JPS63286264A - Alloying method on casting surface - Google Patents

Abstract

PURPOSE:To accurately enable alloying on the specific surface in a casting by holding a porous sheet composing fine pieces containing alloying element under condition of abutting on the specific position in the inner wall of a mold by a porous forming body inserting into inner wall face of the mold. CONSTITUTION:The alloying elements, for example Ni powder and acrylate resin binder are mixed at the prescribed ratio and made to paste-state. This paste is coated on the stainless steel plate 2 and dried in the air to form the porous sheet 4 of the Ni powder bound with the acrylate resin binder. Next, the stainless steel plate 2 and the sheet 4 are heated in N2 gas and the sheet 4 is removed from the stainless steel plate 2 and after that, rapidly put on bottom wall 8a of a cavity 8 in the mold 6. Further, a fiber forming body 10 is put on the sheet 4 under condition of closely contacting. Then, molten Al 12 is poured into the mold cavity 8 and held till solidifying under pressurizing with a plunger 14. After solidifying, the formed casting is taken out with a knock out pin 15.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for alloying the surfaces of castings, ie to manufacturing castings having an alloyed surface layer.

Conventional technology As one of the alloying methods for the surface of castings, for example, Japanese Patent Application Laid-open No.
As described in Japanese Patent No. 238078, a porous sheet made of fine alloying metal powder bonded with a resin binder is placed on the inner wall surface of the mold or the surface of the chiller, and the metal is placed inside the mold. A method of pouring molten metal is conventionally known. According to this method, the poured molten metal enters into the individual voids of the sheet, melts the fine metal powder in the sheet, and thereby alloys a specific surface portion of the casting.

Problems to be Solved by the Invention However, in such conventional methods, the sheet made of metal-powder peels off from the inner wall surface of the mold due to the pressure and flow effect of the molten metal poured into the mold. There is a problem in that the sheet may be bent or displaced from a predetermined location, or the sheet may crack slightly, making it difficult to accurately alloy the desired surface portion of the casting. Such a problem is
This is particularly true when the thickness of the alloyed layer and therefore of the sheet used is small.

In view of the above-mentioned problems in the conventional casting surface alloying method, the present invention provides an improved casting surface alloying method that can accurately and reliably alloy the casting surface area. The purpose is to provide law.

Means for Solving the Problems According to the invention, a porous sheet of fine particles containing alloying elements and a porous sheet which is substantially stable to the molten metal of which the casting is to be made is obtained. forming a porous molded body made of a material such that the molded body engages with the inner wall surface of the mold, and the sheet is maintained in a state in which it is in contact with the inner wall surface of a predetermined portion of the mold by the molded body. This is achieved by a casting surface alloying method in which the sheet and the molded body are placed in the mold, molten metal is poured into the mold, and the molten metal is solidified while being pressurized.

Effects and Effects of the Invention According to the present invention, a porous sheet made of fine particles containing an alloying element is brought into contact with the inner wall surface of a predetermined portion of the mold by a porous molded body that engages with the inner wall surface of the mold. Since the sheets are maintained in contact with each other, even when molten metal is poured into the mold, the sheet is prevented from being peeled off from the inner wall surface of the mold or displaced from a predetermined part by the molten metal.
In addition, the molten metal reaches the sheet in a dispersed state by passing through the porous molded body, thereby avoiding cracks in the sheet, thereby ensuring accurate and reliable alloying of the desired surface area of the casting. can do. Moreover, since the shape and thickness of the sheet may be arbitrary, the surface portion of the casting can be alloyed with an arbitrary shape and thickness.

According to one detailed feature of the casting surface alloying method of the invention, the sheet is pressed by the compact against the inner wall surface of the mold. According to this method, it is possible to produce a casting in which the outermost surface of a predetermined portion is alloyed.

