FUNDAMENTALS OF MANUAL WELDING Main Category: Materials Engineering Sub Category: Welding Course #: MAT-114 Course Content: 123 pgs PDH/CE Hours: 11 COURSE/EXAM PREVIEW (HIT BACK TO RETURN TO ENGINEERING-PDH.COM) WWW.ENGINEERING-PDH.COM TOLL FREE (US & CA): 1-833-ENGR-PDH (1-833-364-7734) [email protected] MAT-114 EXAM PREVIEW Instructions: • Review the course & exam preview below. • Click “Add to Cart” from the course page on the website. You can “Continue Shopping” to add additional courses, or checkout. Don’t forget to apply your coupon code if you have one before checkout. • After checkout you will be provided with links to download the official courses/exams. • At your convenience and own pace, you can review the course material. When ready, select “Take Exam” to complete the live graded exam. Don’t worry, you can take an exam as many times as needed to pass. • Upon a satisfactory completion of the course exam, which is a score of 70% or better, you will be provided with your course completion certificate. Be sure to download and print your certificates to keep for your records. Exam Preview: 1. One of the most popular welding methods uses a gas flame as a source of heat. In the oxyfuel ____ process (fig. 3-2), heat is produced by burning a combustible gas, such as MAPP (methylacetylene-propadiene) or acetylene, mixed with oxygen. a. Arc Welding b. Brazing c. Sub-Arc Welding d. Gas welding 2. Arc welding is a process that uses an electric arc to join the metals being welded. A distinct advantage of arc welding over gas welding is the concentration of heat, because less heat spread reduces buckling and warping. a. True b. False 3. To prevent head burns during overhead welding operations, you should wear leather or flameproof caps under the helmet. Earplugs also should be worn to keep sparks or splatter from entering and burning the ears. a. True b. False 4. Welding cables carry the current to and from the workpiece. One of the cables runs from the welding machine to the electrode holder and the other cable connects the workpiece to the welding machine. The cable that connects the workpiece to the welding machine is called the ground. a. True b. False 5. You use the FILLET-WELDED JOINT TEST to check the ____ of a fillet weld. _____ refers to the degree of freedom a weld has from defects found by visual inspection of any exposed welding surface. a. Stress b. Strength c. Toughness d. Soundness 6. When welding material solidly, you may use ____ to hold it in place temporarily. ____ is one of the most important steps in pipe welding or any other type of welding. a. Fillet weld b. Wearfacing c. Weld gapping d. Tack Welds 7. To produce good quality welds, a welder must learn to recognize and correct possible welding defects. ____ usually results from pulling the torch and gas shield away before the crater has solidified. To correct this problem, you should reduce the travel speed at the end of the joint. You also may try reducing the tip-to-work distance. a. Lack of Penetration b. Crater porosity c. Burn-Through d. Cold Lap 8. Special filler rods are available for GTA welding; therefore, but you can also use welding rods designed for oxyfuel welding because they can contaminate the tungsten electrode a. True b. False 9. For GMA Welding of Aluminum, the joint design for aluminum is similar to that of steel; however, aluminum requires a narrower joint spacing and lower welding current setting. a. True b. False 10. For GMA Welding of Stainless Steel, DCRP with a 1- or 2-percen____ oxygen with argon mixture is recommended for most stainless steel welding. a. 1-2% b. 2-3% c. 4-5% d. 5-10% INTRODUCTION TO WELDING In the Navy as well as private industry, welding is most common welding process. The primary differ- widely used by metalworkers in the fabrication, main- ences between the various welding processes are the tenance, and repair of parts and structures. While there methods by which heat is generated to melt the metal. are many methods for joining metals, welding is one of Once you understand the theory of welding, you can the most convenient and rapid methods available. The apply it to most welding processes. term welding refers to the process of joining metals by heating them to their melting temperature and causing The most common types of welding are oxyfuel gas the molten metal to flow together. These range from welding (OFW), arc welding (AW), and resistance simple steel brackets to nuclear reactors. welding (RW). As a Steelworker, your primary concern is gas and arc welding. The primary difference between Welding, like any skilled trade, is broad in scope and these two