Friday, November 30, 2012

Basic Intro. to Smart Welding for DIYers: Guest Article

Welding is an important skill for farmers, ranchers, DIYers, and people who wish to live in remote areas far from skilled craftsmen for hire.

The previous article on welding contained several links to multiple welding tutorials. Today, we will present a guest article on welding first published on Survival Blog by "GM". This article is a good introduction to the DIY welder.
I am a retired journeyman pipefitter who is a Certified Welding Inspector. I teach at a nearby community college two days a week. Welding encompasses such a large body of knowledge that no one person can know all there is to know and certainly cannot condense everything into a short article, but let me start with some basics.

First of all, if you can’t tell the difference between steel, stainless steel, aluminum or cast iron you shouldn’t be welding. You have to know what process to use and which filler metal to use. Some things will hurt you or kill you if you try to weld on them. Never, under any circumstances, weld on a gas tank, or any container that you don’t know what was in it. Welding is “hot work” so you need to know if there is anything around that can catch on fire. Remove all flammables or cover them so they don’t cause a problem. Be sure what you’re welding on is adequately restrained or supported so as not to injure you or someone else.

The selection of the right filler metal is very important. If the wrong filler metal is selected the weld can have major defects and not be fit for service. Shielding gas selection is also very important. Preheat and postheat is important on cast iron or high strength alloy steel. Preheating is required whenever the metal to be welded is below 70 degrees F because the cold metal quenches the weld. When large welds are needed, it is better to make more small welds than a few large ones. Low carbon steel also called mild steel is easily welded by all common welding processes.

However, long-arcing of the weld will allow air to enter the shielding envelope, so proper welding technique is needed not to induce air which will cause porosity and other bad effects.

If you still have access to electric power, then wire or stick welding would be the preferred method of welding. This also holds true if you have a generator available. If not, then one is left with oxy-fuel welding. Wire welding is the preferred method of welding for any novice. It is much more intuitive for a novice to get the feel of it, but setting the machine can be intimidating. Let’s start with the machine. If you are going to invest in any machine, consider one of the new smaller more portable inverter welding machines that can do four major welding processes i.e.: wire with cover gas, flux cored gasless wire, stick and TIG. Older machines that are strictly constant current or constant voltage are larger, heavier and can basically only do one dedicated type of process with the exception of TIG. If you are going to spend your money on a new welding machine, why not buy the most versatile machine? I own a THERMAL ARC FABRICATOR 211i but others are available. The new machines can operate on either 110 or 220 volt with reduced capacity on 110. The difference would be the necessity of 3000 watts of power for 110 volt operations or 6000 watts for 220 volt operations. The new machines have very clear manuals and charts for welding operations.

But let’s say you have or have the opportunity to buy a used wire welder. You’ll want a wire welder that is rated at a minimum of 130 to 140 amps of power. Why, because it takes one amp of power to weld each 1/1000 of an inch of metal thickness and I wouldn’t recommend a machine that wasn’t capable of welding at least a 1/8 inch of metal thickness.

So now you have a wire welder, how do you go about setting it to weld? With a wire welder your heat is controlled by the wire speed, there is no setting for amperage. The rule of thumb is this: 100 inches per minute (IPM) of wire speed for each 1/16 of an inch in metal thickness plus add another 50 IPM at the end of each calculation, thus, 150 IPM for 1/16” metal thickness, 250 IPM for 1/8”, 350 IPM for 3/16” and 450 IPM for ¼” in metal thickness. It is not recommended to weld over ¼” metal with a wire welder, unless you do multiple pass welds.

Next, you set the voltage. If you are welding 1/8” metal, set your wire speed to approximately 250 IPM and start with your voltage to 17 or 18 volts. Turn your voltage up or down as you practice on a test piece to get the machine “dialed” in. You’ll have to practice setting the machine to get the desired result.

Wire welding can be done with either a push or a pull technique. Pushing the weld from right to left is easier for many right handed people. This method does not penetrate into the parent metal as deep as dragging or pulling the gun from left to right. Be sure you are holding the gun with the tip at a 45 degree angle to the surface that you are trying to weld. Electrode extension is very important. You shouldn’t be more than ½” away from the metal, where the wire comes out of the contact tube. You lose heat or amperage with a long arc.

