stringer bead tack welds tee joint trailing electrode angle weave pattern

Transcription

1 Chapter 9 Shielded Metal Arc Welding Plate OBJECTIVES After completing this chapter, the student should be able to: Demonstrate the safe way to set up a welding station. Explain the differences among F2, F3, and F4 electrodes. Demonstrate welding fabrication skills. Demonstrate welding skills by making square butt, outside corner, lap, and tee joints. KEY TERMS amperage range arc length cellulose-based fluxes chill plate electrode angle electrode manipulation lap joint leading electrode angle mineral-based fluxes outside corner joint rutile-based fluxes spatter square butt joint striking the arc stringer bead tack welds tee joint trailing electrode angle weave pattern INTRODUCTION Shielded metal arc welding (SMAW) or stick welding is the most commonly used welding process. Stick welding is popular for a number of reasons. It can be used to make strong durable welds in a wide range of metal thicknesses and types. Transformer-type welders can sit for years without being used and still work when needed, and the welding rods have an almost unlimited storage life, as long as they are kept dry. These factors mean that the equipment is there when you need it to make a repair or build a project. 165

2 166 CHAPTER 9 In addition to the standard rods that can be used to make welds in steel 1/8 in. (3 mm) and thicker, there are a wide variety of specialty electrodes. These specialty rods allow you to use the same welding machine to weld on cast iron, stainless steel, and aluminum. There are rods for cutting that will cut cast iron and stainless steel; these are metals that cannot be cut with oxygen and acetylene. Wear-resistant and buildup rods can be used to repair scraper and frontend loader blades and buckets. The basic stick-welding skills you will learn in this chapter are used for almost every welding fabrication project. Welding is a skill that takes practice to perfect. The repetition in the chapter practices and projects is designed to give you the opportunity to develop your skills. The more time you spend welding, the better your welding skills will become. ELECTRODES Arc welding electrodes used for practice welds are grouped into three filler metal classes (F number) according to their major welding characteristics. The groups are E6010 and E6011, E6012 and E6013, and E7016 and E7018. F3 E6010 and E6011 Electrodes Both of these electrodes have cellulose-based fluxes. As a result, these electrodes have a forceful arc with little slag left on the weld bead. E6010 and E6011 are the most utilitarian welding electrodes for welding fabrication. They can be used on metal that has a little rust, oil, or dirt without seriously affecting the weld s strength. The E6010 electrodes can weld only with direct current (DC) welding machines. Because E6011 electrodes can be used with alternating current (AC), smaller transformer-type welders that put out only AC welding current can be used. F2 E6012 and E6013 Electrodes These electrodes have rutile-based fluxes, giving a smooth, easy arc with a thick slag left on the weld bead. Both E6012 and E6013 are easy electrodes to use. They do not have forceful arcs, so they can be used on thinner metals such as some thicker sheet metal gauges that are used as guards on equipment. F4 E7016 and E7018 Electrodes Both of these electrodes have a mineral-based flux. The resulting arc is smooth and easy, with a very heavy slag left on the weld bead. Of these two electrodes, E7018 is the one used most often to make high-strength welds on equipment. Store these electrodes in a dry place. If they get wet, they will still weld, but the welds will not be as strong. The cellulose- and rutile-based groups F3 and F2 of electrodes have characteristics that make them the best electrodes for starting specific welds. The electrodes with the cellulose-based fluxes do not have heavy slags that may interfere with the welder s view of the weld. This feature is an advantage for flat tee and lap joints. Electrodes with the rutile-based fluxes (giving an easy arc with low spatter) are easier to control and are used for fillet, stringer beads, and butt joints. Unless a specific electrode is required for a job, welders can select what they consider to be the best electrode for a specific weld. Welders often have favorite electrodes to use on specific jobs. Electrodes with mineral-based fluxes, group F4, should be the last choice. Welds with a good appearance are more easily made with these electrodes, but strong welds are hard to obtain. Without special care being taken during the start of the weld, porosity will be formed in the weld. Figure 9-1 shows a general comparison of the weld penetration and buildup each electrode will produce with approximately the same amperage. More information on electrode selection can be found in Chapter 26. Effect of Too High or Too Low Current Settings Each welding electrode must be operated in a particular current (amperage) range, Table 9-1. Welding with the current set too low results in poor fusion E6010 E6011 E6012 E6013 E7016 E7018 FIGURE 9-1 Comparison of electrode type and weld bead shapes.

3 Shielded Metal Arc Welding Plate 167 AWS CLASSIFICATION E6010 E6011 E6012 E6013 E7016 E7018 ELECTRODE DIAMETER AND AMPERAGE RANGE 3" 1" 5" Table 9-1 Welding Amperage Range for Common Electrode Types and Sizes and poor arc stability, Figure 9-2. The weld may have slag or gas inclusions because the molten weld pool was not fluid long enough for the flux to react. Little or no penetration of the weld into the baseplate may also be evident. With the current set too low, the arc length is very short. A very short arc length results in frequent shortening and sticking of the electrode. The core wire of the welding electrode is limited in the amount of current it can carry. As the current is increased, the wire heats up because of electrical resistance. This preheating of the wire causes some of the chemicals in the covering to be burned out too early, Figure 9-3. The loss of the proper balance of elements causes poor arc stability. This condition leads to spatter, porosity, and slag inclusions. An increase in the amount of spatter is also caused by a longer arc. The weld bead made at a high amperage setting is wide and flat with deep penetration. The spatter is excessive and is mostly hard. The spatter is called hard because it fuses to the baseplate and is difficult to remove, Figure 9-4. The electrode covering is discolored more than 1/8 in. (3 mm) to FIGURE 9-3 Larry Jeffus ELECTRODE BECOMES DISCOLORED DUE TO EXCESSIVE HEAT 1/4 in. (6 mm) from the end of the electrode. Extremely high settings may also cause the electrode to discolor, crack, glow red, or burn. Electrode Size and Heat EXCESSIVE GAS (SMOKE) LARGE MOLTEN WELD POOL WITH LITTLE BUILDUP Welding with too high an amperage. The selection of the correct size of welding electrode for a weld is determined by the skill of the welder, the thickness of the metal to be welded, and the size of the metal. The 1/8-in. (3-mm) electrode is the most commonly used size for metal fabrication. It can be used to make welds on thin metal up to thick plates. Using small diameter electrodes requires less skill than using large diameter electrodes. The deposition rate, or the rate that weld metal is added to the weld, is slower when small diameter electrodes are used. Small diameter electrodes will make acceptable welds on a thick plate, but more time is required to make the weld. SPATTER VERY LITTLE SHIELDING GAS COVERAGE SMALL WELD POOL WELD BEAD HIGH WITH LITTLE FUSION FIGURE 9-2 Larry Jeffus Welding with the amperage set too low. FIGURE 9-4 Hard weld spatter is fused to base metal and is difficult to remove. Larry Jeffus

