102 Flashcards
What are the breakers set to on a resident 220V circuit?
40-50 amps
Who is allowed to install electrical systems for welding machines?
A certified electrician
Define arc?
An arc is created when there is enough amperage and voltage available at the electrode tip to overcome the natural resistance
What is the metal deposition rate?
It’s another term for burn off rate
What controls the core in a coil?
A moveable shunt
What body rates welding machine duty cycles?
National electrical manufacturers association (NEMA)
What is a electron?
Negatively charged particles that move through a conductor when current flowing
If a generator produces AC current what may it also be called?
An Alternator
What’s an inverter?
An inverter is a device that changes DC to AC
What is a rectifier?
A rectifier is a device that changes AC to DC
If you lengthen your stickout during a gmaw welding process what are you changing in the circuit?
You are adding resistance to the circuit which may lead to stubbing
When using straight polarity where is the majority of the heat?
2/3 of the heat will be in the electrode causing the electrode to melt
When using a CV machine how many rheostats will be on it?
2, one to set voltage and one to set wire speed
When looking at a volt-amp curve, if your line goes from volts and droops to amperage what kind of machine are you using?
Constant current
What two ferrous metals can’t be cut with a oxy-fuel torch?
Stainless steel and cast iron
What non ferrous metals can be identified by a spark test?
Nickel and titanium
What is the difference between red brass and yellow brass?
Red brass is more copper and less zinc, yellow brass on average 60% copper and 40% zinc
What are the two types of file hardness tests?
Rockwell and Brinell
This hardness test uses conical diamond penetrator applied to a specific load. The amount that the penetrator indents tells the hardness what test is this?
Rockwell
When flame testing metal what are you looking for?
The speed of melting, changes in colour, the appearance and action of slag, the appearance of the molten puddle, action if the molten puddle under the flame
If the heat identification number is removed from a plate what must be done?
Transfer it to the remaining plate
When metal is shipped what comes attached to the metal?
Mill report and metal specification tag
Define compressive strength
The resistance of material to a force that tends to deform or fail it by crushing
Define shear strength
The maximum load that a metal can take before it fractures across its section
Define tensile strength
The ultimate pull that a material will stand without fracture
Define yield strength
The stress point at which permanent deformation takes place
Define impact strength
The ability of a metal to withstand a sharp high velocity blow
What is the elastic limit?
The maximum stress the metal will endure before permanent deformation takes place
Define ductility
The ability of a material to stretch or deform under load without breaking or failing
Define brittleness
The tendency of a material to fail suddenly by breaking without any permanent deformation before failure
Define hardness
A materials ability to resist penetration or indentation
Define toughness
The ability of metal to withstand a rapidly applied load without breaking
Define elasticity
Is the ability of a metal to return to it original shape and dimensions once a load is removed
Define Malleability
A metals ability to be cold worked without a great deal of resistance
What test is used to determine impact strength?
Notch test
What term describes the rate heat travels through metal?
Thermal conductivity
Ferrous metal has a high content of ________?
Iron
What phase of power supplies are used in most industrial applications?
Three phase power
When talking about electricity what does EMF stand for?
Electromotive force
What charge do electrons hold?
Negative
What is the purpose of a silicon controlled rectifier?
To change AC to DC
What is the melting point of mild steel?
1510^C (2750^F)
What is the heat affected zone?
The area on both sides of the weld directly adjacent to where the weld metal mixes with the parent metal
What is resulting grain structure from a multi pass weld?
A finer grain structure, a general rule is a finer grain structure makes a stronger weld
A finer grain structure provides greater ______ strength and _______ strength
Tensile and yield
What four areas does the HAZ consist of?
Solid/liquid transition zone, grain growth zone, recrystalized zone, partially transformed zone
Define temperature
Measures the Degree or intensity of heat, measured in Celsius (C) or Fahrenheit (F)
Define heat
Expresses volume or quantity of heat, it is measured in British thermal units (BTUs) or in joules (J)
When does solid expansion occur?
