KR101471011B1 - Method for manufacturing Fe-Al bimetal - Google Patents

Abstract

Provided is a method to manufacture a Fe-Al dissimilar metal material. The present invention relates to the method to a Fe-Al dissimilar metal material comprising: a step of detaching graphite attached to the surface after cast iron and cast steel are casted as a core material; a step of cooling the core material at room temperature after the graphite base destabilizes the detached core material; a step of melt bonding the core material and Al, which is a base material, by injecting Al molten metal into a mold after the Fe-based core material cooled at room temperature is charged to the mold; and a step of cooling the melt bonded dissimilar metal at room temperature.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a Fe-Al bimetal,

The present invention relates to a method for producing Fe-Al dissimilar metal materials, and more particularly, to a method for manufacturing a Fe-Al dissimilar metal material by using cast iron castings as a core material and using Al as a base material, A1 The present invention relates to a method for manufacturing an Fe-Al dissimilar metal material which is easy to repair and the like.

In response to the increasingly stringent environmental regulations in the world, eco-friendly light weight, high fuel efficiency has become an important issue in the international transportation machinery market. To accomplish this, it is necessary to increase the strength, weight, and fuel efficiency of various industrial machine parts through the use of high strength and light weight technology. Especially, it is very important to secure technology for casting different materials for manufacturing high-strength and light weight transport equipment parts.

As a conventional heterogeneous material casting technique, a strong pressure regulating diffusion bonding method and a friction bonding method have been developed. However, these methods have been problematic due to a decrease in productivity and difficulty in application of a composite product.

In order to solve the problems of the prior art, a fusion bonding method has been developed. The fusion bonding method has the advantages of high productivity, high bonding speed, and excellent connectivity with complicated shaped casting articles of iron-based materials. However, the melt bonding process has not yet been widely adopted due to the problems of bonding defects, difficulty in securing wettability between dissimilar materials, and bonding strength.

In order to manufacture high-strength heterogeneous material parts at a high production rate, we use iron-based casting materials such as cast iron and cast steel as core materials and develop fusion bonding between different materials using aluminum alloys to secure lightweight parts. Efforts have been made in the past. However, this process includes graphite and carbon on the surface and inside of iron casting materials such as cast iron and cast steel which are commonly used core materials, and graphite and carbon-based particles on the surface thereof act as foreign substances in the case of fusion bonding between dissimilar materials Thereby deteriorating the wettability between the aluminum molten steel and iron-based core as a base material, and causing a problem of weakening the interface bonding force.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a method of manufacturing a cast steel, a cast steel, And a method for manufacturing a Fe-Al dissimilar metal material.

The present invention also relates to a process for producing a Fe-Al-based material by melt-bonding the Fe-based core material and the Fe-Al casting and cooling processes to maximize solute solubility and strengthen the matrix by phase transformation, The present invention provides a method for producing an Fe-Al dissimilar metal which can be effectively improved.

Further, the technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems which are not mentioned can be understood from the following description in order to clearly understand those skilled in the art to which the present invention belongs .

According to an aspect of the present invention,

A step of casting a cast iron main material as a core material and desorbing the graphite adhered to the surface thereof;

A step of destabilizing the graphite desorbed core material and cooling the core material to a normal temperature;

Charging the core material cooled at the room temperature into the mold, and then injecting the Al melt into the mold to melt-bond the Fe-based core material and Al as the matrix material; And

And cooling the melt-bonded dissimilar metal to room temperature. The present invention also relates to a method for manufacturing a Fe-Al dissimilar metal material.

Further, in the present invention, it is preferable to use a wet method or a dry method as the graphite desorption method.

In addition, the above-mentioned dry method is a method in which a mixed gas in which a ratio of nitrogen and hydrogen is appropriately made is injected into water vapor maintained at a constant temperature to form saturated water vapor and then injected into a reactor maintained at a constant temperature, It is preferable that the mixed gas is chemically reacted with the graphite on the surface of the cast steel main body so as to escape into a gas form such as carbon dioxide or methane gas.

The wet method is preferably a method of causing a strong oxidation reaction on the surface of a cast steel main body by applying a current higher than electrolytic degreasing with a cast iron main material as an anode in a conductive salt bath to desorb and remove the graphite present on the surface Do.

In the present invention, it is preferable that the core material is subjected to base destabilization at a temperature of 650 to 800 ° C.

It is also preferable that the core material is subjected to base destabilization treatment and then quenched in a temperature range of 100 to 400 ° C.