4 168 CHAPTER 9 AMOUNT OF HEAT DIRECTED AT WELD WELD POOL TOO LOW HIGH NARROW BEAD WITH A HEAVY SLAG COVER CORRECT TOO HOT FIGURE 9-5 The effect on the shape of the molten weld pool caused by the heat input. FIGURE 9-6 Larry Jeffus Welding with too short an arc length. Large diameter electrodes may overheat the metal if they are used with thin or small pieces of metal. To determine if a weld is too hot, watch the shape of the trailing edge of the molten weld pool, Figure 9-5. Rounded ripples indicate that the weld is cooling uniformly and that the heat is not excessive. If the ripples are pointed, the weld is cooling too slowly because of excessive heat. Extreme overheating can cause a burnthrough, which is hard to repair. To correct an overheating problem, a welder can turn down the amperage, use a shorter arc, travel at a faster rate, use a chill plate (a large piece of metal used to absorb excessive heat), or use a smaller electrode at a lower current setting. Arc Length The arc length is the distance that the arc must jump from the end of the electrode to the plate or weld pool surface. As the weld progresses, the electrode becomes shorter as it is consumed. To maintain a constant arc length, the electrode must be lowered continuously. Maintaining a constant arc length is important, as too great a change in the arc length will adversely affect the weld. As the arc length is shortened, metal transferring across the gap may short out the electrode, causing it to stick to the plate. The weld that results is narrow and has a high buildup, Figure 9-6. Long arc lengths produce more spatter because the metal being transferred may drop outside of the molten weld pool. The weld is wider and has little buildup, Figure 9-7. There is a narrow range for the arc length in which it is stable, metal transfer is smooth, and the bead shape is controlled. Factors affecting the length are the class of electrode, joint design, metal thickness, and current setting. Some welding electrodes, such as E7024, have a thick flux covering. The rate at which the covering melts is slow enough to permit the electrode coating to be rested against the plate. The arc burns back inside the covering as the electrode is dragged along, touching the joint, Figure 9-8. For this class of welding electrode, the arc length is maintained by the electrode covering. E7024 electrodes require very little welding skill to use. Because of the size of the molten weld pool, they are usually used only in the flat position on thick metal. An arc will jump to the closest metal conductor. On joints that are deep or narrow, the arc is pulled to one side and not to the root, Figure 9-9. As a result, the root fusion is reduced or may be nonexistent, FIGURE 9-7 Larry Jeffus Welding with too long an arc length.

5 Shielded Metal Arc Welding Plate 169 ELECTRODE FLUX TOUCHES BASE METAL FIGURE 9-8 Larry Jeffus ARC ROOT OPENING Welding with a drag technique. ELECTRODE FIGURE 9-9 The arc may jump to the closest metal, reducing root penetration. thus causing a poor weld. If a very short arc is used, the arc is forced into the root for better fusion. Because shorter arcs produce less heat and penetration, they are best suited for use on thin metal or thin-to-thick metal joints. Using this technique, metal as thin as 16 gauge can be arc welded easily. Higher amperage settings are required to maintain a short arc that gives good fusion with a minimum of slag inclusions. The higher settings, however, must be within the amperage range for the specific electrode. Finding the correct arc length often requires some trial and adjustment. Most welding jobs require an arc length of 1/8 in. (3 mm) to 3/8 in. (10 mm), but this distance varies. It may be necessary to change the arc length when welding to adjust for varying welding conditions. Electrode Angle The electrode angle is measured from the electrode to the surface of the metal. The term used to identify the electrode angle is affected by the direction of travel, generally leading or trailing, Figure The relative angle is important because there is a jetting force blowing the metal and flux from the end of the electrode to the plate. Leading Electrode Angle A leading electrode angle pushes molten metal and slag ahead of the weld, Figure When welding in the flat position, caution must be taken to prevent cold lap and slag inclusions. The solid metal ahead of the weld cools and solidifies the molten filler metal and slag before they can melt the solid metal. This rapid cooling prevents the metals from fusing together, Figure As the weld passes over this area, heat from the arc may not melt it. As a result, some cold lap and slag inclusions are left. DIRECTION OF TRAVEL TRAILING ANGLE RIGHT ANGLE LEADING ANGLE FIGURE 9-10 Direction of travel and electrode angle.

6 170 CHAPTER 9 DIRECTION OF TRAVEL ELECTRODE WELD BEAD LIMITED DEPTH OF PENETRATION AREA AHEAD OF THE MOLTEN WELD POOL MOLTEN WELD POOL FIGURE 9-11 Leading, lag, or pushing electrode angle. FIGURE 9-13 Metal being melted ahead of the molten weld pool helps to ensure good weld fusion. Larry Jeffus SLAG NO FUSION SLAG TRAPPED UNDER WELD FIGURE 9-12 Some electrodes, such as E7018, may not remove the deposits ahead of the molten weld pool, resulting in discontinuities within the weld. Cengage Learning 2012 The following are suggestions for preventing cold lap and slag inclusions: Use as little leading electrode angle as possible. Ensure that the arc melts the base metal completely, Figure Use a penetrating-class electrode that causes little buildup. Move the arc back and forth across the molten weld pool to fuse both edges. A leading angle can be used to minimize penetration or to help hold molten metal in place for vertical welds, Figure A B C A B C SECTION A-A (A) SECTION B-B (B) SECTION C-C (C) FIGURE 9-14 Effect of a leading angle on weld bead buildup, width, and penetration. As the angle increases toward the vertical position (C), penetration increases.

