JPS6274023A - Carburization hardening method for cup-shaped parts with thick-walled boss part - Google Patents

Abstract

PURPOSE:To cool a boss part and spline part at a uniform rate without entailing a weight increase, etc., and to decrease carburization hardening strain by cooling only the boss part down to a prescribed temp. then hardening the entire part in the stage of hardening said parts after carburizing. CONSTITUTION:For example, a second brake hub stock 1 consisting of the thick-walled boss part 2, a spline part 3 formed with involute splines 5 and a flange part 4 connecting both is put into a carburization furnace and is carburized. The stock 1 is imposed on a receiving tray 6 at the outlet of the carburization furnace and an oil nozzle 7 is inserted to the inside of the boss part 2. Oil 8 kept at about 130 deg.C is sprayed at a prescribed flow rate from the nozzle 7 to cool only the boss part 2 down to the prescribed temp. (650-750 deg.C). The stock 1 is immediately thereafter immersed into a hardening oil kept at about 130 deg.C and is thus hardened.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a carburizing and quenching method for cup-shaped parts with a thick-walled boss part. The present invention relates to a carburizing and quenching method for a cup-shaped part with a thick boss part, in which the boss part and a spline part on the outer circumference thinner than the boss part are connected by a flange part.

[Conventional technology]

Conventionally, in order to manufacture a cup-shaped part with a thick boss part such as a second brake hub, which is an automatic part of an automobile, first, for example, JIS SCM42, which is an alloy steel, was used.
Machine the second brake hub shape from an 0H cylindrical block. As shown in FIG. 1(a), this second brake hub 1 is provided with a thick boss portion 2 approximately in the center, and this boss portion 2 and a spline portion 3 on the outer periphery are connected by a flange portion 4. It has a shape. When the second brake hub 1 is of a sprag type, the inner surface of the boss portion 2 serves as a one-way clutch outer race surface, and the spline portion 3 is provided with an involute spline 5 that engages with the clutch. Therefore, the surface hardness of the inner surface of the boss portion 2 is 720 to 85 (Vickers hardness) (v).
0, as the hardness of the inside of the boss part 2) (V350-500
In addition, the tooth trace error of the involute spline 5 of the spline portion 3 is required to be 14 μm or less.

For this reason, efforts are being made to satisfy these requirements by using JIS SCM420H, which is an alloy steel, as a material and carburizing and quenching it. Here, carburizing and quenching refers to heating steel parts to 850°C to 950 tons in a carburizing gas atmosphere to infiltrate and dissolve carbon into the surface of the part, and then quenching to make the inside dull and the surface hard. , this is a process to strengthen it.

[Problem that the invention seeks to solve]

By the way, by using alloy steel and carburizing and quenching, the requirements for the hardness of the surface and inside of the boss portion can be met, but the carburizing and quenching causes quenching distortion, leaving the spline portion open. As a result, the tooth trace error becomes approximately 40 μm, which does not satisfy the required level of 14 μm or less.

When the cause of this distortion was investigated, it was found that it was caused by thermal stress caused by the difference in cooling rate between the thick boss section and the relatively thin spline section. However, in the past, there was no effective means for preventing warping, and the flange portion and spline portion were made thicker to equalize the cooling rate with respect to the boss portion. However, this method causes problems such as an increase in the weight of the parts and further interference with other parts.

Therefore, there has been a desire for a device to reduce carburizing and quenching distortion by making the cooling rate of the boss portion and the spline portion uniform without causing an increase in weight or the like.

[Means for solving problems]

The above problem is solved by the carburizing and quenching method of a cup-shaped part with a thick boss portion of the present invention, which will be described below.

That is, the present invention is a carburizing and quenching method for a cup-shaped part with a thick boss part, in which a boss part is provided approximately in the center, and the boss part and a spline part on the outer periphery, which is thinner than the boss part, are connected by a flange part. When quenching after carburizing, only the boss portion is first cooled to a predetermined temperature with a quenching liquid, and then the whole is immediately immersed in the quenching liquid for quenching.

Here, the predetermined temperature is 650°C to 750"Ci'7)
Refers to the range.

