JP3350768B2 - Pipe manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a seamless pipe of metal or alloy, particularly a seamless pipe which is difficult to weld or draw.

[0002]

2. Description of the Related Art Conventionally, as a method for manufacturing a seamless thin long tube (tube) made of a metal or an alloy, a billet obtained by melting and casting is formed into a cylindrical coarse tube by machining, and the thickness is increased by hot extrusion. A method is generally used in which a long tube of several mm is manufactured by drawing a plug. Also, the above-mentioned rough pipe is often obtained by powder molding and casting. On the other hand, as a production of a thin short tube, there are electric discharge machining, laser machining, drilling, drawing, and the like.

[0003] In addition, TiNi-based shape memory alloys, which are one of the difficult-to-process materials, have been increasingly used for piping joints, heat pipes, medical catheters and the like. As a method for manufacturing these tubes, in the case of a short tube, cutting and electric discharge machining are technically sufficiently possible. However, in the case of a tube, lengthening of the welded pipe by wire drawing has been studied, but a method of manufacturing a seamless pipe has not yet been proposed.

[0004]

A rough tube for obtaining a tube is usually manufactured by cutting a billet into a cylindrical shape as described above. However, in this conventional method of manufacturing a tube, the raw material is processed. The yield decreases in accordance with the amount of the hollow. Furthermore, when the material of the pipe is a difficult-to-process material, the hollowing method is special, and the processing cost is high. As an example, in the case of a TiNi-based shape memory alloy, the machinability of a TiNi alloy, particularly the machinability by a drill, is extremely poor due to the shrinkage of the diameter and the change in hardness due to the heat generated by the work, and the work due to early wear of the tool. A major problem remains in terms of performance and cost.

Further, when considering the lengthening of a pipe, the conventional method of manufacturing a pipe has a limit of 5 to 10 times the diameter of a drill when drilling, and the diameter of the drill can be reduced to 10 times by electric discharge machining. The limit is ~ 20 times.

[0006] Further, in consideration of application to medical catheters, the dimensions of a tube need to be 500 mm or more with respect to a diameter of 1 to 2 mm, and the conventional method of manufacturing a tube is completely compatible with these processes. Was not possible.

On the other hand, recently, the production of a small-diameter long tube which can be used for a catheter or the like by drawing a welded pipe has been studied. There is a difficulty in the reliability of the mechanical strength of the seam.

An object of the present invention is to reduce the manufacturing cost of a metal or alloy tube and make it difficult to process a material such as TiN
It is an object of the present invention to provide a method of manufacturing a pipe capable of realizing a seamless pipe of an i-type shape memory alloy.

[0009]

According to the present invention, there is provided a method of manufacturing a seamless pipe, comprising holding a metal or an alloy as a molten metal having a temperature equal to or higher than its melting point, and forming one end of a cooling pipe end face on the surface of the molten metal. A method of manufacturing a pipe is provided, wherein the gas is substantially sucked into the cooling pipe at the same time as the molten metal.

[0010]

Embodiments of the present invention will be described below.

FIG. 1 schematically shows an embodiment of a method for manufacturing a tubular tube according to the present invention.

In the first embodiment, Ti-50.5 at%
Heat Ni alloy in an argon atmosphere (1450 ° C)
Then, the molten metal 2 was held in the graphite crucible 1. Next, a suction tube 3 made of quartz (inner diameter φ5 mm) was brought close to the melt surface 2a, and the melt 2 was sucked up together with the gas 4 through the suction tube 3 at a suction pressure of 10 Mpa to produce a seamless tube.

Here, a tube production test was performed by changing the gap g between the suction tube 3 and the molten metal 2 and the suction angle θ of the suction tube 3 with respect to the surface of the molten metal, and the results shown in Table 1 were obtained. Obtained.

