JP3128041B2 - Cylinder block and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cylinder block using an intermetallic compound dispersion strengthened aluminum (Al) alloy for a cylinder liner, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, when an aluminum alloy (AC4C, ADC12, etc.) alone is used for a cylinder block, the abrasion resistance of a cylinder bore surface is inferior. That is, as shown in FIG. 6, the block body 100 is made of a normal Al such as AC4C or ADC12.
Material and cast iron liner 101 into it,
Press fit to improve wear resistance. Further, as shown in FIG. 7, the entire block body 102 is made of hypereutectic aluminum / silicon alloy A390, and the wear resistance is improved by primary crystal Si without liner. Further, as shown in FIG. 8, the cylinder body 103 is made of an ADC 12 or the like, and the cylinder bore is formed as a composite reinforced portion 104 composed of alumina fiber and carbon fiber to improve wear resistance.

[0003]

The conventional methods have the following problems. First, in the case of an aluminum cylinder block containing a cast iron liner shown in FIG. 6, (a) the liner is cast iron, so that the weight is increased as compared with the case of aluminum alone. (b) The cooling efficiency of the cylinder is reduced because cast iron has lower thermal conductivity than aluminum. (c) The clearance setting considering the thermal expansion difference between the cast iron liner and the aluminum piston causes rattling of the piston and causes noise. Next, in the case of a cylinder block made of a hypereutectic aluminum-silicon alloy shown in FIG. 7, the above-mentioned problems (a) to (c) can be solved because the cylinder block is an integral block without a sleeve.
It is indispensable to control the uniformity of the grain size and distribution of primary crystal silicon in order to secure wear resistance. (e) An etching process is required to lift the primary crystal silicon to the surface of the bore. (f)
The machinability is very poor due to the presence of primary crystal silicon. Due to such problems, there are difficulties in cost and productivity. FIG.
As described above, the method of providing the composite reinforced portion involves a high cost of the alumina fiber + carbon fiber preform and a problem of cost and productivity because the casting method for compounding with aluminum is special. The present invention has been made in view of the above circumstances, and has as its object to provide a cylinder block using an intermetallic compound dispersion strengthened aluminum alloy for a cylinder liner and solving the above problem, and a method of manufacturing the same.

[0004]

According to the above object, according to the present invention, there is provided a precursor composite obtained by weighing and mixing powders of respective constituent elements of an intermetallic compound as reinforcing particles in accordance with a stoichiometric composition and subjecting them to mechanical alloying. After adding pure Al powder or Al alloy powder to this precursor composite and subjecting it to mechanical alloying again, the billet molded from this powder is subjected to hot working to form a cylinder liner, and then the cylinder liner Liner for cylinder block body A
This problem has been solved by a method of manufacturing a cylinder block in which a cast alloy is cast with a molten metal and reacted at a contact surface thereof, and a joining surface of the both is integrated. The present invention has solved the above-mentioned problem by providing a cylinder block manufactured by the method according to the first aspect. This makes it lightweight and
A cylinder block having high strength, good thermal conductivity and good combustion efficiency, and improved productivity and cost can be manufactured.

Hereinafter, the present invention will be described in detail with reference to the drawings. First, the material of the cylinder liner used in the present invention will be described with reference to FIG. Each of the constituent elements A, B, C,.
Each powder of (usually two or more types. Here, the case of A and B2 elements will be described) is prepared. Next, powders of A and B elements are weighed and mixed according to the stoichiometric composition of each constituent element of the target intermetallic compound. Here, the stoichiometric composition refers to a chemical composition originally represented by a structural formula. For example, in the case of Al ₃ Ti, a composition ratio of Al atoms to Ti atoms is 3: 1. -2
Since 5 at (atomic)% Ti is the stoichiometric composition of Al ₃ Ti, if Mg ₂ Si, Mg: Si is 2: 1 and Mg-33.3 at% Si is the stoichiometric composition.

[0006] The mixed powder is subjected to ball milling, preferably mechanical alloying using a high energy type attritor. FIG. 5 shows an example of the attritor. In the attritor 1, the agitator 3 is rotated by the rotation of the shaft 2, and the ball 4 is thereby moved. The raw materials are mixed by the movement of the balls 4. During the mixing operation, gas is introduced from the gas inlet 5 to keep the mixed atmosphere constant. Further, cooling water is supplied from the water inlet 6 to keep the temperature constant. In addition, 7 is a gas outlet, and 8 is a water outlet.
The ball 4 is preferably a steel ball of at most 1 inch, preferably 3/8 inch. The ratio of the total weight of the ball to the total weight of the powder is 15%.
0: 1 to 20: 1, preferably 140: 1 to 4
0: 1. The rotation speed of the shaft 2 is preferably 250
rpm. The mixed atmosphere is a non-oxidizing atmosphere using Ar or He. It is preferable that the peripheral speed of the tip of the agitator 3 is 3.5 m / sec or less, and the treatment is performed within 10 hours using a ball of 1 inch at maximum within 20 hours. If the time is longer than 20 hours, the cost increases, and Fe is mixed in, thereby lowering the elongation of the finished product.
At the time of mechanical alloying, methanol or ethanol is added as a dispersant in an appropriate amount in consideration of the dispersibility of the powder or the lubricating effect. The amount of addition was [amount of dispersant (ml) / total weight of powder (g)] × 100 = 1
To 5. However, in the case of methanol, 1 to 5 is preferable, and in the case of ethanol, 1 to 3.5 is preferable.

