Run TIG Beads on Mild Steel

A. Finished-Project Specification

Outcome: a set of flat-position GTAW practice beads on identified mild-steel coupons, including at least one autogenous bead and a series of filler-added beads, each produced with verified setup, controlled arc length and travel, coordinated filler addition, managed heat input, and documented visual inspection. No joint welding is performed as part of this chapter's finished work.

B. Bead Practice Schedule (Component Schedule)

Bead Type	Quantity	Coupon Condition	Filler Condition
Autogenous bead	At least 1 per learner	Clean bright flat mild steel, marked bead line and endpoints	None added
Filler-added bead	As specified by the instructor or evaluator for the session	Clean bright flat mild steel, marked bead line and endpoints	Approved classification and diameter, cleaned before use

C. Material Takeoff

• Coupons: flat mild-steel coupons prepared per Chapters 4 through 6, quantity sufficient for the autogenous and filler-added bead schedule above.
• Filler rod: approved GTAW filler classification and diameter identified in the Chapter 14 setup record, quantity sufficient for the filler-added bead schedule with reasonable allowance for practice consumption.
• Shielding gas: the gas type verified in Chapter 14, consumed continuously during arc time and required post-flow for every bead in this chapter.
• Fastener and hardware schedule: not applicable. This chapter produces practice beads, not a fastened assembly.

D. Acceptance Standards

Check	Standard
Bead width and consistency	Width and reinforcement remain visually consistent along the full bead length with no abrupt narrowing or widening
Oxidation and shielding	Bead surface shows the coloration consistent with adequate gas coverage for the approved procedure; heavy discoloration or sooting is identified and analyzed
Undercut	No undercut exceeding the approved gauge criteria at either toe
Porosity	No visible surface porosity
Crater condition	Crater filled using the approved termination method with no crater crack
Tungsten condition	Tungsten free of contamination, splits, or excessive erosion at the end of each bead
Heat-affected zone	Discoloration and distortion remain within the range expected for the approved amperage and travel speed; excessive heat buildup is identified and corrected before the next bead

E. Preparation — Review and Readiness Verification

1. Review the approved coupon layout, tungsten, filler, gas, polarity, amperage limit, and technique. Confirm these match the Chapter 14 setup record before proceeding.
2. Verify work-area, PPE, ventilation, cylinder, machine, torch, tungsten, and filler readiness. Reinspect each item rather than assuming it remains unchanged since Chapter 14.
3. Prepare the coupon and filler rod to clean bright metal. Remove any oxidation that has formed since Chapters 4 through 6.

F. Layout and Station Verification

1. Mark bead lines and endpoints. Use soapstone or marker referenced to the coupon edge established in Chapter 4.
2. Secure the coupon flat and attach the work clamp. Confirm the clamp contacts clean sound metal close to the practice area.
3. Verify gas flow, pre-flow, post-flow, and torch cooling. Confirm each function operates as set in Chapter 14 before striking an arc.

G. Body Position and Torch Control

1. Assume a stable seated or standing position with forearm support where appropriate. Confirm the position allows uninterrupted travel along the full marked bead line.
2. Arrange torch lead, pedal cable, and gas hose to prevent drag. Confirm no cable pulls the torch off the intended path during travel.
3. Hold the torch at the approved work and travel angle. Confirm the angle matches the approved procedure before striking the arc.
4. Position the tungsten close to the start without touching the work. Confirm tungsten extension before initiating the arc.

H. Autogenous Bead — Arc Initiation and Travel

1. Lower the helmet and initiate the arc using the approved start method. Confirm the arc establishes cleanly before proceeding.
2. Increase current gradually under controlled input where applicable. Do not jump directly to full welding current if the machine and procedure provide a ramp-up control.
3. Establish a small stable puddle. Hold the torch in place until the puddle forms before beginning travel.
4. Maintain a short consistent arc length. Do not allow arc length to drift as travel begins.
5. Travel along the marked line without filler for the first exercise. Keep travel speed steady rather than accelerating or slowing to correct puddle size.
6. Control puddle size through current and travel. Adjust only current or travel speed, not both simultaneously, to correct a puddle that is too large or too small.
7. Terminate current gradually using the approved method. Use the machine's slope-out or foot-pedal control rather than an abrupt current cutoff.
8. Maintain shielding gas over the cooling puddle during post-flow. Hold the torch in position for the full post-flow duration.
9. Do not move the torch away prematurely. Confirm post-flow has ended before repositioning for the next bead.
10. Inspect the tungsten for contamination. Check the tip for discoloration, balling, or pickup before the next arc strike.
11. Regrind contaminated tungsten before continuing. Use the dedicated grinding equipment and procedure from Chapter 14.
12. Inspect the autogenous bead for width, consistency, oxidation, undercut, crater, and heat-affected zone. Record findings before proceeding to filler practice.

I. Filler-Added Bead — Coordination, Heat Control, and Inspection

1. For filler practice, hold the filler rod in the approved hand position. Confirm the rod angle and grip allow controlled, repeated additions.
2. Keep the filler end within the shielding envelope without touching the tungsten. Maintain a consistent distance between the filler tip and the arc.
3. Establish the puddle. Confirm puddle formation before the first filler addition.
4. Add filler to the leading edge using a consistent rhythm. Dip the filler at the front of the puddle rather than into the arc itself.
5. Withdraw the filler slightly without removing it from gas protection. Keep the rod tip inside the shielding-gas envelope between additions.
6. Coordinate torch movement, filler addition, and current control. Advance the torch only as fast as filler additions and puddle control allow.
7. Maintain bead width and puddle size. Adjust filler frequency and travel speed together to hold a consistent bead profile.
8. Control heat buildup as the coupon warms. Watch for an enlarging puddle or increasing travel difficulty as later beads are run on the same coupon.
9. Use approved pauses, sequence, or coupon rotation rather than excessive speed changes. Allow the coupon to cool between beads instead of speeding up travel to compensate for heat buildup.
10. Fill the final crater. Add filler through the termination sequence rather than stopping filler addition abruptly.
11. Maintain post-flow until the tungsten and weld are protected. Hold torch position for the full post-flow duration before moving away.
12. Allow the coupon to cool in the designated location. Mark the coupon hot and place it in the hot-metal cooling zone.
13. Clean the bead only with approved uncontaminated tools. Use the dedicated brush identified for mild steel.
14. Inspect bead appearance, width, reinforcement, ripple spacing, toe fusion, undercut, porosity, oxidation, crater, and contamination. Compare each bead against the Acceptance Standards table.
15. Compare heat input and color among beads. Identify which beads show excessive discoloration consistent with overheating.
16. Identify defects caused by arc length, angle, filler placement, gas coverage, travel, current, or tungsten contamination. Record the probable cause for each defect found.
17. Repeat with one controlled correction at a time. Change only one variable before running the next comparison bead.
18. Record settings, technique, filler, gas, tungsten condition, defects, corrections, and accepted result. Complete the bead practice log for the full session.
19. Close gas, isolate the machine, protect the torch, and complete fire watch. Shut down the station according to the Chapter 1 fire-watch requirement before leaving the area.