JPS6046859A - Production of wear-resistant composite casting - Google Patents

Abstract

PURPOSE:To melt and activate the surface layer of an insert body and to weld and integrate both layers to one body by washing the insert body with a molten metal prior to insert casting then performing insert-casting. CONSTITUTION:A single body of a metal or a mixed body of carbide particles and the metal is fitted as an insert material Kb to the columnar core 11 in a casting mold in the stage of producing a wear resistant composite casting having the single material layer of the metal or the mixed layer of the carbide particles and the metal. A molten metal M1 as a washing metal is then cast into the mold 1 and the material Kb is washed by the molten metal while said metal is discharged from the lower part of the casting mold via a runner 14 to a well 15, by which the surface layer is melted and activated. The casting is thereafter formed by the molten metal mixture or the molten metal M2 of the single metallic material which casts the material Kb therein.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a wear-resistant composite casting by casting, in which a mixed layer of carbide particles and metal and a single metal layer are completely welded and integrated at the interface between the two layers.

A material in which a mixed layer in which carbide particles and metal are uniformly dispersed and a single metal layer is integrated has both the high wear resistance of the mixed layer and the strength and toughness of the single metal layer.

For example, a hollow cylindrical body as shown in FIG. Materials having a layered structure are suitable for rolls that require wear resistance, strength, and toughness.

As a method for manufacturing a hollow cylindrical body having such a two-layer structure, the second method is as follows.
Prepare a single metal cylinder (Kb) as shown in the figure, use it as a wave-filled body, fit it into the cylindrical core 01J of the mold (1) as shown in Figure 10, and place the molten metal inside the mold. One possible method is to cast a mixed molten metal of Kb and carbide particles and cast a single metal cylinder (Kb). After casting, the particles (P) are allowed to settle and coagulate in the molten metal 11, and after solidification is completed, the cast body is taken out of the mold and the upper feeder part (a) is cut and removed, and the lower part (b) is It has a hollow cylindrical shape as shown in Figure 1, and the outer surface layer is a mixed layer formed by casting mixed molten metal, and the inner layer is a single metal layer provided by a wave-preventing slat body (Kb). Obtained as a two-layer casting.

The composite casting thus obtained requires that the mixed layer and the single metal layer are completely welded and integrated at the interface. This is because if the welding is incomplete, the boundary becomes the weakest point in terms of strength, and breakage occurs from this point during use, making it impossible to withstand practical use.

However, if the mixed molten metal is simply cast as described above, the surface of the wave-preventing case body will be sufficiently melted and activated, and the welded metal will solidify without being fully welded. In particular, when the molten metal is mixed with carbide particles and is cast, a considerable amount of heat is absorbed by the particles, making it difficult to secure the amount of heat necessary to achieve complete welding. This tendency becomes more pronounced as the amount of molten metal poured becomes smaller, such as when forming the mixed layer 1 with a thinner layer thickness.

Contrary to the above, a cylinder (Ka) made of carbide particles (a homogeneous mixture of Pl and metal) as shown in Fig. 3 is prepared as a wave-blocking body, and molded as shown in Fig. 11. (1)
It is also possible to perform casting by installing the outer kO wall Q' along the IJ and casting a single metal molten metal (goods) therein. In this case, the molten metal to be cast is different from the above-mentioned one and does not contain carbides and molten metal, so the thermal conditions are relatively advantageous. It is only possible to instantaneously apply enough thermal energy to melt the material.

As an auxiliary measure to promote welding, it may be possible to preheat the wave-preventing case and mold, but heating to high temperatures will cause surface oxidation of the wave-preventing case, which will actually hinder welding. Copper plating is an effective way to prevent surface oxidation, but if the plating melts during preheating, the effect of the plating is diminished, so there is a limit to the preheating temperature, and in the end, it is impossible to completely prevent surface oxidation. It is extremely difficult to provide sufficient thermal energy to achieve proper welding through preheating.

The present invention has been made in order to solve the above problem, and a wave-preventing slug body made of a single metal (or a mixture of carbide particles and metal) is installed in the mold, and this is used to prevent the carbide particles and the molten metal from forming. When casting with mixed molten metal (or single metal molten metal), the molten metal is poured into a mold in advance and discharged from the bottom of the mold, and the heat of the molten metal melts and activates the surface layer of the casing body that prevents waves. Then, the mixed molten metal or the single metal molten metal is poured into a wave-preventing casing. That is, in the present invention, before casting, the wave-preventing casting body is coated with molten metal.
By applying "hot water washing" and then casting the material in a state where sufficient heat energy is applied to the wave-blocking material at the washing island, it was possible to completely weld and integrate both layers. .

