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MIG. Spray Transfer and
Pulsed MIG Welding Reality.


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<2006: Thanks to aggressive weld equipment salesmanship and lets face it, too common weld management "process apathy", during the last two decades, the biggest selling, MIG weld power source for carbon steels / stainless robot welds has been a pulsed MIG unit.. Many of the companies using pulsed MIG to robot weld steel parts > 4 mm, would have been better served, if they had used the more stable, consistent energy, traditional "spray transfer mode" available from the lower cost and more durable traditional CV MIG equipment.

A company that has lack of Best Weld Practices.
and lack of Weld Process Control's.

is usually an indication that managers and
engineers should think about providing
process control training

 

2007: IN A CONFUSED GLOBAL MANUFACTURING INDUSTRY, IT'S EASY FOR WELD EQUIPMENT MANUFACTURERS TO SELL POWER SOURCES THAT PROVIDED USELESS BELLS AND WHISTLES:


THERE IS A RELATIONSHIP BETWEEN PLAYING WITH MIG WELD CONTROLS AND PURCHASING COMPLEX WELD EQUIPMENT.

For more than five decades, the majority of global, MIG weld personnel have "played around" with the "two control", traditional, MIG weld process. It should therefore be no surprise, that this process confused industry, would for the last decade perceive that the more costly, more complex pulsed equipment recommended by weld equipment manufacturers and distributors, was a superior choice for their MIG carbon steel and stainless applications.

 

COME GATHER ROUND WELDERS WHERE EVER YOU ROAM, FOR THE TIMES THEY ARE A CHANGING:

For more than 50 years, the traditional MIG spray transfer mode has been a work horse for manufacturing companies that rarely understood what spray transfer was. Even in 2007, there is not a wire feed weld process that will provide superior weld quality or productivity on most carbon and low alloy steel applications > 5 mm.

<2005: The weld supervision in these auto / truck frame plants are happy to see the MIG weld sparks flying, yet this too common pathetic fire works display, is an indication of weld transfer mode and voltage issues that are resulting in extensive weld quality and productivity issues. In these and many other frame plants, the management is not aware that the manual / robot MIG weld process is out of control and the welds they daily produce are little more than a weld spatter bath.

 

2006: When you walk in a plant and find the manual MIG welders are out of control, take a look in the robot MIG and resistance weld cells and you are sure to find weld production chaos and more weld rework than you need.

After more than 50 years of unnecessary excessive global MIG weld quality productivity issues, I hope there are a few managers and engineers out there that know "it's time for change".

A MIG WELD REALITY. If MIG spray and pulsed MIG spray transfer were two recent weld process developments, an evaluation by qualified weld process persons not influenced by weld salesmanship and weld equipment bells and whistles, would reveal some interesting weld facts. An examination of the spray transfer and pulsed welds; [a] arc physics and plasma profiles, [b] parameter consistency, on weld penetration profiles and suitability for high weld high speed welds on steel and stainless parts > 4mm, would reveal that the regular spray transfer mode typically provides superior weld penetration profiles and superior arc consistency during high speed welds.

 

A MESSAGE YOU WON'T HEAR FROM YOUR
WELD EQUIPMENT MANUFACTURER:

 

Irrespective of the fact that MIG welding power source manufacturers and their distributors achieve much greater profits from their $6000 to $13,000 electronic pulsed equipment, the traditional 300 to 450 amp, $2000 to $3000 CV MIG equipment is still an ideal tool for most carbon and stainless steel applications and especially on carbon steel parts > 4mm.


A common MIG CV power source and wire feeder package will sell in the USA for $2000 to $4000. From a durability perspective, the CV power source should readily outlast the pulsed power source by at least 10 years.

If you have no sense of humor, you
are in the wrong industry. An Ed joke.

 

 

 

< 2005: OF COURSE THERE IS A PRICE TO PAY FOR AN INDUSTRY THAT "PLAYS AROUND" WITH WELD CONTROLS ON THE WORLD'S MOST POPULAR WELD PROCESS, AN INDUSTRY THAT FOR FIVE DECADES HAS BEEN UNABLE TO ESTABLISH BEST WELD PRACTICES WITH A SIMPLE FIFTY YEAR OLD PROCESS.

Global trade may be a great tool for reducing product prices, however it's completely illogical to me that the North American weld industry, an industry that erodes daily as a result of global lower labor costs, has for the last two decades fallen over itself to pay a premium price to purchase poor performing, pulsed Asian, European and North American MIG weld equipment.

