JP4574977B2 - Welding coating method of corrosion-resistant thin metal sheet on thick metal substrate surface - Google Patents

Description

  The present invention relates to a method for welding and coating a thin metal sheet having excellent corrosion resistance and antifouling properties on the surface of a metal structure for corrosion prevention of splashed tidal zones such as seawater in metal structures such as offshore structures and bridges. .

  In recent years, in addition to undersea metal structures such as piers and bridges, large floating offshore structures such as floating oil storage vessels, oil drilling bases, floating breakwaters, and floating pier offshore hotels have been developed from the viewpoint of effective use of ocean space. Constructed or installed in the ocean. In such an offshore structure, a construction member made of a steel member such as a steel plate or a steel pipe having excellent corrosion resistance against seawater is often used. However, among these construction members, particularly in the parts exposed to seawater splashes (hereinafter referred to as splash zones), they are more easily corroded than other parts and have poor durability. The service life of the structure is determined, making it difficult to ensure a long service life.

  For this reason, in order to prevent corrosion in the splash zone, the surface of the metal structure is subjected to heavy anti-corrosion treatment by epoxy resin, fluororesin, urethane elastomer coating, etc., but this also has a service life of 40 It is said to be about a year.

  Therefore, a method of applying a metal lining to the surface of the metal structure has been proposed as a means for further extending the service life. In this method, a thin plate of stainless steel, titanium, monel, copper, and alloys thereof or a clad steel plate of these metals and ordinary steel is bonded to the surface of a metal structure with an adhesive or welded. From the viewpoint of durability and the like, a method of lining by welding joining has become mainstream.

Several proposals have been made regarding the welding method.
In Patent Document 1, in order to easily join a titanium alloy and a titanium clad steel having a thin titanium alloy part, after resistance seam welding is performed in lap welding of titanium or a titanium alloy plate, the resistance seam welding line is disclosed. A method for joining titanium or titanium alloy plates characterized in that arc treatment is performed along the line.

  This method is illustrated in FIG. In the figure, 11 is an indentation, 12 is an indentation end, 13 is a nugget, 14a to 14b are roller electrodes, 15 is an arc treatment torch, 16 is a filler material, and 18 is a weld metal. In FIG. 1, a) is a cross-sectional view of a direct resistance seam weld, b) an example of arc treatment without a filler material after direct resistance seam welding, and c) an arc with a filler material after direct resistance seam welding. It is a figure which shows the example to process. This document describes that the strength could be improved by the effect of improving the shape of the impression by the roller electrode. However, according to this method, the joint strength is improved, but a gap is formed between the thin metal sheet T1 and the thin metal sheet T2, so that seawater enters the gap in a corrosive atmosphere (for example, seawater). It will cause well-known crevice corrosion.

  In Patent Document 2, in the case of welding a thick metal substrate and an ultrathin thin metal sheet, resistance welding is a problem that sufficient strength cannot be obtained because resistance welding results in solid phase bonding. A method is described in which after a thin metal sheet is solid-phase bonded to the surface of a thick metal substrate by welding, the thin metal and the thick metal substrate in the solid-phase bonded portion are melt-bonded by arc welding. This method is shown in FIG. In the figure, 21 is a thick metal substrate, 22 is a thin metal sheet, 24 is a solid phase joint, 25 is a torch of an arc welder, and 26 is a weld bead.

  This document describes that, by providing a solid phase joint by resistance welding and then performing melt welding by arc welding, excessive heat input to the thin plate can be suppressed and appropriate welding can be performed. However, in order to cover a wide range, one or more sheets need to be stacked to join the thin metal plates, and this method alone is insufficient to properly weld the thin metal plates together. FIG. 3 shows a construction example by this method, but the end of the lap joint may be overmelted and welding may be difficult, and a uniform and smooth appearance can be obtained over the entire weld line. Not.

In Patent Document 3, a metal substrate is used for the purpose of providing a method for coating an economical thin metal sheet on a metal substrate using a resistance welding method that does not require special safety measures and is easy to handle. A thin metal sheet having a corrosion resistance or antifouling property, which can be directly welded to a metal substrate, is placed on the surface of the metal, and the surroundings are joined and sealed by indirect resistance seam welding. Are listed.
FIG. 4 shows this method. In FIG. 4, 41 is a metal base material, 42 is a thin metal sheet, 43 is an outer peripheral end portion or overlapping portion, 44 is an intermediate portion (indirect resistance welding is applied to this portion), 46 is a roller electrode, and 47 is resistance welding. Indicates the part. Patent Document 3 describes that a large area can be covered by this method. However, since a gap is generated between the thin metal sheets, crevice corrosion occurs.

