Self-fluxing alloy welding rod, production method thereof and repair method of self-fluxing alloy film

Abstract

To provide a self-fluxing alloy welding rod excellent in fusibility and capable of sufficiently exhibiting a flux effect, and also to provide a method for appropriately producing the self-fluxing alloy welding rod.SOLUTION: The self-fluxing alloy welding rod is a welding rod to be used for padding and welding a defective part of a self-fluxing alloy film formed on a substrate surface, and includes a porous self-fluxing alloy formed into a rod-like shape, with a porosity of 5 to 30%. The production method includes a step of filling a self-fluxing alloy powder into a groove of a metal mold with the groove formed, scanning and irradiating the self-fluxing alloy powder with laser beams in a longer direction of the groove, forming the self-fluxing alloy powder into a rod-like shape by heating, and taking out a formed rod-like body from the metal mold.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a self-fluxing alloy welding rod and a method for manufacturing the same, and a method for repairing a self-fluxing alloy coating, and more particularly to a porous self-fluxing alloy welding rod with excellent melting properties, a method for suitably manufacturing such a self-fluxing alloy welding rod, and a method for repairing a self-fluxing alloy coating using the self-fluxing alloy welding rod. [Background technology]

[0002] As a method for repairing defects in a corrosion-protected object, such as a steel structure, on whose surface a corrosion-protective thermal spray coating is formed, Patent Document 1 below introduces a method of flame-irradiating metal powder using a handy thermal spraying device.

[0003] However, when repairing an article having a self-fluxing alloy coating on the surface of a substrate using such a thermal spraying device, the work efficiency is poor and it is difficult to form a thick repair coating.

[0004] One possible method for repairing an article having a self-fluxing alloy coating on the surface of a substrate is to perform buildup welding on the defective portion of the self-fluxing alloy coating using a welding rod made of a self-fluxing alloy (self-fluxing alloy welding rod).

[0005] Conventionally, self-fluxing alloy welding rods have been manufactured by casting. Furthermore, as an alternative method for producing a self-fluxing alloy welding rod to casting, Patent Document 2 below proposes a method in which a metal or alloy powder blended to form the composition of the welding rod is filled into the hollow portion of a refractory tube, the tube is heated in a non-oxidizing atmosphere, and after cooling, the welding rod is removed from the tube.

[0006] This method is more economical than the casting method, and the self-fluxing alloy welding rod produced has a more beautiful surface than one produced by casting, is free from defects such as tension that occur with casting, and does not require finishing (see the lower right column on page 2 of the same document). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-213988 [Patent Document 2] Japanese Patent Application Publication No. 51-100946 Summary of the Invention [Problem to be solved by the invention]

[0008] However, because self-fluxing alloy welding rods manufactured by conventional methods (casting and the method described in Patent Document 2) are formed by completely melting the self-fluxing alloy, the boron and silicon in the self-fluxing alloy form compounds, which reduce the melting point lowering function of the self-fluxing alloy due to these elements, impairing the good melting properties of the self-fluxing alloy. This requires high-temperature heating when overlay welding, which can result in problems such as welding defects and deformation of the base material due to insufficient melting.

[0009] Furthermore, there is a problem in that the self-fluxing alloy welding rods obtained by conventionally known methods are unable to fully exhibit the flux effects exhibited by boron and silicon (such as the effect of removing oxides in the repair coating, the effect of improving the adhesion of the repair coating to the repaired surface, and the effect of improving the wear resistance, corrosion resistance, and heat resistance of the repair coating).

[0010] The present invention has been made based on the above circumstances. A first object of the present invention is to provide a self-fluxing alloy welding rod that has excellent melting properties and can fully exert its flux effect. A second object of the present invention is to provide a method for suitably producing such a self-fluxing alloy welding rod. A third object of the present invention is to provide a method for repairing a self-fluxing alloy coating that can efficiently repair an article having a self-fluxing alloy coating on the surface of a substrate and can form a thick repair coating. [Means for solving the problem]

[0011] The self-fluxing alloy welding rod of the present invention is a welding rod used for overlay welding to a defect portion of a self-fluxing alloy coating of an article having a self-fluxing alloy coating on a substrate surface, and It is made of a porous self-fluxing alloy formed into a rod shape, and is characterized by its porosity of 5 to 30%.

