JP2000280043A - Forging material and, manufacture of forging member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a forging material and a forging member as well wherein deficiency such as a crack is not caused even if a fast forging is conducted and, sufficient mechanical character can be obtained. SOLUTION: A light alloy forging material containing aluminum at 2 wt.% or more and 10% or less and, formed by a semi-fusion forming method or a semi-fusion casting method is forged at a forging velocity of 100 [mm/s] or higher. Also, a forging material is forged by setting the maximum value of forging ratio at 40% or higher, and a solid phase ratio of a portion to be forged at this maximum forging ratio is at 10% or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light alloy forging material formed by semi-solid molding or semi-solid casting and forged at a certain high speed, and a forged member using such a forging material. And a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, light metals such as, for example, magnesium (hereinafter appropriately denoted by its element symbol Mg) and its alloy or aluminum (hereinafter, appropriately denoted by its element symbol Al) and its alloy are used as materials. The most common method of manufacturing a light metal member is a method based on a casting method. As a kind of this casting method,
The so-called die-casting method, in which the casting process is accelerated by injecting and filling a light metal melt into a mold at a high pressure so that the productivity can be significantly improved, has been well known in the past. ing. Also, in contrast to the normal melting and casting method in which a light metal melt is poured into a mold in a completely molten state at or above its melting point, a light metal melt is poured into a mold in a semi-molten state (basically below its melting point). A semi-solid casting method is also known.

Further, in recent years, a method of manufacturing a light metal member using an injection molding method has been put to practical use, particularly for Δg and its alloys. In this method, a molten light metal in a molten state is injected and filled into a molding cavity of a molding die from an injection nozzle using an injection molding apparatus. Member) can be manufactured. In addition, this injection molding method is, for example, compared with a casting method such as a die casting method,
In the work environment, it is relatively clean (clean) and has higher safety. In terms of quality, it is known as a process capable of obtaining highly accurate and homogeneous light metal molded products with few defects such as shrinkage cavities. ing. Also in this injection molding method, a so-called semi-molten injection molding method is known in which a light metal melt is made into a semi-molten state (essentially less than its melting point) and injected and filled into a molding cavity from an injection nozzle. (For example, see Japanese Patent Publication No. 15620/1990).

In the above-described injection molding method as well as the casting method, when a molten metal in a semi-molten state is used, the temperature of the molten metal (hereinafter referred to as “molten metal” ) Is low, so-called “burrs” are less likely to appear, and are suitable for high-speed and / or high-pressure injection, which is advantageous in improving productivity. Furthermore, by filling the molding cavity with the molten metal in a semi-molten state, the molten metal in which the undissolved solid phase portion is mixed in the completely dissolved liquid phase portion is filled as it is, so it is filled in a state close to laminar flow Gas entrainment is relatively low and a relatively homogeneous tissue is obtained. Thereby, it is possible to enhance the mechanical characteristics of the obtained member as a whole.

[0005] In the present specification, the term "solid phase" refers to "a portion of a light metal melt which is not melted and remains in a solid state when it is in a semi-molten state".
Means "a portion which is completely melted and is in a liquid state". The “solid phase” is obtained by observing the solidified structure of the obtained light metal member, and as a “portion that has been maintained in a solid state without being melted in a semi-molten molten metal state” The liquid phase portion, which has been completely melted in a molten state to be in a liquid state, can be easily identified.
When the obtained member is referred to as a “solid phase”, it refers to “a part that was maintained in a solid state without being melted in a semi-molten molten light metal (solid phase)”. Further, in the present specification, the “solid phase ratio” refers to “the ratio of the solid phase to the entire molten metal (solid phase + liquid phase) in the metal melt in a semi-molten state”. By observing,
It can be obtained numerically as the ratio (area ratio) of the portion that was the “solid phase” to the entire observation region.

Further, in the present specification, the “semi-molten state” of a light metal melt basically means “a raw material in a solid state (solid phase)” and a raw material in a molten state (liquid phase). Is a state obtained by heating a raw material to a temperature lower than its melting point. However,
The case where the temperature of the light metal melt is substantially at or just above the melting point and the solid fraction is substantially equal to 0 (zero)% is also included in the “semi-molten state”. Even when the light metal melt itself has such a substantially solid phase ratio of 0%, one shot (one shot) from the injection nozzle into the mold, for example, in consideration of the actual injection molding process in the semi-solid injection molding method. Between the end of the injection and the next (next shot) injection, the molten metal in the molten metal supply path of the injection nozzle is cooled and solidified at the nozzle tip side (so-called cold plug).
And a high solid phase portion having a high solid phase ratio is generated, so that the molten light metal actually injected into the molding cavity inevitably contains the solid phase portion.

On the other hand, when it is required to obtain a light metal member having higher strength than the above-described casting method or injection molding method, the forging method is most generally employed. In addition, as one type of manufacturing method for manufacturing light metal members by this forging method,
For example, as disclosed in JP-A-6-297127, a material (forging material) suitable for forging is formed by a casting method prior to forging, and this material is set in a predetermined forging die. There is known a so-called casting forging method in which a forging process is performed.

