Hi all. I have a problem. I must make an experiment with cast iron to
estimate it's metallurgical quality. In some book, I found, that
metallurgical quality is defined as relation of Rm and HB. After my
calculations I recived results oscillate about 1. I'dont know that is good
If somebody knows other definition of metallurgical quality of cast iron,
I'll be very grateful for answer on my problems.
EN1561 is this what you are talking about
Annex B (informative)
Additional information on the
relationship between hardness and
Hardness and tensile strength as well as Young's
modulus and the modulus of rigidity of grey cast iron
of a given grade are approximately related to each
other. In most cases, an increase in the value of one
property results in an increase in the values of other
properties  to  (see annex D). The following
empirical relationship between hardness and tensile
HB = RH 3 (A + B 3 Rm)
Commonly accepted values for the constants are:
A = 100, B = 0,44 , .
The factor RH is called relative hardness. This
parameter has been found to vary between 0,8 and 1,2.
Because of the variation in relative hardness it is
difficult to give definitive limits in a standard for both
tensile strength and hardness (see figure B.1). More
details concerning RH are discussed in literature 
to  (see annex D).
The factor RH is influenced mainly by the raw
materials, the melting process and the metallurgical
working method. Within one foundry these influences
can be maintained nearly constant. The manufacturer
can therefore indicate both hardness and the
corresponding tensile strength.