Underwater Shielded Metal Arc Welding Techniques

There are two basic techniques used today in shielded metal arc wet welding: the self-consuming technique and the manipulative or weave technique. Paragraph 3-12.3.3 describes the advantages of the self-consuming technique for the less experienced underwater welder. With the self-consuming technique, the electrode is dragged across the work and a significant amount of pressure must be applied by the diver. With the manipulative technique, the arc is held as it would be when welding on the surface and little or no pressure is applied to the electrode. The electrode can be maneuvered and manipulated by the diver. This method requires a great deal more skill and experience than does the self-consuming technique.

3-12.1 Welding Set Up Procedures. The following steps should be followed to establish optimum welding current and voltages.

a. Before entering the water, set the amperage and run several beads on a plate.

b. Use the tong test ammeter to check the amperage.

c. After the diver enters the water, the first task is to clean a spot for the ground clamp. The spot should be in a position in front of the diver, as close as practical to the weld joint and should be scraped or wire brushed shiny clean. For diver safety, only C-type clamps should be used as grounding clamps for underwater cutting or welding operations. The clamp must be firmly secured to the work piece and the cable should have sufficient slack to prevent it from being pulled loose. The diver may elect to lightly tack weld the clamp in place when there is a possibility of it working loose. The ground should always be kept in the diver's forward line of vision.

d. The diver should make a test weld to check the "heat" at working depth.

e. Via the communications system, the diver can instruct the tender to fine tune the welding machine, that is; increase or decrease the amperage as needed. The open circuit voltage may also require adjustment.

f. After the optimum settings are determined, welding can begin.

g. The diving tender should always maintain a written record of the following:

1) The welding amperage as read from the tong meter.

2) Both open and closed-circuit voltage as read from the volt meter.

3) Electrode diameter, type, manufacturer and waterproofing material.

4) Electrical polarity.

5) Length of welding cable.

6) Depth of work site.

By accurately recording this type of information, lessons may be learned and applied to future dives, thereby decreasing the likelihood of mistakes being duplicated.

3-12.2 Self-consuming Technique. When using the self-consuming technique, the weld metal is deposited in a series of beads or strings by dragging the electrode against the work. The technique is suited to fillet welding and can be readily adapted to underwater work since it provides a natural groove to guide the electrode. Tests have shown that the beads, when in the form of a fillet, result in welds having approximately the same leg length (size) as the diameter of the electrode used; that is, a single pass with a 1/8-inch electrode produces a fillet weld having a 1/8-inch leg.

3-12.3 Fillet Welding in the Horizontal Position (Self-Consuming Technique). In making fillet welds, pay particular attention to lead angles and work angles. The work angle is the angle between the electrode and the work in a plane at right angles to the long axis of the joint. The lead angle is the angle between the electrode and joint in the direction of travel. The following is the recommended procedure for fillet welding in the horizontal position:

a. Make sure the safety switch is open.

b. Thoroughly clean the surfaces to be welded.

c. Set the welding power source to deliver the proper current for the electrode being used (see Table 3-3). This current is higher (0 to 30 percent) than the topside current for the same electrode since the surrounding water absorbs the heat rapidly.

d. Hold the electrode against the plate at a work angle of 45 ° to the plate end surfaces as illustrated in Figure 3-4. Tilt the electrode to a lead angle of 45° ± 15° in the line of intended weld. The angle variance, depends on the size of electrode used and the skill and technique of the diver.

e. Call for SWITCH ON. The arc should start when the tender (phone talker) closes the safety switch. If the arc does not start, tap or rub the electrode tip against the work until the arc is established. Be sure to keep the electrode at the point where the weld is to begin. Once the arc is started, exert enough pressure against the work to allow the electrode to consume itself. Maintain the original work and lead angles between the electrode and line of weld by moving the hand perpendicularly toward the surface being welded (see Figure 3-4). Do not hold an arc as in topside welding, simply keep the electrode in contact with the work. Run straight beads; do not weave. About 8 inches of weld metal will be deposited for every 10 inches of electrode consumed. It is advantageous to use this method, especially when poor visibility makes it difficult to hold an arc in the usual topside manner.

B C

A. POSITION THE ELECTRODE AT AN ANGLE OF APPROXIMATELY 30 DEGREES TO THE LINE OF WELD WITH THE ELECTRODE TIP IN CONTACT WITH THE WORK.