Further, Patent Document 4 discloses that a plurality of corrosion-resistant metals are formed on the surface of a construction member formed of a steel material in order to reduce the joining time by shortening the joining time when the structure surface is coated with a corrosion-resistant metal plate. The plate is abutted so that the side edges of the adjacent corrosion-resistant metal plates overlap, and the non-overlapping part is fixed to the construction member by indirect twin spot welding and / or indirect seam welding, and then the side of the adjacent corrosion-resistant metal plate A method is described in which the overlapping portion of the end portion, the side end portion of the corrosion-resistant metal plate, and the construction member are fixed by indirect seam welding.
However, in this method as well, as in Patent Document 3, a gap is generated between thin metals, and therefore crevice corrosion occurs.

  As described above, each of the conventional techniques has a problem in the corrosion resistance of the welded portion, and there is a problem that it is impossible to ensure a long-term service life.

JP-A-6-320289 Japanese Patent Laid-Open No. 11-129090 Japanese Patent Laid-Open No. 10-175076 JP-A-11-179552

  The present invention provides a welding coating method that has a good appearance and does not reduce the corrosion resistance of the welded portion when the splashed zone portion in a metal structure such as an ocean structure or a bridge is welded and coated with a corrosion-resistant thin metal sheet. The purpose is to provide.

As a result of intensive studies by the present inventors, at the time of coating the surface of the tubular thick steel substrate with a stainless steel plate , at least one piece of 0.2 to 1.5 mm in thickness is formed on the surface of the tubular thick steel substrate. Winding a stainless steel plate, if there is only one stainless steel plate, overlap both ends, and if there are two or more, overlap the ends of adjacent stainless steel plates, and end the upper stainless steel plate of this overlapped portion The present invention has been completed by finding that the above-mentioned problems can be solved by melt-bonding a portion (hereinafter, referred to as “corner portion”) composed of a steel plate and a lower stainless steel plate by laser welding.

That is, the present invention has a configuration as described below.
It is a method of covering at least one stainless steel plate having a thickness of 0.2 to 1.5 mm on the surface of a tubular thick steel substrate ,
(1) When the number of stainless steel plates is one, the both end portions are stacked, and when two or more plates are stacked, the ends of adjacent stainless steel plates are stacked ,
(2) Resistance seam welding between stainless steel plates within 10 mm from the extreme end of the upper stainless steel plate in the overlapped portion,
(3) In the corner portion composed of the end portion of the upper stainless steel plate and the lower stainless steel plate in the overlapping portion, the interval between the upper and lower stainless steel plates is 0.3 mm or less,
(4) Laser welding is performed by controlling the heat input to 2.5 kJ / cm or less so that the upper stainless steel plate and the lower stainless steel plate are melt welded without melting the thick steel substrate at the corner. Do
A method for weld-coating a stainless steel plate onto a surface of a tubular thick steel substrate, characterized in that :

(2) In the above laser welding, welding method for coating a stainless steel sheet into a tubular thick steel substrate surface of (1), characterized in that used as a high corrosion resistance than the stainless steel plate as a filler.

( 3 ) A structure excellent in corrosion resistance, characterized by being manufactured by a manufacturing method including a step of coating a stainless steel plate on a tubular thick steel substrate by the welding coating method described in (1) or (2 ) above Building materials.
( 4 ) The structure excellent in corrosion resistance as described in ( 3 ) above, wherein the stainless steel plate is fixed to the thick steel base material by spot welding or resistance seam welding.

  Since no gap is generated between the stacked thin metal sheets, the corrosion resistance is improved. In addition, a large number of thin metal sheets can be coated on a thick metal substrate while ensuring strength. Further, in the method of Patent Document 3, high accuracy is required for the distance between the solid-phase joint and the fusion welded portion, but the method of the present invention has an advantage in that accuracy management considering only laser welding may be performed.

