JP4059636B2 - Liquid phase diffusion bonding assembly method for fuel injection parts for automobiles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to various fuel injection parts for automobiles manufactured by using diffusion bonding technology, and in particular, conventionally, machining, starting from a material, machining such as punching, die cutting, direct casting from a molten metal, forging, etc. The present invention relates to an automobile fuel injection part manufactured by liquid phase diffusion bonding instead of processing an automobile fuel injection part having an annular or hollow shape.
[0002]
[Prior art]
Conventionally, it has an annular or hollow shape, especially mechanical parts that require various characteristics of wear resistance, corrosion resistance, and fatigue resistance individually or simultaneously for a long time, such as bearings and bearings for rotating parts. In order to satisfy the required quality, the cylinder sliding tube has a relatively high alloy ratio. For example, in the case of a bearing steel represented by JIS-SUJ, C: 1%, Cr: 1%, Mn Although steel materials containing Mo are used, it is often difficult to assemble parts by welding or the like. For this reason, machine parts with complex shapes are machined from massive steel ingots, or roughly formed by hot forging or drilling, and after finishing, spheroidizing and carburizing according to the required specifications. Is manufactured. Therefore, various processing costs in the manufacturing process occupy most of the product price rather than the price of the steel ingot of the raw material. On the other hand, precision machine parts that require reliability such as automobiles are required to have long-term durability at the same time, and are aimed at reducing specification costs over a long period of time. Therefore, even if it is expensive, these precision machine parts manufactured from a block metal by a conventional manufacturing method are frequently used, which causes an increase in the price of many parts and hence the final product price.
[0003]
Moreover, among the methods of processing metal materials into any shape, hot rolling and press molding are adopted as the most mass-productive and low-cost methods. In many cases, it has a simple shape such as a plate and is suitable for mass production. However, it is not possible to directly manufacture a hollow mechanical part or annular part with the above-mentioned rolling or press molding with a high yield. It is difficult because of restrictions, and it is in fact not currently industrialized at all. Therefore, there is no industrially promising technology for efficiently mass-producing complex precision automobile fuel injection parts having an annular or hollow shape, while the manufacturing process is completely different from the conventional one from the viewpoint of cost reduction. Development is anxious.
[0004]
On the other hand, recently, the technique of liquid phase diffusion bonding has attracted attention. In this liquid phase diffusion bonding technique, an alloy having a lower melting point than the material to be bonded, for example, 50% or more of the crystal structure is substantially amorphous between the bonding surfaces of the materials to be bonded, that is, between the grooves. The element is capable of forming a joint through a diffusion-controlled isothermal solidification process, such as B, P, Ni, Fe, etc., and a temperature higher than the melting point of the low-melting-point alloy with the joint inserted It is a technology that forms a joint in the process of isothermal solidification by heating and holding.
[0005]
Unlike the normal welding technique, this liquid phase diffusion bonding technique has characteristics such that there is almost no residual welding stress, or a smooth and precise joint that does not generate surplus as in welding can be formed. Moreover, since this technique is a surface joining, the joining time is constant regardless of the area of the joining surface, and the joining can be completed in a relatively short time. This joining technique is completely different from conventional welding. Therefore, if the joining portion can be maintained at a temperature equal to or higher than the low melting point metal for a predetermined time, joining of the surfaces can be realized regardless of the groove shape. On the other hand, for liquid phase diffusion bonding that can be realized only in a conventional non-oxidizing atmosphere, an alloy foil for liquid phase diffusion bonding that is applicable even in an oxidizing atmosphere is known. (Patent Nos. 1891618, 1891619, and 1837572). However, at present, this liquid phase diffusion bonding technique is applied only to the joining of members having a relatively large area of the joining surface, and is not used for joining precision machine parts and the like.
[0006]
[Problems to be solved by the invention]
The present invention is a diffusion joint capable of mass-producing a complicated precision automobile fuel injection part having an annular or hollow shape at the same time satisfying various characteristics of wear resistance, corrosion resistance, and fatigue resistance with high efficiency and low cost. It aims at providing the fuel-injection components for motor vehicles .
