JPS6380975A - Build-up welding method of lead or lead alloy to corrosion resistant metal - Google Patents

Abstract

PURPOSE:To prevent the exfoliation of build-up weld metal by building up a 1st layer by a reverse polarity plasma arc welding method and building up the ensuing layers up to the final layer by a gas welding method. CONSTITUTION:A base metal 1 consisting of a corrosion resistant metallic plate is slightly inclined and fixed and is subjected to the reverse polarity plasma arc welding successively upward from the lower to the upper part in a flat horizontal position. Lead or lead alloy is used as a filler metal 2 at this time and a reverse polarity plasma arc welding torch 3 is used as a torch. Since the base metal 1 is inclined, the flow of the build-up weld metal in the passive film forming surface direction of the base metal 1 and the generation of defective joining are obviated and the adhesiveness of the metal is maintained over the entire surface. The base metal 1 is then positioned horizontal and subjected to the building-up by gas welding in a flat position. The joining force of the corrosion resistant base metal 1 and the build-up weld metal 4 is improved and the exfoliation thereof is removed by the above-mentioned method.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of manufacturing a composite metal material by overlaying lead or a lead alloy on the surface of a corrosion-resistant metal such as titanium. The composite metal material produced is used as an electrode material, for example, an insoluble anode in electrolytic plating, electrolytic oxidation, gas extraction by electrolysis, etc.

[Prior Art] Metal materials with excellent corrosion resistance, such as titanium, niobium, tantalum, or alloys containing these metals, are commonly used as insoluble anodes used in the above electrolytic treatment. However, these corrosion-resistant metals tend to form a passive film in the electrolytic solution, reducing electrolytic efficiency.

Therefore, as a means to ensure suitability as an insoluble anode, surface treatment is required to impart conductivity. One such surface treatment method is known to coat the surface of the electrode substrate with lead or a lead alloy.In the past, there were concerns about lead pollution, but recently there has been an increase in the recovery of lead leached into the electrolyte. As technology advances and the problem of waste liquid pollution is solved, the cost-effective lead (or lead alloy) N coating method is beginning to be widely used. However, it is very difficult to firmly adhere a lead (or lead alloy) film to the surface of a highly corrosion-resistant gold such as titanium, and products with a film formed by normal plating methods will lose lead (or lead alloy) during use. Lead alloy) film is comparatively? 'J* peels off and loses its conductivity improvement effect, making it impossible to maintain a high level of electrolytic efficiency over a long period of time.

A method of overlaying lead (or lead alloy) on the surface of a highly corrosion-resistant metal base material such as titanium was also considered, but the melting point difference between titanium and lead (or lead alloy) is very large, and titanium etc. Coupled with the fact that high melting point oxides are usually formed as a passive film on the surface of highly corrosion resistant metals,
The overlay weld metal made of lead (or lead alloy) cannot be tightly adhered to the surface of a highly corrosion-resistant metal, and the overlay weld metal easily peels off during use, which has prevented its practical use. was not achieved.

However, with the development of the method described in JP-A-57-184577, it has become possible to put surface conductivity treatment by overlay welding into practical use. That is, the method disclosed in the above publication involves depositing lead (or lead alloy) on the surface of a corrosion-resistant metal by TIG welding, followed by heat treatment, and a series of steps from the deposit to heat treatment and cooling. This process is carried out in an inert gas atmosphere to improve the adhesion between the base material and the overlay metal.

[Problems to be Solved by the Invention] However, even with the above method, it is not always possible to firmly adhere the overlay weld metal to the base metal. If the surface is insufficiently cleaned, satisfactory adhesion cannot be ensured. As a result, the build-up weld metal may peel off during the electrolytic treatment, making it difficult to call this a reliable method. The present invention has been made in view of these circumstances, and its purpose is to improve the method of forming an overlay weld metal layer made of lead or lead alloy on the surface of a highly corrosion-resistant metal, and to provide a simple and The purpose of this study is to establish an inexpensive method for firmly adhering overlay weld metal to a base metal.

[Means for Solving the Problems] The construction of the overlay welding method according to the present invention is such that the first layer The gist of this method is to build up the material by reverse polarity plasma arc welding, and then build up from the second layer to the final layer by gas welding.

