me_350_-_lect_23_-_ch_31.20091112.4afcf4ef012389.94873752

me_350_-_lect_23_-_ch_31.20091112.4afcf4ef012389.94873752 -...

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Welding Processes: 1. Arc Welding 2. Resistance Welding 3. Oxyfuel Gas Welding 4. Other Fusion Welding Processes 5. Solid State Welding 6. Weld Quality 7. Weld Defects 8. Weldability factors ME 350 – Lecture 23 – Chapter 31
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The electrode ( consumable or nonconsumable ) can be the source of filler metal or a filler can be added separately 1. Arc Welding AC is less expensive, but generally restricted to ferrous metals. DC is better at arc control
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Shielding during Arc Welding During Arc Welding, metals are chemically reactive to the gases in air Mechanical properties of joint can be seriously degraded by these reactions The faying surfaces and the filler metal, must be “shielded ” from reaction to the surrounding air Arc shielding is accomplished by: 1. Shielding gases, e.g.: 2.
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Flux Purpose: 1. To prevents the formation or facilitates the removal of: 2. Provides protective atmosphere for welding 3. Stabilizes arc and reduces spattering Sources: 1. Pouring granular flux onto welding operation 2. Stick electrode with flux material that melts during welding: 3. Tubular electrodes in which flux is released as electrode is consumed contained in the:
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Gas Tungsten Arc Welding - Uses a nonconsumable tungsten electrode and an inert gas for arc shielding Used with or without a filler metal
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Advantages / Disadvantages of GTAW Advantages: High quality welds No spatter because filler metal in not part of the arc path Little or no post-weld cleaning because no flux Disadvantages: Generally slower and more costly than consumable electrode AW processes
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Plasma Arc Welding (PAW) Special form of GTAW in which a constricted plasma arc is directed at weld area Tungsten electrode is contained in a nozzle that focuses a high velocity stream of inert gas (argon) into arc region to form a high velocity, intensely hot plasma arc stream
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Advantages / Disadvantages of PAW Advantages: Good arc stability Better penetration control than other AW High travel speeds Excellent weld quality Can be used to weld almost any metals Disadvantages: High equipment cost Larger torch size than other AW Tends to restrict access in some joints
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2. Resistance Welding (RW) A group of fusion welding processes that use a combination of heat and pressure to accomplish coalescence Heat generated by electrical resistance to current flow at junction to be welded
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Advantages / Drawbacks of RW Advantages: 1. No filler metal required 2. High production rates possible 3. Lends itself to automation 4. Good repeatability and reliability Disadvantages: 1. High initial equipment cost 2. Limited to lap joints for most RW processes 3.
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applied, (3) current on, (4) current off, (5) electrodes opened. Spot Welding Cycle
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This note was uploaded on 01/15/2010 for the course ME 350 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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me_350_-_lect_23_-_ch_31.20091112.4afcf4ef012389.94873752 -...

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