ix Welding Rod Position The welding rod is held at a 15°–45° angle from the base metal. This angle is generally used for all welding positions. When horizontal welding, the is placed into the upper edge of the molten weld pool. This permits to melt and cool the weld pool before the molten metal sags. Weld The weld pool may become too hot while welding. To cool the pool, withdraw the fl ame tip about 1″ (25 mm) from the base metal and then return it to within (1.5 mm–3 mm). Making up-and-down motion allows weld pool to cool, Figure 28-12. If undercutting occurs on upper piece, the welding rod the pool more often. This fi lls the undercut (depression). Increasing the upward angle of the fl ame also helps to force molten metal higher into the weld pool. Exercise 28-3 Square-Groove Butt Joint in the Horizontal Welding Position 1. Obtain two pieces of carbon steel measuring 1/16″ × 1 1/2″ × 6″ (1.6 mm × 40 mm × 150 mm). 2. Clean the edges. 3. Select the correct torch tip and welding rod size. Refer to Figure 24-34. 4. Turn on the welding outfit and set the working pressure. Light the torch and adjust to a neutral flame. 5. Place the pieces in the flat welding position and tack weld in three places. 6. Position the pieces for horizontal welding. 7. Weld the joint using the suggested torch and filler metal angles. Inspection: The completed weld should have a convex weld bead with even ripples, an even bead width, and 100% penetration. 1" 1/16"–1/8" (1.5 mm–3 mm) Goodheart-Willcox Publisher Figure 28-12. The flip motion of the torch and flame. This motion may be used if the metals tend to overheat. It allows time for the weld pool to cool slightly. Weld axis 80°–85° 15°–45°°54°51 Tack welds Welding rodd Weld bead Horizontal weld axis Torch is at a 5°–10° upward work angle Top View Front View Goodheart-Willcox Publisher Figure 28-11.the Torch, flame, and welding rod positions for welding a 434 Section 6 Oxyfuel Gas Processes Copyright Goodheart-Willcox Co., Inc. 88 Review Questions Answer the follo wing questions using the information provided in this chapter. Know and Understand 1. True or False? Some steel rules have marks that are spaced one-tenth of an inch (0.1″) apart. 2. What costs should be included when estimating the total cost of a welding project? A. Material costs. B. Welding supply costs. C. Labor costs. D. All of the above. 3. How many inches of weld are required to weld a 1″ × 4″ rectangular tube to a column, as shown below? Hint: What is the perimeter of a 1″ × 4″ rectangle? A. 4 inches. B. 5 inches. C. 10 inches. D. None of the above. 4″ 1″ .18 4. How many millimeters are equal to A. 25.4 mm. B. 254 mm. C. 2540 mm. D. None of the above. 5. How many inches are equal to 1397 mm?found A. 55 inches. B. 110 inches. C. 550 inches.. D. None of the above.the Summary • Two systems of measurement are used in the United States. One is the US customary system, or English system. The second is the International System of Units, or SI metric system. • Welders need to know how to measure lengths in both US customary units (feet and inches) and SI metric units (meters). Welders may be required to use tape measures, scales, or calipers to measure lengths. • Perimeter is the distance around a two- dimensional object. For any object with only straight sides, the perimeter is determined by adding the lengths of all the sides. • The length of the hypotenuse of a right triangle can be determined using the Pythagorean theorem: a2 + b2 = c2. • The area of a parallelogram is determined by multiplying the base times the height: Area = b × h. • The area of a trapezoid is determined using the formula: Area = 1/2 × (b1 + b2) × h. • The area of a triangle is determined by multiplying the base times the height and dividing by 2: 1/2 × b × h. • For a circle, the circumference (perimeter) is determined by the formula: Circumference = πd or 2πr. • The area of a circle is determined using the formula: Area = πr2. • The volume of an object is determined by multiplying the surface area times the length. For a pipe or cylinder, the formula is: Volume = πr2 × Length. • The surface area of a straight-sided, three- dimensional object is the sum of the area of all of the sides. • The surface area of a pipe is determined using the formula: Surface Area = Circumference × Length. • Estimating the overall cost of a job includes determining the cost of base materials, welding supplies, labor, and any other related job costs. Copyright Goodheart-Willcox Co., Inc. e required to e to a column, as h e p erimeter of a 4 ″ 1 ″ q ual to 1100″? ″ ? 2 5 40 mm. No ne o f th e ab o ve. o 139 7 mm? 550 inc h es No ne o f th e ab o ve. odheart-Willcox Co., Inc. 90 Refer to Figure 6-17 to answer Questions 6–10. 6. What is the metric equivalent of a 70,000 pound tensile strength? 7. A gas metal arc welding process deposits 9 lbs/ hr. How many kg/hr is this? 8. A welding process has a travel speed of 12 mm/sec. How many inches/minute is this? Round to the nearest whole number. 9. A spool of gas metal arc welding wire weighs 45 pounds. What is the mass in kilograms? Round the answer to one decimal place. 10. A welding project is estimated to complete in 17 hours. A welder makes $18.75/hour. What is the cost of the welding labor? STEM Connections 1. Science. Nature has been the model for many human inventions. In nature, you can fi nd many of the same shapes used in welding and welding-related professions. Go to a park or forested area near you and observe the shapes in nature. Try to fi nd an example of each of the shapes described in this chapter. Make a list of shapes you fi nd. 2. Engineering. Look around your home or school to fi nd three items that were assembled using welds. Choose an appropriate measuring tool and measure the weld. Provide all dimensions you think are important. Be sure to measure accurately. Prepare a poster that shows photos of the items labeled with the measurements you made. For each item, explain the purpose of the weld you measured from an engineer’s perspective. Curricular Connections 1. Critical Thinking. Explain the meaning of the expression, “measure twice, cut once.” 2. Social Science. Conduct research to fi nd out more about Pythagoras, the person credited with developing the Pythagorean theorem. Write an informative report about his contributions to knowledge and learning. 