When metal is in a solid condition and has not reached its transition temperature
What is the primary purpose of preheating?
To prevent high stress and cracking
What is the temperature range for pre heating on average?
40^C-250^C (100^F-400^F)
What is the primary purpose of post heating?
To slow the cooling rate of the weld and HAZ
How does post heat affect hydrogen in the weld?
It allows hydrogen to migrate out of the weld, these hydrogen induced cracks can show weeks after welding stops
What is the grain structure in martensite like?
Needle-like and the metal becomes very hard and brittle
What causes martensite to form?
When steel is quenched the carbon does not have time to come out of solution which causes it to become trapped in crystalline structures which normal hold very little or no carbon which causes stress within the metal
What determines post heat temperature?
Material thickness, carbon and other alloy content, whether the material was subjected to heat treatment when it was manufactured
What is the purpose and process of normalizing?
Normalizing consists of heating an object above its upper critical limit for 1 hour for every inch of thickness this produces grain uniformity in the grain structure
What is annealing?
The process of softening a material bringing it to its softest toughest, weakest state. This lowers tensile strength and raises softness and toughness
What temperature range does the stress relieving process use?
600^C (1100^F)- 700^C (1300^F)
How does tempering affect metal?
Reduces toughness and promotes toughness, it also reduces fragile brittleness and reduces internal stress
What is hard facing?
Application of a hard, wear resistant metal or metal alloy to a surface of a softer metal by a welding process
What is the purpose of hard facing?
Combat wear, prolong the life of an object, reduce costly down time, and reduce the cost of replacement parts
When talking about hard surfacing what does ABR stand for?
ABR stands for Abrasive Resistance material
When hard surfacing a loader bucket why do you put different patterns in the weld?
To make sure the wear happens only on the dirt and the hard surface material
When hardfacing what polarity do you use?
Reverse polarity (DCEN)
Define abrasion
Sliding/scraping type of wear that removes metal by gouging or grinding
Define impact wear
Pounding or battering type of wear that splits, breaks, chips, mushrooms or otherwise deforms the metal surface
Define erosion
Gouging type of wear that washes away or grooves out the metal surface
What is galling?
Metal to metal wear
Define corrosion
Wear that pits, perforated and eventually dissolves metal parts
Define oxidation
Special form of corrosion that takes place when some metal are exposed to a combination of heat and air
Define compression
Squeezing type of wear usually cause by heavy static load or loads that gradually increase pressure on metal surface
Define thermal shock
Cracking or splitting wear caused by exposing metal parts to temperature extremes such as rapid heating and cooling cycles
What is a common use of austenitic manganese? And why?
Railroad tracks, because it has very good work hardening characteristics
What is dilution, what is a common cause of this?
The mixing of the base metal with the hardfacing material, using the wrong polarity is a very common cause of dilution
What is spalling?
Spalling occurs when the weld metal breaks away from the base metal
What are some ways to help prevent spalling?
Prepare the surface, control the cooling rate, limit deposit thickness
Describe a hidden line, what’s its purpose?
Broken line of medium thickness, it shows edges and outlines not visible to the eye
Describe a long break line, what is its purpose?
Ruled light lines with free hand zigzags, these lines are used to conserve space or to show a partial end of a section
What is an architectural drawing?
A line drawing that shows plan and/or elevation views of the proposed building showing its OVERALL APPERANCE
What does a mechanical drawing show?
It shows all the required mechanical components of the building
What do section lines represent?
Different types of material when there is an imaginary cut surface
What does leader line do?
A leader line I used to add a note or a dimensions
Name the four weld types?
Surfacing, plug or slot, fillet, groove
Name the five basic joints
Butt joint, corner joint, tee joint, edge joint, lap joint
Which joints use fillet welds
Lap joint, tee joint, and corner joints
