JP4854754B2 - Liquid phase diffusion bonding method for machine parts - Google Patents

Description

  The present invention relates to a method for manufacturing various machine parts using diffusion bonding technology, and in particular, conventionally, by cutting, cutting out from a material, machining such as drilling, die cutting, or direct casting from a molten metal or forging. The present invention relates to a method of manufacturing a machine part by liquid phase diffusion bonding instead of processing a machine part having an annular or hollow shape.

  Conventionally, it has an annular or hollow shape, and in particular, bearings for mechanical parts, such as rotating parts, which are required individually or simultaneously for various characteristics of wear resistance, corrosion resistance and fatigue resistance, for a long time. In order to satisfy the required quality, bearings, cylinder slide tubes, etc. have a relatively high alloy ratio. For example, in bearing steels represented by JIS-SUJ, in addition to C: 1% and Cr: 1% Furthermore, although steel materials containing Mn and 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 further subjected to finishing, and then spheroidized according to the required specifications. It is manufactured by carburizing. Therefore, the cost of various processing steps in the manufacturing process occupies 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 by a conventional manufacturing method from a block metal are frequently used, which causes an increase in the price of many parts and hence the final product price.

  Also, 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. It has a simple shape such as a plate in many cases and is suitable for mass production, but directly manufactures hollow mechanical parts and annular parts with the above-mentioned rolling and press molding with high yield. Is difficult due to its shape restrictions, and is currently not industrialized at all.

  Therefore, there is no industrially established technology for efficiently mass-producing complex precision machine parts having an annular shape or hollow shape. On the other hand, from the viewpoint of cost reduction, the manufacturing process is completely different from the conventional one. Development is anxious.

  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 non-between the bonding surfaces of the materials to be bonded, that is, between the grooves. More than the melting point of the low-melting-point alloy that is crystalline and has an ability to form a joint through a diffusion-controlled isothermal solidification process, for example, a multi-element alloy such as B, P, Ni, Fe, etc. In this technique, the joint is formed in the isothermal solidification process.

  Unlike normal welding techniques, this liquid phase diffusion bonding technique has characteristics such as almost no welding residual stress or the ability to form smooth and precise joints that do not generate surplus as in welding. . Moreover, since this technology is surface bonding, it has the advantage that the bonding time is constant and the bonding can be completed in a relatively short time regardless of the area of the bonding surface, which is completely different from conventional welding. It is.

  Accordingly, as long as a groove is inserted and maintained at a temperature equal to or higher than that of the low melting point metal for a predetermined time, bonding between 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 (see Patent Documents 1 to 3). ). However, at present, this liquid phase diffusion bonding technique is applied only to the bonding of members having a relatively large area of the bonding surface, and is not used for bonding precision machine parts and the like.

Japanese Patent No. 1891618 Japanese Patent No. 1891619 Japanese Patent No. 1837572

  The present invention is a liquid phase diffusion capable of mass production of complex precision mechanical parts having annular or hollow shapes simultaneously satisfying various characteristics of wear resistance, corrosion resistance and fatigue resistance with high efficiency and low cost. It aims at providing the method of joining by joining.

  The present invention has been made to solve the above problems, and the gist thereof is as follows.

(1) In a joining method of assembling and joining mechanical parts by liquid phase diffusion bonding using Ni-based alloy for liquid phase diffusion bonding from two or more parts,
(I-1) When the bonding surface is heated from room temperature and reaches a liquid phase diffusion bonding temperature of 1100 to 1300 ° C., a load stress of 2 MPa or more is applied to the bonding surface for 90 to 120 seconds, Reduce the load stress to less than 2 MPa and hold at low stress or no load for 5 minutes,
(I-2) Rapid cooling at a cooling rate of 5 ° C./sec or higher to prevent cracking to a temperature higher than the non-diffusion transformation temperature such as martensitic transformation or bainite transformation of the structure of the material to be joined, By continuing to cool until transformation is completed, by rapidly cooling to room temperature at a cooling rate of 1 ° C./sec or more,
(Ii) a bonding metal formed by the fusion of a Ni-based liquid phase diffusion bonding alloy and a material to be bonded, and a Ni solid solution present on both sides of the bonding metal from the liquid phase diffusion bonding alloy into the material to be bonded. The width of the portion combined with the Ni diffusion region containing 1% or more of Ni generated by phase diffusion is within 50 μm on one side from the center of the bonding metal in the direction perpendicular to the bonding surface, and A part or all of which is a bainite structure or a martensite structure, and finally forms a joint having a joint efficiency of 1 .
A liquid phase diffusion bonding method for mechanical parts.