It is preferable that the quenched Fe-based core material is maintained at a temperature range of 100 to 400 ° C for a predetermined time to control the internal structure of the cast iron cast steel, which is a core material, to a mixed structure of osferite and bainite.

Further, in the present invention, it is preferable that the molten metal injection temperature of Al is set to a temperature range of 700 to 800 ° C.

Further, in the present invention, it is preferable that the molten dissimilar metal is cooled to 450 to 650 ° C, and then rapidly cooled to room temperature.

The method may further include a step of subjecting the dissimilar metal cooled to the melt-bonded normal temperature to a low-temperature heat treatment at a temperature ranging from 100 to 250 ° C.

Preferably, the method further includes a step of subjecting the dissimilar metal cooled to the melt-bonded normal temperature to a high-temperature heat treatment at a temperature of 300 to 500 ° C. prior to the low-temperature heat treatment.

The present invention having the above-described constitution makes it possible not only to improve the strength of the product but also to achieve various shape changes at a high production rate by using the cast iron cast steel as the Fe-based core material, and by using an aluminum alloy as a base material It is possible to effectively provide a heterogeneous material ensuring the light weight of the light emitting device.

Also, by controlling the casting and cooling process of the cast iron main material and the Fe-Al dissimilar metal, which are Fe-based core materials, as well as the graphite desorption process, Fe-Al dissimilar metal material having excellent bonding strength and desired mechanical properties can be effectively provided.

In addition, by maximizing the characteristics of each aluminum and iron material, they can be effectively combined with the complex properties required for future transportation equipment such as automotive silindir blocks.

1 is a graph schematically showing a casting and cooling process of the Fe-Al dissimilar metallic material of the present invention.
FIG. 2 is a graph schematically showing a casting and cooling process of the Fe-Al dissimilar metallic material of the present invention, and is a graph showing a manufacturing process further including a high-temperature heat treatment.
Fig. 3 is a graph showing a comparison of bonding strengths depending on the presence or absence of graphite in the embodiment of the present invention.
4 is a graph showing tensile strengths according to manufacturing processes and the like in the examples of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention is broadly divided into a casting process of cast iron main material which is an Fe-based core material and a casting process of Fe-Al dissimilar metal. The method for manufacturing the Fe-Al dissimilar metallic material of the present invention comprises the steps of casting a cast iron main material into a core material, desorbing the graphite and carbon-based particles adhering to the surface thereof, and then subjecting the graphite-desorbed core material to base destabilization Followed by cooling to room temperature. Subsequently charging the core material cooled at the room temperature into the mold, and then injecting the Al melt into the mold to melt-bond the Fe-based core material and Al as the matrix material; A step of cooling the melt-bonded product to room temperature; And a step of heating the quenched product to room temperature and then performing a low temperature heat treatment.

First, in the present invention, the main cast steel is a Fe-based core material. The present invention is not limited to the specific composition of the Fe-based core material, which is the cast iron cast steel, and Fe-based materials having various composition ranges can be used.

The reason why the cast iron casting material is used as a core material of dissimilar metals in the present invention is that casting can be performed with various shapes of products.

On the other hand, when cast iron main steel is used as a core material of dissimilar metals, there may be a problem of the presence of foreign substances such as graphite and carbon-based materials adhered to the surface of cast iron main steel and deteriorating wettability.

In general, the graphite on the surface of the cast steel main material in the fusion bonding process deteriorates the wettability in the fusion bonding, thereby lowering the bonding strength of the final bonded product.

Accordingly, in the present invention, the graphite adhered to the surface of the cast iron main steel, which is the Fe-based core material, is desorbed.

In the present invention, a wet method or a dry method may be used as the desorption method of the graphite.

The wet method is preferably a method of desorbing and removing graphite present on the surface by causing a strong oxidation reaction on the surface of cast iron main steel by applying a current higher than electrolytic degreasing with a cast iron main material as an anode in a conductive salt bath

In addition, when the surfactant is selectively added to the salt bath, the effect of removing the graphite is increased due to the lipophilic property and the hydrophilic property of the surfactant.

Also, it is better to set the current density to be higher than the existing electrolytic degreasing process by more than 50A / dm per product area. If it is less than 50 A / dm, the rate of oxidation reaction is low and the removal of graphite occurs late. If it is larger than 50 A / dm, the graphite desorption reaction becomes active and the surface roughness increases and the mechanical bonding force between the Al- .

The dry method is a method of removing graphite on the surface of the cast steel main body by appropriately adjusting the mixed gas ratio of hydrogen, nitrogen, and steam in the heat treatment furnace, the reaction temperature, and the time.