[0012] A self-fluxing alloy welding rod (made of a porous self-fluxing alloy) having such a configuration is obtained by solidifying the self-fluxing alloy in an incompletely molten state, and therefore the self-fluxing alloy contains sufficient boron and silicon as elemental elements, and therefore the self-fluxing alloy welding rod has excellent melting properties and can fully exert the flux effect of boron and silicon.

[0013] The method for manufacturing a self-fluxing alloy welding rod of the present invention includes filling a groove formed in a metal mold with a self-fluxing alloy powder, a laser beam is scanned and irradiated onto the self-fluxing alloy powder in the longitudinal direction of the groove, and the self-fluxing alloy powder is heated and formed into a rod shape; The molded rod-shaped body is then removed from the metal mold.

[0014] According to this manufacturing method, the self-fluxing alloy powder filled in the groove of the metal mold is rapidly heated by being scanned and irradiated with the laser light, and the self-fluxing alloy powder particles are fused together in an extremely short time to be formed into a rod-like shape. Then, after the laser light has passed through (irradiated), the formed rod-like body is rapidly cooled, and by removing it from the metal mold, a self-fluxing alloy welding rod can be obtained.

[0015] In this way, the self-fluxing alloy powder is heated by scanning irradiation with laser light, which makes it possible to rapidly heat and cool the self-fluxing alloy, and since oxidation of the self-fluxing alloy does not easily occur even when heated in air, there is no need to prepare a non-oxidizing atmosphere.

[0016] In addition, the self-fluxing alloy powder is uniformly heated by irradiation with laser light, and by appropriately adjusting the irradiation density and scanning speed, the molten state of the self-fluxing alloy and, ultimately, the porosity (the amount of boron and silicon present as simple substances) of the resulting self-fluxing alloy welding rod can be controlled. Furthermore, the molten state of the self-fluxing alloy can be visually confirmed as needed during scanning and irradiation with the laser beam.

[0017] In the manufacturing method of the present invention, it is preferable to heat the self-fluxing alloy powder to a semi-molten state, where the "semi-molten state" refers to a state in which the self-fluxing alloy powder is partially melted and a solid and a liquid coexist.

[0018] According to this manufacturing method, by heating the self-fluxing alloy powder to a semi-molten state (without completely melting it), a self-fluxing alloy welding rod in which boron and silicon are sufficiently present as elemental substances (the self-fluxing alloy welding rod of the present invention having excellent melting properties) can be obtained.

[0019] In the manufacturing method of the present invention in which the self-fluxing alloy powder is heated to a semi-molten state, a laser beam having a wavelength of 640 to 1070 nm is applied at a power of 200 to 400 W / cm 2 It is preferable that the self-fluxing alloy powder is subjected to scanning irradiation at an irradiation density of 1000 nm or more.

[0020] In this manufacturing method, it is preferable that the laser light absorption rate of the metal constituting the metal mold is 20% or less, and it is preferable that the metal constituting the metal mold is copper.

[0021] In the manufacturing method of the present invention, a flux may be added to the self-fluxing alloy powder.

[0022] The method for repairing a self-fluxing alloy coating of the present invention is characterized in that the defective portion of the self-fluxing alloy coating is repaired by overlay welding while the self-fluxing alloy welding rod of the present invention is heated and melted with a gas burner. [Effects of the Invention]

[0023] The self-fluxing alloy welding rod of the present invention has a sufficient amount of boron and silicon present as simple substances, and therefore has excellent melting properties, allowing overlay welding to be performed at relatively low temperatures. In addition, the flux effect of boron and silicon can be fully exerted.

