JP5849863B2 - Manufacturing method of sintered diffusion bonding parts - Google Patents

Description

  The present invention relates to a method for manufacturing a sintered diffusion bonded component in which different materials are bonded by sintered diffusion bonding.

  A movable iron core which is such a sintered diffusion bonding component is disclosed in Patent Documents 1 to 3 and the like. The movable iron core includes a shaft member made of a wear-resistant material made of carbon steel, and an outer peripheral member made of an Fe-based metal that is provided on one end side of the shaft member and has an inner hole. Is. This movable iron core is subjected to a sintering process in which the green compact and the shaft member are heated after performing an integration process in which the green compact having the shape of the outer peripheral member and the shaft member are integrated. The outer peripheral member is formed by sintering the powder, and the green compact and the shaft member are joined by sintered diffusion bonding.

Japanese Patent No. 4702945 Japanese Patent No. 472457 JP 2009-102711 A JP 2010-174353 A

  By the way, as described above, when manufacturing a sintered diffusion bonding component in which a wear resistant material made of carbon steel and a green compact made of Fe-based metal are bonded by sintered diffusion bonding, the green compact is made of Si or the like. It has been found that when a ferritic element is contained, a softened portion exists in the surface layer of the wear-resistant material after joining. The ferritic element is an element that converts the structure of the diffused region into a ferrite phase (α phase) when diffused into the wear-resistant material. Further, the surface layer of the wear-resistant material here means a layer on the surface other than the joint surface of the wear-resistant material.

  The reason for the presence of this softened site is considered as follows.

  As shown in FIG. 8, the case where the green compact 20 has an Fe—P—Si composition and the wear-resistant material 1 contains elements such as Mo and Cr will be described as an example. In the above-described sintering process, Mo element and Cr element in the wear-resistant material 1 diffuse near the bonding surface 20a of the green compact 20, and P element and Si element in the green compact 20 wear-resistant material. 1 diffuses in the vicinity of the joint surface 1a.

  Thereby, as shown in FIG. 9, the diffusion layer 40 is formed between the green compact 20 and the wear-resistant material 1, and the green compact 20 and the wear-resistant material 1 are joined. The diffusion layer 40 includes a diffusion layer 41 formed on the bonding surface 20 a of the green compact 20 and a diffusion layer 42 formed on the bonding surface 1 a of the wear resistant material 1. The diffusion layer 42 formed on the joint surface 1a of the wear resistant material 1 is formed of a ferrite phase by the diffusion of Si as a ferritizing element, and has a lower hardness than the other regions of the wear resistant material 1. Become.

Here, the green compact 20 contains a molding lubricant. For this reason, the degreasing process of heating the wear-resistant material 1 and the green compact 20 to decompose and remove the molding lubricant in the green compact 20 is performed between the integration process and the sintering process. Since the decomposition of the molded lubricant is decarburizing gas CO ₂ and H _{2 O} is produced, in this degreasing step, and eliminates the CO ₂ and H _{2 O} from the heating atmosphere. However, the CO ₂ and _{H 2} O be excluded from the heating atmosphere, remains in the CO ₂ and _{H 2} O is heated atmosphere, the surface 1b of the wear-resistant material 1, 1c to the CO ₂ and _{H 2} O Touch it. For this reason, the surfaces 1b and 1c of the wear-resistant material 1 are decarburized, and a thin layer (not shown) made of a ferrite phase is formed on the surfaces 1b and 1c of the wear-resistant material 1. This thin layer has a high element diffusion coefficient, and this thin layer promotes element diffusion. Even if the H ₂ and O ₂ is decarburizing gas is introduced into the heating atmosphere in the degreasing step, the surface 1b of the wear-resistant material 1, 1c is decarburized, thin layer described above is formed .

  Therefore, at the time of the sintering process, as shown in FIG. 8, Si as a ferritizing element diffuses in the surface layer of the wear resistant material 1, so that the joint surface of the wear resistant material 1 as shown in FIG. 9. The diffusion layer 42 formed on 1 a extends to the surface layer of the wear-resistant material 1. This is the reason why the softened portion exists in the surface layer of the wear-resistant material 1.