In detail, a mixed gas in which a ratio of nitrogen and hydrogen is appropriately mixed is injected into water vapor which is maintained at a constant temperature to form saturated water vapor, which is then injected into a reactor maintained at a constant temperature, Is chemically reacted with the graphite on the surface of the cast steel main body to escape into a gas form such as carbon dioxide or methane gas.

In the present invention, after the graphite removal surface treatment step is performed using the wet method or the dry method, the surface treatment of the cast iron core material may be further carried out in order to further improve the wettability between the different materials in the melt bonding casting.

Subsequently, in the present invention, the graphite desorbed Fe-based core material is subjected to base destabilization treatment and then cooled to room temperature. The reason for performing the base destabilizing treatment (austenitizing treatment) in the present invention is to maximize the employment of carbon and alloying elements in the austenite base of the Fe core material and to stabilize the austenite.

In the present invention, such a base destabilizing treatment temperature range is preferably 800 to 1000 占 폚.

Thereafter, the Fe-based core material in which the structure is homogenized as described above is cooled to room temperature to obtain a cast iron main material, which is an Fe-based core material having an inner structure of martensite and bainite mixed structure.

In the present invention, it is also possible to employ a step of destabilizing the Fe-based core material, followed by quenching in the temperature range of 100 to 400 캜 for a predetermined time, followed by cooling to room temperature.

Specifically, the base unstabilized Fe core material may be quenched and cooled in a salt bath to a temperature of 100 to 400 캜. The quenched and cooled core material is then maintained in a bath for a certain period of time in a salt bath furnace, whereby the internal structure of the cast iron cast steel, which is a core material, becomes a mixed structure of osferite and bainite. Thus, strength and toughness of the final core material are harmonized, .

Next, in the present invention, a core material having been subjected to the casting process of the Fe-based core material is charged into a mold, and molten Al is injected into the mold to melt-bond the core material, namely, Fig. 1-2 is a graph schematically showing a casting and cooling process of the Fe-Al dissimilar metal of the present invention.

As a result of this fusion bonding, the core steel, which is the core material, and the base material, Al, can be fusion bonded to each other to form a dissimilar metal.

In the present invention, the Al injection temperature is preferably in the range of 700 to 800 ° C. If the temperature is lower than 700 ° C., the slurry is likely to become a slurry rather than a complete molten state because the molten state is near the melting point. If the temperature exceeds 800 ° C., hydrogen (gas) This is because the probability of occurrence is high and the probability of property deterioration is high.

In the present invention, the melt-bonded dissimilar metal is cooled to room temperature.

In the present invention, the molten dissimilar metal is cooled (A to B) to 450 to 650 ° C., and then the molten bonded dissimilar metal is quenched to room temperature (BC). The reason why the cooling temperature is set as described above in the present invention is that a substantial amount of the structure can maintain the austenite while the Fe core material can be stably solidified in this temperature range and if the temperature exceeds 650 ° C It is likely to be in a state in which solidification is not achieved and may be in a liquid state or a slurry state, and when the temperature is lower than 450 ° C., a desired tissue can not be obtained through a subsequent cooling process.

 Subsequently, in the present invention, the dissimilar metals cooled to room temperature can be heated to perform the low-temperature heat treatment (E-F in FIG. 1, I-J in FIG. 2). At this time, it is preferable that the heat treatment temperature is controlled within a temperature range of 100 to 250 ° C. The low-temperature heat treatment not only optimizes the mechanical properties of the cast iron main steel, which is the Fe-based core material, but also obtains the aging effect of Al as a base material.

In the present invention, as shown in FIG. 2, the Fe-Al dissimilar metal material cooled as described above may be heated to 300 to 500 ° C. and then subjected to a high-temperature heat treatment (EF of FIG. Due to such high-temperature heat treatment, Al is solubilized and the hardness of the dissimilar metal material becomes higher.

Hereinafter, the present invention will be described in detail with reference to experimental examples.

(Experimental Example 1)

The rod-shaped cast iron main steel was provided with Fe core material. Some of the core materials were subjected to a desorption process for removing graphite on the surface of the core material by a dry method, and some of them were not subjected to a desorption process. In the dry method, a mixed gas in which a ratio of nitrogen and hydrogen is appropriately mixed is injected into water vapor which is maintained at a constant temperature to form saturated water vapor, and then mixed with hydrogen and water vapor Gas is chemically reacted with the graphite on the cast steel main surface to escape into a gas such as carbon dioxide or methane gas.

In this way, each of the cast iron cast steel, which is graphite-desorbed Fe-based core material, and the cast iron main steel material, which was not desorbed graphite, was subjected to base destabilization, then cooled to a temperature of 100 to 400 캜 and tempered, followed by air cooling at room temperature.

