Products Description
HP235 is the preferred material for low-pressure gas cylinders because it strikes an ideal balance between the robust safety requirements for pressure vessels and the economic demands of high-volume manufacturing. As a specialized steel grade under the Chinese GB 6653 standard, it is specifically engineered to meet the unique needs of welded gas cylinders
HP235 welded cylinder stee
As a global leading steel supply chain group with 18+ years of experience, GNEE (Tianjin) Supply Chain Group Co., Ltd. has been dedicated to providing high-quality hot-rolled steel plates for welded gas cylinders since 2008. With over 600 companies across 100+ countries, we specialize in producing and supplying HP235 welded cylinder steel compliant with GB/T 6653 standard.
The Core Reasons for Choosing the HP235 welded cylinder steel
Optimized for Formability and Manufacture
Excellent Ductility: HP235 offers superior ductility compared to its higher-strength counterparts. Its elongation after fracture can be as high as 29% (for material 3mm thick or more), which is significantly better than the 26% of HP295 or 22% of HP325 . This high ductility allows the steel to be stretched into complex shapes without tearing.
Low Yield Ratio: The steel's yield ratio (yield strength divided by tensile strength) is strictly controlled to be ≤0.80 . A low yield ratio indicates that the material has a substantial capacity to deform plastically before it reaches its ultimate breaking point. This is crucial during the forming process, as it provides a wide safety margin and prevents sudden failure during stamping.
Superior Weldability
Low Carbon Equivalent: The chemical composition of HP235 features a low maximum carbon content of 0.16% . This low carbon level minimizes the risk of cold cracking in the heat-affected zone (HAZ) of the weld, allowing for strong, consistent welds without the need for complex and costly preheating procedures.
Controlled Impurities: It also has very low maximum limits for sulfur (≤0.012%) and phosphorus (≤0.025%), which are impurities that can lead to hot cracking during the welding process . This purity ensures the integrity of the welded joint.
Guaranteed Safety and Toughness
Impact Toughness: HP235 is required to absorb a minimum impact energy of 27 Joules in a standard Charpy V-notch test at room temperature . This guarantees that the steel will not fracture in a brittle manner if subjected to a sudden impact.
Low-Temperature Performance: For cylinders used in colder climates, the material can be specified to meet excellent low-temperature toughness. Modern production techniques for this class of steel can achieve -20°C impact toughness values exceeding 50 Joules , far above the standard requirements, ensuring safety even in freezing conditions.
An Economically Viable Choice
HP235 is not only technically suitable but also economically efficient.
Cost-Effective Composition: It uses a balanced alloy design with lower amounts of expensive micro-alloying elements like niobium (Nb) and vanadium (V) compared to higher-strength grades . This makes the raw material more affordable.
Process Efficiency: Its excellent formability and weldability translate to fewer manufacturing rejects and higher production throughput, further lowering the overall cost of cylinder production .
Delivery Condition
Delivery Condition
- Hot-rolled products: Delivered in the hot-rolled, controlled-rolled, or heat-treated condition.
- Cold-rolled products: Delivered in the annealed condition.
- Pickled condition: Upon mutual agreement between the supplier and the purchaser, delivery may be made in the hot-rolled and pickled condition.
Quality Assurance and Acceptance
GNEE shall provide a Quality Certificate compliant with the GB/T 6653-2017 standard, containing at least the following information:
- Supplier Name and Trademark
- Standard Number and Grade
- Heat/Batch Number, Dimensions/Specifications, and Weight
- Chemical Composition Analysis Results
- Mechanical Property Test Results
Selection and Comparison with Other Grades
| Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) | Application Scenarios |
|---|---|---|---|---|
| HP235 | ≥235 | 380–500 | ≥23–29 | Light-duty gas cylinders, complex-shaped parts |
| HP265 | ≥265 | 410–520 | ≥21–27 | General liquefied gas cylinders |
| HP295 | ≥295 | 440–560 | ≥20–26 | Standard LPG cylinders |
| HP325 | ≥325 | 490–600 | ≥18–22 | High-pressure gas cylinders |
| HP345 | ≥345 | 510–620 | ≥17–21 | Special high-pressure vessels |
For components with complex geometries and significant drawing depths, HP235 is the preferred choice, leveraging its superior formability.
For standard LPG cylinders, HP295 remains the mainstream choice.
When design pressures are elevated, grades of HP325 or higher should be selected.
What are the cold bending properties of HP235?
HP235 must be capable of withstanding a 180° cold bending test. The bending mandrel diameter should be d = 1.5a (where 'a' is the thickness of the test specimen), and no cracks shall appear on the outer surface of the specimen after bending. This requirement ensures that the material does not crack during the stamping and forming of gas cylinder heads.
What are the welding properties of HP235? Is preheating required?
HP235 possesses excellent welding properties. Its low carbon equivalent design results in low susceptibility to cold cracking, while its low sulfur and phosphorus content reduces the tendency toward hot cracking. Under normal ambient temperatures and with relatively thin plates, common welding processes-such as gas-shielded welding and submerged arc welding-can be performed without preheating. For thicker plates or low-temperature environments, welding procedures should be executed in accordance with a qualified Welding Procedure Specification (WPS).
What are the grain size requirements for HP235?
The grain size of HP235 shall be no coarser than Grade 6, and the variation in grain size shall be limited to within three consecutive grades. A fine-grained microstructure serves as the foundation for achieving an optimal balance of strength and toughness, as well as stable forming properties.
Is HP235 suitable for deep drawing?
Yes, it is. The elongation requirement for HP235 (a minimum of ≥29%) is significantly higher than that of higher-strength grades such as HP295 and HP325. Furthermore, it features a low yield-to-tensile strength ratio and moderate work-hardening capacity, making it highly suitable for the forming of deep-drawn components, such as gas cylinder heads.
