Welding

Richard Allen's words on Welding

This article is built from a series of articles which Richard Allen dini_44@ablewise.com posted to the ATIS Stationary Engine Mailing List both in answer to peoples questions and by way of extra information he wanted to pass on to the rest of the list members. I decided to join his words in an article on welding because I found his words interesting and informative.

Disclaimer: While Richard is an experienced welder, the responsibility for following any of the adivce is yours.

You need a welder!

If you collect and/or work on old stationary engines you've got to have a welder! Some day you will need an engine cart, and you can make your own.

I taught welding in high school many years ago, and it is not that hard. My class was the evening class and I had adults in it. They were my best students. Go get yourself an inexpensive Lincoln or Miller 225 amp AC welder and a 50 pound box of 1/8" E6011 welding rod to start with and learn. I am sure you know someone who can help you get started. A secret about an arc welder is you can also CUT iron with it, too! It is not as pretty as with an oxy-acetylene cutting torch, but it makes little ones out of big ones, and beats a hack saw for sure! Then when you get good you can weld it all back together using 1/8" E7018AC rod.

Cutting with an Arc Welder

From an article Richard wrote on 30 Jan 2002 in response to some other comments on the same subject...

>>A secret about an arc welder is you can also CUT iron with it, too!

>>It is not as pretty as with an oxy-acetylene cutting torch, but it

>>makes little ones out of big ones, and beats a hack saw for sure!

>I'm all ears here! Can't you get a carbon electrode to do that? I

>looked into plasma cutters, but (A) they're pretty pricey, and (B)

>they require higher voltage than the 30 or so my welder will put out,

>as well as (C) needing a source of compressed air or oxygen. I've

>seen passing references to "gouging" with a carbon electrode, but

>haven't run across anything specific.

>I'd think a rough cut with something like this, followed by a touchup

>with a grinder where essential, would serve a lot of cutting needs. I

>don't want to have to fool with storing and maintaining compressed

>gas cylinders if I can avoid it.

+=++=++=++=++=++=++=++=+

Besides carbon rods, two welding electrode types are commonly used for metal cutting. These work very much faster than carbon rod cutting. For direct current only E6010 run on "reverse polarity" (the electrode is positive and the work piece is negative) is used, and for direct current "reverse polarity" and alternating current E6011 is used. The two types are basically the same electrode, E6011 has a miniscule amount of potassium fluoride added to the electrode covering compound as an arc stabilizer so it will maintain an arc on alternating current. The electrode covering compound used for these rods contains mostly calcium carbonate (powdered oyster shell, limestone, or marble) with a small amount of cellulose fiber and Portland cement as a binder. At the operating temperature the calcium carbonate decomposes into calcium oxide and a fairly large volume of carbon dioxide and carbon monoxide gases, the volume being large due to the extremely high temperature. At room temperature the gas volume generated would barely amount to a polite sneeze. When these rods are used for welding, the carbon dioxide and carbon monoxide generated shield the molten steel from oxygen in the air and prevent it from oxidizing. Because the gases are liberated at the tip of the electrode it is the same as having a small jet of low pressure compressed inert gas blowing outward from the tip. This is different than all other stick welding electrodes.

For metal cutting these rods work best for thin sections of material, about 1/2" thick plate and 1" round bar being the maximum for efficient operation. Thicker material can be cut, but it becomes difficult because the metal flows around the arc zone and has a tendency to weld itself back together. By manipulating the rod tip with a longer than normal arc length and allowing gravity to help, the gas pressure can be used to blow the molten metal away from the arc area leaving a void. As the arc zone is moved, it leaves a kerf behind. On thicker pieces, the molten metal is not blown clear and drips downward, leaving very rough edges. For some applications these drips can be re-incorporated into a weld bead, so their existence is not always a problem. For cutting up metal for scrap, the roughness is of no concern.

