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Material Grades
CARBON STEEL
ASTM
A307
is a special low carbon bolt material used in piping
and flange work. It has properties
similar to other low carbon steel bolts except that it has the added requirement
of a specified maximum tensile strength. The
reason for this is to ensure that the bolt will fracture, before breaking a cast
iron flange on a pump or valve, if the bolt is inadvertently over-tightened. Grade B7, ASTM A193 A heat-treated chromium-molybdenum steel widely used for medium high temperature service. (Liquid quench -50° to 900°F, Air quench -40° to 900°F.) Grade
B7M, ASTM A193 Similar to B7 studs except that the minimum yield
and tensile strength requirements are reduced and the hardness controlled to 235 Brinnell maximum. Designed for use in corrosive environments (-50°
to 900°F). Grade B16, ASTM A193 A heat-treaded chromium-molybdenum, vanadium steel for high pressure, high temperature service. (-50° to 1100°F.)Grade L7, ASTM A320 Intended for low temperature service down to minus 150° and has a minimum Charpy impact value of 20 ft lb at this temperature (-150° to 1100°F). Grade
L7M, ASTM A320
Similar to L7 studs except that the minimum
yield and tensile strength requirements are reduced and the hardness controlled
to 235 Brinnell maximum. This stud
is designed for use in low temperature corrosive environments (-150°
to 1100°
F). Grade
B8, ASTM A193
These Chromium-Nickel (AISI 304) austenitic steel
studs are used in corrosive environments (-325°
to 1500°F). Grade
B8M, ASTM A193
These Chromium-Nickel Molybdenum (AISI 316)
austenitic steel studs are used in corrosive environments (-325°
to 1500°F). CARBON AND ALLOY STEEL NUTS Grade 2H, ASTM A194, Latest Revision Suitable for use in high temperatures and high-pressure conditions. Grade 2HM , ASTM A194 Similar to 2H nuts except this grade is designed for use in corrosive environments. Grade
4, ASTM A194, Latest Revision
Heat-treated molybdenum steel
nuts suitable for severe temperature and pressure conditions. Grade
L7, ASTM A194, Latest Revision
New stamping as per ASTM is 7L.
Heat-treated chrome-molybdenum steel nuts suitable for extreme
temperature and pressure conditions. Suitable
for sub-zero service conditions and have minimum Charpy impact values of ASTM
spec. A320. Grade 7 down to -150°F. Grade L7M, ASTM A194, Latest Revision New stamping as per ASTM is 7ML. Similar to grade L7 nuts except this grade is designed for use in corrosive environments. Grade 8/8M, ASTM A194 Stainless steel nuts designed for use in corrosive environments. STEELS
& EXOTIC METALS Stainless steels achieve “stainless” characteristics by virtue of their ability to form a tight adherent film of iron-chromium oxide which strongly resists attack by the atmosphere and a wide variety of industrial gases and chemicals. This effect, plus the superior high temperature strength characteristics exhibited by many of these alloys, accounts for their wide use at ordinary and elevated temperatures with a wide choice of mechanical properties and several distinct levels of corrosion resistance.
These materials are subdivided
into the following groups: 1.
Martensitic
stainless
steels are iron-chromium alloys which are harden able by heat treatment.
Representative of this group are Types 410, 420, 431 and 440C. 2.
Ferritic
stainless steels are iron-chromium alloys which cannot be hardened
significantly by heat treatment. Representative
of this group are Types 405 and 430. 3.
Austenitic
stainless
steels are iron-chromium-nickel and iron-chromium-manganese-nickel alloys, which
are harden able by cold working. Representative
of this group are Types 201, 304, and 316. 4.
Precipitation
hardening
stainless steels are iron-chromium-nickel alloys with additional elements
which are harden able by solution treating and aging. Martensitic and Ferritic steels are magnetic in all conditions; Austenitic steels are slightly magnetic in the cold worked condition, but non-magnetic in the annealed condition in which they are most often used.
18-8 Stainless Steel
This is the most popular type of stainless used
in the production of fasteners. Its
composition is approximately 18%
Chromium and 8%
Nickel, thus the name 18‑8. Several grades of stainless are included in this
classification including 302, 303, 304 and 305.
These all have good strength and corrosion resistance. 316
Stainless Steel
This is more corrosion resistant than 18-8, but
also more expensive. It is composed
of approximately 18%
Chromium and 12%
Nickel with the addition of 2%
to 4%
Molybdenum. It also maintains its
strength at higher temperatures than 18-8. 410 Stainless Steel It has approximately 12% Chromium with no Nickel. It is not very corrosion resistant and is magnetic, but it can be heat treated to become harder. Alloy
20
This alloy has approximately 20%
Chromium and 34%
Nickel plus 3% to 4% Molybdenum. It
is very corrosion resistant and is especially popular when in contact with
sulfuric acid.
Brass
This metal is approximately 65% Copper and 35% Zinc.
It offers a good combination of strength, corrosion resistance and
workability. Nickel
Copper 400
This alloy is approximately 70% Nickel and 30%
Copper. It has excellent strength
and corrosion resistance and is used in salt water marine and other chemical
environments. Titanium
This has a very high strength to weight ratio, as well as good
corrosion resistance. Inconel
Registered Trademark of Inco Ltd.
Composed of approximately 77% Nickel and 15% Chromium.
It offers superior strength and good corrosion at high temperatures. Silicon Bronze It is composed of approximately 96% Copper, 3% Silicon, and 1% Manganese. It is more corrosion resistant and tougher than brass. It is widely used in the electrical industry.
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