[0024] According to the manufacturing method of the present invention, the self-fluxing alloy powder is heated by scanning irradiation with laser light, which makes it possible to rapidly heat and cool the self-fluxing alloy, and since oxidation of the self-fluxing alloy does not easily occur even in the air, there is no need to prepare a non-oxidizing atmosphere. Furthermore, by adjusting the irradiation density and scanning speed of the laser light on the self-fluxing alloy powder, it is possible to control the molten state of the self-fluxing alloy and, ultimately, the porosity of the resulting self-fluxing alloy welding rod. Therefore, according to the manufacturing method of the present invention, it is possible to suitably manufacture the self-fluxing alloy welding rod of the present invention made of a porous self-fluxing alloy.

[0025] According to the repair method of the present invention, repair operations for articles having a self-fluxing alloy coating on the substrate surface can be carried out efficiently, and a thick and beautiful repair coating can be formed. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a photograph showing the appearance of a self-fluxing alloy welding rod obtained in an example of the present invention. [Figure 2] 1 is a photograph showing the outer surface of a boiler tube including a defective portion of a self-fluxing alloy coating repaired by an embodiment of the present invention. [Figure 3] 1 is a photograph showing the appearance of a repaired portion according to an embodiment of the present invention. [Figure 4] 1 is a photomicrograph showing a cross section of a repaired portion according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] <Self-fluxing alloy welding rod> The self-fluxing alloy welding rod of the present invention is used for overlay welding to a defect portion of a self-fluxing alloy coating in an article having a self-fluxing alloy coating on the surface of the substrate. Examples of "articles" having a self-fluxing alloy coating on the surface of a substrate include boiler parts such as pipe components (boiler tubes) that make up the heat transfer piping of various boilers, and plate-tube composite panels (boiler furnace panels) that make up furnace housings with cooling water channels.

[0028] Furthermore, the "missing portion" of the self-fluxing alloy coating includes a portion where the self-fluxing alloy coating is missing and the substrate surface is exposed, as well as a portion where the substrate surface is not exposed but the self-fluxing alloy coating is thinned.

[0029] The self-fluxing alloy welding rod of the present invention is made of a porous self-fluxing alloy formed into a rod shape. Here, examples of self-fluxing alloys include known self-fluxing alloys that can impart wear resistance and corrosion resistance to metal materials (substrates), but a preferred self-fluxing alloy is a Ni-based alloy having a boron (B) content of 1 to 5 mass%, a silicon (Si) content of 1 to 5 mass%, a chromium (Cr) content of 10 to 40 mass%, a molybdenum (Mo) content of 4 mass% or less, and a carbon (C) content of 1 mass% or less. The self-fluxing alloy constituting the welding rod preferably has the same composition as the self-fluxing alloy coating formed on the surface of the substrate.

[0030] The self-fluxing alloy welding rod of the present invention is made of a porous self-fluxing alloy, and its porosity is 5 to 30%, preferably 10 to 20%.

[0031] Here, porosity is defined as the ratio of the area of ​​pores in the cross section of a welding rod, and is the value obtained by dividing the area of ​​the pores by the area of ​​the cross section, expressed as a percentage. For example, an optical microscope photograph of the cross section (transverse or longitudinal section) of a welding rod is taken, and the photograph is binarized into white and black areas by image processing. The area ratio of the parts corresponding to the pores in the obtained binarized image is calculated, and this value is taken as the porosity.

[0032] A self-fluxing alloy welding rod with a porosity of 5% or more is obtained by solidifying a self-fluxing alloy in a state where it is not completely molten (semi-molten state), and the self-fluxing alloy that constitutes it contains sufficient amounts of boron and silicon as simple substances. Therefore, this self-fluxing alloy welding rod has good melting properties (low-temperature melting properties) due to the function of these elements to lower the melting point of the self-fluxing alloy, and can perform overlay welding at relatively low temperatures. In addition, the flux effect of these elements can be fully exerted.

[0033] The boron and silicon in the self-fluxing alloy that constitutes a welding rod with a porosity of less than 5% form compounds, and the elements are unable to exert their melting point lowering function, so such a welding rod does not have the good melting properties of a self-fluxing alloy. On the other hand, a welding rod with a porosity of more than 30% is extremely brittle, making it difficult to maintain the shape of the welding rod.

