What is the heating principle of fusion welding equipment? (Figure) What are the types of segregation in fusion welding seams?
Speaking of fusion welding, many friends may not have heard of it. So, what is the heating principle of fusion welding equipment? What are the types of segregation in fusion welding seams? I believe this is a question that many friends want to know. Next, let Kehua The editor of the website will tell you about this knowledge. Heating principle of fusion welding equipment What is the heating principle of fusion welding equipment? Because the workpieces to be welded are closely attached together, under the action of temperature field, gravity, etc., without pressure, the melted liquid of the two workpieces will mix. After the temperature is lowered, the molten part condenses, and the two workpieces are firmly welded together to complete the welding method. The heating principle is resistance heating. What are the types of segregation in fusion welds? The phenomenon of uneven distribution of the constituent elements in the alloy during crystallization is called segregation. During the primary crystallization process of the welding pool, due to the fast cooling rate, the chemical components in the solidified weld metal have no time to diffuse, resulting in uneven distribution and segregation. Heating principle of fusion welding equipment There are three segregation phenomena in the weld as follows: 1. Fusion welding (1) When the microsegregation molten pool is crystallized once, the first crystallization center metal is the purest, and the later crystallization part contains other alloying elements and impurities slightly higher, The last crystalline part, that is, the outer end and leading edge of the crystallization, contains the highest amount of other alloying elements and impurities. The phenomenon of uneven distribution of chemical composition within a columnar grain and between grains is called microsegregation. (2) Regional segregation During the primary crystallization of the molten pool, due to the continuous growth and advancement of the columnar crystals, the impurities will be 'driven' to the center of the molten pool, so that the impurity content in the center of the molten pool is more than other parts. This phenomenon is called regional segregation. The cross-sectional shape of the weld has a great influence on the distribution of regional segregation. For a narrow and deep weld, the junction of each columnar crystal is in the center of the weld, so there are more impurities in the center of the weld. This kind of weld is very prone to hot cracks in its center. For wide and shallow welds, impurities are gathered in the upper part of the weld, which has a high resistance to thermal cracking. (3) Layered segregation During the first crystallization process, the molten pool should continuously release the latent heat of crystallization. When the latent heat of crystallization reaches a certain value, the crystallization of the molten pool will temporarily stop. Later, with the heat dissipation of the molten pool, the crystallization starts again, forming periodic crystallization, accompanied by the periodic fluctuation of the impurity concentration in the liquid metal at the crystallization front, resulting in periodic segregation called layered segregation. Laminar segregation concentrates some harmful elements, so defects often appear in lamellar segregation. Pores caused by lamellar segregation. The above is all about the heating principle of fusion welding equipment and the segregation of fusion welding seams. I hope this article can bring you some help. Interested friends can also pay attention to the Kehua website.