A surface hardening heat treatment process for the intermediate shaft of the boom of engineering machinery

Abstract

The invention relates to a surface hardening heat treatment process of a construction mechanical movable arm intermediate shaft. The surface hardening heat treatment process comprises the following steps of (1) cleaning a fine-machined movable arm intermediate shaft; (2) loading the cleaned fine-machined movable arm intermediate shaft into a high-frequency quenching machine; (3) setting parameters of the high-frequency quenching machine as follows: the frequency is 25-30KHz, power is 250Kw, the heating time is 2-2.5 seconds, the cooling condition is a quenching liquid of which the concentration is 5% -10% and the temperature is 40-60 DEG C; adjusting the coupling distance between induction coils, and carrying out high-frequency quenching on the movable arm intermediate shaft; and (4) carrying out tempering treatment on the high-frequency-quenched movable arm intermediate shaft. Because of the rapid heating in the treatment process, the structural transformation occurs after the material is locally heated, martensite transformation microstructure is formed under the action of subsequent cooling medium, at the same time, since the growth of grains is suppressed by an instant heating to ensure that the fine grain microstructures are generated on the surface of the movable arm intermediate shaft, a surface-hardened layer can be precisely controlled and improved, and thus the movable arm intermediate shaft has the advantages of high hardness, high wear resistance and fatigue resistance.

Description

technical field [0001] The invention relates to a process for performing surface hardening heat treatment on an intermediate shaft of a boom of an engineering machine (such as an excavator and a loader), and belongs to the technical field of heat treatment. Background technique [0002] High-frequency heat treatment technology is to use the alternating magnetic field generated by the alternating current in the induction coil to cause the workpiece located in the magnetic field to generate an induced potential of the same frequency, thereby generating an eddy current in the workpiece to a very large value, and the accompanying magnetic hysteresis will cause thermal effects. . The thermal effect dominated by eddy current can heat the workpiece to a very high temperature (200-1000°C / s), and the eddy current decays exponentially from the surface to the center in the workpiece to produce a surface effect and form a certain effective penetration depth. Due to the short heating ti...

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Problems solved by technology

[0004] However, the production technology of the high-frequency processing induction coil is relatively high, and it needs to be completed by professionals. The operation technology is also very important, otherwise it will cause local overheating, over-burning, melting, uneven hardening layer and abnormal structure of the workpiece.

[0005] The intermediate shaft of the boom of construction machinery is an important part. Usually, the overall heat treatment method of 45# steel is adopted, and the heat treatment process of Ac3+50°C heating and quenching+180°C low temperature tempering is used. Due to the long heating time, the workpiece may cause oxidation and decarburization, coarse grains and During the quenching and cooling process, problems such as soft spots, cracking, and large deformation occur, and the corresponding energy consumption and environmental pollution are also relatively large in the process of process implementation, so it is difficult to improve the degree of automation

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