  For this reason, when high hardness is required for one surface 1b located on the upper side in FIG. 9 among the surfaces of the wear-resistant material 1, the removal is performed by removing the softened portion existing in the surface layer by cutting or the like in a subsequent process. It is necessary to perform a process. In this removal process, since the surface layer of the sintered diffusion bonded part has to be removed over a wide range, the time required for the removal process becomes long.

  For example, when it is necessary to finish the surface 1b of the wear resistant material and the surface 20b of the green compact 20 in a flush manner, not only the softened portion but also the final shape A2 surrounded by the one-dot chain line in FIG. The surface layer must be removed over the entire area of the surface 1b, 20b of the diffusion diffusion bonded component. The thickness of the surface layer to be removed at this time is uniform and is a thickness corresponding to the depth from the surface 1b of the wear-resistant material 1 at the softened portion. In addition, when high hardness is requested | required not only on one surface 1b, 20b of the bonding diffusion bonding component but also on the other surface 1c, 20c on the opposite side, both surfaces 1b, 1c, 20b, 20c of the bonding diffusion bonding component are required. The surface layer must be removed.

  Further, even when only the portion where the softened portion exists is removed, if the softened portion exists in a wide range, the surface layer must be removed over a wide range, and the time required for the removal process becomes long.

  In view of the above points, an object of the present invention is to shorten the time required for the removal step when manufacturing a sintered diffusion bonding part.

In order to achieve the above object, in the invention described in claim 1,
A wear-resistant material provided with a protrusion (30) protruding from the surface (1b) of the wear-resistant material at a position adjacent to the joint surface (1a) of the wear-resistant material (1), and a ferritic element An integration step (101) for integrating the green compact (20) to be included;
After the integration process, the wear-resistant material and the green compact are heated to sinter the green compact and the diffusion of ferritic elements in the green compact on the joint surface of the wear-resistant material A layer (42) is formed, and a diffusion layer (41) formed by diffusing elements in the wear-resistant material is formed on the joint surface (20a) of the green compact to burn the wear-resistant material and the green compact. A sintering step (103) for bonding and diffusion bonding, and further inducing and retaining a diffusion layer formed on the bonding surface of the wear-resistant material in the protrusions;
And a removal step (104) for removing the protrusions after the sintering step.

  As in the present invention, by providing the protrusion at a position adjacent to the joint surface of the wear resistant material, the diffusion layer formed on the joint surface of the wear resistant material can be guided to the surface layer of the protrusion. Therefore, the diffusion layer is formed on the joint surface of the wear-resistant material by setting the height and width of the projection so that the diffusion layer exists only on the projection and not on the surface of the wear-resistant material. Can be guided and retained in the protrusions, the diffusion layer is not present on the surface layer of the wear-resistant material simply by removing the protrusions.

  Thus, according to the present invention, the removal range in the removal process can be narrowed and the time required for the removal process can be shortened as compared with the case where no protrusion is formed on the wear-resistant material.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

It is a figure which shows the cross-sectional structure of a solenoid valve provided with the armature in 1st Embodiment. It is a perspective view of the armature in FIG. It is a figure which shows the manufacturing process of the armature in FIG. It is sectional drawing of the shaft member and green compact in the middle of manufacture of the armature in 1st Embodiment. In manufacture of the armature in 1st Embodiment, it is sectional drawing for demonstrating the range of the diffused layer formed in the shaft member after a sintering process. In manufacture of an armature in a 1st embodiment, it is a sectional view for explaining a range of a diffusion layer formed in a shaft member after a removal process. 2 is a metallographic micrograph showing a cross section of a sintered diffusion bonding component in Example 1. FIG. It is sectional drawing for demonstrating the sintering diffusion bonding of a green compact and an abrasion-resistant material. It is a figure for demonstrating the subject which this invention tends to solve, Comprising: It is sectional drawing for demonstrating the range of the diffusion layer formed when sintering compaction and a wear-resistant material are sintered-diffusion joined. is there.

Hereinafter, embodiments of the present invention will be described.
(First embodiment)
1st Embodiment demonstrates the manufacturing method of the armature (movable iron core) of the solenoid type injector of the fuel injection device for vehicles.

  First, the structure of a solenoid valve provided with an armature will be described. As shown in FIGS. 1 and 2, the armature 3 includes a shaft member 1 and an outer peripheral member 2 provided on one end side of the shaft member 1. On the other end side of the shaft member 1 is provided a valve body (not shown) that is in contact with a valve seat (not shown). The outer peripheral member 2 has a flat shape extending in a direction perpendicular to the longitudinal direction of the shaft member 1.

