JP2012035268A - Welding method of galvanized steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method of galvanized steel excellent in durability with usual simple welding work.SOLUTION: There is provided the welding method of galvanized steel in which a part abutted with the galvanized steel is welded by electric welding where a galvanized layer is formed on the surface by galvanized treatment. A stainless steel arc welding electrode is used for welding the abutted part.

Description

  The present invention relates to a method for welding a steel sheet which has been subjected to a rust prevention treatment with zinc plating.

  In general, steel plates such as iron plates used in buildings and structures are immersed in molten zinc ponds as a rust-proofing treatment, soaked in a so-called dove to form a zinc plating layer on the surface. The welded portion is electrically welded (arc welding) with an iron-based welding rod that matches the base material.

  When electric welding is performed in this manner, the temperature of the arc becomes a high heat (about 15000 ° C) much higher than the melting point of zinc (419 ° C) and the transpiration temperature (343 ° C). As it evaporates, the part welded with an iron-based welding rod is exposed and oxidized and easily rusted.

For this reason, conventionally, the exposed welded portion is painted with a brush to prevent rust, or an antioxidant as disclosed in Patent Document 1 is used.
However, it is difficult to apply to every corner with the prevention of oxidation by paint, and if the applied part is peeled off by other objects, pinholes are formed, or the paint surface is damaged due to aging, it is here. Since it becomes easy to oxidize, there was a problem in durability.

In the case of using the antioxidant disclosed in Patent Document 1, there is a problem that not only the structure is complicated and expensive for the antioxidant part, but also its use is limited.
Moreover, when welding steel steel plates, after welding with the welding rod for iron, there also exists the method of carrying out a rust prevention process by immersing in a molten zinc pond and carrying out zinc plating.
However, in this case, since it takes time and labor to perform zinc plating in addition to welding, it may cause delays in delivery time, or it may be immersed in a hot zinc basin at about 450 ° C, resulting in thermal distortion of the product and quality. There was also a problem of inviting a decline.

By the way, in electric welding of galvanized steel sheets, a shield gas containing a high concentration of oxygen should be used in order to prevent blowholes due to zinc vapor generated when welding is performed using a ferrous metal. This has been proposed (Patent Document 2).
However, with such materials, zinc vapor can be changed to zinc oxide to prevent blowholes as much as possible. On the other hand, since the base material is easily oxidized by oxygen, the strength of the welded portion is reduced. There is.

JP 2003-136286 A JP-A-6-262362

  The present invention has been proposed in view of the above-described problems, and an object of the present invention is to provide a method for welding a galvanized steel sheet having excellent durability by a normal simple welding operation.

  In order to achieve the above object, a method for welding a galvanized steel sheet according to the present invention is a method for welding a galvanized steel sheet, in which the surface of the galvanized steel sheet having a zinc plated layer formed by galvanizing treatment is welded by electric welding. However, the most important feature is that the welding portion is welded to the welding rod for welding the butted portions by an arc welding rod made of stainless steel.

  In the welding method of the galvanized steel sheet according to the present invention, when performing the electric welding, welding with a shielding gas containing less than 10% oxygen, a portion welded with a stainless steel coated arc welding rod, and the vicinity thereof It is also characterized in that a paint is applied to the part.

  According to the welding method of the galvanized steel sheet of the present invention, when welding the part where the galvanized steel sheet having a zinc plated layer formed on the surface by galvanizing treatment is welded by electric welding, the welding rod for welding the butted part is made of stainless steel. Since welding is performed with a steel arc welding rod, the welded portion is exposed to the stainless steel of the arc welding rod used for welding.

Thereby, there is an advantage that the galvanized steel sheet having excellent durability can be welded by simply performing a normal simple welding operation without the trouble of applying the anti-corrosion paint as in the prior art.
Further, there is an advantage that welding can be performed by a conventional simple method without using an antioxidant, and the structure is simple and can be implemented at low cost.

