KR102417780B1 - Method for manufacturing blade with multi-layer structure - Google Patents

Abstract

A method for manufacturing a multi-layered blade is provided. The manufacturing method of the multi-layered blade comprises the steps of i) providing a base material comprising carbon steel, ii) providing a nickel coating layer on both sides of the base material, iii) a plate comprising a copper alloy layer and a cupronickel layer, respectively, on the nickel coating layer providing a laminate to form a laminate, iv) hot pressing the laminate to provide a bonding material, v) waterjet cutting the bonding material to provide a blade comprising a blade portion, and vi) a blade portion Corresponding to the high frequency heat treatment coil formed in a curved shape comprises the step of surface strengthening heat treatment with a high frequency heat treatment. In the step of forming the laminate, the thickness of the laminate is 5 mm to 6 mm, and in the step of providing the bonding material, hot pressing heats the laminate at 1030° C. to 1080° C. for 13 minutes to 17 minutes, and then vertically moves the laminate without shear force It is pressed down to provide a thickness of 2.4 mm to 4 mm of the bonding material.

Description

Manufacturing method of multi-layered blades {METHOD FOR MANUFACTURING BLADE WITH MULTI-LAYER STRUCTURE}

The present invention relates to a method for manufacturing a multi-layered blade. More particularly, the present invention relates to a method for manufacturing a multi-layered blade comprising copper and cupronickel.

A knife with a multi-layered pattern inside is manufactured through the folding method of overlapping iron several times. In other words, it has been manufactured as a knife with a wave pattern called a Damascus knife by removing impurities while processing iron made through the smelting of sand iron in a folding method.

This multi-layered knife has excellent strength and toughness. Therefore, attempts are being made to realize better performance while retaining the characteristics of knives manufactured in a traditional manner, mainly in Japan.

Korean Patent Publication No. 2020-0004668

An object of the present invention is to provide a method for manufacturing a multi-layered blade with excellent corrosion resistance.

A method of manufacturing a multi-layered blade structure according to an embodiment of the present invention includes the steps of i) providing a base material comprising carbon steel, ii) providing a nickel coating layer on both sides of the base material, iii) a copper alloy layer on each nickel coating layer and providing a plate material including a cupronickel layer to form a laminate, iv) hot pressing the laminate to provide a bonding material, v) cutting the bonding material by waterjet to provide a blade including a blade part and vi) surface-strengthening heat treatment of the blade portion at a high frequency using a coil for high frequency heat treatment formed in a curved shape corresponding to the blade portion. In the step of forming the laminate, the thickness of the laminate is 5 mm to 6 mm, and in the step of providing the bonding material, hot pressing heats the laminate at 1030° C. to 1080° C. for 13 minutes to 17 minutes, and then vertically moves the laminate without shear force It is pressed down to provide a thickness of 2.4 mm to 4 mm of the bonding material.

In the step of providing the base material, the carbon steel contains 0.6wt% to 1wt% of carbon, 0.1wt% to 0.3wt% silicon, 0.2wt% to 0.6wt% manganese, 0.01wt% to 0.03wt% phosphorus, more than 0 Greater than 0.005 wt% sulfur, greater than zero and less than 0.03 wt% aluminum, greater than zero and less than 0.3 wt% chromium, greater than zero and less than or equal to 0.005 wt% molybdenum, greater than zero and less than or equal to 0.04 wt% titanium, the remainder iron and impurities. In the step of forming the laminate, the cupronickel layer contains 23wt% to 26wt% nickel, greater than 0 and not more than 0.05wt% lead, 0.02wt% to 0.1wt% iron, 0.1wt% to 0.5wt% manganese, the remainder copper and impurities. The copper alloy may include 0.01 wt % to 0.03 wt % lead, the remainder copper and impurities. In the step of providing the blade, the reduction ratio at the time of hot pressing the laminate may be 30% to 40%.

In the step of providing the base material, in carbon steel, the amount of carbon is 0.83 wt%, the amount of silicon is 0.19 wt%, the amount of manganese is 0.44 wt%, the amount of phosphorus is 0.018 wt%, the amount of sulfur is 0.002 wt%, and the amount of aluminum is The amount may be 0.01wt%, the amount of chromium may be 0.15wt%, the amount of molybdenum may be 0.002wt%, and the amount of titanium may be 0.018wt%. In the step of forming the laminate, in the cupronickel layer, the amount of nickel may be 24.85 wt%, the amount of lead may be 0.02 wt%, the amount of iron may be 0.07 wt%, and the amount of manganese may be 0.3 wt%. In the copper alloy layer, the amount of lead may be 0.023 wt%. In the step of providing the bonding material, the laminate may be heated at 1050° C. for 15 minutes. In the step of providing the blade, the reduction ratio at the time of hot pressing the laminate may be 35%.

