Welding method

Abstract

To provide a welding method for performing buildup welding to an object to be welded, which can improve properties such as hardness of a built-up layer, and a welded member having the properties of the built-up layer improved.SOLUTION: A welding method, which performs buildup-welding to a surface 2a to be built up of a slender object 2 to be welded along a longitudinal direction of the object 2 to be welded, comprises a building-up step of supplying filler metal 35 along the longitudinal direction to the surface 2a to be built-up and irradiating the surface with a laser beam 45, so as to form a built-up layer 3 on the surface 2a to be built up using the melted filler metal 35. In the building-up step, information concerning dimensions of the filler metal 35 melted by the laser beam 45 and of molten pool 4 formed of the object 2 to be welded is obtained and output of the laser beam 45 is controlled based on the information.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] An embodiment of the present invention is a welding method law Regarding. [Background technology]

[0002] For the purpose of environmental protection, there is a need to reduce emissions of greenhouse gases such as carbon dioxide. To reduce carbon dioxide emissions, it is desirable to improve the power generation efficiency of thermal power plants that use large amounts of fossil fuels.

[0003] In order to improve the power generation efficiency of thermal power plants, it is effective to increase the temperature of the steam flowing within the plants. For this reason, the components used in thermal power plants must have superior high-temperature strength and improved wear resistance more than ever before.

[0004] For example, a steam valve, which controls the flow rate of steam flowing into a steam turbine, opens and closes while being exposed to high-temperature, high-pressure steam. The valve stem, which constitutes part of the steam valve, is required to be free from wear caused by sliding and the formation of oxide scale. This is for the following reasons: When the valve stem wears due to sliding, the amount of steam leaking from the gap between the valve stem and the valve body increases, reducing the thermal efficiency of the thermal power plant. Furthermore, the valve stem reacts with high-temperature steam, forming oxide scale on its surface. When oxide scale forms, the outer diameter of the valve stem increases. Furthermore, the oxide scale peels off and accumulates around the valve stem. If the outer diameter of the valve stem increases or oxide scale accumulates between the valve stem and the valve body, the valve stem will no longer be able to operate as desired.

[0005] In this regard, Patent Document 1 discloses a method of forming a hardened layer (overlay layer) by overlay welding a cobalt-based alloy onto the surface of the base material of the valve stem, thereby improving the wear resistance of the valve stem and suppressing the formation of oxide scale. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-174126 Summary of the Invention [Problem to be solved by the invention]

[0007] However, it was found that a part of the valve stem manufactured by the method disclosed in Patent Document 1 does not have sufficient wear resistance to withstand use in a thermal power plant where high-temperature steam flows. More specifically, it was found that the hardness of the buildup layer formed on the valve stem is sufficient near the weld start end, but is insufficient from near the weld middle to near the weld end.

[0008] The present invention has been made in consideration of the above points, and aims to provide a welding method for overlay welding on a weld object, which is capable of improving the hardness and other properties of the overlay layer, and a welded member having improved properties of the overlay layer. [Means for solving the problem]

[0009] The welding method according to the present invention comprises: welding a thin film of an elongated object to be welded along a longitudinal direction of the object to be welded; A welding method for overlay welding on a welded surface, comprising: welding a weld along the longitudinal direction of the welded surface; A filler material is supplied and a laser beam is irradiated to the surface to be welded, and the melted filler material is applied to the surface to be welded. a build-up step for forming a build-up layer, A region including a molten pool formed by the filler metal melted by the laser and the workpiece The temperature of each point in the area is acquired. Above the melting point of the object to be welded and the filler material has a temperature of and acquiring information about the dimensions of the area where the molten pool is to be formed as information about the dimensions of the molten pool. To ensure that the dimensions are within the specified range and the dilution rate of the components of the filler metal in the cladding layer is To be between 10% and 40% The larger the size of the molten pool, the lower the intensity of the laser beam. The laser beam is adjusted so that the smaller the size of the molten pool, the higher the intensity of the laser beam. Controls the output of the laser light.

