KR100443951B1 - Supplying device of a mixed powder with high viscosity and method of laser cladding using the same - Google Patents

Abstract

The present invention uses a high viscosity mixed powder supply device composed of a step motor, a screw device, an injection part and a supply nozzle part to perform laser cladding while applying a high viscosity mixed powder mixed with a liquid flux and a metal powder onto an inclined base material. The present invention relates to a viscous powder supply device and a laser cladding processing method using the same, comprising: an injection unit in which high viscous mixed powder is injected into a device, a screw device and a high viscous mixed powder which are driven by a step motor to push high viscous mixed powder Laser cladding using a high viscosity mixed powder supply device, which is composed of an injection device unit configured to supply nozzles for discharging the gas and a step motor positioned in line with the injection device unit to start a screw device, and fixed to a laser beam transfer guide. By processing, the mixed powder is kept at a constant feed rate It is easy to control the feeding position of the mixed powder, it is possible to clad the slanted compound surface and the lower part of the object, and the cladding of various composition and hardness is easy, so the selection of materials is broadened and the production cost is also increased. Can be saved.

Description

Supplying device of a mixed powder with high viscosity and method of laser cladding using the same}

The present invention uses a high viscosity mixed powder supply device composed of a step motor, a screw device, an injection part and a supply nozzle part to perform laser cladding while applying a high viscosity mixed powder mixed with a liquid flux and a metal powder onto an inclined base material. The present invention relates to a viscous powder supply device and a laser cladding processing method using the same, comprising: an injection unit in which high viscous mixed powder is injected into a device, a screw device and a high viscous mixed powder which are driven by a step motor to push high viscous mixed powder Laser cladding using a high viscosity mixed powder supply device, which is composed of an injection device unit configured to supply nozzles for discharging the gas and a step motor positioned in line with the injection device unit to start a screw device, and fixed to a laser beam transfer guide. It relates to a processing method.

Laser cladding is used to scan dissimilar metals and substrates by adding a laser with heterometals on top of the substrate to give them the necessary properties such as wear resistance, corrosion resistance and heat resistance. In the processing method of melting and bonding, laser cladding processing forms a surface layer that can withstand the external environment while maintaining the basic toughness of the base material itself. At this time, in consideration of the adhesive strength at the interface between the base metal and the dissimilar metal, the added dissimilar metal is melt-bonded at the interface, so that the base metal is partially dissolved and forms a molten bonding layer mixed by melting of the supplied powder. The layer will affect the physical properties of the base material and cladding layer. It is therefore desirable to limit the dilution of the additive metal to the smallest possible amount.

The laser cladding process is able to obtain a metal material having a complex characteristic, can cope with the shortage of difficult to purchase strategic metal, and can save expensive metal, many applications are made. In addition, compared with the conventional plasma metallizing and arc welding processes, the overall heat input amount is small, the local heat treatment is possible, and the deformation of the workpiece can be minimized. In particular, the non-contact process is made of impurities do not occur due to the consumption of the electrode, it is easy to automate.

Such laser cladding is partially applied to engine valves, aluminum parts, turbine blades and mechanical parts in the power generation field, and is expected to be used in defense and aerospace industries.

In the method of laser cladding, dissimilar metals are added to the base metal, and a metal paste or plate is attached to the base material, followed by laser cladding, or dissimilar metals in the form of metal powder or metal wire. The laser cladding is performed by supplying the beam to the irradiation surface. When the laser irradiation is performed simultaneously with the supply of the powder, it is easy to control the supply amount of the dissimilar metal added and the heat absorption rate of the dissimilar metal is high, so that the laser cladding processing is more effectively performed.

As shown in FIG . 1 , the powder supplying laser cladding device includes a laser nozzle 21 for scanning a laser on a base material, a powder supply device 22 for supplying powder on a base material, and a transfer gas part 23 for transferring powder. Consists of Specifically, the powder-feeding laser cladding processing in which the dissimilar metal is in powder form forms a molten pool by irradiating a laser beam to the base metal, and injects the dissimilar metal powder into the melt pool at a constant speed and simultaneously Transfer to form a continuous cladding layer. The gas used for conveying the powder also serves to prevent oxidation at the same time.

