JP2009149957A - Method for manufacturing ferrous sintered component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably exhibit a straightening effect at sizing after sintering and to minimize warpage even in the case of a thin ferrous sintered component and also to increase the strength and hardness of the component by a sufficiently practicable method. <P>SOLUTION: The manufacturing of the ferrous sintered component, in which sizing is performed after sintering, is carried out by the following method: the sizing of a sintered compact is performed at 300 to 600°C and then heat treatment is applied. By this method, a thin-walled clutch component 10 etc. can be manufactured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an iron-based sintered part in which sizing and heat treatment are performed after sintering. Specifically, the iron-based sintering is effective in improving the accuracy and reducing the defective rate of a thin-walled sintered part having a thickness of less than 15 mm. The present invention relates to a part manufacturing method.

  One of the known sintered parts is a plate-like clutch part 10 as shown in FIGS. The clutch component 10 has a cam surface 12 that forms a ramp groove on the end surface 11, and a ball 14 held on the counterpart component 13 rolls on the cam surface 12 to constitute a one-way clutch. The clutch component 10 is formed by molding the entire die including the cam surface 12 in order to take advantage of the characteristics of the powder metallurgy method.

  Since the above-mentioned clutch parts are thin parts having a thickness of less than 15 mm (the upper limit of the thickness is generally 7 to 10 mm), distortion and warping (thickness) shown in FIG. Warp in the direction (a state in which the one-dot chain line is not warped) is likely to occur. Therefore, sizing is performed after sintering to correct the shape and return the warp. The following Patent Document 1 discloses sizing after sintering.

The sizing of the sintered body is generally performed at room temperature sizing performed at room temperature. The method disclosed in Patent Document 1 is also considered to be normal temperature sizing, although there is no description about the sizing temperature condition.
Japanese Patent Laid-Open No. 2003-41301

  Room temperature sizing has a small correction effect and cannot sufficiently increase the shape accuracy and dimensional accuracy of sintered parts. Thin-walled parts that are likely to warp remain warped after sizing, and therefore, when high accuracy is required, the warp needs to be removed or suppressed.

  Although warpage is suppressed by increasing the thickness of the part, this method requires additional processing (grinding and polishing) of the end face of the part in the subsequent process in order to make the part thickness that is thicker than necessary into the required dimension. Become. When straightening with room temperature sizing, the warpage of the part remains largely even after straightening, so suppressing the warpage with the method of increasing the thickness of the part increases the amount of increase in the thickness of the part, which increases the processing cost of the end face in additional machining and increases productivity. It will lead to worsening.

  Also, a part that has warped exceeding the limit becomes a defective product that cannot be corrected. In the correction by room temperature sizing, the defect occurrence rate cannot be ignored.

  In addition, when heat treatment such as quenching is performed after sizing (hereinafter referred to as post-treatment heat treatment), shape accuracy and dimensional accuracy are further deteriorated by post-treatment heat treatment. The accuracy must be managed more strictly.

  This invention has a remarkable effect of sizing correction, and is capable of suppressing the warpage of thin-walled iron-based sintered parts as well as increasing the strength, hardness, The challenge is to achieve surface pressure.

  In order to solve the above problems, in the present invention, the iron-based sintered part is manufactured as follows. That is, the sizing of the sintered body is performed at a temperature of 300 to 600 ° C. in order to effectively correct the sintered body that is distorted or warped. Thereafter, heat treatment is performed. When the carbon content of the sintered body used for sizing is controlled within an appropriate range (for example, 0.5 to 1.5 wt%), high strength, high hardness, and high surface pressure can be achieved by this heat treatment.

  The sizing pressure in this method is preferably in the range of 200 to 1000 MPa. If it is 200 MPa or less, the effect of correcting the shape and dimensions may be insufficient. In addition, when the pressure is 1000 MPa or more, it is considered that the life of the mold is shortened and the accuracy of the parts is deteriorated due to the distortion of the mold during sizing.

  Such a method for manufacturing an iron-based sintered part has a thickness of 2 to 15 mm, which is provided with a cam surface which is easily formed and corrected by a mold, and is required to be accurate although it tends to be warped. When applied to the manufacture of thin-walled parts, a particularly great effect can be expected.

  The heat treatment for increasing the strength, hardness, and surface pressure of the parts may be nitriding or soft nitriding, but carburizing and quenching are preferred.

