JPH02268964A - Wear resisting pump parts and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to surface-modified metal parts and a method for manufacturing the same, and is particularly applicable to industrial machine parts such as pump impellers and casings that require wear resistance, and excavators. , relates to a surface-modified part suitable for parts of construction machines such as bulldozers, and a method for manufacturing the same.

[Conventional technology]

Generally, in order to improve the wear resistance of parts, the first method is to make the material of the entire part wear-resistant.
, A method of forming a wear-resistant thin layer on the surface of the part (second method), a method of hardening by subjecting only the surface to heat treatment such as quenching (third method), a method of forming a thin wear-resistant layer on the surface of the part (third method), a method of forming a thin wear-resistant layer on the surface of the part (third method), and a method of forming a thin wear-resistant layer on the surface of the part (third method). (the fourth method).

Examples of materials belonging to the first method include high Cr cast iron in the case of cast iron, and high Mn cast steel (Hutfield M) in the case of cast steel. The latter is aimed at surface hardening through work hardening.

Both methods involve adding alloying elements to improve wear resistance, which improves the hardness of the entire part.

Examples of methods belonging to the second method include hard chrome plating on the surface of parts, electroless Ni plating with dispersed ceramic particles, and ceramic spraying.

As belonging to the third method, there are methods of hardening the metal surface by utilizing the martensitic transformation of iron, such as surface hardening, carburizing, or nitriding hardening by high frequency heating, plasma heating, etc.

As belonging to the fourth method, there is a method in which a ceramic part is fixed to a metal part by some method and used as an integral part.

As belonging to this fourth method, for example, a pipe in which ceramics are shrink-fitted (cast) is also included (Japanese Patent Application Laid-Open Nos. 60-216968 and 60-223655).

[Problem to be solved by the invention]

The above-described method has problems in preventing abrasive wear caused by earth and sand in pump parts, construction machine parts, and the like.

In other words, the first method of making the entire part wear-resistant is to harden not only the surface layer but also the inner surface, which provides good wear resistance. This tends to lead to a decrease in properties because, in general, when a material becomes hard, it becomes brittle on the dark side. Furthermore, since the overall quality is high, the cost tends to increase. Furthermore, since the entire structure is highly hard, machining of the boss and other parts requires a large number of man-hours. Therefore, this method is not suitable for applications where the surface layer requires wear resistance and the part as a whole requires toughness.

The second method of applying a wear-resistant coating such as plating or ceramic spraying to the surface of a component has the following problems.

It is difficult to obtain uniform thickness with thermal spraying. However, in the case of parts that require dimensional accuracy, machining is required after thermal spraying. The thickness of plating is relatively uniform, and the thickness uniformity of electroless plating is particularly excellent. And the hardness of the hard chrome plating "composite plating" itself is H at the front neck.
V900, and the latter has a high Hv of 1300, compared to ordinary steel which has a Hv of about 200 to 300.
It has ~7 times the hardness, and the abrasion resistance of the film is excellent.

However, these thin films (usually plating is about 50 μm)
Hereinafter, thermal spraying is fine as long as the fL film (approximately 500 μm or less) is less than the conditions that can withstand wear, but if the conditions are even more severe and the fL film disappears, the wear loss of the base metal behind it will increase rapidly. However, eventually the parts no longer serve their purpose. For example, when the above plating (20 μm) was applied to the surface of a hammer iron and a mixture of water and sand was sprayed at high speed onto the test surface, all the plating was worn off in about 0.5 minutes.

In the third method, which involves surface heat treatment, the shape and dimensions of the product may be distorted due to heating, and cracks may occur. Therefore, in the case of parts that require flattening precision, machining is required again.

Especially when the material is cast iron, this method is rarely used because the product tends to crack due to expansion of graphite.

The fourth method of casting ceramics is limited to a pipe-like shape and requires the metal to be placed on the outside.
Therefore, it can only be used for very limited purposes, and
There is also a method of adhering (joining) ceramic molded parts to metal parts, but due to the brittleness of ceramic itself, abrasi
veJSil! There are many problems with high-speed rotating bodies that exhibit wear and tear.

