What is the effect of boron on the hardenability of steel plate?

Ti, niobium and zirconium are strong carbide and strong nitride forming elements, and their behavior is similar to that of vanadium. These elements have little or no solubility in austenite and contribute little to hardenability.

Boron is a powerful element in improving hardenability, and its influence on hardenability has its own uniqueness and complexity. Boron has two states in steel, namely, the solid solution state and the bond state. 

Only when boron is dissolved in austenite can it improve hardenability. Boron with oxygen and nitrogen form boron oxide and nitride, caused quite a number of boron content in combining with the state, and thus lose the ability to increase the hardenability, therefore, should be taken to protect the method of boron and boron and reserved for the combination state and moved to the solid solution, become later after quenching can work on hardenability of the so-called "effective boron.