JPH11138261A - Manufacture of welded pipe of high melting point metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for the manufacturing of a welded pipe with which the welded pipe of a high accuracy is continuously manufactured and a metal having a high melting point is prevented from oxidation after being welded. SOLUTION: The surroundings of a welding torch of a welding machine for pipe manufacturing is enclosed with a shield box 1. In welding process, a pipe P of metal having a high melting point is welded in the shield box 1 which is filled with inert gas. In cooling process, a pipe outlet of the shield box 1 is provided with a cooling pipe 3 and the pipe P after being welded is cooled with cooling gas held in the cooling pipe 3. The cooling pipe 3 is of double pipes and the inside of the cooling pipe 3 is cooled with cooling gas which passes in the same. The pipe P after being welded which is projected out from the cooling pipe 3 is cooled again by spraying cooling inert gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a welded pipe made of a high melting point metal such as molybdenum, tantalum, niobium, hafnium and the like mainly used for materials for the chemical industry and electronic parts.

[0002]

2. Description of the Related Art A conventional method of manufacturing a pipe using a rare metal having a high melting point, such as molybdenum, tantalum, niobium, or hafnium, as a pipe material, involves drilling a rod material, cutting the material, and processing the inner and outer diameters. It was formed in a tubular shape. On the other hand, other than rare metals, for example, a method for manufacturing a stainless steel tube is as follows.
Continuous roll forming of hoop rolled material
A method for manufacturing a welded pipe by IG welding is known.

Further, means for preventing the oxidation of the welded portion by sealing the welded portion with a shielding gas at the time of welding the welded pipe is described in Japanese Utility Model Application Laid-Open No. 58-47390 and Japanese Patent Application Laid-Open No. 8-174251. I have. These conventional shielding gas shielding means are means for spraying a shielding gas onto a welding portion, locally sealing the welding portion in an oxygen-free state, and performing welding.

[0004]

However, in the conventional method of manufacturing a rare metal pipe by boring and cutting, the yield of the pipe material is extremely low, and the pipe material is expensive. Also, in the method of manufacturing pipes by drilling and cutting,
The length of the pipe was limited by the performance of processing machines and jigs. The maximum length of the pipe material was 500 mm, and the minimum outer diameter was 6 mm.

On the other hand, in the conventional method for manufacturing a welded pipe, the most problem is prevention of oxidation during welding. That is, among rare metals having a high melting point, for example, molybdenum has a property of rapidly oxidizing at 400 ° C. or higher in the atmosphere. Since the temperature during this welding rises to the melting point of 2,625 ° C, unless the temperature of the welded part that has risen to 2,625 ° C is reduced to 400 ° C or less before contact with oxygen, the welded part after this welding will not It will be oxidized. As described above, in order to manufacture a welded pipe using a rare metal having a high melting point such as molybdenum, it is necessary to rapidly cool the welded pipe to a temperature at which the welded pipe is not oxidized in order to prevent oxidation after welding.

However, in the conventional shielding gas shielding means, the shielding gas is blown onto the welding portion to locally make it oxygen-free, so that the gas shielding of the welding portion is possible, but the gas shielding does not reach until after welding. The welded pipe immediately came into contact with oxygen after welding. Therefore, when a rare metal such as molybdenum having a high melting point is welded by a conventional shielding gas shielding means, even if it can be made oxygen-free at the time of welding, there is a problem that it is oxidized after welding until the weld pipe cools down. .

Accordingly, the present invention has been made in view of the above-mentioned various circumstances, and it is intended to prevent the oxidation of a material after welding and continuously produce a high-precision welded pipe. An object of the present invention is to provide a method for manufacturing a welded pipe of a high melting point metal which can be produced.

[0008]

In order to achieve the above-mentioned object, a first aspect of the present invention is a welding torch for a pipe welding machine.
In a shield box 1 filled with an inert gas, the pipe P made of a metal having a high melting point such as molybdenum, tantalum, niobium, hafnium, etc.
Process of welding the pipe and the pipe outlet 1 of the shield box 1
A cooling step of providing the cooling cylinder 3 in B and cooling the welded pipe P with the cooling gas inside the cooling cylinder 3.

Further, the cooling cylinder 3 of the present invention has a double cylinder shape, and is formed by an outer cylinder 3B and an inner cylinder 3A provided outside the inner cylinder 3A through which the pipe P after welding is inserted. The purpose is to cool the inside of the cooling cylinder 3 with the cooling gas passing through the gap.

A third object of the present invention is to solve the problem by directly injecting an inert cooling gas into the welded pipe P projecting from the cooling cylinder 3 to recool the pipe.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a method for producing a rare-metal welding pipe having a high melting point by a pipe-forming welding machine, and comprises a welding step and a cooling step.

That is, the welding step is a step of surrounding the periphery of the welding torch 2 of the pipe making machine with the shield box 1 and filling the shield box 1 with an inert gas to weld the pipe. As the inert gas, argon or the like is used. In order to fill the inside of the shield box 1 with this inert gas, the shield gas is continuously filled with the inert gas and maintained at a positive pressure equal to or higher than the atmospheric pressure to completely block the intrusion of air. is there. Reference numeral 5 shown in the figure is a box pipe for supplying an inert gas into the inside of the shield box 1. Reference numeral 6 denotes a torch pipe connected to the welding torch 2 and supplying an inert gas to the tip of the welding torch 2 in a concentrated manner. Further, reference numeral 7 is a pipe pipe for supplying an inert gas into the pipe P to be formed. In addition, by providing the sensor 4 for measuring the oxygen concentration in the shield box 1, it can be confirmed that the oxygen concentration is always 0%.