The boss portion is cooled, for example, at 100 ee/sec for 1 second. An oil nozzle or the like can be used for this cooling.

[Effect]

According to the present invention, first, only the boss portion is cooled to a predetermined temperature, and then the entire portion is quenched, so that the cooling curve after cooling the boss portion and the cooling curve of the spline portion are almost the same, and the cooling rate during quenching is is approximately the same for the boss part and the spline part. As a result, the occurrence of thermal stress, which conventionally occurs due to differences in cooling rates, is significantly reduced, and carburizing and quenching distortion is reduced.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Here, FIG. 1 is a schematic configuration diagram showing one step of a carburizing and quenching method for a thick-walled boss part biasing force 7-shaped part according to an embodiment of the present invention, and FIG. 2 is a diagram showing a boss part in an embodiment of the present invention. It is a graph which shows the cooling curve of a spline part.

First, a cylindrical block of JIS SCM420H alloy steel is machined into the shape of a second brake hub. As a result, as shown in FIG. 1(a), a second brake hub material is obtained which consists of a thick boss portion 2, a spline portion 3 on which an involute spline 5 is formed, and a flange portion 4 connecting the two. It was done. At this time, the tooth trace error of the involute spline 5 of the spline portion was 5 μm.

This second brake hub material was placed in a carburizing furnace and carburized and quenched. That is, after replacing the inside of the furnace with a carburizing gas such as Rx gas, the temperature inside the furnace was raised to 930°C to perform carburization, and then the temperature was lowered to -840'C. Then, at the outlet of the carburizing furnace, as shown in FIG. 1(b), the receiver is placed on a tray 6, and the oil nozzle 7 is inserted inside the boss portion 2. Next, from the oil nozzle 7, oil 8 at a temperature of about 130° C. is applied at a rate of 100 ee/sec toward the inner surface of the boss portion 2.
Cool by blowing for a second. Immediately thereafter, the entire second brake hub is placed in quenching oil at about 130°C to be quenched. Subsequently, it was tempered at 130''C to obtain a final product.

In the second brake hub obtained as a result, the surface hardness of the inner surface of the boss portion was 780 (Vickers hardness) (v), and the inner surface of the boss portion was 420 v, which fully met the requirements.

Further, the tooth trace error was 10 μm, which fully satisfied the requirement of 14 μm or less.

As described above, according to this embodiment, the cooling rate during carburizing and quenching can be made uniform as shown in FIG. A second brake hub with hardness and precision is obtained. As a result, the weight of parts can be reduced and vehicle performance can be improved, which is an excellent effect.

Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but includes various embodiments within the scope of the claims.

For example, in the embodiment, the second brake hub was used as an example, but the present invention can be applied to any other brake hub as long as it has a similar shape to the second brake hub.

〔Effect of the invention〕

From the above, according to the carburizing and quenching method for a cup-shaped part with a thick boss part of the present invention, the cooling rate of the boss part and the spline part can be made uniform without increasing the weight of the cup-shaped part with a thick boss part. , thereby significantly reducing carburizing and quenching distortion. Therefore, the weight of the parts can be reduced compared to the conventional one, and the vehicle performance can be improved.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing one step of a carburizing and quenching method for a cup-shaped part with a thick boss portion according to an embodiment of the present invention, and Fig. 2 is a cooling curve of a boss portion and a spline portion in an embodiment of the present invention. This is a graph showing. 1.--.--Second brake hub (cup-shaped part with thick boss section) 2.--Boss section 3.--Spline section 4.--Flange section 5-.. Involute spline 6 =------One receiver is tray 7---Oil nozzle 8---Oil Applicant Toyota Motor Corporation Fig. 1 (b)

Claims (1)

[Claims] (1) A method for carburizing and quenching a cup-shaped part with a thick boss part, in which a boss part is provided approximately in the center, and the boss part and a spline part on the outer periphery, which is thinner than the boss part, are connected by a flange part, the method comprising: A cup-shaped part with a thick boss part characterized in that, when quenching is performed, only the boss part is first cooled to a predetermined temperature with a quenching liquid, and then the entire part is immediately immersed in the quenching liquid and quenched. Carburizing and quenching method.