JP2001321961A - Liquid phase diffusion joints with excellent tensile strength characteristics and joining method - Google Patents

Abstract

(57) [Summary] (Modifications) [PROBLEMS] To provide a joined joint having excellent tensile strength characteristics by heat-resistant steel and stainless steel by liquid phase diffusion joining in an oxidizing atmosphere and a joining method of the joint. SOLUTION: Steel material containing 0.001% by mass or more of C: 0.0001% to 10% by mass of Si, 0.0001% to 15% of at least one type of B or P, and the balance Using a bonding foil made of Fe and unavoidable impurities, there is no oxide having a maximum major axis of 100 μm or more in a liquid phase diffusion bonded portion in an oxidizing atmosphere in which O ₂ is present in an amount of 0.01% by mass or more. A liquid-phase diffusion bonded joint having excellent tensile strength characteristics in which the total area of the oxide is 25% or less with respect to the cross-sectional area of the bonding layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joined joint by liquid phase diffusion joining and a method for producing the same, and in particular, to a material which partially substitutes for conventional welding or which is difficult to perform various kinds of welding, that is, steel, The present invention relates to a joint having excellent tensile strength characteristics by heat-resistant steel or stainless steel by liquid phase diffusion joining in an oxidizing atmosphere, and a joining method for realizing the joint.

[0002]

2. Description of the Related Art Liquid phase diffusion bonding is a technique in which an alloy having a lower melting point than a material to be joined is sandwiched between materials to be joined in the form of foil, plating, or powder (hereinafter, referred to as insert metal). Is heated and held at a temperature equal to or higher than the melting point, and the melted insert metal layer is isothermally solidified and joined. This liquid phase diffusion bonding has been put to practical use as a method for bonding high alloy steel, heat resistant steel, or the like, or for bonding different materials, which are already difficult to weld. On the other hand, in recent years, application of liquid phase diffusion bonding has been attempted for carbon steel as a bonding method capable of achieving a joint having higher efficiency and higher performance than conventional various welding methods.

[0003] Regarding the liquid phase diffusion bonding of steel materials, for example, JP-A-53-81458, JP-A-62-34685, and JP-A-62-34685
JP-227595 discloses a technique relating to liquid phase diffusion bonding in vacuum and in inert gas. In order to join in a vacuum and an inert atmosphere, a chamber or the like for maintaining the joining portion in the atmosphere is necessary. For example, when the materials to be joined are enlarged, the cost of a device for accommodating them increases significantly. Therefore, at present, the applicable range of the liquid phase diffusion bonding is limited.

[0004] The inventors of the present invention have conducted repeated studies on a technique capable of performing liquid phase diffusion bonding in an oxidizing atmosphere for the purpose of expanding the application of the liquid phase diffusion bonding technique to steel materials. As a result, for example, Japanese Patent No. 1891618, Patent No. 1861819, Patent 1837
As disclosed in the publications of Japanese Patent No. 572 and 572, a technique of a liquid phase diffusion bonding alloy foil (insert) capable of bonding in an oxidizing atmosphere has been obtained. In bonding in an oxidizing atmosphere, an oxide film (Fe ₂ O ₃ ) is generated on the bonding surface of the material to be bonded during heating and deteriorates the characteristics of the bonded joint, but the oxidation generated on the bonded surface by adding V to the insert metal. Fe ₂ O ₃ between the film and V
It was found that -V ₂ O ₅ (melting point 800 ° C.) was generated, and this composite oxide became spherical at the bonding temperature and was discharged into the bonding layer, thereby rendering the oxide film formed on the bonding surface harmless.

[0005] However, using a special alloy foil which can be bonded in an oxidizing atmosphere and in the oxidizing atmosphere described above, Patent No. 26
No. 97534, liquid-phase diffusion bonding was performed under conventional bonding conditions as disclosed in JP-A-5-318143.
As shown in Table 1, it became clear that the strength characteristics of the joint were not stably obtained. Analysis of the instability factor of the joint characteristics revealed that coarse inclusions existing in the joint deteriorated the joint characteristics. further,
This inclusion is formed by oxidizing Si and B or P added during the joining in order to sufficiently lower the melting point or maintain the amorphous formation of the insert metal sandwiched between the materials to be joined. Because it was sufficient, it was clarified that it was not sufficiently discharged out of the bonding layer and remained.

