Discussion on Performance Evaluation Method of Welding Process for Welding Rods for Engineering Applications

1 Overview

China has become the world's largest producer of welding materials, but the proportion of high-end and special welding consumables is relatively small. Taking nuclear power welding materials as an example, China has been developing welding materials for nuclear island main equipment since the 1970s, and has achieved a large number of scientific and technological achievements. However, at present, the welding materials for a large number of nuclear islands in nuclear power plants are still mainly imported. In addition to the metallurgical level restrictions, some of the product quality is different from the imported welding consumables. The quality stability of the welding materials and the welding process performance. It has become the main factor restricting the large-scale popularization and application of high-end welding materials for domestic nuclear power. It can be seen that the influence of the welding process performance of welding materials on the application of product engineering, the lack of corresponding qualified standards and quantitative indicators, and the low degree of conformity with engineering applications have become the key influencing factors for the improvement of welding process performance of welding materials.

Taking the electrode as an example, this paper briefly analyzes the influence of the main components of the welding process performance on the engineering application and the detection method of the current welding electrode performance. It proposes the engineering-oriented application and establishes the operation verification and quantitative technical index detection of the industry first-line welder. The corresponding relationship method explores the acceptance indicators of the main components of the welding process performance, in order to promote the improvement of the welding process performance.

2. Analysis of welding process performance impact

The welding process performance of the electrode mainly includes arc stability, slag removal, re-arcing performance, spatter rate, melting coefficient, deposition efficiency, dust generation and welding forming quality, etc. The main influence on engineering application is arc stability. 5 aspects of properties, slag removal, splash rate, dust generation and welding quality.

The stability of the arc determines whether the electrode can be stably and continuously burned. It has a significant influence on the amount of the electrode and the construction progress. It can feedback the form of the droplet transfer of the deposited metal of the electrode, for example, the alkaline stainless steel electrode, the droplet transfer of large particles. Because the short circuit time is long, it is easy to cause arcing, and the fine particle slag wall transition will make the welding process more stable.

Deslagability refers to the ease with which the weld slag covering the weld bead is separated from the surface of the weld after welding. The slag separation mechanism is usually explained by the "combination layer theory between slag and weld metal". The FeO film layer formed on the weld surface has the same composition as the α-Fe of the matrix and the MeO and Me2O3 spinel in the slag. The body-centered cubic lattice features, the coherent arrangement of the crystal structure causes the slag to be tightly bound to the metal surface, and the slag removal is difficult. The tightly combined welding slag makes the project clearing slag time-consuming, labor-intensive, reduces productivity, increases the risk of weld slag defects and poor joint performance, and the slag cleaning process will also worsen the working environment.

Welding spatter refers to metal particles that fly outside the molten pool during the droplet transfer process and remain in the weld and its vicinity after cooling. Taking alkaline stainless steel as an example, the alkaline slag system and the acidic slag system have different welding spatter behaviors, including two types: splash caused by short-circuit transition of molten droplets and splash caused by arc force, coarse droplets determined by the composition of the coating and Explosive behavior in a short circuit transition is a necessary condition for generating a weld spatter. The welding spatter is mainly related to the droplet transfer characteristics, which can indirectly reflect the transition form of the droplet. The main influence on the project is to produce a large number of large or large particles of metal particles, and the welding arc is unstable. Taking pipe welding as an example, in the general engineering welding process, the surface of the base metal is not protected. Excessive splashing will cause a large amount of granular metal to remain on the groove surface and the pipe surface, and sometimes a large particle spatter will adhere to the slope. The mouth or the previous bead surface, which increases the amount of cleaning work and increases the probability of welding defects.

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