Element N. 5 of the periodic system. Atomic weight 10. 82. It is grey in color, ignites at about 1112 (degrees) F. And burns with a brilliant green flame, but its melting point in a non-oxidizing atmosphere is about 4000 (degrees) F. Boron is used in steel in minute quantities for one purpose only- to increase the hardenability as in case hardening and to increase strength and hardness penetration.