Accordingly, the present inventors have conducted detailed studies for obtaining excellent joint strength characteristics in a safe manner when performing liquid phase diffusion joining in an oxidizing atmosphere. As a result, a high joining pressure was applied in the initial stage of joining. By doing so, the inclusions mainly containing Si or B or P-based oxides present in the bonding layer are sufficiently discharged to the outside of the bonding layer, and then the bonding is performed with a bonding stress pattern such that the stress required for maintaining the bonding is reduced. Thus, it has been found that the amount of these inclusions remaining in the bonding layer can be controlled, and that excellent joint strength characteristics can be stably obtained.

[0007] Recently, there has been an increasing demand for carbon steel materials such as steel pipes, reinforcing bars, and thick plates in a short time and at a low jointing cost while securing sufficient joint characteristics. The present inventors have considered that it is difficult to sufficiently satisfy these demands by conventional welding using various types of welding, and have newly studied the application of liquid phase diffusion bonding. When liquid phase diffusion bonding is performed under the conditions,
The joint strength characteristics become unstable due to the large inclusions mainly composed of Si or B or P-based oxides in the bonding layer as described above. It has been ascertained that it is difficult to sufficiently satisfy the above demand only by combining conventional techniques such as applying conditions.

[0008]

SUMMARY OF THE INVENTION The present invention relates to
_In the case where liquid phase diffusion bonding is performed in an oxidizing atmosphere in which ₂ is present in an amount of 0.01% or more, it is possible to obtain a joint capable of stably obtaining excellent tensile strength characteristics and a joint having excellent tensile strength characteristics. To provide a liquid phase diffusion bonding method.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for preparing O ₂ by weight%.
The present invention stably provides a joint having excellent tensile properties in liquid phase diffusion bonding in an oxidizing atmosphere where 0.01% or more is present. (1) C: A steel material containing 0.001% by mass or more is subjected to liquid phase diffusion bonding in an oxidizing atmosphere containing O ₂ at 0.01% by mass or more using a joining foil in any cross section of the joint. A liquid-phase diffusion-bonded joint excellent in tensile strength characteristics, characterized in that there is no oxide having a maximum major axis of 100 μm or more.

[0010] (2) C: a steel containing more than 0.001 mass%, using a bonding foil, O ₂ and all the joints that liquid phase diffusion bonding in an oxidizing atmosphere present above 0.01 wt% A liquid-phase diffusion-bonded joint having excellent tensile strength characteristics, wherein the total area of the oxides in the cross section is 25% or less with respect to the cross-sectional area of the joint. (3) C: A steel material containing 0.001% by mass or more was subjected to liquid phase diffusion bonding in an oxidizing atmosphere in which O ₂ was present in an amount of 0.01% by mass or more, using a joining foil, in any cross section of the joint. There is no oxide having a maximum major axis of 100 μm or more, and the total area of the oxide is 2
A liquid phase diffusion bonded joint having excellent tensile strength characteristics of not more than 5%.

(4) C: Steel material containing 0.001% by mass or more, by mass%, Si: 0.0001 to 10%, B
Or 0.0001 to 15% of at least one kind of P
In any cross-section of the joint using a bonding foil, O ₂ was liquid phase diffusion bonding in an oxidizing atmosphere present above 0.01 wt%, including, wherein the maximum major axis is nil oxide is 100μm or more Liquid phase diffusion bonded joints with excellent tensile strength characteristics.

(5) C: steel material containing 0.001% by mass or more, by mass%, Si: 0.0001 to 10%, B
Or 0.0001 to 15% of at least one kind of P
The total area of the oxide is 2 parts with respect to the cross-sectional area of the joint at any cross-section of the liquid-phase diffusion-bonded joint in an oxidizing atmosphere in which O ₂ is present in an amount of 0.01% by mass or more using the bonding foil containing O 2.
A liquid phase diffusion bonded joint having excellent tensile strength characteristics of not more than 5%.

