JP2001314971A - Plasma powder welding method and welding powder used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve weld ability, preventing the deterioration of welding layer performance by dilution, in the welding method which performs cladding by welding on the surface of a substrate by plasma powder welding (PTA). SOLUTION: In the welding method which performs welding cladding layer (welding layer) by PTA on the surface of a underlying layer 11 or mother material 10 being a substrate, anticipating the content of the substrate 10, 11 which is melted into the content of welding powder by dilution in the cladding layer 20 after welding, the percent composition of the welding powder and the substrate are predetermined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method for performing build-up welding on the surface of a base member by plasma powder welding (plasma transfer arc, hereinafter referred to as PTA) and a welding powder used for the method.

[0002]

2. Description of the Related Art Plasma powder welding (PTA) is a method in which a welding material is powder and its components can be adjusted arbitrarily.
Since the plasma is a heat source, the arc temperature is extremely high, and even a high melting point metal can be welded relatively easily. Because of the extremely high arc temperature, the base material can be melted into the welding material (welding powder), that is, diluted. It has features such as being small.

[0003]

SUMMARY OF THE INVENTION However, PTA
In, although there is a feature that there is little dilution,
It is impossible to eliminate dilution at all. No matter what kind of welding material is used, when overlay welding is used, dilution always occurs, and the components of the base member dissolve into the welding layer and the welding layer is thinned, so the performance of the pre-designed welding layer must be reduced somewhat. Is done.

Incidentally, as a countermeasure against dilution, it has been practiced to obtain a weld layer having a low dilution ratio by forming a multi-layer structure of two or three layers, but there is basically a difference. However, the problem of dilution has not been solved.

[0005] Also, when welding a high melting point metal material such as tungsten or niobium by PTA, sufficient weldability such as cracks and unevenness on the surface of the resulting welded layer is obtained. Was difficult to achieve.

[0006] In view of the above circumstances, the present invention, by PTA,
In a welding method for performing overlay welding on the surface of a base member, an object is to improve weldability while preventing performance degradation of a weld layer due to dilution.

[0007]

SUMMARY OF THE INVENTION In the present invention, the dilution which cannot be avoided in the conventional PTA, on the contrary, may be incorporated into the design from the beginning, that is, the performance of the completed weld layer in the diluted state. Is designed by focusing on the idea that the above object can be achieved if designed.

[0008] That is, according to the first aspect of the present invention, there is provided a welding method for performing build-up welding on the surface of a base member. It is characterized in that the component ratio of the welding powder and the component ratio of the base member are set in advance in consideration of the components.

According to this, the performance of the weld layer in the diluted state is designed, so that there is no problem that the performance of the weld layer is deteriorated due to dilution in the first place. In addition, even if the welding material has poor weldability, such as generation of cracks,
Weldability can be improved by, for example, incorporating a binder material into the component dissolved from the base member by dilution, and thus welding that can be used for a wide range of materials is possible.
Therefore, according to the present invention, the weldability can be improved while preventing the performance of the weld layer from being reduced due to dilution.

[0010] In particular, tungsten has many excellent properties such as high hardness, high strength and high melting point in a metal. When this tungsten is used for PTA, tungsten carbide (hereinafter referred to as WC) is used. ) Or a powder to which a very small amount (about several weight%) of pure tungsten is added (Japanese Patent Application Laid-Open No. Hei 8-
No. 71647, JP-A-5-312006, etc.).

However, according to the study of the present inventors,
When these powders are overlay-welded to the base member, the surface and the internal structure of the weld layer (the overlay) are not uniform, and WC and W ₂ C remain in a granular state at the time of addition, and welding defects occur. It was found that the structure was liable to occur.

In this regard, according to the second to fourth aspects of the present invention, the performance of the weld layer in a diluted state is designed even when PTA is performed using a powder for welding a plasma powder containing tungsten. By doing so, the weldability can be improved while preventing the performance of the weld layer from being reduced by dilution, and thus a weld layer having no welding defects can be realized.

Here, as the base member, any one of an iron-based alloy, a nickel-based alloy, a cobalt-based alloy, copper, a copper alloy, titanium and a titanium alloy is used, and 50 wt. % Or more can be used. Further, as the welding powder, a powder containing 70% by weight or more of pure tungsten,
Further, it is possible to use one containing 90% by weight or more of pure tungsten.