  In this invention, since the sizing of the sintered body is performed at a temperature of 300 to 600 ° C., the strain remaining in the part is removed, the correction effect by sizing is increased, the warpage and strain are reduced, and the flatness of the end face Machining cost is reduced when reworking is modified by additional machining. Further, for a part having a cam surface on the end surface, the shape accuracy and position accuracy of the cam surface are improved, and further, the surface pressure strength is increased and the performance of the part is improved.

  By adjusting the sizing temperature to 300 ° C. or higher, the correction effect by sizing is enhanced. The upper limit of the temperature needs to be lower than the heat treatment temperature in the subsequent process in order to suppress the structural change of the material, and the heat treatment temperature in the subsequent process becomes 800 ° C. or higher in quenching or the like. To 600 ° C.

Embodiments of the present invention will be described below.
Example 1
An alloy powder having a composition of 4 wt% Ni-0.5 wt% Mo-1.5 wt% Cu-residual Fe was added and mixed with 1.0 wt% graphite powder and 0.8 wt% lubricant. The obtained mixed powder was molded at a molding pressure of about 600 MPa using a powder molding apparatus to obtain a disk-shaped green compact 1 shown in FIG. The dimensions of the green compact 1 are an outer diameter D = 90 mm and a thickness t = 6 mm. The end surface 2 of the green compact 1 is provided with a total of four recessed cam surfaces 3 at a constant pitch in the circumferential direction.

  The green compact 1 was introduced into a furnace in a nitrogen gas atmosphere and sintered at 1150 ° C. for 20 minutes to obtain an iron-based sintered body having a true density of 89% and a porosity of 11%.

  Next, the iron-based sintered body was heated to the temperature shown in Table 1. Then, sizing was performed at a pressure of about 700 MPa using a sizing mold in which the heated sintered body was heated to a temperature of 400 ° C.

  For comparison, the same sintered body was sized at the same molding pressure as in the examples at room temperature.

All the sintered bodies after sizing were heated to a temperature of 800 to 900 ° C. to perform carburizing treatment, and then quenched and quenched.

  The amount of warpage in the thickness direction of the sintered body (sample) after heat treatment (carburizing and quenching) was examined. The measurement results are also shown in Table 1. As the warpage of the specimen increases, the machining allowance for the additional work for correcting the flatness of the end face increases.

  As can be seen from Example 1, according to the method of the present invention, distortion and warpage of a thin sintered body can be effectively corrected by correction by sizing, and high accuracy is required. It can reduce the processing cost for additional machining and increase productivity.

  In addition, by suppressing the warpage of the clutch parts and the like, the cam shape of the end face and the positional accuracy of the cam surface are increased, and the surface pressure strength is also increased, thereby improving the performance of the parts themselves.

  Furthermore, since the machining allowance for additional machining is reduced, the reduction of the surface hardened layer is reduced, and it is also possible to provide a component having excellent high surface pressure durability.

Example 2
Using the same material as in Example 1, a disk-shaped green compact was molded under the same molding conditions. The green compact having the diameter and thickness shown in Table 2 was prepared, sintered, sized, and then further heat-treated. The conditions for sintering, sizing, and heat treatment were all the same as in Example 1. And the amount of curvature of the obtained sintered compact was investigated. The measurement results are shown in Table 2.

  As can be seen from Example 2, the amount of remaining warp after the heat treatment tends to decrease as the thickness of the sintered body increases, so that the present invention can be used for manufacturing a thin sintered part having a thickness of 15 mm or less. A particularly large effect can be expected. In addition, since there is almost no request | requirement of the ultra-thin sintered part that thickness is less than 2 mm, it seems that the minimum of the thickness of the sintered part to which this invention is applied will be about 2 mm.

Perspective view of parts manufactured in Example A perspective view showing an example (clutch part) of a sintered part that easily warps. Sectional drawing which shows the outline | summary of the one-way clutch using the sintered component of FIG. The figure which exaggerates and shows the state which the clutch components of FIG. 2 curved

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Green compact 2 End surface 3 Cam surface 10 Clutch component 11 End surface 12 Cam surface 13 Counterpart 14 Ball

Claims (2)

  An iron-based sintered part manufacturing method for performing sizing after sintering, wherein the sintered body is sized at a temperature of 300 to 600 ° C., and then heat-treated. Production method.   The method for producing an iron-based sintered part according to claim 1, wherein a thin-walled part having a thickness of 2 to 15 mm and having a cam surface formed and corrected by a mold on the end face is produced.

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