[0010] Alternatively, the welding method according to the present invention comprises: A welding method in which overlay welding is performed on the surface of an elongated object to be welded along the longitudinal direction of the object to be welded. A method for forming a filler layer by thermally spraying or applying a filler material to the surface to be overlaid. a filler layer forming step, and a filler layer extending in the longitudinal direction after the filler layer forming step; The filler material of the filler material layer is remelted by irradiating the laser beam along the surface to be overlaid, thereby forming a build-up layer on the surface to be overlaid. and a build-up process for forming the laser beam on the workpiece. The filler metal melted by the light and the weld pool formed by the object to be welded are The temperature of each point is acquired, and Above the melting point of the object to be welded and the filler material having a temperature of Information about the size of the region is acquired as information about the size of the molten pool, and the size of the molten pool is So that the law is within its prescribed scope and the dilution rate of the components of the filler metal in the buildup layer is 1. Between 0% and 40% The larger the size of the molten pool, the lower the intensity of the laser beam. The laser beam is arranged so that the smaller the size of the molten pool, the higher the intensity of the laser beam. Controls the light output. [Effects of the Invention]

[0013] According to the present invention, there is provided a welding method for overlay welding a welding object, the method comprising: Welding that can improve the How to can be provided. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a side view showing a welded member according to one embodiment of the present invention, in which an overlay layer is formed on a weld object. [Figure 2] FIG. 2 is a side view showing a welding device for forming the buildup layer shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the welding apparatus shown in FIG. 2 taken along line III-III. [Figure 4] FIG. 4 is a partially enlarged view showing the welding torch and the temperature sensor shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing a welded member according to an embodiment of the present invention. Figs. 2 and 3 are diagrams schematically showing the configuration of a welding apparatus for producing the welded member shown in Fig. 1. Fig. 3 is a diagram showing a cross section of the welding apparatus shown in Fig. 2 taken along line III-III. To simplify the illustration, Fig. 3 omits the illustration of a filler metal supply unit 30, a laser irradiation unit 40, and a shielding gas supply unit 50, which will be described later. Fig. 4 is an enlarged view of a portion of the welding apparatus shown in Figs. 2 and 3.

[0016] The welded member 1 shown in Fig. 1 is produced by overlay welding on the overlay surface 2a of the object 2 to be welded to form an overlay layer 3. The welding device 10 shown in Figs. 2 and 3 performs overlay welding on the overlay surface 2a of the object 1 to be welded. More specifically, the welding device 10 forms the overlay layer 3 on the overlay surface 2a of the object 2 to be welded with a filler metal 35 melted using a laser beam 45.

[0017] As shown in FIG. 1 , the objects to be welded 2 are elongated and have a longitudinal direction. In the illustrated example, the objects to be welded 2 are formed into a solid, cylindrical shape and have a cylindrical surface (a surface to be welded 2a). In the illustrated example, the objects to be welded 2 are forged rods made of a nickel (Ni)-based alloy. Of course, the shape of the objects to be welded 2 and the material constituting the objects to be welded 2 are not limited to this. For example, the objects to be welded 2 may be formed into a hollow cylindrical shape. Furthermore, for example, the material constituting the objects to be welded 2 may be an iron (Fe)-based alloy. In this specification, nickel-based alloy and iron-based alloy refer to materials in which the weight fractions of nickel and iron are the largest, respectively.

[0018] As shown in FIG. 2, the welding apparatus 10 includes a support unit 20 that supports the objects to be welded 2, a filler metal supply unit 30 that supplies filler metal 35 to the objects to be welded 2, a laser irradiation unit 40 that irradiates the objects to be welded 2 with laser light 45, a shielding gas supply unit 50, a longitudinal drive unit 60 that moves the laser irradiation unit 40 relative to the support unit 20, and a rotation drive unit 70 that rotates the objects to be welded 2 supported by the support unit 20.

[0019] The support parts 20 support both longitudinal end parts of the object to be welded 2. The support parts 20 support both longitudinal end parts of the object to be welded 2 so as to be rotatable about a rotation axis 70X along the longitudinal direction.

[0020] As shown in FIG. 4 , the filler material supply unit 30 includes a filler material container 31 that contains powder of filler material 35, a filler material supply pipe 32 that guides the powder of filler material 35 from the filler material container 31 to the vicinity of the workpiece 2 supported by the support unit 20, and a filler material discharge hole 33 that is provided at the tip of the filler material supply pipe 32 and discharges the filler material 35. Examples of the filler material 35 that can be used include a cobalt (Co)-based alloy, a nickel-based alloy, and an iron-based alloy. The filler material supply unit 30 may further include a carrier gas supply unit (not shown) that supplies a carrier gas to the filler material supply pipe 32. In this case, when the filler material 35 is discharged from the filler material discharge hole 33, the filler material 35 can be carried along with the carrier gas and supplied to the workpiece 2.