According to another detailed feature of the casting surface alloying method of the present invention, the material constituting the compact is reinforcing fibers or reinforcing particles. According to this method, the molten metal intrudes into the individual voids of the molded body, so that the original molded body becomes a fiber-reinforced metal composite material or a particle-dispersed metal composite material, so that the alloyed layer on the surface part and A layer of composite material integral with other parts of the casting can be formed at the same time as alloying.

According to yet another detailed feature of the casting surface alloying method of the present invention, the sheet is formed integrally with the surface of the compact. According to this method, the handling properties of the sheet and the molded body are improved compared to the case where the sheet is formed separately from the molded body, and in particular, even when the thickness of the sheet is very small, the thickness of the sheet = 5 - Collapses etc. can be avoided, so that the surface parts of the casting can be alloyed accurately and reliably even when the thickness of the alloy layer is very small.

According to the results of experimental studies conducted by the inventors of the present application, the molded body accurately holds the sheet in a predetermined position, and the molded body does not prevent the molten metal from reaching the sheet properly. In order to achieve this, it is preferable that the average pore diameter of the voids in the molded body is 2 cm or less, and the porosity is 70 to 99%.

The invention will now be described in detail by way of example with reference to the accompanying drawings.

Example I Nl powder (99% purity, average particle size 2 μm) and acrylic resin binder (diluted to 50% with acetone) in a weight ratio of 3
By weighing and mixing so that = 1, a paste consisting of Ni powder and acrylic resin binder was formed.

Then, as shown in FIG.
By applying a 1% paste on a stainless steel plate 2 with an inner diameter of 60 mm and drying the paste in the atmosphere, an outer diameter 1 made of N1 powder bonded with an acrylic resin binder is formed.
00[llIn1 Inner diameter 60IllII11 Thickness 2ml
A porous sheet 4 of 1 was formed.

Next, the stainless steel plate 2 and the sheet 4 are heated to 300° C. in N2 gas, the sheet is removed from the stainless steel plate, and the sheet is immediately placed on the bottom wall 8a of the mold cavity 8 of the mold 6 as shown in FIG. Alumina short fibers (AI 203-5
%5i02) Fiber length 2-3 [1lII11 Average fiber diameter 2
μm), outer diameter 110IIlff11 inner diameter 60n
A fiber molded body 1o heated to 500° C. and shaped like an annular plate with a thickness of 5IIIm and a thickness of 5IIIn was placed. In this case, the outer periphery of the fiber molded body 10 is press-fitted into the mold cavity 8, and by pressing it slightly against the sheet 4, the sheet is maintained in close contact with the bottom wall 8a and the fiber molded body. It was done.

Next, as shown in FIG. 3, an aluminum alloy (JIs standard AC8
The molten metal 12 of A) was poured, and the molten metal was pressurized with a surface pressure of 1000 kg/♂ by a plunger 14 fitted into the mold cavity, and the pressurized state was maintained until the molten metal completely solidified. After the molten metal had completely solidified, the formed casting was taken out using the knockout pin 15.

FIG. 4 is a partially cutaway perspective view of the casting 16 thus formed. As can be seen from FIG. 4, on the surface of the upper end of the casting 16, an alloy layer made of Ni-50% A1 alloy is formed in an area substantially corresponding to the original sheet. It was observed that no alloying defects caused by sheet displacement or cracking occurred. Also, the alloy layer 18
In the figure, a composite layer 22 made of an aluminum alloy composite reinforced with alumina short fibers 20 is formed below, and the composite layer 22 is made of an alloy layer 18 and other main parts 24 of the casting.
It was recognized that it is continuous with and integrated with this.

Additionally, the coefficient of thermal expansion of the alloy layer 18 is less than that of the composite layer 22, which has a lower coefficient of thermal expansion than the coefficient of thermal expansion of the main portion 24, so that the upper end of the casting is resistant to thermal shock. It was also recognized that it had good properties.

Note that even if colloidal silica (10% aqueous solution) is used instead of the acrylic resin in this example, no binder is used and only N1 powder is mixed in N2 with a
Even when a sheet is formed by heating and holding at ℃ for 30 minutes to perform temporary sintering, and casting is performed using that sheet, it has been observed that the predetermined surface area of the casting is accurately alloyed. Ta.

