JPH11335767A - Aluminum alloy for forging, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To open up, for an Al-Si alloy having sufficiently reduced grain size of an intermetallic compound, avenues of use capable of exhibiting its usefulness. SOLUTION: The aluminum alloy for forging has a composition containing aluminum as a primary component and also containing at least <12 wt.% Si component and 0.7 wt.%, in total, of element components forming a refractory intermetallic compound together with aluminum, and also an average grain size of the intermetallic compound is <=10 μm. Particular attention is paid to the fact that ductility at the time of forging can be increased and cracking can be inhibited by making the average size of the intermetallic compound to <=10 μm and, as a result, forgeability can be improved, and this alloy can be used in the form of a forged product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum alloy for forging and a method for producing the same.

[0002]

2. Description of the Related Art As a material exposed to high temperature and high load, such as a piston, a cylinder liner, and a connecting rod of an internal combustion engine formed by forging, the material has excellent fatigue strength and abrasion resistance at high temperatures and has a forging property capable of forming a thin-walled shape. Excellent materials are required.

Conventionally, for example, an aluminum (Al) alloy has been used as a piston material for an internal combustion engine. Silicon (Si) is added to this aluminum alloy to crystallize hard primary crystals or eutectic silicon particles in the metal structure to increase the wear resistance and seizure resistance required for the sliding surface of the piston. Is being planned.

[0004] Such an aluminum alloy is melted in a melting furnace in the form of an ingot of the alloy or in the form of an ingot or powder of each component, and is cooled and solidified to be drawn out as a continuous continuous rod-shaped cast. Is cut to form a billet, and the billet is put into a mold to forge a piston.

[0005]

However, when the silicon content is less than about 12% by weight,
Element (F) that forms a high melting point intermetallic compound with aluminum
e, Mn, Cr, Ti, V, Zr, etc.), as shown in the Al-Si phase diagram of FIG. The particle size of the aluminum intermetallic compound affects the properties of the metallographic structure.

In the conventional method for manufacturing an aluminum alloy, the particles of the intermetallic compound grow during the cooling process, and
It becomes a size of μm or more and is scattered in the eutectic structure. When the particle size of the intermetallic compound is large as described above, the elongation of the structure is small and the crystal is easily cracked, so that the forgeability is reduced. Further, the crystal particle size becomes non-uniform and the wear resistance is reduced.

Further, when a continuous cast body is drawn from the melting furnace, a temperature distribution is generated between the periphery and the center of the round bar, and the periphery is rapidly cooled, solidifies first, and the center solidifies slowly.
The particles at the center further grow and become larger, and the particle size becomes more uneven.

On the other hand, it is known that, by applying a stirring action in the cooling process of the molten alloy, crystal nuclei are stirred and dispersed, the cooling action is enhanced, and the growth of crystal grains is suppressed. Therefore, it is considered that the particle size of the intermetallic compound can be sufficiently reduced to, for example, about 10 μm or less in the Al—Si alloy by performing the stirring action in the process of cooling the molten alloy.

[0009] However, there is no known application of the Al-Si alloy in which the particle size of the intermetallic compound is sufficiently reduced to exert its usefulness.

The present invention has been made in consideration of the above points, and has been made in consideration of the above circumstances.
An object of the present invention is to provide an aluminum alloy that has been developed for use that can exhibit its usefulness with respect to a -Si alloy.

[0011]

According to the present invention, in order to achieve the above object, in the present invention, aluminum is used as a basic component, and at least a Si component having a weight ratio of less than 12% is used in a total of 0.1 to 0.1%.
An aluminum alloy for forging, comprising 7% by weight or more of aluminum and an elemental component for forming a high melting point intermetallic compound, wherein the average particle size of the high melting point intermetallic compound is 10 μm or less. I do.

That is, in the present invention, the elements (Fe, Mn, Cr, Ti, V, Zr) which form a high melting point intermetallic compound with Al are used.
Etc.) in a total amount of 0.7% or more, and by setting the average size of the particles of the high melting point intermetallic compound to 10 μm or less, ductility during forging is increased, cracks are suppressed, and forgeability is enhanced. The present invention provides an aluminum alloy for forging used as a forged product.

