About Stainless Steel

Stainless steel is an alloy of iron that has had at least 10% chromium added to improve corrosion resistance. The designation 18-8 refers to stainless steel that has approximately 18% chromium and 8% nickel—it generally applies to types 301, 302, 303, and 304.

Most types of stainless steel harden while being worked and cannot be hardened by heat treating. They usually are provided in an annealed (not hardened) condition although some of these alloys, such as Type 301, may be work-hardened to a greater hardness ( 1/2 hard, full hard, or spring temper) for applications such as springs.
Other types of stainless steel, such as Type 410 and Type 440C, can be heat treated to improve strength and toughness.

Usually these are provided in an annealed (not hardened) condition to make them easier to work. They also may be heat treated after the final product is formed to achieve better strength and toughness.
For applications requiring limited machining and cutting prior to use, some alloys are provided already heat treated.

 
Finish

Unpolished (Mill) Finish— No finish is applied. Alloy is sold as fabricated by the mill.
Unpolished (#2B Mill) Finish— Semi reflective finish as fabricated by the mill.
Brushed (#3 Satin) Finish— Polished to a brushed finish on one side so grain lines will be in one direction.
Brushed (#4 Satin) Finish— Polished to a fine brushed finish on one side so grain lines will be in one direction.
Mirror-Like (#8) Finish— Polished to a mirror-like finish on one side. It's free of grain lines.

 
Hardness
The hardness of a material is its resistance to another material penetrating its surface. Harder metals have more wear resistance, but they are also more brittle. Note: The types listed below are annealed (unless noted).

 
Yield Strength
Yield strength is the point at which metal bends and will not return to its original shape. At this point the metal has changed shape permanently but does not break. All are rated in annealed condition (not hardened).

 
Forming and Working
Stainless steel offers excellent forming and working (also known as bendability) due to its mechanical properties.
Note: 420V, Nitronic 60, 15-5 PH, 17-4 PH, and A286 are not rated.
  Excellent Good Fair Difficult
Blanking 410, 430 301, 302, 303, 304, 309, 316, 321, 416, 420 --- 440C
Brake Forming 302, 304, 309, 316, 321, 410, 430 301 416, 420 303, 440C
Punching 410, 416, 430 302, 303, 304, 309, 316, 321 301, 420 440C
Sawing --- 303, 410, 416, 430 301, 302, 304, 309 316, 321, 420, 440C ---

 
Machinability
Stainless steel is more difficult to cut, drill, ream, tap, thread, etc. than steel because of its higher strength and hardness. It tends to become gummy when machined, however, high-speed steel tooling generally can be used. The ratings given are in relation to speed, life of the tooling, and the ease of attaining a satisfactory post-machining finish.
Excellent Good Fair Poor
303, 416 304, 316, 410, 430 301, 302, 309, 321, 420 420V, 440C, 15-5 PH, 17-4 PH, Nitronic 60, A286

 
Weldability
Stainless steel is more difficult to weld than steel due to the additional cleaning and machining required to create a weldable surface that won't corrode.
Note: 309, 420, 420V, 430, 15-5 PH, Nitronic 60, and A286 are not rated.
Good Fair Difficult
301, 302, 304, 316, 321, 17-4 PH 410 303, 416, 440C