[0021] As shown in FIG. 4 , the laser irradiation unit 40 irradiates the workpieces 2 supported by the support 20 with laser light 45. The laser irradiation unit 40 includes a laser oscillator 41, an optical fiber 42 that guides the laser light 45 generated by the laser oscillator 41 to the vicinity of the workpieces 2 supported by the support 20, and a laser emission unit 43 that is provided at the tip of the optical fiber 42 and emits the laser light 45 guided by the optical fiber 42 toward the workpieces 2 supported by the support 20. The laser oscillator 41 may be any laser, such as a semiconductor laser or a solid-state laser. The laser oscillator 41 is preferably capable of emitting laser light 45 in a wavelength range of 400 to 1100 nm. The laser light 45 emitted from the laser emission unit 43 melts the powdered filler material 35 discharged from the filler material discharge hole 33. The laser light 45 emitted from the laser emission unit 43 also partially melts the workpieces 2. Then, the components of the molten filler metal 35 dissolve into the molten workpieces 2, and the components of the molten workpieces 2 dissolve into the molten filler metal 35. The molten filler metal 35 and the molten workpieces 2 form a molten pool 4 on the welded surface 2a. The molten pool 4 then solidifies to become the buildup layer 3.

[0022] 4, the shielding gas supply unit 50 includes a shielding gas storage unit 51 that stores shielding gas 55, a gas supply pipe 52 that guides the shielding gas 55 discharged from the shielding gas storage unit 51 to the vicinity of the workpiece 2 supported by the support unit 20, and a shielding gas discharge hole 53 that is provided at the tip of the gas supply pipe 52 and discharges the shielding gas 55. As the shielding gas 55, for example, an inert gas such as helium, argon, or nitrogen can be used.

[0023] In the illustrated example, welding device 10 has welding torch 15. The above-mentioned filler material discharge hole 33, laser emission part 43, and shield gas discharge hole 53 are formed in tip surface 15a of welding torch 15. Welding torch 15 is arranged so that tip surface 15a faces overlay surface 2a of workpiece 2 supported by support part 20. Welding torch 15 is provided so as to be movable relative to support part 20 in the longitudinal direction.

[0024] 2 and 3 moves the laser emitter 43 along the longitudinal direction relative to the workpiece 2 supported by the support 20. In the example shown, the longitudinal driver 60 moves the welding torch 15 in the longitudinal direction relative to the support 20. The longitudinal driver 60 moves the welding torch 15 in a direction D1 from one end to the other end of the workpiece 2 supported by the support 20. Of course, the longitudinal driver 60 may also move the support 20 in the longitudinal direction relative to the welding torch 15.

[0025] The rotation drive unit 70 rotates the objects to be welded 2 supported by the support unit 20 around a rotation axis 70X. In the illustrated example, the rotation axis 70X is a line that coincides with the axis 2X (the central axis of the cylindrical build-up surface 2a) of the objects to be welded 2. The rotation drive unit 70 rotates the objects to be welded 2 at a predetermined rotation speed. Note that in the example shown in FIG. 3, the rotation drive unit 70 rotates the objects to be welded 2 clockwise in FIG. 3, but this is not limiting. The rotation drive unit 70 may also rotate the objects to be welded 2 counterclockwise in FIG. 3.

[0026] Welding torch 15 is moved longitudinally relative to workpiece 2 by longitudinal drive unit 60, and workpiece 2 is rotated about rotation axis 70X by rotation drive unit 70, so that welding torch 15 traces a spiral trajectory around build-up surface 2a of workpiece 2. Furthermore, molten pool 4 formed on workpiece surface 2a moves away from laser beam 45 as welding torch 15 moves and workpiece 2 rotates, and solidifies to become build-up layer 3.