According to the casting and forging method, it is possible to form a semi-finished product having a shape relatively similar to the shape of a finished product (forged member) by forging in a casting (material) stage. This makes it possible to simplify the forging step to only one step of finish forging, and to forge even a member having a complicated shape. Further, it is possible to adjust the structure of the material so that the forging process can be performed without difficulty even with a material having poor forgeability. Incidentally, the molding of the forging material in the casting forging method can be performed by an injection molding method instead of the casting method.

Light alloys such as the above-mentioned Mg alloys have already been put to practical use as materials for wheels and the like in automobiles, for example. When considering application as a material for a mechanical component (for example, a valve lifter of an engine intake / exhaust valve) around an internal combustion engine (engine), not only strength characteristics at room temperature but also, for example, 15
Even at a high temperature of about 0 ° C. or higher (for example, 220MP
a degree or more) and excellent creep resistance. In such cases, in particular, it is generally difficult to obtain the required characteristics stably in molding processes such as casting and injection molding, and plastic working in which a dense material structure is obtained at the time of working, in particular, forging at a forging ratio of a certain level or more Most preferably, it is necessary to ensure good forgeability.

[0010]

When a forging material is forged to obtain required mechanical properties, in practice, the cycle time in the forging process is reduced from the viewpoint of securing productivity during mass production. It must be as short as possible. For this reason, as forging conditions related to the cycle time, it is generally required to perform high-speed forging at a forging speed of approximately 100 [mm / s] or more. However, in a range where the forging speed is low (a range of less than 100 [mm / s]), forging can be performed without any trouble, and even if the material is capable of effectively improving the strength by plastic working, it is easy to perform high-speed forging. Cracks may occur, or even if the forging rate is increased, the strength may tend to decrease,
There has been a problem that a case where a sufficient effect of improving mechanical properties cannot be obtained may occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above technical problem, and is capable of providing sufficient mechanical characteristics without causing defects such as cracks even when high-speed forging is performed. It is a basic object to provide a material and a method for manufacturing a forged member.

[0012]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above technical problems, and as a result, have found that a light alloy forging material formed by a semi-solid molding method or a semi-solid casting method. By adding a certain amount or more (2% by weight or more) of Al, improvement in room temperature strength and / or ensuring castability can be effectively achieved, and other elements (calcium: Ca) are added together. By the high temperature (150
C)), a high tensile strength (about 220 MPa or more) can be ensured, and as the solid fraction increases, the tensile strength generally decreases, but the strength improving effect of forging increases. In this case, when the forging ratio is increased to a certain degree or more, a phenomenon occurs in which the tensile strength is rather lowered. However, when the solid phase ratio is set to be higher than a certain value (10% or more), such a tendency that the strength decreases does not occur. Furthermore, in a forging material made of a Mg alloy containing Al and calcium (Ca), as the Ca content increases within a certain range (4% by weight or less), the creep resistance improves as the content of Ca increases. And the Ca / Al ratio (A
l Ratio of Ca content (weight) to content (weight))
It is found that the cracking rate in high-speed forging can be suppressed to a very low level while ensuring a required forging rate in a range of less than or equal to (0.8 or less).

Therefore, the forging material according to the invention of claim 1 of the present application (hereinafter referred to as the first invention) is 100 [mm / mm].
s] A forging material made of a light alloy forged at a forging speed of not less than 2% by weight and containing not more than 10% by weight of aluminum and formed by a semi-solid molding method or a semi-solid casting method. It is characterized by the following.

The reason why the lower limit of the Al content is set to 2% by weight is that the content of Al not less than this value is
Even when a forging speed of 100 [mm / s] or more is performed, improvement of room temperature strength and / or ensuring of castability can be effectively achieved, and other elements (calcium: Ca) can be obtained.
Is also added, it is possible to secure a sufficient tensile strength (about 220 MPa or more) at a high temperature (150 ° C.), and the upper limit of the Al content is set to 10% by weight. This is because the effect of adding Al saturates even if the amount of Al exceeds this value.

The invention of claim 2 of the present application (hereinafter referred to as “second
In the first invention, the maximum value of the forging ratio is 40% or more, and the solid phase ratio of a portion forged at the maximum forging ratio is set to 10% or more. It is what it was.

The reason why the maximum value of the forging ratio is set to 40% or more and the solid phase ratio of the portion forged at the maximum forging ratio is set to 10% or more is that the solid phase ratio is set to this value or more. By doing so, it is possible to prevent a tendency of a decrease in tensile strength from occurring even at a high forging rate of 40% or more, and to reduce the variation in strength of the obtained forged member.

Further, the invention of claim 3 of the present application (hereinafter referred to as third invention)
The present invention is characterized in that the solid phase ratio is set to 80% or less in the first or second invention.

The reason why the upper limit of the solid phase ratio is set to 80% is that if the solid phase ratio exceeds this value, the viscosity of the molten metal in a semi-molten state becomes too high, and molding or molding using such molten metal is performed. This is because casting becomes extremely difficult in practice.

