MSE 2100: Chapter 11

Carbon concentrations in medium-carbon steel

0.25 - 0.60 wt%

Carbon concentration range of high-carbon steels

0.60 - 1.4 wt%

Graphite formation promoted by silicon concentrations above:

1 wt%

Three steps of heat treatment for medium-carbon alloys

1) Austenitizing 2) Quenching 3) Tempering

Three reasons for widespread use of ferrous alloys

1) Availability as a natural resource 2) Economical processing methods 3) Extremely versatile

Applications of HSLA steel (4)

1) Bridges 2) Towers 3) Support columns 4) Pressure vessels

Applications of low-carbon steel

1) Car body components 2) Structural beams

Components commonly added to med-carbon alloys in order to improve strength-ductility combinations

1) Chromium 2) Nickel 3) Molybdenum

Applications of high-carbon steels

1) Cutting tools 2) Tools 3) Dies 4) High-strength wire

Four advantages of low-carbon steel

1) Ductility 2) Toughness 3) Easy to work with 4) Cheapest to produce

The two types of alloys:

1) Ferrous 2) Nonferrous

Applications of high-strength stainless steels

1) Gas turbines 2) High-temp steam boilers 3) Heat-treating furnaces 4) Aircraft 5) Missiles 6) Nuclear power generating units

Three characteristics of high-carbon steel in comparison to low- and med-

1) Hardest 2) Strongest 3) Least ductile

Three stages of annealing

1) Heating 2) Hold at temperature 3) Cooling

Three limitations to ferrous alloys

1) High density 2) Low electrical conductivity 3) Vulnerable to corrosion

Advantages of HSLA

1) Higher strengths than plain low-carbon steel 2) More resistant to corrosion

Benefits of CGIs

1) Higher thermal conductivity 2) Better resistance to thermal shock 3) Lower oxidation at elevated temperatures

Three characteristics of aluminum alloys

1) Low density 2) High electrical and thermal conductivities 3) Corrosion resistance

Three classifications of SS

1) Martensitic 2) Ferritic 3) Austenitic

Corrosion resistance can be enhanced in SS with the addition of __ and __.

1) Nickel 2) Molybdenum

Internal residual stress develops in metals as a result of:

1) Plastic deformation 2) Nonuniform cooling 3) Phase transformation that is induced upon cooling

Applications of med-carbon steel

1) Railway wheels & tracks 2) Gears 3) Crankshafts 4) Structural components

Purposes of annealing

1) Relieve stresses 2) Increase softness, ductility, and toughness 3) Produce a specific microstructure

The two types of precipitation hardening

1) Solution heat treatment 2) Precipitation heat treatment

Applications of superalloys

1) Turbines 2) Nuclear reactors 3) Petrochemical equipment

Two downsides of low-carbon steel

1) Weak 2) Soft

Silicon content range in gray cast iron

1.0 - 3.0 wt%

Compacted graphite iron (CGI) range of silicon content

1.7 - 3.0 wt%

Combined concentrations of alloying elements (besides copper) in HSLA steel

10 wt%

Ductility range of ferritic ductile iron

10% - 20% EL

Minimum chromium concentration in stainless steel

11 wt%

Minimum carbon concentration of cast iron

2.14 wt%

Carbon content range in gray cast iron

2.5 - 4.0 wt%

Ductility of low-carbon steel

25% EL

Typical yield strength for low-carbon steel

275 MPa

Most cast iron has a carbon concentration range of:

3.0 - 4.5 wt%

Range of carbon content in CGI

3.1 - 4.0 wt%

Ferritic ductile irons have tensile strengths ranging from __ to __.

380 MPa, 480 MPa

Range of tensile strengths for low-carbon steel

415 - 550 MPa

Heat treated HSLA can have tensile strengths exceeding

480 MPa

Low-carbon steels concentration

<0.25 wt% carbon

Wrought alloys

Compliant to mechanical deformation

Steels

Fe-C alloys that may contain other alloying elements

Which type of alloy is most widely produced?

Ferrous

HSLA

High-strength, low alloy

Ferrous alloys

Iron is the primary component

Cast alloys

So brittle that forming or shaping is impractical

Properties maximized in spheroidized steels

Softness, ductility

Hardenability

ability of an alloy to be hardened by the formation of martensite as a result of a given heat treatment

Alloy steels

additional alloying elements (besides carbon and manganese) are added in specific amounts

Solution heat treatment

all solute atoms are dissolved to form a single phase solid solution

First two digits in steel classification number

alloy content

Normalizing

an annealing heat treatment intended to refine the grains

Most common copper alloy type

brasses

Last two digits in steel classification number

carbon concentration

The mechanical properties of steels are greatly affected by:

carbon concentration

Refractory metals

characterized by extremely high melting temperatures

Predominant alloying element in stainless steel

chromium

Process annealing negates the effects of __

cold working

Strengthening method for low-carbon steels

cold working

Mechanical strength of aluminum is enhanced through

cold working and alloying

Tendency to form graphite is dependent on __ and ___

composition, rate of cooling

Primary alloying element in bronze

copper

Stainless steel is highly resistant to:

corrosion

Disadvantage of cold working and alloying of alumninum

decreased corrosion resistance

Jominy end-quench test

determine hardenability

Heat-treated med-carbon steels sacrifice __ and __ for __

ductility, toughness, strength

Microstructure components for low-carbon steel

ferrite and pearlite

Cast iron is classified as a ____ alloy.

ferrous

CGI has a microstructure that is intermediate between:

gray iron and ductile iron

High-carbon steels are almost always used in a __ and __ condition.

hardened, tempered

Precipitation hardening

hardening by formation of precipitates

HSLA steel strengthening method

heat treatment

Annealing

heat treatment where a material is exposed to a high temperature and then slowly cooled

Temper designation

indicates mechanical and/or heat treatment to which the aluminum alloy has been subjected

Severity of quench

indicates rate of cooling

HSLA steel has a low/medium/high-carbon content

low

Full annealing is used in ___ steels that will be machined or experience plastic deformation

low- and medium-carbon

Three classification levels of steel based on carbon content:

low-, medium-, and high-

Carbon classification of steels is most commonly produced:

low-carbon

Cast iron has a higher/lower melting temperature than steel

lower

Material with lowest density of all structural metals

magnesium

White iron is used to produce:

malleable iron

Hardenability, simple def

qualitative measure of the rate at which hardness drops off with distance into the specimen as a result of diminished martensite content

Ductile (nodular) iron

result of adding magnesium and/or cerium to gray iron before casting

Which type of precipitation hardening involves a higher temperature?

solution

Jominy end-quency test procedure

specimen heated, then sprayed with water

Applications for which med-carbon is used require combination of high ___, ____, and ____.

strength, wear resistance, toughness

Metal that is immune to chemical attack under 150 deg C

tantalum

Microstructures of tempered medium-carbon alloys

tempered martensite

Medium-carbon alloys are most often used in the ___ condition

tempering

Specific strength

tensile strength - specific gravity ratio

SS is classified based on:

the primary phase constituent of the microstructure

Precipitation heat treatment involves both temperature and ___ as important factors

time

Austenitizing

transformation of an alloy to austenite

Metal with highest melting temp

tungsten

Alloying elements are added to high-carbon steels to result in:

very hard, wear-resistant carbide compounds

The primary disadvantage of ferrous alloys

vulnerable to corrosion

Microstructure of CGI resembles

worms

Primary alloying element in brasses

zinc