B. CALL FOR SWITCH "ON." TAP THE ELECTRODE MOMENTARILY, IF NECESSARY, TO START THE ARC.

C. APPLY SUFFICIENT PRESSURE IN THE DIRECTION OF THE ARROW TO ALLOW THE ELECTRODE TO CONSUME ITSELF.

f. When the electrode is consumed, break the arc, call for SWITCH OFF. Keep the electrode in welding position until the tender (phone talker) has confirmed switch off, then tap the electrode twice to make sure the switch is off. Only then proceed to change the electrode.

g. Before starting to deposit a new weld, clean the previous weld thoroughly, especially the end where the arc was broken. Look for any visible pin holes or porosity which may affect the quality of the weld. Grinding is the best method as all slag, high points, lumps and any arc craters will be removed. The deposit from the new electrode should slightly overlap the previous deposit. All succeeding welds must be thoroughly cleaned and inspected for defects.

h. Do not call for SWITCH ON until the new electrode is in position against the work and ready for welding. In general, try not to let the bubbles interfere with visibility when welding.

3-12.3.1 Fillet Welding in the Vertical Position. The self-consuming technique can also be used for fillet welding in the vertical position by following the same steps outlined above for horizontal fillet welding. The weld must start at the top and move down as shown in Figure 3-5 so the bubbles generated will not interfere with the diver's visibility as he follows the line of the weld. Under certain conditions, it might be necessary to vary the lead angle of the electrode or adjust the current when welding in the vertical position.

3-12.3.2 Fillet Welding in the Overhead Position. The self-consuming technique can be applied to fillet welding in the overhead position (Figure 3-6) when using approved electrodes (see Table 3-2) and when the amperage is carefully adjusted. THE AMPERAGE RANGE FOR OVERHEAD WELDING IS NARROW. Welds deposited using current levels outside of this range will result in very poor deposits or no deposit at all. Good penetration and fusion can be obtained readily but undercutting and convex beads are difficult to avoid with this technique. Before attempting an actual overhead weld, the diver should make several practice runs under working conditions. These welds should be brought topside and examined to ascertain that the current setting is correct and that the diver has mastered the technique. Dripping beads indicate that (1) the current was too high, (2) the operator applied insufficient pressure or (3) both conditions were present. Skill, coupled with practice, is essential to the production of consistently good overhead welds.

The more experienced underwater welder can also use a modified self-consuming technique for overhead welding. The diver can vary the work angle from 35 to 55° while traveling down the line of the weld (Figure 3-6) maintaining slow, steady movement. With practice, overhead welds made this way will not have the undercutting and convexity which often result from using the standard self-consuming technique.

RISING BUBBLES AND PRODUCTS OF COMBUSTION INTERFERE WITH VISIBILITY

RISING BUBBLES AND PRODUCTS OF COMBUSTION INTERFERE WITH VISIBILITY

3-12.3.3 Self-Consuming and Manipulative Techniques. The self-consuming technique is recommended for divers of average or less than average skill who have little time for practice. Naturally, the self-consuming technique does not produce as strong a weld as does one laid down by a skilled underwater welder using the manipulative technique. However, for salvage purposes, sound welds made using the self-consuming technique are considered acceptable. The manipulative or weave technique and the 35° to 55° self-consuming techniques are recommended for skilled operators only.

3-12.3.4 Fillet Welding Where There is Poor Fit-Up. Where there is poor fit-up of members or plates to be welded, additional weld metal is needed to fill the gap at the root of the fillet. This can be done by feeding in the electrode toward the joint faster than it is usually fed in when using the self-consuming technique. Approximately 6 inches of weld for 10 inches of electrode can be deposited instead of the usual 8 inches of weld by feeding in. When this technique is used under water, the additional weld metal laid in the opening solidifies rapidly as shown in Figure 3-7; it does not run out of the gap as it would in the air. Fillets with gaps at the root up to 1/8 inch have been successfully welded using this process, although it is not recommended for use on thin metals. Paragraph 3-12.4. addresses welding on thin metals.

Do not attempt to bridge a gap greater than 1/8-inch with weld metal. This will result in a cracked weld bead which will eventually have to be removed. The correct procedure is to run successive stringer beads on the continuous member until the gap is less than 1/8-inch. Then bridge the gap to join the members.

3-12.4 Welding on Thin Plates. The techniques for welding plates, which are 20-gauge or less, are basically the same as those described above. However, the following practices are required in order to successfully complete the weld and prevent the electrode from burning through the metal.

a. The maximum electrode size shall be 1/8-inch.

b. Maximum travel speed and minimum amperage should be used consistent with depositing a sound weld bead.

c. Minimum electrode pressure is essential.

d. Electrodes must be properly manipulated to avoid overheating a specific area.

e. When welding a thicker material onto a thinner material by using manipulative or self-consuming technique, the majority of the heat should be directed toward the thicker metal. Ultrasonic equipment may be used to determine the actual thickness of the base metal to be welded.

f. The arc should always be struck on previously deposited weld metal or on thicker metal.

PRESSURE APPLIED IN THE DIRECTION OF THE ARROWS TO DEPOSIT ENOUGH FILLER METAL TO FILL THE GAP

g. The arc should always be broken by pulling back on the previously deposited metal.

h. It is always good practice to establish proper heat and travel speed on practice material of thickness equivalent to the base metal of the intended weld and under similar conditions.

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