JP2002178156A - Welding member using plasma powder welding and welding method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding member using plasma powder welding which realizes a homogeneous welding structure containing tungsten and not having cracks and is cuttable and a welding method which is capable of forming such welding member. SOLUTION: A build-up layer 20 is formed by plasma powder welding on the surface of a base metal 10 consisting of iron and steel materials, etc. The powder which is prepared by mixing a binder material composed of >=1 components exclusive of tungsten with pure tungsten and in which the binder material is incorporated within a range of <=70 wt.% therein when the total amount of the pure tungsten and the total components of the binder material is defined as 100 wt.% is used as the powder for forming the build-up layer 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding member using plasma powder welding comprising a base material and a build-up layer formed by build-up welding on the surface of the base material by plasma powder welding. And its welding method.

[0002]

2. Description of the Related Art Tungsten has many excellent properties such as high hardness, high strength and high melting point in metals, but due to such properties, workability is extremely poor. In particular, only some fields (electrodes, blades, filaments, pantographs, weights, etc.) have been used in a limited way.

[0003] In the field of overlay welding of a powder composed of a metal component (iron, cobalt, nickel, etc.) to the surface of a base material composed of iron or the like by plasma powder welding,
In order to take advantage of the excellent characteristics of tungsten, powders containing tungsten carbide (hereinafter referred to as WC) and powders containing a small amount (about several percent by weight) of pure tungsten have been conventionally used (Japanese Unexamined Patent Application Publication No. -7
1647, JP-A-5-312006, etc.).

When these powders are overlay-welded to the surface of the base material by plasma powder welding, the surface is modified by the build-up layer formed on the surface of the base material, thereby improving the wear resistance, heat resistance, and the like. It has been done.

[0005]

However, when the present inventors conducted microscopic observation by visual inspection using a microscope or the like on the build-up layer formed by the above-mentioned conventional powder, the surface and internal structure were found to be small. Not homogeneous, WC, W
_{Since 2} C remains in a granular state at the time of addition, or tungsten, which is originally an active element, combines (melts) with other surrounding components to form a compound, the main components of the powder and these WC and compound It was found that the structure was apt to cause welding defects.

As described above, in the cladding layer formed by the conventional powder for tungsten-containing plasma powder welding, a uniform and crack-free welded structure cannot be realized, and defects are not generated. Because of its fragile structure, it was not possible to perform cutting, and relied on grinding for processing, which resulted in a problem of poor machinability.

In view of the above problems, the present invention has realized a welding member using plasma powder welding which can realize a uniform welding structure containing tungsten and has no crack, and which can be machined, and such a welding member. It is an object to provide a welding method that can be formed.

[0008]

First, according to the first aspect of the present invention, the base material (10) and the binder material composed of pure tungsten and one or more components other than tungsten are made of pure components out of all components. A build-up layer (20) formed by build-up welding to the surface of the base material by plasma powder welding using a welding powder in which tungsten is mixed at a compounding ratio such that the maximum weight component is obtained. ), Wherein the build-up layer provides a welding member using plasma powder welding, characterized in that pure tungsten remains in a state where it does not combine with the binder material and can be cut. It is.

Here, pure tungsten means that the purity of tungsten is 99 wt% or more, and this value is a general value of pure tungsten in industrial welding powder.

According to the present invention, a binder effect is exhibited by the binder material, and pure tungsten remains in the build-up layer after welding without being combined with the binder material. 4)
Therefore, a homogeneous and crack-free structure can be realized.

Therefore, according to the present invention, it is possible to provide a welding member using plasma powder welding which can realize a uniform welding structure containing tungsten and having no cracks and which can be machined. In addition, actually, when the visual observation with a microscope or the like was performed on the build-up layer in the present invention,
No cracks were generated and it was confirmed that the structure was homogeneous.

Here, as the binder material, a material containing at least one component of a cobalt-based alloy, a nickel-based alloy and stainless steel can be adopted.

[0013] As a result of various experiments and examinations on the case where the mixing ratio of pure tungsten and the binder material was changed, the total amount of the pure tungsten and the binder material was 100 wt. %, When the binder material is contained in a range of more than 0% by weight and 70% by weight or less, a uniform and good structure can be realized in the structure of the build-up layer after welding. Confirmed experimentally.

