JP2012110900A - Laser build-up method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser build-up method of performing build-up welding with a laser without generating sputter and without carbonating a binder agent even when metal powder with the binder agent mixed is used as filler metal.SOLUTION: The laser build-up method includes: a step of applying the filler metal 1 mainly containing the metal powder and also containing an organic binder agent on a member 2 subjected to build-up welding; a step of applying a first laser at a first output Pf on the applied filler metal 1; and a step of applying a second laser, which moves to follow the first laser at a predetermined distance interval, at a second output Pa on the filler metal 1 after the first laser is applied. When a melting point of the metal powder is Tm, and a decomposition temperature of the organic binder agent is Tb, relationship between the first output and the second output satisfies 0.8×(Tb/Tm)×Pa≤Pf<(Tb/Tm)×Pa.

Description

  The present invention relates to a laser cladding method, and more particularly to a powder cladding method using a laser.

  Conventionally, methods such as MIG welding, TIG welding, and laser welding are applied when overlay welding a furnace wall panel of a land boiler. However, when MIG welding is applied, the overlay layer tends to be as thick as 2 to 4 mm, and the waste of the filler metal increases. Moreover, when TIG welding is applied, although the thickness of the overlay layer may be reduced to 1 to 2 mm, it takes time because the welding speed is slow. On the other hand, when laser welding is applied, the thickness of the built-up layer can be about 1 mm. Patent Documents 1 to 3 disclose a welding method using a laser.

  For laser welding, a powder material (filler material) is supplied to the workpiece to be welded, and a powder supply method in which the powder material is melted by laser and welded by welding, or a wire (filler material) is supplied. Further, there is a wire supply method in which the wire is melted with a laser and build-up welded.

JP-A-10-85971 (Claim 1) JP 2002-332504 A (Solution means) Japanese Patent No. 4505197 (Claim 1)

  In the powder supply method generally applied in laser welding, not all of the supplied powder material can contribute to welding, and some powder material remains without being scattered or melted. Therefore, the yield of the powder material is as low as about 50%. In addition, when overlay welding is performed on the entire surface of the member 3 having a complicated shape such as the furnace wall panel shown in FIG. 2, the powder material supplied to the inclined surface (for example, the region A) moves in the direction of gravity. There is a problem that it is difficult to form a built-up layer on the inclined surface. Therefore, as shown in FIG. 3, it is necessary to incline the furnace wall panel (member 3) to make the weld-in-welded surface substantially horizontal, and the capital investment increases accordingly.

  In the wire supply type, the bead width is as small as about 5 mm. The bead width in the MIG welding is about 8 mm or more, and the number of weld beads increases in the wire supply type laser welding as compared with the MIG welding, so that the welding time becomes longer.

  In laser welding, there is a method in which a filler material in which a binder agent such as a thickener is mixed with metal powder is applied and fixed on a build-up welding member, and then melted with a laser. In this method, since the laser powder is rapidly heated to a temperature at which the metal powder can be melted, the binder agent is rapidly decomposed. As a result, spatter is generated or the binder agent is carbonized, so that the quality of the built-up layer is lowered and the yield of the metal powder is also lowered.

  The present invention has been made in view of such circumstances, and even when a metal powder mixed with a binder agent is used as a filler material, spatter is not generated and the binder agent is carbonized. An object of the present invention is to provide a laser overlaying method in which overlay welding is performed with a laser without using the laser.

  In order to solve the above-described problems, the present invention provides a process of applying a filler metal mainly composed of metal powder and containing an organic binder agent to a build-up weld member, and a first applied to the applied filler material. A step of irradiating a laser with a first output Pf, and a second output of a second laser that moves following the first laser at a predetermined distance from the filler material after the first laser irradiation. And a step of irradiating with Pa, wherein the relationship between the first output and the second output is 0.8 × when the melting point of the metal powder is Tm and the decomposition temperature of the organic binder agent is Tb. A laser cladding method that satisfies (Tb / Tm) × Pa ≦ Pf <(Tb / Tm) × Pa is provided.

  In the said invention, it can prevent that the apply | coated filler material falls off from the overlay welding member by including an organic binder agent in a filler material. The applied filler metal is preheated by irradiating the first laser, and then subjected to main welding by a second laser that moves following the first laser at a predetermined distance. By setting the first output Pf to be equal to or greater than {0.8 × (Tb / Tm) × Pa}, the organic binder agent can be decomposed and volatilized without causing spattering and carbonization. Further, by setting the first output to {(Tb / Tm) × Pa} or less, the holding power is such that the metal powder does not fall off from the overlay welding member after the first laser irradiation until the main welding. Can be secured. By doing so, it is possible to improve the build-up quality and the material yield of the filler metal.

