JPH02268982A - Build-up welding method of titanium or titanium alloy - Google Patents

Abstract

PURPOSE:To obtain a good bead shape without forming a brittle compd. phase and inclusion at the boundary of a joint part in build-up welding of a titanium or titanium alloy by using an AC plasma arc of a specific frequency as a heat source and welding the titanium or titanium alloy. CONSTITUTION:A titanium alloy plate 12 which is a material for the build-up welding is installed below a plasma arc build-up welding torch 1 and a powder building-up material 10 is fed through a powder feeding pipe 5 into the plasma arc 11 with an inert gas, such as gaseous argon, as a feed gas, by which a build-up metal 13 is successively formed on the surface of the titanium plate 12. The welding is executed by using the AC plasma arc of 300 to 5000Hz frequency for the heat source. The oxide film on the base metal surface to deteriorate the joinability is removed in this way, by which the formation of the brittle compd. phase and inclusions at the boundary of the joint surface is obviated and the good bead shape is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma arc build-up welding method for performing build-up welding on the surface of titanium or a titanium alloy.

[Prior Art] Titanium or titanium alloy materials are used for automobile and aircraft parts, taking advantage of their advantages such as having a light specific gravity of about 60% compared to iron and excellent corrosion resistance.

However, since titanium or titanium alloy is softer than iron, it cannot be used as is in areas where wear resistance is required.

Therefore, a method of overlaying a titanium-based material with a different material having excellent properties such as wear resistance and heat resistance has been considered so that the titanium-based material can be used in areas where wear resistance is required.

Conventionally, the overlay welding method for this titanium-based material is
Gas welding using an oxygen-acetylene flame, arc welding using a TIG arc, plasma arc, and build-up methods using laser light have been adopted.

As a hardfacing welding method for such materials, Japanese Patent Application Laid-Open No. 61-2
As described in Japanese Patent No. 3574, a method has been proposed in which a mixed powder of titanium and metal carbide is used for plasma arc overlay welding on an engine valve face made of a titanium-based alloy material. In this proposal, a DC positive polarity plasma arc build-up welding method, which is commonly used as a plasma arc build-up welding method, is used. It is generally known that positive polarity plasma arc build-up welding involves greater dilution into the base metal than reverse polarity plasma arc build-up welding.

[Problems to be solved by the invention] When a CO metal alloy with good wear resistance and heat resistance is overlay welded to a titanium-based material, intermetallic compounds are generated at the bonding interface between the base material and the overlay metal. Forms brittle joints. As the dilution into the base material increases, the width of formation of the brittle compound phase increases, which poses a practical problem. In addition, if positive plasma arc build-up welding, which has no cleaning effect, is applied to build-up welding of materials such as titanium-based materials, which form an oxide film with a high melting temperature on 1 m of base metal coating, welding may occur at the joint interface. There are problems such as the formation of objects and the inability to obtain a sound joint.

Furthermore, JP-A-59-78774 discloses a welding method in which a hardening agent containing hardened particles of metal carbide in pure titanium powder is deposited on the surface of titanium or titanium alloy by TIG welding or plasma arc welding. is proposed.

As the plasma arc build-up welding method in the above proposal, a reverse polarity plasma arc build-up welding method is used. It is known that the reverse polarity plasma arc build-up welding method has a small dilution of the base material and has a cleaning effect of removing an oxide film on the surface of the base material. However, in a reverse polarity connection where the base material is the # pole and the electrode is the anode, the electrons generated from the base material are constantly
A large-diameter, water-cooled copper electrode is generally used instead of a W electrode, since it collides with the electrode and heats and damages the electrode.

Therefore, reverse polarity plasma arc welding torches are larger than positive polarity plasma arc welding torches, are not suitable for overlay welding of small items, and have problems in welding operability.

In addition, both the reverse polarity plasma arc build-up welding method and the positive polarity plasma arc build-up welding method use direct current as the current, so they are affected by magnetic blowing, so there are problems such as difficulty in obtaining a good bead shape. .

[Means for Solving the Problems] The above-mentioned problems are solved by the following overlay welding method for titanium or titanium alloy of the present invention.

That is, the present invention provides a heat source with a frequency of 00 Hz to 50 Hz.
This is an overlay welding method in which welding is performed using an alternating current plasma arc of 00 Hz.

[Function] In the present invention, the reason why welding is performed at a frequency of 300 Hz or more is because if the frequency is less than 300 Hz, arc breakage occurs during polarity change, resulting in an unstable arc and a continuous bead cannot be obtained. In addition, when it exceeds 5000t-1z, a metallic sound peculiar to high frequencies is generated, which is unpleasant for welding workers.
The frequency range has been reduced to 300 Hz because it creates an unbearable working environment and significantly increases the manufacturing cost of the welding power source.
~5000Hz.

[Example] Next, the overlay welding method of the present invention will be explained based on FIG. 1. FIG. 1 is an explanatory diagram showing an example of an AC plasma arc overlay welding apparatus suitable for overlay welding a powder overlay material onto the surface of a titanium alloy plate using an AC power supply.