In a welded structure in which welding is performed using a powder containing less than 2% by weight of a binder material, a weld bead is likely to be disturbed under the same conditions, but by changing and adjusting the base material and the welding conditions, It has been confirmed that sufficiently good results can be obtained.

This is because the base material functions as a binder material as a result of diluting the powder component. From this fact, as in the invention according to claim 4, if the content of the binder material is 2% by weight or more and 70% by weight or less, there is no need to particularly change and adjust the base material and welding conditions. The same effect as the third invention can be obtained.

As a result of further study of the mixing ratio of the welding powder, in order to realize a homogeneous welded structure without cracks and to sufficiently exhibit the high hardness characteristics of tungsten, it is desirable that the present invention be applied to a method for producing a welded powder. It has been found that the binder material is preferably contained in the range of 2 to 50% by weight as in the described invention.

Furthermore, it is preferable that the binder material be contained in the range of 10 to 30% by weight, as in the invention of claim 6, since a more uniform welding structure can be realized.

According to a seventh aspect of the present invention, there is provided a plasma powder welding method in which a buildup layer (20) is formed on the surface of a base material (10) by buildup welding by plasma powder welding. And a welding powder in which pure tungsten and a binder material composed of one or more components other than tungsten are mixed at a mixing ratio such that pure tungsten is the maximum weight component among all components. Prepare and use welding powder on the surface of the base metal so that the pure tungsten remains in the build-up layer in a state where it does not combine with the binder material and the build-up layer can be cut. An object of the present invention is to provide a plasma powder welding method characterized by performing build-up welding by welding.

According to the present invention, it is possible to provide a welding method capable of realizing a homogeneous welding structure containing tungsten and having no crack and forming a welding member using plasma powder welding capable of being machined. .

Here, in such a plasma powder welding method, the welding current is 100 to 250 A (ampere).
And more preferably 140 to 200
It is about A.

By the way, as described above, it was confirmed that if the powder component was diluted with the base material, the base material could function as a binder material. It has been confirmed that a homogeneous welded structure without cracks can be realized. The inventions of claims 9 and 10 have been made based on such a study.

That is, according to the ninth aspect of the present invention, the surface of the base material (10) is overlaid by plasma powder welding using a welding powder consisting of pure tungsten alone. Accordingly, it is possible to provide a welding method having the same effect as the welding method of the seventh aspect.

According to the tenth aspect of the present invention, the base material (10) and the welding powder made of pure tungsten only are formed on the surface of the base material by build-up welding by plasma powder welding. A cladding layer (20), wherein the cladding layer can be cut and processed, and a welding member having the same effect as the welding member of claim 1 can be provided. .

The reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. The present embodiment relates to a powder for plasma powder welding, a welding member formed by overlaying the powder on a base material by plasma powder welding, and a plasma powder welding method using the powder. .

FIG. 1 is a perspective view showing a welding member according to the present embodiment. This welding member is machined according to the purpose, and is used, for example, as a part of tools, equipment parts, or equipment excellent in heat resistance, seizure resistance, wear resistance, and the like.

Reference numeral 10 denotes a metal base material which is made of, for example, a steel material such as stainless steel or a non-ferrous metal such as copper, and has a rectangular plate shape in the illustrated example. More specific materials for the base material 10 include SS400, S25C, S45C, and SKD-6.
Rolled steel materials for general structures, carbon steels for machine structures, and special-purpose steels such as 1 can be used.

Reference numeral 20 denotes a build-up layer formed on the surface of the base material 10 by build-up welding plasma powder welding powder (hereinafter simply referred to as powder) by plasma powder welding (hereinafter referred to as PTA). (Bead). In the illustrated example, four pass overlay layers 20 are formed substantially in parallel.
The thickness is not limited, but can be, for example, about 2 to 3 mm.

The build-up layer 20 is such that pure tungsten remains without being combined with the binder material and can be cut (see FIG. 4 described later). And this overlay 2
As a powder for forming 0, pure tungsten (W) and a binder material composed of one or more components other than W have a compounding ratio such that W is the largest weight component among all components. Is used. Also, as the powder,
A powder consisting only of W may be used.

