Assessments - 4, GPA: 4.3
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If possible, the work piece should be positioned so that the bead will run on a flat surface. Preparing The Joint For effective welding, the surfaces to be joined must be free of dirt, rust, scale, oil or paint. Welding on metals not properly cleaned will cause a brittle and porous weld. If the base metal pieces to be joined are thick or heavy, it may be necessary to bevel the edges, with a metal grinder, at the point of contact, as shown below. The angle of the bevel should be approximately 60 degrees. If utilizing a grinder, be sure to follow all manufacturer warnings and procedures. See the chart below for detailed instructions for preparing the weld joint. During the welding, the work pieces will become hot and will tend to expand. The expansion may cause the pieces to shift from the regular position. If possible, the work pieces should be clamped into the position they are to occupy when the welding is completed. Selecting The Proper Electrode 4.3 The welding electrode is a rod, or wire, of electrically conductive metal, coated with a layer of flux. When welding, electrical current flows between the electrode (rod) and the grounded metal work piece. The intense heat of the arc between the rod and the grounded metal melts the wire and the flux. The rod wire joins with the base metal in the work piece to form the weld bead. The burning flux forms a gas shield around the arc and helps to control the flow of the fusing metals that form the weld bead. The type and thickness of the metal and the position of the work piece determines the electrode type and the amount of heat needed in the welding process. Heavier and thicker metals require more heat (amperage). There is no hard and fast rule that determines the exact rod or heat setting required for every situation. To check the rod requirements for particular applications, refer to the rod guide on your welder, and then experiment on some scrap metal. Low vs High Voltage Welding Electrodes Make certain you have the best electrode for the welding job you intend to do. Electrode manufacturers make most of the standard welding electrodes in two basic types. One type has been designed to run on welders with high Open Circuit Voltage. The other type electrode is designed to run on welders with Low Open Circuit Voltage. Most of your welding will probably be done with low open circuit voltage AC rods such as E-6013 or E-7014 general purpose rods. Use rods of 1/16, 5/64, or 3/32 inch diameter (the thicker the rod, the more experience you need.) High open circuit voltage rods such as 6011, 7018, etc. will not work with most low power welders (100 amps and smaller). Electrode manufacturers have adopted a uniform marking code for welding electrodes. Each electrode is marked with a prefix letter and four numbers. Each of the numbers has a particular significance. For example: a commonly used general purpose electrode is marked E-6013. The E signifies the electrode is for electric arc applications. The first two digits in the number indicate the minimum tensile strength, of the deposited metal, in thousands of pounds per square inch. In this instance, 60 indicates the melting rod will have a minimum tensile strength of 60,000 p.s.i. The third number indicates the welding position for which the rod is intended. A number 1 indicates for use in any position. Number 2 represents an electrode restricted to welding in horizontal and flat positions. Number 3 represents an electrode intended for use in the flat position only. The fourth digit shows some special characteristics of the electrode such as weld quality, type of current, or amount of penetration. For all practical purposes, fourth position marking will not affect the rod you would normally purchase. Striking The Arc 4.4 To strike an arc, bring the tip of the rod in contact with the work surface and then quickly raise it until there is about 1/8 inch (3.2 mm) gap between the rod and the work, as can be seen below. The easiest way to strike an arc is to scratch the tip of the rod (for a short distance) on the work surface (as you would strike a match), then quickly lift it the required 1/8 inch (3.2 mm). It is important that the gap be maintained during the welding process and that it be neither too wide or too narrow. If the gap becomes too narrow, the electrode will freeze or stick to the work piece. Striking a proper arc and maintaining the gap between the electrode and the base metal takes practice. A beginner may expect to extinguish any number of arcs and freeze more than a few electrodes before acquiring the necessary skill. Knowing when the arc is just right is a matter of experience. A crisp, cracking sound, accompanies a good arc. The sound is similar to that made by eggs frying. To lay a weld bead, only 2 movements are required; downward and in the direction the weld is to be laid. Always watch the weld puddle to keep the slag from flowing in front of it to prevent causing inclusions and gas pockets. GENERAL ...
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