JPH11114672A - Joining method for titanium clad steel to steel structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve corrosion resistance by preventing sea water, etc., from intruding into a steel part as a base metal of a titanium clad steel of a butt welding part and to make working at site easy. SOLUTION: A butt joint part 5 is formed by welding a base metal 1 of a butt joint of titanium clad steel plate 3a, 3b. A titanium spacer 7 is inserted at a fixed distance from both end parts of the butt weld part 5 and is joined to the titanium clad metal 2 by TIG welding. A titanium cover plate 8 is placed on an upper part of the titanium 2/the titanium spacer 7 while allowing an end part of the titanium spacer 7 to remain, the cover plate 8 is TIG welded to the titanium clad metal 2 and the titanium spacer 7. A thermal spray film is formed by thermally spraying a pure titanium around an end part of the titanium spacer 7, a weld metal inside the cover plate 8 and the base metal 1 are completely sealed by a coated film having the roughly same material property as one of the titanium clad metal 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining method for covering a large steel structure such as an offshore structure with a titanium clad steel by abutting the outer periphery thereof.

[0002]

2. Description of the Related Art Titanium can be joined to metals similar to titanium, but the joining of titanium clad steel involves the joining of dissimilar materials, and titanium and the base material of carbon steel or low alloy steel are bonded with argon, helium or the like. When arc welding is performed using an inert gas, a large amount of iron dissolves in the weld metal and Fe-
It may be said that the intermetallic compound of Ti or a compound such as TiC or TiN is formed in a large amount, and these compounds embrittle the weld metal, so that it is impossible to join. For this reason, conventionally, in the case of so-called dissimilar material joining in which titanium and steel material or titanium clad steel are joined, they are joined by brazing in a vacuum furnace, or an insert material that does not form an intermetallic compound such as diffusion joining is inserted. Are joined. For this reason, there were great restrictions when joining, and joining on site was not possible.

In order to solve the problem that this titanium clad steel cannot be joined on site, for example, Japanese Patent Laid-Open No. 52-92839
Butt welding of titanium clad steel without using a vacuum furnace or the like in Japanese Patent Application Laid-Open Nos. Sho 52-126643, JP-A-2-52176, JP-B-6-71669, and JP-B-7-236. Alternatively, a TIG brazing method is disclosed.

In the butt welding method disclosed in Japanese Patent Application Laid-Open No. 52-92839, a carbon steel as a base material is welded, and a titanium plate having a groove-shaped recess is inserted into a groove of the titanium composite material. The base metal and the weld metal are covered, and the titanium composite material and the titanium plate are welded. Further, the welding method disclosed in Japanese Patent Application Laid-Open No. 52-126463 discloses a method in which a base plate is welded, a titanium plate is placed on a thin titanium composite material, and the titanium plate is welded to the titanium composite material by series seam resistance welding. It is joined by. In the welding method disclosed in Japanese Patent Application Laid-Open No. 52176/1990, a notch is provided in the portion of the titanium joint material of the butt joint, and the end of the base metal is welded from the back surface, and then a titanium spacer is placed in the notch. After brazing the titanium spacer and the titanium composite material with silver brazing, place a patch on the titanium spacer and the titanium composite material and weld the fillet to the titanium composite material, or use the titanium composite material side of the base metal. A notch is formed in the base material, and the end of the base material is welded from the back surface, and the end of the titanium material is welded from the front surface so that the welded portion of the titanium material does not contact the base material.

[0005] In the welding method disclosed in Japanese Patent Publication No. 6-71669, a notch is provided in a portion of a titanium mating material of a butt joint, and the end of the base metal is welded. Welding Co bead is formed by TIG welding or brazing at the joint corner of the material, or heat-resistant, heat-insulating and fire-resistant ceramic is applied, and the coating material is inserted into the notch and the titanium bonding material and the coating material are welded. ing. In addition,
No. 236 discloses a welding method, in which a notch is provided in a portion of a titanium joint material of a butt joint, and an end of the base material is welded, a spacer is inserted into the notch, and silver is added to the 71.0- 73.0%
The titanium composite material and the spacer are joined by TIG arc welding using the molten material.

[0006] When titanium clad steel is butt-coated on the outer periphery of a large structure such as an offshore structure, seawater is prevented from entering the steel portion of the butt-welded portion, which is the base material of titanium clad steel. There is a need. For this reason, as shown in Japanese Patent Publication No. 7-68711, for example, a notch is provided in the portion of the titanium mating material of the butt joint, the end of the base metal is welded, and then the titanium mating material of the butt joint is welded. A titanium backing plate is placed on the upper part of the notch so as to crosslink, and the titanium backing plate is fillet welded to the titanium matching material. Then, in order to prevent seawater from entering from the notch and corroding the base metal weld, the notch at the end face of the welded portion is TIG-seal-welded using an Ag-Cu-based welding material and hermetically covered with a molten metal. ing.