Here, pure tungsten means that the purity of tungsten is 99 wt% or more, and this value is a general value of pure tungsten in industrial welding powder. The powder of the present embodiment is a mixture in which pure tungsten and a binder material are mixed as independent powder particles without forming an alloy or a compound.

The binder material is for uniformly binding W particles, and is made of a cobalt-based alloy (such as stellite),
There are nickel-based alloys (Hastelloy, etc.), stainless steel, carbon, and other various types. However, although there is a difference in hardness, there is not much difference in weldability, so each alloy or Various combinations utilizing the characteristics of the metal are possible.

When W and the binder material are compounded, the specific mixing ratio is such that the total component of the binder material is contained in a range of 70% by weight or less based on the total weight of the powder. be able to. The range of the compounding ratio is a range in which the powder was actually subjected to PTA to form the build-up layer 20, and a visual observation was performed with a microscope or the like. is there.

Here, in a welded structure in which PTA is performed using a powder having a binder material of less than 2% by weight (including only W), the weld bead is likely to be disturbed under the same conditions as the powder of 2% by weight or more. However, a sufficiently good result can be obtained by changing and adjusting the material of the base material 10 and the welding conditions in order to dilute the powder component by the base material 10 and to function as a binder material.

For example, a nickel-based alloy (Hastelloy or the like) is previously welded to the surface of the base material 10 and overlaid thereon, or the current value in the welding is increased, so that a uniform overlay without cracks is obtained. Layer 20 can be obtained.

Therefore, in particular, in order to obtain a good build-up layer 20 without changing and adjusting the base material and the welding conditions, the mixing ratio is preferably 2% by weight or more and 70% by weight or less. Further, the mixing ratio is preferably 2 to 50% by weight in order to sufficiently exhibit the high hardness characteristics of W, and more preferably 5 to 50% by weight in order to make the material hardly restricted by the base material. From the viewpoint that a more uniform welding structure can be realized.
0-30% by weight is preferred.

For both the maximum weight component W and the binder material, those having a powder particle size of about several tens to several hundreds μm can be used. In other words, the range for the commonly used PTA (63 μm to 250 μm) may be used.
The granular state is desirably a spherical state or a state close to the spherical state as seen in an atomized product rather than an irregular pulverized product. This is because if the feeding property is poor, especially in the case of a mixture having a greatly different density, the mixture may be separated at the time of feeding to form a non-uniform build-up layer, resulting in welding defects.

It should be noted that the powder obtained by adding the binder material to W and mixing is gradually segregated (a state in which an oxide of W is formed) as time passes while being mixed. Overlay welding using segregated powder may cause welding defects and must be mixed immediately before use in welding.

The build-up layer 20 formed of PTA using such a powder has excellent heat resistance, seizure resistance, abrasion resistance, etc., and has a crack-free homogeneous welded structure. In addition, since there is no welding defect that appears in a product formed by a conventional powder, the material has excellent machinability that can be cut by a lathe or a milling machine.

Next, a description will be given of a welding method using PTA for forming the overlay 20 on the surface of the base material 10 in the above-mentioned welding member. The welding device (PTA overlay welding device) used for PTA in the present embodiment is a well-known device as described in, for example, Japanese Patent Application Laid-Open No. 10-52758, and FIG. FIG.

The torch 100 is driven by driving means (not shown) in a direction perpendicular to the welding direction (for example, in the left-right direction in the figure).
It is possible to move to. Here, the pilot arc power supply 101 is for generating a voltage between the tungsten electrode 102 and the base material 10, and the plasma arc power supply 1
Reference numeral 03 denotes control for stabilizing the generated voltage.

Numerals 104 and 105 denote a plasma arc converging and powder feeding nozzle and a shield gas nozzle, respectively. Arrows 106 and 107 indicate the flow of the plasma gas and the flow of the shield gas, respectively. Reference numeral 108 denotes a powder supply gas and powder.

