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Monday

aluminum welding tips

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This page is far from a comprehensive tutorial; it's just some tips and some links to more authoritative information. It's intended for people who want to learn to weld aluminum, but have little no experience in welding aluminum, or even in welding in general. This was a description of me a couple of months ago. In my attempts to learn to weld aluminum, I gathered all the information I could find from a lot of different sources – the very simplistic and under-informative manual that came with the welder, lots of reading on the web, basicwelding books with very short sections on aluminum, and very advanced books that were written for engineers which had more equations and formulas than practical welding advice. Then using what I had learned, coupled with a lot of trial and error, I eventually figured out how to get two pieces of aluminum to stick together without cracking, warping, shriveling, or breaking. Along the way I made several key discoveries that would have saved me a lot of trial and error time if someone had just told me about them. I thought I’d share the little I do know and maybe it’ll help someone out there learn to weld aluminum faster than they would have otherwise.
    What do you equipment do you need?
  1. A TIG (GTAW) welder. Most sources say a TIG (Tungsten Inert Gas) welder, also called a GTAW (Gas Tungsten Arc Welder), is the best method of welding aluminum. I’ve heard aluminum can also be welded with a MIG welder or a stick welder or even a with a gas torch. Since I’ve only used the TIG for aluminum, that’s what I’ll be writing about. TIG welders are fairly expensive and it’s hard to justify buying even the lowest quality units unless you are making money with your welding. The more expensive units ($6000) have a bunch of features that make doing high quality welding on aluminum possible. We have a bottom-of-the-line ($2500) Hobart welder that is described as good for the hobbyist or farmer. As tempting as it was to blame the machine while I was making charred bits of twisted metal instead of neatly welded joints, I came to realize that adequate welds can be made, even with a cheapo machine. What do you get when you spend the extra money on a welder? More amperage (meaning the ability to weld thicker metal), water cooling (I don’t know what advantage this provides, but the gas hood glows orange on our air cooled unit when it’s at maximum output, and it’s only 165A), square wave AC (this allow grinding a ceriated tungsten to a point for a more stable arc), frequency adjustment, and adjustment of the ratio of positive to negative current for better cleaning or penetration. Since my machine has none of these features, I can’t offer any advice on how to make use of them.
  2. Good welding gloves. I have crappy welding gloves and the painful blisters to prove it.
  3. A good welding helmet. I hear the gold tinted auto darkening helmets are the best. I have a $20 helmet with a tiny window that falls off my head when I flip it down.
  4. Argon gas. Mixes will not work for aluminum with the exception of an Argon / Helium mix. Don’t take the tank from you MIG welder to use on your TIG welder – it won’t work at all. You will just make a bunch of burned metal and soot.
  5. Aluminum welding rod. I got the 4043, which seems to be the most recommended. There is a good chart at http://www.tinmantech.com/ on which rod to use for which alloys as well as a ton of excellent metalworking and aluminum welding information. At this point I don’t have any idea how to tell one alloy from another, and I'm not doing any mission critical welding, so don't worry about it. The 4043 has been working well for me.
  6. A dedicated stainless steel brush that you only use for aluminum. Write “aluminum” on it so it doesn’t get used for anything else.
  7. A metal bench would be nice. I don’t have one. Stopping your weld to put out a fire is a pain in the ass. This happens to me all the time.
  8. A squirt bottle with water. This is not for cooling the work, it’s for putting out small fires that aren’t big enough to use a fire extinguisher on. Cooling aluminum rapidly may cause it to crack in or near the weld.
  9. A fire extinguisher might not be a bad idea if you don’t want to get fired for burning down the shop.
  10. This next one is VERY important: a heavy long sleeve cotton work shirt. TIG welding produces more UV radiation than any other welding process. The first time I used the TIG I was wearing a tee shirt. I used the welder for 10 min if even that. The front of my biceps and a spot at the bottom of my neck were painfully burned with blisters and peeling skin. I just takes a few minutes to do some serious burning.
  11.  Clamps or Vise Grips or whatever your going to use to hold your work in place and some blocks or bars of aluminum or copper to use as heat sinks.
That’s enough of the shopping list. On with the useful tips
Tip #1 -- Clean the aluminum. This is the most important tip I have. I read this in several places before I began to practice welding, but it didn’t seem so sink in and I wasted a lot of metal by trying to weld two pieces of dirty aluminum together. ALUMINUM THAT LOOKS BRAND NEW AND CLEAN IS ACTUALLY DIRTY. IT’S NOT LIKE STEEL.
    Here are some of the signs that your aluminum is dirty.
  • A wandering arc -You can’t get a puddle started without burning through or distorting the metal
  • Your filler won’t blend into the puddle, instead it rolls into a difficult to re-melt ball.
  • The aluminum seems to have surface tension, like beads of water on a waxed surface.
  • When trying to join 2 pieces the edges curl away from each other and form an even bigger gap.
Here's what's happening: Aluminum quickly forms an more or less invisible coating of aluminum oxide. Aluminum oxide melts at three times the temperature of aluminum. When you try to weld uncleaned aluminum, the aluminum under the aluminum oxide coating will melt but the aluminum oxide coating will stay solid and act as a membrane, much like a water balloon. When you finally succeed in penetrating the coating, the very runny aluminum inside will flow out all at once, much like a bursting water balloon.
    Here’s how I prep the aluminum for welding.
  • First, I spray the aluminum with acetone. Don't use brake cleaner unless it's 100% acetone. If you need convincing, check this out -- http://www.brewracingframes.com/id75.htm Thanks for the tip Andrew!
  • Then, I rinse the aluminum in water, just in case there's any nasty residue. The aluminum should be completely dry before welding, including all of the nooks and crannies.
  • Then, I use a stainless steel brush (make sure the brush is stainless, I've read this is important) to scrub the aluminum shiny clean around the area to be welded.
Some articles I've read suggest that the aluminum should be scrubbed in one direction only to avoid working contaminants into the aluminum. I don't always follow this rule and I haven't noticed any problems stemming from it, but I'm not working on anything too critical and I'm far from an expert. I've also read that 3M Scotchbrite pads are a good way to prep aluminum. If you do not weld on the aluminum immediately after cleaning, you should give it a touch up cleaning before you start to weld. I've read eight hours exposure after cleaning is the maximum acceptable without re-cleaning.

