JP2014172057A - Powder padding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder padding method, being low like 10% or less in the dilution ratio of a weld bead, capable of using even metallic powder composed of a hard-to-work material and a hard-to-weld material, capable of quickening a weld speed, and also easy in padding on a surface of a metal base material of a vertical attitude.SOLUTION: In the powder padding method, a torch 1 is arranged in a horizontal attitude having the axial direction orthogonal to a surface on the surface of a metal base material W1 set in a vertical attitude, and a plasma arc pa is emitted from a central part of a tip 11 positioned on the tip of the torch 1, and the metallic powder mp to be padded on the upper side in the tip part vicinity of the plasma arc pa is supplied from a discharge hole 9 opening in an upper part of a tip surface 12 of the tip 11, and confronting downward advance weld is executed by moving any one of the metal base material W1 or the torch 1 along the vertical direction.

Description

  The present invention relates to a powder overlay welding method for overlay welding a metal powder for enhancing various properties on a surface of a metal base material.

For example, in order to form a highly corrosion-resistant build-up layer on the outer peripheral surface of a boiler tube for a waste incinerator, the plasma arc is set to a horizontal posture from the center of the front end surface of the plasma torch with the axial direction vertical. Radiating perpendicularly to the outer peripheral surface of the boiler tube, supplying metal powder from the discharge hole that opens to the peripheral side of the tip surface of the torch to the inside of the arc, and at the outermost peripheral side of the tip surface of the torch There has been proposed a manufacturing method of a highly corrosion-resistant boiler overlay that performs powder overlay welding by blowing an inert shielding gas in a cylindrical shape around the arc from the blowout opening (see, for example, Patent Document 1). .
The powder overlay welding method is generally referred to as a PTA method (Plasma Transferred Arc Welding).

  In the powder overlay welding method used in Patent Document 1 or the like, the dilution ratio of the alloy component by the component of the base material in the build-up layer (weld bead) built up from the metal powder on the surface of the metal base material is about 10. % Or less, and it has the advantage that it can be easily welded even with metal powder made of difficult-to-process materials or difficult-to-weld materials. However, in such a powder overlay welding method, the welding speed is slower than MIG welding using a welding wire, so that the productivity is inferior, and the welding conditions are lowered in order to stably supply the metal powder for overlaying. There was a problem that it was limited to the welding method.

On the other hand, the metal panel of the water-cooled wall for the refuse incinerator is held in a vertical position, and the welding wire is supplied at a high speed in a shield gas atmosphere to supplement the thickness of the metal panel against corrosion reduction on the surface. On the other hand, there has also been proposed a vertically descending overlay welding method in which MIG welding is performed while vertically descending (see, for example, Patent Document 2).
The vertical downward overlay welding method by MIG welding described in Patent Document 2 has high productivity because the welding speed is faster than the powder overlay welding method, and the metal base material in a vertical posture is applied to the surface. Although there is an advantage that overlay welding can be easily performed, there is a problem that it is not suitable for overlay welding made of difficult-to-process materials or difficult-to-weld materials.

JP 2008-179865 A (pages 1 to 13, FIG. 1) JP 2000-84565 A (pages 1-7, FIGS. 1-5)

The present invention solves the problems described in the background art, and the dilution rate of the weld bead (ratio of the cross-sectional area of the penetration portion inside the metal base material with respect to the cross-sectional area of the entire weld bead) is low. It is an object of the present invention to provide a powder overlay welding method that can use metal powder made of a welding material, can increase the welding speed, and can easily perform overlay welding on the surface of a metal base material in a vertical posture.
In addition, the said dilution rate is low that the height of the surplus in the welding bead which protrudes from the surface of a metal base material is high, and the penetration to the inside of a metal base material is shallow.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-mentioned problems, the present invention, as a result of intensive studies and investigations by the inventors, performs powder overlay welding by vertical downward welding, and the inside of a plasma arc radiated along a substantially horizontal direction. The supply path of the metal powder to be supplied to is formed from the top of the arc (backward in the downward direction).
That is, the powder overlay welding method of the present invention (Claim 1) is a horizontal posture in which the axial direction is perpendicular to or close to the surface with respect to the surface of the metal base material in a vertical posture or a nearly vertical posture. The torch is disposed at the top of the tip of the tip, and a plasma arc is radiated from the center of the tip located at the tip of the torch. While supplying from the opening | release discharge | release hole which opens, either one of the said metal base material or the said torch is moved along the perpendicular | vertical direction or the direction close | similar to perpendicular | vertical, and vertical downward welding is performed, It is characterized by the above-mentioned.

