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Alloy steels

Dr. Dmitri Kopeliovich

Alloy steels are iron-carbon alloys, to which alloying elements are added with a purpose to improve the steels properties as compared to the Carbon steels.

Due to effect of alloying elements, properties of alloy steels exceed those of plane carbon steels.

AISI/SAE classification divide alloy steels onto groups according to the major alloying elements:

According to the four-digit classification SAE/AISI system:

First digit indicates the class of the alloy steel:

2- Nickel steels;

3- Nickel-chromium steels;

4- Molybdenum steels;

5- Chromium steels;

6- Chromium-vanadium steels;

7- Tungsten-chromium steels;

9- Silicon-manganese steels.

Second digit indicates concentration of the major element in percents (1 means 1%).

Last two digits indicate carbon concentration in 0,01%.

Example: SAE 5130 means alloy chromium steel, containing 1% of chromium and 0.30% of carbon.

Chemical compositions of some alloy steels

SAE/AISI grade C, % Mn,% P,% max S,% max Ni,% Cr % Mo% V%
2340 0.38-0.43 0.70-0.90 0.035 0.04 3.25-3.75 - - -
3115 0.13-0.18 0.40-0.60 0.035 0.04 1.1-1.4 0.55-0.75 - -
4027 0.25-0.30 0.70-0.90 0.035 0.04 - - 0.20-0.30 -
4130 0.27-0.33 0.35-0.60 0.035 0.04 - 0.80-1.15 0.15-0.25 -
4340 0.38-0.43 0.60-0.80 0.035 0.04 1.65-2.00 0.7-0.9 0.20-0.30 -
5140 0.38-0.43 0.70-0.90 0.035 0.04 - 0.7-0.9 - -
6150 0.48-0.53 0.70-0.90 0.035 0.04 - 0.8-1.1 - 0.15 min
8620 0.18-0.23 0.60-0.90 0.035 0.04 0.40-0.70 0.40-0.60 0.15-0.25 -
9255 0.51-0.59 0.75-1.00 0.035 0.04 - - - -

Properties of some alloy steels

(Materials Data)

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