What are the physical properties of metals, and the physical properties of metals

1 Density: Density is the mass of a certain substance per unit volume.

2. Thermal properties: melting point: the melting temperature of metal materials when the solid state is transformed into a liquid state.

Specific heat capacity: The amount of heat absorbed by a substance per unit mass when the temperature rises1 or the heat emitted when the temperature decreases1.

Thermal conductivity: The amount of heat that is allowed to be conducted per unit area per unit time when the temperature decreases by 1 per unit length along the direction of heat flow.

Coefficient of thermal expansion: The ratio of the length of the metal to its original length for every 1 increase in temperature.

3. Electrical properties: Resistivity: is a parameter that indicates the conductivity of an object. It is equal to the resistance between the two ends of a wire with a length of 1 m and a cross-sectional area of 1 mm2. It can also be expressed by the resistance between two parallel end faces of a unit cube.

Resistance temperature coefficient: The ratio of the change in the resistance of the material to the original resistivity for every 1 rise and fall of temperature is called the temperature coefficient of resistance.

Conductivity: The reciprocal of resistivity is called conductivity. Numerically it is equal to the current flowing through the unit area while the conductor maintains the unit potential gradient.

4. Magnetic properties: Permeability: It is a performance index to measure the difficulty of magnetization of magnetic materials, and it is the ratio of magnetic induction intensity (b) and magnetic field strength (h) in magnetic materials.

Magnetic materials are usually divided into two categories: soft magnetic materials (very high value, up to tens of thousands) and hard magnetic materials (value of about 1).

Magnetic induction intensity: The magnetization process in the magnetic medium can be regarded as adding a new magnetic field determined by the magnetization intensity (J) to the original magnetic field strength (H), the quantity is equal to 4 J, so the new magnetic field in the magnetic medium B=H+4 J is called the magnetic induction intensity.

Magnetic field strength: When an electric current is passed through a conductor, a magnetic field is generated around it. The magnitude of the force exerted by the magnetic field on the original magnetic moment or current is a characterization of the strength of the magnetic field.

Coercivity: After the sample is magnetized to saturation, due to the hysteresis phenomenon, in order to reduce the magnetic induction intensity to zero, a certain negative magnetic field HC must be applied, and HC is called coercivity.

Iron loss: The energy dissipated by ferromagnetic materials due to hysteresis and eddy current effects under dynamic magnetization conditions.

Others such as mechanical properties, process properties, service performance, etc.

Simple performance parameters include density, melting point, thermal expansion (coefficient of expansion), electrical conductivity, and thermal conductivity.

Electrical conductivity. Ductility. Thermal conductivity. It has a metallic sheen.

These include density, melting point, electrical conductivity, thermal expansion, and magnetism, among others.

Metals have a metallic luster: most metals have a silvery-white metallic luster, and a few metals have a unique color, such as copper is purple-red and gold is golden-yellow.

2. Solids: Except for mercury, which is liquid, most metals are solids.

3. Conductivity: In the electric field, free electrons can move directionally, and there is an electric current.

4. Thermal conductivity: free electrons collide with metal ions to exchange energy.

5. Ductility: It will not break the metal bond of the metal when deformed. Ductility: The property of drawing into filaments. Malleability: The property of pressing into thin sheets.

It has physical properties such as electrical conductivity, thermal conductivity, high hardness, high strength, high density, high melting point, and good metallic luster; At the same time, the chemical properties of metals are active, and most metals can react with oxygen, acid solutions, and salt solutions.

It is worth emphasizing that some metals have special physical properties, such as: tungsten has an extremely high melting point, copper has good conductivity, gold has good ductility, platinum has good ductility, mercury at room temperature is liquid, etc. In addition, alloys have better corrosion resistance, greater hardness and strength, and lower melting points than metals.

Metal is a substance with lustrous (i.e., strong reflection of visible light), malleable, easy to conduct electricity, heat and other properties.

1. Status: Solid at room temperature, except for mercury.

2. Color: most of them are metallic, silvery-white, a few have special colors, block metals have metallic luster, and some powdered metals are black or dark gray.

3. Characteristics: most of them are malleable and malleable, the best ductility is platinum, and the best malleability is gold; It has good heat transfer conductivity, and the conductivity is preferably silver.