Cladding powders are available in a variety of cobalt- and nickel-based alloys, such as stellite and inconel, tungsten and titanium carbide, Fe-Cr-Ni-B alloys, Fe-Cr-CX alloys, copper alloys and ceramics. Materials are used, and as a base material for cladding, low carbon steel, low alloy steel, stainless steel, aluminum, cast iron, tool steel and superalloy are used.

The powder supply method is a method widely used in a plasma spray apparatus, and a method of transporting a certain amount of powder together with a transporting gas. In order to transport the powder, a certain amount of gas flow and gas pressure must be given. These conditions appear to be disadvantages in the laser cladding process. In other words, due to the high gas pressure, the powder passing through the nozzle is dispersed and the use efficiency is lowered. Therefore, there is a difficulty in removing the gas pressure. It's hard to do

As shown in FIG . 2 , the wire-type laser cladding device is provided with a laser nozzle 31 for scanning a laser on a base material, a wire supply device part 32 for supplying a wire, and a wire supply device 32 supplied from the wire supply device part 32. It consists of a wire nozzle 33 which provides a wire on the base material, and a protective gas nozzle 34 which serves to prevent oxidation during cladding processing. Specifically, it is the same as the powder-feeding laser cladding processing method except that cladding processing is performed using a form of dissimilar metal as a metal wire.

Wire fed cladding uses prefabricated wires, so all you need to do is laser the fabricated wires. In other words, the manufactured wire is manufactured to maintain a certain shape and components uniformly, so if only the wire is manufactured according to the desired processing conditions, there is no problem in fine processing, but the material having high rigidity such as titanium is difficult to manufacture with wire. There are disadvantages. This causes an increase in production costs.

In recent years, the use of aluminum alloys has been increasing in the situation where the use of aluminum alloys has been expanded throughout the industry, and the need for laser cladding technology is increasing. In developed countries, the laser direct casting process technology, which uses laser cladding to produce three-dimensional parts such as molds or dies with complex shapes, is developed and applied in a short period of time. have. In contrast, the level of cladding technology using domestic lasers is in its infancy and the necessary equipment is also dependent on imports. In particular, the conventional powder fed and wire fed laser cladding is impossible or difficult to clad on the inclined compound surface and the lower part of the object, and the wire fed laser cladding is difficult to process with wire in the case of metal with high hardness. I need a quick solution.

In order to solve the above problems, the present inventors supply a high-viscosity mixed powder mixed with a high-viscosity liquid flux and a metal powder onto a base material at a constant amount and speed by using a high-viscosity mixed powder supply device, thereby providing laser cladding. As a result of the cladding process, the mixed powder can be continuously transferred at a constant feeding speed, the mixed powder feeding position can be controlled easily, and it is easily applied to the cladding processing on the inclined composite surface, and the composition and hardness of the desired base material The present invention was completed by finding out that the control is possible.

It is an object of the present invention to provide a highly viscous mixed powder supply apparatus capable of spraying a highly viscous liquid powder and a highly viscous mixed powder composed of metal powder at a constant rate.

In addition, another object of the present invention is to provide a method for laser cladding processing using the high viscosity mixed powder supply apparatus.

1 shows a cross-sectional view of a conventional powder fed laser cladding device,

Figure 2 shows a cross-sectional view of a conventional wire fed laser cladding device,

Figure 3 shows a cross-sectional view of the high viscosity mixed powder fed laser cladding device of the present invention,

Figure 4 shows a cross-sectional view of the high viscosity mixed powder supply apparatus of the present invention,

5 is a graph showing the feed rate of the highly viscous mixed powder according to the voltage of the present invention,

6 is a schematic diagram of a laser cladding process using a highly viscous mixed powder of the present invention,

7 is a graph showing the hardness distribution of the cross section of the cladding specimen according to the present invention,

-□-: When the mixed powder feed rate is 0.35 g / s,

-○-: When the mixed powder feed rate is 0.50 g / s,

8 is a scanning electron micrograph showing the cross-sectional shape of the cladding according to the present invention,

9 is a scanning electron micrograph showing a cladding surface according to the present invention,

10 is a scanning electron micrograph showing the bonding layer of the high viscosity mixed powder melt-bonded with the base material of the present invention,

11 is a scanning electron micrograph showing the boundary line between the base material and the mixed powder layer of the present invention.