7 Shielded Metal Arc Welding Plate 171 Trailing Electrode Angle A trailing electrode angle pushes the molten metal away from the leading edge of the molten weld pool toward the back where it solidifies, Figure As the molten metal is forced away from the bottom of the weld, the arc melts more of the base metal, which results in deeper penetration. The molten metal pushed to the back of the weld solidifies and forms reinforcement for the weld, Figure Electrode Manipulation WELDING DIRECTION FIGURE 9-15 Trailing electrode angle. Cengage Learning 2012 The movement or weaving of the welding electrode, called electrode manipulation, can control the following characteristics of the weld bead: penetration, buildup, width, porosity, undercut, overlap, and slag inclusions. The exact weave pattern for each weld is often the personal choice of the welder. However, some patterns are especially helpful for specific welding situations. The pattern selected for a flat (1G) butt joint is not as critical as is the pattern selection for other joints and other positions. Many weave patterns are available for the welder to use. Figure 9-17 shows 10 different patterns that can be used for most welding conditions. The circular pattern is often used for flat position welds on butt, tee, and outside corner joints, and for buildup or surfacing applications. The circle can be made wider or longer to change the bead width or penetration, Figure The C and square patterns are both good for most 1G (flat) welds but can also be used for vertical (3G) positions. These patterns can also be used if there is a large gap to be filled when both pieces of metal are nearly the same size and thickness. The J pattern works well on flat (1F) lap joints, all vertical (3G) joints, and horizontal (2G) butt and lap (2F) welds. This pattern allows the heat to be concentrated on the thicker plate, Figure It also allows the reinforcement to be built up on the metal deposited during the first part of the pattern. As a result, a uniform bead contour is maintained during out-of-position welds. A B C A B C SECTION A-A (A) SECTION B-B (B) SECTION C-C (C) FIGURE 9-16 Effect of a trailing angle on weld bead buildup, width, and penetration. Section A-A shows more weld buildup due to a greater angle of the electrode.

8 172 CHAPTER 9 SHELF SUPPORTS MOLTEN WELD POOL, MAKING THE SHAPE OF THE WELD BEAD UNIFORM V UPSIDE DOWN V CIRCULAR C SQUARE ZIGZAG J T LESS HEAT CAN CONDUCT INTO THE EDGE THAN INTO THE BASEPLATE FIGURE 9-19 The J pattern allows the heat to be concentrated on the thicker plate. STRAIGHT STEPPED FIGURE 9-17 Weave patterns. FIGURE 8 The T pattern works well with fillet welds in the vertical (3F) and overhead (4F) positions, Figure It can also be used for deep groove welds for the hot pass. The top of the T can be used to fill in the toe of the weld to prevent undercutting. The straight step pattern can be used for stringer beads, root pass welds, and multiple pass welds in all positions. For this pattern, the smallest quantity of metal is molten at one time as compared to other patterns. Therefore, the weld is more easily controlled. At the same time that the electrode is stepped forward, the arc length is increased so that no metal is deposited ahead of the molten weld pool, Figure 9-21 and Figure This action allows the molten weld pool to cool to a controllable size. In addition, the arc burns off any paint, oil, or dirt from the metal before it can contaminate the weld. WEAVE PATTERN THIS WEAVE PATTERN RESULTS IN A NARROW BEAD WITH DEEP PENETRATION THIS WEAVE PATTERN RESULTS IN A WIDE BEAD WITH SHALLOW PENETRATION FIGURE 9-18 Changing the weave pattern width to change the weld bead characteristics. VERTICAL FILLET WELD FIGURE 9-20 T pattern.

9 Shielded Metal Arc Welding Plate 173 STEPPING ELECTRODE BACK AND FORTH SHELVES MOLTEN WELD POOL FIGURE 9-21 The electrode is moved slightly forward and then returned to the weld pool. Larry Jeffus FIGURE 9-23 Using the shelf to support the molten pool for vertical welds. Larry Jeffus The figure 8 pattern and the zigzag pattern are used as cover passes in the flat and vertical positions. Do not weave more than two-and-a-half times the width of the electrode. These patterns deposit a large quantity of metal at one time. A shelf can be used to support the molten weld pool when making vertical welds using either of these patterns, Figure Practice Welds Practice welds are grouped according to the type of joint and the class of welding electrode. The welder or instructor should select the order in which the welds are made. The stringer beads should be practiced first in each position before the welder tries the different joints in each position. Some time can be saved by starting with the stringer beads. If this is done, it is not necessary to cut or tack the plate NO METAL WAS DEPOSITED FIGURE 9-22 The electrode does not deposit metal or melt the base metal. Larry Jeffus together, and a number of beads can be made on the same plate. Students will find it easier to start with butt joints. The lap, tee, and outside corner joints are all about the same level of difficulty. Starting with the flat position allows the welder to build skills slowly so that out-of-position welds become easier to do. The horizontal tee and lap welds are almost as easy to make as the fillet welds. Overhead welds are as simple to make as vertical welds, but they are harder to position. Horizontal butt welds are more difficult to perform than most other welds. Positioning of the Welder and the Weld Plate The welder should be in a relaxed, comfortable position before starting to weld. A good position is important for both the comfort of the welder and the quality of the welds. Welding in an awkward position can cause welder fatigue, which leads to poor welder coordination and poor-quality welds. Welders must have enough freedom of movement so that they do not need to change position during a weld. Body position changes should be made only during electrode changes. When the welding helmet is down, the welder is blind to the surroundings. Due to the arc, the field of vision of the welder is also very limited. These factors often cause the welder to sway. To stop this swaying, the welder should lean against or hold onto a stable object. When welding, even if a welder is seated, touching a stable object will make the welder more stable and will make welding more relaxing.

