KR102302539B1 - Heat treatment method for dissimilar material gap minimizes of die-casting products - Google Patents

Abstract

According to one aspect of the present invention, there is provided a heat treatment method for minimizing the heterogeneous gap of a die-casting material. The heat treatment method for minimizing the heterogeneous gap of the die-casting material includes: a first heat treatment step of heating a first member made of cast iron before insertion into a mold to generate a compound containing oxygen on at least a portion of the surface of the first member; and forming a second member in contact with at least any part of the first member and fixing the first member by performing aluminum die casting after inserting the first member into the mold. A separation distance between the member and the interface of the second member may be 10 μm to 35 μm.

Description

Heat treatment method for minimizing dissimilar material gap of die-casting material {Heat treatment method for dissimilar material gap minimizes of die-casting products}

The present invention relates to a heat treatment method for minimizing heterogeneous gaps in die casting materials, and more particularly, to a heat treatment method for minimizing heterogeneous gaps in die casting materials applied to automobile engines.

Die casting is a very important basic technology in the automobile industry. It is a method of manufacturing products by filling metals such as aluminum or magnesium in a molten state at high speed and high pressure in a precisely manufactured mold. It is widely used in the manufacture of parts.

Among automobile engine parts, the low crankcase (or bed plate) bolted to the skirt part of the engine block is a vibration (explosive load) generated in the bearing cap as the crankshaft rotates when the engine is driven. In order to effectively attenuate by sharing the body support, it is to include a bearing insert installed in the middle portion of the main body support, that is, in the journal portion serving to directly distribute the explosive load of the engine.

The low crankcase as described above was mainly applied with a single material made of cast iron as a whole, but in recent years, in order to optimize the front-to-rear weight ratio of the vehicle, and to respond to the demands for weight reduction and high output, the main body is manufactured by aluminum die-casting method, The bearing insert was inserted with a cast iron material with high rigidity.

However, in the conventional low crankcase as described above, since the bearing insert is manufactured by sand casting, the production amount is low, and since dissimilar metals are inserted into the aluminum forming the body support, due to the difference in thermal expansion characteristics, the low crankcase body The bondability is lowered, and thus, a gap is generated on the joint surface, which causes a problem in that the load distribution is not performed smoothly.

In addition, the conventional low crankcase requires simultaneous processing of cast iron and aluminum, but since it is made of heterojunction, productivity is lowered due to post-processing according to different cutting conditions, and it is difficult to manage processing roughness, which increases the manufacturing cost as well as defective products. When this occurs, there is a problem in that it is virtually impossible to reproduce.

Recently, in order to solve the problem of the low crankcase made of cast iron and aluminum as described above, a method of manufacturing a bearing insert by a hot forging method using a high-strength aluminum alloy has been developed. There are disadvantages in that the manufacturing process is complicated and the manufacturing cost is increased due to the diversity and excessive process steps. Also, since hot forgings are made through a number of forging operations and trimming, not only the working time and working process are long, but also excessive There were various problems, such as the production cost is generated and the overall productivity is lowered.

Accordingly, the present invention is to solve various problems including the above problems, and provides a heat treatment method for minimizing heterogeneous gaps in die casting materials capable of improving bondability by minimizing a gap on a joint surface with a low crankcase body aim to do However, these problems are exemplary, and the scope of the present invention is not limited thereto.

According to one aspect of the present invention for solving the above problems, there is provided a heat treatment method for minimizing the heterogeneous gap of a die-casting material.

The heat treatment method for minimizing the heterogeneous gap of the die-casting material includes: a first heat treatment step of heating a first member made of cast iron before insertion into a mold to generate a compound containing oxygen on at least a portion of the surface of the first member; and forming a second member in contact with at least any part of the first member and fixing the first member by performing aluminum die casting after inserting the first member into the mold. A separation distance between the member and the interface of the second member may be 10 μm to 35 μm.

In the heat treatment method for minimizing the heterogeneous gap of the die-casting material, the first heat treatment may be performed in a temperature range of 200°C to 800°C.

