KR101832732B1 - Method for manufacturing Fe-Cu bimetal - Google Patents

Abstract

A method for producing an Fe-Cu dissimilar metal is provided. The method for producing the Fe-Cu dissimilar metal of the present invention comprises: a step of providing a cast iron steel material as a core material; a step of attaching and detaching graphite attached to the surface of the cast iron steel material using a dry method or a wet method; a step of melting and bonding cast iron steel as a core material and copper alloy as a cast material at a high temperature by injecting molten copper alloy having a temperature range of 1000-1300°C into the mold after disposing the cast iron steel material attached and detached with the graphite; and a step of demolding the melt-bonded product at 700-900°C, followed by quenching in a temperature range of 250-500°C, followed by a certain period of time, followed by cooling.

Description

METHOD FOR MANUFACTURING Fe-Cu BIMETAL [0002]

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

Dissimilar materials, especially dissimilar metal parts, refer to the use of two or more metals in the manufacture of one part. These disparate material parts are effective parts for reducing cost by reducing the parts weight, improving the performance, realizing multi-characteristics, improving the degree of freedom of parts design and reducing the use of high-priced metal materials by selecting suitable parts for each part of parts. Therefore, it has been used in various forms in transportation equipment such as automobile, heavy equipment, etc. Recently, efforts to broaden the scope of application have been made all over the world.

As a conventional manufacturing technology for dissimilar materials, 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 shape product.

In order to solve the problems of the prior art, a fusion bonding method has been developed. The above fusion bonding method has an advantage 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 been widely adopted until now due to the generation of bonding defects, the difficulty in securing the wettability between different materials, and the lack of reliability due to the problem of bonding force.

In order to produce high-productivity heterogeneous material parts, iron base casting materials such as cast iron and cast steel are used as core materials. In order to secure the operating characteristics of the parts, the base is made of fusion bonding between different materials using non-ferrous alloys such as Al and Cu The effort to develop has long been done. Examples of the wear resistant core parts such as a hydraulic pump, a cylinder block for a hydraulic motor, and a bushing in a heavy equipment field such as an automotive journal bearing and an excavator are made of a cast iron material for the body and an iron- Cu-based alloys are used.

However, when an iron casting material such as a cast iron or a cast steel is inserted as a core material and a molten Cu-based alloy is injected and fused, the graphite and carbon existing on the surface and inside of the iron-based cast materials act as foreign substances during the fusing process. There is a problem that acts as a cause.

This means that cementite, which is a metastable compound of C and Fe with high brittleness, can be extracted from quenched or melted state, and can be used as a cementite for joining to a junction box such as journal bearing, hydraulic pump, cylinder block for hydraulic motor, bushing, This is because it contains a large amount of graphite particles and carbon which degrade the interface wettability and reactivity with the core non-ferrous material of the Cu-based alloy.

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, The present invention also provides a method for producing a Fe-Cu dissimilar metal.

In addition, the present invention provides a Fe-Cu dissimilar metal material capable of effectively improving the mechanical properties of a different material by maximizing solid solution strengthening and strengthening the matrix by phase transformation by controlling the casting and cooling processes in the melt- And a method for producing the same.

According to an aspect of the present invention,

Providing a cast iron main steel material as a core material;

A step of desorbing the graphite attached to the surface of the cast steel main body using a dry method or a wet method;

Disposing the graphite-detached cast iron main steel material in a mold, and then injecting a molten copper alloy having a temperature range of 1000 to 1300 캜 into the mold, thereby melting the cast iron cast steel and the copper alloy as a core material at a high temperature;

And a step of cooling the melt-bonded product at a temperature ranging from 250 to 500 ° C, desorbing the melt-bonded product at 700 to 900 ° C, holding the product for a predetermined time, and cooling the melt-quenched product. .

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 .

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 The gas is chemically reacted with the graphite on the surface of the cast steel main body to be discharged into a gas such as carbon dioxide or methane gas.

In the present invention, it is preferable to further include a step of preheating the graphite-desorbed core material to a temperature range of 700 to 900 캜 before being placed in the mold.

In the present invention, it is preferable to further include a step of maintaining the temperature of the melt-bonded product at 700 to 900 ° C for a predetermined time between demolding the product at 700 to 900 ° C and quenching at 250 to 500 ° C .

In the present invention, it is preferable to further include a step of raising the temperature of the melt-bonded and low-temperature-cooled product to 700 to 900 ° C, followed by high-temperature heat treatment, quenching to 250 to 500 ° C, and low temperature heat treatment.

