Application cases and solutions for welding materials for pressure vessel manufacturing

Main Products and Common Welding Consumables

Our company is a specialized manufacturer and designer of pressure vessels, serving industries such as energy, chemicals, petrochemicals, coal chemicals, fine chemicals, fertilizers, paper, clean energy, and offshore engineering. We produce various equipment like towers, heat exchangers, reactors, and converters.

Common welding consumables we use include carbon steel, chrome-molybdenum steel, low-temperature steel (2.5Ni, 3.5Ni), low-alloy high-strength steel, stainless steel (including duplex and urea-grade), and nickel-based alloys. Carbon steel, chrome-molybdenum steel, low-temperature steel, and low-alloy high-strength steel are mainly used with welding rods and submerged arc welding wires. Stainless steel and nickel-based alloys are typically applied using welding rods and welding strips.

In recent years, as equipment capacity and technology have advanced, the level of welding automation has also increased. This has led to a gradual reduction in the use of welding rods, while the usage of welding wires and welding belts has risen. As a result, both production efficiency and welding quality have improved significantly.

Welding Material Application Cases and Solutions

In actual production, the recommended welding consumables based on standards may not always meet additional performance requirements. For example, certain mechanical properties after normalization and tempering, or new welding methods, may require specific testing before full-scale application. Below are some examples from our factory for reference.

Case 1: Selection of Welding Consumables for Q345R Steel Joints After Normalizing + Tempering

According to GB713-2008 and National Standard No. 1, the tensile strength (Rm) of Q345R steel varies with plate thickness: Rm ≥ 490 MPa for plates between 60–100 mm thick, and Rm ≥ 480 MPa for plates between 100–150 mm thick. Testing with different welding consumables showed that test results for specimens 5-11, 9-83, and 121087 met the lower limit requirements. By upgrading the welding rod grade and customizing the flux, the tensile strength at room temperature reached or exceeded the standard’s minimum requirement.

Case 2: Selection and Application of Electrode Surfacing Welding Consumables

First, reducing surfacing thickness can help cut costs, especially when surface finishing is not required after welding.

For an equipment project, 8 sets of machinery required a 5mm stainless steel surfacing layer. Using submerged arc welding, the thickness was about 8mm, costing around 1.6 million yuan. By reducing each layer by 1mm, we saved 200,000 yuan, making it a highly beneficial approach. The target was to reduce by at least 2mm. Initial tests were conducted, and the results are shown in Table 2. A second test was performed, and the results are listed in Table 3.

As seen in Table 3, increasing the CrNi content of the base material and modifying the electroslag flux allowed us to achieve a 5.5mm surfacing layer that met the minimum thickness requirement of 5mm. The dilution rate for submerged arc surfacing is 18%–25%, while for electroslag it's 7%–10%. Reducing the dilution rate is crucial for corrosion-resistant surfacing, which electroslag welding effectively achieves. From a consumable perspective alone, we saved at least 400,000 yuan.

Second, replacing the nickel-based flux ensured better appearance and quality, especially when the surface was processed after welding. For an ammonia synthesis tower casing made by our company, the bottom forging material was 12Cr2Mo1IV. When welding a specific type of material, the initial results with flux and submerged arc welding were poor. Even after adjusting parameters and following lab recommendations, the weld formation remained unsatisfactory. The issue likely stemmed from the flux itself, which requires high technical expertise. After negotiation, we sourced an electroslag flux from Jingqun, resulting in excellent surface quality. The post-penetration testing results are shown in Figure 2.

Expectations and Suggestions for the Future Development of Welding Consumables

As a non-standard pressure vessel manufacturer, we still face challenges with certain special welding materials in China compared to those from Europe, the U.S., and Japan. These include nickel-based alloys, duplex steels, urea-grade stainless steels, and 12Cr2Mo1CrMo steel. Some domestic manufacturers' test samples do not meet technical requirements, and their weldability is not as good as imported products. However, the biggest issue with imported consumables is long procurement cycles and high costs, which affect production schedules and increase manufacturing expenses. We hope that domestic welding consumables will improve and offer competitive alternatives. Additionally, some companies do not produce their own wire or strip. Therefore, we also hope the government will support the development of self-manufactured wire and strip to ensure better compatibility and performance of welding consumables.

The product is widely used in high-end manufacturing fields such as automotive industry, mold manufacturing, engineering machinery, power generation equipment, precision machinery, aerospace, medical industry, etc.