  According to this, a torch (welding torch) is arranged in a horizontal posture whose axis is perpendicular or nearly perpendicular to the surface of a metal base material in a vertical posture or a posture close to vertical, and is positioned at the tip of the torch. A plasma arc is emitted from the center of the tip, and metal powder to be deposited on the upper side in the vicinity of the tip of the arc is supplied from an emission hole opened at the top of the tip of the tip. As a result, the metal powder is efficiently charged into the molten pool near the surface of the metal base material, which is near the center of the tip of the plasma arc, while receiving a gravitational action, so a relatively low dilution rate of 10% or less. Therefore, overlay welding by vertical downward welding that forms a sound weld bead can be performed at a relatively high speed. In addition, since either the metal base material or the torch moves along the vertical direction or a direction close to the vertical direction, the shape and thickness of the metal base material along the vertical direction are substantially constant. It becomes possible to form a stable weld bead stably.

The metal base material is, for example, a steel material for constituting a boiler tube, a water-cooled wall panel having a plurality of the boiler tubes separated from each other, and is made of, for example, chrome molybdenum steel (low alloy steel). Specifically, alloy steel pipes for boilers and heat exchangers (JIS: G3462, steel type symbols: STB340, STBA22, STBA24) and chrome molybdenum steel plates for boilers and pressure vessels (JIS: G4109, steel type symbols: SCMV2, SCMV3) are exemplified. The
The metal base material includes not only a flat plate having a flat surface but also a curved surface (curved surface) such as a steel pipe. However, even in the case of a curved surface, when the radius is large, the local surface portion adjacent to the vicinity of the tip of the torch can be regarded as a pseudo flat surface and subjected to the welding.
Further, the metal powder is overlay welded by the vertical downward welding in order to impart the required characteristics to the surface of the metal base material. For example, in the case of imparting heat resistance, Ni base or stainless steel When the alloy powder gives wear resistance, a Co-based alloy powder is applied. The metal powder is conveyed by a carrier gas such as Ar.
The Ni-based alloy includes C-276 (Ni-16% Cr-16% Mo-4% W-5% Fe) and Inconel 625 (Ni-22% Cr-10% Mo), Examples of the stainless steel include SUS316 and SUS310.
Further, the Co-based alloys include Stellite No. 6 (Co-28% Cr-4.5% W-1% C-1% Si), No. 12 (Co-29% Cr-8.5%). W-1.4% C-1% Si), and No, 21 (Co-27% Cr-0.25% C-5.5% Mo-1.5% Si).
In addition, the metal powder discharge port may be singular or plural, and the shape may include a circular, oval, elliptical, or arcuate curved shape.
Further, the tip may be separately provided from the powder nozzle of the torch and attached to the tip of the torch by screwing or the like, or may be provided integrally with the tip of the nozzle.
In addition, the flow of the metal powder supplied by the plasma arc and the carrier gas is shielded from the outside by a shielding gas such as Ar radiated in a cylindrical shape from the peripheral side of the tip end surface of the chip. The

