Products Description
HP345 is a hot-rolled steel plate specifically designed for manufacturing welded gas cylinders, belonging to the high-end grade in the national standard GB6653 "Steel Plates for Welded Gas Cylinders". "HP" represents the first letters of the Chinese pinyin for "welded cylinder", while "345" indicates its minimum yield strength of 345 MPa.
This steel is mainly used to manufacture process welded cylinders for containing harsh media such as liquid chlorine, liquid ammonia, sulfur dioxide, ethylene oxide, methylamine, and acetylene. These media are often toxic, corrosive, or flammable and explosive, thus placing extremely stringent performance requirements on the cylinder materials.
HP345 Gas Cylinder Steel
As a leading professional steel manufacturer, GNEE provides high-grade HP345 steel plates and coils that strictly adhere to the JIS G3116 standard. With decades of manufacturing experience and a robust supply chain, GNEE ensures that your LPG cylinder production meets the highest international safety benchmarks, providing peace of mind to millions of households.
The core mechanical properties of HP345
HP345's ability to fulfill the role of a "high-risk media transporter" relies on its excellent combination of mechanical properties. According to the national standard GB6653-1994, the main mechanical performance indicators of HP345 are as follows:
| Performance Indicator | Numerical Requirement | Simple Explanation |
|---|---|---|
| Yield Strength | ≥ 345 MPa | The threshold at which a material begins to undergo permanent deformation. |
| Tensile Strength | ≥ 510 MPa | The maximum tensile force a material can withstand. |
| Elongation | ≥ 20% | The material's ability to deform before fracture. |
| Impact Energy Absorption | ≥ 27 J (10×10 mm specimen, room temperature) | The ability to resist sudden fracture. |
| Cold Bending Performance | Bending mandrel diameter d=2a (180° bend) | Bending without cracking, similar to bending a wire. |
HP345 Gas Cylinder Steel Strength
A yield strength of 345 MPa means that each square millimeter of steel can withstand approximately 35 kg of tensile force without permanent deformation. This ensures that the gas cylinder will not bulge under internal high pressure. Simultaneously, a tensile strength of over 510 MPa provides sufficient safety margin-even if the pressure unexpectedly exceeds the limit, the material has enough "buffer capacity" to prevent fracture.
HP345 Gas Cylinder Steel Surface inspection
More importantly, HP345's yield strength ratio (yield strength/tensile strength) is controlled at a low level. Shougang's research and development practice shows that through reasonable composition design and process control, HP345 achieves a low yield strength ratio. This means that the material has a large plastic deformation space from the initial yielding to the final fracture, providing valuable safety warnings for the gas cylinder.
HP345 Gas Cylinder Steel Plasticity
An elongation of ≥20% means that HP345 can stretch more than 20% before fracture. This is crucial for gas cylinder manufacturing-the cylinder end caps need to be stamped, much like using a mold to "press" a steel plate into the shape of a pot lid. If the material's plasticity is insufficient, cracking will occur during the stamping process.
It is worth mentioning that the elongation requirement for HP345 is for transverse specimen testing. The properties of steel plates often differ in the rolling direction (longitudinal) and the perpendicular direction (transverse). Requiring transverse properties to meet the standard means that the material has good plasticity in all directions-which is essential for multi-directional stress structures like gas cylinders.
Why is HP345 suitable for soldering?
Carefully Designed Chemical Composition
Low Carbon Content: Carbon (C) ≤ 0.20%. Carbon is a key element determining the strength of steel, but it is also an "enemy" of welding-the higher the carbon content, the more prone it is to cracking during welding. HP345 controls carbon to below 0.20%, significantly reducing the risk of weld cracking while ensuring strength.
Appropriate Manganese (Mn): Manganese content reaches approximately 1.50%. Manganese is both a strengthening element and can combine with sulfur in steel to form manganese sulfide, preventing sulfur-induced "hot cracking."
Extremely Low Harmful Impurities: Phosphorus (P) ≤ 0.025%, Sulfur (S) ≤ 0.012%. Phosphorus and sulfur are "troublemakers" in steel-phosphorus causes "cold brittleness," and sulfur causes "hot brittleness." HP345 has extremely strict limits on both, ensuring weld quality from the source.
Microalloying "Secret Recipe": By adding trace amounts of vanadium (V) and titanium (Ti), the content of each does not exceed 0.025%. These two elements form nanoscale carbonitride particles that act like "micro-rivets" inside the steel, providing precipitation strengthening. This strengthening mechanism has minimal impact on welding heat and will not "fail" due to welding heat.
Purity
HP345 has extremely high requirements for the purity of molten steel. During production, efficient desulfurization and precise composition control are employed to ensure minimal inclusions in the steel. Inclusions are like "sand" in the weld – they disrupt weld continuity and become the starting point for cracks. HP345's high purity ensures the density and uniformity of the weld metal.
Low Yield-to-Strength Ratio
The low yield-to-strength ratio mentioned above is not only related to safety but also to weld quality. Only when the strength and plasticity of the weld and base metal are well matched can the overall performance of the welded joint meet the standards. HP345's low yield-to-strength ratio design minimizes performance degradation in the weld heat-affected zone, allowing the weld and base metal to "work together" rather than "act independently."
Applications of HP345
Liquefied Petroleum Gas (LPG) Cylinders: While lower grades like HP295 are also commonly used for LPG cylinders, HP345 is suitable for applications requiring higher pressure.
Industrial Gas Cylinders: Storage and transportation of industrial gases such as acetylene, oxygen, and hydrogen.
Chemical Media Storage Tanks: Packaging containers for chemical products such as liquid chlorine, liquid ammonia, sulfur dioxide, and ethylene oxide.
Fire Extinguisher Cylinders: Require high strength and welding quality.
It's worth mentioning that the HP345 has not only established a firm foothold in the domestic market but has also been exported to countries along the Belt and Road Initiative, such as Thailand and Pakistan, obtaining several international certifications.This demonstrates that the performance and quality of the HP345 have gained international market recognition.
Why Choose GNEE as Your HP3455 Welded Gas Cylinders Steel Supplier?
- 18+ years manufacturing experience
- Full certification support (EN, JIS, GB standards)
- Custom sizes, thickness, and surface treatment
- Fast delivery and global logistics
- Strict quality inspection (chemical + mechanical testing)
We don't just sell steel-we provide complete gas cylinder material solutions.
What are the cold bending performance requirements for HP345?
180° cold bending test, mandrel diameter d=2a (a is plate thickness), no cracks should appear on the outer surface of the specimen after bending.
What are the impact toughness requirements for HP345?
Rearward impact at room temperature, the average value of three specimens ≥27 J, with one specimen allowed ≥19 J.
What is the yield strength ratio? What is the required yield strength ratio for HP345?
The yield strength ratio is the ratio of yield strength to tensile strength (ReL/Rm). The yield strength ratio of HP345 is generally required to be controlled below 0.80, with an ideal value ≤0.77.
What are the hazards of an excessively high yield strength ratio?
An excessively high yield strength ratio means insufficient plasticity reserve in the material, making it prone to cracking during processing, and reducing the safety margin of the gas cylinder during use.
How to reduce the yield strength ratio of HP345?
By optimizing the controlled rolling and cooling process, appropriately increasing the final rolling temperature and coiling temperature, and adopting a laminar flow cooling mode in the later stage, the yield strength ratio can be reduced from 0.81 to 0.76.