Comparative Example 1 A casting was formed in the same manner and under the same conditions as in Example 1 above, except that a fiber molded body made of short alumina fibers was not used.

When the cross section of the casting 26 thus formed was observed,
As shown in FIG. 5, there is a portion 30 where the alloy layer 28 is displaced away from the surface of the casting due to peeling of the sheet from the inner wall surface of the mold, and as shown in FIG. It was found that due to the cracking of the sheet, there were unalloyed portions 32 on certain surfaces of the castings and alloy layers 34 formed at portions away from the surfaces of the castings.

Example 2 Ni powder (purity 99%, average particle size 2 μm) and acrylic resin binder (diluted to 50% with acetone) were mixed in a weight ratio of 2
:1 by weighing and mixing to form a paste consisting of Nl powder and acrylic resin binder.

Next, as shown in FIG. 7, alumina staple fibers (AI 203-5% SiO2) with a volume fraction of 5% and a fiber length of 2
~3 m, ms average fiber diameter 2 μm), outer diameter 11
0 +++II, inner diameter 60II 1m1 thickness 5In[Il
By applying a paste on one end surface of a fiber molded body 36 having an annular plate shape and drying the paste in the atmosphere, an outer diameter of 100fflff11 made of N1 powder bonded with an acrylic resin binder is obtained. 60 "", thickness 2 [
A porous sheet 38 of ll[Il was formed integrally with the fiber molded body 36. Next, the fiber molded body 36 and the sheet 38 are heated to 300° C. in H2 gas, and the sheet side is quickly placed on the bottom wall 8a of the mold cavity 8 of the mold 6 as shown in FIG. It was placed downward. In this case, the outer peripheries of the fiber molded body 36 and the sheet 38 are press-fitted into the mold cavity 8, and by pressing them slightly against the bottom wall 8a, the sheet is brought into close contact with the bottom wall 8a and the fiber molded body. was maintained in that state.

Next, casting was performed using molten aluminum alloy (JIS standard AC8A) in the same manner and under the same conditions as in Example 1, to form a substantially cylindrical casting.

When the cross section of the tip of the casting thus formed was investigated, it was found that, as in Example 1, an alloy layer made of a Ni-Al alloy with an N1 content of approximately 80% was formed at the tip. It was observed that no alloying defects caused by peeling or cracking of the sheet occurred. In addition, a composite layer made of aluminum alloy reinforced with alumina short fibers is formed between the alloy layer and the main part of the casting, and the composite layer is integrated with the alloy layer and the main part of the casting. It was recognized that there was.

11 Example 3 N1 powder (purity 99%, average particle size 2 μm) and 20% colloidal silica aqueous solution were weighed and mixed at a weight ratio of 1:1 to form N1 powder and colloidal silica. A paste was formed. Next, as shown in Fig. 9, the outer diameter is 10011111% and the inner diameter is 50 m.
m, length 20 m + a, and a cylindrical fiber molded body 40 made of the same alumina short fibers as the alumina short fibers used in Example 1 and having a fiber volume percentage of 5%. A 2 mm thick cylindrical porous sheet 42 of N1 powder bonded with silica was formed by applying the paste and drying the paste in the atmosphere.

Next, the fiber molded body 40 and sheet 42 are heated to 300° C., and then immediately placed in the cylindrical hole 46a of the lower mold 46 of the mold 44, as shown in FIG. 48 were placed. In this case, the fiber molded body 40 is held in a predetermined position by being held between the bottom wall 46b of the lower mold 46 and the upper mold 48, and the sheet 42
0, the outer peripheral surface was held in close contact with the cylindrical surface of the cylindrical hole 46a.

Next, 740° C. molten aluminum alloy (JIS standard AC4A) is poured into the mold cavity 52 defined by the lower mold 46, the upper mold 48, and the knockout pin 50, and the molten metal is fitted into the upper mold 48. 1000 kg/anl by Nja54! The pressurized state was maintained until the molten metal completely solidified.

