JPH1147954A - Method of joining titanium and steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a product with large joining strength and high precision by diffusion welding, with a compound insert material interposed for which a titanium group or a copper group amolphous alloy foil and a nickel foil are combined, between titanium or titanium alloy and carbon steel or stainless steel. SOLUTION: The surface to be joined of a base material 4 and a clad material 1 are ground, so that an oxide film on the surface is removed. A copper group amolphous alloy film 2 and a nickel film 3, which are a compound insert material, are also cleaned by ultrasonic cleaning and the like, so that an oil film for example is removed. A nickel film is laminated on the base material 4 of carbon steel or stainless steel, a copper group amolphous alloy film 2 is laminated over it, and a clad material 1 of titanium or a titanium alloy is further laminated over it, with diffusion welding performed inside a vacuum welding equipment. As a result, the formation of a brittle intermetallic compound or carbide is suppressed by the nickel film, in the boundary between the base material 4 and the nickel film 3 or in the area of the copper group amolphous alloy film 2, with the formation of the intermetallic compound controlled in the boundary between the copper group amolphous alloy film 2 and the clad material 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for joining carbon steel or stainless steel to titanium or a titanium alloy having excellent corrosion resistance and strength.

[0002]

2. Description of the Related Art Conventionally, titanium has been used in the fields of chemistry and electricity due to its excellent corrosion resistance, and its demand has been growing as a titanium alloy because of its high specific strength. However, they have been adopted only in special fields because they are very expensive, difficult to machine, easy to bake, and difficult to weld and join. However, although the price of titanium is simply about 10 times that of stainless steel, its specific gravity is about 60% of that of stainless steel, it can be reduced in size except for corrosion allowance, and it has a long life and is maintenance-free For example, since it is relatively inexpensive if evaluated from the viewpoint of cycle cost for each application, application as a clad material having excellent functions and economical properties by joining layers with different metals has been studied. In particular, a titanium clad steel sheet having excellent strength, heat conductivity and weldability of steel and high corrosion resistance of titanium has been developed.

[0003] Examples of the method for producing the titanium clad steel include an explosion pressure bonding method, a rolling method, a brazing method, and a diffusion bonding method. Explosive crimping is a method of joining metals using the shock wave and high pressure generated when an explosive explodes. Since it is performed cold, there is little thermal effect, and the joining is completed in an extremely short time And that a brittle intermetallic compound is not easily generated at the bonding interface. Titanium clad steel has been produced mainly by this method, but there are problems such as handling explosives and noise and vibration generated when explosives explode. In addition, since the rolling method makes the base material and the composite material adhere to each other by hot rolling and reduces the size to a predetermined size, the manufacturing size range is wide and suitable for mass production, but since titanium is an active metal, In addition, a brittle intermetallic compound was formed at the bonding interface by heating, and it was very difficult to put it to practical use.

[0004] Further, the brazing method is a method in which a brazing material is flown into gaps of a joining portion without melting the base material, and cooled and solidified to join. A strong oxide film is formed on the surface of titanium. It is formed and requires flux to promote wetting of the wax. This complicates the joining procedure, leaving flux at the joining interface as an impurity,
It affected the corrosion resistance and joint strength of the joint. Furthermore, the diffusion bonding method can assemble and join complicated shaped parts, so that it is possible to manufacture high-precision products that were structurally difficult to manufacture using other methods, and to achieve higher quality and cost reduction of products. In addition, it is possible to join composite materials, dissimilar materials, sintered alloys, ceramics, etc., which are difficult to melt weld due to metallurgical problems. In this method, plasticizing is performed under temperature conditions equal to or lower than the melting point of the base material or the bonding material to such an extent that plastic deformation is not generated as much as possible, and bonding is performed by utilizing diffusion of atoms generated between bonding surfaces.

