Effect of interpass distance on the arc stability and its effect on the automated wire arc additive manufacturing of 5 Cr - 4 Mo tool steel

다국어 초록 (Multilingual Abstract)

Recently, global environmental regulations getting more strict, and hence it is increasing that the interest and investment of automobile companies on the aluminum die casting parts to make light-weight vehicles. Die casting molds are fabricated by the machining of billets of tool steels such as AISI 4140 or H13, in general. But, it has disadvantages like a large material loss and long lead time. Meanwhile, a Wire Arc Additive Manufacturing (WAAM) process could be an alternative fabrication method of the die casting mold. It has advantages such as less material loss, short lead time, easy repair and modification, the chance to make a reinforced mold using dissimilar materials, etc. The 5 Cr - 4 Mo tool steel wire is a commercial tool steel solid wire which designed for the repair and modification of tools and molds. It has superior hot wear resistance and toughness as well as the high strength, thus has high potential to produce die casting molds via the WAAM process.
On the other hand, the WAAM process is basically the process that stacking the layers repetitively using a conventional arc welding process based on the designed tool paths by CAD/CAM. Thus, the predictability and the reproducibility of every single layer are the most important core factor to obtain the advantages of the automated WAAM process. Due to its nature, a new process parameter whose named an interpass distance should be considered as well as the conventional process parameters such as current, voltage, travel speed, etc. However, there are lack of researches on the interpass distance of WAAM process.
In this research, it was found that the interpass distance greatly affect the arc stability due to arc interference induced by the variation of distance from the prior deposited pass. That is to say that the more arc interference was observed as the less interpass distance was given. This phenomenon had been proven through the analysis of high-speed camera results and the variation in the amount of spatter. Further, it was observed that the interpass distance affects the dimension precision and predictability of automated WAAM process of the 5 Cr - 4 Mo tool steel. And it was found the critical interpass distance that could be utilized in the automated WAAM process of the 5 Cr - 4 Mo tool steel. The effect of the interpass distance on the arc interference would exist unless the interpass distance would be given over 100 %, thus, it is important to find out a point of compromise based on the arc stability, dimension predictability, and reproducibility.