[0027] Recently, there has been a demand for improving the wear resistance of components used in thermal power plants and suppressing the formation of oxide scale on such components, with the aim of improving the power generation efficiency of such plants. For example, when the welded component shown in FIG. 1 is used as a valve stem of a steam valve, improving the wear resistance of the buildup layer can reliably maintain the opening and closing function of the steam valve using the valve stem. Specifically, wear of the buildup layer due to the sliding of the valve stem increases the amount of steam leaking from the gap between the valve stem and the valve body, reducing the thermal efficiency of the thermal power plant. Furthermore, when oxide scale forms on the valve stem, the outer diameter of the valve stem increases. Alternatively, the oxide scale peels off and accumulates around the valve stem. If the outer diameter of the valve stem increases or oxide scale accumulates between the valve stem and the valve body, the valve stem will not function as intended. Regarding this issue, Patent Document 1 discloses a method for improving the wear resistance of the valve stem and suppressing the formation of oxide scale by overlay welding a cobalt-based alloy to the overlay surface of a welded object.

[0028] However, the present inventors discovered that when welded components are fabricated using the method described in Patent Document 1, the hardness of the buildup layer varies along the longitudinal direction of the workpiece. Specifically, if the portion of the buildup layer where welding begins is the weld starting point and the portion where welding ends is the weld ending point, the hardness of the buildup layer near the weld ending point is lower than the hardness of the buildup layer near the weld starting point. After extensive research, the present inventors discovered the cause of the lower hardness of the buildup layer near the weld ending point compared to the weld starting point. Specifically, heat is input to the workpiece by a laser beam from the start to the end of buildup welding. This causes the temperature of each part of the workpiece to increase along the welding progress direction (the welding torch progress direction). As a result, the dilution rate of the filler metal components in each part of the buildup layer increases along the welding progress direction (i.e., from the weld starting point to the weld ending point). If the dilution ratio becomes too high, the hardness of the buildup layer will be insufficient for use in thermal power plants where high-temperature steam flows. Naturally, the buildup layer properties other than hardness will also differ between the weld start and weld termination. Specifically, the buildup layer properties at the weld termination will differ from the filler metal properties before welding compared to the buildup layer properties at the weld start.

[0029] Taking these points into consideration, the welding device 10 and welding method of this embodiment are devised to suppress an increase in the dilution rate of the components of the filler material 35 in the buildup layer 3 from the weld start end toward the weld end, and to improve the characteristics of the buildup layer 3 (to make the characteristics closer to those of the filler material 35). That is, the welding device 10 is provided with a means for controlling the output of the laser beam 45 oscillated from the laser oscillator 41 during buildup welding, and suppressing a temperature rise in the workpiece 2 caused by the heat input of the laser beam 45.

[0030] Here, as a method for suppressing a temperature rise in the objects to be welded 2 during overlay welding, it is conceivable to interrupt the irradiation of the laser beam to the objects to be welded 2 during overlay welding (i.e., interrupt the overlay welding) to dissipate the heat of the objects to be welded 2. However, when the overlay welding is interrupted, the time required from start to finish of the overlay welding becomes longer, and the overlay welding cannot be performed efficiently. In this regard, when the overlay welding is performed while controlling the output of the laser beam 45 oscillated from the laser oscillator 41, it is possible to suppress a temperature rise in the objects to be welded 2 and the resulting increase in the dilution rate, without interrupting the overlay welding.

[0031] Furthermore, when controlling the output of laser beam 45 emitted from laser oscillator 41, it is also possible to directly measure the temperature of workpiece 2 and control the output of laser beam 45 based on the measured temperature. However, in order to control the output of laser beam 45, it is necessary to measure the temperatures of multiple points on workpiece 2. Controlling the output of laser beam 45 based on multiple measured temperatures is cumbersome.

[0032] In this regard, by taking advantage of the fact that the higher the temperature of the workpiece 2, the larger the size of the molten pool 4, and controlling the output of the laser light 45 based on the size of the molten pool 4, the temperature rise of the workpiece 2 can be reliably and efficiently suppressed.

[0033] Specifically, the welding apparatus 10 of this embodiment is equipped with a dimension measuring unit 80 for acquiring information regarding the dimensions of the molten pool 4, and a control unit 90 for controlling the laser irradiation unit 40 based on the information.

[0034] The dimension measuring unit 80 acquires information about the dimensions of the molten pool 4 as follows: That is, the temperature of each location in the area including the molten pool 4 on the workpiece 2 where overlay welding is being performed is acquired, temperature mapping of the area including the molten pool 4 is performed, and a temperature distribution diagram is created. Then, it is assumed that the area including the molten pool 4 that has a temperature equal to or higher than a predetermined temperature corresponds to the area containing only the molten pool 4, and information about the dimensions of this area is acquired based on the temperature distribution diagram, thereby acquiring information about the dimensions of the molten pool 4.

