JPH01309906A - Method for forming sintered layer - Google Patents

Abstract

PURPOSE:To form sintered layer without developing crack by setting wear resistant eutectic alloy powder sheet to a jig and executing pre-sintering and regular-sintering after molding by sandwich-pressing. CONSTITUTION:Plural pieces of the alloy powder sheets 5 composing of 94-99wt.% the wear resistant eutectic alloy powder and 1-6% modacrylic sticky binder are piled and set to the lower molding member 7 having projecting curved surface of a molding jig 6. Successively, the upper molding member 9 is fitted and positioned with bolt member 8 to pile on the alloy sheets 5. By descending the upper molding member 9, the alloy powder sheets 5 are sandwich-pressed with both molding members 7, 9 for >=10hr and the molding is executed so as to follow the surface shape of sintered layer forming position of metal base body. The molded alloy powder sheets 5 are pre-sintered and after removing gas generated by decomposition of resin component in the binder, the regular sintering is executed as laying on the sintered layer forming position of the metal base body to form the sintered layer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is characterized by sintering and bonding an alloy powder sheet made of wear-resistant eutectic alloy powder and an acrylic adhesive binder to the surface of a metal substrate. The present invention relates to a method of forming a sintered layer.

(Prior Art) Conventionally, wear resistance has been required for the cam sliding part of a rocker arm that constitutes the valve mechanism of a vehicle engine such as an automobile, so wear-resistant sintered bonding has been applied to the cam sliding part. It is common practice to form a gold layer. As a method for forming a wear-resistant sintered alloy layer on a metal base that constitutes the body of a metal member such as a rocker arm that requires wear resistance, the following method is often used.

■ A method in which a wear-resistant sintered alloy member sintered into a predetermined shape is bonded to the surface of a metal base by brazing.

■ A method in which an alloy powder sheet is fixed to the surface of a metal substrate using adhesive tape, and the two are diffusion bonded through preliminary sintering and main sintering.

■ A method in which a pre-sintered alloy powder sheet is engaged with and fixed to the collar of a metal base, and the two are diffusion bonded through main sintering.

However, the above method (2) has the disadvantage that the manufacturing cost increases because it involves two steps: a sintering step and a brazing step. In addition, the above-mentioned method (1) has a problem in that gas is generated from the adhesive tape during main sintering, and a blistering phenomenon appears on the alloy powder sheet. Furthermore, although the method (■) above can eliminate the blistering phenomenon in the case (■) above, it is unstable compared to the case of fixing with adhesive tape (■) because the alloy powder sheet is engaged with the collar. As a result, the alloy powder sheet tends to shift easily, and a step of removing the flange is required after sintering and joining, resulting in an increase in manufacturing costs.

Therefore, as disclosed in JP-A-60-181202, for example, an alloy powder consisting of 94 to 99% wear-resistant eutectic alloy powder and 1 to 6% by weight of an acrylic adhesive binder is proposed. The sheet is brought into close contact with the surface of the metal substrate and pre-sintered by holding the sheet at a pre-sintering temperature of 150 to 380°C for at least 5 minutes in a non-oxidizing atmosphere, followed by main sintering by heating and raising the temperature. A method has been proposed to overcome the above-mentioned drawbacks by firmly adhering an alloy powder sheet to a metal substrate.

(Problem to be Solved by the Invention) By the way, when the surface shape of the sintered layer forming portion of the metal base exhibits a curved surface, the molding of the alloy powder sheet as in the above-mentioned proposed example may be performed using a jig, for example. It is necessary to mold the alloy powder sheet so as to follow the surface shape of the sintered layer forming area, and to perform preliminary sintering by placing the molded alloy powder sheet on the sintered layer forming area of the metal base.

However, if the alloy powder sheet is simply molded, the compressive stress and tensile stress acting on the acrylic adhesive binder that binds the metal powder particles, which are the main component of the alloy powder sheet, will be affected during pre-sintering. As a result, the alloy powder sheet tends to return to its original flat sheet shape, and this restoring force causes a problem in that cracks occur on the surface of the alloy powder sheet.

The present invention has been made in view of the above points, and its purpose is to appropriately mold an alloy powder sheet to conform to the surface shape of the sintered layer forming portion of the metal base by taking a means. Another object of the present invention is to eliminate the restoration of the alloy powder sheet during preliminary sintering to form a sintered layer that does not generate cracks.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention first uses wear-resistant eutectic alloy powder 94-99 as a method for forming a sintered layer on the surface of a metal substrate. % by weight and 1 to 6% by weight of an acrylic adhesive binder is set in a jig and pressed for 10 hours or more.
A mold is formed so as to follow the surface shape of the sintered layer forming portion of the metal base. Next, after preliminary sintering of this molded alloy powder sheet, it is placed on the sintered layer forming portion of the metal base and main sintering is performed.

