MIG / MAG. Short Circuit Transfer.

Thin Gage Welding
Process Considerations:

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Short circuit or pulsed MIG on

CARBON STEELS AND STAINLESS STEELS.

2007: As the pulsed process evolved over two slow painful development decades, the short circuit application potential has slowly been reduced.

In 2006, thanks to low cost pulsed equipment that actually worked, the pulsed process became a prime process for welding most thin gage, carbon steel and stainless applications.

See the MIG equipment section for a low cost pulsed power source that belongs in every weld shop that welds thin gage steel or stainless applications.

Note: As weld process technology evolves, the information at this site is dated by the time it's relevant.

During short circuit weld transfer,
the weld voltages and current
utilized are low. When the weld wire makes contact with the grounded part, an effect of the power source slope output is the resistance to the current is lowered, the voltage goes down and the current rises to the slope limit.

The short circuit current rise is sufficient to form a droplet on the wire tip and melt and detach this drop when the wire makes contact with the work or weld. As the molten droplet touches the weld, it's drawn by capillary motion into the weld puddle.

Note: The argon mix plasma partially covers the fluid droplet. In contrast with straight CO2, the CO2 plasma would be at the bottom of the weld droplet, supporting and disturbing the drop till it gets larger and transfers in a more erratic manner, (spatter-globular).

 

 

A UNIQUE ATTRIBUTE OF SHORT CIRCUIT, (SC):
The SC mode is the only weld metal transfer in which the arc goes on - off an average of approximately 70 to 140 times per second. The "arc on - off" attribute can benefit many thin gage or gap applications.

If welding stainless or carbon steel gage applications from 20 gage to 12 gage, short circuit is an excellent weld transfer mode. If using specific > 2005 pulsed equipment and the correct pulsed settings, the pulsed mode which in the past has been unstable in the low current range can now also produce consistent weld quality with no weld weld spatter.

 

 

 

 

Designers and manufacturing engineers often suffer from a lack of MIG weld process knowledge and that can lead to dramatic weld cost consequences.

When welding thin, carbon steel or stainless robot welded parts < 2mm you will often find;

[a] unacceptable part part tolerances,
[b] poor part fixtures,
[c] inappropriate weld joint designs,
[d] poor consumable size selection,
[e] poor weld parameter and technique selection.

Of course A to E will have weld issues and cost ramifications from weld burn through, weld rejects and extensive or rework. To add to the thin gage weld issues, its a sad fact that the majority many automotive and truck manufacturing plants that use MIG welding robots, lack the engineering ability to select the correct size MIG wire for the application.

 

To avoid bad weld choices and implement highly effective weld process controls visit Ed's books and Process Control training resources. My unique MIG Process Control Training CD program has a section dedicated to logical design tips to improve robot MIG weldability along with a seven step management program to eliminate all common robot weld issues.

 

 

CARBON STEEL GAGE APPLICATIONS:
IDEAL WELD TRANSFER MODE,
IDEAL MIG WIRES SIZES AND GAS SELECTION.

 

E-mail. Weld Question, 06 /20/03

Hi Ed, I would like to know what the critical factors are that determine fusion to the base metal. I wonder if short circuit transfer simply won't put heat into the base metal fast enough to achieve fusion on anything greater than gage thickness. Right now I have a single phase, Miller 185 power source. We weld steel and silicon bronze base metal for architectural work, balconies, railings, etc. Typically we are joining 1/2 to 3/4 inch square to 1/2 x 1 to 1/2 x 2 with single and double bevel prep. I find I must run in globular mode with the 0.035 wire we use. I don't think the Miller 185 will get me into spray transfer and am trying to decide if a machine in the 250 amp class is the solution. We are currently stuck with single phase power . What is your take on all this?

Regards, Erik Lander.

 

 

Ed's reply. Erik, with manual short circuit transfer, depending on the steel application you should be concerned about fillet weld fusion on components over 0.100 and consider pulsed or spray for these applications.

Using argon 10 to 20% CO2, an 0.035 (1 mm) steel wire will require >200 amps to attain optimum spray transfer, that's why the CV. "250 amp" power source is a popular choice. You can get a lower spray transition current if you use argon oxygen oxy mix (try 5% oxy ). With argon oxy mixes you will get into spray around 180 amps, however, note this gas mix is not suited for short circuit transfer. If you really want to get into spray with argon CO2 mixes on your power source, you would have to use an 0.030 (0.8mm) MIG wire. Expect wire feed issues with this small wire.