processes is the method used to generate the you cannot become a welder simply by reading a book. heat. You need practice and experience as well as patience; however, much can be gained through study. For in- stance, by learning the correct method or procedure for GAS WELDING accomplishing a job from a book, you may eliminate many mistakes that otherwise would occur through trial One of the most popular welding methods uses a gas and error. flame as a source of heat. In the oxyfuel gas welding process (fig. 3-2), heat is produced by burning a com- This chapter is designed to equip you with a back- bustible gas, such as MAPP (methylacetylene-propadi- ground of basic information applicable to welding in ene) or acetylene, mixed with oxygen. Gas welding is general. If you take time to study this material carefully, widely used in maintenance and repair work because of it will provide you with the foundation needed to be- the ease in transporting oxygen and fuel cylinders. Once come a skilled welder. you learn the basics of gas welding, you will find the oxyfuel process adaptable to brazing, cutting, and heat treating all types of metals. You will learn more about WELDING PROCESSES gas welding in chapter 5. Welding is not new. The earliest known form of ARC WELDING welding, called forge welding, dates back to the year 2000 B.C. Forge welding is a primitive process of Arc welding is a process that uses an electric arc to joining metals by heating and hammering until the met- join the metals being welded. A distinct advantage of arc als are fused (mixed) together. Although forge welding welding over gas welding is the concentration of heat. still exists, it is mainly limited to the blacksmith trade. In gas welding the flame spreads over a large area, sometimes causing heat distortion. The concentration of Today, there are many welding processes available. heat, characteristic of arc welding, is an advantage be- Figure 3-1 provides a list of processes used in modern cause less heat spread reduces buckling and warping. metal fabrication and repair. This list, published by the This heat concentration also increases the depth of pene- American Welding Society (AWS), shows the official tration and speeds up the welding operation; therefore, abbreviations for each process. For example, RSW you will find that arc welding is often more practical and stands for resistance spot welding. Shielded metal arc economical than gas welding. welding (SMAW) is an arc-welding process that fuses (melts) metal by heating it with an electric arc created All arc-welding processes have three things in com- between a covered metal electrode and the metals being mon: a heat source, filler metal, and shielding. The joined. Of the welding processes listed in figure 3-1, source of heat in arc welding is produced by the arcing shielded metal arc welding, called stick welding, is the of an electrical current between two contacts. The power 3-1 ENGINEERING-PDH.COM | MAT-114 | MASTER CHART OF WELDING AND ALLlED PROCESSES Figure 3-1.—We1ding processes. ENGINEERING-PDH.COM3-2 | MAT-114 | Figure 3-2.—0xyfuel gas welding (OFW). source is called a welding machine or simply, a welder. Figure 3-3.—Shielded metal arc welding (SMAW). This should not be confined with the same term that is also used to describe the person who is performing the welding operation. The welder (welding machine) is therefore the process is called shielded metal arc either electric- or motor-powered. In the Naval Con- welding. The main advantages of shielded metal arc struction Force (NCF), there are two main types of welding are that high-quality welds are made rapidly at arc-welding processes with which you should become a low cost. You will learn more about shielded metal arc familiar. They are shielded metal arc welding and gas welding in chapter 7. shielded arc welding. Gas Shielded Arc Welding Shielded Metal Arc Welding (SMAW) The primary difference between shielded metal arc welding and gas shielded arc welding is the type of Shielded metal arc welding (fig. 3-3) is performed shielding used. In gas shielded arc welding, both the arc by striking an arc between a coated-metal electrode and and the molten puddle are covered by a shield of inert the base metal. Once the arc has been established, the gas. The shield of inert gas prevents atmospheric con- molten metal from the tip of the electrode flows together tamination, thereby producing a better weld. The pri- with the molten metal from the edges of the base metal mary gases used for this process are helium, argon, or to forma sound joint. This process is known as fusion. carbon dioxide.