Further, in the present invention, the torch arranged in a horizontal posture in which the axial direction is nearly orthogonal to the flat surface of the metal base material in a vertical posture, the axial center of the torch is below the horizontal line or A powder build-up welding method (Claim 2) that is inclined upward within a range of 10 degrees is also included.
According to this, the vertical downward welding is performed in a posture in which the axial center of the torch is inclined to the lower side or the upper side of the horizontal line within 10 degrees with respect to the flat surface of the metal base material in the vertical posture. Therefore, it is possible to perform powder overlay welding similar to the case where the axial center of the torch is parallel to the horizontal line and is orthogonal to the flat surface of the metal base material. In particular, in a posture in which the axial center of the torch is inclined to the lower side within 10 degrees with respect to the horizontal line, the axial direction of the torch is obliquely upward, and is formed by the arc near the surface of the metal base material due to the action of gravity. Therefore, it is possible to form a weld bead having a lower dilution ratio because the metal powder can be efficiently put into the molten pool.
In addition, if the axis of the torch tilts more than 10 degrees below or above the horizontal line, a considerable amount of metal powder is difficult to weld to the flat surface of the metal book, so this range is excluded. It is.

Further, according to the present invention, the flat surface of the metal base material in a posture close to vertical is higher than the torch in a side view with respect to the torch in the horizontal direction in the axial direction. A powder build-up welding method (Claim 3) in which the surface portion is tilted within 10 degrees in a direction away from the vertical line is also included.
According to this, with respect to the torch in which the axial direction is horizontal, the flat surface of the metal base material is inclined in a direction in which the surface portion above the torch is away from the vertical line within 10 degrees. The vertical downward welding is performed in the posture. As a result, combined with the action of gravity, the metal powder can be formed into a weld bead with a lower dilution rate.
When the flat surface of the metal base material is inclined in a direction in which the surface portion above the torch is more than 10 degrees away from the vertical line with respect to the horizontal posture torch, a considerable amount of metal powder is formed on the metal book material. Since it becomes difficult to weld to a flat surface, this range is excluded.

Further, according to the present invention, the tip has a radiation hole for radiating the plasma arc at the center of the tip surface facing the surface of the metal base material, and the periphery of the tip surface above the radiation hole. A powder build-up welding method (Claim 4) having one or a plurality of discharge holes for supplying metal powder to be built up on the side is also included.
According to this, since the metal powder to be built up is supplied above the plasma arc radiated from the tip surface of the tip, even if the powder is subjected to the action of gravity, the metal base material facing the tip Is efficiently put into the molten pool by the arc located in the vicinity of the surface. As a result, a weld bead having a relatively low dilution rate can be formed continuously and stably along the vertical direction of the metal base material.
In addition, in the upper part of the circular (round) tip surface of the chip, the center of the discharge hole from which the metal powder is discharged is within a range of 60 degrees to the left and right from the vertical line passing through the center of the tip surface (the whole Range angle: 120 degrees or less), desirably within 30 degrees from left to right from vertical line (same as above: 60 degrees or less), more desirably within 45 degrees from left to right from vertical line (same as above: 90 degrees or less) ) Are opened in plural or singular. However, within the range of 20 degrees to the left and right (same as above: 40 degrees or less), there is a difficulty that the discharge hole becomes difficult to process.
Further, the metal powder discharge holes are piled up by setting the diameter to 1.0 mm or more in the case of a circle, and to 1.0 mm or more in the case of an oval or arc shape. It is possible to ensure the fluidity of the power metal powder. On the other hand, the diameter of the plasma arc radiation hole is larger than that of the discharge hole.

In addition, the present invention includes a powder overlay welding method (Claim 5) in which the welding speed by the torch is in the range of 5 to 120 cm / min.
According to this, since an appropriate amount of metal powder can be supplied to the molten pool formed near the surface of the metal base material, a weld bead having a good shape and having no defects at the toe is formed. It can be reliably formed along the surface at a relatively fast rate.
When the welding speed is less than 5 cm / min, the molten pool formed on the surface of the metal base material hangs down and it is difficult to form a weld bead. On the other hand, when the welding speed exceeds 120 cm / min, the melting Since the supply amount of the metal powder to the pond becomes too small and a defect may occur at the toe portion of the weld bead, the above-described range is excluded.
The metal powder is preferably supplied from the tip surface of the chip with a carrier gas of 1.0 L / min or more.
Furthermore, the average particle size of the metal powder is recommended to be about 63 to 250 μm from the viewpoint of feedability, and the supply amount is recommended to be in the range of about 3 to 200 g / min, for example.