[0007]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problems, and the gist of the present invention is that it has a plurality of pipelines inside and is divided into at least two or more planes parallel to the axial direction of the pipelines. When assembling an automobile fuel injection part having a formed surface by liquid phase diffusion bonding, the temperature of the part is heated to a temperature equal to or higher than the solidus of the bonded metal foil to be inserted between the bonded surfaces within 60 seconds. Even after reaching the bonding temperature of 1000 to 1300 ° C. , a constant bonding stress is continuously applied to the bonding surface at 2 MPa or more for 60 seconds or more, preferably 90 to 120 seconds, and then the bonding stress is reduced to 3 MPa. It is a method of assembling and joining a fuel injection part for a liquid phase diffusion bonding automobile, wherein the invention is held for less than one and less than the above-mentioned joining stress or no load for one minute or more, and the present invention is divided into at least two or more. Automatic with flat surface When the fuel injection component is joined and assembled by liquid phase diffusion bonding, the temperature of the component is heated to a temperature equal to or higher than the solidus of the bonding metal foil to be inserted between the bonding surfaces within 60 seconds. Even after reaching the joining temperature , a constant joining stress is continuously applied to the joining surface at 90 MPa or more and 120 seconds or less at 2 MPa or more , and then the joining stress is reduced to less than 3 MPa and below the joining stress or none. Hold under load for 1 minute or longer, then rapidly cool to a temperature above the martensitic transformation start temperature of the material to be joined at a cooling rate of 5 ° C / sec or more, allow to cool to the end of bainite transformation, and to 1 ° C / sec or more to room temperature It is an assembly joining method of fuel injection parts for liquid phase diffusion joining automobiles characterized by cooling at a cooling rate of.
[0008]
In addition, the liquid phase diffusion bonding in the present invention is preferably performed in an oxidizing atmosphere.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In practicing the present invention, the material of the target automobile fuel injection component is not particularly limited. The technique of the present invention can be applied to all metal materials that are considered to be capable of liquid phase diffusion bonding. For example, liquid phase diffusion bonding can realize a joint joint even for materials that are difficult to apply normal welding, such as normal carbon steel, high carbon steel, and low carbon steel. Also, stainless steel, high corrosion resistance alloy steel containing various proportions of Cr or Ni, Ni-based alloys and other alloys based on Ni, Al, Ti, Zn and other practical metals that are non-ferrous materials If a bonding alloy suitable for them is used, all liquid phase diffusion bonding is possible. Further, there is no limitation on the amorphous alloy composition that realizes liquid phase diffusion bonding, including the alloys described in US Pat. No. 4,144,058, and JP-A-49-91014. It is possible to use a liquid phase diffusion bonding alloy containing P, B, C and the like as diffusion atoms.
[0010]
In the present invention, using the material to be joined and the alloy for liquid phase diffusion bonding as described above, a pipe line having a purpose such as fluid conveyance, weight reduction, or sliding component passage is provided inside. Conventional fuel injection parts for precision automobiles, which were originally manufactured by integral molding, are divided into multiple parts on the surface including the conduit first, for example, conventional integral molding and machine such as press molding or rolling, grinding, polishing, etc. It is necessary to manufacture through a cheap manufacturing process with respect to the combination of processing, to assemble them through an alloy for liquid phase diffusion bonding, and to integrate them by liquid phase diffusion bonding.
[0011]
The parts to be divided at this time must be divided on the surface passing through the pipe line existing in the interior in comparison with the final shape, thereby making each part inexpensive and simple such as press molding. If it can be manufactured by the method. Any number of divisions can be used as long as the number is two or more, and as long as the manufacturing is simplified and the manufacturing process becomes complicated or increases in number, the cost may be appropriately selected as long as the manufacturing process is not expensive. Further, the dividing surface may be a flat surface, a curved surface, a continuous or discontinuous multiple surface or a curved surface, and the shape may be appropriately selected so that each part can be easily manufactured by dividing. In addition, the pipe line that the final shape part has may be a single continuous path or a plurality of independent paths, the shape of the pipe line itself is free, and it is only necessary that the surfaces to be joined at the time of assembly correspond. There is no limit. The pipe can be assembled with or without opening to the outer surface. It should be noted that the characteristics of the joint portion vary depending on the combination of the material to be joined and the alloy for liquid phase diffusion joining.
[0012]
In the present invention, a fuel injection part for a precision automobile divided into a plurality of pipes having an internal pipe as described above, for example, Cr: 1.0%, Mo: 0.5% as shown in FIG. From a Ni-based or Fe-based amorphous metal containing a small amount of elements such as P, B, C, etc. on a split surface that is divided in two by a plane parallel to the pipe line of an automobile fuel injection part made of high-carbon steel The above components are assembled together with each other through a 30 μm thick alloy for liquid phase diffusion bonding, and fixed with a pressing jig from the outer surface of each component to perform liquid phase diffusion treatment.
