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.

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	-	-	-	-