Casting according to the present invention uses a single metal as a wave-preventing sill material, and casts it with a mixed molten metal of carbide particles and molten metal, and uses a mixture of carbide particles and metal as a wave-preventing siding material. This can be roughly divided into two types: one in which a single metal is cast using molten metal.

A specific example of the casting procedure of the present invention will be explained with reference to the drawings. Fourth
The example shown in the figure is made of 114 metal bodies as shown in Figure 2.
A cylinder 0(+)) having the desired wall thickness and body length is attached to a cylindrical core 01) in a mold as a wave-proofing body, and this is cast in a molten metal mixture of carbide particles and molten metal. By doing so, a hollow cylindrical casting having two layers as shown in FIG. 1 is obtained. At the bottom of the mold (1), a plurality of sump parts 0■ are provided at appropriate intervals in the circumferential direction for discharging and storing the washing islands that are cast before being cast from inside the mold. ing.

The mold is first washed with molten metal (Ml) in a ladle (
From step 2), the surface layer of the wave-proofing body (Kb) is poured through the casting hopper (3) and washed with hot water. If the molten metal flowing down from the hopper is directed toward the center of the hemispherical shape of the core 01) as shown, it will be distributed radially from the center of the top and evenly supplied to each part of the mold in the circumferential direction. In this hot water washing, the casting speed of the molten metal (washing water) (S I K
If the product forming part (■) in the mold is filled with molten metal by increasing the flow rate (S2 instant/5 sec) from the runner 04) to the sump Q51, the molten metal will be filled with waves. Sufficient thermal energy is provided to the body. At the same time, the mold itself receives a large amount of heat and is heated to a high temperature. The casting speed of this molten metal (washing island) (5IK9/5e
c) and the ratio of the outflow velocity (52K9/sec) (
51/S2) is preferably 1.2 or more. 1.2
If the amount is less than 1, the amount stored in the mold will be small and the supply of thermal energy to the wave-covered material will be insufficient.

However, if the ratio of (S1/S2) becomes too large,
The storage time of the molten metal in the mold becomes longer, and the temperature decreases due to stagnation of the molten metal, which actually reduces the amount of heat supplied to the wave-filled body.For this reason, the upper limit of (Sl/S2) is preferable. is set to 2.5.

When the surface layer of the wave-filled material (Kb) has been sufficiently melted and activated by the hot water washing, and the molten metal has completely flowed out of the mold and filled the sump 09, as shown in Fig. 5, When a molten mixture of carbide particles (P) and molten metal (M2) is cast, the interface between the wave surrounding material and the molten mixture is completely welded, forming a strong integral bond between the two layers. In addition, the molten metal mixed in the mold at the time of casting does not rapidly cool down or become viscous, and maintains sufficient fluidity, so the amount of molten metal is reduced as in the case of forming a thin mixed layer. Even if the amount is relatively small, particles in the molten metal can be sufficiently settled and coagulated,
Moreover, it is possible to form a homogeneous mixed layer in which the gaps between the aggregated particles are filled with molten metal. After the above-mentioned casting, wait until solidification is completed, take out the cast body, and cut and remove the two feeder parts and the lower runner part to completely separate the outer surface mixed layer and the inner single metal layer. A hollow cylindrical composite casting as shown in FIG. 1 which is tightly integrated is obtained.

In addition, in the above-mentioned casting, in order to prevent some of the carbide particles in the molten metal that is cast as a mixed molten metal from flowing out to the runner (conveying section), it is necessary to make the runner a small diameter and long shape. good.

When manufacturing a hollow cylindrical casting with a two-layer structure as shown in Fig. 1 using a cylinder (Ka) made of a mixture of particles and metal shown in Fig. 3 as a wave-filled body, as shown in Fig. 6. , along the outer wall 02 of the mold (1) (Ka)
is installed, and in the same manner as above, first pour the molten metal (washing water), preferably by adjusting the ratio of the casting speed to the flow rate from the mold (
S1152) may be set to 1.2 to 2.5 to sufficiently melt and activate the surface layer of the wave-covered body, and then cast a molten metal (M2) in which the wave-covered body is to be cast. In this case, it is also possible to use the same molten metal for the washing area and the casting molten metal, and to cast continuously.

The above casting examples all show examples in which the outer layer is a mixed layer and the inner layer is a single metal layer, but depending on the intended use and usage mode, the two-layer structure may be reversed in the relationship between the inner and outer layers. In some cases, a multilayer structure is formed in which both the inner and outer surface layers are a mixed layer and the intermediate layer is a single metal layer. Of course, the present invention includes not only hollow cylindrical castings but also solid body castings.