The present invention having the above-described constitution can maximize the characteristics of the copper and iron-based materials by fusing and melting the copper alloy molten metal by using the cast steel main material, which is a core material, , And the composite characteristics required for hydraulic parts and wear-resistant parts for transportation equipment such as heavy equipment can be effectively implemented.

1 is a graph schematically illustrating a casting and cooling process of a Fe-Cu dissimilar metal material according to an embodiment of the present invention.
FIG. 2 is a graph schematically showing a casting and cooling process of an Fe-Cu dissimilar metal material according to an embodiment of the present invention. FIG. 2 is a graph showing a manufacturing process that further includes a step of preheating an Fe- Fig.
FIG. 3 is a graph schematically showing a casting and cooling process of a Fe-Cu dissimilar metal material according to an embodiment of the present invention, and further includes a step of demolding a melt-bonded product and then maintaining a high temperature for a certain period of time Fig.
FIG. 4 is a graph schematically showing a casting and cooling process of a Fe-Cu dissimilar metal material according to an embodiment of the present invention. FIG. 4 is a graph showing a process of melting and thermally treating a product cooled at a low temperature, And a process for producing the same.
Fig. 5 is a photograph showing the change in wettability with the copper alloy melt according to graphite desorption oil / water deposited on the surface of the main steel material.
Fig. 6 is a microstructure photograph showing the change of the fusion-bonded interface of cast iron-copper alloy with graphite desorption oil / fog attached to the surface of the primary iron.
7 is a photograph showing a microstructure in which a copper alloy is solidified by solidification of graphite in the place where the graphite is desorbed after the graphite adhered to the surface of the primary iron material is melted and bonded.
FIG. 8 is a graph showing the interface bonding strength according to whether graphite is detached or not in contrast with the embodiment of the present invention.
Fig. 9 is a graph showing changes in hardness of cast iron according to changes in casting and cooling processes in the embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

The method for producing an Fe-Cu dissimilar metal of the present invention comprises the steps of: providing a cast iron main material as a core material; A step of desorbing the graphite attached to the surface of the cast steel main body using a dry method or a wet method; Disposing the graphite-detached cast iron main steel material in a mold, and then injecting a molten copper alloy having a temperature range of 1000 to 1300 캜 into the mold, thereby melting the cast iron cast steel and the copper alloy as a core material at a high temperature; The step of demolding the melt-bonded product at 700 to 900 ° C, followed by rapid cooling to a temperature range of 250 to 500 ° C, followed by a certain period of time, followed by cooling.

First, in the present invention, a cast iron main steel material is provided as a core material. The present invention is not limited to specific compositional components of such a cast iron casting material, but cast iron and cast steels having various composition ranges can be used. In the present invention, such a cast iron and cast steel material is used as a core material of dissimilar metals because the cast iron can be cast into various shapes of products.

Next, in the present invention, the graphite attached to the surface of the cast steel main body is desorbed by a dry method or a wet method.

When cast iron main steel is used as the core material of dissimilar metals, there may be a problem of the presence of foreign substances such as graphite or carbon-based material adhered to the surface of the cast iron main steel, which deteriorates the wettability with copper. 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 attached to the surface of the cast steel main body, which is the core material, is desorbed, and the graphite can be desorbed by a wet method or a dry method.

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 is delayed. If it is larger than 50 A / dm, the graphite desorption reaction is active and the surface roughness is increased to increase the mechanical bonding force between the Fe- .

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-detached cast iron main steel is placed in a mold, and a molten copper alloy is injected into the casting mold, thereby melting the cast iron cast steel, which is a core material, and Cu, which is a known material, at a high temperature. Figs. 1-4 are graphs schematically showing the steps of casting and cooling a Fe-Cu dissimilar metal of the present invention.

At this time, the injection temperature is preferably in the range of 1000 to 1300 ° C in the injection of the molten copper alloy (FIGS. 1, 3, 4 A, and 2 C). If the injection temperature is less than 1000 ° C, the solidification is terminated and the excellent interface bonding strength can not be obtained before the interfacial bonding is sufficiently performed. If the injection temperature exceeds 1300 ° C, the gas dissolved amount in the molten metal increases, This is because the thermal stress caused by the thermal expansion / contraction of the core material and the casting material becomes large during cooling after the fusion bonding, and the excellent interface bonding strength can not be obtained.

