The physical properties of metals are mainly considered:
(1) Density (specific gravity): Ï = P / V unit gram / cubic centimeter or ton / cubic meter, where P is the weight and V is the volume. In practical applications, in addition to calculating the weight of metal parts based on density, it is important to consider the specific strength of the metal (the ratio of the intensity σb to the density Ï) to aid in material selection, and the acoustic impedance in acoustic detection associated with nondestructive testing. (The product of the density Ï and the sound velocity C) and the material having different densities in the radiation detection have different absorption abilities to the ray energy and the like.
(2) Melting point: The temperature at which a metal changes from a solid to a liquid, has a direct influence on the melting and hot working of the metal material, and has a great relationship with the high temperature performance of the material.
(3) The thermal expansion property changes with the temperature, the volume of the material also changes (expansion or contraction) phenomenon is called thermal expansion, measured by the coefficient of linear expansion, that is, when the temperature changes by 1 ° C, the increase or decrease of the material length and its 0 ° C The ratio of length. Thermal expansion is related to the specific heat of the material. In practical applications, the specific volume (the ratio of the volume to the mass of the material per unit weight, that is, the ratio of volume to mass) is considered when the material is affected by external influences such as temperature, especially for working in a high temperature environment, or in cold or hot. Metal parts that work in alternate environments must consider the effects of their expansion properties.
(4) Magnetic properties The property of attracting ferromagnetic objects is magnetic, which is reflected in parameters such as magnetic permeability, hysteresis loss, residual magnetic induction, coercive force, etc., so that the metal material can be divided into paramagnetic and antimagnetic, soft magnetic and hard. Magnetic material.
(5) Electrical properties mainly consider its conductivity, which affects its resistivity and eddy current loss in electromagnetic non-destructive testing.
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