Like other materials, the physical properties of stainless steel strip mainly include the following three aspects: thermodynamic properties such as melting point, specific heat capacity, thermal conductivity and linear expansion coefficient, electromagnetic properties such as resistivity, electrical conductivity and magnetic permeability, and Young's modulus of elasticity , stiffness coefficient and other mechanical properties. These properties are generally considered to be inherent properties of stainless steel materials, but are also affected by factors such as temperature, degree of processing and magnetic field strength. Generally speaking, stainless steel has lower thermal conductivity and higher resistance than pure iron, and the properties such as linear expansion coefficient and magnetic permeability vary according to the crystal structure of stainless steel itself.
The physical properties of the main grades of martensitic stainless steel, ferritic stainless steel, austenitic stainless steel, precipitation hardening stainless steel and duplex stainless steel are listed in Table 4-1 to Table 4-5. Such as density, melting point, specific heat capacity, thermal conductivity, coefficient of linear expansion, resistivity, magnetic permeability and longitudinal elastic coefficient and other parameters.
Dependence of physical properties on temperature
(1) Specific heat capacity
The specific heat capacity will change with the change of temperature, but once the phase transition or precipitation occurs in the metal structure during the temperature change, the specific heat capacity will change significantly.
(2) Thermal conductivity
Below 600℃, the thermal conductivity of various stainless steels is basically in the range of 10~30W/(m·℃), and the thermal conductivity tends to increase with the increase of temperature. At 100℃, the order of thermal conductivity of stainless steel from large to small is 1Cr17, 00Cr12, 2 Cr 25N, 0 Cr 18Ni11Ti, 0 Cr 18 Ni 9, 0 Cr 17 Ni 12Mο2, 2 Cr 25Ni20. The order of smallest is 1 Cr 13, 1 Cr 17, 2 Cr 25N, 0 Cr 17Ni12Mο2, 0 Cr 18Ni9Ti and 2 Cr 25Ni20. The thermal conductivity of austenitic stainless steel is slightly lower than that of other stainless steels. Compared with ordinary carbon steel, the thermal conductivity of austenitic stainless steel at 100 °C is about 1/4.
(3) Linear expansion coefficient
In the range of 100-900°C, the linear expansion coefficients of the main grades of various stainless steels are basically 10ˉ6~130*10ˉ6°Cˉ1, and show an increasing trend with the increase of temperature. For precipitation hardening stainless steel, the size of the linear expansion coefficient is determined by the aging treatment temperature.
At 0~900℃, the specific resistance of various stainless steel grades is basically 70*10ˉ6~130*10ˉ6Ω·m, and it tends to increase with the increase of temperature. When used as a heating material, materials with low resistivity should be selected.
(5) Magnetic permeability
The magnetic permeability of austenitic stainless steel is extremely small, so it is also called non-magnetic material. Steels with stable austenitic structures, such as 0 Cr 20 Ni 10, 0 Cr 25 Ni 20, etc., will not be magnetic even if they are processed with a large deformation of more than 80%. In addition, high carbon, high nitrogen, high manganese austenitic stainless steel, such as 1Cr17Mn6NiSN, 1Cr18Mn8Ni5N series and high manganese austenitic stainless steel, etc., will undergo ε phase transformation under large reduction machining conditions, so it remains non-magnetic. At high temperatures above the Curie point, even strongly magnetic materials lose their magnetic properties. However, some austenitic stainless steels such as 1Cr17Ni7 and 0Cr18Ni9, because of their metastable austenite structure, will undergo martensitic transformation during large-reduction cold working or low-temperature working, and they will be magnetic and magnetic. Conductivity will also increase.
(6) Elastic modulus
The longitudinal elastic modulus of ferritic stainless steel at room temperature is 200 kN/mm2, and the longitudinal elastic modulus of austenitic stainless steel is 193 kN/mm2, which is slightly lower than that of carbon structural steel. As the temperature increases, the longitudinal elastic modulus decreases, the Poisson's ratio increases, and the transverse elastic modulus (stiffness) decreases significantly. The longitudinal elastic modulus will have an effect on work hardening and tissue aggregation.
Ferritic stainless steel with high chromium content has low density, and austenitic stainless steel with high nickel content and high manganese content has high density.randompackingfactory.com