AC DC, and E6010 and E6011

When welding, the release of gas can be used to push away the molten puddle of steel creating a pocket. Because of this action, E6010 and E6011 are used for welds that need very deep penetration. Normally, the molten steel is allowed to flow back into the pocket as the weld bead progresses, and by manipulating the rod while welding, the gas pressure can be used to push the molten puddle around and make it go places it would not go on its own. For welds done up or down walls and across ceilings E6010 or E6011 are the rods of choice, especially E6011 using alternating current when working near an edge. Direct current creates a strong magnetic field near edges and points that pushes the ionized arc gases away from where they are wanted. This phenomenon is called arc blow and is one of the serious drawbacks to direct current welding. Alternating current doesn't have this problem. The gas pressure generated can be used to keep the molten weld puddle from running down hill or dripping out of the weld area. The big disadvantage to these two electrodes is they do not produce especially strong welds, typically being around 60,000 to 70,000 psi tensile strength where 70,000 psi and upward is the norm. To get around this, the weld beads are simply made a little larger. However, for up and down walls and across ceilings they sometimes produce welds vastly stronger than any other electrode. This is simply because the weld goes quickly and easily, there not being time for slag pockets to develop due to operator error. Of course, a welder who specializes in overhead welding can use a different stronger electrode type and produce a stronger weld by being familiar with the quirks of overhead work. Lately, there is a new type of E7018 class stick electrode available called E7018AC that is vastly superior to anything else ever made, and works just as well as E6010 and E6011 for welding up or down the wall and across the ceiling.

John Culp had some questions about 6010, 6011, and 7000 series

John Culp johnculp@chartertn.net wrote:

Thanks for that explanation, Richard. I'd wondered what it was about 6010 and 6011 that made for such deep penetration and especially wondered how the vertical and overhead welding worked. I've seen both of these electrodes recommended for beginners to start with, as well as statements that 6010 is especially difficult to use. Sounds to me like the idea is that if you practice with 6010 until you can do it well, you're pretty well getting the technique down.

Now, about the 7000 series electrodes: Aren't these low hydrogen electrodes, requiring storage in a hot cabinet at 250 F or so to keep out moisture and allow the 70,000 PSI range tensile strength to be achieved?

Richard responded to Johns questions...

Richard responded on 31 Jan 2002

You're welcome, I'm glad to help explain!

The E6010 electrode is a real pain to use on AC because it doesn't have the potassium fluoride arc stabilizer in the coating. E6011 is about the easiest electrode to use, it strikes an arc very easily, and is difficult to stop the arc. Occasionally a welder will set the stinger down on a live piece of work, like a ship deck, and later the stinger cable gets kicked or jostled so the E6011 bare tip will make contact with the deck, and it will weld a bead on its own just laying there! The E7014 and E7024 electrodes will also do that, but they are purposely designed to be worked by dragging.

The codes used for electrode types are that the designation always begins with "E". The first two numbers refer to the strength of the weld in thousands of pounds per square inch. The third number refers to the welding position the electrode type can be used successfuly for (but don't you believe it!), 1 refers to all positions, 2 refers to up, down, or horizontal along a wall plus flat on the floor, and 3 refers to flat on the floor only. In practice, I have never seen a XX3X type electrode, and XX2X will not work on a wall at all, being usable for flat work only. The fourth number refers to the composition and characteristics of the electrode coating. Most 70XX electrodes are "low hydrogen", which means there is no hydrogen-containing material in the electrode coating. Weldment is subject to becoming porous if hydrogen is present during welding. The main sources of hydrogen contamination is from water, oil, and paint; and many electrode coatings are hygroscopic. As such, low hydrogen electrodes have to be baked to evaporate the water they absorb during storage. I put the electrodes I will use for a project in my gas barbecue grill and bake them for about an hour at 350F before using them. The work pieces also have to be free of hydrogen contamination from rust, water, paint, oil, grease, wood, and all other biologicals. Also, most 70XX electrodes have powdered iron in the coating, and it rusts if it is left damp. Most electrodes come in a big tin can sealed just like canned food to keep them dry for indefinate storage. The new E7018AC is not as hygroscopic as the older E7018, but it needs to be dried before use, too. My welding supplies consist mostly of E6011, E7018AC, and smaller amounts of E6013, E7014, E7024, and various specialty rods, like Ni-Rod for cast iron and high carbon steel, and Stellite hard facing. Most of my rods are 1/8" size to run at around 80 to 160 amps on my 225 amp AC welder.