[0035] The predetermined temperature used to determine the region of only the molten pool 4 is determined in consideration of the melting points of the workpiece 2 and the filler material 35 .

[0036] To measure the molten pool 4 in this manner, in the illustrated example, the dimension measurement unit 80 includes a non-contact radiation temperature sensor 81 and a processing device 82 that performs temperature mapping of the area including the molten pool 4 based on the temperatures acquired by the temperature sensor 81 and creates a temperature distribution diagram. The temperature sensor 81 detects infrared rays emitted from the area including the molten pool 4 on the workpiece 2, and acquires the temperature of each location in the area. The dimension measurement unit 80 may include a reflecting element (e.g., a dichroic mirror) that reflects the infrared rays and directs them toward the temperature sensor 81.

[0037] Temperature sensor 81 is provided so as to be movable longitudinally relative to workpiece 2 supported by support 20. Temperature sensor 81 is moved longitudinally together with welding torch 15 by longitudinal drive unit 60. This makes it possible to continuously measure the temperature of the above-mentioned region, including molten pool 4, from the start to the end of the build-up process described below. In the illustrated example, temperature sensor 81 is fixed to welding torch 15.

[0038] The processing device 82 generates information about the dimensions of the molten pool 4 based on the temperature distribution map and passes it to the control unit 90. The temperature sensor 81 measures the temperature of the above-mentioned area including the molten pool 4 from the start to the end of the build-up process described below, so that the processing device 82 can continuously pass information about the dimensions of the molten pool 4 to the control unit 90 from the start to the end of the build-up process.

[0039] The control unit 90 controls the laser oscillator 41 based on the information regarding the size of the molten pool 4 received from the processing device 82. Specifically, the control unit 90 controls the laser oscillator 41 so that the intensity of the laser beam 45 emitted from the laser emitter 43 decreases as the size of the molten pool 4 increases. The control unit 90 also controls the laser oscillator 41 so that the intensity of the laser beam 45 emitted from the laser emitter 43 increases as the size of the molten pool 4 decreases. This allows the size of the molten pool 4 to be controlled within a predetermined range. This means that the temperature of the workpiece 2 during overlay welding can be controlled as desired. Furthermore, it means that the dilution rate of the components of the filler metal 35 in the overlay layer 3 can be controlled as desired. As a result, the properties of the overlay layer 3 can be adjusted to the desired characteristics. Since the processing device 82 continuously transmits information regarding the size of the molten pool 4 to the control unit 90 from the start to the end of the overlay welding process, the control unit 90 can continuously control the laser oscillator 41 from the start to the end of the overlay welding process. As a result, it is possible to suppress the temperature rise of the object to be welded 2 and the resulting increase in the dilution ratio without interrupting the build-up process.

[0040] In the illustrated example, the output of the laser beam 45 is controlled so that the dilution ratio is 10% or more and 40% or less, more preferably 15% or more and 35% or less. This is because if the dilution ratio is less than 10%, there is a risk of poor penetration occurring between the buildup layer 3 and the work-piece 2. Furthermore, if the dilution ratio exceeds 40%, the hardness of the buildup layer 3 will be insufficient for use in a thermal power plant through which high-temperature steam flows. When the output of the laser beam 45 is controlled so that the dilution ratio is 15% or more and 35% or less, the Vickers hardness of the buildup layer 3 can be more reliably adjusted to Hv320 or more and Hv500 or less.

[0041] Next, the operation of the present embodiment configured as described above will be described, along with a welding method using the above-described welding device 10.

[0042] First, as shown in FIG. 2, both end portions of the object to be welded 2 are supported by the support portions 20.

[0043] Next, welding torch 15 and temperature sensor 81 are placed near one end of object 2 to be welded.

[0044] Next, object 2 to be welded is rotated around rotation axis 70X by rotation drive unit 70. Additionally, longitudinal drive unit 60 starts moving welding torch 15 and temperature sensor 81 along the longitudinal direction. Welding torch 15 and temperature sensor 81 are moved in the movement direction D1.

[0045] Next, a build-up process is carried out to form build-up layer 3 on object-to-be-welded 2. In the build-up process, filler material 35 is supplied from welding torch 15 to build-up surface 2a of object-to-be-welded 2, and laser light 45 is irradiated. The build-up process is carried out while rotating object-to-be-welded 2 by rotation drive unit 70 and while moving welding torch 15 and temperature sensor 81 by longitudinal drive unit 60.