Flux cored wire welding is cheaper than normal wire welding, though not as good. The normal gas for wire welding is 75% argon 25% CO2 but straight CO2 can be used, although it causes more splatter. We won’t go into inductance in this short article. Wire welding is not tolerant of contamination nor is it recommended to use outdoors. Any rust, grease, oil dust, paint or contamination of any kind will cause porosity. If you are going to wire weld, you have to start out with the metal clean at least an inch on each side of the weld. There is more expense in setting up a wire welder as compared to a stick welder but less practice is required to make an acceptable weld.

Stick welding is more portable than wire welding and more versatile. Stick welding is a very versatile process, because the same SMAW (Shielded Metal Arc Welding) machine can be used to make a wide variety of welds in different weld joint designs, metal types, metal thickness, and in all positions. Stick welding is more portable in that it requires less equipment and is easier to move, especially an engine driven generator-welder. Stick welding can be performed outside. Most major construction of new buildings, plants and piping is done outside with either stick or TIG welding. Wire welding and stick welding are negative ground positive electrode processes and TIG welding, flux cored wire welding being positive ground, negative electrode process.

Stick welding is harder to learn than wire welding and takes much more practice. If possible, take a course at your local college or high school. The difficulty comes in maintaining a constant length arc off of the parent metal, electrode angle, speed of welding progression, and manually weaving the electrode, in some cases, to make the bead profile. Low hydrogen (E7018) electrodes are the best for welding mild steel, but require a pretty steady hand to weld good beads. E6011 is the best electrode for a novice to learn with but requires more electrode manipulation to achieve a good bead i.e.: small circles, a C shaped or other pattern as recommended in any good text on welding. E6011 welds will be less ductile in service than E7018, the welds will break in time with hard usage, thus the bad name for “farm rods”. If you are using and old AC only farm welder, try to buy the newer AC-E7018 electrodes. There is no substitute for practice when it comes to stick welding, only with practice will you be able to lay down good serviceable weld beads that will hold your project together.

Now for oxy-fuel welding. During its prime, plates up to 1” thick were wire gas welded to produce ocean-going ships, to large industrial machinery. Today, due to improvements in other processes, gas or oxy-fuel welding is seldom used on metal thicker than 1/16 of an inch. Newer processes are faster, cleaner and cause less distortion from heat than oxy-fuel welding. However, when nothing else is available, welds can be made using this process. All that is required is a compressed gas bottle of oxygen and a cylinder of fuel, usually acetylene, the appropriate torch set, which will have regulators, a Siamese hose and a combination torch, for both welding and cutting. I will discuss important safety factors in both cutting and general welding at the end. Needless to say, once you have your “rig” properly set up (refer to your manual), turn on the gas just enough to let some gas escape, light the gas with a spark lighter near the end. With the torch lit, increase the flow of acetylene until the flame stops smoking. Slowly turn on the oxygen and adjust the torch to a neutral flame. Too much fuel and you won’t get a decent inner cone of flame, too much oxygen and the inner flame turns whitish blue. In either case, too much of one or the other increases the size of the flame. The neutral flame will produce the most concentrated heat at the end of the inner cone of flame. The maximum gas flow rate for the size of tip will give the flame enough flow so that when adjusted to the neutral setting it does not settle back on the tip. This will keep the tip cooler so that it does not backfire.

Factors affecting torch welding: torch tip size, torch angle, welding rod size and torch manipulation.

Torch tip size is used to control the weld bead width, depth of penetration into the parent metal, and speed. Tip sizes should be changed to suit the thickness and overall size of the metal being welded. Lowering the gas flow rate on a larger tip to weld thinner metal will just make it overheat and backfire. You should have a tip size chart with your torch outfit and each manufacturer has a different size which is proprietary to that manufacturer. Consult your chart and pick the tip needed to cut or weld that thickness of metal.

Torch angle – the ideal angle for torch welding is at 45 degrees to the metal. At the end of the welding tip it curves downward, if this end of the torch is pointed straight down into the parent metal this is 90 degrees, a compromise angle of half way between this and parallel with the surface of the metal is best. Hold the inner cone between 1/8” and ¼” off the surface of the parent metal.