In the present invention, if necessary, the graphite desorbed Fe-based core material may be further preheated (AB in FIG. 2) to a temperature range of 700 to 900 ° C as shown in FIG. 2 before being placed in the mold It is possible. In the present invention, the reason why the Fe-based core material is preheated before being placed in the mold is as follows. First, the thermal stress generated due to the thermal expansion / contraction of the core material and the cast material during cooling after the fusion bonding prevents the interface detachment and the decrease in interfacial bonding strength Second, the base destabilizing treatment (austenitizing treatment) effect of the Fe-based core material is brought about, thereby maximizing the employment of carbon and alloying elements in the austenite base of the Fe core material and stabilizing the austenite, Strength and mechanical properties such as strength. If the preheating temperature is less than 700 ° C, the effect of preventing the generation of thermal stresses of the core material and the cast material during cooling after the fusion bonding becomes insufficient, and it takes a long time to obtain the base destabilizing treatment (austenitizing treatment) There is a problem. If the preheating temperature exceeds 900 ° C, the surface oxidation tendency of the Fe-based core material is increased and the interfacial bonding property is deteriorated.

Next, in the present invention, the melt-bonded product is cooled to 700 to 900 ° C. (CD in FIGS. 1 and 3, CD in FIG. 2), demolded and cooled to 250 to 500 ° C. in a bath of water , DE in Fig. 2, CD in Fig. 3). By mechanically cooling the Fe-Cu melt-bonded product and keeping it in the bath for a certain period of time, not only the mechanical properties of the cast iron main material as the Fe-based core material can be optimized, but also the aging effect of the copper alloy as the cast material can be obtained. The cast iron cast steel, which is an Fe core material, becomes a mixed structure of osferite and bainite due to the quenching cooling and the low-temperature heat treatment, so that the strength and toughness of the final core material produced are appropriately matched to each other to provide excellent mechanical properties. In addition, the internal structure of the Cu casting material becomes microstructure in which fine precipitates are generated due to quenching cooling and low temperature heat treatment, and excellent wear resistance characteristics are obtained. If the demolding temperature is lower than 700 캜, coarse precipitates start to be generated in the iron-based core material and the copper alloy casting material, and the desired microstructure and mechanical characteristics can not be obtained at the subsequent quenching cooling and low temperature heat treatment. If the deformation temperature exceeds 900 ° C., there is a risk that the solidification may not be terminated due to the segregation phenomenon necessarily occurring at the time of casting, and there is a risk that the interface fracture may occur due to thermal shock during quenching cooling.

In the present invention, if necessary, the melt-bonded product is demolded at 700 to 900 ° C. and then cooled to a predetermined temperature in the range of 700 to 900 ° C., (FIG. 3, step BC). By maintaining the temperature in the range of 700 to 900 ° C. for a certain time, it is possible to maximize the employment of the alloying elements in the copper alloy casting base which is the core material and the casting material, thereby improving the microstructure and the aging effect to obtain excellent mechanical characteristics in the subsequent quenching cooling and low temperature heat treatment. . If the holding temperature of the melt-bonded product is less than 700 캜, coarse precipitates start to be generated in the iron-based core material and the copper alloy casting material, and the desired microstructure can not be obtained at the subsequent quenching cooling and low temperature heat treatment. If the holding temperature of the melt-bonded product exceeds 900 ° C, micro-cracks may occur at the interface due to thermal shock during quenching cooling, which may lower the interface bonding strength.

In the present invention, as shown in FIG. 4, the product which is melt-bonded and cooled to a low temperature (AB in FIG. 4) is heated to a temperature range of 700 to 900 ° C. (BC in FIG. 4) ), And a series of heat treatment processes for performing quenching cooling (DE in FIG. 4) and low temperature heat treatment (EF in FIG. 4) for a certain time in a bath of 250 to 500 ° C temperature range.

Hereinafter, the present invention will be described in detail by way of examples.

(Example 1)

A plate-like cast iron main steel was provided as an 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 manner, the graphite-desorbed cast iron casting and the graphite-free cast iron main steel are placed in a preheated atmosphere heat treatment furnace at a temperature in the range of 1000 to 1300 ° C, and a copper alloy ball having a diameter of 3 mm is placed on the cast steel main steel, And the change in melting and wetting angle of the copper alloy was observed and is shown in Fig. It can be confirmed that the molten copper alloy located on the graphite-removed cast iron main steel is spread more widely than when the graphite desorption treatment is not performed, which means that the wettability is improved by graphite desorption.

The graphite-desorbed cast iron and graphite-free cast iron main steels are each placed in a preheated mold at a temperature in the range of 250 to 500 ° C, and then a molten copper alloy at a temperature of 1000 to 1300 ° C is injected into the mold, Experiments were carried out to melt-bond the main alloy of cast iron and the base alloy. In this experiment, the comparative example shows a case where the copper alloy is air-cooled in a state where the copper alloy is not deformed so as to reach room temperature after the copper alloy is injected in a conventional manner without performing the graphite desorption treatment. The product was firstly cooled to 700 to 900 ° C., demolded and then subjected to a high-temperature heat treatment at a temperature of 700 to 900 ° C. for a predetermined time. Thereafter, the product was cooled to 200 to 250 ° C. by a secondary- And then subjected to a low-temperature heat treatment in which the substrate is kept in a salt bath at a temperature of ~ 250 ° C. for a certain period of time and then air-cooled at room temperature.

