Upon completion of this module

Transcription

1 Welding 1.4

2 Upon completion of this module 1. Cite the advantages of welding over other joining methods 2. Name & identify the various welding and cutting processes currently used in industry 3. Recognize the American Welding Society abbreviation for each of the welding and cutting processes currently in use in the industry 4. Describe the operation of each welding and cutting process

3 Welding is a general term for a number of processes (methods) used to join metallic and non-metallic materials Heating materials to welding temperature Filler metal is typically added when molten materials can also be welded with pressure

4 Its application and purpose Energy source to produce heat Controls used in process Operation of the process Safety considerations

5 Uses an electric arc between a flux-covered metal electrode and the base metal Electric current may be AC (Alternating Current) DC+ (Direct Current Positive) DC- (Direct Current Negative) Manual Process Stick Welding

6 Heat of electrode may be controlled by the current settings or by arc length Arc between the electrode and base metal is struck by the welder Correct arc length must be controlled by welder Covering on electrode turns into protective gas shield that surrounds the arc as the electrode melts Covering melts to form a slag that covers the completed weld Slag layer protects hot metal from oxidizing while it cools

7 Uses heat of an electric arc between a tungsten electrode and base metal Electric current may be AC (Alternating Current) Aluminum DC- (Direct Current Negative) Steel Manual Process TIG (Tungsten Inert Gas)

8 Uses heat of an electric arc between a tungsten electrode and base metal A separate filler rod is fed into molten base metal Shielding gas flows around the arc to keep air away and other harmful materials Gas typically 100% Argon Desirable for stainless steel, aluminum and other nonferrous material and thin sheet-metal

9 Uses an electric arc between a continuously fed metal electrode and base metal Electric current may be DC+, DC-, AC Shielding Gas 25% Carbon Dioxide 75% Argon Semi-Automatic Process MIG (Metal Inert Gas)

10 Popular in production and repair shops Constant voltage (dc) welder Current changed by adjusting the wire feed speed Operation Select electrode size Set desired voltage Adjust shielding gas flow Adjust rate of electrode feed Welder controls torch movement and electrode extension

11 Heat is produced by an arc between a flux cored electrode and the base metal Electric current (DC-) Flux inside tube Semi-Automatic Process

12 Good process for outside structural welding Constant voltage (dc) welder Heat of the arc depends upon the arc length, voltage settings, and wire feed speed Smoky

13 Arc is submerged in a granular flux Flux melts and forms a shielding slag Automatic or semi-automatic process Welds thick plate in one pass

14 Hopper and feeding mechanism is used to provide a flow of flux over the joint Arc is submerged in the flux As the weld progresses, some of the flux is melted and forms a slag over the weld Vacuum machine cleans up unused flux

15 Combine oxygen and acetylene to provide high temperature flame May be used for brazing as well Manual Process Similar to TIG welding Gas is supplied from cylinders controlled by regulators to control pressure Torch is connected to hoses using quick connect couplers Thickness of metal determines the size of tip to be used

16 Carburizing flame is blue with an orange and red end Excess acetylene with oxygen Release black smoke A neutral flame has a blue-white inner cone Perfect mixture acetylene and oxygen Oxidizing Flame results in a short, noisy, hissing inner cone Excess oxygen

17 Base metal is heated enough to allow the solder to melt and then bond to the base metal Soldering occurs at temperatures less than 840 Used to fill a seam or to make an airtight joint Solder fills joint through capillary process

18 Oxy-fuel gas flame heats the base metal, and the heated base metal melts the brazing rod Soldering occurs at temperatures above 840 Less warping due to lower temperatures Process Parts must be carefully cleaned Flux material is used to keep metal clean Oxy-fuel flame is used to heat the base metal Brazing material melts when touched to the heated metal and flows into the joint

19 Oxy-fuel gas flame raises the temperature of the metal to 1472 High pressure jet of oxygen burns the metal and rapidly blows it away Process requires cylinders of oxygen and fuel gas Acetylene

20 Uses an electric arc and fast flowing ionized gas to melt and cut metal Process cuts steel, stainless steel, aluminum, and other materials Concrete Molten metal is blown away by the high velocity of the shielding gas Manual Process

21 Uses an electric arc to melt the base metal A jet of air then blows the melted metal away Electrical supply (ac) or (dc) Compressed air Manual Process

22 Welders must wear approved Helmet Gloves Protective clothing Hood with correct shading (10) Ear plugs Workstation must be ventilated Keep work area neat and organized Cleanup after welding is completed

23 Transformation Range Range steels undergo internal atomic changes which radically effect the properties of the material Lower Transformation Temp 1340 Below consists of Ferrite and pearlite Upon heating, they dissolve to form Austenite which is non-magnetic Continues until a solid solution is complete at Upper Transformation Range Upper Transformation Range 1700 Above this temperature, the structure consists wholly of Austenite Upper transformation range decreases as carbon increases