Further, the invention of claim 4 of the present application (hereinafter referred to as a fourth invention) is characterized in that in the third invention,
The solid phase ratio is set to 60% or less.

The reason why the upper limit of the solid phase ratio is set to 60% is that if the solid phase ratio exceeds this value, the viscosity of the molten metal in a semi-molten state becomes too high, and the molten metal is continuously used. This is because it becomes practically extremely difficult to produce a forging material by a production process (for example, injection molding).

Further, the invention according to claim 5 of the present application.
(Hereinafter, referred to as a fifth invention) is a method according to any one of the first to fourth inventions, wherein Δg containing 4% by weight or less of Ca is used.
It is characterized by being formed using an alloy as a material.

The reason why Ca was included was to improve the creep resistance, and the upper limit of the Ca content was set to 4% by weight because the Ca content exceeded this value and increased. Even so, the effect of improving the creep resistance characteristics is saturated.

Further, the invention according to claim 6 of the present application.
(Hereinafter referred to as a sixth invention) is the fifth invention, wherein the ratio of Ca content to Al content (Ca / Al
Ratio) is set to 0.8 or less.

The reason why the Ca / Al ratio is set to 0.8 or less is that the required forging ratio (50%) is within this range.
The reason for this is that the cracking rate can be kept extremely low even in high-speed forging after ensuring the above.

Further, the invention according to claim 7 of the present application.
(Hereinafter referred to as a seventh invention) is characterized in that, in any one of the first to sixth inventions, the forging material is formed by injection molding.

Further, a method for manufacturing a forged member according to the invention of claim 8 of the present application (hereinafter referred to as an eighth invention) is as follows.
Forging a light alloy forging material containing 2% by weight or more and 10% by weight or less of aluminum and formed by semi-solid molding or semi-solid casting at a forging speed of 100 [mm / s] or more. It is characterized by. Here, the lower limit of the Al content is set to 2% by weight and the upper limit is set to 10% by weight for the same reason as in the first invention.

Further, the invention of claim 9 of the present application (hereinafter referred to as a ninth invention) is characterized in that in the eighth invention,
The forging rate is set to a maximum value of 40% or more, and a forging material having a solid phase rate of 10% or more at a portion forged at the maximum forging rate is forged. The reason why the maximum value of the forging ratio is set to 40% or more and the solid phase ratio of the portion forged at the maximum forging ratio is set to 10% or more is the second reason.
For the same reason as in the invention of the present invention.

Further, in the invention of claim 10 of the present application (hereinafter referred to as a tenth invention), in the eighth or ninth invention, the solid phase ratio of the forging material is set to 80% or less. It is characterized by having. Here, the upper limit of the solid phase ratio of the forging material is set to 80% for the same reason as in the third invention.

Further, the invention of claim 11 of the present application (hereinafter referred to as an eleventh invention) is characterized in that, in the tenth invention, the solid phase ratio of the forging material is set to 60% or less. It is a characteristic. Here, the upper limit of the solid phase ratio of the forging material is set to 60% for the same reason as in the fourth invention.

Further, the invention according to claim 12 of the present application is further provided.
(Hereinafter referred to as a twelfth invention) is characterized in that, in any one of the eighth to eleventh inventions, forging is performed at a forging temperature of 250 ° C to 400 ° C.

The reason why the lower limit of the forging temperature is set to 250 ° C. is that if the forging temperature is equal to or higher than this value, the forgeability is good and a high critical upsetting ratio (70% or more) is ensured. This is because it can be applied to members and parts that require a certain strength or higher, such as mechanical parts around the engine (for example, valve lifters).
The reason for setting the temperature to 00 ° C. is that if the forging temperature exceeds this value, the effect of improving the forgeability by increasing the forging temperature is saturated, and furthermore, the material surface is oxidized or a part of the material is melted to cause forging cracks. This is because, in some cases, grain growth occurs in the material structure during holding at a high temperature, which may cause deterioration of forgeability.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings, taking as an example a case where a semi-solid injection molding method is employed for molding a forging material. First, the forming of the forging material according to the present embodiment will be described. FIG. 1 is a partial cross-sectional explanatory view showing a schematic configuration of an injection molding apparatus for performing injection molding of a light metal forging material according to the present embodiment. As shown in this figure, the injection molding apparatus 1 is a so-called screw type, and has a nozzle 3
A cylinder 2 which is heated by a heater 4 disposed on the outer periphery thereof, a screw 6 rotatably supported in the molding machine main body 5 connected to the cylinder 2 and the cylinder 2, and a motor mechanism and a reduction mechanism, for example. The apparatus includes a rotary driving device 7 for rotating the screw 6, a hopper 8 into which raw materials are charged and stored, and a feeder 9 for measuring the raw materials in the hopper 8 and feeding the raw materials into the molding machine main body 5.

Although not specifically shown, a high-speed injection mechanism for advancing the screw 6 toward the nozzle 3 is provided in the molding machine main body 5. This high-speed injection mechanism advances the screw 6 at a predetermined timing, and when the screw 6 is retracted by a preset distance, detects this and stops the rotation of the screw 6,
At the same time, the retreat operation is also stopped.