10 174 CHAPTER 9 (B) WELDING TABLE SURFACE (A) (C) FIGURE 9-24 Not all field welding can be done in a comfortable position. Larry Jeffus Welding is easier if the welder can find the most comfortable angle. The welder should be in either a seated or a standing position in front of the welding table. The welding machine should be turned off. With an electrode in place in the electrode holder, the welder can draw a straight line along the plate to be welded. By turning the plate to several different angles, the welder should be able to determine which angle is most comfortable for welding, Figure 9-24A, B, and C. PRACTICE 9-1 Shielded Metal Arc Welding Safety Skill to be learned: The safe setup of a welding station and the use of proper personal protective equipment (PPE). Using a welding workstation, welding machine, welding electrodes, welding helmet, eye and ear protection, welding gloves, proper work clothing, and any special protective clothing that may be required, demonstrate to your instructor and other students the safe way to prepare yourself and the welding workstation for welding. Include in your demonstration appropriate references to burn protection, eye and ear protection, material specification data sheets, ventilation, electrical safety, general work clothing, special protective clothing, and area cleanup. STRIKING AN ARC All welds start with an arc strike. It is the process of establishing a stable arc between the end of the electrode and the work. At first, striking an arc can be difficult because it may seem that the end of the electrode wants to stick to the plate. With practice, you will be able to strike an arc and establish a weld bead without much thought. One important thing to remember is that on

11 Shielded Metal Arc Welding Plate 175 most code welding jobs, an arc strike outside of the weld zone may be considered a defect. Start now building a habit of always striking the arc in the weld joint just ahead of where you are going to be welding. That way the arc strike will become part of the finished weld. PROJECT 9-1 Striking the Arc to Build a Hot Plate Skill to be learned: The ability to start and hold an arc to produce a weld bead. Project Description Hot plates serve two main purposes to protect the surface of a kitchen countertop or table from damage caused by a hot skillet or other cooking utensil and to prevent a cold surface from cooling a dish before the food can be served. The hot plate you are going to fabricate serves both of these purposes. The cork or felt pads placed on the four corners of the bottom of the hot plate serve as insulators and surface protectors. They keep any heat picked up by the hot plate from being transferred to the surface and keep the metal hot plate from scratching the surface. The short welds on the surface of the hot plate limit the contact area between the hot plate and the hot dish. This reduces the heat transfer from the dish to the hot plate. Project Materials and Tools The following items are needed to fabricate the hot plate. Materials 5 to 10 1/8-in. diameter E6011 electrodes 1 6-in. square piece of 1/4-in. thick mild steel plate 4 cork or felt pads Paint Clear finish Tools Arc welder PPE Angle grinder Wire brush Square Soapstone Layout Using a square, 12-in. rule and soapstone, lay out the plate as shown in the project drawing, Figure " " 16 1" 116 7" 16 1"* 6" 1"** 2 A A 45 o 6" 1"* 1"** 2 1" 2 G 1" - 1 1" 2 GRIND TOP OF WELD FLAT SECTION A-A HOT PLATE FIGURE 9-25 Project 9-1.

12 176 CHAPTER 9 Welding Using a properly set up and adjusted arc welding ma chine and the proper safety protection as demonstrated in Practice 9-1, you will make a series of weld beads on the hot plate surface following the soapstone layout. BROKEN FLUX NOTE: Before starting on any project, test the setup of the welder by making a few test welds on a piece of scrap metal. That way you can make any adjustments in the welding amperage settings before starting on the project. With the electrode held over the plate, lower your helmet. Scratch the electrode across the plate (like striking a large match), Figure As the arc is established, slightly raise the electrode to the desired arc length. Hold the arc in one place until the molten weld pool builds to the desired size. Slowly lower the electrode as it burns off, and slowly move it forward to start the weld bead. NOTE: If the electrode sticks to the plate, quickly squeeze the electrode holder lever to release the electrode. Break the electrode free by bending it back and forth a few times. Do not touch the electrode without gloves because it will still be hot. If the flux breaks away from the end of the electrode, throw out the electrode because restarting the arc will be very difficult, Figure Break the arc by rapidly raising the electrode after completing a 1-in. long weld bead. You will be making ARC FORCED TO THE BACK SIDE FIGURE 9-27 If the flux is broken off the end completely or on one side, the arc can be erratic or forced to the side. Larry Jeffus another weld on the next marked spot. Move the electrode end over the starting point for the next weld. Restart the arc as you did before, and make another short weld. Repeat this process until you have made all of the welds. A more accurate way of striking the arc is to hold the electrode steady by resting it on your free hand like a pool cue over the desired starting point. After lowering your helmet, swiftly bounce the electrode against the plate, Figure A lot of practice is required to develop the speed and skill needed to prevent the electrode from sticking to the plate. But striking an arc in an incorrect spot may cause damage to the base metal. NOTE: Sometimes the welding fumes may partially cover the marks next to the weld you just made. If that happens, do not wipe the fumes off because you may erase the lines. Instead, use the soapstone to retrace ELECTRODE WORKPIECE FIGURE 9-26 Scratch striking an arc. Cengage Learning 2012 FIGURE 9-28 Bounce striking an arc to start it on a spot.