Tip #2 -- Clamp your work to a heatsink made of copper or aluminum whenever possible. Aluminum transmits heat very well. Once the area you trying to weld gets hot enough to melt, the rest of the work is likely to be so hot that it's shrinking and warping. Using a heat sink under the area being welded will absorb some of the heat and help keep the work from warping.
Tip #3 -- Preheat before welding. This makes it a LOT easier to weld aluminum. This is not a subject that is without controversy. The issue is that some aluminum is heat treated, and by heating and cooling heat treated aluminum it will get softer. I've read opinions ranging from "heat treated aluminum should never be preheated" and "preheating is a crutch for inexperienced welders", to the opposite extreme, "aluminum should always be preheated to prevent cracking". Recommended preheating temperatures range from 275 deg. F, to 500 deg. F. I suspect that many of these opinions are correct in their own contexts. The proper procedure likely varies for a welding a space shuttle door in a vacuum chamber and welding a cracked cylinder head. One thing I know for sure is welding thicker pieces of aluminum with our 165A welder without preheating is impossible. I once tried to weld two pieces of 8 mm thick aluminum together without preheating The result were a very shallow and weak weld, a circuit breaker that tripped twice and the welder overheated and shut down after every two inches welded. I don't have an oven handy, so I use a propane torch aimed at the heat sink I clamp the work to and an infrared thermometer to tell when it's hot enough. I usually can't get the work any hotter than 350 deg., so that's the temperature I use. I've considered getting a cheap used electric oven or an electric hot plate but haven't yet. I don't use the torch directly on the work. I don't know if it would cause a problem or not, I feel more comfortable heating the heat sink instead.

