JPS6312121B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an aluminum-silicon-graphite cylinder liner that has excellent wear resistance and sliding properties. The cylinder liner referred to here is a component in internal combustion engines, compressors, etc. whose inner wall slides against a reciprocating piston. Al-Si graphite cylinder liner is
It is known that when used in automobile engines, various internal combustion engines, compressors, etc., it significantly increases the engine life and efficiency. However, it is not easy to uniformly disperse graphite, and for example, Ni-plated graphite powder is mixed with Al-plated graphite.
This required expensive manufacturing processes such as pouring into molten alloy and casting under pressure. Moreover, the Al-Si craftite alloy obtained in this way has coarse precipitated Si particles of several micrometers or several thousand micrometers, and the graphite is similarly coarse, so its performance as a cylinder liner is not sufficient. It was hot. On the other hand, as a method for making Al-Si-craftite cylinder liners using powder metallurgy, the usual method of embossing and sintering is difficult to sinter, and the added graphite is difficult to sinter. As a result, the strength necessary for cylinder liners could not be obtained, and it was not put into practical use. A method of hot extruding the powder was also attempted, but
It is technically difficult to hot extrude powder into a thin-walled pipe such as a cylinder liner, and the hot extrusion equipment has to be enlarged, so it has not been put to practical use. In addition, attempts to manufacture by powder hot forging are difficult to achieve high density by compression of thin-walled cylinders.
Sufficient densification could not be achieved, and therefore, satisfactory performance could not be obtained. The method of obtaining true-density powder by isostatic pressing has already been put to practical use with various alloys and ceramics, and it was easy to imagine its application to Al-Si graphite alloys. It has not yet been successful due to the difficulty of sintering Al--Si alloy powder. This is because Al or Al alloy powder has an extremely thin but strong irreducible oxide film of alumina or the like on its particle surface. This oxide film inhibits the diffusion of solvent atoms, ie, Al atoms, from the base layer, which causes almost no sintering of Al. Therefore, although hot isostatic pressing can plastically deform individual Al or Al alloy powder particles and almost eliminate pores, chemical or physical Since there was no bonding force, only mechanical bonding force, sufficient mechanical performance could not be obtained. The present invention was made to solve the above-mentioned problems.
By mixing one or more of Mg and Ni, the disadvantages of the coining method in the conventional powder hot forging method are avoided, and by using a completely different idea, hot backward extrusion is performed and the excess bottom is punched out at the same time. By adopting this method, it is possible to easily and economically produce cylinder liners that are homogeneous, have good precision, and have excellent wear resistance and sliding properties without using large-scale extruders or hot isostatic pressing machines. The purpose is to provide a manufacturing method. In the present invention, 10 to 20% by weight of Si and 1 to 20% of graphite
A powder mixture containing 10% by weight and 0.3 to 7% by weight each of one or more elements selected from the group consisting of Fe, Cu, Mg, and Ni as alloying elements, and the balance consisting of Al is pressed. Heating the formed preform,
The above preformed body is inserted into a mortar having a cylindrical inner surface in which a hollow lower punch whose upper end surfaces are aligned and a middle stopper inside thereof is inserted into the bottom, and the upper punch is press-fitted into the molded body and the upper punch is inserted backward After extrusion, only the inner stopper is retreated downward, and at the same time, the upper punch is entered into the space into which the inner stopper has retreated, thereby punching out the bottom surface of the extrusion molded body into a disk shape. This is a method for manufacturing cylinder liners. In the present invention, the Si content in the powder mixture is specified to be 10 to 20% by weight (hereinafter simply referred to as %).The reason why a hypoeutectic alloy containing less than 10% Si as a cylinder liner is that the amount of eutectic Si particles precipitated is If it is too low, the wear resistance will not be sufficient, while if it exceeds 20%, the molded product will be prone to cracking during plastic deformation, so it must be avoided. Furthermore, the reason why graphite is specified as 1 to 10% is because when adding graphite, which functions as a solid lubricant, if it exceeds 10%, the molded product will crack during plastic deformation, so it is difficult to maintain a good cylinder. This is because a liner cannot be obtained, and if it is less than 1%, the effect of graphite addition is not significant, resulting in insufficient lubricity and insufficient wear resistance. In addition, one or more elements selected from the group consisting of Fe, Cu, Mg, and Ni as alloying elements are used.
The reason for specifying 0.3 to 7% is that these elements are all selected to strengthen the Al material through precipitation hardening, etc., and the amount of each element added is 0.3%.
If the content is less than 7%, the strengthening effect will not be significant, and if it exceeds 7%, the precipitates will become excessive and become brittle, making plastic deformation difficult, making it unsuitable. . These elements and the above-mentioned Si are preferably used in the form of a powdered alloy obtained by adding it to Al and melting it. Hereinafter, the present invention will be explained by examples using the drawings. First, the required amount of Si and one or more elements selected from the group consisting of Fe, Cu, Mg, and Ni were added.