In response, John Culp had some more questions...

John Culp johnculp@chartertn.net wrote on 31 Jan 2002.

I really like the idea of baking low-hydrogen electrodes for a while in the barbeque grill. I have an electric grill, and my welder has a 110VDC outlet that'll power it fine!

I've read that E6010, and also E6011 are pretty tolerant of rust, grease and dirt on work. Is that because of the gas-blast effect from the flux clearing it away?

Also, E6010 is supposed to work only on DC reverse polarity to the extent that one welding equipment maker recommends using it as a test to see which way the polarity's hooked up. I've been trying to reason this out, also why reverse polarity is supposed to give extra deep penetration into the work. My thinking is that with reverse polarity the heavy positive gas ions in the arc will be attracted to the negative workpiece, so the DC arc will create a steady draft of hot plasma against the negative side. That'd tend to blow the puddle out of the work as you mentioned, and it'd tend to splatter the filler rod material and flux away from the tip if it were the negative side. Am I even close? If I am, why doesn't this mess up other kinds of rods being used with straight polarity? Are they just more tolerant of the plasma blast when their flux isn't so gassy to start with?

Arc Welding Dirty Metal

Richard responded with some dirty metal tips on 1 Feb 2002.

A very good source of cheap high quality steel is from scrap and recycling yards. It is almost always painted or extremely dirty with rust and grease, which make it unweldable without first cleaning the areas to be welded. Here is a cleaning trick used by welders when they have greasy, dirty, rusty, damp steel to weld. Before making the first actual weld pass, take a rod of E6010 or E6011 on reverse polarity (the normal polarity for these rods, anyway) and make an initial pass over the weld zone with a very long arc length. Watch where the hot spot on the work piece is, and move it just fast enough so as to not quite melt the steel surface. It may be necessary to run the arc over the weld zone a few times before all the grease, dirt, paint and/or rust is burned and blown off by the arc gases. The metal from the rod will cover the area with thick spatter, but it will pretty much brush off with a wire brush, along with all the other stuff you don't want in your weld. Lead is a source of weakened welds, and paint is a big source of lead. Lead was banned in house paint only, it is still used for industrial coatings. By the way, after heating or welding something and you have a sickeningly sweet taste in your mouth, nose, and throat, there is lead present, so take precautions not to breath the fumes.

Reverse Polarity DC Arc

About reverse polarity, penetration, etc: Well, John, your reasoning is pretty close, if you had one or two more pieces of information to this puzzle, you would have had it figured! One of the first discoveries (perhaps going all the way back to Sir Humphry Davy 180 years ago) about DC arcs is that approximately 40% of the heat released on the two objects present is on the negatively charged piece and 60% is released on the positively charged piece. The majority of welding is done using "straight polarity" (work piece positive) so that the more massive metal object gets more heat for its greater mass, and at the same time limiting the heat on the much less massive electrode to keep from prematurely destroying it. To get penetration, straight polarity is needed so more heating takes place on the positive work piece. The backward-appearing logic to penetration achieved with running E6010 and E6011 on reverse polarity is partly the result of the gas flow from the electrode tip to the work piece. THIS APPLIES TO E6010 AND E6011 ONLY! MOST OTHER ELECTRODES BEHAVE IN THE OPPOSITE FASHION. The gases just beyond the tip of the electrode become very hot, but because they are flowing away from the electrode they heat up the work piece by impinging on it, and their force pushes the molten steel out of the molten zone; this is called "digging". Also protecting E6010 and E6011 electrodes from reverse polarity heating is an endothermic (energy consuming) chemical reaction taking place (most other types of electrode coatings don't offer this protection) which helps cool the electrode tip. This is the decomposition of the calcium carbonate into calcium oxide and carbon monoxide (carbon dioxide does not exist at the temperature generated). Another really important factor for needing reverse polarity is that the constituents of the plasma that are unique to E6010 and E6011 act as a semi-rectifier. The electrode has to be positive for maximum current to flow. The rectification is not complete; on AC the electrons flow both directions between positive and negative halves of the sine wave. In actuality, what happens in a welding arc is very complex, and I haven't run across many really comprehensive articles to help understand arc welding theory. What is known is that using reverse polarity or AC with E6010 and E6011 creates a pronounced flow of gas and metal from the electrode tip to the work piece, making E6010 and E6011 uniquely useful for fighting gravity in overhead work. Using reverse polarity with electrodes that don't generate a lot of gas causes them to burn up rapidly. Both electrophoresis and magnetophoresis (movement of material caused by electric and magnetic fields) take place, but their effects are sometimes overwhelmed by the violent stirring of the expanding gases, molten steel, and liquid slag. The magnetic forces are quite evident using DC under some conditions. Like I mentioned before about "arc blow", when working near an edge or a point, the plasma is forced from the arc zone either toward or away from the edge or point, depending on the polarity being used. As I recall from experience, using straight polarity (work piece positive) the arc is bowed in the direction of the edge. As the work gets closer to the edge or point, the effect of the magnetic field will extinguish the arc. When this happens, it is necessary to clamp a large flat piece of steel to the work piece to create a "new" edge far away from the arc zone. Either that, or use AC.

