Final Flashcards
A metals ability to change shape without breaking is called?
Malleability / Ductility
The ability of a metal to return to its original shape after being deformed is called?
Elasticity
Some alloys have better magnetic properties than pure metals, one example is?
Alnico
A solid and a liquid can exist together at the melting point. Adding heat melts…
More of the solid, but does not change the temperature
Alloys that contain iron as the base metal including all common steels and special steels are?
Ferrous alloys
The speed and ease with which a metal can be cut on a machine tool is called?
Machinability
Tensile yield strength is?
The maximum tensile stress a sample of the metal can apply to the testing machine before it begins to deform permanently
Tensile strength formula
At high temperatures, an extremely slow, continuous distortion of certain metals produces another type of failure called?
Creep
What is density
Is the mass of a material per unit of volume
Specific gravity is the ratio between?
The density of a given material and the density of water
Permanent-mold casting uses what kind of cores?
Metal and sand cores
What is centrifugal casting
The process in which centrifugal force makes the metal flow away from the center and against the sides of the mold
What is the most rapid of all castings?
Die casting, it is used in casting metals having no iron in them, non ferrous metals
What is the most common method of cold forging?
Upsetting
What is pulled through a tapered die to form the wire?
A rod
The main difference between cast iron and steel is the?
Carbon content, steels have less than 2% and cast iron has 2% to 4%
An alloy with a high carbon content has a relatively low melting point, which makes it?
Easier to cast than steel
Malleabilized iron is softer and less brittle than white cast iron but?
Has better resistance to wear than gray iron
High-alloy cast iron is used in making parts that must?
Be hard and tough, but not brittle
What are the different steel making processes?
Open-hearth process
Basic oxygen process
Electric furnace process
When making steel, the most important element to be added to iron is?
Carbon
In both AISI and SAE coding systems each code number specifies?
The chemical composition of one kind of steel
The amount of sparking, the length, and color of the sparks and the appearance of any bursts within the sparks will help you identify?
The metal
What is the best grading for cold-rolled sheets?
Commercial quality
How much chromium must steel contain to be considered stainless steel?
12%
What causes weld shrinkage distortion?
Results from the uneven heating and cooling of metal parts during welding
How do you anneal the star drill?
Slowly heat up with oxyacetylene torch
Reach above its critical temperature
Should glow pink
Pack drill into container of hot sand
Allow to cool slowly
Why do you preheat?
To greatly reduce internal stresses that would otherwise build up during welding, as a result little or no distortion will occur during welding
Low carbon steels are more often ____
High carbon steels are often ____
Forged
Cast
Steels containing .55 to 1.00 percent carbon are
High-carbon steels
Cold-working makes the alloys
Harder and stronger
A copper alloy containing a little lead is?
Much easier to machine
What is beta-brass?
Contains 36-50% zinc. And it is harder than alpha brass and less ductile
Which is the strongest of the brasses?
Muntz Metal
The copper alloy most widely used for casting is?
Leaded red brass, aka ounce metal
What happens when aluminum is exposed to air?
An aluminum-oxide coating that forms rapidly on its surface when the metal is exposed to air
What does the first digit indicate when describing alloys
The first digit indicates the main alloying element
What is cladding
Thin layers of aluminum can be rolled into a base metal
Aluminums strength decreases as?
It’s strength decreases greatly as the temperature of the metal rises
Intermediate-temperature solders melt at temperatures?
500 to 700 degrees Fahrenheit
Magnesium is extracted from brines and ores by two methods?
Electrolysis and reduction
The EK, EZ and ZE alloys are used at temps of 300 to 500 degrees Fahrenheit, their high temp strengths are greater than those of?
AZ alloys
What does the letter “a” indicate in alloys?
It indicates an annealed sheet
Magnesium can be gas welded however
It should only be gas welded for emergency repairs and special applications
The usual melting and casting methods cannot be used for titanium the reason being
Melting titanium reacts with gases in the air. Usually an arc melting process is used in an atmosphere of inert gas ( argon and helium )
Various portions of lead and tin are alloyed to make?
Solder
What is lead wool
The lead forms into fine fibers, when hammered into a small space, the fibers become welded together in a solid mass, which seals a space tightly
Nichrome wire is found in?
Toasters
Zinc is widely used as a corrosion resistant coating for steel sheet, called?
Galvanizing
The proper lubricants to use when machining zinc include
Lard oil and kerosene
A liquid has a fixed volume but?
It’s shape can change
What is density measured in?
Grams per cubic centimeter (g/cm3) or in kilograms per cubic meter (kg/m3)
What kind of process is evaporation?
Cooling process
How does the fluid move in laminar flow?
In layers parallel to the pipe
The solubility is usually zero at the ______ point of the liquid
Boiling
How do thermoplastic’s react to temp?
Soften when heated and harden when cooled
What is injection molding
A high speed, low cost method of forming intricate parts
What is a part of filament welding
A glass fiber around a special form called a Mandrel
To avoid chipping or cracking while machining?
Reduce the feed rate just before the drill
Point penetrates the other side of the material
When patching corroded surfaces
Clean both sides of the material
Elastomers have the ability to?
Be stretched to at least twice their original length and then return rapidly to there original shape
Class T for properties of rubber means?
