TIP TIG Welding is always better quality than TIG and 100 to 500% faster with superior quality than TIG - MIG - FCAW.

MIG Spray Section. 1.



WELCOME TO MIG SPRAY TRANSFER

SECTION 2.

MIG WIRE WELD FACTS CONTINUED:

Two primary concerns with any welder using MIG spray transfer on steel and stainless fillet applications >5mm.

[1] Be aware that with the MIG process, that the side wall, fillet weld fusion is typically minimal, especially if the pulsed mode. Keep your focus on attaining "optimum ROOT AND SIDE WALL weld fusion".



[2] Try to control the "high weld fluidity" generated from the hot, spray / pulsed welds, irrespective of the MIG electrode used.




• The E70S-6 wires and high energy argon CO2 mixes can benefit spray welds on plate with mill scale. Mill scale has a higher melting temperature than the steel and if enough scale is present, sluggish welds can result, impacting weld fusion and porosity. A high energy gas mix helps to reduce the sluggishness. Increased silicon in the S6 MIG wire not only provides increased deoxidizers the silicon also provides an increase in the weld fluidity which can be a benefit or possibly create undercut issues. If the mill scale is causing weld issues, consider eliminating the scale with grinding or shot blast before welding.
  
  
• The E70S-6 wires also benefit MIG spray welds on plate with excess rust, as 70S-6 wires have additional de-oxidizers = oxide scavengers, howeve keep in mind that gas shielded, flux cored
  wires are preferred for applications that provide excess scale, rust or other contaminates.
  
  
• Weld Fact: On plate which has the weld area ground clean, plate that is sand blasted, and cold rolled steels, irrespective of what your knowledgeable friendly sales rep informs you, the E70S-2-4-6 wires provide no measurable benefits in contrast to E70S-3 wires.
  
  
• If manual and robot welding on parts < 3/16 < 5mm, or welded parts that suffer from excess weld heat, a benefit of the E70S-3 wire is this wire will have less propensity for weld burn through or for undercut, in contrast to the S-6.
  
  
• If manual or robot welding on clean parts with "multi-pass welds", the weld heat build up and its influence on the weld fluidity needs consideration. The use of the E70S-3 wire limits the silicon and manganese build up in the multi-weld passes maintaining desired weld mechanical properties. Using the E70S-3 wire also helps in keeping the inter-pass weld slag to a minimum.
  
  
• If welding on galvanized or aluminized, or any coated carbon steels use E70S-3. Avoid higher silicon wires like the E70S-6 wires as the silicon / zinc oxide reactions can cause hot
  micro-cracking in the welds.
  
  
• If concerned about the weld surface from a paint perspective, keep the weld slag oxide
  formation on the weld surface to a minimum by using the E70S-3 rather than the E70S-6.
  
  
  
  
  
  
  

  LINCOLN AND MIG WIRE WELD ISSUES?

  I was assisting a weld manufacturing plant in S. Dakota. This company is a large user of Lincoln L50 and L56 wires and, these two wires are what I prefer for MIG steel applications.
  
  While at the plant, the management asked if I would look at two different wires they were evaluating, the Lincoln "Easy Feed" MIG wires and the Lincoln "Super Arc" MIG wires.
  
  When I tested the Easy Feed MIG wires, I noted that in contrast to the traditional L50 -L56 wires the Easy Feed wires were "voltage sensitive", To maintain spray arc stability with the Easy Feed wire, I noted the weld voltage had to be constantly fine tuned. This voltage adjustment was on a robot application in which the wire stick out was constant, and the the arc length should have been stable. The weld voltage sensitivity was also noted using short circuit transfer with the Easy Feed wires. The spray transfer weld plasma generated with this wire was narrow and favored the center of the 6 mm fillet weld puddle. This weld performance is a contrast to the traditional and superior L50 / 56 wires which are noted for their arc consistency and a wider plasma that provides greater coverage of the weld puddle surface. The narrower plasma resulting from the Easy Feed wire produced poor wetting of the weld edges, resulting sometimes in convex weld beads with scalloped edges. This factor increases potential for lack of weld fusion issues on specific applications.
  
  I found that the Lincoln Easy Feed wires also were inconsistent in the slag island production. Sometimes on clean plate with no mill scale the Easy Feed S3 would produce much more surface slag islands than the Easy Feed S6. This slag result , was a surprise as there is supposed to be more slag producers in the S6 wire.
  
