Brazing method

Abstract

To provide a brazing method that can effectively braze a ceramic material to a steel material.SOLUTION: According to a method for brazing a ceramic material to a steel material, a brazing filler metal is arranged between the steel material and the ceramic material, and temperature rising is performed to a heating temperature that exceeds a Curie point of the steel material and is a melting point of the brazing filler metal or higher, thereby performing induction heating.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a brazing method for brazing a ceramic material to a steel material. [Background technology]

[0002] Patent Document 1 describes a high-frequency induction heating brazing method that can simplify flux brazing work, in which a flux-containing brazing material containing a brazing material component and a flux component is placed at the joint between metal workpieces to be joined, a high-frequency induction heating coil is placed nearby, and the flux-containing brazing material is melted by the induction heating action of the coil to join the workpieces. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 7-9119 A [Claim 1] [Figure 1] Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Document 1 does not disclose a brazing method for brazing a ceramic material to a steel material. SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a brazing method capable of effectively brazing a ceramic material to a steel material. [Means for solving the problem]

[0005] The brazing method according to the present invention is a brazing method for brazing a ceramic material to a steel material, characterized in that a brazing material is placed between the steel material and the ceramic material, and induction heating is performed by raising the temperature to a heating temperature that exceeds the Curie point of the steel material and is equal to or higher than the melting point of the brazing material. Effect of the Invention

[0006] According to the present invention, a brazing method capable of effectively brazing a ceramic material to a steel material can be provided. [Brief description of the drawings]

[0007] [Figure 1] 1A to 1C are conceptual diagrams illustrating each step of a brazing method according to an embodiment of the present invention. [Diagram 2] 1 is a conceptual diagram illustrating the positional relationship between a heating coil and a workpiece 1A during induction heating according to an embodiment of the present invention. FIG. [Diagram 3] FIG. 2 is a conceptual diagram for explaining a brazing method for brazing a ceramic material to a steel material in the embodiment. [Figure 4] FIG. 2 is a conceptual diagram for explaining heating temperature measurement points and hardness test evaluation points in the present embodiment. [Diagram 5] 1 shows a plot of the temperature rise tendency of heating temperature (° C.) versus heating time (sec) at positions 10 mm and 35 mm from the end of the brazing region α1 of S45C steel material 10a during induction heating in Example 1. [Figure 6] 1 is a graph showing the results of hardness measurements (at a total of five locations) performed on the test specimens obtained in Example 1, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The brazing method according to the present invention is a brazing method for brazing a ceramic material to a steel material, in which a brazing material is placed between the steel material and the ceramic material, and induction heating is performed by raising the temperature to a heating temperature that exceeds the Curie point of the steel material and is equal to or higher than the melting point of the brazing material.

[0009] Normally, when a magnetic field is generated inside a steel material, a current flows around the outer periphery of the steel material, which causes the steel material to be induction heated. The smaller the depth of this current (eddy current) from the outer periphery surface (hereafter referred to as the current penetration depth), the more the steel material heats up, and the higher the heating temperature can be achieved by heating. However, if the heating temperature becomes too high by heating, there is a possibility that the induction heating will have a negative effect on the steel material or ceramic material (such as reducing hardness). Therefore, as a result of extensive research, the inventors have discovered that by induction heating by raising the temperature to a temperature exceeding the Curie point of the steel material and equal to or higher than the melting point of the brazing material, brazing can be effectively performed while suppressing adverse effects on the steel material and ceramic material, and have completed the present invention.

[0010] A brazing method according to an embodiment of the present invention will be described below. FIG. 1 is a conceptual diagram illustrating each step of a brazing method according to an embodiment of the present invention. In the brazing method according to this embodiment, first, a brazing material 30 is placed on a brazing area 10A of a steel material 10, and a brazing area 20A of a ceramic material 20 is placed on the brazing material 30 placed on the brazing area 10A to form a workpiece 1A (FIG. 1(a)). Next, a region (brazing region α) including at least the ferrous material 10 and the ceramic material 20 on which the brazing material 30 is disposed is subjected to induction heating 45 (FIG. 1(b)). This induction heating 45 is performed by raising the temperature to a heating temperature that is higher than the Curie point of the ferrous material 10 and is equal to or higher than the melting point of the brazing material. Through the above steps, a weld 1B in which the steel material 10 and the ceramic material 20 are brazed can be obtained (FIG. 1(c)).

[0011] The term "steel material" as used herein includes ordinary steel (carbon steel) and special steel in general, and refers to, for example, carbon steel such as rolled steel for general construction, steel for low temperature use, steel plate material for nuclear reactors, etc., and includes steel materials such as cold-rolled steel, hot-rolled steel, hot-rolled steel plate material for automobile construction, hot-rolled high-tensile steel plate material for automobile processing, etc. Furthermore, the steel material as used herein is not limited to the above steel materials, and includes, for example, all steel materials standardized by the Japanese Industrial Standards (JIS "SS400") and the like.