(6) C: steel material containing 0.001% by mass or more, by mass%, Si: 0.0001-10%, B
Or 0.0001 to 15% of at least one kind of P
Using the bonding foil containing, in any cross section of the O ₂ is Joints liquid phase diffusion bonding in an oxidizing atmosphere present above 0.01% by weight, none oxides maximum diameter is 100μm or more, and oxidation A liquid-phase diffusion-bonded joint having excellent tensile strength characteristics, wherein the total area of the object is 25% or less with respect to the cross-sectional area of the joint.

(7) The liquid-phase diffusion-bonded joint excellent in tensile strength characteristics according to (4) to (6), wherein the bonding foil further contains 0.001 to 10% by mass V. . (8) Steel material containing 0.001% by mass or more of C: 0.0001 to 10% by mass of Si, 0.0001 to 15% of at least one type of B or P, and V: 0. 0
A single or composite oxide of Si and B or P is used in all cross sections of a liquid-phase diffusion-bonded joint in an oxidizing atmosphere in which O ₂ is present in an amount of 0.01% by mass or more using a bonding foil containing 01 to 10%. A liquid-phase diffusion-bonded joint having excellent tensile strength characteristics, wherein the maximum major axis is 100 μm or less.

(9) C: steel material containing 0.001% by mass or more, Si: 0.0001 to 10% by mass%, B:
Or at least one of P is 0.0001 to 15
%, V: using a bonding foil containing 0.001 to 10%, and O ₂
Is present in all cross sections of the liquid-phase diffusion-bonded joint in an oxidizing atmosphere in which 0.01% by mass or more of Si and
A liquid-phase diffusion-bonded joint having excellent tensile strength characteristics, wherein the total area of B or P alone or a composite oxide is 25% or less with respect to the cross-sectional area of the joint.

(10) C: steel material containing 0.001% by mass or more, by mass%, Si: 0.0001 to 10%,
0.0001 to 15 of at least one of B or P
%, V: using a bonding foil containing 0.001 to 10%, and O ₂
Is present in all cross sections of the liquid-phase diffusion-bonded joint in an oxidizing atmosphere in which 0.01% by mass or more of Si and
The maximum major axis of B or P alone or a composite oxide is 100
A liquid-phase diffusion-bonded joint having excellent tensile strength characteristics, wherein the joint thickness is not more than 25 μm and the total area of the oxide is not more than 25% of the cross-sectional area of the joint.

(11) In an oxidizing atmosphere containing 0.01% or more of O _{2 by} mass%, the temperature rise time is 10 minutes or less, the bonding temperature is 850 ° C. to 1300 ° C., and the holding time is 0.1%.
5 to 30 minutes, and the bonding pressure is increased to 5 to 50
MPa, the joining pressure is reduced within 30 seconds after the joining temperature reaches the target joining temperature, and then 0.1 to
A method for joining a liquid-phase diffusion-bonded joint having excellent tensile strength characteristics, wherein the joint is maintained at 14 MPa.

(12) In an oxidizing atmosphere in which O ₂ is present in an amount of 0.01% or more by mass%, the temperature rise time is 10 minutes or less, the bonding temperature is 850 ° C. to 1300 ° C., and the holding time is 0.1 minute.
5 to 30 minutes, and the bonding pressure is increased to 5 to 50
A liquid having excellent tensile strength characteristics, wherein the liquid is loaded and maintained at a pressure of MPa, and the bonding pressure is reduced by 3 MPa or more within 30 seconds after the bonding temperature reaches the target bonding temperature, and then maintained at 0.1 to 14 MPa. Joining method of phase diffusion joint.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, as defined in the present invention,
The reason for limiting the particle size and the occupancy of the Si-based and B-based inclusions in a certain joint section will be described. The present inventors conducted detailed experiments to clarify the relationship between the amount of oxide in the joint and the joint strength. A test piece was set as shown in FIG. 1 using the steel material shown in Table 2 as a material to be welded (φ50 mm) and the bonding foil in the air shown in Table 3 as shown in FIG. 1 and then joined at a joining temperature of 1200 ° C. and a holding time of 5 minutes. Then, the structure of the joint was observed and a tensile test was performed. The observation of the structure of the joint portion was performed on a vertical cross section of any 20 visual fields with respect to the joint surface.

