Does Quenching Brass Harden It?

Quenching brass in water does NOT harden the brass. Brass work hardens due to sizing and firing etc. That is why the brass cracks after multiple firings and loadings if they have not been annealed.

Can you harden brass?

Brass does work harden so bending it to shape will harden it to a certain extent. You will not be able to harden it by heat treatment. Another way of hardening it is planishing (otherwise known as beating it to death with a hammer!) but I doubt you will want to do that.

How do you harden brass?

Unlike other metals, brass cannot be heat-hardened as this will only make it softer. Brass must be work-hardened by heating it and then hammering or rolling it together.