The World Is Not Flat: Tips to Improve Out-of-Position Welding—Part 1, TIG Welding

By Ken Alrick, product manager, Thermadyne Industries

Everybody learns to weld in the flat position, but advancement in the skilled welding trades requires learning to weld in the Horizontal (2F, 2G*), Vertical (3F, 3G), Overhead (4F, 4G) and 45-degree fixed (6G) positions. Further, codes and weld procedure specifications in the power generation, petrochemical and process piping industries call for both TIG and Stick process. Of course, structural steel welding also heavily involves all-position Stick welding.

In short, the more processes on which an apprentice or journeyman can become qualified, the greater their income potential. Part 1 of this article emphasizes the mechanics for welding out-of-position for TIG welding, and Part 2 focuses on Stick welding.

Welding Objectives

Pipe welding is considered the ultimate all-position application: the position changes constantly as the operator works around the circumference of the pipe, covering the flat, overhead, horizontal and vertical positions. As a result, the TIG mechanics described in this article are largely applicable to both pipe and plate.

Sharing his experience on the mechanics of welding is Todd Hidde, Shop Superintendent for the Pipe Fabrication Division of J. F. Ahern Co. and journeyman with UA Local 400. Hidde has been welding for 29 years and supervises a crew of up to 40 welders. J. F. Ahern Co., Fond du Lac, Wis., is ranked the 25th largest mechanical contractor in the country according to Contractor magazine’s 2011 Book of Giants. In addition to supplying prefabricated piping for internal mechanical projects, J. F. Ahern Co.’s Pipe Fabrication Division annually supplies for than $25 million of piping to outside mechanical contractors, owners and municipalities for industrial, power, utility and water/wastewater projects. It holds ASME "PP" and "U" stamps, a National Board "R" stamp and welds to ASME codes B31.1, B31.3, B31.9 and API-1104 codes.

“Before discussing welding in various positions, it is useful to review what the operator needs to accomplish,” says Hidde. He notes three key tasks:

1. Achieve required penetration at the root of the weld. For an open root joint on pipe, this requires complete penetration through to the backside of the joint. On plate, the procedure generally involves gouging out the backside of the weld and completing the joint from the backside.

2. Have good tie-in at the toes of fillet weld without any undercut. On a groove weld, this especially means good sidewall fusion.

3. Produce a weld bead face that conforms to codes and specifications, being neither too concave nor convex. A rule of thumb states that the bead crown should be no more than one electrode diameter high and no more than three diameters wide (or “dime wide, nickel high” when using a 1/8” diameter electrode).

* F=fillet weld, G=groove weld

When welding in the flat position, gravity pulls the molten pool into the root opening, making penetration easier. In all other positions, the molten weld puddle wants to roll out of the joint. For this reason, Hidde says that, “Out-of-position groove welds tend to be more difficult than fillet welds. Operators need to concern themselves with directing the molten metal at the bottom of the root and tying in to the sidewalls vs. just having good tie-in at the toes of a fillet weld.”

Variables to Control

When welding out of position, operators must rely on their skill to deposit filler material and use the force of the arc direct the weld puddle into the joint. Chris Brownlee regularly works with Hidde. He is a CWI and weld process specialist for Weld Specialty Supply Corp. based out of Fond du Lac. Brownlee notes that operators can control weld puddle and weld bead profile by manipulating the following variables:

  • Amperage. Reduce amperage by 15% for out-of-position welding.
  • Arc length. Generally, arc length should equal electrode diameter. Because voltage is directly proportional to arc length, operators often hold a shorter arc to reduce heat when welding out-of-position.
  • Electrode work angle. The angle of the electrode relative to the joint. TIG welders also must concern themselves with filler rod angle (more on this later).
  • Direction of travel. Usually described in terms of push/forehand or drag/pull/backhand. TIG welding always uses a push technique.
  • Electrode travel angle. The angle at which the electrode travels (e.g., how far back the torch is tipped; more below).
  • Electrode (torch) manipulation. More on this below.
  • Travel speed.
Fig 1
For out-of-position welding, reduce amperage by about 15 percent compared to welding in the flat position.
Fig 2
Notice the tight arc used for welding out of position. Also, keep the tungsten directed at the center of the weld puddle.

 

Reference Point: Flat Position

Setting aside the technical terms, pipe fabricators commonly use a clock face reference to welding positions. When the pipe can be fixed in a positioner and rolled, operators in the “flat” position typically hold the torch at 1:30 to 2 O’clock. In this position, the combination of gravity and weld puddle surface tension helps “pull” the molten metal off the end of the filler rod and into the root.

Fig 3
This image provides a reference point for welding in other positions. Electrode position: 90 degrees relative to work. Travel angle: 15 to 20 degrees back from perpendicular. Filler rod angle: 10 to 25 degrees up from the pipe and roughly a 100-degree relationship between the filler rod and the torch.
Fig 4
For tighter gaps, weld more toward top of the pipe where gravity will help pull the puddle into the root.

