Have someone remain in the area for at least a half hour after the welding or cutting is finished to watch for smoke from a smoldering fire.
This book is not intended to teach detailed manual welding techniques. Oxyacetylene welding, however is, a useful process to learn and may not be familiar to those who have some skill at MIG and TIG welding.
Project: Welding Plate Practice
EXERCISE 1: WELDING BEADS
This exercise starts with weld beads and butt welds made downhand in 1/8-inch-thick steel, and then progresses to welds made in tubing. Select a number-2 or -3 welding tip size or one recommend by the manufacturer for use with 1/8-inch-thick steel. Manufacturers also supply recommended oxygen and acetylene pressures for various tip sizes and gas mixers used with their torches. Run a weld bead on a plate. Make the first weld passes without filler metal. Hold the inner cone about 1/8 inch from the plate and hold the torch stationary until a small molten puddle forms. Move the torch tip in a small semicircle and direct it slowly along the plate.
Fig. 3.12. Some simple oxyacetylene welding practical exercises help develop skills. A good exercise is to run a weld bead on plate using a 1/6-inch-diameter filler rod and hold as shown. (Figure adapted from ESAB’s Oxyacetylene Handbook with sketch by Walter Hood)
EXERCISE 2: PRACTICE FORMING A WELD PUDDLE
For the next practice welds, hold a 1/16-inch rod as shown in Figure 3.12. Insert the rod into the leading edge of the weld puddle until a few drops flow into the deposit. Then pull the rod back slightly and advance the torch a small amount, allow a puddle to form, and repeat the process of inserting the rod.
Fig. 3.13. To fill gaps you need two pieces of steel 9 inches long and 1/8 inch thick. Place them 1/16 inch apart at one end and 3/16 inch apart at the other end. Make a tack weld at the narrower end first and then tack weld the larger gap. Advance the torch tip as the weld progresses. (Figure adapted from ESAB’s Oxyacetylene Handbook with sketch by Walter Hood)
EXERCISE 3: ADD FILLER WELD BETWEEN TWO PLATES
Filling gaps is the next thing to learn. Place two pieces of steel approximately 9 inches long, 3/32 to 1/8 inch thick, 1/16 inch apart at one end and 3/16 inch at the other. Make a tack weld at the tighter end and tack weld the end with the 3/16-inch gap. The next tack weld is somewhat more difficult because of the greater gap. Move the flame slowly from one edge to the other. As the edges melt, place a small amount of filler metal on the edge and allow it to cool slightly. This is usually best performed when the flame is on the opposite side of where the metal is added. Increase the size of the tack by adding more filler rod.
After tack welding the piece, start at the tighter end and add filler as you did for the tack; move the flame in a small arc from side to side. Advance the torch tip as the weld progresses.
Figure 3.14 is a view of the middle of the joint. The technique becomes obvious as the weld progresses. More time is spent at the edges as the torch is moved side to side. Too much time spent in the middle of the joint causes the metal to burn through. The end objective is to have the weld bead drop through slightly at the bottom while being reinforced about 1/16 inch on top.
Test the weld quality by cutting a section about 3 inches long and placing one plate in a vice and striking the other with a hammer. You should be able to bend it at a 90-degree angle without breaking it.
Fig. 3.14. This is the perspective in the middle of the joint. The technique becomes obvious as the weld progresses. More time is spent at the edges as the torch is moved side to side. Too much time spent in the middle of the joint causes the metal to burn through. (Figure adapted from ESAB’s Oxyacetylene Handbook with sketch by Walter Hood)
Fig. 3.15. To weld heavier sections use two pieces of 1/4-inch-thick steel. Bevele each plate at a 45-degree angle with a 1/16-inch nose. Concentrate the flame on melting the square-edge nose and forming the underbead. (Figure adapted from ESAB’s Oxyacetylene Handbook with sketch by Walter Hood)
EXERCISE 4: ESTABLISH ROOT WELD
Heavier sections can be welded using a similar technique (but with the appropriate tip size and filler rod). Use two pieces of steel 1/4-inch thick. Bevel each plate at a 45-degree angle. Use a grinder to make a flat nose at the bottom about 1/16 inch in width. This leaves a 90-degree bevel 3/16 inch deep. Assuming the test plates are about 9 inches long, gap them 1/8 inch at one end and 3/16 inch on the other.
Make tack welds on both edges as was done for the thinner sheet metal. Once the tack welds have been made, make a weld as before, but it should only fill up about half the thickness. This is the first of two weld passes. Focus on making a good underbead. The top edges of the plate should not have melted. The flame is concentrated on melting the square-edge nose and forming the underbead.
As the root pass approaches completion, the top corners of both pieces should still be sharp and unmelted. This first pass achieves complete root penetration and little else. The appearance of the top of the weld is not very important because it will be melted and covered by the finish pass. The puddle can be kept relatively small, which is also a help if the gap varies.
Make sure the bottom-squared nose is brought up to melting temperature before the weld puddle advances across them. Be sure not to add too much filler metal at one time.
Move the filler rod in and out of the weld puddle to control the rate of filler addition.
Move the flame across the joint, spending more time on the sides of the V, being sure they are melted up to about halfway up to the top edge of the plate.
Fig. 3.16. The objective of the first pass is to complete root penetration (here, the root pass is approaching completion). Keep in mind the appearance of the top weld is not very important. Move the flame across the joint, spending more time on the sides of the V so they are melted up to about halfway. (Figure adapted from ESAB’s Oxyacetylene Handbook with sketch by Walter Hood)
Fig. 3.17. With the second pass, keep the end of the rod in the puddle at all times. Rub the end against the solid metal below the puddle, maintaining a constant back-and-forth motion across the joint. When the flame is melting one side of the joint, the rod is pushing on the puddle on the opposite side. (Figure adapted from ESAB’s Oxyacetylene Handbook with sketch by Walter Hood)
EXERCISE 5: COMPLETE FINISH WELD
Make a second pass over the first one. A larger 1/8-inch-diameter rod can be used as the weld progresses slowly and more filler rod is needed. Start at the beginning and form a weld puddle and proceed to fill the joint completely.
Much more filler is required in this pass. Keep the end of the rod in the puddle at all times, actually rubbing the end against the solid metal below the puddle and keeping