In the heat treatment method for minimizing the heterogeneous gap of the die-casting material, the first heat treatment may include heating the first member to the temperature range and then cooling the first member to room temperature.

In the heat treatment method for minimizing the heterogeneous gap of the die-casting material, the first heat treatment may be performed for 0.5 to 1.5 hours.

In the heat treatment method for minimizing the heterogeneous gap of the die-casting material, after the first heat treatment step, a second heat treatment step of reheating the first member may be performed.

In the heat treatment method for minimizing the heterogeneous gap of the die-casting material, the second heat treatment may be performed in a temperature range of 100°C to 250°C.

In the heat treatment method for minimizing the heterogeneous gap of the die-casting material, the second heat treatment may be performed for 0.5 to 1.5 hours.

According to the embodiment of the present invention made as described above, it is possible to provide a heat treatment method for minimizing heterogeneous gaps in die casting materials capable of improving bondability by minimizing a gap on the joint surface with the low crankcase body through optimization of the heat treatment process. can Of course, the scope of the present invention is not limited by these effects.

1 is a process flow chart schematically illustrating a heat treatment method for minimizing a heterogeneous gap of a die-casting material according to an embodiment of the present invention.
2 is a photograph of a sample prepared by a heat treatment method for minimizing a heterogeneous gap of a die-casting material according to an experimental example of the present invention.
3 and 4 are photographs analyzed with a scanning electron microscope of the bonding surfaces of samples prepared by a heat treatment method for minimizing heterogeneous gaps in a die-casting material according to an experimental example of the present invention.
5 is a line scan analysis result of the components in the vicinity of the bonding surface of the samples prepared by the heat treatment method for minimizing the heterogeneous gap of the die-casting material according to the experimental example of the present invention.
6 is a result of point analysis of components according to positions in the region shown in FIG. 5 .

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. Examples of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, and the scope of the present invention is as follows It is not limited to an Example. Rather, these embodiments are provided so as to more fully and complete the present disclosure, and to fully convey the spirit of the present invention to those skilled in the art.

According to one aspect of the present invention, there is provided a heat treatment method for minimizing the heterogeneous gap of a die-casting material. Here, the heterogeneous gap means a gap formed on the joint surface between the aluminum low crankcase body and the cast iron bearing cap.

Due to automobile fuel efficiency and carbon dioxide (CO2) emission regulations, weight reduction must be accompanied. Conventionally, the bed plate of an automobile is made of cast iron and satisfies all of the wear resistance, strength and hardness, so it is suitable for friction parts. However, since the weight is heavy at 10.5 kg, the weight was reduced by half by applying an aluminum material to the bed plate. However, it was unsuitable for use as a friction part because of its lack of abrasion resistance, strength and hardness.

To solve this, cast iron was used for the bearing cap, but the bad plate was replaced with aluminum, and the cast iron material was applied to the areas requiring abrasion resistance. . However, since it is a different material, a gap is generated on the bonding surface due to the difference in the coefficient of thermal expansion. In the present invention, in order to solve this problem, the gap is minimized by pre-heating the bearing cap.

1 is a process flow diagram schematically illustrating a heat treatment method for minimizing a heterogeneous gap of a die-casting material according to an embodiment of the present invention.

Referring to FIG. 1 , in the heat treatment method for minimizing the heterogeneous gap of a die-casting material according to an embodiment of the present invention, a first heat treatment for generating a compound containing oxygen on at least a portion of the surface of the first member by heating the first member Step (S100), a second heat treatment step of reheating the first member (S200), and forming a second member for fixing the first member by performing aluminum die casting after inserting the first member into the mold (S300) may include.

The first heat treatment step ( S100 ) of heating the first member may be performed at a temperature range of 200° C. to 800° C. for 0.5 hours to 1.5 hours. Here, the first member is manufactured from cast iron, and is heated to a predetermined temperature before being inserted into the mold and then cooled to room temperature. The surface of the first member is oxidized by performing the first heat treatment in the temperature range. A compound containing oxygen is produced on the surface of the first member by the oxidation reaction.