Tip #4 -- If the tungsten gets contaminated, stop welding and fix it. When the tungsten gets touches the weld pool or the filler, the arc becomes unstable and the weld quality goes way down. This happens to me a lot, unfortunately. The best method for fixing this is to remove the tungsten, lay it on a flat surface with the contaminated part hanging over the edge, hit the contaminated part of the tungsten (it will snap right off), reinstall the tungsten, change the polarity to DCEP (direct current electrode positive), strike an arc on some scrap metal to re-ball the tungsten, switch back to AC high, and you're ready to weld again. By the way, KEEP YOUR GLOVES ON WHILE YOU DO THIS! Otherwise you gonna have a nasty burn. This only takes about 30 seconds once you've done it a few times.

Tip #5 -- Fit the parts together as tightly as possible leaving no gaps. When using a MIG welder, I've found it fairly easy to fill gaps between the two pieces of steel being welded. However, I've found it very hard to do this while welding aluminum with the TIG. The heat from the TIG is very localized. When there is a gap, and heat is applied to the metal on one side, the metal pools on that side, but metal on the other side stays solid. You can alternate from side to side to get both sides to pool, but when I do this, I usually end up with a wider gap than when I started. The only way I've found to fill a gap is to "slop" a glob of filler across the gap, then work on the filler until it melts into both sides, then build off of the filler. This is hard to do. You can save a lot of time by using a file or die grinder and making the part fit together better before you start welding. The tighter the pieces are pressed together and the fewer the gaps, the easier the welding is.
    Tip #6 -- A few "rules of thumb" for base settings
  • Use one amp per .001" of material thickness. Set the amperage a higher than the maximum you expect to use and use the foot pedal to back it down.
  • Use pure tungsten for aluminum if you have a cheaper (non-square wave) welder like me.
  • Use a 2% ceriated tungsten ground to a point if you have a more expensive (square wave) welder
  • Use a 1/16" pure tungsten for 30 to 80 amps
    Use a 3/32" pure tungsten for 60 to 130 amps
    Use a 1/8" pure tungsten for 100 to 180 amps
    Use 15 to 20 CFH Argon flow
  • Use a filler rod size equal to the tungsten size. Adjust the tungsten to project from the hood a distance roughly equal to the diameter of the tungsten.
  • The arc length should be roughly equal to the diameter of the tungsten.
The first 3 tips were my major breakthroughs while learning to weld. They were the things I wished somebody had told me before I began my frustrating experimentation. There are, of course, many other things to know about welding aluminum, but there are many more complete articles available on the Internet. Follow the links below for some of my favorites.
Click Here!

MIG welding—The basics and then some - Arc Welding Tech Cell - TheFabricator.com

MIG welding—The basics and then some - Arc Welding Tech Cell - TheFabricator.com

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Sunday

MIG WELDING OR flUX CORE

ARTICLE FROM INSTRUCTABLES PM ON MIG WELDING




MIG welding was developed in the 1940's and 60 years later the general principle is still very much the same. MIG welding uses an arc of electricity to create a short circuit between a continuously fed anode (+ the wire-fed welding gun) and a cathode ( - the metal being welded).

The heat produced by the short circuit, along with a non-reactive (hence inert) gas locally melts the metal and allows them to mix together. Once the heat is removed, the metal begins to cool and solidify, and forms a new piece of fused metal.

A few years ago the full name - Metal Inert Gas (MIG) welding was changed to Gas Metal Arc Welding (GMAW) but if you call it that most people won't know what the heck your talking about - the name MIG welding has certainly stuck.

MIG welding is useful because you can use it to weld many different types of metals: carbon steel, stainless steel, aluminum, magnesium, copper, nickel, silicon bronze and other alloys.

