Materials Practices 3.0-4.0

Ferrous

Metal based on iron

Non-ferrous

all other metals

Ferrous Alloys

Iron is the prime constituent
produced in larger quantities than any other metal type

–exist in abundant quantities within the earth’s crust

–produced using relatively economical extraction, refining, alloying, and fabrication techniques

-extremely versatile, may be tailored to have a wide range of mechanical and physical properties

Advantages of ferrous alloys

–their susceptibility to corrosion.

Disadvantages of ferrous alloys

Steel

–an iron‑carbon alloy

–containing from 0.02% to 2.1% carbon

Cast iron

–an iron‑carbon alloy

–containing  from 2.1% to about 4% or 5% carbon

Plain carbon steel

Low alloy steel

stainless steel

tool steel

Categories of Steel

Plain Carbon Steels

Carbon is the principal alloying element, with only small amounts of other elements (about 0.5% manganese is normal)

Steel

10XX

Low carbon steels

contain less than 0.20% C

Medium carbon steels

range between 0.20% and 0.50% C

High carbon steels

contain carbon in amounts greater than 0.50%

Low Alloy Steels

•Iron‑carbon alloys that contain additional alloying elements in amounts totaling less than ~ 5% by weight

true

Low alloy steels’ mechanical properties superior to plain carbon steels for given applications

Low alloy steels

YYXX

Manganese steel

13XX

Nickel steel

20XX

Nickel‑chrome steel

31XX

Molybdenum steel

40XX

Chrome‑molybdenum steel

41XX

Stainless Steel

•Highly alloyed steels designed for corrosion resistance

Stainless Steel

•Principal alloying element is chromium, usually greater than 15%

True

Carbon is used to strengthen and harden SS, but high C content reduces corrosion protection since chromium carbide forms to reduce available free Cr

Nickel

Another alloying ingredient for stainless steels to increase corrosion protection

Austenitic stainless

Ferritic stainless

Martensitic stainless

Types of stainless steel

Martensitic stainless

as much as 18% Cr but no Ni, higher C content than ferritic stainless

Ferritic stainless

1.about 15% to 20% Cr, low C, and no Ni

Austenitic stainless

1.typical composition 18% Cr and 8% Ni

Three-digit AISI numbering scheme

• first digit indicates general type

• last two digits give specific grade within type

Stainless steel designation scheme

Austenitic SS

Type 302

Ferritic SS

Type 430

Martensitic SS

Type 440

High‑speed tool steels, cutting tools in machining

T, M

Hot‑working tool steels, hot‑working dies for forging, extrusion, and die‑casting

H

Cold‑work tool steels, cold working dies for sheet metal pressworking, cold extrusion, and forging

D

Water‑hardening tool steels, high carbon but little else

W

Shock‑resistant tool steels, tools needing high toughness, as in sheet metal punching and bending

S

Mold steels, molds for molding plastics and rubber

P

Cast irons

Iron alloys containing 2.1% to about 4% carbon and from 1% to 3% silicon

Grey

Ductile Iron

White cast iron

Malleable iron

Types of cast irons

•graphite flakes

•weak & brittle in tension

•stronger in compression

•excellent vibrational dampening

•wear resistant

Grey Iron

•add Mg and/or Ce

•graphite as nodules not flakes

•matrix often pearlite – stronger but less ductile

Ductile iron

•< 1 wt% Si

•pearlite + cementite

•very hard and brittle

White iron

•heat treat white iron at 800-900ºC

•graphite in rosettes

•reasonably strong and ductile

Malleable iron

Aluminum and Magnesium

Light Metals

Aluminum

it exhibits corrosion resistance and high electrical and thermal conductivity (ferrous)

Wrought Aluminum

XXXX

Cast Aluminum

XXX.X

Aluminum Alloy

1XXX, 1XX.X

Copper Alloy

2XXX, 2XX.X

Manganese Alloy

3XXX, not castable

Silicon Alloy

4XXX, 4XX.X

Zinc Alloy

7XXX, 7XX.X

Tin Alloy

8XX.X

Fabricated

Temper designation of Al alloys: F

H

Temper designation of Al alloys: Strain Hardened

O

Temper designation of Al alloys: Heat treatment to increase ductility

T

Temper designation of Al alloys: Thermal treatment to produce stable tempers other than F,H, or O

Magnesium

Lightest of the structural metals

Magnesium

in pure form, magnesium is relative soft and lacks sufficient strength for most engineering applications

A, E, H, K, M, Q, T, Z

Al, rare earth elements, thorium, zinc, magnesium, silver, tin, zinc (magnesium designation scheme)

Copper

low electrical resistivity widely used as an electrical conductor

Bronze

alloy of copper and tin (90%Cu, 10%Sn)

Brass

Alloy of copper and zinc (65% Cu, 35% Zn).

Beryllium copper

Highest strength of copper alloy (2% Be)

C10100

99.99% pure copper

C17000

98% Cu, 1.7% Be

C24000

80% Cu, 20% Zn

C52100

92% Cu, 8% Sn

Nickel

More corrosion resistant to iron, alloying element to steel, high temperature properties of alloys are superior

Nickel

Alloys of this are important due to its corrosion resistance and high temperature performance

Superalloys

contain substantial amounts of three or more metals, rather than consisting of one base metal plus alloying elements

Iron-based alloys

Nickel-based alloys better high temperature strength than alloy steels

Cobalt-based alloys

Groups of superalloys

Alloying

important technique to strengthen metals

Cold working

strain hardening during deformation to increase strength (also reduces ductility)

Heat treatment

heating and cooling cycles performed on a metal to beneficially change its mechanical properties

Grain refinement

Alloys with finer grains typically have higher strength and superior toughness compared to the same alloy with physically larger grains