JPH0223827B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Field of Industrial Application The present invention relates to an induction hardening inspection method for determining the quality of the surface hardening results of the inner circumferential surface of a concave part at the same time as the hardening process. (b) Prior art Conventionally, in induction hardening work incorporated in fully automatic manufacturing processes, surface hardening of the inner surfaces of concave parts, especially the outer race and inner race of constant velocity joints of automobiles whose ends are closed, has been carried out. In general, the opening of the part faces downward and the induction hardening coil is inserted from the bottom to perform the hardening work, so there is no way to visually check the hardening results during the assembly process. Therefore, when the above-mentioned parts proceed to the next step and are finally assembled into an assembly, it is no longer possible to distinguish between those that have been induction hardened and those that have not. In addition, since the part to be hardened is the inner surface, it is not possible to judge the quality of hardening by measuring hardness, so the only option is to test the quality of hardening by sampling rather than 100% inspection. When incorporating this into a fully automatic manufacturing process, there was a problem in that there was a risk that unhardened parts would flow into the next process due to an unexpected accident during fully automatic operation. (C) Purpose As mentioned above, the present invention aims to provide an induction hardening inspection method that can prevent parts to be hardened from flowing into the next process as unhardened or incompletely heat-treated parts. (d) Structure The present invention measures the amount of expansion in the diametrical direction during hardening of a concave-shaped part whose inner peripheral surface is to be surface hardened, using a measuring means such as a dial gauge, etc., on the outer peripheral surface of the part. , is an induction hardening inspection method that determines the quality of the hardening result by comparing it with a preset reference expansion amount. (E) Example FIG. 1 is a perspective view illustrating the method of the present invention,
Reference numeral 10 denotes a concave part to be hardened, which is held substantially vertically with its opening facing downward, and is rotated in the direction of the arrow by a drive device (not shown). 20 is inserted. The coil 20 is equipped with an injection cooling pipe for quenching (not shown). Reference numeral 50 denotes a workbench 50 which is provided with a hole 51 near the lower end of the part 10 to be hardened, through which the induction hardening coil 20 passes. Further, a dial gauge 40 is fixedly installed on the upper surface of the workbench 50, and a measuring element 43 equipped with a roller is fixedly installed at the tip of a spindle 42 that slides within a stem 41 of the dial gauge 40. The roller of the measuring element 43 is in contact with the outer peripheral surface of the rotating part 10 to be hardened. After setting as described above, when a high-frequency current is applied to the induction hardening coil 20, a high-frequency eddy current is induced near the inner peripheral surface of the part to be hardened 10, and the inner peripheral surface is locally heated by Joule heat. is heated to. As a result, the outer diameter of the part to be hardened 10 increases due to thermal expansion. Thus, the measuring tip 43 of the dial gauge is pushed in the direction of the arrow, and the amount of thermal expansion is indicated on the surface of the dial gauge 40. Therefore, the upper limit S ₂ and lower limit of the allowable standard expansion amount
If S ₁ is set, if the amount indicated by the dial gauge is less than S ₁ , it means that the heating is not done or the heating is insufficient, and if it exceeds S ₂ , it means overheating. It is inappropriate.
If the expansion amount is between S ₁ and S ₂ , it indicates that a proper hardened layer 12 has been formed. Next, as a specific example, we measured the amount of increase in the outer diameter due to expansion during quenching heating for a part to be quenched that has a ring-shaped peripheral wall with an outer diameter of approximately 50 mm and an inner diameter of approximately 40 mm. A list of those that have been confirmed to have good hardening results is shown in the table below.

[Table] The above expansion amount is the value when the temperature rises to the set value, and taking into account other measured values that are not displayed, the upper limit of the standard expansion amount S ₂ is set to 0.6 mm, and the lower limit S ₁ is set to 0.6 mm.
could be set as 0.5mm. In addition, in the above-mentioned embodiment, the case where the value of the dial gauge was visually observed was explained as an example. However, the present invention is not limited to this. For example, the quality of hardening can be determined by extracting the indication of a dial gauge as an electric signal and comparing this value with a reference expansion amount stored in advance in a microcomputer or the like. It's okay to be hot. Furthermore, it goes without saying that various types of dial gauges, such as mechanical or optical types, can be used. Furthermore, in the example, a case was explained in which a change in the outer diameter of a part to be hardened is measured using a contact type dial gauge, but this is not possible to measure a change in the outer diameter of a part to be hardened using a non-contact method, for example, using an optical sensor or a magnetic sensor. It may be. (f) Effects By using the present invention, when performing surface hardening on the inner circumferential surface of a concave hardened part, it is possible to judge the quality of the hardening result at the same time as the hardening operation, and it has the effect of making it possible to perform a 100% inspection. In addition, in a fully automatic manufacturing process, it has the effect of preventing defective hardening parts from being sent to the next process.

[Brief explanation of drawings]

FIG. 1 is a perspective view illustrating the method of the present invention. 10... Parts to be hardened, 20... Induction hardening coil, 40... Dial gauge, 50... Workbench.

Claims (1)

[Scope of Claims] 1. Measuring the amount of change in thermal expansion of the outer diameter of the part caused by quenching and heating the inner peripheral surface of the concave part, and comparing this amount of change with a preset reference amount of expansion. An induction hardening inspection method, comprising: determining the quality of the surface hardening results applied to the inner circumferential surface of the component. 2. The measurement of the amount of change in thermal expansion of the outer diameter of the concave part is performed by bringing a dial gauge probe into contact with the outer peripheral surface of the part. induction hardening inspection method.