  In the electromagnetic valve 10 shown in FIG. 1, a fixed iron core 4 is disposed at a position facing the armature 3 in the longitudinal direction of the shaft member 1, and a solenoid coil 5 is wound around the fixed iron core 4. In this electromagnetic valve 10, by supplying current to the solenoid coil 5 wound around the fixed iron core 4, the armature 3 is attracted to the fixed iron core 4, and the valve is opened, and the armature 3 is wound around the fixed iron core 4. By shutting off the current flowing through the solenoid coil 5, the armature 3 returns to the original position by the return force of a spring (not shown), and the valve is closed.

  Here, the armature 3 is a diffusion bonded component formed by sintering diffusion bonding the shaft member 1 and the outer peripheral member 2 made of different materials.

  The shaft member 1 is made of an abrasion-resistant material made of carbon steel having a hardness of Hv600 or higher. Examples of the wear resistant material include high speed tool steel such as JIS standard SKH51 material and SKH2 material, bearing steel such as JIS standard SUJ2 material, and alloy tool steel such as JIS standard SKD11 material. It is done.

  The outer peripheral member 2 is obtained by sintering a green compact made of Fe-based metal whose main component is Fe. The green compact is obtained by compacting a raw material powder. Examples of the raw material powder include Fe-Si-P-based and soft magnetic powder having an Fe-Si-based composition. Si and P are elements for forming sintered diffusion bonding, and among these elements, Si is also a ferritizing element that causes the structure of the diffused region to become a ferrite phase when diffused into the wear-resistant material. .

  Next, a method for manufacturing the armature 3 will be described.

  As shown in FIG. 3, an assembling step 101 for assembling the shaft member 1 having a desired shape and the green compact having the shape of the outer peripheral member 2 is performed. This assembly process 101 corresponds to the integration process described in the claims.

  Specifically, a shaft member 1 made of a wear-resistant material having the shape shown in FIG. 4 is prepared. 4 corresponds to a region A1 surrounded by a broken line in FIG. The shaft member 1 is provided with a protruding portion 30 having a shape protruding from the surface 1 b of the shaft member 1 at a position adjacent to the joint surface 1 a of the shaft member 1 on the surface 1 b of the shaft member 1. The protrusion 30 is removed in a removal step 104 described later. The protrusion 30 has a surface 30a continuous with the joint surface 1a. When the surface 1b of the shaft member 1 is viewed from above in FIG. 4, the protrusions 30 are arranged along the entire range of the joint surface 1a positioned linearly on the surface 1b of the shaft member 1.

Moreover, the green compact 20 obtained by compacting raw material powder so that it may become the shape of the outer member 2 which has an inner hole is prepared. At this time, the green compact 20 contains a molding lubricant. This molding lubricant is made of an organic compound that is decomposed into CO ₂ and H ₂ O by heat treatment. As this molding lubricant, a lubricant for compacting metal powder such as wax and stearic acid can be used.

  Then, the shaft member 1 is fitted into the inner hole of the obtained green compact 20 and integrated. Thereby, as shown in FIG. 4, the bonding surface 20 a of the green compact 20 and the bonding surface 1 a of the shaft member 1 are in contact with each other.

Then, the degreasing process 102 which decomposes | disassembles the shaping | molding lubricant in a green compact is performed by heating the shaft member 1 and the green compact 20 after an assembly | attachment. The heating temperature is a decomposition temperature of the molded lubricant, for example, 600 ° C. At this time, in order to suppress decarburization on the surface of the shaft member 1, it is preferable to eliminate CO ₂ and H ₂ O generated by the decomposition of the molded lubricant as much as possible from the heating atmosphere. Moreover, it is preferable not to introduce decarburizing gas H ₂ or O ₂ into the heating atmosphere.

  Thereafter, by heating the assembled shaft member 1 and the green compact 20, the green compact 20 is sintered to form the outer peripheral member 2, and the shaft member 1 and the outer peripheral member 2 are diffusion bonded. Step 103 is performed. The heating temperature at this time is 1100 degreeC-1300 degreeC.

