JPH02112886A - Production of clad titanium wire rod - Google Patents

Abstract

PURPOSE:To reduce the production cost of the clad titanium wire rod by coating a core material consisting of Ti with an outside layer material consisting of Ni and maintaining the inside part of the outside layer material in a specific vacuum state, then subjecting the clad stock to cross helical rolling at a specific temp., then to cold working to a specific diameter. CONSTITUTION:The core material 11 consisting of the Ti or Ti-based alloy is coated with the outside layer material 12 consisting of the Ni or Ni-based alloy and caps 13 are provided thereto. The inside of the outside layer material 12 is then maintained under 1X10<-1>Torr vacuum state and the clad stock 10 is assembled. This clad stock 10 is heated to <=850 deg.C and is elongated by the cross helical rolling mill 4 having >=3 pieces of cone type rolls 1, 2, 3. The outside layer material 12 and the core material 11 are diffusion joined in this way. The elongated stock 10 is then subjected to cold drawing to <=50mum diameter. The production cost of the clad titanium wire rod is reduced in this way.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a method for coating a core material made of titanium (Ti) or titanium (Ti) base metal with an outer layer material made of nickel (Ni) or nickel (Ni) 5 alloy. and the finished diameter is 50um.
The present invention relates to a method of manufacturing a clad titanium wire having an ultra-thin diameter as described below.

[Prior art] The conventional method for processing Ti-Ni clad wire rods with a Ti core material is to warmly extrude a laminated bar material made of a Ti-based metal core material covered with a Ni-based metal outer layer material at a predetermined temperature. After processing, annealing is performed to soften the material, followed by cold working (Japanese Patent Publication No. 60-13424), or Ti or T
A method has been proposed in which a core material made of an i-based alloy is covered with a hollow outer layer material made of Ni or a Ni-based alloy, and then hot extrusion processing, annealing treatment, wire drawing processing, and annealing treatment are sequentially performed (especially (No. 159216, 1983).

However, in these methods, Ni-Ti intermetallic compound (T
There was a drawback that the bonding strength between the core material and the outer layer material was low due to the formation of Ni, T1Ni, and Ti (old).

As a way to solve the problem of intermetallic compound formation, we have developed
i. A method for manufacturing cladding materials has been proposed in which the cladding materials are subjected to strong processing to make the intermetallic compounds in the boundary layer finer, and then heat treated at a temperature of 600°C or less (Japanese Patent Laid-Open No. 1983-1999).
-156879),.

This is due to the brittle Ni-
By using a method to refine the Ti intermetallic compound by machining and then heat-treating it again at a relatively low temperature, the temperature constraints during cladding are significantly relaxed, resulting in a Ni-Ti clad material with improved overall bonding strength. This is the way to try to get it.

In other words, the intention was not to control the generation of Ni-Ti intermetallic compounds, but to allow the generated intermetallic compounds to exist in the cladding material with relatively little influence, thereby improving the bonding strength. ■ Process of forming a cladding by press-welding and heating Ni and Ti materials Examples of methods of press-welding and heating include (1) hot rolling, hot extrusion, hot drawing, explosion bonding (press welding and heating are (ii) 'Cold rolling/cold drawing' - Heating Generally, the heating temperature is 700°C or higher.■ Strong processing is a process in which intermetallic compounds are refined by performing strong processing using processing methods such as rolling and extrusion. It may be hot or cold. The temperature in the hot room is 500
Although temperatures below 600°C are preferred, temperatures below 600°C can also be used.

(2) This is a processing method that includes a step of heat-treating at a temperature of 600° C. or lower, preferably 550 to 450° C., for 10 minutes to 2 hours to cause diffusion at the boundary between Ni and Ti materials.

On the other hand, as a method for drawing a titanium or titanium alloy wire, a method is generally practiced in which an oxide film is attached to the titanium or titanium alloy wire and then the wire is drawn (Japanese Unexamined Patent Application Publication No. 1983-1979-1).
No. 34605). In this method, a clad material is heated in the atmosphere to form an oxide film on its surface, and this oxide film is used as a lubricant to prevent the die from galling while drawing the wire. However, this method requires heat treatment at a high temperature (over 650°C) for a long time (2 to 3 hours) to form an oxide film on the core material, and the finished diameter is limited to about 1 mm. The problem was that the process was extremely complicated in order to achieve the desired diameter, making it impractical.

Therefore, in recent years, plating technology has been used to apply Ni plating to the surface of a titanium or titanium alloy wire and then draw the wire.

