How to designate a copper alloy

Copper has a great aptitude for forming alloys; It is estimated that at least 400 of them are used in the world. Given the spread, importance and ... the age of the metal, it is not surprising that each country had developed its own classification system. For example, a common fast turning brass was C36000 for the Americans, CZ124 for the British, 2.0375 for the Germans, C3601 for the Japanese, Mässing 51 70-xx for the Swedes and LS63-3 for the Russians and other ex-Soviets , while we used alloys for the same jobs called - still in common language - OT57 and OT58 ... In short, a Babel. Therefore the need arose to uniquely designate the various alloys through internationally recognized numbers or symbols, which are gradually replacing the local ones. In these pages, we report the three most popular.

American system

The American copper alloy designation system was certainly the most widespread.
The alloys were initially designated by a three-digit code (e.g. 377), established by the Copper Development Association, that is, the American correspondent of our Italian Copper Institute. This code was subsequently expanded to five digits, preceded by the prefix "C" (eg C37700) so that it was included in the more "universal" standards of the North American UNS (Unified Numbering System) code. The latter consists in fact of a letter followed by five digits: the letter designates the base metal of the alloy, such as A for aluminum, L for lead, R for rare metals and so on; for copper the C was chosen (initial of copper).

As for the numbers, the first three indicate the main alloy family and can be followed by two zeros. For example, cupronickel 90-10 is indicated by the abbreviation C70600; this indicates a copper alloy with Fe 1.0-1.8 and Ni 9-11, plus the relative impurities. Very similar alloys but which do not fall within the composition ranges seen above can be classified as C70601, C70602 and so on: in this way we are able to designate new alloys or variations of the old ones.

In the tab. 1 there are the codes of the main families of alloys for semi-finished products, in tab. 2 casting alloys.

The designation system is "administered" by the Copper Development Association. There is the possibility of new designations when a new copper alloy meets the following three criteria:

  • the complete chemical composition is known;
  • the alloy is on the market or is proposed for trade;
  • the composition does not fall within the limits of another alloy already present.

ISO / TR 7003 system and uni designation

The use of the ISO designation is increasingly widespread, applied and deepened by the UNI EN 1412 standard (Copper and copper alloys - European numerical designation system).

This system provides a six-character code, which can be digits (0) and uppercase letters (X) depending on their position (see tab.3). The letter C must always be placed in the first position, which indicates the copper alloy (copper in English, but also cuivre in French and cobre in Spanish). The second position must be occupied by a letter, which has the task of "qualifying" the material:

  • B = materials in the form of ingots for remelting, intended for the production of castings;
  • C = materials in the form of castings (in English: cast);
  • M = primary alloys (master alloys);
  • R = refined copper, not worked plastically (refined);
  • S = filler materials for soldering and soldering (solder alloys);
  • W = materials in the form of semi-finished products (wrought);
  • X = unified materials.

Positions 3 to 5 are occupied by numbers that form a number that can go from 000 to 999; if the material is unified, it falls between 000 and 799, while if it is not, it falls between 800 and 999.

Finally the sixth position is occupied by a letter indicating the group of materials:

  • A or B = copper;
  • C or D = copper alloys, with less than 5% of other elements;
  • E or F = various copper alloys, with more than 5% of other elements;
  • G = copper-aluminum alloys;
  • H = copper-nickel alloys;
  • J = copper-nickel-zinc alloys;
  • K = copper-tin alloys;
  • L or M = copper-zinc binary alloys;
  • N or P = copper-zinc-lead alloys;
  • R or S = copper-zinc alloys, complex.

For example, a classic 99.90% pure copper sheet (to be clear: like those used in construction) is designated by the code CW024A, while a 70-30 cupronickel plate used in the marine sector is the CW354H.

The responsible for the attribution, registration and management of the numerical designations of materials is CEN / TC 133. In detail, CEN is the European Standardization Committee, whose members are the national standardization bodies (UNI for Italy ), while TC 133 is the technical sub-committee dealing with copper and copper alloys.