(2) From two or more parts, using a Fe-based liquid phase diffusion bonding alloy containing Si necessary for maintaining a low melting point or maintaining a structure in which 50% or more is amorphous, In the joining method of assembling and joining machine parts by diffusion joining,
(I-1) When the bonding surface is heated from room temperature and reaches a liquid phase diffusion bonding temperature of 1100 to 1300 ° C., a load stress of 2 MPa or more is applied to the bonding surface for 90 to 120 seconds, Reduce the load stress to less than 2 MPa and hold at low stress or no load for 5 minutes,
(I-2) Cooling at a cooling rate of 5 ° C./sec or more to prevent burning cracking to a temperature higher than the non-diffusion transformation temperature such as martensitic transformation or bainite transformation of the structure of the material to be joined, By continuing to cool until transformation is completed, by rapidly cooling to room temperature at a cooling rate of 1 ° C./sec or more,
(Ii) a bonding metal formed by the fusion of the Fe-based liquid phase diffusion bonding alloy and the material to be bonded, and the presence of Si solidified on the both sides of the bonding metal from the liquid phase diffusion bonding alloy into the material to be bonded. The width of the portion formed by phase diffusion combined with the Si diffusion region containing 1% or more of Si is within 50 μm on one side from the center of the bonding metal in the direction perpendicular to the bonding surface, and Part or all is a bainite structure or a martensite structure, and finally forms a joint where the joint efficiency is 1 .
A liquid phase diffusion bonding method.

  (3) The liquid phase diffusion bonding method for machine parts according to (1) or (2), wherein the liquid phase diffusion bonding is performed in an oxidizing atmosphere.

  In the present invention, precision machine parts such as automobile fuel injection valves that are originally manufactured by integral molding and have complicated and precise pipes inside are joined by liquid phase diffusion joining technology. Therefore, it is possible to manufacture metal precision machine parts inexpensively and efficiently.

It is a figure which shows the division | segmentation component shape at the time of dividing | segmenting the machine part manufactured by integral molding by the surface which passes through the pipe line which exists in the inside, and is a figure which shows the example of a fluid injection valve especially. It is a figure which shows the relationship between the pressing force at the time of joining in liquid phase diffusion joining, and the distance from the center of a joining metal of the area | region width | variety of Ni content 1% or more containing joining metal. It is a figure which shows the relationship between the tensile strength of a 1Cr-0.5Mo steel joint, and the distance from the center of a joining metal of the area | region width | variety of Ni content 1% or more containing a joining metal.

  In carrying out the present invention, the material of the target machine part is not particularly limited. The technique of the present invention can be applied to all metal materials that are considered capable of liquid phase diffusion bonding. For example, even in the case of a material that is difficult to apply normal welding, such as normal carbon steel, high carbon steel, and low carbon steel, liquid phase diffusion bonding can realize a joint.

  Stainless steels containing various proportions of Cr or Ni, highly corrosion-resistant alloy steels, Ni-based alloys based on Ni, other alloys, non-ferrous materials such as Al, Ti, Zn, and other practical metals However, if a bonding alloy suitable for them is used, liquid phase diffusion bonding is possible.

  Also, the amorphous alloy composition for realizing liquid phase diffusion bonding is not particularly limited, including the alloys described in US Pat. No. 4,144,058, and JP-A-49-91014. Liquid phase diffusion bonding alloys containing the described P, B, C, etc. as diffusion atoms can be used.

  In the present invention, the above-mentioned material to be joined and liquid phase diffusion bonding alloy are used, and a pipe line having the purpose of fluid conveyance, weight reduction, or passage for sliding parts is provided inside. The precision machine parts that were originally manufactured by integral molding are divided into multiple parts on the surface including the pipeline first, for example, conventional integral molding and machining such as press molding, rolling, grinding, polishing, etc. It is necessary to manufacture the combination through an inexpensive manufacturing process, assemble them through an alloy for liquid phase diffusion bonding, and integrate them by liquid phase diffusion bonding.

  The parts to be divided at this time must be divided on the surface passing through the pipeline existing in the interior in comparison with the final shape, thereby making each part inexpensive and simple such as press molding. It can be manufactured in a simple way. In addition, any number of divisions can be used as long as the number is two or more. As long as the manufacturing process is simplified and the manufacturing process is complicated or increases in number, the cost can be appropriately selected as long as the manufacturing process is not expensive. Good.

