Heat Treatment Of Food Machinery Knives

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1.The development of heat treatment of food machinery knives

With the continuous development of the processing technology of metal cutting machine tools, many advanced processing technologies have been introduced in blade processing, which has effectively improved the automation degree of blade processing, and greatly improved the production efficiency while reducing the production cost of the blade. . Sintered tungsten-containing cemented carbide materials and high-speed steel materials are widely used in the blade machining process, because these two materials are not only inexpensive, but also have the advantages of high strength, high wear resistance and simple processing. In the process of finishing and semi-finishing steel parts, materials such as titanium carbide and titanium carbonitride have become the first choice. In addition, hard fine-grained alloys are used to replace high-speed steel, which can effectively improve the production efficiency of blades. The ceramic coating can also be obtained by chemical vapor deposition, which can effectively improve the cutting performance of the insert. In the process of unfolding and quenching, the application of cemented carbide is also very ideal.

In fact, the effect of inlaying the artificial hard material polycrystalline cubic boron carbide on the alloy blade is very good. Generally, it can be applied to the processing of nickel-chromium steel with a hardness of HRC68. In this way, the blade obtained The cutting speed can reach 130m/min. For non-metallic materials with strong abrasiveness, polycrystalline diamond is generally the main one. In the process of adding L to the blade, in order to maximize the increase of oxide ceramics, it is necessary to use silicon carbide fibers. This processing technology is mainly used in nickel alloys, heat-treated steel materials and carburizing. With the continuous development of science and technology, silicon nitride ceramics have also begun to be widely used in blade processing, because its cutting speed has basically reached 1000m/min, and its anti-diffusion and wear resistance are extremely high.

2. Heat treatment process of mechanical blade

(1) Annealing. Generally, the steel plates provided by steel mills are in an annealed state, mainly for the convenience of direct blanking and quenching treatment during blade processing. However, if the steel plate needs to be further forged and rolled after entering the factory, it must be in an annealed state, so that the obtained spheroidized structure is the most ideal, because after quenching and tempering, the performance of the steel plate will be at its best. in good condition. – Generally, there are many annealing processes after the spheroidization is completed, but the most widely used isothermal spheroidization annealing method. The so-called isothermal spheroidizing annealing is actually. The steel plate is heated to between 40 and 60 degrees. After heating, it needs to be kept for 4 hours. After 4 hours, it is cooled to 720° and then kept again. When the heating furnace is cooled to 600° , the incubator needs to be opened for air cooling.

In fact, the forging and rolling process can directly determine the improvement of the network structure or the original band shape of the high-speed steel and alloy steel materials, but the improvement effect after heat treatment is not obvious, and when the annealing temperature is too high, there will be a certain – certain alleviate the phenomenon. However, generally, the distribution of secondary carbides inside will change greatly after two annealings. In the alloy steel after annealing, except for a small amount of large-grained carbides, the rest can be changed due to the annealing process. effective control. In addition, the holding time after annealing should be reasonably controlled, and it should not be too long because a long time will lead to segregation of carbides, resulting in a substantial decrease in the hardness of the steel plate after quenching and annealing, thus affecting wear resistance. .

(2) Quenching. For mechanical blades, there are many quenching methods, which can be subdivided into dozens of types according to the furnace type, heating method, heating temperature and heating medium of the heating furnace during quenching. But at this stage, there are also many choices of equipment in the process of blade processing, such as: vacuum quenching furnace, mesh belt furnace and sealed box furnace.

The specific process construction sequence is: preheating, heating temperature, heating time, quenching medium and straightening and other processes.

☆Generally speaking, in the process of tempering, it is necessary to select an appropriate process according to the specific material of the blade edge steel. For low-alloy steel and medium-alloy steel, the temperature after quenching can basically reach 180~220°, and two tempering processes are required, and the average tempering time is about 2~3 hours. The best; Cr12MoV steel generally needs to be tempered in a furnace with a temperature in the range of 220~240°; while the tempering temperature of high-speed steel and base steel is relatively high at 500~580°, and it needs to be tempered 3 times. , The time of each tempering is about 2~3 hours.

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