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while there are thousands of different alloys of stainless steel, they can all be divided into three broad categories:
1. austenitic stainless steels. these are the most frequently used types of stainless steels. austenitic stainless steels tend to have a high chromium content compared to other steel alloys, giving them a higher resistance to corrosion. another common characteristic of austenitic stainless steel alloys is that they tend to be non-magnetic—though they may become magnetic after cold working.
2. ferritic stainless steels. the second most common form of stainless steel after austenitic alloys. as the name implies, ferritic stainless steel is magnetic. these alloys can be hardened through cold working. they also tend to be less expensive because of their reduced nickel content.
3. martensitic stainless steels. the least common category of stainless steel alloy. their corrosion resistance tends to be lower than either ferritic or austenitic alloys, but they have a high hardness. martensitic stainless steel alloys are often ideal for applications requiring extraordinarily high tensile strength and impact resistance. when said applications also require corrosion resistance, these alloys may be used with a protective polymer coating.
pipes and tubes are sometimes difficult to classify, and tend to be distinguished based on function. in addition to these classifications, stainless steel is also distinguished by type and grade.
stainless steel tubing for general corrosion-resistance
this general category of steel is appropriate for applications that require corrosion resistance above other traits. ferritic or martensitic types of steel (those made with the most chromium) are manufactured to be either heat-treated or annealed. austenitic stainless steels (those with high chromium and nickel contents) offer even more resistance, and can be used under the same general conditions as ferritic and martensitic types.
stainless steel pressure pipe
this type of stainless steel pipe is made from either solid chromium or a chromium and nickel combination. types of stainless steel pressure pipe include seamless and welded pipe, electric fusion welded pipe for high-pressure applications, large diameter welded pipe for corrosive or high-temperature applications, and seamless and welded ferritic and austenitic stainless steel pipe.
stainless steel sanitary tubing
for applications where stainless steel tubing or piping must come into contact with food and other sensitive products, sanitation is a high priority. stainless steel sanitary tubing is used in such applications because it has high corrosion-resistance, doesn’t tarnish, and is easy to keep clean. for specific applications, different tolerances can be achieved. the grade typically used for these applications is astma270.
stainless steel mechanical tubing
in applications such as cylinders, bearings, and other hollow formed parts, stainless steel mechanical tubing is typically used. tubing can manipulated to have a variety of cross-sectional shapes, such as square and rectangular, in addition to the more traditional, round tubing cross-section. typically, astma 511 and a554 grades are employed for mechanical tubing applications.
stainless steel aircraft tubing
in highly-specific aircraft applications, chromium and nickel type stainless steel is used because of their heat and corrosion-resistance. found in applications that require high-strength, stainless steel aircraft tubing can be work-hardened or welded, although work-hardened pieces shouldn’t be used with some kinds of corrosive substances. low-carbon types of stainless steel are a common choice for welded parts.
for applications that require seamless and welded tubing in larger sizes (1.6 to 125 mm in outside diameter), aircraft structural tubing is used—this type of stainless steel is manufactured according to aerospace material specifications (ams) or military specifications (mil specs).
aircraft hydraulic-line tubing
another type of aircraft tubing, aircraft hydraulic-line tubing is used in aerospace applications as fuel-injection lines and hydraulic systems, and tends to be small. it is often manufactured from types 304 or 304 l stainless steel because of the steel’s high-strength, corrosion-resistance, and ductility.
