Arc Welding

Objectives Apply your welding knowledge to construct a butt weld in a group activity with 75% accuracy. Demonstrate how to properly weld a set of beads in a class activity with 90% accuracy. Decide the correct electrode that you should use in a class activity with 90% accuracy. Retell in your own words how to start an arc weld given oral questions with 95% accuracy. List the proper safety techniques that the class needs to follow while welding with 100% accuracy.

Reasons to Learn Why do we need to knock off the slag? Why do we need to use proper safety procedures?

Questions to Answer What are some types of metal that we can weld with an arc welder? What is another name for arc welding? What is a bead?

Interest Approach

What is welding? Welding is fusing or joining two pieces of material together by using a heat process. Fusion occurs when the two pieces being joined are being heated to the point of melting and the melted metals “flow” together. Arc welding uses an electric arc between a base metal and a coated electrode. Otherwise known as stick welding.

Equipment Consists of a machine that allows variable settings of amperage Made of transformers and controllers that can be adjusted for the desired arc heat. Some machines are AC, DC, or a combination of both

Equipment Also contains a ground cable and electrode cable attached to the machine and an electrode holder Securely clamp the ground cable to the metal that is being welded or to the table on which the metal is on The electrode cable is connected to the electrode holder.

Equipment All cables must be well insulated to prevent shock. Arc welder machines must be properly connected to a power source with good grounding.

What is an Electrode? An electrode is a section of straight wire about 14 inches long coated with flux. The flux forms slag over the molten metal protecting it from atmospheric gases. The heat of an arc can reach about 6,500 degrees F. Much hotter than the melting point of most metals After the metal cools, chip away the slag.

Selecting an Electrode Common electrode sizes are 1/8, 5/32, 3/32, and 3/16 inch With steel, the 1/8 inch is selected with amperage setting of 70 to 120 Electrodes are selected based on the kind of material that you are welding on The size is the diameter of the wire inside the flux. Larger electrodes are used on thicker metal and with higher amperage settings

Electrodes Electrodes are identified by a code number that is stamped on the flux near the bare end of the wire. The codes tell the composition of the electrode, the strength of the weld that will be produced, and the position for which the electrode is recommended Common electrodes are E- 6011, E-6013, E-7018 The strength of the weld is measured by pounds per sq. inch (psi) of tensile strength

Safety Always wear a properly adjusted helmet with an approved lens in good condition Never look at an arc without eye protection Warn others around you that you are about to weld and they need to cover their eyes Wear leather gloves, long sleeved clothing, and protective shoes Never weld in water or moist areas with arc equipment Make sure you have good ventalation

Starting a weld 1. Clean the metal 2. Use clamps to hold your metal in place (if welding two pieces) 3.Select the correct electrode and adjust your machine for the work that you are doing 4.Put the electrode into the electrode holder 5.Use the ground clamp and clamp it to your metal or the table you are welding on 6. Turn the machine on, pull your helmet down, and strike an arc!

Starting a weld Strike the arc by scratching or tapping the end of the electrode against the grounded metal. Lift the electrode from the metal to maintain the arc. The electrode can freeze or “stick” to the metal Maintain an arc about the diameter of the electrode or about an 1/8 inch.

What is a bead? A bead is the mix of base metal, and filler that remains after a weld. The best beads result when a uniform travel speed is used. Once the bead has cooled, wear safety glasses and chip away the slag with a slag hammer, then use a wire brush

Summary What is the electrode rod covered in? What is another name for arc welding? What are the safety precautions that we must take before welding? What are the three types of electrodes that we can use to weld with?