[Function] The base metals selected for the overlay welding method according to the present invention are titanium, titanium alloys, zircon, zircon alloys, tantalum, and tantalum alloys that form an oxide-based passive film on the surface. These metals are corrosion-resistant metals, and it is not easy to overlay and weld low-melting-point lead or lead alloys to these metals with good adhesion. Therefore, we investigated various reasons why it is difficult to improve adhesion and found that, in addition to the extremely large melting point difference between the base metal and lead (or lead alloy) as mentioned above, It was thought that a metal oxide (passive film) at a melting point was present at the bonding interface between the base metal and the overlay weld metal, and was preventing the strengthening of the bonding force through metal bonding. In order to eliminate the problems caused by the passive film, it may be possible to remove the film before overlay welding, but this passive film is quite tough and not only is it difficult to completely remove, but it is difficult to completely remove it. Even if it can be removed, a clean metal surface will quickly oxidize in the air and form a passive film again, so in practice it is extremely difficult to perform overlay welding in the absence of any passive film. It is. Therefore, if we adopt a DC reverse polarity arc welding method, which is commonly used for aluminum welding, and make effective use of the cleaning effect obtained with this welding method, we can achieve good @adhesion despite the presence of a passive film. I thought that I might be able to obtain this.

Therefore, when we applied the normal DC reverse polarity TIG welding method to build up lead or lead alloy, the adhesion between the base metal and the overlay weld metal was improved to some extent, but the adhesion was not as high as expected. I didn't get it.

However, in the normal DC reverse polarity TIG welding method, penetration into the base metal is generally low, and in particular, in the present invention, lead (or lead alloy) with a low melting point is used as the overlay welding metal, so the heat input during welding is It was thought that this was because the high-melting point base metal and lead (or lead alloy) could not be sufficiently fused, and that these factors were hindering the improvement of adhesion. Therefore, in order to improve the adhesion between the base metal and the overlay weld metal, we thought that it was necessary to promote the fusion of the base metal and lead (or lead alloy) during overlay welding, and we conducted further studies. As a result, if the initial layer is built up by reverse polarity plasma arc welding, the passive film on the surface of the base material is removed by the cleaning effect brought about by the reverse polarity, and the convergent plasma arc welds the base metal and lead ( It has become clear that the fusion of the base metal and the overlay weld metal can be promoted to a satisfactory extent.

Due to the above-mentioned circumstances, the first feature of the present invention is that the first layer is built up by reverse polarity plasma arc welding, but the build up of the 21st and subsequent layers has already been done on the surface layer. Since a lead (or lead alloy) layer is formed on the
＜The build-up can be carried out using the most suitable method for welding lead (or lead alloy). In the present invention, lead (or lead alloy), which has a much lower melting point than titanium, is used as the build-up weld metal. When overlaying such low melting point metals,
The easiest and most economical method to control welding heat input is gas welding, which allows lead (or lead alloy) to be welded smoothly and inexpensively while minimizing the thermal effect on the base metal. You can fill it up. For this reason, in the present invention, the build-up from the second layer to the final layer is performed by gas welding.

For these reasons, in the present invention, overlay welding of the first layer (1st rIs) is performed by reverse polarity plasma arc welding,
The build-up from the second layer to the final layer will be done by gas welding, but the following considerations should be taken when overlaying the first layer to more reliably achieve the effect of improving adhesion. be able to. That is, FIG. 1 is a schematic perspective view showing a preferred embodiment when performing first layer overlay welding, in which 1 is a base material (corrosion-resistant metal plate), 2 is a filler metal (lead or lead alloy), and 3 is a reverse polarity plasma arc welding torch, 4
As shown in the figures, the base material 1 is fixed at a slight inclination during initial layer overlay welding, and overlay welding is sequentially performed upward from the lower part in a downward horizontal position. If the first layer overlay welding is performed in this way, there is no risk that the overlay weld metal will flow toward the surface of the base metal where the metal layer is formed, resulting in poor bonding, and a high level of adhesion can be achieved over the entire surface. It is possible to ensure sex. The preferred inclination angle θ at this time is about 5 to 20 degrees, and the most common is about 10 degrees.

When overlaying the second and subsequent layers using the gas welding method, the overlay metal layer made of lead (or lead alloy) has already been formed on the surface of the base material, so there is no need to consider adhesion failure due to a passive film. , the base material can be fixed horizontally and welded by gas welding in a downward facing position.Flammable gases used together with oxygen in gas welding include hydrogen, acetylene,
Methane, ethane, propane, butane, natural gas, city gas, etc. are used.

Sho No. 2/! When performing overlay welding after the first stitch, if the base metal 1 is thin (approximately 5 mm or less), the final overlay product may warp due to the heat effect during gas welding. In this case, for example, as shown in Fig. 2 (cross-sectional explanatory diagram showing the overlay welding situation from 2nd TI! 6 is fixed, and 7 in the figure indicates a gas welding burner),
By suppressing the thermal influence on the base material 1 by performing overlay welding while cooling the base material 1 from the back side, the above-mentioned problem of warping can be minimized.