After mixing the Al alloy powder and a required amount of graphite, the mixture is pressed and molded to produce a preformed body in the shape of, for example, a tablet or a ring. 1 to 3 are longitudinal sectional views illustrating, in order of steps, an embodiment of the method of the present invention using a tablet-shaped preform. In FIG. 1, reference numeral 1 denotes a mortar having a cylindrical inner surface, into which a hollow lower punch 3 and an inner stopper 4 are inserted. The inner stopper 4 is inserted into the center of the hollow lower punch 3,
The upper end surface 5 of the hollow lower punch 3 and the upper end surface 6 of the inner stopper 4 are held so as to coincide with each other. The tablet-shaped preform 7 described above is inserted into the die 1, and the upper punch 2 having the same diameter as the inner stopper 4 is press-fitted from above. In the figure, a tablet-shaped preform 7 is used, but a ring-shaped one may also be used, which may be even more effective depending on the final shape. By the above-described press-fitting, the preformed body 7 is extruded backward as shown in FIG. 2, and a cap-shaped extrusion molded body 8 having a bottom surface 9 is formed. In FIGS. 2 and 3, the same reference numerals as in FIG. 1 indicate the same parts. FIG. 2 shows a state in which the upper punch 2 is press-fitted into the molded body while keeping the upper end surfaces 5 and 6 of the hollow lower punch 3 and the inner stopper 4 aligned. At this time, the preform is subjected to significant shear deformation stress and flow occurs, so the pores disappear and the preform is extruded into the gap between the upper punch 2 and the die 1, forming an ultra-high density extruded product 8. . Next, as shown in FIG. 3, the inner stopper 4 is retreated downward (in the direction of the arrow) inside the hollow lower punch 3, and
When the upper punch 2 enters the gap created by the retreat of the inner stopper 4, the excess bottom surface 9 of the extruded body 8 can be punched out into a disk shape, as shown in the figure. In this case, it is also possible to raise the inner stopper 4 while retracting the upper punch 2 and punch out in the same way.
This is generally not preferred because the press operation becomes complicated. In the series of steps described above, the interlocking of the die 1 with the upper and lower punches 2 and 4 is not necessarily required, but since the flow during plastic deformation of the preform 7 is large, it is necessary to prevent wear with the mold. It is preferable that the mortar 1 adopts the so-called floating die method and moves downward in conjunction with the lowering of the upper punch 2 under pressure. FIGS. 4 to 6 are cross-sectional views illustrating, in order of steps, an embodiment of the method of the present invention using a ring-shaped preform. The same parts as in FIGS. 1 to 3 are designated by the same reference numerals.
In FIG. 4, a hollow lower punch 3 and a middle plug 4 are inserted into the bottom of the mortar 1 having a cylindrical inner surface, the middle plug 4 is inserted into the center of the hollow lower punch 3, and the upper end surface 5 of the hollow lower punch 3 and the middle Stopper 4
The fact that the upper end surfaces 6 of the apparatus are held in alignment with each other and the operation of each part of the apparatus after that are the same as those shown in FIGS. 1 to 3. A ring-shaped preform 7' is inserted into such a die 1. Needless to say, the inner diameter of the ring of the preform 7' is larger than the diameter of the upper punch 2 and the middle stopper 4, which face each other and have the same diameter, and the outer diameter has a shape that almost matches the inner diameter of the die 1 and has an appropriate thickness. It has the following. As shown in FIG. 5, if the upper punch 2 is press-fitted into the preformed body 7' while keeping the upper end surfaces 5 and 6 of the lower punch 3 and the inner stopper 5 aligned, the preformed body will be significantly damaged. When subjected to shear metamorphic stress, a flow occurs, the pores disappear, and the material is extruded into the space between the upper punch 2 and the die 1, forming an ultra-high density extruded product 8'. Next, as shown in FIG. 6, the inner stopper 4 is retreated downward (in the direction of the arrow) inside the hollow lower punch 3, and
When the upper punch 2 enters the gap created by the retreat of the inner stopper 4, the excess bottom surface 9' can be punched out from the extruded body 8', as shown in the figure. Example: After adding and mixing 5% of graphite powder to Al-12%Si-1.1%Cu-1.2%Mg-0.9%Fe alloy powder,
A tablet-shaped preformed body with an outer diameter of 32 mm and a thickness of 20 mm and a ring-shaped preformed body with an outer diameter of 32 mm, an inner diameter of 16 mm and a thickness of 25 mm were formed by stamping with a press. This molded body
After heating it to 500℃, insert it into the die 1 of the mold as shown in Fig. 1, which is set in a mechanical brace.
Extrude backwards using the method shown in Figures 1 to 3 and 4 to 6, and the outer diameter is 32 mm, the inner diameter is 28 mm, and the height is 50 mm.
I made a mm cylinder liner. For comparison, pipe-shaped samples with the same dimensions were made from the same Al alloy-graphite mixed powder by hot isostatic pressing at 500°C and hot powder extrusion at 500°C with an area reduction of 80%. Table 1 shows the results of measuring the density and radial crushing strength of test pieces obtained by cutting these samples into 10 mm thick test pieces at three locations at the top, middle, and bottom as shown in FIG. 7.

