Die-cast product rigidity evaluation method and die-cast product

Abstract

Provided are a die-cast product rigidity evaluation method and a die-cast product, the rigidity whereof is evaluated by the rigidity evaluation method, with which it is possible to appropriately evaluate the rigidity of a die-cast product. To this end, after carrying out a post-casting fracture test with a simple rigidity testing device, a rigidity deterioration rate is estimated on the basis of the proportion at which cold flakes are present on the fracture surface, which is obtained by observing a breakage surface. An internal defect of a prescribed range of a high-stress part of a die-cast product which is pre-derived with a stress analysis is detected with ultrasound, and when a defect rate which is the quotient of the total surface area of the internal defects of the prescribed range divided by the total defect detection surface area is less than or equal to a prescribed value, the die-cast product is evaluated as having a prescribed rigidity.

Description

technical field [0001] The present invention relates to a strength evaluation method of a die-cast product and a die-cast product (for example, a column housing made of aluminum die-cast) used in an electric power steering device of a vehicle. Background technique [0002] Conventionally, in order to prevent the theft of a car, a steering lock device is generally used, which not only stops the engine but also prevents the steering wheel from turning when the ignition key is pulled out. [0003] The main body of the steering lock device used in this way and the steering column as the attachment must be strong and not easily damaged. For example, it is stipulated in JIS D5812 or the like that the steering shaft is locked, and even if a torque of 200 Nm is applied to the steering shaft, the function cannot be abnormal. [0004] Here, in order to reduce weight, steering columns are mostly made of die-casting parts of light metals such as aluminum or magnesium, and there are int...

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Problems solved by technology

[0004] Here, in order to reduce weight, steering columns are mostly made of die-casting parts of light metals such as aluminum or magnesium, and there are internal defects. Therefore, when excessive torque is applied, fractures may occur, and how to evaluate the strength becomes difficult. very important

[0005] In particular, as an internal defect of die castings, fractured chilled layers are known to cause a decrease in strength, and inspection of fractured chilled layers is required for strength evaluation.

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