The Joint Apprentice Committee (JAC) of Iron Workers Locals 40 & 361, Astoria, New York, provides both the training time and guidance necessary for passing the exam. Its 12,000-sq-ft Iron Workers Training Facility is an American Welding Society (AWS) Accredited Test Facility serving the greater New York City area. The center features 35 welding stations and can administer welding tests to provide same-day certifications for contractors. The Locals have more than 1,100 certified welders and 2,500 journeymen who continually return to the school to sharpen their skills.
This article collects a JAC instructor’s advice to help readers pass the Welder Performance Qualification Test. It focuses on areas that tend to cause the most weld failures, while illustrating how to correct them.
Brief overview
The specifications for the welder qualification test include the following:
? Process: shielded metal arc welding, direct current electrode positive
? Electrode: AWS E7018, 1?8 in
? Base metal: ASTM A36 plate
? Plate thickness: 1.0 in. with 22.5-deg bevel
? Backing plate: 1?4 or 3?8 in
? Root opening: 1?4 in
? Test position: 3G (vertical — uphill progression), 4G (overhead)
The test requires making a complete joint penetration groove weld that extends completely through the thickness of components joined, transmitting the full load-carrying capacity of the structural components they join.
“The fundamental principles for making a good weld in the 3G and 4G positions are no different from welding flat,” advised Allister Lawrence, AWS Certified Welding Inspector (CWI) and Certified Welding Educator (CWE), as well as journeyman instructor, Iron Workers Locals 40 & 361. “The more you do it, the more you’ll get a feel for it. Practice the right way until it all becomes muscle memory.”
Preparation
Passing the AWS D1.1 qualification exam starts with good plate setup.
Figure 1: Clamp the backing bar firmly to prevent gaps that could trap slag.
1) Use three clamps, one for each piece of metal, to prevent distortion from drawing the joint shut and to keep the backing bar solidly against the other two pieces — see Figure 1. If distortion twists the backing bar, it creates a void between the plates that can trap slag.
Figure 2: AWS D1.1 requires 7018 electrodes to be used fresh from hermetically sealed packages or stored in a rod oven.
2) Select fresh electrodes. AWS D1.1, 7.3.2.1 Low-Hydrogen Electrode Storage Conditions, states, “All electrodes having low-hydrogen coverings conforming to AWS A5.1 and AWS A5.5 shall be purchased in hermetically sealed containers or shall be baked by the user in conformance with 7.3.2.4 prior to use. After opening the hermetically sealed container, electrodes not immediately issued for use shall be stored in ovens held at a temperature of at least 250° F [120° C]” — see Figure 2. Because “electrodes shall be rebaked no more than once [and] electrodes that have been wet shall not be used,” smaller hermetically sealed packages can prevent wasting electrodes, especially on a jobsite (see side bar for more details).
Figure 3: Professional-grade inverter power sources have controls for setting “crisp” or “soft” arc characteristics.3) Before creating any test welds, make practice welds to set amperage and any additional controls, such as electrode selection, hot start, and arc force control — see Figure 3. Every operator welds differently, as do different machines, so these settings will need to be fine tuned.
Setting up for success
Operators physically control four factors: arc length, electrode angle, electrode manipulation and travel speed.
With a power source in constant current mode, remember that the operator sets amperage but the machine sets voltage according to its volt/amp curve. That said, operators can somewhat affect voltage by increasing or decreasing the arc length. Instructors invariably tell beginners to “hold a tight arc,” which would be about half the electrode diameter to no more than an electrode diameter. A “l(fā)ong” arc would be 1.5 times the electrode diameter.
According to Lawrence, because the 4G position intimidates welders, they hold a long arc and move too fast, both of which increase the spatter and sparks they want to avoid.
“With a long arc, you lose control over the puddle [weld pool]. When you move too quickly, the puddle [weld pool] doesn’t have enough time to fuse to the base metal, so it droops. Slow down and hold a tight arc for good control,” he said.
It is recommended that prior to welding, you practice “air moves” to ensure unhindered movement. Tuck your elbows into your body to stabilize your hands and position your head adjacent to the joint so you can see the weld pool — see Figure 4.
Figure 4: Position your head adjacent to the joint to see the electrode and its relationship to the weld pool.“You don’t want to get in a position where you drag the electrode directly toward or away from you, because it’s like welding blind,” said Lawrence. “Get comfortable so you can maintain arc length, angle, or travel speed. It also helps if you come up with your shoulder, not your elbow.”
