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Jim Cuhel Welding Engineer Miller Electric Mfg. Co.

AWS New Welding Technologies The Key to Higher Productivity Controlled Short Circuit GMAW – Root Pass Pipe Weldling. Jim Cuhel Welding Engineer Miller Electric Mfg. Co. Typical STD MIG Waveform. 150 IPM .035" S-6. 42. 350. Voltage. 36. Current. 300. 30. 250. 24. 200.

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Jim Cuhel Welding Engineer Miller Electric Mfg. Co.

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  1. AWS New Welding TechnologiesThe Key to Higher ProductivityControlled Short Circuit GMAW – Root Pass Pipe Weldling Jim Cuhel Welding Engineer Miller Electric Mfg. Co.

  2. Typical STD MIG Waveform 150 IPM .035" S-6 42 350 Voltage 36 Current 300 30 250 24 200 Voltage (volts) Current (amps) 18 150 12 100 6 50 0 0 912 914 916 918 920 922 924 926 928 930 Time(mS) Short Circuit Transfer

  3. Typical RMD Waveform 150 IPM .035" S-6 40 400 Voltage Typical STD MIG Waveform Current 35 350 150 IPM .035" S-6 30 300 42 350 25 250 Voltage 36 300 Current Current (amps) Voltage (volts) 20 200 30 250 15 150 24 200 Voltage (volts) Current (amps) 10 100 18 150 5 50 12 100 0 0 108 109.5 111 112.5 114 115.5 117 118.5 120 121.5 123 6 50 Time(mS) 0 0 912 914 916 918 920 922 924 926 928 930 Time(mS) Taking Control Short Arc RMD

  4. What Is RMD? BACKGROUND PINCH CLEAR PRE-SHORT BLINK ARC 300 Voltage 250 200 Current (amps) 150 Current 100 50 0 300 301.5 303 304.5 306 307.5 309 310.5 WET Time (Ms) BLINK PREDICT BALL

  5. Power Density in the Necking Region Wire Molten Wire Necking Region dl Puddle

  6. Short Circuit Clears (standard MIG) Detect Clearing Event Power in Necking Region Necking Begins Reduce Current (hence, power) Short Circuit Clears at Much Lower Power Level (RMD) Time

  7. Heat Input Resistive Heating Arc Heating Term

  8. How Much Energy is Needed to Burn off the Incoming Wire? First we need to bring the wire temperature from something near room temp up to the melting point of the wire: Temperature Change: Heat Input Required to Effect Temperature Change: (where C=specific heat of material and Mwire =Mass of the wire being heated) Then, we need to supply sufficient energy to cause a phase transformation from solid to liquid (we need to melt it): (where Hm=latent heat of fusion of material) So, the total* energy required to burn off the incoming wire is:

  9. Putting This Knowledge to Use I(t)*α + I2(t)*β Heat In =

  10. Little ‘l’ I(t) I(t)*α Error Term Arc Heating Σ ARC OFF ARCON Little ‘l’ Jset I2(t)*β1/2” Resistive Heating -Jset Jset = (Heat in @ ½” Stickout)

  11. Keeping Track of Wire Heating History dt=1/(100*v(in/sec)) after each time interval (dt), each array element shifts down one position. The last one gets dumped and an empty one is inserted on top 1 Holds info from the last i2Rdt 2 3 Holds info from the second to last i2Rdt Wire Segments (Real World) History Array (microprocessor world) Determined by controller based upon current feedback. Calibrated to read out in units of inches times 100. This tells us how far back in time to go with our summing of array elements l Typically, there are multiple array elements per wire segment Holds i2Rdt info from m samples ago Each array element represents .01” of wire (1.28” total) m-1 m m+1 Actual End of the Wire Holds i2Rdt info from 127 samples ago Virtual Wire Holds i2Rdt info from 128 samples ago 127 128

  12. Typical RMD Waveform 150 IPM .035" S-6 40 400 Voltage Current 35 350 30 300 25 250 Current (amps) Voltage (volts) 20 200 15 150 10 100 5 50 0 0 108 109.5 111 112.5 114 115.5 117 118.5 120 121.5 123 Time(mS) Duration of Ball Phase is Modified Based Upon Heat Content of Wire Tball Width of ball pulse is adjusted in response to the heat input in the wire

  13. Stick out variation video

  14. Constant Voltage GMAW Comparison Conventional GMAW RMD: 0.035” ER70S-6 on 8” Sch. 80

  15. Establishing Good Technique • As with any welding process, success with RMD process requires establishing and maintaining good preparation and welding techniques. • The following guidelines lead to proven success and increased productivity for welding pipe

  16. Joint Configuration • Standard 75 degree included angle • Land: 0” – 3/32” • Root Opening: 1/8”

  17. Five Critical Items For Stainless Steels • The techniques for welding carbon are the same for stainless alloys • To qualify procedures for welding 300 series stainless steel piping – Without backing gas, fabricators should do the following: 1.) Ensure a minimum 1/8” gap around the entire circumference of the joint. This gap allows the shielding gas to flow through to protect the backside of the joint from oxidation

  18. Five Critical Items Cont. 2.) Clean the pipe both inside and out to remove any contaminates or unwanted substances. Use a wire brush to clean at least 1 in. back from the edge of the joint 3.) Use only a stainless steel wire with a high silicon content, such as 316LSi or 308LSi. Higher silicon contents helps the puddle wet out and acts as a deoxidizer

  19. Five Critical Items Cont. 4.) For optimum performance, use a “Tri-H” gas that’s 90 He/ 7 ½ Ar/ 2 ½ CO2 Alternatively, use 98 Ar/ 2 CO2 5.) For best results, use a tapered nozzle for the root pass because it localizes the shielding gas coverage. Tapered nozzles with built-in gas diffusers provide exceptional coverage

  20. Thank You Any Questions

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