During the die-casting process of aluminum alloy die castings, the mold temperature may be too low, the alloy liquid temperature may be too low, the filling speed may be too low, the release agent may be sprayed excessively or not dried, the gate design may be unreasonable, and the fast injection point setting may be unreasonable, all of which may cause cold insulation in the die castings.
The shape of the cold barrier is the shape of the initial liquid flow, with a single lubrication and rounded edges. Therefore, in radiographic images, it often appears as a smooth strip-shaped black line mirror with a relatively uniform width and lack of variation. The width of the line appears relatively large, and the blackness also changes in the width direction.
The area where aluminum alloy die castings exhibit cold insulation is usually located far from the sprue. It is because the metal flow is divided into several streams, and the flow front of each stream has already shown a condensation state. However, under the push of the metal flow at the back, it is still filled. When the metal flow that meets it also has a condensation front, the condensation layer that meets it cannot fuse anymore, and the joint presents a gap. The severe cold insulation has certain obstacles to the use of castings, which should be determined according to the conditions of casting use and the degree of cold insulation.