When coating a thick metal substrate surface with a corrosion-resistant thin metal sheet, it is necessary to satisfy the following requirements.
(1) The corrosion-resistant thin metal sheet is not peeled off from the surface of the thick metal substrate.
(2) The welded part should not rust.
(3) Seawater should not enter

  That is, when the thick metal substrate is melted through the corrosion-resistant thin metal sheet, the composition of the welded portion is changed during welding, which is usually inferior to the corrosion resistance of the original material. For example, when carbon steel is used as the base material, the metal composition of the welded portion becomes an intermediate composition between the corrosion-resistant metal and the base metal, and the components such as Cr, Ni, and Mo are reduced to ensure the corrosion resistance. It becomes difficult. Depending on the material, an intermetallic compound may be formed during welding, the composition may change, the weld may be easily cracked, or the bonding strength may be insufficient. Will invade.

In the method of the present invention, when the stainless steel plate is a single stainless steel plate on the surface of the tubular thick steel substrate, both ends thereof overlap , and when two or more, the ends of adjacent stainless steel plates overlap each other. In this manner, the overlapped portion (hereinafter, the overlapped portion is referred to as “overlap portion” and the other portion is referred to as “non-overlap portion”) is melt-welded by laser welding. Since fusion welding is performed by laser welding, the joint strength is sufficiently high, and there is no gap because the end of the plate is welded, and welding is performed so that fusion welding does not reach the thick metal base material. Corrosion resistance is not impaired. By adopting the above-described configuration, the present invention enables welding that satisfies the above requirements (1) to (3), and can dramatically extend the service life. .

As the coating material used in the present invention, a stainless steel plate having corrosion resistance and antifouling properties is used. The thickness of the stainless steel plate is 0.2 to 1.5 mm.

The weld coating method of the present invention will be described based on the block diagram of FIG.
In FIG. 5, 51 indicates a thick metal substrate, and 52 indicates a thin metal sheet. First, a highly corrosion-resistant thin metal sheet 52 is temporarily fixed on a thick metal substrate 1 such as a steel plate or a steel pipe by spot welding or resistance seam welding. Next, welding is performed while running a carriage 57 on which a welding torch 53, a presser roller 54, and a pressure spring 55 are arranged. Thereby, welding can be performed while pressing the thin metal sheet.

  Moreover, all the laminated thin metal sheets which coat a metal structure by sequentially applying the above method to the thin metal sheets laminated on the surface of the thick metal substrate and to the thin metal sheet and the thick metal substrate. In addition, since the welded portion exists at the end of the stacked plates, a gap as shown in FIG. 1 is not formed, and a highly corrosion-resistant coating can be realized. It becomes. In a portion where the corrosion resistance may be somewhat lowered such as being away from the tidal part, the thin metal sheet and the thick metal base material may be joined by a direct arc welding method using an appropriate molten material. it can. Further, by appropriately selecting the range in which the sheets are overlapped, sufficient corrosion resistance can be ensured by moving the joint between the thin metal sheet and the thick metal base material to a portion where the corrosion resistance may be lowered.

  The welding of the non-overlapping portion or the overlapping portion is preferably fixed to the thick metal substrate by spot welding or resistance seam welding. This welding method has the advantage that it can be welded from one side and the inner part of the sheet, not the sheet end, can be welded and fixed, and requires less skill than laser welding. There are also benefits. Further, according to this welding method, the surface of the thin metal sheet is basically not melted, so that there is an advantage that there is no problem with respect to corrosion resistance. FIG. 6 shows an example in which the non-overlapping portion is welded by spot welding or resistance seam welding.

Point performing laser welding to the end portion of the upper stainless steel plate overlapping portion. In this way, no gap is generated, and therefore crevice corrosion can be prevented.
Moreover, although the case where the method of this invention used the steel pipe as a thick metal base material was shown in FIG. 7, the clearance gap (L) between the stainless steel plates in the welding part of the overlap part at the time of laser welding shall be 0.3 mm or less . . If the gap (L) exceeds 0.3 mm even under appropriate conditions, perforation tends to occur. If it is 0.3 mm or less, no perforation occurs.
Examples of a method for controlling the gap (L) to 0.3 mm or less include the following method.