In addition, by using a stainless steel arc welding rod as the welding rod, it is not necessary to dip it in a hot hot zinc basin after welding and to apply zinc plating, thereby eliminating the need for zinc plating treatment.
This makes it possible to produce products in a short period of time, eliminate delays in delivery time, and produce high-quality products by preventing the occurrence of thermal distortion of products caused by immersion in hot hot galvanized ponds. There are advantages.
Further, in the welding method of the galvanized steel sheet according to the present invention, when the welding is performed in a shield gas atmosphere containing less than 10% oxygen, the base metal is prevented from being oxidized and excellent in strength. There is an advantage that the galvanized steel sheet can be welded.

In addition, if paint is applied to the part welded with the arc welding rod of stainless steel and its neighboring parts, the parts of the welded part made of stainless steel and other galvanized parts may be covered and made inconspicuous. it can.
Incidentally, even if it is applied to a portion welded by a stainless steel arc welding rod and another object hits the portion to which the paint is applied, a pinhole can be generated without causing rust.

These are the perspective views of the steel materials which welded by implementing the welding method of the galvanized steel plate concerning this invention. These are the longitudinal sectional front views of the steel materials which welded by implementing the welding method of the galvanized steel plate concerning this invention. These are front views which show the groove angle when joining and welding in the reverse T shape in the welding method of the galvanized steel plate concerning this invention. These are front views which show the groove angle when joining and welding in flat form in the welding method of the galvanized steel sheet concerning this invention.

  The most preferred embodiment of the welding method of the galvanized steel sheet according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a galvanized steel sheet welded by carrying out a welding method of a galvanized steel sheet, FIG. 2 is a longitudinal front view thereof, and reference numeral 1 in the figure denotes an inverted T formed by the welded galvanized steel sheet. The overall shape of the steel is shown.
This inverted T-shaped steel material 1 is reversely composed of a lower galvanized steel plate 2 serving as a base and an upper galvanized steel plate 3 welded in a state of being raised from the central portion of the upper surface of the lower galvanized steel plate 2. It is formed in a T shape.

Each of these galvanized steel plates 2 and 3 is formed by immersing a thick iron plate (base material) 4 in a molten zinc pond to form a galvanized layer 5 on the surface, and the upper galvanized steel plate 3 is located on the lower side. Grooves 6 are formed at corners (welded portions) that contact the galvanized steel sheet 2 (see FIG. 3).
As shown in FIG. 3, the groove 6 is formed with an opening as shown in FIG. 3 so that the stainless steel melted by welding with an austenitic stainless steel covered arc welding rod (for example, SUS304 and SUS430) can flow easily. The angle θ of the tip 6 is formed at 25 degrees in the T-shaped joint of this example, but in the V-type, Y-type, and Le-shaped joints including such a T-shape, the angle θ of the groove 6 is It is desirable to set to 20 degrees or more and 30 degrees or less.

Incidentally, as shown in FIG. 4, in the case of butt welding of flat galvanized steel plates 7 and 7, it is desirable that the angle θ of the groove 6 be 60 degrees or more and 80 degrees or less.
The reason why the angle θ of the groove 6 is set to 20 degrees or more and 30 degrees or less in the V-shaped, Y-shaped, and L-shaped joints including the T-shape is as follows. In the case of exceeding the degree, melting of the upper galvanized steel sheet 3 is greatly caused by a high-temperature arc during electric welding, and the balance with the lower galvanized steel sheet 2 cannot be achieved, so that sufficient welding strength cannot be obtained. It is.

  Also, the angle θ of the groove 6 in the case of butt welding of the flat galvanized steel plates 7 and 7 shown in FIG. 4 is set to 60 degrees or more and 80 degrees or less, as described above, 60 degrees or less. In the case where the molten stainless steel is difficult to flow in and exceeds 80 degrees, not only is the melting of the galvanized steel sheets 7 and 7 of the joining portion flattened due to the high-temperature arc during electric welding, This is because sufficient welding strength cannot be obtained due to thermal effects.

