A/C MATERIALS DATE :

SAE CLASSIFICATION OF STEELS NAME :

GENERAL

A standardized numerical index system, originally developed by the Society of Automotive Engineers (SAE), is used to designate the steel used in aircraft and automotive construction with this system, it is possible to use numerical on the shop drawings and blueprints to describle in part the quality of material covered by such numbers. For instance, high-carbon steel is designated as 1070.

NUMERICAL INDEX SYSTEM

The first figure (digit) of the classification number indicates to which class the steel belongs : thus, the figure (1) in the number 1070 indicates a carbon steel ; if figure were (2), a would indicate a nickel steel, and, if (3), a nickel-chromium steel. The second figure in the SAE number 1070 is zero. This indicates that there is no alloying element; which is the case in plain carbon steels. In the case of alloy steels, the second figure generally indicates the approximate percentage % of the principle alloying element.

Carbon steels 1 Nickel steels 2 Nickel-Chromium steels 3 Molybdenum steels 4 Chromium steels 5 Chromium-vanadium steels 6 Tungsten steels 7 Manganese-Molybdenum and nickel-Chromium-Molybdenum steels 8 Silicon-Manganese steels 9

SAE 1 0 70 First figure (1), carbon steel Second figure (0), no alloy Last two figures (70), approximately 0.70 % carbon

SAE 2 3 30

First figure (2), nickel steel Second figure (3), approximately 3 % nickel Last two figures (30), approximately 0.40 % carbon Usually, the last two or three figures (digits) indicate the average carbon content in points or hundredths of 1 %. The last two figures in SAE 1070 being 70 tells us that the steel contains 0.70 % carbon, which is less than 1 %. Thus, the number 2340 indicates a nickel steel of approximately 3 % nickel (3.25 to 3.75 %)

and 0.40 % carbon (0.35 to 0.45 %) ; and the number 71360 indicates, a tungsten steel of about 13 % tungsten (12 to 15 %) and 0.60 % carbon (0.50 to 0.70 %). The basic numerals of the various qualities of steels specified are as follows :

SAE 7 13 50

First figure (7), tungsten steel second figure (13), approximately 13 % tungsten Last two figures (50), approximately 0.60 % carbon In determining the approximated composition of steel from the SAE number, it should be noted that the class or basic alloying element is indicated by the first figure. That the percentage of the basic alloying element is indicated by the second figure in the most classes; and the carbon content in hundredths of one per cent is indicated by the last two figures. SAE 4130 is in exception to the general rules previously mentioned. Because the SAE code was set up in, or about the year 1906, there was no provision made for 4130, a chrome molybdenum steel, introduced later in about the year 1918. Actually, chromium is the predominating alloy in 4130 steel, and not molybdenum, even through it is classed as a group (4) steel. The second figure (1) in 4130 steel indicates approximately 1 % chromium. The molybdenum content, being lower than the chromium, is not given. This is show in the following analysis and example :

SAE 4 1 30

(Contains) Carbon 0.28%-0.33%Chromium 0.80%-1.10%Manganese 0.40%Molybdenum 0.15%-0.25%Phosphorus (max) 0.40%Sulphur (max) 0.40%Silicon 0.20%-0.35%

SAE Chrome Moly 4 1 30

First figure (4), molybdenum steel Second figure (1), approximately 1 % chromium Last two figures (30), approximately 0.30 % carbon