(A) Method of welding while pressing the vicinity of the welding point with a roller As such a roller, a small-diameter bearing can be used, and the roller position is located on the upper plate of the overlap portion, and is separated from the end by about 5 mm to 15 mm. It is necessary to position at least one forward in the traveling direction. Since the wire is fed from the front, it is difficult to approach 5mm or more in general to prevent interference with the wire and overheating due to radiation from the welded part. It becomes impossible.
FIG. 8 shows a conceptual diagram of this method. An example of the arrangement is shown in FIG. Here, a presser roller is also arranged at the rear.

(B) Method of folding the upper thin metal sheet end of the overlapped portion toward the thick metal substrate side This method is when the thick metal substrate is a steel pipe and the thin metal sheet is wrapped around the steel pipe so that the end overlaps This is a particularly effective method. FIG. 10 shows a conceptual diagram of this method.
First, it winds so that the edge part of the thin metal sheet which bent the edge part around the steel pipe may overlap with the edge part which is not bent. At this time, it is preferable to fix a portion at an appropriate distance from the lower end portion in the overlapped portion to the thick metal substrate by spot welding or resistance seam welding. As shown in the figure, there is no gap between the ends as the ends are bent, and the steel sheet surface is covered with the thin metal sheet by melting and joining the upper thin metal sheet end of the overlapped portion by laser welding. Fix it.

(C) A method of pre-joining the overlapped portion prior to laser welding the overlapped portion The gap between the upper thin metal sheets of the overlapped portion may be reduced by pre-joining the overlapped portion prior to laser welding the overlapped portion. it can.
A resistance seam welding method, an intermittent resistance seam welding method, or a resistance spot welding method can be employed as a welding method for pre-joining the overlapping portions. The intermittent resistance seam welding method referred to here is, for example, a cooling time longer than the energization / rest cycle of 1 to 6 cycles of heating time and 2 to 14 cycles of cooling time used in the normal resistance seam welding method. It is a method aiming to reduce heat input to the material by making it about a cycle.
If the intermittent resistance seam welding method is used, the deformation of the entire structure can be reduced, so that it becomes easy to reduce the gap. The pre-bonding position may be within 10 mm from the end. Thus, a gap can be prevented by pre-joining the overlapping portion.

The heat input during welding is preferably 2.5 kJ / cm or less. During welding, the thin metal sheet is heated and expands. The thin metal sheet swells locally due to expansion and contracts behind the welding, and as a result, undulation in the plate thickness direction or rotation within the plate surface occurs. The deformation in the plate thickness direction changes the gap, and if the rotational deformation is large, it becomes necessary to copy during welding.
Since these deformations are caused by expansion due to heating and subsequent cooling, the deformation increases as the heat input to the steel increases, and the deformation decreases as the heat input decreases.
For TIG welding, heat input is 2.25 kJ / cm at 75 A, 10 V, 20 cm / min, heat input is 0.9 kJ / cm at 60 A, 20 V, 80 cm / min for plasma welding, and output for laser welding. Good welding was achieved with a heat input of 0.72 kJ / cm at a speed of 100 Km / min at 1.2 KW, and a heat input of less than 2.5 kJ / cm is desirable from the above consideration.

In laser welding, it is preferable to use a filler having a higher corrosion resistance than the corrosion resistance of the thin metal sheet. For example, high corrosion resistance stainless steel ensures various performances by rolling and heat treatment in addition to controlling the composition. When welding is performed, the weld metal only melts and solidifies, so that the base material cannot be expected to improve corrosion resistance by rolling and heat treatment.
Therefore, it is necessary to use a highly corrosion-resistant filler whose components are adjusted so as to satisfy the required performance only by melting and solidifying.

The following materials and equipment were used.
Thin metal sheet: 1000 mm wide x 1400 mm long x 0.4 mm thick SUS
Thick metal substrate: Carbon steel pipe with outer diameter of 900mm x 1500mm Tightening band: With cloth tightening buckle Welding device: Handy spot welder
YAG laser welding machine (portrait type)

  One SUS material was wound around the steel pipe leaving 50 mm at both ends of the steel pipe, clamped with a clamping band, and then subjected to positioning spot welding. This spot welding was performed on all sides at a pitch of 500 mm at a position 30 mm from the edge of SUS.

