mig wire selection



mig wire selection

Postby grumpyvette » February 24th, 2009, 11:49 am

http://www.esabna.com/us/en/education/k ... ection.cfm

http://www.tregaskiss.com/hm/228/61/sel ... -wire-size

viewtopic.php?f=60&t=77

viewtopic.php?f=60&t=1669

viewtopic.php?f=60&t=10601

viewtopic.php?f=60&t=9745



http://reviews.ebay.com/Mig-Welder-Sele ... 0003813279

http://www.airgas.com/content/details.a ... 0000000143

http://www.airgas.com/content/details.a ... 0000000164

http://www.bakersgas.com/mig-shielding- ... guide.html

http://www.mig-welding.co.uk/tutorial.htm

http://www.hobartwelders.com/elearning/#mig

http://www.weldingtipsandtricks.com/mig ... icles.html

keeping mig wire rust free is the key, most quality mig wires lightly copper wash coated ,if your not using the spool in the welder for weeks at a time ,take it out, put it in a re-sealed 2 gallon zip lock plastic bag, laid on a couple sheets of paper towel with WD40 lightly sprayed on the towels, it will last for years sealed like that

heres a few tips
If you have a hard time judging MIG wire diameter or sheet metal gauges, they make a tool for that little issue in lack of judgmental skills
even the $20 import version is accurate enough for that use!
Image
this link might be useful
http://www.engineersedge.com/gauge.htm
Image
http://www.harborfreight.com/6-inch-dial-caliper-66541.html
Image
An easy way to think of the two is this:

DC(-) Straight = more heat in the base metal (the metal melts faster)
DC(+) Reverse = more heat in the wire (the wire melts faster)

larger wire diam. takes more amps to melt and tends to result in more heat transfer to the area surrounding the weld, thinner wire tends to melt faster and impart a bit less heat to the surrounding area, obviously weld gun movement speed and wire feed speeds and amp settings can vary the results also, but smaller diam. wire tends to localize the heat to some extent, thats one reason youll tend to use thinner wire on thinner sheet steel as your going to use less average amps and less over all heat on a smaller area to generate the molten weld pool.

mig wire should be selected based on what your welding, a .025 wires great for sheet steel body parts and .030 makes a good compromise choice for both sheet metal body parts and thicker stuff up to about 3/16" thick.

youll usually get a better weld if your a bit too high on the amp setting than a bit too low, so if your not real sure try to keep it hot

most mig welders have a chart or a manual that gives suggested wire diam. feed speeds and amp ranges for different applications.
naturally you'll need to make adjustments to the wire feed mechanism if you change wire diam. and you'll need to keep the wire clean and dry to prevent corrosion.

shield gas flow rates will also need to vary but 25 cubic feet per hour is a good basic rate to start with with a .030 wire most guys working on cars will use.

youll need a good die grinder and stiff stainless steel brush to clean potential weld surfaces of corrosion and paint.

beveling the edges of two parts to be welded where they will join tends to allow a better weld joint.

welding so the joint is directly down is obviously preferred, as hot molten metal tends to run with gravity, if working on a vertical surface joint working from the top down tends to leave a cleaner less bulged or protruding joint bead surface requiring less clean-up grinding,than working from the bottom upward.

tack welding thin metal joints in a stitch, skip, stitch pattern limits heat distortion


Making a Sound MIG Weld

Image

Image

The ability to make a good MIG weld is extremely important to the success of an auto repair technician. In fact, almost every welding repair made on a unibody car, light truck or van can be made with the Metal Inert Gas (MIG) welding process. For this reason, there are well-accepted standards and practices for producing sound MIG welds.

Note: This article is written for the person with a basic familiarity with welding who wants to practice and improve their welding technique. The process of arc welding poses several potential hazards that must be guarded. Therefore, all information relating to the safe operation of welding equipment and welding processes must be fully understood before attempting to begin work. Always read and follow the safety information in the operator's manual or contact the manufacturing company when in doubt.

What Needs Welding?

The front driver's side corner of a vehicle receives more damage than any other area. Parts damaged in this area include the upper rail, frame rail, radiator core support, and fender aprons. Other parts often damaged include the rear body panels, trunk floor, and lower rear rails. To make these repairs, the technician must thoroughly master all-position welding. It is important to practice so that you feel confident with making sound welds in all positions.

One way to become confident in your welding quality is to use a simple welding machine, such as the Millermatic® 185 from Miller Electric Mfg. Co. It comes complete with a package to get you started, including a 6 ft. power cord with plug, 10 ft. MIG gun and cable assembly, and 10 ft. work cable with heavy duty clamp. The package also includes a gas solenoid valve, flow gauge and 5 ft. gas hose, and factory installed running gear/cylinder rack.

