JP7584384B2 - Brazing Method - Google Patents

Description

The present invention relates to a brazing method for brazing a ceramic material to a steel material.

Patent Document 1 describes a high-frequency induction brazing method that can simplify flux brazing work, in which a flux-containing brazing material containing brazing material components and flux components 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.

JP-A-7-9119 [Claim 1] [Figure 1]

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.

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 temperature that exceeds the Curie point of the steel material and is equal to or higher than the melting point of the brazing material.

The present invention provides a brazing method that can effectively braze ceramic materials to steel materials.

1A to 1C are conceptual diagrams illustrating each step of a brazing method according to an embodiment of the present invention. 1 is a conceptual diagram illustrating a positional relationship between a heating coil and a workpiece 1A during induction heating according to an embodiment of the present invention. FIG. FIG. 2 is a conceptual diagram for explaining a brazing method for brazing a ceramic material to a steel material in the embodiment. FIG. 2 is a conceptual diagram for explaining heating temperature measurement points and hardness test evaluation points in the present embodiment. This shows a plot of the temperature rise tendency of heating temperature (°C) against heating time (seconds) 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. 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.

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.

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 (hereinafter referred to as the current penetration depth), the more the steel material is heated, 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 an adverse effect (such as a decrease in hardness) on the steel material or ceramic material.
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.

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 then 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 welded body 1A (FIG. 1(a)).
Next, a region (brazing region α) including at least the steel 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 steel material 10 and is equal to or higher than the melting point of the brazing material.
Through the above steps, a welded body 1B in which the steel material 10 and the ceramic material 20 are brazed can be obtained (FIG. 1(c)).

The term "steel material" as used herein includes ordinary steel (carbon steel) and special steel in general, such as carbon steels, such as rolled steel for general construction, steels for low temperatures, steel plate materials for nuclear reactors, and other steel materials, including cold-rolled steel materials, hot-rolled steel materials, hot-rolled steel plate materials for automobile construction, and hot-rolled high-tensile steel plate materials for automobile processing. The term "steel material" as used herein is not limited to the above steel materials, but includes, for example, all steel materials standardized by the Japanese Industrial Standards (JIS "SS400") and the like.

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, for example, a typical silver brazing material, a gold brazing material, a copper brazing material, or a Ni brazing material.
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.

Figure 2 is a conceptual diagram 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 A-A in (a). Note that in Figure 2(a), the workpiece 1A and fixing mechanism 100 inside the heating coil 50 are shown by dotted lines for convenience.

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

The fixing mechanism 100 includes a first support part 110 which is a plate-like body that supports the upper surface of the ceramic material 20, which is one end (the brazing region α side) of the workpiece 1A and is made up 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 or wall of a factory or the like and 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 includes a positioning body 135 arranged above the first support portion 110 and the second support portion 120, a first screw member 140 that can be screwed into a screw hole (not shown) that penetrates one end (the side of the brazed region α) of the positioning body 135 from the top to the bottom of the paper, supports the first support portion 110 with its tip 140A, and can adjust the support load by means of the screw hole, and a second screw member 150 that can be screwed into a screw hole (not shown) that penetrates the other end (the side opposite the brazed region α) of the positioning body 135 from the top to the bottom of the paper, and has its tip 150A fixed to the second support portion 120.

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 welded body 1A can be placed in the heating coil 50, the ceramic material 20 can be supported from the top 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. Also, the fixing mechanism 100 is not particularly limited as long as at least the brazing region α side of the welded body 1A can be placed in the heating coil 50, the ceramic material 20 can be supported from the top 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.

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 material in the present invention refers to the melting point of the brazing material 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 Figure 5).

Therefore, the heating temperature of the induction heater 45 according to this embodiment is a 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 30, so that brazing can be performed. In addition, the heating temperature of the induction heater 45 according to this embodiment is a temperature that is uniformly heated with a temperature rise tendency as shown in FIG. 5 (approximately 775°C in the example described later), 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.

The temperature adjustment to exceed the Curie point of the steel material 10 is performed by adjusting the current value and frequency in the induction heating 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 ...Formula (1)
where δ is the cross-sectional distance (mm) of the ferrous material 10, ρ is the resistance (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).