A more logical solution. You may want to consider using an 0.035,
E71T-1, gas shielded flux cored wire with argon - 20-25% CO2. With these consumables and your small power source you could weld any metal thickness in any position. Good luck Ed.

 

 

 

Weld Fact: MIG weld data recommendations can change dramatically when changing from manual to automated welds. In contrast to manual welding, when welding thin applications with robots, the welds typically can be made with "higher weld travel speeds" which allows higher weld current settings.

 

MIG Weld rules change when robots are utilized. Pulsed spray transfer " allows manual / robot welds to be made on carbon steel or alloy steels in the thickness range of 1 mm to any thickness.

Robot welds using 0.035 (1mm) wire with regular "spray transfer" set at low welding spray parameters can be used on parts as thin as >0.070, >1.8mm. No weld gaps and short weld lengths preferred.

Globular Benefit: For welding those exhaust components or bike frames with "weld gaps" in which it's difficult for weld spatter to attach, an alternative weld transfer mode is "globular transfer". For globular transfer use 0.035 wire set at 450 to 700 ipm with a weld voltage range of 20 to 24 volts. This mode provides low to medium weld energy at higher weld deposition than short circuit.

 

 

 

I BELIEVE THERE ARE THREE BOOKS EVERY MIG WELD DECISION WILL BENEFIT FROM.

[1] MY MIG AND ROBOT WELD PROCESS CONTROL BOOK.
[2] MY MANAGEMENT AND ENGINEERS GUIDE TO MIG.
[3] MY MANUAL MIG & FLUX CORED BOOK.

Note: These books and my MIG training video and process control CD's are found in the training resources section of this site (click here).

My process control training resources, simplify the selection of optimum MIG wire feed and volt settings for all common electrode diameters used on manual and robot applications. The process control CD's will provide your robot personnel and welders with the ability to instantly set the optimum MIG welding parameters for any steel application.

 

Lets see, Ed mentioned two important steps for effective weld process controls.

[1] Avoid weld sales advice.

[2] Take a logical process approach in selecting the optimum MIG wire diameter for your applications.

If we have traditional CV MIG equipment, the 0.035 or 0.040 (1 - 1.1mm) MIG wire diameters provide a short circuit weld current range that is best suited for the common thin gage, steel and stainless applications. Avoid using smaller MIG wires they are not necessary, (unless you have a small power source that provides less than 150 amps). And if we use pulsed there is no need to use 0.035 wires, use the lower cost 045 wires



Since the nineteen eighties my first choice of the best wire diameter for weld shop welding thin gage and parts to 8 mm using traditional CV equipment, has been the 0.040 (1.1mm) wire, a wire rarely requested by the global welding industry..

 

2006: One of the major weld issues found in auto / truck plants during the last two decades is the use of MIG wires which are "too large" and also use the use of self shielded flux cored wires, electrodes that should never be part of a weld in which engineering pride is attached to that weld

SELF SHIELDED FLUX CORED WIRES, PROCESS
IGNORANCE AND MILLIONS IN UNNECESSARY WELD COSTS:

2006: WHEN I SEE SELF SHIELDED FLUX CORED WIRES USED IN ROBOT CELLS,
I KNOW THE PLANT SUFFERS FROM A BAD CASE OF WELD MANAGEMENT PROCESS IGNORANCE. AT THIS TIME BOTH CHRYSLER AND GM ARE REQUESTING USE OF THESE WELD WIRES FOR THEIR GALVANEALED PARTS. THANKS TO THE WELD ISSUES THESE USELESS WELD WIRES GENERATE, THESE WELD CONSUMABLES HAVE COST AND WILL COST CORPORATIONS MILLIONS OF DOLLARS ANNUALLY IN LOSS OF WELD PRODUCTIVITY AND WELD REWORK.

MANY PLANTS USE 0.045 (1.2mm) and 0.052 (1.4mm) MIG WIRES AND THE CV SHORT CIRCUIT MODE TO ROBOT WELD PARTS LESS THAN 0.090. DEPENDING ON THE WELD TRANSFER MODE SELECTED THE LARGE WELD WIRES SELECTED CAN CAUSE WELD BURN THROUGH ISSUES.