Using copper alloy and cupronickel as materials, a blade with excellent corrosion resistance and strength can be manufactured. That is, by manufacturing a knife using a dissimilar metal material, a blade with excellent corrosion resistance can be manufactured. In addition, by applying the waterjet process and the high frequency heat treatment process specialized for dissimilar metal materials, it is possible to manufacture a blade with a multi-layer structure of excellent quality.

1 is a schematic flowchart of a method for manufacturing a blade according to an embodiment of the present invention.
Figure 2 is a schematic exploded cross-sectional view before hot pressing of the blade according to an embodiment of the present invention.
3 is a schematic cross-sectional view of a blade after hot pressing according to an embodiment of the present invention.
Figure 4 is a view schematically showing the process of cutting the blade with a water jet in the method of manufacturing a blade according to an embodiment of the present invention.
Figure 5 is a view schematically showing the process of surface strengthening heat treatment of the blade at high frequency by a coil for high frequency heat treatment in the method of manufacturing a blade according to an embodiment of the present invention.
6 is a photograph of a heating furnace and a hot pressing device used in an experimental example of the present invention.
7 is a photograph of hot pressing the blade in the hot pressing device of FIG.
8 is a photograph of a processing process of a water jet used in an experimental example of the present invention and a bonding material using the same.
9 is a photograph of a blade cut using the waterjet of FIG. 8 and a cross-section thereof.
10 is a photograph of the high frequency induction heat treatment machine used in the experimental example of the present invention.
11 is a photograph of the surface hardening of the blade portion of the blade using the high frequency induction heat treatment machine of FIG. 10 and a photograph of the blade obtained as a result.
12 to 16 are photographs of bonding materials prepared according to Experimental Examples and Comparative Examples of the present invention.
19 and 20 are graphs of tensile strength of bonding materials prepared according to Experimental Examples 1 and 2 of the present invention.

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of “comprising” specifies a particular characteristic, region, integer, step, operation, element and/or component, and other specific characteristic, region, integer, step, operation, element, component, and/or group. It does not exclude the existence or addition of

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and unless defined, are not interpreted in an ideal or very formal meaning.

1 schematically shows a flowchart of a method for manufacturing a blade according to an embodiment of the present invention. The manufacturing method of the blade of FIG. 1 is only for illustrating the present invention, and the present invention is not limited thereto. Therefore, the manufacturing method of the blade can be modified to another form.

As shown in Figure 1, the manufacturing method of the blade, providing a base material comprising carbon steel (S10), providing a nickel coating layer on both sides of the base material, respectively (S20), on the nickel coating layer, respectively copper alloy and cupronickel Forming a laminate by providing a plate comprising a (S30), providing a bonding material by hot pressing the laminate (S40), cutting the bonding material with a waterjet to provide a blade including a blade part Step (S50), and a step (S60) of surface-strengthening heat treatment of the blade portion with a high frequency by a high-frequency heat treatment coil formed in a curved shape corresponding to the blade portion. In addition, the method of manufacturing the blade may further include other steps.

In step S10, a base material including carbon steel is provided. Carbon steel contains 0.6wt% to 1wt% carbon, 0.1wt% to 0.3wt% silicon, 0.2wt% to 0.6wt% manganese, 0.01wt% to 0.03wt% phosphorus, greater than 0 and not more than 0.005wt% sulfur. , greater than zero and less than or equal to 0.03 wt% aluminum, greater than zero and less than or equal to 0.3 wt% chromium, greater than zero and less than or equal to 0.005 wt% molybdenum, greater than zero and less than or equal to 0.04 wt% titanium, the remainder iron and impurities. More preferably, the amount of carbon is 0.83 wt%, the amount of silicon is 0.19 wt%, the amount of manganese is 0.44 wt%, the amount of phosphorus is 0.018 wt%, the amount of sulfur is 0.002 wt%, the amount of aluminum is 0.01 wt%; , the amount of chromium is 0.15 wt%, the amount of molybdenum is 0.002 wt%, and the amount of titanium is 0.018 wt%.

