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ME 330 Manufacturing Processes WELDING PROCESSES.

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Presentation on theme: "ME 330 Manufacturing Processes WELDING PROCESSES."— Presentation transcript:

1 ME 330 Manufacturing Processes WELDING PROCESSES

2 Overview of processes

3 Principle of the process Structure and configuration Process modeling Defects Design For Manufacturing (DFM) Process variation

4 Welding 1.Process in which two (or more) parts are coalesced at their contacting surfaces by application of:  Heat and pressure 2.Some welding processes use a filler material added to facilitate coalescence

5 Principle of welding Assembly two parts together by creating a fusion and/or deformation in the interaction area, which is further based on the physics laws such as fusion and solid state deformation.

6 Principle of welding Fusion welding (FW) Heat materials to melt the materials of compositions and melting points. Due to the high-temperature phase transitions inherent to these processes, a heat-affected zone is created in the material

7 Principle of welding Solid State welding (SSW) On the interface between two materials there is no melting that happens but the interface of materials is reconfigured to form many structure.

8 Two Categories of Welding Processes 1.Fusion welding - coalescence is accomplished by melting the two parts to be joined, in some cases adding filler metal to the joint  Examples: arc welding, oxyfuel gas welding, resistance spot welding 2.Solid state welding - heat and/or pressure are used to achieve coalescence, but no melting of base metals occurs and no filler metal is added  Examples: forge welding, diffusion welding, friction welding

9 The general function of welding 1.Provides a permanent joint 2.One of the most economical ways to join parts in terms of material usage and fabrication costs Mechanical fastening usually requires additional hardware (e.g., screws) and geometric alterations of the assembled parts (e.g., holes) 3.Not restricted to a factory environment Welding can be accomplished "in the field"

10 Limitations and Drawbacks of Welding 1.Most welding operations are performed manually and are expensive in terms of labor cost. 2.Most welding processes utilize high energy and are inherently dangerous. 3.Welded joints do not allow for convenient disassembly. 4.Welded joints can have quality defects that are difficult to detect.

11 Welding Fusion Welding (FW) Solid State Welding (SSW) Arc Welding (AW)

12 Principle of the process Structure and configuration Process modeling Defects Design For Manufacturing (DFM) Process variation

13 Fusion Welding: Arc Welding (AW) A fusion welding process in which coalescence of the metals is achieved by the heat from an electric arc between an electrode and the work 1.Electric energy from the arc produces temperatures ~ 10,000 F (5500 C), hot enough to melt any metal. 2.Most AW processes add filler metal to increase volume and strength of weld joint.

14 A pool of molten metal is formed near electrode tip, and as electrode is moved along joint, molten weld pool solidifies in its wake Fusion Welding: Arc Welding (AW)

15 Welding Fusion Welding (FW) Solid State Welding (SSW) Consumable electrodes Non-consumable electrodes Arc Welding (AW)

16 Two Basic Types of Arc Welding (Based on Electrodes) 1.Consumable electrodes  consumed during welding process  added to weld joint as filler metal  in the form of rods or spools of wire 2.Non-consumable electrodes  not consumed during welding process but does get gradually eroded  filler metal must be added separately if it is added

17 Arc welding (AW): Arc Shielding 1.At high temperatures in AW, metals are chemically reactive to oxygen, nitrogen, and hydrogen in air  Mechanical properties of joint can be degraded by these reactions  Arc must be shielded from surrounding air in AW processes to prevent reaction 2.Arc shielding is accomplished by  Shielding gases, e.g., argon, helium, CO 2  Flux

18 Arc welding (AW): Flux  A substance that prevents formation of oxides and other contaminants in welding, which comes from 1.granules that are created from the welded material. 2.a coating on the stick electrode that melts during welding to cover operation. 3.a core that is within tubular electrodes and is released as electrode is consumed.  Melts during welding to be liquid slag that hardens when cooled. The slag should be removed for a clean look by brushing or grinding off.

