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STAINLESS STEEL - Wikipedia - History and great details on a wide range of SS alloys.

STAINLESS-ONLINE - General information about consumer SS in everyday life.

NON MAGNETIC vs. MAGNETIC STAINLESS STEEL

CORROSIONIST - Very detailed data on Stainless Steel and Corrosion.

STAINLESS STEEL INFORMATION CENTER

CARPENTER TECHNOLOGY - One of the largest producers of RAW Stainless Steel.

MAGNETIC COMPONENT ENGINEERING - Magnetic characteristics of SS.

NACE INTERNATIONAL - Stainless Steel & Corrosion.

MCNALLY INSTITUTE - Useful info on corrosion & Chloride.

eSTAINLESSSTEEL - General information about Stainless Steel.

 

Classifications and types of stainless steel

Stainless steel is a low carbon steel which contains chromium at 10% or more by weight. It is this addition of chromium that gives the steel its corrosion resistant properties. The chromium content of the steel allows the formation of an invisible chromium-oxide film on its surface. If oxygen is present, even in small quantities, this film self-repairs if damaged mechanically or chemically. Corrosion resistance of stainless steel is enhanced by increased chromium content and the addition of other elements such as molybdenum, nickel, and nitrogen. 

The three main classifications of stainless steel are identified by the alloying elements which form their microstructure. Austenitic steels have austenite (face centered cubic crystal) as their primary phase. These are alloys containing chromium and a major proportion of nickel. Austenitic steels are not thermally hardenable but have excellent corrosion resistance. Ferritic steels have ferrite (body centered cubic crystals) as their main phase. These steels have a low carbon content and contain chromium as the main alloying element , usually between 13% and 17%. Ferritic steel is less ductile than austenitic steel and is not thermally hardenable. Martensitic steels are low carbon steels typically containing 12% chromium, a moderate level of carbon, and very low levels of nickel. Martensitic steels are distinguished from other stainless steels in their ability to achieve high hardness by a heat treatment that produces martensite (a supersaturated solid solution of iron characterized by a needle-like microstructure)   

Type 304:

Type 304 is an austenitic steel with a minimum of 18% chromium and 8% nickel, combined with a maximum of .08% carbon. It is non-magnetic and cannot be hardened by heat treatment, and must be cold-worked to obtain higher tensile strengths. Corrosion and oxidation resistance is provided by the minimum 18% chromium content. The alloy's metallurgical characteristics are established primarily by the nickel content which also extends resistance to corrosion caused by chemicals.

This stainless alloy resists most oxidizing acids and can withstand ordinary rusting. It is immune to most organic chemicals, dyes, foodstuffs, and a wide variety of inorganic chemicals. Because of its ability to withstand the corrosive action of various acids found in fruits, meats, and vegetables, 304 is widely used for sinks, tabletops, refrigerators, cooking appliances, pots, pans, and flatware.

    Type analysis of 304 stainless steel

Carbon   0.08% max. Manganese   2.00% max Phosphorus   0.045% max
Sulfur   0.030% max Silicon    1.00% max Chromium   18.00/20.00%
Nickel   8.00/10.50%    

Type 316:

Similar to 304, 316 is an austenitic, non-magnetic, and thermally non-hardenable steel alloy. Carbon is held at .08% maximum, while the nickel content is increased slightly. What distinguishes 316 from 304 is the addition of molybdenum up to a maximum of 3%. 

Molybdenum is one of the most useful additives in the fight against corrosion. It increases the resistance of the alloy against many industrial chemicals and solvents and inhibits pitting caused by chlorides. 316 can withstand corrosive attack by sodium and calcium brines, hypochlorite solutions and phosphoric acid. This alloy is used for industrial equipment that handles the corrosive process chemicals used to produce inks, rayons, photographic chemicals, paper, textile, bleaches, and rubber.