[0046] In the illustrated example, laser beam 45 is emitted from laser emission part 43 of welding torch 15. During this emission, powdered filler metal 35 is supplied from filler metal discharge hole 33 of welding torch 15. The filler metal 35 is supplied from around and along laser beam 45. As a result, powdered filler metal 35 is melted by laser beam 45. Furthermore, laser beam 45 partially melts object-to-be-welded 2. The molten filler metal 35 and the molten object-to-be-welded 2 form a molten pool 4 on welded surface 2a. Then, components of the molten filler metal 35 dissolve into the molten object-to-be-welded 2, and components of the molten object-to-be-welded 2 dissolve into the molten filler metal 35. In addition, the powdered filler metal 35 discharged from the filler metal discharge hole 33 and the molten pool 4 formed by the molten filler metal 35 and the workpiece 2 are surrounded by shielding gas 55 supplied from the shielding gas discharge hole 53, and are prevented from being oxidized by the atmosphere.

[0047] During the build-up process, as welding torch 15 is moved relative to the workpiece 2, molten pool 4 formed on the workpiece surface 2a moves away from laser beam 45 and solidifies to become build-up layer 3. Furthermore, during the build-up process, as welding torch 15 traces a spiral trajectory around the workpiece surface 2a of the workpiece 2, molten pool 4 and build-up layer 3 are formed on the workpiece surface 2a along the spiral trajectory.

[0048] During the build-up process, the temperature sensor 81 measures the temperature of the area on the workpiece 2, including the molten pool 4. The position of the molten pool 4 on the workpiece 2 moves along the spiral trajectory, and the position of the temperature sensor 81 on the workpiece 2 also moves to follow the molten pool 4. The processing device 82 creates a temperature distribution map based on the temperature measured by the temperature sensor 81. Then, it creates information about the dimensions of the molten pool 4 based on the temperature distribution map. The control unit 90 controls the laser oscillator 41 based on the information about the dimensions of the molten pool 4 created by the processing device 82.

[0049] After the build-up step, a surface treatment step may be carried out in which the surface of the build-up layer 3 is machined to make the surface smooth (to form a cylindrical surface).

[0050] Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0051] (Example) Using the above-described welding device 10, overlay welding was performed on a workpiece 2, and one layer of overlay 3 was formed on the overlay surface 2a of the workpiece 2 as shown in Figure 1. A cylindrical forged rod of a nickel-based alloy was used as the workpiece 2, and powder of a cobalt-based alloy was used as the filler material 35. A laser oscillator using a solid-state laser was used as the laser oscillator 41. Overlay welding was performed under the following welding conditions. <Welding conditions> Filler metal feed rate: 10g / min~60g / min Welding speed: 200mm / min~1000mm / min Laser output: 2kW~10kW The term "welding speed" used herein means the speed of welding torch 15 relative to surface 2a to be welded (the speed along the spiral trajectory).

[0052] Under the above conditions, a surface treatment step was carried out in which the buildup layer 3 formed on the object to be welded 2 was machined, resulting in a thickness of the buildup layer 3 of 0.5 mm. Here, the thickness of the buildup layer 3 was measured using the buildup surface 2a of the object to be welded 2 before buildup welding as a reference. In other words, the thickness of the buildup layer 3 is the difference T between the radius 3R of the outer peripheral surface 3a of the buildup layer 3 formed on the object to be welded 2 and the radius 2R of the outer peripheral surface (buildup surface) 2a of the object to be welded 2 before buildup welding, as shown in FIG. 1 .

[0053] After the surface treatment step was carried out, a cross-sectional sample of the obtained welded member 1 was prepared, and the hardness of the buildup layer 3 and the dilution ratio of the filler metal 35 in the buildup layer 3 were measured. The hardness was measured in Vickers hardness.

[0054] (Comparative Example) Except for not controlling the output of the laser beam 45 during the overlay welding, overlay welding was performed in the same manner as in the Example, and the surface treatment process was performed on the overlay layer 3 formed on the object to be welded 2 in the same manner as in the Example. Then, the hardness of the overlay layer 3 and the dilution rate of the components of the filler metal 35 in the overlay layer 3 were measured.

