Steels_ Metallurgy and Applications, Third Edition

Engineering steels 213

Cr

, I 4.6

4.2 "1 - " "

I i

3.8 ~. i "4.2

3.4 /- i - '/ NI ......... 4.0

! J ,_.___.__

3.0 I " " " m Mo (>0.75Ni)

2.6 I I " 9 /, / .... ;' 3.6

2.2 / .-/ ' 3.4

1.8 ... ~------' 3.2

1, r:; : ~ Mo ,

2.81'.... 1.0 1.5 2.0 2.5 3.0 3~5 Cr I

m i - / 2.8

9 ,2.e Q. I. , L , .., 1

E = i /"

= "4~1' ~ ----

2.2 ~

2.0~ ~ '/

1.8 -/~

'"--------7

1.2----~ '

4.4

3.8

1.0

0.2 0.4 0.6 0.8 1.0 1.2 1.4

Alloying element (%)

Figure 3.14 Average multiplying factors for several elements in alloy steels containing
0.15- 0.25% carbon (After deRetana and Doane 7)

hardenability effects of a similar magnitude to carbon. Although vanadium has
a powerful effect on hardenability, it has a low solubility in steels due to the
formation of vanadium carbide. Therefore the level of addition is generally small
and, as illustrated shortly, may be used more to retard the tempering process than
as a hardenability agent.

Boron

In the context of low-alloy engineering steels, boron is a unique alloying element
from the following standpoints:

1. The addition of 0.002-0,003% B to a suitably protected base composition
   produces a hardenability effect comparable with that obtained from 0.5% Mo,
   0.7% Cr or 1.0% Ni.