The welding method is performed as follows. That is, the nozzle 1 for plasma arc convergence and powder feeding
A plasma arc 109 is generated by generating a voltage between the tungsten electrode 102 and the base material 10 while supplying the powder together with the plasma gas and the powder supply gas (carrier gas) by the use of the plasma 04 and the torch. 10
The overlay layer 20 is formed on the surface of the base material 10 while the base material 10 and the base material 10 are relatively moved. At this time, the welded portion in the base material 10 is shielded by the shield gas sent by the shield gas nozzle 105.

Here, an example of specific welding conditions will be described. For example, when the TN6A type manufactured by Tokushu Denshi Co., Ltd. is used as the torch 100, the welding current is 190 Amp.
(Ampere), preheating temperature (preheating temperature of base material 10): 30
0 to 350 ° C (executed by burner heating in this example), interpass temperature (base metal temperature during welding): 500 to 550 ° C, weaving width (transition width of tungsten electrode 107 during welding): 10 mm, welding speed : 80 mm / min, shielding gas flow rate: 20 l / min, plasma gas flow rate: 5 l / min, carrier gas pressure: 29.4
× 10 ^-2 MPa, and cooling after welding is air-cooled and no post heat treatment is performed. As the shield gas 109, the plasma gas 106, and the carrier gas, for example, an argon gas can be used.

As described above, in the PTA of this embodiment, the powder is prepared, and pure tungsten remains in the build-up layer 20 without being combined with the binder material.
The surface of the base material 10 is subjected to build-up welding using the powder so that the surface of the base material 10 can be cut. In this embodiment, specifically, in the PTA,
The welding current is preferably set to 100 to 250 A (ampere), and more preferably about 140 to 200 A.

By the way, according to the present embodiment, by setting the above-mentioned mixing ratio, the formation of the build-up layer 20 which is uniform, has no welding defects such as cracks, and is excellent in machinability which can be cut. It is possible to provide a powder for PTA which can be easily achieved.

According to the present embodiment, such a P
In the build-up layer 20 where the TA powder is build-up welded to the base material 10, pure tungsten remains without being combined with the binder material (pure tungsten is in a supersaturated state, FIG. 4).
Therefore, a homogeneous and crack-free structure can be realized.

Therefore, according to the present embodiment, a welding member using plasma powder welding capable of cutting and realizing a homogeneous welding structure containing tungsten and having no crack is provided. A plasma powder welding method that can be formed can be provided.

In contrast to the conventional powder containing WC or the like which can only perform grinding processing that requires special tools and equipment, the homogenous overlay layer 20 of this embodiment having no welding defects such as cracks is more processed. Since it is possible to perform a cutting process with excellent operability, the shape formation is inexpensive and the range of use can be dramatically expanded.

Further, by utilizing the build-up layer 20 having excellent machinability, the heat resistance, seizure resistance and wear resistance of the base material 10 are further improved, and the range of utilization of W is expanded. It is possible to improve the performance of the equipment and significantly reduce costs such as consumable tools and equipment costs.

As for welding conditions, it is effective to take measures such as shielding with argon gas or the like (argon shield) in order to prevent oxidation of W. On the contrary, by oxidizing, it is possible to achieve another purpose. Since it can be utilized, it may be performed under general conditions of PTA.

The PTA welding machine can be a commercially available PTA welding machine, but a large-capacity large-sized welding machine is more preferable for welding high melting point W. Further, the welding current value changes the dilution ratio (the ratio at which the powder component is diluted by the dissolution of the powder and the base material) depending on the welding current value. Next, this embodiment will be described.
This will be described in more detail in the following examples.

[0052]

EXAMPLES (Example 1) Welded members were manufactured under the configuration shown in FIG. 1 and the specific welding conditions described above. The base material is a rolled steel material for general structure SS400 (JIS G31).
01) and the length A1 is 1 in the dimensions in FIG.
Those having a size of 50 mm, a width A2 of 100 mm, and a thickness A3 of 22 mm were used. The cladding layer (bead) was subjected to four passes of cladding in parallel over a region where the length A4 in the length A1 direction of the base material was about 100 mm and the width A5 was about 60 mm.

In this example, the powder composition (powder mixture composition, unit:% by weight) used for PTA overlay welding and the hardness after overlay (hardness according to Rockwell C scale, H
The measured values of (RC) are shown in FIG. Note that tungsten (W) corresponds to JIS H2116, cobalt-based alloy (binder material) corresponds to JIS D3251, and nickel-based alloy (binder material) corresponds to JIS Z33.
Those corresponding to No. 34 were used.