[0055] (evaluation) Table 1 shows the hardness of the buildup layer 3 and the dilution ratio of the examples and comparative examples.

[0056] [Table 1]

[0057] As shown in Table 1, the dilution ratio of the components of the filler metal 35 in the overlay layer 3 of the comparative example was 18.0% at the weld start point and 41.3% at the weld end point. That is, in the comparative example, the dilution ratio of the overlay layer 3 was higher at the weld end point than at the weld start point. The dilution ratio of the overlay layer 3 of the comparative example exceeded 40% at the weld end point. Furthermore, the hardness of the overlay layer 3 of the comparative example was Hv 418 at the weld start point and Hv 319 at the weld end point. That is, in the comparative example, the hardness of the overlay layer 3 was lower at the weld end point than at the weld start point. The hardness of the overlay layer 3 of the comparative example was less than Hv 320 at the weld end point.

[0058] In contrast, the dilution ratio of the components of the filler metal 35 in the overlay layer 3 of the example was 10.0% at the weld start point and 21.8% at the weld end point. That is, in the example, the dilution ratio of the overlay layer 3 was higher at the weld end point than at the weld start point. The dilution ratio of the overlay layer 3 of the example was 10% or more and 40% or less at both the weld start point and the weld end point. Furthermore, the hardness of the overlay layer 3 of the example was Hv492 at the weld start point and Hv353 at the weld end point. That is, in the example, the hardness of the overlay layer 3 was lower at the weld end point than at the weld start point. The hardness of the overlay layer 3 of the example was Hv320 or more at both the weld start point and the weld end point.

[0059] From the above results, it can be seen that the characteristics of the buildup layer 3 can be controlled by controlling the output of the laser beam 45 based on information about the dimensions of the molten pool 4.

[0060] In the above-described embodiment and examples, the buildup step is described with reference to a case in which the filler material 35 is supplied to the workpiece surface 2a along the longitudinal direction and the laser beam 45 is irradiated to form the buildup layer 3. However, this is not limiting. The buildup layer 3 may be formed by irradiating the laser beam 45 onto a filler material layer formed by thermally spraying or applying the filler material 35 onto the workpiece surface 2a. In this case, the welding apparatus 10 may include, instead of the filler material supply unit 30, a filler material layer forming unit that forms the filler material layer by thermally spraying or applying the filler material 35 onto the workpiece surface 2a. The support unit 20 may support the workpiece 2 on which the filler material layer is formed, and the laser irradiation unit 40 may irradiate the workpiece 2 on which the filler material layer is formed with laser beam. In this case, the welding method may include a filler material layer forming step in which the filler material 35 is sprayed or applied to the workpiece surface 2a to form the filler material layer. Then, in the build-up step, after the filler material layer forming step, the filler material layer may be irradiated with laser light 45 to re-melt the filler material 35 of the filler material layer, thereby forming the build-up layer 3 on the surface 2a to be built up.

[0061] As described above, the welding method according to this embodiment is a welding method for performing overlay welding on the overlay surface 2a of the elongated object to be welded 2 along the longitudinal direction of the object to be welded, and includes a build-up step in which filler metal 35 is supplied along the longitudinal direction of the object to be welded and laser light 45 is irradiated onto the surface to be welded 2a, and the molten filler metal 35 forms an overlay layer 3 on the surface to be welded 2a. In the build-up step, information about the dimensions of the molten filler metal 35 formed by the object to be welded 2 and the filler metal 35 melted by the laser light 45 is obtained, and the output of the laser light 45 is controlled based on this information. According to this welding method, the temperature of the object to be welded 2 during overlay welding and the dilution rate of the components of the filler metal 35 in the overlay layer 3 can be controlled as desired, and as a result, the properties of the overlay layer 3 can be adjusted to desired values.

[0062] Alternatively, the welding method according to this embodiment may be a welding method for overlay welding on the overlay surface 2a of the elongated workpiece 2 along the longitudinal direction of the workpiece 2, and may include a filler layer formation step of spraying or applying a filler material 35 onto the workpiece 2a to form a filler layer, and a buildup step of irradiating the filler material layer with a laser beam 45 along the longitudinal direction after the filler layer formation step to re-melt the filler material 35 in the filler layer and form an overlay layer 3 on the workpiece 2a. Furthermore, in the buildup step, information regarding the dimensions of the molten molten filler material 35 melted by the laser beam 45 and the workpiece 2 may be obtained, and the output of the laser beam 45 may be controlled based on this information. This welding method also makes it possible to control the temperature of the workpiece 2 during overlay welding and the dilution rate of the filler material 35 in the overlay layer 3 as desired. As a result, the properties of the overlay layer 3 can be adjusted to desired values.