13 Shielded Metal Arc Welding Plate 177 the line. You can usually do this by hand without the need for a straightedge. 3" 16 As you make more and more of the welds, you will become more efficient at starting the arc. When you have completed all of the welds, turn off the welding machine and clean up your work area. Finishing Cool off the metal, chip the slag, and wire brush the surface. Sometimes the metal may warp from the heat and welds. If necessary, you can flatten your hot plate enough for it to be used by using a hammer and anvil. Paint the top and side surfaces with a latex paint. Once the paint is dry, grind the tops off of the welds as shown in the drawing. Do not grind too hard because that could cause excessive heat, which could damage the paint. Check the surface to see that it is flat enough to prevent a pot or dish from rocking. Do any additional grinding to make the tops of the welds flat. Paint the hot plate with a coat of clear latex finish to keep it from rusting. Paperwork Complete a copy of the time sheet in Appendix I, the bill of materials in Appendix III, or use forms provided by your instructor. TACK WELDS Tack welds are a temporary method of holding parts in place until they can be completely welded. Usually, all of the parts of a weldment should be assembled before any finishing welding is started. This will help reduce distortion. Tack welds must be strong enough to withstand any forces applied during assembly and any force caused by weld distortion during final welding. They must also be small enough to be incorporated into the final weld without causing a discontinuity in its size or shape, Figure PROJECT 9-2 Tack Welding Assembly of a Pencil Holder Skill to be learned: The tack welding of parts in place so they can be finished welded. Project Description The pencil holder will be assembled and tack welded in preparation for welding. The same skills you learned by making short welds as you fabricated the hot plate TACK WELDS 3" FIGURE 9-29 Tack welding outside corner joint. will be used to make the pencil holder. In this application short stringer welds will be used as tack welds to hold the parts in place so they can be welded. Project Materials and Tools The following items are needed to fabricate the pencil holder. Materials 1 to 2 1/8-in. diameter E6012 or E6013 electrodes 4 4-in. rectangular pieces of 3/16-in. thick mild steel plate 1 3-in. square piece of 3/16-in. thick mild steel plate Tools Arc welder Plasma cutting torch, oxyfuel cutting torch, or shear PPE Wire brush Chipping hammer Square C-clamp or magnetic clamp Soapstone 4"

14 178 CHAPTER 9 3" 3" (A) (B) FIGURE 9-31 Magnetic clamps. Larry Jeffus 3" 8 4" 3" 8 gloved hand and make a small tack weld. If you use your square, keep it as far away as possible from the tack weld so it will not be damaged. Make the tack welds as shown in the project drawing, Figure Keep the tack welds small so they will not affect the finished weld. 3" 1" 4 3" 8 8 LOCATIONS Paperwork Complete a copy of the time sheet in Appendix I, the bill of materials in Appendix III, or use forms provided by your instructor. FIGURE 9-30 Project 9-2. STRINGER BEADS Layout Using a square, 12-in. rule and soapstone, lay out the plate as shown in the project drawing, Figure Cutting Out If flat 3/16-in. bar stock is available, all you will have to do is shear the metal to length. However, if you are using sheet stock, you will have to thermally cut the parts using either a flame or plasma torch. (See Chapters 21 and 22 for details on flame and plasma cutting.) If the parts are thermally cut, clean off any slag before you assemble the parts. Fabrication The parts will need to be held square as they are tack welded. A C-clamp or magnetic clamp can be used to hold the parts in place for tack welding, Figure Sometimes you can hold the parts in place with your A straight weld bead on the surface of a plate with little or no side-to-side electrode movement is known as a stringer bead. Stringer beads are used by students to practice maintaining arc length, weave patterns, and electrode angle so that their welds will be straight, uniform, and free from defects. They are also used by experienced welders to set the welding machine amperage. An example of an application for stringer beads is using them to build up a worn surface or apply a chemical- or mechanical-resistant weld metal to the surface. They may also be used to add an effect to the surface of a piece of art. The stringer bead should be straight. A beginning welder needs time to develop the skill of viewing the entire welding area. At first, the welder sees only the arc, Figure With practice, the welder begins to see parts of the molten weld pool. After much practice, the welder will see the molten weld pool (front, back, and both sides), slag, buildup, and

15 Shielded Metal Arc Welding Plate 179 FIGURE 9-34 Another arc striking project. Cengage Learning 2012 FIGURE 9-32 New welders frequently see only the arc and sparks from the electrode. Larry Jeffus the surrounding plate, Figure Often at this skill level, the welder may not even notice the arc. A straight weld is easily made once the welder develops the ability to view the entire welding zone. The welder will occasionally glance around to ensure that the weld is straight. In addition, it can be noted if the weld is uniform and free from defects. The ability of the welder to view the entire weld area is demonstrated by making consistently straight and uniform stringer beads. PROJECT 9-3 WELD SPATTER ARC SOLID SLAG MOLTEN FLUX MOLTEN WELD POOL FIGURE 9-33 More experienced welders can see the molten pool, metal being transferred across the arc, and penetration into the base metal. Larry Jeffus Stringer Bead to Surface a Pencil Holder Skill to be learned: The control of the welding electrode to produce uniform weld beads in the flat position. Project Description The surface welds applied to the pencil holder are for artistic decoration only. They add depth and individual interest to the finished project. Other projects with a similar application of welds might include a fish on which the welds appear to be scales or birds on which they appear to be feathers, Figure Project Materials and Tools The following items are needed to finish the pencil holder. Materials 5 to 10 1/8-in. diameter E6012 or E6013 electrodes 1 assembled pencil holder 4 cork or felt pads Paint or clear finish Tools Arc welder PPE Square Steel rule Angle grinder Wire brush Soapstone Welding Using a properly set up and adjusted arc welding machine and the proper safety protection as demonstrated in Practice 9-1, you will make a series of stringer weld beads on the surface of the pencil holder that was assembled in Project 9-2. The first stringer weld bead will actually be a square butt joint weld. It will be used to prevent the plates from excessively distorting as the remainder of the stringer welds are made. Start the weld at the edge