  In one embodiment of the present invention, the relationship between the irradiation area Af of the first laser and the irradiation area Aa of the second laser is 0.8 × (Tb / Tm) × Aa ≦ Af <(Tb × Tm) × Aa. It is preferable to satisfy.

  According to the said one aspect | mode, by making irradiation area Af at the time of preheating or more into {0.8 * (Tb / Tm) * Aa}, an organic binder agent is not generated without spattering and carbonization. It can be decomposed and volatilized. Further, by setting the first output to {(Tb / Tm) × Aa} or less, the holding power is such that the metal powder does not fall off from the overlay welding member after the first laser irradiation until the main welding. Can be secured.

  According to the present invention, since the filler material contains the organic binder agent, the overlay welding member need not be inclined. Even when a metal powder containing an organic binder agent is used as a filler material, by preheating with a predetermined output using the first laser, no spatter is generated and the binder agent is not carbonized. Overlay welding is possible. The second laser is moved following the first laser at a predetermined distance, thereby suppressing the carbonization of the organic binder agent and performing the main welding in a state in which fixing of the metal powder to the overlay welding member is ensured. can do. Thereby, it is possible to improve the quality of the built-up layer and improve the yield of the powder.

It is the schematic explaining the laser overlay welding which concerns on this embodiment. It is the schematic which shows the cross-section of a furnace wall panel. It is the figure which inclined the furnace wall panel shown in FIG.

Hereinafter, an embodiment of a laser cladding method according to the present invention will be described with reference to the drawings. In FIG. 1, the schematic explaining the laser overlay welding which concerns on this embodiment is shown.
The laser cladding method according to the present embodiment includes a step of applying the filler material 1 to the overlay welding member 2, a step of irradiating the applied filler material 1 with the first laser, and irradiating the first laser. And a step of irradiating the filler material 1 after the irradiation with the second laser.

  First, the filler material 1 is applied and fixed to the overlay welding member 2. The application method is spray coating, brush coating, or the like. The thickness of the filler material 1 to be applied is, for example, about 0.5 mm to 1.5 mm in the case of Inconel (registered trademark) overlaying applied to a furnace wall panel of a land boiler for corrosion resistance purposes. Set.

  The filler material 1 is mainly composed of metal powder and further contains an organic binder agent. The metal powder is Inconel (registered trademark) or stainless steel. The organic binder agent is a polyvinyl alcohol resin or a cellulose resin. The mixing ratio of the metal powder and the organic binder agent is appropriately set depending on the types of the metal powder and the organic binder agent, combinations thereof, and the like.

Next, the first filler and the second laser are sequentially irradiated onto the applied filler material 1. As the laser, YAG, a semiconductor laser, a fiber laser, or the like is used. The laser traveling speed is set to 400 mm / min to 800 mm / min.
Specifically, the first laser is moved along the filler material 1 (in the X direction) while irradiating the filler material 1 with the first output Pf. After moving the first laser by a predetermined distance, irradiation with the second laser is started. The second laser is irradiated to the filler material 1 after the first laser is irradiated with the second output Pa. The second laser moves following the first laser while maintaining a predetermined distance d from the first laser. The predetermined distance interval d is preferably 5 mm or more and 10 mm or less.

It is assumed that the relationship between the first output Pf and the second output Pa satisfies the formula (1). Tm is the melting point of the metal powder, and Tb is the thermal decomposition temperature of the organic binder agent.
0.8 × (Tb / Tm) × Pa ≦ Pf <(Tb / Tm) × Pa (1)

The relationship between the irradiation area Af of the first laser and the irradiation area Aa of the second laser preferably satisfies the formula (2). The shape of the laser may be either circular or rectangular (slit).
0.8 × (Tb / Tm) × Aa ≦ Af <(Tb / Tm) × Aa (2)

  According to the said embodiment, the melt material 1 is preheated by irradiating a 1st laser, and the organic binder agent contained in the melt material 1 is decomposed | disassembled. Since the second laser follows the first laser at a predetermined distance and is applied to the filler metal 1, the second laser can be finally welded before the metal powder falls off.

  According to the above embodiment, the first laser and the second laser move along the filler material 1 while being simultaneously irradiated with a predetermined distance interval. The relationship between the first output Pf and the second output Pa satisfies the formula (1), so that the metal powder does not fall off the overlay welding member after the first laser irradiation and before the second laser irradiation. It is possible to suppress the occurrence of spatter and carbonization of the organic binder agent due to the irradiation of the second laser, while maintaining the fixing power.

