JP2020084267A - Production method of composite sintered body - Google Patents

Abstract

To provide a production method of a composite sintered body capable of suppressing occurrence of warpage due to a difference of a shrinkage factor during sintering the respective materials and an interfacial peeling due to the warpage, while suppressing a cost increase and function deterioration, by using a common iron-based powder and a high functional metal powder that are a parent material.SOLUTION: A production method of the present invention includes the steps of: preparing a plurality kinds of metal powders containing a graphite-added iron-based metal powder to which an addition agent for increasing an amount of a liquid phase containing graphite is added at a sintering temperature, and a high function metal powder having a relatively large shrinkage factor during sintering, to an iron-based metal powder having relatively small shrinkage factor during sintering; composite molding the plurality of kinds of the metal powders; and sintering the obtained composite compact. When an addition amount of the addition agent is adjusted relative to the iron-based metal powder, a difference of the shrinkage factor during sintering the graphite added iron-based metal powder and the shrinkage factor during sintering the high function metal powder is made smaller.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a composite sintered body.

A composite molded body can be manufactured by obtaining a composite molded body using a plurality of types of materials and sintering this. Generally, in the production of a composite sintered body, when there is a large difference in shrinkage rate between the respective materials during the sintering, the material having the larger shrinkage rate tends to warp. When focusing on the material with the higher shrinkage, the surface (bonding interface) joined to the material with the lower shrinkage is constrained by the material with the lower shrinkage, while As a result of the large shrinkage occurring on the unbonded surfaces, warpage occurs. When the material having the higher shrinkage ratio is warped, peeling may occur at the bonding interface.

Patent Document 1 has, as a main component, a first member obtained by sintering a first raw material powder containing a first powder as a main component and a second powder having a sintering start temperature higher than that of the first powder. The present invention relates to a composite sintered body including at least a second member obtained by sintering a second raw material powder, and adjoining members being integrally joined by sintering.
In Patent Document 1, in a preparation step of obtaining a first mixture containing a first raw material powder and an organic binder and a second mixture containing a second raw material powder and an organic binder, at least one of the first mixture and the second mixture is used. A manufacturing method has been proposed in which the second mixture contains the powder which is the main component of the other mixture in a compounding amount within a range capable of ensuring the required characteristics of the second member (claim 4).
In the method described in Patent Document 1, it is possible to effectively suppress interfacial peeling due to sintering contraction that occurs unilaterally only on one member side in the initial stage of sintering, and it is possible to improve the bonding strength. (Paragraph 0024).

JP 2004-292878 A

It is expensive to obtain a composite sintered body by using a general-purpose iron-based powder as a base material and a high-performance metal powder capable of imparting functions such as high strength (for example, high-speed tool steel powder) It is possible to achieve high functionality while suppressing the amount of high-performance metal powder used.
In such a case, even if an attempt is made to apply the method described in Patent Document 1 in order to suppress warpage due to the difference in shrinkage rate of each material during sintering and interface peeling due to this, the following problems occur. When the high-performance metal powder is added to the side of the general-purpose iron-based powder that is the base material, the amount of expensive high-performance metal powder used increases and the cost increases. On the contrary, when a general-purpose iron-based powder is added to the high-performance metal powder side, the amount of use of the high-performance metal powder is reduced, so that functions such as strength are deteriorated.

The present invention has been made in view of the above circumstances, using a general-purpose iron-based powder as a base material and a high-performance metal powder, while suppressing an increase in cost and functional deterioration, shrinkage during sintering of each material It is an object of the present invention to provide a method for manufacturing a composite sintered body capable of suppressing the occurrence of warpage due to the difference in the ratio and the interfacial peeling caused thereby.

The manufacturing method of the composite sintered body of the present invention,
Graphite-added iron-based metal powder that contains graphite-containing additive that increases the amount of liquid phase at the sintering temperature, and iron-based metal powder that has a relatively low shrinkage ratio during sintering A step of preparing a plurality of types of metal powder including a high-performance metal powder having a large shrinkage rate,
A step of composite molding the plurality of kinds of metal powders,
And a step of sintering the obtained composite molded body,
By adjusting the addition amount of the additive to the iron-based metal powder, the difference between the shrinkage rate of the graphite-added iron-based metal powder during sintering and the shrinkage rate of the high-performance metal powder during sintering is small. To do.

According to the present invention, by using a general-purpose iron-based powder and a high-performance metal powder as a base material, while suppressing an increase in cost and a decrease in function, warpage due to a difference in shrinkage rate during sintering of each material and this It is possible to provide a method for manufacturing a composite sintered body capable of suppressing interfacial peeling due to the above.

It is a schematic cross section of the compound sintered compact of one embodiment concerning the present invention. It is a Fe-C type|system|group phase diagram. It is a graph which shows the shrinkage rate at the time of sintering of samples (a) and (b).

[Composite sintered body]
A configuration of a composite sintered body according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view.
The composite sintered body 1 of the present embodiment is a composite sintered body of a first sintered body 11 and a second sintered body 12. In the illustrated example, the second sintered bodies 12 are joined to both surfaces of the first sintered body 11. The design and number of each sintered body can be changed as appropriate.
The first sintered body 11 is a graphite-containing iron-based metal powder in which an additive that increases the amount of liquid phase at a sintering temperature containing graphite is added to iron-based metal powder having a relatively small shrinkage rate during sintering. It is a sintered body of.
The second sintered body 12 is a sintered body of highly functional metal powder (for example, high-speed tool steel powder) having a relatively large shrinkage rate during sintering.