Furthermore, since the overall quality is high, the cost increases significantly. Therefore, this method is not suitable for applications that require abrasion resistance in the surface layer and toughness of the entire part.

With the above-mentioned understanding of the problems of the prior art, the object of the present invention is to provide a surface-modified component that has both good wear resistance and toughness in a harsh environment where it is subjected to severe abrasive wear, and a method for manufacturing the same. Our goal is to provide the following.

[Means to solve the problem]

The above purpose is to improve the surface layer of parts that truly require wear resistance (e.g., approximately 2 to 6 degrees deep from the surface layer) in iron alloy cast parts used for industrial machinery and construction machinery, depending on the base material composition. This is achieved by creating a different high wear resistance structure.

The differences between the present invention and the fourth method of the prior art described above are as follows.

That is, a method of obtaining wear-resistant parts by casting ceramics (JP-A-60-216968, 60-2
No. 23655), the shape of the part is limited to a pipe as shown in FIG. 7, and the metal must be on the outside.

This is because ceramics are strong against compressive stress but extremely brittle against tensile stress.

Therefore, although the cited method is an effective method, it can only be used in extremely limited cases.

On the other hand, in the case of the present invention, as shown in Figure 2, the composition of the surface layer of the component, whether it is the outer surface or the inner surface, is changed arbitrarily to impart properties such as wear resistance. be able to.

Furthermore, properties such as abrasion resistance can be imparted not only to the entire outer and inner surfaces but only to necessary portions of the surface layer.

In addition, in the cited prior art, the conversion from metal to ceramic is discontinuous, so to speak, but in this book, the boundary between the two changes gradually, so there is no possibility of destruction at this boundary. Cracks hardly occur.

[Effect]

In addition, in the case of the present wIt invention, only the truly necessary portions are changed in characteristics (for example, imparted with high wear resistance), so that no adverse effects such as deterioration in machinability occur.

In this way, an iron alloy part can be obtained which has hybrid properties in which the necessary parts of the surface layer have high hardness and wear resistance, and the parts other than this surface layer have high toughness and good machinability.

Next, the principle of the manufacturing process of the present invention will be explained.

(1) Applying a mixture of Fe-Cr powder and a small amount of binder (organic binder such as PVA aqueous solution) to the inner wall of the cavity 4 of the mold 3 shown in FIG. 3 by some method;
It is applied to a carrier and set on the inner wall to form Fe-CrM5.

(2) Assemble this mold and use the medium (water, etc.) in the binder.
After evaporating, molten cast iron 6 is poured from the sprue (see Figure 4).The molten metal 6 reacts with the Fe-Cr powder present on the inner wall of the mold space until it solidifies, forming a constant surface layer of 1. A large number of CrCz particles are dispersed in the thick portion (see FIG. 6).

(3) After the molten metal solidified, it was demolded to form a CrCz particle-dispersed layer with a constant thickness of the surface layer.

The above principle greatly improves the wear resistance of the necessary parts of mechanical parts.

Moreover, since only the surface layer of this part is highly hardened, it does not exhibit the brittleness that is common in general high-hardness parts and general ceramic parts, which have high hardness throughout, and can be rotated at high speeds. You can use it with confidence even if you have it.

The outline of the present invention has been described above, and next, the main components in each step will be defined and explained.

(10 Reactant) It is necessary to be Fe-Cr powder, and its form may be a powder or one formed into a predetermined shape by compression molding. Pack it or apply it to the required place and place it on the inner wall of the mold.

The latter can be inserted in the required location in cassette format.

(2, Casting metal) Any molten iron, i.e., molten cast iron or molten cast steel, will do.The casting temperature should be slightly (100 m
~200℃) The higher the temperature, the better.

(3. Castings) In principle, the type does not matter, but if the mold is heated before casting to ensure a more reliable reaction with the molten metal, the type may be determined based on the heating temperature. It is.

