JPH05245648A - Method for joining dissimilar material - Google Patents

Abstract

PURPOSE:To simply obtain through arc welding the welded metal without embrittlement in welded part or degradation in corrosion resistance by using a hot charge composed mainly of Ag-Cu, in reference to the joining of dissimilar materials of titanium and steel. CONSTITUTION:In joining titanium-clad steel 1, base material (soft steel) 2 and, after a multi-layer welding is performed on the base material 2 by plasma welding to form a welded part 5, a Ti spacer material 6 in the same property as material 3 to be clad are placed on a notched part. The material 3, 3 to be clad and this spacer 6 are plasma-welded with the hot charge mainly composed of Ag-Cu by using an inert gas such as Ar and He for a sealed gas and Ar gas for a center gas, and a welded part 7 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining dissimilar materials between titanium and steel or joining titanium clad steels (hereinafter referred to as dissimilar material joining), that is, a method for joining dissimilar materials of titanium.

[0002]

2. Description of the Related Art Titanium can be joined to a metal similar to titanium. For example, in joining titanium clad steel, titanium and carbon steel or a low alloy steel, which is a base material, are made of Ar, He.
When arc welding is performed using an inert gas such as Fe, a large amount of Fe dissolves in the molten metal, and Fe-Ti intermetallic compounds and T
It can be said that joining is impossible because a large amount of compounds such as iC or TiN are formed and this makes the weld metal brittle.

Therefore, in the case of so-called dissimilar material joining in which conventional titanium and steel materials or titanium clad steels are joined together, the joining is performed by brazing in a vacuum furnace, or an insert material that does not form an intermetallic compound such as diffusion joining is used. Inserted and joined. For this reason, there are restrictions on the size, and at the same time, there are drawbacks such as inability to perform on-site joining, high cost due to the use of precious metals such as electron beam welding, and low joining strength.

FIGS. 5 (a) and 5 (b) show a joining method of titanium clad steel 1 in which a commercial Ti composite material 3 is joined to the upper surface of a base material 2 mainly composed of Fe. Welds both ends 4 of the clad steel 1 and then places a Ti spacer material 6 of the same quality as the laminated material 3 on the cutout portion, welds the laminated material 3 and this spacer material 6 7 ′, It constitutes the joint. However, in this joint portion, a space 10 is formed between the surface of the base material edge 4 and the spacer material 6, and this space reduces the bonding strength. On the other hand, when the joining material 3 and the spacer material 6 are welded, a part of the clad steel base material 2 is melted, and this is mixed into the weld metal of the welded portion 7 to form TiC, T
A brittle layer of a compound such as iN or a Fe—Ti intermetallic compound is formed, and this may be the cause.

In order to prevent the formation of such a weld fragile layer,
As shown in FIG. 5 (b), the spacer material 6 is not welded to the mating material 3 and only the space between the mating materials 3 is covered and placed, and the upper part thereof is covered with the pad plate material 8 and the mating material 3 is covered. A lap fillet weld 9 is formed to form a joint.

[0006] The patch plate material 8 is a mating material 3 and a spacer material 6.
It is made of titanium similarly to the above, and therefore, the problem of the embrittlement layer in the overlap fillet weld 9 does not occur. But,
This joint is for welding the pressure plate on the laminated material,
Since the welded structure becomes complicated and the void is enlarged by the bending process, it cannot be applied to a structure accompanied by working.

A welding method for titanium clad steel is disclosed in Japanese Patent Application Laid-Open No. 2-52176.

[0008]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and when joining dissimilar materials such as titanium and steel material or titanium clad steel, a special process such as in-furnace joining is adopted. It is an object of the present invention to provide a plasma welding method using an inert gas such as Ar or He, which does not embrittle by a simple method and is excellent in corrosion resistance, without performing the above.

[0009]

The present invention has the following features in order to achieve the above object. That is, when joining titanium and steel, or joining titanium clad steel, etc., a molten material containing Ag-Cu as a main component,
This is a method for joining dissimilar materials between titanium and steel, which is characterized by performing plasma welding using an inert gas such as Ar or He as a shield gas. He gas is preferably used as the center gas in the plasma welding, but Ar gas may be used if necessary. In addition, L
Either or both of i and Sn may be added.

The present invention will be described in detail below.

[0011]

Since titanium has excellent corrosion resistance, it is used in chemical plants and aircraft parts, and its applications are expanding. However, its practical limitation is that it is expensive. Therefore, titanium is used in the corrosive atmosphere, and on the other hand, clad steel made of low alloy steel, high strength steel or the like is used in order to maintain the role as a strength member. Titanium to be used may be any one of 1 to 3 specified in JIS. The clad steel is used in various devices, parts, etc. as described above, but in forming these constituent members, it is important to obtain a bonded portion having no brittleness and a strong bonding strength as described above.