[0005] Recently, as a method of joining a heat-resistant superalloy with higher strength than brazing, a filler metal having a lower melting point than a base material or a bonding material is inserted between joining surfaces, and temporarily at a predetermined joining temperature. A liquid phase diffusion bonding method has been developed in which a liquid phase is generated and bonded by isothermal solidification using diffusion. This bonding method is an intermediate bonding method between brazing and diffusion bonding, and is effective for various base materials and combinations of fillers and filler metals.Amorphous alloy foil is used as filler metal to be inserted into the bonding interface. No.
This amorphous alloy foil is uniformly melted by the amorphous structure without segregation, crystal grains, grain boundaries, etc., the flow at the interface is good, there is no local change in melting point inside the foil material, This is because phenomena such as melting are unlikely to occur. Amorphous alloys can be processed into thin ribbons by quenching the liquid, and the thin ribbons are rigid. Therefore, they are easier to install between a base material and a composite material than powdered brazing or the like.

[0006]

However, in the method of liquid-phase diffusion bonding using titanium or a titanium alloy, carbon steel or stainless steel, and an amorphous alloy foil as a filler metal, the method is difficult under certain specific conditions. Although the joint strength was obtained, the joint strength was large,
TiFe and TiFe ₂ , which are Ti—Fe intermetallic compounds, and TiC, which is a carbide, are formed at the bonding interface, and there is a problem that the strength of the bonding part is significantly reduced.

Therefore, the present invention solves such a problem and increases the joining strength without forming a brittle intermetallic compound at the joint between titanium or a titanium alloy and carbon steel or stainless steel. It is an object of the present invention to provide a bonding method that can manufacture a highly precise product.

[0008]

In order to achieve the above object, a bonding method according to the present invention combines a titanium-based or copper-based amorphous alloy foil and a nickel foil between titanium or a titanium alloy and carbon steel or stainless steel. The structure is such that the composite insert material is interposed and diffusion bonding is performed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. In the present invention, titanium or titanium alloy as a joining material and carbon steel or stainless steel as a base material are joined by liquid phase diffusion bonding. First, the surfaces to be joined of the base material and the joining material are polished. To remove the oxide film on the surface. Further, the copper-based amorphous alloy foil and the nickel foil, which are composite insert materials, are also cleaned by ultrasonic cleaning or the like to remove an oil film or the like. As shown in FIG. 1, a nickel foil 3 is placed on a base material 4 of carbon steel or stainless steel, a copper-based amorphous alloy foil 2 is placed on the nickel foil 3, and a nickel-based amorphous alloy foil 2 is placed on the copper-based amorphous alloy foil 2. A composite material 1 of titanium or a titanium alloy is sequentially laminated. The laminated material is placed in a vacuum bonding apparatus for 85
A bonding temperature of 0 to 980 ° C., a holding time of 1 to 10 minutes,
Diffusion bonding is performed at a bonding pressure of 0.5 to 0.7 kgf / mm ² load. As a result, the formation of intermetallic compounds and carbides that are fragile at the interface between carbon steel or stainless steel and the nickel foil or in the copper-based amorphous alloy region is suppressed by the nickel foil. The formation of intermetallic compounds at the interface can be appropriately controlled.

[0010]

[Example] Titanium as a bonding material has a thickness of 3 mm and a purity of 99.
5% industrial pure titanium, carbon steel as the base material having a thickness of 9
mm SS400 steel was used. Insert material is 50μ thick
mm based copper alloy foil and a 20 mm thick nickel foil. These materials are laminated in the order of titanium, copper-based amorphous alloy foil, nickel foil, and carbon steel. The laminated sample is heated to a bonding temperature at a heating rate of 180 ° C. per minute in a vacuum bonding apparatus having an initial degree of vacuum of about 7 × 10 ⁻⁴ torr, and is held at a predetermined temperature for a predetermined time. Cooled in. This bonding temperature is 850-9
30 ° C., holding time 1-10 minutes, bonding pressure 0.5-
It was changed to 0.7 kgf / mm ² .