  By the way the wire test welds were carried out both manually and also with a robot. The welds were made on clean, ground plate using optimum weld parameters in extremely controlled conditions. So much for the Easy Feed wire and on to the Super Arc wire. The bottom line was when I tested this wire , it appeared that the Super Arc and Easy Feed had more in common with each other than they had in common with the traditional USA manufactured Lincoln L50 / 56 wires which were far superior.

  The five questions that came out of this weld wire test.

  [1] WasIs the Easy Feed and the Super Arc the same wire in two different packages?
  
  [2] What was the Easy Feed wire and the Super Arc wire called before it was given the new Lincoln brand names?
  
  [3] If a company has asked the weld distributor for a traditional Lincoln L50 or L56 wire, and that distributor provides them with the Easy Feed Lincoln product, a product that appears to provides inferior weld quality performance to the L50/56?. Should that customer be a little upset
  
  [4] Is Lincoln concerned about the inconsistencies with the silicon and manganese content of the wires under discussion?
  
  [5] The once completely American made Lincoln L50/56 wires were for decades the best and most consistent MIG wires in North America. If today you examine the side of the Lincoln MIG wire boxes or drums you may note that the MIG wire products you selected may have generated in Mexico, China, South America and many other places from around the globe. Can Lincoln today guarantee to it's weld customers that these wires are identical in performance to the Cleveland made L50/L56 products that have been incorporated into the majority of MIG weld procedures in North America?

  We had to waste a costly day testing MIG wires that did not perform in the way that the designated wires were supposed to perform. One of the great benefits of a robot with optimum weld data is it will quickly show the inconsistencies of a poor quality MIG wire. Its a pity Lincoln does not inform it's well established consumables customers that these products are inferior to the US. made products it's sold in the past

  
  
  
  

Weld Question: Ed, who makes the best carbon steel MIG
wires in North America and why?

Answer: Its still Lincoln Electric, however they also supply MIG wires they make in other countries and the one I tested are definately inferior to the Cleveland wires.

I have tested and used numerous MIG wires from all over the world, and the Cleveland made Lincoln copper coated L50 (E70S-3) and L56 (E70S-6) wires that have been sold for decades, are MIG weld consumables that can be considered optimum.

In North America. I also like ESAB (Linde products).

When you order a MIG wire from Lincoln, if you use pulsed or spray transfer and want their best product don't order an E70S-3 or E70S-6 wire or one of their special super wire deals, be specific, ask for "L50 or L56. Remember, irrespective of what a sales rep informs you, the best wire diameter for short circuit and spray welds on parts 0.060 to 3/16 (1.6 to 5 mm) is the wire I have been recommending since the nineteen eighties, the 0.040" wire. For all pulsed welds use the 0.045 wires.

If you are having problems with inconsistent high speed welds and you have determined it's not caused by that inconsistent pulsed MIG equipment you just purchased, try a Lincoln L50 wire against the wire you are using for comparison.

The MIG wires I would rather not have to work with are products from National Standard and Hobart. With the Hobart wires I frequently found inconsistent wire chemistry (inconsistent arcs), excess helix. From NS. I did not like the excess weld fluidity in the spray welds due to the high level of deoxidizers they use, or the poor winding and poor wire weld splices.

Spray Transfer & MIG Wire Burn Backs to the Gun Tip.

 

Ed, I work at Monroe, we are one of the largest producers in North America of auto / truck shocks. Our robots weld on average 200 to 400 parts per-shift. At some plants we average 2 to 5 burn backs per robot per shift. The burn backs requires that we replace the MIG gun contact tips. As the robot down time and time required to rectify the problem takes 5 - 10 minutes per burn back you can imagine the production consequences. What is the primary cause of this common robot problem? Also why does this not happen as frequently with manual welders?

 

The most common reasons for carbon or stainless steel MIG wire burn-backs to the contact tip:

• Wire burn backs due to the use of oversized MIG wires in which the weld current cannot be used in the spray mode, so the welds are made in the "globular mode". The excessive weld spatter globs block the contact tip orifice and restrict the wire.
  
  
• Wire burn backs caused by the use of globular weld data at the robot weld start or weld end data.
  
  
• Wire burn backs caused at the robot " weld starts". At a weld start the wire may not have enough forward feed momentum caused by any number of causes.
  
  
• Wire burn backs " during the weld". One common cause of burn-back during a weld is when the MIG wire is restricted in the liner, or the tip or from lack of sufficient wire tension from the drive rolls. Restricted gun liners or a robot axis issues in which the gun cable is twisted are a frequent robot causes for wire restriction. These problems frequently result in a wire burn back which can melt the end of the contact tip. These problems can occur at the arc start or during the a weld.
  