  Further, the dividing 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 as to facilitate the production of each component 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 particular limitation.

  The pipe can be assembled with or without opening to the outer surface. In addition, the characteristics of a joint part variously change with the combination of a to-be-joined material and a liquid phase diffusion bonding alloy.

  In the present invention, a precision machine part divided into a plurality of parts having a pipe line inside as described above, for example, a high content containing Cr: 1.0% and Mo: 0.5% as shown in FIG. Assemble the Ni-based liquid phase diffusion bonding alloy on the split surface divided into two planes parallel to the pipe of the automobile fuel injection valve made of carbon steel, heat to a temperature above the solidus line, 1000-1300 ° C At a temperature of 90 ° C., a stress of 2 MPa or more is continuously applied to the joining surface for 90 to 120 seconds from the start of heating, and thereafter, the stress is reduced and liquid phase diffusion bonding is maintained for 1 minute or more as low stress or no load. The method is adopted.

  By this liquid phase diffusion bonding, a region containing 1% or more of Ni generated by the diffusion of Ni into the material to be bonded and the bonding metal formed by the fusion of the Ni-based alloy for liquid phase diffusion bonding and the material to be bonded If the width is a length in a direction perpendicular to the bonding surface and can be diffused within 50 μm on one side, a strong bonding surface can be obtained.

  On the other hand, when an Fe-based liquid phase diffusion bonding alloy is used as the liquid phase diffusion bonding alloy, the low melting point maintenance necessary to enable liquid phase diffusion bonding of the liquid phase diffusion bonding alloy, or When assembling and joining by liquid phase diffusion bonding using an Fe-based liquid phase diffusion bonding alloy containing Si necessary for maintaining a structure that is substantially 50% or more amorphous, 1% or more of Si generated by solid phase diffusion of Si from the Fe-based liquid phase diffusion bonding alloy and the material to be bonded and the liquid phase diffusion bonding alloy into the material to be bonded If the width of the included Si diffusion region can be set within 50 μm on one side from the center of the bonding metal in the direction perpendicular to the bonding surface, a strong bonding surface can be obtained.

  In the above liquid phase diffusion bonding conditions, the heating temperature and the heating time are usually the conditions used in liquid phase diffusion bonding, but in the present invention, in order to obtain the bonding strength necessary for precision mechanical parts, Therefore, it is important to join the joining surfaces, that is, the materials to be joined, while applying a pressing force necessary for joining from the outside.

  This pressing force is the temperature at which Ni or Si contained in the liquid phase diffusion bonding alloy can diffuse into the material to be bonded from the start of heating, that is, under the condition that liquid phase diffusion starts between 1000 and 1300 ° C. It is necessary to apply a pressing force, and this pressing force applies a stress of 2 MPa or more to the joint surface.

  Next, it is a necessary condition that the load stress is gradually reduced to maintain a low stress or no load for 5 minutes or more. If the liquid phase diffusion bonding is performed in an unloaded state, even if the alloy for liquid phase diffusion bonding is melted, a healthy joint can be obtained because the isothermal solidification is not completed. Therefore, the required bonding strength cannot be obtained. In addition, although the position of the stress load given to a to-be-joined member changes with member sizes, it may be one place and may be multiple places.

In the liquid phase diffusion bonding according to the present invention, N ₂ or Ar is blown onto the inner and outer surface 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, the width of the Ni diffusion region produced by solid phase diffusion of Ni from the bonding metal having a Ni content of 1% or more at the bonding portion and the alloy for liquid phase diffusion bonding into the material to be bonded is defined as the bonding metal. The reason why the width is limited to 50 μm or less from the center of the case is that, if the width is larger than this, a sufficient pressing force is inevitably not obtained, or there is a deficiency in the butting of the joining surfaces, This is because it has been found experimentally and empirically that the joint is not healthy.

  On the other hand, when the width of the diffusion bonding is too small, the result is that the bonding metal necessary for the diffusion bonding is not sufficiently supplied to the bonding surface. ~ 50 μm.

  In the above joint portion, the Ni content is 1% or more, the width of the Ni diffusion region produced by solid phase diffusion of Ni from the alloy for liquid phase diffusion bonding into the material to be joined, and the pressing force. The relationship was determined based on the following detailed experimental results.

  Fig. 2 shows the pressing force applied in the direction perpendicular to the joint surface when joining commercially available steel materials such as structural carbon steel, machine structural steel, and low alloy steel by liquid phase diffusion bonding. In the joint joint formed as a result, the region width with Ni content of 1% or more, that is, the relationship with the alloy region including the joining metal and Ni diffusion layer (region with Ni content of 1% by mass or more). FIG.