How to determine the maximum major axis and the occupancy of the oxide in the junction will be described with reference to FIG. The major axis Li of each oxide observed in the joint was measured in any 20 visual fields with respect to the joint surface, and the largest one of the major axes of each oxide was determined as the maximum major axis Lmax. On the other hand, the occupancy X
Is in a cross section perpendicular to the junction plane of each arbitrary 20 visual field,
After measuring the cross-sectional area of each oxide and calculating its sum S1 and measuring the cross-sectional area S0 of the junction, the value of S1 / S0 is defined as the occupancy. In addition, as shown in FIG. 3, the tensile characteristics of the joint were measured by collecting a tensile test piece such that the joint was centered.
A tensile test was performed at room temperature.

FIG. 4 shows the relationship between the ratio of the tensile properties of the joint to the joint properties of the base metal and the maximum major axis of the oxide in the joint. When the maximum major axis of the oxide is 100 μm or less, the tensile properties of the joint show values equal to or greater than the tensile properties of the base material. But,
If the maximum major axis of the oxide exceeds 100 μm, the tensile properties of the joint are lower than that of the base metal. Therefore, in order to stably obtain good joint tensile properties, the maximum major axis of the oxide in the joint is limited to 100 μm or less.

FIG. 5 shows the relationship between the ratio of the tensile properties of the joint to the joint properties of the base metal and the occupancy of the joint oxide. When the occupancy of the oxide is 25% or less, the tensile properties of the joint are equal to or higher than that of the base metal. However, when the occupancy exceeds 25%, the tensile properties of the joint deteriorate compared to that of the base metal. Therefore, in order to stably obtain good joint tensile properties, the occupancy of the oxide in the joint is limited to 25% or less. Preferably, the oxide in the joint has a maximum major axis of 100 μm
If it is less than or equal to 25% and the occupation ratio is 25% or less, the tensile properties of the joint can be stably equal to or higher than those of the base material.

Next, the joining conditions which enable the joint of the present invention to have excellent tensile properties will be described in detail. In the present invention, a joining method for obtaining a liquid-phase diffusion joined joint having excellent tensile strength characteristics is as follows: an oxidizing atmosphere in which O ₂ : 0.01% by mass or more is present; At 1300 ° C., the holding time is 0.5 to 30 minutes, and the joining stress is 5 at the start of joining.
Load and hold at ~ 50 MPa, and reduce the bonding stress within 30 seconds after the bonding temperature reaches the target bonding temperature, preferably 3MPa.
a to reduce the pressure to at least a and continuously maintain the pressure at 0.1 to 14 MPa. This joining condition will be described in detail.

First, the temperature rise time refers to a time a until the junction temperature reaches the junction temperature as shown in FIG. The joining surface of the material to be joined and the surface of the insert metal are oxidized during the heating, and if the joining is performed for a heating time of more than 10 minutes, the joining surface is significantly oxidized and liquid phase diffusion joining is impossible. Therefore, the heating time was limited to 10 minutes or less. As for the joining temperature, the melting point of the insert metal is about 1000 ° C., and the joining temperature needs to be 1050 ° C. or more to completely melt the insert metal. On the other hand, if the joining temperature exceeds 1300 ° C., the grain size of the heat-affected zone in the vicinity of the joined portion becomes extremely coarse, and the proof stress decreases. Therefore, the bonding temperature is preferably in the range of 1050C to 1300C. The holding time is a time c for maintaining the joining temperature as shown in FIG. 6, but if the holding time is 30 seconds or less, all of the melted insert metal does not solidify at the same temperature and causes deterioration of the joint tensile properties. On the other hand, when the holding time exceeds 30 minutes, the crystal grains of the joint structure become coarse and the proof stress decreases.
Therefore, the holding time is preferably from 30 seconds to 30 minutes.