The shape of the mold used in the casting of the present invention is not limited to the example illustrated above, but for example, for the purpose of hollow cylindrical composite casting, the outer wall (2) and the inner wall 03 are concentrically formed as shown in FIG. A cylindrical mold (1) may also be used. In this case, the mold (1) is placed on a rotary table (4) as shown in the figure, and rotated around the spindle (5) at an appropriate rotation speed (for example, 100 to 150 rpm) by a drive device (not shown). It is best to perform casting while

In this way, the flow point of the molten metal (or mixed molten metal) poured from the casting hopper between the outer wall α2 and the inner wall 03 of the mold will shift sequentially in the cylindrical direction as the mold rotates, so the washing area will be The temperature distribution in the circumferential direction inside the mold of the molten metal that is cast as a molten metal, and the molten metal of a single metal or a mixed molten metal that is subsequently cast to fill the wave-filled body, is relaxed, and the mixed layer and metal are spread throughout the local direction. Complete adhesion and integration with the single layer can be achieved.

The carbide particles and metal that constitute the composite casting of the present invention are
Appropriate selection is made depending on the application and required performance of the casting. Typical examples of carbide particles include tungsten carbide (WC,
W2C) particles, tungsten titanium double carbide particles, etc. These may be used alone or in any combination. The particle size may be about 40-350 μm. In a casting mode in which carbide particles are mixed with molten metal and cast, the molten metal may be preheated to an appropriate temperature, for example, 400° C., in order to reduce the temperature drop during mixing. On the other hand, metals are generally ferrous metals such as cast iron and steel, but also nickel (Ni), cobalt (co),
Metals such as (Fe) or alloys thereof may also be used. Note that the metal constituting the mixed layer (A) and the metal constituting the single metal layer (B) may be the same type of metal,
Alternatively, it may be a combination of different metals.

Wave-protecting pads can be constructed in a variety of ways. For example, a cast body or the like may be used as a wave-proofing body made of a single metal. On the other hand, the wave-proofing body of the mixture is prepared by preparing a mixed powder of carbide powder and metal powder using a sintering method.
If necessary, a suitable molding aid or sintering aid can be mixed with this and subjected to a conventional compacting and firing process to produce a sintered body, or a casting method can be applied to produce carbide particles. It is also possible to produce a cast body by pouring the molten metal into a mold and allowing the particles in the molten metal to settle and agglomerate.

The filling rate of particles in the mixed layer can be determined as desired, but in terms of volume ratio, it can generally be 60 to 70%.

Although there are no restrictions on the material of the mold used for the casting of the present invention,
For example, a firing mold (1) for precision casting can be used by installing it in a case (7) with a back sand (6) as shown in the figure, and it is heated in a heating furnace to
Preheating to 800°C helps reduce heat loss of the molten metal in the mold at the time of casting. If surface oxidation of the wave-preventing body becomes a problem during preheating, copper plating or other oxidation-preventing coating may be applied to the surface in advance.

Example In the casting apparatus shown in Fig. 1, a mold (firing mold) (1
), a single metal cylinder (Kl) made of nihard cast iron was adhered to a columnar core 01) as a wave-preventing slug body, and 12 tons of molten cast iron at 1600°C was poured into it as a wash.
After the surface layer of the single metal cylinder was melted and activated, a mixed molten metal of tungsten carbide (W2C) particles and nihard cast iron molten metal was cast.

The molten metal pouring speed (Sl) during hot water washing is IK9/sec, and the outflow speed (S2) from the runner 04) to the sump α9
The dimensions of the runner 04) were determined so that the ratio was 0.5 to /sec, and the ratio of (Sl/S2) was set to 2.0. There are a total of four potholes, and their total volume is equivalent to six glazes of cast iron.

Details of the casting conditions are as follows.

[1] Set the mold (1) in the case (7) with back sand (6), and after attaching a wave-proofing body, preheat it in a heating furnace. Mold temperature 700℃ just before casting.

(11) Shape (see Figure 8): Outer diameter (DI) 200mm
, Core diameter (Da) 100mm0 [2] Wave-preventing body (1) Cast body of nihard cast iron. The surface is coated with copper plating.

(11) Shape (see Figure 8): Outer diameter (D2) 150 plates,
Inner diameter (Da) 100mm, height Hl) 60mm0 [
3] Mixed molten metal (1) Pouring temperature: 1600°C (11) Casting amount: In Figure 8, the melt surface height H2 (800
mm).

flail W2C particle size: average 280 mesh.