  When the pressing force at the time of joining increases, the original amorphous metal melted at the time of joining and the alloy produced by the melting of the material to be joined are pushed out from the joining interface, and the width of the joining metal that can be measured by the joint joint, and As a result, the width of the alloy including the region where Ni diffused from the bonding metal to the material to be bonded reaches 1% by mass or more after bonding decreases.

  It can be seen that when the pressing force is 2 MPa, the region width with the Ni content of 1% or more may reach 50 μm. In addition, the unevenness | corrugation of a joint surface contains the joining result of the joint which has reached the maximum of 100 micrometers before joining.

  In addition, the region width of Ni content of 1% or more is measured in correspondence with the structure based on the result of line analysis or surface analysis of the joint cross section after bonding using a scanning electron microscope capable of quantitative elemental analysis. And decided. That is, there is a close relationship between the pressing force at the time of joining and the region width where the Ni content is 1% or more.

  FIG. 3 shows the relationship between the region width of the Ni content of 1% or more and the tensile strength in the vertical direction of the joint joint, measured in the same manner. The material used for the joining test and the tensile test is a low alloy steel having a composition of 0.3% C-1% Cr-0.5% Mo, and the joint after joining is cooled at a rate of 1 ° C / min. From here, a tensile test piece having a circular cross section with a diameter of 6 mm was collected, and the tensile strength was measured at room temperature.

  Further, since it has been found that the stress applied to the joint at the time of actual use is 180 MPa at the maximum, here, it is assumed that the target strength required for the joint is 180 MPa, and the value is shown in the figure. It is shown in It is clear that when the region width with the Ni content of 1% or more increases, the joint strength decreases, and when the region width with the Ni content of 1% or more exceeds 50 μm, the target strength cannot be achieved.

  The above tendency is exactly the same when using an iron-base bonded metal foil instead of a liquid phase diffusion bonding alloy, even when considering the diffusion layer of Si contained in the same foil as the bonding metal. there were.

  Further, the bonding temperature showed almost the same tendency in the range of 1000 to 1300 ° C., and the bonding temperature dependency was not clearly observed. Further, in this temperature range, ordinary steel materials have almost the same strength characteristics, and therefore the difference between the steel materials was not clear.

  The chemical components of the bonding metal used for bonding are Si = 3%, B = 3.5%, and V = 3% for the Ni group, and Si = 4.5% and B for the Fe group. = 3.0%, V = 5.0%. The same was true when a foil containing P equivalent in mass% instead of B was used.

  The structure of the material to be bonded obtained by the liquid phase diffusion bonding process described above is martensite or bainite classified as a low temperature transformation generation structure, and the bonding metal and the metal to be bonded are contained in the bonding metal. If a structure having a part or all of the same low temperature transformation structure as the material to be joined is obtained by alloying generated by fusion, a homogenous joint can be obtained by homogenizing the structure. become.

  In addition, after the liquid phase diffusion bonding process described above, the structure of the material to be bonded is rapidly cooled at a cooling rate of 5 ° C./sec or higher until the structure of the material to be bonded is heated to a temperature equal to or higher than the bainite transformation start temperature. After allowing to cool and maintaining this cooling until transformation is completed, by adopting a condition of 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.

  In the present invention, the characteristics of the joint surface can be freely changed according to the specifications of the machine parts 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 material is preferable from the standpoint of mechanical part characteristics, but can be determined according to the manufacturing cost of the part.

  It is possible to perform various heat treatments, chemical conversion treatments, and processing on machine parts after the assembly is completed. For example, in the case of steel materials, heat treatment processes such as quenching, tempering, normalizing, and annealing are performed alone or in combination. In some cases, repeated application 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.

<Example 1>
In the present invention, the manufacture of an automobile fuel injection valve having a fuel supply conduit inside will be described. This automobile fuel injection valve 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 small amount of 30 μm is sandwiched between the split surfaces 1 and 2 of the above, the parts are butted together, and the parts are pressed from the upper and lower surfaces of the outside Hold down with a jig, and then start heating the entire part from room temperature in a high-frequency induction heating furnace with a high-frequency induction heating coil that can control the atmosphere, and reach the liquid phase diffusion bonding temperature range of 1100 ° C to 1300 ° C At that time, the load surface is continuously loaded with a load stress of 2 MPa or more with a holding jig for 90 to 120 seconds, and then the load stress is reduced and held as low or no load for 5 minutes. The material structure is martensitic transformation or In order to prevent burning cracking to a temperature higher than the non-diffusion transformation temperature such as innite transformation, quenching is performed at a cooling rate of 5 ° C./sec or more, followed by standing to cool until the transformation is completed. After maintaining, it was rapidly cooled to room temperature at a cooling rate of 1 ° C./sec or more.

