JP2001259833A - Method and device for cladding by welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for cladding by welding, by which a cladding part with a high quality can be stably formed even when cladding by welding on the thin part of a work and a welding deformation can be reduced. SOLUTION: When cladding by welding on the work 1 by a torch 3, by generating a Lorentz force driving molten metal in the molten pool of the work 1 by an exciting coil 3a disposed so that the outer periphery of the lower part of the torch 3 is surrounded, weld beads are smoothed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a build-up welding method and apparatus suitable for performing build-up welding on a relatively thin work such as an edge portion of a blade in a wind machine or a turbine.

[0002]

2. Description of the Related Art Conventionally, there are a gas overlay method, an arc overlay method, a plasma overlay method, and the like, and a member to be overlaid (hereinafter referred to as a work) is a relatively thick plate. There are many examples of practical application for those with large heat capacity. But,
When the work is a relatively thin plate such as a turbine blade, and the end of the work is coated, the edge of the work is very easy to melt, so the proper overlay shape and quality (hardness etc.) There are problems such as difficulty in obtaining and deformation of welding easily, which makes application difficult.

[0003] That is, in the conventional overlaying means, FIG.
In the case where the work 1 as a thin plate member as shown in FIG. (1) If the input heat quantity is high, (a) If a bead (facing metal) 2 is welded to the edge of the work 1, the edge is melted too much and droops as shown in FIG. The specified shape cannot be secured. (b) Due to the high dilution of the work 1, excellent properties (high hardness, etc.) inherent in the overlay material cannot be obtained. (2) Conversely, if the input heat is too low so that the edge of the work 1 is not melted too much, (a) a defective fusion point k is likely to occur at a portion away from the edge as shown in FIG. 1 (c). Become. (b) As shown in FIG. 1 (c), the bead 2 becomes convex, the wetting angle increases, the conformability decreases, the bead shape deteriorates, and the fatigue strength at the bead end decreases. Or a weld defect occurs at the end of the bead when performing multi-layer overlaying. (c) Since the temperature of the molten metal is low and fluidization and stirring are not performed much, the structure becomes coarse or non-uniform.

[0004] The above-mentioned problems make it extremely difficult to obtain a stable and good build-up portion. In addition, when the work 1 is a thin plate, there is a problem that welding deformation easily occurs. .

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a build-up welding in which a high-quality build-up portion can be formed stably even when building up a thin portion of a work, and welding deformation can be reduced. It is an object to provide a method and an apparatus.

[0006]

In order to solve the above-mentioned problems, the overlay welding method according to the present invention is characterized in that when overlay welding is performed on the surface of a work, the weld is welded by electromagnetic means into a weld pool at the weld. It is characterized in that build-up welding is performed while generating Lorentz force for driving metal.

According to the above-mentioned overlay welding method of the present invention, when overlay welding is performed on a thin portion of a work such as a turbine blade, the molten metal is stirred by Lorentz force by electromagnetic means in a molten pool of the welded portion. Or a flow in one direction, so that a good build-up portion can be obtained.

When the Lorentz force is generated by an alternating magnetic field, the coating film properties such as hardness are improved by the refinement of the crystal grains and the homogenization of the structure. Further, the flattening of the bead shape and the improvement of the conformability to the welded surface can prevent a decrease in the fatigue strength of the overlay portion and prevent welding defects at the time of multilayer overlaying. Furthermore, the effect of reducing excessive melting, poor fusion, and the like of the edge portion of the work can be obtained by making the penetration of the overlay portion shallower and wider.

When the Lorentz force is generated by a DC magnetic field, an increase in the thickness of the bead on the edge side of the work and the sagging of the edge portion due to the unidirectional flow of the molten metal can be prevented. In particular, when the Lorentz force is generated in a biased AC magnetic field having an average value other than 0, such as a magnetic field in which AC and DC are superimposed or an AC magnetic field in which the duty ratio is changed. And the respective effects in the case of the DC magnetic field can be obtained together, and a better built-up portion can be obtained.

Next, a build-up welding apparatus according to the present invention includes a work fixing jig for fixing a work to be subjected to build-up welding,
A build-up welding torch disposed directly above the work fixing jig; and an excitation coil for generating Lorentz force for driving molten metal in a molten pool formed on the work by the torch is provided by the torch. Are arranged so as to surround the lower periphery of the lower part.

Further, in the overlay welding apparatus according to the present invention, the work fixing jig comprises: a water-cooled copper block having a mold function for forming an appropriate bead for holding the work; a vise for supporting the block in a tightenable manner; And a support base that supports the vice so as to adjust its rotation so as to adjust the posture of the vise.

In the above-mentioned overlay welding apparatus of the present invention, when the work fixed by the work fixing jig is formed into a molten pool by the welding torch disposed immediately above the work fixing jig, the same torch is used. The excitation coil disposed so as to surround the lower periphery of the metal plate appropriately generates a Lorentz force for driving the molten metal in the molten pool, thereby forming a good overlay.