Further, according to the present invention, aluminum as a basic component, at least a Si component having a weight ratio of less than 12%, and an aluminum component having a total weight ratio of at least 0.7% and an element component forming a high melting point intermetallic compound are provided. After forging, in a cooling process of cooling the molten alloy to the solidification temperature in the forging aluminum alloy obtained by solidification, the average of the particles of the high melting point intermetallic compound by stirring the molten alloy in the vicinity of the solidification temperature. An aluminum alloy for forging characterized in that the size is 10 μm or less.

As described above, in the cooling process of the molten alloy, by performing the stirring action near the solidification temperature of the molten alloy, the average size of the particles of the high melting point intermetallic compound can be reliably reduced to 10 μm or less.

Further, according to the present invention, aluminum as a basic component, at least a Si component having a weight ratio of less than 12%, and an aluminum component having a total weight ratio of at least 0.7% and an element component forming a high-melting intermetallic compound, In the method of manufacturing an aluminum alloy for forging that has been solidified after being melted, in the cooling step of cooling the molten alloy to the solidification temperature, the molten alloy is stirred near the solidification temperature. And a method for producing the same.

According to this method, as described above, the average size of the particles of the high melting point intermetallic compound can be reliably reduced to 10 μm or less.

Further, in the present invention, the forging aluminum alloy is heated to a predetermined temperature lower than the melting temperature in the forging die and then forged, or heated to a predetermined temperature lower than the melting temperature outside the forging die. Provided is a method for forging a product made of an aluminum alloy for forging, which is characterized in that forging is performed in the inside.

According to this structure, the forging aluminum alloy is heated to such an extent that it is not melted and then forged, so that the forgeability is further enhanced.

One example of the forging use of the above aluminum alloy for forging is a piston for an internal combustion engine.

Another example of the forging aluminum alloy forging application is a cylinder liner for an internal combustion engine.

A cylinder block for an internal combustion engine is constructed by casting a cylinder liner using the aluminum alloy of the present invention.

[0022]

FIG. 1 is a configuration diagram of an example of an internal combustion engine to which the present invention is applied. This example shows a four-cycle engine 1. A cylinder liner 3 is mounted on the inner surface of the cylinder block 2 by press fitting or casting, and a piston 4 slides on the inner surface. The piston 4 has a piston pin 5,
It is connected to a crankshaft 8 via a connecting rod 6 and a crank arm 7. An intake pipe 9 and an exhaust pipe 10 are connected to a cylinder head portion above the cylinder block 2, and an intake valve 11 and an exhaust valve 12 are mounted respectively. The throttle 13 and the fuel injection valve 1 are provided on the intake pipe 9.
4 is attached. Reference numeral 15 denotes a spark plug. Piston 4
A valve relief 16 is formed on the upper surface of the.

The piston 4, the cylinder liner 3, and the connecting rod 6 of the engine 1 operate at a high temperature and a high rotation with an increase in the output of the engine, so that sufficient heat resistance, wear resistance and strength are required. In addition, forgeability during manufacturing is required. The present invention provides an aluminum alloy satisfying such requirements.

FIG. 2 is a block diagram of a melting furnace for producing an aluminum alloy for forging according to the present invention, and FIG. 3 is a flow chart showing a process for producing a forged product from this aluminum alloy for forging.

As shown in FIG. 2, a heater 19 is wound around a melting furnace 18 having an inlet 17 at an upper portion to heat a molten metal 20 therein. Molten alloy (molten) 20
Is drawn out from the bottom of the melting furnace 18 by a roller 21 as a rod-shaped solid cylindrical continuous casting 23 while being cooled. When the solid continuous cast body 23 is pulled out, cooling from the periphery of the round bar delays the cooling of the central portion, and a temperature distribution is generated as shown by A, and the periphery is solid and the inside is in a liquid state. In the present embodiment, a stirrer 24 composed of an electromagnet or an ultrasonic oscillator is provided near such a solidification position.
Is provided to stir the molten metal by electromagnetic induction or ultrasonic vibration to disperse crystal nuclei. As a result, the temperature difference between the central portion and the outer peripheral portion is relaxed, the temperature distribution A is suppressed, the cooling rate is increased, the growth of the particles is suppressed, the particle size is reduced, and the crystal particles are uniformly dispersed and stable. Product is obtained.

