JPH03210992A - Wire for submerged arc welding and surface treatment thereof - Google Patents

Abstract

PURPOSE:To decrease the quantity of the diffusive hydrogen in a weld metal after welding by subjecting the non-plated surface of the wire for submerged arc welding to a dehydrogenation treatment and bluing treatment. CONSTITUTION:The non-plated surface of the wire for submerged arc welding is subjected to the dehydrogenation treatment and bluing treatment. The wire subjected to drawing to a prescribed wire diameter is subjected to pickling and/or scalping. Further, the wire is subjected to a heat treatment of at least >=100 deg.C. The wire drawn to the prescribed wire diameter is subjected to a heat treatment of at least the thermal decomposition temp. of a lubricant or above. The rusting on the wire surface is suppressed to a practicably negligible level in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a submerged arc welding wire and a surface treatment method thereof.

[Conventional technology 1] In the past, steel welding wire used for submerged arc welding of steel was generally coated with copper on its surface to prevent rust during storage and for other purposes. There is a tendency to omit copper plating from the perspective of cost reduction. Such a wire is called a non-plated wire. To prevent the unplated wire from rusting, measures are taken to either leave the lubricant that adheres to the wire surface during the wire drawing process or to apply rust preventive oil to the wire surface in the final process.

[Problems to be Solved by the Invention] When submerged arc welding of steel is performed using a wire on which lubricant or rust preventive oil remains on the surface, the lubricant or rust preventive oil inevitably contains There is a problem in that the hydrogen valve introduced into the weld metal enters the weld metal as diffusible hydrogen, causing low-temperature cracking, or so-called hydrogen cracking.

In recent years, the tensile strength of steel to be welded has increased, increasing the susceptibility to hydrogen cracking, and the problem of hydrogen cracking described above is drawing even more attention. Additionally, it is possible to eliminate the hydrogen source on the wire surface by mechanically or chemically removing the lubricant and anti-corrosion oil on the wire surface, but this is not practical as it activates the wire surface and makes it more likely to rust. There was a problem.

In order to solve the above-mentioned problems, the present invention aims to reduce the lubricant that adheres to the wire surface during wire drawing using chemical methods, mechanical methods,
A wire for submerged arc welding and its surface treatment, which is removed by one or a combination of two or more thermal methods and further treated with blue ink to improve rust prevention without applying rust preventive oil to the surface. The present invention provides a method.

[Means for Solving the Problems] The present invention is characterized by an unplated submerged arc welding wire having a surface subjected to dehydrogenation treatment and blue ink treatment. Such a wire can be obtained by subjecting a wire drawn to a predetermined wire diameter to one or both of pickling and peeling, and then heat-treating the wire at a temperature of at least 100° C. or higher. Here, peeling processing refers to chemical processing,
Mechanical surface treatment refers to processes such as immersion in a solution and surface layer removal using a grinder or die.

Further, the above submerged arc welding wire and surface treatment method thereof can be obtained by a method in which a wire drawn to a predetermined wire diameter is subjected to dehydrogenation treatment by heat treatment at least at a temperature equal to or higher than the lubricant thermal decomposition temperature.

Here, dehydrogenation treatment means that hydrogen in the lubricant is, for example, H2O
It depends on the type of lubricant.For example, calcium stearate carbonizes at about 350℃, so the temperature should be higher than this, and positional base fatty acid esters of -hydric alcohols decompose at 150℃ and hydrogen is removed. Therefore, this temperature should be used.

[Effect]

Since the submerged arc welding wire of the present invention removes lubricant from the wire surface and does not apply rust preventive oil, when submerged arc welding is performed using the submerged arc welding wire of the present invention, the The amount of diffusible hydrogen can be significantly reduced compared to conventional wires. Furthermore, since the wire surface is treated with blue ink, there will be no rust, which is a practical problem.

According to the method of the present invention, a submerged arc welding wire having the above characteristics can be easily manufactured.

[Example 1] Table 1 shows the wire manufacturing process of Examples 1 to 8 of the present invention and Comparative Examples A to G. Table 2 shows the surface treatments, final wire surface condition, amount of diffusible hydrogen in the molten metal after submerged welding, and rusting condition during storage.

A steel wire with a wire diameter of 6 mmφ was subjected to intermediate wire drawing to 5.0 mmφ using metal soap, specifically calcium stearate, and then finished wire drawing to 4.8 mmφ.
Next, the wire surface was subjected to chemical treatment, mechanical treatment, and thermal treatment to produce a welding wire.

Submerged arc welding was performed using these wires, and the amount of diffusible hydrogen was measured according to the JIS Z3113r method for measuring the amount of hydrogen in deposited metal. At this time, CaO-CaF2
- JISSM5 using 5i02 type melting flux
Welded onto 0C steel plate.

Further, the wire was left in a room maintained at a temperature of 20° C. and a humidity of 80% for 7 days, a storage test was performed, and the state of rust on the wire surface was observed.

The above wire surface treatment conditions, the final surface condition of the wire, the amount of diffusible hydrogen in the submerged arc weld metal, and the rusting condition are summarized in Table 1.