As shown in FIG. 3, according to the present example, both powders No. 1 and No. 2 have a higher hardness than the hardness of the base material alone (about 10 in Rockwell hardness). It can be seen that a fill layer can be formed. According to a visual inspection, the surface of the buildup layer was flat, and there was no defect such as a crack or a pinhole in a dye flaw detection test (PT test).

Further, 50 mm from the vicinity of the center of the overlay.
When a test piece with a corner and a thickness of 20 mm was taken out, there were no defects such as poor melting, and even by PT inspection, defects near the boundary between the welded layer and the base material and near the boundary of each pass in the overlay were I couldn't see it.

As described above, in this example, plasma powder welding capable of realizing a crack-free and homogeneous welding structure is achieved by performing PTA using powder containing 90% by weight of W and 10% by weight of a binder material. Powder, a welded member obtained by building up such a powder on a base material, and a plasma powder welding method using such a powder.

Here, with respect to the welded member having the build-up layer 20 formed using the powder of powder number 1, the sections of the build-up layer 20 and the base material 10 were observed with a microscope.
FIG. 4 schematically shows the observed cross section based on a micrograph (magnification: 50).

In FIG. 4, a base material 1 made of SS400
On the surface of No. 0, a build-up layer 20 is formed by build-up welding using powder No. 1 (W: 90% by weight, cobalt-based alloy (stellite): 10% by weight).

In the build-up layer 20 in FIG. 4, a region A1 indicated by dotted lines is a region where pure tungsten (W) remains without being combined (melted) with the binder material (W is in a supersaturated state). The needle-shaped region A2 is a region where W is a main component and the base material component and the binder material component are molten, and regions other than these regions A1 and A2 are regions where the base material component is the main component and W And a region where the binder material component is molten.

Specifically, elemental analysis was performed on each of the regions A1, A2, and A3. As a result, for example, the area A
No. 1 is 99% by weight of W and 1% by weight of Fe.
No. 2 is W: 70% by weight, Fe: 26% by weight, Cr: 1% by weight, Co: 3% by weight, and the area A3 is Fe: 59% by weight.
% By weight, W: 26% by weight, Cr: 5% by weight, Co: 10
% By weight.

The result of elemental analysis in the area A1 is actually a result of slightly taking in the area A3 on the outer periphery of the area A1, so that the area A1 is substantially made of pure tungsten having a purity of 99% by weight or more, It can be said that this is a region which remains as it is without being alloyed with the component or the base material dilution component.

Further, at the time of welding, the base metal component is diluted from the surface of the base material 10 and melts into the fusion zone, and W having a relatively large specific gravity sinks downward in the fusion zone. It has a similar cross-sectional structure.

As described above, according to the results of the actual observation, pure tungsten remains in the build-up layer 20 after welding without being combined with the binder material (pure tungsten is in a supersaturated state) and has a homogeneous structure without cracks. It was confirmed that there was. This is also the case with powder number 2 in this example.
The same applies to the following Example 2 as well.

(Example 2) In Example 2, a welded member was manufactured under the form shown in FIG. 1 and the specific welding conditions described above, and a characteristic test was performed in the same manner as in Example 1. .
The shapes of the base material and the build-up layer were the same as in Example 1 above.
Each powder (numbers 3 to 11) of this example is shown in FIG.

In FIG. 5, the unit of the composition of the powder mixture is% by weight, the PT test is for the presence or absence of cracks and pinholes, the hardness (hardness after overlaying) is the hardness by Rockwell C scale, and the base material is The material and workability are the workability of a lathe or milling machine, and the weldability is the appearance of a bead (facing layer) shape by visual inspection.

In each of the powders, the build-up layer after welding was homogeneous and free from cracks and pinholes, and the PT inspection was OK and the weldability was good. Here, although not shown, STL-21, Hastelloy C and SUS3
In the case where the binder material such as 16 was used at 2% by weight (W was 98% by weight), although the achievability was different depending on the welding conditions, a uniform build-up layer free of cracks and pinholes could be realized.