  Robot Issue. When welding with a robot especially when using an 0.035 (1mm) wire, sometimes the robot arm over twists the gun cable restricting the wire. This is noted more with the small wire diameters and specifically when the burn back consistently occurs at a single weld location.
  

  Why the common wire burn-back problem occurs.
  
  Many factors other than wire feed issues can influence a wire burn back.

  1. Wire stick out length too long and the wire almost touches the part at the start. A wire burn back variable that can be adjusted on most equipment.
     
     
  2. Robot program, poor arc start data. Programmers will benefit from the data found in my books.
     
     
  3. Lack or insufficient shielding gas at the weld starts.
     
     
  4. Wire feed restrictions.
     
     
  5. Parameters set in the globular mode.
     

The following weld data and much more is found in my books and in my training programs , click here:

Wire stick-out influence on burn-backs.
As the robot starts an arc, the robot control sends a signal to the power source to open the contactor to energize the wire. When the wire makes contact with the work, the wire feed should be feeding forward with full inertia. In all instances the electronics work quicker than the mechanical feed and the high start current available during the wire short circuit can melt the MIG weld wire before it can be fed forward at it's full speed.

Many robot personnel are not aware of the influence of their wire burn back data on weld start issues. They may set the "wire burn back" data in the weld program so the wire stick out is approximately 12 to 15 mm at the weld completion. As this long wire extension makes contact with the grounded work at the next weld, before the wire has a chance to be fed forward the weld current and voltage is delivered creating an explosive short circuit. The wire short circuit depending on the start voltage utilized can produce very high current causing the weld wire to disintegrate or melt back to the contact tip.

The MIG wire stick out at a weld completion is controlled by the "wire burn-back control data". The wire stick out at the weld completion should always be kept as short as possible. The wire burn back should be set so the wire stick out is approx. 5 - 6mm from the end of the nozzle. A normal nozzle to work distance should 1/2 to 3/4 (12 - 18 mm) depending on the welding circumstances. With spray transfer, the contact tip should be recessed inside the nozzle 2 to 4 mm.

Important. At a weld start there should be sufficient wire to work distance
3 - 6 mm to ensure the wire is feeding forward before the wire makes contact with the work.

IF YOU LIKE WELDING DATA, YOU ARE ONLY SCRATCHING THE WELD PROCESS DATA SURFACE HERE. IF YOU WANT TO BE CONSIDERED A WELD PROCESS EXPERT. DON'T BE THE WEAKEST LINK ON YOUR WELD TEAM, FOLLOW THIS LINK TO ED BOOKS AND PROCESS CONTROL.

Contact tip stick-out. Up to two years ago the standard robot MIG gun produced in North America had the contact tip located either flush with the end of the nozzle, or "sticking outside the nozzle"

BOTH OF THESE CONTACT TIP POSITIONS CAUSED NUMEROUS ROBOT WELD ISSUES FOR COMPANIES USING THE WORLD'S MOST COMMON WELD TRANSFER MODES, SPRAY OR PULSED.

The MIG gun manufactures who delivered their robot guns with the contact tip sticking outside the gun nozzles simply did not know better, then again I suppose we should not expect MIG gun manufacturers to be aware of the fundamental weld process requirements, after all they still classify their automated MIG guns for use with straight CO2 when less than one percent of robot MIG welds are carried out with straight CO2.

Lets face it when it comes to MIG gun manufactures and process expertise they are no different than the companies who make MIG equipment and weld consumables. At most of the plants I visited that were using spray transfer on parts >3 mm, the robot MIG guns would be welding with the contact tip stuck outside the nozzle and numerous contact tip issues would be occurring. I would tell the people on the floor to cut 3 to 6 mm of the contact tips.

It should not have taken a rocket scientist to figure out that if you stick a contact tip too close to that spray weld, with the high weld parameters, high weld heat and spatter will increase the potential for contact tip issues. As for that pulsed weld, if the contact tip extends outside that nozzle that typically means less wire to work distance is available to create that stupid little weld drop and allow it to transfer across an arc gap without being in contact with both the wire tip and work.

Many factors influence arc start with robots, "electronic time" has extensive influence. All MIG robot programmers should be aware of the factors that effect arc starts, and aware of optimum start welding parameters of each available mode of transfer, for each wire diameter used. This data is in all in my books.

How many companies are aware that pulsed welding is much more prone to wire burn back then traditional MIG weld spray transfer.