The injection molding apparatus 1 is set such that the internal passage of the nozzle 3 and the runner 12 connected to the molding cavity 11 communicate with each other. Used. The raw material charged into the hopper 8 and stored therein is measured in a predetermined amount by a feeder 9 and supplied into the molding machine main body 5.
Is fed into the heated cylinder 2 by the rotation of.
The fed raw material is heated to a predetermined temperature while being sufficiently stirred and kneaded by the rotation of the screw 6 inside the cylinder 2. In the present embodiment, by such a process, more preferably, a light metal melt in a semi-molten state lower than the melting point of the raw material is obtained.

As the semi-molten light metal melt thus obtained is extruded forward of the screw 6,
The screw 6 moves backward by the pressure. As another method, the screw may be forcibly retracted at a desired speed. When the screw 6 retreats by a preset distance, the high-speed injection mechanism (not shown) in the molding machine main body 5 detects this and stops the rotation of the screw 6 and at the same time stops the retreat operation. The measurement of the raw material may be performed by setting the retreat distance of the screw 6.

Then, the screw 6 which has stopped rotating and is in the retracted position is advanced by a high-speed injection mechanism (not shown) and is pushed out with a predetermined force, so that the light metal melt in a semi-molten state enters the mold 10 from the nozzle 3. Be injected. That is, the molten metal is injected and injected from the nozzle 3 into the molding cavity 11 through the runner portion 12. In the present embodiment, a magnesium (Δg) alloy, which is a kind of light metal, is used as a raw material, and is supplied to the hopper 8 of the injection molding apparatus 1 in the form of, for example, chip-shaped pellets. An inert gas (for example, argon gas) is more preferably provided in a passage leading from the hopper 8 into the molding machine body 5.
To prevent the oxidation reaction of the raw material (Mg alloy pellets).

The molding cavity 11 of the mold 10 is more preferably formed in a shape similar to a molding cavity of a forging die (not shown) used for forging performed after the injection molding. It is possible to obtain an injection-molded product (forging material) having a semi-finished product shape similar to a forged member which is a product to be obtained in (1). This makes it possible to simplify the forging process to only one forging process.
In addition, it becomes possible to forge even a member having a complicated shape. Further, forging can be performed without any problem even with a material having poor forgeability.

The screw 6 of the injection molding apparatus 1
Has a forward speed (preferably also a reverse speed) of 1 [m / s]
It was set to be above. The screw speed is set to be 1 [m / s] or more even when the forging material is formed by an injection molding method using a molten metal in a completely molten state instead of the above-described semi-molten injection molding method. Is preferred. Further, even when the forging material is manufactured by die casting instead of injection molding, it is more preferable to set the plunger speed to 1 [m / s (meter / second)] or more. Here, the lower limit of the plunger speed in the die casting method and the screw speed in the injection molding method is set to 1 [m / s]. If the value is less than this value, the generation of gas defects due to gas entrainment during the production of a forging material is considered. Although it can be reduced, the cycle time at the time of manufacture becomes too long, and thus lacks practicality.

Further, in the present embodiment, when the forging material made of a light alloy is injection-molded using the above-mentioned injection molding apparatus 1, molding is performed with the solid phase ratio set to 60% or less. The reason why the upper limit of the solid phase ratio is set to 60% is that if the solid phase ratio exceeds this value, the viscosity of the molten metal in a semi-molten state becomes too high, and a continuous injection molding process using the molten metal is performed. Is extremely difficult in practice. When a process other than such injection molding such as semi-solid casting is applied, the solid phase ratio is set to 80%.
% Is preferable. In this case, the upper limit of the solid phase ratio is set to 80%. When the solid phase ratio exceeds this value, the viscosity of the molten metal in a semi-molten state becomes too high, and molding or casting using the molten metal is performed. Because it becomes extremely difficult in practice.

The forging speed of the light alloy forging material injection-molded using the injection molding apparatus 1 is 100
Various tests were carried out so that even when high-speed forging exceeding [mm / s] was performed, defects such as cracks did not occur and sufficient mechanical properties could be obtained. Hereinafter, these tests will be described. 2 to 4
1 schematically shows a method for obtaining a sample of a forged member using a light alloy forged material according to the present embodiment. In the present embodiment, as shown in FIG. 2, a rectangular parallelepiped forged material M1 made of magnesium alloy having a length A1 × width B1 × length L1 is prepared, and as shown in FIG. Is sandwiched between a pair of fixed plates P1, and a plastic load (forging) is performed by applying a compressive load in the vertical direction (the paper surface direction in FIG. 3) in this state, thereby creating a sample of a forged member as shown in FIG. did.

As a result, the vertical dimension of the material M1 changes from the initial A1 to A2 (shortens), and the length changes from the initial L1 to L2 (longens). in this case,
The forging rate by this forging is calculated by the following equation. Forging rate = (A1−A2) / A1 × 100 [%] In this embodiment, forged magnesium alloy material M1
The initial basic dimensions (see FIG. 11) are, for example, A1 = A
2 = 12 [mm] and L1 = 50 [mm]. The forged member samples thus obtained were used as test materials, and test pieces having dimensions and shapes suitable for various tests were cut out from the test materials, and various tests as described below were performed. . In the following tests, the forging speed was 100 to 400 [mm / s]. Table 1 shows the chemical compositions of the alloys used as samples in these series of tests.

