2.casting process

casting process

1. CASTING PROCESS 7/4/2014 1

2. Terms involved in casting 7/4/2014 2

3. Terms involved in casting process Mould box (flask) : It is usually a metallic frame used for making and holding a sand mould. The mould box has two parts: the upper part called 'cope', and the lower part called 'drag'. Parting line/parting surface : It is the zone of separation between cope and drag portions of the mould in sand casting. Sprue : It is vertical passage through which the molten metal will enter the gate. Pouring basin : The enlarged portion of the sprue at its top into which the molten metal is poured. 7/4/2014 3

4. Terms involved in casting process Gate/ingate : It is a short passage way which carries the molten metal from the runner/ sprue into the mould cavity. Riser : A riser or feed-head is a vertical passage that stores the molten metal and supplies (feed) the same to the casting as it solidifies. Gate/ ingate : It is a short passage way which carries the molten metal from the runner/ sprue into the mould cavity. Riser : A riser or feed-head is a vertical passage that stores the molten metal and supplies (feed) the same to the casting as it solidifies. Mould cavity : The space in a mould that is filled with molten metal to form the casting upon solidification. Core : A core is a pre-formed (shaped) mass of sand placed in the mould cavity to form hollow cavities in castings. Core print : It is a projection attached to the pattern to help for support and correct location of core in the mould cavity. 7/4/2014 4

5. STEPS INVOLVED IN MAKING A CASTING The basic steps in making a casting are: (a) Pattern making (b) Mould preparation (including gating and risering) (c) Core making (d) Melting and Pouring (e) Cleaning and Inspection 7/4/2014 5

6. a) Pattern making A pattern is a replica of the object to be cast . It is used to prepare a cavity into which the molten metal is poured. A skilled pattern maker prepares the pattern using wood, metal, plastic or other materials with the help of machines and special tools. Many factors viz., durability, allowance for shrinkage and machining etc., are considered while making a pattern. 7/4/2014 6

7. b) Mould preparation Mould preparation involves forming a cavity by packing sand around a pattern enclosed in a supporting metallic frame called 'flask' (mould box). When the pattern is removed from the mould, an exact shaped cavity remains into which the molten metal is poured . Gating and risering are provided at suitable locations in the mould. Gating - Passage through which molten metal flows and enter the mould cavity. Risering - A reservoir of molten metal connected to the mould cavity to supply additional metal so as to compensate for losses due to shrinkage, as the metal solidifies. 7/4/2014 7

8. c) Core making In some cases, a hole or cavity is required in the casting. This is obtained by placing a core in the mould cavity. The shape of the core corresponds to the shape of the hole required. 7/4/2014 8

9. d) Melting and Pouring Metals or alloys of the required composition are melted in a furnace and poured into the mould cavity. Many factors viz., temperature of molten metal, pouring time, turbulence etc., should be considered while melting and pouring. 7/4/2014 9

10. e) Cleaning and Inspection After the molten metal has solidified and cooled, the rough casting is removed from the mould, cleaned and dressed. This involves removing cores, adhered sand particles, gating and risering systems, fins, blisters etc., from the casting surface. then sent for inspection to check for dimensions or any defects like blow holes, cracks etc. 7/4/2014 10

11. Procedure for making the casting 7/4/2014 11

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15. Components Produced by Casting Process Casting is the first step and the primary process for shaping any material. All materials have to be cast before it is put to use. The ingots produced by casting process are used as raw material for secondary processes like machining, forging, rolling etc. More than 90 % of all manufactured goods and capital equipment use castings for their manufacture. To list the components produced by casting is an endless process. A few major components produced by casting are given below. 7/4/2014 15

16. Components Produced by Casting Process Automotive sector - Nearly 90 % of the parts in automobiles are-manufactured by castings. A few parts include brake drum, cylinder, cylinder linings, pistons, engine blocks, universal joints, rocker arm, brackets etc., Aircraft - Turbine blades, casing etc. Marine propeller blades . Machining - Cutting tools, machine beds, wheels and pulleys, blocks and table for supports etc. Agriculture and rail road equipments . Pumps and compressors frame, bushings, rings, pinion etc. Valves, pipes and fittings for construction work. Camera frames, parts in washing machine , refrigerators and air-conditioners. Steel utensils and a wide variety of products. 7/4/2014 16

17. Advantages of casting process Large hollow and intricate shapes can be easily cast. Quick process , and hence suitable for mass production. No limit to size and shape . Parts ranging from few millimeters to meters and few grams to tons can be cast efficiently and economically. Better dimensional tolerances and surface finish can be obtained by good casting practice. Castings exhibit uniform properties in all the directions - longitudinal, lateral and diagonal. The casting process is usually the cheapest process . Unrelieved internal stresses are absent in cast components. Certain metals and alloys can be manufactured by means of casting only, e.g., Phosphor-Bronze. 7/4/2014 17

18. Limitations of casting process Presence of defects in cast parts is a major disadvantage. Casting process is not economical for small number of parts . Properties of cast materials are generally inferior when compared to those made by machining or forging process. Casting process mostly deals with elevated temperatures . There are limitations regarding thin sections . Casting process is not suitable for very small number of components . 7/4/2014 18