JPH11123617A - Microscopic crack progress preventive method and earth abrasion resistant part obtained by applying its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent progress of a crack by applying a pastelike powdery brazing material containing flux to a surface part where at least a microscopic crack is generated, and permeating the brazing material inside the microscopic crack by melting the brazing material by heat treating thereafter. SOLUTION: A pastelike powdery brazing material containing flux is applied to a surface part of a repairing object material containing a microscopic crack generated in hardfacing part or a crack progressing up to a base material. The brazing material is melted by heat treating thereafter, and the brazing material is permeated inside the microscopic crack. Therefore, the repairing object material is repaired. In this case, the flux has a function of improving wettability of the brazing material by reducing a thin oxide film inside of the crack, and can permetate the brazing material up to the crack tip by a capillary phenomenon without performing special treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing the growth of microcracks formed on a hardfacing material after a hardfacing material has been applied, and to a sediment-resistant wear component obtained by applying the method.

[0002]

2. Description of the Related Art Conventionally, for example, in a site where abrasion resistance is locally required, such as a cutter bit in a tunnel excavator or a wear plate used as a bulldozer discharge plate,
It has been practiced to provide wear resistance by forming a hardfacing layer.

[0003] Incidentally, since the hardfacing portion formed on the base material as described above is formed of a material having high hardness and good abrasion resistance, it is difficult for plastic deformation to occur and cracks are generated. It has the property that the generated crack is easy to grow. Therefore, for example, when the hardfacing is allowed to cool in the cooling process after application of the hardfacing, a tensile stress is generated in the hardfacing part by thermal stress, and a crack is generated in the hardfacing layer by the stress and the case is developed. There is. In addition, the base material on which the hardfacing is applied is often formed of a material in which a crack is likely to develop, though not as much as the hardfacing portion. For this reason, cracks generated from the surface of the hardfacing portion may extend into the base material after hardfacing or when the component is used, and in the worst case, breakage may occur.

[0004] When an impact force is applied in the vicinity of a crack generated in the hardfacing portion, chipping, cracking, etc. may occur and the overlay portion may be damaged. This damage is 0.1mm
In some cases, minute defects occur continuously, or large defects of about 10 mm occur, which significantly shortens the life of components. For example, in the case of earth and sand wear parts in construction machines and tunnel excavators, they often come into contact with rocks or the like in an impact manner, and the situation in which wear progresses due to the continuation of defects as described above tends to occur.

As prior art related to the present invention,
Repair methods for repairing cracks or the like generated on the surface of a structural member or the like have been proposed in the following publications. SUMMARY OF THE INVENTION A method for repairing surface cracks such as surface cracks, surface scratches, and cracks in tanks and the like, in which a low melting point powder is filled in a surface crack portion, and the surface crack portion filled with the low melting point powder is filled. Alternatively, by heating the surroundings with a gas flame or the like, the powder is melted to close the crack. A method for repairing damage to a super heat-resistant alloy, in which a metal alloy powder mixture containing no silicon is directly applied to a damaged portion of a super heat-resistant alloy body, or the damage or abrasion is caused. The surface extension is regenerated, the low melting point powder is brought into contact with that part, the high melting point powder and the nickel powder are alloyed, heated for a sufficient time, and then cooled. JP, 3-275288, A In addition to irradiating a laser beam to the surface of a build-up layer where a defect has occurred, and supplying a build-up powder material to perform repair build-up. JP, 2-250727, A method of repairing a crack of a brazing part, performing vacuum sealing by brazing to a crack generated in a brazing part,
Next, a hot isostatic pressure treatment is applied to close and repair cracks.

[0006]

However, in the above-mentioned prior art, the low melting point powder is fed into the crack together with a non-reducing penetrant such as kerosene, etc., and is heated and melted. There is a problem that the powder does not enter the inside of the crack when the crack is minute. In addition, none of the above-mentioned conventional examples can be a means for preventing the development of the micro-cracks generated in the hardfacing portion intended for the present invention.

[0007] The present invention has been made in view of the above-mentioned problems, and it is possible to seal a crack even at the tip thereof even if it is a small crack, thereby preventing the crack from growing. Provided is a method for preventing the growth of micro-cracks, which can prevent cracks and chips caused by cracks and corrosion of cracks. It is intended to provide.

[0008]

Means for Solving the Problems and Action / Effect To achieve the above-mentioned object, the method for preventing the growth of microcracks according to the first aspect of the present invention relates to a method for preventing microcracks from forming on a hardfacing portion after a hardfacing material is applied. A method for preventing the growth of cracks, in which a paste-like powdered brazing material containing a flux is applied to at least the surface portion where the microcracks have occurred, and then the brazing material is melted by heat treatment and penetrated into the microcracks. It is characterized by the following.

