ALLOY CHARACTERISTICS
STAINLESS STEEL
TYPE 303
Type 303 was developed especially for machining purposes. The ordinary 18-8 types of stainless steel are somewhat more difficult to turn, mill, and drill, which restricts their use when considerable machining is required. A larger proportion of sulphur than is used in Type 302 assists in breaking up the turnings which reduces the drag on the cutting tool. This permits greater machining speeds and tends to produce smoother machined finishes, which assist in lowering production costs.
Type 303 has reduced transverse ductility, and care must be taken in forging to avoid splitting. Steel with a slightly modified chemistry should be specified if forging or upsetting operations are to be employed.
Type 303 has slightly less corrosion resistance than Type 302. However, the laboratory corrosion data shown for Type 302 are generally applicable.
Type 303 is useful whenever a combination of good corrosion resistance and considerable machining is required for a part
Typical applications for Type 303 are: Aircraft fittings; bolts, nuts and screws; bushings; fasteners; fittings; machined parts; rivets; screw machine products; pump parts; studs; shafts.
TYPE 304
Commonly called the "all purpose" stainless steel, Type 304 has properties desirable for many applications. For welded construction of light sections where annealing is not practical or possible, but good corrosion resistance is needed, Type 304 is recommended. Where heavier gauge material is used (over 1 /4"), it is suggested that you use Type 304L, which contains less carbon than the standard Type 304. Other desirable properties of Type 304 are its satisfactory service at high temperatures (800-1600 °F), and the deep drawing properties and good mechanical properties.
However, if Type 304 is exposed to high temperatures (in the 800-1600 °F range) prolonged periods carbide precipitation may occur. Provided that corrosive conditions are not severe, Type 304 will give satisfactory service life even in high temperature applications. Because the incidence of carbide precipitation decreases as the carbon content decreases, Type 304, which has a maximum carbon content of 0.08 percent (as compared to 0.15 percent in Type 302) is considered a good material for most welding applications.
Harmful carbide precipitation should not ordinarily occur when welding light sections (up to 1 /4" thick) of Type 304. When welding thicker sections and the exposure to welding temperatures is longer, Type 304L, with a carbon content of 0.03 minimum, is recommended.
In welding applications where carbide precipitation occurs and annealing is possible, harmful carbides can be eliminated by annealing followed by rapid cooling. Annealing also relieves the residual stresses at the weld area
Typical applications of Type 304 are: Atomic reactor equipment; chemical processing equipment; food processing and handling equipment; heat exchangers; pharmaceutical equipment; still tubes; valves and fittings; beverage equipment; dairy equipment; hospital equipment; pulp and paper equipment; textile dyeing equipment.