From 1985 to 2005, the global pulsed equipment typically used on carbon steel and stainless applications cost 200 to 500% more than traditional CV MIG equipment which provided more benefits. I know its no good harping on about the past, however is it possible that present day weld decision makers could learn from this?

 

 

 

Pulsed MIG and Spray Transfer Awareness: Pulsed MIG equipment when purchased for welding carbon steels > 5 mm, can in contrast to regular lower cost MIG equipment provide the following issues.

[a] Pulsed equipment is typically much less durable than regular CV equipment, and it's often impossible for the maintenance department to make repairs to the pulsed power source. Thanks to this fact, many companies will waste $6,000 to $12,000 and purchase an extra pulsed unit as a spare for the robot lines.

[b] Most pulsed equipment offers unnecessary bells and whistles and process / program choices and therefore adds to the general weld process confusion in the weld shop.

[c] Pulsed equipment is often used by weld personnel who don't have a clue about weld current compatibility with the part thickness or the relationship between wire feed settings and weld deposition rates they could daily attain. With the pulsed equipment parameter focus typically on weld current rather than on the wire feed rates, you can assume that the majority of welders will not be aware they may be producing;

[] welds with less than optimum weld fusion profiles,
[] welds at lower weld deposition rates,
[] welds with lower robot weld speeds than that which can be attained with regular spray transfer.

[d] The pulsed process which shifts between a high and "low" weld current, can on specific carbon steel and stainless applications > 4 mm produce welds with inferior weld fusion.

Extensive data on pulsed MIG is available in the
MIG pulsed, MIG short circuit and MIG equipment sections.

< 2005: It's not just the costly Japanese and European pulsed MIG weld equipment that North American weld shops should be concerned about. If during the last decade your company purchased Miller, ESAB and Lincoln "pulsed" MIG equipment made in the USA, to weld their carbon and low alloy steel applications, they wasted thousands of dollars on unstable weld equipment that provided minimal weld quality or production benefits.

For those that doubt my words, it would take me less than 60 minutes at any facility to prove this statement. By the way you could purchase one of my weld process control books, walk over to that traditional MIG power source, set my weld data, pull down your weld shield and make a believer of yourself. Click for Ed's books.

 

Do these two sentences define the
majority of the Global MIG Weld Industry.

[1] Give them bells and whistles and watch them buy it.

[2] When you want weld advice, ask weld salesman?

 

Hopefully one day, the umbilical cord between
the weld shop and distributor will be broken.



Come on chicklets miglets , we have to follow
him, after all he is a "salesman".

Is a salesman running your weld shop?
Are you having an identity crisis?

Experienced weld process control individuals in the majority of global manufacturing facilities have for decades been in short supply, it's therefore understandable that many weld shops became dependent on the local weld sales-rep for weld equipment or process advice, even though this individual rarely will have had weld shop experience.

< 2005: Many of the weld decision makers in the North American, European and Japanese welding industry have had strong opinions on their justification for the purchase and utilization of costly, pulsed MIG equipment, yet the vast majority of these persons will not be qualified to evaluate a MIG weld process.

 

To correctly evaluate the pulsed mode versus short circuit or spray transfer, a weld decision maker should first be aware of the real world arc and weld differences between the traditional spray transfer, short circuit, globular transfer and pulsed mode.

Are you a process control expert?
Why not Test Your MIG Weld Process Knowledge
with Ed's Spray Transfer Weld Quiz

Spray transfer is an "open arc" mode of weld transfer which requires specific weld parameters along with argon or argon mix.

In the spray transfer parameter range, the spray arc weld will produce a combination of weld stream and small weld droplets. The consistent energy spray transfer molten metal cascades axially through the ionized, white colored, bell shaped, arc plasma.

Note. The "medium" size weld droplets in the video shown, are transferring from an 0.045 (1.2mm) steel weld wire. The size of the weld droplets indicates that the weld transfer is in the transition parameter zone that occurs with argon mixes. This zone is found between the globular and spray mode. As the weld current is increased, the weld drops in the video that look like pulsed transfer will decrease in size and change into a continuous weld stream. Depending on the MIG gas used, the spray transition weld current with the 0.045 (1.2 mm) steel wire diameter will be approximately 230 - 255 amps.

 

If the MIG spray wire feed (weld current) is increased above the short circuit to spray transition current, the higher magnetic forces that result from the increased weld current will influence the profile of the hot wire tip. The increased weld current, (increased magnetic field) will pinch the MIG molten wire tip to a fine point resulting in a stream of weld metal.

