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The 26 stainless steel forms
regularly
available in the USA
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Go to
the 26
Stainless Steel
Forms
General Stainless
Steel Information
What
is an alloy?
An alloy is simply a
mixture of
metals melted together to form a new metal with characteristics
distinct from those metals from which it is made.
What
is a Stainless Steel Alloy?
A Stainless Steel alloy
is an
alloy primarily of iron, with a relatively substantial content of
chromium and nickel added during the alloying process. Metallurgists
have produced a whole range of different stainless steel alloys,
the most notable for architects being the variation of the chemistry of
stainless
steel alloy #316 to produce a higher corrosion-resistant alloy which is
used in many
marine environments.
Chromium
and nickel impart
the
“stainless” aspect to an otherwise rustable steel (and are also
responsible for the price of stainless steels being 10 times that of
hot rolled and cold finished steels).
What
Stainless Steel alloys are commonly available?
There are 24 or so
commonly
available stainless steel alloys you can get, though most of them are
available only in plate form, and not really very relevant to
architectural metalwork.
The
three that are
regularly encountered are:
1) Alloy 303
- a free machining
grade that cuts, drills and machines very well, but doesn't weld as
nicely as 304. It is available in most shapes except sheet.
2) Alloy 304
- a nicely welding
alloy that does not machine quite as nicely as 303, available more
commonly in sheet and plate but is available in some bar forms as well.
3) Alloy 316
- a high corrosion
resistant alloy that is used in environments of extreme weathering such
as chemical environments or marine environments. This alloy also
has been found by architects to polish to a brighter high polish than
the other alloys. This alloy is
not as common as the other two, but it is available in most of the same
shapes as the other two but in fewer sizes.
Do
the different alloys have a different color or aspect?
No. Aside from the
quality of alloy
316 appearing to polish up brighter than the other alloys, they
are
aesthetically interchangeable.
Is
it necessary to specify the alloy?
Only if there is some
physical
characteristic of the alloy that will have some bearing on the success
of the project (such as corrosion resistance) is it necessary to
specify the actual alloy. Generally, the fabricator will purchase the
material on the basis of shape or form, and it will arrive with the
most commonly available and least expensive alloy present locally.
These alloys will for the most part be restricted to alloy 303 or alloy
304, and will be interchangeable, weld, machine, and finish
interchangeably, and can be treated aesthetically as though they are
the same alloy. It must be mentioned that alloy 316, which is a
high-corrosion resistant alloy, is sometimes specified in architectural
metal projects that are in more extreme environments, such as seaside
houses, or chemical plants. This alloy is regularly produced in a
somewhat restricted subset of shapes and sizes, so if you are designing
in this alloy, contact a local supplier of stainless steels to get an
idea of what would be available to your local fabricator before you
steam ahead with specifying alot of material.
If
there is any
question of the integrity of the material in any way, the designs must
be approved by an engineer, but you will be able to accept
substitutions of alloys with confidence that the resulting product will
be aesthetically acceptable.
Is
this really the full set of shapes available in stainless steel?
Well...There
are thousands of proprietary stainless steel products made on a regular
basis, from
thousands of individual companies around the country - but this group
of basic stock stainless
steel products is where they all went to get the fundamental materials
they made
their own products from.
Stainless Steel is regularly produced in only a restricted
set of shapes and dimensions due to the nature of the material and the
shapes and sizes in which
people need it and will buy it (it's
tough to work with, and expensive).
What we are publishing on this website are the alloys,
shapes, and size ranges that are the regularly
produced stock metal products in each of the metal groups. There
are some stainless steel suppliers that stock different specialty
stainless products for a particular company or sector of the industry,
and you may run across them occasionally (for example, stainless steel
"zee"s, or a different size of I beam, etc). While you should keep
track of these suppliers, these products are not included here because
they are not generally available coast to coast.
"Stock metal products" are
the bottom rung of the US metals industry
- the angles, beams, channels, sheets, plates, tubing, coil, round,
square, hex, and flat bars regularly produced in the USA from which
most architectural and ornamental metalwork is made.
The
shapes and sizes of the metals represented in this website
represent the products at the bottom rung of the stock metal products
carried on a regular basis in warehouses around the country, produced
and sold for general use, without any specific request from any
particular sector of the fabrication market.
Once you
familiarize yourself with these materials and the nomenclature by which
they are known, it will be far easier to wander into the vast array of
specialty materials and proprietary products that are produced in metals
Stainless steel, hot rolled steel, cold finished steel, and aluminum
are all fairly common, and most shapes are carried by most suppliers.
Where you'll see a difference in suppliers stocks is in the numbers of
different sizes of each shape that is stocked.
Some things to be aware of:
1) It Is Poor
Quality Material
In general, stainless steel products are of fairly
poor finish, inaccurate dimensions, soft, and difficult to work.
Overall, it is a fairly low quality product. Some exceptions to this
are the cold finished stainless steel shapes, such as round, square,
and hex bar, and
of course, stainless steel sheet is a consistently good quality
product. Stainless steel sheet is even available in a
pre-finished satin polished condition, with protective
vinyl on the surface.
2) High Polish
Stainless steel sheet and plate are both
occasionally available in stock in the high polished condition, but not
regularly, and so samples of these are not present in the Guide. You
should, however, be aware that these do exist, and it could create a
substantial savings if you were to locate already prefinished material.
3) Magnetic?
Stainless steel is not magnetic, nor does it rust.
Even in the worst natural environments it will simply get dingy and
grey, easily brightened by abrading the surface. However, in marine
environments it is recommended that alloy 316 is specified as it has
superior corrosion resistance, and is available in most shapes, albeit
in a somewhat restricted set of dimensions.
4) Corrosion,
and your fabricator's dirty abrasives
Occasionally a fabricated stainless steel piece will
begin to have specks or streaks of rust that appear on the surface
after a short time of weathering. Unless there are extraordinarily
corrosive conditions present near the piece, this type of discoloration
is most likely due to contamination of the surface of the stainless
steel with particles of another metal such as steel, or any of the
copper alloys.
This often happens if the fabricator sands or
polishes the stainless steel piece using an abrasive belt, paper, or
cloth that was previously used on another metal, and the particle
residue in the used abrasive cloth or sandpaper gets embedded in the
stainless steel as it is sanded.
It is imperative that only abrasives that are fresh,
or have previously been used on stainless steel be used on new
stainless steel work.
5) Temper
This is the quality of metal that describes its
ability to spring back after it is flexed - in effect, the stiffness. It doesn't have anything
to do with how hard the metal is. Soft temper means that when it is
bent, it stays bent, and it doesn't take much force to bend it. Hard
temper means that when it is bent, it springs back flat, and it takes a
lot of force to put a kink into it. There are several degrees of
temper; Soft, 1/4 Hard, 1/2 Hard, 3/4 Hard, and Hard. All metals are
subject to temper, and it is a quality of the product that is imparted
at the mill. It has no impact on hardness, color, machinability or
weldability. However, bending (kinking) and heating to a high
temperature can remove the temper and soften the metal at that point.
This is called annealing.
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