Thereafter, a second heat treatment step ( S200 ) of selectively reheating the first member may be performed. The second heat treatment step (S200) may be performed at a temperature range of 100° C. to 250° C. for 0.5 hours to 1.5 hours. The second heat treatment step ( S200 ) removes stress generated in the process of cooling after heating to a predetermined temperature range in the first heat treatment step ( S100 ).

By inserting the first member into the mold and then performing aluminum die casting, the step of forming the second member for fixing the first member (S300) is by inserting the first member made of cast iron into the mold and then performing aluminum die casting, A second member that contacts at least any part of the first member and fixes the first member may be formed.

In order to perform die casting, the first member must be cooled to room temperature after performing the first heat treatment before inserting the first member into the mold. If the second heat treatment is continuously performed after the first heat treatment, the first member must be inserted into the mold after cooling to room temperature after the second heat treatment.

A separation distance between the interface of the first member and the second member may be 10 μm to 35 μm. Conventionally, the gap between the interfaces is 40 μm or more, and the gap is considerably widened. However, by oxidizing the surface of the cast iron material through the first heat treatment, it was possible to reduce the heterogeneous gap. This is a very important factor. By selectively oxidizing the surface of the cast iron material and then reacting with aluminum during die casting, a compound containing oxygen is generated at the interface between the first member and the second member, so that the gap can be controlled small. and improve interfacial bonding. Through the second heat treatment, diffusion of atoms is induced to form an intermetallic compound, and the heterogeneous gap is reduced.

On the other hand, the second heat treatment step (S200) may be omitted depending on the heating temperature range and cooling rate of the first heat treatment step (S100). For example, as shown in FIG. 1 , die casting may be performed after sequentially performing the first heat treatment and the second heat treatment, or die casting may be performed immediately after the first heat treatment.

Hereinafter, embodiments for helping understanding of the present invention will be described. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited only to the following examples.

<Example>

A bad plate sample to which a dissimilar material is applied was prepared by using the heat treatment method for minimizing the dissimilarity gap of the die-casting material according to an embodiment of the present invention. Before inserting the bearing cap made of cast iron (FCO 500) into the mold, the first heat treatment was performed at a temperature of 200 ° C. and 800 ° C. for 1 hour, and after being inserted into the mold, aluminum (ADC 12) die casting was performed. Samples and Example 2 samples were prepared respectively.

The same bearing cap is subjected to a first heat treatment at a temperature of 800° C. for 1 hour, a second heat treatment is performed at 100° C., 150° C., 200° C. and 250° C. for 1 hour, and then is inserted into a mold and then aluminum die-casting is performed. Thus, Example 3 samples to Example 6 samples were prepared, respectively.

Meanwhile, for comparison, a sample of Comparative Example 1 was prepared by performing die casting without performing heat treatment on the same bearing cap.

Each experimental condition is summarized in Table 1 below.

division first heat treatment second heat treatment Temperature (℃) Hour (Hr) Temperature (℃) Hour (Hr) Comparative Example 1 0 0 0 0 Example 1 200 One 0 0 Example 2 800 One 0 0 Example 3 800 One 100 One Example 4 800 One 150 One Example 5 800 One 200 One Example 6 800 One 250 One

2 is a photograph of a sample prepared by a heat treatment method for minimizing heterogeneous gaps in a die casting material according to an experimental example of the present invention, and FIGS. 3 and 4 are heat treatment methods for minimizing heterogeneous gaps in a die casting material according to an experimental example of the present invention. It is a photograph of the junction of the prepared samples analyzed with a scanning electron microscope.

Figure 2 (a) is a photograph of a sample of Example 1 prepared by a heat treatment method for minimizing heterogeneous gaps in a die casting material according to an embodiment of the present invention. and confirmed that it was fixed. In (b) of FIG. 2, a number is designated for each position of the bearing cap, and the measurement position is described in FIGS. 3 and 4 . For example, when the gap was measured at the first position of the sample of Comparative Example 1, Comparative Example 1 (1), when the gap was measured at the third position, it was denoted as Comparative Example 1 (3).