[Problems to be Solved by the Invention] However, in the case of the above-mentioned processing step for increasing the bonding strength between the outer layer material and the core material, a subsequent heat treatment step is always required, which complicates the processing and increases the product cost. I can't. Moreover, the bonding strength of the clad material thus obtained is only about 0.18 kg/2 shells.

If the bonding strength is low, the Ni material and Ti material will be separated in the next wire drawing process.
This causes the inconvenience that the material peels off and the defective rate increases. In order to reduce the defect rate, a bonding strength of 20 kg/2 or more is required in the wire drawing process, and the bonding strength cannot be said to be sufficient even with the above manufacturing method.

Other methods for increasing bond strength include explosive crimping and hot isostatic pressing. However, even when hot isostatic pressing is used, the bonding strength is about 17 kg/mm2, which is insufficient to improve the defective rate. According to this point explosion full crimping, the joint strength is 20
kg/mm", and it is thought that the defect rate will be relatively improved in the wire drawing process, but on the other hand, it is difficult to obtain long clad material using the explosive crimping method, and the processing cost is high, and for safety reasons. There is the problem of having to secure a special place for

By the way, in addition to the extrusion method or isostatic extrusion method, hole rolling method, forging method, etc. have been conventionally used as hot working methods, but hole rolling method, forging method, etc. Since there is always a free surface (unrestricted surface) and a phenomenon occurs where the core material and outer layer material separate at the boundary layer on the free surface, it is difficult to apply it to dissimilar metal clad materials.

The present inventors have also investigated hot working methods using groove rolling or forging, but have confirmed that poor joints are formed at the boundaries of rolled materials.

On the other hand, among the conventional wire drawing methods, it is difficult to make the plating thickness uniform with the method of applying Ni plating to the surface, so if the wire is drawn to a thickness of 50 μm or less, there will be no plating layer in areas with thin plating. This causes problems such as galling by the die during processing, and there is a problem in that wire can only be drawn up to a diameter of about 50 μm.

The present invention was made in view of the above circumstances, and its purpose is to dramatically increase the bonding strength between the core material made of Ti or Ti>J alloy and the outer layer material made of Ni or Ni-based alloy. The light weight and corrosion resistance of Ti can be improved.

To provide a method for manufacturing a crund titanium wire rod with high bonding strength without the need for post-processing heat treatment as in conventional methods, by making use of Ni's surface treatment properties such as workability, pressability, cuttability, and brazeability. That's true.

Another object of the present invention is to provide a method capable of manufacturing a clad titanium wire having an extremely fine finished diameter of 50 μm or less by diffusion bonding an outer layer material and a core material.

[Means for Solving the Problems] The present invention provides a core material made of Ti or Ti5 alloy containing Ni or Ni.
Cover with an outer layer material made of base alloy, and cover the inside of this outer layer material with I
A process of assembling the clad material by keeping it in a vacuum state of X 10-1 Torr or less and sealing it, and heating the clad material to 850°C or less and stretching and rolling it with an inclined rolling mill having three or more cone-shaped rolls. The method includes a step of diffusion bonding the outer layer material and a core material, and a step of cold drawing the stretched and rolled material to a diameter of 50 μm or less using a die.

[Effect]

According to the present invention, the Ni material and the Ti material can be joined with high bonding strength without heat treatment, and the diameter can be reduced to 50 μm or less by cold wire drawing.

〔Example〕

The present invention will be specifically explained below based on the drawings.

FIG. 1 is a block diagram showing the main manufacturing steps according to the method of the present invention, including a step of assembling a cladding material with a core material and an outer layer material, a step of heating the cladding material to a predetermined temperature,
The assembled cladding material is hot-stretched and rolled in an inclined rolling mill with 3 to 4 cone-shaped rolls, and the outer layer material and core material are diffusion bonded, and the scale of the hot-stretched and rolled cladding material is removed. and a step of cold-drawing the hot-rolled clad material to a diameter of 50 μm or less using a die.

Each step will be specifically explained below.

(2) Assembling process of cladding material FIG. 2 is an explanatory diagram showing, partially in cross section, the manufacturing process of the cladding material used in the present invention.

A core material 11 made of Ti or Ti-based alloy and a cylindrical outer layer material 12 made of Ni or Nj-based alloy are prepared, and after degreasing and cleaning both materials with acetone etc., the core material 11 is inserted into the outer layer material 12. Then, in a room maintained at a vacuum level of less than I A cladding material 10 is obtained in which the inside of the cladding material 12 is maintained at a vacuum level of 1×10 −1 Torr or less.

