Chapters 24 and 25, TYK set

What safety precautions must be observed when lighting a gas-fired heat-treating furnace?

1) Never attempt to heat-treat metals while your senses are impaired. 2) Make sure the furnace is in good operating condition. 3) Avoid lighting a furnace until you have been instructed on its safe operation. 4) Never stand in front of a gas furnace while lighting it. 5) Never look into the furnace unless you are wearing proper eye/face protection. 6) Wear heat resistant gloves and a leather apron. 7) Work only in areas that are well ventilated. 8) Gas furnaces are noisy. Hearing protection must be worn when working near them.

List three commonly used hardness testers

Brinell, Rockwell, Webster and scleroscope.

How are carbon steels calssified?

By the amount of carbon they contain. Low is 0-.30%, medium is .31% to .60%, and high is .61% to 1.50%. 100 points = .01 percent.

What are composites?

Composites utilize fibers of common and uncommon materials, in both pure and alloy forms. The fibers are bonded together in a special plastic matrix under heat and pressure. These materials are generally lighter, stronger, and more rigid than many conventional metals.

What is the steel color code?

It is a method of identifying the many kind of steels. Each commonly used steel is designated by a specific color.

What advantages does an electric heat-treating furnace have over a gas fired heat-treating furnace?

Modern electric furnaces are fitted with numerous safety devides and are quieter.

What is the structural material known as honeycomb?

Sections of thin material are bonded together to form a structure in appearance to the wax comb that bees create to store honey. When honeycomb is rigidly bonded between two metal or composite sheets to form a sandwich panel, it becomes a strong structure.

What is the difference between strength and toughness?

Strength holds weight without bending or buckling; while, toughness are shatter resistant to severe blows.

What does temper designation indicate when identifying the grade of aluminum?

The degree of hardness of the alloy.

The four digit code in identifying metals is

The first digit classifies the steel 1) referrs to carbon steels 2) referrs to nickel steels 3) referrs to nickel-chromium steels The second digit indicates the approximate % of the alloying element in the steel. The last two digist show the approximate carbon content of the steel in points or hundredths of a percent. (Ex: SAE 1020 is a carbon steel with aproximately 20 points or 0.20% carbon)

What is red hardness?

The quality of remaining hard when red hot.

__________ melts at a higher temperature than any other known metal

Tungsten

How are carbon steels classified

according to the amount of carbon they contain, 100 pts. = 1%.

Drills, reamers, some milling cutters, and similar tools are usually made from ______ steel

alloy tool

Ductile metals

are easily deformed.

Hardness testing

are techniques used to determine the degree of hardness of heat-treated material.

List three basic groups of stainless steel

austenitic, martensitic, and ferritic.

Hot rolled steel is characterized by the __________ on its surface

black oxide coating.

Tempering a piece of hardened steel makes it

brittle, soft and tough... None of the above.

Cast irons

can be hammered into shape; are best machined with carbide cutting tools; air is recommended as a coolant; and, irons rigidity and stability are some of the main reasons why it is widely used in industry.

What are three case hardening techniques?

carburizing, cyaniding and nitriding.

Brass and bronze are _______ based alloys.

copper

Stainless steel is

corrosion resistant.

The chief characteristic of stainless steel is its resistance to

corrosion.

Iron and steel are classified as __________ metals

ferrous

What are the four main categories of metals

ferrous, non-ferrous, (high-temperature and rare metals have space and military applications).

Nickel, chromium, molybdenum, vanadium, and tungsten are used to make steel ______, ______, and ______

harder, stronger, and tougher.

Tempering

heating hardened steel to just below its critical temperature, then slowly cooling the steel to reduce brittleness and toughness.

What does heat-treating involve?

heating the metal to a predetermined temperature, under a specified time, and then cooling it gradually, or quenching it (cooling it rapidly) in water, brine, oil, blasts of cold air, or liquid nitrogen.

Nickel-based alloys, molybdenum, tantalum, and tungsten are classified as _______ metals.

high-temperature

Cold and hot rolled steels

hot rolled steel is characterized by a black oxide coating. Cold finished steel has a shiny smooth surface.

Annealing

involves heating the metal to slightly above its critical temperatire and then permitting it to cool slowly in insulating material. The hardness of the metal is reduced.

carbon steel is an alloy of __________ and __________

iron and carbon.

Carburizing

is a process that introduces carbon to the surface of the steel by heating the metal to just below its melting temperature in contact wth carbonaceous solids, liquids, or gases. The piece is held at that temperature for a predetermined time and then quenched.

Hardening

is accomplished by heating metal to its critical range and cooling it rapidly.

Stress-relieving

is done to reduce stress that had developed in parts that have been welded, machined, or cold worked during processing.

Tensile strength

is the amount that a metal will resist a direct pull.

Heat treatment

is the careful application of a combination of heating and cooling cycles to a metal or alloy in a solid state to bring about certain desireable properties, such as hardness and toughness.

Cyaniding

is the introduction of carbon and nitrogen simultaneously into a ferrous alloy by heating while in contact with molten cyanide.

Induction hardening

is the rapid heating of a part surrounded by a high-frequency electric coil to above its critical temperature for a few seconds, followed by rapid cooling.

Surface hardening

is used only when a medium-hard surface is required on high-carbon or alloy steels.

Normalizing

is used to refine the grain structure of steel and improve its machinability.

Magnesium is the __________ of the structural metals

lightest.

Other than steel, list four other metals that are capable of being heat-treated?

magnesium, copper, beryllium and titanium.

Malleable metals

may be easily formed or shaped.

Aluminum, magnesium, and titanium are __________ metals

non-ferrous.

Heat-treating is done to

obtain certain desireable changes in the metal's physical characteristics; increase the hardness of the metal; and, soften (anneal) the metal.

carbide cutting tools are recommended for machining cast iron because

of the abrasive nature of the iron scale.

In addition to water, ______, ______, blasts of cold ______ or liquid ______ may be used as a quenching medium.

oil, brine, air, and nitrogen. Additionally, mineral oil and sand may be used.

Case hardening

only the outer surface of low-carbon steel is hardened while the inner portion remains relatively soft and tough.

The ______ is used to measure and monitor the high temperatures needed in heat treating.

pyrometer

Hard metals

resist penetration.

Elastic metals

return to their original shape after the load is removed.

titanium is a metal that is as ______ as steel but only _______ as _______.

strong, half, and heavy.

The machinability of carbon steel is improved if ______ or ______ is added as an alloying element

sulfur or lead.

Spark test

the metal is touched to the grinding wheel lightly and the resulting sparks are carefully observed.

Bronze is an alloy of copper and _______.

tin.

Beittle metal

will not bend bbut will break easily.

Brass is an alloy of copper and _______.

zinc