Arc Welding Instructions While the preceding information is important to your intelligent progress in welding - we suggest you re-read at the start of each practice session in the early stages - the actual skills of laying down a weld can only be achieved by practical application. "Practice makes perfect" must also be interpreted as "Practice makes imperfect" if you are not using the correct techniques. In manual welding a number of actions must take place simultaneously, such as maintaining a correct electrode feed in, correct arc length, correct placement of metal, etc. - certainly too many for continuous conscious effort by the welder over a long period. Many of these aspects will soon become a natural reflex action or habit with practice. So learn good habits, not bad habits.
Striking the Arc
(Are you wearing suitable clothing, gloves, etc., and have you checked the area for fire hazards?)
Select a piece of clean steel (say 250 x 75 x 6mm) - heavy rust is a poor conductor and makes bad electrical contact - and attach your work clamp to it or seat it in good contact on your welding bench. Set your machine at 120 amps and place the bared end of a 3.2mm o electrode (Austarc 12P is fine) in the holder. Turn on the welder.
If you lightly touched the end of the electrode on to work, you would complete the circuit and current would flow, the electrode end rapidly getting hot and possibly melting sufficient to momentarily weld the electrode on to the work. (No doubt you'll see what we mean before this session is finished!) On the other hand, the low voltage current we are using won't jump an air amp (as in a spark plug). We must therefore establish an arc by first touching the electrode to the work and then immediately lengthening the distance between electrode and work until the droplets of metal and slag melting from the end of the electrode can cross to the molten pool below without bridging the gap and causing a short circuit with the electrode freezing onto the work.
A simple action of striking-an-arc with Arc Welding in much of the same manner as striking a match achieves this effect.
The electrode tip moves down and across, touches (a flash) and up, the arc still going until it becomes too long and extinguishes. Now, restrict your raising of the electrode tip to a maximum of 6 mm after striking the arc and endeavor to hold it steady at that point for about 10 seconds. This will necessitate feeding the electrode into the arc as the end burns off. Practice striking and holding an arc until it becomes child's play. This arc length is, of course, too long for useful welding, but will give you the feel of maintaining a length without fear of shorting. Any longer becomes unmanageable or may extinguish it, the resistance to current flow across the arc becoming too great.
If for one reason or another your action is incorrect and the electrode freezes on to the work, i.e. becomes welded to it, a sharp backward angling of the electrode should break the weld. Maintain your shield over the face until freed as it release from the plate or the electrode, will be accompanied by an arc flash.
Laying Down a Weld Bead
Once the arc has been established, reduce the arc length to about 3 mm and note that metal is beginning to mount up under the tip. Start moving the tip of the rod slowly away to the right (to the left if you are left-handed) endeavoring to maintain a pool behind the arc approximately 6-8mm wide. you will have to feed in the electrode at a steady rate, progress at a steady rate across the plate, maintain a steady arc length etc. Don't lose heart - a little more practice and some of these actions will begin to happen automatically!
For the present, concentrate on just two things as illustrated here on Arc Welding
(i) Maintain your arc length and as you get more experienced shorten it a little further. your other senses, like hearing, will come to your aid as you begin to recognise the sounds of the arc. By maintaining a steady and correct arc length, you must automatically be feeding the electrode in at the right speed!
(ii) The size of your molten pool. There is a natural tendency for most beginners to travel across the plate to fast. Slow down. Angle you electrode so that it leans some 25° forward in the direction you are traveling, to tip pointing back on to the molten pool If you keep that pool at a constant width and your arc length constant you must be moving along at a steady pace. By concentrating your attention into this one small area and on these two points - arc length and weld pool size - you will be learning the fundamentals of steady, even progression - but you may be surprised at the snaking path you weaved in the process. Don't worry-that aspect will fall into place as we progress with the next step. Practice!
Before leaving this section, try two more things:
1. Aim for a bigger constant weld pool - you will have to travel slower and they try for a slightly narrower bead, traveling faster. Even with the one size electrode we often use different rates of travel on different joints.
Reduce your arc length further until the electrode coating just touches the work. Easy welding if you have a suitable electrode and the right angle. As the coating burns off, the arc length and travel speed is automatically maintained. Raise the angle of the electrode and you travel slower (bigger weld), lower it and you travel faster. This touch welding technique is easy and handy, but not all electrodes are suited to it, nor is it suitable for all joints and positions. So remember it as the occasional bonus once your know how to run an electrode and can hold a steady arc and direct your metal at will.
As a general rule, the arc should be held as short as possible while still giving a stable burn off and good weld appearance. Too long an arc gives an unwieldy flow of metal with rough weld appearance and reduced penetration. Too short an arc gives a high narrow bead and a stutter characteristic with the electrode liable to freeze on to the work.
Building a Pad
For economical use of your steel and all-round practice at the principle of achieving a straight even weld bead, there is not better practice than laying down a solid pad of weld metal. Take a fresh piece of steel (say 200 x 75 x 1 Omm) and mark two lines down the centre of the length of plate approx. 6mm apart with chalk or regular pop marks.
This is your guide line for the first weld bead. Use 3.2mm a and approximately 125 amps.
Lay the plate on the bench so as its length is across your body. Get used to welding across your body-this is the only way you can see where you're going from start to finish of the electrode. While welding towards yourself may seem easier for achieving a straight line, the electrode and holder will soon block your view. After having placed a bead down the centre of the plate, chip off the slag and put down another alongside so that the edge (toe) of the second bead just laps up to the top of the first bead. Continue laying down beads of even width and height. After several runs, the pad may begin to get too hot. You may reduce to hand hot by periodic quenching in water in your practice session although this is not a recommended practice for most actual welding applications.
Always fill the crater at the end of the bead by raising the electrode tip slightly and moving back over the crater area, pausing a little before withdrawing to break the arc. Unfilled craters are weak and a possible source of weld cracking.
When joining up to a previous bead, first chip the old crater free of slag. strike an arc in the joint a little ahead and move back into the crater and establish a full width molten pool before progressing along the weld.
In carrying out a series of welds, experiment with a little higher current (say 140 amps) and lower current (say 90 amps) and note the differences in running, spatter, bead shape, etc. you will note that you can obtain satisfactory welds with lower currents once the pad is hot. Also you should now be trying to differentiate between the slag and metal in the molten pool and achieve the feel of controlling both.
Do your experimenting with electrode angles, travel speeds, joining up beads etc., while doing your pads. It's more economical on steel and will assist you in laying down better fillet welds and butt welds at an early stage.
Weaving
So far we have concentrated on straight weld beads, varying the rate of travel to vary the bead width. A wider bead can of course be obtained by using a larger electrode, but there are some occasions where we wish to achieve a slightly wider bead or better shape with the same size electrode. A technique of lateral movement of the tip across the weld puddle called weaving can be employed. The width of weaving is usually restricted to a movement of twice the diameter of the electrode. Try a few weaves to produce a slightly wider bead, ensuring that the molten pool is maintained under the arc and keeping the slag back, pausing slightly at the end of each lateral movement.
You may obtain full value out of your steel pad by laying down a second pad at right angles to the preceding pad layer and building up the height indefinitely. Padding, properly done is a means of rebuilding worn areas to size and is used extensively in maintenance work on shafts etc.
Concentrated welding in one spot can cause distortion by localized overheating and residual stresses. Wherever possible, balance the welding evenly over the job.
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