Welding rod size and torch manipulation can be used to control the weld bead characteristics. A larger filler rod can be used to cool the molten weld pool, increase weld buildup above the parent metal and reduce penetration. The torch can be manipulated so the direct heat from the inner flame is flashes off the molten weld pool for just a moment to let it cool, keeping the secondary flame over the pool. The weld pool must be protected by the secondary flame (the larger outer flame) to prevent the air from contaminating the weld pool. If this flame is suddenly moved away the pool will throw off a large number of sparks. This is a real problem when the weld is stopped. The torch should be raised or tilted at the end, keeping the outer flame over the molten weld pool until it solidifies. Often the number of sparks increases just before a burn through when the molten metal drops through the backside of the plate.

Novices should practice pushing a molten pool on a clean piece of plate before attempting to add filler metal. Start at one end, hold the torch tip at a 45 degree angle in the direction you intend to weld. Establish a molten weld pool at the end of the inner cone of the torch. When the metal starts to melt, move the torch in a circular pattern down the sheet toward the other end. Try to get a uniform bead all the way along the weld. You may have to speed up or slow down to keep an even bead. Practice this until you can keep the width of the molten weld pool uniform and the direction of travel in a straight line. You should try this process next adding filler rod. Always bend one end of your filler rod, usually in a U-shape to know which end is hot. The straight end is dipped in the molten weld pool, as filler rod, is added to the weld pool, the flame can be moved back so as not to melt and drip the rod into the pool. The rod should be melted by the leading edge of the pool only. Once you can make good welds in the flat position then it is time to try other positions and other styles of joints. Try butt joint, T joints, lap joints in the flat position. Try welding these joints vertical up or overhead. Get a good book on welding and see what you can do. Now, for the most important part of welding: SAFETY. All welding involves heat and the possibility of burns can never be over emphasized. Your safety is your own personal responsibility and you must address it yourself. Many burns are caused by contact with hot metal or slag. I have seen students try to reach out and grab something they just welded and you can get burned even though you are wearing welding gloves. Be careful of hot weldments and sparks and splatter from your own welds and others. Ultraviolet light from welding will cause flash burn to the eyes. Wear shade 5 lenses for cutting and oxy-fuel welding. Wear shade 10 or greater in your welding hood for stick welding. Always wear safety glasses when doing any work and ear protection when necessary. Actual welding should be well ventilated. Fume sources that are bad for your health include: paint, oil, grease, coatings on metals such a zinc and cadmium. Older machinery and farm equipment may still have lead based paint. No welding or cutting on refrigeration or air conditioner piping. Wear the appropriate welder clothing: long sleeve shirts, long pants, leather shoes, a welders cap or beanie to protect your head. Special welding jackets of leather or flame proof canvas and leather welding gloves should be worn. Oxygen and acetylene cylinders should be chained securely in separate areas at least 20 ft. apart unless they are in a bottle cart and chained to it. Never lift a bottle by the cap or safety valve. When in use, oxygen bottles and cover gas bottles should be opened all the way to the back seat position after the regulators are properly screwed on. Open the valve on a full cylinder just briefly to blow out any dust, then attach the regulator. Acetylene bottles that have been laid on their side should be stored upright for at least 4 hours before being used. After attaching the regulator open the acetylene bottle enough just to get full pressure on the gauges.

Again, welding is considered to be “hot work” so you are responsible for fires. Keep a fire extinguisher handy. A 5 gallon bucket of water wouldn’t hurt either. Welding can cause electrical shock, so keep your leads and other equipment in good shape. Use the right type of regulator for the process you are setting up. Acetylene and fuel gases use left hand connections with a notched nut. Back off the adjusting screw of all regulators after use so as not to distort the diaphragm.

I’m sure I haven’t covered everything and maybe forgotten a few things that should have been included, but if at all possible, take a welding course. You’ll have a skill that will stand you in good stead and be very valuable, especially in a TEOTWAWKI situation. _GM at SurvivalBlog
Quite a good introduction to some basics of welding, for such a short and easily readable article. Consult experienced practitioners when getting started or when progressing to a new technique or equipment, to make sure you are not overlooking serious safety problems.

At least one person in a rural or practical suburban family should be able to weld basic iron and steel. More complex and difficult metals will require more training and practise.

1 comment:

Unknown said...

Know first the basics of welding before you put it into practice, especially if you’re a novice! You can also ask for the help or advice of skilled welders. Anyway, use it if you know how to. Just be extra careful or you might end up hurting yourself or causing damage.

-Jeanette West