When we investigated the cross section of the cylindrical outer periphery of the casting thus formed, we found that the outer periphery contained N1 with an N1 content of approximately 50%.
An alloy layer made of -Al alloy was formed, and it was observed that no alloying defects caused by peeling or cracking of the sheet occurred.

In addition, a composite layer made of aluminum alloy reinforced with alumina short fibers is formed between the alloy layer and the main part of the casting, and the composite layer is integrated with the alloy layer and the main part of the casting. It was recognized that there was.

Although the present invention has been described above in detail with reference to several embodiments, the present invention is not limited to these embodiments, and various other embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art that For example, the alloying element and the metal to constitute the casting may be any element or metal other than the N1 and aluminum alloys in the above embodiments, respectively. Further, the casting method in the method of the present invention is not limited to the high-pressure casting method as in the above-mentioned embodiments, but may also be a die-casting method, a centrifugal casting method, or the like.

[Brief explanation of drawings]

Fig. 1 is an oblique view showing a porous sheet made of Ni powder formed on a stainless steel plate, and Fig. 2 shows a manner in which the sheet and fiber molded body shown in Fig. 1 are arranged in a mold. 3 is a sectional view showing the casting process of the casting surface alloying method according to the present invention, which is carried out using the sheet and fiber molded body shown in FIG. 2, and FIG. 4 is the casting process shown in FIG. 3. A partially cut-away oblique view of the casting obtained as a result of the process, and Figures 5 and 6 show the defective alloying part of the casting when alloying is carried out without using a fiber compact. Figure 7 is a slanted view showing an annular plate-shaped porous sheet formed integrally with a fiber molded body, and Figure 8 is a slanted view showing the sheet and fiber molded body shown in Figure 7 in a mold. A sectional view showing how it is arranged,
Fig. 9 is an oblique view showing a porous sheet made of Ni powder formed integrally with the cylindrical outer peripheral surface of a cylindrical fiber molded body, and Fig. 10 is a sheet shown in Fig. 9. FIG. 3 is a cross-sectional view showing how the fiber molded body is placed in the mold. 2... Stainless steel plate, 4... Sheet, 6... Mold. 8... Mold cavity, 10... Fiber molded body,
12... Molten metal, 14... Plunger, 15... Knockout pin, 16... Casting, 18... Alloy layer,
20...Alumina short fiber, 22...Composite layer, 24.
・Main parts of castings. 26... Casting, 28... Alloy layer, 36... Fiber molded body. 38... Sheet, 40... Fiber molded body, 42...
sheet. 44... Mold, 46... Lower mold, 48... Upper mold, 5
0...Knockout pin, 52...Mold cavity, 54...Plunger Patent applicant: Toyota Motor Corporation representative
Attorney Patent Attorney Akashi 8 Tsuyoshi Figure 1 Figure 2 Figure 3 Figure 4 Figure 1N Kaisho 63-286264 (6);

Claims (4)

[Claims] (1) Forming a porous sheet made of fine particles containing an alloying element and a porous molded body made of a material that is substantially stable with respect to the molten metal that is to constitute the casting; arranging the sheet and the molded body in the mold so that the molded body engages with the inner wall surface of the mold and the sheet is maintained in contact with the inner wall surface of a predetermined portion of the mold by the molded body; A method for alloying the surface of a casting, in which molten metal is poured into the mold and the molten metal is solidified while being pressurized. (2) The method for alloying the surface of a casting according to claim 1, wherein the sheet is pressed against the inner wall surface of the mold by the molded body. (3) In the method for alloying the surface of a casting according to claim 1 or 2, the material constituting the molded body is reinforcing fiber or reinforcing particles. Law. (4) In the method for alloying the surface of a casting according to any one of claims 1 to 3, the sheet is formed integrally with the surface of the molded body. Alloying method for casting surfaces.