* Description of the symbols for the main parts of the drawings *

21, 31, 43: laser nozzle 22: powder supply device

23: transfer gas portion 32: wire supply device

33: wire nozzle 34, 44: protective gas nozzle

40: high viscosity mixed powder feeder

41 injection device portion 42 step motor

45: laser beam transfer guide 51: injection unit

52: screw device 53: supply nozzle part

54: piston

In order to achieve the above object, the present invention provides a high viscosity mixed powder supply apparatus capable of spraying a high viscosity mixed powder composed of a high viscosity liquid flux and a metal powder at a constant speed.

The present invention also provides a method for laser cladding processing using the high viscosity mixed powder supply device.

The present invention constitutes a high-viscosity mixed powder supply device capable of continuously spraying a high-viscosity mixed powder composed of a high-viscosity liquid flux and a metal powder at a constant speed, which will be described in more detail with reference to the accompanying drawings.

Figure 3 is a cross-sectional view showing a high viscosity mixed powder fed laser cladding apparatus of the present invention, the high viscosity mixed powder laser cladding apparatus is a laser nozzle 43 for irradiating a laser beam on a base material, such as argon during laser cladding processing It consists of the high viscosity mixed powder supply apparatus 40 fixed to the protective gas nozzle 44 which discharges gas, and the laser beam conveyance guide 45. As shown in FIG. The high viscosity mixed powder supply device 40 is fixed to the laser beam transfer guide 45 for ease of position control of the mixed powder, the injection device portion 41 for injecting and discharging the high viscosity mixed powder and the high It consists of a step motor 42 which provides power by the power regulator to discharge the viscous mixed powder.

Specifically, according to Figure 4 , the injection device portion 41 is a screw device for operating the piston by using a screw transmitted to the injection portion 51, step motor 42 for injecting a high viscosity mixed powder ( 52) and a supply nozzle part 53 for discharging the highly viscous mixed powder. The injection part 51 is made to separate the middle portion to facilitate the injection of the high viscosity mixed powder, the screw device 52 is a screw device (the rotation of the step motor 42 of the injection device portion 41) ( 52) to move the piston. In addition, the supply nozzle unit 53 is manufactured to change the size according to the viscosity of the powder can be replaced for the cladding processing of the desired size or shape.

Step motor 42 in the present invention is a device for continuously conveying the mixed powder at a constant supply speed by the power regulator, the rotational speed is changed according to the voltage and can be moved back and forth at a constant speed by the rail. The voltage by the power regulator is preferably 5 to 10 volts (V), with a feed rate of 0.3 to 0.8 g / s. As the voltage increases according to FIG. 5 , the feed rate of the mixed powder increases, and when it is 10 volts (V) or more, it is almost constant at a feed rate of 0.8 g / s.

The present invention also provides a method for laser cladding processing using the high viscosity mixed powder supply device.

6 is a schematic diagram of a laser cladding method using the highly viscous mixed powder supplying laser cladding apparatus, and the laser cladding processing method using the high viscous mixed powder is

Preparing a highly viscous mixed powder (step 1);

Injecting the highly viscous mixed powder into a feed device (step 2);

Supplying a highly viscous mixed powder on the base material (step 3); And

And performing laser cladding (step 4).

The high viscosity mixed powder of step 1 is prepared by mixing a certain amount of dissimilar metal powder and high viscosity liquid flux for cladding on the base material. As the metal powder, all metals commonly used may be used. Preferably, a general welding member may be used, and more preferably copper, nickel, bronze and stainless steel powders are used. The liquid flux prevents oxidation of the cladding material and the base metal to enhance the fusion effect, and prevents pinhole phenomenon and overheating of the base material and the liquid flux to maintain excellent welding quality. Accordingly, the low temperature welding should be possible. The liquid flux may use a conventional welding liquid flux, preferably a low temperature welding liquid flux, and more preferably, a commercially available AMCO 446 WHITE (AMERICAN SOLDER & FLUX) which is a high viscosity liquid flux. Use

The highly viscous mixed powder is prepared by mixing and stirring 50 to 60% by weight of the liquid flux and 40 to 50% by weight of the metal powder using a mixer, and preferably, 50% by weight of the liquid flux and 50% by weight of the metal powder are mixed. As for stirring conditions, 17-20 degreeC is preferable, and the viscosity coefficient of the highly viscous mixed powder mixed at this time is preferable 0.0001-0.0003 m <2> / sec. If it exceeds the above range, the viscosity is too high, difficult to convey in processing, and if it is below the above range, the viscosity is low to make the laser cladding difficult on the inclined composite surface and the lower part of the object.