FIG. 3 is a flowchart of a process for manufacturing a forged product using such an alloy. First, an ingot of an Al—Si alloy having a composition shown in Table 1 below, which is one example of the alloy of the present invention, was prepared, and this was placed in a melting furnace 18 (FIG. 2).
(Step S1).

[0027]

[Table 1]

In this case, an ingot in an alloy state may be charged, or an ingot or powder of each component may be charged and melted and mixed in the melting furnace.

Next, the ingot is melted, and the molten metal is stirred by the stirring device 24 (FIG. 2) such as an electromagnet to solidify while dispersing the nuclei as described above (step S).
2). At this time, when the Si content is less than 12% by weight, as can be seen from the phase diagram of FIG. 9, primary crystal silicon does not precipitate with the temperature drop, and the influence of silicon particles is reduced. On the other hand, the influence of particles of the intermetallic compound formed between Fe, Mn, Cr, and Ti and Al increases. In the present embodiment, the particle size is about 10 μm or less because the growth of the intermetallic compound is suppressed by the stirring action.

In this case, as the inoculant of aluminum,
Phosphorus (P), sodium (Na), strontium (S
By adding r), antimony (Sb) or the like, the number of crystal nuclei increases, and the miniaturization of the intermetallic compound is further promoted.

The weight percentage of Si is 10.0 to 12.
Although the example of 0 is shown, it may be 10% or less, for example, 5% to 10%.

The continuous cast body in which the particle size of the intermetallic compound is reduced to about 10 μm or less is drawn out while being naturally cooled (step S3), and cut into forgings to form billets (step S4). . Each billet is put into a mold to form a forged product (step S
5). At this time, the aluminum alloy billet is heated so as not to melt, that is, the eutectic temperature (about 570)
It is desirable to forge after heating to a temperature not exceeding (° C). In this case, it may be heated in a forging die and forged after heating, or may be heated outside the forging die and forged in the forging die. Thereby, forgeability is enhanced and a high quality forged product is obtained.

Subsequently, in order to increase the strength of the forged product, heat treatment such as T6 treatment of quenching and tempering is performed (Step S).
6) After performing machining, the shape is adjusted, and the forging process is completed (step S7).

FIG. 4 is a diagram showing the structure of a piston die forged using the aluminum alloy according to the present invention.
FIG. 3 is a sectional view of a forged piston.

As shown in FIG. 4, an upper mold 27 having a convex portion 25 corresponding to the valve relief 16 (FIG. 1) and a concave portion 26 for forming a reinforcing fiber flow, and a frame mold 28a.
And a lower mold 28 composed of a middle mold 28b, a billet 2 made of the forging aluminum alloy according to the present invention described above.
9 is inserted. A protrusion 30 is provided on the shoulder of the middle mold 28b to remove the forged product after it has been formed, and the protrusion 30 is driven by a hydraulic cylinder 30A.

As shown in FIG. 5A, a fiber flow 31 is formed in the forged piston material 32 in accordance with the irregular shape of the outer shape, thereby increasing the strength of the material. Such a piston material is machined to form a top land, a ring groove, a piston pin hole, and the like, thereby completing the piston 33 as shown in FIG. 5B.

FIG. 6 is a sectional view of a cylinder block to which the present invention is applied. A cylinder block 34 having a cooling water jacket 36 and a crank chamber 37 formed at a lower portion.
A cylinder liner 35 is mounted by press-fitting or casting on the inner surface of the cylinder. Since the piston slides along the inner surface of the cylinder liner 35, the cylinder liner 35 has sufficiently high heat resistance, like the piston,
Abrasion resistance, strength and forgeability are required. Therefore, also for the cylinder liner, by forging using the forging aluminum alloy according to the present invention, a forged product having excellent forgeability, sufficient strength, and excellent heat resistance and wear resistance can be obtained. Further, the connecting rod may be manufactured through the forging process by using the aluminum alloy for forging of the present invention.

FIG. 7 is a graph showing the relationship between the average particle size of the intermetallic compound of the Al-Si alloy and the frequency of occurrence of cracks in the intermetallic compound. As can be seen from the figure, when the average particle diameter is about 10 μm or less, the crack generation rate sharply decreases. Therefore,
The average particle size of the intermetallic compound of the aluminum alloy for forging according to the present invention is desirably 10 μm or less.

