JPS59197371A - Production of casting having wear-resistant surface layer - Google Patents

Abstract

PURPOSE:To obtain a casting having a highly wear-resistant surface layer with good accuracy by placing a film on the surface of a pattern in tight contact therewith then a nonmagnetic female mold on said film, packing ferromagnetic alloy powder into the cavity formed in such a way, solidifying the powder, replacing the solidified female mold with the dry sand, removing the pattern, and charging a molten metal into such casting mold. CONSTITUTION:A cast iron pattern 2 is stuck on a plate 1, and a heated plastic film 3 is put thereon and is brought into tight contact therewith by evacuation. A nonmagnetic female mold 4 is placed thereon and alloy powder 6 of a ferromagnetic material having high hardness is packed into the space between said mold and the film 3. Electricity is then conducted to an electromagnet 7 to magnetize and solidify the powder 6 and thereafter the mold 4 is removed. A molding flask 8 for vacuum molding is further placed on the plate 1 and dry sand 9 is packed therein. A plastic film 10 is put on the flask and the sand and the sand 9 is solidified by evacuation. The evacuation in an evacuating chamber 1a and the conduction of electricity to the electromagnet 7 are stopped, and the mold is removed, by which a top mold (bottom mold) formed of the alloy powder 6 is obtd. A molten metal is charged into such casting mold to burn away the film and is intruded among the particles of the powder 6 and thereafter the solidification of the sand 9 is released.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a casting having a wear-resistant surface layer.

When manufacturing machine parts that require wear resistance by casting, there are methods to apply surface treatment to the surfaces of parts that require wear resistance, and for cast iron castings, use a chilled casting method to produce cast iron parts. However, even with the method described above, the wear resistance may still be insufficient for machine parts that are used under harsh conditions. For parts, one possible method is to adhere a thin piece of ceramic that has particularly high wear resistance to the surface of a part that requires wear resistance, or to overlay a wear-resistant alloy such as Stellite. However, with this method, it is difficult to manufacture with good dimensional accuracy, and with the former method, the adhesion between the base material and the flakes is uncertain, and the flakes may peel off from the base material during use. There is a possibility that

The present invention has been made in consideration of the circumstances described in "U", and is made by forming a surface layer with excellent wear resistance on the surface of the part of a cast product that requires wear resistance. The object of the present invention is to provide a method for producing a cast product having a wear-resistant surface layer, which produces Sl'r products with good dimensional accuracy and exhibiting sufficient wear resistance even when used under various conditions. .

As a result of repeated research, the inventor found that 1.
- Succeeded in achieving the stated objectives.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 6 show the manufacturing procedure of a camshaft by the method of the present invention.

First, as shown in FIG. 1, a cast iron model 2 attached to a vacuum molding plate 1-1 and a plate having a vacuum chamber 1a inside is heated to impart plasticity. Cover with the synthetic resin film 3.

The surface 2b of the cam nose portion 2a of the model 2 is located below the cam nose surface of the camshaft shown by the dotted line in the figure by the thickness of the wear-resistant surface layer 2C to be formed, and will be described later. This is done so that a space is formed between it and the female mold.

Next, as shown in FIG. 2, the pressure inside the vacuum chamber Ia is reduced by the usual vacuum molding method, and the air between the plate 1, the model 2, and the film 3 is removed through a small diameter exhaust hole provided in the plate 1. 1b, and the film 3 is brought into close contact with the surfaces of the plate 1 and the model 2.

Next, as shown in FIG. 3, a film 3 is placed on the surface of a female die 4 made of a non-magnetic material, for example made of an aluminum alloy, and having an inner wall surface 4a that is open at the lower end surface and corresponds to the surface of the cam nose portion of the camshaft. Place it on the cam nose part 2a of the model that is in close contact with it. The lower end surface of the female die 4 is brought into contact with the plate 1 via the film 3. The negative part of the female mold 4 is provided with a dish part 4b4- which is open to the upper end surface, and the bottom of the dish part 4b and the upper part of the inner wall surface 4a are communicated by a communicating part, and the communicating part has a communicating hole 5a. A plate-shaped valve 5 is provided so as to be able to reciprocate in a direction perpendicular to the clear cross section of the figure, and is configured to open and close between the dish portion 4b and the inner wall surface 4a. The plate-shaped valve 5 may be shaped like a round bar having a communication hole passing through it in a direction perpendicular to the axis, and may be rotatably fitted into a circular hole provided in the communication portion of the female mold 4 to be opened and closed.