 Type analysis of 316 stainless steel

Carbon   0.08% max. Manganese   2.00% max Phosphorus   0.045% max
Sulfur   0.030% max Silicon    1.00% max Chromium   16.00/18.00%
Nickel   10.00/14.00% Molybdenum   2.00/3.00%  

 

Type 405 is a ferritic, thermally non-hardenable, magnetic chromium steel. By controlling the carbon content  (0.08% max.) and adding aluminum (0.30% max.), processing is simplified because heat treatment is eliminated. 405 resists corrosion from soap, sugar solutions, mine water, steam, carbonic acid, ammonia, alcohol, and other mild reagents

Type analysis of 405 stainless steel

Carbon   0.08% max. Manganese   1.00% max Phosphorus   0.040% max
Sulfur   0.030% max Silicon    1.00% max Chromium   11.50/14.50%
Aluminum   0.10%/0.30%    

 

Type 410 is a martensitic alloy similar to to 405 but with a higher carbon content and no aluminum. It is this increase in carbon and absence of aluminum that improve the mechanical properties and strength of 410 by making it a hardenable steel similar to regular carbon and alloy steels.

Type analysis of 410 stainless steel

Carbon   0.15% max. Manganese   1.00% max Phosphorus   0.040% max
Sulfur   0.030% max Silicon    1.00% max Chromium   11.50/13.50%

 

Type 420 stainless steel is a martensitic alloy that is strengthened by the addition of carbon at a 0.15% minimum (0.30% nominal) compared to the 0.15% maximum for type 410. Along with carbon, chromium content is also slightly  increased to offset the tendency of the higher carbon content to lower the alloy's resistance to corrosion. In the hardened and tempered condition, the alloy's yield strengths are substantially greater than type 410. Type 420 is used for such applications as surgical and dental instruments, cutlery, scissors, valves, and ball bearings.

Type analysis of 420 stainless steel

Carbon   0.15% min. Manganese   1.00% max Phosphorus   0.040% max
Sulfur   0.030% max Silicon    1.00% max Chromium   12.00/14.00%

 

Type 440-C is a thermally hardenable, martensitic stainless steel alloy combining corrosion-resistant properties with maximum hardness. Both carbon (0.95% - 1.2%) and chromium (16-18%) contents are increased substantially to impart hardness. While it is the strongest of all stainless steel alloy, its high carbon content reduces its corrosion resistance.

Type analysis of 440-C stainless steel

Carbon   0.95/1.20% Manganese   1.00% max Phosphorus   0.040% max
Sulfur   0.030% max Silicon    1.00% max Chromium   16.00/18.00%
  Molybdenum   0.75% max  

17-4PH is a martensitic precipitation hardening alloy which offers high strength and hardness while maintaining excellent corrosion resistant properties. In this it surpasses the 400 series, more closely resembling the corrosion resistant properties of type 304.

Type analysis of 17-4PH stainless steel

Carbon   0.07% max. Manganese   1.00% max Phosphorus   0.040% max
Sulfur   0.030% max Silicon    1.00% max Chromium   15.00/17.50%
Nickel   3.00/5.00% Copper   3.00/5.00% Columbium & Tantalum 0.15/0.45%

Custom 455 is a proprietary alloy from Carpenter Technology. Like 17-4PH, is a martensitic precipitation hardening stainless steel. A single-step aging treatment develops exceptionally high yield strengths with good ductility and toughness. Its low work hardening rate allows extensive cold-forming and permits close-tolerance machining. This alloy combines high strength, corrosion resistance, and ease of fabrication

Type analysis of 455 stainless steel

Carbon   0.050% max. Manganese   0.50% max Phosphorus   0.040% max
Sulfur   0.030% max Silicon    0.50% max Chromium   11.00/12.50%
Nickel   7.50/9.50% Copper   1.500/2.50% Columbium & Tantalum 0.10/0.50%
Titanium 0.80/1.40% Molybdenum   0.50% max

Custom 465, also a proprietary Carpenter Technology alloy, is a martensitic, age-hardenable alloy capable of about 200 ksi ultimate tensile strength in the H900 condition. With corrosion resistant properties approaching that of type 304, this alloy is designed to yield an exceptional combination of strength and corrosion resistance. Read the Carpenter press release for Steritool products made from Custom 465.

Type analysis of 465 stainless steel

Carbon   0.020% max. Manganese   0.25% max Phosphorus   0.015% max
Sulfur   0.010% max Silicon    0.25% max Chromium   11.00/12.50%
Nickel   10.8/11.20% Copper   1.500/2.50% Titanium 1.5/1.8%
Molybdenum  0.75/1.2% max

You can view more specific data on any of these stainless steel alloys on Carpenter Technology's website: www.cartech.com

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