SMAW Flashcards
Electrical Circuit
Path taken by electric current flowing from one terminal, through a conductor, to the other terminal
Current
Amount of electron flow through an electrical circuit, measured in amps, I x R = V
Conductor
Any material through which electricity flows easily, ex: wires, cables, busbars
Resistance
Opposition of the material in a conductor to the passage of electric current, causing the electrical energy to be transformed into heat, measured in Ohms
Ohm
Basic unit of measure for resistance, I x R = V
Direct Current
Electrical current that flows in one direction only, DCEP, DCEN
Alternating Current
Electrical current that has alternating positive and negative values, first half-cycle (positive) - current flows in one direction, second half-cycle (negative) - current flows in opposite direction
Frequency
Number of cycles (AC sine waves) per second, measured in Hertz (Hz)
What frequency does North America operate at?
60 Hz
What frequency does Europe operate at?
50 Hz
Polarity
Positive or negative state of an object, determines the direction of current flow in DC
DCEN
Electrode - negative, workpiece - positive, current flow from electrode to workpiece
DCEP
Electrode - positive, workpiece - negative, current flows from workpiece to electrode
Voltage
Amount of electrical pressure in a circuit, doesn’t flow, has most effect on height and width of weld deposit
Open Circuit Voltage
Voltage produced when welding machine is ON but no welding is being done
What is the open circuit voltage of constant current machines?
50-100V
Hot Start
Provides an extra boost of current to help establish an arc when using hard to start electrodes
Arc Voltage
Working voltage, voltage present after an arc is struck and maintained, 10-35V
Constant Current Welding Machine
Welding machine that maintains a relatively constant current over a wide range of welding voltages caused by changes in arc length, manual
Arc Blow
Deflection of the welding arc by magnetic forces that occur due to current flow, common problem in DC in corners and near joint ends, results in incomplete fusion and excessive spatter
What is the best way to prevent arc blow?
Use AC
Undercutting
Creating a groove in the base metal that is not completely filled by weld metal during the welding process
What causes undercutting?
Using excessive current, traveling too fast, improper work angle
Overlapping
Extending the weld metal beyond the weld toes
When does overlapping happen?
When current is set too low and molten metal is deposited without actually fusing into the base metal
Transformer
Electrical device that changes AC voltage from one level to another, transforms a high-voltage/low-current input into a safe and useable low-voltage/high-current output
Rectifier
Electrical device that changes AC into DC
Inverter
Electrical device that changes DC into AC
What are the electrode F-groups?
F1: Fast-Fill, F2: Fill-Freeze, F3: Fast-Freeze, F4: Fill-Freeze
F1: Fast-Fill Group
High iron powder coating with soft arc and high deposit rates, ex: E7024
F2: Fill-Freeze Group
Moderately forceful arc with medium deposition rate, ex: E6013
F3: Fast-Freeze Group
Produces a crisp, deep-penetrating arc and a fast-freezing weld bead, ex: E6010
F4: Fill-Freeze Group
Produces sound welds with excellent notch toughness and high ductility, ex: E7018
What are the 5 essentials of SMAW?
Electrode selection, arc length, current, travel speed, electrode angle
Electrode Selection
Electrode type and diameter
Arc Length
Distance from the tip of the electrode to the weld pool
What happens when arc length is too long?
Unstable arc, large globules, excessive spatter, incomplete fusion
What happens when arc length is too short?
Fails to generate enough heat to melt base metal properly, high, uneven beads with irregular ripples, high chance of sticking
Arc Length Size
Size = 1 x Diameter of Electrode
Current Selection
Correct current (AC, DCEP, DCEN) for a particular electrode must be used
What happens when amperage is too low?
Not enough heat to melt the base metal, weld pool is too small, poor fusion, sticking
What happens when amperage is too high?
Electrode melts too fast, weld pool is large and hard to control, excessive spatter
Travel Speed
Rate at which an electrode moves along a joint
Electrode Angle
Combination of travel angle and work angle
Travel Angle
Angle less than 90 degrees between the electrode axis and a line perpendicular to the work piece
Push Travel Angle
Travel angle where the electrode points toward the direction of travel, less heat input, shallow penetration
Drag Travel Angle
Travel angle where the electrode points away from the direction of travel, more heat input, deeper penetration
Work Angle
Angle less than 90 degrees in a line perpendicular to workpiece and in a plane determined by the electrode axis and the weld axis
Duty Cycle
Percentage of time during a specified period that a welding machine can be operated as its rated load without exceeding the temperature limits of the insulation on the component parts
What is the time period NEMA has set the standard for a duty cycle?
A 10 min period
What do the first two (and sometimes three) digits of an electrode classification number specify?
The minimum tensile strength of the deposited weld metal in thousands per square inch (ksi), ex: 60 ksi or 60,000 psi
What does the third digit of an electrode classification number specify?
Welding position
1 - all positions
2 - flat position groove (1G), fillet welds (1F), horizontal fillet welds (2F)
4 - flat, horizontal, vertical down, overhead
What does the last digit of an electrode classification number specify?
Type of coating, welding current, operating characteristics (0-8)