[0012] The ceramic material in the present invention is a material that contains a metal carbide or a metal oxide and is sintered by heat treatment at a high temperature. Examples of the ceramic material include tungsten carbide, alumina, magnesia, titania, and zirconia. The brazing material in the present invention may be exemplified by common silver brazing material, gold brazing material, copper brazing material, Ni brazing material, and the like. The method of disposing the brazing material 30 of the present invention can be appropriately performed by a known method depending on the shapes of the brazing areas 10A, 20A of the steel material 10 and the ceramic material 20, respectively. Furthermore, the induction heating method of the present invention may be any heating method in which, when a magnetic field changes across a conductive material (such as steel), eddy currents are generated near the surface of the conductive material, and the object to be heated is heated by the resulting Joule heat. For example, the induction heating method may be performed by well-known high-frequency induction heating using a heating coil.

[0013] 2 is a conceptual diagram for explaining the positional relationship between the heating coil and the workpiece 1A during induction heating according to this embodiment, where (a) is a side view and (b) is a front view taken along line AA in (a). Note that in Fig. 2(a), the workpiece 1A and the fixing mechanism 100 inside the heating coil 50 are shown by dotted lines for the sake of convenience.

[0014] In this embodiment, the method of placing the brazing filler metal 30 between the ferrous material 10 and the ceramic material 20 and inductively heating it involves placing the workpiece 1A, in a heating coil 50, so that at least the region (brazing region α) of the workpiece 1A, in which the brazing filler metal 30 is placed between the ferrous material 10 and the ceramic material 20, including the ferrous material 10 and the ceramic material 20 in which the brazing filler metal 30 is placed, is inductively heated, as shown in Figures 1(b) and 2. The workpiece 1A, which is placed inside the heating coil 50, is fixed by a fixing mechanism 100, as shown in FIG.

[0015] The fixing mechanism 100 comprises a first support part 110 which is a plate-shaped body that supports the upper surface of the ceramic material 20, which is one end (the side of the brazing region α) of the workpiece 1A and is made of a steel material 10, a brazing material 30 and a ceramic material 20 stacked in this order, so as to prevent the stack from shifting; a second support part 120 which is a fixed jig fixed to the floor, wall, etc. of a factory, etc., and which supports the other end (the opposite side of the brazing region α) of the workpiece 1A by a fixing means not shown outside the heating coil 50; and a positioning member 130 which is a ceramic member that is arranged above the first support part 110 and the second support part 120 and positions the first support part 110 and the second support part 120. This positioning member 130 comprises a positioning body 135 arranged above the first support portion 110 and the second support portion 120, a first screw member 140 which can be screwed into a screw hole (not shown) that penetrates one end (the side of the brazing region α) of the positioning body 135 from top to bottom on the paper, supports the first support portion 110 at its tip 140A, and the supporting load can be adjusted via the screw hole, and a second screw member 150 which can be screwed into a screw hole (not shown) that penetrates the other end (the side opposite the brazing region α) of the positioning body 135 from top to bottom on the paper, and whose tip 150A is fixed to the second support portion 120.

[0016] The components, shapes, and materials constituting the fixing mechanism 100 are not particularly limited as long as at least the brazing region α side of the workpiece 1A can be placed in the heating coil 50, the ceramic material 20 can be supported from the upper surface thereof so that the stacked layers of the steel material 10, the brazing material 30, and the ceramic material 20 do not shift, and the induction heating 45 can be performed without thermal deformation, etc. The fixing mechanism 100 is also not particularly limited as long as at least the brazing region α side of the workpiece 1A can be placed in the heating coil 50, the ceramic material 20 can be supported from the upper surface thereof so that the stacked layers of the steel material 10, the brazing material 30, and the ceramic material 20 do not shift, and the induction heating 45 can be performed without thermal deformation, etc.

[0017] In the induction heating 45 according to this embodiment, the temperature is raised to a heating temperature that exceeds the Curie point of the ferrous material 10 and is equal to or higher than the melting point of the brazing material. The Curie point in the present invention refers to the magnetic transformation temperature of the ferrous material 10 used. The melting point of the brazing filler metal in the present invention refers to the melting point of the brazing filler metal 30 used. In the induction heating 45 according to this embodiment, when the temperature exceeds the Curie point of the ferrous material 10 (approximately 760°C in the embodiment described later), the current penetration depth described above increases, the current on the front and back surfaces of the ferrous material 10 is cancelled and the current becomes smaller (heating efficiency drops significantly), the temperature rise is suppressed, and the temperature is uniformly increased (i.e., the temperature is uniformly increased with a temperature rise trend as shown in FIG. 5).

