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-Proverbs EB-160 heavy-duty roadheader used in important mechanisms, the design materials are 20Ci2Ni4A. This material is a high-hardenability carburizing steel, the process is complex, heat treatment is difficult, and the first application in Jiamusi coal mill There is very little information available. In this regard, a small batch trial production was carried out, and the heat treatment process of the material gear was tested to find out the reasonable heat treatment process of the material gear and the heat treatment deformation law.
1 Gear sample trial production process and analysis 650C, 5h high temperature tempering, after tempering, several gears are selected for machining, and the inner hole reserves machining allowance.
The furnace is cold. The depth of the layer is 1.2 and the carbide level meets the requirements. At this time, the surface layer is martensite and a large amount of retained austenite. This kind of structure cannot be directly reheated and quenched, otherwise it is easy to recover the coarse austenite grains formed during carburization, that is, to generate a secondary texture.
Therefore, before quenching and heating, high temperature tempering is required to decompose martensite and retained austenite into tempered sorbite to reduce the content of carbon and chromium in the matrix. In this reheating and quenching, since the content of elements such as carbon and chromium which are melted in the austenite is reduced, not only the amount of retained austenite is reduced but also the martensite is fine after quenching. However, after the carburizing, the hardness of the measured gear reaches HRC40, so a normalizing process is added after carburizing, and then high temperature tempering (650C, 6h) is performed. At this time, the original process route is to go to the inner hole carburizing layer, and then quenching. , then pull the inner spline. However, the steel Ac3 is 780C after quenching at 810C. Even if the car goes to the carburized layer, the inner hole can be hardened. Try one piece, when pulling the inner spline, it really does not move because the hardness is too high. In view of this situation, the process route is changed to insert, double and pull splines before quenching.
The narrow range of degrees is conducive to one quenching, which can ensure that the core is completely quenched and the quenching temperature of the carburized layer is not too high. After quenching, low temperature tempering, surface hardness average HRC60 or so, the core hard through the above test, determined the heat treatment process of 20Cr2Ni4A steel gear, see.
In order to ensure the correct machining allowance of the inner hole, the key dimensions of some gears before and after carburizing and quenching and tempering are tracked. The measurement is shown in Table 1. Table 1 Heat Treatment Deformation Measurement Name Item Xi Bu Diameter Inner Normal Normal Line From the above situation, the outer diameter, the common normal line, and the width of the key width are not changed much after heat treatment, and the inner hole and the key are changed. Deep dimensional changes are large, after quenching (down to page 15) fund project: Eighty-five 'national key scientific and technological projects (85 N total two (2) roller shaft fatigue life calculation is as follows: N total = measuring point position According to the test results, the linearity and repeatability of the test data are good. For this reason, the experimental data is reliable. After the fatigue safety life estimation of the main components, it can be seen that the structural design of the entire dredging machine is reasonable. The strength requirements of the main components are guaranteed, and the service life of the main components exceeds the design requirements. Therefore, the SLQ-40 amphibious dredging machine can meet the design requirements.
(Continued from page 6) The size of the inner hole and the key depth is increased after the fire, which is the result of the combined action of thermal stress and tissue stress. The result of the above tracking measurement can be used as a reserved margin for the inner hole during machining, which avoids the inaccuracy of the reserved amount during processing.
Table 2: After 500h gear wear, common method, long line wear, 500h, name, number of teeth, cross-counting number, male/normal length, common normal length, 2 test results, after wear, 500h, wear condition measurement, see Table 2. It can be seen from Table 2. After 500 hours of use, the partial gear common normal length has not even exceeded its tolerance range. The gears used in each part have stood the test. At the same time, the test results of the reducer bench are also satisfactory.
3 Conclusion Through the trial production of gear samples, the heat treatment process and process arrangement of the wheel were determined. Practice has proved that the heat treatment process and process arrangement of the gear of 20Cr2Ni4A material is reasonable.
―160 boring machine prototype passed the underground industrial test, Ministry