[0013]
Furthermore, in the present invention, when the liquid phase diffusion treatment is performed, the heating is started at a temperature equal to or higher than the solidus of the liquid phase diffusion bonding alloy, that is, a temperature of 1000 to 1300 ° C. at which liquid phase diffusion is started. During 90 to 120 seconds , a constant joining stress is continuously applied to the joining surface at 2 MPa or more, preferably 4 MPa or more , and thereafter the joining stress is reduced to less than 3 MPa and below the joining stress, or held for 1 minute or more as no load. To do. Even during this diffusion bonding, a constant bonding stress can be continuously applied by applying a considerable bonding stress in the temperature range where the diffusion between the element in the bonding metal and the metal element contained in the bonded component reaches a peak. This is because the progress of diffusion is further promoted to obtain a strong joint surface. From the point of time when the liquid phase diffusion bonding is completed, the bonding stress is reduced, or the bonding stress is released and the unloaded state is maintained, and the state is maintained as it is for 5 minutes or more in order to make the bonded portion structure uniform. By performing the above-described liquid phase diffusion treatment, a necessary amount of a bonding layer of the metal element contained in the liquid phase diffusion bonding alloy and the metal element contained in the bonded component is formed on the bonding surface.
[0014]
When performing liquid phase diffusion bonding, N ₂ or Ar is blown onto the inner and outer surfaces of the materials to be bonded in an oxidizing atmosphere containing 0.01% by mass or more of oxygen, preferably in the air. Preferably it is done.
Further, in the present invention, the structure of the material to be bonded obtained by the liquid phase diffusion bonding described above is martensite or bainite classified as a low-temperature transformation generation structure, and the bonding metal and the material to be bonded are included in the bonding metal. If a structure having part or all of the same low-temperature transformation structure as that of the material to be joined is obtained by alloying produced by fusion with metal, a stronger joint surface can be obtained. For this purpose, the structure of the material to be joined is rapidly cooled at a cooling rate of 5 ° C./sec or higher to prevent baked cracking to a temperature higher than the bainite transformation start temperature, and then this release is continued until the transformation is completed. By maintaining the cooling and then rapidly cooling to room temperature at a cooling rate of 1 ° C./sec or more, the intended joint structure and joint strength can be obtained.
[0015]
The rapid cooling condition from the joining temperature requires 5 ° C./second or more in order to suppress the formation of ferrite. However, if it is rapidly cooled below the non-diffusion transformation point, it becomes a martensite structure and causes cracking near the joint. If it is further allowed to cool below the transformation end temperature, the embrittlement phase will precipitate, so it is necessary to cool again at 1 ° C./second or more after the transformation end.
[0016]
In the present invention, the characteristics of the joint surface can be freely changed depending on the specifications of the automobile fuel injection component to be applied, and the characteristics as a joint joint are not particularly limited. The joint efficiency need not be unity, nor does it need to be completely homogenized in terms of organization. Of course, a joint efficiency of 1 and a completely homogeneous body are preferable in terms of the characteristics of the fuel injection component for automobiles, but can be determined according to the manufacturing cost of the component. In addition, it is possible to perform various heat treatments, chemical conversion treatments, and processing on machine parts after the assembly is completed.For example, if steel materials are used, the heat treatment steps such as quenching, tempering, normalizing, and annealing are performed alone. Alternatively, it may be combined and repeated in some cases is effective in improving the characteristics as a part and does not hinder the effects of the present invention. In addition, surface treatment such as carburizing, nitriding, plating, painting, spraying of powder, shot blasting, etc. is also effective.
[0017]
【Example】
<Embodiment 1> In the present invention, the manufacture of an automobile fuel injection part having a fuel supply pipe line therein will be described. This fuel injection part for automobiles is divided into two parts in a plane parallel to the pipe line by forging made of high carbon steel containing Cr: 1.0% and Mo: 0.5% as shown in FIG. A liquid phase diffusion bonding alloy made of a Ni-based amorphous alloy containing a small amount of B and P with a thickness of 30 μm is sandwiched between the divided surfaces 1 and 2 of the parts, the parts are butted together, and the parts are placed from the upper and lower surfaces First, an alloy for bonding, in which the entire part is pressed in a high-frequency induction heating furnace (not shown) having a high-frequency induction heating coil and the temperature of the part is first inserted between the bonding surfaces. Heating to 1150 ° C. above the solidus of the foil within 60 seconds was performed to preheat the parts and melt the bonding alloy foil, thereby improving the mutual wettability and making it easy to perform liquid phase diffusion bonding.
