Main forms of building metal corrosion①Uniform corrosion. Corrosion of the metal surface makes the cross section evenly thin. Therefore, the average annual thickness loss value is commonly used as an indicator of corrosion performance (corrosion rate). Steel generally corrodes uniformly in the atmosphere.②Hole corrosion. The corrosion of the metal points and forms deep pits. The occurrence of pitting is related to the nature of metal and its medium. Cavitation is prone to occur in media containing chlorine salts. Large hole depth is commonly used as the evaluation index. The corrosion of pipeline should be considered.③Galvanic corrosion. Corrosion at the contact of different metals due to different electrical potentials.④Gap corrosion. Local corrosion of metal surfaces in gaps or other hidden areas often occurs due to the difference in the composition and concentration of the medium between different parts.⑤Stress corrosion. Under the combined action of corrosive medium and high tensile stress, the metal surface corrodes and expands inward into micro-cracks, often leading to sudden breakage. High strength steel bars (steel wires) in concrete can cause such damage.

Time：2023-06-01

Plasticity refers to the ability of metal materials to deform (plastic deformation) without being destroyed under the action of external loads. When the metal material is stretched, the length and cross-sectional area are changed, so the plasticity of the metal can be measured by the elongation of the length (elongation) and the contraction of the section (shrinkage of the section).The larger the elongation and section shrinkage of the metal material, the better the plasticity of the material, that is, the material can withstand large plastic deformation without damage. Generally, metal materials with an elongation greater than 5% are called plastic materials (such as low carbon steel, etc.), and metal materials with an elongation less than 5% are called brittle materials (such as gray cast iron, etc.). Good plastic material, it can produce plastic deformation in a large macro range, and at the same time make the metal material due to plastic deformation and strengthen, so as to improve the strength of the material, to ensure the safe use of parts. In addition, the plastic material can be smoothly processed by some forming processes, such as stamping, cold bending, cold drawing, straightening and so on. Therefore, when choosing metal materials for mechanical parts, certain plasticity indicators must be met.

Time：2023-06-01

Many mechanical parts and engineering components are subjected to alternating loads. Under the action of alternating load, although the stress level is lower than the yield limit of the material, but after a long time of repeated stress cycle, sudden brittle fracture will occur, this phenomenon is called fatigue of metal materials.The characteristics of fatigue fracture of metal materials:①The load stress is alternating;② the operation time of the load is longer;③ The fracture is instantaneous;④Whether it is plastic material or brittle material, it is brittle in the fatigue fracture zone.Therefore, fatigue fracture is a common and dangerous fracture form in engineering.

Time：2023-06-01

In the design and use of machine tools and tools, it is necessary to apply the cutting principles of cutting force, cutting temperature and cutting tool performance data. For example, when determining the basic parameters such as high torque and rigidity of the spindle of the machine tool, the data of the cutting force should be applied; In the development of new materials with high cutting performance, it is necessary to master the law of tool wear and damage; When analyzing the influence of thermal deformation on machining precision, the cutting temperature and its distribution should be studied. In the automatic production line and digital control machine tool, in order to make the machine tool can work normally and stably, and even realize unmanned operation, it is necessary to apply the research results on chip formation and control, and realize the automatic compensation of tool wear and automatic alarm of tool damage in the processing. To this end, various countries have developed a wide variety of online detection tool wear and damage sensors, most of which use cutting force or torque, cutting temperature, tool wear as sensing signals. In addition, in order to make full use of machine tools, improve machining economy and develop computer-aided manufacturing (CAM), it is often necessary to apply optimization data such as cutting conditions, tool geometry and tool life. Therefore, the principle of metal cutting is increasingly widely used in production, countries have accumulated a large number of cutting data through cutting tests or field collection, and mathematical models are used to describe the relationship between tool life, cutting force, power and machining surface roughness equal to cutting conditions, and then stored in computers to establish metal cutting databases or compiled into cutting data manuals, for users check.