Carbon is added to ensure the hardness of the blade. Carbon improves the hardness of the martensitic structure contained in the knife. If the amount of carbon is too small, the hardness of the blade decreases. Conversely, if the amount of carbon is too large, M7C3 primary carbide may be precipitated as the blade is sharpened while continuously using the blade, which may be the starting point of corrosion. As a result, the corrosion resistance of the knife is lowered and it is also vulnerable to grinding. Therefore, the amount of carbon is adjusted in the above-mentioned range.

Silicon is required for the blade manufacturing process. Silicon lowers the martensite onset temperature (Ms) and reduces chromium oxide. However, when the amount of silicone is large, a high-temperature curing effect that limits the possibility of deformation during knife processing may occur. Therefore, the addition amount is controlled in the above-mentioned range.

Manganese is required to stabilize the structural structure of carbon steel. If the amount of manganese is too large, the amount of martensite after quenching is insufficient to lower the hardness of the knife.

Phosphorus and sulfur are impurities, and the smaller the amount, the better. However, when the amount of phosphorus and sulfur is limited, the cost of removing impurities increases. Therefore, phosphorus and sulfur are controlled in the above-mentioned range.

Aluminum combines with nitrogen in carbon steel to form AlN, and exists at the austenite grain boundary to suppress grain growth. When the amount of aluminum is too small, the effect of grain refining is small. In addition, when the amount of aluminum is too large, AlN may be coarsely formed and non-uniform crystal grains may be formed. Therefore, the amount of aluminum is adjusted to the above-mentioned range.

Chromium improves the hardenability of carbon steel. Chromium forms a passivation film in the atmosphere to suppress rust in carbon steel. However, if the amount of chromium is too large, it is not easy to separate the scale during the manufacturing process, and an edge crack occurs during cooling.

Molybdenum improves hardenability and pitting resistance, and promotes the formation of M(C, N). However, molybdenum is expensive, and when the amount of molybdenum is too large, the martensite transformation end temperature (Mf) is lowered. Therefore, the amount of molybdenum is appropriately limited.

Titanium produces carbides and nitrides that are more stable than chromium carbides and chromium nitrides, contributing to the stabilization of the knife structure. However, when the amount of titanium added is too large, the hardness of martensite generated after rapid cooling may be limited. Therefore, the amount of titanium is appropriately adjusted.

On the other hand, high-chromium steel may be used instead of high-carbon steel. In addition, high carbon steel and high chromium steel may be used together.

In step S20, a nickel coating layer is provided on both sides of the base material, respectively. Bonding the base material and the plate material through the nickel coating layer can significantly improve the bonding strength. The nickel coating layer can be formed by coating an intermetallic compound on a base material and then depositing nickel by thermal decomposition, a method of depositing nickel on the surface of the base material in a vapor phase, and a method using a physical method such as vapor deposition or sputtering. In addition, the nickel coating layer can be formed through an easy and economical electroplating process.

The thickness of the nickel coating layer may be 10 μm to 50 μm. When the thickness of the nickel coating layer is too small, the bonding strength with the base material cannot be sufficiently secured. In addition, when the thickness of the nickel coating layer is too large, the thickness is too large, the bonding strength with the base material may be reduced. Therefore, the thickness of the nickel coating layer is maintained in the above-described range.

Next, in step S30, a laminate may be formed by providing a plate material including a copper alloy layer and a cupronickel layer, respectively, on the nickel coating layer. That is, a copper alloy layer may be provided on the nickel coating layer and cupronickel may be formed thereon, or a cupronickel layer may be provided on the nickel coating layer and a copper alloy layer may be provided thereon. The copper alloy layer and the cupronickel layer function as corrosion-resistant reinforcement materials. Hereinafter, a case in which a copper alloy layer is provided on a nickel coating layer and a cupronickel layer is formed thereon will be described with reference to FIG. 2 .

Figure 2 schematically shows the disassembled cross-sectional structure of the blade 100 before hot pressing according to an embodiment of the present invention. The disassembled cross-sectional structure of the blade 100 of FIG. 2 is only for illustrating the present invention, and the present invention is not limited thereto. Therefore, the cross-sectional structure of the blade 100 can be transformed into another form.

As shown in FIG. 2 , a nickel coating layer 20 is formed on the upper and lower surfaces of the base material 10 , respectively. And the plate material 30 is positioned on the upper surface of the upper nickel coating layer 20 and the lower surface of the lower nickel coating layer 20, respectively. The plate material 30 includes a copper alloy layer 301 and a cupronickel layer 303 .

