JP2573055B2 - Aluminum or aluminum alloy overlay welding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plasma arc build-up welding method for performing build-up welding on the surface of aluminum or an aluminum alloy.

[Conventional technology and its problems]

Aluminum-based materials are used in automobile parts, aircraft parts, etc., because they have a specific gravity of about 1/3 lighter than steel and have good thermal conductivity. However, the melting point of an aluminum-based material is as low as 660 ° C. at the highest, and its hardness is very low as compared with steel, and its heat resistance and wear resistance are inferior. Therefore, the heat resistance of the aluminum material as it is,
It cannot be applied to members requiring abrasion resistance.

Therefore, a method of joining a different material having excellent heat resistance and wear resistance to an aluminum material so that the aluminum material can be used for a member requiring heat resistance and wear resistance has been considered.

As a method for joining a dissimilar material to the aluminum-based material, there is a method such as brazing, but the joining strength is not sufficient. Recently, in order to increase the bonding strength, a build-up welding method using a laser beam capable of obtaining metallurgical bonding has been adopted.

Japanese Patent Application Laid-Open No. 62-16894 discloses a method for overlay welding of such a material.
As described in the official gazette, a copper base overlay alloy material having excellent heat resistance, wear resistance, corrosion resistance, etc. is applied or fed to an aluminum base material, and a laser beam is irradiated thereon. There has been proposed a build-up welding method in which welding is performed. However, the initial cost and the lining cost of the laser overlay welding device are very high, and the cost of the parts to be applied is very high.

Conventionally, the following problems have been pointed out in such aluminum-based materials.

(1) An aluminum-based material is very easily oxidized during welding, and produces an oxide film and alumina having a higher melting point than the base material. If this alumina is present at the time of welding, it causes poor fusion and causes deterioration of the jointability.

(2) In a molten state, an aluminum-based material easily absorbs hydrogen and water vapor, and easily generates welding defects such as pits and blowholes.

[Problems to be solved by the invention]

The present invention removes a strong and high melting temperature oxide film formed on the surface of aluminum or aluminum alloy,
An object of the present invention is to provide an inexpensive plasma arc build-up welding method that can obtain a metallurgical bond having a high bonding strength and does not generate welding defects such as blow holes.

[Means for solving the problem]

To achieve the above object, the gist of the aluminum or aluminum alloy plasma arc build-up welding method according to the present invention is to use an AC plasma arc in the aluminum or aluminum alloy build-up welding method. Arc frequency from 300Hz to 5000H
z, and when the positive polarity component time of the voltage waveform is t _a , and the reverse polarity component time is t _b , welding is carried out at a time ratio satisfying the following equation, and the overlay welding method for aluminum or aluminum alloy is characterized in that: It is in.

[Action] In the AC plasma arc overlay welding method of the present invention,
Overlay welding at a frequency of 300 Hz or more and 5000 Hz or less requires 3
If the frequency is less than 00 Hz, arc breakage tends to occur during polarity conversion, and blow holes and pits are formed. When the frequency exceeds 5,000 Hz, a metallic sound peculiar to high frequency is generated, which makes the working environment difficult for the welding worker, and the dilution into the aluminum-based base material becomes large, so that the overlaid metal of the predetermined component can be obtained in a higher level. This is because they cannot be put to practical use. So the frequency range is 300Hz
50005000 Hz.

Further, in the AC plasma arc welding method of the present invention, the time ratio between the positive polarity and the opposite polarity component has a close relationship between the cleaning effect of removing the oxide film formed on the surface of the base material and the dilution ratio of the base material. Do you get it. In the relationship between the two, the opposite polarity component removes the oxide film formed on the base material, and the positive polarity component increases the dilution of the base material, but has the effect of cooling the electrode and preventing damage to the electrode. Therefore, as shown in FIG. 1, by setting the ratio of the positive polarity component time (t _a ) to the reverse polarity component time (t _b ) of the electrode applied voltage within a predetermined range, damage to the electrodes can be prevented and the mother component can be prevented. It is possible to suppress dilution of the material and secure an appropriate cleaning effect area width.

FIG. 2 is a graph showing the relationship between the time ratio of the positive polarity component and the reverse polarity component in the AC plasma arc overlay welding according to the present invention, and the relationship between the cleaning effect area width and the dilution ratio. Positive component time ratio Is less than 60%, the amount of heat generated by the electrode is such that electrons generated from the base material at the time of reverse polarity components collide with the electrode, the amount of heat generated by the electrode increases rapidly, and the electrode is damaged, resulting in unstable arcing.
Sound overlay welding cannot be performed. On the other hand, if the positive polarity component time ratio exceeds the upper limit of 90%, the dilution ratio to the base material becomes large, the cleaning effect is not recognized, and welding defects such as poor fusion caused by the surface oxide film occur. For the above reasons, the positive component time ratio The range of 60% or more and 90% or less is appropriate.

(Example) Next, the overlay welding method of the present invention will be described with reference to FIG.

FIG. 3 is an explanatory diagram showing an example of an AC plasma arc welding apparatus suitable for overlay welding of a powder overlay material to the surface of an aluminum alloy plate using an AC power supply.

