JP2002263855A - Method for assembling and welding high-temperature mechanical, component by liquid phase diffusion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a metal precision mechanical component by liquid phase diffusion welding in assembling the mechanical component internally having complicated and precise pipe lines for carrying liquid and lightening weight. SOLUTION: In the method for assembling and welding the high-temperature mechanical component by the liquid phase diffusion welding, when the mechanical component which is divided into at least two or more is welded by liquid phase diffusion welding and is assembled, the divided surfaces are finished into surface roughness of 100 μm or less, moreover a butting gap between the divided surfaces having surface roughness is set to 1 mm or less in the whole welding surface and assembling is performed. Thereafter, the divided surfaces are mutually welded by liquid phase diffusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various types of mechanical parts manufactured by using a diffusion bonding technique, and more particularly, to machining such as cutting, shaving, punching, and die cutting from a material, or casting directly from a molten metal. The present invention relates to a mechanical part manufactured by liquid phase diffusion bonding instead of processing of a mechanical part having an annular or hollow shape by forging or the like.

[0002]

2. Description of the Related Art Conventionally, it has an annular or hollow shape,
In particular, mechanical parts that require various properties such as wear resistance, corrosion resistance, and fatigue resistance individually or simultaneously and over a long period of time, such as bearings for rotating parts, bearings, and sliding pipes for cylinders, have the required quality. For example, in a bearing steel represented by JIS-SUJ, which has a relatively high alloy ratio, in addition to C: 1% and Cr: 1%, Mn,
Although a steel material containing Mo is used, it is often difficult to assemble parts by welding or the like. For this purpose, machine parts with complex shapes are cut out of massive steel ingots or roughly formed by hot forging or drilling, and after finishing, spheroidizing and carburizing according to required specifications. And manufacturing. Therefore, the cost of various processing steps in the manufacturing process accounts for the majority of the product price, rather than the price of the raw material ingot. On the other hand, precision mechanical parts, such as automobiles, which require high reliability are also required to have long-term durability, and are aimed at reducing specification costs over a long period of time. Therefore, even if expensive, these precision machine parts manufactured from the bulk metal by the conventional manufacturing method are frequently used, and this causes an increase in the price of many parts and eventually the price of the final product.

[0003] Of the methods of processing a metal material into an arbitrary shape, hot rolling and press molding are generally employed as methods with the highest mass productivity and low cost. It has a simple shape, often a simple shape such as a plate, and is suitable for mass production.However, it is not possible to directly manufacture hollow machine parts and annular parts with high yield by the above-mentioned rolling and press molding. It is difficult due to the shape restrictions, and it is currently not industrialized at all. Therefore, there is no industrially established technology for efficiently mass-producing complicated precision machine parts having an annular or hollow shape. On the other hand, from the viewpoint of cost reduction, there is a long-awaited need to develop a completely different manufacturing process. Have been.

On the other hand, recently, the technique of liquid phase diffusion bonding has been spotlighted. This liquid-phase diffusion bonding technique uses an alloy having a lower melting point compared to the material to be bonded, for example, 50% or more of the crystal structure is substantially amorphous in the bonding surface of the material to be bonded, that is, between the grooves. A multi-element alloy, such as B, P, Ni, Fe, etc., which is a material and has the ability to form a joint through a diffusion-controlled isothermal solidification process, is brought to a temperature equal to or higher than the melting point of the low melting point alloy into which the joint is inserted. This is a technique for forming a joint in the isothermal solidification process by heating and holding.

The liquid-phase diffusion bonding technique has a feature that, unlike ordinary welding techniques, there is almost no welding residual stress, or a smooth and precise joint can be formed without generation of excess as in welding. ing. Moreover, since this technology is surface bonding, the bonding time is constant regardless of the area of the bonding surface,
It has the advantage that the joining is completed in a relatively short time, and is a joining technique completely different from conventional welding. Therefore, if even a groove can be inserted and maintained at a temperature equal to or higher than the low melting point metal for a predetermined time, bonding between surfaces can be realized regardless of the shape of the groove. On the other hand, with respect to conventional liquid phase diffusion bonding that can be realized only in a non-oxidizing atmosphere, an alloy foil for liquid phase diffusion bonding that can be applied even in an oxidizing atmosphere is known. (Patent No. 189
No. 1618, No. 1891619, No. 183775
No. 2). However, at present, this liquid phase diffusion bonding technique is applied only to the bonding of members having a relatively large bonding surface area, and is not used for bonding precision mechanical parts and the like.