The reason why the degree of vacuum is set to I.times.10.sup.1 Torr or less is because if the degree of vacuum is exceeded, the bonding strength between the core material 11 and the outer layer material 12 will be extremely reduced in the later process of inclined rolling.

Note that Ti or Ti-based alloys include Ti alone or Ti as a main component, Ti and Affi, ■, Mn, Fe, C
Contains an alloy with one or more of the following components: u, Mo, Cr, W, etc., and the Ti content in the alloy is 90%.
(% by weight, hereinafter the same shall apply unless otherwise specified) or more is preferable. This is because if it is less than 90%, the specific gravity increases and the characteristics as a lightweight metal are lost.

In addition, Ni or Ni-based alloys include Ni alone or Ni as a main component, Nt, Cr, Cu, re, Ag, Si,
S, Pb.

PL, Au, rare earth elements, Ti, Nb, Affi
, Mo, Sn.

It includes alloys with one or more components such as Co.

2) Heating process of the cladding material The obtained cladding material 10 is heated to a temperature of 850°C or less. Heating temperature of clad material 10 is 850°
The reason for setting it below C is as follows.

Normally, the intermetallic compound of titanium and nickel starts to melt at 955°C, but in the slope rolling performed in the next hot elongation rolling process, when the working degree (area reduction rate) is increased, processing heat is generated and the temperature rises to 100°C. Since the material temperature rises by about .degree. C., the temperature is set at 850.degree. C. or less to ensure safety so that the intermetallic compound does not melt. The lower limit of the heating temperature is not particularly limited as long as hot rolling (or warm rolling) is possible, but it is preferably 40
The temperature is 0°C or higher.

This is because the required capacity of the inclined rolling mill becomes very large if the heating temperature is lower than this.

3) Hot stretching and rolling process of cladding material In the hot stretching and rolling process, the thickness of the outer layer material 12 is 1! Stretch rolling is performed so that the ratio (t/D) between V(t) and its outer diameter (D) is 0.02 to 0.1. This is because if the ratio (t/D) is less than 0.02, there is a risk that the outer layer material will break during the wire drawing process. Furthermore, if the ratio exceeds 0.1, the light weight characteristic of Ti is lost. The equipment for this hot stretching and rolling is No. 3.
4.5 An inclined rolling mill having three or more cone-shaped rolls as shown in Figure 5 is used.

The reason why the number of rolls is set to three or more is that in an inclined rolling mill having two rolls, a so-called Mannesmann fracture phenomenon occurs, and cracks occur in the center of the rolled material.

As the inclined rolling mill, it is desirable to use a cross-type inclined rolling mill.

FIG. 3 is a front view showing the rolling state by the inclined rolling mill 4 used in the present invention, FIG. 4 is a cross-sectional view along the line ■-■ in FIG. 3, and FIG. 5 is a direction along the line V--■ in FIG. 3. FIG. The inclined rolling mill 4 has three cone-shaped rolls 1.2.3 facing around the pass line, and the three rolls 1, 2.3 form a gorge part la at a position near the exit end of the crund material 10. ,
2a and 3a, the entrance side of the cladding material 10 is gradually reduced in diameter toward the shaft end with the gorge parts 1a, 2a, and 3a as boundaries, and the exit side is expanded to form a truncated conical shape.
b, 2b, 3b and exit surfaces 1c, 2e, 3c, and the exit surface 1c + 2c + 3c has a distance from the pass line to the gorge portions 1a, 2a, 3a and the pass line X-x.
Match the distance with the distance.

Such cone-shaped rolls 1 and 2.3 are all in a state in which their entrance surfaces 1b, 2b, and 3b are located on the upstream side in the moving direction of the clad material 10, and the axis Y-Y and the gorge part 1a, 2a, and 3a (hereinafter referred to as the roll setting center) are located at approximately equal intervals around the bus line XX on the same plane orthogonal to the pass line XX of the cladding material 10. At least it is arranged. The axial cotton Y-Y of each roll 1.2.3 is centered around the roll setting center 0, and the front axial end is located in relation to the pass line X-x of the crund material 10 as shown in Fig. 3.4. Intersect (tilt) by the intersection angle γ so as to approach the path line x-X
Further, as shown in FIGS. 4 and 5, the front shaft end is inclined toward the same side in the circumferential direction of the cladding material 10 by an inclination angle β.

Crossing angle T and inclination angle β are 0° and γ<15°, 3°<β<
20° and 5° are set to satisfy T+β<30°.