The Auto / Truck Industry. Robots, downtime and the daily Globular Weld Scourge:

 

MANY WELD AND ROBOT ISSUES ARE CAUSED IN THE AUTOMOTIVE INDUSTRY FROM THE USE OF OVER SIZE MIG WIRES AND ROBOT PROGRAMMERS SETTING GLOBULAR WELD TRANSFER INSTEAD OF SETTING SPRAY TRANSFER SETTINGS.

Many robot steel welding programs that should be using spray transfer, have their weld data set in the "globular mode". The globular transfer is a common problem for auto and truck part suppliers who frequently purchase MIG wires which are too large for the application thickness. The spray current required for the large wires is to hot for the thin parts.

 

As this Ford 150 frame weld indicates, when the weld management selected an oversize MIG wire 0.052 1.4 mm) for the frame part thickness, what the engineers were not aware of was the minimum spray weld current required for the 0.052 wire was too hot for the thin frame parts. The lower weld parameters selected resulted in globular transfer. Globular transfer can produce cold welds with lack of weld fusion and excess spatter.

Combine the common poor management practice of selecting large diameter wires with the common lack of weld process control expertise on the shop floors and you are sure to have extensive robot and weld issues.

Globular transfer produces a weld transfer consisting of large weld droplets that cascade in an erratic transfer. The high energy globular weld droplets will explode when in contact with both the weld wire and work resulting in excessive, difficult to remove weld spatter.

Globular transfer is a prime cause of robot down time as the weld droplets will attach themselves to the contact tip often restricting the weld wire as it exits the contact tip bore.


Globular weld transfer, not only produces excess weld spatter, it's also a prime reason for lack of weld fusion. The large globular drops lack the weld energy and plasma velocity of the conventional spray transfer.

 

Weld process expertise is not rocket science,
you just have to read the right books.

Weld Process Expertise in the Auto Truck Industry? The weld magazine publishers in the USA are well aware that the auto / truck companies that utilize arc welding robots, are least likely to subscribe to their welding magazines. Even when the welding magazines are free, it's rare to find one in an auto / truck manager's or engineer's office. In the auto / truck industry weld process knowledge is typically acquired from a weld salesman or a slightly biased Lincoln or Miller rep.

E-Mail.from KD - P&F.
12/07


Ed, how are you doing? You would be interested to know that by the end of the year I will have close to 100 robots welding with 0.035 wire using spray transfer with no pulsing. It took 10 years Ed, but we are finally using the recommendations you made in the nineteen nineties. I now have the top guy in North America convinced traditional spray it is the way to go with the MIG applications. In regards to your MIG process control training, we now have two plants that should be interested in using you. I sent a copy of your book to one of the managers at one of those plants.Are you still available?

Note from Ed: This is a USA, Mid West tier one company that produces parts for Honda and Toyota. The plant has hundreds of robots and Panasonic pulsed MIG equipment. The Panasonic weld equipment and pulsed process was a requirement of the Japanese parent company. For more than a decade, the Panasonic pulsed MIG equipment generated numerous pulsed MIG weld issues that dramatically impacted the daily robot weld quality and production. With all the problems, the engineers in Japan were reluctant to hear that the the traditional, more durable, lower cost, North American CV equipment would provide solutions to the majority of their welding isssues. I guess even Japanese engineers with time (ten years) will figure out the solution to simple welding problems.

 

The inability to establish Best Weld Practices and the general lack of manufacturing weld process control expertise from manufacturing managers, engineers and robot technicians is completely unacceptable when low cost, highly effective robot / manual weld process control training resources are available. Click for Ed's Training resources.



E-mail Question to Ed. 07 /03.
From TD

Ed, We have used your training techniques at 3 of our manufacturing plants that I have worked at over the past number of years and thanks a million, they really WORK.

The other day, I got into a heated discussion with a welder, he was welding mild steel, laying 3/16 to 1/4 inch fillets. He was using 0.045. (1.2 mm) steel wire on 1/4" and 5/16" (6-8 mm) plate. The gas mix, argon - 15 CO2. He was welding with 28 - 30 volts, wire feed 250 ipm 190 - 220 amps. This welder used this one setting for all position welds - even vertical down. The arc sounded terrible ... as you can guess, he had nothing but spatter, and spent much time cleaning his welds. I tried to help him out, but he more or less told me to go back to the office where I belonged. I was going to tell him to switch to an 0.035 wire, starting at about 500 ipm, set the voltage to an initial setting of about 28 volts - lay a bead, then adjust the voltage for the correct sound of the arc - slight crackle. Who is right? If I'm wrong, please let me know. Thanks a bunch.

Ed's Answer.