Step 2 injects the high-viscosity mixture powder in the injection device (51) isolated as a high viscosity and a mixed powder mixture comprising: injecting a viscous mixture powder supply device 40 shown in FIG.

Step 3 is a step of supplying the high viscosity mixed powder on the base material in a constant amount and speed in the mixed powder supply apparatus, the speed and amount can be adjusted according to the base material, the type of dissimilar metal and the cladding thickness. Preferably, the supply amount of the mixed powder is 0.3 to 0.8 g / s, and the supply range of the mixed powder is preferably an area smaller than 5 mm which is a laser beam irradiation area.

Step 4 is a step of performing the laser cladding, in the present invention using a 2 kW CO ₂ laser and 200 W class Nd: YAG laser, etc., the laser output can be adjusted according to the mixed powder, the base material and the cladding time Preferably, it is 1.8-2 kW, and the feed rate of a laser beam is 1-3 mm / s is preferable.

The highly viscous mixed powder can be processed by injecting and adhering the highly viscous mixed powder to the lower and inclined surfaces of the object due to the viscosity of the highly viscous flux. By mixing with the powder material, laser cladding processing of the desired composition and hardness can be performed, and the cladding processing is easy on the inclined composite surface and the lower part of the object, which was very difficult to process with conventional wire and powder feed cladding. In particular, in the conventional wire supply method, the cost of manufacturing the wire increases in proportion to the hardness of the material, but the material cost increases, but the present invention reduces the cost because the powder is made of a material of high hardness.

An embodiment of the present invention will be described below.

However, the present invention is not limited by the examples.

EXAMPLES Preparation of High Viscosity Mixed Powder

100 g of the metal powder having the composition shown in Table 1 was mixed with 100 g of AMCO 466 WHITE, which is a high viscosity liquid flux, and stirred for 15 minutes using an upright stirrer to prepare a mixed powder. At this time, the viscosity was measured by the Hagen-poiseille equation method to obtain a kinematic viscosity coefficient of 0.0003 m 2 / sec.

After the mixed powder is injected into a high viscosity powder supplying device, the mixed powder is supplied at a feed rate of 0.35 g / s at a feed rate of 1 mm / s on a substrate (AC2B, smelted in a laboratory) having the composition shown in Table 1 below. It was. Cladding was performed by irradiating a length of 20 mm for 20 seconds with a laser power of 2 KW (± 5 W) using a 2 KW CO ₂ laser.

Composition table of metal powder and base metal (wt%) Cu Sn Si Mn Al Ni Bronze Powder 91.3 8.7 - - - - Base material (AC2B) 0.3 0.1 7.0 0.5 91.8 0.3

Experimental Example 1 Hardness Measurement

The hardness of the specimen subjected to laser cladding according to the above example was measured using a fine Vickers hardness tester (Mitutoyo, Japan).

Figure 7 shows the hardness distribution of the cross section of the cladding specimen, the hardness value is generally related to the cooling rate. The hardness value is higher from the clad surface to the dilution layer, because rapid heat transfer occurs through the base material having high thermal conductivity, thereby rapidly cooling. The dilution layer is in a state in which the base material and the bronze powder are combined and show a relatively higher hardness value than the bronze powder and the base material. This is because the bronze and the base metal are bonded to each other by complete melting, thereby forming an alloy layer having a relatively high hardness value.

Experimental Example 2 Heat Resistance Measurement

For the heat resistance test, the clad specimens of the above example were heated to 600 ° C., and then the hardness of the laser cladding surface was measured.

In general, if the hardness is measured after heating to a certain temperature for the heat test, the hardness value is lowered to about 50 to 60%. For the heat resistance test, the cladding layer of the preheated specimen was heated to about 600 ° C., then cooled in air, and then measured for hardness. It was confirmed that the hardness value was maintained at 600 to 700 Hv.

Experimental Example 3 Cladding Shape and Surface Characteristics

The cladding cross-sectional shape and the tissue photograph of the clad specimens in the permanent embodiment were taken by SEM. Upper images of the specimens were taken using a NiKcon EPIPHOTO-TIME tissue optical microscope. The cladding shape and size of the specimens were measured using a scale size attached to the SEM photographs and a micrometer attached to the Mitutoyo Micro Hardness Tester.