Before making a repair weld, make test welds on material of the same type, thickness, and joint configuration. Visually inspect and destructively test the practice weld to ensure that it is sound before welding on the vehicle. Fine tuning the welding parameters and your technique on test welds improves the quality of the repair.

Welding In the Flat Position

For a flat joint, such as a butt joint, hold the gun at a 90 degree angle to the workpiece, directing the filler metal straight into the joint. A small, back and forth motion with the gun can help fill a large gap or when making multiple passes.

For a fillet weld on a T-joint, keep the gun at a 45 degree angle, or equal distance from each piece. When making multiple weld passes, the work angles change slightly. This helps avoid uneven weld beads and undercuts.

For a fillet weld on a lap joint, angle the gun between 60 and 70 degrees. The thicker the metal being welded, the greater the angle.

Plug welds should be made with the weld in the flat position if at all possible. Using a spiral-type technique, weld in a slow motion around the edges of the hole, making a complete circle before working toward the center (starting the spiral too soon can create pinholes). When welding around the edge, angle the gun slightly, somewhat like you would for a lap joint. Keep the gun perpendicular when filling the rest of the hole.

Horizontal

Because of the effects of gravity, the gun work angle must be dropped slightly by 0 to 15 degrees when welding horizontally. Without changing the work angle, the filler metal may sag or rollover on the bottom side of the weld joint. The travel angle, whether using a push or a drag technique, generally remains the same as for a weld joint in the flat position.

On thick metal when making multi-pass welds, or to bridge a slight gap where fit-up is poor, weave beads may be used to fill a weld joint. A back-and-forth weave, with or without a slight arch, is used in the horizontal position. A slight hesitation at the top toe of the weld helps prevent undercut and ensure proper tie-in of the weld to the base metal.

Voltage and amperage settings for welding in the horizontal position are usually the same, or very slightly less, than settings for welding in the flat position. However, note that if the wire diameter is too large, the resulting heat and size of the weld puddle may be too great to allow the weld puddle to freeze quickly, and the weld may rollover.

Vertical Positions

Vertical welding, both up and down, can be difficult. This makes pre-weld set-up very important for making high quality welds. Since you are fighting gravity, consider reducing the voltage and amperage 10 to 15 percent from the settings for the same weld in the flat position.

Know when to weld vertical down and when to weld vertical up. For vertical down welding, the welder begins at the top of a joint and welds down. This technique helps when welding thin metals because the arc penetrates less due to the faster travel speed. Because vertical down welding helps avoid excessive melt-through, welders sometimes place very thin materials in the vertical position even if they can weld them in the flat position.

When welding vertical down, angle the gun slightly back into the weld puddle at a 5 to 15 degree angle. For thin metal where burn-through is a concern, angle the gun slightly up and pull it downward (i.e., direct the wire away from the weld puddle). Either way, keep the electrode wire on the leading edge of the weld puddle. A very slight weave may help flatten the weld crown.

The vertical up technique - beginning at the bottom of a joint and welding up - can provide better penetration on thicker materials (typically 1/4 in. or more). The travel angle of the gun is a 5 to 15 degree drop from the perpendicular position. A slight weaving motion can help control the size, shape and cooling effects of the weld puddle.

Making a plug weld in the vertical position is somewhat similar to making a vertical up fillet weld. For a vertical plug weld, the filler metal is deposited upward along one side of the hole. Then, another bead is deposited from the bottom to the top on the other side of the hole. Alternate sides until the hole is filled. For thin metal, use a similar technique, but weld in the vertical down position to prevent burn-through.

Overhead Position

Drag, push or perpendicular gun techniques can be used for welding overhead. But, because of gravity, travel speeds must be fast enough so that the weld metal does not fall out of the joint. Also for this reason, weave beads should not be too wide. Using smaller diameter electrodes (e.g., .023 in.) and lowering the voltage and amperage help keep the weld puddle small and more controllable, too.

Work angles and travel angles for the overhead position can be thought of as the same angles for the flat position, only upside down. However, be sure to keep the gun nozzle clean, as spatter can build up much faster when overhead welding. Also, because the shielding gas flows upward, you may have to increase the gas flow rate to ensure proper coverage.

Travel Speed and Stickout

Travel speed and electrode extension (or stickout) also influence the shape and quality of a weld bead to a significant degree. Travel speed is the rate at which you move the gun along the joint. Many experienced MIG welders can determine the correct travel speed by judging the weld puddle size - in relation to the joint thickness - and keeping the arc on the leading edge of the puddle.