[0042]

[Table 1]

First, a test was conducted to examine the effect of the solid fraction on the strength improvement effect of forging. In this test, the solid phase ratio was changed in a range of 10 to 50% for a sample obtained by injection molding only (as forging material) and a sample forged at a forging rate of 25% after injection molding. Then, each tensile strength was measured. In this test, the sample as-forged material was of high quality with almost no internal defects.

FIG. 7 shows the test results. As can be seen from the graph of FIG. 7, the tensile strength decreases as the solid phase ratio increases in both before and after forging, but the degree of the decrease is small in the case of forging. . That is, it was found that the higher the solid fraction, the greater the effect of forging to improve the strength. Therefore, for those used at a high solid phase ratio, forging works more advantageously.

Next, a test was conducted to examine the effects of the solid phase ratio and the forging ratio on the tensile strength of the forged member. In this test, three types of forging materials with different solid fractions (solid fraction: 7%,
13% and 45%), the forging ratio was changed in the range of 0 to 50%, and the tensile strength of each was measured.

FIG. 8 shows the test results. As can be seen from the graph of FIG. 8, the solid phase ratio is 10% or more (solid phase ratio: 13%).
% And 45%), the higher the forging ratio, the higher the tensile strength. On the other hand, for those having a solid fraction of less than 10% (solid fraction: 7%), the tensile strength increases as the forging rate increases, up to a forging rate of about 40%.
It was found that when the forging ratio exceeded about 40%, the tensile strength was rather lowered.

Next, a test was conducted to examine the influence of the solid phase ratio and the forging ratio on the tensile strength of the forged member and its variation. In this test, the solid phase ratio was changed in the range of 7 to 45% for the forging rate of 25% and the forging rate of 50% in the forging performed after injection molding, and the tensile strength (maximum strength and Minimum strength).

The test results are shown in FIG. 9 (forging rate: 25%) and FIG. 10 (forging rate: 50%). As can be seen from these graphs, in the range where the solid phase ratio is 10% or more, the variation width between the maximum value and the minimum value of the tensile strength is substantially constant, but in the range where the solid phase ratio is less than 10%, this variation is obtained. The width is increasing rapidly. That is, it was found that it is preferable to set the solid fraction to 10% or more in order to minimize the variation in tensile strength.

As described above, even at a high forging ratio of 40% or more, the tendency of the tensile strength to decrease does not occur.
It was found that the solid phase ratio should be set to 10% or more in order to suppress the variation in strength of the obtained forged member.

Next, aluminum (Al), which is a main additive element of the forging material made of a Мg alloy according to the present embodiment,
A test was conducted to examine the effect of the content of calcium and calcium (Ca) on the mechanical properties of the forged member (particularly, mechanical properties at high temperatures). Table 2 shows the chemical components and Ca / Al ratios of the samples (Examples 1 to 7 of the present invention and Comparative Examples 1 and 2) used in various tests for examining the properties of the forged magnesium alloy material according to the present embodiment. Ratio of calcium content to aluminum content). That is, samples of forged members were manufactured using the respective samples (forged materials) shown in Table 1, and subjected to various tests as described below. In Table 2, each numerical value represents% by weight, and the remainder other than Al (aluminum), Ca (calcium), Mn (manganese), Si (silicon) and other (impurities) is Mg (magnesium). ).

[0051]

[Table 2]

FIG. 11 shows the test results of examining the effect of the Ca content on the steady-state creep speed of a forged member. In addition, the test conditions of this creep test and the setting conditions of the test material were as follows.・ Test temperature: 150 ° C. ・ Load condition: 100 MPa ・ Forging rate of test material: 50%

As shown in the test results of FIG. 11, the steady-state creep rate was determined when the Ca content was in the range of 0.5% by weight (Example 2 of the present invention) to 4% by weight (Example 5 of the present invention).
The amount decreases as the amount increases.
It was found that the creep resistance was improved as the content increased. On the other hand, when the Ca amount exceeds 4% by weight (Comparative Example 2), the steady-state creep rate is substantially constant,
It has been found that the effect of improving the creep resistance characteristics by increasing the content exceeds this value (4% by weight) and saturates. still,
In the case of Comparative Example 1 containing no Ca, the creep rate did not reach a steady state, the test piece broke at 10 [hr] (hour) after the start of the test, and the creep characteristics were significantly poor. I understood.

