After the liquid titanium is cast into the holding type, the liquid titanium will be solidified from the liquid state to the room temperature, and the volume and linear size will be reduced, that is, body shrinkage and linear shrinkage.
The solidification shrinkage process of titanium and titanium alloy castings is closely related to the quality of the castings subsequently obtained. Various defects (such as shrinkage, shrinkage, porosity, hot cracks, cold cracks, stress and deformation, etc.) that often occur in castings are related to this Process. The whole process of solidification and shrinkage of titanium and titanium alloy castings is actually body shrinkage. For ease of use in engineering, liquid shrinkage and solidification shrinkage are represented by body shrinkage, and solidification shrinkage after solidification is directly related to the shape structure and dimensional accuracy of shaped castings. Linear shrinkage is often considered at this stage of shrinkage.
In the solidification process of titanium and titanium alloy castings, if the liquid shrinkage and solidification shrinkage cannot be compensated, concentrated holes or scattered holes will appear in the final solidification of the casting. Concentrated holes are called shrinkage holes; scattered holes are called shrinkage holes. Whether shrinkage or shrinkage occurs in the end of the casting is closely related to the type of alloying elements added. All the alloy elements added with titanium form a solid solution alloy casting with a narrow crystallization temperature interval, which tends to form concentrated shrinkage pores; all alloy castings containing alloy elements that can widen the crystallization temperature interval of titanium tend to form branches Shrink or sponge-like shrinkage. The size of shrinkage cavity and shrinkage volume in titanium alloy castings is affected by the addition of alloying elements.
In titanium alloy castings, whether forming shrinkage holes or shrinkage, gas plays a big role. Liquid titanium cools and solidifies and shrinks. When the final solidification point is not compensated, holes appear. These holes are vacuum. The gas released when the liquid titanium solidifies will diffuse and fill here. Therefore, the holes in titanium and titanium alloy castings are often referred to as shrink holes, and the holes are silver-white, which is one of the characteristics of titanium alloy castings.