The copper alloy layer 301 includes lead, copper, and impurities. The amount of lead may be 0.01wt% to 0.03wt%. More preferably, the amount of lead may be 0.023 wt %. Lead forms a precipitate to improve the cutting property of the copper alloy layer 301 . Lead has a large amount of heat of mixing with copper and a large melting point difference. Therefore, a segregation reaction by liquid phase separation is formed between lead and copper. Lead separates from the liquid phase upon solidification to form a microstructure. Therefore, most lead precipitates are formed inside grains rather than at grain boundaries. And since lead has a very large interfacial energy in the liquid phase, the precipitates grow in a spherical shape. When film-type precipitates are formed along the crystal grains, rapid fracture occurs along the grain boundaries, which can be prevented by lead precipitates. In addition, lead precipitates have a great utility because they lubricate during cutting.

Cupronickel layer 303 contains 23wt% to 26wt% nickel, greater than 0 and not more than 0.05wt% lead, 0.02wt% to 0.1wt% iron, 0.1wt% to 0.5wt% manganese, the remainder copper and impurities do. More preferably, the amount of nickel may be 24.85 wt%, the amount of lead may be 0.02 wt%, the amount of iron may be 0.07 wt%, and the amount of manganese may be 0.3 wt%. Cupronickel has the advantage of easy hot working while having corrosion resistance, so it is used as a blade material in an embodiment of the present invention.

Nickel is added to ensure the strength and high temperature oxidation resistance of the cupronickel layer 303 . On the other hand, when the amount of nickel is too large, the martensitic transformation end temperature (Mf) becomes low, and the material cost increases. Therefore, the amount of nickel is appropriately adjusted within the above-mentioned range.

Lead is added to improve the cutability of the cupronickel layer 303 . However, the lead content is appropriately controlled to form a precipitate in the cupronickel layer 303 .

Iron and manganese are contained in a trace amount in the cupronickel layer 303 and function as reinforcing elements of the cupronickel layer 303 . When the amount of iron or manganese is too large, the amount of martensite becomes insufficient after quenching to decrease the hardness of the cupronickel layer 303, so the amount is appropriately controlled.

Meanwhile, the thickness t of the laminate 80 may be 5 mm to 6 mm. When the thickness t of the laminate 80 is too large, a large load may be applied when the laminate 80 is hot-pressed. In addition, the thickness t of the laminate 80 cannot be made too small by design. Therefore, the thickness t of the laminate 80 is adjusted to the above-mentioned range.

Referring back to FIG. 1 , in step S40 , a bonding material is provided by hot pressing the laminate 80 (shown in FIG. 2 , the same hereinafter). The hot pressing process is completely different from the hot rolling process. When the laminated material 80 is hot-rolled, the respective layers are pushed in, making it unsuitable for manufacturing a blade. That is, in the hot rolling process, a horizontal force is applied to generate a shear force, and the laminated material 80 may be pushed. Therefore, through the hot pressing process, the bonding material is manufactured using only the vertical pressing force without shear force. In particular, in a hot pressing device, a laminate can be inserted into a mold to vertically press down with a mold. As a result, there is no increase in the length of the laminated material 80 in the longitudinal direction of the laminated material 80 , that is, in a direction perpendicular to the thickness direction of the laminated material 80 .

When the hot pressing process is described in more detail, the laminate 80 is first heated. The laminate 80 is heated to a temperature of 1030°C to 1080°C. More preferably, the laminate 80 may be heated to 1050°C. When the heating temperature of the laminate 80 is too low, it may be difficult to vertically press the vertical laminate 80 in a subsequent process. Moreover, when the heating temperature of the laminated material 80 is too high, process cost increases. Therefore, the heating temperature of the laminate 80 is adjusted to the above-mentioned range.

The laminate 80 may be heated for 13 to 17 minutes. More preferably, the laminate 80 may be heated for 15 minutes. If the heating time of the laminated material 80 is too short, the laminated material 80 is too hard, so that vertical reduction processing of the laminated material 80 may be difficult in a subsequent process. Moreover, when the heating time of the laminated material 80 is too long, the process cost increases. Therefore, the heating time of the laminated material 80 is adjusted in the above-described range.

3 schematically shows the cross-sectional structure of the bonding material 90 after hot pressing in the method for manufacturing a blade according to an embodiment of the present invention. The cross-sectional structure of the bonding material 90 of FIG. 3 is merely for illustrating the present invention, and the present invention is not limited thereto. Accordingly, the cross-sectional structure of the bonding material 90 may be modified into other shapes.