The bonding pressure is the most important factor in the present invention for supplying a bonded joint having excellent tensile properties in liquid phase diffusion bonding in an oxidizing atmosphere containing 0.01% or more by weight of O _2. It is a joining parameter. The Si-based and B or P-based inclusions generated at the joint when the temperature is increased are discharged out of the joint due to the joining pressure. The inventors have repeated many experiments in order to obtain a joint having excellent tensile properties.
The system interposed part is discharged out of the joint part, and the maximum joint diameter of the Si-based and B, P-based interposed parts of all joint sections is 100 μm or less and the joint occupancy is 25% steadily obtained. Pressure pattern that can produce The details are described below.

FIGS. 7 and 8 show the effects of the bonding pressure on the oxide occupancy and the maximum major axis of the bonding portion. If the joining pressure is 5 MPa or more, the oxide at the joint is sufficiently discharged outside the joint, and the maximum major axis of the oxide at the cross section of the joint is 100 mm.
μm or less, and the occupancy of these oxides is 25 μm or less.
% Or less. However, if the material to be joined under a stress of 5 MPa or more is held for a long time in a high temperature region of 1000 ° C. or more, the joints will buckle due to creep deformation and cannot be joined. Therefore, as shown in FIG.
A joint stress pattern was considered in which the oxide at the joint was discharged to the outside of the joint by applying a load of Pa or more, and the joint stress was reduced before the joint buckled due to creep deformation.

Based on this stress pattern, the joining (joining temperature 1200) is changed by changing the initial joining stress a, the retained joining stress b, and the time b until the joining portion reaches the target joining temperature and then reducing the joining stress. ℃, holding time 10 minutes constant), and the tensile strength of the joint was investigated. Table 4 shows the results. From now on, the joining stress is 5 to 50 at the start of joining.
It is preferable that the pressure is applied to and maintained at MPa, the bonding stress is reduced to preferably 3 MPa or more within 30 seconds after the bonding temperature reaches the target bonding temperature, and then maintained at 0.1 to 14 MPa.

[0028]

EXAMPLES The test steels shown in Table 5 were subjected to a converter-continuous casting-hot rolling process to produce steel plates having a thickness of 50 mm. From this steel plate, 30 mm in diameter and 70 m in length in the rolling direction from the center of the plate
m round specimens for bonding were collected. The joining surface of the round bar test piece was mechanically polished and finished to 100 μm or less.

The liquid phase diffusion bonding was performed by using a heating power supply of 20 kW and butting a 30 mm diameter round bar test piece with a high frequency induction coil. Table 6 shows the chemical components of the joining foil used for joining. From the joined test pieces, JI
S No. 4 round bar tensile test pieces were collected and subjected to a tensile test at room temperature to evaluate the tensile strength characteristics of the joint. In addition, a cross-sectional structure of an arbitrary 20 visual field at the joint was observed, and the maximum major axis and the occupancy of the oxide in the joint were measured as described above.

Table 7 shows the results of examination of the characteristics of the joints obtained by joining under the joining conditions of the present invention. In any case, there is no oxide having a maximum major diameter of more than 100 μm in the joint, and the occupation ratio of the oxide is 25%. Therefore, the tensile strength of the joint is equal to or higher than that of the base metal. on the other hand,
Table 8 shows the results of examining the characteristics of the joints that were joined under the comparative joining conditions. Nos. 1 to 4 are examples in which the stress a was out of the optimum range and oxides could not be sufficiently discharged out of the joint, resulting in a decrease in joint strength. Nos. 5 to 7 are examples in which the joint a buckled and the joint strength was reduced due to the stress a being applied for an unnecessarily long time. Nos. 8 to 10 are examples in which the joints were creep-deformed and the joint strength and tensile strength were reduced because the stress b was applied more than necessary. Nos. 11 to 13 are examples in which a large amount of oxide was generated on the joint surface during heating due to a long heating time, and joint strength was reduced. No. 14 and 15
No. 16 and No. 17 show that the diffusion of B or P was not sufficient due to the low joining temperature and the joint strength was reduced.
Is an example in which the temperature of the joint was high, the crystal grains in the heat-affected zone were coarsened, and the proof stress and tensile strength of the joint were reduced.