In addition, when overlay welding is performed on a very easily melted portion such as an end portion of a thin plate work, a water-cooled copper block for clamping the work and a vice for fastening the block in the work fixing jig are used. By appropriately restraining and cooling the work, and by appropriately adjusting the posture of the work by the support base that supports the vise so that the rotation can be adjusted, the overlay welding work on the work can be performed efficiently, Due to the function of the appropriate bead forming mold of the water-cooled copper block that holds the work, welding deformation of the work is reduced and a good bead-shaped overlay is obtained.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a cladding welding method and apparatus according to an embodiment of the present invention; FIG. FIG. 4 is an enlarged view of a weld pool when the overlay welding is performed by the apparatus of FIG. 2, and FIG. 4 is an explanatory view showing a bead shape improving effect when an AC magnetic field is used in the apparatus of the present invention. Side view showing the overlaid state of the convex bead by the apparatus of FIG.
FIG. 5 is a side view showing a flat bead buildup state by the apparatus of the present invention, FIG. 5 is an explanatory view showing a bead shape improving effect when a DC magnetic field is used in the apparatus of the present invention, and FIG. FIG. 4 is an explanatory view of a magnetic field applying condition in the apparatus of the present invention. FIG. 5A is a graph showing a waveform in which AC and DC are superimposed,
FIG. 7B is a graph showing an AC waveform with the duty ratio changed, and FIG. 7 is an explanatory diagram showing the structure of a work fixing jig in the apparatus of the present invention.

As shown in FIG. 2, a build-up welding apparatus as one embodiment of the present invention includes a work fixing jig 20 for fixing a work 1 to be subjected to build-up welding, and a work fixing jig.
And a torch 3 for overlay welding, which is disposed immediately above the torch 20. The torch 3 is supplied with powder by a powder supply device 4, and also has a center gas and a shielding gas controlled by a control device 7. Is to be sent. Further, the torch 3 includes a plasma power supply 5 and a cooling water circulating device 6.
Is connected. Further, a remote control box 9 is provided in this apparatus. In this way, the workpiece 1 is subjected to the plasma powder overlay welding.

In the present apparatus, an exciting coil 3a is disposed so as to surround the lower periphery of the torch 3, and a molten pool (see FIG. 3) formed on the work 1 by the torch 3 at the time of overlay welding on the work 1. In FIG. 17, a Lorentz force for driving the molten metal is generated by the exciting coil 3a. In FIG. 3, reference numeral 14 indicates a magnetic field, 15 indicates an arc current, 16 indicates an arc pole, and 18 indicates an electromagnetic force.

The direction and strength of the magnetic field 14 applied by the exciting coil 3a can be adjusted by the direction and magnitude of the exciting current supplied from the exciting power supply 8 to the exciting coil 3a.

As shown in FIG. 7, the work fixing jig 20 holds (clamps) the work 1 with a water-cooled copper block 10 through which cooling water 11 is passed. Is possible. The fastening of the water-cooled copper block 10 is performed by a fastening piece 12 a of the vise 12.

The water-cooled copper block 10 has a proper bead forming mold function and is shaped to receive the back surface of the edge of the work 1. Further, in order to adjust the posture of the work 1, the vise 12 is supported by the support base 13 so as to be rotatable about a rotation shaft 13a.

In the plasma powder build-up welding, a powder material as a filler material is charged into a plasma arc generated between the work 1 and the welding torch 3, and a welding metal film is formed on the surface of the work 1. A bead 3 is formed.

As shown in FIG. 3, in a molten pool 17 formed by a plasma arc, an arc current 15 flows almost radially around an arc pole 16. Here, a magnetic field 14 perpendicular to the surface of the workpiece 1 is generated by the exciting coil 3a.
, Lorentz force is generated by the interaction with the arc current 15 according to Fleming's left-hand rule.

First, when an alternating current is applied to the exciting coil 3a and an alternating magnetic field is applied to the molten pool 17, the direction of the generated Lorentz force changes with time, so that the molten metal is stirred. become.

As a result, (1) the coating film characteristics such as hardness are improved by the refinement of the crystal grains and the homogenization of the structure. (2) The bead shape is improved by flattening the bead shape (preventing convexity) and improving the end conformability. That is,
According to the conventional method without magnetic stirring, the bead 2 has a large wetting angle and generates a poorly conformable portion n as shown in FIG. 4 (a). As shown in FIG. 4 (b), the bead 2 is flattened, and the wet state becomes small with a small wetting angle. (3) By making the penetration shallower, excessive melting of the edge portion and poor fusion are reduced. And the like, and a high quality overlay is stably obtained. This effect has a magnetic field strength of 10
It is remarkable in the range of 0 to 1000 Gauss and the magnetic field frequency of 1 to 10 Hz.

Next, when a unidirectional magnetic field is applied to the molten pool 17 with the current flowing through the exciting coil 3a being a direct current, the direction of the generated Lorentz force does not change with time, but the molten metal in the molten pool becomes an arc. It exists more behind the arc than ahead (welding progress direction), and the electromagnetic force behind the arc greatly affects the flow of the molten metal and further the bead formation. For example, if the rotational force is clockwise as shown in FIG. 3, the left side (downward in the drawing) Lorentz force always acts in the welding progress direction behind the arc, so that the molten metal is leftward in the welding progress direction. (Downward in the plane of the paper), and a thick overlay bead can be formed on the left side with respect to the welding progress direction.