In the welding method of the first aspect, the base member may be a nickel-based alloy, a cobalt-based alloy, copper,
Using any one of copper alloy, titanium, titanium alloy and stainless steel, as a welding powder, pure tungsten,
It is also possible to use one or more components of niobium, molybdenum, tantalum and titanium, and to use a total of 50% by weight or more (the invention of claim 5).

Further, the inventions of claims 6 and 7 relate to a welding powder used in the welding method of claims 1 to 5, and the powder of claim 6 is made of pure tungsten and 1%. It is characterized in that the above-mentioned binder material composed of components other than tungsten is contained in a mixing ratio such that pure tungsten is the maximum weight component among all components.

Further, the powder according to claim 7 is characterized in that the pure tungsten and the binder material are contained in such a composition that the pure tungsten remains in a state where it does not combine with the binder material after welding.

If welding is performed using the powder according to claim 6 or claim 7, the binder effect is exhibited by the binder material previously contained in the powder, in addition to the binder effect of the component dissolved from the base member by dilution. Is done. In addition, since the composition is such that pure tungsten remains without being combined with the binder material after welding, a structure in which the features of tungsten are sufficiently ensured can be realized.

Here, as the binder material of the powder for welding, a material containing at least one component of a cobalt-based alloy, a nickel-based alloy and stainless steel can be used (the invention of claim 8). When the total amount of pure tungsten and all components of the binder material is 100% by weight, the content of the binder material is 0% by weight.
It is preferable to use those contained in a range of more than 70% by weight.

Further, when a powder containing a ceramic or a cermet-based material is used as the welding powder as in the ninth aspect of the present invention, in addition to the binder effect of the component dissolved from the base member by dilution, it is possible to use a more diverse powder. High performance welding layers can be obtained.

[0020] Further, the invention of claims 10 and 11 is also directed to a case where PTA is carried out using the above-mentioned powder for plasma powder welding containing tungsten, while preventing the performance of the weld layer from being reduced due to dilution, The purpose of the present invention is to improve the weldability, and in particular, to achieve the purpose of a welding powder consisting only of pure tungsten.

More specifically, the invention according to claims 10 and 11 is a welding method for performing build-up welding on the surface of a base member by plasma powder welding, wherein a welding powder comprising pure tungsten alone is used. In the later welding layer, the ratio of pure tungsten to the component of the base member is set in advance in consideration of the component of the base member that is dissolved by the dilution with respect to the component of the welding powder.

According to the present invention, when designing the welding layer, the performance of tungsten in a state diluted by the base component is designed. No problem. Further, in the conventional PTA, even if pure tungsten having poor weldability such as cracks is generated, due to the binder effect of the component dissolved from the base member by dilution,
Weldability can be improved. Therefore, according to the present invention, the weldability can be improved while preventing the performance of the weld layer from being reduced due to dilution.

[0023]

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.
FIG. 3 is a view showing a welding member according to the embodiment. This welding member is machined according to the purpose, for example, heat resistance,
Excellent tools such as seizure resistance and abrasion resistance, equipment parts, or
It is used as part of equipment.

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.
1A has a rectangular plate shape, and FIG. 1B has a round bar shape.
As a material of the base material 10, for example, SS400, S25
C, S45C, rolled steel for general structures such as SKD-61,
Carbon steel for machine structure and special purpose steel can be adopted.

In the round bar-shaped welding member shown in FIG. 1B, the surface of the base material 10 has an underlay made of an iron-based alloy, a nickel-based alloy, a cobalt-based alloy, copper, a copper alloy, stainless steel or the like. The layer 11 is formed by welding or the like. In addition, in the rectangular plate-shaped welding member shown in FIG. 1A, the underlay layer is not formed, but may be formed. Also,
In the round bar-shaped welding member shown in FIG. 1B, the underlay layer 11 may not be formed.

In FIG. 1, the surface of the base material 10 or the underlay layer 11 is build-up welded by plasma powder welding (PTA) using plasma powder welding powder (hereinafter simply referred to as powder). As a result, a build-up layer (bead, weld layer) 20 is formed. Therefore, in the present embodiment, the base material 10 or the underlay layer 11 is a base member of the overlay layer (weld layer) 20.