Each roll 1, 2.3 is connected to a drive source (not shown) and is driven to rotate in the same direction as shown by arrows in FIG. 4, and the hot clad material 10 caught between these rolls is
The material is elongated and rolled while being rotated about its axis and moved in the axial direction, ie, so-called spiral movement.

While being spirally moved between rolls, the outer diameter of the cladding material IO is reduced by part A of the roll-by 1 as shown in Fig. 4, and is subjected to high pressure with a maximum area reduction rate of 80 to 90%, for example. , After the rolled surface B of the cladding material 10 is formed into a truncated conical shape, the gorge parts 1a2a, 3a and the outlet surfaces 1c, 2c are formed.
, 3c, it is processed into a clad material 14 having a circular cross section with a predetermined outer diameter and in which the outer layer material 12 and the core material 11 are diffusion bonded.

In general, when diffusion bonding is performed by heat treatment diffusion, the thickness of the diffusion layer is thick (and, moreover, due to growth during the repeated softening and annealing process during the wire drawing process, it becomes about 10 to 20 μm, and the thickness is extremely small with a diameter of 50 μm or less. When the wire is drawn, it has a structure that is more like a composite wire than a clad wire.For this reason, in order to maintain the structure of a clad wire with an ultra-thin diameter wire, the diffusion layer thickness must be small. However, the diffusion bond formed by this inclined rolling mill has a high bonding strength and is extremely thin, and even after repeated softening annealing at 700°C to 600°C, its thickness remains It remains in the order of μ, and no peeling occurs even during repeated wire drawing processes.

In addition, in this diffusion bonding step, it is also possible to employ hot isostatic extrusion, which is an axially symmetrical processing method, from the viewpoint of suppressing the prevention of uneven thickness of the outer layer material.

4) Cold wire drawing process In an inclined rolling mill that generally has three rolls, as the diameter of the rolled material becomes smaller, the diameter of the rolling rolls must also be made smaller due to geometric constraints, which inevitably reduces the rolling speed. In addition, since the temperature of the cladding material 10 decreases, the diameter of
Hot rolling by inclined rolling is possible up to about 0 cylinders, but 10 [ltl! When it is less than 1, hot rolling becomes difficult in practice. Therefore, when making a wire rod with a diameter of 10 mm or less, cold wire drawing is performed.

This wire drawing method includes die wire drawing method, roller die wire drawing method, cold wire drawing method using groove rolling method, etc., but from the viewpoint of suppressing variation in wall thickness, die wire drawing is used. It is preferable to employ this method to suppress variations in the thickness of the outer layer material 12 in the cladding material 14 as much as possible. The reason why cold processing is used is because an intermetallic compound layer generated at the bonding interface grows when hot or warm heating is performed. Ti.

Intermetallic compounds such as Ni+T1Ni are brittle and must be cold-processed in order to prevent separation between the outer layer material and the core material in this intermetallic compound layer.

FIG. 6 is a schematic diagram showing a cold wire drawing process using a die. After removing scale from the surface of the hot-rolled cladding material 14, a lubricant is applied to the cladding material 14, and the wire is drawn in a die 5, and finally processed into a Tararad titanium wire 15 having a diameter of 50 μm or less.

[Numerical example]

A cladding material 14 consisting of a combination of materials and dimensional specifications as shown in Table 1 as a core material and an outer layer material was subjected to wire drawing using a die to produce a cladding titanium wire material 5 having a diameter of 50 μm or less.

(The following is a blank space) Table ■ The pure Ti material and the pure Ni material in Table 1 have the component compositions shown in Table 2.

Table 2 First, a clad material 14 before wire drawing with a die was obtained in the following process.

Outer diameter 54.6mm with polished outer periphery, length 800m
m pure Ti core material and an outer diameter of 60 mm with the inner surface polished in the same way.
．． Prepare a pure Ni outer layer material with a thickness of 2.8 @3 and a length of 806 mm, and after degreasing and cleaning the contact surfaces of both, cover the core material with the outer layer material, and prepare a 3 x 10- ”Tor
Both end surfaces of the outer layer material were sealed with Ni plates by electron beam welding in a vacuum chamber of R.

The degree of vacuum in the vacuum chamber was set to the following five conditions.

5X10-1Torr lXl0-1Torr
3X10-”Torr3×10zuTorr 3
Xl0-1 Torr Next, the clad material 10 thus obtained was heated to 800°C and then subjected to inclined rolling using a cross-type inclined rolling mill having three cone-shaped rolls.

The inclined rolling conditions are as follows.