Here are some advantages to MIG welding:

  • The ability to join a wide range of metals and thicknesses
  • All-position welding capability
  • A good weld bead
  • A minimum of weld splatter
  • Easy to learn
Here are some disadvantages of MIG welding:

  • MIG welding can only be used on thin to medium thick metals
  • The use of an inert gas makes this type of welding less portable than arc welding which requires no external source of shielding gas
  • Produces a somewhat sloppier and less controlled weld as compared to TIG (Tungsten Inert Gas


MIG welding was developed in the 1940's and 60 years later the general principle is still very much the same. MIG welding uses an arc of electricity to create a short circuit between a continuously fed anode (+ the wire-fed welding gun) and a cathode ( - the metal being welded).

The heat produced by the short circuit, along with a non-reactive (hence inert) gas locally melts the metal and allows them to mix together. Once the heat is removed, the metal begins to cool and solidify, and forms a new piece of fused metal.

A few years ago the full name - Metal Inert Gas (MIG) welding was changed to Gas Metal Arc Welding (GMAW) but if you call it that most people won't know what the heck your talking about - the name MIG welding has certainly stuck.

MIG welding is useful because you can use it to weld many different types of metals: carbon steel, stainless steel, aluminum, magnesium, copper, nickel, silicon bronze and other alloys.

Here are some advantages to MIG welding:

  • The ability to join a wide range of metals and thicknesses
  • All-position welding capability
  • A good weld bead
  • A minimum of weld splatter
  • Easy to learn
Here are some disadvantages of MIG welding:

  • MIG welding can only be used on thin to medium thick metals
  • The use of an inert gas makes this type of welding less portable than arc welding which requires no external source of shielding gas
  • Produces a somewhat sloppier and less controlled weld as compared to TIG (Tungsten Inert Gas



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Tuesday

How to Weld. Solid or Flux Cored Wire?



From Miller Welds

Which is better, solid wire or flux cored wire?
Neither wire is superior over the other. They simply have different properties, which work better on certain applications. As far as performance is concerned, both types of wire produce sound welds with good weld bead appearances when applied correctly and used within the proper parameter settings. Solid wire provides deep penetration in the root and usually has little spatter. Flux cored wire has a larger ball type transfer and produces low spatter levels. In addition, flux cored wire produces a rounder penetration profile with excellent sidewall fusion.
As far as user appeal, both solid wire and flux cored wire are relatively easy to use and are ideal for novice and occasional welders working in automotive, farming and home hobby applications. Operator appeal on solid wire may be better on thinner applications because there is no slag to remove; it is ready to paint; and the weld beads may be more aesthetically pleasing.
Conclusion
The most important thing to remember is not to fall into the "one-size-fits-all" mindset.  Solid wire, self shielded flux cored wire and gas shielded flux cored wire all work well provided they are applied correctly. The type of wire you choose will be contingent upon the location of the work site, thickness of the application, proper shielding gas combination and the type of equipment available. The operator should always clean the work piece prior to welding to ensure optimum weld quality and prevent impurities from becoming trapped in the weld bead. In order to achieve the best possible results, the operator must be willing to make adjustments based on the worksite variables and consider having both solid and flux cored wire available.

More on Welding here

How to Weld. Solid or Flux Cored Wire Continued

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How to Weld.  Solid or Flux Cored Wire Continued