To complete the discussion, it is good to also mention the designation of the metallurgical state, which can characterize the material almost as much as the composition and is specified in the orders between the manufacturer and the customer.

Here too there is an alphanumeric code, reported by UNI EN 1173 ("Copper and copper alloys - designation of metallurgical states") and consisting of a capital letter followed generally by 3 digits (see tab.4). The letter indicates the characteristic to be designated. The figures following the letter indicate the minimum value of the characteristic to be designated: for example, a copper plate indicated with R220 indicates a tensile strength of 220 N / mm2: this is the typical value of an annealed plate.

Clearly the designations D and M are not followed by digits, while after G not a minimum value is indicated, but an average value. Sometimes very high values ​​of a certain characteristic are sought and obtained: then the figures are brought from 3 to 4, as in the case of alloys with very high tensile strength.

Note that the letters give no indication of the heat or mechanical treatment of the manufacturing process.

ISO 1190-1 and CR 13388

A much more "immediate" alphanumeric code is that of ISO 1190-1 ("Copper and copper alloys-Code of designation. Part 1: designation of material") and reported in CR 13388, the document prepared by CEN which collects the compositions of the copper alloys.

The alloy is designated by a variable length code, which shows the elements present in the form of a chemical symbol and their nominal percentage in the form of an integer. If the quantity of the alloy element is within a composition range, the average is done, while if the composition shows only the minimum content, that is used. At the beginning of each abbreviation the symbol "Cu" must be reported, that is the base metal. For example, fast turning brass (the one with many abbreviations mentioned at the beginning of the article) containing on average 39% zinc and 3% lead is designated with CuZn39Pb3.

It is not necessary to list all the alloy elements, but only those necessary for the correct identification of the same: as in the case of CuZn13Al1Ni1Sn1, having important elements around 1%. It should be noted that significant elements can be listed with percentages below 1%, but in this case the figure is omitted, as in CuZn43Pb1Al, with aluminum ranging between 0.2 and 0.8%. Sometimes an element can have a negligible percentage (at the level of impurities!) But a very "metallurgically" important function such as to characterize the alloy, and therefore it is named: this is the case of CuZn30As, with the arsenic content between 0, 02 is 0.06% which acts as an antidezincifying agent.

A little different is the matter for almost pure copper alloys, around the minimum 99.90%; it is the remaining 0.10% which characterizes the chemical-physical properties of the alloy. As you can guess, managing the decimals and inserting them in the acronyms with the same criterion adopted for the alloys can be inconvenient. Therefore it was decided to indicate the compositions with the acronyms already entered into common use and universally used by professionals: so we have copper Cu-DHP (Deoxidized High residual Phosphor), Cu-ETP (Electrolitic Tough Pitch), the Cu-OF (Oxygen Free) and so on.

To conclude, let's take a look at the European standard that deals more closely with the sheets, ie UNI EN 1652 ("Copper and copper alloys - Plates, plates, tapes and disks for general uses") in which the chemical characteristics are reported and mechanics of 42 copper alloys.

The tables designate for each of them the material with both ISO codes, followed by the composition ranges: it is therefore simple to trace from one to the other. So, to give some examples, it is found that Cu-OF corresponds to CW004A, CuBe2 to CW101C, CuAl8Fe3 to CW303G, CuZn37 to CW508L, and that on a technical and commercial level it is indifferent to designate a certain alloy in one way or another.



[1] UNI EN 1173, Rame e leghe di rame – Designazione degli stati metallurgici.

[2] ISO 1190-1, Copper and copper alloys - Code of designation. Part 1: designation of material.

[3] CR 13388, Copper and copper alloys - Compendium of composition and products.

[4] UNI EN 1412, Rame e leghe di rame - Sistema europeo di designazione numerica.

[5] Copper Development Association,

[6] S.L. Chawla, R.K. Gupta, Material selection for corrosion control.

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