Intersection angle γ: 3° Inclination angle β: 13° Roll gorge diameter: 117 Roll material: SCl'1440 Roll rotation speed: 80 rpm Area reduction: 88.5% (60.3 mm - 20.5 mm) Manufactured clad material In order to investigate the bonding strength of
Two test pieces were prepared for each material to be investigated using different degrees of vacuum, with the other end cut into a cylindrical part with an outer diameter smaller than the outer diameter of the core material. The outer layer material on one end of the test piece is brought into contact with the edge 25 of the circular opening with a diameter slightly larger than the diameter, and in this state, a pressing force is applied from the other end to break the core material and the outer layer material. The load P to be applied was measured, and the measured value was substituted into the following formula: Shear strength=P/(π·D−h) where D=outer diameter shear strength of the core material was determined. Table 1 shows the pressure of the vacuum chamber at 3
The shear strength when set to

As is clear from Table 1, the shear strength of the core material and the outer layer covering it in the clad material is 20 (kg, f/m1I).
IZ) or higher, indicating that a crund material with excellent bonding strength was obtained. On the other hand, in Figure 8, the horizontal axis represents the degree of vacuum (Torr), and the fir axis represents the shear strength of the clad material (k).
g, f/nu++”).

As is clear from this graph, the degree of vacuum is 10-' (T
It can be seen that the shear strength decreases rapidly when the shear strength exceeds (orr). By the way, the basic value of shear strength of titanium clad steel (JI
SG3603) is 14 kg, f/trrr
a” or more.

Therefore, when manufacturing the cladding material 10, it is desirable that the degree of vacuum in the vacuum chamber be less than or equal to I.times.10-ITorr.

Next, the clad material 14 was descaled by shot blasting, and then the clad material 14 having the dimensions shown in Table 3 was drawn using a die.

(Margin below) Table 3 One side of the path schedule is as follows.

A clad material with a diameter of 20 mm was drawn to a diameter of 20 mm, 19 mm...-7,9 mm by passing the die 10 times, then washed and heat treated, and drawn to a diameter of 3.1 mm by passing the die 10 times. A second wash, heat treatment, and 13 passes on the die to a diameter of 0.9 mm, and a third wash, heat treatment, and 15 passes on the die, to a diameter of 0.2 mm. Then, a fourth cleaning, heat treatment, and 43 passes were performed on the die to reduce the diameter to 0.
It was finished into a 025mm clad wire.

The heat treatment in each step was at 600°C (for 2 minutes to 20 minutes).
minutes) went.

When the cross section of the produced ultra-fine clad wire was observed at 2,000x magnification using a scanning electron microscope (SEM), peeling,
No defects such as oxides were observed. FIG. 9 shows a SEM photograph. This photograph shows no peeling defects at all.

〔effect〕

As described above, in the method of the present invention, the clad material is hot-stretched in an inclined rolling mill, and then cold-drawn to heat-treat the clad titanium wire rod with a diameter of 50μ or less (large joints). The present invention has excellent effects, such as being able to obtain strength and significantly reducing the manufacturing cost of clad titanium wire rods.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the main manufacturing steps in the method of the present invention, Fig. 2 is an explanatory diagram showing the assembly mode of the cladding material in the method of the present invention, and Fig. 3 is hot stretching by an inclined rolling mill in the method of the present invention. A front view showing the rolling process, FIG. 4 is a sectional view taken along the line ■-■ in FIG. 3, and FIG. 5 is a cross-sectional view taken along the line V-- in FIG.
A side view taken along the V line, FIG. 6 is a schematic diagram showing the cold wire drawing process in the method of the present invention, FIG. 7 is a schematic diagram showing the aspect of the shear strength test of the test piece, and FIG. A graph showing the relationship between the degree of vacuum and shear strength, and FIG. 9 is an SEM photograph of a cross section of an ultra-fine diameter clad wire obtained by the method of the present invention. 1.2.3...Rolling roll

Claims (1)

[Claims] 1. A core material made of Ti or Ti-based alloy is covered with an outer layer material made of Ni or Ni-based alloy, and the inside of this outer layer material is 1 x 10^
- A step of assembling the cladding material by keeping it in a vacuum state of 1 Torr or less and sealing it, heating the cladding material to 850°C or less and stretching and rolling it with an inclined rolling mill having three or more cone-shaped rolls, and forming the outer layer. A method for producing a clad titanium wire comprising the steps of diffusion bonding a material and a core material, and cold drawing the stretched and rolled material to a diameter of 50 μm or less.