In the example shown in FIG. 1A, four pass overlay layers 20 are formed substantially in parallel. In the example shown in FIG. 1B, the surface of the cylindrical lower build layer 11 is formed. A tubular build-up layer 20 is formed so as to cover the whole. Here, in both of these examples, although not particularly limited, the thickness of the buildup layer 20 can be about 5 mm, and when the lower buildup layer 11 is formed, the thickness can be about 2.5 mm.

As the powder (welding powder) for forming the build-up layer 20, a powder containing 50% by weight or more of pure tungsten can be used, or a powder made of pure tungsten alone may be used. Further, other than tungsten (W), niobium (Nb), niobium carbide (NbC), or a metal other than a high melting point metal such as W or Nb may be used.

Further, as the powder, a mixing ratio of pure tungsten (W) and a binder material composed of one or more components other than W is such that W is a maximum weight component among all components, or In addition, a material that contains W in such a manner that W remains without being combined with the binder material after welding is used.

Here, the binder material is for uniformly binding the W particles, and includes a cobalt-based alloy (such as stellite), a nickel-based alloy (such as Hastelloy), titanium, stainless steel, and various other materials. As a result, the difference in hardness and the like is large, and various combinations utilizing the characteristics of each alloy or metal can be made according to the purpose.

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 within 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.

Further, as the welding powder, tungsten carbide (W ₂ C), chrome bolite (Cr)
B), a material containing a ceramic or cermet-based material such as nickel bolite (NiB) is used, in addition to a binder effect of a component dissolved from the base members 10 and 11 by dilution, a more diverse and high-performance welding layer. Can be obtained.

The particle size of the powder may be in the range for commonly used PTA (63 μm to 250 μm), but the particle state is spherical or spherical, as seen in atomized products rather than irregular ground products. It is desirable to have a state close to that. 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.

In the case of a powder obtained by adding a binder material to W and mixing the same, segregation (a state in which an oxide of W is formed) progresses as time passes while mixing. Overlay welding using segregated powder may cause welding defects and must be mixed immediately before use in welding.

Next, in the above-mentioned welding member, a P for forming a build-up layer 20 on the surface of the base material 10 or the underlay layer 11 is formed.
The welding method using TA will be described. 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 a driving means (not shown) in a direction perpendicular to the welding direction (for example, in the horizontal direction in the figure).
It is possible to move to. Here, the pilot arc power supply 101 is connected to the tungsten electrode 102 and the underlying members 10 and 1.
The plasma arc power supply 103 controls the voltage so as to stabilize 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 a flow of the plasma gas and a flow of the shield gas, respectively, and a broken line 108.
Denotes powder for feeding powder and powder.

The welding method is performed as follows. That is, the nozzle 1 for plasma arc convergence and powder feeding
The plasma arc 109 is generated by generating a voltage between the tungsten electrode 102 and the base members 10 and 11 while supplying the powder together with the plasma gas and the powder supply gas (carrier gas) by the use of the powder 04. ,
The cladding layer 20 is formed on the surfaces of the base members 10 and 11 while relatively moving the torch 100 and the base members 10 and 11. At this time, due to the shielding gas supplied by the shielding gas nozzle 105,
The welded portions of the base members 10 and 11 are shielded.

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 160 Amp.
(Ampere), preheating temperature (preheating temperature of base members 10, 11): 100 to 150 ° C. (executed by burner heating in this example), weaving width (tungsten electrode 10 during welding)
7): 10 mm, welding speed: 80 mm / mi
n, shield gas flow rate: 20 l / min, plasma gas flow rate: 3 l / min, carrier gas pressure:
It can be 29.4 × 10 ^-2 MPa, and cooling after welding is air-cooled, and no post-heat treatment is performed. The above shielding gas 1
09, the plasma gas 106 and the carrier gas, for example, argon gas can be used.

By performing the overlay welding on the surfaces of the base members 10 and 11 in this manner, a welded member is formed. In the present embodiment, in the welded layer 20 after welding,
The component ratio of the welding powder and the component ratio of the base member are set in advance in anticipation of the components of the base members 10 and 11 that dissolve into the components of the welding powder by dilution.