3. Critical Thinking. Obtain a steel rule that has US customary units on one edge and SI metric units on the opposite edge. Suppose you know that the exact measurement of an item is 3 3/16 inches, but you need to know the measurement in centimeters. Use a second rule or straightedge to compare the marks on the two sides. Can you use the rule as a “shortcut” instead of calculating the conversion? Explain why this is or is not a good idea. Communicating about Welding 1. Speaking and Listening. With another classmate, role-play a situation in which you are an instructor explaining the importance of learning basic math concepts to a skeptical student. Provide examples of real-life scenarios in which an understanding of math is critical, using technical terms in this chapter and the previous chapter. Adjust your vocabulary as needed while responding to your partner’s questions and clarifying information. Then, switch roles. 2. Speaking. Debate the topic of adopting the metric system in the United States. Divide into two groups. Each group should gather information in support of either the “pro” argument (the metric system should completely replace the US customary system) or the “con” argument (use of the metric system should not be mandatory). Use defi nitions and descriptions from this chapter to support your side of the debate and to clarify word meanings as necessary. You will want to do further research to fi nd expert opinions, potential consequences of either approach, and other relevant information. Copyright Goodheart-Willcox Co., Inc. Welding Ro d Pos ition T h e welding ro d is h e ld a the base metal. This angle is welding positions. W h en ho rrod od is placed into the upp e we ld p oo l. T h is p ermits tthee h rrod o weld pool before the molten m Weld PPool ool T h e we ld poo l may be welding. To cool the pool, w ab out 1 ″ (25 mm) from the ″ return it to wit h in 11/166″–1/8″ / 1 ″ –1 ″ Making tthisInc.rapid h is rapi d up-and- tthee h we ld p oo l to coo l, Fig ur e o ccurs on tthee h upper piece, iinsert n iin n the p ool more often. T h (d i ) I i h – Tack welds We ldi ng ro T op Vi e w Fr o nt Vi ew Fi gure 28-11 . Torch, flame, and we ldi ng a hhorizontall ori zonta bbutt utt jjoint.o int. 43 4 Section 6 Oxyfuel G 2. Light the preheating fl ames with a spark lighter. All fl ames should light at the same time. If all the fl ames do not light, shut down the torch and clean any dirty orifi ces. 3. Continue opening the acetylene torch valve until the smoking stops. The fl ame must remain in contact with the end of the tip. See Figure 25-15A. 4. Open the oxygen torch valve until a neutral fl ame is obtained. See Figure 25-15C. The cutting oxygen valve must be closed during this adjustment. 5. Press or squeeze the cutting oxygen valve (lever). The preheating fl ames should remain neutral. If a carburizing fl ame is obtained, as shown in Figure 25-15B, open the torch oxygen valve a little more. Slightly adjust both the acetylene and oxygen torch valves until neutral preheating fl ames remain while the cutting oxygen valve is open. Note A cutting torch attachment has an extra cutting oxygen finger valve near the cutting oxygen lever. When using a positive pressure cutting torch attachment, one additional step is required to light the torch. Prior to performing the five steps above, open the cutting torch attachment’s oxygen valve one full turn. Then carefully follow the five steps as listed. After opening this cutting oxygen valve, all oxygen adjustments will be made at the torch oxygen valve on the torch body. Shutting Down a Positive- Pressure Cutting Torch The cutting outfi t must be shut down when the cutting operation is completed or when the welder is leaving the cutting station. Be certain the correct procedure is followed so all gauges read zero when the shutdown is completed. Remember to turn regulator adjusting screws counterclockwise until they feel loose. Use the following procedure to properly shut down the outfi t. 1. Turn off the acetylene torch valve. See Figure 25-17. 2. Turn off the oxygen torch valve. See Figure 25-18. 3. Turn off the acetylene cylinder valve. See Figure 25-19. 4. Turn off the oxygen cylinder valve. See Figure 25-20. 5. Reopen the acetylene and oxygen torch valves. See Figure 25-21. Inner flame cone Outer flame Intermediate flame area Bullet-shaped inner cone Sharply pointed inner cone A B C Goodheart-Willcox Publisher Figure 25-16. A—Carburizing flame. The flame begins to burn cleanly as oxygen is turned on. Three distinct areas of the flame can be seen. B—Neutral flame. When the oxygen and acetylene are properly adjusted, the inner cone is bullet-shaped or rounded on the end. C—Oxidizing flame. When too much oxygen is present, the inner cone becomes pointed. The flame is noisy and gives off a hissing sound. This flame is undesirable because it causes the weld area to oxidize (rust). 386 Section 6 Oxyfuel Gas Processes Copyright Goodheart-Willcox Co., Notes provide you with advice and guidance that is especially applicable for on-the-job. Step-by-Step Exercises are highlighted throughout the textbook to provide clear instructions for hands- on activities that reinforce concepts and techniques presented in the text. Summary feature provides an additional review tool for you and reinforces key learning objectives. Review Questions allow you to demonstrate knowledge, identification, and comprehension of chapter material. STEM Connections are activities that help you relate the material presented in the chapter to the areas of science, technology, engineering, or math. Curricular Connections are activities that help you apply your welding knowledge to other academic areas, including social studies, language arts, and critical thinking. Communicating about Welding improves your language skills by having you listen, write, and speak about welding-related topics.