The primary reason there is a contact tip concern with pulsed welding and robots, is with the pulsed process there is a time factor and arc length concern required to create and transfer the pulsed weld drop that provides no steel weld benefits. For a spatter free weld transfer the pulsed weld droplet has to keep to a minimum size, then cascade across an arc gap into the weld without contacting the wire tip and weld at the same time. If the pulsed weld drop makes contact with the work and wire at the same time an explosive short circuit in the pulsed weld drop will occur. The pulsed drop short circuit explosion will cause spatter and disrupting the controlled formation of the next weld drop which can effect the weld and fusion consistency. The pulsed mode requires a longer arc gap than that is necessary for spray transfer, two to three times the length. The longer arc gap means a shorter wire stick out from the end of the contact tip. The shorter wire stick out increases the potential for wire burn backs. Want a 100 pages of why pulsed can cause weld issues you won't get this data from Lincoln, Miller or ESAB, you will get it from my 600 page "Managers and Engineers Guide to MIG book"

You can not control that
MIG weld with a tip like this.

How many manufacturing companies do you think will daily MIG weld with contact tips in which the tip bore diameter is worn to twice the diameter of the MIG weld wire?

My Management Engineers book 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 from pulsed to flux cored."Management Engineers Guide To MIG"

ROBOT WELD TRAVEL RATES.

The weld speed rates for fillet welds are obviously first determined by the weld size which influences the required weld deposition rate. Another restriction is the weld fusion requirements. Travel too fast with that robot and irrespective of the weld current or weld mode utilized you will have a weld fusion issue. The weld surface condition, the weld length and the shape of the steel (round components are more sensitive to lack of fusion than plate), will also influence the weld speed and weld fusion.

 

LETS HOPE YOUR SHOCK WELDS ARE OK

Many years ago Monroe a major USA shock manufacturer requested my assistance as they could not get their robot spray welds on their shock bracket welds to qualify for a Chrysler "shock load test spec" Chrysler engineers required the bracket welds on the shocks to absorb at least a 13,000 lb test load. After robot welding the steel brackets with 5 mm fillet welds on the shocks that were only 2 to 3mm thick, Monroe found that the shocks bracket welds would fail prematurely, typically in the 7000 to 9000 lb range


The Chrysler weld spec for the shock bracket welds required that the welded brackets should pass a test load of 13,000 lbs. It took me less than two days of manual welding and testing on the shock bracket welds to reveal that any test load of less than 19,000 lbs indicated lack of weld fusion in one of the four bracket welds.

There were three reasons the Monroe shocks could not meet the minimum shock weld test load requirements,

[1] the robot spray transfer welds were made on "cold rolled round parts",

[2] the robot weld speeds were "set too high",

[3] the robot weld lengths on the brackets "were to small".

After I figured out the weld problems, I changed the weld wire size to a smaller wire which increased the weld current density. I reset the spray parameters, extended the shock bracket weld length by another 3 mm. The shocks bracket weld than average a load test of 21,000 lbs.

HOW FAST, HOW SLOW, SHOULD THE ROBOT GO?

Many robots today are either welding too fast or too slow. It's not just the lack of weld process expertise or lack of information on robot weld speed potential that proliferates throughout this industry, a common problem is that the MIG wire size may be wrong, or maybe it's because pulsed, globular or short circuit is being utilized when spray would be superior. Maybe the weld issue is the part design, joint type, part thickness or ridiculous gaps many auto / truck companies present to the robot weld cell. Optimum weld speeds for all applications and weld compensation data for potential weld issues are covered in my books.

THE GOOD SOUNDS OF SPRAY TRANSFER.

As most of you are aware to fine tune that MIG weld voltage (tune the weld sound) the best weld calibration device can be one's ear.

For MIG spray transfer welds including all carbon steel, stainless, aluminum and nickel wires, the optimum spray transfer arc is set when a consistent, quite smooth crackle sound is attained.

If the MIG spray "arc length" is too long, the weld volts are set too high. In this situation the spray weld drops and weld stream transfers uninterrupted "quietly" from the wire tip to the weld. The long arc length will produce a quite (whoosh) spray sound. A long spray arc length will also result in a wider plasma on the part surface. This can result in too much energy on the weld surface resulting in too much surface weld fluidity and possibly weld undercut.





If the spray current is sufficient. and the arc length (distance from the wire tip to the weld) is too short, the weld voltage is set too low. In this condition the weld wire is driven into the weld causing explosive short circuits, resulting in weld expulsion, (spatter) and an inconsistent harsh crackle sound. To set the optimum spray volts. The tip of the spray transfer MIG wire (arc length) should be less than < 0.040 from the weld surface. As the weld stream transfers from the wire tip, part of the weld stream will short circuit with the weld producing a consistent crackle sound. If the spray volts are set too high, no short circuits take place and the weld produces a quite spray sound.

