Analysis of physical properties of large diameter stainless steel pipes

The physical properties of stainless steel include many contents such as density, melting point, thermal conductivity, electrical conductivity, thermal expansion, magnetic permeability and temperature coefficient of resistance. They can be used as performance, and some are also process performance. This is an important part of metal performance. The following is a brief description of several physical properties commonly used. The density of stainless steel is the mass (weight) of metal per unit volume, which is the ratio of the mass of the metal to its volume. Each metal has its own fixed density value, denoted by the symbol p. The method for determining the density is relatively simple. As long as the volume and mass of a stainless steel are measured, it can be obtained by using the density formula.

The density of stainless steel is an important performance data commonly used in the machine industry. When selecting materials, the factors of density must be considered. To manufacture materials such as aircraft, automobiles, vehicles and bridges, the material weight should be as light as possible, and the metal material with low density should be selected for this purpose. Density is often used in the processing of metal parts. For example, it is necessary to use density to calculate how much quality casting alloy is needed to cast a part. In daily work, the density is commonly used to calculate the quality of large parts. In scientific research, the method of measuring density is used to identify metal and determine certain The degree of compactness of some metal castings, etc. For convenience in use, a metal having a density of less than 5 × 10 Skg/m 3 is generally referred to as a light metal, and a metal having a density of more than 5 × 10 3 kg/m 3 is referred to as a heavy metal.

The temperature at which a melting point stainless steel or alloy is melted from a solid to a liquid during heating is called a melting point and is usually expressed in degrees Celsius. The melting point is fixed for each metal. The melting point of stainless steel can be accurately determined by thermal analysis. Among the commonly used stainless steel materials, tungsten has the highest melting point, which is the most difficult to melt. Metals such as tin and lead have a lower melting point and are called low melting point metals. The selection and manufacture of metallic materials is closely related to the melting point. In the casting and welding of stainless steel and alloys, the temperature must be higher than its melting point, and the temperature of the heat treatment must be lower than its melting point. Alloys with a low melting point can be used to create solders, fuses (alloys of lead, tin, antimony, antimony), typefaces (alloys of lead and antimony), etc., when manufacturing mechanical parts, structural parts and heat-resistant parts, they are exposed according to the conditions of use. For the requirements, choose a suitable melting point for the metal or alloy.

The volume and length of the heat-expandable solid metal stainless steel or alloy change correspondingly when the temperature changes. Generally, the volume increases when heated, and the volume decreases when cooled. The stainless steel metal is characterized by thermal expansion and contraction with temperature. Thermal expansion. The magnitude of the thermal expansion of the metal is expressed by the coefficient of linear expansion and the coefficient of bulk expansion, and their approximate relationship is; the coefficient of bulk expansion is three times the coefficient of linear expansion. In actual work, the impact on thermal expansion should be highly valued. For example, the piston moves and rotates between the cylinder liners (neither leaking nor jamming), and the gap coefficient between the sleeves and the bushings is used to control the gap size. When casting mechanical parts, in order to ensure the size of the parts, reduce and avoid Casting defects such as shrinkage cavities and looseness must take into account the thermal expansion effects of the material. Local volume shrinkage may cause cracking during heat treatment of parts and cooling of castings, and precision readings may cause reading errors due to temperature changes. The property of a thermally conductive stainless steel metal that conducts heat during heating, heat or cooling is called thermal conductivity. The magnitude of the thermal conductivity of a metal is expressed by the thermal conductivity of the metal, and the symbol is A, and the unit is W/(m.K). The value of the thermal conductivity of five can be measured by a thermal conductivity meter. The method is broadly divided into a dynamic method and a static method, and the static method is generally used.

The silver in all large-diameter stainless steel pipes has the best thermal conductivity, and the second is the second. The pure metal has better thermal conductivity than the alloy. In the process of heat conduction, the thermal conductivity marks the speed at which the temperature changes, so mastering the concept of thermal conductivity is extremely important for heat treatment. For example, when formulating a heat treatment specification for a metal or alloy, the heating rate is determined by taking into account the thermal conductivity of the metal. The thermal conductivity of alloy steel is worse than that of carbon steel, and the heating speed should be slower. When quenching and cooling, the temperature of the workpiece is high and the surface temperature is low. The temperature difference between the inner and outer parts of the steel with poor thermal conductivity is relatively large, and it is easy to quench. Deformation or even cracking occurs, so alloy steel is often oil-cooled when quenched. It can be seen that the thermal conductivity of steel is very important for heat treatment. In general, metals with good thermal conductivity have good heat dissipation. Therefore, when manufacturing parts such as radiators, heat exchangers, and pistons, pay attention to selecting stainless steel metals or alloys with high thermal conductivity.