Presentation on theme: "Arc Welding By: John Templeton. Objectives Identify and explain safety practices and procedures as related to electric and oxy- fuel welding Identify."— Presentation transcript:
Objectives Identify and explain safety practices and procedures as related to electric and oxy- fuel welding Identify equipment used in SMAW welding Explain the SMAW process Identify the 2 types of welding current and machines
Arc Welding The process of fusing two or more pieces of metal together by using the heat produced from an electric arc welding machine. Otherwise known as SMAW (shielded metal arc welding) –The electrode produces a gas which shields the arc from the atmosphere as the electrode melts.
SMAW Advantages Scrap metal can used make repairs Repairs can be made quickly before a problem becomes severe Metal repair and construction can be accomplished more economically Arc welders can be used to accomplish jobs like cutting, piercing, gouging and beveling
Direct Current Welding DC (direct current) –Can produce direct current of both straight (negative) and reverse (positive) polarity. –Polarity is the direction in which the current flows across the arc. –Makes a continuous flow of electrons
Straight/Reverse Polarity Straight Polarity (DC-) –Work is positive and electrode is negative –Used to weld thinner metals –Shallow penetration Reverse Polarity (DC+) –Work is negative and electrode is positive –Used to weld thicker metals –Deeper penetration
Types of Welding Machines AC machine –Only works on alternating current (+-)
Types of Welding Machines AC/DC –Can run on three different types of current Alternating Direct current + (reverse polarity) Direct current – (straight polarity) This machine will have a rectifier switch which will allow it to switch between the three Or the leads will need to be placed in certain parts of the machine.
Types of Welding Machines AC/DC Machines –Are capable of handling most agriculture and construction. –Are the most popular. –Allow the operator to weld metal of all thickness.
Types of Welding Machines Machines can either be gasoline engine driven or they can be powered be electricity.
Duty Cycle Tells the operator how long his machine can operate without causing damage to the machine. It is how long a machine can run in ten minute intervals, and is measured by a percentage.
Duty Cycle If a machine has a duty cycle of 25%, for every ten minutes the machine is operated you can only weld for 2.5 minutes. The remaining 7.5 minutes must be spent letting the machine idle.
Electrodes All major manufacturers of welding electrodes use the American Welding Society (AWS) code of specifications. Each company makes basically the same quality which is established by the AWS.
Electrodes Electrodes are classified according to type of coating, composition of the weld metal and operating characteristics. The numbering system is started with “E” for electrode and then followed by a four digit number
Electrodes Each number in the four number sequence has a specific meaning. 60XX = Tensile Strength in pounds (X 1,000) 60,000 lbs per square inch XX1X = Welding Position 1 =All 2 = Flat and Horizontal 3 = Flat XXX1 = Polarity 1,3,4,8=AC or DC Reverse 2 = AC or DC straight 0 = DC Reverse
Electrodes What is the classification of an E 7018? –E –70 –1 –8
Electrode Diameter Electrodes are also measured by their diameter (the diameter of the electrode without including the flux. The diameter is measured in thirty-seconds of an inch. Always use an electrode ½ the size of you base metal –What does this mean?
Electrodes What diameter electrode should you use if your base metal is ½ in thick? 1/8 inch? ¼ inch?
Electrodes When selecting an electrode you need to consider the following: –How thick is your base metal? –What condition is your metal in? –What type of machine do you have access to? –Welding position?
Welding Safety Electrical shock –Make sure the machine is grounded. –Make sure the cables are not cut or frayed. –Do not stand in wet surfaces. –Wear leather gloves. –Wear rubber-soled shoes
Radiant Energy Radiant Energy can cause burn –Make sure you helmet is in good repair and lenses are not cracked. –Make sure all skin is covered with cotton material –Say cover before welding, so that everyone can protect themselves from radiant energy
Eye Protection Make sure you are welding with a shade of 12-14 lens Make sure your helmet has a Z87 clear lens with a shaded 12-14 lens on top.
Ventilation Make sure you are welding in a well ventilated area If you become sick do not continue and drink milk. Use fans to blow out smoke
General Safety Keep work area clean and free from hazards. –Welding leads –Flammables –Cover eyes while chipping slag