That is, when joining titanium clad steel, a groove is formed in a base material (mild steel or alloy steel), the base materials are welded together by using the same quality of molten material, and at this welded portion,
Base material and laminated material (Ti) Comrade or laminated material (T
The plasma welding is performed on the spacer material of the same quality as that of i) using a molten material containing Ag-Cu as a main component. Further, at the end faces of these welded portions, for example, in order to seal the gap between the base material and the spacer material, seal welding is performed by the above-mentioned plasma welding method with a molten material containing Ag-Cu as a main component between the two. is there. That is, in such a case, the dissimilar material joining of the steel base material and titanium is performed in each case.

As the melting material used for joining in the present invention, a material containing Ag-Cu as a main component as described above is used. For example, BAg8 or BAg-8A (Li defined in JIS Z3261 is used. : 0.1
5 to 0.3% added) type material may be used. S for these materials
N may be contained, and Zn can be added as long as it does not impair the workability, but if a large amount is added, the generation of fumes increases, so the addition amount is limited to a small amount. Ag and Sn keep the melting point low, prevent reaction with Fe and Ti, Cu improve joint strength and L
i is used to improve compatibility with mild steel.

According to the present invention, the plasma welding method is used for positive fusion bonding, and the TIG welding method is used because the molten material containing Ag-Cu as a main component does not form an intermetallic compound and has a low melting point. Since the plasma welding method has a high heating rate and a good arc concentration, the molten metal is not melted.

He is preferable as the center gas for plasma welding, but a small amount of Ar may be used if necessary. Normally, hydrogen is used as the center gas,
When hydrogen is used, a brittle hydrogen compound is formed as a compound with Ti, so it is not preferable to mix hydrogen.
Further, when welding with this type of melt, it is preferable to make the groove shape as small as possible from the viewpoint of joint strength.

[0016]

The drawings show examples of welds obtained by the welding method of the present invention. FIG. 1 (a) shows a state in which titanium clad steel 1 is joined. Base materials (mild steel) 2 and 2 are multi-layer welded by plasma welding to form a welded portion 5, and then a laminated material 3 is formed.
A Ti spacer material 6 of the same quality as the above is placed in the notch, and the joining materials 3 and 3 and the spacer material 6 are made of Ag-Cu as a main component, and an inert gas such as Ar or He is used as a shield gas. Plasma welding using Ar gas as the gas,
The weld 7 is formed.

In FIG. 1B, the spacer material 6 and the mating materials 3 and 3 are made of Ag-Cu as a main component and are Ar and He.
After the TIG welding is performed using an inert gas such as, the welded portion 7 is formed, the upper portion of the welded portion is covered with the pad plate material 8 and the laminated material 3 is overlapped with the fillet welded portion 9 to form a joint. .. The patch plate material 8 is overlapped and fillet welded to the laminated material 3 to form a fillet weld portion 9. However, since the joint plate 8 is welded onto the spacer material 6 in this joint, a gap portion 10 is formed between the base material (mild steel) 2 and the spacer material 6 on the joint end face side as shown in the figure. Therefore, it is necessary to perform seal welding in order to block this, but since this is dissimilar material joining, in the present invention, an inert gas such as Ar or He is used as a shield gas with a melting material containing Ag-Cu as a main component. Plasma welding is performed using He as the center gas to form the dissimilar material seal weld portion 14. Further, the space 10a formed between the spacer material 6 and the patch plate material 8 is plasma welded using the same Ti melt as the spacer material 6 and the patch plate material 8 to form the seal welded portion 15. ing.

FIG. 2 (a) shows that titanium 12 is used as an inner lining when corrosion resistance is required in a steel reaction vessel or the like,
This figure shows the dissimilar material joining state of titanium and steel.
That is, as shown in the principal part explanatory view of FIG. 2B, a titanium backing material 3 as a backing material is attached to the inner surface of the base material 2 by Ag.
-Cu-Li-Sn as a main component, fillet welding was performed using a plasma welding method with an inert gas atmosphere such as Ar or He as a shield gas, and He gas as a center shield gas, and titanium 3 was formed. A fillet weld 11 is formed by joining dissimilar materials to the steel material 2, and titanium 12 which is lined in the upper layer portion of the titanium laminated material 3 is butt welded by plasma welding using a Ti melt of the same quality to form a butt welded portion 13. The method of forming is shown.

