In the actual production and processing of motors , deformation or cracks in the motor base or end cover are frequently encountered. Cracks mostly occur in castings, especially in drilled areas, where the probability of this problem is much higher. Another relatively concentrated characteristic is that the problem is also more concentrated in cold climates. Ms. Can will briefly discuss with you why these problems occur from two aspects: the analysis of the causes of casting deformation and aging treatment.
1. Summary of the causes of casting deformation
Deformation of castings generally refers to overall deformation. Common deformations include warping, twisting, and bending. The main causes of deformation include: ● Inadequate structural design of the casting itself, leading to deformation due to solidification shrinkage. ● Inappropriate matching of the casting mold structure. ● During demolding, excessively high casting temperature, poor demolding structure, impact during demolding, and uneven stress can all cause deformation. ● Sticking to the mold, but not to the point of being unable to be demolded, can also cause deformation during demolding. ● Inadequate arrangement of the gating and venting system, causing deformation during shrinkage.
2. Analysis of the Time-Effect Principle
Aging treatment is a process in which materials are stored at room temperature or a relatively high temperature for an extended period of time to achieve aging. Aging treatment refers to a heat treatment process in which metal or alloy workpieces, after solution treatment, high-temperature quenching, or a certain degree of cold working deformation, are placed at a relatively high temperature or room temperature to maintain their shape, size, and properties over time.
Generally speaking, aging increases hardness and strength, while decreasing plasticity, toughness, and internal stress. High-carbon steels immediately gain high hardness after quenching, but their plasticity becomes very low. In contrast, aluminum alloys do not immediately reach their peak strength or hardness after quenching; their plasticity not only does not decrease but actually increases.
After being left at room temperature for a considerable period of time, the strength and hardness of this quenched alloy significantly increase, while its plasticity decreases. This phenomenon, where the strength and hardness of the quenched alloy change significantly over time, is called aging. Aging performed at room temperature is called natural aging, while aging performed at a specific temperature is called artificial aging.
To achieve the desired strengthening effect, strict control of heating temperature and holding time is essential for artificial aging treatment. In production, segmented aging is sometimes employed, involving initial holding at room temperature or slightly above room temperature for a period, followed by holding at an even higher temperature for a further period. This method yields better results.
3. What is solution treatment?
Solution treatment is a heat treatment process in which an alloy is heated to a high-temperature single-phase region and held at a constant temperature to allow the excess phase to fully dissolve into the solid solution, followed by rapid cooling to obtain a supersaturated solid solution.
Because the process is similar to quenching, it is also called "solution quenching." It is suitable for alloys with a solid solution matrix and whose solubility changes significantly with temperature. The alloy is first heated to a suitable temperature above the solubility curve and below the solidus line, and held for a certain time to allow the second phase to dissolve into the solid solution. Then, it is rapidly cooled in water or another medium to suppress the re-precipitation of the second phase, resulting in a supersaturated solid solution at room temperature or a solid solution phase that typically only exists at high temperatures. Because it is thermodynamically metastable, it will undergo desolvation or other transformations under appropriate temperature or stress conditions. It is generally considered a preparatory heat treatment, its purpose being to prepare optimal conditions for subsequent heat treatment.
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