  According to the above embodiment, the relationship between the irradiation area Af of the first laser and the irradiation area Aa of the second laser satisfies the formula (2), so that the period after the first laser irradiation until the second laser irradiation is performed. In addition, it is possible to suppress the occurrence of spatter and carbonization of the organic binder agent by irradiating the second laser while maintaining a fixing force that does not cause the metal powder to fall off the overlay welding member. This is because the laser density is lowered by shifting the irradiation focus of the laser, and heat input to the overlay layer can be suppressed.

(Example)
Inconel (registered trademark) 625 (melting point Tm: 1290 ° C. to 1350 ° C.) was used as the metal powder. The organic binder agent was an aqueous polyvinyl alcohol solution (polyvinyl alcohol thermal decomposition temperature Tb: 500 ° C.). A slurry in which metal powder and an organic binder agent were mixed at 90:10 (weight ratio) was used as a filler material.

  The filler material prepared above was spray-applied on the surface of the carbon steel plate inclined at 45 ° so as to have a thickness of about 1 mm.

  A semiconductor laser was used for the first laser and the second laser, the laser scanning speed was 600 mm / min, and the output Pa of the second laser was 5.0 kW. The interval between the laser irradiation positions of the first laser and the second laser was 10 mm. The output Pf of the first laser was 1.0 kW, 1.4 kW, 1.5 kW, 1.8 kW, or 2.0 kW.

Laser welding was performed by sequentially irradiating the laser beam applied on the surface of the carbon steel plate with the respective lasers under the above conditions. The results are shown in Table 1.

  According to Table 1, when the output of the first laser was 1.0 kW and 1.4 kW, spatter occurred after irradiation of the second laser, and the organic binder agent was carbonized. When the output of the first laser was 2.0, spattering and carbonization of the organic binder agent did not occur, but the metal powder dropped off before irradiation with the second laser. On the other hand, when the output of the first laser was 1.5 kW and 1.8 kW, spattering and carbonization of the organic binder agent did not occur, and fixing of the metal powder to the carbon steel plate could be maintained.

  According to Table 1, when (output Pf of the first laser) / (output Pa of the second laser) is larger than 0.28 and smaller than 0.4, it is more surely 0.3 or more and 0.36 or less. It was shown that the metal powder can be held while suppressing the generation of spatter and carbonization of the organic binder agent. That is, by setting 0.28 <Pf / Pa <0.4, the organic binder agent contained in the filler material after the irradiation with the first laser is applied to the second laser while maintaining the fixing of the metal powder. Even if irradiated, the amount can be set such that no spatter is generated and carbonization is also suppressed.

The amount of the organic binder agent in the filler material after irradiation with the first laser, and the organic binder agent in the filler material that does not cause sputtering when irradiated with the second laser and carbonization does not become a problem. The amount of can be related to the thermal decomposition temperature Tb of the organic binder and the melting point Tm of the metal powder.
When Inconel (registered trademark) 625 is used for the metal powder and polyvinyl alcohol is used for the organic binder agent, Tb / Tm is 0.37 to 0.39, which is less than 0.4. Therefore, from the results in Table 1, the upper limit value of Pf / Pa can be defined as less than Tb / Tm. Moreover, when Tb / Tm is multiplied by 0.8, 0.8 × Tb / Tm is 0.288 to 0.312, which exceeds 0.28. Therefore, from the results in Table 1, the lower limit value of Pf / Pa can be defined as 0.8 × Tb / Tm or more.

  From the above results, the optimum relationship between the first output Pf of the first laser and the second output Pa of the second laser is 0.8 × (Tb / Tm) × Pa ≦ Pf <(Tb / Tm) × Pa. Can be defined.

1 Filler Material 2 Overlay Welding Member 3 Member

Claims (2)

A step of applying a filler material mainly composed of metal powder and containing an organic binder agent to the overlay welding member;
Irradiating the applied filler material with a first laser at a first output Pf;
Irradiating the filler material after irradiation with the first laser at a second output Pa with a second laser that moves following the first laser at a predetermined distance interval;
With
When the melting point of the metal powder is Tm and the decomposition temperature of the organic binder agent is Tb, the relationship between the first output and the second output is 0.8 × (Tb / Tm) × Pa ≦ Pf < Laser overlaying method that satisfies (Tb / Tm) × Pa. The relationship between the irradiation area Af of the first laser and the irradiation area Aa of the second laser satisfies 0.8 × (Tb / Tm) × Aa ≦ Af <(Tb × Tm) × Aa. Laser overlaying method.

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