[0007]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 52-92839 is disclosed.
According to the joining method disclosed in Japanese Patent Application Laid-Open Nos. Sho 52-1266643 and Hei 2-52176, a gap is formed between the base material and the spacer inserted between the titanium joining materials in the welded portion. Seawater etc. will enter from the part. Since the intruded seawater accelerates the corrosion of the base material, it cannot be used for structures that come into contact with seawater, such as marine structures.

Further, Japanese Patent Publication No. 6-71669 and Japanese Patent Publication No.
As disclosed in JP-236-236A, in the method of TIG welding or brazing using cobalt or silver solder as a welding material, if the welding current becomes too high, there is a possibility that the base material under the spacer is largely melted. There is. The components of the molten base metal enter the molten pool. Even if cobalt or silver solder is used as a welding material, an Fe-Ti-based intermetallic compound is easily generated, and the weld metal is embrittled. Therefore, it was necessary to keep the welding current low, and the workability was poor. Further, if cobalt or silver brazing is used as a welding material, the cost increases. In addition, when brazing in an upright or upward posture, a high level of technology was required. Further, the method using a brazing material has a disadvantage that the seawater corrosion resistance of the brazing material is lower than the seawater corrosion resistance of titanium. Furthermore, galvanic corrosion of brazing filler metal and titanium may be promoted.

As disclosed in Japanese Patent Publication No. 7-68711, a method of sealing a notch at the end face of a welded portion by TIG seal welding using an Ag-Cu-based welding material and sealingly coating the same with a molten metal is disclosed in Japanese Patent Application Laid-Open No. 7-68711. Although it is possible to prevent the seawater from entering from the end face and corrode the base metal welding portion, if the welding current is too high, the base material may be largely melted. Since the intermetallic compound of the system may be generated, it is necessary to keep the welding current low, and the workability is poor.

The present invention improves such disadvantages, prevents seawater and the like from entering the steel portion, which is the base material of the titanium clad steel at the butt weld, improves corrosion resistance, and facilitates on-site work. It is an object of the present invention to provide a method for joining titanium clad steel to a steel structure that can be performed.

[0011]

A method for joining titanium clad steel to a steel structure according to the present invention comprises the steps of welding a base material of a grooved titanium clad steel to the surface of the steel structure. A butt joint of a steel plate is formed, and a base material excluding the titanium joint material of the formed butt joint portion is welded, and both ends of the groove formed by the base metal of the butt joint portion, the weld metal and the titanium joint material, Titanium spacers are inserted at a certain distance from both ends, and the titanium spacer and the titanium spacer are welded together and joined, leaving the ends of the titanium spacers at both ends and the titanium cover on top of the titanium spacer and the titanium spacer. The plate is placed, the cover plate is welded to the titanium composite and the titanium spacer, and pure titanium or a titanium alloy is thermally sprayed around the ends of the titanium spacers at both ends.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A welding method according to the present invention is a method for welding a base material of a titanium clad steel plate welded to the surface of a steel structure except for a titanium joining material in a butt joint portion, and welding the base material of the butt joint portion with the base material. A groove is formed with a metal and titanium composite material. Titanium spacers are inserted into both ends of the groove at a certain distance from both ends, and are joined to the titanium joining material by TIG welding. A titanium cover plate is placed on top of the titanium spacer and the titanium spacer except for the ends of the titanium spacers at both ends, and the cover plate is joined to the titanium spacer and the titanium spacer by TIG welding. Pure titanium is sprayed around the ends of the titanium spacers at both ends to form a sprayed coating, closing the gap between the titanium spacer and the weld metal or base metal,
The weld metal and base metal inside the cover plate are completely sealed with a coating of substantially the same material as the titanium composite material.

As a method of spraying the pure titanium, there are various spraying methods. However, from the viewpoint of easiness of on-site construction, denseness of a sprayed coating, and economical efficiency of construction, high-speed flame spraying (HV) is used.
It is preferable to perform thermal spraying using OF thermal spraying).

[0014]

1 is a process diagram showing a welding method according to one embodiment of the present invention. In the welding method of this embodiment, when the outer circumference of a steel structure 4 such as an offshore structure is coated with a titanium clad steel 3 in which a titanium composite material 2 is bonded to the surface of a base material 1, the titanium clad steel 3 to be coated is coated. This is a butt-welding welding method. When the titanium clad steel 3 is butt-welded to cover the outer periphery of the steel structure 4, first, the grooved titanium clad steel 3 a, 3 b is applied to the steel structure 4 as shown in FIG. The titanium clad steels 3a, 3b are fixed to the steel structure 4 by fillet welding the ends of the base material 1 of the titanium clad steels 3a, 3b to the surface of the steel structure 4. The butt joint 5 is formed at the joint. Butt joint part 5 of titanium clad steel 3a, 3b
The base material 1 excluding the titanium composite material 2 and the steel structure 4 and the base material 1 are joined by TIG welding, MAG welding or covered arc welding.

