2 ObjectivesIdentify and explain safety practices and procedures as related to electric and oxy-fuel weldingIdentify equipment used in SMAW weldingExplain the SMAW processIdentify the 2 types of welding current and machines
3 Arc WeldingThe 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.
4 SMAW Advantages Scrap metal can used make repairs Repairs can be made quickly before a problem becomes severeMetal repair and construction can be accomplished more economicallyArc welders can be used to accomplish jobs like cutting, piercing, gouging and beveling
9 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
10 Straight/Reverse Polarity Straight Polarity (DC-)Work is positive and electrode is negativeUsed to weld thinner metalsShallow penetrationReverse Polarity (DC+)Work is negative and electrode is positiveUsed to weld thicker metalsDeeper penetration
11 Types of Welding Machines AC machineOnly works on alternating current (+-)
12 Types of Welding Machines AC/DCCan run on three different types of currentAlternatingDirect current + (reverse polarity)Direct current – (straight polarity)This machine will have a rectifier switch which will allow it to switch between the threeOr the leads will need to be placed in certain parts of the machine.
13 Types of Welding Machines AC/DC MachinesAre capable of handling most agriculture and construction.Are the most popular.Allow the operator to weld metal of all thickness.
14 Types of Welding Machines Machines can either be gasoline engine driven or they can be powered be electricity.
15 Duty CycleTells 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.
16 Duty CycleIf 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.
17 ElectrodesAll 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.
18 ElectrodesElectrodes 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
19 ElectrodesEach number in the four number sequence has a specific meaning.60XX = Tensile Strength in pounds (X 1,000)60,000 lbs per square inchXX1X = Welding Position1 =All 2 = Flat and Horizontal 3 = FlatXXX1 = Polarity1,3,4,8=AC or DC Reverse2 = AC or DC straight0 = DC Reverse
20 ElectrodesWhat is the classification of an E 7018?E7018
21 Electrode DiameterElectrodes 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 metalWhat does this mean?
22 ElectrodesWhat diameter electrode should you use if your base metal is ½ in thick?1/8 inch?¼ inch?
23 ElectrodesWhen 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?
24 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
25 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 materialSay cover before welding, so that everyone can protect themselves from radiant energy
26 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 lens on top.
27 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
28 General Safety Keep work area clean and free from hazards. Welding leadsFlammablesCover eyes while chipping slag