In FIG. 1, reference numeral 1 indicates the tip of a plasma arc build-up welding torch, and the plasma arc build-up welding torch 1 is equipped with a tungsten electrode Vi2 in the center, and on the outside of this electrode 2, A torch inner cylinder 3 and a torch outer cylinder 4 are provided. Then, a plasma working gas passage 14 is provided between the tungsten electrode 2 and the torch inner cylinder 3, a shielding gas passage 15 is provided between the torch inner cylinder 3 and the torch outer cylinder 4, and a powder feed material lO is supplied. A feeding vibe 5 is provided. Inert gas such as argon gas is supplied to the plasma working gas passage 14 as a plasma working gas. Inert gas such as argon gas is supplied to the shield gas passage 15, and the overlay metal 13 is supplied with an inert gas such as argon gas.
It is designed to shield the air from the atmosphere.

A titanium alloy plate 12, which is a material to be welded, is installed below the plasma arc overlay welding torch 1 configured as described above. Then, the powder overlay material 10 is supplied into the plasma arc 11 through the powder feed pipe 5 using an inert gas such as argon gas as a feed gas, and the overlay metal is sequentially applied onto the surface of the titanium plate 12. 13 is formed.

Note that between the tungsten electrode 2 and the torch inner cylinder 3,
A predetermined pilot current is supplied from a pilot power source 6. Moreover, a predetermined welding power source can be supplied between the tungsten electrode 2 and the titanium alloy plate 12 from a main AC power source 7 equipped with a frequency adjustment device 9 that can arbitrarily adjust the frequency. Further, a high frequency generator 8 for igniting a plasma arc is disposed between the tungsten electric ViA 2 and the torch inner cylinder 3.

Next, in order to confirm the effects based on the present invention, the titanium plates and titanium alloy plates shown in Table 1 were combined with the powder overlay materials shown in Table 2, and the materials shown in Fig. 1 were combined. Overlay welding was performed using an AC plasma arc overlay welding apparatus according to an embodiment of the invention. Table 3 shows the results of investigating the bondability, bead shape, etc. of the build-up parts obtained by welding under the following welding conditions.

Welding conditions: Welding current 80A Welding speed 45 (1++o+/win Plasma working gas flow rate (^'') 2λ/min Shielding gas flow rate (Ar) 21!/min Powder feed gas flow 5j (Ar) 21/min Table 3 No in
, l-No. 7, overlay welding was performed using the AC plasma arc overlay welding apparatus shown in FIG. N
o, 8. No. 9 was performed using the commonly used positive plasma arc build-up welding method, and No. IO
, No., l] were performed for comparison using the reverse polarity plasma arc build-up welding method. In addition, N008~No, 11
Both the positive polarity plasma arc build-up welding method and the reverse polarity plasma arc build-up welding method were performed under the same welding conditions as the AC plasma arc build-up welding method.

Nos. I to No. 5 satisfied the requirements of the present invention, no inclusions or compound phases were observed at the bonding interface of the built-up portion, and good bondability and bead shape were obtained. Furthermore, it goes without saying that arc breakage did not occur and stable welding was performed.

No, 6. No. 7 is an example in which AC plasma arc build-up welding was performed, but the frequency was outside the range of the present invention. In No. 6, the frequency was lower than the lower limit of the range of the present invention, arc breakage occurred during welding, stable welding was not possible, and the bead shape was poor.

No. 017 had a frequency exceeding the upper limit of the range of the present invention, and the bondability and bead shape were good.

It produced a metallic sound peculiar to high frequencies, and was not suitable for welding work.

No, 8. For comparison, No. 9 was made using the positive plasma arc build-up welding method. In both cases, cracks were observed along with compound phases at the joints.

Also, by magnetic blowing, a satisfactory bead shape could not be obtained.

No, 10. No. 11 is by reverse polarity plasma arc build-up welding. Although the cleaning effect was observed and the bondability was good, the bead toe became irregular due to magnetic blowing, and a satisfactory bead shape could not be obtained.

[Effects of the Invention] From the above, according to the method for overlay welding of titanium or titanium alloy of the present invention, it is possible to remove the oxide film on the surface of the base material that deteriorates the bondability of the overlay weld of titanium or titanium alloy. ,
No brittle compound phase or inclusions are formed at the joint interface, and a good bead shape can be obtained. Therefore, it is possible to obtain a titanium-based part overlaid with a different material that has excellent properties such as wear resistance and heat resistance, and has great industrial value.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus for carrying out the overlay welding method for titanium or titanium alloy according to the present invention using an AC power source.

Claims (1)

[Claims] 1. In the overlay welding method of titanium or titanium alloy,
A method for overlaying titanium or titanium alloy, the method comprising welding using an alternating current plasma arc with a frequency of 300 Hz to 5000 Hz as a heat source.