TD. In the thickness range welded, the 0.045 wire is fine. The wire feed setting however is in the globular transfer mode which results in both poor penetration and lots of spatter. If he wants to weld vertical down with the 0.045 wire he should be at the start point of spray, 350-370 ipm, 260 - 270 amps (just past 12 o'clock) with 24 to 26 volts.

Vertical down welds would be easier with the 0.035 (1 mm) wire. For vertical down welds with the 0.035 wire, set the wire setting at 500 ipm, (just past 2 o'clock). Set 24 - 27 volts. For horizontal fillets with the 0.035 wire set 600 ipm,
(3 to 4 o'clock) with 28 - 30 volts. The key to dealing with process ignorance, thick skin and closed minded weld personnel, is first take the gun from their hands, change the weld settings and show them a better weld. You could also provide them with what they really need, process training. Regards. Ed.

 

ROBOTS AND WELD SPEEDS:

Many companies who purchased pulsed MIG equipment for their robot cells may have had high weld speed and consistent, high weld production expectations. Some weld decision makers were under the impression that with the pulsed process and that multi-wave form, fuzzy weezzy power source that they can now 'weld faster" than spray transfer on applications > 5 mm. The weld reality is, the low cost MIG equipment that delivers spray transfer has always provided consistent, high speed welds on carbon and stainless steels > 5 mm.

When welding carbon and stainless steels under 5mm, if you have the right pulsed >2006 MIG equipment, the present day pulsed MIG mode can provide high weld speeds. When welding parts thinner than 5 mm , the spray mode may be too hot and restrict the wire size and wire feed potential for the application.



The > 2006 pulsed mode is unique in that this open arc mode can be used on parts as thin as 20 gage using an 0.045 (1.2mm) wire.

As the world's weld shops have a few million traditional CV MIG power sources that provide spray transfer, the following are a few Spray Transfer Weld Facts:


[1] For those of you that believe the pulsed equipment is depositing more weld or delivering faster automated weld speeds, on applications > 4 mm, compare what you are achieving with this weld reality. With low cost, traditional, durable CV MIG equipment, spray transfer when used on parts > 4 mm typically deposits weld metal in the range of 8 - 15 lb/hr. On these applications, the pulsed MIG mode can not deposit more weld metal than spray transfer.

[2] Typical spray transfer "robot or automated 1/4 (6 mm) fillet welds" made on parts > 5 mm, are made at weld travel speeds of 18 to 23 in./min. On these parts pulsed cannot provide faster weld speeds.

[3] When welding a 3/16 (5 mm) fillet weld, the typical weld deposition rates with an 0.045 (1.2mm) wire using spray transfer will be 10 to 12 lbs/hr with automated weld speeds for this weld in the 40 to 60 ipm range. With extended wire stick outs, (information in "Management Engineers MIG" book) I have produced these spray welds at robot weld speeds up to 80 ipm. On parts that require 3/16 fillet welds the pulsed process will not provide faster weld speeds, however the pulsed mode can provide lower weld heat (lower distortion) and less than the minuscule spatter that results from spray.

Note: The pulsed mode when used and set correctly, on applications less than 4 mm, can provide higher weld deposition rates than short circuit or globular transfer.

 

When reading process or equipment recommendations or articles in welding magazines, its possible their will be a bias in the writing and don't forget where the magazine get the majority of its revenue from.

E-mail Nov. 2004.

Hi Ed. Its Matt Finn, I spoke with you on the phone a couple of weeks ago. Well contrary to the beliefs of my coworkers I must say your concepts on GMAW are worth trying. Your story of reading and more reading weld literature and finding it was not as it seems, inspired me to do the same.

Over the last three years all I have done and continue to do is read from a variety of welding resources. So this past week I have focused my study on the "hands-on" practical aspect. Its amazing what you learn from having your nose in the arc rather than observing from out side the robot fence.

After reading your books and getting hands on experience I now fully understand how and why Globular transfer is not a reliable mode of transfer, especially when utilizing it for high travel speeds (50- 70ipm). Tonight I was able to figure out how you were able to achieve over 70 ipm when welding in spray mode. I went snooping around the plant and found an old style of diffuser that was shorter than our common ones. I then took your advice from your Management Engineers book and cut about a quarter inch off the end of a contact tip. With having the tip well recessed in the nozzle, this allowed for a longer than normal wire stick out, dropping the weld amperage but still maintaining the current within the spray range. The longer wire stick out permitted me to run higher WFS (higher deposition rates) without the extra amperage that would cause unwanted weld heat defects. The weld spatter that resulted was minimal and the spatter was easy to remove. Also the recessed tip and diffuser were spotless. After thinking about your ideas on high deposition welds in your "Management Engineers MIG book" it now makes sense.