  Then, the removal process 104 which removes the projection part 30 of the shaft member 1 by grinding etc. is performed. In the present embodiment, the final shape of the armature 3 is obtained by removing the protrusion 30. In this way, the armature 3 is manufactured.

  Next, features of the present embodiment will be described.

  In the above-described sintering step 103, as described in the section “Problems to be Solved by the Invention”, as shown in FIG. 8, the Cr element, the Mo element, etc. contained in the shaft member 1 are joined to the green compact 20. The Si element and the P element that are diffused near the surface 20 a and added to the green compact 20 are diffused near the joint surface 1 a of the shaft member 1. Thereby, also in this embodiment, as shown in FIG. 9, the diffusion layer 40 which diffusely bonds both is formed between the shaft member 1 and the outer peripheral member 2. The diffusion layer 40 includes a diffusion layer 41 formed on the bonding surface 20 a of the green compact 20 and a diffusion layer 42 formed on the bonding surface 1 a of the shaft member 1.

Here, even if CO ₂ and H ₂ O are excluded from the heating atmosphere in the degreasing step, CO ₂ and H ₂ O remain in the heating atmosphere, and the surface of the wear-resistant material 1 is CO ₂ and H ₂ O. Will touch. For this reason, the surface of the wear resistant material 1 is decarburized, and a thin layer made of a ferrite phase having a high element diffusion coefficient is formed on the surface of the wear resistant material 1.

  For this reason, unlike this embodiment, when the projection part is not provided in the shaft member 1, the Si element diffuses into the surface layer of the shaft member 1, as shown in FIG. The diffusion layer 42 formed on 1 a extends to the surface layer of the shaft member 1.

On the other hand, in this embodiment, the protrusion 30 is provided on the shaft member 1. A thin layer made of a ferrite phase having a high element diffusion coefficient is also formed on the surface 30a of the protrusion 30 by the CO ₂ and H ₂ O remaining in the degreasing step. Therefore, in this embodiment, as shown in FIG. 5, the Si element diffuses along the surface 30 a of the protrusion 30, so that the diffusion layer 42 formed on the joint surface 1 a of the shaft member 1 becomes the protrusion 30. Extends to the surface layer.

  Furthermore, in the present embodiment, the extension distance of the diffusion layer 42 is obtained in advance by experiments or the like so that the diffusion layer 42 exists only on the protrusion 30 and does not exist on the surface layer of the shaft member 1. Based on this, the height and width of the protrusion 30 are set. As a result, the diffusion layer 42 formed on the joint surface 1 a of the shaft member 1 can be guided and retained in the protrusion 30. For this reason, in the removing step, as shown in FIG. 6, the diffusion layer 42 that becomes the softened portion can be removed simply by removing the protrusion 30.

  As described above, according to the present embodiment, by removing only the protrusion 30 in the removal step, the surface layer of the shaft member 1 can be made to have no diffusion layer, and thus the protrusion 30 is not formed on the shaft member 1. Compared to the case, the removal range can be narrowed, and the time required for the removal process can be shortened.

  In the present embodiment, the diffusion layer 42 formed on the bonding surface 1a remains on the bonding surface 1a. Moreover, the thin layer which consists of the ferrite phase formed in the surface 1b of the shaft member 1 is left. This is because the influence of the thin layer on the hardness of the surface 1b of the shaft member 1 is small.

  Moreover, in this embodiment, although the thin layer which consists of a ferrite phase formed in the surface 1b of the shaft member 1 is left, you may remove this thin layer. In this case, in addition to the removal of the protrusion 30 in the above-described removal step, the thin layer of the surface 1b of the shaft member 1 is removed by grinding or the like. Even if this thin layer is removed, the time required for the removal process can be shortened because the layer to be removed is thin compared to the case where no protrusion is formed.

(Other embodiments)
In the assembly process 101 of the first embodiment, the shaft member 1 and the green compact 20 molded into the shape of the outer peripheral member 2 are prepared, and the shaft member 1 is fitted into the inner hole of the green compact 20. Although integrated, instead of the assembling step 101, an integration step of integrating the shaft member 1 and the green compact 20 at the same time as forming the green compact 20 is performed as described in Patent Document 4. Also good. That is, an integrated part of the shaft member 1 and the green compact 20 may be insert-molded by pressing the raw material powder in the mold while holding the shaft member 1 in the mold.

