模具设计与制造专业英语 黄义俊_ 电子教案统一模板(模具)Unit4.pptVIP

Unit 4 Pressure Die-Casting Die Design 4.1 Lesson 9 The Assembly of Pressure Die-Casting Dies A pressure die-casting die is an assembly of materials, mostly ferrous metals, each of which plays a part in a mechanism which will operate under conditions of rapidly changing temperatures, as the molten metal is injected under pressure and then immediately cooled.[1] Some parts of the die merely act as holding elements; others, such as the die inserts and the cores, have to withstand the impact and high temperature of the molten metal. The mechanisms for moving the ejectors and cores must work smoothly in the constantly changing temperature of a die. Parts which act as bearings are made either of non-ferrous metals such as phosphor bronze, or the steel surfaces are given a nitride or other treatment to resist wear. The die insert for producing of the shape of the casting has to be machined accurately and heat-treated to provide the best possible mechanical properties at high temperature. Most die-casting dies operate automatically and, while this leads to high productivity when there are no delays, the cost of breakdowns is correspondingly high.[2] During the past decade the manufacture of dies has been revolutionized by sophisticated methods ranging from improved spark erosion to computer-controlled die making. Among other efforts the Science Research Council is supporting a large scale research programme to include die heat treatment and surface coatings, computer-aided die design, special machining processes and the economics of die manufacture. A single die may contain l0 or more different steels plus several non-ferrous metals and special heat resisting alloys. Figures 4-1 and 4-2 illustrate schematically a die which typifies the various components, each of which involves design, engineering and metallurgical problems. 4.2 Reading Materials 9 The Die Insert The die insert is the heart of the die, since it keeps the