Welding Process
Applications
- Aluminum Welding
Welding Benefits
- Improved Quality
TIG Aluminum Advice to Help Train SkillsUSA Students
Just as every Olympic athlete goes through years of training to compete with the best athletes in the world, so, too, do SkillsUSA participants. The performances required to win a championship are no less amazing, either.
For example, students entering the GTAW (TIG) aluminum competition are provided with:
- A blueprint and general instruction sheet (which they have not previously seen)
- An AC/DC TIG welder
- A welding bench without fixtures
- A pile of aluminum pieces
Using only their ability to read blueprints and welding skill, the students have a mere two-and-half-hours to complete the fabrication process. Each piece is scored by a judge for its adherence to criteria such as conformance to blue print specifications, tacks, tie-ins, appearance (porosity) weld contour (e.g., must be convex; a flat or concave weld fails) and weld size. On the aluminum project, particular welds must be a minimum of 3 mm wide with tolerance of –0/+2 mm. That is, any weld less than 3 mm or greater than 5 mm results in a point deduction.
The judging standards are high, and the competition gets tougher as the top scorers proceed to the next level of competition. At any one time, thousands of welding students are training, testing and competing at the state and national levels (the SkillsUSA Championships are held every year in June in Kansas City, Kan.). For a select few, the ultimate goal will be to represent SkillsUSA at the WorldSkills Competition, next held in Calgary, Alberta in Sept. 2009.
The pressure is even greater considering that students must be no older than 22 by the time they compete at the world level!
Training Champions
SkillsUSA is a national, nonprofit organization serving teachers and high school and college students preparing for careers in trade, technical and skilled service occupations, including health occupations. It was formerly known as VICA (Vocational Industrial Clubs of America). The organization is a partnership of students, teachers and industry representatives, working together to ensure America has a skilled work force by helping students excel.
Just as athletes have coaches and trainers, SkillsUSA participants receive guidance from industry experts. One of the people from Miller Electric Mfg. Co. who supports SkillsUSA efforts is Neal Borchert, a business development manager and Certified Weld Inspector (CWI).
Borchert is also an official judge. So that all welding students can benefit from his guidance, Borchert recently took a few minutes of time to offer advice about a GTAW aluminum project. To the anonymous student whose work he critiques, thank you for your efforts to hone your welding skills and dedication to becoming a welding professional.
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Fig. 1: Neal Borchert, Miller business development manager and CWI, gives this SkillsUSA student’s weldment an overall inspection prior to judging. |
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Fig. 2: The tungsten point indicates a spot that varies in width and height. Recognizing he was losing control and adding too much heat, the student stopped and restarted the arc. |
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Fig. 3: The tungsten indicates the point where the student decreased amperage to narrow the weld puddle. |
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Fig. 4: At this point, the puddle started getting wider and flatter, which suggests that the student increased heat input. |
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Fig. 5: The higher crown indicates that student quickly reduced heat input at this point. |
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Fig. 6: The student started a new weld in the crater of another weld to fill the crater, leaving a crown of weld reinforcement. This is a good technique, as a crater on the outside edge of a weld is a good spot for a crack to start. |
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Fig. 7: The student ended the weld at the edge of the plate, which left a slightly concave weld (or crater). Recognizing that this might promote a crack, the student added another drop of filler metal. A better technique would have been to start the weld here so the end of this weld would tie in to another plate or weld, as shown in the previous photo. |
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Fig. 8: This crater was improperly filled. The abrupt change creates a stress riser, and the weld would likely fail at this point. |
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Fig. 9: This weld shows uniform crown and width, indicating consistent travel speed and heat input. It is an excellent weld. When welding aluminum, maintaining a uniform bead requires reducing heat input as the weld progresses. Had the student not reduced heat, the weld would get flatter and wider. |
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Fig. 10: The aesthetics of uniform weld beads clearly stand out when compared to others. Also shown is the blueprint from which the student worked. |
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Fig. 11: What’s on the surface of a weld often indicates what lies beneath. While this is a relatively good weld, the area just to the left of the tungsten indicates a slight crown on the face of this weld. |
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Fig. 12: The backside of the weld shown in the previous photo. Notice the change in penetration (or lack thereof), which was created when the student backed off on the heat. |
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Fig. 13: A top view of the weld shown in the previous two photos. The heat input variations that produce the changes we’re discussing aren’t very wide. To improve performance, get the best resolution possible from your remote foot control. |
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Fig. 14: So that small movements of the foot control don’t produce wide amperage variations, use the master control on the welding machine to limit overall amperage. For example, welding this .125-in. 6061-T6 aluminum requires about 125 amps, so set the main amperage control to about 145 amps. This way, the entire range of motion of the foot control only adjusts 0 to 145 amps, not the full 400-amp output of the welder (which would happen if you set the main control at maximum). |