Resist damage by extreme high and low temperatures
Are most rubber compounds flammable?
Yes
The less sulfur used when vulcanizing rubber the ________?
Softer the vulcanized product
The ability to flex is important in what wired insulation?
Extension cords, welding cables and power tool cords
How is a radial cut produced on a log?
Cutting the log lengthwise, with the cut going through or very near the centerline of the log
Measurements of running feet also called lineal feet refer to?
The actual length of the board
The quality of veneer plywood falls under what section
N
What wood is not good for load bearing surfaces?
Wood with many knots , each knot weakens the wood
In softwoods how deep should the pilot hole be?
Only half as deep as the length of the screw
What is air entrained concrete used for?
For building structures exposed to severe cold
Are cinderblocks used above or below ground?
Above ground
Type N mortar is a medium strength mortar used for
Exposed and load bearing clay tile construction
Plaster of Paris sets very quickly, about?
15 minutes, so it can be used only for small patching jobs
Before inserting new glass what should you do?
Place about a 1/16th of glazing compound along the window frame
Convection in fluids is where
The material is free to move around ( gases and liquids )
Mineral wool, has low K meaning it withstands both high and low temps, will not burn, and is chemically inert. It is used in
Ovens, boilers, hot-water tanks, freezers, refrigerators, and air ducts
How can you reduce vibration in rattling pipes or ducts?
By wrapping pipes or ducts with lead sheet or plastic film containing lead powder
An asphalt coating serves as a ______ on the outside of underground or basement walls
Moisture barrier
Mica provides?
Necessary insulation, that being 1580 ( kV/cm )
The liquid part of a paint is called the?
Vehicle, it consist of an oil plus a thinner. The vehicle is also called a binder, because it binds the pigment particles into a uniform film
What is the single most important factor for success in applying a protective coating?
Surface preparation
While blasting cleans a surface to the bare metal. It also?
Completely removes all scale and corrosion and creates the best anchor pattern
What happens in metalizing?
An oxyacetylene flame melts the zinc and sprays it onto the substrate
On the PH scale the numbers below 7 indicate?
Acidity
Why should gasoline never be used for cleaning?
It’s highly flammable
What is sulfamic acid used for?
Removing hard water deposits in heating and cooling systems
Separators or stabilizers called sequestrants prevent?
Scale in piping systems and boilers
Class C fire extinguishers are used for
Live electrical systems
What is curing?
The completion of all chemical and physical reactions that affect bonding
Water-soluble gums and starches from plants are made into natural vegetable glues called?
Mucilage
What is the high strength adhesive joint?
Bevel-lap joint
Rubber tape makes a very good insulating barrier for?
Electrical wiring
What is activated charcoal , sometimes called activated carbon?
A porous material that has a tremendous amount of surface area that can trap other materials
Carbon combines more rapidly with oxygen as temperatures increase but is chemically inert at?
Room temperature
Noise operation with carbon brushes usually indicates?
Brush problems
Why are non porous seals used in refrigeration?
The don’t allow even the tiniest leak in a system where it could be harmful
When installing packing, If there are only 2 rings _______
They should be positioned 180 degrees apart From the joints
How is welding started?
Touching the end of the electrode to the base metal, then lifting the electrode about a 1/4 inch. This action forms the arc which immediately produces temperatures exceeding 11000 degrees Fahrenheit
What does the word shielded in shielded metal arc welding refer to?
The cloud or shield of gas that forms around the arc area as the electrode covering or flux burns away
As the arc length increases what happens?
The resistance increases, thus causing a rise in the arc temperature
What are electrodes classified by?
Their core material
A welding helmet with a least a number ____ filter must always be worn while arc welding for protection against the arc flash and weld spatter
9
The type of covered electrode chosen for a given job depends on many factors, some of the most important are?
The composition of the base metal
The aws system uses the letter “E” for arc welding electrodes, in a four digit number the first 2 digits indicate?
The tested minimum tensile strength of the deposited metal
The current range for a particular electrode depends on its?
Diameter
Iron-powder electrodes have very thick coverings that contain between 25 and 50 percent iron powder. The thick cover allows?
You to use high welding amperage’s without causing excessive penetration
Electrodes with cellulose coverings need?
A certain amount of moisture to function properly
When metal is transferred from the electrode to the base metal by a series of rapid make and break short circuits it is called?
Short-circuit transfer, when the electrode touches the base metal a short circuit is created
The most common shielding gases used in GMAW are?
argon, helium, and carbon dioxide
Argon gas is heavier than air, this characteristic is advantageous because?
It readily settles and spreads when flat or horizontal fillet welding
In GMAW the main consideration when selecting a wire is to make sure that?
It has the same composition as the base metal
To start the arc and glad flow you?
Press the gun trigger, hold the gun nozzle about 5/8 to 3/4 in. above the work and tilt it about 20 degrees off vertical in the direction of welding
A GTAW torch holds?
The non consumable tungsten electrode in a collet, the torch nozzle guides the shielding gas into and around the area. Some torches are air cooled and others are water cooled
GTAW electrodes
The only purpose of the tungsten electrode is to serve as an electrical conductor to carry current to the welding arc