MANY PLANTS, ESPECIALLY AUTO / TRUCK FRAME PLANTS THAT WELD PARTS < 4 mm, USE LARGE 0.052 (1.4mm) OR LARGER WELD WIRES.

THE INFAMOUS FORD FRAME PLANT IN DETROIT ALWAYS USED OVERSIZED MIG WIRES ON IT'S ROBOT MIG WELDING FRAME LINES. THIS PLANT HAS NEVER PRODUCED A FRAME WITHOUT MOST OF THE WELDS REQUIRING WELD REWORK.


OVERSIZE MIG WIRES WILL NOT ALLOW THE USE OF SPRAY TRANSFER, (TOO HOT) AND TYPICALLY THE WIRES END UP BEING USED IN THE GLOBULAR TRANSFER MODE. GLOBULAR TRANSFER IS VERY COMMON AT FORD, DANA, TOWER AND CHRYSLER PLANTS. THE GLOBULAR WELDS WILL LACK FUSION, CAUSE EXCESS SPATTER AND CAUSE CONTACT TIP ISSUES RESULTING IN EXCESS ROBOT DOWN TIME.

 

 

 

Weld Fact: Welding carbon steels or stainless steels with an 0.035 or 0.045 (0.9 - 1.2 mm) MIG wire, short circuit transfer on most applications is found in the weld current range of approx. 80 to 200 amps.

Optimum short circuit transfer with the most suited MIG wire diameter, 0.035 (0.9mm) is typically found between 100 and 175 amps with a voltage range 15 to 18 weld volts.

On the applications that utilize the 0.035 wires and the optimum short circuit current range, pulsed MIG using an 0.045 wire with can also be used with similar or slightly higher weld deposition rates.

In contrast to the arc on - arc off short circuit transfer mode, the pulsed mode is an "open arc" mode that delivers the droplets across the arc in a consistent transfer, (if you have decent pulsed equipment). While the the pulsed parameters on gage applications appear to be low, remember in contrast to short circuit transfer, the open, continuos pulsed arc will provide more weld energy and weld fluidity than attained with short circuit transfer.

Optimum Short Circuit Transfer and Pulsed MIG Wire Diameter Selection for Gage Applications. CV Regular MIG Equipment. The best two MIG wire diameters for short circuit transfer are 0.035 and 0.040 (0.9 and 1.1 mm). In industrial shops, there is simply no justification for the use of smaller weld wires. Pulsed MIG Equipment. The best MIG wire diameter for all carbon steels, stainless and aluminum gage applications is the 0.045 (1.2 mm) wire.

 

 

Weld Fact: Using traditional MIG CV equipment: If you could get your hands on the 0.040 (1.1 mm) wire it would be the most practical choice for most "robot" short circuit and low current spray carbon and stainless applications in the 1.5 to 5 mm range. The worlds best wire for regular MIG equipment and gage application is rarely used, this is no surprise in an industry that has never been able to implement Best Weld Practices.

March 2001. Weld Question: Ed. Why is the 0.040 (1.1 mm) carbon steel MIG wire such a good choice for gage, short circuit and low spray parameter applications, and why is it so difficult to get?

Answer: The 0.040 wire is available, however MIG wire manufactures who have a difficult time keeping up with the demand for 0.045 and 0.035 wires were not necessarily dedicated or focused on supplying the most practical, logical, cost effective weld consumables to a process naive welding market.

It's a sad weld reality that many of the companies that make MIG welding consumables do not fully comprehend the weld applications considerations of the electrode wires that they market. This is a prime reason MIG wires have changed little in fifty years. It's also a prime reason why in the last five decades, you have not seen any MIG weld parameter recommendations on the box of MIG wire sitting in your plant.

In North America, Lincoln Electric is in a monopoly position in the MIG wire business. Lincoln does make small quantities of the 0.040 carbon steel MIG wire. Lincoln typically has had a hard time keeping up with the demand for it's traditional 0.035 - 0.045 steel wire products. It's understandable that from their perspective, that without extensive customer demand which would come from process educated consumers, there was little incentive for them to market the 0.040 wires. There is even less incentive now that pulsed process is finally stable and the pulsed process works well with > 0.045 wires.