Next, the second SUS material was overlapped with the first SUS material with a lap allowance of 50 mm, wound, tightened with a tightening band, and then subjected to positioning spot welding. This spot welding was performed on three sides other than the lap edge at a pitch of 500 mm at a position 30 mm from the SUS edge.
Next, restraint spot welding was performed on the edge of the lap. This restraint spot welding was performed at a pitch of 100 mm at a position 10 mm from the edge of both the lower plate and the upper plate.

The above spot welding conditions are shown in Table 1.
Moreover, after spot welding was completed, the gap between the restrained spot hit points of the SUS overlapping portion at the lap edge was measured, and the upper plate edge of the overlapping portion was subjected to laser welding. When the weld was examined, there were some irregular beads where the gap was 0.4 mm or more, but there were no holes in the places where the gap was 0.3 mm or less, and the bead appearance was good.

In the same manner as in Example 1, positioning spot welding and restraint spot welding were performed.
Next, as shown schematically in the figure, laser welding was performed by pressing with a pressing roller so that the gap in the laser welded portion was 0.3 mm or less. As a result, there was no hole in the weld and the bead appearance was good.

Example 1 except that in Example 1, a SUS material having a width of 400 mm × 1400 mm length × 0.4 mm was used and the upper plate end of the second SUS material was bent to the steel pipe side. Welding was carried out in the same manner as in 1.
In this example, since the clearance (L) of the laser welded portion was 0 mm by bending the SUS material, no perforation occurred. Also, the bead appearance was good.

  Since the structure obtained by the welding coating method of the present invention has a good appearance and does not deteriorate the corrosion resistance of the welded portion, the service life can be drastically increased, so the corrosion resistance of offshore structures and the like is required. Is highly available for use.

It is a figure which shows the example of the conventional welding coating method. It is a figure which shows the example of the conventional welding coating method. It is a figure which shows the example of the conventional welding coating method. It is a figure which shows the example of the conventional welding coating method. It is a figure which shows an example of the welding coating method of this invention. It is a figure which shows the example of the spot welding or resistance welding in this invention. It is a figure which shows an example of the welding coating method of this invention. It is a figure which shows the example of the welding coating method of this invention using a pressing roller. It is a figure which shows the example of arrangement | positioning of the apparatus in the case of implementing the welding coating method of this invention using a pressing roller. It is a figure which shows the example which applied the welding coating method of this invention to the steel pipe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Indentation 12 Indentation edge part 13 Nugget 14a-14d Roller electrode 15 Arc processing torch 16 Filler material 18 Weld metal 21 Thick metal base material,
22 Thin metal sheet,
24 Solid phase junction,
25 Torch of arc welding machine,
26 Indicates a weld bead.
41 metal substrate,
42 thin metal sheet,
43 peripheral edge or overlapped part,
44 Middle part 46 Roller electrode,
47 resistance weld 51 thick metal substrate,
52 Thin Metal Sheet 53 Welding Torch 54 Pressing Roller 55 Pressurizing Spring 56 Laser Welding Portion 57 Dolly

Claims (4)

It is a method of covering at least one stainless steel plate having a thickness of 0.2 to 1.5 mm on the surface of a tubular thick steel substrate ,
(1) When the number of stainless steel plates is one, the both end portions are stacked, and when two or more plates are stacked, the ends of adjacent stainless steel plates are stacked ,
(2) Resistance seam welding between stainless steel plates within 10 mm from the extreme end of the upper stainless steel plate in the overlapped portion,
(3) In the corner portion composed of the end portion of the upper stainless steel plate and the lower stainless steel plate in the overlapping portion, the interval between the upper and lower stainless steel plates is 0.3 mm or less,
(4) Laser welding is performed by controlling the heat input to 2.5 kJ / cm or less so that the upper stainless steel plate and the lower stainless steel plate are melt welded without melting the thick steel substrate at the corner. Do
A method for weld-coating a stainless steel plate onto a surface of a tubular thick steel substrate, characterized in that : In the laser welding, the welding method of coating a stainless steel sheet into a tubular thick steel substrate surface according to claim 1, characterized in that used as a high corrosion resistance than the stainless steel plate as a filler. A structural building member excellent in corrosion resistance, manufactured by a manufacturing method comprising a step of coating a stainless steel plate on a tubular thick steel base material by the welding coating method according to claim 1 or 2 . The structure excellent in corrosion resistance according to claim 3, wherein the stainless steel plate is fixed to the thick steel substrate by spot welding or resistance seam welding.

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