Stainless steel is usually chosen because it is resistant against corrosion—but it is also chosen because it is steel. Properties such as strength, yield, toughness, hardness, response to work hardening, weldability, and heat-tolerance make steel an incredibly useful metal in engineering, construction, and manufacturing, especially given its cost. An engineer considers the working load and atmospheric conditions of the stainless steel before deciding on a grade.
Tensile properties
Tensile properties of metals are measured by pulling. A representative tensile bar is subjected to pulling force, also known as tensile loading. Upon failure, the tensile strength, yield strength, elongation, and reduction of area are measured.
Hardness
Hardness is the ability of steel to resist indentation and abrasion. The two most common hardness tests are Brinell and Rockwell. In the Brinell test, a small hardened steel ball is forced into the steel by a standard load, and the diameter of the resulting impression is measured. The Rockwell test measures the depth of the indentation. Hardness can be increased in some metals by cold-working, also known as work-hardening. In some metals, hardness can be increased through heat treatment.
Toughness
Toughness is the capacity of steel to yield plastically under very localized stress. A tough steel is resistant to cracking, making toughness a highly desirable quality used in engineering applications. The level of toughness is determined using a dynamic test. A sample bar is notched to localize the stress, then struck by a swinging pendulum. The energy absorbed in breaking the sample bar is measured by how much energy the pendulum loses. Tough metals absorb more energy, while brittle metals absorb less.