The vertical sectional view showing the outline of the powder overlay welding method of one form by the present invention. (A)-(C) are the fragmentary views which show the mutually different pattern of the front end surface of the chip | tip attached to the torch used for the said welding method. The vertical sectional view showing the outline of the modification of the above-mentioned welding method. The vertical sectional view which shows the outline of the powder overlay welding method of a different form. The schematic sectional drawing which illustrates the dilution rate in a weld bead. The fragmentary figure which shows the front end surface of the welding tip used for the method of the comparative example. Schematic drawing showing a weld bead having a good shape. Schematic drawing which shows the weld bead of a shape defect.

Hereinafter, modes for carrying out the present invention will be described.
FIG. 1 is a vertical sectional view showing an outline of one embodiment of the powder overlay welding method according to the present invention. As shown in the drawing, the axial center is in the vicinity of the surface of the metal base material W1 in a vertical posture in advance. A welding torch (torch) 1 is arranged in a horizontal posture so as to be orthogonal to each other.
As shown in FIG. 1, the torch 1 has a generally cylindrical shape, a cylindrical shield cap 2 that is positioned on the outer peripheral side and has a tapered tip, and is coaxially disposed inside the cap 2. The cylindrical powder nozzle 5, the pointed tungsten electrode 6 disposed at the center of the hollow portion 7 passing through the center of the nozzle 5, and the tip 11 screwed to the tip side of the nozzle 5. It has.
The cap 2, the powder nozzle 5, and the chip 11 are all made of a heat-resistant metal material. The chip 11 may be integrated with the tip of the powder nozzle 5.
Between the shield cap 2 and the powder nozzle 5, a ring-shaped gas supply path 3 is located, and from the discharge hole 4 opened in a ring shape at the tip thereof toward the surface side of the metal base material W1, A shielding gas sg such as Ar gas is released in a cylindrical shape.

In addition, a ring-shaped hollow portion 5a through which cooling water circulates is formed inside the powder nozzle 5 on the tip side, so that the nozzle 5 and the adjacent chip 11 can be cooled.
Further, a powder flow path is provided at a position along the axial direction of the powder nozzle 5 and the tip 11 and above the radiation hole 8 of the plasma arc pa that is reduced in diameter and opened toward the distal end side of the hollow portion 7. 10 is horizontal and on the tip side, it is inclined toward the center and penetrates. The discharge hole 9 of the powder channel 10 that opens to the tip surface 12 of the chip 11 also opens at a position above the radiation hole 8 on the tip surface 12. A metal powder mp to be built up is fed into the powder flow path 10 together with a carrier gas such as Ar gas, and is fed from the discharge hole 9 to the vicinity of the surface of the metal base material W1.
As shown in FIG. 1, the metal base material W <b> 1 and the tungsten electrode 6 can be electrically connected via a main arc power source 15, and between the tip of the powder nozzle 5 and the tungsten electrode 6. Is electrically conductive through a pilot arc power supply 16 and a high frequency generator 17.