  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 the bonding metal has the same low temperature transformation formation structure as the material to be joined. Had in part or all.

  The width of the Ni diffusion region generated by solid phase diffusion of Ni from the bonding metal having the Ni content of 1% or more and the liquid phase diffusion bonding alloy into the material to be bonded is perpendicular to the bonding surface. The length in the direction was 40 μm on one side from the center of the bonding metal. 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 integrated with actual automobile parts, the characteristics of the parts were evaluated, and the same usage performance as a conventional machined fuel injection valve for automobiles was obtained. High-temperature oxidation resistance, wear resistance, joint surface against fluid pressure A value comparable to the strength was obtained.

  As described above, the present invention is based on the liquid phase in which a precision machine part such as a fuel injection valve for automobiles, which is originally manufactured by integral molding and has complicated and precise pipes, can be easily manufactured. Since it joins and manufactures by a diffusion bonding technique, it is possible to manufacture a metal precision machine component cheaply and efficiently. Therefore, the present invention has great applicability in the precision machine component manufacturing industry.

Claims (3)

In a joining method of assembling and joining machine parts by liquid phase diffusion bonding using Ni-based alloy for liquid phase diffusion bonding from two or more parts,
(I-1) When the bonding surface is heated from room temperature and reaches a liquid phase diffusion bonding temperature of 1100 to 1300 ° C., a load stress of 2 MPa or more is applied to the bonding surface for 90 to 120 seconds, Reduce the load stress to less than 2 MPa and hold at low stress or no load for 5 minutes,
(I-2) Rapid cooling at a cooling rate of 5 ° C./sec or higher to prevent cracking to a temperature higher than the non-diffusion transformation temperature such as martensitic transformation or bainite transformation of the structure of the material to be joined, By continuing to cool until transformation is completed, by rapidly cooling to room temperature at a cooling rate of 1 ° C./sec or more,
(Ii) a bonding metal formed by the fusion of a Ni-based liquid phase diffusion bonding alloy and a material to be bonded, and a Ni solid solution present on both sides of the bonding metal from the liquid phase diffusion bonding alloy into the material to be bonded. The width of the portion combined with the Ni diffusion region containing 1% or more of Ni generated by phase diffusion is within 50 μm on one side from the center of the bonding metal in the direction perpendicular to the bonding surface, and A part or all of which is a bainite structure or a martensite structure, and finally forms a joint having a joint efficiency of 1 .
A liquid phase diffusion bonding method for mechanical parts. From two or more parts, using a Fe-based liquid phase diffusion bonding alloy containing Si necessary for maintaining a low melting point or maintaining a structure in which substantially 50% or more is amorphous, by liquid phase diffusion bonding In a joining method for assembling and joining machine parts,
(I-1) When the bonding surface is heated from room temperature and reaches a liquid phase diffusion bonding temperature of 1100 to 1300 ° C., a load stress of 2 MPa or more is applied to the bonding surface for 90 to 120 seconds, Reduce the load stress to less than 2 MPa and hold at low stress or no load for 5 minutes,
(I-2) Cooling at a cooling rate of 5 ° C./sec or more to prevent burning cracking to a temperature higher than the non-diffusion transformation temperature such as martensitic transformation or bainite transformation of the structure of the material to be joined, By continuing to cool until transformation is completed, by rapidly cooling to room temperature at a cooling rate of 1 ° C./sec or more,
(Ii) a bonding metal formed by the fusion of the Fe-based liquid phase diffusion bonding alloy and the material to be bonded, and the presence of Si solidified on the both sides of the bonding metal from the liquid phase diffusion bonding alloy into the material to be bonded. The width of the portion formed by phase diffusion combined with the Si diffusion region containing 1% or more of Si is within 50 μm on one side from the center of the bonding metal in the direction perpendicular to the bonding surface, and Part or all is a bainite structure or a martensite structure, and finally forms a joint where the joint efficiency is 1 .
A liquid phase diffusion bonding method.   The liquid phase diffusion bonding method for machine parts according to claim 1, wherein the liquid phase diffusion bonding is performed in an oxidizing atmosphere.

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