[0006]

SUMMARY OF THE INVENTION The present invention provides a complex precision machine part having an annular or hollow shape, which simultaneously satisfies various characteristics of wear resistance, corrosion resistance and fatigue resistance, with high efficiency and low cost. It is an object of the present invention to provide a mass-produced diffusion bonding machine part.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the gist of the present invention is to join at least two or more divided mechanical parts by liquid phase diffusion bonding. In assembling, the divided surface is finished to a surface roughness of 100 μm or less, and the butt gap between the divided surfaces having the surface roughness is set to 1 mm or less in the entire joint surface, and then liquid phase diffusion bonding is performed. A method for assembling and joining high temperature machine parts by liquid phase diffusion. Further, the present invention is a method for assembling and joining a high-temperature mechanical part by liquid phase diffusion, wherein the liquid phase diffusion bonding is performed in an oxidizing atmosphere.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In practicing the present invention, the material of a target mechanical part is not particularly limited. The technology of the present invention can be applied to all metal materials that can be liquid-phase diffusion bonded. For example, liquid phase diffusion bonding can realize a joining joint even with a material to which normal welding is difficult to apply, such as normal carbon steel, high carbon steel, and low carbon steel. Also,
Stainless steel containing various ratios of Cr or Ni,
Liquid phase diffusion bonding of highly corrosion-resistant alloy steel, Ni-based alloys and other alloys based on Ni, and non-ferrous materials such as Al, Ti, Zn and other practical metals, all using the appropriate joining alloy Becomes possible. Further, there is no limitation on the composition of the amorphous alloy for realizing the liquid phase diffusion bonding, and the alloys described in U.S. Pat. No. 4,144,058 and the alloys described in JP-A-49-91014 are disclosed. Of P,
Liquid phase diffusion bonding alloys containing B, C, etc. as diffusion atoms can be used.

In the present invention, using the above-mentioned material to be joined and the alloy for liquid phase diffusion bonding, a pipe having a purpose for carrying a fluid, reducing the weight, or passing a sliding part therein is provided. The precision machine parts originally manufactured by integral molding were divided into a plurality of parts on the surface including the pipeline first, for example, press molding or rolling, grinding, polishing, etc. It is necessary to carry out a manufacturing process through an inexpensive manufacturing process for a combination of processing, assemble them via a liquid phase diffusion bonding alloy, and integrate them by liquid phase diffusion bonding.

At this time, it is necessary that the parts to be divided be divided by a surface passing through a pipe existing inside, in comparison with the final shape. And it can be manufactured by a simple method. Also, this division can be made as many as two or more,
As a result of simplification of the production and complicated or large number of the production steps, it may be appropriately selected within a range that does not become expensive compared to the conventional production steps. Further, the division surface may be a flat surface, a curved surface, a continuous or discontinuous multi-surface or a curved surface, and the shape may be appropriately selected so that the division facilitates production of each part. In addition, the conduit inside the component of the final shape may be a single continuous path or a plurality of independent paths, the shape of the conduit itself is free, and the surfaces to be joined at the time of assembly only need to correspond, particularly No restrictions. The conduit can be assembled with or without an opening to the outer surface. In addition, the characteristics of the joint vary variously depending on the combination of the material to be joined and the alloy for liquid phase diffusion joining.

In the present invention, precision machine parts divided into a plurality of parts having a pipe inside as described above, for example,
As shown in FIG. 1, a split surface divided into two by a plane parallel to a pipe of an automobile fuel injection valve made of high carbon steel containing 1.0% Cr and 0.5% Mo, that is, a joining surface The surface roughness of the divided surface is finished to 100 μm or less, preferably 50 μm or less by hot or cold forging or press working. In liquid phase diffusion bonding, there is a fixed relationship between the surface roughness of the bonding surface and the bonding strength, and the closer to the mirror surface, the smoother the diffusion between the material to be bonded and the diffusion bonding alloy.
However, finishing the joint surface to a mirror surface cannot be profitable from the viewpoint of labor and cost. However, the joining accuracy of the joining surfaces is substantially improved by hot plastic deformation due to the joining stress applied during liquid phase diffusion joining and melting of the joining material by the joining metal. The present inventors have found that studies are possible and that the joint is practical.