3 and 4 show the average by analyzing the bonding surfaces of the samples with a scanning electron microscope, and measuring the gaps for each sample repeatedly several times.

3 and 4, in the case of the sample samples prepared using the heat treatment method for minimizing the heterogeneous gap of the die-casting material according to the present invention, the heterogeneous gap in the Example 2 sample had the smallest value of 14.77㎛, In the sample of Example 1, it was measured to have the largest value at 33.38 μm. It was confirmed that all of the Example samples had an improvement in the number of heterogeneous gaps compared to the Comparative Example 1 sample. In addition, in the case of the samples of Examples 1 and 2, it was confirmed that the heterogeneous gap was improved even though the second heat treatment was not performed. This means that the second heat treatment can be optionally omitted depending on the conditions of the process.

5 is a line scan analysis result of the components near the bonding surface of the samples prepared by the heat treatment method for minimizing the heterogeneous gap of the die-casting material according to the experimental example of the present invention, and FIG. 6 is the region shown in FIG. It is the result of point (point) analysis of the component according to the position in .

5 is a line scan analysis result in the direction of the arrow, in the case of the Example 4 sample prepared by using the heat treatment method for minimizing heterogeneous gaps in the die-casting material according to the present invention, the iron (Fe) near the bonding interface compared to the Comparative Example 1 sample ) component is contained in a large amount, and it can be confirmed that the interval in the vicinity of the intersection of the compound containing the iron component with the compound containing the aluminum (Al) component is relatively narrow.

6 is a result of arbitrarily selecting 3 points for each position in the same region as shown in FIG. 5 and averaging them after analysis. In the case of the Example 4 sample, 25.8 wt% of oxygen (O ) component was detected. On the other hand, in the sample of Comparative Example 1, no oxygen component was detected in any region including the bonding interface. The oxygen component was generated by the first heat treatment, and it was confirmed that the oxygen-containing compound was formed on the surface of the cast iron bearing cap.

In addition, it was confirmed that an AlFeSi-based compound was formed at the bonding interface. Therefore, by the first heat treatment according to the present invention, a compound containing oxygen is generated at the interface between the cast iron bearing cap and the aluminum die-casting material, and thereafter, the AlFeSi-based compound is generated at the interface between the cast iron bearing cap and the aluminum die-casting material by the second heat treatment. It can be seen that the heterogeneity gap is reduced.

Although the present invention has been described with reference to the embodiment shown in the drawings, which is merely exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

Claims (7)

As a heat treatment method for minimizing the heterogeneous gap of a die-casting material applied to an automobile engine,
a first heat treatment step of heating a first member made of cast iron before insertion into a mold to generate a compound containing oxygen on at least a portion of a surface of the first member; and
By performing aluminum die-casting after inserting the first member into the mold, forming a second member in contact with at least a portion of the first member and fixing the first member;
after the first heat treatment step, cooling the first member to room temperature; and a second heat treatment step of reheating the first member in order to remove the stress generated in the process of performing the first heat treatment step and the cooling step;
The separation distance between the interface of the first member and the second member is 10㎛ to 35㎛,
Heat treatment method to minimize the gap between the die casting materials. The method of claim 1,
The first heat treatment is carried out in a temperature range of 200 ℃ to 800 ℃,
Heat treatment method to minimize the gap between the die casting materials. delete The method of claim 1,
The first heat treatment is performed for 0.5 hours to 1.5 hours,
Heat treatment method to minimize the gap between the die casting materials. delete The method of claim 1,
The second heat treatment is performed in a temperature range of 100 ℃ to 250 ℃,
Heat treatment method to minimize the gap between the die casting materials. The method of claim 1,
The second heat treatment is performed for 0.5 hours to 1.5 hours,
Heat treatment method to minimize the gap between the die casting materials.

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