HP345 is a high-strength low-alloy (HSLA) steel specifically designed for welded gas cylinders and pressure vessels. It offers a balanced combination of strength, toughness, weldability, and formability, making it a preferred material in high-pressure applications.
As a dedicated manufacturer, GNEE provides full Mill Test Certificates (MTC) with every order, detailing the exact chemical breakdown of your HP345 shipment to ensure compliance with your project specifications.
Basic Properties of HP345 Steel Plate
Chemical Composition
HP345 is produced with controlled alloying elements to ensure strength and toughness while maintaining good weldability.
| Element | Content (%) |
|---|---|
| C (Carbon) | ≤ 0.20 |
| Si (Silicon) | ≤ 0.55 |
| Mn (Manganese) | 1.20 – 1.70 |
| P (Phosphorus) | ≤ 0.025 |
| S (Sulfur) | ≤ 0.015 |
| Nb/V/Ti | Micro-alloyed (trace) |
Low carbon content improves weldability, while Mn and micro-alloying elements enhance strength and grain refinement.
Mechanical Properties
HP345 is known for its high yield strength and excellent toughness.
| Property | Value |
|---|---|
| Yield Strength (ReL) | ≥ 345 MPa |
| Tensile Strength (Rm) | 510 – 640 MPa |
| Elongation (A%) | ≥ 21% |
| Impact Energy (KV2, -20°C) | ≥ 34 J |
The relatively high yield strength allows thinner material usage without compromising safety.
Delivery Condition
- Hot-rolled (most common)
- Controlled rolling / TMCP (Thermo-Mechanical Controlled Processing)
- Normalized (optional)
Applicable Standards
- GB/T 6653 (Gas Cylinder Steel Plates)
- Widely used in compliance with pressure vessel manufacturing codes
Technical Advantages of HP345 Steel Plate
High Strength and Lightweight Design
Compared to conventional lower-grade cylinder steels like HP295, HP345 offers significantly higher yield strength while maintaining excellent formability. This improved mechanical performance allows cylinder manufacturers to use thinner wall thickness during production without compromising pressure resistance or structural safety. As a result, the finished gas cylinder achieves a lighter overall weight, which greatly improves handling efficiency, reduces transportation costs, and eases loading and unloading operations in industrial and logistics scenarios.
Excellent Weldability
HP345 is specially engineered to support reliable and high-efficiency welding processes essential for gas cylinder fabrication. With a carefully controlled low Carbon Equivalent (CE), this steel minimizes the risk of cold cracking, hot cracking, and porosity during welding. It demonstrates stable performance across multiple industrial welding methods, including MIG (Gas Metal Arc Welding), TIG (Gas Tungsten Arc Welding), and SAW (Submerged Arc Welding). This outstanding weldability ensures strong, consistent weld joints and supports high-volume automated production lines.
Exceptional Low-Temperature Toughness
HP345 maintains outstanding impact toughness even at temperatures of -20°C and lower, making it highly suitable for use in cold climates, high-altitude areas, and low-temperature storage environments. By resisting brittle fracture under extreme low-temperature conditions, it significantly improves the safety and reliability of gas cylinders during outdoor use, long-distance transport, and cold-region industrial applications. This property is critical for preventing sudden structural failure in harsh working conditions.
Good Formability
Designed specifically for deep drawing and cold forming processes in gas cylinder production, HP345 delivers superior formability for seamless and welded cylinder manufacturing. It exhibits excellent deep-drawing performance, reliable cold-bending properties, and low sensitivity to edge cracking during the forming process. These characteristics allow manufacturers to produce cylinders with uniform wall thickness, smooth surface quality, and consistent dimensions, while reducing material waste and production defects.
High Safety in Pressure Applications
HP345 provides exceptional safety performance for pressure-containing equipment such as welded gas cylinders. This is ensured through strict control of the yield ratio, uniform mechanical properties across the entire coil or plate, and a fine-grained microstructure obtained through advanced smelting and rolling processes. Stable and predictable mechanical behavior reduces the risk of uneven deformation or premature failure under internal pressure, meeting stringent national and international safety standards for pressure vessels.
Robust Fatigue Resistance
Gas cylinders are frequently subjected to repeated gas filling, discharging, and pressure cycling, which places high demands on fatigue performance. HP345 exhibits excellent resistance to cyclic loading and fatigue damage, greatly extending the service life of cylinders under long-term repeated use. By reducing the potential for fatigue cracking and gradual structural degradation, it enhances operational safety and lowers maintenance and replacement costs for end-users.
Enhanced Microstructure Control
The superior performance of HP345 is achieved through precise micro-alloying technology with trace elements such as niobium (Nb), vanadium (V), and titanium (Ti). These micro-alloying elements effectively refine the grain structure during controlled rolling and cooling, significantly improving both strength and toughness. This metallurgical design allows HP345 to achieve higher mechanical strength without increasing carbon content, thus preserving good weldability and formability while meeting the strict performance requirements of modern welded gas cylinder materials.
Typical Applications of HP345 Steel
Gas Cylinders
LPG cylinders
Industrial gas cylinders (O₂, CO₂, N₂)
Pressure Vessels
Medium to high-pressure containers
Storage tanks
Energy and Chemical Industry
Gas storage and transportation systems
Petrochemical equipment
Comparison: HP345 vs HP295
| Property | HP295 | HP345 |
|---|---|---|
| Yield Strength | ≥ 295 MPa | ≥ 345 MPa |
| Weight Efficiency | Medium | High |
| Cost | Lower | Slightly higher |
| Safety Margin | Good | Higher |
| Suitable Pressure | Medium | Medium–High |
HP345 is ideal when higher strength and safety margins are required, while HP295 is more cost-effective for standard applications.
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Why choose HP345 over HP295?
HP345 offers higher strength, allowing thinner walls and improved safety for high-pressure applications.
Is HP345 suitable for welding gas cylinders?
Yes. It is specifically designed for welded cylinders with excellent weldability and low crack sensitivity.
Does HP345 require heat treatment?
Not always. It can be used in hot-rolled or controlled-rolled conditions, though normalization may be applied for critical applications.
Can HP345 be used in low temperatures?
Yes. It has good impact toughness at -20°C, making it suitable for cold environments.
What industries commonly use HP345?
LPG and industrial gas manufacturing
Petrochemical
Energy storage and transportation