FIG. 3 (a) shows a state in which a titanium clad steel plate is processed into a pipe and the mild steel pipe 2 (a) and the formed titanium clad steel pipe 1 are butt-joined to each other. As shown, the end face 4 of the clad material is composed of a titanium laminated material 3 and a base material 2 which are molten materials containing Ag-Cu-Li as a main component, and an inert gas such as Ar or He is used as a center gas. This shows a method of forming a dissimilar material welded portion 11 by plasma welding using Ar gas, and then forming a welded portion 5 by multi-layer welding of a base material (mild steel) 2 by plasma welding.

FIG. 4 shows a state of abutment with a steel pipe pile when a titanium clad steel plate is processed into a pipe and is used as an anticorrosion method for splashes and tidal parts in the ocean. That is, this is an example of use of the present invention when wound around a pedestal 15 of an offshore structure, and by using this for joining a clad steel plate installed in a seawater splash zone, erosion due to wave of the pedestal is protected, It can help prolong life. In the case of joining the titanium clad steel 1 to the pedestal 15 as shown in the figure, the structural member 15 and the clad steel base material 2 are subjected to multi-layer fillet welding by TIG welding to form the welded portion 5, and then the titanium composite material 3 is formed. A Ti spacer material 6 of the same quality is placed in the cutout portion, and after the plasma welding 7 of the bonding material 3 and this spacer material 6 with the Ti melt material of the same quality, the end surfaces of these welded parts are the base material 2, the bonding material and the spacer material. Over the entire length, the dissimilar material seal welded portion 14 is formed by plasma welding using an inert gas such as Ar and He as a shield gas and a Ar gas as a center gas with a molten material containing Ag-Cu-Sn as a main component. .. As a result, even if a gap is formed between the spacer material and the base material, the weld end surface can completely seal the gap and prevent brittleness and corrosion due to intrusion of seawater into the weld portion through the gap.

As described above, in the present invention, since the material containing Ag-Cu as the main component is used as the welding material, a welding component containing Ag as the main component is obtained, and although Fe is penetrated, it is a small amount and Ag
A rich weld metal is obtained. Further, since the present invention is melt-welded, the joining strength is high as compared with brazing, and welding work can be performed on site.

In the present invention, it is possible to apply TIG welding to part or all of the plasma welding application part.

[0023]

As described above, according to the method of the present invention, welding without causing brittleness or deterioration of corrosion resistance of a welded portion which has been a neck in joining dissimilar materials between titanium and steel or joining titanium clad steels together. Metal can be easily obtained by arc welding similar to the conventional one, and its industrial effect is extremely large.

[Brief description of drawings]

1A and 1B are schematic views showing a welded portion of titanium clad steel according to the method of the present invention.

FIG. 2 (a) is a schematic view showing a welding method of titanium and a steel material, and FIG. 2 (b) is a partially enlarged explanatory view of the same (a).

3A is a sectional perspective view showing a welding method of a titanium clad steel pipe and a carbon steel pipe, and FIG. 3B is a partially enlarged explanatory view of the same FIG.

FIG. 4 (a) is a schematic view showing a method of welding a dissimilar material to steel by winding a titanium clad steel pipe around a carbon steel structure, and FIG. 4 (b).
FIG. 7 is a partially enlarged explanatory view of the same (a).

5A and 5B are cross-sectional views showing a conventional joining method of titanium clad steel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Clad steel plate 2 ... Base metal 2 (a) ... Mild steel piping 3 ... Laminated material 4 ... Both ends of clad steel 1 5 ... Clad steel plate Mild steel part base metal multi-layer welded part 6 ... Spacer material 7, 7 '... Spacer material Welded part 8 ... Patch plate material 9 ... Overlap fillet welded part 10 ... Void 11 ... Fillet welded 12 ... Inner beam titanium 13 ... Butt welded part 14 ... Dissimilar material seal welded part 15 ... Sealed welded part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiichi Soeda 2-6-3 Otemachi, Chiyoda-ku, Tokyo Shin Nippon Steel Corporation

Claims (4)

[Claims] 1. A method for joining dissimilar materials, characterized in that, when joining titanium and steel or titanium-clad steel to each other, a welding material containing Ag-Cu as a main component is used and welding is performed by a plasma welding method. 2. The dissimilar material joining method according to claim 1, wherein plasma welding is performed by using a molten material composed of Ag—Cu—Li and unavoidable impurities. 3. The method for joining dissimilar materials according to claim 1, wherein plasma welding is performed using a molten material composed of Ag—Cu—Sn and unavoidable impurities. 4. The method for joining dissimilar materials according to claim 1, wherein the plasma welding is performed using a molten material composed of Ag—Cu—Li—Sn and inevitable impurities.