In the present invention, a micro-crack (having a width of, for example, 0.15 mm or less) or a base material formed in a hardfacing portion (bead) on which a hardfacing material such as a high chromium iron alloy or tungsten carbide is applied. A paste-like brazing material containing flux is applied to the surface of the repaired material containing cracks that have grown to the surface, followed by heat treatment to melt the brazing material and reduce the size of the brazing material. The material to be repaired is repaired by infiltrating into the crack. At this time, the flux has the function of reducing the thin oxide film inside the crack and improving the wettability of the brazing material, and allows the brazing material to penetrate to the crack tip by capillary action without special treatment. Since the molten brazing material flows into the crack from the surface in this way, even if the crack is thin and long, the brazing material can easily penetrate, and even if it is an irregular crack with a narrow entrance and a large depth, there is no problem. Cracks can be filled with brazing material. Here, the brazing material and the flux are preferably selected in consideration of the wettability with the hardfacing portion or the base material as the material to be repaired, the heat treatment temperature, and the like. For example, in the case of a hardfacing portion made of a high chromium iron-based alloy, the wettability is poor, but the wettability can be improved by adding Ni to the brazing material. In order not to impair the original performance of the material to be repaired, the melting point of the brazing material is preferably set to a temperature not lowering the performance of the material to be repaired, such as hardness and wear resistance. When the brazing material does not penetrate into the crack, it is preferable to use a material having a low viscosity as the brazing material. According to the method of the present invention, the repair can be performed even if the material to be repaired has a complicated shape, and the side surface can also be repaired depending on the viscosity of the paste.

Next, a method for preventing the growth of microcracks according to the second invention is a method for preventing the growth of microcracks that have occurred in a hardfacing portion after a hardfacing material has been applied. The method is characterized in that a flux is applied to the portion and heat treatment is performed, and thereafter the brazing material is penetrated into the inside of the micro-crack by means of a filler.

In the present invention, the material to be repaired including the microcracks and the like generated in the hardfacing part on which the same hardfacing as described above is applied is subjected to a heat treatment by applying a flux to the surface part thereof. Thereafter, the material to be repaired is repaired by infiltrating the brazing filler metal into the inside of the micro-crack by means of the brazing. The method of the present invention is particularly effective when partially constructing a part of a large component, and can repair even a complicated shape. However, it is not suitable when the crack is not visible.

Further, a method for preventing the growth of microcracks according to the third invention is a method for preventing the growth of microcracks that have occurred in a hardfacing portion after a hardfacing material has been applied, wherein at least a surface portion where the microcracks have occurred. And a rod-shaped or foil-shaped brazing material is placed thereon, followed by heat treatment to allow the brazing material to penetrate into the microcracks.

According to the present invention, a flux is applied to the surface of a repaired material including microcracks and the like generated in the hardfacing portion on which the same hardfacing as described above has been applied, and a bar-shaped or foil-shaped material is applied. The material to be repaired is repaired by placing the brazing material and then heat-treating the material so as to penetrate the inside of the microcracks. In addition, it reheats as needed and a brazing material penetrates into the inside of a crack. The method of the present invention is a simple method when applied to the entire area where a crack may occur. However, the work surface is limited to a flat surface.

In each of the above inventions, the heat treatment may be a treatment in which the brazing material is heated to a temperature at which the brazing material melts to the tip of the microcracks by a heating furnace. If the heat treatment by the heating furnace is adopted, the repair work can be automated. The heat treatment may be heating to a temperature at which the brazing material melts to the tip of the microcrack by heating with a high frequency or a gas burner. In the case of such a heat treatment, there is an advantage that repair can be easily performed at an operation site. Note that this heat treatment may be combined with ordinary quenching and tempering heat treatments.

The method for preventing the growth of microcracks according to each of the above-mentioned inventions is a method for exchanging parts almost impossible, such as a sand-wearing part of a tunnel excavator, or a sand-wearing part weighing several tens kg of a large construction machine. It is particularly suitable to be applied to those in which the replacement of parts is difficult, and those in which the life of the parts is expected to be prolonged are particularly required. Examples of these parts are cutting blade parts or wear plates of construction machines such as bucket teeth, bucket edges, cutter bits, side cutters, ripper points, etc.
Traveling equipment parts of construction machines such as lower wheel rollers and crawler track links. Of course, the present invention can also be applied to a cutting blade for crushing wood, concrete, and metal products.

[0016]

Next, specific examples of a method for preventing the growth of microcracks according to the present invention and a sediment-resistant wear component obtained by applying the method will be described with reference to the drawings.