The powder obtained by the mechanical alloying is obtained by mechanically incorporating A (B) into B (A) to form an alloy powder, not an intermetallic compound. That is, it is the precursor complex X of the intermetallic compound. When the precursor composite X is composed of a component composition containing Mg having a high ignitability, the precursor composite X is not discharged to the outside of the container, but is charged with Al powder or Al alloy powder into a mixing container in which it is contained, and mechanical alloying is performed again. Is carried out. The amounts of the precursor composite X and the aluminum powder to be added are as follows by weight ratio. 1 to 3% by weight ≦ X / [X + aluminum powder] ≦ 40% by weight When the content is 40% by weight or more, the extrudability is reduced and the impact value is also reduced. The effect of addition is small unless 1 to 3% by weight is added. The mechanical alloying in this step is also performed in a non-oxidizing atmosphere by adding an organic solvent such as alcohol (methanol, ethanol, etc.) using an attritor.

After the above steps, the powder is discharged. The powder that has been discharged is classified and the powder finer than 150 mesh is used thereafter. Preferably, finer than 400 mesh, but coarser than 150 mesh is returned to the mechanical alloying process. Next, the mechanical alloying powder is put into a closed mold and compressed to form a billet. The billet is degassed by heating it in a vacuum heat treatment furnace. That is, 400 to 5 in vacuum
Heat at 00 ° C. for 4-5 hours. Next, the degassed billet is subjected to hot extrusion to produce a cylinder liner. As a result, the precursor composite reacts to form an intermetallic compound, which becomes a structure finely dispersed in the Al matrix.

Table 1 shows the physical properties of the cylinder liner materials I and II manufactured as described above and comparative examples.

[0010]

[Table 1]

According to Table 1, the raw materials I and II have high strength, and have a specific gravity of about 1/3 that of cast iron (such as FC250), so that they are lightweight. Further, since the difference in the coefficient of linear expansion between the piston material and the cylinder block material is small, the strain is low, the clearance between the piston and the liner can be reduced, the combustion efficiency is improved, and the noise is reduced. A39
The tensile strength, the longitudinal elastic modulus, and the coefficient of linear expansion are equal to or greater than 0 and FRM. FIG. 3 shows this Mg ₂ S
The micrograph of the structure of the i-dispersion strengthened aluminum alloy is shown. Mg ₂ Si and Si of 5 μm or less are finely dispersed, thereby improving wear resistance. In addition, since hard particles are fine, the machinability is good and ordinary high-speed steel can be used.

Next, using the cylinder liner, a specific procedure for manufacturing a cylinder block will be described. For the cylinder liner made of dispersion-strengthened intermetallic compound aluminum, the selection criteria for the dispersion-strengthened intermetallic compound are as follows: (a) If the purpose is to pursue lighter weight and higher strength, use Mg ₂ S
i, Al ₃ Ti, TiAl and the like are preferable. (b) If the purpose is to improve the high-temperature strength, use Al ₃ T
i, Al ₃ Ni, Al ₃ Fe, Ni ₃ Al, FeAl,
Al ₃ V, Al ₃ Zr, Al ₆ Mn and the like are preferable. (c) When the purpose is to pursue high strength and low cost, use Mg
₂ Si, CuAl ₂ or the like is preferable. Therefore, in the present invention, aiming at lightweight, high strength and low cost,
_It uses 2Si.

In FIG. 2, the cylinder liner made of the Mg ₂ Si dispersion strengthened aluminum alloy manufactured by the process of FIG. 1 reduces distortion due to heat during casting.
In addition, 100 to 50
Preheat to 0 ° C. In this case, if the preheating temperature is 100 ° C. or lower, the temperature difference from the molten aluminum (680 to 720 ° C.) is large, so that the deformation of the liner becomes too large, and the liner and the molten metal do not sufficiently react with each other, so that it is difficult to obtain sound bonding.
On the other hand, when the temperature exceeds 500 ° C., the strength of the liner itself is not maintained, and the amount of deformation increases, and local melting occurs partially.
Therefore, the preheating temperature of the liner is desirably between 100 and 500 ° C., and is preferably around 400 ° C. from the viewpoint of suppressing distortion and reacting / joining. As the melt used for the block body, AC4 which has been conventionally used as a cylinder block material is used.
B, AC4C, ADC12, etc. are used.
C4C was used.