The microstructure of the bonding interface of the thus prepared Fe-Cu heterogeneous material was observed and shown in Fig. 6-7. In the case of the comparative example of Fig. 6 (a) in which the copper alloy was melt-bonded without performing the graphite desorption treatment, black alliances were observed at the bonding interface in the microstructure photograph and a distinct bonding interface line was observed. However, It can be inferred that the fusion bonding is better performed because the black allium is not present at the bonding interface and the bonding interface line is blurred.

In the high magnification microstructure photograph of the bonded interface of the inventive example of Fig. 6 in which the copper alloy after the graphite desorption shown in Fig. 7 is melt-bonded, it can be confirmed that the molten copper alloy has penetrated into the place where the graphite is desorbed and solidified. Considering that three-dimensionally interconnected three-dimensionally interconnected network structures appear as flakes in the cross-section structure, the copper alloy, which solidifies into the vacant space where the graphite is desorbed, also has a three-dimensional network structure It can be seen that Therefore, it can be deduced that, in the case of the invention example in which the graphite particles are desorbed and melt-bonded, the interface bonding strength can be further increased by the binding effect of the mechanical structure in addition to the effect of promoting the metallurgical bonding reaction by the improvement of the interface wettability.

In order to quantitatively measure the interfacial bonding force between the prepared Fe-Cu heterogeneous materials, the bonding strength was measured by processing the bonding test piece. The bonding strength test was carried out with three pieces per each condition, and an average value was obtained, which is shown in FIG.

As shown in FIG. 8, it can be seen that the inventive example in which the graphite adhered to the surface of the cast steel main material, which is the core material, is desorbed and removed is superior in the interface bonding strength as compared with the comparative example in which the graphite desorption treatment is not performed.

On the other hand, FIG. 9 shows the measured hardness for evaluating the mechanical properties of the iron-based core portion of the produced Fe-Cu heterogeneous material. As shown in FIG. 9, in the inventive example in which the graphite adhered to the surface of the cast iron main steel, which is the core material, was removed and removed, the hardness of the iron-based core portion is higher than that of the comparative example in which the graphite desorption treatment is not performed. In the case of the inventive example, the high-temperature heat treatment in which the melt-bonded product is demolded at 700 to 900 ° C and maintained at a temperature range of 700 to 900 ° C for a predetermined time allows the employment of alloying elements in the cast iron core base matrix to be quenched in a maximized state, A mixed microstructure of austenite and bainite was obtained during the low temperature heat treatment in the temperature range of ~ 500 ° C, whereas in the case of the comparative example in which the continuous microstructure was continuously cooled to room temperature without melting after the fusion bonding in the usual manner, coarse pearlite was produced (Hardness) as the obtained microstructure was obtained. In addition, when the bonded interface between the different materials has a sound metal bond without defects in the casting, the interfacial heat transfer characteristics are improved, and the heat treatment characteristics for improving the mechanical characteristics such as improvement of the quenching cooling property are also improved.

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 (6)

Providing a cast iron main steel material as a core material;
A step of desorbing the graphite attached to the surface of the cast steel main body using a dry method or a wet method;
The graphite pre-casted pre-cast steel is pre-heated to a temperature range of 700 to 900 ° C and placed in the mold, and a molten copper alloy having a temperature range of 1000 to 1300 ° C is injected into the cast mold, At a high temperature;
The step of demolding the melt-bonded product at 700 to 900 ° C, followed by maintaining the product at a temperature range of 700 to 900 ° C for a predetermined time, followed by rapid cooling to a temperature range of 250 to 500 ° C, Of Fe-Cu dissimilar metals.
The method according to claim 1,
The wet method is 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 graphite present on the surface thereof Of Fe-Cu dissimilar metals.
The method according to claim 1,
In the dry method, a mixed gas in which the ratio of nitrogen and hydrogen is mixed is injected into water vapor which is maintained at a constant temperature to form saturated water vapor, and then injected into a reaction tube maintained at a constant temperature to produce a mixed gas of hydrogen and water vapor 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, methane gas or the like.
delete delete The method according to claim 1, further comprising a step of raising the temperature of the melt-bonded, low-temperature-cooled product to 700 to 900 ° C to perform a high-temperature heat treatment, rapidly cooling the product to a temperature range of 250 to 500 ° C, Of Fe-Cu dissimilar metals.

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