As the material to be repaired, L200 × W50 × t2
No. 0 mild steel with a hardfacing part containing ultra-hard particles, and the hardfacing layer (4 to 5 mm thick) has many cracks (part of the cracks ), And a crack sealing experiment was performed at an experimental level as shown in Table 1. As a result of this experiment, the sealing effects were all good.

[0018]

[Table 1]

The chemical components and characteristics of the brazing filler metal used in the above-described experiments are as follows. In addition, the number showing each component is wt%. (1) Silver solder (BAg-1) Ag: 45.3, Cu: 15.6, Cd: 23.8, Z
n: The rest Characteristics: Excellent flowability, narrow melting temperature range,
Can be used for any type of slow heating. (2) Silver solder (BAg-3) Ag: 49.8, Cu: 15.3, Cd: 15.7, N
i: 3, Zn: balance Feature: Contains Ni, has excellent wettability to tungsten carbide and the like, and is used for brazing cemented carbide. (3) Copper foil Cu: 99.9 Features: Good wettability, penetrates even very small gaps.

Examples of the flux-containing paste silver solder used herein include Nice Pa .;
There is Ste PS 103, and as an example of a bar-shaped or foil-shaped silver solder, there is Sil 103 made by the company. An example of the paste-like flux is F103 manufactured by the company.

FIGS. 1 to 4 show metallographic photographs obtained by observing the places where the cracks were sealed in the above-mentioned experiment with an optical microscope.
Shown in FIG. 1 shows an experiment level (1), FIG. 2 shows an experiment level (2), FIG. 3 shows an experiment level (3), and FIG. 4 shows an experiment level (4). In each of these figures, (a) shows the range including the entire width of the deposited metal, the upper interface shows the surface of the deposited metal, and the lower interface shows the interface between the deposited metal and the base material. Spherical particles indicate ultra-hard particles (average particle size 1.2 mm). (B) and (c) are enlarged views of the brazing material permeated part of (a).

In FIG. 1, it can be seen that the silver braze penetrates into the crack details and the inside of the ultra-hard grains to seal the crack. Similarly, FIGS. 2 and 3 show that the silver solder has penetrated into the cracks. In particular, it can be seen that a vertically extending crack having a width of 3 to 4 μm has spread to the base material at the central interface in FIG. 2C, and silver solder has penetrated to the tip of the crack. Further, as shown in FIG. 4, even when a copper foil is used, copper penetrates into the crack similarly to silver solder. In addition, as seen in FIG. 4C, it can be seen that the crack reaching the base material is sealed by copper, as in FIG. 2C.

[Brief description of the drawings]

FIGS. 1 (a), 1 (b), and 1 (c) are photomicrographs showing a metal structure of a crack sealing portion in one example of the present invention.

2 (a), 2 (b) and 2 (c) are photomicrographs showing a metal structure of a crack-sealed portion in one embodiment of the present invention.

FIGS. 3 (a), 3 (b) and 3 (c) are photomicrographs showing a metal structure of a crack sealing portion in one example of the present invention.

4 (a), 4 (b) and 4 (c) are photomicrographs showing a metal structure of a crack-sealed portion in one example of the present invention.

Claims (7)

[Claims] 1. A method for preventing the growth of microcracks generated in a hardfacing part after a hardfacing material has been applied, wherein a paste-like brazing powder containing a flux at least on a surface part where the microcracks are generated is provided. A method for preventing the growth of microcracks, which comprises applying a brazing material by heat treatment and then permeating the inside of the microcracks. 2. A method for preventing the growth of micro-cracks generated in a hardfacing portion after applying a hardfacing material, wherein a flux is applied to at least a surface portion where the micro-cracks have occurred and heat-treated. A method for preventing the growth of microcracks, wherein a brazing material is made to penetrate inside the microcracks by means of a wax. 3. A method for preventing the growth of microcracks generated in a hardfacing part after applying a hardfacing material, comprising applying a flux to at least a surface part where the microcracks have occurred to form a rod or foil. A method for preventing the growth of micro-cracks, comprising placing a brazing material and then heat-treating the brazing material into the inside of the micro-cracks. 4. The method according to claim 1, wherein the heat treatment is a treatment in which the brazing material is heated to a temperature at which the brazing material melts to the tip of the microcracks by a heating furnace. 5. The micro-crack according to claim 1, wherein the heat treatment is a process of heating the brazing material to a temperature at which the brazing material melts to the tip of the micro-crack by heating with a high frequency or a gas burner. How to prevent progress. 6. A sediment-resistant wear component obtained by applying the method for preventing the growth of microcracks according to any one of claims 1 to 5. 7. Any of cutting edge parts of a construction machine such as a bucket tooth, a bucket edge, a cutter bit, a side cutter, a ripper point or a traveling equipment part of a construction machine such as a wear plate, a lower roller, a track link, and the like. The earth-and-sand-resistant wear part according to claim 6, wherein