As shown in FIG. 2A, the metal powder mp and the carrier gas discharge hole 9 opening on the tip surface 12 of the chip 11 have an inner diameter (diameter) of 1.0 mm or more, and the central portion of the tip surface 12. A pair (two pieces) are opened symmetrically in the peripheral part above the radiation hole 8 of the plasma arc pa opened in the left and right directions. The center of the pair of discharge holes 9 is located within a range of 45 degrees to the left and right from an imaginary vertical line that passes through the center of the tip surface 12 (the total range angle θ1: 90 degrees or less). Most recommended from the standpoint of efficiency of overlay welding by vertical downward welding using powder mp.
Further, as shown in FIG. 2B, three of the discharge holes 9 may be opened symmetrically in the peripheral portion above the opening position of the radiation hole 8 on the tip surface 12 of the chip 11. . In this case, the center of the discharge hole 9 positioned on the left and right in the drawing is within a range of 60 degrees to the left and right from the virtual vertical line passing through the center of the tip surface 12 (the angle θ2 of the entire range is 120 degrees or less). It is desirable to be positioned.
Further, as shown in FIG. 2 (C), one arc hole 9a that is curved in an arc shape is opened at the periphery of the tip surface 12 of the tip 11 in the vicinity of the position immediately above the opening position of the radiation hole 8. It is also good. The width of the arc hole 9a is set to 1.0 mm or more.

Hereinafter, the powder overlay welding method of the present invention will be described with reference to FIG.
The torch 1 including the tip 11 having the plurality of or single radiation holes 9 (9a) shown in FIGS. 2 (A) to 2 (C) in the distal end surface 12 is set in a vertical posture as shown in FIG. It arrange | positions with a horizontal attitude | position so that the axial direction may orthogonally cross with respect to the flat surface vicinity of the base material W1. At this time, a shield gas sg made of an inert gas such as Ar gas is discharged in a cylindrical shape from the ring-shaped discharge hole 4 located outside the chip 11.
Next, when the main arc power source 15 is turned on after the pilot arc power source 16 is turned on, the inside of the hollow portion 7 penetrating the center portion of the torch 1 is previously supplied with Ar gas or the like fed to the discharge hole 8 side. Of the plasma gas, in a plasma gas atmosphere outside the radiation hole 8, an elongated spindle-shaped plasma arc pa is radiated from the front end of the tungsten electrode 6 toward the surface of the metal base material W1.

  In this state, as shown by the broken line in FIG. 1, the metal powder mp fed by the carrier gas such as Ar gas is opened in the tip surface 12 of the chip 11 through the powder flow path 10 in the powder nozzle 5. From the above-mentioned radiation hole 9 (9a), the plasma arc pa is sent from above to the vicinity of its center through the upper side of the tip of the arc pa. At this time, the continuously supplied metal powder mp group is subjected to the action of gravity. As a result, a molten pool due to the high temperature of the plasma arc pa is formed on the flat surface of the metal base material W1, and the metal powder mp is continuously and efficiently charged into the molten pool and continuously melted. .

While maintaining the above state, the metal powder mp group is charged and melted by moving (downward) the torch 1 at a relatively high speed as indicated by the white arrow in FIG. Since the metal base material W1 is continuously generated along the vertical direction of the flat surface of the metal base material W1, the flat surface of the metal base material W1 protrudes higher than the surface (that is, the dilution rate is 10%). A sound weld bead B is formed which is low and below. At this time, when so-called weaving is performed in which the torch 1 is continuously swung in a zigzag shape in the width direction intersecting the welding direction (downward direction), a relatively wide weld bead B is obtained.
As a result, a sound weld bead B can be continuously formed along the vertical direction of the surface of the metal base material W1. Further, when the torch 1 is shifted to the front side or the rear side in FIG. 1 and the powder overlay welding by the vertical downward welding as described above is continuously performed, the entire surface of the metal base material W1 is moved to the weld bead. It can be covered with the overlay of B. Therefore, characteristics such as corrosion resistance and wear resistance based on the characteristics of the metal powder mg can be imparted to the entire surface of the metal base material W1, and the surface of the metal base material W1 can be modified.
Note that vertical downward welding may be performed in such a manner that the metal base material W1 is moved along the vertical direction in a state where the position of the torch 1 in a horizontal posture is fixed.