 

SPRAY TRANSFER & THE CLASSIC AUTOMOTIVE FRAME WELDS

Its a sad statement this is a Ford truck frame, the welds are made by robots. In this instance you see poor robot welds that have been repaired with poor manual MIG welds.


The next photo shows poor manual MIG weld repairs. As you can see with the manual MIG welds, the parameters utilized are producing more weld spatter than weld. The manual welders making these repair welds had just finished a MIG training course from a well known Detroit weld training facility that provides MIG training for the big three companies and their suppliers. The manual MIG welds are actually globular transfer as evident by the globs at the end of the sparks.



The repair welders were provided with MIG weld training. As with most MIG training programs the training focus was on the welder's skills rather than on weld process control expertise. Unfortunately this is just not a welder process awareness problem, the engineers and managers in this frame plant also know little about MIG weld best practices and weld process controls. For many global auto / truck frame suppliers this is the way it's been done for decades.

A Message to all major auto / truck manufacturers and part suppliers. You may have spent millions on training programs for your employees, yet you could line up all the weld decision makers in your global plants and I doubt you could find five individuals who can see past the weld salesmanship and establish effective MIG Robot Weld Process Controls. This general lack of weld process expertise with the world's most important weld process is a major management issue in the big three and with tier one suppliers.

VISUAL IDENTIFICATION OF INCORRECT MIG WELD PARAMETERS. With a spray transfer weld, imagine a frame or window around the gun nozzle in the center of the window as the gun welds. If that frame is 12 square inches and the spray transfer weld voltage is set correctly, the weld spatter produced will be contained in that 12 inch window.

If the weld spatter profile you see is outside the window and round ball shapes are evident at the end of the weld spatter streaks, you are watching a weld set with globular weld parameters. With globular transfer the weld voltage is typically less than 24 volts and the weld current is less than that required for spray transfer for the electrode wire diameter selected. If the weld spatter profile is straight streaks and outside the 12 inch window as in this picture, the spray parameters are set with the weld voltage set too low and the weld wire is driving into the weld.

Remember with "short circuit transfer welds" that the prime cause of weld spatter results when the welder sets the weld voltage too high.

With "spray transfer welds" we have the opposite, with spray the prime cause of weld spatter occurs when the weld volts are set too low.

 

This Web Site has taken thousands of hours to produce and it will take you many hours to cover, consider purchasing one of my books so you can spend some time with your family?

 

 

This Motorman robot produced poor
welds with excess weld spatter

If the weld decision maker had spent $90 on Ed's Weld Process Control
book he would have set the correct, spatter free weld parameters.

 

Lets see, to reduce weld spatter with short circuit transfer you typically have to decrease the welding voltage. To reduce weld spatter with spray you typically have to increase the weld volts.

I should put this information on a bloody big sign in the middle of the weld shop, or maybe I could invest $90 for each of my welders, and provide them with Ed's process control training books. God what am I thinking? I better not do that, if these guys start reading about weld process controls the next thing you know is they will want my job.

 

USING THE WRONG MIG WELDING TECHNIQUES:
Are personnel in your plant using stick welding techniques for their MIG welds. Many of you will know the following scenario, the plant weld supervisor was hired because he had extensive experience as a stick welder.

The weld supervisor typically knows little about MIG process controls, however he would never tell anyone that. The supervisor made sure all the MIG welders in the plant are using a "whipping weld technique". This is a technique he used when welding with his E6010 electrodes. It's common in North America for many of the weld school instructors to also recommend whipping or weaving actions when they teach the MIG process.

Whipping the MIG gun back and forth, not only produce that distinctive "whoosh whoosh" sound, it also leaves a distinct freeze pattern in the weld. The clearly defined freeze lines on the weld surface are typically 1 to 3 mm apart. The problem with the whipping technique is whenever you take a MIG gun away from the leading edge of the weld you reduce the weld root fusion potential.

When using the whipping technique, the thicker the part the greater the potential for lack of weld fusion. Cut and macro the welded parts in which a whipping technique has been used and you will likely find serious lack of fusion issues especially on fillet welds. The MIG weld penetration is greatly influenced by the force and concentrated heat of the MIG arc plasma. Welders should keep their forward motion as steady as possible, with the MIG wire always on the leading edge of the weld.