The cast iron main steel material prepared as described above was charged into a mold, molten Al at a temperature of 700 to 800 ° C. was injected into the mold and maintained for a predetermined time to melt-bond the main cast iron material and aluminum as the base material.

Subsequently, graphite undissociated dissimilar metals among the melt-bonded dissimilar metals were air-cooled to room temperature to produce the final Fe-Al dissimilar metal material.

Meanwhile, the graphite-desorbed dissimilar metal among the melt-bonded dissimilar metals was cooled to 450 ~ 650 ° C, demoulded, and then cooled to room temperature to prepare a final Fe-Al dissimilar metal material. In this experiment, for comparison, some of the dissimilar metals of the graphite-desorbed specimen were further subjected to a low-temperature heat treatment at a temperature of 100 to 250 ° C and then air-cooled to produce a final Fe-Al dissimilar metal material.

In order to quantitatively measure the interfacial bonding force between the Fe-Al heterogeneous materials produced in this way, the bonding strength was measured by processing the bonded test pieces. The bonding strength test was carried out with three pieces per each condition, and an average value was obtained, which is shown in FIG. In addition, the effective tensile strength was measured for three pieces per each test piece, and the average value thereof is shown in FIG. In this experiment, the comparative example shows the case where the graphite is not desorbed, Example 1 shows that the graphite is desorbed but the low temperature heat treatment is not performed, and Inventive Example 2 shows the case where the low temperature heat treatment is performed.

As shown in FIG. 3, it can be seen that Inventive Example 1-2 in which graphite adhered to the surface of cast iron main material, which is an Fe core material, is desorbed and removed has a higher bonding strength than the comparative example.

Further, as shown in FIG. 4, it can be seen that the present invention 1-2 having a graphite desorption and a predetermined cooling process has a higher tensile strength than the comparative example. In particular, Inventive Example 2 subjected to the low-temperature heat treatment shows superior tensile strength to Inventive Example 1 which is not, which is considered to be the result of the aging of Al due to the low-temperature heat treatment.

As described above, the preferred embodiments of the present invention have been described, and the present invention can be embodied in other forms without departing from the spirit or scope of the present invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the foregoing description, but may be modified within the scope and equivalence of the appended claims.

Claims (10)

A step of casting a cast iron main material as a core material and desorbing the graphite adhered to the surface thereof;
A step of destabilizing the graphite desorbed core material and cooling the core material to a normal temperature;
Charging the core material cooled at the room temperature into the mold, and then injecting the Al melt into the mold to melt-bond the Fe-based core material and Al as the matrix material; And
And cooling the melt-bonded dissimilar metal to 450 to 650 ° C. and rapidly cooling the melt to a normal temperature.
The method for producing a Fe-Al dissimilar metallic material according to claim 1, wherein the graphite desorption method employs a wet method or a dry method.
The method according to claim 2, wherein the dry process is performed by forming a mixed gas in which a ratio of nitrogen and hydrogen is appropriately mixed and injecting the mixed gas into water vapor which is maintained at a constant temperature to form saturated water vapor, Wherein the mixed gas of hydrogen and steam is chemically reacted with the graphite on the surface of the cast steel main body to escape into a gas form such as carbon dioxide or methane gas.
The method for producing a Fe-Al dissimilar metallic material as set forth in claim 1, wherein the core steel material is subjected to base destabilization in a temperature range of 800 to 1000 占 폚.
The method for producing an Fe-Al dissimilar metallic material according to claim 1, wherein the core material is subjected to base destabilization treatment and quenched in a temperature range of 100 to 400 ° C.
6. The method of claim 5, wherein the quenched Fe-based core material is maintained at a temperature range of 100 to 400 DEG C for a predetermined time to control the internal structure of the cast iron cast steel, which is a core material, to a mixed structure of osferite and bainite A method for producing Fe-Al dissimilar metal material.
The method for producing a Fe-Al dissimilar metallic material according to claim 1, wherein the temperature of the molten metal is set at 700 to 800 ° C.
delete The method of claim 1, further comprising a step of subjecting the Fe-Al dissimilar metal cooled at a normal temperature to a low-temperature heat treatment at a temperature in the range of 100 to 250 占 폚.
The method of manufacturing a Fe-Al dissimilar metal material according to claim 9, further comprising a step of subjecting the Fe-Al dissimilar metal cooled to a normal temperature to a high-temperature heat treatment in a temperature range of 300 to 500 ° C prior to the low- .

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