Heat treatment of workpieces such as thin-walled complex components and high-carbon alloy steel has long been plagued by deformation and cracking issues. The core crux lies in the imbalance between stress accumulation and release throughout the heating, heat preservation and cooling processes. The successful R&D of the new-generation multi-stage stress relief pit-type vacuum tempering furnace, equipped with a vertical heating structure and a precise stress control system, has achieved micron-level control over workpiece deformation and reduced the cracking rate by more than 95%.
The vertical layout of the pit furnace enables uniform heat radiation, which meets the charging requirements of thin-walled complex components. Combined with the vacuum environment that isolates oxidation interference, it further ensures the surface quality of workpieces and the stability of stress relief.
Compared with the limitation of single-temperature control in traditional tempering furnaces, the core advantages of the multi-stage stress relief pit-type vacuum tempering furnace lie in its customized multi-stage stress relief procedures and vertical uniform heating structure. According to the material and structural characteristics of thin-walled complex components, the equipment can preset a four-stage process: preheating - low-temperature tempering - medium-temperature holding - low-temperature aging. In the preheating stage, the temperature is slowly raised to below Ac1 to accurately release the residual stress from casting or forging. In the low-temperature tempering stage, the instantaneous stress generated by martensitic transformation after quenching is quickly relieved. In the medium-temperature holding stage, the residual stress from structural transformation is thoroughly eliminated. Finally, in the low-temperature aging stage, the dimensional accuracy of workpieces is locked in.
Meanwhile, the furnace is equipped with customized flexible suspension fixtures, which avoid clamping stress on thin-walled components and reduce deformation inducements from the source. Cooperating with the pit-type vertical heating design, the fixtures ensure uniform temperature distribution across all parts of the workpiece.
This pit-type vacuum tempering furnace has been maturely applied in the production of high-end products such as thin-walled casings of aero-engines and cavities of precision injection molds. Field test data shows that the workpiece flatness error has been reduced from 0.15mm/m in traditional processes to 0.02mm/m, and the delayed cracking rate has plummeted from 8% to 0.4%. This technological breakthrough not only solves the heat treatment pain points of high-precision complex structural workpieces, but also facilitates the localized high-precision processing of core components in aerospace, precision manufacturing and other fields.
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