Boron in Steels

Boron in Steels  Boron (B) (atomic number 5 and atomic weight 10.81) has density of 2.34 gm/cc. Melting point of B is 2076 deg C and boiling point is 3927 deg C. B is a solid material at the atmospheric pressure and at 0 deg C temperature. The phase diagram of the Fe-B binary system and equilibrium phase diagram at low concentrations of B  is given at Fig 1. Fig 1 Fe-B phase diagram and equilibrium phase diagram at low B concentrations  B steels are becoming increasingly popular and their application is becoming more diverse. Their high properties, at a reasonable price, are achieved through advanced manufacturing technology. Although B steels were originally designed mainly for the hard, wear resistant elements, now they are also being used for a wider application. B is useful as an alloying element in the steel because of its effect on hardenability enhancement. It is added to carbon (C) and low alloyed steels at concentration levels of 0.0015 % to 0.0030 % for increasing the hardness level through the enhancement of hardenability. B reacts readily with oxygen (O) and nitrogen (N) and is not useful to steels if it is in  combined form. Hence care is to be taken during steelmaking to ensure that B is adequately protected. If this precaution is not taken then it can lead to erratic heat treatment response. Addition agents B is used in steelmakers as ferro-boron (Fe-B) which is a low cost addition agent. Fe-B comes in several grades. High C Fe-B contains up to 2 % C and normally comes in three grades containing (i) 10 %- 15 % B, (ii) 15 % – 20 % B, and (iii) over 20 % B. Low  C Fe-B contains less than 0.5 % C...