1G Position
Welding can be done in any position, the operation is simplified if the joint is flat. When placed in this way, the welding speed is increased, the molten has less tendency to run, better penetration can be secured and the work is less fatiquing. Some structure may appear at first glance to require horizontal, vertical or overhead welding, but upon careful examination you may be able to change them to flat position.
Carrying out some welding operations, very often the pieces have to be tack-welded. Tack welds are simply short section of weld heads 6.35mm to 12.7mm long used to maintain the proper root opening between the two sections of metal being welded. These tack welds are spaced along the seam and must be firmly fused into the joint.
Once the joint is tacked, the remaining weld passes are deposited. The first pass, known as the root pass or stringer bead is a narrow bead laid in the bottom of the vee. Its function is to fill the root opening and the join the two metal sections. It serves as the base for the other passes it is very important that it produces complete penetration. The next layer is called the fill or filler pass. One or more filler passes may be needed to fill the groove, depending on the thickness of the metal. In depositing the filler passes a slight weaving motion is generally advisable to insure proper fusion to the previously laid beads and sides of the groove joint. The final pass called the cap or cover pass sometimes referred to as the wash bead, is intended to provide additional reinforcement to the weld and give nice appearance. The cover pass should not extend more than 1.58mm above the plate surface.
Types of weld passes
Welding sequence in 1G
When a multiple pass is to be made in a grooved joint, be sure to hold the electrode down in the groove so it almost touches both sides of the joint while depositing the root pass. Move the electrode fast enough to keep the slag following back on the finished weld. If the electrode is not moved rapidly enough, the slag may become trapped in the bottom of the weld, thereby preventing proper fusion.
After completing the root pass proceed with whatever filler passes are required and the complete the weld with a cover pass. See below figure. (Note: always remove the slag completely after each pass. If any slag practices are allowed to remain they will weaken the weld.
Single pass fillet lap weld
The lap joint is one of the most frequently used joint in welding. It is a relatively simple joint since no bevelling or machining is necessary. The joint consists of lapping one edge over another and jointing. The amount should overleap depends upon the thickness of the plates and the strength required of the welded piece. Usually the thicker the plates the greater the amount of overleap.
When the structure is subjected to heavy bending stresses, it is advisable to weld the edges of both sides of the joint as shown in below figure
Single pass fillet lap weld
Multiple-pass fillet lap weld
When a strong lap joint is required, especially on heavy plates of 9.535mm and over in thickness, a multiple-pass fillet weld is recommended. This joint has two or more layers of beads along the seam, with each lapping over other.
To make such a weld, deposit the first bead as shown in below figure by moving the electrode straight down the seam without any weaving motion. Clean the weld carefully and lay the second pass over the stringer bead. Second pass weave the electrode, pausing for an instant at the top of the weaves to deposit extra metal on the vertical edge of the upper plate.
Multiple-pass fillet lap weld
Single-pass T-fillet joint
The T-fillet joint is frequently used in fabricating straight, rolled shape and beam. The strength of this joint depends considerably on having the edges of the joint fit close together. The T-joint should not be used if it is subject to heavy stresses from the opposite direction of the welded seam. This weakness can be partially overcome by using a double fillet that is, welding both sides of the joint. See below figure
Single pass T-fillet joint
Multiple-pass T-fillet joint
When a very strong T-joint is required, make a wider fillet along the seam. You can get a wider fillet by running several layers of beads. Deposit the first bead as describe in making a single pass T-fillet joint. Remove the slag and lay the second bead over the first, weaving the electrode sufficiently to secure the desired width fillet. Deposit additional layers if necessary to get the right size fillet, but make sure to clean off the slag each pass. See figure
Multiple-pass T-fillet joint
Outside corner weld
The outside corner weld, as shown in below figures, is often used in constructing rectangular shape objects such as tanks, metal furniture and other machine sections where the outside corner must have a smooth radius.
To make a outside corner weld, tack the two plates and run a bead along the edge with the electrode held as indicated figure. On the light stock, one bead is usually enough. Heavy stock will probably require a series of passes to fill in the corner.
| Outside corner weld using clamp and tack welding |
Single pass outside corner weld |
Multiple-pass outside corner weld |
2G position
A weld is in a 2G (horizontal) position when the joint in on a vertical plate and the line of weld runs on a line with the horizon.
