JPH0970670A - Powder plasma welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a powder plasma welding method where a welding layer as the object can be formed easily by using a powder as the welding material. SOLUTION: In this plasma welding method to supply powder as the welding material to a plasma column 9 formed between an electrode inside a plasma torch 2 and the front face of a base material 1, to form a globule and to execute buildup welding by welding the globule on the front face of the base material. At the time of forming the globule, at least two kinds of powders A, B as the welding material are mixed in proportion so as to make the composition of globule to be formed, and these are supplied to the plasma column 9. At least two hoppers 3a, 3b are connected to the plasma torch 2, and respective hoppers 3a, 3b house the powders granule A, B of the welding material of different composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder plasma welding method, and more specifically, it uses a plurality of kinds of powders having different compositions as raw materials for droplets, and changes the supply amount of each powder mutually. The present invention relates to a novel powder plasma welding method capable of forming a weld bead having a desired composition and characteristics.

[0002]

2. Description of the Related Art The surface of a rolling roll or an anvil of a forging machine is required to have high hardness and excellent wear resistance. And if the surface wears after long-term use,
Measures are taken to repair the surface and restore the surface hardness to the original state again. Generally, in order to make the surfaces of these members have high hardness, for example, the following overlay welding is performed.

First, on the surface of a base material made of a predetermined alloy,
For example, by the MIG method, the droplets are deposited on the surface of the base material using a welding wire made of a relatively soft welding material to form a lower welding layer having a predetermined thickness. Then, a welding wire made of a welding material having a predetermined hardness is used to deposit the droplets on the lower welding layer, whereby the upper welding layer having a predetermined thickness is laminated.

As described above, in the case of conventional overlay welding, when forming the underlay welding layer, a specific welding wire having the same composition and characteristics as the underlay welding layer to be formed is used, and When forming the welding layer, a specific welding wire having the same composition and characteristics as the overlay welding layer to be formed is used. That is, overlay welding is performed by properly using a plurality of welding wires that have already been manufactured and are commercially available.

For example, DSalloy U520 (trade name, manufactured by Daido Steel Co., Ltd.) used for anvil of a four-sided forging machine has C: 0.02 to 0.06% by weight and Si: 0.5.
0% by weight or less, Mn: 2.00% by weight or less, S: 0.010
Wt% or less, Cr: 18.00 to 2.00 wt%, Co:
11.00 to 13.00% by weight, Fe: 2.00% by weight or less,
Cu: 0.10 wt% or less, Mo: 5.50 to 6.50 wt%, W: 0.90 to 1.20 wt%, Al: 1.90 to 2.00
% By weight, Ti: 2.90 to 3.27% by weight, B: 0.004 to
Ni-based superalloy consisting of 0.010% by weight and Ni as the balance. When the total amount of Ti and Al (Ti + Al) is about 4.9% by weight, the Shore hardness (Hs) of the surface is 5 at room temperature.
It is about 8 and about 45 at the maximum temperature (about 800 ° C.) during use, which is a very high hardness material.

In this material, the Hs value increases as the (Ti + Al) content increases and decreases as the Hs value decreases.
The value is low, and the relationship between the Hs value and the (Ti + Al) content is substantially linear. When repairing the surface hardness of this material with MIG, first, (Ti +
Al) content of the DSal prepared to about 2.4 wt%
A welding wire is manufactured using a material having a composition equivalent to that of the Uloy U520. The Hs value of this material is about 52, which is relatively soft.

Then, using this welding wire, the base metal (D
The underlay welding layer is formed on the surface of the Salloy U520). On the other hand, separately, the (Ti + Al) content is adjusted to about 4.9% by weight and a welding wire is manufactured in advance using a material equivalent to DSalloy U520. The Hs value of this material is about 58, which is relatively hard.

