Structural alloy steel for hardening and tempering is a group of steel used in toughening *, used in the production of 
heavily loaded machine parts and components that are meant to work in temperatures up to 300 C and the environment 
in which they work are not chemically aggressive. By using the improvement large span in the parameters of mechanical 
properties which fall between the maximum strength and a minimum ductility or strength or minimum and maximum 
value of plastic can be obtained for the same steel grade. Steel, which is composed of nickel + molybdenum, 
nickel + molybdenum + vanadium is used for parts and components for larger cross-sections, the elements of small 
cross-sections used steel containing manganese, silicon manganese & chrome. Structural alloy steels for hardening 
contain from about 0.20 to 0.60% of carbon.  

Symbol of steel grade according to the PN marking at the beginning of the grade number means the 
average carbon content in hundredths %, followed by letters denoting
H - Chrome
G - Manganese 
S - Silicon
N - Nickel
M - Molybdenum
F - Vanadium
W - Tungsten
then if there are numbers after the letters they refer to the average content of a certain component in%. 
If there is a letter A at the end of the marking of steel, it means a higher quality so the reduced content of sulfur and phosphorus. 

 

* Heat treatment consisting of hardening and tempering (high or medium), aimed to obtain the 
best possible mechanical properties while maintaining the possibility of machining.

12HN3A -chromium-nickel steel 1.5752,15CrNi13
20HN3A -chromium-nickel-steel
30HGSA -chrome-manganese-silicon
30HGSNA -chrome-manganese-silicon-nickel
30H2N2M -chrome-nickel-molybdenum and 30CrNiMo8,1.6580
36HNM -chrome-nickel-molybdenum and 36CrNiMo4, 16511
40H2MF -chrome-molybdenum-vanadium
40HNMA -chrome-nickel-molybdenum
45HN -chromium-nickel steel
45HNMF / 45HNMFA -chrome-nickel-molybdenum