Arc Welding Equipment Arc Welding Arc welding Arc welding uses electricity to heat and melt the metal. Shielded metal arc welding Shielded metal arc welding Where fusion is produced by heating with an arc between electrode and the work piece. An electrode is a bare metal rod which is usually coated with chemical compounds called flux. An electrode is a bare metal rod which is usually coated with chemical compounds called flux. The flux forms a blanket of smoke and gas that shields the weld puddle from the air. Electricity and Welding Must have a basic understanding of electricity to understand welding Must have a basic understanding of electricity to understand welding Electricity is the flow of tiny particles called electrons through a conductor. Electricity is the flow of tiny particles called electrons through a conductor. Electrons are negatively charged particles. A conductor allows the flow of electrons. Voltage is a measure of electrical pressure. Voltage is a measure of electrical pressure. Electrical Terms Most welders operate on a 220 volt source. Most welders operate on a 220 volt source. A welder changes the 220 volt pressure to a lower pressure between 15 and 25 volts. A welder changes the 220 volt pressure to a lower pressure between 15 and 25 volts. Amperage is a measure of electrical current flow Amperage is a measure of electrical current flow The amount of current available is determined by the amperage setting on the welder. Polarity is the direction the current is flowing. Polarity is the direction the current is flowing. Electrical Terms Resistance is the opposition to the flow of current in a circuit. Resistance is the opposition to the flow of current in a circuit. Resistance is what causes the electric energy to be transformed into heat. When electricity is through a conductor, the movement of electric energy heats the conductor due to the resistance of the conductor to the flow of electric current When electricity is through a conductor, the movement of electric energy heats the conductor due to the resistance of the conductor to the flow of electric current The higher the amps setting, the greater the heat produced. more resistance The higher the amps setting, the greater the heat produced. more resistance When electrical current alternates or reverses the direction of electron flow it is called alternating current (AC). When electrical current alternates or reverses the direction of electron flow it is called alternating current (AC). Electrical Terms The arc is extinguished every half-cycle as the current passes through zero, usually at the rate of 120 times per second. The arc is extinguished every half-cycle as the current passes through zero, usually at the rate of 120 times per second. Direct Current (DC) Electron flow in one direction When the electrons flow from the electrode to the work piece it is straight polarity. When the electrons flow from workpiece to the electrode it is reverse polarity. Welding machines are classified in several different ways. Welding machines are classified in several different ways. One common way is by the type of output current produced by the welder, One common way is by the type of output current produced by the welder, AC DC AC/DC. Classifying Welders Classify by service. Limited input welders provide satisfactory operation and inexpensive Limited input welders provide satisfactory operation and inexpensive Dollar per amp Limited service welders are used where lower cost is desired, Limited service welders are used where lower cost is desired, Industrial welders have a high duty cycle, but expensive. Industrial welders have a high duty cycle, but expensive. Power source Electric motor driven Electric motor driven requires three-phase power. Electric power runs the a generator to produce DC An internal combustion engine An internal combustion engine Line voltage welders run on the power supplied by the power company. Line voltage welders run on the power supplied by the power company. Duty cycle Duty cycle is the percentage of a 10 minute period that a welder can operate at a given current setting Duty cycle is the percentage of a 10 minute period that a welder can operate at a given current setting 60 per-cent duty cycle can be operated safely for six minutes of a ten minute cycle repeated indefinitely. 60 per-cent duty cycle can be operated safely for six minutes of a ten minute cycle repeated indefinitely. Welding equipment Two cables, No. 2 gauge, are required. The electrode holder Two cables, No. 2 gauge, are required. The electrode holder Ground Clamp Ground Clamp Chipping Hammer\Wire Brush Chipping Hammer\Wire Brush Pliers Pliers Safety Glasses\Welding Shield Safety Glasses\Welding Shield Gloves Gloves Electrodes Convey electric current from the welding machine into a hot arc. Convey electric current from the welding machine into a hot arc. Covered in flux Covered in flux When heated flux turns to a gas shield that protects the weld from oxygen Flux mixes with the metal and floats to the top as slag Classifying Electrodes Ex E7014 Ex E7014 E = electrode is used for electric welding. E = electrode is used for electric welding. The first two digits of a four indicate tensile strength in thousands psi. The first two digits of a four indicate tensile strength in thousands psi. EX: E7014 electrode produces a weld with 70,000 psi of tensile strength If the number has 5 digits the 1 st 3 are for tensile Strength The next to last digit indicates welding position for which the electrode is recommended. The next to last digit indicates welding position for which the electrode is recommended. The last digit indicates the operating characteristics of the electrode The last digit indicates the operating characteristics of the electrode