Thanks Ed for your site and weld process expertise. Matt Finn. USA.

A prime benefit of pulsed transfer is that it can provide open arc weld transfer welds that provide "less weld energy than spray welds". However this is a unique pulsed benefit that is beneficial for thin carbon steel and stainless parts < 4 mm, this benefit does little for most steel fillet welds on parts > 5 mm, parts as these parts will benefit from consistent, high energy.

When asked for his opinion on spray transfer versus pulsed,
Albert might have said the following.

"Constant weld energy attainable from CV spray transfer
is a requirement for constant weld fusion".

The primary weld concern with most steel welds over 5mm is attain "sufficient weld fusion in a consistent manner"

A primary concern with most steels under 5 mm is distortion.



A common concern you will find with high deposition rate pulsed welds; When pulsed is used in the high, "stable spray transfer wire feed range", the pulsed arc influenced by the necessary high pulsed Hz and high peak current can depending on the pulsed equipment utilized provide an agitated pulsed arc that results in a narrow, high velocity plasma. This pulsed plasma can provide a digging effect resulting in crater problems and narrow weld penetration profiles that can lead to hot, center weld cracking.

Ed made this manual spray transfer weld with a $1700 traditional
MIG CV power source with an 0.045 (1.2 mm) E70S-3
MIG wire set at 450 ipm. 12-13 lb/hr.

$1700 FOR THIS POWER SOURCE.
WHATS THE $12000 POWER SOURCE GOING TO ACHIEVE?

To attain the open arc spray transfer for carbon steel or common stainless steels, an argon mix is required along with a specific minimum amount of weld current (wire feed rate) and voltage for each electrode wire diameter selected. The resulting weld stream is protected from the atmosphere by the spray plasma, (the ionized, white, bell shaped cloud).

The spray transfer arc plasma not only conducts the weld current, the plasma with argon mixes also shrouds the electrode wire tip. In contrast, when using straight CO2, the arc plasma occurs "under the weld droplet being formed" supporting the weld drop as it gets bigger till eventually it drops off the wire tip in an erratic manner. This unique plasma LOCATION from the reactive CO2 gas is the reason you cannot get spray transfer from straight CO2, it's also the reason the CO2 content is limited to 20% in argon mixes. See MIG gas mixes if you want to cut through gas salesmanship and read more practical gas data.

 

Some one in the weld shop has to know the optimum
weld transfer mode that should be utilized

NO PLACE FOR SHORT CIRCUIT OR PULSED
ON THESE BOMB WELDS:

In 2005 a major North American military contractor wanted to me to optimize the bomb lug welds that attached the bombs to the planes. I was asked to review the weld processes available. The focus was optimize the vee prep weld fusion attained between the lugs and bombs.

I had my choice of any weld equipment, processes or consumables. I selected MIG spray transfer and after weld tests it provided superior weld fusion than the available pulsed mode.

 

 

From Ed's Robot MIG Process Controls Training Program

 

 

SPRAY TRANSFER & MILL SCALE:

The mill scale on that hot rolled plate surface to be MIG welded can be a poor electrical conductor causing arc instability. The electron conductivity of spray transfer is influenced by both the mill scale thickness and mill scale composition. Mill scale acts as an insulator which can impede the electron flow from the cathode spots on the weld surface as they travel to the MIG wire tip. As mill scale increases in thickness the MIG weld voltage has to be increased and the weld will become more sluggish.


If you spray transfer on carbon steel without mill scale, and then without changing the weld parameters, spray weld on an application with mill scale, the welder would note the arc distance from the wire tip to the weld has reduced. The arc length reduction is a result of a decrease in electron conductivity, less electrons = less energy to melt tip of MIG wire so the wire gets closer to the weld. The shorter arc length often results in the MIG wire running into the weld, displacing the weld causing weld spatter. To reduce the weld spatter would require that the welder increase the weld voltage to increase the arc length. As we don't teach welders this simple fundamental fact we end up each day spending millions removing excess weld spatter.

As the mill scale has a higher melting temperature than the weld, the weld can be sluggish affecting the weld fusion potential and frequently the weld will solidify in a convex shape with a roll over at a fillet weld toe. The influence of mill scale and the process requirements to compensate for the sluggish welds and spatter control, is another reason why weld personnel would benefit from my weld process control training book and video.

 

A WELD DECISION MAKER IS ONLY AS GOOD AS HIS OR HER WELD PROCESS EXPERTISE. IF YOU WANT IN-DEPTH WELD PROCESS KNOWLEDGE CONSIDER ED'S WELD BOOKS.