FIG. 12 shows the effect of the Al content on the tensile strength of a forged member at a high temperature. The test conditions of this high-temperature tensile test and the setting conditions of the test material were as follows.・ Test temperature: 150 ° C ・ Forging rate of test material: 50%

As can be clearly understood from the test results shown in FIG. 12, the tensile strength at a high temperature is substantially constant at a high Al content of 3% by weight (Example 1 of the present invention: 2.9% by weight of Al). Value, the Al content is below this value and 2% by weight
In the case of (Example 7 of the present invention), a slight decrease tendency is shown, but the value still remains high (220 MPa or more). It should be noted that each of the “Examples of the present invention” in this test contains Ca. That is, if the Al content is 2% by weight or more, a sufficient tensile strength can be ensured even at a high temperature (150 ° C.). More preferably, if the Al content is 3% by weight or more, a higher tensile strength is obtained. It turned out that it can be maintained more stably. Further, when the Al content exceeds 3% by weight, the effect of improving the tensile strength at high temperatures shows an almost saturated tendency even in a relatively low range of the content.
It was confirmed that the effect was definitely saturated when the content exceeded 0% by weight.

As for the high temperature tensile strength, when a forged member is used for a member / part which requires a certain high strength in a high temperature atmosphere of about 150 ° C., for example, a valve lifter of an engine, it is practically at least 220 MPa or more. Is preferably ensured. In the case of each of the samples used in the high-temperature tensile test of FIG. 12, a member that can secure a tensile strength of 220 MPa or more in a high-temperature atmosphere of 150 ° C. and requires a certain high strength as described above -It can be sufficiently applied to parts and the like.

Next, a test was conducted to examine the effect of the Ca / Al ratio on the forgeability of the forged Mg alloy material. FIG.
Effect of Ca on cracking rate in high-speed forging
The effect of the / Al ratio is shown. In this specification, "high-speed forging" refers to forging performed at a forging speed of about 100 [mm / sec] or more. The test conditions of the high-speed forging test in FIG. 13 and the setting conditions of the test material were as follows. -Forging temperature: 350 ° C-Forging speed: 400 [mm / sec]-Forging rate: 10%, 25%, 50%

As can be clearly understood from the test results shown in FIG.
When the Ca / Al ratio is 0.8 or less (Example 4 of the present invention), the crack generation rate can be suppressed to an extremely low value of 0.1% or less at most, regardless of the forging rate.
On the other hand, when the Ca / Al ratio exceeds 0.8 (Example 5 of the present invention), the crack generation rate rapidly increases for the forging rates of 25% and 50%. However, when the forging ratio was 10%, as in the case where the Ca / Al ratio was 0.8 or less, no cracking was observed. As described above, if the forging ratio is 10% although the practicality is relatively low, Ca
Cracking did not occur even in high-speed forging regardless of the / Al ratio, and the forging rate was 25% or more (25% and 50%).
%), It was found that by setting the Ca / Al ratio to 0.8 or less, the crack occurrence rate in high-speed forging can be suppressed to an extremely low level, and sufficient forgeability can be secured.

In addition to the above-mentioned high-speed forging test, approximately 10
Forging test at a low speed of [mm / sec] (forging temperature: 350
° C), it was found that Ca / Al not only when the forging rate was 10%, but also when the forging rate was 25% and 50%.
No cracking was observed regardless of the ratio. That is, it was found that when the forging speed was low, no cracking occurred regardless of the forging ratio and the Ca / Al ratio, and there was no problem in the forgeability.

Next, a test was conducted to examine the effect of the forging temperature on the critical upsetting ratio. Here, the critical upsetting ratio is, as schematically shown in FIG. 5, a column-shaped test piece M2 having a diameter D × length L3, and a compressive load applied to the test piece M2 in the longitudinal direction. In addition, as shown schematically in FIG. 6, when the test piece is compressed and deformed (length L4 after deformation), it refers to the limit upsetting ratio at which a crack (crack) occurs in the test piece. 5 and 6, the initial length
Assuming that a minute crack occurs when the test piece M2 of L3 is compressed and deformed to the length L4, the critical upsetting ratio in this case is calculated by the following equation. Limit upsetting rate = (L3−L4) / L3 × 100 [%] In this embodiment, the initial state of the test piece M2 (FIG. 14)
Basic dimensions of D = 16 [mm], L3 = 24
[Mm].

FIG. 14 shows the effect of the forging temperature and the pre-forging heat treatment on the critical upsetting rate during forging. The test conditions of the limit upsetting test and the setting conditions of the test material shown in FIG. 14 were as follows. -Type of test material: Example 4 of the present invention-Heat treatment condition of test material: No heat treatment / 410 ° C before forging
Air cooling after holding for 16 hours at

As can be clearly understood from the test results shown in FIG.
Regardless of the presence or absence of heat treatment, in the range where the forging temperature is approximately 400 ° C. or lower, the limit upsetting rate increases as the forging temperature increases, and in this range, the forgeability is improved by increasing the forging temperature. The effect was confirmed. On the other hand, if the forging temperature exceeds 400 ° C., the effect of improving the forgeability is saturated, and furthermore, the material surface may be oxidized, or a part of the material may be melted to cause forging cracks. There is a fear that grain growth occurs in the material structure and forgeability deteriorates. Therefore, the forging temperature is preferably 400 ° C. or lower, and more preferably 350 ° C. or lower from the viewpoint of preventing oxidation. In addition, when heat treatment was performed before forging, the marginal upsetting rate was higher than when heat treatment was not performed, and the effect of heat treatment before forging to improve the marginal upsetting rate was confirmed. Was completed.

