The Appropriate Welding Process for all Welds - Assignment Example

SCENARIO: This assignment is aimed at preparing for the practical welding in Assignment 3 TASKS: In Assignment 3 you will have to complete the welds shown below. For this assignment (2) you will need to - i) Select a welding process for part 1 (either MIG or MMA) (P2a) In all the welds the MIG is chosen as the appropriate welding process. This was formally referred to as Gas Metal Arc Welding abbreviated MIC is the short form of metal inert gas and it describes the process of welding where there is use of shielding gas that is emitted from the welding gas along with a very high temperature electric arc together with a metal filler wire. In this set up the wire the wire melts and it is transferred to the workpiece (Quigley, M. B. C. 1984). It is a welding arc process that makes use of the heat that is generated by the electric arc that comes about because of the interaction between the wire that is continuously fed and the work piece (Funderburk, 1999). The advantages of MIC that are important in choosing it are • The process is seen as being economical because it allows high welding speed and with the frequency of changing electrodes being minimal a long arc time is maintainable. • Though MIC it is possible to have a rational welding of materials where it would be difficylt with other processes. • Welding can be accomplished in various positions • There is clear visibility of the arc and weld pool in this process • The need for after weld treatment is minimal. 1. The following samples are to be welded in 3 mm plain carbon steel A. Bead on plate in the flat position. Work plan In this welding we will have the stringer beads where there will be pull of the torch along the surface with minimal side to side movement. The pull or dragging involves the electrode pointing backwards in the direction of the puddle a condition that will ensure maximum penetration. This is motivated by the fact that the welding takes place in a flat position where there is no danger of the weld being distorted by spreading out of the puddle. Welding procedure sheet Property Value Thickness 3 Welding position 1/f Number of runs 1 Wire diameter (mm) 1 Shielding gas 80/20 Wire speed (m/min) 6.0 Current (A) 175 Voltage (V) 21.5 Gas consumption l/min 12 B. Lap fillet in the horizontal vertical position Work plan This will involve use of a stringer beads with push of torch along the joint which will involve the torch being pointed forward. This is because the molten metal will tend to fall on the plate on the lower side. So when the heat is directed away from the puddle it allows quick solidification of the weld. The disadvantage of the approach is less penetration into the base metal. Welding procedure sheet Property Value Thickness 3 Welding position 1/f Number of runs 1 Wire diameter (mm) 1 Shielding gas 80/20 Wire speed (m/min) 6.0 Current (A) 175 Voltage (V) 21.5 Gas consumption l/min 12 C. Tee Fillet in the flat position Work plan In this welding we will have the stringer beads where there will be pull of the torch along the surface with minimal side to side movement. The pull or dragging involves the electrode pointing backwards in the direction of the puddle a condition that will ensure maximum penetration. This is motivated by the fact that the welding takes place in a flat position where there is no danger of the weld being distorted by spreading out of the puddle. Welding procedure sheet Property Value Thickness 3 Welding position 1/f Number of runs 1 Wire diameter (mm) 1 Shielding gas 80/20 Wire speed (m/min) 6.0 Current (A) 175 Voltage (V) 21.5 Gas consumption l/min 12 D. Tee Fillet in the horizontal / vertical Work plan This will involve use of a stringer beads with push of torch along the joint which will involve the torch being pointed forward. This is because the molten metal will tend to fall on the plate on the lower side. So when the heat is directed away from the puddle it allows quick solidification of the weld. The disadvantage of the approach is less penetration into the base metal. Welding procedure sheet Property Value Thickness 3 Welding position 1/f Number of runs 1 Wire diameter (mm) 1 Shielding gas 80/20 Wire speed (m/min) 6.0 Current (A) 175 Voltage (V) 21.5 Gas consumption l/min 12 D. Open corner weld in the flat position Work plan In this welding we will have the stringer beads where there will be pull of the torch along the surface with minimal side to side movement. The pull or dragging involves the electrode pointing backwards in the direction of the puddle a condition that will ensure maximum penetration. This is motivated by the fact that the welding takes place in a flat position where there is no danger of the weld being distorted by spreading out of the puddle. Welding procedure sheet Property Value Thickness 3 Welding position 1/f Number of runs 1 Wire diameter (mm) 1 Shielding gas 80/20 Wire speed (m/min) 6.0 Current (A) 175 Voltage (V) 21.5 Gas consumption l/min 12 2. You will be required to produce the following welded test pieces in 1.6mm thick plain carbon steel using the spot welding process. (P7, P8) ii) Produce a work plan and welding procedure sheet for each joint. (P3, P4) A. Lap Joint mm Welding procedure sheet Property Value Thickness 3 Welding position 1/f Number of runs 1 Wire diameter (mm) 1 Shielding gas 80/20 Wire speed (m/min) 6.0 Current (A) 175 Voltage (V) 21.5 Gas consumption l/min 12 B. Flange Butt weld Welding procedure sheet Property Value Thickness 2 Welding position 1/f Number of runs 1 Wire diameter (mm) 0.8 Shielding gas 80/20 Wire speed (m/min) 6.0 Current (A) 125 Voltage (V) 19 Gas consumption l/min 12 3. a) List the welding parameters associated with both the MIG and MMA welding processes. (amperage, voltage, gas flow, welding speed, arc length etc) Amperage One of the factors that determine amperage is the thickness of the workpiece where 0.002inch thickness requires 1 ampere which translates to 0.125 in. = 125 amps( Gourd LM,1995) Wire size The size of the wire to be used depends on amperage which has been established by the workpiece thickness. Since the sizes of wire are standardized it is advisable to make a section that is close to the commonly used thickness. The amperage vs wire sizes are as given in table Size in inch Amperage 0.023 30-130 0.030 40-145 0.035 50-180 0.045 75-250  Set the voltage. The voltage will determine the height and width of bead that is welded and this are established from charts. Short arc means reduced voltage resulting to a rope like bead. On the other hand a high voltage (longer arc ) will yield flatter and wide bead. Very long ark results to a bead that is excessively flat which is likely to result to undercut. Set the wire feed speed. The speed of wire is the control of amperage and also the amount of weld penetration. Very high speed of wire may result to workpiece burn through. The feed speed depends on the diameter of wire and the amperage where for example in a 0.020 inch the feed speed is established by multiplying 2inch per amp to establish feed speed (Lavigne, D., 1988). b) Analyse the effect on quality and safety that the incorrect setting of each would have on the finished welding component. (M1) Parameter Effect Amperage Very high amperage will lead to result to piece burn through Voltage Excess voltage leads to flat wide bead that result to undercutting Wire size Small wire size means excess amperage for wire that could translate burn through Wire feed rate Too high feed rate result to very wide bead Excess travel speed Insufficient penetration as no sufficient time for heat build up References Bakes H and Benjamin D (1979) Metals Handbook, Volume. 2. (Ed.) Kirkpatrick CW, ASM, Metals Park, OH. pp: 3–23. Funderburk SR (1999) Key Concepts in Welding Engineering. Welding Innovation, Vol. XVI, No. 1. Gourd LM (1995) Principles of Welding Technology, 3rd ed. Edward Arnold. Lavigne, D., (1988). Automatic plasma arc welding. Joining & Materials. July, pp. 19-25. Quigley, M. B. C. 1984. High power density welding. The Physics of Welding, ed.J. F. Lancaster. Pergamon Press, pp. 268-291 Read More