When a high-hardness alloy powder 6 that is a ferromagnetic material and imparts wear resistance is put into the dish portion 4b of the female mold 4 and the valve 5 is opened, the alloy powder 6 is applied to the surface of the cam nose of the film 30 model 2. It is supplied to the space formed between the part that is in close contact with the mold 2b and the inner wall surface 4a of the female mold 4, and the space is filled. At this time, alloy powder 6
It is effective to apply slight vibrations to the model 2 in order to sufficiently fill the above space with. Alloy powder 6 is a ferromagnetic material as shown in "-" and has 1liJ abrasion resistance! ? For example, a mixture of one or more of high carbon powders such as ferrochrome, ferrotanksten, ferromolybdenum, and ferroboron is preferable.

Next, the electromagnet 7 provided on the back side of the model 2 is energized to magnetize and solidify the alloy powder 6 filled in the space.

Next, when the valve 5 is closed and the female mold 4 is removed, a film 3 is placed on the cam nose surface 2b of the model 2, as shown in FIG.
The solidified alloy powder 6a forms a surface layer on top of the solidified alloy powder 6a.

Next, as shown in FIG. 5, a vacuum molding flask 8 having a vacuum chamber 8a through which a small-diameter hole 8b passes through the inner wall is placed on the plate 1, and dry sand 9 is poured into the flask 8. and fill.

At this time, 1 to play 1 to ensure filling of dry sand 9.
It is effective to apply vibration to Next, a synthetic resin film 10 is placed over the casting flask 8 and the dry sand 9, and then the pressure inside the vacuum chamber 8a is reduced to remove the air coexisting with the dry sand through the holes 8.
The dry sand 9 is discharged to the outside of the flask 8 via the pipe b, and the dried sand 9 is solidified. If there is a risk that the surface layer formed on the model by the alloy powder 6a will collapse when dry sand is added due to its shape or position, the layer formed on the model by the alloy powder 6a may be It is preferable to cover with solidified mold material, such as a shell sand mold, which has a wall surface of the same shape as the inner wall surface of the mold, or with a film made with small diameter holes to provide air permeability.

Further, a suction pipe 8C having a small diameter hole (not shown) provided in the radial direction at a position facing inward away from the model 2 is connected to the flask 8.

It is desirable to ensure the evacuation of the air coexisting with the dry sand 9.

Next, the depressurization of the decompression chamber 1a of the plate 1 and the energization of the electromagnet 7 are stopped, the mold is removed, and a surface layer is formed with the alloy powder 6a on the surface of the cam nose portion as shown in FIG. is obtained.

The -1- mold and lower mold thus obtained are combined to form a mold,
When molten metal is injected into this, the part of the film 3 except for the cut surface is burned out, and the pressure inside the mold cavity is also reduced.
In the layer formed by the alloy powder 6a, molten metal easily penetrates between the particles of the alloy powder 6a and fills the gaps between the particles. The gas produced by the combustion of the film 3 is sent to the mold and the vacuum chamber 8.
It is discharged out of the flask via a and will not cause defects in the cast product due to gas.

When the pressure reduction in the vacuum chamber 8a of the flask 8 is stopped after solidification of the molten metal is completed, the inside of the mold returns to atmospheric pressure and the assimilation of the dry sand 9 is canceled, and the dry sand 9 is removed from the flask 8 along with the cast product. Can be taken out easily. The casting is thus removed and the dry sand is recovered.

The camshaft cast product manufactured as described above has alloy powder that significantly improves wear resistance on the surface of the cam nose, either rusted or melted and solidified to form alloy powder. The composition is rich in alloy components, and the durability of the camshaft can be greatly improved.