Further, powder having less than 2% by weight of binder material and 100% by weight of W has slightly poor weldability and machinability. However, as described above, by changing and adjusting the base material and welding conditions, A uniform overlay without cracks and pinholes was realized.

As described above, according to this example, the powder containing 70% by weight or less of the binder material (including the powder containing only W).
If so, a homogeneous and crack-free structure can be realized in the welding structure using PTA, and a cutting process that cannot be realized by the conventional overlay using powder containing W can be realized.

Further, as shown in FIG.
The powder having a weight percentage of not more than 60% by weight (No. 11) and the powder having a binder material of 60% by weight (No. 10) realizes a higher level of hardness of the build-up layer as compared with the powders. Also,
Powder containing 10% by weight of binder material (No. 3, 6, 8)
It has been confirmed that a powder of No. 4 and 30% by weight (Nos. 4 and 7) can realize a uniform hardened layer without cracks, which is hardly affected by the base material.

The powder of the present invention may contain trace amounts of other components (for example, ceramics and cermet-based metals) in addition to the pure tungsten and the binder material. In addition, when overlay welding is performed using the powder of the present invention, it is most preferable to perform welding with PTA, but it is also possible to perform welding with a material capable of outputting the same energy as PTA such as electron beam welding and high frequency welding.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a welding member according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a basic configuration of a PTA overlay welding apparatus.

FIG. 3 is a table showing Example 1 of the present invention.

FIG. 4 is a diagram illustrating a cross section of a build-up layer and a base material in the welded member of Example 1 based on observation with a microscope.

FIG. 5 is a table showing Example 2 of the present invention.

[Explanation of symbols]

 10: Base material, 20: Overlay layer.

Claims (10)

[Claims] 1. A mixing ratio of a base material (10), pure tungsten and a binder material composed of one or more components other than tungsten so that the pure tungsten is a maximum weight component among all components. And a build-up layer (20) formed by build-up welding to the surface of the base material by plasma powder welding using a welding powder obtained by mixing. A welding member using plasma powder welding, wherein the pure tungsten remains in a state not combined with the binder material and can be cut. 2. The plasma powder welding according to claim 1, wherein the binder material contains at least one component of a cobalt-based alloy, a nickel-based alloy, and stainless steel. Welding parts. 3. The welding powder has a total content of the pure tungsten and all components of the binder material of 100% by weight.
When the binder material is more than 0% by weight and 70% by weight.
The welding member using plasma powder welding according to claim 1, wherein the welding member is contained in a range of not more than weight%. 4. The welding member using plasma powder welding according to claim 3, wherein the welding powder contains the binder material in an amount of 2% by weight or more. . 5. The welding member using plasma powder welding according to claim 4, wherein the welding powder contains the binder material in a range of 50% by weight or less. . 6. The plasma powder welding method according to claim 5, wherein the welding powder contains the binder material in a range of 10% by weight or more and 30% by weight or less. Welded members using. 7. A plasma powder welding method in which a buildup layer (20) is formed on the surface of a base material (10) by buildup welding by plasma powder welding, comprising: pure tungsten; Preparing a welding powder in which a binder material composed of one or more components other than tungsten is mixed at a mixing ratio such that the pure tungsten is the maximum weight component among all components; Plasma powder welding using the welding powder to the surface of the base material so that the pure tungsten remains in a state where it does not combine with the binder material and the buildup layer can be cut. A plasma powder welding method characterized by performing build-up welding by using. 8. The plasma according to claim 7, wherein said binder material contains at least one component selected from the group consisting of a cobalt-based alloy, a nickel-based alloy, and stainless steel. Powder welding method. 9. A build-up layer (20) is formed on the surface of the base material by performing build-up welding on the surface of the base material (10) by plasma powder welding using a welding powder made of pure tungsten only. A plasma powder welding method for forming a plasma powder, wherein the build-up welding is performed so that the build-up layer can be cut. 10. A base material (10), and a build-up layer (20) formed on the surface of the base material by build-up welding of a welding powder consisting of pure tungsten only by plasma powder welding. A welding member using plasma powder welding, wherein the buildup layer can be cut.