On the other hand, it is most preferable to perform the liquid phase diffusion treatment in a state where the materials to be joined are completely adhered to each other with the alloy for diffusion joining alloy interposed therebetween. If a certain stress is applied with a holding jig and held for a certain period of time, the material to be joined will deform beyond the allowable dimensions of the product during hot work. It may need to be reduced depending on the high temperature strength of the material. However, even in such a case, the gap between the joining surfaces obtained under such a stress load condition is very small, and if it is 1 mm or less throughout the joining surface, smooth diffusion bonding can be performed and the necessary diffusion It was found that bonding strength could be obtained.

The bonding surfaces set in such a state are abutted in advance via a Ni-based liquid phase diffusion bonding alloy, heated to a temperature not lower than the solidus temperature, at a temperature of 1000 to 1300 ° C., and 1000 ° C. from the start of heating. 90 to 12 including heating time until
During 0 seconds, continue to apply a stress of 2 MPa or more to the joint surface,
Thereafter, liquid phase diffusion bonding is performed in which the applied stress is reduced to a low stress or no load and maintained for 1 minute or more. By this liquid phase diffusion bonding, a mechanical component having a sound bonding portion can be obtained.

When performing liquid phase diffusion bonding, N ₂ or Ar is blown onto the inner and outer surfaces of the material to be bonded in an oxidizing atmosphere containing 0.01% by mass or more of oxygen, preferably in the air. It is preferable to work. The relationship between the bonding surface roughness and the bonding conditions as described above was determined based on the following experiment.

FIG. 2 shows the strength of the joints when various pressing forces are applied, in comparison with the joint surface roughness before joining. Here, the dotted line in the figure indicates the minimum value for each surface roughness regardless of the pressing force. In each case, the pressing force is 2 MPa or more. If the pressing force is less than this, the liquid phase diffusion bonding may not be completed, and the strength of the joint may not be measured accurately.

The materials subjected to the joining test and the tensile test are as follows:
It is a low alloy steel having a composition of 0.3% C-1% Cr-0.5% Mo. After joining, the joint is cooled at a rate of 1 ° C./min. Test specimens were collected and measured for tensile strength at room temperature. In addition, when the material is used, the stress applied to the joint during actual use is 180 M at maximum.
Since it is known that the pressure is Pa, the target strength required for the joint is assumed to be 180 MPa, and the value is shown in the figure. From this figure, the target value of 180 MPa
It can be seen that it is necessary to control the surface roughness of the bonding surface to 100 μm or less in order to achieve the above.

In the present invention, the term "surface roughness" refers to an industrial contact surface roughness meter, a three-dimensional shape measuring device to which a laser is applied, or a surface undulation measuring device. It is equivalent to typical "maximum roughness", and is a value generally represented by Rmax. In the evaluation of FIG. 2, the chemical components of the bonding metal used for bonding were as follows: Ni = Si = 3%, B = 3.5
%, V = 3%, and Si = 4.5 for the Fe group.
%, B = 3.0%, and V = 5.0%. The same tendency as in FIG. 2 was shown when a foil containing the same P in mass% instead of B was used.

The structure of the material to be joined obtained by the above-mentioned liquid phase diffusion bonding treatment is martensite or bainite, which is classified as a low-temperature transformation formation structure, and the joining metal and the joining material metal are contained in the joining metal. If a structure having the same low-temperature transformation generation structure as that of the material to be joined in part or all is obtained by the alloying generated by the fusion of the materials, a similarly strong joint surface can be obtained.