(lvl Mixed amount of W 2 C particles: In Fig. 8, the area from the lower end to the upper end of the wave-blocking body (height Hl-60
mm) in an amount sufficient to form a mixed layer (particle filling rate of approximately 60%).

(v) Particle preheating temperature during mixing into molten metal: 400°C.

By the above casting, a hollow cylindrical casting having two layers, an outer mixed layer (mixed molten metal casting part) and an inner single metal layer (wave-preventing case part) was obtained. It was confirmed that the interface between the two layers was completely welded and integrated (100% welded) over the entire circumference and entire length. As a comparative example, a hollow cylindrical casting with a two-layer structure was obtained under the same casting conditions as above, except that a mold without a sump was used and the hot water washing preceding the casting was omitted. was incomplete, showing only about 70% welding.

Example 2 A cylinder (Ka) made of a mixture of carbide particles and nihard cast iron as a wave-preventing sill material was installed in a casting mold (firing mold) (1) as shown in Fig. 6, and nihard cast iron heated at 1600°C was placed in it. Molten metal is poured as washing water, and the surface layer of the cylinder is melted.
While activated, the molten metal was continuously cast as the molten metal to be cast into a cylinder, and the casting was stopped when the height H2) of the molten metal level in the mold reached 300 mm.

The casting speed (Sl) of cast iron melting at 1 hour is 1/s.
ec, and the outflow speed (s2) to the water reservoir 09 is 0.
The dimensions of runner 0 (a) were determined so that the time would be 77 seconds, and the ratio of (S 1 /S 2 ) was set to 1.4. The total volume of the sump corresponds to cast iron 5Y4.

[1] Mold (1) Attach a wave-preventing body and preheat in a heating furnace. Mold temperature 600℃ just before casting.

(II) Shape (see Figure 9): Outer diameter (DI) 180m
m.

Core diameter (D3) 90mm0 [2] Cast body with a particle filling rate of 65% made by mixing wave-preventing slug body (11w2c 2 layers (average grain size 280 mesh) and nihard cast iron elution. The surface is coated with copper plating. Used.

(11) Shape (see Figure 9): Outer diameter (DI) 180
mm, inner diameter (D2) 140mm, height Hl) 60mm
A hollow cylindrical casting having two layers, an outer mixed layer (wave-preventing case part) and an inner single metal layer (molten metal casting part) was obtained by the second casting. It was observed that the interface between both layers exhibited a state of complete welding and integration (100% welding) over the entire circumference and entire length. As a comparative example, a casting obtained by using a mold without a 1gJ reservoir, omitting hot water washing before casting, and setting the other conditions the same as above showed only 90% welding. .

As described above, according to the present invention, a composite casting in which a mixed layer and a single metal layer are completely welded and integrated can be obtained. Such composite castings have both the high wear resistance of a mixed layer and the strength and toughness of a single metal layer due to the strong bonding relationship between both layers.
It is suitable for various uses that require these characteristics, such as rolls.

[Brief explanation of the drawing]

Figure 1 shows an example of a composite casting consisting of a mixed layer and a single metal layer ([■] is a plan view, CrD is a XX cross-sectional view), and Figures 2 and 3 show an example of a composite casting made of a mixed layer and a single metal layer. The illustrative figures ([■] are plan views, [II] are XX cross-sectional views, and Figure 4 CI) are longitudinal cross-sectional views showing examples of the casting procedure of the present invention;
■] is a plan view of the mold part, FIG. 5 is a vertical cross-sectional view showing the casting situation inside the mold, FIGS. 6 and 7 are vertical cross-sectional views illustrating another casting method of the present invention, and FIG. FIG. 9 is an explanatory cross-sectional view of a mold part related to an example, and FIGS. 10 and 11 are longitudinal cross-sectional views of a mold part showing a comparative example. 1: Mold, 11: Core, 14: Runway, 1C: Reservoir, A
: Mixed layer, B: Single metal layer, Ka, Kb: Wave-preventing solid body, P: Carbide particles, M: Metal. Agent Patent Attorney Miyazaki Shinhachibe

Claims (1)

[Claims] (1) A method for manufacturing a wear-resistant composite casting having a single metal layer and a mixed layer of carbide particles and metal, in which the single metal or the mixture of carbide particles and metal is installed as a wave filling material in the mold. Then, when casting this in a mixed molten metal of carbide particles and molten metal or a dormant molten metal, the molten metal as a washing liquid is poured into the mold in advance and is not discharged from the bottom of the mold. A method for producing a wear-resistant composite casting, which comprises melting and activating the surface layer of the surumi material by washing it with hot water, and then casting a mixed molten metal or a single metal molten metal into which the surumi material is cast.