Nos. 18 and 19 were examples in which the holding time was insufficient and B or P was insufficiently diffused, resulting in a decrease in joint strength. Nos. 20 and 21 maintained the joint at a high temperature for a long time. As a result, the crystal grains in the heat-affected zone became coarse,
This is an example in which the proof stress and tensile strength of the joint are reduced. Table 9
Fig. 4 shows the results of the characteristics of the joints joined under the conventional joining conditions in the atmosphere. In each case, a large amount of oxide in the joints remained and the tensile strength characteristics of the joints were reduced.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

[Table 5]

[0037]

[Table 6]

[0038]

[Table 7]

[0039]

[Table 8]

[0040]

[Table 9]

[0041]

[Table 10]

[0042]

As described above, according to the present invention, a liquid phase in an oxidizing atmosphere can be used for a material which partially replaces the conventional welding or which has been difficult to weld, such as carbon steel, heat resistant steel and stainless steel. Diffusion bonding makes it possible to provide a joint having excellent tensile strength characteristics and a method of joining the joint.

[Brief description of the drawings]

FIG. 1 is a layout diagram of liquid phase diffusion bonding.

FIG. 2 is a definition of the longest particle size and occupancy of an oxide in a junction.

FIG. 3 shows a method of collecting a tensile test piece of a joint.

FIG. 4 shows the relationship between the maximum length particle size of the oxide in the joint and the joint strength.

FIG. 5 is a graph showing the relationship between the occupancy of the oxide in the joint and the joint strength.

FIG. 6 is a bonding condition pattern of the present invention.

FIG. 7 is a view showing the influence of the oxide occupation ratio and the maximum major axis of the bonding portion on the bonding pressure.

FIG. 8 is a graph showing the influence of the bonding pressure on the oxide occupancy and the maximum major axis of the bonding portion.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Eiji Tsuru 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Yuichi Sato 20-1 Shintomi, Futtsu-shi, Chiba New Japan 4E067 AA02 AB02 AB05 AD03 BA05 DB05 DC03 DC06

Claims (12)