 
Corrosion Resistance
Excellent— Resists outdoor, industrial, marine, and most chemical environments.
Good— Resists outdoor, industrial, marine, and mild chemical environments.
Fair— Resists outdoor, industrial, and mild chemical environments.
Poor— Resists outdoor environments.
Excellent Good Fair Poor Not Rated
316, A286, Nitronic 60 301, 302, 304, 309, 321 303, 430 410, 416, 420, 440C 420V, 15-5 PH, 17-4 PH
Material descriptions
High-Strength Wear-Resistant Stainless Steel (Type 15-5 PH)
Commonly used in gears, cams, and aircraft parts. Combines high strength and wear resistance. Can be heat treated at low temperatures to increase mechanical properties. Magnetic. Temperature range not rated.
Corrosion-Resistant High-Strength Wear-Resistant Stainless Steel (Type 17-4 PH)
Maintains high strength and wear resistance. Slightly higher chromium content for improved corrosion resistance over Type 15-5 PH. Can be strengthened by precipitation hardening at low temperatures. Magnetic. Temperature range not rated.
Corrosion-Resistant High-Strength Wear-Resistant Stainless Steel (Type 17-7 PH)
High strength. Good response to heat-treating. Moderate corrosion resistance.
Ultra Corrosion-Resistant Stainless Steel (Nitronic 60)
Nitrogen provides better corrosion resistance than Type 304 plus more strength in temperature extremes. Commonly used in chemical industry. Nonmagnetic. Cannot be heat treated. Temperature range not rated.
Ultra Corrosion-Resistant Stainless Steel (A286)
Nitrogen provides better corrosion resistance and more strength in temperature extremes than Type 316. Used in chemical industry. Nonmagnetic. Temperature range not rated.
Wear-Resistant High-Strength Stainless Steel (Type 301)
Most strain-hardenable chromium-nickel stainless steel. Better wear resistance, fatigue strength than Type 304. Retains strength while stretching like 1095 steel. Good weldability, temperature resistance. May be slightly magnetic. Cannot be heat treated. Maximum corrosion resistance temperature 1550° F; minimum not rated.
High-Strength Stainless Steel (Type 302)
Higher carbon content for slightly higher strength than Type 304 with same corrosion resistance. Cannot be heat treated. Maximum corrosion resistance temperature 1600° F; minimum not rated.
Multipurpose Stainless Steel (Type 302/304)
Corrosion resistant. Meets Type 302 and Type 304 standards. Wire meets ASTM A580; spring wire meets ASTM A313 (choose extra-bright when a fine surface finish is important).
Easy-to-Machine Stainless Steel (Type 303)
Sulfur and phosphorus increase machinability. Low-carbon chromium-nickel (austenitic). Good corrosion, temperature resistance. Only strain harden (cold form - may become slightly magnetic). Can't be heat treated. Maximum corrosion resistance temperature 1600° F; minimum not rated.
Multipurpose Stainless Steel (Type 304)
Most widely used stainless steel. Good weldability, formability, and temperature resistance. Only strain harden (cold form - may become slightly magnetic). Cannot be heat treated. Corrosion resistance temperature range -320° to 1600° F.
Multipurpose Stainless Steel (Type 304/304L)
This dual certified 304/3004L stainless steel is a reduced carbon version of Type 304 stainless steel.
High Temperature Stainless Steel (Type 309)
Similar composition to Type 304. Low carbon chromium-nickel (austenitic). Excellent temperature resistance. Good corrosion resistance. Only strain harden (cold form - may become slightly magnetic). Can't be heat treated. Maximum corrosion-resistance temperature 1795° F; minimum not rated.
Super Corrosion-Resistant Stainless Steel (Type 316)
Higher molybdenum content provides better corrosion resistance. Low carbon chromium-nickel (austenitic). Good weldability and temperature resistance. Only strain harden (cold form - may become slightly magnetic). Cannot be heat treated. Maximum corrosion resistance temperature 1600° F; minimum not rated.
Super Corrosion-Resistant Stainless Steel (Type 316/316L)
This dual certified 316/316L stainless steel is a reduced carbon version of Type 316 stainless steel.
Easy-to-Weld Stainless Steel (Type 321)
Low carbon chromium-nickel (austenitic). Titanium provides superior weldability. Only strain harden (cold form - may become slightly magnetic). Cannot be heat treated. Maximum corrosion resistance temperature 1600° F; minimum not rated.
Wear-Resistant Stainless Steel (Type 410)
Chromium alloy (martensitic). Can be heat treated for extra hardness and improved wear resistance. Not recommended for highly corrosive environments. Not recommended for welding. Maximum corrosion resistance temperature 1300° F; minimum not rated.
Easy-to-Machine Wear-Resistant Stainless Steel (Type 416)
Sulfur provides better machinability than Type 410. Chromium alloy (martensitic). Can be heat treated. Magnetic. Maximum corrosion resistance temperature 1250° F; minimum not rated.
Mold-Quality Wear-Resistant Stainless Steel (Type 420)
Excellent polishability. High hardness. Ideal for manufacturing plastic molds. Composition and properties fall between Type 410 and Type 440C. Can be heat treated. Magnetic. Maximum corrosion resistance temperature 1150° F; minimum not rated.
Hardened Tool-Grade Shim Stock Stainless Steel Sheets (Modified Type 420)
Shim stock material. High wear resistance. Rockwell hardness is C49-C53.
Ultra Wear-Resistant Corrosion-Resistant Stainless Steel (Type 420V)
Base of Type 420C with added vanadium and carbon for improved wear resistance. Powder metal process improves corrosion resistance. Can be used in place of tool steels, such as D2, when extra corrosion resistance is important. Temperature range not rated.
General Purpose Stainless Steel (Type 430)
Chromium-based (ferritic) alloy. Good formability. Magnetic. Cannot be heat treated (strain-hardening has little effect). Room temperature alloy. Not recommended for temperature extremes or outdoor use. Chosen more for aesthetic purposes.
Hardened Tool-Grade Shim Stock Stainless Steel Sheets (Modified Type 440A)
Also known as razor blade stainless steel. Rockwell hardness C49-C53.
Ultra-Hard Wear-Resistant Stainless Steel (Type 440C)
When heat treated, one of the hardest stainless steels. High carbon content provides good wear resistance. Magnetic. Ideal for bearings, valve parts, and knife blades. Temperature range not rated.