4. Density: Except for lithium, sodium, and potassium, which are lighter than water, the rest of the densities are larger, and the lightest is lithium.

5. Melting point: generally high, but the difference is large, the most difficult metal to melt is tungsten, and the lowest melting point is mercury.

6. Hardness: generally larger, but the difference is larger, the hardest is chromium, in addition to mercury liquid, the softest metal is cesium, alkali metal can be cut with a knife.

1. Strength refers to the performance of metal materials to resist damage (excessive plastic deformation or fracture) under static load. Since the load acts in the form of tensile, compression, bending, shear, etc., the strength is also divided into tensile strength, compressive strength, bending strength, shear strength, etc. There is often a certain relationship between various strengths, and tensile strength is generally used as the most basic strength indicator in use.

2. Plasticity refers to the ability of metal materials to produce plastic deformation (permanent deformation) without destruction under load.

3. Hardness is a measure of the hardness of metal materials. At present, the most commonly used method for determining hardness in the production of Wu imitation is the indentation hardness method, which is to use a certain geometric indenter to press into the surface of the tested metal material under a certain load, and determine its hardness value according to the degree of indentation. Commonly used methods include Brinell (HB), Rockwell (HRA, HRB, HRC) and Vickers (HV).

4. Fatigue, the strength, plasticity, and hardness discussed above are all indicators of the mechanical properties of metals under static load. In fact, many machine parts work under cyclic loads, and under such conditions the parts develop fatigue.

5. Impact toughness, the load acting on the parts at a great speed is called impact load, and the ability of metal to resist damage under impact load is called impact toughness.

Performance of metal materials 1Density (specific gravity): The unit volume of the material.

The mass possessed, i.e., the density of the mass volume, is in g cm3. 2.Mechanical properties.

Various properties of metal materials under the action of external forces, such as elasticity, plasticity, toughness, strength, hardness, etc. 3.Strength: The ability of a metal material to resist deformation and fracture under the action of external forces. Yield point, tensile strength.

It is an extremely important strength index and an important basis for the selection of metal materials. The magnitude of strength is expressed in terms of stress, that is, the load (external force) that can be borne per unit area. 4.

Yield point: The phenomenon that the load of the metal does not increase during the tensile test, but the specimen continues to deform, which is called "yield". The stress at the time when the yield phenomenon occurs, that is, the stress when the plastic deformation begins to occur, is called the yield point, which is represented by the symbol s and is in MPa.

5.Tensile strength: The maximum stress that a metal can withstand before breaking during a tensile test, represented by the symbol B, in MPa.

6.Plasticity: The ability of a metal material to be permanently deformed under the action of an external force (a deformation that cannot be restored to its original state after removing the external force), but not to be destroyed.

7.Elongation.

In the tensile test of metal, after the specimen is pulled off, the percentage of the length of the gauge part increased to the original gauge length is called the elongation. It is denoted by the symbol δ, %. The elongation reflects the plasticity of the material, and the greater the elongation, the greater the plasticity of the material.

8.Toughness: The ability of a metal material to resist shock loads, known as toughness, is usually measured in terms of work of impact absorption or the value of impact toughness.

9.Impact absorption work: The work absorbed by the specimen when it breaks under the action of impact load.

With the symbol a?k denotes that the unit is j. 10.

Hardness: The hardness of a metal material, generally refers to the ability of a local area of the surface of the material to resist deformation or cracking. According to the test method and the scope of application, it can be divided into Brinell hardness.

and Rockwell hardness. Brinell hardness is represented by the symbol HB: Rockwell hardness is represented by the symbol HRA, HRB or HRC.

The mechanical properties of metals mainly include: strength, toughness, plasticity, fatigue strength, elongation at break and impact toughness.

1. Physical properties: density, melting point, thermal expansion, thermal conductivity, electrical conductivity and magnetism, etc. Due to the different uses of machine parts, their physical properties are also different.

2. Chemical properties: mainly refers to the ability to resist the erosion of various media, such as acid resistance, alkalinity, oxidation resistance, etc., at room temperature or high temperature.

3. Process performance: It is a comprehensive reflection of the physical, chemical and mechanical properties of metal materials in the processing process, and refers to the performance of cold and hot processing. According to the different process methods, it can be divided into castability, malleability, welding and machinability.