[Claims] 1. A cross-section of all joints formed by liquid phase diffusion bonding of a steel material containing C: 0.001% by mass or more in an oxidizing atmosphere containing 0.01% by mass or more of O ₂ using a joining foil. 3. The liquid-phase diffusion-bonded joint having excellent tensile strength characteristics, wherein there is no oxide having a maximum major axis of 100 μm or more. 2. A cross section of any joint of a steel material containing C: 0.001% by mass or more in a liquid phase diffusion bonding in an oxidizing atmosphere in which O ₂ is present at 0.01% by mass or more using a joining foil. , Wherein the total area of the oxide is 25% or less with respect to the cross-sectional area of the joint portion. 3. All cross-sections of a joint formed by liquid phase diffusion bonding of a steel material containing C: 0.001% by mass or more in an oxidizing atmosphere containing O ₂ at 0.01% by mass or more using a joining foil. Liquid phase diffusion excellent in tensile strength characteristics, characterized in that there is no oxide having a maximum major axis of 100 μm or more, and the total area of the oxide is 25% or less with respect to the cross-sectional area of the joint. Joint fitting. 4. For joining containing steel material containing 0.001% by mass or more of C: 0.0001 to 10% by mass of Si and 0.0001 to 15% of at least one type of B or P by mass%. Tensile characterized in that there is no oxide having a maximum major axis of 100 μm or more in any cross-section of a liquid-phase diffusion-bonded joint in an oxidizing atmosphere containing O ₂ at 0.01% by mass or more using a foil. Liquid phase diffusion bonded joint with excellent strength properties. 5. A joining material containing 0.0001 to 10% by mass of a steel material containing 0.001% by mass or more of C and 0.0001 to 15% of at least one type of B or P by mass%. The total area of the oxide was 25% of the cross-sectional area of the joint in all cross sections of the liquid-phase diffusion-bonded joint in an oxidizing atmosphere in which O ₂ was present in an amount of 0.01% by mass or more using a foil.
A liquid-phase diffusion-bonded joint having excellent tensile strength characteristics, characterized in that: 6. For joining containing a steel material containing 0.001% by mass or more of C: 0.0001 to 10% by mass of Si and 0.0001 to 15% of at least one type of B or P by mass%. Using a foil, in any cross section of the liquid-phase diffusion-bonded joint in an oxidizing atmosphere in which O ₂ is present in an amount of 0.01% by mass or more, there is no oxide having a maximum major axis of 100 μm or more. Area is 2 with respect to joint cross-sectional area
A liquid phase diffusion bonded joint having excellent tensile strength characteristics of not more than 5%. 7. The liquid-phase diffusion-bonded joint according to claim 4, further comprising 0.001 to 10% by mass of V in the joining foil. 8. A steel material containing 0.001% by mass or more of C: 0.0001 to 10% of Si by mass%, and 0.0001 to 15% of at least one type of B or P.
V: Using a bonding foil containing 0.001 to 10%, Si and B were used in all cross sections of the liquid-phase diffusion-bonded joint in an oxidizing atmosphere in which O ₂ was present in an amount of 0.01% by mass or more.
Or the maximum major axis of the single or complex oxide of P is 100μ
m, a liquid-phase diffusion-bonded joint having excellent tensile strength characteristics. 9. A steel material containing 0.001% by mass or more of C: 0.0001 to 10% of Si by mass%, 0.0001 to 15% of at least one of B or P,
V: Using a bonding foil containing 0.001 to 10%, Si and B were used in all cross sections of the liquid-phase diffusion-bonded joint in an oxidizing atmosphere in which O ₂ was present in an amount of 0.01% by mass or more.
Alternatively, a liquid-phase diffusion-bonded joint excellent in tensile strength characteristics, wherein the total area of single or complex oxides of P is 25% or less with respect to the cross-sectional area of the joint. 10. A steel material containing 0.001% by mass or more of C: 0.0001 to 10% of Si by mass%, and 0.0001 to 15% of at least one type of B or P.
V: Using a bonding foil containing 0.001 to 10%, Si and B were used in all cross sections of the liquid-phase diffusion-bonded joint in an oxidizing atmosphere in which O ₂ was present in an amount of 0.01% by mass or more.
Or the maximum major axis of the single or complex oxide of P is 100μ
m, and the total area of the oxide is 25% or less with respect to the cross-sectional area of the joint. 11. In an oxidizing atmosphere in which O ₂ is present in an amount of 0.01% or more in terms of mass%, a heating time is 10 minutes or less, a joining temperature is 850 ° C. to 1300 ° C., and a holding time is 0.5 to 3 minutes.
0 minutes, and the bonding pressure is increased to 5 to 50 MPa at the start of temperature rise.
After the junction temperature reaches the target junction temperature,
Decrease the bonding pressure within 0 seconds, and then
A method for joining a liquid-phase diffusion-bonded joint having excellent tensile strength characteristics, wherein the joint is maintained at Pa. 12. In an oxidizing atmosphere containing 0.01% or more of O _{2 by} mass%, a temperature rise time is 10 minutes or less, a bonding temperature is 850 ° C. to 1300 ° C., and a holding time is 0.5 to 3 minutes.
0 minutes, and the bonding pressure is increased to 5 to 50 MPa at the start of temperature rise.
After the junction temperature reaches the target junction temperature,
A method for joining liquid phase diffusion joints having excellent tensile strength characteristics, wherein the joining pressure is reduced to 3 MPa or more within 0 seconds and is continuously maintained at 0.1 to 14 MPa.