For example, if the mold is heated to 700°C before casting, molds that are usually said to be organic (furan resin molds, shell molds, etc.) cannot be used due to their heat resistance. It's self-evident.

(4. Heating method for castings) This is carried out as needed, and the general method is to place the entire mold in a furnace and heat it in an atmosphere. A method of heating may also be used.

(5. Vacuum suction during casting core) This is also performed as necessary. Simultaneously with casting, by vacuum suction from the outside of the mold, the molten metal is subjected to a force that presses it against the inner wall of the mold cavity. Therefore, the molten metal and the inoculating alloy agent (Fe-Cr) come into close contact, thereby sufficiently promoting the inoculating reaction. However, in this case, if the degree of vacuum is too high, defects such as metal-pemtration will occur.

Appropriate suction force should be determined and applied in practice by also considering the roughness of the mold particles, that is, the air permeability of the mold.

〔Example〕

First, to explain the basic structure of surface-modified parts, the cross-sectional layer of a metal part that requires wear resistance has a structure as shown in Figure 1. As shown in Figure 8.

In other words, the surface layer, for example, the thickness of 5rrn from the surface (this value can be changed freely depending on the case) is a high hardness layer [5], and the other part is a normal iron alloy as the base metal 8. It becomes.

FIG. 9 shows the hardness distribution of a cross section of a part in which the present invention was applied. As shown in the reference photo, Cr Cz particles are dispersed over the entire surface with a thickness of about 2.5Mn, and the thickness is about Hv = 700.
It has a hardness of ~1500, which is extremely high hardness. On the other hand, the hardness of the base metal was Hv'4220, which shows that the effect of the present invention is remarkable.

Therefore, even if hard particles such as earth and sand collide with the special alloy structure on the surface of the component, for example, the high hardness layer 5 having wear resistance, the surface structure has a high hardness (Hv 700 to 1500), so there is almost no wear.

Furthermore, even when an impact force is applied during use, the impact resistance of the part as a whole does not deteriorate, and since it maintains tensile strength, it does not easily break, resulting in good results due to the surface wear resistance. You can get it, but there is no harm at all.

In addition, in the above, high M
The hardness, corrosion resistance and other properties of gold according to the invention, such as the thickness of the n-layer, can be varied.

Above, the constituent elements of the present invention have been defined and the overall structure has been described.

Specific examples of the present invention will be described below.

(Example 1) As shown in FIG. 10, high carbon Fe-Cr powder (C'
r: 50%): 100 parts of PVA aqueous solution (PVA 20%
) was compacted and molded to a thickness of 5 mm, and then dried to solidify the molded product.

Thereafter, molten ordinary cast steel 6 at 1700° C. was injected from the top of the mold 3 through the sprue 9. When the mold 3 was removed after the molten metal 6 had solidified, a highly hard part (wear-resistant part) in which CrC2 particles were dispersed 0 to 5 nm below the surface of the casting could be obtained.

(Example 2) As shown in Fig. 14, 100 parts of Fe-Cr powder and the PVA binder of Example 1 are mixed uniformly on the surface of a porous carrier 10 made of a three-dimensional metal strip made of aluminum. The slurry is applied by any method (eg, dipping, coating, etc.).

After setting this at a predetermined part of the inner wall of the mold, a quasi-steel molten metal was poured in the same manner as in Example 1, thereby making it possible to obtain a thicker layer of high hardness than in Example 1 (see FIG. 16).

According to this example, the thickness of the cured layer can be changed arbitrarily by changing the thickness of the carrier depending on the location.

(Example 3) As shown in FIG.
iron powder = 100 parts by weight, No. 3 water glass aqueous solution (Sgl,
6): The inoculating alloy layer 5 shown in Example 2 is placed on the inner wall of a 6-part COz mold to a thickness of 6 m.

A high-frequency coil 11 is installed outside the mold 3, and the iron powder mold 3 is induction-heated by high frequency to about 300'C, and the heat is transferred to the inoculum alloy M5.
5 at a similar temperature.

