History of Stainless Steel
Harry Brearley is given credit by most for the invention of stainless steel. French scientist Leon Guillet documented the constitution of stainless steel in 1904. While Guillet noted the composition and properties of his alloy mix, he never recognized the corrosive resistance of the material. In 1911 Philip Monnartz of Germany published the first detailed work on the corrosion resistance of stainless steel. In 1912, two German's at the Krupp Iron Works, Eduard Maurer and Benno Strauss, patented the first austenitic stainless steel of 21% chromium and 7% nickel combination. Brearley patented the first marensitic stainless steel in 1913. While Brearley is generally given credit for the discovery of stainless steel, many historians feel this is disputable.
Harry Brearley was born February 18, 1971. In 1907 Brearley was in charge of the Brown-Firth Research Laboratory in Sheffield, England. The lab was investigating ways to eliminate rust in gun barrels, when by accident; Mr. Brearley noticed a discarded sample from an earlier test was not rusting, while others were. His analysis of the rifle barrels involved having to dissolve them in acid, which is when he noticed that steel with high chromium content did not dissolve in the acid. The result was a chrome alloy steel, much more rust resistant than seen before. Two months later on August 20, 1912, stainless steel was cast for the first time.
Brearley set out to market his new invention. He called his new metal "rustless steel". Sheffield, known as a city of cutlery manufacturers and the new material seemed to be a perfect replacement for silver or nickel plated steel. Manufacturers were hesitant on change so Brearley had to make some knives. Refinements were necessary as early versions of stainless steel knives were difficult to produce and polish, and they would not cut as well as existing knifes. Ernest Stuart, upon testing the material in vinegar suggested marketing the name of "stainless steel". By 1914 the George Ibberson & Co, using stainless manufactured by Thomas Firth & Sons, began producing stainless steel knives.
Brearley left Firth, over an ownership dispute of the stainless steel invention, and W.H. Hatfield became his successor. In 1924, Hatfield patented the 18-8 stainless steel, 18% chromium and 8% nickel. This austenitic stainless steel would soon rise to become the most popular and widely used type of stainless. Adding titanium to the 18-8, Hatfield is also credited with the invention of 321 stainless. In earlier years, German scientists, from Krupp Research Institute were the quickest to realize the potential of austenitic stainless, inventing 316, among others.
Stainless Steel Families.
There are five stainless steel families: ferritic, martensitic, austenitic, duplex and precipitation hardening.
Ferritic stainless steels are plain chromium stainless steels with a chromium content varying between 12% and 18% and low carbon content. They are magnetic and can not be hardened by heat treatment.
Martensitic stainless steels were the first stainless steels that were commercially developed, as cutlery, and have high carbon content (0.1% - 1.2%). They are plain chromium steels containing between 12% and 18% chromium. Alloy 410 is the basic, general purpose and magnetic grade that can be hardened by quenching and tempering. These stainless steels can be heat treated to obtain high strength with good ductility.
Austenitic stainless steels are non-magnetic. Nickel is added to this stainless steel in sufficient amounts, changing the crystal structure to "austenite". The basic composition of 300 series austenitic stainless steels is 18% chromium and 8% nickel. This enhances their corrosion resistance and modifies the structure from ferritic to austenitic. Austenitic grades are most common and account for 70% of all stainless steel production. Alloy 304 and 304L followed by alloy 316L are the most common grades. They can not be hardened by heat treating.
Duplex are stainless steels containing relatively high chromium levels (18%-28%) and moderate amounts of nickel (4.5%-8%). The high corrosion resistance and excellent mechanical properties of this stainless steel can be explained by their chemical composition and balanced microstructure of equivalent volume fractions of ferrite and austenite. Alloys 2304 and 2205 are most common.
Precipitation hardening stainless steels can be hardened by heat treating like Martensitic types. The mechanism is metallurgical different fro the process in the Martensitic types. This means either Martensitic or austenitic precipitation hardening structures can be produced. These stainless steels combine high strength and hardness with corrosion resistance superior to that of the martensitic chromium stainless steels.
300 Stainless Steel Series
- 301 Stainless Steel is austenitic chromium-nickel alloys, highly ductile for formed products, hardens rapidly, good weld ability, and better wear resistance and fatigue strength than 304.
- 302 Stainless Steel is austenitic chromium-nickel alloys and the same corrosion resistance as 304, with higher strength due to the addition of carbon.
- 304 Stainless Steel is austenitic chromium-nickel alloys, the most common grade; the classic 18/8 stainless steel.
- 304L Stainless Steel is austenitic chromium-nickel alloys, the same as 304 grade but less carbon to increase weld ability and slightly weaker than 304.
- 304LN Stainless Steel is austenitic chromium-nickel alloys, same as 304L, but also nitrogen is added to obtain a much higher yield and tensile strength than 304L.
- 309 Stainless Steel is austenitic chromium-nickel alloys, excellent corrosion resistance plus good strength at room and elevated temperatures.
- 316 Stainless Steel is austenitic chromium-nickel alloys, the second most common grade (after 304); the addition of molybdenum prevents specific forms of corrosion.
All Foils, Inc. currently supplies a variety of stainless steel alloys from Type 302 to 347, with other alloys available upon request. Our stainless steel is available in gauges from 0.001" to 0.020" and in tempers from annealed through full hard and as-rolled.
All Foils, Inc. also stocks annealed stainless steel tool wrap for heat treating. Our tool wrap finished goods consist of alloys 304, 309 and 321. Tool Wrap is stainless steel 0.002 inches thick foil. It is used for the surface protection of tools, dies and other parts during the hardening process by preventing decarburization (scaling).
- Type 304 - Can be used in temperatures up to 1800° F
- Type 309 - Can be used in temperatures up to 2240° F
- Type 321 - Can be used in temperatures up to 2000° F
- They are all annealed stainless steel