Gas Cylinders
HP345 Steel Plates & Strips for Welded Gas Cylinders
Lower yield strength ≥345MPa, maximum strength grade for welded gas cylinders, excellent high-strength toughness, superior weldability and pressure resistance. Designed for the most demanding high-pressure welded gas cylinders, large LPG vessels, and critical pressure equipment. CEHE Steel supplies globally with full certification and customized processing.
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📖 Grade Explanation | HP Series Naming Rules
🔍 The steel grade consists of the first letters "HP" from the Chinese Pinyin of "Welded Cylinder" and the lower yield strength minimum value.
Example: HP345 → "HP" stands for welded gas cylinder steel; "345" represents the minimum lower yield strength of 345 MPa.
✅ This standard includes grades HP235, HP265, HP295, HP325, HP345. HP345 is the maximum strength grade for the most demanding high-pressure welded gas cylinder applications.
※ According to GB/T 6653-2017 standard, chemical composition and mechanical properties strictly comply with Table 1 and Table 2.
🏭 Domestic Grade Comparison | HP295 / HP325 / HP345
HP345 equivalent domestic grades and performance comparison:
HP295
GB/T 6653-2017
- C ≤0.20%
- YS ≥295MPa
- TS 440~590MPa
- High strength, pressure vessels
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HP325
GB/T 6653-2017
- C ≤0.20%
- YS ≥325MPa
- TS 490~610MPa
- Ultra-high pressure cylinders
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HP345
GB/T 6653-2017
- C ≤0.20%
- YS ≥345MPa
- TS 510~620MPa
- Maximum strength grade
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📌 HP345 equivalent domestic grades: HP295, HP325 | International equivalent grade: P355NB (EN 10120)
🌍 International Grade Comparison | HP345 vs P355NB
Chemical composition comparison between HP345 (GB/T 6653) and P355NB (EN 10120):
HP345
GB/T 6653-2017 (China)
- C ≤0.20%
- Si ≤0.35%
- Mn ≤1.50%
- P ≤0.025%, S ≤0.012%
- Alt ≥0.015%
- Nb+V ≤0.12%
YS ≥345MPa, maximum strength pressure vessel steel
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P355NB
EN 10120 (EU)
- C ≤0.20%
- Si ≤0.40%
- Mn ≤1.50%
- P ≤0.025%, S ≤0.015%
- Total Al ≥0.020%
- Nb+Ti ≤0.05%
YS ≥355MPa, European standard pressure vessel steel
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📌 HP345 and P355NB are close equivalents for high-pressure cylinder applications, fully interchangeable for global projects.
🔧 Customizable Services
Full flexible production to meet gas cylinder and pressure vessel requirements:
- ✓ Custom dimensional tolerances (GB/T 708, GB/T 709)
- ✓ Delivery: Oiled / Pickled / Black / Bright surface
- ✓ Slitting, cut-to-length, flat steel processing
- ✓ Ultrasonic testing (UT) for thick plates
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- ✓ Yield ratio control ≤0.80 upon request
- ✓ -40°C low-temperature impact test available
- ✓ Strict non-metallic inclusion control
- ✓ Small trial orders, lead time 35~45 days
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📏 Available Dimensions
🔥 Hot Rolled Plates/Strips
Thickness: 2.0~14.0mm
Width: 800~2000mm |
❄️ Cold Rolled Plates/Strips
Thickness: 1.5~4.0mm
Width: 800~1800mm
Annealed condition |
✂️ Tolerance Standards
GB/T 709 (Hot Rolled)
GB/T 708 (Cold Rolled) |
🎯 Special Dimensions
Length ≤12m custom cut
Slit width ≥50mm |
※ Coil ID 508/610mm, export standard packing. Regular stock: 2.5/3.0/4.0/5.0/6.0/8.0/10.0mm.
🧪 Chemical Composition (Ladle Analysis, %)
| Grade |
C |
Si |
Mn |
P≤ |
S≤ |
Nb≤ |
V≤ |
Ti≤ |
Nb+V≤ |
Alt≥ |
| HP345 |
≤0.20 |
≤0.35 |
≤1.50 |
0.025 |
0.012 |
0.05 |
0.10 |
0.06 |
0.12 |
0.015 |
| Residual elements Cr, Ni, Mo ≤0.30%, Cu ≤0.20%. Acid-soluble aluminum (Alt) standard. |
⚙️ Mechanical Properties & Process Performance
| Grade |
Lower Yield Strength (MPa) ≥ |
Tensile Strength (MPa) |
A(L₀=80mm)% ≥ |
A(L₀=50mm)% ≥ |
180° Bend Test |
| HP345 |
345 |
510~620 |
17 |
21 |
D=2a |
❄️ Charpy V-Notch Impact Properties
| Grade |
Specimen Size (mm) |
Room Temperature KV₂ (J) ≥ |
-40°C Impact (Optional) |
| HP345 |
10×10×55 (t≥12mm) |
34 |
27 (upon request) |
Impact average of three specimens meets standard; one value allowed ≥70% of required. Transverse specimens for tensile & bending.
🏭 Application Areas
Maximum Pressure LPG Cylinders High-Pressure Industrial Gas Cylinders Large Pressure Vessels CNG Storage Tanks Hydrogen Transport Cylinders High-Pressure Fire Extinguishers
HP345 steel offers maximum strength and excellent pressure resistance, fully meeting GB/T 6653 and comparable to EN 10120 P355NB, ideal for the most demanding high-pressure welded gas cylinder applications globally.
❓ Frequently Asked Questions (FAQ)
1. What are the equivalent grades of HP345?
Domestic: HP295, HP325 | International: P355NB (EN 10120). HP345 is the highest strength grade in HP series.
2. What is the yield strength of HP345?
Lower yield strength ≥345MPa, tensile strength 510~620MPa, for maximum pressure gas cylinders.
3. Minimum order quantity and delivery time?
MOQ: 20 tons, trial order ≥5 tons. Normal production lead time: 35~45 days.
4. Can you provide international certification?
Yes, we provide EN 10204 3.1 MTC, SGS/BV inspection report and GB/T 6653 certification.
📩 Get a Quote / Custom Inquiry
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