16 180 CHAPTER 9 CORRECT TOO HOT AND TOO SLOW FIGURE 9-35 Making the weld narrow with a higher buildup by using a short arc length can add dimension to the finished project s surface appearance. Larry Jeffus FIGURE 9-37 Comparison of the appearance of weld beads with correct temperature and overheated base metal. of the plate and weld all the way to the opposite end. Try to keep the weld width and travel speed consistent all the way down the plate, Figure When the first weld is completed, roll the pencil holder over so that the next weld can be made to close the next butt joint. Repeat this until all four corners are welded. Cool the part and look at the welds. See how consistent you were in your travel speed and electrode movement. You can tell when you were welding faster because the weld will be thinner with less buildup, Figure The weld will be wider with more buildup when you travel slower. The width of the weld, spacing of the weld bead ripples, and smoothness of the sides of the weld are all indicators of how constant you were in your side-to-side manipulation. Alternate both the direction of the weld and the side that you are welding on. The alternating of the direction will make the finished welds look neater, and AMOUNT OF HEAT DIRECTED AT WELD TOO LOW CORRECT TOO HOT WELD POOL FIGURE 9-36 Comparison of weld beads and heat input. by switching sides you will not be as likely to overheat the metal. Watch the back side of the weld pool to see if the weld is getting too hot, Figure Chip and wire brush the welds after each pass. Look at the weld bead for uniformity in width, height, and spacing of ripples. NOTE: If the project is becoming overheated, you can cool it by quenching it in water. Normally, welds are not quenched in water because that might cause cracks and it makes them brittle. But the weld s strength is not a factor in the usability of this artistic project. When all of the sides are completely covered with weld beads, cool the project. Next, you will make the last series of welds, numbers 3 and 4, as shown in the drawing, Figure Finishing Cool off the metal, chip the slag, and wire brush the surface. A power wire brush can be used to give the welds a polished, shiny appearance. The project can be painted with a clear coat or colored coat of latex paint. Stick the felt or cork pads on the corners of the bottom to protect the surface of the furniture. Paperwork Complete a copy of the time sheet in Appendix I, the bill of materials in Appendix III, or use forms provided by your instructor. Square Butt Joint The square butt joint is made by tack welding two flat pieces of plate together, Figure The space between the plates is called the root opening or root

17 Shielded Metal Arc Welding Plate 181 3" 3" 3 2 gap. Changes in the root opening affect penetration. As the space increases, the weld penetration also increases. The root opening for most butt welds varies from 0 to 1/8 in. (3 mm). Excessively large openings can cause burnthrough or a cold lap at the weld root, Figure Square butt joints are used to join plate and structural steel shapes up to 1/4-in. thick. The advantage of using the square butt joint is that often the edges of the metal can be used just as they are without having to do additional edge beveling. Not having to bevel the edge of the metal saves time and money for the fabricator, Figure " PENCIL HOLDER FIGURE 9-38 Project 9-3. FIGURE 9-39 The tack weld should be small and uniform to minimize its effect on the final weld. Larry Jeffus 1 4 PROJECT 9-4 Butt Welds to Build a Smoke Box Skill to be learned: The control of the welding electrode to produce uniform butt weld joints in the flat position. Project Description A smoke box is a small flat box that wood chips are placed in so that food cooked on a gas barbecue grill will have a wood fire flavor. The smoke box is used by placing several hickory, mesquite, or other aromatic wood chips in the box and covering them with the box lid. The lid prevents the wood from burning so it only smokes. With the box closed, place it as close to the grill burners as possible. If your barbeque grill has lava stones, move enough of them aside so you can place the smoke box just above the burner flames. If your barbeque grill uses ceramic plates, one can be moved to make room for the smoke box, or just set it on top of the ceramic plate. The only thing that is important is that the box be placed so it will get hot enough for the wood chips inside to smoke. ROOT OPENING INCREASING ROOT OPENING LACK OF FUSION FIGURE 9-40 Effect of root opening on weld penetration.

18 182 CHAPTER 9 3'-3" 6'-6" 10'-0" Tape measure C-clamp or magnetic clamp Soapstone Layout Using a square, 12-in. rule and soapstone, lay out the bar stock as shown in the project drawing, Figure Cutting Out The first step is to cut the mild steel bar stock to length with a shear or thermally ' 5" DETAIL DETAIL B-B TRAILER DETAIL C-C FIGURE 9-41 Square butt joints on utility trailer. 6'-3" Fabrication This project will be fabricated in steps. 1 st Step Assemble the top Assemble and tack weld together six of the 5 1/2-in. long bars into a square flat plate with no root space, Figure nd Step Assemble the smoke box Assemble and tack weld together six of the 6-in. long bars into a square flat plate with a 1/8-in. root space, Figure Tack weld the two 1 7-in. and two of the 1 6-in. long bars on the sides of the first plate, tack welded together to form a shallow box. Project Materials and Tools The following items are needed to fabricate the smoke box. Materials 24 to 30 1/8-in. diameter F2 or F3 class electrodes in. pieces of 3/16-in. to 1/4-in. thick mild steel plate /2-in. pieces of 3/16-in. to 1/4-in. thick mild steel plate in. pieces of 3/16-in. to 1/4-in. thick mild steel plate Tools Arc welder Plasma cutting torch, oxyfuel cutting torch, or shear PPE Wire brush Angle grinder Chipping hammer Square 3 rd Step Forming the handle The smoke box handle will be made from one of the 5 1/2-in. long pieces of metal bar. Using an oxyfuel torch, heat across one end of the bar 1/2 in. from the end. Place the hot end in a vise, and bend it at a right angle. Repeat this process on the other end to make the long U-shaped handle. Welding Using a properly set up and adjusted arc welding machine and the proper safety protection as demonstrated in Practice 9-1, you will make a series of welds on the joints on the top of the smoke box. These welds can be made using the skills that you developed while doing the stringer beads on the pencil holder. The difference in making these welds and the stringer beads is that these welds must join two pieces of metal together. To do this you must watch the weld bead to see that it is flowing together and make the weld straight down the joint. The molten weld metal formed on the two sides of the joint will not just flow together forming a single weld bead joining the plates. You must make sure you are traveling

19 Shielded Metal Arc Welding Plate 183 6" 1" 5 2 1" 8 0" FIGURE 9-42 Project 9-4. slowly enough so that the weld side is adequate to allow the molten weld pools to flow together and not just form on the two edges of the weld, Figure The welds must be straight so that the weld beads are evenly spaced on both sides of the weld joints, Figure You must watch the leading edge of the weld pool to make sure your weld bead is centered on the weld joint. If the weld does not follow along the center of the weld joint, the joint will not be as strong as it should be. Weak weld joints can be serious. Cool, chip, and inspect each weld joint after you have finished the weld. Look at the weld to see if it has uniform width and buildup and follows the weld joint. A lack of uniform width might indicate you were not using a consistent weave pattern. A lack in uniformity in buildup might indicate that your rate of travel down the joint was not steady. Finish welding the top by making all the welds along both sides of the weld joint on the top plate WELD JOINT WELD DOES NOT FOLLOW JOINT WELD FOLLOWS JOINT FIGURE 9-43 Moving the electrode from side to side too quickly can result in slag being trapped between the plates. Larry Jeffus FIGURE 9-44 The weld bead must track down the center of the joint so it is equally distributed on both sides.