[Table] From Table 1, it was found that the product according to the present invention had sufficient radial crushing strength (standard: 20 Kg/mm ² ), and the dimensional accuracy was sufficient. As described above, the method of the present invention can be applied to Si, graphite, Fe, Cu, Mg,
Since a powder mixture containing one or more elements selected from the group consisting of Ni and the balance consisting of Al is used, Al-Si-graphite contains Fe, Cu,
By adding alloying elements such as Mg and Ni, Al
The matrix is strengthened by precipitation strengthening, etc., and the preformed powder mixture is heated and extruded backwards using the die, upper punch, hollow lower punch, and middle plug as described above. As the inner stopper retreats, the upper punch enters the gap and punches out the bottom of the extruded body in the form of a disc. Therefore, due to the sufficient material flow during backward extrusion, the density is high and the bonding force of the particles is high. Products with large dimensions and good dimensional accuracy can be easily obtained without using large-scale equipment, so aluminum-silicon-graphite cylinder liners with excellent strength, wear resistance, sliding properties, and dimensional accuracy are available. It has the advantage of being easy and economical to manufacture.

[Brief explanation of the drawing]

1 to 3 and 4 to 6 show, in longitudinal section, the implementation of the invention in tablet-shaped and ring-shaped preforms, respectively, in the order of steps. 7th
The figure is an explanatory diagram of the position of cutting out a test piece from a sample. 1... Mortar, 2... Upper punch, 3... Hollow lower pestle, 4... Middle stopper,
5, 6... Upper end surface, 7, 7'... Preformed body, 8,
8'...Extruded body, 9,9'...Bottom surface.

Claims (1)

[Claims] 1 10 to 20% by weight of Si, 1 to 10% of graphite, and 0.3% each of one or more elements selected from the group consisting of Fe, Cu, Mg, and Ni as alloying elements.
A cylindrical shape is obtained by heating a preformed product made by pressing a powder mixture containing ~7% by weight and the remainder being Al, and inserting a hollow lower rod whose upper end surfaces match each other and an inner plug inside the rod into the bottom. After inserting the preformed body into a mortar having an inner surface and press-fitting an upper punch having the same diameter as the inner plug into the molded body to perform backward extrusion,
A method for manufacturing a cylinder liner, which comprises: retracting only the inner plug downward, and at the same time inserting the upper punch into the recessed gap of the inner plug to punch out the bottom surface of the extrusion molded body into a disk shape.