 

When should you use a MIG weld weave? When manual MIG welding, manual welders will provide inconsistent weld weaves that will result in inconsistent side wall weld fusion. In contrast with a robot, any time it's necessary consider a weld weave, especially for fillet welds >1/4 >6mm. The reason a robot can use a weld weave successfully is the robot weld weave is a "controlled consistent function" The robot weld weave can benefit sidewall weld fusion on fillet welds > 5 mm, or reduce weld burn through on gage heat sensitive parts. If a robot weld weave is necessary, try a slight oscillation in the center of the weld puddle rather than setting the weave so it visits the weld edges.

 

MIG GALVANIZED

Question: Ed, I was wondering what is the best MIG weld transfer mode to use on coated, galvanized steels < 2.5mm and what is the best way to deal with the zinc to avoid weld porosity? We currently use E70S-6 wire with 92%Ar - 8% CO2.

Answer: The first thing to consider is the part thickness. If the parts are less than 0.070 short circuit is the logical choice as it reduces weld burn through potential especially when those thin gage parts have gaps When welding > 0.070 with robots, the pulsed mode, globular or spray transfer may be used. Please remember f you have zinc on the weld surface you have zinc in the welds irrespective of what the weld salesman informs you or the weld transfer mode utilized. It's logical when welding on galvanized parts to;

[a] Provide as much weld energy as possible to reduce the weld porosity potential.
[b] Maximize weld current density by using the smallest weld wire diameter.
[c] Use the highest possible weld current.
[d] Remember fast weld speeds result in fast weld solidification which adds to the porosity trap.
[e] Avoid concave fillet welds, make the welds a little larger or longer than they need to be.
[f] Use 035 E70S-3 wire as it has less silicon than E70S-6.
[g] Use high energy 80 argon - 20 CO2 for your short circuit and spray applications.
[h] Use short wire stake out 3/8 - ½.
[i] If the coating is really thick consider two weld passes.
[j] When the arc becomes very unstable use the back hand technique as it will improve arc stability.

The bottom line, as this weld will always have excess contaminates in the weld keep your focus on providing a little more weld and ensure the welds you produce at least provide consistent weld penetration.

ELIMINATE WELD POROSITY:

Weld porosity, a cavity, a discontinuity that forms from a gas reaction. The porosity can be trapped in the weld or at the weld surface. The porosity is typically round in shape but can also be elongated


ROBOTS AND MIG POROSITY. When you find the robot weld porosity is always at the same location and the porosity is not at the weld starts or ends, examine the robot movement and see if the robot arm is causing a restriction of the gas flow line. Also it's common with robot cells to see a severe gas flow restriction due to the narrow orifice found in gas line connections. In a robot cell its critical to measure gas flow as it exits the gun. If the porosity is at the weld start or stop increase the gas pre flow and post flow times.

MIG & FCAW POROSITY:
Weld porosity, a cavity or a discontinuity that forms in the weld from a gas reaction in molten metal.

The porosity can be trapped in the weld or evident at the weld surface. The weld porosity is typically round in shape, but can also be elongated.

Porosity is caused by the absorption of oxygen, nitrogen and hydrogen into the molten weld pool. The gases are then released on solidification and may become trapped in the weld metal.

Nitrogen and oxygen absorption in the weld pool usually originates from inadequate or contaminated gas shielding, leaks in the MIG gas line, excess gas flow rates, draughts and plate contamination.

Hydrogen can originate from a number of sources including moisture from the electrodes,moisture on the parts, contaminates on the workpiece surface. Hydrogen trapped in the aluminum porous surface is common.

Special mention should be made of the weldable (low zinc) primers. Its typically not necessary to remove these primers, however if the primer is put on too thick, porosity can result.

CLUSTER WELD POROSITY. A localized group of pores with random distribution. Causes. Arc blow, insufficient, inconsistent or excessive weld gas flow, material or weld wire contamination, (low) weld parameters or poor technique.

PIPING, WORM HOLE, WAGON TRACKS POROSITY. Sometimes called "wagon tracks". Typically found in the center of the weld, parallel to weld axis. Classic porosity when moisture is evident in gas shielded flux cored wires, (the cheaper the product the more prone to wagon tracks). When I have to demo Lincoln all position gas shielded flux cored products I am always concerned about the porosity I may find. I have less trouble with Alloy Rods flux cored products.


Increasing the flux cored wire stick out and increasing the wire feed rate helps by adding energy to the wire. Baking flux cored wires and storing the wires in a dry environment also reduces porosity potential. Slow weld speeds, make welds larger, avoid weaves. All recommendations are intended to increase the weld arc energy and decrease the weld cooling rate.

