Unit 3 Casting

3.1 Introduction

Several different methods, such as casting, forging, welding and machining are available to shape metals into useful products. Customarily, casting, forging, welding etc. are referred to as forming processes which generally use molds, dies or other tooling to force the molten metal or metal blanks shaped into final parts. Machining (including turning, milling, shaping, grinding and drilling, etc.), however, means remove the unwanted material from the blank surface in the form of chips with cutting tools or other physical and chemical means.[1] One of the oldest forming processes is casting, which basically involves pouring molten metal into a mold cavity where, upon solidification, it takes the shape of the cavity. Casting was first used around 4000 B.C. to make ornaments, copper arrowheads, and various other objects. The casting process is capable of producing intricate shapes in one piece, including those with internal cavities, such as engine blocks. Almost all metals can be cast to the final shape desired, often with only minor finishing operations required. This capability places casting among the most important net-shape manufacturing technologies.