(Function) With the above configuration, in the method of the present invention, the alloy powder sheet is set in a molding jig and pressed for 10 hours or more, so that it conforms to the surface shape of the sintered layer forming area of the metal substrate. Because the mold is removed from the jig, the compressive stress and tensile stress acting on the acrylic adhesive binder in the alloy powder sheet are removed inside the mold. , the restoring force that tries to return to the original flat sheet shape is eliminated, thereby preventing the occurrence of cracks during preliminary sintering and forming a sintered layer free of cracks.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a method for forming a sintered layer according to an embodiment of the present invention on a rocker arm 1 constituting a valve mechanism of an engine for a vehicle such as an automobile.
In order to explain the formation procedure of the sintered layer 3, first, the wear-resistant eutectic alloy powder 9 is applied to the cam sliding part 2.
An alloy powder sheet consisting of 4 to 99% by weight and 1 to 6% by weight of an acrylic adhesive binder is prepared.

The wear-resistant eutectic alloy powder, which is the main component of the alloy powder sheet, has a metal composition of C: 1.5-3.0% by weight, P:
o, 5-1.5% by weight, Mo: 3°5-10.0% by weight
, C": Particle size 150 consisting of 5 to 15 2%, balance Fe
The following are used:

In the above metal composition, C combines with Fe, P, Mo and Cr to form a hard phase, and at the same time combines with Fe and P or Mo to form a low melting point eutectic, crystallizes a liquid phase and sinters. This increases the density of the aggregate and is useful for diffusion bonding with the rocker arm body 4 (cam sliding portion 2), which is the metal base of the rocker arm 1. The blending ratio of this C is 1.5 to 3
．． The reason why it is set to 0% by weight is that if it is less than 1.5% by weight, the amount of liquid phase will decrease, resulting in poor bonding with the rocker arm body 4, and the hard phase will decrease, resulting in a decrease in wear resistance. . On the other hand, if it exceeds 3.0% by weight, the hard phase will be too large, resulting in a decrease in toughness, and the amount of liquid phase will be too large, making it impossible to maintain the shape.

In addition, P combines with Fe and C to form a phosphorus eutectic, crystallizes a liquid phase and increases the density of the sintered body, and also helps in diffusion bonding with the rocker arm body 2 and improves wear resistance. It is something that makes you The blending ratio of this P is 0.5 to 1
．． The reason why it is set to 5% by weight is that if it is less than 0.5% by weight, the amount of liquid phase will be small and a defective connection with the rocker arm body 4 will occur, while if it exceeds 165% by weight, the amount of liquid phase will be too large and the shape will be distorted. Although it becomes impossible to hold it.

Furthermore, Mo combines with C to form a hard phase to improve wear resistance, and also combines with Fe and C to form a low melting point eutectic, crystallizing a liquid phase and increasing the density of the sintered body. It is something that raises the level. The blending ratio of Mo is 3.5 to 10.0
The reason for setting the weight% is that if it is less than 3.5% by weight, the hard phase will decrease and wear resistance cannot be ensured, but if it exceeds 10.0% by weight, the effect will be saturated and it will not be economical. This is because it would be disadvantageous.

Further, Cr combines with C to form a hard phase to improve wear resistance, and is also dissolved in the matrix to help increase the strength of the sintered body. The blending ratio of this Cr is 5~
The reason why it is set at 15% by weight is that if it is less than 5% by weight, the above effect cannot be obtained, while if it exceeds 15% by weight, the effect is saturated and becomes economically disadvantageous.

In addition, in cases where B is included in addition to the above elements, B
is combined with Fe and C to form a low melting point eutectic, crystallizes a liquid phase, and is useful for bonding to the rocker arm main body 4. Further, when V, Nb, Ta, etc. are included, these combine with C to form a hard phase, which helps improve wear resistance.

In addition, the particle size of the wear-resistant eutectic alloy powder was set to 150 mesh or less because if it exceeds 150 mesh, the porosity of the sintered layer will increase accordingly, impeding the wear resistance of the sintered layer. be.