[0034] The cross-sectional shape of the self-fluxing alloy welding rod of the present invention is not particularly limited, but from the viewpoint of manufacturing by irradiation with laser light, a rectangular shape is preferable.

[0035] <Manufacturing method of self-fluxing alloy welding rods> The method for manufacturing a self-fluxing alloy welding rod of the present invention includes the steps of filling a groove of a metal mold having a groove formed therein in the shape of a desired welding rod with a self-fluxing alloy powder (hereinafter also referred to as the "powder filling step"); a step of scanningly irradiating the self-fluxing alloy powder with a laser beam in the longitudinal direction of the grooves to heat the self-fluxing alloy powder and thereby form it into a rod shape (hereinafter also referred to as a "forming step"); and a step of removing the formed rod-shaped body (self-fluxing alloy welding rod) from the metal mold (hereinafter also referred to as the "removal step").

[0036] The powder filling step in the manufacturing method of the present invention is a step of filling a groove of a metal mold having a groove formed in the shape of the desired welding rod with a self-fluxing alloy powder.

[0037] The metal mold used in the manufacturing method of the present invention is preferably made of a metal that has low absorption of the laser light irradiated in the forming step, specifically, a metal that has an absorption of the laser light of 20% or less, particularly 10% or less. Examples of such metals include copper, aluminum, and silver. Among these, copper is particularly preferred because of its large heat capacity and good formability of the welding rod.

[0038] By using a metal mold made of a metal with low laser light absorption, it is possible to avoid excessive heating of the metal mold by laser irradiation during the molding process, and as a result, the filled self-fluxing alloy powder is selectively heated, making it easy to control the molten state of the self-fluxing alloy (for example, heating the self-fluxing alloy powder to a semi-molten state). Furthermore, it is possible to prevent the constituent metal of the metal mold from fusing with the self-fluxing alloy, thereby ensuring the mold releasability of the self-fluxing alloy welding rod.

[0039] The metal mold is formed with a groove (recess) in the shape of the desired welding rod. Here, the cross-sectional shape of the groove is preferably rectangular, and the groove preferably has a width of 3 to 10 mm and a depth of 0.3 to 2.5 mm.

[0040] A flux may be added to the self-fluxing alloy powder filled in the grooves. The flux is not particularly limited as long as it penetrates into the interior of the self-fluxing alloy welding rod obtained and exhibits a sealing effect on the welding rod and, in turn, an anti-oxidation effect on the repaired surface; for example, one containing borax is preferred. By adding flux to the self-fluxing alloy powder, the flux effect (such as the effect of removing oxides from the repair film, the effect of improving the adhesion of the repair film to the repaired surface, and the effect of improving the wear resistance, corrosion resistance, and heat resistance of the repair film) can be further improved.

[0041] The forming step of the manufacturing method of the present invention is a step of irradiating a laser beam in a scanning direction along the length of the groove with a self-fluxing alloy powder filled in the groove of a metal mold, thereby heating the self-fluxing alloy powder and forming it into a rod shape.

[0042] The self-fluxing alloy powder irradiated with the laser beam is rapidly heated, and the particles of the self-fluxing alloy powder are fused together in an extremely short time to be formed into a rod-like shape. After the laser beam has passed through (after irradiation), the formed rod-like body is rapidly cooled.

[0043] In this way, by heating the self-fluxing alloy powder by scanning and irradiating it with laser light, it is possible to rapidly heat and cool the self-fluxing alloy, and oxidation of the self-fluxing alloy does not easily occur even when heated in air. For this reason, there is no need to heat it in a non-oxidizing atmosphere. Furthermore, the self-fluxing alloy powder is uniformly heated by the scanning irradiation of the laser beam, making it possible to manufacture a homogeneous self-fluxing alloy welding rod with no unevenness in porosity or the like. In addition, by appropriately adjusting the irradiation density and scanning speed of the laser light, it is possible to control the molten state of the self-fluxing alloy and, ultimately, the porosity (the amount of boron and silicon present as simple substances) of the resulting self-fluxing alloy welding rod. The molten state of the self-fluxing alloy during scanning and irradiation with the laser beam can be visually confirmed as appropriate.

