Metallurgy: Identifying Metals

Metallurgy: Identifying Metals

TSM 233

Unit 9

TSM 233 Metallurgy and Welding Processes

Materials Properties for MetalsFour categories for classifying the properties of materials:

Chemical PropertiesPhysical PropertiesMechanical PropertiesProcurement/Manufacturing

Considerations


Chemical Properties

“Chemical properties are material characteristics that relate to the structure of a materials and its formation from the elements.”

Examples of chemical properties: Composition of the metal Microstructure Grain sizes Corrosion resistance


Physical Properties“Physical properties are characteristics of materials that pertain to the interaction of these materials with various forms of energy and with other forms of matter.”

Examples of Physical Properties: Melting point Magnetic Electrical conductivity Color Luster


Mechanical Properties of Metals?“Mechanical properties are the characteristics of a material that are displayed when a force is applied to the material.”

Tensile strength – “resists pulling apart” Compression strength – “squeezing, smashing” Hardness – “indentation, penetration” Elongation – “drawn out before it fails, breaks” Ductility – “stretched, formed” Brittleness – “fracturing, cracking” Toughness – “prevent cracking, withstand stress” Shear strength - “opposing forces” Torsion strength - “twisting forces’


Procurement/Manufacturing Considerations

“Procurement/manufacturing considerations are not specific properties, but are selection factors.”

Available shapesAvailable sizesAvailable surface texturesManufacturing tolerances.


Methods for Identifying Metals

Use - what the metal was/is designed to do.

Shape – some metals are commonly found as certain shapes.Manufacturing parts - such as forging, casting type markings.Grain structure – appearance of a fractureRelative weight – wide variationBending - cold or hot bend testHardness – perform some form of indentation test or try to cut with a file, hacksaw or chisel.Magnetic?? – may indicate ferrous contentColor/finish – overall appearance, shiny? dull? light? dark?Spark test – use a grinder for ferrous metal.Torch test – see how the metal responds to heat.


What are the basic shapes of metals?Bar stock:

Rods, squares, flats, hexagon, octagon

Structural: Angle, I-beam, channel, t-beams, z-beams

Sheets: Solid, expanded, plated (ex. Diamond)


What are the two majors classifications of metals?

Ferrous - primary element is iron

Non-ferrous - has little or no iron content


What is carbon steel?Carbon is used to increase the hardness of steel

Wrought iron <.003% Carbon basically pure iron, not very common uses.

Low Carbon steel <.30% Carbon relativity soft, malleable, workable, easily weldable. used for common types of nails, bolts

Medium Carbon steel .30 - .55% Carbon Moderate strength characteristics, weldable. Used for structural pieces, angle iron, I- beams, etc. Used for equipment frames.

High Carbon steel .55 - .80% Carbon Hard, does not bend, can be heat treated Used for tools which are hammered, pounded. Used for drills, chisels, hammers, etc

Tool Steel (Very High Carbon).8 –1.70% C Very hard, higher quality tools. Often have alloying metals added. Used for drills, files, saws,

Cast Iron 1.8 – 4 % Carbon Very hard, brittle, low bending strengths used for machinery, engine, transmission housings.


What is alloy steel?

When other metals are “mixed” with steel (iron).

Examples : Stainless Steel, Nickel Steel, etc.

Note: galvanized steel is not an alloy steel, as the zinc is a coating.


What are some common alloy metals with iron?

Chromium- improves corrosion resistant, toughness, hardness

Manganese- increases strength and heat treatment properties.

Molybdenum -increases strength and maintaining strength when heated.

Nickel - increases strength, ductility, toughness. Tungsten - produces smaller, more dense grains, and

retain hardness. Vanadium - provides slow grain growth and toughness

when heated. Stainless steel - iron, nickel and chromium, resistance to

corrosion.


How is steel classified?SAE four digit classification system:

First digit indicates the grouping Second digit is the relative percentage of the primary

alloying element Third and fourth (sometimes fifth) digits are the median

percentage of carbon in hundredths of a percent.


Common SAE Steel Classifications

Carbon Steels 10XXManganese Steels 13XX and 15XXNickel Steel 23XX and 25XXNickel-Chromium Steels 31XX, 33XXMolybdenum Steels 40XX, 41XX, etc.Chromium Steels 51XX, 52XXChromium-Vanadium Steel 61XXMultiple Alloy Steels 8XXX, 9XXX

Ex.: 86XX, Nickel 0.55%, Chromium 0.50%, Molybdenum 0.20%


How is Stainless Steel Classified?Stainless steel is group of metals based upon three primary alloying elements used with steel (Fe and C) and Chromium with many variations of alloying elements such as Manganese and Nickel.

AISI Numbering System uses three digits: 2xx series - Chromium, Manganese, Nickel alloys 3xx series- Chromium-Nickel alloys. 4xx series - Chromium alloys

An UNS numbering system has been recently developed which uses the AISI numbers plus two more digits as a suffix for easier classifications of stainless steels.


Stainless Steel TerminologyFerritic – These steels contain less than 0.10% carbon and are

magnetic. They cannot be hardened via heat treatment limits the use of these metals somewhat, but they are still suitable for a wide range of applications.

Austenitic – This is the most common type of stainless steel, accounting for up to 70% of all stainless steel production. Its versatility is in large part down to the fact that it can be formed and welded with successful results.