In general, it is preferable that the critical upsetting ratio is at least 50% or more in practical use. In particular, the forged member is required to have a certain strength or higher such as an engine valve lifter. In such a case, it is more preferable to secure 70% or more. In the case of the sample of Example 4 of the present invention, 70% even at a forging temperature lower than 250 ° C. without heat treatment before forging.
The above-described critical upsetting rate can be ensured, and the present invention can be sufficiently applied to members and components that require a certain or higher strength as described above.

The heating temperature and the holding time in the heat treatment before forging are as follows.
It is preferable to perform a heat treatment of maintaining the temperature in a temperature range of 00 ° C. for 5 hours to 50 hours. In this case, the reason why the lower limit of the heat treatment temperature is set to 300 ° C. is that if it is less than that, the effect of improving the forging formability by the heat treatment is small, and the upper limit of the heat treatment temperature is set to 500 ° C. This is because, even if it is higher, the effect of improving the forgeability is saturated, and oxidation or partial dissolution may occur, and there is no merit.
On the other hand, the reason why the lower limit of the heat treatment temperature holding time is set to 5 hours is that if it is less than that, the effect of improving the forging formability by the heat treatment is small, and the upper limit of the heat treatment temperature holding time is set to 50 hours. This is because the effect of improving the forgeability is saturated even if the heat treatment is performed for a longer time.

In the above embodiment, the semi-solid injection molding method is used for molding the forging material. However, the present invention is not limited to such a case, and the present invention is not limited to such a case. The present invention can also be effectively applied to a case where other various processes such as an injection molding method using a completely melted light metal melt or a casting method such as a die casting method are used for molding a forging material. Further, in the above embodiment, the case where the Мg alloy is used as the injection material is described. However, the present invention can be effectively applied to the case where another kind of light metal is used as the material. As described above, the present invention is not limited to the above embodiments, and it goes without saying that various changes or design improvements can be made without departing from the spirit of the present invention.

[0066]

According to the forging material according to the first invention of the present application, a forging material made of light alloy forged at a forging speed of 100 [mm / s] or more, Since it contains 10% by weight or less of aluminum and is formed by semi-solid molding or semi-solid casting, the forging speed is 100%.
Even when high-speed forging of [mm / s] or more is performed, improvement in room temperature strength and / or securing of castability can be effectively achieved, and by adding other elements (calcium: Ca) together, Even at a high temperature (150 ° C.), a sufficient tensile strength (about 220 MPa or more) can be effectively secured.

According to the second aspect of the present invention, basically the same effects as those of the first aspect can be obtained. In particular, since the maximum value of the forging ratio is set to 40% or more and the solid phase ratio of the portion forged at this maximum forging ratio is set to 10% or more, the tensile strength tends to decrease even at a high forging ratio of 40% or more. This can be prevented from occurring, and the variation in strength of the obtained forged member can be reduced.

Further, according to the third aspect of the present invention, basically the same effects as those of the first or second aspect can be obtained. In particular, since the solid fraction is set to 80% or less, the viscosity of the molten metal in a semi-molten state can be prevented from becoming too high, and molding or casting using the molten metal can be performed without any trouble.

Further, according to the fourth invention of the present application,
Basically, the same effects as in the third aspect can be obtained. In particular, since the solid phase ratio is set to 60% or less, the viscosity of the molten metal in the semi-molten state can be more reliably prevented from becoming too high, and a continuous manufacturing process (such as injection molding) using such molten metal. The forging material can be manufactured without any trouble.

Further, according to the fifth invention of the present application,
Basically, the same effect as any one of the first to fourth inventions can be obtained. In particular, less than 4% by weight of C
Since the Мg alloy containing a is used as a material, the creep resistance of the forged member obtained by high-speed forging can be improved, and the effect of improving the creep resistance by increasing the amount of Ca can be obtained. It is economical.

Further, according to the sixth invention of the present application,
Basically, the same effects as those of the fifth aspect can be obtained. In particular, since the ratio of the Ca content to the Al content (Ca / Al ratio) is set to 0.8 or less,
After securing the required forging rate (50%), the rate of occurrence of cracks can be extremely low even in high-speed forging, and good forgeability can be obtained.

Further, according to the seventh invention of the present application,
Basically, the same effects as those of any one of the first to sixth aspects can be obtained. In particular, since the forging material is formed by injection molding, the advantage of manufacturing the forging material by semi-solid injection molding can be enjoyed.

Further, according to the method for manufacturing a forged member according to the eighth aspect of the present invention, the forged member is formed by a semi-molten molding method or a semi-molten casting method containing 2% by weight or more and 10% by weight or less of aluminum. Forging a light alloy forging material, the improvement of room temperature strength and / or ensuring of castability can be effectively achieved even when a forging speed of 100 [mm / s] or more is performed. , Other elements (calcium:
High temperature (150 ° C.) by adding Ca)
In this case, a sufficient tensile strength (about 220 MPa or more) can be effectively secured.