Next, as shown in FIG. 1 (b), the ends of the titanium cladding 2 made of titanium clad steel 3a, 3b and both ends of the groove formed by the weld metal 6 are fixed at a distance L from both ends. A titanium spacer 7 processed according to the shape of the groove formed by the end of the titanium composite 2 and the weld metal 6
Insert The titanium spacer 7 inserted into the groove and the ends of the titanium composite materials 3a and 3b are joined by TIG welding to prevent titanium from brittlely reacting actively with many elements and compounds at high temperatures.

Thereafter, as shown in the plan views of FIGS. 1 (c) and 2, the end portions of the titanium spacers 7 at both ends are left with a fixed length, and the titanium composite material 2 of titanium clad steel 3a, 3b and the titanium spacer The cover plate 8 made of titanium is placed on the upper portion of the cover 7, and the cover plate 8 is fixed by performing TIG welding around the cover plate 8 to the titanium composite material 2 and the titanium spacer 7. Next, pure titanium is sprayed around the end portions 9 of the titanium spacers 7 at both ends to form a sprayed film 10 as shown in the sectional view of FIG. Close the gap. Thermal spray coating of pure titanium
The method of forming 0 is to form the thermal spray coating 10 by high-speed flame spraying (HVOF spraying) in which the oxygen mixed fuel is burned in the combustion chamber of the splene gun to spray titanium particles at high speed. By this thermal spraying, a dense thermal sprayed coating having a low oxygen content can be laminated. This formed thermal spray coating 1
With 0, the weld metal 6 and the base material 1 inside the cover plate 8 can be completely sealed.

[Specific Example] For example, a titanium clad steel 3 comprising a titanium composite material 2 having a thickness of 1 mm and a base material 1 having a thickness of 4 mm
a and 3b are welded to a steel structure 4 made of a steel plate having a thickness of 12 mm, and a titanium spacer 7 is inserted into a groove formed by the end of the titanium composite material 2 and a weld metal 6 and welded, and welded. After welding the cover plate 8 of titanium, forming a sprayed coating having a thickness of 30 μm in one pass by high-speed flame spraying is repeated 10 passes to form a sprayed coating 10 having a thickness of 300 μm. And weld metal 6 and base metal 1
And closed the gap. Then, a hole was formed in the cover plate 8 and high-pressure air was sent to the gap inside the cover plate 8 to check for leakage. As a result, there was no air leakage, and the weld metal 6 and the base material 1 inside the cover plate 8 were not leaked. It was confirmed that it was completely sealed.

[0018]

As described above, according to the present invention, the base metal of the butt joint of the titanium clad steel plate welded to the surface of the steel structure is welded to the base material of the butt joint except for the titanium joint material. A groove is formed with metal and titanium composite material. Titanium spacers are inserted into both ends of the groove and welded to the titanium composite material, and the upper portions of the titanium composite material and titanium spacers are left except for the ends of the titanium spacers at both ends. Titanium cover plate is placed on it, and the cover plate is welded to the titanium filler and titanium spacer, and then pure titanium or titanium alloy is sprayed around the ends of the titanium spacers at both ends to form a thermal spray coating and form a titanium spacer. Since the gap between the weld metal and the base material is closed, the weld metal and the base material inside the cover plate can be completely sealed. Therefore, even when used for a structure that comes into contact with seawater, such as an offshore structure, seawater does not come into contact with the base material of titanium clad steel, and the corrosion resistance of the offshore structure can be improved.

Further, since the end of the welded portion is sealed by the thermal spray coating, it is possible to prevent the titanium bonding material and the titanium spacer from brittlely reacting with many elements and compounds at a high temperature, and to have a stable strength. And the work can be easily performed on site.

[Brief description of the drawings]

FIG. 1 is a process chart showing a welding method according to an embodiment of the present invention.

FIG. 2 is a plan view showing a region where a thermal spray coating is formed.

FIG. 3 is a cross-sectional view showing a formed thermal spray coating.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Titanium composite material 3 Titanium clad steel 4 Steel structure 7 Titanium spacer 8 Cover plate 10 Thermal spray coating

Claims (1)

[Claims] 1. A beveled titanium clad steel base material is welded to the surface of a steel structure to form a butt joint part of a titanium clad steel sheet, and the formed butt joint part of the titanium joint material is removed. Weld the base material, insert a titanium spacer at both ends of the groove formed by the base metal of the butt joint part, the weld metal and the titanium composite material, at a fixed distance from both ends, and make the titanium composite material and the titanium spacer Are welded together, leaving the ends of the titanium spacers at both ends, placing the titanium cover plate on top of the titanium filler and the titanium spacer, and welding the cover plate to the titanium filler and the titanium spacer, A method of joining titanium clad steel to a steel structure, characterized by spraying pure titanium or a titanium alloy around the end of the steel structure.