Figure 7 shows 28 mesh fii made into alloy powder as described above.
Using lij- high carbon ferrochrome powder, cast iron FC3
This is a micrograph at a magnification of 50 times showing the structure of the surface layer of the cam nose of a camshaft produced by casting 0.0 molten metal into the gap 12 between the high carbon ferrochrome powder particles 11. It has a structure in which a small amount of cementite crystallizes due to rapid cooling. Figure 8 shows the surface layer of the cam nose portion of a camshaft manufactured in the same manner as described in Figure 8, using high carbon ferrotinum powder as the alloy powder, which was sieved under a 65 mesh sieve and 100 mesh sieve. This is a micrograph with a magnification of 100 times showing the microscopic structure of the ferrochrome. It is soft tissue.

The camshaft manufactured in this way has high carbon ferrochrome 1. Because the particles have a surface layer of a structure surrounded by cast iron, they have extremely excellent wear resistance.In particular, camshafts with a surface layer of a structure as shown in Figure 8 are made of hard alloy powder particles. It can be seen that since the structure is surrounded by white cast iron, which is harder than that of through-casting A2i, it has even better wear resistance.

FIG. 9 shows the process shown in FIG. 3 when the method of the present invention is applied to the production of a toothed gear and a surface layer having the same structure as the force t1 nose portion of the camshaft is formed on the outer periphery. (a) is a cross-sectional view taken along the line IXa'Xa shown in (b), and (b) is a cross-sectional view taken along the line IXb-IXb shown in (a). Decompression chamber 12a and small diameter exhaust hole 21. A synthetic resin film 23 is in close contact with the second part of the cast iron model 22 attached to the plate 1-21 having the shape b and the second part of the cast iron model 22, and the second part of the model 22 has a film 23 of a certain thickness with respect to the dimensions of the product. It's just that small.

In the model 22, there is an inner wall surface 2/corresponding to the outer peripheral surface of the product.
An annular female die 24 made of aluminum alloy having a radius of 1.1 a is placed, and its lower end surface abuts the plate 21 via the film 23 so that the inner wall surface 24 a surrounds the model 22 .

At the upper part of the female mold 24, there is provided a dish part 24b which is open to two end faces. The bottom of the dish portion 2'lb is the outer peripheral surface 2 of the model 22.
2b and the inner wall surface 24a of the female mold, and the female mold 24 is positioned above the ridge or valley of the space between the inner wall surface 24a of the female mold 2b and the inner wall surface 24a of the female mold 24. This is done by means of a guide pin 21c erected thereon.

A disk-shaped valve 25 having a communication hole 25a located at the bottom of the female mold plate portion 24b is fitted between the upper end surface of the tooth portion 22a of the model 22 and the female mold 24, and the valve 25 is rotated. This allows opening and closing between the bottom of the female mold and the i'll2 space.

Put the abrasive alloy powder 2G into the Iuf type dish part 1b, rotate the valve 25 to position the communication hole 25a in the space, and open the valve 25. ,
The space [two alloys? 5) The alloy powder 26a filled in the space is magnetized and solidified by energizing the electromagnet 27 provided on the back side of the model 22.

Next, the valve 25 is rotated to shut off the alloy powder 26 in the female mold plate 2/Ib and the solidified alloy powder 26a, and the female mold 24
Cut out the mold.

The steps before and after the step shown in FIG. 9 are the same as those in manufacturing the camshaft.

In this way, a spur gear casting product is obtained in which a surface layer having extremely excellent wear resistance and having a structure similar to that shown in FIGS. 7 and 8 is formed on the outer circumferential surface.

In addition, in Example 1, the model was made of cast iron, and the alloy powder was magnetized together with the model by energizing the electromagnet.
Depending on the shape of the cast product, the model may be made of a non-magnetic material, and one or several electromagnets may be placed behind the back of the model.

