Alternative spelling of case hardened / Hardened by experience.

(metallurgy) To impart greater hardness to the surface of a piece of metal.

Alternative spelling of case hardening

(metallurgy) Designating, or pertaining to, any of various steels that harden when heated to above a red heat and cooled in air, usually in a blast of cold air with moderate rapidity, without quenching. Such steels are alloys of iron and carbon with manganese, tungsten and manganese, chromium, molybdenum and manganese, etc. They are chiefly used as high-speed steels.

(metallurgy) The repeated plastic deformation of a material, causing a permanent distortion of its crystal structure, and an increase in its strength

(literally and figuratively) Unfeeling or lacking emotion due to experience in battle; callous.

(of metal) Age hardening; a heat treatment technique to increase the yield strength of malleable materials.

to cold-hammer

(idiomatic, usually reflexive, dated) To make someone more resistant to something.

(obsolete) To grow more obstinate.