19 Consumable Electrode AW Processes  Shielded Metal Arc Welding (or Stick Welding)  Gas Metal Arc Welding (or Metal Inert Gas Welding)  Flux ‑ Cored Arc Welding  Electro-gas Welding  Submerged Arc Welding

20  Uses a consumable electrode consisting of a filler metal rod and coating around rod.  Coating composed of chemicals that provide flux and shielding.  Low cost welding system: Power supply, connecting cables, and electrode holder available for $300 to $400. AW: Consumable: Shielded Metal Arc Welding (SMAW)

21 SMAW Applications  Used for steels, stainless steels, cast irons, and certain nonferrous alloys.  Not used or rarely used for and its alloys, copper alloys, and titanium.  Can be used in windy weather.  Can be used on dirty metals (i.e. painted or rusted surfaces).  Good for repair work.  Makes thick welds.

22 AR: Consumable: Gas Metal Arc Welding (GMAW) or Metal Inert Gas (MIG) Welding Uses a consumable bare metal wire as electrode with shielding by flooding arc with a gas 1.Wire is fed continuously and automatically from a spool through the welding gun. 2.Shielding gases include argon and helium for aluminum welding, and CO 2 for steel welding. 3.Bare electrode wire (no flux) plus shielding gases eliminate slag on weld bead. No need for manual grinding and cleaning of slag 4.Medium cost welding system: $1000 to $1200

23 Gas Metal Arc Welding

24 GMAW Advantages over SMAW 1.Continuous welding because of continuous wire electrode. Sticks must be periodically changed in SMAW. 2.Higher deposition rates. 3.Eliminates problem of slag removal. 4.Can be readily automated. 5.Has better control to make cleaner & narrower welds than SMAW.

25 GMAW Applications 1.Used to weld ferrous and various non-ferrous and metals. 2.Good for fabrications such as frames and farm equipment. 3.Can weld thicker metal (not as thick as SMAW). 4.Metal must be clean to start weld.

26 Non-consumable Electrode Processes  Gas Tungsten Arc Welding  Plasma Arc Welding  Carbon Arc Welding  Stud Welding

27 AW: non-consumable: Gas Tungsten Arc Welding (GTAW) or Tungsten Inert Gas (TIG) Welding Uses a non-consumable tungsten electrode and an inert gas for arc shielding 1.Melting point of tungsten = 3410  C (6170  F). 2.Used with or without a filler metal. When filler metal used, it is added to weld pool from separate rod or wire. 3.Applications: aluminum and stainless steel mostly. 4.High cost for welding system: $4000.

28 Gas Tungsten Arc Welding Filler rod

29 Advantages and Disadvantages of GTAW Advantages: 1.High quality welds for suitable applications - Welds are cleaner and narrower than MIG 2.No spatter because no filler metal through arc 3.Little or no post-weld cleaning because no flux Disadvantages: 1.More difficult to use than MIG welding 2.More costly than MIG welding

30 GTAW Applications 1.Used to weld ferrous and various non-ferrous and metals. 2.Can weld various dissimilar metals together. 3.Good for fabrications such as aircraft or race car frames. 4.Used for welding thinner metal parts (not as thick as MIG). 5.Metal must be very clean to start weld.

31 Welding Fusion Welding (FW) Solid State Welding (SSW) Arc Welding (AW) Oxyfuel gas welding

32 Oxyfuel Gas Welding (OFW) Group of fusion welding operations by a high temperature flame that burns various fuels mixed with oxygen  Oxyfuel gas is also used in flame cutting torches to cut and separate metal plates and other parts  Most important OFW process is oxyacetylene welding (has high temperatures – up to 3480  C)  Filler metal is sometimes added  Composition must be similar to base metal  Filler rod often coated with flux to clean surfaces and prevent oxidation  Low cost for welding system: $400

33 Oxyacetylene Welding

34 1.Maximum temperature reached at tip of inner cone, while outer envelope spreads out and shields work surface from atmosphere 2.Shown below is neutral flame of oxyacetylene torch indicating temperatures achieved Oxyacetylene Torch

35 Oxyacetylene Gas Welding Applications  Suitable for low quantity production and repair jobs  Used for welding thinner parts

36 Welding Fusion Welding (FW) Solid State Welding (SSW) Consumable electrodesNon-consumable electrodes Summary Shielding Flux Various welding processes (AW) are developed to address the two issues: shielding and flux Arc welding Oxyfuel welding


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