Both DC and AC have their own extremely useful characteristics, the ideal welding machine should have both.

Mark L. Shattuck responded

Mark L. Shattuck Mark.Shattuck@Verizon.Net responded on 1 Feb 2002...

Richard : being a retired welder with thirty years experience of Field welding I find your post interesting to say the least I like it . you know your stuff . But I used to leave my 7018 out in the open (real world) when I wanted to use the rod I would dry it out by just sticking on plate until it dryed it out in the field you just do what works

Colin McKinnon responded

Colin McKinnon cmac@zip.com.au responded humourously when he gave us all an excuse for the thing that happens to all of us ameteur welders - getting stuck...

Ah, and I thought it was my bad welding - getting the rod stuck to the job and having to prise it loose, before it melted completely.

Now I can say I was just drying out the rod!

Colin

Striking an Arc for beginners and more about rod types

On 3 Feb 2002 Richard gave us some more information for beginners and a bit more information about rod types...

If you are a beginning welder, practice striking an arc on a scrap block of graphite or aluminum. Graphite is the much preferred of the two, but aluminum is easier to find. Starting with those can be a good confidence builder because there is instant success. After practicing with those materials, the next step is to a real work piece, and is usually very easy.

The easiest welding electrodes to start an arc with are E7024, E7014, E6011, E7018AC, and E6013. Like I mentioned before, sometimes one of the above rods in a stinger clamp gets accidentally laid down on a "live" surface like a ship deck, and it will strike its own arc and weld a bead without human intervention! On the other end of the spectrum, the absolute hardest electrode type to get "lit" is the old E7018. It mostly just sticks, and like Colin said, you have to prise the miserable thing off and then try again, and again, and again - - -. Sometimes it takes a hammer and chisel to get the electrode unstuck from the work piece. I destroyed my electrode holder stinger clamp in one day because in trying to get the electrodes unstuck it would often pull out of the clamp, drawing the arc in the clamp and quickly burning it out. After spending $25 I didn't have for a new stinger clamp, I wizened up and got a scrap block of graphite, which I put in electrical contact next to where my weld bead was going to start from. I struck the arc on the block of graphite, which NOTHING will stick to, and then once the arc got going good and strong, transferred it over to the work piece. An aluminum block will also work, it also has fair non-stick properties. Of course the way out of this is not to use E7018. It is miserable stuff that requires an air hammer to clean up after and it is just too hard to start. The E7018AC that has replaced it is a dream to work with! It usually makes self-cleaning welds, strikes an arc without any hassle, restarts VERY easily, is stronger than the original it has replaced, and is easier to use in difficult positions (like overhead). But, if you have a bunch of old rod to use up that is difficult to strike an arc with, start the stuff on a graphite or aluminum block first.

Work and play safely,-------Richard Allen