  Further, in the first embodiment, the example in which the method for manufacturing a sintered diffusion bonding part of the present invention is applied to the method for manufacturing an armature of an injector has been described. It is also possible to apply to the manufacturing method of a joining component. The sintered gear part is composed of a shaft portion and a gear portion provided on one end side of the shaft portion, and includes a wear-resistant material having a shape of the shaft portion and a green compact having a shape of the gear portion. Is obtained by sintering diffusion bonding.

Examples of the present invention will be described below.
Example 1
A specimen having a desired shape made of an abrasion-resistant material and a specimen having a green compact in a desired shape were joined by sintered diffusion bonding to produce a sintered diffusion bonded part.

  Specifically, a wear-resistant material having a columnar shape made of SKH51 material and having the above-described protrusions was prepared. The height of the protrusion from the surface of the wear resistant material was 0.5 mm. Further, a pressure obtained by pressure-molding a metal powder having a composition of Si: 2.0 wt%, P: 0.35 wt%, Mn: 0.2 wt%, S: 0.08 wt%, the balance being Fe and inevitable impurities in a cylindrical shape. Powder was prepared. This green compact is obtained by adding 0.5 wt% of a wax-based lubricant to the whole green compact.

  Then, after one surface of the wear-resistant material and one surface of the green compact were brought into contact with each other and assembled, a degreasing step and a sintering step were sequentially performed. In the degreasing process, heating was performed at 635 ° C. for 1 hour in a vacuum furnace of 0.5 Torr. In the sintering process, heating was performed at 1215 ° C. for 1 hour in a vacuum furnace of 0.5 Torr.

  Then, while observing the cross section of the sintered diffusion bonding part in a state where the protrusions were left with a metal microscope, the hardness of the surface layer of the wear resistant material was measured by a micro Vickers measurement method.

  As a result, as shown in FIG. 7, it is confirmed that the structure of the surface layer of the protrusion 30 of the wear resistant material 1 is different from the other regions, and the diffusion formed on the joint surface 1 a of the wear resistant material 1. It is presumed that the layer 42 extends to the surface layer of the protrusion 30. The prepared wear-resistant material 1 had a hardness of Hv600, but the hardness of the surface layer of the protrusion 30 after bonding was Hv200, and it was confirmed that a softened portion was formed on the surface layer of the protrusion 30. It was.

1 Shaft member (Abrasion resistant material)
2 Peripheral member 3 Armature 10 Solenoid valve 20 Green compact 30 Protruding part 42 Diffusion layer formed on joint surface of shaft member (abrasion resistant material)

Claims (3)

A wear-resistant material made of carbon steel having a hardness of Hv600 or more and made into a desired shape and a green compact made of Fe-based metal containing Fe as a main component and made into a desired shape are joined by sintered diffusion bonding. In the manufacturing method of sintered diffusion bonding parts,
The wear resistant material provided with a protrusion (30) protruding from the surface (1b) of the wear resistant material at a position adjacent to the joint surface (1a) of the wear resistant material (1), and ferrite An integration step (101) for integrating the green compact (20) containing the chemical element;
After the integration step, the wear-resistant material and the green compact are heated to sinter the green compact, and the ferritization in the green compact is bonded to the joint surface of the wear-resistant material. A diffusion layer (42) formed by diffusing elements is formed, and a diffusion layer (41) formed by diffusing elements in the wear-resistant material is formed on the joint surface (20a) of the green compact to form the above-mentioned resistance. Sintering diffusion bonding of the wearable material and the green compact, and further, a sintering step (103) for inducing and retaining a diffusion layer formed on the bonding surface of the wear-resistant material in the protrusions;
And a removal step (104) for removing the protrusions after the sintering step. The green compact (20) contains a molding lubricant (21),
A degreasing step (102) for decomposing the molding lubricant in the green compact by heating at a decomposition temperature of the molding lubricant between the integration step and the sintering step; The method for producing a sintered diffusion bonding part according to claim 1, wherein The sintered diffusion bonding component is an injector armature (3) having a shaft member and an outer peripheral member (2) located on one end side of the shaft member,
3. The diffusion bonding according to claim 1, wherein the wear-resistant material (1) having the shape of the shaft member and the green compact having the shape of the outer peripheral member are integrated. A manufacturing method for parts.