Discussion on Performance Evaluation Method of Welding Process for Welding Rods for Engineering Applications
1. Overview
China has emerged as the world's largest producer of welding materials, yet the share of high-end and specialized welding consumables remains relatively low. For instance, in the field of nuclear power welding materials, China has been developing welding solutions for nuclear island main equipment since the 1970s, achieving numerous technological advancements. However, despite these efforts, many nuclear power plants still rely heavily on imported welding materials for their nuclear islands. This is partly due to metallurgical limitations, as well as differences in product quality compared to foreign alternatives. The stability of the welding material and its performance during the welding process have become major barriers to the widespread adoption of domestic high-end welding materials in the nuclear industry. It is clear that the impact of welding process performance on real-world applications, the lack of appropriate qualification standards, and the mismatch between available products and engineering needs are key factors hindering improvements in welding performance.
Taking electrodes as an example, this paper briefly examines how the main components of welding performance affect practical engineering applications and discusses current methods used to evaluate electrode performance. It emphasizes the need for an engineering-focused approach, proposing a system that includes operational verification and quantitative technical indicators tested by frontline welders. By exploring the relationship between the main components of welding performance and acceptance criteria, this study aims to enhance the overall welding performance of materials.
2. Analysis of Welding Process Performance Impact
The welding process performance of electrodes typically involves several key aspects: arc stability, slag removal, re-ignition capability, spatter rate, melting coefficient, deposition efficiency, dust generation, and the quality of the weld formation. Among these, arc stability plays a crucial role in engineering applications, along with slag removal, spatter, dust, and weld quality. Arc stability determines whether the electrode can maintain a consistent and continuous burn, significantly affecting electrode consumption and construction progress. It also reflects the droplet transfer mode of the deposited metal. For example, in alkaline stainless steel electrodes, large droplet transfer can lead to longer short-circuit times, making it easier to cause arc instability. On the other hand, fine droplet transition results in a more stable welding process.
Slag removal refers to how easily the weld slag covering the weld bead can be separated from the surface after welding. The mechanism behind this is often explained by the "combination layer theory" between the slag and the weld metal. A FeO film forms on the weld surface, which has a similar composition to α-Fe in the base material and spinel phases like MeO and Me₂O₃ in the slag. Due to the body-centered cubic lattice structure, the crystal arrangement causes the slag to adhere tightly to the metal surface, making it difficult to remove. This not only increases labor and time required for slag removal but also reduces productivity and raises the risk of weld defects and poor joint performance. Additionally, the slag cleaning process can negatively affect the working environment.
Welding spatter refers to metal particles that fly out of the molten pool during droplet transfer and remain on the weld or nearby areas after cooling. In the case of alkaline stainless steel electrodes, the behavior of spatter differs between alkaline and acidic slag systems. There are two types of spatter: one caused by short-circuit droplet transition and another due to arc force. Coarse droplets formed during short-circuit transitions are more likely to result in spatter, which directly affects the welding process. Spatter can cause significant issues in engineering applications, such as excessive metal particles remaining on the groove or pipe surface, increasing cleaning work and the likelihood of weld defects. In pipe welding, for example, unprotected base metal surfaces can lead to large spatter adhering to the joint or previous beads, further complicating the process.
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