In FIG. 3, reference numeral 1 denotes a tip of a plasma arc welding torch. The plasma arc welding torch 1 is provided with a tungsten electrode 2 at the center thereof. And a torch outer cylinder 4 are provided. Powder supply for supplying a plasma working gas passage 15 between the tungsten electrode 2 and the torch inner cylinder 3 and a shielding gas passage 16 and a powder overlay material 11 between the torch inner cylinder 3 and the torch outer cylinder 4 A pipe 5 is provided. An inert gas such as an argon gas is supplied to the plasma working gas passage 15 as a plasma working gas. The shield gas passage 16 is supplied with an inert gas such as an argon gas to shield the overlay metal from the atmosphere. Below the plasma arc welding torch 1 configured as described above, an aluminum alloy plate 13 of a build-up welding material is disposed. And plasma arc 12
Inside, the powder overlay material 11 is passed through the powder feed pipe 5,
An inert gas such as an argon gas is supplied as a supply gas, and a build-up metal 14 is sequentially formed on the surface of the aluminum alloy plate 13.

A predetermined pilot current is supplied from a pilot power supply 6 between the tungsten electrode 2 and the torch inner cylinder 3. Further, between the tungsten electrode 2 and the aluminum alloy plate 13, a positive polarity reverse polarity time ratio adjusting device 9 capable of arbitrarily adjusting the time ratio between the positive polarity and the reverse polarity and a frequency adjusting device 10 capable of arbitrarily adjusting the frequency are provided. A predetermined welding current can be supplied from the attached main AC power supply 7. Further, a high frequency generator 8 for plasma arc ignition is disposed between the tungsten electrode 2 and the torch inner cylinder 3.

Next, in order to confirm the effects based on the present invention, the aluminum plate and the aluminum alloy plate shown in Table 1 were coated with a powder overlay material having excellent heat resistance and abrasion resistance shown in Table 2. In combination, overlay welding was performed using the AC plasma arc overlay welding apparatus according to one embodiment of the present invention shown in FIG. The weldability of the build-up weld metal obtained under the following welding conditions was examined for bondability and occurrence of welding defects such as blowholes and pits. Table 3 shows the results.

Overlay welding condition; welding current 90A welding speed 80mm / min Plasma working gas flow (Ar) 2 / min Shield gas flow (Ar) 20 / min Powder feed gas flow (Ar) 2 / min No. in Table 3 No. 1 to No. 10 were obtained by overlay welding using the AC plasma arc overlay welding apparatus shown in FIG. No. 11 and No. 12 are commonly used positive polarity plasma arc overlay welding methods, which were performed for comparison.The welding conditions were the same as those for the above AC plasma arc overlay welding method. Was.

No. 1 to No. 6 satisfy the requirements of the present invention, the dilution into the base material is small, poor fusion, blow holes, pits and other welding defects are not observed in the welded part, good jointability and bead shape Obtained.

No. 7 to No. 10 were performed by AC plasma arc overlay welding, but No. 7 and No. 8 were positive component time ratios. Are examples outside the scope of the present invention. In No. 7, the positive component time ratio was lower than the lower limit of the range of the present invention, the electrode was severely damaged, the arc became unstable during welding, and the operation was stopped.
In No. 8, the positive component time ratio exceeded the upper limit, the cleaning effect was small, and poor fusion was observed. In addition, the base material was greatly diluted, inclusions and compound phases were formed at the interface of the joint, and cracks were observed.

No. 9 and No. 10 are examples in which the frequency is out of the range of the present invention. In No. 9, the frequency was lower than the lower limit of the range of the present invention, the arc was broken several times during welding, and many blow holes and pits were also generated. In No. 10, the frequency exceeded the upper limit of the range of the present invention, the dilution of the base material was increased, and cracks were observed at the joint interface together with the compound phase. In addition, a metallic sound peculiar to high frequency was generated, and was not endurable to welding work.

Nos. 11 and 12 are comparative examples using the positive polarity plasma arc build-up welding method. In each case, welding defects such as poor fusion and blowholes caused by the surface oxide film occurred, and satisfactory joining properties and bead shapes could not be obtained.

[Effect of the Invention] As described above, according to the aluminum or aluminum alloy overlay welding method of the present invention, the oxide film on the surface of the base material that deteriorates the bondability of the aluminum or aluminum alloy overlay weld is removed. In addition, welding defects such as poor fusion, blowholes and pits do not occur, and good overlay welding can be performed. Therefore, it is possible to obtain an aluminum-based component in which different materials having excellent properties such as heat resistance and abrasion resistance are built up, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a graph showing a voltage waveform applied to the electrode of the present invention, FIG. 2 is a graph showing a relationship between a positive component time ratio, a cleaning effect area width and a dilution ratio of a base material, and FIG. It is explanatory drawing which showed an example of the apparatus which performs build-up welding of an aluminum-based material using a. 1 ... plasma arc welding torch, 2 ... tungsten electrode, 3 ... torch inner cylinder, 4 ... torch outer cylinder, 5 ... powder feeding pipe, 6 ... pilot power supply, 7 ... main AC power supply, 8 ... High frequency generator, 9 ... Positive electrode reverse polarity time ratio adjusting device, 10 ... Frequency adjusting device, 11 ... Powder overlay material, 12 ... Plasma arc, 13 ... Aluminum alloy plate, 14 ... Hardfacing metal, 15 ... Plasma working gas passage, 16
…… Shield gas passage.

Continuing on the front page (72) Inventor Yasutoshi Nakata 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding Industry Co., Ltd. (72) Inventor Hiroyuki Koike 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding (56) References JP-A-62-21465 (JP, A)

Claims (1)

(57) [Claims] In the method for overlay welding of aluminum or aluminum alloy, an AC plasma arc is used, the frequency of the AC plasma arc is 300 Hz to 5000 Hz, the positive component time of the voltage waveform is t _a , and the reverse polarity component time is If the set to t _b, overlay welding method of aluminum or aluminum alloy, characterized in that the welding time ratio that satisfies the following equation.