20 184 CHAPTER 9 HANDLE LID while you are welding, stop and locate the broken tack. Use clamps, if necessary, to force the joint back into position before tack welding it into place again. FIGURE 9-45 Smoke box handle. until you have completed all 12 welds. Remember to cool and chip the welds between each one so you can see what changes in technique you need to make. This also ensures that the weldment does not become overheated. Measure the length of the box handle and center it from both sides and the ends of the box top. Tack weld both ends before welding it in place with short welds across the outside of both ends of the handle, Figure The root space on the box may make it easier to follow the weld joint, but it makes it harder to get the weld metal to flow together. Too fast a travel speed along this joint will result in a lack of fusion between the two plates. To ensure that this does not happen, you must watch the back edge of the molten weld bead. If it is smooth and rounded, the molten weld metal is joining. Sometimes this can be difficult to see because of the flux covering. The lighter flux produced by F3 class electrodes does not cause this problem as much as the class F2 and F4 electrodes do. One indicator that the weld metal is not joining is a slight difference in the shade of red at the trailing edge of the weld. When there is a gap in the weld metal, the flux will have a slightly lighter red color. NOTE: There can be enough weld stresses produced to break a tack weld. When tack welds break, they often produce a sharp pinging sound. If you hear this sound Weld the joint on the outside of the box first. As before, cool, chip, and inspect each of the welds after they are completed. Make the butt welds around the side of the plate so that the sides are secured to the bottom plate. Use the same techniques for these welds as you did for the other butt joint welds. The butt welds inside the box may have some degree of arc blow. If arc blow occurs, refer back to that section in this chapter to see how you might solve the problem. Try changing from a DC to AC welding current, and try changing the direction in which you are welding in addition to the other suggested arc blow controls. Observe how each arc blow control worked in this application. Under different conditions the results you observed here, other than changing the class of welding current, may differ. Limited visibility may be another problem you might have when making the inside welds. The welds must be started all the way at the end, next to the side. This will require a trailing electrode angle, but you cannot end the weld with the same angle. There are several ways of solving this problem. One way is to gradually change from a trailing angle at the beginning to a leading angle at the end of the weld, Figure The second way to ensure that the weld is made all the way across the joint is to stop the weld in the center of the joint. Clean and chip the weld end crater and complete the weld by starting on the opposite end and welding back to the center, Figure Try both methods to see which works best for you. Remember to cool, chip, and inspect the welds after each pass to see what changes you might need to make in your technique. Finishing Cool off the metal, chip the slag, and wire brush the surface. Grind any welds that interfere with the FIGURE 9-46 Rotating the electrode to improve visibility helps when welding in a confined space. Cengage Learning 2012

21 Shielded Metal Arc Welding Plate 185 FIRST WELD 3'-3" 6'-6" 10'-0" SECOND WELD FIGURE 9-47 Starting the weld at the edge and welding to the center. 6'-3" top fitting into the box. No additional finishing is required. Paperwork Complete a copy of the time sheet in Appendix I, the bill of materials in Appendix III, or use forms provided by your instructor. Outside Corner Joint An outside corner joint is made by placing the plates at an angle to each other, with the edges forming a V-groove, Figure The angle between the plates may range from a very slight 15 angle to almost flat at a 165 angle. There may or may not be a slight root opening left between the plate edges. Small tack welds should be made approximately 1/2 in. (13 mm) from each end of the joint. The weld bead should completely fill the V-groove formed by the plates and may have a slightly convex surface buildup. FIGURE 9-48 V formed by an outside corner joint ' 5" DETAIL Outside corner joints are used at the corners of tanks, boxes, and ships. Four plates can be made into a square tube; three can be made into a triangular tube, Figure PROJECT 9-5 DETAIL B-B TRAILER Outside Corner Welds to Build a Candlestick Skill to be learned: The control of the welding electrode to produce uniform outside corner welds in the flat position. Project Description Candles come in a variety of sizes and lengths. It is common to display them on some type of stand. The stand can serve to raise a short candle above other decorations, or several different heights of candlesticks may be used to display candles in an arrangement. Most candles today are made from drip-free wax to avoid wax damaging furniture or fabric such as tablecloths. Some people prefer the nostalgic appearance of candle wax running down the side of a candle. You can build your candlestick holder with a top plate large DETAIL C-C FIGURE 9-49 Outside corner joints on utility trailer.

22 186 CHAPTER 9 enough to catch this dripping wax or small enough to allow the wax to run down the holder too. 2" Project Materials and Tools The following items are needed to fabricate the pair of four-sided candlestick holders. Materials 10 to 15 1/8-in. diameter F2 or F3 class electrodes 8 1 1/2 8-in. pieces of 3/16-in.- to 1/4-in. thick mild steel plate 2 2-in. square pieces of 3/16-in. to 1/4-in. thick mild steel plate 2 3-in. square pieces of 3/16-in. to 1/4-in. thick mild steel plate 8 cork or felt pads 8" A A Tools Arc welder Plasma cutting torch, oxyfuel cutting torch, or shear PPE Wire brush Angle grinder Chipping hammer Square Steel rule C-clamp or magnetic clamp Soapstone Layout Using a square, 12-in. rule and soapstone, lay out the bar stock as shown in the project drawing, Figure Cutting Out The first step is to cut the mild steel bar stock to length with a shear or thermally. Fabrication Tack weld the 1 1/2-in. metal bars together so they make a square tube. The corners of the plates should meet so they form a 90 V, Figure Place the tack welds about 1 in. from the ends of the joints so they do not interfere with the starting or stopping of the welds. The top and bottom plate will be assembled following the welding of the outside corner joints. 3" CANDLESTICK SECTION A-A FIGURE 9-50 Project 9-5. Welding Make sure to strike the arc in the V-groove of the outside corner joint. Although F3 class electrodes may produce a lot of weld spatter that can stick to the sides of the plates, it does not have the same effect that THE PLATES OF AN OUTSIDE CORNER JOINT FORM A V - SHAPED GROOVE. FIGURE 9-51 Outside corner joint layout.

