1、毕 业 设 计（论 文）外 文 参 考 资 料 及 译 文译文题目： Casting 铸造 学生姓名： 学号： 专业： 所在学院： 指导教师： 年 2月 3日CastingCasting is a manufacturing process in which molten metal is poured or injected and allowed to solidify in a suitably shaped mold cavity. During or after cooling, the cast part is removed from the mold and then proc
2、essed for delivery. Casting processes and cast-material technologies vary from simple to highly complex. Material and process selection depends on the parts complexity and function, the products quality specifications,and the projected cost level. Castings are parts that are made close to their fina
3、l dimensions by a casting process. With a history dating back 6,000 years, the various casting processes are in a state of continuous refinement and evolution as technological advances are being made. Sand Casting Sand casting is used to make large parts (typically iron, but also bronze, brass, alum
4、inum). Molten metal is poured into a mold cavity formed out of sand (natural or synthetic). The processes of sand casting are discussed in this section, including patterns, sprues and runners, design considerations, and casting allowance.The cavity in the sand is formed by using a pattern (an approx
5、imate duplicate of the real part), which are typically made out of wood, sometimes metal. The cavity is contained in an aggregate housed in a box called the flask. Core is a sand shape inserted into the mold to produce the internal features of the part such as holes or internal passages. Cores are p
6、laced in the cavity to form holes of the desired shapes. Core print is the region added to the pattern, core, or mold that is used to locate and support the core within the mold. A riser is an extra void created in the mold to contain excessive molten material. The purpose of this is to feed the mol
7、ten metal to the mold cavity as the molten metal solidifies and shrinks, and thereby prevents voids in the main casting. In a two-part mold, which is typical of sand castings, the upper half, including the top half of the pattern, flask, and core is called cope and the lower half is called drag, as
8、shown in Fig.3.1. The parting line or the parting surface is line or surface that separates the cope and drag. The drag is first filled partially with sand, and the core print, the cores, and the gating system are placed near the parting line. The cope is then assembled to the drag, and the sand is
9、poured on the cope half, covering the pattern, core and the gating system. The sand is compacted by vibration and mechanical means. Next, the cope is removed from the drag, and the pattern is carefully removed. The object is to remove the pattern without breaking the mold cavity. This is facilitated
10、 by designing a draft, a slight angular offset from the vertical to the vertical surfaces of the pattern. This is usually a minimum of 1.5mm(0.060in.), whichever is greater. The rougher the surface of the pattern, the more the draft to be provided. The molten material is poured into the pouring cup,
11、 which is part of the gating system that supplies the molten material to the mold cavity. The vertical part of the gating system connected to the pouring cup is the sprue, and the horizontal portion is called the runners and finally to the multiple points where it is introduced to the mold cavity ca
12、lled the gates. Additionally there are extensions to the gating system called vents that provide the path for the built-up gases and the displaced air to vent to the atmosphere. The cavity is usually made oversize to allow for the metal contraction as it cools down to room temperature. This is achie
13、ved by making the pattern oversize. To account for shrinking, the pattern must be made oversize by these factors on the average. These are linear factors and apply in each direction. These shrinkage allowances are only approximate, because the exact allowance is determined by the shape and size of t
14、he casting. In addition, different parts of the casting might require different shrinkage allowances. Sand castings generally have a rough surface sometimes with surface impurities, and surface variations. A machining (finish) allowance is made for this type of defect. In general, typical stages of
15、sand casting operation include (as shown in Fig.3.2): 1. Patterns are made. These will be the shape used to form the cavity in the sand. 2. Cores may also be made at this time. These cores are made of bonded sand that will be broken out of the cast part after it is complete.3. Sand is mulled (mixed) thoroughly with additives such as bentonite to increase bonding and overall strength. 4. Sand is formed about the patterns, and gates, runners, risers, vents and pouring cups are added as needed. A compaction stage is typically used to ensure good coverage
