Localization trend and improvement direction of stainless steel strip surfacing for pressure vessels

Our company was established in June 1954. It specializes in designing and manufacturing thermal power generating boilers with capacities ranging from 50 to 1000MW, which are its main products. In addition, we design and produce auxiliary equipment, petrochemical containers, nuclear energy equipment, industrial boilers, and military products. Since the founding of the People's Republic of China, our company has been a key player in the domestic thermal power equipment market, holding more than 35% of the installed capacity and ranking first in output nationwide. Due to the wide range of products, diverse base materials, complex structures, and high manufacturing difficulty, our welding capabilities and expertise are among the best in the country. We have extensive experience in the localization and application of welding consumables. The deposited metal grades for commonly used welding materials are listed in the attached table. Currently, nearly 90% of our products use locally produced welding consumables.

Localization Trends

In some coal and petrochemical products, the inner walls of the containers are often designed with a double-layer stainless steel surfacing corrosion-resistant structure. For large-diameter, thick-walled products with extensive stainless steel surfacing on the inner wall, electroslag surfacing (ESW) or submerged arc welding surfacing (SAW) is typically used. Although ESW offers advantages such as high deposition efficiency, low dilution rate, and a narrow heat-affected zone, it also has drawbacks like shallow penetration, poor resistance to hydrogen stripping, and relatively low bonding strength. Additionally, ESW may cause issues with workpiece roundness tolerance. Therefore, SAW is often preferred for such applications. Imported surfacing welding consumables once dominated the market due to their superior process performance and quality. However, they come with high costs and long lead times. With increasing competition in the manufacturing sector and the need for cost-effective solutions, the localization of welding consumables has become a major focus for both buyers and suppliers. As domestic technology advances and localization efforts accelerate, many local welding consumable manufacturers have seized new business opportunities. They have actively invested in R&D, significantly narrowing the technological gap with imported products. At the same time, they offer more favorable conditions in terms of manufacturing costs, transportation, and after-sales service, breaking the previous monopoly of imported materials and rapidly expanding the variety of stainless steel welding consumables available domestically.

Challenges and Improvement Directions

After extensive testing and application of various domestic stainless steel welding strips and fluxes, our company has observed that these materials have significantly narrowed the gap in mechanical properties compared to similar imported products. They also offer clear advantages in price and delivery time. However, we have also identified several subtle flaws in domestic welding consumables.

(1) Appearance, Packaging, and Identification Issues

1. Some domestic stainless steel welding strips only have basic information such as grade and batch number printed on the outer packaging, but lack relevant details on the inner packaging. This can make it difficult to identify the seal layer and corrosion-resistant layer after opening. To address this, we recommend that manufacturers add a label or logo on the innermost part of the welding strip. 2. Imported welding strips typically have smooth edges with minimal burrs, while domestic ones often show signs of rough edges, which can affect feeding during welding. To improve usability, it is recommended to include a trimming process before the welding consumables are used.

(2) Process Performance of Domestic Submerged Arc Surfacing Stainless Steel Strips

First, some sintered fluxes have uneven particle sizes and often fail to meet the lower limit requirements. These fluxes tend to appear powdery, leading to several issues: 1. During use, they can generate excessive dust, causing environmental pollution and affecting welder health. 2. The weld bead may not be well-formed, and slag removal can be difficult, leading to porosity and slag inclusion. 3. If welding defects occur, additional steps like grinding, repair welding, and re-inspection may be required, increasing workload, resource waste, and production costs. To mitigate these issues, manufacturers should strictly follow standards to ensure consistent flux quality. Second, some domestic welding strips and fluxes exhibit problems such as incomplete weld bead formation, undercutting, poor fusion, and difficulty in slag removal (see Figure 1). In contrast, imported fluxes demonstrate more stable and reliable performance (see Figure 2). When replaced with the same type of imported flux, these issues were largely resolved (see Figure 3). Analysis suggests that the problem may stem from low-melting substances in the flux, which can interfere with the solidification of the weld bead when the molten metal cools. To address this, manufacturers should optimize and refine the flux production process.

Figure 1: Domestic welding tape / flux bead

Figure 2: Imported solder ribbon / flux welding

Figure 3: Domestic welding belt / imported flux welding channel

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