On the other hand, as acrylic adhesive binders, polymers and copolymers of acrylic esters and methacrylic esters, or copolymers with polymerizable monomers having functional groups that can be copolymerized with these esters are used. preferable. The blending ratio of this acrylic adhesive binder and the wear-resistant alloy powder is 94 to 99% by weight of the wear-resistant eutectic alloy powder and 1 to 6% by weight of the acrylic adhesive binder. The reason for this setting is that if the acrylic adhesive binder is less than 1 mm%, the adhesiveness will be insufficient and the sheet will become brittle, making it impossible to secure the necessary flexibility of the sheet. This is because if the resin content exceeds this amount, the resin content becomes excessive, which adversely affects the porosity of the sintered layer, and the bonding with the rocker arm main body 4 becomes insufficient.

The procedure for forming an alloy powder sheet using the above-mentioned wear-resistant eutectic alloy powder and an acrylic adhesive binder is to apply a solvent such as acetone, toluene, and methyl ethyl ketone to the acrylic adhesive binder. 100ff
After adding 100 to 1,000 parts by weight of 7 to 1000 parts by weight per part of ifi and kneading the mixture, it is poured into a mold covered with release paper, and after the solvent is evaporated, it is passed through rolling rolls to a temperature of, for example, 0°5. Form into a sheet having a thickness of ~5.0 mm.

Alternatively, without using a solvent, a mixture of wear-resistant eutectic alloy powder and acrylic adhesive binder is kneaded with heating if necessary, and then formed into a sheet.

Next, as shown in FIG. 2, a plurality of alloy powder sheets 5 formed as described above are formed. 5. . . . is set by overlapping the lower molding jig 6 with the convex curved surface on the member 7, and then the lower molding is set using a plurality of bolts extending upward from the member 7. Member 8.8. ..., by inserting and positioning the upper mold member 9 having a concave curved surface, the upper mold molding member 9 is placed on the alloy powder sheet 5.
,5. Lay it on top of... Thereafter, by screwing the nut members 10 screwed onto each of the bolt members 8, the upper molding member 9 is lowered, and the alloy powder sheet 5. 5. ... is pressed between the member 7 for the lower mold and the member 9 for the upper mold for 10 hours or more to form the surface shape of the sintered layer forming part (cam sliding part 2) of the rocker arm main body 4. Shape it to match.

Each of the alloy powder sheets 5 molded in this manner has the compressive stress and tensile stress acting on the acrylic adhesive binder in each alloy powder sheet 5 removed during molding. Even if it is taken out from the jig 6, it does not return to its original flat sheet shape.

Thereafter, each molded alloy powder sheet 5 is taken out from the molding jig 6, placed in a sintering furnace, and presintered at a predetermined presintering temperature in a non-oxidizing atmosphere. As a result, gas generated by thermal decomposition of the resin component of the acrylic adhesive binder is removed from each alloy powder sheet 5.

The decomposed gas is removed from each alloy powder sheet 5 in advance by going through the pre-sintering process in this way.If the main sintering is performed without pre-sintering, the decomposed gas generated will cause the decomposed gas to be removed during the sintering process. This is because large pores are formed in the layer, making it impossible to obtain sufficient strength and wear resistance.

Further, the reason why the preliminary sintering is performed in a non-oxidizing atmosphere is to prevent oxidation of the wear-resistant eutectic alloy powder and the acrylic adhesive binder. A non-oxidizing atmosphere is, for example, N2
Examples include gas, inert gas such as Ar gas, reducing gas such as N2 gas, and in vacuum.

No cracks occurred in each of the alloy powder sheets 5 pre-sintered in this manner. This means that the compressive stress and tensile stress acting on the acrylic adhesive binder in each alloy powder sheet 5 during the molding process are removed during the molding process, and the This is due to the fact that each alloy powder sheet 5 maintains a molded shape. In order to prove this, an experiment was conducted in which the molding time of the alloy powder sheet 5 was varied and whether or not cracks occurred after preliminary sintering. The experimental data are shown in Table 1 below. In Table 1, the numbers in parentheses represent the frequency of crack occurrence, with the denominator being the number of experiments and the numerator being the number of crack occurrences. The cam sliding part 2 of the rocker arm body 4 used to obtain this experimental data
The radius of the sample was 27 mm, and the preliminary sintering conditions were held at 300° C. for 60 minutes in a N2 gas atmosphere.

Table 1 As is clear from this experimental data, the frequency of cracks in molding increases up to 8 hours, but
It can be seen that no cracks have occurred after the time has elapsed.

Thereafter, each pre-sintered alloy powder sheet 5 is placed on the cam sliding part 2 of the rocker arm main body 4 and heated to a predetermined temperature to perform main sintering to form a sintered layer 3. do.

Next, a specific example and a comparative example will be explained.

