How to weld
THE FIRST IN A SERIES ON HOW TO WELD
Part one of a seven-part series: The basics of arc welding
The form of welding commonly known as ‘stick welding’ or ‘manual arc welding’ is the most versatile and widely used welding process in the world.
It can be used to weld most common metals and alloys and welding mild steel —
low-carbon steels with good weldability — and this process is wonderfully uncomplicated. It can be used outdoors and it’s normally portable, especially with the small powerful machines on the market today.
A complete welding set was first made by the Lincoln brothers in 1909 and in 1911 Lincoln Electric introduced for sale the first variable-voltage, singleoperator, portable welding machine. The world of welding machines has changed since then yet the basics and the techniques remain very much the same.
Arc welding over the past few years has had a resurgence. It’s very cost-efficient as well as simple to do once the basics are mastered. Successful arc welding is essentially about good position (it comes with practice) and choosing the best of many types of electrodes to suit a multitude of base materials and uses.
For this article on arc welding — more correctly, shielded metal arc welding (SMAW) or manual metal arc welding (MMAW) — I am dealing with the basics.
Many people ask me what they are doing wrong when arc welding but most problems they encounter are all related to things not being set up properly or being ignored.
How it works
The current flows from the machine or power source through the electrode cable to the electrode holder in the handpiece, down through the electrode, and across the arc to the base metal. This commonly is the positive side.
On the work side of the arc, the current flows through the base material to the work clamp and back to the welding machine. This is usually the negative or earth side.
An arc occurs when the electrode comes in contact with the workpiece and completes the circuit … like turning on a light. This electric arc between the end of the electrode and the work reaches temperatures around 5500°C, which melts both the electrode and base metal.
The electrode, with an inner core rod and a flux coating, carries the welding current and then becomes part of the weld.
Most problems they encounter are all related to things not being set up properly or being ignored
The flux melting forms a shielding gas that prevents oxidization and porosity in the weld pool. Without this shield, we would end up with a very brittle weld– metal matrix. Chemicals can be added to the flux to enhance tensile strength, ductility, and user appeal.
As the core rod, flux coating, and workpieces heat up and melt, they form a pool of molten material referred to as a ‘weld puddle’ or ‘weld pool’. The weld pool is what a welder watches and manipulates while welding.
‘Slag’ is a combination of the flux coating and impurities from the base metal that float to the surface of the weld. Slag quickly solidifies to form a solid coating, a bit like a mini lava flow.
Slag also slows the cooling rate of the weld while also inhibiting surface oxidization.
Once the slag has solidified, you can chip it away and clean the weld with a wire brush. Sometimes it will peel off by itself, but if it looks a bit like bird poo it’s not going to be too easy to chip. How easy it is to chip depends on how smooth or rough your finished weld is. Often it’s harder to obtain a good slag release from the higher tensile or more specialized electrodes. With standard, general-purpose Easyarcstyle electrodes, a half-decent weld should be easy enough to chip.
Selecting the correct amperage depends on electrode size and the size and thickness of the material. Thin metals require less current than thicker sections and small-diameter electrodes require less power also.
Depending on the accuracy of your machine, these settings will give you a reasonable start for a bead on a flat plate:
• 2.5mm thick = 85A
• 3.2mm thick = 120A
• 4mm thick = 150A.
If you can weld in the flat or horizontal position it will make welding a lot easier. I have a rule of thumb that for vertical-up welding, drop the amps down 10–15A; for vertical down, go up 15–20A.
Striking an arc
This is the part that frustrates most learners. An arc is started and maintained when the welding current is forced across a gap between the stick electrode and the base metal. But often it doesn’t start; it just sticks to the plate.
There are basically two methods of striking an arc using a non–voltage reduction device (VRD) machine:
• scratching, and
Be sure to have your helmet on and face shield down first. The ‘scratch’ start method is generally considered easier for beginners and when using some of the older AC machines. It’s a bit like striking a large match or swiping a smartphone.