Next, a decompression box 12 is installed at the bottom of the mold 3, and molten cast iron 6 is poured from the sprue, and then immediately thereafter.

By reducing the pressure in the vacuum box 12 at the bottom of the mold 3, the molten metal 6 and the inoculum metal N5 are brought into close contact with each other to integrate and react.

After solidification of the molten metal 6, the mold was removed to obtain a cast iron product having a wear-resistant surface.

(Embodiment 4) FIGS. 18, 19, 20, and 21 show the casing 13, the centrifugal impeller 14 inside the casing 13, and the inducer 16 that rotates together with the impeller 14 in the suction port 15. , a pressure relief valve 27 connected to both sides of the inducer for returning fluid to the upstream end of the inducer 16 when the pressure differential across the inducer 16 occurs above a predetermined level. It is arranged to be open.

As shown in FIG. 18, the inducer 16 and the impeller 14
The present invention was applied to a centrifugal pump that is integrated with.

That is, the applied parts are the outer surface of the inducer 16, the outer surface of the impeller 14, and the inner surface of the casing 13, on which the modified layers 13a, 14a+16 according to the present invention are applied, respectively.
Indicated by a.

〔Effect of the invention〕

According to the present invention, the surface layer can have special wear resistance such as high hardness or work hardening, and the inside can have special surface characteristics such as ordinary cast iron (cast steel). , ordinary cast iron products (normal M steel weight) can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a surface-modified component according to an example of the present invention, FIG. 2 is a schematic diagram comparing and explaining the cross-sectional characteristics of the present invention and a conventional example, and FIGS. FIG. 6 is a sectional view illustrating the steps of the present invention, FIG. 7 is a sectional view of a conventional example,
Fig. 8 is a schematic diagram showing the distribution of C r Cz particles according to an example of the present invention, Fig. 9 is a characteristic diagram showing the hardness distribution of the Fe-Cr reaction cross section in the present invention, Figs. 1
Figure 2 and Figure 13, Figure 14, Figure 15 and Figure 1
6 is a sectional view illustrating other steps of the present invention. FIG. 17 is an exemplary sectional view of one step of the present invention, and FIG.
The figure is a cross-sectional view of a pump casing to which an example of the present invention is applied, Figures 19, 20, and 21 are partial cross-sectional views of Figure 18, respectively, and Figure 22 is a Fs-Cr reaction according to an example of the present invention. This is a 400x micrograph of a cross-sectional metal structure. 3... Mold, 4... Mold cavity, 5... Inoculum layer (
Fe-Cr), 6... Molten metal for casting, 7... Special surface layer (wear-resistant layer), 8... Base metal layer, 9... Runway, 10... Support rod diagram Unfigured 5 =-': df/14 (, CrCzZft sec R Jiro - Snore Ittaka (Rice snore sure figure) Nth Exit No. z Diagram ■ /7 Diagram B Diagram x 4ρθ

Claims (1)

[Claims] 1. An iron alloy casting characterized in that CrC_2 particles are dispersed only in a predetermined portion of the surface layer. 2. A wear-resistant pump component characterized in that CrC_2 particles are dispersed to a constant thickness only in a predetermined portion of the surface layer that requires wear resistance. 3. Fe-Cr powder is present in a predetermined part of the inner wall of the mold cavity, and then molten iron is poured in. By reacting the molten metal with Fe-Cr, CrC_2 particles are dispersed only in the above-mentioned surface layer and a certain thickness directly below it. A method for producing surface-modified castings characterized by high hardness. 4. Surface-modified iron characterized by applying Fe-Cr powder to the coating mold and the inner wall of the mold cavity, and then casting molten iron to make the surface layer of the casting a high-hardness structure with CrC_2 particles dispersed therein. Manufacturing method for castings. 5. A surface modification characterized in that a Fe-Cr powder compact molded into a predetermined shape is placed in a predetermined position in a mold cavity, and then molten iron is cast to make the surface layer of the casting a high hardness structure in which CrC_2 particles are dispersed. Manufacturing method for quality castings.