  And the electric welding which welds the part which butted the galvanized steel plate 2, 3, 7, 7 which formed the galvanized layer 5 by carrying out the galvanizing process of the surface was omitted although illustration was general, An austenitic stainless steel coated arc welding rod is used as the welding rod.

  That is, an electrode is connected on the negative side to the lower galvanized steel plate 2, a stainless steel coated arc welding rod of the positive side electrode is brought close to the groove portion, and arc discharge is started. The high-heated stainless steel coated arc welding rod is melted and poured into the groove 6 portion, and the upper galvanized steel plate 3 and the lower galvanized steel plate 2 are welded.

At this time, the zinc plating layer 5 formed on the surface of the lower galvanized steel sheet 2 due to the generated high-temperature arc has a transpiration temperature of 343 ° C., which is much lower than the arc discharge temperature. The generated galvanized layer 5 is instantly evaporated, and the flowing stainless steel is melted between the iron plate 4 of the lower galvanized steel plate 2 and the iron plate 4 of the upper galvanized steel plate 3 to form an alloy. Is done.
As a result, the upper galvanized steel plate 3 is welded to the lower galvanized steel plate 2 in a firmly fixed state.
The welded portion 8 thus welded has an arc welding rod stainless steel 9 appearing on the surface thereof, and oxidation (rusting) of the portion is prevented.

Incidentally, when adopting the gas shielded arc welding method as disclosed in Japanese Patent Application Laid-Open No. 2009-39724, a gas containing a small amount of oxygen in an inert gas such as argon or carbon dioxide is used as the shielding gas. To do. This oxygen amount is desirably less than 10%.
In other words, oxygen is included in the shielding gas in the galvanized steel sheet because the zinc vapor generated during welding is oxidized to zinc oxide to prevent the occurrence of blowholes. The discharge temperature is about 44 times higher than the transpiration temperature of zinc, and the zinc vapor is instantly evaporated, while the stainless steel melted by the arc discharge flows more slowly than the iron welding rod.

Thereby, generation | occurrence | production of a blowhole can be prevented as much as possible, Therefore Oxygen can be made into the trace amount which only oxidizes zinc vapor | steam in shielding gas.
Incidentally, it is most desirable to use 2% (volume ratio) argon gas with a small amount of oxygen in the gas shielded arc welding for carrying out the present invention.
Of course, the amount of oxygen can be reduced to zero because the zinc vapor generated by arc discharge has little influence on the welded portion as described above.

In addition, when a zinc paint (not shown) is applied to the stainless steel 9 portion appearing on the surface, it can be well-familiar with the surrounding zinc plating layer 5 portion to eliminate the uncomfortable feeling.
Also, when zinc paint is applied to the surface of stainless steel 9 appearing on the surface, even if paint spots or other objects hit and pinholes occur, rusting will not occur from this part and durability will be improved. However, the application of this zinc paint can be omitted.

  In the above embodiment of the present invention, the welding rod is an austenitic stainless steel coated arc welding rod. However, the present invention is not limited to this, and it is possible to use other stainless steel welding rods. It goes without saying that there are.

DESCRIPTION OF SYMBOLS 1 ... Reverse T-shaped steel material 2 ... Lower galvanized steel plate 3 ... Upper galvanized steel plate 4 ... Iron plate (base material)
5 ... Zinc plating layer 6 ... Groove 7 ... Flat galvanized steel plate 8 ... Welded part 9 ... Stainless steel

Claims (3)

  A welding method for a galvanized steel sheet in which a butt-welded portion of a galvanized steel sheet having a zinc-plated layer formed on the surface by galvanizing treatment is welded by electric welding. A method for welding galvanized steel sheets, characterized by being welded by the method described above.   2. The method for welding a galvanized steel sheet according to claim 1, wherein the welding is performed with a shielding gas containing less than 10% oxygen.   The method for welding galvanized steel sheets according to claim 1 or 2, wherein a paint is applied to a portion welded by an arc welding rod of stainless steel and a portion in the vicinity thereof.

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