Pulsed MIG and Mill Scale. Characteristics of a MIG arc that
have an important impact on mill scale.

An Intense Arc: A consistent high energy arc as found with spray transfer is beneficial
for mill scale issues. This arc type will;

[a] assist in maintaining consistent electron, and arc stability,
[b] assist in the consistent removal of surface contaminates,

[c] provide improved consistent wetting for a sluggish weld,
[d] provide consistent weld fusion.

Mill scale melts at a higher temperature than the base metal. Mill scale will cause sluggish solidifying welds. Fillet welds influenced by mill scale will often result in a convex, rollover appearance. The sluggish MIG welds made on heavy mill-scale parts will often result with unacceptable or marginal side wall weld fusion.

In contrast to pulsed, when using optimum spray transfer weld parameters with argon - 15 to 20% CO2, the spray plasma arc intensity is much more "constant" and the average energy generated is typically greater than that attained from the pulsed welds made in their optimum parameter range. With pulsed MIG, the plasma is influenced by the peak to low background current variations and the weld current and voltage fluctuations which are common from the electronic pulsed MIG equipment along with the low energy levels that can result from gas mixes like argon oxygen or argon 5 - 10 CO2.

 

Weld Voltage and Current Stability?

2004: As this oscilloscope graph of a carbon steel "pulsed MIG weld" set at optimum weld parameters indicates, when using one of the most costly, popular and sophisticated pulsed MIG power sources sold in the USA, weld current and voltage instability is the norm.

 

 

 

In contrast this is regular spray transfer
from a power source that cost 75% less

[2] The MIG plasma shape: Spray transfer produces a bell shaped plasma. The wider the plasma in the cathode spots area, ( the work / weld surface), the greater the weld area that benefits from the MIG plasma surface cleaning attributes.

In contrast the pulsed process typically provides a narrow plasma that fluctuates with the change from peak to back ground current. As you increase the pulsed welding parameters to traditional high spray transfer wire feed (current) levels, when welding steels >5mm, the pulsed plasma zone influenced by the "high frequency, high peak pulsed weld current" can become intense. Typically the high frequency, high peak current can result in an intense pulsed plasma that's conical and narrow in shape. This narrow intense plasma configuration can cause an arc digging effect that can result in deep weld penetration and welds that may produce,

[a] narrow weld beads that produce (hot center weld cracks),
[b] undercut,
[c] crater cracks.



The MIG Arc Length and Robot Weld Speeds. The short arc length allowed by spray transfer can provide a highly localized, intense plasma configuration that is very beneficial on robot high speed steel welds, high deposition welds or when welding plate with surface contaminates such as mill scale.

< 2005: How many of you have used pulsed for high speed welds >30 ipm, and found the welds skipped. Just about every wheel or torque converter manufacture found this problem with their costly pulsed equipment, yet these manufactures continue to purchase pulsed weld equipment.

The pulsed mode requires for the uninterrupted formation and transfer of a pulsed weld drop per-pulse, a slightly longer arc length than traditional spray transfer. The bottom line, depending on the settings and equipment, the pulsed mode can be arc length (voltage) sensitive. In contrast, the traditional spray mode in which the metal transfers in a stream can utilize much shorter arc lengths and the continuous weld stream is hardly affected by arc length variations. This arc length is an important point as it affects;

[a] Shorter less sensitive arc lengths derived from spray transfer improve arc stability when welding at a high speeds.
[b] Shorter less sensitive arc lengths allows longer wire stick reduce wire burn backs to the contact tip.
[c] Shorter less sensitive arc lengths are beneficial when welding on mill scale or coated metals.

 

REMEMBER THE WELDING INDUSTRY WANTS YOU TO PURCHASE IT'S COSTLY PULSED MIG EQUIPMENT IRRESPECTIVE OF THE WELD APPLICATION. THIS SITE FOCUSES ON OPTIMUM COST EFFECTIVE WELD MODE / CONSUMABLE SELECTION AND PROCESS OPTIMIZATION TO SPECIFIC APPLICATIONS, THICKNESS OR WELD TYPES.

MIG Gas Notes for Mill Scale:

When spray transfer welding on troublesome mill scale applications, a high energy MIG gas mix such as argon with 15 to 20% CO2 is recommended. The 15 to 20% CO2 gas mix in contrast to a lower CO2 mix, or argon oxygen mix, enables higher weld voltage and promotes higher energy at the cathode locations on the plate or weld surface.