8 is a cross-sectional shape cladding at a feed rate of 0.35 g / s, it can be seen that a range of dilution layer formed in a suitable range for the laser cladding characteristics and a solid bond formed between the bronze powder and the base material. .

The cladding surface can be seen that the wave shape in the laser traveling direction according to Figure 9 can be obtained and the same surface as the conventional wire or powder cladding.

Experimental Example 4 Microstructure and Dilution Analysis

The microstructure of the clad specimens in the permanent Example was photographed using SEM, and the dilution analysis was analyzed by EDX.

10 and 11 , no cracks were found in the connective tissues of the base material and the cladding layer, and it was found that they were firmly bonded. Specifically, Figure 10 shows the bonding layer of the high viscosity mixed powder melt-bonded with the base material. Since the cladding was performed using the base material and the bronze powder, a dilution layer was clearly formed when observed through a scanning electron micrograph.

11 is a boundary line between the dilution layer and the mixed powder layer, and the boundary between the dilution layer and the mixed powder layer is clearly distinguished, and it can be seen that the bonding surface of the mixed powder and the base material is bonded without cracking. The dilution layer in the direction of the base material can be confirmed that the structure is dense, because the heat transfer from the cladding layer to the base material is made faster because the base material with good thermal conductivity is used, so that the tissue becomes dense. It is also possible to observe the dents in the clad, which is produced when the vaporized solvent is trapped inside the cladding layer without being discharged to the outside before solidification.

When cladding is performed using the mixed powder of the present invention, care must be taken to ensure that the vaporized flux is completely discharged to the outside before solidifying after melting with the cladding material and proper preheating of the base material and the cladding material should be performed.

As described above, the laser cladding method using the high-viscosity mixed powder feeding laser cladding apparatus of the present invention can continuously convey the mixed powder at a constant feeding speed, easily control the mixed powder feeding position, and inclined composite surface And it can be cladding on the lower part of the object, the cladding of various compositions and hardness is easy to widen the choice of materials, it is possible to reduce the production cost.

Claims (14)

In the high-viscosity mixed powder supply apparatus for laser cladding processing of the inclined composite surface using the high-viscosity mixed powder, The supply device is composed of an injection device unit for injecting a high viscosity mixed powder and discharged on the base material, and a step motor for providing power by rotating to discharge the high viscosity mixed powder on the base material, The injection device unit injection unit for injecting a high viscosity mixed powder; A screw for transmitting a force transmitted from the step motor; A piston connected to the screw; And Consists of a supply nozzle for discharging the high viscosity mixed powder on the base material, At this time, the injection portion is a high viscosity mixed powder supply, characterized in that the middle portion is separated. delete delete The high viscosity mixed powder supply apparatus according to claim 1, wherein the supply nozzle part is replaceable for a cladding process of a desired size or shape so that the supply nozzle part can be changed in size according to the viscosity of the powder. The high viscosity mixed powder supply device according to claim 1, wherein the high viscosity mixed powder supply device is attached to a laser beam transfer guide. The high viscosity mixed powder supply device according to claim 1, wherein the step motor supplies a mixed powder by adjusting a supply speed according to a change in voltage by a power regulator. 7. The high viscosity mixed powder supply device according to claim 6, wherein the voltage is 1.5 to 15 volts (V). In the method of laser cladding on a base material using a high viscosity mixed powder, the method Mixing the liquid flux and the metal powder to produce a highly viscous mixed powder (step 1); Injecting the prepared highly viscous mixed powder into the powder feeder (step 2); Supplying a highly viscous mixed powder on the base material (step 3); And And a laser cladding process (step 4). 9. The processing method according to claim 8, wherein the liquid flux is a liquid flux for low temperature welding. 9. The processing method according to claim 8, wherein the highly viscous mixed powder is composed of 50 to 60 wt% of liquid flux and 40 to 50 wt% of metal powder. 9. The processing method according to claim 8, wherein the high viscosity mixed powder has a viscosity coefficient of 0.0001 to 0.0003 m 2 / s. 9. A processing method according to claim 8, wherein a feed rate of the high viscosity mixed powder is 0.35 to 0.65 g / s. 9. The processing method according to claim 8, wherein the feeding speed of the laser beam is 1 to 3 mm / s. 9. The processing method according to claim 8, wherein the powder feeder is the high viscosity mixed powder feeder of claim 1.