Time：2023-06-01

Cutting ForceWhen cutting the front and back of the tool are subjected to normal force and friction, these forces constitute the resultant force F, when turning the outer circle, generally this cutting force F is broken down into three vertical components (Figure 3[cutting force and component force]) : tangential force F - it is perpendicular to the cutting speed direction of the tool base surface, often called the main cutting force; Radial force F -- in the plane parallel to the base surface, perpendicular to the feed direction, also known as thrust; Axial force F -- in the plane parallel to the base plane, parallel to the feed direction, also known as the feed force. Under normal circumstances,F is large,F and F are small, due to the geometric parameters of the tool grinding quality and wear conditions are different and the change of cutting conditions,F,F to F ratio changes in a large range.The actual cutting force in the cutting process can be measured by the dynamometer. There are many kinds of dynamometer, the more commonly used are resistance wire and piezoelectric crystal dynamometer. After calibration, the dynamometer can measure the size of each component force in the cutting process.Cutting HeatWhen cutting metal, the work made by the shear deformation of the chip and the work made by the friction in front of the tool and behind the tool are converted into heat, which is called cutting heat. When the cutting fluid is used, the cutting heat on the tool, workpiece and chips is mainly carried away by the cutting fluid. When the cutting fluid is not used, the cutting heat is mainly taken away or transmitted from the chips, workpieces and tools, of which the heat taken away by the chips is large, and the heat transmitted to the tool is small, but the temperature in front and behind affects the cutting process and the wear of the tool, so it is very necessary to understand the changing law of the cutting temperature.Cutting TemperatureThe temperature of the cutting area is different throughout the cutting process, forming a temperature field of chip and workpiece temperature distribution, this temperature field affects chip deformation, the size of the chip tumor, the quality of the processing surface, processing accuracy and tool wear, but also affects the improvement of cutting speed.Generally speaking, the metal in the cutting zone becomes chips after shear deformation, and then further develops severe friction with the front of the tool, so the high point of the temperature distribution in the temperature field is not at the edge of the positive pressure, but at a distance from the edge in the front. The temperature distribution in the cutting zone must be measured by artificial thermocouple method or infrared temperature measurement method. The temperature measured by the natural thermocouple method is only the average temperature in the cutting zone.Tool WearThe wear during cutting is the comprehensive result of the physical and chemical action caused by cutting heat and mechanical friction. The tool wear is characterized by the wear bands, notches and falling edges on the back of the tool, the crescents on the front, and the oxidation pits and grooves on the back of the tool. When these wear extend to a certain extent, it will cause the tool to fail and cannot be continued. The factors of the gradual wear of the tool usually include abrasive wear, adhesive wear, diffusion wear, oxidation wear, thermal cracking wear and plastic deformation. Under different cutting conditions, especially at different cutting speeds, the tool is subjected to one or more of the above wear mechanisms. For example, at lower cutting speeds, tools are generally damaged by abrasive wear or adhesive wear; At higher speeds, diffusion wear, oxidation wear and plastic deformation are easy to occur.Tool LifeThe cutting time passed before the cutting tool life criterion is called the tool life (once called tool durability), the tool life criterion generally adopts a predetermined value of the tool wear, and can also be used as a criterion for the appearance of a phenomenon, such as vibration intensification, machining surface roughness deterioration, poor chip breaking and falling edge. After reaching the tool life, the tool should be reground, transposed or discarded. The sum of each tool life before the tool is discarded is called the total tool life.In production, the tool life and working hour quota are often determined according to the principle of low production cost or high productivity according to the processing conditions.MachinabilityRefers to the degree of ease of machining parts into qualified products. According to the specific processing objects and requirements, the length of tool life, the quality of the machining surface, the level of metal removal rate, the size of the cutting power and the difficulty of chip breaking can be used as criteria. In production and experimental research, it is often used as an indicator of the machinability of a material, and its meaning is: when the tool life is minutes, the cutting speed allowed to cut the material. The higher it is, the better the process ability, generally 60, 30, 20 or 10 minutes.Machining Surface QualityUsually includes surface roughness work hardening residual stress, surface cracks and metallographic microstructure changes. There are many factors that affect the quality of the machining surface, such as the feed amount of the tool tip arc radius and chip nodulation are the main factors that affect the surface roughness. The blunt edge radius, wear and cutting conditions are the main factors affecting work hardening and residual stress. Therefore, the machining surface quality is often improved by changing the geometry of the tool and selecting reasonable cutting conditions in production.Cutting VibrationDuring the cutting process, there are often types of mechanical vibrations such as free vibration, vibration or self-excited vibration (flutter) between the tool and the workpiece. Free vibration is caused by some sudden impact on the parts of the machine tool, and it will gradually decay. Vibration is caused by the continuous alternating interference force inside or outside the machine tool (such as unbalanced machine tool moving parts, intermittent cutting, etc.), and its impact on the cutting depends on the size and frequency of the interference force. Self-excited vibration is caused by the sudden interference force between the tool and the workpiece (such as hard points encountered in cutting) and the initial vibration, so that the front Angle of the tool, the back Angle and the cutting speed are changed, and the vibration mode coupling is generated, and the energy of the periodic action is obtained from the energy of the steady state action to promote and maintain the vibration. Usually, according to the cutting conditions may produce a variety of primary self-excited vibration, so that the vibration marks left on the machining surface will produce a more common regenerative self-excited vibration. The above vibrations usually affect the surface quality of the tool, reduce the life of the machine tool and the tool, reduce productivity, and cause noise, which is extremely harmful and must be eliminated or reduced.Chip ControlRefers to controlling the shape and length of chips. By controlling the crimp radius and discharge direction of the chips, the chips hit the workpiece or the tool, and the crimp radius of the chips is increased, and the stress in the chips is gradually increased, until the crimp radius of the broken chips can be controlled by changing the thickness of the chips, grinding the chip-rolling groove or the chip-breaking table in front of the tool. The discharge direction is mainly controlled by selecting reasonable main declination Angle and edge inclination Angle. Modern people have been able to use two or three digit coding to indicate the shape of various chips, and it is usually considered that the short arc chip is a reasonable chip shape.Cutting FluidAlso known as cooling lubricant, it is used to reduce friction and reduce cutting temperature during cutting to improve tool life, processing quality and production efficiency. Commonly used cutting fluids include cutting oil, emulsion and chemical cutting fluids.

Time：2023-06-01

Non-ferrous metals are essential basic materials and important strategic materials for the national economy, People's Daily life, national defense industry, science and technology development. Agricultural modernization, industrial modernization, national defense and science and technology modernization are inseparable from non-ferrous metals. For example, aircraft, missiles, rockets, satellites, nuclear submarines and other weapons, as well as atomic energy, television, communications, radar, electronic computers and other technologies required components or components are mostly made of light metals and rare metals in non-ferrous metals; In addition, without nickel, cobalt, tungsten, molybdenum, vanadium, niobium and other non-ferrous metals, there is no alloy steel production. Non-ferrous metals in some uses (such as the power industry, etc.), the use is also considerable. Many countries in the world, especially industrially developed countries, are competing to develop non-ferrous metal industry and increase the strategic reserves of non-ferrous metals.Today, non-ferrous metals have become an important material basis for determining the development of a country's economy, science and technology, and national defense construction, and are key strategic resources for enhancing the country's comprehensive strength and safeguarding the country. As a large non-ferrous metal production country, China has made great progress in the field of non-ferrous metal research, especially in the development and utilization of complex low-grade non-ferrous metal resources.

Time：2023-06-01