To perform weld of this kind, you must use a slightly shorter arc at a slight reduction in the amperage setting than you would for flat position welding. The shorter arc will minimize the tendency of the molten puddle to sag and cause overleaps. An overleap occurs when the puddle runs down to the lower side of the bead and solidifies on the surface without actually penetrating the metal. See figure below. A sagging puddle usually leaves an undercut on the top side of the seam as well as improperly shaped beads, all of which weaken a weld.
How to hold the electrode
For horizontal welding, hold the electrode so that it points upward 5° to 10°, and slant approximately 20° away from the deposited bead as illustrated in fig 1. In laying the bead, use a narrow weaving motion as shown in figure 2. by weaving the electrode , the heat will be distributed evenly thereby reducing still further any tendency for the puddle to sag ,keep the arc as short as possible, if the force of the arc has a tendency to undercut the plate at the top of the bead ,drop the electrode a little to increase the upward angle.
As the electrode is moved in and out of the crater, pause slightly each time it is returned. This keeps the crater a small and the bead is less likely to drop.
Fig 2 Weaving pattern at left will result in a normal width bead, while the pattern at the right will result in a wilder bead width.
Fig 2 Weaving pattern at left will result in a normal width bead, while the pattern at the right will result in a wider bead width
Deposit straight bead in horizontal position
Depositing straight bead in horizontal position
- Obtain 6.350mm plate and draw a series of lines 12.7mm apart
- Fasten the plate on the bench in a vertical position as shown in below figure . To keep the pieces in place, tack it to flat pieces.
- Adjust the machine to the correct current and, with a weaving motion, deposit beads between the horizontal lines. Lay one bead by starting from the left side of the plate and working to the right. Then reverse the direction and run the bead from the right side to the left. Continue this operation until uniform beads can be made without overlapping and under-cutting.
Tack plate in vertical position
Single pass lap joint in a horizontal position
- Tack two plates 6.350mm to form a lap joint. Clamp the pieces in a vertical position shown in below figure.
- Run a single bead along the edge, using a slight weave motion.
- Watch the surface of the top plate closely to prevent undercutting. Continue this operation on additional lap joints until a satisfactory weld is made.
Single pass lap weld
Multiple pass fillet weld T-joint in a horizontal position
- Tack two plates to form a T-joint and fasten the base plate in a vertical position as shown in figure 1.
- Run a bead along the root of the joint without any weaving motion. Remove the slag and deposit second bead, using a slight weaving motion, penetrating the first bead and the plate. See fig 2
- Clean the slag off the second bead and deposit a third layer. Notice that the third bead penetrates into the first and second layers well as into the upright plate. This penetration is important, otherwise a weak weld will result, and the layer may spate from each other.
Fig 1 Depositing a multiple bead on a T-joint
Fig 2 Position of the butt joint for horizontal welding
Welding a multiple-pass butt joint in a horizontal position
- Obtain two pieces of 6.350mm metal steel plate and bevel the edge of one plate.
- Tack the two plates together to form a butt joint. Fasten the plates in a vertical position with the bevelled plate on top as shown in fig 2. The plate that is not bevelled should be on the bottom since its flat edge serves as shelf, thus helping to prevent the molten metal from running out of the joint.
- Deposit the first bead deep in the root of the joints. Remove the slag and lay the second bead. Then follow with a third bead.
- On many welding jobs, the practice is to bevel both edges to form a 60° included angle. Since such a joint does not provide a retaining self for the bead as the one shown in fig 2, a little more skill required to produce a satisfactory weld. In practicing this type of weld, notice in below figure, the position of the electrode is changed.
- The number of passes on the joint will depend on the thickness of the metal as well as the diameter of the electrode. The important thing is to secure sufficient penetration into each adjacent layer. It is common practice on a wide joint to finish the weld with a wash bead, commonly known as a cover pass or cap pass as shown in below figure to produce smooth finish. A wash is made by using a wide weaving motion that covers the entire area of the deposited beads.
| Single pass butt joint | Double pass butt joint | Multiple pass butt joint |
A wash bead produces a smooth finish
Conditions That Affect Weld Bead Shape
Weld bead shape is affected by electrode angle, arc length, travel speed, and thickness of base metal.