The cross-sectional structure of the bonding material 90 of FIG. 3 is basically the same as the cross-sectional structure of the laminated material 80 of FIG. 2 except that the thickness is different, so the same reference numerals are used for the same parts, and the detailed description thereof will be omitted. .

The thickness t' of the bonding material 90 may be 2.4 mm to 4 mm. If the thickness (t') is too large, it is not suitable for use as a blade. In addition, when the thickness t' is too small, the hot pressing process cost may increase and the bonding material 90 may be damaged. Therefore, it is preferable to adjust the thickness (t') in the above-mentioned range.

On the other hand, the reduction ratio during hot pressing of the laminate 80 may be 30% to 40%. Preferably, the reduction ratio may be 35%. If the reduction ratio is too large, the laminate 80 may be damaged. In addition, when the reduction ratio is too small, each layer constituting the laminate 80 may not be well bonded. Therefore, the reduction ratio is adjusted in the above-mentioned range.

Meanwhile, after the hot pressing process, if necessary, heat treatment may be performed again to further strengthen the bonding force between the layers of the bonding material 90 . In this case, the bonding strength of the bonding material 90 can be further improved by diffusion between the layers.

Again, when returning to FIG. 1, in step S50, the bonding material is cut with a water jet to provide a blade including a blade part. This will be described in detail with reference to FIG. 4 .

Figure 4 schematically shows a process of cutting the blade with a water jet in the method of manufacturing a blade according to an embodiment of the present invention. The waterjet cutting process of FIG. 4 is only for illustrating the present invention, and the present invention is not limited thereto. Therefore, it can be transformed into other forms.

As shown in FIG. 4 , the bonding material 90 prepared in step S40 of FIG. 1 is shape-processed using a water jet 1000 . That is, the bonding material 90 having a rectangular shape is manufactured by a hot pressing process in step S40 . This is cut with the blade 100 by spraying water (W) using the water jet (1000). When the waterjet 1000 is used, the bonding material 90 can be stably cut using the waterjet 1000 without melting and interlayer separation at the bonding interface of the bonding material 90 .

When the bonding material 90 is cut using a mechanical tool such as a grinder or a cutter, the dissimilar metal joint of the bonding material 90 may fall off due to mechanical vibration. In addition, when the bonding material 90 is cut by laser processing, the bonding interface of the non-ferrous material such as cupronickel or copper having a low melting point may be melted. However, when the waterjet 1000 is used, a phenomenon in which the joint part falls off or the joint interface is melted does not occur. For this reason, it is preferable to manufacture the blade 100 by cutting the bonding material 90 using the water jet 1000 .

Returning to FIG. 1 again, in step S60, the surface strengthening heat treatment is performed on the blade part at a high frequency by a coil for high frequency heat treatment formed in a curved shape corresponding to the blade part. This will be described in detail with reference to FIG. 5 .

Figure 5 schematically shows a process of surface strengthening heat treatment of the blade in a high frequency by a coil for high frequency heat treatment in the method of manufacturing a blade according to an embodiment of the present invention. The surface strengthening heat treatment process of the blade of FIG. 5 is only for illustrating the present invention, and the present invention is not limited thereto. Therefore, it can be transformed into other forms.

As shown in FIG. 5 , the coil 2000 for high frequency heat treatment is formed in a shape corresponding to the blade portion 1001 of the blade 100 . Here, the blade part 1001 means a portion corresponding to 5 mm in the direction of the back of the blade from the end of the blade 100 . That is, the coil 2000 for high frequency heat treatment has a curved shape to correspond to the blade part 1001 . Therefore, only the blade part 1001 is subjected to surface strengthening heat treatment at a high frequency. This is because the blade 100 is formed by bonding dissimilar metal materials of cupronickel, copper and carbon steel. That is, in the case of surface-strengthening heat treatment by heating the entire blade as in manufacturing a kitchen knife made of a commonly used iron-based material, a separation may occur at the bonding interface between dissimilar materials. Therefore, while maintaining the bonding state of the dissimilar metals, the blade part 1001 is heat-treated with a high-frequency heat treatment machine capable of locally rapid heating and rapid cooling. On the other hand, in addition to the above-mentioned process, quenching, tempering, and grinding may be sequentially performed to finally manufacture a multi-layered blade.

Experimental example

Hereinafter, the present invention will be described in detail through experimental examples. These experimental examples are only for illustrating the present invention, and the present invention is not limited thereto. Therefore, the experimental example may be modified into other forms.