The joined sample was heated at 852 ° C., 877 ° C., 92
As shown in FIGS. 2 (a), (b), and (c), the joint structure obtained by joining with a holding time of 10 minutes at each joining temperature of 7 ° C. was placed in the titanium original part and the Ti-matrix from the top. It was roughly classified into a region where precipitates exist densely (precipitation layer), a bonding interface portion including a nickel foil, and a carbon steel raw material region. As a result, at a joining temperature of 852 ° C., the shear strength gradually increased as the holding time was increased, and was about 18 kgf / mm ^{2 on} average when the holding time was 20 minutes or longer. Joining temperature 8
At 77 ° C, the shear strength is about 18kgf / mm with a holding time of 1 minute.
^{Although the} value was as high as ² , it dropped sharply when the holding time became 10 minutes, and the shear strength was almost constant even after the holding time increased, and was about 13 kgf / mm ² . Further bonding temperature 9
When the temperature increased to 27 ° C., the shear strength was constant at about 13 kgf / mm ² irrespective of the holding time, and there was almost no variation in strength.

Here, the average shear strength is about 18 kgf / mm.
^{2. The} relatively high value of 24.5 kgf / mm ² at the maximum was obtained at a bonding temperature of 852 ° C and a holding time of 10 minutes. The shear fracture surface on the titanium side, as shown in Fig. , And traces of rubbing upon peeling were observed on almost the entire fractured surface. When a composition analysis of this part was performed, no copper-based amorphous alloy component was recognized, and only Ni and Fe were recognized. Further, a Ni peak was mainly observed on the titanium-side fracture surface, and a d-Fe peak was mainly observed on the carbon steel side. Therefore, when the bonding temperature is low, the interdiffusion between the Ni / Fe interfaces, which becomes solid-phase diffusion bonding, is not sufficiently performed, and the breakdown mainly occurs at the Ni / Fe interface. However, Ni
And Fe form a solid solution with each other and do not form a low-strength intermetallic compound, so that the joint has a high joint strength.

On the other hand, at a joining temperature of 927 ° C. with a low shear strength and a holding time of 10 minutes, the shear fracture surface is shown in FIG.
As shown in (c), the flat surface was present in a step-like manner, and projections, which were considered to be tongues, were scattered on the fracture surface, and thus the surface was brittle. From the results of the composition analysis, peaks of Ti and Ni were recognized from the fracture surface. Further Ti-N
i-based intermetallic compound (Ti ₂ Ni, TiNi, TiNi ₃ )
Was observed from both the titanium side and the carbon steel side fracture surface. Therefore, when the bonding temperature is high, Ni / F
The e interface has sufficient interdiffusion and is joined, but Ti /
Since a brittle Ti-Ni-based intermetallic compound is formed at the Ni interface, and the fracture occurs at the brittle Ti / Ni interface, the bonding strength is reduced. FIG. 3B shows a shear fracture surface at a bonding temperature of 877 ° C. and a holding time of 10 minutes.

Although the embodiments which are considered to be representative of the present invention have been described above, the present invention is not necessarily limited to only the structures of the embodiments, and has the above-mentioned constitutional requirements according to the present invention. The present invention achieves the object of the present invention and can be appropriately modified and implemented within the range having the following effects.

[0015]

As is clear from the above description, the joining method according to the present invention employs a titanium-based or copper-based amorphous alloy foil and a nickel foil between titanium or a titanium alloy and carbon steel or stainless steel. In this case, the composite insert material is interposed and diffusion bonded, so that the bonding strength is reduced without forming a brittle intermetallic compound between titanium or titanium alloy and carbon steel or stainless steel. It is possible to expect a remarkable effect that the size can be increased and a highly precise product can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a stack according to an embodiment of the present invention.

FIG. 2 is a photograph of a joint structure of an example of the present invention.

FIG. 3 is a photograph of a shear fracture surface structure of an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laminated material 2 ... Copper base amorphous alloy foil 3 ... Nickel foil 4 ... Base metal

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code FI B23K 20/00 360 B23K 20/00 360E (72) Inventor Minoru Nishida 3rd Bunkyocho, Matsuyama-shi, Ehime Pref.

Claims (1)

[Claims] 1. A bonding method in which a composite insert material comprising a combination of a titanium-based or copper-based amorphous alloy foil and a nickel foil is interposed between titanium or a titanium alloy and carbon steel or stainless steel, and diffusion-bonded.