Because of its high strength-to-weight ratio, the ease of working with it, and its resistance to both chemical and atmospheric corrosion, Aluminum has become very popular for all types of fasteners.
Yellow Brass
Commercial brass and naval bronze, composition B, can be cold
headed.
Free-cutting Brass
Commercial bronze and naval bronze, composition A, are used for
products milled-from-bar.
AISI 1010
Direct drawn and Phillips quality, is used for machine screws and
bolts of limited strength, where heat treating is not needed.
AISI 1018, 1019, 1022
Direct drawn and Phillips quality, is used for sheet metal screws,
thread cutting screws, and thread forming screws. These materials
are also used for special parts wherever case hardening is needed.
AISI 1038
High strength bolts and cap screws and specials that require thru
hardening.
AISI 4037
In wide use for socket head cap screws as well as socket set
screws.
When copper is alloyed with a hardening element such as tin, we have bronze. When alloyed with zinc, we have brass. The most popular brasses or bronzes are cold heading brass, naval bronze, silicon bronze and leaded brass.
Cold Heading Brass
Is used for screws, rivets, nuts, bolts, etc.
Naval Bronze
Alloys with approx. 62% copper, are used for hot forging. Alloys
with about 65% copper and low lead are good for cold heading.
Silicon Bronze
Can be cold headed. The material has good strength and corrosion
resistance.
Leaded Brass
Cannot be cold headed or forged. It is used for screw machine work
only.
Nickel-Copper Alloys
Are used for all types of fasteners. It may be cold worked, hot
formed, or milled-from-bar.
Nickel
Has good strength at high and sub-zero temperatures. Used for all
types of fasteners.
Inconel
Most types of fasteners can be made of this alloy. Inconel is
excellent for high temperature applications.
Nylon is resistant to heat, shock vibration, and chemicals. It is light in weight, self-extinguishing and is U.L. approved. Because of the ease with which nylon is molded, almost all of the fasteners that are made in metal are made in nylon.
18-8 Chromium-Nickel
While other materials match these alloys in corrosion resistance,
few can take the mechanical wear and abuse that the 18-8 stainless
steels can.
Type 302
Is the basis alloy of the group and the one finding most general
use in the production of fasteners. It has good corrosion
resistance, is non-magnetic when annealed, slightly magnetic when
cold worked. It retains its good mechanical properties to very low
temperatures.
Type 303
Has a combination of reduced galling and easy machining
characteristics thus making it an excellent material for the
production of fasteners that must be machined from bar stock.
Type 304
Is the low-carbon grade with maximum carbon content of 0.08
percent. It is often used where extensive welding must be done in
fabrication of equipment.
16-18
(Shown as "non-magnetic" in fastener stock tables) is a modified
austenitic 18-8, chrome-nickel steel particularly suited for
recessed head screws and other severe cold-heading operations. It
work-hardens at a much slower rate than any of the conventional 18-
8 analyses, and remains non-magnetic after severe cold-working.
Its corrosion resistance is slightly better than Types 302, 303 and
304. This grade has not been assigned an ASA Type Number, and is
generally designated as 16-18 nickel bearing stainless.
Types 308, 309 and 310
Stainless steels contain more chromium and nickel than the 18-8's.
These types are usually used for their excellent heat and scale-
resisting qualities and their strength at elevated temperature
conditions. The addition of alloying elements in greater quantity
does increase corrosion resistance somewhat, but if more corrosion
resistance is the only requirement, one of the molybdenum-bearing
grades (such as Types 316 and 317) should generally be specified.
Types 316 and 317
Are designed to improve the corrosion resistance of the 18-8 types
by the addition of molybdenum. Nickel content is increased to make
the alloys more workable. Improved corrosion resistance allows
these grades to be used in the textile, paper and chemical
industries. Improved resistance to pitting, the highest creep
strength at elevated temperatures of any conventional stainless
grade, and high short-time tensile strength at elevated
temperatures are additional advantages.
Types 321 and 347
Are both resistant to intergranular corrosion. Both types offer
excellent resistance to oxidation at temperatures up to 1700 F.
These steel should be used where temperatures between 800 and 1500
F are encountered in the presence of a corrosive atmosphere.
Their use is also necessary if the equipment, when cold, is exposed
to corrosive atmospheres or solutions after exposure in the 800-
1500 temperature range. In general, the fields of applications of
Types 321 and 347 are where corrosive conditions are encountered;
heavy welded equipment cannot be annealed; or the equipment is
operated between 800-1500 F or slowly cooled thorough this range.
Type 410
Like other alloys in the 400 series, is not recommended for use
where severe corrosion is encountered. It does, however, offer
excellent mechanical properties, wear resistance, and resistance to
scaling at temperatures up to 1200 degrees F. This grade can be
hardened by heat treatment.
Type 416
The most readily machinable of all stainless steels, has similar
physical, mechanical, corrosion and heat-resisting properties to
Type 410. This grade can also be hardened by heat treatment.
Type 430
Is the basis 17 percent chromium stainless steel. It has better
corrosion resistance than Type 410, but is not recommended for low-
temperature work because of a tendency toward brittleness. Type
430 is satisfactory in many applications where resistance to
oxidation scaling at high temperatures is important. This grade
cannot be hardened by heat treatment.
Type 431
Is a hardenable nickel bearing chromium steel with good corrosion
resistance. It is magnetic at all times. It has a higher strength
and toughness (developed by heat treatment) than the 16% straight
chromium steels, partly due to the nickel content (2%).