[0008] By using this welding wire, the droplets are deposited on the above-mentioned lower welding layer and the upper welding layer is laminated, whereby a two-layer overlay welding is performed. In the case of the above overlay welding, Hs of the overlay welding layer forming the uppermost layer
Since the value is substantially the same as the Hs value of the base material (DSalloy U520), the surface of the base material has been restored to the original hardness characteristics. Since the lower welding layer located in the middle has a relatively soft Hs value of 52, it exhibits a buffering function for the hard base material and the upper welding layer.

By the way, the above overlay welding may be performed by using plasma as a heat source for melting the welding wire. In this case, A, which is a non-consumable electrode placed in the plasma torch and the surface of the base material, is
forming a plasma column using a working gas such as r gas,
The high heat of the plasma column forms droplets of the welding wire, and the droplets are deposited on the surface of the base material to form a lower welding layer and an upper welding layer.

[0010]

Even in the overlay welding by the plasma welding method described above, for example, when a plurality of welding layers are to be laminated on the surface of the base material, each welding layer is formed as in the case of the conventional MIG. The composition and characteristics (eg hardness) of
It is uniquely defined by the composition and characteristics of the welding wire used when forming the weld layer.

Therefore, when forming a welding layer having a desired composition and characteristics, it is necessary to manufacture a welding wire having the composition and characteristics in advance.
However, when a plurality of welding layers are laminated and overlay welding is performed, the composition and characteristics of the welding layers are varied, and if the number of layers is increased, the types of welding wires to be prepared in advance are also varied. It will be diverse and will impose a heavy economic burden.

That is, when overlay welding is attempted by sequentially and continuously changing the composition and characteristics of the welding layers to be laminated, the number of types of welding wires used becomes extremely large, and it is practically impossible. Becomes The present invention solves the above-mentioned problems when performing plasma welding using a welding wire, and even when changing the composition or characteristics of the welding layer to be formed, without producing a welding wire according to it. An object of the present invention is to provide a powder plasma welding method capable of easily forming an intended welding layer.

[0013]

In order to achieve the above object, in the present invention, a powder is used as a welding material instead of a conventional welding wire. That is,
In the present invention, the welding material powder is supplied to the plasma column formed between the electrode in the plasma torch and the surface of the base material to form droplets, and the droplets are deposited on the surface of the base material. In the powder plasma welding method for overlay welding, the powders of at least two kinds of welding materials are mixed in a ratio such that the composition of the droplets to be formed is obtained. A powder plasma welding method is provided, which comprises supplying to the plasma column.

In the present invention, the welding material powder supplied to the plasma column is melted by the high heat of the plasma column to form droplets. Then, these droplets are deposited on the surface of the base material,
It becomes a weld layer after cooling. In the case of the present invention, the welding material converted into droplets in the plasma column is a mixed powder formed by mixing powders of at least two kinds of welding materials having different compositions from each other at a predetermined ratio. The mixed powder in that case is prepared so that its composition may be the same as that of the weld layer to be formed, that is, the droplet.

The preparation can be performed by controlling the mixing ratio of the powders of the welding materials to be mixed with each other. Therefore, in the present invention, by appropriately setting the composition of each of the powders of two or more kinds of welding materials, and by supplying them to the plasma column by mixing them in a welding layer having an arbitrary composition. Since it can be easily formed, the degree of freedom in overlay welding is significantly improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram for explaining the plasma welding method of the present invention performed using powders of two kinds of welding materials. In the figure, two hoppers 3a and 3b are connected to a plasma torch 2 arranged above a base material 1 via respective powder supply paths 4a and 4b.

The hopper 3a contains a powder A of a welding material having a certain composition, and the hopper 3b contains a powder B of a welding material having a different composition from the powder A. Flow rate controllers 5a and 5b are respectively provided at the connecting portions of the hoppers 3a and 3b and the powder supply paths 4a and 4b, and these are operated by a remote control by a control mechanism 6 to operate in the hopper. A predetermined amount of powder A, B is supplied to the powder supply paths 4a, 4b. Also, each hopper 3
A carrier gas supply device (not shown) is connected to a and 3b, and the powders A and B in the hopper are conveyed through the powder supply paths 4a and 4b by the carrier gas, and the plasma torch 2
It is supplied to.