[0063] In the welding method according to this embodiment, information about the dimensions of the molten pool 4 is obtained using a non-contact radiation temperature sensor 81.

[0064] The welded member 1 according to this embodiment is a welded member 1 in which a filler material 35 is overlay-welded to the overlay surface 2a of an elongated object to be welded 2 to form an overlay layer 3, and the dilution rate of the components of the filler material 35 in the overlay layer 3 is 10% to 40%, preferably 15% to 35%. With such a welded member 1, the risk of poor penetration occurring between the overlay layer 3 and the object to be welded 2 is reduced, and the hardness of the overlay layer 3 is suitable for use in a thermal power plant where heated steam flows.

[0065] Furthermore, the welded member 1 according to this embodiment is a welded member 1 in which a cobalt-based alloy 35 is overlaid on the welded surface 2a of an elongated object to be welded 2 to form an overlay layer 3, and the Vickers hardness of the overlay layer 3 is Hv320 or more and Hv500 or less. With such a welded member 1, the hardness of the overlay layer 3 is suitable for use in a thermal power plant through which heated steam flows.

[0066] The above-described embodiments and modifications thereof are included within the scope and spirit of the inventions, and are also included in the inventions and their equivalents set forth in the claims. Naturally, the above-described embodiments and modifications thereof may be partially combined as appropriate within the spirit of the present invention. [Explanation of symbols]

[0067] 1: welding process member, 2: welding object, 2a: build-up surface, 3: build-up layer, 10: welding equipment, 15: welding torch, 20: support part, 30: filler metal supply part, 35: filler metal, 40: laser irradiation part, 45: laser light, 50: shielding gas supply part, 60: longitudinal direction drive part, 70: rotation drive part, 80: dimension measurement part, 81: temperature sensor, 90: control part

Claims

1. A welding method for overlay welding an elongated object to be welded along the longitudinal direction of the object to be welded. A contact method, A filler material is supplied to the surface to be overlaid along the longitudinal direction, and a laser beam is irradiated. and a build-up process of forming a build-up layer on the build-up surface by the molten filler metal. In the overlaying process, the filler material and the and the temperature of each point in the area including the molten pool formed by the welding object, The information on the dimensions of the area having a temperature equal to or higher than the melting point of the welding object and the filler metal is The information on the dimensions of the molten pool is acquired, and the dimensions of the molten pool are set to fall within a predetermined range. and the dilution rate of the components of the filler metal in the buildup layer is 10% or more and 40% or less. The larger the size of the molten pool, the lower the intensity of the laser beam. The output of the laser beam is controlled so that the intensity of the laser beam increases as the welding distance decreases. Law.

2. A welding method for overlay welding an elongated object to be welded along the longitudinal direction of the object to be welded. A contact method, Filler layer formation: Forming a filler layer by spraying or applying a filler material onto the surface to be overlaid The process and After the filler layer forming step, a laser beam is irradiated onto the filler layer along the longitudinal direction. a build-up process in which the filler material of the filler material layer is re-melted to form a build-up layer on the surface to be built up; and, Equipped with In the overlaying process, the filler material and the and the temperature of each point in the area including the molten pool formed by the welding object, The information on the dimensions of the area having a temperature equal to or higher than the melting point of the welding object and the filler metal is The information on the dimensions of the molten pool is acquired, and the dimensions of the molten pool are set to fall within a predetermined range. and the dilution rate of the components of the filler metal in the buildup layer is 10% or more and 40% or less. The larger the size of the molten pool, the lower the intensity of the laser beam. The output of the laser beam is controlled so that the intensity of the laser beam increases as the welding distance decreases. Law.

3. The information about the size of the molten pool is obtained using a non-contact radiation temperature sensor. Item 3. The welding method according to item 1 or 2.

4. A welding method as described in claim 1 or 2, wherein the dilution rate is 15% or more and 35% or less.

5. Claims 1 to 4, wherein the Vickers hardness of the buildup layer is Hv320 or more and Hv500 or less. The welding method according to any one of the preceding claims.

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