Design for casting and weldments design of casting

Design for casting and weldments
design of casting

1. DESIGN FOR CASTING AND WELDMENTS M. SANTHOSH 2021507312 N.GOKULAKANNAN 2021507313 B.S. VENU GOPAL 2021507314

2. Welding Machine A  welding machine   is used to create the heat and apply the filler metal. The filler metal is supplied to form the joint, either from the electrode itself (or) by filler material. The temperature of the heat produced is of the order of 6000° to 7000°c.

3. Types of Welding Processes MIG welding TIG welding Stick welding Flux cord arc welding Plasma Arc welding Electron beam welding Laser beam welding Gas welding Automic hydrogen welding Electroslag welding

4. WELD DESIGN RECOMMENDATION Cost Reduction Minimizing Distrotion Weld Strength

5. COST EDUCTION Reduce no of weld parts Easy to Access weld joints Provide minimum amount of weld

6. Provide minimum amount of weld Define, stack weld, intermitten weld ( if the application doesn’t involve high stress or leak proof)

7. DESIGNER SHOULD AWARE OF POOR AND GOOD FIT UP PARTS

8. Minimizing Distortion Use good Fitup to minimize weld time, control distortion

9. Continue… Weld gap should be as per standard Use thicker component to reduce weld distortion Use short flange to reduce distortion

10. Continue… Weld flange

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12. Design for solder and brazed assembly One of the most common joining processes, Brazing, works on the principle of capillary action. It uses a filler metal that is melted and distributed between the faying surfaces by capillarity. The process ensures that only the filler metal melts and the base metals are unaffected. This is because the filler metal has a melting temperature lower than that of the base metal that is to be joined.

13. Continue… The most common brazing metals are alloys of silver or of copper. Filler metals of these materials have a melting point greater than 425°C. Following are some of the heat sources via which the filler metal is melted : Heated iron (solder only) Gas torch Furnace Induction coils Dipping in either molten filler metal or a molten salt bath Electrical resistance (of the work piece itself) Infrared lamps

14. Brazing has several advantages over welding. These are Any metal including dissimilar metals can be joined Thin wall parts that cannot be welded can be brazed Less heat and power required than that in fusion welding As the working temperature is low, problems in the heat affected zone in the base metal are reduced Joint areas that are inaccessible by many welding processes can be brazed

15. Some disadvantages and limitations of brazing include Joint strength is less as compared to that in a welded joint. Joint strength is less than that of the strength of the base metal. The brazed joint is weakened by high service temperatures. Sometimes color of the brazed surface and base metals are dissimilar

16. Uses of the Brazing process Some of the industries that use brazing on a large enough scale include automotive (joining tubes and pipes), electrical equipments (joining wires and cables), cutting tools (brazing cemented carbide inserts to shanks), and jewelry marking industries.

17. Soldering Somewhat similar to brazing, soldering is a joining process in which the filler metal has a melting point less than 4250C and is melted and distributed by capillary action between the faying surfaces of the metal parts being joined. The filler metal is called solder and is added to the joints, which distributes itself between the closely fitting parts. Common materials which act as solders are based on lead and tin (for higher temperatures) or on brass and silver. Details of soldering are similar to brazing.

18. Advantage Low energy input relative to brazing and welding Variety of heating methods available After soldering the joint has good electrical and thermal conductivity. Capable of making air-tight and liquid tight seams for containers Rework and repair are easy.

19. Continue… Disadvantage : Low joint strength unless reinforced by mechanical means Possible weakening or melting of the joint in elevated temperature service Application : Wide applications in the electronics industry. Used for mechanical joint but not for joints subjected to elevated stresses or temperature

20. TYPICAL CHARACTERISTICS Usually brazed and soldered assembly types are recommended if either the configuration with single piece is not possible or it is not economical to make from a single piece. Such situation arises when: Metals are dissimilar The requirement is an intricate lightweight assembly Machining is not feasible on parts that are very thin and that have a high chance of breakage Faced with leak proof joints of hollow shapes such as tanks, floats and evaporators 1. Metals are dissimilar 2. The requirement is an intricate lightweight assembly 3. Machining is not feasible on parts that are very thin and that have a high chance of breakage 4. Faced with leak proof joints of hollow shapes such as tanks, floats and evaporators 1. Metals are dissimilar 2. The requirement is an intricate lightweight assembly 3. Machining is not feasible on parts that are very thin and that have a high chance of breakage 4. Faced with leak proof joints of hollow shapes such as tanks, floats and evaporators

21. SUITABLE MATERIALS Various forms of solders available are - bar, wire (solid or flux-cored) and paste forms. Solderable metals in the order of decreasing solderability are listed below. 1. Tin 2. Cadmium 3. Silver 4. Copper 5. Brass 6. Bronze 7. Lead 8. Nickel 9. Monel 10. Zinc 11. Steel 12. Inconel 13. Stainless steel 14. Chromium 15. Nichrome 16. Silicon bronze 17. Alnico 18. Aluminum

22. DETAILED DESIGN RECOMMENDATIONS Joint Design : Lap joint is the recommended form for these assemblies. Generally, the area of overlap in the joint is kept large in order to make it stronger than the weakest member of the assembly. A common thumb rule: Allow an overlap of at least three times the thickness of the thinnest member. The clearance between the joint surfaces varies from 0.025 to 0.20 mm with an average value of about 0.10 mm and usually depends on the fluidity of the filler metal.

23. Continue… Assembly : Parts considered for brazed assemblies process are designed for easy assembly. The most economical soldered and brazed assemblies are those that are self-jigging, i.e., the assembled parts and the filler metal hold together during the heating cycle without any external fixture. The approaches involved for holding parts together are gravity, spot and tack welding, friction and press fits, staking and peening, swaging, crimping and forming, threading, and riveting. These methods have been illustrated

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25. Continue… Placement of Braze Metal : Metals used for soldering and brazing can be in a number of forms namely, wire (commonly formed into rings for circular joints), slugs, shims, paste and sprayed or plated coatings and these permit pre-placement before heating. Sprayed or plated coatings are especially applicable to copper brazing.

26. Continue… 1. If filler metal is in shims, the assembly should be such that the parts are free to move when the filler metal melts. This allows a stronger, narrow-gap joint 2. One of the ways of avoiding gas entrapment in joints is to provide a vent hole in the joint.