A sudden burst of light will be produced on contact with the plate. Use this burst of light to get your direction and start position. In the ‘tap’ start method, the electrode is moved downwards to the base metal in a vertical direction. The problem with this is ‘sticking’, or ‘freezing’. This is when the electrode fuses to the plate.
You can just about guarantee that you will lift up your shield just in time to flash yourself as the rod breaks loose. So, with your shield down, tap and pull up, as once again the burst of light will show you the way. When restarting half-way through a weld, check the end of the electrode. You will notice the central rod will have burnt back up inside the flux, leaving a coneshaped crater. With your glove on, break this flux off until the metal is showing. For the novice I would recommend the scratch technique for a restart.
Constant-current (CC) power sources are used in the manual arc welding process. A CC power source is one in which current or amperage remains constant even as changes in welding voltage occur with changes in ‘arc length’, the distance between the plate and the tip of the electrode. CC welding machines are either AC, DC, or AC/DC. Welding polarity will depend on the polarity of the electrode (written on the packet) or the limitations of the welding power source.
The popular multiprocess or threein-one welding machines can perform many different welding processes (i.e., stick, TIG, and MIG). The stick and
TIG modes are CC. The Powercraft 180i (I used a 160 here) is a great example of this three-in-one aspect.
The ‘bead’ of the weld is a continuous deposit of weld metal formed by the arc on the surface of the base metal, creating a fused mixture of base-material and filler-metal chemistry. A smooth, uniform weld bead in arc welding involves moving the electrode along the plate at the correct speed while hopefully achieving adequate penetration.
Notice how the arc digs into the base metal for penetration, how it fills the crater and builds up the bead shape.
Practice will help you recognize the character of the slag and a good or bad bead while you are actually welding it.
Keep your eye on the back of the weld pool as the arc transfers the weld deposit and builds up the bead. You can then vary the arc length, electrode angle, or travel speed to correct a poor weld-pool appearance. A good arc length, which comes with practice, should be slightly less than the diameter of the electrode, usually around 1.5 to 3mm. If the arc length is too long you will notice an increase in spatter, matched with a hissing, spitting sound, not the nice, soft, even crackle that you should hear. Penetration will be poor, you may have undercut, and the slag will more than likely be difficult to remove. We have all suffered that problem.
Too higher amps can do this too. So don’t be afraid to come down a bit if needed.
Travel speed affects the shape of the weld bead. Too fast and the bead will be thin and stringy, matched with poor penetration. Too slow and the weld metal will build up and roll over with an excessive overlap. Getting it just right is a matter of practice. Excess weld metal usually means excess heat. Excess heat, particularly on thinner materials, can make the parent material brittle and weak.
Just a quick note on penetration. Usually you will notice the arc digging into the base plate. If you are not sure how much penetration you are getting, do a short weld 25–35mm and break it open in the vice. If the toe of the weld has fused, penetration has been achieved.
To start, position your workpiece flat on a metal tabletop or plate and attach the clamp securely to the work (metal) or table. A good earth is important. Check the condition of the clamp and fittings. Set the polarity and amperage on the machine: DC+ (negative earth), say 110–115A for the E6013 electrode. Place the bare end of the electrode in the holder so that it is gripped securely at a 90-degree angle to the jaws.
Buy decent electrodes and you might find you can weld better than you thought
Don’t forget to turn the welder on. Make sure you are comfortable; get yourself into a natural position and grasp the electrode holder firmly but comfortably by using either one or both hands. Using both hands helps to steady electrode and reduce fatigue. To use both hands (as I do), rest your left elbow on work table and, with the left hand, steady the right hand by holding the right wrist. The opposite if you are left-handed.
Move the electrode down until it is about 25mm above the metal plate, vertical to the plate, inclined at an angle of 65–70 degrees in the direction of travel.