Further, according to the ninth invention of the present application,
Basically, the same effect as the eighth invention can be obtained. In particular, the maximum value of the forging ratio is set to 40% or more, and the solid phase ratio of the portion forged at this maximum forging ratio is 10%.
Since the forging material set as described above is forged, it is possible to prevent a tendency of a decrease in tensile strength from occurring even at a high forging rate of 40% or more, and to suppress a variation in strength of the obtained forged member.

Further, according to the tenth aspect of the present invention, basically the same effects as those of the eighth or ninth aspect can be obtained. In particular, since the solid fraction is set to 80% or less, the viscosity of the molten metal in a semi-molten state can be prevented from becoming too high, and molding or casting using the molten metal can be performed without any trouble.

Further, according to the eleventh aspect of the present invention, basically the same effects as in the tenth aspect can be obtained. In particular, since the solid phase ratio is set to 60% or less, the viscosity of the molten metal in the semi-molten state can be more reliably prevented from becoming too high, and a continuous manufacturing process (such as injection molding) using such molten metal. The forging material can be manufactured without any trouble.

Further, according to the twelfth aspect of the present invention, basically, the same effects as any one of the eighth to eleventh aspects can be obtained. In particular, since the forging temperature in the forging is set in the range of 250 ° C. to 400 ° C., a good limit upsetting rate (70% or more) is secured,
For example, it can be applied to members and parts that require a certain level of high strength, such as engine valve lifters.
Since the upper limit of the forging temperature is 400 ° C., it is economical to obtain the effect of improving the forgeability by increasing the forging temperature, and has an adverse effect such as oxidation of the material surface due to the high temperature holding and deterioration of the forgeability. Can also be effectively avoided.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional explanatory view showing a schematic configuration of an injection molding apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of a forged magnesium alloy material according to the present embodiment.

FIG. 3 is an explanatory view schematically showing a forging step of the magnesium alloy forging material.

FIG. 4 is an explanatory view of a magnesium alloy forged member sample after the forging step.

FIG. 5 is an explanatory diagram showing an initial state of a critical upsetting test of a forged magnesium alloy material according to the present embodiment.

FIG. 6 is an explanatory view schematically showing a forging material made of a magnesium alloy at the time of forging in the above-mentioned marginal upsetting test.

FIG. 7 is a graph showing the effect of solid fraction on the strength improvement effect of forging.

FIG. 8 is a graph showing the influence of the solid fraction and the forging ratio on the tensile strength of a forged member.

FIG. 9 is a graph showing the influence of the solid phase ratio and the forging ratio on the tensile strength of a forged member (forging ratio: 25%) and its variation.

FIG. 10 is a graph showing the influence of the solid phase ratio and the forging ratio on the tensile strength of a forged member (forging ratio: 50%) and its variation.

FIG. 11 is a graph showing the effect of the calcium content on the steady-state creep rate of a forged magnesium alloy member.

FIG. 12 is a graph showing the effect of aluminum content on the high-temperature tensile strength of a forged magnesium alloy member.

FIG. 13 shows the effect of Ca on the crack occurrence rate in high-speed forging.
6 is a graph showing the effect of / Al fire.

FIG. 14 is a graph showing the effect of forging temperature on the critical upsetting ratio.

[Explanation of symbols]

 1: Injection molding equipment M1, M2: Material for forging Mg alloy

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 23/02 C22C 23/02

Claims (12)

[Claims] 1. A forging material made of a light alloy forged at a forging speed of 100 [mm / s] or more, containing 2% by weight or more and 10% by weight or less of aluminum, and a semi-solid molding method. A material for forging characterized by being formed by a semi-solid casting method. 2. The forging according to claim 1, wherein a maximum value of the forging ratio is 40% or more, and a solid phase ratio of a portion forged at the maximum forging ratio is set to 10% or more. Material. 3. The forging material according to claim 1, wherein the solid phase ratio is set to 80% or less. 4. The forging material according to claim 3, wherein the solid phase ratio is set to 60% or less. 5. The forging material according to claim 1, wherein the material is formed using a magnesium alloy containing 4% by weight or less of calcium as a material. 6. The forging material according to claim 5, wherein the ratio of the calcium content to the aluminum content is set to 0.8 or less. 7. The forging material according to claim 1, which is formed by injection molding. 8. A light alloy forging material containing 2% by weight or more and 10% by weight or less of aluminum and formed by semi-solid molding or semi-solid casting is forged at 100 [mm / s] or more. A method for manufacturing a forged member, comprising forging at a speed. 9. The maximum value of the forging ratio is set to 40% or more,
9. A material for forging having a solid phase ratio of 10% or more in a portion forged at the maximum forging ratio is forged.
A method for producing a forged member as described in the above. 10. The method for producing a forged member according to claim 8, wherein the solid phase ratio of the forging material is set to 80% or less. 11. The method for manufacturing a forged member according to claim 10, wherein the solid phase ratio is set to 60% or less. 12. The method for manufacturing a forged member according to claim 8, wherein forging is performed at a forging temperature of 250 to 400 ° C.