[0018]
The said parts, the heating start time, temperature range diffusion peaks: 1100 ° C. from 1150 ° C., until reaching, for 90 to 120 seconds to promote the diffusion, 3 to a jig pressing the bonding surface Sufficient diffusion bonding was performed by continuously applying a constant bonding stress of 5 MPa. Thereafter, when the diffusion was completed, the bonding stress was reduced and held for less than 3 MPa and less than or equal to the bonding stress or no load for 5 minutes to make the structure of the bonded portion uniform.
[0019]
Further, in this embodiment, in order to make the structure of the material to be joined into a structure such as martensite transformation or bainite transformation, a cooling rate of 10 ° C./sec is used to prevent baked cracks to a temperature higher than the non-diffusion transformation temperature. Then, the mixture was allowed to cool and then left to cool until the transformation was completed, and then rapidly cooled to room temperature at a cooling rate of 10 ° C./sec. By performing such treatment, it was possible to form a martensite or bainite structure in which the structure of the material to be joined was classified as a low temperature transformation generation structure. Moreover, in the part joined by diffusion fusion of the joining metal and the material to be joined in the joining metal, the same low-temperature transformation generation structure as that of the material to be joined was included in part or all. The strength of the diffusion bonded 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 fuel injection valve product for automobiles. When this is incorporated and used as an actual automobile part, the same usage performance as that of a conventional machined automobile fuel injection part can be obtained, and there is nothing in terms of high-temperature oxidation resistance, wear resistance, and joint strength against fluid pressure. A comparable value was obtained.
[0020]
【The invention's effect】
As described above, the present invention can be used to manufacture fuel injection parts for precision automobiles, which are originally manufactured by integral molding and have complicated and precise pipes, from divided parts that can be easily manufactured. By adopting the bonding process using the phase diffusion bonding technique, it is possible to inexpensively and efficiently manufacture metal fuel injection parts for precision automobiles .
[Brief description of the drawings]
FIG. 1 is a view showing a shape of a divided part when a fuel injection part for automobiles manufactured by integral molding is divided on a surface passing through a pipe line provided therein, and particularly shows an example of a fluid injection part .

Claims (3)

When a fuel injection part for automobiles having a plurality of pipelines inside and having a plane parallel to the axial direction of the pipeline and divided into at least two or more is joined by liquid phase diffusion bonding, and assembled, heating the temperature of the component to the junction temperature of 1000 to 1300 ° C. over solidus bonding metal foil to be inserted between the bonding surfaces within 60 seconds, within 120 seconds 9 0 seconds or more from the start of heating, 2 MPa to the bonding surface A liquid phase diffusion bonded automobile fuel characterized in that a constant bonding stress is continuously applied , and thereafter the bonding stress is reduced to be less than 3 MPa and below the bonding stress or at least 1 minute in an unloaded state. Assembling and joining method of injection parts. When a fuel injection part for automobiles having a plurality of pipelines inside and having a plane parallel to the axial direction of the pipeline and divided into at least two or more is joined by liquid phase diffusion bonding, and assembled, heating the temperature of the component to the junction temperature of 1000 to 1300 ° C. over solidus bonding metal foil to be inserted between the bonding surfaces within 60 seconds, within 120 seconds 9 0 seconds or more from the start of heating, 2 MPa to the bonding surface As described above , a constant bonding stress is continuously applied , and thereafter, the bonding stress is reduced to less than 3 MPa and less than the bonding stress, or maintained for 1 minute or longer in an unloaded state, and continuously higher than the martensitic transformation start temperature of the materials to be bonded. The fuel injection part for a liquid phase diffusion bonding automobile, characterized in that it is rapidly cooled to a temperature of 5 ° C./sec or more at a cooling rate of 5 ° C./sec, allowed to cool to the end of bainite transformation, and cooled to room temperature at a cooling rate of 1 ° C./sec or more. Assembling and joining method.   The liquid phase diffusion bonding according to claim 1 or 2, wherein the liquid phase diffusion bonding is performed in an oxidizing atmosphere.

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