In the plasma torch 2, as shown in FIG. 2, a hollow cylindrical gas nozzle body 2a having a cooling water passage 7a and a shield gas passage 8a and a hollow cylindrical convergent nozzle body 2b having a cooling water passage 7b. Are coaxially arranged, and a non-consumable electrode 2c such as a W electrode is arranged at the entire axial center position in the hollow portion of the convergent nozzle body 2b. Then, between the outer wall of the convergent nozzle body 2b and the inner wall of the gas nozzle body 2a, only the lower side is opened and the annular opening 2d is formed.
An annular closed space 2e which constitutes the above is formed.

The upper portion of the closed space 2e is connected to the powder supply paths 4a and 4b shown in FIG. 1, and the powders A and B carried by the carrier gas merge and mix in the closed space 2e. However, a jet flow can be made from the annular opening 2d.
The plasma torch 2 applies a main voltage between the base material 1 and the electrode 2c to discharge the main arc, and applies a pilot voltage between the convergent nozzle body 2b and the electrode 2c to discharge the pilot arc. In the converging nozzle 2b, for example, A
The plasma column 9 of Ar is formed between the electrode 2c and the base material 1 by introducing r as the working gas.

In this state, the powders A and B carried by the carrier gas via the powder supply paths 4a and 4b are filled with the closed space 2
When introduced into e, the powders A and B merge in the closed space 2e and then mix, and the mixed powder is jetted from the annular port 2d and supplied to the plasma column 9. Then, the mixed powder is melted by the high heat of the plasma column 9 to form droplets, which are welded to the surface of the base material 1 to form the welding layer 10.

At this time, the flow rate controller 5a shown in FIG.
The amount of powder A supplied from the hopper 3a to the powder supply path 4a and the hopper 3 by adjusting 5b respectively.
The supply amount of the powder B supplied from b to the powder supply path 4b can be set to a desired value. Therefore,
In the closed space 2e, the powder A and the powder B are mixed in the above-mentioned set amount, so that the component composition of the obtained mixed powder can be made arbitrary by changing the above-mentioned respective supply amounts.

Consider, for example, the case of forming the welding layer 10 having a composition in which the content of a certain component p is q% by weight. In that case, powder A having a p component content of a ₁ % by weight and powder B having a p component content of a ₂ % by weight are prepared, and these are respectively provided in the hoppers 3a and 3b. Be accommodated. Then, it is assumed that the flow rate controllers 5a and 5b are respectively adjusted to set the supply amount of the powder A to W ₁ and the supply amount of the powder B to W ₂ .

The total amount of the mixed powder supplied to the plasma column 9 is W ₁ + W ₂ . Then, the absolute value of the supply amount of the component p in this mixed powder is a ₁ × W ₁ + a ₂ × W ₂ . Therefore, the content of the component p in the mixed powder is (a ₁ × W ₁ + a ₂ × W ₂ ) / (W ₁ + W ₂ ).

Since a ₁ and a ₂ are eigenvalues of the powders A and B, W ₁ and W ₂ should be selected so that the value represented by the above formula is q% by weight. You can That is, the flow rate controllers 5a, 5a, 5b are adjusted so that the amounts of the powders A, B supplied from the hoppers 3a, 3b are W ₁ and W ₂ , respectively.
By adjusting 5b, the above formula becomes q% by weight, so that a droplet having the desired composition is formed here, and by welding it to the surface of the base material, the welding layer 1 having the desired composition is formed.
0 can be formed.

As described above, in the present invention, if powders A and B made of a welding material having a certain composition are prepared, a welding layer having an arbitrary composition is formed by changing the mixing ratio of them. can do. Note that the above description is for the case of two hoppers, but the number of hoppers connected to the plasma torch is not limited to two, and any suitable number may be used.