[0018] Therefore, the heating temperature of the induction heater 45 according to this embodiment is a temperature exceeding the Curie point of the ferrous material 10 and a temperature equal to or higher than the melting point of the brazing material 30, so that brazing can be performed. In addition, the heating temperature of the induction heater 45 according to this embodiment is a temperature (approximately 775°C in the example described later) that has a temperature rise tendency as shown in Fig. 5 and is uniformly heated, so that the brazing can be effectively performed while suppressing adverse effects such as a decrease in hardness on the ferrous material 10 and the ceramic material 20.

[0019] The temperature adjustment to exceed the Curie point of the ferrous material 10 is performed by adjusting the current value and frequency in the induction heater 45, and the frequency is preferably set to an f value calculated by the following formula (1). δ = 5.03 × 10 5 (ρ / (μ f)) 1 / 2 ...Equation (1) where δ is the cross-sectional distance (mm) of the steel material 10, ρ is the resistance (Ω·m) at the Curie point of the steel material 10, μ is the relative permeability (1 at temperatures above the Curie point of the steel material), and f is the frequency (Hz).

[0020] The Curie point temperature of the ferrous material 10 and the melting point temperature of the brazing filler metal 30 can be confirmed by the materials of the ferrous material 10 and the brazing filler metal 30 to be brazed, etc. The cross-sectional distance between flat surfaces of the ferrous material 10 is the cross-sectional distance 10bb between flat surface 10a1 and a back surface 10a2 opposed to flat surface 10a1 in a cross section obtained by cutting a flat surface 10a1 of a brazing area 10aa of the ferrous material 10a as shown in Fig. 3 parallel to the thickness direction (stacking direction β1).

[0021] The temperature at which the heat is uniformed is determined by utilizing the phenomenon in which the currents on the front and back surfaces of the ferrous material 10 are cancelled, reducing the current and achieving uniform heat, as described above. That is, the temperature to be soaked is, where δ is the current penetration depth (mm), ρ is the resistance value (Ω·m) at the Curie point of the ferrous material 10, μ is the relative permeability (1 at a temperature exceeding the Curie point of the ferrous material), and f is the frequency (Hz), and the f value (frequency (Hz)) calculated by the above formula (1) and the current value are adjusted to perform induction heating 45, thereby making it possible to generate the above phenomenon.

[0022] That is, when a current with an f value that satisfies the above formula (1) is passed through the heating coil 50, the currents flowing around (above, below, left, right) the ferrous material 10 interfere with each other, and these currents cancel each other out, causing the cancellation of the induced current. As a result, the heating efficiency drops drastically with the decrease in induced current, and the heating target area (brazing area α) can be heated uniformly. Therefore, by setting the frequency in the induction heating 45 to the f value calculated by the above formula (1) and adjusting the current value in the induction heating 45 (including adjusting both the power value and the voltage value), the temperature can be raised to a heating temperature that is above the Curie point of the ferrous material 10 and above the melting point of the brazing material 30, and the heating can be uniformly performed. When magnetic steel is heated at a predetermined frequency by induction heating, the relative magnetic permeability (μ) becomes 1 when the temperature exceeds the Curie point (magnetic transformation point) of the steel.

[0023] In conventional brazing using induction heating, it was difficult to uniformly heat the area to be heated (brazing area α) when heating a part of the heated member (welded body). In addition, the surface of the heated member (welded body) is prone to concentrated heating due to the skin effect. However, with the brazing method according to the present invention, the occurrence of these problems can be suppressed by setting an appropriate frequency. EXAMPLES

[0024] The present invention will now be described in more detail with reference to examples and comparative examples, although the present invention is not limited to these examples in any way. Example 1 FIG. 3 is a conceptual diagram for explaining a brazing method for brazing a ceramic material to a steel material in the embodiment, and more specifically, shows a mode of disposing a brazing material in the embodiment. In this embodiment 1, as shown in Figure 3, silver solder (bar crushing / melting point: 650°C to 760°C: symbol 30a) was stacked in a stacking direction β1 on the brazing region 10aa of S45C steel material 10a, and further, a carbide tip 20a (made of tungsten carbide: ceramic material) was stacked in the stacking direction β1 of the brazing region 20aa on the silver solder 30a to form the welded body 1a. Next, at least the brazing region α1 of the workpiece 1a was fixed to a fixing mechanism 100 as shown in FIG. 2, and placed in a coil 50, and induction heating 45 was performed. The heating temperature in this induction heater 45 was adjusted to the following values ​​for power, voltage and frequency (i.e., current and frequency) so as to raise the temperature to a temperature exceeding the Curie point of the S45C steel material 10a and equal to or higher than the melting point of the brazing material 30a used.