Alloy specimen preparation

A blade of a multi-layer structure was manufactured according to the manufacturing method of the multi-layer structure of FIG. 1 . A blade with a multi-layer structure was manufactured using carbon steel, copper alloy and cupronickel.

SK5 was used as carbon steel, and the dimensions of the specimen were 300 mm x 60 mm x 2 mm. Carbon steel contained 0.8wt% to 0.9wt% of carbon that can be heat treated in an alloy of iron and carbon, and its detailed composition (wt%) was shown in Table 1 below.

Fe C Si Mn P S Al Cr Mo Ti 98.34 0.83 0.19 0.44 0.018 0.002 0.010 0.150 0.002 0.018

As the copper alloy, electrolytic copper having a copper (Cu) content of 99 wt% or more was used. The specimen size of the copper alloy was 300 mm x 60 mm x 1 mm. The copper alloy contained 99.96 wt% of copper (Cu) and 0.023 wt% of lead (Pb).

Cupro Nickel, a binary alloy of copper (Cu) and nickel (Ni) that does not contain zinc (Zn), was used as cupronickel. The size of the cupronickel specimen was 300mm x 60mm x 1mm. The detailed composition (wt%) of cupronickel was shown in Table 2 below.

Cu Ni Pb Fe Mn Zn 74.69 24.85 0.02 0.07 0.3 0

hot pressing

A laminate was prepared by selecting variously a cupronickel specimen, a copper alloy specimen, and a carbon steel specimen having the above composition. The carbon steel surface was electroplated with nickel. Depending on the specimen selection, the thickness of the laminate was varied to 4 mm or 6 mm. And the laminate was heated in a heating furnace for 15 minutes. The heating temperature of the laminate was adjusted to 950°C, 1000°C or 1050°C. The heated laminate was placed in a hot pressing apparatus and vertically reduced at a reduction ratio of 33.3% or 37.5%. The laminate was vertically pressed sequentially from an initial thickness of 4 mm to 6 mm to a final thickness of 2.4 mm to 4 mm at a rate of 0.4 mm to 0.5 mm per time. As a result, the laminate was pressed to produce a bonding material of 2.5 mm or 4 mm.

6 shows a photograph of a heating furnace and a hot pressing apparatus used in an experimental example of the present invention. The left side of FIG. 6 is a photograph of the Kanthal-type electric furnace used in this experimental example, the center is a photograph of the 110 ton pressure welding press used in this experimental example, and the right side shows a partially enlarged photograph of the pressure welding press rail type mold.

The pressure welding press of FIG. 6 is a crank-driven type, and can perform pressure welding with a load of 110 tons per unit area. For the mold, a rail-type mold made of SKD-61, a hot tool steel material in the form of a flat plate, was used. The minimum number of press-welding was performed to transmit the vertical load to the entire area of the laminate to ensure stable bonding.

7 shows a photograph of hot pressing the laminate in the pressure welding press of FIG. 6 . As shown in FIG. 7 , the laminated material heated to red was vertically reduced to prepare a bonding material.

In the high-temperature welding method of FIG. 7, the laminated material heated uniformly while controlling the temperature to 950° C., 1000° C. or 1050° C. in an electric furnace was pressed 8 to 12 times until the red color was lost between the molds. The pressed bonding material was air-cooled.

blade manufacturing

8 shows a photograph of a processing process of a water jet used in an experimental example of the present invention and a bonding material using the same. The left side of FIG. 8 shows a water jet, and the right side of FIG. 8 shows a state in which the bonding material is cut using the water jet.

When water jet was used, the bonding interface of the bonding material was not melted. In addition, the separation phenomenon of the bonding material did not occur. Therefore, the use of a water jet was suitable for the manufacture of blades joined with dissimilar metals.

9 shows a photograph of a blade cut using the waterjet of FIG. 8 and a cross-section thereof. That is, the left side of FIG. 9 is a photograph of cutting the blade from the bonding material using a water jet, and the right side of FIG. 9 shows a cross-sectional photograph thereof.

As shown on the right side of FIG. 9 , it was observed that the specimens were laminated and pressed. That is, it was confirmed that the blade of the multi-layer structure was formed.

Surface hardening heat treatment of the blade part

10 shows a photograph of the high frequency induction heat treatment machine used in the experimental example of the present invention. The left side of FIG. 10 shows a photo of the high frequency induction heat treatment machine, and the right side of FIG. 10 shows an enlarged view of a coil for high frequency heat treatment, which is a jig included in the high frequency induction heat treatment machine.

