Metal Joining process. soldering welding pptx

metal Joining Process for mechanical components

1. Joining Process 12/11/2024 1

2. Metal joining Process Joining is one of the manufacturing processes by which two or more materials can be permanently or temporarily joined together with or without the application of external element in order to form a single unit. Ex - Welding, Soldering, Brazing, Screwing & Riveting. etc., Types of Joining Process Permanent Joining Process Temporary Joining Process 12/11/2024 2

3. Welding, Brazing & Soldering 12/11/2024 3 Welding Brazing Soldering Permanent Joining Process

4. Temporary Joining Process Fasteners & Rivets 12/11/2024 4

5. Welding Welding Is a process of joining similar metals by application of heat with or without application of pressure and addition of filler material. Resulting a single metal. Welding may be classified under two broad headings Plastic welding Fusion welding 12/11/2024 5

6. Plastic welding/Pressure welding The pieces of metal to be joined are heated to plastic state and then forced together by external force Types of Plastic welding are Friction Explosive Forge Resistance 12/11/2024 6

7. Fusion /Non-pressure welding The material at the joint is heated to a molten state and allowed to solidify Types of fusion welding are Arc welding Gas welding 12/11/2024 7

8. Arc welding 12/11/2024 8

9. Cont.…. An arc welding is a metallurgical process in which the junction of the parts to be joined are heated and then fused together with or without application of pressure to produce a continuity of homogenous material. It is a type of welding that uses a  power supply to create an electric arc between a metal stick ("electrode") and the base material to melt the metals at the point of contact produce concentrated heat through out length of the arc at a temperature of 5000-6000ºC. 12/11/2024 9

10. Cont.…. In Arc welding either direct (DC) or alternating (AC) current can be used, the most common classification is constant current power supplies and constant voltage power supplies. In arc welding, the voltage is directly related to the length of the arc, and the current is related to the amount of heat input. One of the most common types of arc welding is shielded metal arc welding (SMAW) or stick welding. 12/11/2024 10

11. Cont.…. The direction of current used in arc welding also plays an important role in welding. Consumable electrode processes such as shielded metal arc welding generally use direct current, but the electrode can be charged either positively or negatively. In general, the positively charged anode will have a greater heat concentration (around 60%). "Note that for Arc welding in general, DC+ polarity is most commonly used. It produces a good weld profile with a higher level of penetration. DC- polarity results in less penetration and a higher electrode melt-off rate.  12/11/2024 11

12. Cont.…. The electrode rod is made of a material that is compatible with the base material being welded and is covered with a flux that gives off vapors that serve as a shielding gas and provide a layer of slag, both of which protect the weld area from atmospheric contamination. The electrode core itself acts as filler material, consumable or non-consumable electrodes can be used. Furthermore the process is generally limited to welding ferrous materials. 12/11/2024 12

13. Non-consumable electrode methods Non-consumable electrode processes, is a manual welding process that uses a non-consumable electrode made of Tungsten/Metal, an inert or semi-inert gas mixture, and a separate filler material. Tungsten Inert Gas(TIG)/ Metal Inert Gas (MIG) arc welding, can use either type of direct current (DC), as well as alternating current (AC). With direct current however, because the electrode only creates the arc and does not provide filler material . 12/11/2024 13

14. Tungsten Inert Gas(TIG) welding 12/11/2024 14

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16. Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area and electrode are protected from oxidation or other atmospheric contamination by an inert shielding gas (argon or helium). A filler metal is normally used, a constant-current welding power supply produces electrical energy, which is conducted across the arc through a column of highly ionized gas and metal vapors known as a plasma. 12/11/2024 16

17. GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminum, magnesium, and copper alloy. To strike the welding arc, a high frequency generator (similar to a Tesla coil) provides an electric spark. This spark is a conductive path for the welding current through the shielding gas and allows the arc to be initiated while the electrode and the work piece are separated, typically about 1.5–3 mm. 12/11/2024 17

18. Once the arc is struck, the welder moves the torch in a small circle to create a welding pool, the size of which depends on the size of the electrode and the amount of current. Gas tungsten arc welding uses a constant current power source, meaning that the current (and thus the heat flux) remains relatively constant, even if the arc distance and voltage change. 12/11/2024 18

19. Gas tungsten arc welding, because it affords greater control over the weld area than other welding processes, can produce high-quality welds when performed by skilled operators. GTAW welding torches are designed for either automatic or manual operation and are equipped with cooling systems using air or water. The electrode used in GTAW is made of tungsten or a tungsten alloy, because tungsten has the highest melting temperature among pure metals, at 3,422 °C (6,192 °F). 12/11/2024 19

20. As a result, the electrode is not consumed during welding, though some erosion (called burn-off) can occur. 12/11/2024 20

21. Metal Inert Gas(MIG) welding 12/11/2024 21

22. metal inert gas (MIG) is a welding process in which an electric arc forms between a consumable MIG wire electrode and the work piece metal, which heats the work piece metal(s), causing them to fuse (melt and join). Along with the wire electrode, a shielding gas feeds through the welding gun, which shields the process from atmospheric contamination. A constant voltage, direct current power source is most commonly used with MIG, but constant current systems, as well as alternating current, can be used.  12/11/2024 22

23. The typical GMAW welding gun has a number of key parts—a control switch, a contact tip, a power cable, a gas nozzle, an electrode. The contact tip, normally made of copper and sometimes chemically treated to reduce spatter, is connected to the welding power source through the power cable and transmits the electrical energy to the electrode while directing it to the weld area. 12/11/2024 23

24. The electrode is a metallic alloy wire, called a MIG wire, whose selection, alloy and size, is based primarily on the composition of the metal being welded, the process variation being used, joint design, and the material surface conditions. Electrode selection greatly influences the mechanical properties of the weld and is a key factor of weld quality. The choice of a shielding gas depends on several factors, most importantly the type of material being welded and the process variation being used. 12/11/2024 24

25. Pure inert gases such as argon and helium are only used for nonferrous welding 12/11/2024 25

26. Oxy-fuel (Oxyacetylene) Welding   Oxy-fuel welding is fusion welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the United States) and oxy-fuel cutting are processes that use fuel gases (or liquid fuels such as gasoline) and oxygen to weld or cut metals. In  oxy-fuel welding , a welding torch is used to weld metals. Welding metal results when two pieces are heated to a temperature that produces a shared pool of molten metal. 12/11/2024 26

27. 12/11/2024 27 Fig-Oxy-fuel (Oxyacetylene) Welding

28. The molten pool is generally supplied with additional metal called filler. Filler material selection depends upon the metals to be welded Oxy-fuel processes may use a variety of fuel gases, the most common being acetylene. Other gases that may be used are propylene, liquefied petroleum gas (LPG), propane, natural gas and hydrogen.   12/11/2024 28

29. Oxygen is not the fuel. It is what chemically combines with the fuel to produce the heat for welding. This is called 'oxidation', but the more specific and more commonly used term in this context is 'combustion'.  The apparatus used in gas welding consists basically of an oxygen source and a fuel gas source (usually contained in cylinders), two pressure regulators and two flexible hoses (one for each cylinder), and a torch, This sort of torch can also be used for soldering and brazing. 12/11/2024 29

30. Welding torch is used to mix both oxygen and Acetylene gas in proper proportions and burn the mixture at its tip producing a flame. By adjusting the pressure regulators, suitable proportions of oxygen and acetylene gas enters into the welding torch, the gases gets mixed in the torch to burn in the atmosphere. The resulting flame at torch tip has a temperature ranging from 3200-3500ºc and this heat sufficient enough to melt the work piece. 12/11/2024 30