The 0.035 (1mm) wire has been the traditional first choice wire diameter for thin gage short circuit welds.

[] The optimum weld current for the 0.035 wire is approx. 100-180 amps.

[] The "optimum" short circuit weld current for the 0.045 wire is approx. 180 - 200 amps.

In contrast to the 0.035 or 0.040 wires, the 0.045 (1.2 mm) wire operates in a narrow, short circuit wire feed range that delivers higher weld current, thus being less suited to thin gage parts and increasing the weld burn-through potential.

[] For the 0.040 wire the optimum short circuit current is approx.
150 - 190 amps. This current range is well suited to short circuit weld the very common and 14 - 18 gage carbon steel and stainless applications. In contrast to the 0.035 wires, with short circuit and the 0.040 wire, you can expect slightly higher weld deposition rates and improved wire feedability. The 0.040 wire needs less current to get into spray than the 0.045 wire making it very suited to 3 to 6 mm steel applications.

In the 1980s, while working in a marketing role for AGA, Ed was the first person and to this date in Nov. 2007, the only only person in North America to have MIG parameters placed on the covers the MIG wire boxes sold by AGA.

 

The bottom line on weld products and
"Supply and Demand".

Weld Fact: When the unqualified manager or engineers ask the unqualified welders who have skills but minimal weld process expertise, to try out that new weld wire, is it any surprise when the welders don't like the product?

<2007: At least fifty percent of the robots installed in North America are using a welding wire diameter which impedes the weld production or quality potential. A frequent weld management's solution to welding problems, when you have robot weld productivity issues, order more robots.

0.040 (1.1mm) MIG WIRE BENEFITS WHEN USING TRADITIONAL SHORT CIRCUIT OR SPRAY TRANSFER:

• For short circuit or thin applications, with enough volume sold, the 0.040 MIG wire would "cost less" than an 0.035 wire, (larger wires typically cost less than smaller due to less wire drawing requirements)
  
  
• The 0.040 wire would have "less wire feed issues" than 0.035.
  
  
• In contrast to the 0.035 wire, the 0.040 short circuit "weld deposition rate" potential would be increased resulting in more manual weld deposited or faster robot weld travel speeds.
  
  
• The 0.040 wire is better suited than the 0.035 and 0.045 wires for welding "spray transfer on thin applications especially < 6mm. On these applications the 0.040 wire would enable higher weld deposition rates than the 0.035, and in contrast to the 0.045 wire used on spray applications, the 0.040 wire would have less weld burn-through, less distortion and undercut, potential and with robots less arc starting problems.
  
  
  
  
  Lets see, Ed is saying that if we are worried about quality and productivity, management and engineers should take responsibility for the weld wire selection. Boy in this company that would be a first. Perhaps it's time for me to read a book on weld process controls.
  
  
  
  
  GAGE METAL AND MIG GAS MIXES: The MIG gas influence on the short circuit steel weld arc stability and weld energy should be a primary consideration in MIG gas selection. For welding thin gage carbon steels less than <0.060 "weld burn through" is always a primary issue.
  
  For welding thin gage <0.060 steel applications consider a low energy, two part gas mix like an argon mix with 10% CO2 for carbon steels and argon - 2- 5% CO2 for stainless gage parts. (See MIG gas section).
  
  If you use three part gas mixes for any carbon steels or stainless applications, you are not using weld process logic, you are using the advice of a weld gas salesman.
  
  For welding thicker gage short circuit carbon steel applications >0.070, improving the short circuit weld fusion is a prime concern. For these higher energy short circuit applications, consider Ed's MIG / FLUX CORED MIX as shown in the MIG gas section.

Question: Ed. Where can I get practical MIG, gas information without sales influence?

Answer: Visit the weld gas section of this web site for your weld gas questions. Also go to this sites education resources and view my welding books, These books provide more practical, real world information on MIG welding and weld gas selection than any other global reference source available. Need information on gas mixes, click here.

 

 

 

Let's see, we have another important step for weld process control. When it comes to MIG gas selection we don't need to try a different MIG gas six times a year. We don't need the advice of a gas salesman and we should get rid of those costly, useless three part gas mixes. The bottom line is all our steel and stainless MIG welds can be made with a couple of simple argon CO2 gas mixes.

 

The weld process mode you select will depe