Tom Hagen, age 15, of Utica, N.Y., for his quesion:

CAN YOU TELL ME ABOUT TEMPERING STEEL?

In metallurgy and engineering, tempering is the low temperature process in the heat treatment of steel by which a desirable balance is obtained between the hardness and toughness of the finished article.

Steel articles that have been hardened by quenching, which is a process of heating to about 1,600 degrees Fahrenheit and then cooling rapidly in oil or water, become hard and brittle. Reheating to a lower temperature decreases the hardness somewhat but improves the toughness.