Arc start
Keep every strike within the joint, as any outside strike marks disqualify the joint. E7018 electrodes require a specific arc start process:
1) Strike the arc about 1.5 electrode diameters in front of where the weld begins, e.g., 3?16 in from the edge of the plate or in front of the previous weld for a tie-in.
2) During arc start, hold a longer arc (about 3?16 in) to prevent the electrode from sticking while the arc becomes established.
3) When the arc stabilizes, tighten arc length and move the electrode back to melt the edge of the joint or tie-in with the previous weld.
4) Move forward so the fully established arc welds over the spot of the arc strike.
Angles
For the 3G position, hold the electrode so it has a slight push angle (e.g., tilted back from the direction of travel) to nearly perpendicular to the plate. For the 4G position, tilt (drag) the rod about 15 degrees in the direction of welding. However, as the electrode approaches the end of the joint, this guideline changes.
“The magnetic fields start going crazy because of arc blow,” said Lawrence. “Changing to a more perpendicular position can minimize the distortion of the magnetic field and prevent blowing out the edge of the plate.”
Figure 5: On the root pass (shown here) and hot pass, hold to the sides of the joint to prevent undercut.Arc blow occurs in direct current welding when the material being welded has residual magnetism that interacts with the magnetic field of the welding arc. While individual items may have relatively low residual magnetism, the magnetic field across the root opening can increase significantly when they are brought together for welding. When the electrode is near the edge of the plate, the normally circular lines of magnetic force can become distorted and concentrated, pushing the arc forward or backward.
Manipulation and speed
On the root pass, the operator must incorporate the backing plate and side plates — see Figure 5. Some operators can completely fuse all elements with a straight stringer bead. Others find they need to use a slight side-to-side motion to ensure good sidewall fusion, especially for the 4G position.
“To prevent undercut, hold to the sides and speed across the middle,” said Lawrence. “Avoiding undercut is the biggest challenge apprentices face. You don’t want to leave ‘wagon tracks’ on the sides of the bead, especially since they can trap slag.” As noted in AWS D1.1, 6.10.1.1 Visual Inspection of Groove Welds, fourth requirement, undercut shall not exceed 1?32 in.
The duration of the “hold” is as long as it takes for the weld pool to flow to that side of the joint and melt and incorporate the beveled edge. The flux electrode touching the side will start to burn off first as well.
“The other reason people fail D1.1 on the root pass is because they move too quickly. Slow down so you incorporate the backing bar,” explained Lawrence.
The hot pass will require more of a weave. Again, hold the sides but speed across the middle to keep the bead flat. Forward motion of the electrode should be about 1?8 in.
“Small movements make tighter bead ripples,” said Lawrence. “To me, tight ripples indicate the electrode stayed at the front of the puddle [weld pool], so the chance of trapping slag is much less compared to larger ripples.”
After the hot pass, the groove will be wide enough to accommodate stringer beads, which is what Lawrence uses for all the remaining passes. He feels stringers make a stronger weld because weaving necessitates a slower travel speed and increases total heat input. Furthermore, a hotter plate makes the weld pool more likely to sag out of position.
“Remember that the plate gets hotter as you progress, so you may need to reduce amperage. Better yet, allow the plate to cool between passes,” said Lawrence.
Figure 6: Alternate travel directions. Starting the new pass where the previous one ended fills in the “bowl” that tends to form at the end of the joint.
When making stringers, do not butt them up against each other. Instead, make sure each new bead overlaps a previous one. Also, switch directions between passes — see Figure 6. Starting on alternating ends fills the groove all the way to the end.
Final advice
“Practice in the welding booth like you weld in the field,” stressed Lawrence. For example, do not stabilize the electrode between the fingers of the off-hand or drape the electrode cable over a shoulder. Both get hot during welding and could lead to a flinch and a weld defect.
Finally, there is no substitute for hard work. Lawrence encourages apprentices by telling them that, “With training, anything is possible.”
Acknowledgments
The authors would like to thank the JAC for its support. To bring the experience to life, we worked in the welding booth with Allister Lawrence, CWI, CWE and journeyman instructor, and Memesha Davis, a third-year apprentice, both with Iron Workers Locals 40 & 361.
This article was written for the American Welding Society by Halinson Campos, product business manager — filler metals, ESAB Welding & Cutting; and Jason Chadee, quality assurance manager, Joint Apprentice Committee Iron Workers Locals 40 & 361.