The shrinkage ratio of the general-purpose iron-based metal powder during sintering is, for example, about 0.2%, whereas the shrinkage ratio of the high-speed tool steel powder during sintering is, for example, 10 to 15%. If general-purpose iron-based metal powder and high-speed tool steel powder are compound-sintered without any special measures, the difference in shrinkage will be large, and the material with the larger shrinkage will warp and the joint interface Peeling may occur. Therefore, in the present invention, an iron-based metal powder having a relatively small shrinkage rate during sintering is added with an additive that increases the amount of liquid phase at a sintering temperature containing graphite to reduce the shrinkage rate during sintering. Increase and decrease the difference in shrinkage.

The manufacturing method of the composite sintered body of the present invention,
Graphite-added iron-based metal powder that contains graphite-containing additive that increases the amount of liquid phase at the sintering temperature, and iron-based metal powder that has a relatively low shrinkage ratio during sintering A step of preparing a plurality of types of metal powder including a high-performance metal powder having a large shrinkage rate,
A step of composite molding a plurality of kinds of metal powders,
And a step of sintering the obtained composite molded body.

Composite molding and sintering can be performed by known methods. The composite molding can be performed by filling a mold with a plurality of kinds of metal powders in a desired stacking order and applying pressure. Then, the composite molded body is taken out of the mold and can be sintered by heating at a temperature at which the material is sintered.

In the method for producing a composite sintered body of the present invention, by adjusting the addition amount of the above additive to the iron-based metal powder, the shrinkage rate at the time of sintering the graphite-added iron-based metal powder and the sintering of the high-performance metal powder The difference with the shrinkage rate is reduced. The difference between the shrinkage rate of the graphite-added iron-based metal powder during sintering and the shrinkage rate of the high-performance metal powder during sintering is preferably 1.0% or less. It is particularly preferable to match the shrinkage rate with the shrinkage rate during sintering of the high-performance metal powder.

An example will be described.
FIG. 2 is an Fe-C system phase diagram (cited from: https://em.ten-navi.com/dictionary/85/). An appropriate amount was weighed for each of the Fe-C based powder material containing 0.8 wt% C (sample (a)) and the Fe-C powder material containing 2.0 wt% C (sample (b)), and 98 It was molded into a cylindrical shape of 17 mmφ under a pressure condition of 0.1 MPa, and the obtained molded body was sintered for 1 hour at 1260° C. which is preferable as the sintering temperature of the high speed tool steel powder.
According to the state diagram shown in FIG. 2, at 1260° C., sample (a) does not contain a liquid phase, whereas sample (b) is in the solid phase liquid phase coexistence region and contains a liquid phase. If graphite is added to the sample (a) to obtain the composition of the sample (b), the amount of liquid phase at the time of sintering can be increased.
FIG. 3 shows the shrinkage rates of Samples (a) and (b) during sintering. The sample (b) had a higher shrinkage ratio during sintering than the sample (a), and was within the range of 10 to 15% which is the shrinkage ratio during sintering of the high speed tool steel powder. This means that if graphite is added to the sample (a) to make the composition of the sample (b), the shrinkage rate at the time of sintering becomes large due to the increase of the amount of liquid phase at the time of sintering, and the high speed tool It is shown that the difference from the shrinkage rate of the steel powder during sintering can be reduced.

As shown in the data of the above examples, in the Fe-C-based powder material, the amount of liquid phase at the time of sintering is increased by adding an additive that increases the amount of liquid phase at the sintering temperature containing graphite. It is possible to increase the shrinkage rate during sintering and reduce the difference in shrinkage rate between the high-performance metal powder and the relatively high shrinkage rate during sintering. As a result, it is possible to suppress the occurrence of warpage due to the difference in shrinkage rate during sintering of each material and the interfacial peeling caused thereby.
As described in the section [Means for Solving the Problems], in order to suppress the occurrence of warpage due to the difference in shrinkage ratio during sintering of each material and the interfacial separation due to the warpage, the method described in Patent Document 1 is adopted. Even if it tries to apply, there are the following problems. When the high-performance metal powder is added to the side of the general-purpose iron-based powder that is the base material, the amount of expensive high-performance metal powder used increases and the cost increases. On the other hand, when a general-purpose iron-based powder is added to the high-performance metal powder side, the amount of the high-performance metal powder used is reduced, so that desired functions such as strength may not be obtained.
In the method of the present invention, since it is not necessary to add expensive high-performance metal powder to the first sintered body in order to reduce the difference in shrinkage, the amount of expensive high-performance metal powder used is minimized. be able to. Graphite is inexpensive, and adding it does not significantly increase the cost. In the method of the present invention, since it is not necessary to add a general-purpose iron-based powder to the high-performance metal powder side in order to reduce the difference in shrinkage ratio, desired functions such as strength can be stably obtained.

As described above, according to the present invention, by using a general-purpose iron-based powder and a high-performance metal powder as a base material, while suppressing an increase in cost and a decrease in function, the shrinkage ratio of each material during sintering can be reduced. It is possible to provide a method for manufacturing a composite sintered body capable of suppressing warpage due to a difference and interfacial peeling caused thereby.

The present invention is not limited to the above-described embodiment, and appropriate design changes can be made without departing from the spirit of the present invention.

1 Composite Sintered Body 11 First Sintered Body 12 Second Sintered Body

Claims (1)

Graphite-added iron-based metal powder that contains graphite-containing additive that increases the amount of liquid phase at the sintering temperature, and iron-based metal powder that has a relatively low shrinkage ratio during sintering A step of preparing a plurality of types of metal powder including a high-performance metal powder having a large shrinkage rate,
A step of composite molding the plurality of kinds of metal powders,
And a step of sintering the obtained composite molded body,
By adjusting the addition amount of the additive to the iron-based metal powder, the difference between the shrinkage rate of the graphite-added iron-based metal powder during sintering and the shrinkage rate of the high-performance metal powder during sintering is small. A method for manufacturing a composite sintered body.

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