Tensile, yield, elongation, section shrinkage, impact energy, these properties can basically meet the mechanical application of a metal, if it involves fatigue and fracture, then it is necessary to refine the metal pants Qingwax grains, which belong to the microscopic level.

The properties of metal materials can generally be divided into two categories: use performance and process performance. The use performance refers to the properties that the material must have under working conditions, including physical, chemical and mechanical properties.

Physical properties refer to the properties of metal materials under various physical conditions. Including: density, melting point, thermal conductivity, electrical conductivity, thermal expansion and magnetism, etc.

Chemical properties refer to the ability of a metal to resist chemical attack by an external medium at room or high temperatures. Includes: Corrosion resistance and oxidation resistance.

The mechanical properties of metals are the most important properties of metal materials, and the so-called mechanical properties of metals refer to the properties of metals that are related to elastic and inelastic reactions or involve stress-strain relations under mechanical action. It includes: strength, plasticity, hardness, toughness and fatigue differential strength.

The process performance of metal materials directly affects the process quality of parts after processing, and is one of the factors that must be considered when selecting materials and formulating parts processing routes. It includes casting performance, pressure processing performance, slip welding performance, cutting performance and heat treatment performance.

1. Density. The mass of a substance per unit volume, denoted by symbols. Generally, metals with less density are called light metals, and vice versa are called heavy metals. The concept of density can be used to solve a series of practical problems, such as calculating the mass of the blank and identifying metal materials.

2. Melting point. The melting temperature at which pure metals and alloys are transformed from solid to liquid states. Pure metals have a fixed melting point, and the melting point of an alloy depends on its composition.

For example, Hong Kong-style iron-carbon alloys have different carbon content and different melting points. Melting point is an important parameter for smelting, casting and welding of metals and alloys.

3. Electrical conductivity.

It is the ability of a metal material to conduct electric current. The index that measures the electrical conductivity of metal materials is resistivity, the smaller the resistivity, the smaller the resistance of the metal, and the better the conductivity. Among the metals, silver has the best electrical conductivity, followed by copper and aluminum.

4. Thermal conductivity.

It is the ability of metal materials to conduct heat. The magnitude of thermal conductivity is usually measured in terms of thermal conductivity, and the symbol of thermal conductivity is , the greater the thermal conductivity, the better the thermal conductivity of the metal. Silver has the best thermal conductivity, followed by copper and aluminum.

5. Thermal expansion.

It is the property of metal materials that expands and contracts with changes in temperature. Generally speaking, metals expand and increase in volume when heated, and shrink and decrease when cooled. The index of thermal expansion is generally the linear expansion coefficient, which refers to the ratio of the length of the metal to the original length for every 1 increase in metal temperature.

The coefficient of linear expansion of a metal is not a fixed value, and as the temperature increases, its value increases accordingly. In the welding process, the uneven thermal expansion of the welded workpiece due to uneven heating will lead to deformation and welding stress of the weldment.

The physical performance of commonly used metal materials is mainly manifested in the following aspects:

1. Density: The mass of a substance per unit volume is called the density of the substance. The density of a metal is the mass of the metal per unit volume;

2. Melting point: The temperature at which pure metals and alloys transition from solid to liquid is called melting point. Pure metals all have a fixed melting point. The melting point of an alloy is determined by its composition;

3. Thermal conductivity: The performance of metal materials to conduct heat is called thermal conductivity. The magnitude of thermal conductivity is usually measured in terms of thermal conductivity.

The symbol of thermal conductivity is in, the greater the thermal conductivity, the better the thermal conductivity of the metal. Silver has the best thermal conductivity, followed by copper and aluminum. The thermal conductivity of alloys is worse than that of pure metals.

The symbolic representation of each index of metal mechanical properties is:

S Yield Strength, B Tensile Strength, δ Elongation, Section Shrinkage, AK Impact Toughness, H.R. Rockwell Hardness, HV Vickers Hardness, HBS Brinell Hardness.

Mechanical properties of metals: refers to the properties of metals that are related to elastic and inelastic reactions or involve the relationship between force and strain under the action of force. It mainly introduces the mechanical properties of metals under static load, impact load and environmental medium, the fracture and fracture toughness of metals, the fatigue, wear, high temperature properties, process properties and bending tests of metals.