Hardness Values

HBW

Brinell hardness number (BHN) using a 10-mm 3,000 kgf carbide ball (HBW 10/3000)

HBS

Brinell hardness number (BHN) using a 10-mm 500 kgf steel ball (HBS 10/500)

HRC

Rockwell C hardness number (using a 150 kgf load)

HRB

Rockwell B hardness number (using a 100 kgf load)

Material Conditions

The material condition is the form, heat treatment, temper, etc. of the material. Some common forms of heat treatment include:

Aging

Keeping an alloy at an elevated temperature for a long period of time to allow precipitation to take place. See also precipitation hardening.

Annealing

Heating to and holding at a specific temperature and then cooling at a specific rate. Generally used to soften material for cold working. improve machinability, or alter/improve physical and sometimes chemical

Normalizing

Austenitizing a ferrous alloy (heating above the transformation range) and subsequently cooling it in open air to relieve internal stress and provide uniform composition and grain size. Results in a harder, stronger steel than annealing.

Precipitation Hardening

Keeping an alloy at an elevated temperature for a long period of time (see aging) to allow the controlled release of constituents (alloying elements) to form precipitate (fine particles separated from the solid solution) clusters which increase the yield strength of the alloy.

Quenching

Rapidly cooling a metal after heating it above the critical temperature. Usually produces a harder metal in ferrous alloy, while most non-ferrous alloys become softer.

Tempering

Heating to a temperature below the transformation range for a specific time and then allowing it to cool in open air. Usually performed after hardening to reduce excess hardness and increase toughness (ability to absorb energy and plastically deform without breaking).

Subgroups – Exotic Metals

Nickel Alloy

Commercially pure grades ( or low alloy nickel) such as Nickel 200 and Nickel 201 have excellent corrosion resistance. Nickel alloys generally contain .38% to 76% nickel. Nickel alloys such as Hastelloy, lnconel, and Wacspaloy are classified as superalloys.

Titanium Alloy

Highest strength-to-weight ratio of all metals with good corrosion resistance as well. High thermal resistance that contributes to poor ma.ch inability.

Cobalt Alloy

Generally contains .35% to 65% cobalt. Although not typically as strong as nickel alloys, they retain their strength at higher temperatures.

Tungsten Alloy

Used for high temperature applications due to its very high melting point. High strength at elevated temperatures, but tends to be brittle at low temperatures. Poor oxidation resistance.

Subgroups – Cast Iron

Gray Cast Iron

Contain flake graphite. Moderate strength, but good machinability and damping capacity. Cannot be worked (forged, extruded, rolled, etc.).

Malleable Cast Iron

Good ductility, strength, and shock resistance (better fracture toughness at low temperatures than nodular irons) . Moderate machinability. Can be shaped through cold working.

Nodular Cast Iron

Contain nodular graphite. Good ductility and shock resistance. Moderate machinability.

Subgroups – Stainless Steel

Austenitic SS

(200 and 300 series) Nonmagnetic with excellent corrosion resistance and ductility. Hardened by cold-working (not heat-treatable).

Martensitic SS

(400 and 500 series) Magnetic with high strength, hardness, fatigue resistance, and ductility, but only moderate corrosion resistance. Very machinable and hardenable by heat treatment.

Ferritic SS

(400 series) Magnetic with good corrision resistance. Hardened by cold-working (not heat-treatable).

PH SS

(Precipitation-hardening) Has good corrosion resistance and ductility. Can be precipitation hardened to higher strengths than the martensitic grades.

Duplex SS

Has a mixed microstructure of austenite and ferrite. Have higher resistance to corrision and stress-corrosion cracking than austenitic grades.

Subgroups – Steel

Low Carbon Steel

(Also called mild steel) Has less than 0. 3% carbon. Used for components that do not require high strength. Improved machinability is found in the 11xx and 12xx series steels.

Medium Carbon Steel

Has 0.3% to o.6% carbon. Used for components requiring higher strength than low-carbon steels. Improved machinability is found in the 11xx and 12xx series steels.

High Carbon Steel

Has more than o.6% carbon. The higher carbon content results in higher strength, hardness, and wear resistance.

Low Alloy Steel

Contain significant amounts of other alloying elements in addition to carbon. Exhibit improved strength, hardness, toughness, wear resistance, corrosion resistance, hardenability, and hot
hardness (compared to carbon steels).

Tool Steel

Specially alloyed steels designed for high strength, impact toughness, and wear resistance. Commonly used for machining and/or forming metals.

Specialty Steel

Generally contain 32% to 67% iron. This group includes low-expansion steel, maraging steel, and some of the iron-based superalloys.

Subgroups – Non-Ferrous Metals

Wrought Aluminum Alloy

Aluminum alloy “worked” into shape by rolling, extrusion, drawing, forging, etc. High thermal and electrical conductivity, good corrosion resistance. Excellent machinability.

Cast Aluminum Alloy

Directly casted into final form (sand-casting, die or pressure die casting). Contains high levels of silicon to improve cast ability, resulting in abrasiveness.

Magnesium Alloy

Lightest of structural metals. Can be precipitation hardened to improve mechanical properties. Excellent machinability.

Copper Alloy

High thermal and electrical conductivity. Good corrosion and wear resistance. Includes brass (copper-zinc alloy) and bronze (copper-tin alloy).

Material Groups

Typically, materials are categorized into color-coded groups as shown below. These groups are made up of different types of similar materials. Each of these material types typically consist of numerous subgroups (listed below, under each material type):

 

MAIN MATERIAL GROUPS NON-FERROUS METALS STEEL STAINLESS STEEL CAST IRON EXOTIC METALS
MATERIALS Aluminum Alloy
Magnesium Alloy
Copper Alloy
 Low Carbon Steel
Medium Carbon Steel
High Carbon Steel
Low Alloy Steel
Tool Steel
Specialty Steel
Austenitic SS
Martensitic SS
Ferritic SS
PH SS
Duplex SS
Gray Cast Iron
Malleable Cast Iron
Nodular Cast Iron
 Nickel Alloy
Titanium Alloy
Cobalt Alloy
Tungsten Alloy