Moreover, the powder overlay welding method of a form as shown in FIG. 3 is also contained in this invention.
As shown in FIG. 3, with respect to the vicinity of the flat surface of the metal base material W1 in a vertical posture, the axis of the torch 1 is provided with an inclination angle θ3 within 10 degrees below the horizontal line, and the torch 1 Is placed diagonally upward. In other words, the surface of the metal base material W1 is in a direction in which the surface portion of the metal base material W1 above the axis of the torch 1 in a side view is away from the vertical line with respect to the torch 1 having the horizontal axis. Even if it is inclined at an inclination angle θ3 within 10 degrees, it is the same as described above.
Similarly to the above, the shield gas sg is emitted in a cylindrical shape from the discharge hole 4 of the tip 11 in advance, and the plasma arc pa is emitted in a spindle shape from the radiation hole 8 of the tip surface 12 of the tip 11. In this state, similarly to the above, on the tip surface 12 of the chip 11, as shown in the figure, the metal powder mg together with the carrier gas from the discharge hole 9 (9a) located above the radiation hole 8 is subjected to the action of gravity. In addition, the plasma arc is fed from the upper part of the plasma arc pa to the vicinity of the center through the path above the tip of the arc pa.

As a result, as shown in FIG. 3, the weld bead B having a low dilution rate of 10% or less and a healthy weld bead B can be continuously formed along the vertical direction on the flat surface of the metal base material W1. At this time, the weaving may be performed. Further, the same welding torch 1 as in the previous period is shifted to the front side or the rear side in FIG. 3, and the same vertical downward welding is continuously performed, so that the entire surface of the metal base material W1 is soundly welded as described above. Can be covered with bead B.
Note that the axial center of the torch 1 is set in a horizontal posture, and the overlay welding is performed on the flat surface of the metal base material W1 inclined within a range of 10 degrees from the vertical line to the rear (back) side. Also good.
Further, the torch 1 is fixed in position with the axis as the horizontal posture, and further, the metal base material W1 inclined within a range of 10 degrees from the vertical line to the rear (back) side is moved along the plane direction. The overlay welding may be performed on the surface of the base material W1.
Still further, the vertical downward welding may be performed in such a manner that the torch 1 is fixed in a position inclined as described above and the metal base material W1 is moved so as to rise along the vertical direction.

Furthermore, a powder overlay welding method having a form as shown in FIG. 4 is also included in the present invention.
As shown by a thick arrow in FIG. 4, for example, a metal base material W2 that is a large-diameter steel pipe is rotated in the circumferential direction and upward, with respect to the surface that is the outer peripheral surface of the metal base material W2. The torch 1 is arranged in the radial direction and along the horizontal line so that the axes are aligned.
Similarly to the above, the shield gas sg is emitted in a cylindrical shape from the discharge hole 4 on the tip side of the torch 1 in advance, and the plasma arc pa is radiated in a spindle shape from the radiation hole 8 on the tip surface 12 of the tip 11. ing. In this state, the metal powder mg together with the carrier gas from the discharge hole 9 (9a) located above the radiation hole 8 on the tip surface 12 of the chip 11 includes the action of gravity in the same manner as described above. Then, it is fed from the upper side of the plasma arc pa to the vicinity of the center of the tip of the arc pa.

As a result, as shown in FIG. 4, the weld bead B having a dilution rate as low as 10% or less as described above is continuously applied to the curved surface of the metal base material W2 in the vertical direction and along the circumferential direction. Can be formed. At this time, the weaving may be performed. Further, by rotating the metal base material W2 made of a steel pipe along the circumferential direction and gradually moving it along the axial direction, the weld bead B is moved along the surface that is the outer peripheral surface of the metal base material W2. It can be wound and coated in a spiral.
In addition, the radial direction and the horizontal line are parallel to the outer peripheral surface (surface) of the metal base material W2 that rotates in the circumferential direction and in the same manner as described above, and the axial center is from the radial direction of the metal base material W2. Alternatively, the torch 1 may be arranged slightly above (upward) to perform overlay welding similar to the above.
Further, in the same manner as described above, with respect to the outer peripheral surface (surface) of the metal base material W2 rotating in the circumferential direction and upward, the axis is within 10 degrees below or above the radial direction and the horizontal line. The build-up welding may be performed by arranging the torch 1 in an inclined posture.