As shown in Fig. 10, the blade part of the blade processed by water jet was subjected to induction heat treatment. As a result, the surface of the blade part was strengthened.

11 is a photograph of the surface hardening of the blade portion of the blade using the high frequency induction heat treatment machine of FIG. 10 and a photograph of the blade obtained as a result. The left side of FIG. 11 is a photograph of surface hardening the blade part using a high frequency induction heat treatment machine, and the right side of FIG. 11 is a photograph of the resulting blade.

Through the above-described processes, it was possible to manufacture a blade having excellent corrosion resistance and a good bonding state. Therefore, it was possible to manufacture a blade with good properties by joining dissimilar metals. Hereinafter, the experimental results of the bonding materials manufactured through the above-described experimental examples and comparative examples will be described.

Experimental Example 1

A bonding material was manufactured through the above-described alloy specimen preparation process and hot pressing process. The laminate was manufactured by sequentially laminating cupronickel, copper alloy, carbon steel, copper alloy, and cupronickel. The heating temperature of the laminate was 1050°C, and the heating time was 15 minutes. The heated laminate was vertically reduced to prepare a bonding material having a thickness of 4 mm at a reduction ratio of 33.3%. The rest of the experimental procedure was the same as in the above-described experimental example.

Experimental Example 1

A bonding material was prepared in the same manner as in Experimental Example 1 described above, but the heating temperature of the laminate was set to 1000°C.

Experimental Example 3

A bonding material was prepared in the same manner as in Experimental Example 1 described above, but the heating temperature of the laminate was 950°C.

Experimental Example 4

The laminate was prepared by sequentially laminating cupronickel, carbon steel and cupronickel. The heating temperature of the laminate was 1000° C., and a 2.5 mm thick bonding material was prepared at a reduction ratio of 37.5%. The rest of the experimental procedure was the same as in the above-described experimental example.

Experimental Example 5

The heating temperature of the laminated material was 1050°C. The rest of the experimental procedure was the same as in Experimental Example 4 described above.

Comparative Example 1

The bonding material was manufactured using a forging bonding process rather than hot pressing. The forging bonding process corresponds to the welding process. There was no process of heating the bonding material. The rest of the experimental process was the same as the above-described experimental example, and since the detailed experimental process can be easily understood by those of ordinary skill in the art to which the present invention pertains, a detailed description thereof will be omitted.

Comparative Example 2

The bonding material was manufactured using a hot rolling process rather than hot pressing. The rest of the experimental process was the same as the above-described experimental example, and since the detailed experimental process can be easily understood by those of ordinary skill in the art to which the present invention pertains, a detailed description thereof will be omitted.

Experiment result

Experimental results of bonding materials according to Experimental Examples 1 to 3, Comparative Examples 1 and 2 will be described below.

12 to 14 show photos of bonding materials of Experimental Examples 1 to 3, respectively. Each left side of FIGS. 12 to 14 shows a plan photograph of the bonding material, and each right side of FIGS. 12 to 14 shows a side picture of the bonding material.

As shown in FIG. 12 , in Experimental Example 1, an overall uniform bonding was possible at 1050°C. Through these experiments, it was possible to manufacture a bonding material in which each layer was perfectly bonded. On the other hand, although the reduction ratio during vertical rolling of the laminate was 33.3%, it was confirmed that a more ideal bonding material was obtained when it was reduced slightly to 35%.

On the other hand, in Experimental Example 2 of FIG. 13 , the heating temperature of the laminate was low, indicating that each layer was only partially adhered. That is, adhesion between dissimilar metals was not performed well. In addition, in Experimental Example 3 of FIG. 14 , it was confirmed that the heating temperature of the laminate was too low, so that the bonding state of each layer was unstable. Therefore, it was confirmed that the heating temperature of the laminate is preferably at least 1030° C. or higher.

15 and 16 are photographs of bonding materials prepared according to Comparative Examples 1 and 2, respectively. 15 and 16 show experimental results of manufacturing a plurality of bonding materials by a forging bonding process and a hot rolling process, respectively.

As shown in FIG. 15 , in the forging bonding process of Comparative Example 1, uniform bonding was almost impossible. However, some parts were joined. In Comparative Example 1, it was confirmed that an oxide film was formed on the surface of cupronickel due to high-temperature oxidation, making it impossible to achieve uniform bonding as a whole.

