Guy Hode, age 11, of South River, N.J., for his question.
WHAT IS STAINLESS STEEL?
Some pure metals are too soft, rust too easily or have other mechanical or chemical disadvantages to be useful by themselves. But often these disadvantages can be overcome if the metals are combined with other metals into what is called an alloy. An alloy is a mixture of two or more metals or of a metal and some other material.
Iron is the most vital industrial metal we have. It is almost always used in an alloy rather than as a pure metal. Alloys that contain iron are known as ferrous alloys while those that do not contain iron are called nonferrous alloys.
Wrought iron is one of the purest forms of iron. It contains only a very small percentage of carbon, which is found in nearly all types of iron and steel. Cast iron, the next purest, contains two percent or more of carbon.
The term steel is used for many different alloys. All steels contain small amounts of carbon and manganese. Manganese increases the hardness of steel.
Stainless steel is noted for its ability to resist rust and tarnish as well as the effects of heat and wear: It contains about 74 percent steel, 18 percent chromium and eight percent nickel. There is actually a family of alloy steels that fall into the stainless class.
As a family, stainless steels have an easily maintained, attractive appearance. They show remarkable strength and ductility and are unique in their general resistance to the elements and to most corrosives.
Some 30 grades of stainless steels have been developed that have different combinations of strength and resistance to corrosion and heat. Most are used in the home and are highly polished, with a silvery appearance, but they do not need this finish to resist corrosion.
Most familiar use of stainless steel in the home is in kitchen knives, table flatware, sinks, pots and pans and in places where cleanliness and easy maintenance are essential. Stainless steel equipment is used in hospitals, restaurants, chemical factories, dairies and food processing plants.
Stainless steel parts are also used in automobiles, aircraft and in railroad passenger cars.
Chromium is the chief metal alloyed with iron, carbon, manganese and silicon in making stainless steel. One or more of the following elements are also added to iron from time to time to make stainless steel: molybdenum, titanium, columbium, aluminum, nitrogen, phosphorus, sulfur and selenium.
The addition of various chemical elements modifies stainless steel so that it can be used for various specific purposes.