Is to ensure that the mechanical properties of steel end-use of steel properties (mechanical properties) is an important indicator, it depends on the chemical composition and heat treatment of steel system. In the steel standard, according to different requirements, the provisions of the tensile properties (tensile strength, yield strength or yield point, elongation) and hardness, toughness, as well as user requirements high and low temperature properties.
First, the percentage elongation (��) in the tensile test, the specimen fractured the increase of its gauge length and the percentage of the original gauge length, called elongation. To �� said that the unit is%. The formula is: where: L1 - specimen fractured in the gauge length, mm L0 - the original specimen gauge length, mm.
Second, section shrinkage (��) in the tensile test, the specimen fractured at its reduced diameter to reduce the amount of cross-sectional area of the maximum percentage of the original cross-sectional area, known as section shrinkage. To �� said that the unit is%. The following formula: where: S0 - the original specimen cross-sectional area, mm2 S1 - necking specimen fractured at least cross-sectional area, mm2.
Third, the hardness index hard metal object against the ability of the surface indentation, called the hardness. According to the different test methods and scope of application, can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, micro hardness and high temperature hardness.
Fourth, the tensile strength (��b) during the tensile test specimens, in pulling off the most vigorously when exposed (Fb), out to sample the original cross-sectional area (So) from the stress (��), called the anti- tensile strength (��b), in units of N/mm2 (MPa). It said that under the action of metallic materials to resist damage in the tensile maximum capacity. The formula is: where: Fb - sample pulled off the most vigorously when exposed, N (Newton) So - the original specimen cross-sectional area, mm2.
Fifth, yield point (��s) with a yield phenomenon of metal materials, the specimen during the tensile force does not increase (remain constant) is still able to stretch the stress, called yield point. If the power drops occur, it should distinguish between the upper and lower yield point. Yield point of the unit N/mm2 (MPa). The yield point (��su): The power of the sample yield the first drop occurred before the maximum stress lower yield point (��sl): When the effect of excluding the initial transient, the yield phases of minimum stress. Yield point is calculated as: where: Fs - the process of tensile yield strength (constant), N (Newton) So - the original specimen cross-sectional area, mm2.