[0044] In the manufacturing method of the present invention, it is preferable to heat the self-fluxing alloy powder to a semi-molten state. By heating the self-fluxing alloy powder to a semi-molten state and not completely melting it, the boron and silicon contained therein are prevented from forming compounds, and a self-fluxing alloy welding rod (a self-fluxing alloy welding rod of the present invention with excellent melting properties) in which these elements are sufficiently present as simple substances can be obtained. Furthermore, by heating to a semi-molten state, the self-fluxing alloy can be prevented from adhering to the constituent metal of the metal mold, making it easier to remove (improving mold releasability).

[0045] The wavelength of the laser light used to scan and irradiate the self-fluxing alloy powder is preferably 640 to 1070 nm, and a suitable example is 1060 nm. The output of the laser light is, for example, 300 to 400 W, and a suitable example is 350 W.

[0046] The beam shape of the laser light is preferably rectangular. The size of the rectangular beam is, for example, 5 to 15 mm (groove width direction) x 5 to 15 mm (scanning direction), and a suitable example is 11 mm x 13 mm.

[0047] The laser beam irradiation density is 200 to 400 W / cm 2 A suitable example is 245 W / cm 2 is.

[0048] The scanning speed of the laser light is preferably 1 to 10 mm / s, and a suitable example is 4 mm / s.

[0049] The heating temperature of the self-fluxing alloy powder by scanning and irradiating it with laser light is set to about 950 to 1100°C. If the heating temperature is too low, the self-fluxing alloy powder particles will not fuse together easily, making it difficult to form the powder into a rod-shaped body. On the other hand, if the heating temperature is too high, the self-fluxing alloy powder will be completely melted, and lumps of self-fluxing alloy with low porosity will be formed intermittently in the longitudinal direction of the groove, making it impossible to form a rod-shaped body.

[0050] In the removal step, the formed rod-shaped body (self-fluxing alloy welding rod) is cooled and then removed from the metal mold.

[0051] <Method for repairing self-fluxing alloy coating> The method for repairing a self-fluxing alloy coating is a method for repairing defective parts of the self-fluxing alloy coating by overlay welding while heating and melting the self-fluxing alloy welding rod of the present invention (a porous self-fluxing alloy welding rod with a porosity of 5 to 30%) with a gas burner.

[0052] The heating temperature is usually 1000°C or higher, preferably 1020 to 1080°C, and a suitable example is 1050°C. This melts the self-fluxing alloy welding rod, reducing its porosity and resulting in a dense repair coating. The porosity of the repair coating is generally less than 10%, and preferably less than 5%. Repair coatings with a porosity of less than 5% are highly dense and can fully demonstrate the wear resistance and corrosion resistance required of self-fluxing alloy coatings. [Example]

[0053] (1) Manufacturing of self-fluxing alloy welding rods: A copper plate (width 30 mm × length 212 mm × thickness 15 mm) with a groove 5 mm wide and 1 mm deep formed therein was prepared, and the groove in the copper plate was filled with self-fluxing alloy powder [self-fluxing alloy (equivalent to SFNi4) specified in JIS H 8303].

[0054] Next, the self-fluxing alloy powder filled in the grooves was irradiated with a laser beam in a scanning manner in the longitudinal direction of the grooves, thereby heating the self-fluxing alloy powder. The self-fluxing alloy powder was heated to a semi-molten state, and after the laser beam passed through it was rapidly cooled to obtain a rod-shaped body. The conditions for irradiating the self-fluxing alloy powder with the laser beam were as follows:

[0055] ·Wavelength: 1060nm Beam shape and size: Rectangular (11mm width x 13mm scanning direction) Output: 350W ·Irradiation density: 245W / cm 2 ·Scanning speed: 4mm / s Heating temperature (measured): 1080℃ Atmosphere: Oxidizing atmosphere (air)

[0056] After cooling, the formed rod (self-fluxing alloy welding rod) was removed from the groove in the copper plate. FIG. 1 is a photograph showing the appearance of the obtained self-fluxing alloy welding rod. The cross section of this self-fluxing alloy welding rod was observed with an optical microscope, and the porosity measured by image analysis was 10 to 18%.

