Chapter 4

1 Shielded Metal ArcWelding of PlateAfter completing this Chapter , the student should be able toset the welding amperage the effect of changing arc length on a weld bead contour during welding by using the properweave an ability to control undercut, overlap, porosity, andslag inclusions when the effect of electrode angle on a rangearc lengthcellulose-based fluxeschill plateelectrode anglelap jointmineral-based fluxesrutile-based fluxessquare butt jointstringer beadtee jointweave patternINTRODUCTIONS hielded metal arc welding (SMAW), or stick welding, is the most oftenused method of joining plate. This method provides a high temperature andconcentration of heat, which allow a small molten weld pool to be built upquickly.

2 The addition of filler metal from the electrode adds reinforcementand increases the strength of the weld. SMAW can be performed on almostany type of metal 1/8 in. (3 mm) thick or thicker. A minimum of equipmentis required, and it can be welds can be consistently produced on almost any type ofmetal and in any position. The quality of the welds produced dependslargely upon the skill of the welder. Developing the necessary skill levelrequires practice. However, practicing the welds repeatedly withoutchanging techniques will not aid in developing the required skills. Eachtime a weld is completed it should be evaluated, and then a changeshould be made in the technique to improve the next TERMSOBJECTIVESC hapter 46566 Section 2 Shielded Metal Arc WeldingPRACTICE 4-1 Shielded Metal Arc Welding SafetyUsing a welding work station, welding machine, weld-ing electrodes, welding helmet, eye and ear protection,welding gloves, proper work clothing, and any special pro-tective clothing that may be required, demonstrate, to yourinstructor and other students, the safe way to prepare your-self and the welding work station for welding.

3 Include inyour demonstration appropriate references to burn protec-tion, eye and ear protection, material specification datasheets, ventilation, electrical safety, general work clothing,special protective clothing, and area clean-up. Complete a copy of the Student Welding Report listedin Appendix I or provided by your instructor. EXPERIMENT 4-1 Striking the ArcUsing a properly set up and adjusted arc weldingmachine, the proper safety protection, as demonstrated inPractice 4-1, E6011 welding electrodes having a 1/8-in. (3-mm) diameter, and one piece of mild steel plate, 1/4-in.(6-mm) thick, you will practice striking an arc, Figure the electrode held over the plate, lower your hel-met.

4 Scratch the electrode across the plate (like striking alarge match), Figure the arc is established, slightlyraise the electrode to the desired arc length. Hold the arcin one place until the molten weld pool builds to thedesired size. Slowly lower the electrode as it burns off andmove it forward to start the the electrode sticks to the plate, quickly squeeze theelectrode holder lever to release the electrode. Break theelectrode free by bending it back and forth a few times. Do1"(25 mm) 3"4(19 mm)Welding Principles and ApplicationsMATERIAL:1/4" x 6" MILD STEEL PLATESMAW ARC STRIKINGEXPERIMENT 4 1 JACK CHIPMANPROCESS:NUMBER:DRAWN BY:FIGURE4-1 Striking an Striking the arc.

5 Photo courtesy of Larry 4 Shielded Metal Arc Welding of Plate67not touch the electrode without gloves, because it will stillbe hot. If the flux breaks away from the end of the elec-trode, throw out the electrode because restarting the arcwill be very difficult, Figure the arc by rapidly raising the electrode after com-pleting a 1-in. (25-mm) weld bead. Restart the arc as youdid before, and make another short weld. Repeat thisprocess until you can easily start the arc each time. Turnoff the welding machine and clean up your work areawhen you are finished welding. Complete a copy of the Student Welding Report listed in Appendix I or provided by your instructor.

6 EXPERIMENT 4-2 Striking the Arc AccuratelyUsing the same materials and setup as described inExperiment 4-1, you will start the arc at a specific spot inorder to prevent damage to the surrounding the electrode over the desired starting point. Afterlowering your helmet, swiftly bounce the electrodeagainst the plate, Figure lot of practice is requiredto develop the speed and skill needed to prevent the elec-trode from sticking to the more accurate method of starting the arc involvesholding the electrode steady by resting it on your free handlike a pool cue. The electrode is rapidly pushed forward sothat it strikes the metal exactly where it should.

7 This is anexcellent method of striking an arc. Striking an arc in anincorrect spot may cause damage to the base starting the arc until you can start it within1/4 in. (6 mm) of the desired location. Turn off the weld-ing machine and clean up your work area when you arefinished a copy of the Student Welding Report listed in Appendix I or provided by your instructor. Effect of Too High or Too LowCurrent SettingsEach welding electrode must be operated in a particularcurrent (amperage) range, Table with the cur-rent set too low results in poor fusion and poor arc stability,Figure weld may have slag or gas inclusionsbecause the molten weld pool was not fluid long enough forthe flux to react.

8 Little or no penetration of the weld into theFIGURE4-3 If the flux is broken off the end completely oron one side, the arc can be erratic or forced to the of Larry FLUXARC FORCED TO THE BACKSIDEFIGURE4-4 Striking the arc on a Welding with the amperage set too of Larry LITTLE SHIELDINGGAS COVERAGEWELD BEAD HIGH WITH LITTLE FUSIONSMALL WELD POOLE lectrodeClassificationSizeE6010E6011E601 2E6013E7016E70183/32 in. ( mm)40 8050 7040 9040 8575 10570 1101/8 in. ( mm)70 13085 12575 13070 120100 15090 1655/32 in. (4 mm)110 165130 160120 200130 160140 190125 220 TABLE4-1 Welding amperage 2 Shielded Metal Arc Weldingbase plate may also be evident.

9 With the current set too low,the arc length is very short. A very short arc length results infrequent shortening and sticking of the core wire of the welding electrode is limited in theamount of current it can carry. As the current is increased,the wire heats up because of electrical resistance. This pre-heating of the wire causes some of the chemicals in the cov-ering to be burned out too early, Figure loss of theproper balance of elements causes poor arc stability. Thiscondition leads to spatter, porosity, and slag increase in the amount of spatter is also caused bya longer arc. The weld bead made at a high amperage set-ting is wide and flat with deep penetration.

10 The spatter isexcessive and is mostly hard. The spatter is called hardbecause it fuses to the base plate and is difficult to remove,Figure electrode covering is discolored morethan 1/8 in. (3 mm) to 1/4 in. (6 mm) from the end of theelectrode. Extremely high settings may also cause theelectrode to discolor, crack, glow red, or 4-3 Effects of Amperage Changes on a Weld BeadFor this experiment, you will need an arc weldingmachine, welding gloves, safety glasses, welding helmet,appropriate clothing, E6011 welding electrodes having a1/8-in. (3-mm) diameter, and one piece of mild steel plate,1/4 in.