Overhead welding also called 4G position as per ASME and PE position as per ISO 6947 when welding groove welds. For fillet weld welding position is called 4F. In overhead position, the welder perform the welding from bottom side of the job as shown in below picture. Overhead welding requires very skillful welder to manipulate the welding electrode and control the weld puddle which keep falling down due to gravity. The welder skill to weld uniform stringer beads is highly important when welding overhead welds as weaving techniques which will produce lot of heat and weld metal is not suitable for overhead welds.
Tips for Stick Welding in Overhead position
Flat, horizontal, vertical and overhead are the welding positions classified as per ASME Section IX and ISO 6947. Out of these 4 positions, flat being the easiest one and overhead is the most difficult one position for welders. There are lot of challenges for welders when welding in overhead positions such as:
- Weld deposit against the gravity.
- Falling spatters
- Controlling the weld puddle
- Controlling the welding speed
Welding groove welds in overhead position
Electrode: E6010 for root pass, diameter 3/32 inch or 2.5 mm.
E7018 or E6013 for fill passes, Diameter 3.15 mm or 1/8 inch for overhead welding.
Welding current: It is always the best option that welder choose the welding parameters what suit him best. As stick welding is a manual skills and each person adapt to different welding parameters and setup. Ideally, you should start with the lower range and then slowly setup higher current.
Starting the weld: First of all With the electrode pointed slightly into the joint, strike the arc in the joint & maintain a constant arc length. During welding make sure to:
■ Keep a very short arc length.
■ Use the stepped pattern and move the electrode forward slightly when the molten weld pool grows to the correct size.
As the molten weld pool gets larger, it has a tendency to quickly become convex. If you keep the arc in the molten weld pool once the joint is filled and the weld face is flat, it will quickly overfill and become convex. This can result in the weld face forming drips of metal hanging from the weld like icicles.
■ When the molten weld pool cools and begins to shrink, move the arc back near the center of the weld.
■ Hold the arc in this new location until the molten weld pool again grows to the correct size.
■ Step the electrode forward again and keep repeating this pattern until the weld progresses along the entire weld joint length.
■ Cool, chip, and inspect the weld for uniformity and defects.
■ Repeat the welds as needed with all three (F) groups of electrodes until you can consistently make welds free of defects. Turn off the welding machine and clean up your work area when you are finished welding.
Welding Fillet welds or Lap joint in Overhead position
Welding of fillet weld or lap joint is similar to like welding fill pass in a overhead groove weld and can be easier than welding groove weld joints in this position. When welding fillet weld in overhead with stick welding, welder need to master the skills of stringer bead with combination of little weaving. Weaving techniques in general is not beneficial in overhead welding as they will produces heavy molten metal and its difficult to hold in the overhead position due to gravity.
When welding fillet weld or lap joint in overhead position, setup the parameters as stated above. Start the arc by electrode pointed slightly into the weld joint and strike the arc. A constant welding arc need to be maintained to ensure throughout control on the weld puddle.
- Deposit the weld pass using stringer beads.
- Keep the power on lower side to avoid undercut.
- Don’t keep slow pace, slight faster weld passes produces good weld finish.
- Control weld interpass i.e. let weld cool a bit before you deposit next pass or weld layer.
- Repeat the welds as required until the weld is finished.
Tips and techniques for MIG welding in overhead position
in MIG welding the molten weld pool should be kept as small as possible for easier control. A small molten weld pool can be achieved by using lower current settings, by using a longer wire stickout, by traveling faster, or by pushing the molten weld pool. The technique used is the welder’s choice for best results. Lower current settings require closer control of gun manipulation to ensure that the wire is fed into the molten weld pool just behind the leading edge. The low power will cause overlap and more spatter if this wire to-molten weld pool contact position is not closely maintained.
Choose the right diameter of the wire
Welding MIG in overhead position should be carried out using small diameter wires e.g. 0.8 mm (0.030 inch) or 1.0 mm (0.035 inch). Smaller wire diameters produce small weld puddle and require lower power thus suit best for overhead positions. 0.045 inch diameter MIG wire can also be used but welding ampere shall be kept to low and short circuit mode to be chosen.
Choose the right metal transfer mode
Short circuit transfer mode must be selected when welding in overhead position. Spray transfer or globular transfer is not going to work in overhead position. Pulsed metal transfer mode can also be used if a pulsed welder (power source) is available. Short circuit mode produces small metal droplet by short circuit transfer and gives better control on weld puddle. Similarly, a pulsed transfer mode work with low heat input and controlled total heat into the weld puddle allows minimal spatters in overhead welding position.
Click here to learn Metal Transfer Mode in GMAW, FCAW & SMAW
Short circuit mode gives small molten weld pool size—The smaller size of the molten weld pool allows surface tension to hold it in place. Less molten weld pool sag results in improved bead contour with less undercut.
Check your wire feed rate
The wire speed shall not be kept very high and also it must now be too low. Most of welder, keep wire speed very low thinking they need very less wire and end up with bad looking welds. So, maintain a proper wire feed rate for out of position welding.
Root run and fill pass importance
Each pass in overhead welding is differently controlled. A root pass in groove weld is open and need very low heat input and small wire deposit. So root run welding must be welded with low ampere and stringer beads. Fill passes require higher power than root run and can be combined with little weaving to allow more weld deposit.
Count your wire stickout
The wire stickout must be kept to short. Making a higher stickout will give rise to voltage and create mess in the welding. The most important part in MIG welding for overhead welds is to keep your stickout short.
Click to know What is Welding Electrode Stickout for GMAW & TIG?
Maintain short arc length
Another important thing that require to be short is the arc length along with the stickout in MIG welding. A short arc length helps to control the welding voltage and allow little fluctuation in the current. So, shorter your arc length in MIG welding, better looking and cleaner your weld beads.
Faster Travel speed
Faster travel speeds allow the welder to maintain a high production rate even if multiple passes are required to complete the weld. Weld penetration into the base metal at the start of the bead can be obtained by using a slow start or quickly reversing the weld direction. Both the slow start and reversal of weld direction put more heat into the start to increase penetration. The higher speed also reduces the amount of weld distortion by reducing the amount of time that heat is applied to a joint.
Keep your extra protection ON
When welding overhead, extra personal protection is required to reduce the danger of burns. Leather sleeves or leather jackets and caps should be worn. Always wear fully maintained coverall and especially protect your skins from hot molten spatters and NEVEL loose your helmet. Any spatter fall in eyes, can be pain of the life.