Critical Factors in Material Selection for Pressure Vessels

In the design and manufacturing process of pressure vessels, the selection of materials is of paramount importance. The correct choice of materials not only directly affects the safety and service life of the vessel but also influences its economic benefits and overall performance. Since pressure vessels are widely used in industries such as petroleum, chemical, and energy, where working conditions vary greatly, the selection of materials must be meticulous and meet the actual needs of the working conditions. Incorrect material selection can lead to serious safety accidents and property loss. Therefore, when designing pressure vessels, careful material selection is the foundation for ensuring the safe and efficient operation of the equipment.
 

The Importance of Material Selection for Pressure Vessels

 
Material selection is one of the most critical decisions in the design of pressure vessels. Incorrect material selection can lead to serious safety accidents. For instance, manufacturing pressure vessels with steel that has poor weldability may result in cracks at the weld joints, leading to leaks or explosion accidents. Similarly, the improper selection of nickel-chromium stainless steel can lead to intergranular corrosion and stress corrosion, causing irreversible damage to the vessel during use. Moreover, if ferritic steel is used to manufacture cryogenic pressure vessels and the steel's transition temperature is higher than the working temperature of the vessel, the vessel is prone to brittle fracture in low-temperature environments. These cases all emphasize that when selecting steel for pressure vessels, a comprehensive assessment of the material's mechanical properties, physical properties, and corrosion resistance must be made to adapt to the specific working conditions of the vessel.

Basic Principles for Material Selection

 
When selecting materials for pressure vessels, the following basic principles should be followed.

1. Operating Conditions

 
Material selection should consider the design pressure, design temperature, and the corrosiveness and characteristics of the medium. According to different operating conditions, materials with corresponding mechanical properties and corrosion resistance should be selected.

2. Processing Performance

 
The weldability, cold and hot processing performance, and heat treatment characteristics of the material also need to be considered. The material should have good processability to ensure the quality stability and reliability during the manufacturing process.

3. Structural Requirements

 
The structural design of the vessel significantly influences the selection of materials. For example, in situations where rigidity or structural design is the main consideration, ordinary carbon steel is usually the preferred choice, while in situations where strength design is the main consideration, materials with higher strength, such as Q235A, Q235B, 20R, 16MnR, and other steels, are required.

4. Economic Rationality

 
Under the premise of meeting performance requirements, materials that are economically rational should be prioritized to reduce equipment costs. The price of materials is an important factor, and there is a significant difference in the prices of different steels, so the performance and cost of materials need to be balanced when selecting materials.

Application Scenarios for Various Materials

 
According to different working conditions and performance requirements, the selection of common materials for pressure vessels can be summarized as follows.

1. Carbon Steel

 
Suitable for atmospheric and low-pressure vessels with weak medium corrosiveness, as well as medium-pressure vessels with not too thick walls. This type of steel is usually used for forgings, pressure-bearing steel pipes, non-pressure-bearing components, and other occasions where wall thickness is determined by rigidity or structural factors.

2. Low Alloy High Strength Steel

 
Suitable for pressure-bearing vessels with weak medium corrosiveness and thicker walls. Its high strength and good corrosion resistance make it an ideal choice for medium and high-pressure vessels, especially when the wall thickness is not less than 8mm.

3. Pearlitic Heat-Resistant Steel

 
Used for pressure vessels resistant to high-temperature hydrogen or hydrogen sulfide corrosion, or for heat-resistant applications with design temperatures between 350 and 650°C. Due to its excellent high-temperature performance, it is commonly used for pressure vessels in high-temperature and high-pressure environments.

4. Stainless Steel

 
Suitable for vessels with strong medium corrosiveness, where iron ion pollution prevention is required, or for special applications with design temperatures above 500°C or below -100°C. Stainless steel has excellent corrosion resistance and oxidation resistance and is widely used in the chemical and pharmaceutical industries.

Economic Considerations

 
The selection of materials must not only meet technical requirements but also consider their economic viability. A large part of the equipment cost is determined by the price of materials, so it is necessary to understand the price and cost-effectiveness of various materials when selecting materials. For example, taking the price of carbon steel plate Q235-A as the baseline, the price of 16MnR is 1.4 times that of Q235-A, the price of 20R (20g) is 1.8 times, chromium steel (1Cr13, 2Cr13) is 5.1 times, and high-alloy steel 0Cr18Ni10 is as high as 14.1 times. Therefore, under the premise of meeting the requirements, materials with lower costs should be selected as much as possible.
 
In summary, selecting materials for pressure vessels requires careful consideration of operating conditions, processing performance, structural design, and cost-effectiveness. Proper material choice ensures safe operation under complex conditions, optimizes costs, and enhances efficiency. A rigorous selection process is crucial for long-term stability and accident prevention, underpinning the success of engineering projects. As technology and material science advance, material selection will become more precise, driving the pressure vessel industry towards greater safety, reliability, and efficiency.