CLADDING TECHNOLOGY SHANXI CO., LTDResearch on Domestication of Consumables for High-Speed Strip Electroslag Overlay Welding
Literature Overview
This 2017 paper by Song Baorui, Fan Yangyang, Wang Yingjun, Cao Jia, and Lei Li from Sichuan Xiyi New Materials Co., Ltd., the Sichuan Special Welding Materials Research and Development Engineering Laboratory, and Erzhong Group (Deyang) Heavy Equipment Co., Ltd. addresses a critical challenge in the domestication of welding consumables for high-speed strip electroslag welding (ESW) overlay applications. High-speed strip ESW is a widely used process for applying corrosion-resistant overlay layers to hydrogenation reactors, heat exchangers, and other pressure vessels operating in aggressive chemical environments. The study focuses on the development and qualification of domestically produced strip consumables that can replace imported materials, reducing costs and ensuring supply chain security.
Core Technical Content
The authors investigated the composition, melting behavior, and welding performance of domestically produced strip consumables designed for ESW overlay welding. The target overlay materials were austenitic stainless steels such as 304, 321, and 347 grades, as well as nickel-based alloys including Inconel 625 and Monel 400. The strip consumables were evaluated in terms of chemical composition, melting point, fluidity, and weldability, with particular attention to the effects of trace element content on the welding process and overlay layer quality.
The study found that the melting point and fluidity of the strip consumable are critical parameters that directly influence the stability of the ESW process. A strip with a melting point that is too high relative to the base metal results in poor penetration and incomplete fusion, while a strip with too low a melting point leads to excessive penetration and dilution of the overlay layer. The optimal melting point of the strip consumable should be slightly lower than that of the base metal to ensure complete melting and good fusion without excessive dilution.
Composition Comparison of Domestic and Imported Strip Consumables
| Element | Domestic Strip (304 grade) | Imported Strip (304 grade) | Specification Requirement |
|---|---|---|---|
| C (%) | ≤0.03 | ≤0.03 | ≤0.03 |
| Mn (%) | 1.2-2.0 | 1.5-2.5 | 1.0-2.5 |
| Si (%) | 0.3-0.7 | 0.4-0.8 | 0.3-0.7 |
| Cr (%) | 18.5-20.5 | 19.0-21.0 | 18.0-21.0 |
| Ni (%) | 8.5-10.5 | 9.0-11.0 | 8.0-11.0 |
| S (%) | ≤0.003 | ≤0.002 | ≤0.005 |
| P (%) | ≤0.020 | ≤0.015 | ≤0.025 |
The study revealed that the domestically produced strip consumables had slightly higher sulfur and phosphorus content compared to imported materials, which could potentially affect the weldability and corrosion resistance of the overlay layer. The authors proposed modifications to the production process, including enhanced desulfurization and dephosphorization during the smelting stage, to reduce these harmful elements to acceptable levels.
Process Performance Evaluation
The welding performance of the domestic strip consumables was evaluated using a high-speed strip ESW machine with typical process parameters. The overlay layers were subjected to macroscopic and microscopic examination, hardness testing, tensile testing, and intergranular corrosion testing to assess the quality and properties of the overlay layer.
The macroscopic examination showed that the domestic strip consumables produced overlay layers with good surface quality, uniform bead profile, and no visible defects such as porosity, cracking, or lack of fusion. The microscopic examination revealed a fine-grained austenitic microstructure with no harmful phase precipitation, indicating good weldability and resistance to sensitization.
The mechanical properties of the overlay layers were found to be comparable to those produced with imported strip consumables. The hardness values were within the expected range for austenitic stainless steel overlay layers, and the tensile strength met the requirements specified in relevant standards such as ASTM A263 and GB/T 150. The intergranular corrosion testing, conducted according to ASTM A263 Method E, confirmed that the overlay layers produced with domestic strip consumables exhibited excellent resistance to intergranular corrosion, with no signs of grain boundary attack.
Typical ESW Process Parameters
| Parameter | Value | Remarks |
|---|---|---|
| Welding Current | 1200-1800 A | Depends on strip width and thickness |
| Welding Voltage | 35-45 V | Maintains stable arc and slag pool |
| Travel Speed | 150-300 mm/min | High speed reduces dilution |
| Preheat Temperature | 150-250 °C | Reduces residual stress |
| Interpass Temperature | Below 250 °C | Prevents sensitization |
| Strip Width | 50-150 mm | Depends on application |
| Strip Thickness | 1.5-3.0 mm | Thicker strips for thicker overlays |
Domestication Challenges and Solutions
The primary challenges in domesticating high-speed strip ESW consumables include achieving the required purity level, ensuring consistent melting behavior, and meeting the stringent chemical composition specifications. The authors identified several key issues and proposed corresponding solutions.
The first challenge is the control of trace elements such as sulfur, phosphorus, and nitrogen, which can significantly affect the weldability and corrosion resistance of the overlay layer. The solution involves implementing advanced smelting and refining technologies, such as vacuum induction melting and argon oxygen decarburization, to achieve the required purity level. The second challenge is ensuring consistent melting behavior across different batches of strip consumables, which requires tight control of the chemical composition and microstructure during production. The third challenge is meeting the dimensional tolerances and surface quality requirements of the strip consumables, which necessitates precision rolling and finishing processes.
Engineering Practice Implications
The successful domestication of high-speed strip ESW consumables has significant implications for the cost and supply chain security of the Chinese pressure vessel and chemical equipment manufacturing industry. Imported strip consumables are subject to high costs, long lead times, and supply chain risks, which can delay project schedules and increase fabrication costs. The domestic consumables developed in this study offer a cost-effective alternative with comparable performance, enabling domestic manufacturers to reduce their dependence on imported materials.
However, the adoption of domestic consumables requires thorough qualification and validation in accordance with applicable standards such as NB/T 47014, ASME IX, and API 934. The welding procedure specification must be qualified for the specific base metal/overlay metal combination, and the welder qualification must be verified for the ESW process. The qualification records should be maintained as part of the quality assurance documentation for the fabrication project.
Study Reflections and Outlook
This study represents a significant contribution to the domestication of welding consumables for critical industrial applications. The systematic approach to consumable development, including composition optimization, process evaluation, and qualification testing, provides a model for future domestication efforts in other welding consumable categories. The study also highlights the importance of collaboration between research institutions, consumable manufacturers, and end users in the development and qualification of new welding materials.
Future work should focus on extending the domestication efforts to more advanced overlay materials such as nickel-based alloys (Inconel 625, Hastelloy C276) and titanium alloys, which are increasingly used in high-performance pressure vessel applications. The development of consumables with enhanced properties, such as improved resistance to hydrogen attack, sulfide stress corrosion, and high-temperature creep, will be essential for meeting the demands of next-generation chemical and petrochemical equipment.