[0057] (2) Preparation of items to be repaired A self-fluxing alloy (equivalent to SFNi4) specified in JIS H 8303 was sprayed onto the outer surface of a carbon steel pipe for boilers and heat exchangers (equivalent to JIS G 3461, STB410) with an outer diameter of 57.1 mm and a wall thickness of 5 mm, forming a self-fluxing alloy coating with a thickness of 2300 μm. The cross section was observed with an optical microscope and the porosity was measured by image analysis, and the boiler tube was manufactured by this method. A portion of the self-fluxing alloy coating formed on the obtained boiler tube was removed using a grinder, forming a defect portion of the self-fluxing alloy coating (a mortar-shaped reduced thickness portion with a diameter of 8 mm). FIG. 2 is a photograph showing the outer surface of a boiler tube including a defective portion (surface to be repaired).

[0058] (3) Repair of self-fluxing alloy coating: The defective portion of the self-fluxing alloy coating on the object to be repaired prepared in (2) above was preheated to approximately 800°C by roasting with a gas burner, and then the self-fluxing alloy welding rod obtained in (1) above was heated and melted to approximately 1050°C with the gas burner, while the defective portion was overlaid with welding to form a repair coating.

[0059] Figure 3 is a photograph showing the appearance of the repaired portion (the formed repair coating) according to this example. As shown in Figure 3, the surface of the repair coating was excellent in smoothness. In addition, the repair coating was integrated with the self-fluxing alloy coating.

[0060] FIG. 4 is a photomicrograph showing the cross-sectional state of the repaired portion (the formed repair coating) according to this example. The cross-section of the repaired portion cut in a direction perpendicular to the axial direction of the boiler tube was etched using the nitric acid ethanol method described in JIS G 0553, and the photo was taken with an optical microscope.

[0061] As shown in Figure 4, the interface between the repair coating and the self-fluxing alloy coating is smooth, with no partial peeling observed between the two, indicating excellent adhesion of the repair coating. Additionally, no large voids (voids) or cracks are observed within the repair coating. Furthermore, the cross section of this repair coating was observed under an optical microscope, and the porosity measured by image analysis was 1 to 5%, indicating that the coating was dense.

Claims

1. A welding rod used for overlay welding to a defect portion of a self-fluxing alloy coating of an article having a self-fluxing alloy coating on a substrate surface, A self-fluxing alloy welding rod comprising a porous self-fluxing alloy formed into a rod shape, the porosity of which is 5 to 30%.

2. Filling the grooves of a metal mold with a self-fluxing alloy powder; a laser beam is scanned and irradiated onto the self-fluxing alloy powder in the longitudinal direction of the groove, and the self-fluxing alloy powder is heated and formed into a rod shape; The method for manufacturing a self-fluxing alloy welding rod comprises removing the formed rod-shaped body from the metal mold.

3. 3. The method for manufacturing a self-fluxing alloy welding rod according to claim 2, wherein the self-fluxing alloy powder is heated to a semi-molten state.

4. Laser light with a wavelength of 640 to 1070 nm is used at 200 to 400 W / cm 2 4. The method for manufacturing a self-fluxing alloy welding rod according to claim 3, wherein the self-fluxing alloy powder is scanned and irradiated with an irradiation density of 1000 nm or more.

5. 5. The method for manufacturing a self-fluxing alloy welding rod according to claim 4, wherein the laser light is absorbed by the metal constituting the metal mold at an absorptance of 20% or less.

6. 6. The method for manufacturing a self-fluxing alloy welding rod according to claim 5, wherein the metal mold is made of copper.

7. 7. The method for manufacturing a self-fluxing alloy welding rod according to claim 2, wherein a flux is added to the self-fluxing alloy powder.

8. 2. A method for repairing a self-fluxing alloy coating, comprising overlay welding a defective portion of the self-fluxing alloy coating while heating and melting the self-fluxing alloy welding rod according to claim 1 with a gas burner.

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