FIG. 8 is a photomicrograph of the aluminum alloy for forging according to the present invention. (A) shows 100 times and (B) shows 400 times. It was confirmed that the black portion was an intermetallic compound, and the particles had a size of about 10 μm or less and were almost uniformly scattered.

[0040]

As described above, the present invention contains less than 12% by weight of Si, 0.7% or more by weight of aluminum in total, and an elemental component forming a high melting point intermetallic compound. In an aluminum alloy, the average particle size of the intermetallic compound can be reduced to 10 μm or less by stirring the molten alloy in the vicinity of the solidification temperature, and more preferably by adding an inoculant. An aluminum alloy with excellent forgeability, excellent wear resistance, and high strength is obtained. By forging with this aluminum alloy, thin sections have good moldability, high strength, high heat resistance, and excellent heat resistance and reliability. A highly forged product can be obtained.

By forming a piston and a cylinder liner of an internal combustion engine as such a forged product, it does not seize at high temperature and high load, and is excellent in heat resistance and wear resistance in response to the high output of the engine. An engine that achieves strong and reliable operation is obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an engine to which the present invention is applied.

FIG. 2 is a configuration diagram of a melting furnace used in the present invention.

FIG. 3 is a flowchart of a forged product manufacturing process of the present invention.

FIG. 4 is a configuration diagram of a forging die used in the present invention.

FIG. 5 is a sectional view of a piston forged by using the mold of FIG. 4;

FIG. 6 is a sectional view of a cylinder block to which the present invention is applied.

FIG. 7 is a graph showing the frequency of occurrence of cracks in an intermetallic compound.

FIG. 8 is a micrograph of the aluminum alloy according to the present invention.

FIG. 9 is a state diagram of Al—Si.

[Explanation of symbols]

1: engine, 2: cylinder block, 3: cylinder liner, 4: piston, 5: piston pin, 6: connecting rod, 7: crank arm, 8: crankshaft, 9: intake pipe, 10: exhaust pipe, 11: intake Valve, 12: exhaust valve, 1
3: throttle, 14: fuel injection valve, 15: spark plug, 16: valve relief, 17: inlet, 18: melting furnace,
19: heater, 20: molten metal, 21: roller, 23: continuous casting, 24: stirrer, 25: convex, 26: concave, 2
7: upper mold, 28: lower mold, 29: billet, 30: protruding rod, 31: fiber flow, 32: piston material, 3
3: piston, 34: cylinder block, 35: cylinder liner, 36: cooling jacket, 37: crank chamber.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C22F 1/043 C22F 1/043 // C22F 1/00 601 1/00 601 630 630K 630G 630D 651 651B 683 683 694 694B

Claims (7)

[Claims] An aluminum-based basic component comprising at least a Si component having a weight ratio of less than 12% and an aluminum component having a total weight ratio of at least 0.7% and an element component forming a refractory intermetallic compound. The average particle size of the high melting point intermetallic compound particles is 10 μm
An aluminum alloy for forging, characterized in that: 2. An aluminum component as a basic component, at least a Si component having a weight ratio of less than 12%, and an aluminum component having a total weight ratio of at least 0.7% and an element component forming a refractory intermetallic compound. Thereafter, in the aluminum alloy for forging obtained by solidification, in the cooling step of cooling the molten alloy to the solidification temperature, the average size of the particles of the high melting point intermetallic compound is 10 μm by stirring the molten alloy near the solidification temperature.
An aluminum alloy for forging, characterized in that: 3. An aluminum component as a basic component, at least a Si component having a weight ratio of less than 12%, and an aluminum component having a total weight ratio of at least 0.7% and an element component forming a refractory intermetallic compound. A method for manufacturing an aluminum alloy for forging that is to be solidified, wherein in the cooling step of cooling the molten alloy to the solidification temperature, the molten alloy is agitated near the solidification temperature. . 4. The aluminum alloy for forging according to claim 2, which is heated to a predetermined temperature lower than the melting temperature in a forging die and then forged, or heated to a predetermined temperature lower than the melting temperature outside the forging die. A forging method of a product made of an aluminum alloy for forging, which is forged in a forging die. 5. A piston for an internal combustion engine comprising the aluminum alloy for forging according to claim 1. 6. A cylinder liner for an internal combustion engine comprising the aluminum alloy for forging according to claim 1. 7. A cylinder block for an internal combustion engine, wherein the cylinder liner according to claim 6 is cast.