As mentioned above, the corrosion-resistant metal used in the present invention is a general term for metals that exhibit high corrosion resistance by forming an oxide-based passive film on the surface, and specific examples include titanium, zircon, tantalum, etc. Non-limiting examples include various alloys containing these metals, alloys of these metals with noble metals such as palladium, and cladding materials of gold (including alloys) with copper and the like. Lead alloys used for overlaying include alloys made of lead mixed with one or more of tin, cadmium, bismuth, zinc, antimony, silver, indium, etc., or lead with a small amount of calcium,
Non-limiting examples include alloys containing antimony, arsenic, and the like.

[Example] Pure titanium plate (KS50: thickness 5 mm) as the base material, 0
．． 2% Pb-containing titanium alloy plate (thickness: 5 mm), and titanium clad copper plate (1 mm Ti-1 mm Ti-1 m
3 fffi of mCu-1 was used, and lead-tin alloy (6% 5n-Pd) was used as the overlay weld metal.

Overlay welding experiments were conducted using a 3 mm square).

In the first layer welding, as shown in Figure 1, each base metal is fixed at an inclination angle of 10 degrees, and the first layer is built up sequentially from the bottom to the top using the reverse polarity plasma arc welding method. After overlay welding, the base metal was held horizontally and the second and third layers were overlaid by gas welding. Each welding condition is as follows.
It was as shown in the table.

Regarding the base metal of pure titanium plates and titanium plates containing PB, it was confirmed in advance that the base metal would warp due to gas welding after the second layer, so the initial The base metal after layer build-up was fixed on a copper water-cooled jacket surface plate, and build-up welding of the second and third layers was performed while cooling from the back side of the base metal so that the interlayer temperature was 200° C. or less.

Table 1 For each of the obtained overlay weld materials, the shear peel strength at the bonding interface between the base metal and the overlay weld metal was investigated using the following method.

That is, from each overlay welded metal plate, the width is 10a as shown in Fig. 3.
Collect test pieces with a length of +m and a length of 70 mm. 1: Base material, 4:
Overlay weld metal, B: joint boundary), 21 at approximately the center
1s slit on the base material side above and below leaving the joint boundary of
A slit 4s was made on the overlay weld metal side, and the sample piece was pulled in the vertical direction to measure the degree of shear peeling at the joint boundary.

The results are shown in Table 2.

Table 2 The tensile strength of (Pb + 6% Sn) used as the near filler material was 2.4 to 2.6 Kg/mm2, and the shear peeling of each sample material shown in Table 2 was 2.4 to 2.6 Kg/mm2. Strength is filler metal PB+6%Sn
The tensile strength is substantially the same as that of the alloy, and all bonding interfaces are Pb-6%Sn overlay welds, and no fractures are observed at the interface between the base metal and the overlay welds. It was confirmed that the adhesion between the material and the overlay weld material was extremely poor.

In addition, an overlay welding test was conducted in the same manner as above except that lead was used as the overlay weld metal, and the shear peel strength at the boundary between the base metal and the overlay weld metal was 1.3 to 1.7.
Kg/If! 1'', which is equivalent to the tensile strength of white lead, and it was confirmed that shearing occurred in the overlay weld metal in both cases.

[Effects of the Invention] The present invention is configured as described above, and it is possible to firmly overlay and weld lead or a lead alloy onto the surface of a corrosion-resistant metal such as titanium with a relatively simple operation.

Therefore, even when this overlay welding material is used as an insoluble anode, a phenomenon such as peeling of the overlay weld metal layer on the surface does not occur at all, and an insoluble anode with high reliability can be obtained. This invention is applicable not only to the manufacture of insoluble anodes, but also to a wide variety of methods for overlaying lead or lead alloys on all types of corrosion-resistant metal materials that form oxide-based passivity, such as titanium, niobium, tantalum, etc. can do.

[Brief explanation of the drawing]

Fig. 1 is a perspective explanatory view showing a preferable first-layer overlay welding method employed in the present invention, Fig. 2 is a cross-sectional explanatory view showing a preferable overlay welding method for second and subsequent layers, and Fig. 3 is an embodiment. FIG. 2 is a perspective view showing a test piece for measuring shear strength employed in the above. 1: Base material (corrosion-resistant metal plate) 2: Filler metal (lead or lead alloy) 3: Reverse polarity plasma arc welding torch 4: Overlay weld metal 5: Copper water-cooled jacket surface plate 6: Fixing jig 7: Gas welding burner for

Claims (1)

[Claims] In a method of overlaying lead or lead alloy on the surface of a corrosion-resistant metal that forms a passive film through oxidation, the first layer is overlaid by reverse polarity plasma arc welding, and then the second layer to the final layer is welded using gas. A method for overlaying lead or lead alloy on a corrosion-resistant metal, which is characterized by overlaying using a welding method.