Bill Hassel, age 11, of Milwaukee, Wis., for his question:

HOW IS STAINLESS STEEL MADE?

About 30 grades of stainless steels have been developed that have different combinations of strength, ductility and resistance to corrosion and heat. Stainless steel is used in the home for kitchen knives, flatware, sinks, pots and pans and other places where cleanliness and easy maintenance are important. Hospitals, restaurants, dairies and food processing plants use lots of stainless steel equipment.

Chromium is the chief metal alloyed with iron, carbon, manganese and silicon in making stainless steel. The more common stainless steels usually have about 8 percent nickel.

One or more of the following elements may also be added to iron to make stainless steel: molybdenum, titanium, aluminum, nitrogen, phosphorus, sulfur and selenium.