熔模铸造十大经常被问到问题.docVIP

熔模铸造十大经常被问到的问题 The Top 10 Frequently Asked Questions About Investment Casting 1. What is an Investment Casting? The term investment may bring dollar signs before the eyes of those who are not familiar with the process. Actually, it refers to the ceramic materials that are used to build a hollow shell into which molten metal is poured to make the castings. The origin of the term investment comes from the solid mold process where a plaster type material is poured or invested into a container that holds a clustered tree of small plastic patterns that are identical to the casting being produced. After the plaster has set, the disposable patterns are burned out leaving a hollow cavity into which the metal is poured. The same hold true for the investment or lost wax casting process. Wax is injected into an aluminum die to produce a pattern that is an exact replica of the part to be produced. For every casting, a wax pattern must be manufactured. The patterns are then clustered around a coated sprue and repeatedly dipped into an agitated vat of ceramic and allowed to dry. After a shell thickness of approximately 3/8 has been built, the molds are dewaxed by either flash firing at high heat (1400 degrees F) or autoclaving (pressure and steam). The hollow shells are then preheated to 800 - 2000 degrees F depending on the alloy to be poured and the molten metal cast immediately into the hot shell. After cooling, the ceramic is vibrated and blasted off the metal parts and discarded. The balance of the cleaning operations (cut off, grind, heat treat, straightening, blast) are straight forward and quite similar to the other casting processes. 2. What alloys can be poured as an investment casting? Generally, all ferrous and non-ferrous materials can be investment cast. On the ferrous side, carbon, tool and alloy steel along with the 300, 400, 15-5PH and 17-4Ph stainless steels are most commonly poured. most aluminum, copper base, and other non-ferrous materials can be cas