The Curie point temperature of the ferrous material 10 and the melting point temperature of the brazing material 30 can be confirmed by the materials of the ferrous material 10 and the brazing material 30 to be brazed. The cross-sectional distance between flat surfaces of the ferrous material 10 is the cross-sectional distance between flat surfaces 10a1 and the back surface 10a2 opposite to flat surfaces 10a1 in a cross section when a flat surface 10a1 of the brazing area 10aa of the ferrous material 10a as shown in FIG. 3 is cut parallel to the thickness direction (lamination direction β1).

The temperature at which the heat is uniformed is achieved by utilizing the phenomenon in which the currents on the front and back surfaces of the steel material 10 are cancelled out, 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 induce heating 45, thereby causing the above phenomenon.

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 the ferrous material 10 (above, below, left, right) interfere with each other, and these currents cancel each other out, causing 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 heating temperature can be raised to a 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 30, and the heating can be uniformly performed.
In addition, when a magnetic steel material is heated at a predetermined frequency by induction heating, when the temperature exceeds the Curie point (magnetic transformation point) of the steel material, the above μ (relative magnetic permeability) becomes 1.

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 of the present invention, the occurrence of these problems can be suppressed by setting an appropriate frequency.

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) is 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) is 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 heating 45 exceeds the Curie point of the S45C steel material 10a, and is adjusted to the following values of power, voltage and frequency (i.e., current and frequency) so as to raise the temperature to a temperature equal to or higher than the melting point of the brazing material 30a used.

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

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 a chromel-alumel (K-type) thermocouple welded to each of the joining surfaces 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 test specimen by a micro Vickers hardness test. The Vickers hardness Hv was measured by cutting the test specimen along the line B-B shown in Fig. 4(a), polishing the cut cross section to make it smooth, and then measuring the hardness at a total of 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).

(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 prepared 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 occurred.
Then, in the same manner as in Example 1, a hardness test was carried out.

(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.

(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 temperature 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 thought 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.

In addition, in Example 1, the heating temperature for soaking, approximately 770°C to 775°C, was a temperature exceeding the Curie point (760°C) of the S45C steel material 10a and was a temperature equal to or higher than the melting point (650°C to 760°C) of the silver solder 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.

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 of Fig. 6, no decrease in hardness was confirmed in Example 1. Therefore, it was confirmed that Example 1 can effectively braze the carbide tip 20a to the S45C steel material 10a, as compared with Comparative Example 1 and Comparative Example 2, and no decrease in the hardness of the carbide tip 20a (i.e., no adverse effect on the carbide tip 20a) was confirmed.

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 more difficult to effectively braze the carbide tip 20a to the S45C steel material 10a in Comparative Example 1 and Comparative Example 2 than in Example 1 and Example 2, and that adverse effects such as a decrease in hardness occurred in the brazed carbide tip 20a.

The brazing method according to the present invention allows for effective brazing of ceramic materials to steel materials. Therefore, the steel-ceramic material weld brazed using the brazing method according to the present invention can be suitably used for cutting tools for lathes of machine tools, etc.

1A: Object to be welded 1B: Welded object 10: Steel material 10A: Brazing area 20: Ceramic material 30: Brazing material 45: Induction heating 50: Heating coil

Claims (1)

A brazing method for brazing a ceramic material to a steel material, comprising the steps of:
A brazing material is placed between the steel material and the ceramic material, and the brazing material is induction-heated by increasing the temperature to a heating temperature that is higher than the Curie point of the steel material and is equal to or higher than the melting point of the brazing material;
The temperature adjustment to exceed the Curie point of the steel material is performed by adjusting the current value and frequency of the induction heating,
The frequency is
The following formula (1)
δ=5.03×10 ⁵ (ρ/(μ・f)) ^1/2 ...Formula (1)
In the brazing method, δ is the cross-sectional distance (mm) of the steel material, ρ is the resistance value (Ω m) at the Curie point of the steel material, μ is the relative permeability (1 at a temperature exceeding the Curie point of the steel material), and f is the f value calculated from the above formula (Hz) .

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