Place the shield down in front of your eyes — you may ask why I’ve bothered to mention this: once you have flashed yourself a few times, you will know why. Strike the arc using the scratch method. A sudden burst of light will be produced on contact with the plate.
A good exercise is to get yourself a decent piece of plate, flat bar, tube, or angle iron, etc. Not too small if possible.
Alert: the more you practise, the hotter your weld piece becomes and this affects your amperage settings.
Clean the base material by brushing the metal free of dirt and scale.
Set your machine to 110–115A, which will probably be a bit on the hot side, depending on the type of machine
you have, your power supply, and how accurate the dial/power indicator is. We can always drop the power back if our arc is too fierce.
Get a 3.2mm 6012 or 6013 electrode, strike your arc using the scratch start method, pull a long arc length for a second or two (6–10mm). This will help you get your bearings and avoids sticking or freezing.
Begin welding very slowly, keeping a close arc length, which as already noted is the distance the spark travels between the end of the electrode and the base metal. Hold the electrode into the corner and drag the electrode while touching the parent metal. Let the weld pool build up behind you. Slowly speed up as the rod burns away.
If you find that you are moving the electrode at a uniform speed, you will also need to make sure you are feeding the electrode into the weld pool at a constant speed as it melts. This will come naturally.
The travel angle is 60–70 degrees, give or take. Eventually you will see a nice-looking weld, with a nice bead
shape and the slag will detach more easily. This won’t come straight away.
The reason I say to start out slowly is that most learners/novices tend to start off going far too fast. Stick welding is certainly not racey.
Practise starting the arc, holding it, and breaking it until it is easy to strike an arc on the first try.
Beginners often weld with a long arc length. This will produce a rough bead shape and lots of spatter. So the tighter, controlled arc length will improve your bead appearance, give a narrower, more uniform bead, and hopefully minimize spatter.
When finishing the weld and breaking the arc, you may find you have a small crater. Good practice at the finish is to pause for a second or two. A slight back step with the electrode (12–15mm) at the end of the weld to fill in this crater is another option. Large craters can be the cause of weld cracking.
Vertical-down welding using a generalpurpose electrode will give you low penetration, which is not good for welding heavy sections, but really good for thinner, sheet metals. Note, not all electrodes will run vertical down. Check the packet, as normally it will be stated here.
A fast-freezing electrode is ideal. The Easyarc 6012 and 6013 are excellent for up or down.
When welding vertical down on thin sheets, speed is important. Move as fast as possible while maintaining a continuous bead. Use currents in the higher portion of the range.
Anyone who has tried vertical-up welding and made a mess of it will realize by now that gravity is not your friend. Everyone does this a bit differently but ends up with a similar result. So here is my version that I know works well.
Once you have struck the arc, let the rod burn for two or three seconds to build up a shelf at the bottom of the joint. Then add layer upon layer, using a straight weave, pausing on each side for about two seconds. This will ensure penetration and proper wash-in.
Do not whip or take the electrode out of the molten pool. Point the electrode slightly upwards so arc force assists in controlling the puddle.
Travel slowly enough to maintain the shelf without spilling. The slag will run down each side of the electrode. But you should be concentrating on the weld pool. If the weld bead looks too convex, try pausing for three seconds on the side. Don’t stop in the middle. Just concentrate on the sides; the middle will take care of itself, trust me. Use currents in the lower portion of the range.
As stated earlier, galvanizing, paint, and rust should all be removed. But for those of us who know better, try a little flick-forward technique. As you are welding, flick forwards 3–4mm every second or so, as if you were sketching with a pencil. This will burn a little bit of foreign matter as you go. This works really well on galvanizing pipe.
Striking the arc
The weld pool
Practice weld beads
Poor bead and spatter from too-high amps and too-long arc
Good practice welds
Chipping off slag with hammer
About to strike an arc. Note supported position
Cone formed in used electrode
Slag lifts off good weld
… good fillet weld
Interior controls for helmet
… weaving …
Vertical welding …
… from side to side