Martensitic – This type of steel shares some characteristics with ferritic, but boasts higher levels of carbon, up to a full 1%. This means that they can be tempered and hardened and are thus highly useful in situations where the strength of the steel is more important than its resistance to corrosion.


100, 200, 300 Stainless Steels

200 Series—austenitic chromium-nickel-manganese alloys Type 201—austenitic that is hardenable through cold working Type 202—austenitic general purpose stainless steel

300 Series—austenitic chromium-nickel alloys Type 301—highly ductile, for formed products. Good weldability. Better wear

resistance and fatigue strength than 304. Type 304—the most common grade; the classic 18/8 (18% chromium, 8% nickel)

stainless steel. Type 304L—same as the 304 grade but lower carbon content to increase

weldability. Is slightly weaker than 304. Type 308—used as the filler metal when welding 304. Type 310 — used for high temperature applications. The high chromium and

nickel content give the steel excellent oxidation resistance as well as high strength at high temperature. This grade is ductile, and has good weldability.

Type 316—the second most common grade (after 304); for food and surgical stainless steel uses.


400, 500, 600 Stainless Steels400 Series—ferritic and martensitic chromium alloys

Type 409—cheapest type; used for automobile exhausts. Type 410—martensitic (high-strength iron/chromium). Wear-resistant,

but less corrosion-resistant. Type 416—easy to machine due to additional sulfur Type 420—Cutlery Grade martensitic. Type 430—decorative, e.g., for automotive trim; ferritic. Type 439—ferritic grade, a higher grade version of 409 used for

catalytic converter exhaust sections. Increased chromium for high temperatures

Type 440—a higher grade of cutlery steel, with more carbon, allowing for much better edge retention when properly heat-treated.

500 Series—heat-resisting chromium alloys

600 Series—originally created for proprietary alloys, which are no longer given SAE grade numbers.


What are some common Non-ferrous metals?Copper – electrical and heat conductivity, easily formed and soldered/brazed, resistant to water corrosion.

(electrical wires, water pipes and tubes, food processing equipment)

Aluminum – lightweight, resistant to corrosion, can be made into a variety of shapes, electrical and heat conductivity.

(electrical wires, conduit, tubes, window/door frames, refrigeration equipment, sheet metal applications)

Lead – heavy, toxic, easily formed. (weights, batteries, protective vessels)

Magnesium – very lightweight, flammable, similar to aluminum, but lighter. (lightweight moving parts like wheels, lightweight frames, ladders, energy

conserving applications)

Titanium - high strength, good weight to strength ratio, high temperature properties, alloying with many metals. Used for aircraft, transports.

(used high strength, lightweight applications like aircraft parts)


How is Aluminum classified?A complex system of:

Four digit system used for wrought aluminum Three digit system used for cast aluminum Letter suffixes used to designate the heat treatment

Common types: 1XXX Pure Al, (99.0%) 2XXX Aluminum w/Copper as a major alloy 3XXX Aluminum w/Manganese as a major alloy 4XXX Aluminum w/Silicon as a major alloy 5XXX Aluminum w/Magnesium as a major alloy 6XXX Aluminum w/ Magnesium and Silicon alloys 7XXX Aluminum w/Zinc


Cast Aluminum AlloysThe Aluminum Association(AA) has adopted a nomenclature similar to that of

wrought alloys.

The second two digits reveal the minimum percentage of aluminum, e.g. 150.x correspond to a minimum of 99.50% aluminum.

The digit after the decimal point takes a value of 0 or 1, denoting casting and ingot respectively.• 1xx.x series are minimum 99% aluminum• 2xx.x series copper• 3xx.x series silicon, copper and/or magnesium• 4xx.x series silicon• 5xx.x series magnesium• 7xx.x series zinc• 8xx.x series tin• 9xx.x other elements


Aerospace Aluminum AlloysThe following aluminum alloys are commonly used in aircraft

and other aerospace structures:

• 7068, 7075, 6061, 6063, 2024, 5052, 7050

• Aluminum-Scandium alloys for aerospace industry components. These alloys contain between 0.1% and 0.5% (by weight) of Scandium. Also used for high performance sports equipment: baseball bats, lacrosse sticks, bicycle

frames.

Note that the term aircraft aluminum or aerospace aluminum usually refers to 7075.


Automotive Aluminum Alloys• 6111 and 2008 Aluminum alloys are extensively used for

external automotive body panels

• 5083 and 5754 used for inner body panels.

• Hoods have been manufactured from 2036, 6016, and 6111 alloys.

• Truck and trailer body panels have used 5456 Aluminum.

• Automobile frames often use 5182 Aluminum or 5754 Aluminum formed sheets, 6061 or 6063 extrusions.

• Wheels have been cast from A356.0 Aluminum or formed 5xxx sheet.


What are some common Non-ferrous alloys?

Bronze – alloy of copper and tin (up to 11%), resistant to corrosion, appearance.

Brass - copper and zinc (10%-40%), resistant to acids, two basic types: Machine Brass - (32-40% zinc) Red brass - (15%-25% zinc)

Solders - tin, lead, antimony.


Die Cast MetalsLow melting point metals used to produce identical castings at a rapid rate

Examples: die cast toys, pulleys, “non-critical” automobile, truck, tractor parts.

Also called “pot metals”

Six Major Groups: Tin-based alloys Lead-based alloys Zinc-based alloys Aluminum-based alloys Copper, bronze and brass-based alloys. Magnesium-based alloys.

Documents

Metallurgy: Identifying Metals