23 Shielded Metal Arc Welding Plate 187 HARDNESS ZONE SECTION A - A A STEEL RULE A FIGURE 9-52 Effect of arc strike outside of the weld bead. Larry Jeffus SQUARE striking the arc has on the plate surface, Figure The weld spatter can be cleaned off or left to add texture to the finished candlestick. There may be some arc blow at the ends of the weld. The appearance of these welds is part of the finished part s appearance. So, you cannot start at the ends and weld to the center of the weld as you may have done when welding out the smoke box. Because the welds appearance is important, if arc blow does occur, you cannot just stop. You will need to control the arc and weld pool to keep them uniform. Try holding a very short arc length as a way of controlling the arc blow if it becomes a problem. Cool, chip, and inspect each weld joint after you have finished the weld. Look at the weld to see if it has uniform width and buildup and follows the weld joint. A lack of uniform width might indicate you were not using a consistent weave pattern. A lack in uniformity in buildup might indicate that your rate of travel down the joint was not steady. When all of the welds are completed on both candlesticks, lay out the center of the top and bottom plates. Center the square tube on the bottom plate and square it to the baseplate before making a single small tack weld on one corner. Stand the candlestick up next to the square, Figure Measure the distance from each of the sides of the top of the tube to see that it is standing up vertically on the base. If the tube is not vertical within 1/8 in., the tack weld can be bent slightly to make the tube vertical. If the tack weld cannot bend enough, it can be broken off and a new tack made. NOTE: A magnetic level can be used to check if the tube is vertical before tack welding, Figure FIGURE 9-53 Checking squareness with a square. Once the tube is vertical on the baseplate, make two or three more tack welds to hold it in place. Recheck the tube to see that it is still vertical within tolerance. The top plate must be centered on the tube and square to the tube and to the baseplate. One way to accomplish this is to stand the tube on the top plate and use a square and measuring tape to align the plate before tack welding it in place, Figure Make a fillet weld around the top and bottom plates to hold the tube in place. Refer to the following tee joint welding instruction, if necessary, to make these welds. The height of the second candlestick must be within ±1/8 in. of the first one. You may need to grind the end of the tube or increase the joint spacing to ensure that both candlesticks are the same height. Finishing Cool and chip the welds. There are a number of ways to finish this project in addition to painting it a color or a clear finish. Following are some possibilities: Leave the welds and spatter as they are. Grind all the welds and surfaces smooth. Write a greeting, holiday saying, your name, draw a heart or other symbol with weld beads, or cut them in with a torch.

24 188 CHAPTER 9 FILLET WELDS MAGNETIC LEVEL AMOUNT OF OVERLAP FIGURE 9-56 Lap joint. Paperwork Complete a copy of the time sheet in Appendix I, the bill of materials in Appendix III, or use forms provided by your instructor. Lap Joint A lap joint is made by overlapping the edges of the two plates, Figure The joint can be welded on one side or both sides with a fillet weld. In most cases, both sides of the joint should be welded. When just one side is welded, the joint is not as strong, and water can cause rust to form in the joint space, Figure As the fillet weld is made on the lap joint, the buildup should equal the thickness of the plate, Figure FIGURE 9-54 Checking squareness with a level. RUST FORMED BETWEEN WELDS FIGURE 9-57 Crevice corrosion caused by water trapped in the space between metal plates at a lap joint. Larry Jeffus STEEL RULE SMOOTH WELD TRANSITION THICKNESS SQUARE MEASURE ONE SIDE THEN THE OTHER FIGURE 9-55 Centering the top plate. FIGURE 9-58 Correct lap joint bead shape. SMOOTH WELD TRANSITION

25 Shielded Metal Arc Welding Plate 189 3'-3" 6'-6" 10'-0" GOOD ROOT FUSION FIGURE 9-59 Larry Jeffus Correct crater fill at the end of a lap joint. 6'-3" 2-6 2' 5" DETAIL DETAIL B-B TRAILER DETAIL C-C FIGURE 9-60 Lap joint weld. Larry Jeffus A good weld will have a smooth transition from the plate surface to the weld. If this transition is abrupt, it can cause stresses that will weaken the joint. Penetration for lap joints does not improve their strength; complete fusion is required. The root of fillet welds must be melted to ensure a completely fused joint, Figure But if the molten weld pool shows a notch during the weld, this is an indication that the root is not being fused together. The weave pattern will help prevent this problem, Figure Lap joints are often used when joining plates or when plates are stiffened with an angle iron or another structural shape. They are also used when joining structural steel, Figure PROJECT 9-6 Fillet Welds in Lap Joints to Build a Birdhouse Roof Skill to be learned: The control of the welding electrode to produce uniform fillet welds in lap joints Courtesy of Larry Jeffus FIGURE 9-61 Lap joints on utility trailer. in the flat position. In addition, the square butt and outside corner welding skills learned in the previous projects will be reinforced. Measuring, fitting, and assembling fabrication skills and techniques will be developed. Project Description The roof of a house is usually covered with shingles that are lapped one on top of the other. The lap joints on the roof of your birdhouse are designed to give it the look of shingles. This project will be fabricated in three parts. Part 1 The roof of the birdhouse will be fabricated using lap joint welds. Part 2 The walls and floor will be fabricated using butt joint welds. Part 3 The corners of the walls, floor, and roof ridge will be joined using outside corner welds. Part 1 Project Materials and Tools The following items are needed to fabricate the birdhouse roof.