Core type and applications (1.2)

various types of cores, chaplets ,core prints.

1. Core 1.2 core type and applications you can

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3. The normal required characters are Strength - to maintain the shape and resist erosion Permeability - to allow hot air and gasses to pass through voids in sand Thermal stability – to resist cracking on contact with molten metal Collapsibility - ability to give way and allow casting to shrink without cracking the casting you can

4. Core Sands Preparation: Sand- Silica sand is mostly used. Coarse silica sand is used for higher refractoriness particularly for steel industries . Finer sand are used for cast irons and nonferrous alloys . Sodium silicate is mixed with CO 2 gas and form silica gell . So It became very hard. you can

5. Types of Cores(Level one Question) Condition of core- Green sand core, Dry sand core Nature of core material- Oil Bonded, Resin Bonded, Shell And Sodium Silicate Cores Core hardened process- CO 2 process, Hot Box Process, Cold Set Process Shape and position – Horizontal,Vertical,Cover Core, Balanced Core, Drop Core, Kiss Core you can

6. Green sand cores: These are obtained by the pattern itself during moulding . Though this is the most economical way of preparing a core, the green sand being low in strength cannot be used for fairly deep holes . Also a large amount of draft is to be provided so that the pattern can be withdrawn you can

7. Dry sand cores It is made by special core sands in a separate core box, backed and then placed in the mould before pouring. you can

8. Nature of core material Oil bonded core : silica + linseed oil. Resin bonded cores : phenol resin bonded sand is rammed in a core box. Backing temp is 450˚F you can

9. Core hardening process Hot box core : It uses heated core boxes for the production of core. Cast iron, steel or aluminium core box are used. Core box are heated to 500˚F. Cold set process: while mixing the core-sand an accelerator is added to the binder. It is easily rammed. A little heating make it harderns it. It is employed for large cores. CO 2 process you can

10. Shape and positioning Horizontal core: It is positioned horizontally in the mould . Depends upon the cavity the shape is prepared. It is supported at both ends . you can

11. Shape and positioning Vertical core: Its axis is vertical. The two ends are supported in core seats in cope and drag. you can

12. Shape and positioning Cover core: It is supported from above and it hangs vertically in mold cavity . This type is mostly used if the cored casting is to be completely moulded in the drag with the help of a single piece solid pattern. you can

13. Shape and positioning Balanced core: It is supported and balanced from its one end only. Some times chaplets used. you can

14. Shape and positioning Drop core or Stop off core: (tail core chair core or saddle core) It is employed to make a cavity which cannot be made with other types cores. To make a cavity above or below the parting line it is used. you can

15. Shape and positioning Kiss core: A kiss core does not require core seats for getting supported. A kiss core is held in position between drag and cope due to the pressure exerted by cope on the drag. A number of kiss cores can be simultaneously positioned in order to obtain a number of holes in a casting. you can

16. Shape and positioning Kiss core : you can

17. Core Boxes These are used for making cores. A core box is a wooden or metallic type of pattern and are made either single or in two parts. They may be classified according to the method of making the core or shape of core. The common types of core boxes are described below: Half Core Box Dump core box Split core box Core making methods you can

18. Core making with machines Jolt machine Sand slinger Core extrusion machine you can

19. Core positioning and supports To support the core A projection made in the pattern is called core print . It is used to form a core seat in the mould . you can

20. Chaplets- A metallic support which can avoid the core shifting. It is the same material of molten metal. you can