HARDENABILITY OF HARDENABILITY OF STEELSTEEL

(JOMINY TEST)(JOMINY TEST)EXPERIMENT # 11EXPERIMENT # 11

Instructor: M.YaqubInstructor: M.Yaqub

HARDENABILITYHARDENABILITY

Can we make steel hard if it is not hard?Can we make steel hard if it is not hard? Yes, by quenching process. Yes, by quenching process. Why steel become hard after quenching Why steel become hard after quenching

process?process? Because its structure become Martensite Because its structure become Martensite

which is very hard and brittle.which is very hard and brittle. Formation of Martensite depends on Formation of Martensite depends on

cooling rate.cooling rate.

HARDENABILITY (Cont’d.)HARDENABILITY (Cont’d.)

Faster cooling rate, formation of martensite Faster cooling rate, formation of martensite more and more hardness. more and more hardness.

Therefore surface is more hard than the core Therefore surface is more hard than the core of steel because of different cooling rates. of steel because of different cooling rates.

Hardenability is a steel property which Hardenability is a steel property which descirbes the depth to which the steel may be descirbes the depth to which the steel may be hardened during quenching. It depends mainly hardened during quenching. It depends mainly on the composition of steel. on the composition of steel.

JOMINIY TESTJOMINIY TEST

HARDENABILITY CURVEHARDENABILITY CURVE

EFFECT OF TEMPERING EFFECT OF TEMPERING TEMPERAURETEMPERAURE

EFFECT OF TEMPERING TIMEEFFECT OF TEMPERING TIME