In addition, it is not necessary for alloy powder 1 to remain as particles in the surface layer of the cast product; even if it is melted into the molten metal poured into the mold, the surface layer contains alloying elements that improve wear resistance. Needless to say, since it is contained in a high concentration, it is effective in improving wear resistance. In this case, the alloying elements described in "2" will be slightly diffused into the molten metal, and the thickness of the wear-resistant surface layer formed will be slightly thicker, so the space between the model and the female mold will be formed on the female mold side. In this way, it is also possible to perform finishing processing on a cast product.

When manufacturing non-ferrous metal castings such as copper alloys and aluminum alloys, alloy powders are free of additives in order to improve the wettability of molten metal to alloy powders or to prevent the crystallization of harmful intermetallic compounds. It is effective to use alloy powder particles whose surfaces are coated with copper, nickel, aluminum, etc. by electrolytic plating, vacuum evaporation, or the like.

As explained below, when the method of the present invention is used, it is possible to easily manufacture a cast product with a surface layer having excellent wear resistance and high dimensional accuracy. The utility value of ``Deki, Industry'' is great.

[Brief explanation of drawings]

1M to 6 are each of camshaft manufacturing by the method of the present invention]
7 and 8 are micrographs showing the structure of the wear-resistant surface layer formed on the surface of the cam nose of the force 11 axis manufactured by the method of the present invention. FIG. 9 shows one step of manufacturing a spur gear by the method of the present invention, (a) is a sectional view taken along the line IXa-IXa shown in (b), and (
b) is a sectional view taken along the line II b-IXb shown in (a). 1.2] - Play I-5la, 21a... Decompression chamber of Play 1-, Ib, 21b... Exhaust hole,
2.22...Model, 3,10.23...
Film, 4, 24...Female type, 4a, 24a
...Inner wall surface of female mold, 4b, 24b...Dish part of female mold, 5, 25, self, valve 6.26...Alloy powder,
6a, 26a... solidified alloy powder, 7,
27... Electromagnet, 8... Casting flask, 8a...
・Decompression chamber of casting flask, 9... Dry sand Applicant: Riken Co., Ltd. 15- Figure Section 7 8 Figure 400- 1°314

Claims (1)

[Claims] "Plate for vacuum molding having a vacuum chamber and said plate 1~"
A heated synthetic resin film is placed on the surface of the model placed on the second plate, and the pressure inside the vacuum chamber is reduced to exhaust the air below the filter 11 through a small diameter exhaust hole provided on the plate. In the first step of bringing the film into close contact with the plate and the model, an inner wall surface is opened at the lower end surface and corresponds to the part of the cast product that requires wear resistance, a dish section is opened at the upper end surface, and A female mold made of a non-magnetic material is provided with a communication part that communicates between the upper part of the wall and the bottom of the dish part, and a valve that allows the communication part to be opened and closed. Place the film from the bottom so as to form a space between the corresponding part and the part corresponding to the part, put ferromagnetic alloy powder having wear resistance into the dish part of the female mold, and insert the valve of the female mold. the valve of the female mold is closed, and the alloy powder is supplied and filled into the space formed by the film of the second model and the inner wall surface of the female mold through the communication part of the female mold; and the valve of the female mold is closed. 2nd step: energize the electromagnet provided on the back side of the model to magnetize and solidify the alloy powder filled between the fabrics, then remove the female mold to test the wear resistance of the cast product of the model. Form a surface layer made of the alloy powder on the part corresponding to the required part. Third step: Place a vacuum molding flask having a vacuum chamber on the plate, and fill the flask with dry sand. and then a fourth step of covering the flask and the dry sand with a synthetic resin film, reducing the pressure in the vacuum chamber of the flask to solidify the dry sand, and reducing the pressure in the vacuum chamber of the plate and the electromagnet. The fifth step is to cut out the current to obtain an upper or lower mold, and the sixth step is to combine the upper mold and lower mold to form a mold, inject molten metal into it, and solidify it. a seventh step of stopping the vacuum in the vacuum chamber of the flask to take out the cast product from the flask and recovering the IA dry sand; A method for manufacturing a cast product having a wear-resistant surface layer, in which the wear-resistant surface layer is formed in areas where properties are required.