By appropriately setting the direction of the magnetic field by utilizing this phenomenon, it is possible to form a bead 2 having a thick edge on the workpiece 1 as shown in FIG. A good bead shape with little droop can be obtained. This effect is remarkable when the magnetic field strength is in the range of 100 to 1000 Gauss.

Further, the current flowing through the exciting coil 3a is changed to a waveform obtained by superimposing an alternating current and a direct current as shown in FIG. 6A or an alternating current waveform obtained by changing the duty ratio as shown in FIG. As described above, when the average value is set to an AC waveform having a bias instead of 0, the respective effects of the case where the exciting current is AC and the case of DC as described above can be simultaneously obtained,
A better overlay weld is obtained. This effect is magnetic field strength 1
It is remarkable in the range of 00 to 1000 Gauss and the magnetic field frequency of 1 to 10 Hz.

When the jig 20 for fixing the work 1 as shown in FIG. 7 is used in addition to the above, the following effects can be obtained. (1) The work 1 is clamped by the water-cooled copper block 10 and is restrained and cooled, so that welding deformation can be reduced. (2) If the water-cooled copper block 10 has a shape to receive the back of the edge, and the block plays a role of a mold,
The dripping of the molten metal at the edge can be reduced, and a bead having a good shape can be obtained.

[0028]

As described in detail above, the following effects can be obtained by the overlay welding method and apparatus of the present invention. (1) In the overlay welding method of the present invention, when performing overlay welding on a thin-walled portion of a work such as a turbine blade, the molten metal is stirred by Lorentz force by electromagnetic means in a molten pool of the welded portion. Since an action of flowing in the direction is performed, a good build-up portion can be obtained. (2) In the overlay welding apparatus of the present invention, when the work fixed by the work fixing jig forms a molten pool by the welding torch arranged immediately above the work fixing jig, the lower part of the torch is formed. The excitation coil disposed to surround the outer periphery appropriately generates a Lorentz force for driving the molten metal in the molten pool, thereby forming a good overlay. (3) When overlaying on very easily melted parts such as the end of a thin plate work, the work fixing jig uses a water-cooled copper block for clamping the work and a vise for fastening the block. With proper restraint and cooling, and proper adjustment of the work position by the support base that supports the vice so that the rotation can be adjusted, overlay welding work on the work can be performed efficiently, especially when the work is clamped. Due to the proper bead forming mold function of the water-cooled copper block, welding deformation of the work is reduced and a good bead-shaped overlay is obtained.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a conventional overlay welding, in which FIG. 1 (a) shows a workpiece before overlaying, and FIGS. 1 (b) and 1 (c) each show an workpiece after overlaying. It is.

FIG. 2 is an explanatory view schematically showing a build-up welding apparatus according to the present invention.

FIG. 3 is an enlarged view of a molten pool when overlay welding is performed by the apparatus of FIG. 2;

4A and 4B are explanatory views showing a bead shape improving effect when an AC magnetic field is used in the apparatus of the present invention, wherein FIG. 4A is a side view showing a built-up state of a convex bead by a conventional apparatus, and FIG. FIG. 4 is a side view showing a flat bead buildup state by the apparatus of the present invention.

FIG. 5 is an explanatory diagram showing a bead shape improving effect when a DC magnetic field is used in the apparatus of the present invention.

6A and 6B are explanatory diagrams of magnetic field application conditions in the apparatus of the present invention. FIG. 6A is a graph showing a waveform in which AC and DC are superimposed, and FIG. 6B is an AC waveform in which the duty ratio is changed. It is a graph.

FIG. 7 is an explanatory view showing a structure of a work fixing jig in the apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Work 2 Bead 3 Overlay welding torch 3a Excitation coil 4 Powder supply device 5 Plasma power supply 6 Cooling water circulation device 7 Control device 8 Excitation power source 9 Remote control box 10 Water-cooled copper block 11 Cooling water 12 Vise 12a Tightening piece 13 Support Table 13a Rotating axis 14 Magnetic field 15 Arc current 16 Arc pole 17 Melt pool 18 Electromagnetic force 20 Work fixing jig

Claims (3)

[Claims] 1. The method according to claim 1, wherein, when overlay welding is performed on the surface of the workpiece, the overlay welding is performed while generating Lorentz force for driving the molten metal by electromagnetic means in a molten pool in the welded portion. Overlay welding method. 2. A work fixing jig for fixing a work to be subjected to build-up welding, and a build-up welding torch disposed immediately above the work fixing jig, and the work is attached to the work by the torch. A build-up welding apparatus, wherein an excitation coil for generating a Lorentz force for driving a molten metal in a formed molten pool is provided so as to surround a lower outer periphery of the torch. 3. The overlay welding apparatus according to claim 2, wherein the work fixing jig comprises a water-cooled copper block having a mold function for forming an appropriate bead for holding the work, and a vice for supporting the block in a tightenable manner. And a support base for supporting the vise so as to adjust the rotation of the work so as to adjust the posture of the work.