Poor Weld Bead Characteristics
Good Weld Bead Characteristics
Checking the weld
All welds are visually inspected to determine whether they have been adequately placed and have the necessary strength to hold steel together. While it is technically possible to perform weld inspection with specialized diagnostic equipment, this is generally not necessary in anything but a welding certification testing situation. Basic welding allows for quick inspections so that work can either progress or be redone in a quick and efficient.
The finished weld should be inspected for undercut, overlap, surface checks, cracks, or other defects. Also, the degree of penetration and side wall fusion, extent of reinforcement, and size and position of the welds are important factors in the determination as to whether a welding job should be accepted or rejected, because they all reflect the qualify of the weld.
- Look at the back of any type of weld after it has cooled, but before the part is cleaned. You should see discoloration on the back of the steel that has been welded that ranges in color from dark blue to nearly brown. If this area is uniformly smooth and coloured, the weld penetration, or how deeply the weld penetrated the steel, was successful. If there is a hole in the metal, this is called weld burn-through, and is a weld failure. On the other hand, the appearance of small bumps within the coloured region are called weld melt-through. These are acceptable in most welding situations.
- Inspect the weld fillet in steel welded at angles to each other. This is the actual deposited weld filler that builds up during the welding process. It should be uniform and attractive, with edges smoothed into the surrounding metal rather than clumped up on top of one another. In addition to this, the fillet should not exhibit any signs of cavities in the filler metal. This is indicative of poor weld quality, and the part should be remade.
- Inspect butt welds to make certain that they exhibit the proper coloration on the back of the welded steel. If they have the right coloration, inspect the weld itself. The weld should not exceed 3/16 inch in width, and should be no higher than 1/16 inch above the steel being welded. In addition, the weld should completely cover any gap between the two pieces of steel being welded. A hole or a gap indicates a poor quality weld, and the part should be remade.
Welding troubleshooting
Porosity − small cavities or holes resulting from gas pockets in weld metal.
| Possible cause | Corrective actions |
| Arc length too long. | Reduce arc length. |
| Workpiece dirty. | Remove all grease, oil, moisture, rust, paint, coatings, slag, and dirt from work surface before welding. |
| Damp electrode. | Use dry electrode. |
Excessive Spatter- scattering of molten metal particles that cool to solid form near weld bead.
| Possible cause | Corrective actions |
| Amperage too high for
electrode. |
Decrease amperage or select larger electrode. |
| Arc length too long or voltage
too high. |
Reduce arc length or voltage. |
Incomplete fusion– failure of weld metal to fuse completely with base metal or a preceding weld bead.
| Possible cause | Corrective actions |
| Insufficient heat input. | Increase amperage. Select larger electrode and increase amperage. |
| Improper welding technique. | Place stringer bead in proper location(s) at joint during welding.
Adjust work angle or widen groove to access bottom during welding. Momentarily hold arc on groove side walls when using weaving technique. Keep arc on leading edge of weld puddle. |
| Workpiece dirty. | Remove all grease, oil, moisture, rust, paint, coatings, slag, and dirt from work surface before welding. |
Lack of penetration- shallow fusion between weld metal and base metal
| Possible cause | Corrective actions |
| Improper joint preparation. | Material too thick. Joint preparation and design must provide access to bottom of groove |
| Improper weld technique. | Keep arc on leading edge of weld puddle.
Reduce travel speed. |
| Insufficient heat input. | Increase amperage. Select larger electrode and increase amperage. |
Excessive penetration-weld metal melting through base metal and hanging underneath weld.
|
Possible cause |
Corrective actions |
| Excessive heat input. | Select lower amperage. Use smaller electrode. |
| Improper weld technique. | Adjust travel speed. |
Burn through – weld metal melting completely through base metal resulting in holes where no metal remains
|
Possible cause |
Corrective actions |
| Excessive heat input. | Select lower amperage. Use smaller electrode.
Increase and/or maintain steady travel speed. |
Waviness of bead weld metal that is not parallel and does not cover joint formed by base metal.
|
Possible cause |
Corrective actions |
| Unsteady hand. | Use two hands. Practice technique. |
Distortion- contraction of weld metal during welding that forces base metal to move.
|
Possible cause |
Corrective actions |
| Excessive heat input. | Use restraint (clamp) to hold base metal in position.
Make tack welds along joint before starting welding operation. Predict anticipated weld distortion and precamber base metal. Select lower amperage for electrode. Increase travel speed. Weld in small segments and allow cooling between welds. |
