Certain basic elements in earlier development ofprocess, as well as many advanced current of the process, some because of the rapid growth in technology, are described in this chapter. Investment casting is often called ‘lost wax’ casting, and is based on one of the oldest metal forming processes. The Egyptians used the process, some 5,000 years ago, making gold jewelry, as an exact replica of the many intricate shapes, cast in gold from patterns artfully created beeswax.
In the investment, the ceramic slurry is applied, or ‘invested’, about a disposable pattern, usually wax, and is allowed to harden to form a disposable casting mold. The wax pattern is ‘lost’, when it is melted out of the ceramic mold ‘disposable’, are later destroyed recovery solutions. In investment casting, the ceramic molds are made by two different methods: the strong mold process and the ceramic shell process. The solid mold process is used primarily for the dental and jewelry castings, currently only a small role in engineering applications, and so will not be covered in this chapter. The ceramic shell process to be the main technique for the majority of applications engineering, process displacing the solid model.
The ceramic shell process precision casting process, developing unique and tailored to produce complex-shaped castings, with near-net-shape, and in different alloys. Continued progress in materials and techniques used in the process, are driven and supported research and development on many fronts, in the industry as well as many schools for metallurgy foundry. For example, research has earlier funded by Rolls Royce Limited, UK, University of Birmingham, UK, investigated the behavior of feeding high temperature alloys assistance in the development of systems gating and feeding best possible investment castings . The influence of alloy and process variables in producing sound investment castings described later in this chapter, under the section on the design of gating and feeding system.The ceramic shell process, however, requires careful control during many steps or operations . The basic steps in the process, involving both material and techniques presented here.