Stickout is the length of unmelted electrode extending from the tip of the contact tube. Changing the stickout - which occurs with variations in the distance of the contact tube to the workpiece - causes the voltage and amperage to vary, as well as changes the shape of the weld bead.

Generally, maintain a stickout of 1/4 to 1/2 in. Note that when starting a weld, a short stickout helps ensure a good, hot start; a longer stickout - once you've established the arc - can help bridge a gap when encountering poor fit-up. [Note: Long stickouts promote poor starts.] For critical welds, maintain a constant stickout.

More Practice

To make a sound weld, you must learn to combine the mechanical techniques noted in this article into one fluid welding motion. Practice so that welding on all joints in all positions becomes second nature.

For more information on Miller Electric and its MIG welding products, call 1-800-4-A-Miller (1-800-426-4553) or visit the website at http://www.MillerWelds.com.

Miller's 142-page Gas Metal Arc Welding handbook provides a comprehensive, yet easy to read, explanation of the GMAW, or MIG, process. It contains detailed instructions on how to set up MIG equipment, set MIG variables, select the correct shielding gas, welding techniques, safety, and troubleshooting. Cost is $25. Call Miller at (920) 735-4356 and ask for publication #151 682, Gas Metal Arc Welding
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: mig wire selection

Postby grumpyvette » October 18th, 2011, 1:45 pm

I was over at a friends house today for a couple minutes ,as he called me op to show me his new toy!,
he just purchased a miller 140 amp mig he paid $750, then needed to rent a bottle of gas and buy mig wire, self darkening helmet, gloves, etc so he had about $1100 in the deal when he had it operational
he had tried welding and gotten less than ideal results, but within a few minutes and a few minor changes got him grinning

READ THRU THIS THREAD AND SUB LINKS
viewtopic.php?f=60&t=1594

Millermatic® 140 with Auto-Set™
http://www.welders-direct.com/mm5/merch ... Code=m-mig
welding package welds 24 gauge - 3/16 in


I had strongly suggested he get a miller 211 as its a good deal more versatile and the total cost difference would be only about $300 more, if your going to spend $1100, for a good welder it seems rather foolish to me not to kick in $300 more for one with MARKEDLY more VERSATILITY

http://www.welders-direct.com/mm5/merch ... Code=m-mig
Millermatic 211 Auto-Set with MVP
Welds material from 24 gauge to 3/8 in thick in a single pass.

but what he will use it for (mostly body work and sheet metal welding) I can see why he might have made the choice he did, well anyway he starts to get familiar with the welder and he like all new welders, he needs to practice a good deal, to get good results,like we all did,......or still do... but he was at a serious disadvantage, as he had loaded the mig welder with cheap imported .035 wire and he was trying to weld on a scrap fender that looked to be 22 gauge, .035 wires a bit to heave for best results on a 22 gauge fender. I had a spool of .025 wire and upping the gas flow rate and swapping to the thinner welding wire made welding, that thin fender a totally different and more easily learned on experience.
the reason I bring it up is that even with a really nice welder use of the wrong gauge wire and not having the gas flow rates correct produced really far less impressive results, than he might expect, and if he had not had someone watching what he was doing that had some experience he could very easily have concluded that the welder was at fault, when the welder was working just fine, but you obviously need to match the welders amp and gas flow settings and wire size to the application. so read the manual and do a bit of research before you start, it made a world of difference in his welding results
youll want to carefully measure the cars body sheet metal gauge and ideally get replacement floor pans made from the same or heavier gauge metal,
youll tend to get better welds if the mig wires on the smaller end of the range for the gauge of sheet metal being welded.
DON,T IGNORE the fact that MIG WELDING REQUIRES A SHIELD GAS, welding without that makes the weld less solid and messy, harder to clean up and surely less solidly connected.


READ THE LINKS
viewtopic.php?f=60&t=1283
Image
Image

a 140 amp lincoln MIG welder you can buy for under $500 will make good sheet metal welds if properly set up,
but a 180 amp mig ,from miller or lincoln, is going to handle FAR more applications and be more versatile in the long run, so ID advise spending a bit more up front, youll not regret it later

http://www.welders-direct.com/mm5/merch ... Code=l-mig

http://www.welders-direct.com/mm5/merch ... Code=m-mig

Image

http://www.harborfreight.com/adjustable ... 46092.html

http://www.harborfreight.com/welding-gloves-39664.html

http://www.harborfreight.com/3-piece-we ... 94128.html
dirt cheap yet functional
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida


Return to Welding Tips and Welders

Who is online

Users browsing this forum: No registered users and 2 guests

cron