The higher CO2 weld voltages combined with the molecular arc dissociation properties of CO2, improves the electron flow, improving arc stability. This additional energy improves the weld fusion and weld wetting. An additional benefit also is less weld porosity potential.


What makes CO2 gas unique? The CO2 plasma provides unique "gas dissociation properties". In the MIG arc, the CO2 molecules break down from CO2 to CO and O2. When close to the cooler weld surface the
CO - O2 molecules form back to CO2. The gas dissociation, "molecular change" adds energy to the weld. Also in contrast to oxygen, the CO2 gas requires higher weld voltages.


For those companies that use argon oxygen mixes, or the heavily marketed, useless three part mixes containing argon - CO2 - oxygen on CARBON steel applications that have mill scale, (applications >3/16), they should realize they are jeopardizing the weld fusion potential and increasing weld porosity potential.




The oxygen and low CO2 in the argon tri-mix results in a spray transfer plasma in which low to medium weld energy is generated in the outer periphery of the plasma. This results in finger weld penetration. As the narrow finger solidifies rapidly this increases the opportunity for weld porosity to form especially in the finger shaped weld root. It's very common for this to show up in ultrasonic evaluation or x-rays on fillet welds on parts > 5mm.

In contrast to what your weld gas sales rep tells you, two or three component gas mixes containing oxygen can result in welds with greater potential to create


[a] weld porosity,
[b] welds with lower weld energy, resulting in inferior weld fusion profiles,
[c] less gas in the cylinders than that attained with argon 15 - 20% CO2 mixes.

 

For extensive weld gas data see the weld gas section or better still invest a few dollars on yourself and purchase one of my welding books.

 

Ed's book "A Management Engineers Guide TO MIG" has over 600 pages on how to control the MIG and flux cored process. From robot and manual MIG weld process controls, to pipe welding.

 

Note: ED WAS A KEY WRITER OF THE AWS "MIG GAS SPECIFICATIONS".


E Mail.

July 05.

Ed. It looks like we are just starting out on a new Chrysler project welding a galvannealed product, Galvanneal NS 6000 D series 44a. According to the Chrysler spec, we would be allowed to use a solid carbon steel ER 70S-3 MIG wire, but they require a 75 argon / 25 CO2 gas mixture for this. I think Chrysler takes the cake on this gas selection. By the way if our engineers had selected galvanized material, according to the Chrysler spec we would have been forced into using the terrible self shielded FCAW process.....Is the Chrysler weld engineer from this planet? What I also don't understand is the fact that they are specifying a coated material, and then we are still required to e-coat the part. I wonder what the reasoning is behind double coating the cradles.....I'm sure they don't even know.

Regards GR. Tier One.

Ed's Answer

There is no rationalization for most of the weld logic that comes from the mouths of Corporate Chrysler. Their chief welding engineer has for more than a decade been in the wrong profession. The choice of the 75-25CO2 gas restricts the use of spray transfer on robot welded parts over 0.070, this gas will be the cause of weld spatter or weld burn through. As for the use of the self shielded wire, no one knows why the Chrysler corporate engineer still insists on the world's worst electrode for coated materials. As for the double coating, it makes no sense. What does make sense is to coat the parts after welding as irrespective of the coating type, the weld destroys the coating in the weld area. As I have said on numerous occasions on this site don't look for weld reality when dealing with Chrysler.

Want to know how to reduce arc blow.

Minimum Spray Transfer Weld Current
With Argon > 10% CO2 Mixes.

When welding carbon steels with the 0.035 (1 mm) wire, and a 15 to 20 CO2 mix, to achieve spray transfer, a minimum weld current of >180 amps is desired.

For the 0.045 (1.2mm) wire and the 15 to 20 CO2 mix. To achieve spray transfer, a weld current approximately >250 amps is desired.

These minimum spray transfer weld current settings are reduced with lower CO2 mixes, or when argon oxygen mixes are used.

Many welders and robot programmers are not aware of the minimum weld current or minimum wire feed rates necessary to attain optimum spray transfer. Its therefore not surprising to frequently find welders or robots welding with globular transfer and creating a weld spatter mess.

 

There is an optimum MIG Wire Diameter
for every MIG application.

The auto / truck industry is one industry that for decades has been notorious in it's selection of unsuited MIG and flux cored electrode diameters for welding applications < 6mm.

As minimal focus is placed on the importance of weld process expertise, general confusion exists in the weld industry when selecting the optimum MIG electrode size. Few companies understand the weld wire, weld mode, weld current, weld size and "weld part thickness relationships. This is an extensive part of my books and weld process control training programs.