[0026]

EXAMPLE In the apparatus shown in FIG. 1, hoppers 3a and 3b contained powders A and B of Ni-based superalloys having the following compositions (both have an average particle size of 150 mesh). Powder of hopper 3a A: C: 0.025 wt%, Si: 0.4
0% by weight, Mn: 1.85% by weight, S: 0.009% by weight,
Cr: 18.60% by weight, Co: 12.4% by weight, Fe: 1.
5% by weight, Cu: 0.07% by weight, Mo: 5.9% by weight,
W: 1.17 wt%, Al: 3.2 wt%, Ti: 4.4 wt%, B: 0.006 wt%, balance Ni.

Powder of hopper 3b B: C: 0.025% by weight, Si: 0.41% by weight, Mn: 1.90% by weight, S: 0.
009 wt%, Cr: 18.11 wt%, Co: 12.3 wt%, Fe: 1.3 wt%, Cu: 0.08 wt%, Mo:
5.7% by weight, W: 1.06% by weight, Al: 1.2% by weight, T
i: 2.2% by weight, B: 0.008% by weight, balance Ni.

As a base material, DSalloy U520
(Product name, manufactured by Daido Steel Co., Ltd.) was selected. The surface hardness (Hs) was 58. After cleaning the surface of the base material,
The plasma torch 2 shown in FIG. 2 is set above it and driven under the conditions of a current of 200 A, a voltage of 50 V and an Ar gas flow rate of 2.5 N liter / min, and a temperature of 10000 ° C. between the W electrode 2 c and the base material 1. The above Ar plasma column 9 was formed.

Flow rate controller 5 using Ar as a carrier gas
By operating a and 5b, the powders A and B having the flow rates shown in Table 1 are fed into the closed space 2e of the plasma torch to form a mixed powder, and the bottom welding layer having the thickness shown in Table 1, The overlay welding layer was sequentially formed and overlay welding was performed. When the formation of each welding layer was completed, the content of (Ti + Al) in each welding layer was analyzed, and the surface hardness (Hs) was measured.

No cracks or cracks were found in the formed overlay welding, and no settling occurred. Furthermore, the powders A and B were supplied onto the above-mentioned welding layer at the flow rates shown in Table 1 to form the outermost layer. No cracks or chips were observed in the outermost layer. Its hardness was also measured.
Table 1 summarizes the above results.

[0031]

[Table 1]

[0032]

As is clear from the above description, according to the method of the present invention, the powders of the welding materials having different compositions are mixed at a predetermined ratio and the composition is supplied to the plasma column. It is possible to form a welding layer having the following characteristics. Therefore, the composition of each welding layer can be arbitrarily designed at the time of overlay welding, and the degree of freedom of the design concept is greatly increased as compared with the conventional method using a welding wire.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for explaining a method of the present invention.

FIG. 2 is a cross-sectional view showing an example of a plasma torch used in the present invention.

[Explanation of symbols]

 1 Base Material 2 Plasma Torch 2a Gas Nozzle Body 2b Converging Nozzle Body 2c Electrode 2d Annular Port 2e Sealed Space 3a, 3b Hopper 4a, 4b Powder Supply Channel 5a, 5b Flow Controller 6 Control Mechanism 7a, 7b Cooling Water Channel 8a Shield Gas Channel 9 Plasma column 10 Welding layer A, B Welding material powder

Claims (2)

[Claims] 1. A droplet of a welding material is supplied to a plasma column formed between an electrode in a plasma torch and a surface of a base material to form a droplet, and the droplet is welded to the surface of the base material. In the powder plasma welding method for overlay welding, the powders of at least two kinds of welding materials are mixed in a ratio such that the composition of the droplets to be formed is obtained. A powder plasma welding method, which comprises supplying to the plasma column. 2. At least two hoppers are connected to the plasma torch, each of the hoppers contains a powder of welding material having a different composition, and when the droplets are formed, each of the hoppers receives the powder. The powder plasma welding method according to claim 1, wherein a predetermined amount of powder of welding material is supplied to the plasma column.