Worm holes are elongated gas pores producing a herring bone appearance on a radiograph. Worm hole porosity is common in gas shielded flux cored welds when the electrodes have too much moisture in the wire flux.

WELD ROOT POROSITY.
Weld root porosity frequently occurs when MIG welding using "argon oxygen" (oxidizing) mixes on parts >6 mm. With these gas mixes the resulting root is typically narrow, finger shaped. The root finger area solidifies rapidly trapping porosity. To reduce the root weld porosity, change to a higher energy,argon 15 - 20 CO2 gas mix. Increase the weld parameters, slow the weld speed and avoid weld weaves.

ALIGNED WELD POROSITY. Linear porosity, an array of small round pores typically found in a line. Often caused from the base metal lubricants or metal surface contaminate. Add weld energy (increase wire feed), increase push angle allowing the arc to break up surface oxides ahead of weld.


SCATTERED WELD POROSITY. Weld porosity scattered randomly throughout the weld or welds. If the MIG weld surface is gray and looks oxidized, the porosity is typically a result of insufficient gas flow. If the weld surface looks clean with scattered porosity the porosity is usually caused by the base metal part or electrode contamination, or perhaps the weld data used causes the weld to freeze too rapidly

LARGE PORE WELD POROSITY. If weld surface is clean and does not look oxidized, the large pore MIG / FCAW porosity could be a result of excessive gas flow. Gas turbulence is caused with gas flow greater than 40 CFH/hr. Optimum MIG and flux cored gas flow for carbon steels is 25 to 35 CFH/hr, the gas flow should be measured as it exits the gun nozzle. If the weld surface is dirty (oxidized) the cause of larger pore porosity is often a result of insufficient gas flow, less than 20 CFH /hr.

Do you suffer from arc blow?

CORPORATE WELDING LIABILITY:

WELDING, HOT ROLLED STEELS & MILL SCALE.

The following are typical concerns generated when MIG welding hot rolled carbon steels with mill scale.

[a] inferior, sluggish external weld appearance,
[b] excess weld spatter if parameters not adjusted correctly,
[c] increased porosity,
[d] lack of weld fusion,
[e] slower weld travel rates.

Many weld shops ignore the marginal or lack of weld fusion that can be attained from MIG welds when the sluggish melting mill scale is added to the steel weld melt pot.

I am always amazed by the weld shops that are quick to inform me they have no time to devote to "grinding the steel before the welds are made", however after welding the welders typically spend extensive time grinding the spatter that was influenced by the mill scale.

The wise weld decision maker does not allow MIG welds on steel applications in which the surface condition of the steel can negatively influence the weld quality. Automated plate blast equipment can today be purchased for around $100,000.00 and lets face it, grinders cost less than $60.

When it comes to welding on mill scale or contaminated plate there is an alternative to the MIG process, "flux cored". The bottom line, the influence of the mill scale or any contamination to a weld should be given careful consideration. The liability consequences of weld failures should be of concern to all involved in welding.

The 0.035 (1mm) Electrode Wire. You do not need sophisticated electronics to attain the spray weld transfer sweet spot.

Hopefully you have been in my MIG short circuit section and learnt the simple unique clock method I developed for both MIG and flux cored weld parameter selection. With an 0.035 (1mm) carbon steel or stainless MIG wire you were provided the optimum short circuit wire feed and weld parameters range.

The following is an example of the way I used my clock method to simplify setting spray transfer weld parameters with the 0.035 wire. Just as short circuit has an optimum narrow weld parameter range so does spray transfer.

For decades most wire feeders have provided a wire feed rate of 600 to 800 in./min The average wire feed rate is 700 in./min (18 m/min) or approximately 70 inches/min (1.8 m/min) per wire feed control turn.

The Traditional MIG Wire Feed and Ed's Weld Parameter Clock Method,
as taught in all his reference books and process control training resources:

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The optimum 0.035 (1mm) spray transfer wire feed range is found
on most traditional, none digital wire feeders
between 1 and 5 o'clock positions, >420 ipm.

The Clock Method, 0.035 (1mm) Carbon Steel MIG Wire.
The Spray Transfer Weld Current and Wire Feed Settings

A MIG weld decision maker should always be aware for a specific electrode diameter:

[a] the weld transfer mode, weld current "start point"
[b] the weld transfer mode wire feed "start point"
[c] the weld transfer mode start voltage,
[d] the weld transfer mode weld "parameter range",
[e] the weld transfer mode "optimum" wire feed and voltage start points.

Understand the MIG settings, now that would be a fresh approach toMIG welding in my shop. You know this weld process control stuff is starting to make sense.