[0025] [Heating conditions] Power: 47kW Voltage: 180V Frequency: 3000Hz (calculated using formula (1)) δ:9.29mm ρ:1.02×10 -6 μ:1 Output control method: constant power control Heating time: 10 seconds

[0026] In this Example 1, the welded body 1b obtained under the above-mentioned conditions was used as a test specimen. FIG. 4 is a conceptual diagram for explaining the heating temperature measurement points and the evaluation points of the hardness test in this embodiment. In Example 1, the heating temperature was measured by using a chromel-alumel (K-type) thermocouple welded to each joining surface at a position TH1 10 mm from the end of the brazing region α1 of the S45C steel material 10a and a position TH2 35 mm from the end of the brazing region α1 of the S45C steel material 10a during induction heating 45, thereby confirming the tendency of the heating temperature to increase with the heating time (seconds) of the S45C steel material 10a during induction heating 45. In addition, the following hardness test was performed on the obtained specimen. The hardness test was carried out on the obtained specimen by micro-Vickers hardness measurement. The Vickers hardness Hv was measured by cutting the specimen along the line BB shown in Fig. 4(a), polishing the cut surface to make it smooth, and then measuring the Vickers hardness Hv at five points (within the carbide tip 20a) at a pitch of 0.5 mm upward from the interface of the brazing material 30a as shown in Fig. 4(b) using a Vickers hardness tester (measurement load 1 kgf).

[0027] Comparative Example 1 In Comparative Example 1, a copper phosphorus brazing filler metal (commercial product / melting point: 730°C to 815°C) was used as the brazing filler metal, and a test specimen was produced under the same conditions as in Example 1, except for the frequency. The frequency was set to a frequency (1000 Hz) at which no cancellation of the induced current occurs. Then, in the same manner as in Example 1, a hardness test was carried out.

[0028] Comparative Example 2 In Comparative Example 2, silver brazing filler metal (foil brazing filler metal / melting point: 650° C. to 760° C.) was used as the brazing material, and brazing was performed by gas welding rather than induction heating. Then, in the same manner as in Example 1, a hardness test was carried out.

[0029] (Results and Evaluation) FIG. 5 shows a plot of the temperature rise tendency of heating temperature (° C.) versus heating time (seconds) at positions 10 mm and 35 mm from the end of the brazing region α1 of the S45C steel material 10a during induction heating in Example 1. As shown in Fig. 5, in Example 1, it can be confirmed that, despite the constant power control, the rise in heating temperature is suppressed and the heating tends to be uniform at both the position 10 mm and the position 35 mm from the end of the S45C steel material 10a. This is considered to be because the current on the front and back surfaces of the S45C steel material 10a is canceled, the current is reduced, and the heating efficiency is significantly reduced.

[0030] In Example 1, the soaking heating temperature of about 770°C to 775°C exceeded the Curie point (760°C) of the S45C steel material 10a and was equal to or higher than the melting point (650°C to 760°C) of the silver brazing material 30a. On the other hand, in Comparative Examples 1 and 2, no temperature rise tendency in which the heating efficiency significantly decreases as shown in FIG. 5 was observed, and a tendency for the temperature to constantly rise from the start to the end of heating was confirmed.

[0031] FIG. 6 is a graph showing the results of hardness measurements (at a total of five locations) performed on the test specimens obtained in Example 1, Comparative Example 1, and Comparative Example 2. As can be seen from the results in Fig. 6, no decrease in hardness was confirmed in Example 1. Therefore, it was confirmed that Example 1 can effectively braze the cemented carbide tip 20a to the S45C steel material 10a, as compared with Comparative Examples 1 and 2, and no decrease in hardness of the cemented carbide tip 20a (i.e., no adverse effect on the cemented carbide tip 20a) was confirmed.

[0032] On the other hand, a decrease in hardness was confirmed in Comparative Example 1 and Comparative Example 2. Therefore, it was confirmed that it was difficult to effectively braze the cemented carbide tip 20a to the S45C steel material 10a in Comparative Example 1 and Comparative Example 2 compared to Example 1 and Example 2, and that adverse effects such as a decrease in hardness occurred in the brazed cemented carbide tip 20a. [Industrial Applicability]

[0033] According to the brazing method of the present invention, a ceramic material can be effectively brazed to a steel material. Therefore, a steel-ceramic material weld brazed by the brazing method of the present invention can be suitably used for cutting tools of lathes of machine tools, etc. [Explanation of symbols]

[0034] 1A Welded object 1B Welding body 10. Steel 10A Brazing Range 20 Ceramic materials 30 Brazing material 45 Induction heating 50 Heating coil

Claims

[Claim 1] A brazing method for brazing a ceramic material to a steel material, comprising the steps of: A brazing method in which a brazing material is placed between the steel material and the ceramic material, and induction heating is performed by raising the temperature to a temperature that exceeds the Curie point of the steel material, is equal to or higher than the melting point of the brazing material, and is further increased to a heating temperature at which the heating efficiency decreases and the heating is uniform.

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