According to the powder overlay welding method of the present invention as described above, the horizontal position of the torch 1 is orthogonal or close to orthogonal to the surface of the metal base materials W1 and W2 in a vertical attitude or a nearly vertical attitude. And a plasma arc pa is emitted from the center of the tip 11 attached to the tip of the torch 1, and the metal powder mp to be built up near the tip of the arc pa is the tip of the tip 11. 12 is supplied from a discharge hole 9 (9a) that opens to the top of 12. As a result, the metal powder mp is relatively low because it is placed in the vicinity of the center of the tip of the plasma arc pa while being subjected to the gravitational action and is efficiently put into the molten pool on the surfaces of the metal base materials W1 and W2. Powder build-up welding by vertical downward welding to form a weld bead B having a healthy dilution rate can be performed at a relatively high welding speed.
In addition, since any one of the metal base materials W1, W2 or the torch 1 moves along the vertical direction, the circumferential direction, or the direction close to the vertical direction, the vertical direction with respect to the surface of the metal base materials W1, W2 Alternatively, it is possible to stably form a sound weld bead B whose shape and thickness are almost constant and stable along the circumferential direction.

In the following, specific examples of the present invention will be described together with comparative examples.
A plurality of steel plates made of chromium molybdenum steel for boilers (JIS G 4109) and having the same thickness and vertical and horizontal dimensions are prepared in advance as a metal base material W1 having a flat surface, and these base materials W1 Was restrained in a vertical posture. With respect to the metal base material W1 in such a vertical posture, the torch is placed at a distance of 5 to 10 cm with respect to the flat surface of the base material W1 in the same manner as in FIG. 1 was placed in a horizontal posture and allowed to move down (downward).

  Next, the metal powder mp consisting of SUS316 and having an average particle size of about 150 μm is supplied in a vertical posture by supplying about 6 to 80 g / min together with Ar gas (carrier gas) of about 2 to 2.5 L / min. With respect to a part of the metal base material W1, the pair of left and right discharge holes 9 opened in the tip surface 12 of the tip 11 for each torch 1 shown in FIG. It supplied to the front end side of the generated plasma arc pa from the upper side, and the vertical downward welding was performed, and it was set as the Example.

On the other hand, with respect to the remaining metal base material W1 in the vertical position, as shown in FIG. 5, from a pair of discharge holes 9 that open below the radiation holes 8 located at the center of the tip surface 12 of the tip 11z. The same metal powder mp as described above was supplied from the peripheral side to the tip side of the plasma arc pa generated downward under the same conditions as described above, and the vertical downward welding was performed. did. That is, the chip 11z is upside down with respect to the chip 11 shown in FIG.
The vertical downward welding of the above examples and comparative examples was performed with the same length, and as shown in Table 1, the torch 1 was classified according to the moving speed (welding speed) and the welding current.
In addition, the welding conditions (weaving width and weaving frequency) indicated by (Note) in Table 1 were all common and the above-described welding was performed.

According to Table 1, in Examples 1 to 8 according to the present invention in which the welding is vertical downward welding and the welding speed is in a wide range of 8 to 100 cm / min, the welding speed and the surface of the metal base material W1 are formed. Since the amount of metal powder mp charged into the molten pool per unit area was in an appropriate relationship, the weld bead B having a low dilution ratio (high surplus) and a good shape or a substantially good and sound weld bead B was obtained. Obtained. That is, according to Examples 1-8, not only when the welding speed was relatively slow, but also when the welding speed was relatively high at 100 cm / min, it was possible to obtain a good and healthy weld bead B. .
On the other hand, in Comparative Examples 3, 4, 7, and 8 among Comparative Examples 1 to 8 using vertical tip welding and the tip 11z, the welding speed was 30 cm / or more and the welding speed was too high. Due to the insufficient amount of metal powder mp per unit area into the pond, a weld bead B having a poor dilution and a high dilution rate (low surplus) was obtained.