On the other hand, as shown in FIG. 16 , in the hot rolling process of Comparative Example 2, most of the layers were separated or pushed out, making it impossible to uniformly bond as a whole. This was estimated to be due to the effect of surface oxides on each material specimen and the difference in elongation of each material specimen. That is, in the heating temperature range of 950° C. to 1050° C. during hot rolling, surface oxides were generated on all materials. As a result, rolling bonding of the laminate was impossible. In addition, it was confirmed that bonding was impossible due to different elongation rates for each material during high-temperature rolling.

Tensile strength test

The tensile strength of the bonding materials prepared according to Experimental Examples 1 and 2 was measured. That is, the tensile strength of the bonding material according to the difference in hot pressing temperature was measured.

17 and 18 show graphs of tensile strength of bonding materials prepared according to Experimental Example 1 and Experimental Example 2 of the present invention, respectively.

As shown in FIG. 17 , in the bonding material prepared according to Experimental Example 1, deformation and fracture occurred at a final elongation (e) of 0.11 as the intermediate bonding layer was separated. In contrast, as shown in FIG. 18 , in the bonding material prepared according to Experimental Example 2, deformation and fracture occurred at a final elongation (e) of 0.08 while the intermediate bonding layer was separated. Therefore, it was confirmed that the final elongation (e) of the bonding material of Experimental Example 1 was increased by about 28% compared to the bonding material of Experimental Example 2. That is, when the bonding material was heated to 1050° C., a blade having excellent strength could be manufactured.

Although the present invention has been described as described above, it will be readily understood by those skilled in the art to which the present invention pertains that various modifications and variations are possible without departing from the spirit and scope of the appended claims.

10. Base material
20. Nickel coating layer
30. Plate
301. Copper alloy
303. Cupronickel
80. Laminate
90. Bonding material
100. Blade
1000. Waterjet
1001. Blade part
2000. Coil for high frequency heat treatment
W. water

Claims (3)

providing a base material comprising carbon steel;
providing a nickel coating layer on both sides of the base material,
forming a laminate by providing a plate material including a copper alloy layer and a cupronickel layer, respectively, on the nickel coating layer;
providing a bonding material by hot pressing the laminate;
Cutting the bonding material with a water jet to provide a blade including a blade portion, and
A step of surface strengthening heat treatment of the blade portion with high frequency by a coil for high frequency heat treatment formed in a curved shape corresponding to the blade portion
including,
In the step of forming the laminate, the thickness of the laminate is 5 mm to 6 mm,
In the step of providing the bonding material, the hot pressing is performed by heating the laminate at 1030° C. to 1080° C. for 13 minutes to 17 minutes and then vertically pressing the laminate without shear force to reduce the thickness of the bonding material to 2.4 mm to 4 mm. provide,
In the step of providing the base material,
The carbon steel is 0.6wt% to 1wt% of carbon, 0.1wt% to 0.3wt% of silicon, 0.2wt% to 0.6wt% of manganese, 0.01wt% to 0.03wt% of phosphorus, greater than 0 and 0.005wt% or less sulfur, greater than zero and not greater than 0.03 wt% aluminum, greater than zero and not greater than 0.3 wt% chromium, greater than zero and not greater than 0.005 wt% molybdenum, greater than zero and not greater than 0.04 wt% titanium, the remainder iron and impurities;
In the step of forming the laminate,
The cupronickel layer contains 23wt% to 26wt% of nickel, greater than 0 and not more than 0.05wt% lead, 0.02wt% to 0.1wt% iron, 0.1wt% to 0.5wt% manganese, the remainder copper and impurities;
The copper alloy contains 0.01wt% to 0.03wt% of lead, the remaining copper and impurities,
In the step of providing the blade, the reduction ratio at the time of hot pressing the laminate is 30% to 40%. delete In claim 1,
In the step of providing the base material,
In the carbon steel, the amount of carbon is 0.83 wt%, the amount of silicon is 0.19 wt%, the amount of manganese is 0.44 wt%, the amount of phosphorus is 0.018 wt%, the amount of sulfur is 0.002 wt%, and the amount of aluminum is The amount is 0.01wt%, the amount of chromium is 0.15wt%, the amount of molybdenum is 0.002wt%, the amount of titanium is 0.018wt%,
In the step of forming the laminate,
In the cupronickel layer, the amount of nickel is 24.85wt%, the amount of lead is 0.02wt%, the amount of iron is 0.07wt%, the amount of manganese is 0.3wt%,
In the copper alloy layer, the amount of lead is 0.023 wt%,
In the step of providing the bonding material, the laminate is heated at 1050° C. for 15 minutes,
In the step of providing the blade, the reduction ratio at the time of hot pressing the laminate is 35%.

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