According to this, the welding layer 2 in a diluted state
Since the performance is designed to be 0, the problem of the performance deterioration of the weld layer 20 due to dilution, which has been a problem in the past, does not occur in the first place. Further, even if the welding material has poor weldability such as cracks, the base member 1 may be diluted.
The weldability can be improved by, for example, incorporating a binder material into the dissolution components from 0 and 11, so that welding suitable for a wide range of materials can be performed.

For example, even if powder such as tungsten or niobium carbide is PTA-welded to a base material made of a normal steel material as it is, almost no welding can be performed, or even if it can be performed, the shape of the weld layer (bead) will be poor. Significant welding defects such as large collapse or cracks are likely to occur. This is because the binder material is not contained in the powder (welding material), and iron which is a base material component is mixed due to dilution (penetration) at the time of welding, but this does not sufficiently exert the binder effect. .

On the other hand, in the present embodiment, for example, when the powder mainly composed of tungsten is build-up welded with PTA, the surface of the base material 10 contains a nickel-based alloy (Hastelloy or the like) as a binder material in advance. Underlay welding is performed on the material to form an underlay layer 11, and PTA welding is performed on the upper overlay using a powder of pure tungsten 100%.

At this time, in the welded layer 20 after welding,
The amount of the nickel-based alloy is adjusted when forming the underlayment layer 11 so that the nickel-based alloy achieves a compounding ratio in which the binder effect is sufficiently exhibited with respect to pure tungsten. That is, the components in the powders of the base members 10 and 11 and the welding layer 20 are set in consideration of the dilution. The welding conditions (welding current, preheating temperature, etc.) are adjusted so that the designed dilution ratio (dissolution rate of the base member component into the welding material) is achieved, so that the overlay has a desired component ratio. Layer 20 is completed.

As a result, it is possible to obtain a good weld layer 20 having a good bead shape, no cracks, and various materials, dimensions and shapes used for the base material. That is, the buildup layer 20 formed of PTA using the powder of the present embodiment is used for the base member 10 by dilution,
Since the dissolution component from 11 exerts a binder effect, the weldability is improved.

Then, using the powder of the present embodiment, P
The build-up layer 20 formed by TA has heat resistance, seizure resistance,
It has excellent wear resistance, etc., and has a uniform weld layer structure without welding defects such as cracks that appear in those formed by conventional powder, so cutting with a lathe or milling machine is possible It has excellent machinability.

Next, with reference to FIGS. 3 and 4, an example of a specific component ratio (% by weight) of the materials of the base members 10 and 11 and the welding layer 20 of the present embodiment will be described. The evaluation of each of the samples 1 to 24 is performed by a hardness test (Rockwell hardness, etc.), a crack inspection by a visual inspection or a dye flaw detection test (PT inspection), etc., to obtain a flat, uniform weld layer structure having no welding defects. Were evaluated as “○”, and those not were evaluated as “×”. According to the visual inspection, the surface of the overlay is flat,
No defects such as cracks and pinholes were found by the dye flaw detection test (PT inspection).

Here, the welding members of sample Nos. 18 to 23 are plate-shaped base materials 10 made of SS400 shown in FIG. 1A, and have a length A1 of 200 mm and a width A2 of 1
The base material has a length A4 in the direction A1 of about 150 mm and a width A5 of about 70 mm and a thickness A3 of 19 mm.
This is one in which four pass overlay layers 20 are formed in parallel over an area of mm.

The welding members of Sample Nos. 1 to 10 and 24 had a diameter D of φ58 mm made of S25C shown in FIG.
The base member 10 of the round bar is used, and the welding members of the sample numbers 11 to 17 use the base member 10 of the round bar having the diameter D of φ50 mm made of SS400, and the axial length A of the round bar, respectively.
Reference numeral 6 denotes a cylindrical overlay layer 20 formed over 80 to 100 mm. Here, in each of the sample numbers 1 to 24, when the lower embossed layer 11 is formed, the thickness thereof is 2.5.
mm, and the thickness of the cladding layer 20 was 5 mm.