 

With the clock method, If you know the part thickness, for any steel application you can instantly set the correct wire feed setting, weld speed and voltage for any MIG or flux cored consumable and application. FOLLOW THIS LINK.

HOW TO SOLVE THE GREAT MYSTERY OF MIG WELDING. USE WELD PROCESS CONTROL EXPERTISE, INSTEAD OF SALES ADVICE.

 

As frequently mentioned, today's primary welding equipment and consumable manufacturers bear a great part of the responsibility for the extensive MIG weld process chaos and confusion that dominates global MIG weld shops. Unfortunately in 2008 many welding personnel will still rely on these companies weld advice.

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So you Want Free, Effective Welding Advice. More than twenty years after the MIG process was developed, in a time when I was starting to develop the MIG weld clock method, the most popular welding book available to North American welding shops was the Lincoln "Procedure Handbook of Arc Welding" twelve edition. Many Lincoln employees refer to the Procedure Handbook as their "welding bible". This book provided four whole pages on the MIG process welding carbon steels.

The following is the MIG advice Lincoln provided it's weld customers from its welding bible

Lincoln welding advice after the MIG weld process had been around for more than thirty years.

[a] Lincoln advised that spray transfer is not attainable with argon CO2 mixes. All the other major weld equipment, consumable and gas companies, would make similar statements, such as spray transfer is not attainable with argon plus 25 - 20 or 15% CO2.

Weld reality check. The Lincoln and other ridiculous CO2 gas statements were common right up to the late nineties. Its obvious that the weld decision makers in the welding product companies never bothered to put on a welding shield on to evaluate the MIG spray arc. I also doubt that most of the individuals responsible for the written books and brochures from the corporations that produced welding products, simply lacked the necessary MIG process expertise to provide practical MIG welding facts.

[b] Lincoln advised that for MIG spray transfer on carbon steel welds use a MIG welding gas flow set at 40 to 60 CFH/hr.

Weld reality check. A gas flow rate of >50 CFH/hr would possibly cause weld puddle turbulence leading to porosity, also it could almost double the weld gas bill.

[c] Lincoln advised for short circuit welding use a gas flow rate of 10 to 15 CFH/hr.

Weld reality check. For gods sake if you MIG weld with this low gas flow rate don't weld anyplace near a draft.

[d] Lincoln advised for spray welding 3/16 (5mm) plate use an 062 wire at 375 amps.

Weld reality check. No wire size logic with this advice, also this welding current will melt through the 3/16 part.

[e] Lincoln advised For short circuit welding 062 (1.6mm) gage use an 0.030 MIG wire at a wire speed of 170 in./min.

Weld reality check, with an 0.030 wire the practical setting would be close to 300 in./min, and why bother with an 0.030 wire with its higher costs and ridiculous feed problems?

Yesterday. It was not just Lincoln that had no clue on the fundamentals of the MIG process. Linde, Miller, Hobart, Liquid Air, BOC, Air Products, Liquid Carbonic all made major inappropriate welding process statements about the welding and consumable requirements for MIG welding.


Today many of the companies mentioned still have minimal depth in the MIG process and it's potential. If these companies have welding employees with MIG process expertise, typically their opinions will be less important than what comes out of the mouths of the individuals in their sales and marketing departments.

The bottom line of course for these organizations is increased market share and increased profitability, always has and still does come through weld sales hype.

 

FOR THE LAST FOUR DECADES THE WELDING INDUSTRYHAD TO GET IT'S WELD PROCESS EXPERTISE AND ADVICE FROM SOMEWHERE, UNFORTUNATELY IN TOO MANY INSTANCES THE WELD SHOPS WENT TO THE WRONG SOURCES.

I hope that if you have got this far you will have got the message. The weld reality is weld process expertise will not typically come from a salesman or from someone with an AWS certificate. If you are a weld decision maker focus should always be maintained on your level of weld process and application expertise.

Of the 20.000 weld decision makers that visit this site each day, I would guess that nine out of ten may this week spend $30 - 40 on booze, $60 in a restaurant, $10 on coffee, $30 for cigarettes, $30 on cable TV, and $6 for videos. Many of the same welding personnel when requiring weld information will ask a salesman for their "free welding advice". Its a sad statement that only a few individuals will consider investing a few dollars in their careers and purchase a practical weld book or video to control the process.

Career opportunities occur sometimes through fate, sometimes by being in the right place at the right time, sometimes from knowing someone. The greatest opportunities for career advancement in the welding industry will always come to those individuals with the most weld process control expertise. Click here for your keys.

 

 

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