6 O’clock, or Overhead Position

“When welding overhead, operators need to manipulate the puddle faster or it will fall into the cup,” says Hidde.

Fig 5
Intentionally created flaw: slow travel speed and excessive heat input blew a hole through the root and caused the puddle to sag inside the pipe.

Manipulation refers to the zigzag motion of the torch. The welder’s wrist/forearm motion most closely resembles that of a sideways Figure 8. Rhythm is the key to cup walking (or a good freehand). Hidde says that, “Good rhythm has a 1-2, 1-2 metronome-like tempo. Journeymen can help inexperienced welders by counting out the tempo and even grabbing their hand and showing them the motion.”

When cup walking, the cup rests directly on the top of the joint. For this reason, start with perhaps a #6 or #7 cup and increase cup size after the root or hot pass. Set the electrode in the root opening or bottom of the joint, start the arc in the center of the joint, establish the puddle and place a small amount of pressure on the cup. Slide the left side of the cup forward about 1/16 of an inch using the right side of the cup as the pivot point. As the cup pivots, direct the tungsten at the left edge of the joint (toward the leading edge of the cup) and pause momentarily. Next, slide the right side of the cup up 1/16 of an inch, move the electrode across the root, direct it at the right side, pause and repeat the steps described.

The timing, pauses and movement involved with cup walking are as intricate as a waltz. Things happen quickly in any position and need to happen even faster when welding overhead. “Fast manipulation keeps the puddle and its freeze rate under control,” says Hidde. “Slow manipulation either causes the filler metal to pile up or puts too much heat into the joint and blows open the ‘window’ or ‘keyhole’.”

Fig 6
As seen from the inside of the pipe, the welding arc opens a window that closes up (bottom of image) as filler metal is added. The rod is just visible at the top of the joint.

Windows, Travel Speed and Tie-in

When welding an open root joint, operators look for several things. First, they look for a window or keyhole to open up in front of the arc and close behind it as fusion occurs. The objective is to maintain a consistent window size by achieving the optimum balance between travel speed and filler rod feeding rate.

Brownlee notes that, “Another indicator of a quality weld is that as the molten puddle ties into the sidewalls, it starts circulating. Impurities and non-worrisome elements such as silicon rise to the top of the puddle and become clearly visible.” If this “scum line” of impurities circulates, it indicates good tie-in. A still puddle usually means little or no sidewall fusion, which is a common bigger mistake.

Fig 7
Todd Hidde shows off one of his key training tools: a piece of Plexiglas taped to the end of the pipe (the pipe must be sealed when using a backing gas). The window enables him to observe the weld puddle for good circulation and backside reinforcement.
Fig 8
Good backside reinforcement means no more than 1/16th of an inch of reinforcement on the inside diameter of the pipe.

5 O’clock: The Hazard Zone

The 5 O’clock position is the most hazardous. Hidde says beginners fail here for two reasons. “First, as a transition zone, it’s the least practiced, being neither overhead, nor vertical nor flat. Second, it’s where their 6 O’clock position becomes stretched and uncomfortable.”

Brownlee adds, “An uncomfortable operator should stop before the cup slips or the tungsten becomes contaminated because the operator dipped it into the weld pool or pushed the filler rod into it. If the tungsten becomes contaminated, stop, grind out any flaws and redress the tungsten. Electricity likes to come off a point, and a contaminated tungsten cannot precisely direct arc force.”

Other “uncomfortable” errors include holding the filler rod too perpendicular to the pipe (which could lead to excessive reinforcement) or holding the filler metal too far in front of the arc and removing it from shielding gas coverage. It’s always better to make a short weld and stay in control through frequent repositioning than it is to make a longer weld that might have a flaw.

Fig 9
To weld in control, operators use (and clearly tend to be possessive about) an adjustable-height rest for their torch arm. Also, notice the index finger of the rod hand and how it’s braced on the bottom of the pipe.

3 O’clock Slow Down

As operators approach the 3 O’clock position, they can slightly reduce manipulation speed compared to overhead welding. In this position, the puddle freezes and provides a “shelf” on which additional molten weld metal can be stacked without falling out of the joint. For a horizontal weld, remember to direct the arc slightly more toward the top of the joint.

Once the torch position reaches 2 O’clock, gravity takes over and helps pull the puddle into the joint and makes it easier to direct at the sidewall. Return manipulation speed to normal.

In conclusion, beginning welders need to learn different manipulation speeds for different positions and the freeze rate of the metal. They need to learn how gravity affects the weld puddle in terms of how it falls into the root opening, how it affects penetration and how their manipulation enables good sidewall fusion.

“The only way to understand welding mechanics and how they affect the weld puddle is to get under the hood and practice—a lot,” says Hidde.

Fig 11
To weld in control, operators use (and clearly tend to be possessive about) an adjustable-height rest for their torch arm. Also, notice the index finger of the rod hand and how it’s braced on the bottom of the pipe.