[0014]

[Table 1] In Table 1, the gap g between the molten metal 2 and the suction pipe 3 indicates the distance between the molten metal surface 2a and the tip of the suction pipe 3, and the minus sign indicates that the tip of the suction pipe 3 has penetrated into the molten metal 2. Means that. The suction angle θ is 0 degree when the suction pipe 3 is parallel to the melt surface 2a, and the suction pipe 3 is
A state perpendicular to a is 90 degrees, and 30 to less than 90 degrees means a contact angle in a state where a part of the suction pipe 3 is in contact with the molten metal 2.

According to the results shown in Table 1, it is necessary to suction the molten metal 2 into the suction pipe 3 simultaneously with the gas 4 and to solidify the molten metal 3 on the inner peripheral surface of the suction pipe 3 to obtain a tubular seamless pipe. It has become clear that a part of the suction pipe 3 is preferably brought into contact with the molten metal 2 and the suction angle θ of the suction pipe 3 should be within 60 degrees. No. 1 in Table 1. In 8, a tube was obtained, but a hole was found in a part of the tube.

Here, the suction angle θ of the suction pipe 3 depends on the viscosity of the molten metal 2, and the suction pressure depends on the diameter of the suction pipe 3 and the viscosity of the molten metal 2.

In the second embodiment, Fe5 wt% -Al1
0 wt% -Si alloy was placed in an alumina crucible 1 ′
A manufacturing test similar to that of the first embodiment was performed by changing the suction pressure of the suction pipe 3 to the melt 2 ′ at 00 ° C. Table 2 shows the results.

[0018]

[Table 2] From this result, whether or not the pipe can be manufactured in the second embodiment depends on the gap g between the molten metal 2 ′ and the suction pipe 3 and the suction angle θ.
And the suction pressure. That is, in order to obtain a predetermined pipe, the gap g is set to be equal to or less than a distance at which the molten metal 2 ′ can be sucked (this condition is determined by the suction pressure and the molten metal viscosity), and the suction angle θ is set so that the gas 4 and the molten metal 2 ′ are simultaneously formed. Any condition can be used as long as it can be sucked.

In the third embodiment, Ti-50.5 at%
The Ni alloy was held as a molten metal 2 in a graphite crucible 1 under an argon atmosphere. Next, a suction tube 3 made of quartz (inner diameter φ5
mm) was inserted into the molten metal 2 by about 2 to 5 mm, and the molten metal 2 was sucked.

When the suction length of the molten metal 2 became 50 mm, the suction pipe 3 was quickly pulled out onto the molten metal surface 2a, and argon was sucked to produce a pipe.

Here, when various conditions were changed and the feasibility of manufacturing the tube was investigated, the results shown in Table 3 were obtained.

[0022]

[Table 3] As is apparent from FIG. Under conditions other than 16, the production of tubes was all possible. That is,
In the third embodiment, when sucking the argon after the suction of the molten metal 2, the viscosity of the molten metal 2 cooled in the suction pipe 3 is maintained at such a level that argon can be introduced into the center of the suction pipe 3. If it is, a predetermined tube can be manufactured. In the third embodiment, the suction length of the molten metal 2 is set to 50 mm. However, the suction length of the molten metal 2 can be set arbitrarily according to the size and shape of a tube to be obtained. it can.

[0023]

According to the present invention, the production cost of metal or alloy tubes can be reduced, and difficult-to-machine materials such as Ti
A seamless tube of a Ni-based shape memory alloy can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the configuration of an embodiment of a pipe manufacturing method according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 graphite crucible 1 'alumina crucible 2, 2' molten metal 3 suction pipe 4 gas g gap between molten metal 2 (2 ') and suction pipe 3 θ suction angle of molten metal 2 (2')

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B22D 18/06 B22D 25/02

Claims (1)

(57) [Claims] 1. A method for manufacturing a seamless pipe, comprising: holding a metal or an alloy as a molten metal having a temperature equal to or higher than its melting point;
Method for producing a tube, characterized in substantially suck it simultaneously gas and touches the molten metal portion of the cooling tube end face to the surface of the molten metal to the cooling tube.