As can be seen from FIGS. 3 and 4, HTL-C (Hastelloy), which is a nickel-based alloy, is used as the base member.
Alternatively, STL-21 (Stellite) which is a cobalt-based alloy is used, or stainless steel, S25C, SS
400 (sample Nos. 17, 2 without underlying layer 11)
2, 23), it is possible to satisfactorily weld powders containing 50% by weight, 70% by weight, 90% by weight, and 95% by weight of pure tungsten as welding powders for the overlay, and those containing pure tungsten only. I understand.

Here, among the powders of the respective samples, those containing a nickel-based alloy (HTL-C), a cobalt-based alloy (STL-21) or titanium as a binder material with respect to pure tungsten (W). , W is the maximum weight component, and the composition is such that W remains after being welded without being combined with the binder material.

In addition, tungsten carbide (W
₂ C), chromium Bo write (CrB), nickel Bo light (NiB), also containing ceramic or cermet material such as niobium carbide (NbC), which can realize a good welding condition. Sample No. 24 is a comparative example in which cracks occurred. Depending on the setting of the powder component ratio, etc., the effect of improving the weldability may not be able to be exhibited, but in general, according to the present embodiment, it is possible to improve the weldability even for materials that are conventionally difficult to weld. Is obvious.

As described above, according to the present embodiment, the weldability can be improved while preventing the performance of the weld layer 20 from being reduced by dilution. The effect of improving weldability is
Copper, copper alloys, and titanium alloys can also be used as the base members 10 and 11. Further, as a welding powder, one or more components of niobium, molybdenum, tantalum, and titanium other than a tungsten-containing material may be used. The same effect can be exerted by using the same.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing a welding member according to an embodiment of the present invention, wherein FIG. 1A is a perspective view showing a rectangular plate, and FIG. 1B is a sectional view showing a round bar.

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

FIG. 3 is a table showing an example of a specific component ratio in the embodiment.

FIG. 4 is a chart showing an example of a component ratio following FIG. 3;

[Explanation of symbols]

 10: Base material, 11: Underlay layer, 20: Overlay layer.

Claims (11)

[Claims] 1. A welding method for performing build-up welding on the surface of an underlying member by plasma powder welding, wherein the component of the underlying member melts into the welding layer after welding by dilution with respect to the component of the welding powder. Anticipating,
A plasma powder welding method, wherein a component ratio of the welding powder and a component ratio of the base member are set in advance. 2. The base member is made of any one of an iron-based alloy, a nickel-based alloy, a cobalt-based alloy, copper, a copper alloy, titanium, and a titanium alloy, and 50 wt. The method according to claim 1, wherein the content is at least 1%. 3. The plasma powder welding method according to claim 2, wherein a powder containing 70% by weight or more of pure tungsten is used as the welding powder. 4. The plasma powder welding method according to claim 2, wherein a powder containing 90% by weight or more of pure tungsten is used as the welding powder. 5. A nickel-based alloy as the base member,
Using one of a cobalt-based alloy, copper, a copper alloy, titanium and a titanium alloy, and using one or more components of pure tungsten, niobium, molybdenum, tantalum and titanium as the welding powder, the total of which is 50 2. The method according to claim 1, wherein the powder is used in an amount of at least 1% by weight. 6. A welding powder used in the welding method according to claim 1, wherein pure tungsten and a binder material composed of one or more components other than tungsten are completely used. A powder for welding, characterized in that the pure tungsten is contained in a composition ratio such that the pure tungsten is the maximum weight component. 7. The method according to claim 6, wherein the pure tungsten and the binder material are contained in such a composition that the pure tungsten remains without being combined with the binder material after welding. The welding powder described. 8. The welding powder according to claim 7, wherein the binder material contains at least one of a cobalt-based alloy, a nickel-based alloy, and stainless steel. Powder for welding. 9. The welding powder according to claim 6, wherein the welding powder contains a ceramic or a cermet-based material. 10. A welding method for performing build-up welding on the surface of a base member by plasma powder welding, wherein a welding powder made of pure tungsten only is used, and a component of the welding powder in a weld layer after welding. A ratio of the pure tungsten to a component of the base member is set in advance in consideration of a component of the base member which is dissolved by dilution. 11. The base member is made of one of a nickel-based alloy, a cobalt-based alloy, copper, a copper alloy, titanium, and a titanium alloy.
4. The plasma powder welding method according to 1.