(Specific Example I) Metal composition: C: 2.0% by weight, P: 1.1% by weight, Mo
Wear-resistant eutectic alloy powder 97 with a particle size of 150 mesh or less, consisting of: 4.6% by weight, Cr: 8.9% by weight, and the balance Fe.
% by weight and 2% of acrylic adhesive binder Type 3 diluted with toluene, and then formed into a sheet with a thickness of 1.5 mm and cut into a size of 20 mm x 21.5 m + a to obtain alloy powder. Sheet 5 was obtained. This alloy powder sheet 5 was molded to a radius of 27 mm by setting it in a jig 6 and pressing it for 10 hours, then heating it to 300°C in an N2 gas atmosphere.
Preliminary sintering was performed by holding for 60 minutes and then cooling. As a result, no cracks were generated in the alloy powder sheet 5. Next, this pre-sintered alloy powder sheet 5 was placed on the cam sliding part 2 of the rocker arm body 4, heated in vacuum at a temperature increase rate of 10°C/mfn, and held at 1080°C for 20 minutes. Thereafter, the temperature was lowered to 900° C., held for 30 minutes, and then quenched with N2 gas for main sintering. As a result, a sintered layer 9 without cracks was obtained in the cam sliding portion 2 of the rocker arm body 4.

(Specific example ■) Metal composition: C: 2.2% by weight, P: 1.2% by weight, Mo
Wear-resistant eutectic alloy powder 97 with a particle size of 150 mesh or less, consisting of: 4.8% by weight, Cr: 8.0% by weight, and the balance Fe.
% by weight and 2% of acrylic adhesive binder Type 3 diluted with toluene, which was formed into a sheet with a thickness of 1.1 mm and cut into a size of 16.5 + am x 16.5 mm. An alloy powder sheet 5 was obtained. This alloy powder sheet 5
For molding with a radius of 25m+e, it was set in jig 6 and pressed for 15 hours, then heated to 300° C. in a N2 gas atmosphere, held for 60 minutes, and then cooled for preliminary sintering. As a result, no cracks were generated in the alloy powder sheet 5. Next, this pre-sintered alloy powder sheet 5 was placed on the cam sliding part 2 of the rocker arm body 4, heated in vacuum at a temperature increase rate of 10°C/mln, and held at 1070°C for 20 minutes. Thereafter, the temperature was lowered to 900° C., held for 30 minutes, and then quenched with N2 gas for main sintering. As a result, a sintered layer 3 free from cracks was obtained in the cam sliding portion 2 of the rocker arm body 4.

(Comparative example) Using the same alloy powder sheet 5 as in Example 1, this alloy powder sheet 5 was set in a jig 6 for molding with a radius of 27 mm.
After being compressed for a period of time, preliminary sintering was performed by heating to 300° C. in a N2 gas atmosphere, holding for 60 minutes, and then cooling.

As a result, cracks occurred in the alloy powder sheet 5.

In addition, in the above embodiment, the case is shown in which the application is applied to the cam sliding part 2 of the rocker armco that constitutes the valve mechanism of an engine for a vehicle such as an automobile, but the application is not limited to this. Of course, this method can also be applied to the case of forming the stratification layer 3.

(Effects of the Invention) As explained above, according to the method of the present invention, when forming a sintered layer on the surface of a metal substrate, the molding is set in the jig at a stage before preliminary sintering of the alloy powder sheet. By pressing the alloy powder sheet for 10 hours or more, the compressive stress and tensile stress acting on the acrylic adhesive binder in the alloy powder sheet are removed. It is possible to prevent the occurrence of cracks and form a crack-free sintered layer.

[Brief explanation of the drawing]

FIG. 1 is a front view of a rocker arm with a sintered layer formed by the method of the present invention, and FIG. 2 is a front view showing a molding jig with an alloy powder sheet set therein. 2... Cam sliding part (sintered layer forming part), 3... Sintered layer, 4... Rocker arm body (metal base), 5...
Alloy powder sheet, 6...Jig used for molding. C abrasion wound Figure 1/Figure 2

Claims (1)

[Claims] (1) A method for forming a sintered layer on the surface of a metal substrate, the alloy powder sheet comprising 94 to 99% by weight of wear-resistant eutectic alloy powder and 1 to 6% by weight of an acrylic adhesive binder. is set in a molding jig and pressed for 10 hours or more to mold it so as to follow the surface shape of the sintered layer formation site of the metal base, and then, after preliminary sintering of this molded alloy powder sheet, A method for forming a sintered layer, which comprises placing the metal substrate on the sintered layer formation site and performing main sintering.