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Stainless steel naming system Overview: Let you easily grasp the professional terms of the stainless steel industry!

The American three-digit numbering system, the AISI system, has been used for forging stainless steel since 1933. In this system, the 3xx series is used for chrome-nickel stainless steel, starting with 301; The 4xx series is used in chrome stainless steel, starting with 401. Although the amount of chromium increases with the number, the second and third digits have no specific meaning. In 1935, AISI published the AISI Standard containing 44 types of stainless steel. If the three digits are followed by the suffix letter "F", then this means that the "free cutting" performance of the stainless steel has been improved. For example, free-cutting stainless steel with a sulphur content of not less than 0.15% is 414F, 430F and 431F. In addition, 302B is an improved steel grade of 302, which has a higher silicon content. Finally, more than a dozen modified stainless steels were added. However, in 1965, the AISI numbering of stainless steel was discontinued. In the same year, the Society of Automotive Engineers (SAE) established the second stainless steel numbering system in the United States. The SAE numbers were improved on the AISI numbers by adding the prefix 30 to the 300 series numbers, so that 304 corresponds to the SAE number 30304. The 400 series number is prefixed with 51, giving the 410 SAE number 51410.

In 1941, the American Alloy Casting Association established a naming system for cast stainless steel. In this system, C stands for corrosion-resistant cast stainless steel and H stands for heat-resistant stainless steel. The second letter, from A to Z, classifies the chrome-nickel content combinations, such as CA-14 for the lowest alloy content and HX for the highest alloy content.

In 1941, during World War II, Britain published another set of country numbers. EN (Engineering Steel) numbers 56 to 61 are reserved for stainless steel. Special alloys are suffixes, for example, En 58E for AISI 304.

The French AFNOR standard enables a dual system of names and numbers to name stainless steel. The name begins with the letter Z, and the abbreviations for chromium and nickel are denoted by the letters C and N respectively, so the name 304 is Z6CN18-09.

In 1943, the German VDEh published a list of German alloy steels in which the 4xxx series was reserved for stainless steel.

304 is named 0Cr19Ni9 in China.

The GOST standard in Russia defines 304 as 08Ch18N10.

Sweden uses a four-digit series to name stainless steel, such as 2332 for 304.

Canada, Mexico, Brazil, Australia, Japan and South Korea all use AISI numbers with prefix letters to name stainless steel. In Japan, 304 is named with the prefix SUS.

The Spanish UNE standard uses X6CrNi19-10 for 304. It is also represented by the alphanumeric combination T3504.

In 1987, ISO used a unified name for stainless steel with DIN.

Over time, naming systems in many countries have become obsolete or replaced. For example, the British En numbering system, created in the 1940s, was replaced by a five-digit numbering system in 1967. This five-digit numbering system includes AISI numbers and letters, where S stands for "stainless", as in 304S18. In the 1960s, the three-digit numbering of the American AISI was also discontinued. ASTM continued to use "XM numbering" for new stainless steel until 1973, when SAE and ASTM jointly developed the Uniform Numbering System for Metals and Alloys (UNS) in order to establish a numbering system for all metals produced in the United States.

A year-long feasibility study to create a new numbering system that many thought would be futile was followed by the creation of a committee made up of representatives from aluminum, copper, steel mills, the automotive industry, the U.S. government, ASME, SAE and ASTM. The proposal is to establish a new numbering system incorporating the existing numbering systems of the professional bodies. Specific plans have been drawn up and implemented according to this concept.

A.G. Cook of Arrigani and H. M.Cobb of ASTM were responsible for the development. They divided the alloy elements into 18 groups, with the names of each group consisting of a letter and five digits. For example, aluminum alloy is A30030, and copper alloy is represented by the letter C and a number. Mr. Cook developed the stainless steel numbering system, in the UNS numbering system, 304L is numbered S30403, and the fourth and fifth digits indicate improved grades of high-carbon, free-cutting and nitrogenous stainless steels. The last two digits 80 to 89 indicate welding alloys.

Mr. Cobb developed the J Series for casting steel, stainless steel cast steel is classified in the J9xxx series.

In 1988, the EN system was established in Europe, mainly using the DIN Werkstoff numbering method for European Community countries. For example, the EN number of 304 stainless steel is EN1.4301.

In 1995, China introduced the Steel Code (ISC), which is similar to the UNS, with the letter S and five digits representing stainless steel. For steel grades with the same chemical composition, some numbers in ISC are the same as those in UNS, such as S30403, but some are alloy numbers that are not in the UNS system.


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