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The laser heat treatment can make the gear obtain a phase change hardened layer with higher surface hardness and uniform hardness distribution than the conventional heat treatment, and has the characteristics of small deformation of the workpiece, clean working environment, and no need for finishing processes such as grinding. After the laser phase change, a certain thickness of the treatment layer is formed on the surface of the material, which can improve the mechanical properties, metallurgical properties and physical properties of the surface of the gear material, thereby improving the wear resistance, corrosion resistance, impact resistance and fatigue resistance. This process can meet a variety of different application requirements, and can easily achieve selective treatment of local surfaces. At the same time, the laser quenching of the tooth surface solves the deformation problem existing in the conventional gear carburizing and quenching process, which can save the subsequent grinding process and reduce the production cost. The principle of laser phase transformation strengthening treatment of grain gears with uniform distribution of macroscopic sections after toughness testing is laser quenching is to irradiate the surface of the workpiece with high energy density laser beam, so that it needs the hardness part to absorb light energy instantaneously-thermal energy When the temperature rises sharply above the critical point, the structure rapidly changes to austenite, and the core is still the original tempered sorbite structure, which is rapidly cooled to produce martensite.
The tempering phase change strengthening treatment of the electric tape two enamel due to rapid cooling, so that the austenite grains can not grow up, and reach the level of precision, the resulting martensite structure is very small, generally under the electron microscope to distinguish the figure, thus The distortion strength of the material is greatly improved.
The quenching has a higher defect density, and the retained austenite also has a very high dislocation density, which makes the metal have a distortion strength. Therefore, the method can effectively improve the wear resistance and contact fatigue strength of the gear, and the core structure still has a certain strength and toughness.
Figure shows the rise of the structure after laser quenching. The effect of the laser phase transformation strengthening treatment of the gear is the heating and cooling direction of the working layer. The heating and cooling directions of the working layer are the fastest, and the cooling rate of the core is gradually increased. When it is lowered, a gradient distribution in which the hardness value of the surface and the inside is lowered is obtained. The heating direction of the gear laser phase transformation is the same, but the surface temperature is high. The heating time is generally about right and left.
Surface austenitization is done instantaneously, resulting in a higher carbon concentration in the surface austenite. The direction of laser quenching and cooling is opposite to that of conventional heat treatment. The temperature in the inner layer is low, but the cooling rate is the fastest. However, the outer temperature is high, but the cooling rate is the slowest. Although the inner carbon concentration is slightly lower, the distortion enhancement and dispersion strengthening are stronger. Thus, in the hardened layer, an almost constant hardening value distribution is formed. Therefore, the gear can avoid the phenomenon that the wear of the gear is accelerated once the surface is worn after the conventional heat treatment.
The tissue distribution laser phase transformation strengthens the austenite structure rapidly and the martensite transformation occurs on the metal surface. In this heating environment, the austenite formed, whether it is the surface layer or the inner layer, does not grow for a long time, and the dispersed austenite grains form a dispersed martensite phase.
While its structure has lattice solid solution strengthening, it also has the effect of dispersion strengthening. Moreover, the martensite lattice formed under chilling conditions is mainly the fatigue strength required for a small amount of material analysis and pretreatment gear material after laser quenching of the core structure.
There is roughly the following relationship between fatigue strength and tooth surface hardness. The fatigue strength of a tooth surface hardness and a material constant are obvious. The higher the surface hardness, the higher the fatigue strength. Low carbon steel has low hardness after quenching because of its low carbon content. Therefore, the material of laser phase change strengthening gear is generally made of medium carbon steel or alloy medium carbon steel, such as low speed and low load available steel, for medium and high speed.
The original organization plant changes the resistivity caused by the temperature change, after being converted and amplified by the line amplifier, and then judged by the discriminator. After reaching a certain threshold value signal, the actuator is driven to cut off the circuit, and finally achieves temperature regulation and control.
Generally, the thermistors are divided into four types according to the structure: rod type, wafer type, gasket and resistance beads.
The thermocouple thermocouple thermocouple can convert the temperature change into a small potential difference, and through the corresponding conversion, signal amplification, identification and driving, to achieve the function of temperature regulation and temperature control.
The thermocouple temperature control principle is somewhat similar to the thermistor temperature control principle, but the general temperature control accuracy is higher than the latter. Two thermocouples of different materials are welded to one end and the other end to the input circuit of the corresponding control circuit.
Usually we refer to the spot or short end as the hot end or the working end. When it is used, it is placed at the temperature measurement or temperature control, and the temperature is measured. The other end is called the cold end or the free end. When the temperature is a few, when a few hours, the electromotive force will be generated between the two cold end of the thermocouple, generally in the millivolt level, through the conversion, signal amplification, identification and driving to achieve the function of temperature regulation and temperature control.
At the same time, when the thermocouple is used for temperature measurement, it is necessary to compensate and correct the cold junction temperature, that is, the zero point is adjusted. This is because the temperature reflected by the thermocouple is the temperature difference between the cold end and the hot end, not the actual temperature of the measured object. Temperature fuses and thermal circuit breakers Temperature fuses are temperature-sensitive components made of temperature-sensitive materials. They are widely used in the temperature protection of various electric heating appliances, such as rice cookers and electric kettles. Usually, they are connected in series in the main circuit of the heating element of the electric heating appliance, and are placed on or near the heating element. When the temperature exceeds the set limit, the temperature fuse is blown and the heating appliance is de-energized. The thermal fuses provided in general electric heating appliances are classified into replaceable temperature fuses and non-displaceable temperature fuses. The thermal circuit breaker is usually a responsive thermal protector. Its structure is generally composed of temperature sensing elements, springs, action mechanisms, contacts and housings. The sensitivity and accuracy are high, and it is often used in temperature protection. In household appliances.
Temperature fuses and thermal circuit breakers are not only widely used in household electric heating appliances, but also in electric power tools, especially portable power tools, as a means of improper use protection. In short, in the household electric heating appliance, relying on the heating principle of the electric heating element, the temperature regulation and temperature limiting means of the temperature control component are used to achieve the thermal efficiency in the normal use of the electric heating appliance, fully embodying the application of the automatic controller in the electric heating appliance.
On the page of the above page, the microstructure of the laser quenched by the heat treatment after quenching and tempering can ensure the fatigue strength of the matrix after heat treatment, and ensure the accuracy and hardness of the gear after laser treatment. Low carbon steel is generally used for carburizing ten surface quenching, and its bending fatigue strength is low and deformed. For small-modulus high-speed gears working in more important occasions in the power tool industry, material pretreatment is also very important. The best original structure of the laser phase transformation strengthening treatment of the gear is the tempered structure. This not only ensures the toughness and strength of the gear core. It also makes the structure uniform and the grain refinement, preventing microcracks during quenching. The usual manufacturing processes are gear blanking, forging, normalizing, roughing, quenching, finishing, and laser processing.