Did you ever consider why, after nearly 50 years of making MIG welding equipment and welding consumables, that Lincoln, ESAB (Linde), Miller or Hobart did not put practical MIG weld parameter information on their MIG wire packages or along side the relevant MIG wire feed or power source parameter controls?

I believe the reasons the MIG welding electrode wire manufacturers never provided their welding customers with practical, cost effective MIG or flux cored welding data on the wire boxes, is they had never figured out the simple relationship between the few required wire feed and voltage settings necessary for the majority of all the common global MIG and flux cored applications.

In the weld equipment and consumable supply companies, marketing and real world data were often far apart. The incredible lack of weld process expertise that prevailed from most of the world's largest weld consumable manufacturers is not that unusual. As we all are aware just because you make something does not necessarily mean you are an expert in it's use. The sad issue today for the self taught global weld industry, after 50 years of weld misinformation, too many weld shop still rely on these same companies for weld advice.

 

The MIG process celebrates 50 years as being the worlds most important weld joining process yet, how many of you have watched weld equipment and consumable reps "play with the weld parameter controls" during a demonstration of their companies MIG / flux cored equipment and consumables?


For an experience you may not enjoy. Next time you visit a Fabtech or AWS weld show, ask the Lincoln - Miller - ESAB - Panasonic rep the following technical question. Look for someone demonstrating pulsed MIG, then ask them to do a vertical up, carbon steel or stainless fillet weld on 1/4 (6mm) plate. After the weld look the rep in the eye and ask how his pulsed wire feed rate compares weld deposition wise with an 0.045 (1.2 mm) E71T-1 wire set at a feed rate of 400 in./min. The answers you receive to this fundamental simple weld question will show you how little or how much is known by the so called weld equipment / consumable experts.

Before weld personnel provide an opinion on a welding process or weld consumable, they should have all the facts on the processes and consumables that compete with their process or consumables. And of course if they were a true professional they would then provide an answer without product or process bias.

 

 

< 2005: The sales reps promoting pulsed weld equipment at the AWS or Fabtech trade shows may extol the virtues of their weld equipment benefits, however, the bottom line is those benefits may dwindle quickly when you take a real look at the poor and inconsistent arc characteristics and then provide a realistic comparison of their process or equipment against other processes, mode of weld transfers, equipment and consumables.

With 2007 on the door step we have a global weld Industry that lacks a professional approach to best weld practices or process controls. It's frustrating to find the general lack of weld process expertise that comes from welding individuals who are paid to be better informed. Too many weld decision makers in ship building, power plants refineries and auto industries are notorious for their lack of semi-automated and automated MIG / flux cored weld process expertise.

The general lack of weld process expertise and management / engineering weld process apathy that prevails frequently, adds to the common lack of professionalism and the poor image that inundates the welding industry.

 

< 2001: When Ed set the robot welds for the new, more robust Harley bike frames, he resisted the use of the pulsed mode and used spray transfer. Ed set 3 simple weld schedules for the more than 50 welds required on the frames.

If you want a quick evaluation of the weld expertise in your shop, ask three of your welders or the weld shop supervisor to show you the 0.045 (1.2mm) wire feed position in which the start point occurs for spray transfer, you may be surprised at the diverse incorrect answers provided for the worlds most popular wire size and the worlds most utilized weld transfer mode.

If you think your weld personnel fully understand the weld process they make a living from, why not give them my weld process control quiz?

In one manufacturing facility I visited, I sat in a a meeting in which three weld engineers and nine robot personnel discussed for more than two hours the robot MIG weld spatter problem on a motor bike gas tank. At the end of two hours the problem was unresolved. It would have taken two minutes to resolve the issue simply by resetting the weld voltage.

 

 

 

HOW MANY ENGINEERING MAN HOURS ARE LOST EACH YEAR TO WELD TEAM DISCUSSIONS ON ROBOT WELD ISSUES THAT WITH A LITTLE PROCESS EXPERTISE COULD BE RESOLVED IN A FEW MINUTES? Ed Craig. 1985.

 

 

"PLAY AROUND" NO MANAGER OR ENGINEER SHOULD ALLOW THESE TWO WORDS TO BE USED FOR THE MANUFACTURING PROCESSES CRITICAL TO THEIR ORGANIZATION?

 

The good news is the common lack of MIG and flux cored weld process expertise can be quickly eradicated. First managers have to put their focus on the root causes of their weld issues and always remember that product liability starts in the front office, not on the factory floor.

 

Click here for information on Ed's books and training resources.

 

WHEN PURCHASING PERSONNEL MAKE WELD DECISIONS YOU KNOW THAT ORGANIZATION HAS NO WELD MANAGEMENT.