Further, in the present invention, the characteristics of the joint surface can be freely changed depending on the specifications of the machine parts to be applied, and the characteristics as the joint are not particularly limited. The joint efficiency does not need to be 1 and does not need to be completely homogenized organizationally. Of course, it is preferable that the joint efficiency is 1 and the body is completely homogenous in terms of the characteristics of the mechanical part, but it can be determined according to the manufacturing cost of the part. In addition, after the assembly is completed, it is possible to perform various heat treatments, chemical conversion treatments, and processes on the mechanical components.For example, in the case of steel materials, quenching, tempering, normalizing, annealing, and the like are performed alone. Alternatively, a composite and repeated application in some cases is effective for improving the characteristics as a component, and does not hinder the effects of the present invention at all. Further, carburizing treatment, nitriding treatment, plating, or spraying treatment such as painting or powdering, and surface processing such as shot blasting are also effective.

[0020]

<Embodiment 1> In the present invention, the manufacture of an automobile fuel injection valve having a fuel supply pipe therein will be described. This automobile fuel injection valve has a Cr:
The joining surfaces 3 and 4 of the divided surfaces 1 and 2 of the halved part divided into two by a surface parallel to the pipeline by forging made of high carbon steel containing 1.0% and Mo: 0.5%, respectively. Polished to 80μ
m surface roughness and a thickness of 30 between these parts
μm B: 3%, Si: 4%, or P: 2%, Si:
A gap between the components is set to a maximum of 0.5 with a liquid-phase diffusion bonding alloy made of a Ni-based amorphous alloy having a composition of 3% interposed therebetween.
mm, butted against each other, holding the parts from the top and bottom outer surfaces with holding jigs, and then liquid-phase diffusion bonding temperature: 1000 ° C. in an atmosphere-controllable high-frequency induction heating furnace having a high-frequency induction heating coil. Liquid phase diffusion bonding was performed at 1300 ° C. Thereafter, the applied stress is reduced to 1 MPa, kept for 2 to 10 minutes, and then cooled. The structure of the material to be joined is rapidly cooled to a temperature equal to or higher than the non-diffusion transformation temperature such as martensite transformation or bainite transformation, and subsequently, quenching cracking is prevented. This cooling was continued until the transformation was completed, followed by rapid cooling in water. By performing such a treatment, the structure of the material to be joined is martensite or bainite, which is classified as a low-temperature transformation generation structure, and diffusion bonding is performed by fusion of the joining metal and the material to be joined into the joining metal. Some or all of the sites had the same low-temperature transformation generation structure as the material to be joined. The strength of the diffusion bonding surface thus obtained was equal to or higher than the strength of the material to be bonded. After that, it was finished to the final outer shape to obtain a product of an automotive fuel injection valve. When this was incorporated as an actual automobile part and its performance was evaluated, the same performance as that of a conventional machined automobile fuel injection valve was obtained, and high-temperature oxidation resistance, abrasion resistance, and joint strength against fluid pressure were obtained. , A value comparable to that obtained was obtained.

[0021]

As described above, the present invention makes it easy to manufacture precision machine parts such as fuel injection valves for automobiles having a complicated and precise pipe inside, which are originally manufactured by integral molding. By adopting the process of bonding them from the manufacturable divided parts by liquid phase diffusion bonding technology,
The present invention makes it possible to manufacture metal precision machine parts at low cost and efficiently.

[Brief description of the drawings]

FIG. 1 is a view showing a divided part shape in a case where a mechanical part manufactured by integral molding is divided by a surface passing through a pipe provided therein, particularly showing an example of a fluid injection valve.

FIG. 2 is a view showing the relationship between the surface roughness of a joining surface and the strength (minimum joining strength) of a joint in liquid phase diffusion joining.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Shinohara 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Yutaka Takagi 4005 Nishi-Oguma, Ogumacho, Hashima-shi, Gifu Prefecture Fukuju Industrial Co., Ltd. F term (reference) 4E067 BA05 DA09 DA13 DA17 DB05 EB00

Claims (2)

[Claims] 1. A method for joining at least two or more divided mechanical parts by liquid-phase diffusion bonding to assemble them, wherein the divided surfaces are finished to a surface roughness of 100 μm or less, and the divided surfaces having the surface roughness are joined together. A liquid phase diffusion bonding method for a high temperature mechanical part, comprising: assembling with a butt gap of 1 mm or less over the entire bonding surface and then performing liquid phase diffusion bonding. 2. The method according to claim 1, wherein the liquid phase diffusion bonding is performed in an oxidizing atmosphere.