Carbon steels properties

Carbon steels are produced in greater tonnage and have wider use than any other metal because of their versatility and low cost.There are now almost 50 grades available in the nonresulfurized series 1000 carbon steels and nearly 30 grades in the resulfurized series 1100 and 1200. The versatility of the carbon steel group has also been extended by availability of the various grades with lead additions.The rate of heating parts for quenching has a marked effect on hardenability under certain conditions. If the structure is non-uniform, as a result of severe banding or lack of proper normalizing or annealing, extremely rapid heating such as may be obtained in liquid baths, will not allow sufficient time for diffusion of carbon and other elements in the austenite. As a result, non-uniform or low hardness will be produced unless the duration of heating is extended. In heating steels that contain free carbide (for example, spheroidized material), sufficient time must be allowed for the solution of the carbides; otherwise the austenite at the time of quenching will have a lower carbon content than is represented by the chemical composition of the steel, and disappointing results may be obtained.These medium-carbon steels should usually be either normalized or annealed before hardening, in order to obtain the best mechanical properties after hardening and tempering. Parts made from bar stock are frequently given no treatment prior to hardening, but it is common practice to normalize or anneal forgings. Most of bar stocks, both, hot finished and cold finished, are machined as received, except the higher-carbon grades and small sizes, which require annealing to reduce the as-received hardness. Forgings are usually normalized, since this treatment avoids the extreme softening and consequent reduction of machinability that result from annealing.In some instances a "cycle treatment" is used. In this practice the parts are heated as for normalizing, and are then cooled rapidly in the furnace to a temperature somewhat above the nose of the S-curve - that is, within the transformation range that produces pearlite