Full Article Here MillerWelds

WHAT TO CONSIDER WHEN CHOOSING SOLID OR FLUX CORED WIRE
Appearance
Many welding operators believe that weld appearance is an important factor.  When you are working on materials less than 3/16 inches down to thin sheet metal (24 ga.), solid wire will produce a clean looking weld. For example, a short circuit transfer with .030-inch solid wire set at 18-19 volts with 160-170 amps and using 75 percent Argon and 25 percent CO2 shielding gas will usually produce little spatter, create a smaller heat affected area and reduce chances of burn-through. As a result, many automotive enthusiasts who specialize in bodywork or those who work with thinner applications prefer solid wire in their operations.
Location
The welder must also consider the location of the work site when choosing between solid and flux cored wire. There are certain environments such as windy locations, where solid wire or gas shielded flux cored wire cannot be used; exposing the shielding gas to wind can compromise the weld integrity. Typically the loss of shielding gas will produce porosity visible in the weld bead.
On the other hand, self shielded flux cored wire is ideal for welding outdoors or in windy conditions. The operator does not have to set up windshields to protect the shielding gases from being blown away because the shielding gas is generated from the burning flux. Since self shielded flux cored wire does not require external shielding gas, it is also more portable than solid wire. This portability is ideal in agricultural applications where field equipment can break down far from the shop. If you are welding thicker metals (16 ga. and above), self shielded flux cored wire also provides excellent penetration.
Thickness, Type of Application and Parameter Settings   
Many novice operators attempt to use "a-one-size-fits-all" wire and shielding gas combination for multiple applications. The most common wire and gas combinations (for solid wire) are .035-inch diameter wire used with a 75 percent Argon and 25 percent CO2 shielding gas. When welding thicker material, however, consideration needs to be given to welding power source output, as well as welding wire diameter. If the .035-inch wire is selected for thicker materials, and the power source is one that is plugged into a 115-volt circuit, the resulting amperage output may not be sufficient to make quality welds. The chance of "cold lap" or "lack of fusion" may increase.
Attempting to use too small of a solid wire for thicker applications (such as on A-frames of an automobile), increases the chance of lower penetration in the root, and could require more than one welding pass. Misapplication of the solid wire (even though strong enough) may also not provide adequate penetration on thicker material.
Although more expensive than solid wire, flux cored wire could help you gain productivity. Flux cored wire typically has the ability to handle the welding of dirtier materials that may have higher levels of rust, mill scale, or oil. Although cleaning is always the proper method of preparing the steel, flux cored wires contain de-oxidizing elements that trap these contaminants in the weld pool and hold them in the slag coverage typically preventing the associated weld problems found when welding "dirtier" steels. Flux cored wire also increases penetration on the side walls and offers the advantage of better deposition rates (the amount of weld metal deposited in a given time period, measured in pounds per hour) when compared to solid wire. Although the operator is initially spending more on materials for flux cored wire, the savings are realized in the decreased production time. 

Miller - Solid Wire Versus Flux Cored Wire: When to Use Them and Why

Gas metal arc welding (GMAW) and flux cored arc welding (FCAW) possess different characteristics that welding operators must evaluate when selecting them for welding applications. To achieve the best results, consider the following factors: thickness of the material, proper shielding gas, wire feed speed and voltage settings, location of the work site and weld appearance. There is no "one-size-fits-all" welding solution and all of the above variables will affect the operator's decision to use solid or flux cored wire. This article will help the novice or occasional welding operators such as farmers, ranchers, motorsports enthusiasts and home hobbyists, understand the basics of solid and flux cored wire and how to maximize the advantages of each.
Read the full Article Here
Solid Wire/MIG Basics
MIG power sources use a continuous solid wire electrode for filler metal and require a shielding gas delivered from a pressurized gas bottle. Mild steel solid wires are usually plated with copper to prevent oxidation, aid in electrical conductivity and help increase the life of the welding contact tip. The shielding gas protects the molten weld pool from contaminants present in the surrounding atmosphere. The most common shielding gas combination is 75 percent Argon and 25 percent CO2. While using solid wire outdoors, the operator should use caution and prevent any wind from blowing the shielding gas coverage away from the welding arc. Windshields may need to be used.
Flux Cored Wire Basics
There are two types of flux cored wires: gas shielded and self shielded. Gas shielded flux cored wires require external shielding gas and the slag is easy to remove. The operator may want to consider using gas shielded flux cored wires when welding on thicker metals or in out-of-position applications. Gas shielded flux cored wires have a flux coating that solidifies more quickly than the molten weld material. As a result, it creates a "shelf" to hold the molten pool when welding overhead or vertically up. Self shielding flux cored wire does not require external shielding gas; the weld pool is protected by gas generated when flux from the wire is burned. As a result, self shielding flux cored wire is more portable because it does not require an external gas tank.

Related Articles
Miller - Solid Wire Versus Flux Cored Wire: When to Use Them and Why

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