Next, the pre-heated cylinder liner is set in a cylinder block mold, the molten metal is poured, and the liner is cast-in. At this time, the molten metal temperature becomes 68
Since the temperature is 0 to 720 ° C. and the base of the liner is aluminum, a reaction occurs between the molten metal and the liner, and the liner and the block are joined. Figure 4 shows the liner (preheating temperature 400 ° C)
And cylinder block (AC4C, pouring temperature 720 ° C)
3 shows a structural photograph of the joint of Example 1. No defects are present at the interface between the liner and the block (melt), indicating that the liner and the block are completely bonded and integrated. Thereby, the lightness, high strength, and high wear resistance of the material can be utilized, and at the same time, the thermal conductivity can be improved by integration. In addition, the Mg ₂ Si dispersion strengthened aluminum liner has excellent high-temperature strength,
There is little deformation, and any of low pressure casting, pressure die casting, and molten metal forging can be used.

Next, after casting to improve the strength, the block containing the liner is subjected to a heat treatment such as T5 or T6.
As can be seen from Table 1, since the Mg ₂ Si dispersed material has excellent high-temperature strength, there is no problem even if such a heat treatment is performed.
Conversely, the diffusion of the bonding interface proceeds by the heat treatment, and the bonding strength increases. Next, machining is performed. Since the block body is AC4C (AC4B and ADC12 are also used) which has been conventionally used, and the liner has Mg ₂ Si finely dispersed therein, the workability is good. The conventional processing line for aluminum cylinder blocks containing cast iron liners can be used as is. Therefore, the productivity is higher and the cost is lower than the conventional cylinder block shown in FIGS.

The Mg ₂ Si-dispersed Al cylinder liner can also be manufactured by press-fitting the cylinder liner. In this case, the thermal conductivity between the liner and the block is lower than in the case of cast-in, but it is much better than the conventional cast iron liner.

[0017]

According to the present invention, the following effects can be obtained. (1) Both the molten metal and the liner, which are to be blocks, are made of an Al-based material. Therefore, a reaction occurs between the two at the time of casting, and bonding is performed simultaneously with casting. (2) Since the block and the liner are integrated, the thermal conductivity is improved and the cooling efficiency is improved. (3) The weight can be reduced by using a lightweight and high-strength Mg ₂ Si dispersion strengthened aluminum alloy for the liner. (4) Since the difference in linear expansion coefficient between the piston and the liner is small, it is possible to reduce the piston clearance, thereby improving combustion efficiency and reducing noise. (5) Since ordinary cutting can be performed by joining the block body and the liner, the conventional processing line can be used as it is. (6) Since the high-temperature strength of the liner is high, any casting method can be used when casting. (7) Since the material is a non-heat-treatable alloy, the strength of the liner does not decrease even if heat treatment is performed after joining.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a manufacturing process of a cylinder liner according to the present invention.

FIG. 2 is an explanatory view of a manufacturing process of casting the same cylinder liner into a cylinder block.

FIG. 3 is a photograph instead of a drawing showing a metal structure of the cylinder liner.

FIG. 4 is a photograph instead of a drawing showing a metal structure of a joint surface between the cylinder liner and the cylinder block.

FIG. 5 is an explanatory diagram of an attritor used in the present invention.

FIG. 6 is an explanatory view of a conventional joining procedure of a cylinder block and a cylinder liner.

FIG. 7 is an explanatory diagram of the linerless cylinder block.

FIG. 8 is an explanatory view of a cylinder block forming the composite reinforced portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Attritor 3 Agitator 4 Ball 5 Gas inlet 6 Water inlet 7 Gas outlet

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Claims (4)

(57) [Claims] 1. A precursor composite is produced by subjecting a powder of each constituent element of an intermetallic compound to be reinforced particles to weighing and mixing in accordance with a stoichiometric composition, and then subjecting the precursor composite to pure Al powder. Alternatively, after adding Al alloy powder and subjecting to mechanical alloying again, a billet molded from this powder is subjected to hot working to form a cylinder liner, and then this cylinder liner is melted with a molten aluminum alloy for the cylinder block body. A method for manufacturing a cylinder block, comprising: casting and reacting at a contact surface thereof to integrate a joint surface between the two. 2. The method according to claim 1, wherein the mixing ratio of the precursor composite powder used for the cylinder liner is 40% by weight or less of the Al powder. 3. The method according to claim 1, wherein the cylinder liner is 100 to 50.
The method according to claim 1, characterized in that the casting is carried out after preheating to 0 ° C, preferably about 400 ° C. 4. A cylinder block manufactured by the method according to claim 1.