1. Jim Cuhel Welding Engineer Miller Electric Mfg. Co.

2. Short Circuit Transfer Time(mS) Voltage (volts) Current (amps) Typical STD MIG Waveform 150 IPM.035" S-6 912914916918920922924926928930 00 650 12100 18150 24200 30250 36300 42350 Voltage Current

3. Short Arc RMD Taking Control Time(mS) Voltage (volts ) Current (amps) Typical STD MIG Waveform 150 IPM.035" S-6 912914916918920922924926928930 00 650 12100 18150 24200 30250 36300 42350 Voltage Current Time(mS) Voltage (volts) Current (amps) Typical RMD Waveform 150 IPM.035" S-6 108109.5111112.5114115.5117118.5120121.5123 00 550 10100 15150 20200 25250 30300 35350 40400 Voltage Current

4. What Is RMD? Current Voltage Current (amps) Time (Ms) 300301.5 303 304.5306307.5309310.5 0 50 100 150 200 250 300 WET PINCHCLEAR BLINK PREDICT BLINK ARC BALL BACKGROUND PRE-SHORT

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

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

8. Heat Input Arc Heating Term Resistive Heating

9. 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 M wire = 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 H m =latent heat of fusion of material) So, the total* energy required to burn off the incoming wire is:

10. Putting This Knowledge to Use Heat In = + I 2 (t)*βI(t)*α

11. ARC ON Little ‘ l’ I(t) I(t)*α I 2 (t)*β 1/2” Σ -Jset Arc Heating Resistive Heating Jset = (Heat in @ ½” Stickout) Error Term ARC OFF Jset

13. T ball Width of ball pulse is adjusted in response to the heat input in the wire Duration of Ball Phase is Modified Based Upon Heat Content of Wire Time(mS) Voltage (volts) Current (amps) Typical RMD Waveform 150 IPM.035" S-6 108109.5111112.5114115.5117118.5120121.5123 00 550 10100 15150 20200 25250 30300 35350 40400 Voltage Current

14. Stick out variation video

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

16. 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

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

18. 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

19. 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

20. 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

21. Thank You Any Questions