As shown schematically in FIG. 6, the dilution rate is the cross-sectional area Y of the penetration portion b1 located on the base material W1 side of the surface of the weld bead B formed on the surface of the metal base material W1. Is divided by the total value of the penetration depth d and the cross-sectional area X of the surplus b2 protruding outward from the surface. That is, as the ratio (%) of the dilution rate is lower, the extra b becomes higher or the penetration becomes shallower, and the weld bead B having a good shape and soundness is obtained.
Furthermore, the dilution rate decreases as the cross-sectional area Y of the melted portion b1 decreases. However, if the cross-sectional area Y is too small, there is a risk that peeling easily occurs.
An example of a weld bead B having a good shape according to Example 3 is shown in FIG. 7, and an example of a weld bead B having a poor shape according to Comparative Example 3 is shown in FIG.
The effect of this invention has been confirmed by the vertical downward welding of Examples 1-8 as described above.

The present invention is not limited to the above embodiments and examples.
For example, the metal base material includes a water cooling wall of a boiler in which pipe portions and flat plate portions are alternately adjacently disposed, a heat exchange wall of a heat exchanger, and the like.
Further, the metal base material is not limited to a steel material, and may be made of an alloy such as Ni base or Ti base, and the metal powder may be made of an alloy such as Co base or Ni base.
Further, the discharge hole 9 opening in a circular shape on the tip surface 12 of the tip 11 is formed with one relatively large diameter, or four or more relatively small diameters, and is formed in the range of the angle θ1 or the angle θ2. Is also possible.
In addition, the discharge hole 9a opening in the arc shape on the tip surface 12 of the chip 11 may be, for example, an oval or an ellipse, and may be formed as a single unit, or a plurality thereof.

  According to the present invention, the welding bead dilution ratio is low, metal powder made of difficult-to-process materials and difficult-to-weld materials can be used, welding speed can be increased, and overlay welding to the surface of a metal base material in a vertical posture It is possible to reliably provide a powder overlay welding method that can be easily performed.

1 ......... Torch 8 ............... Radiation hole 9, 9a ... Release hole 11 ......... Tip 12 ......... Tip surface W1, W2 ... Metal base material pa ............ Plasma arc mp ………… Metal powder

Claims (5)

With respect to the surface of the metal base material in a vertical posture or a posture close to vertical, the axial direction is orthogonal to the surface, or the torch is arranged in a horizontal posture close to orthogonal,
A plasma arc is radiated from the center of the tip located at the tip of the torch, and metal powder to be deposited on the upper side in the vicinity of the tip of the plasma arc is supplied from an emission hole opened above the tip of the tip. As well as
Vertically downward welding is performed by moving either the metal base material or the torch along the vertical direction or a direction close to vertical.
A powder overlay welding method characterized by that. The torch that is disposed in a horizontal posture in which the axial direction is close to orthogonal is at a position within 10 degrees below or above the horizontal line with respect to the flat surface of the metal base material in a vertical posture. Inclined in range,
The powder overlay welding method according to claim 1, wherein: The flat surface of the metal base material in a posture close to the vertical position has a surface portion above the metal base material away from the vertical line from the torch in a side view with respect to the torch in a horizontal posture in the axial direction. Tilted within 10 degrees in the direction,
The powder overlay welding method according to claim 1, wherein: The tip has a radiation hole for radiating the plasma arc at the center of the tip surface facing the surface of the metal base material, and is a metal to be deposited on the peripheral side of the tip surface above the radiation hole. Having one or more discharge holes for feeding powder,
The powder overlay welding method according to any one of claims 1 to 3, wherein The welding speed by the torch is in the range of 5 to 120 cm / min.
The powder overlay welding method according to any one of claims 1 to 4, wherein

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