Comparative Examples A and B are typical examples of the prior art.

In Comparative Example A, intermediate wire drawing, copper plating, and final wire drawing were performed. Comparative Example B is an example in which the copper plating of Comparative Example A was omitted. In either case, the amount of lubricant applied to the wire surface during finishing wire drawing is 1.0 to 3 per 1 - of the surface area of the wire.
．． 0g remains. Because hydrogen is unavoidably contained in these lubricants, the amount of hydrogen in submerged arc welding metal (
(hereinafter abbreviated as Hd) is 6-7cc/100g (weld metal)
It becomes. This value is a value at which hydrogen cracking may occur when high-strength steel is welded with a high degree of restraint.

Furthermore, as is clear from the storage test, Comparative Example B has a tendency to rust a little. In order to increase the rust prevention ability of such unplated wire, it is industrially practiced to apply rust prevention oil to the wire surface as in Comparative Example C, but as shown in Table 2, This is not desirable from the HD point of view.

Next, examples of the present invention will be described. Example 1 is an example in which a wire manufactured using the same process as Comparative Example B was pickled to remove the lubricant, and then passed through a coil to heat the wire surface to 100°C by induction heating and treated with blue ink. It is. In this case, the lubricant remaining on the wire surface is O,
1 to 0.2 g/m', which is about 1/10 compared to Comparative Example B. Therefore, Hd in submerged arc welding is 2 to 3c.
c/, lOOg (weld metal), which is significantly improved. Also, since a thin oxide film is formed on the wire surface by blue ink treatment, there is almost no problem of rusting during storage. Comparative Examples E are examples in which the blue ink treatment was omitted from Examples 1 and 2, but although Hd was improved, there was a big problem with rust formation during storage. Needless to say, such wire surface rust causes various defects in the weld metal, making it impractical.

Furthermore, the heat treatment for blue ink treatment is not limited to induction heating; the wire surface is heated by an appropriate method such as direct energization in Example 2 or immersion in a lead bath in Example 7 to form an oxide film. A similar effect can be obtained by doing so.

Furthermore, the method for removing the lubricant is not limited to pickling treatment (electrolytic pickling, immersion in a solution that can dissolve the lubricant, or even mechanical removal as in Examples 3 and 4). Furthermore, hydrogen in the lubricant can be removed from the wire surface as H20 by using thermal decomposition of the lubricant.An example of this is shown in Example 5.6.7.In this case, the hydrogen in the lubricant can be removed from the wire surface as H20. The lubricant used (calcium stearate) was approximately 35
400-450℃ by taking advantage of carbonization at 0℃ or higher
This suppresses the increase in Hd caused by hydrogen in the lubricant. In the example of Example 5, some carbonized lubricant remained on the wire surface, so the residual lubricant was 0.4 to 0.
Although it is 6 g/rn', which is slightly higher than in Examples 1 to 4, the Hd after submerged arc welding is improved as in Examples 1 to 4 due to the above effects. However, if the carbonized lubricant remains on the wire surface and impairs the electrical conductivity between the wire electrodes, the residual lubricant may be removed by using a wire brush after the thermal treatment as in Examples 6 and 7. It is possible.

As in Examples 5 to 7 above, the lubricant on the wire surface can be removed or rendered harmless (remove hydrogen) by thermal treatment, and at the same time, blue ink treatment can be carried out in the same process. In this case, as in Comparative Example F, a heating temperature of 300° C., which is lower than the carbonization temperature of the lubricant, is not effective in reducing Hd and requires caution. In addition, in the example of Example 8, a monoester with a low decomposition temperature is used as a lubricant.
Heating at 0°C is effective in removing hydrogen. In this way, the heating temperature can be determined depending on the characteristics of the lubricant, but from the perspective of forming an oxide film that has a rust-preventing effect,
As can be seen from the comparison between Example 1 and Comparative Example G, the temperature is preferably at least 100°C.

From the above, it is clear that the present invention has an effect of improving the amount of diffusible hydrogen (Hd) in the submerged arc weld metal and also preventing rust from occurring during wire storage.

[Effects of the Invention] Compared to conventional submerged arc welding wires, the present invention ignores lubricant residue and rust preventive oil on the wire surface and reduces the amount of weld metal after submerged arc welding. The amount of diffusible hydrogen in the fuel can be significantly reduced. Furthermore, since the wire surface is finally treated with blue ink, rusting on the wire surface can be suppressed to a level that poses no problem for practical use.

Claims (1)

[Claims] 1. An unplated submerged arc welding wire having a surface treated with dehydrogenation and blue ink. 2. A method for surface treatment of a wire for submerged arc welding, which comprises subjecting a wire drawn to a predetermined wire diameter to pickling and/or peeling, and further heat treatment at at least 100°C or higher. 3. A method for surface treatment of a wire for submerged arc welding, which comprises subjecting a wire drawn to a predetermined wire diameter to a heat treatment at least at a lubricant pyrolysis temperature or higher.