Next, the cooling step is a step of cooling the pipe P welded in the welding step to a temperature at which it is not oxidized. That is, the cooling cylinder 3 is provided at the pipe outlet 1B of the shield box 1, and the pipe P after welding is cooled by the cooling gas inside the cooling cylinder 3.
Is to cool. The cooling cylinder 3 shown in the figure has a double cylinder shape, and a cooling gas passing through a gap between the outer cylinder 3B and the inner cylinder 3A provided outside the inner cylinder 3A through which the pipe P after welding is inserted. Cools the inside of the cooling cylinder 3. At this time, the cooling cylinder 3 is provided with a supply pipe 8 for supplying a cooling gas and a discharge pipe 9 for discharging the cooling gas after cooling the pipe. Further, by using compressed air cooled to -40 ° C. as a cooling gas passing through the inside of the cooling cylinder 3, the gas is passed through the gap between the inner cylinder 3 </ b> A and the outer cylinder 3 </ b> B having a double cylinder shape. The entire length of the cooling cylinder 3 is a cooling zone. The pipe P after welding is cooled by inserting the pipe P after welding into the inside of the cooling cylinder 3 which is formed as the cooling zone.

In this cooling step, after cooling by the cooling cylinder 3, furthermore, an inert cooling gas is directly injected into the pipe P for recooling (see FIG. 3). That is, an inert cooling gas is directly injected into the welded pipe P projecting from the cooling cylinder 3 to re-cool the pipe. This inert cooling gas is, for example,
Use cooled argon gas. In the illustrated example, a hollow annular spray nozzle 3C is provided on the outer periphery of the distal end of the cooling cylinder 3, and a high-pressure inert cooling gas is blown around the pipe P from the spray nozzle 3C. An inert cooling gas is supplied from a nozzle pipe 10 to the spray nozzle 3C.

Among the rare metals having a high melting point, molybdenum (Mo) has a melting point of 2,625 ° C. in particular. ) The welding temperature is extremely high, such as 1,845 ° C, titanium (Ti) 1,730 ° C, and beryllium (Be) 1,278 ° C. Therefore, in order to further enhance the cooling effect in the cooling process, it is desirable to set the welding speed at the time of welding to be low, reduce the current value at the time of welding, and suppress the heat rise at the time of welding as much as possible (for example, 1.2 m / min. , 50A
etc). Also, by reducing the welding speed, the time for the pipe P to pass through the inside of the cooling cylinder 3 becomes longer, and the pipe P can be sufficiently cooled.

[0016]

According to the manufacturing method of the present invention, the original object is achieved.

That is, according to the first aspect, even with a metal having a high melting point, such as molybdenum, tantalum, niobium, hafnium, etc., oxidation of the material after welding can be prevented, and a highly accurate welded pipe can be continuously manufactured. . Therefore, like the conventional method of manufacturing rare metal pipes by drilling and cutting,
The inconvenience that the length of the pipe is limited by the performance of the processing machine and the jig is eliminated, and it is possible to freely manufacture high-precision pipes P from small-diameter pipes to long pipes, which were impossible by drilling and cutting. it can.

According to the second aspect of the present invention, the pipe P immediately after welding is passed through the cooling cylinder 3 so that even if the welding temperature rises up to about 2,000 ° C., the pipe P passes through the cooling cylinder 3. Thus, the heat of the pipe P can be efficiently discharged and cooled.

Further, according to the third aspect, since the pipe P cooled by the cooling cylinder 3 is further re-cooled by an inert cooling gas, it is completely cooled to an oxidation temperature or lower, and a highly accurate welded pipe can be formed. It can be manufactured continuously.

As described above, according to the present invention, even with a metal having a high melting point, oxidation of the material is prevented from the time of welding to after the welding, and a highly accurate welded pipe can be continuously manufactured. It has various industrially beneficial effects.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention.

FIG. 2 is a sectional view showing a shield box of the present invention.

FIG. 3 is a cross-sectional view of a main part showing a distal end portion of a cooling cylinder of the present invention.

[Explanation of symbols]

 P pipe 1 Shield box 1A Rotating shaft 1B Pipe outlet 2 Welding torch 3 Cooling cylinder 3A Inner cylinder 3B Outer cylinder 3C Spray nozzle 4 Sensor 5 Box pipe 6 Torch pipe 7 Pipe pipe 8 Supply pipe 9 Discharge pipe 10 Nozzle pipe

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B23K 31/00 B23K 31/00 A

Claims (3)

[Claims] 1. A welding box for a pipe making machine, which is surrounded by a shield box around a welding torch, and a metal pipe having a high melting point such as molybdenum, tantalum, niobium, hafnium is welded in a shield box filled with an inert gas. Welding process
Providing a cooling cylinder at the outlet of the welding pipe of the shield box, and cooling the welded pipe with a cooling gas inside the cooling cylinder. . 2. The cooling cylinder has a double cylinder shape,
2. The method for producing a welded pipe of a high melting point metal according to claim 1, wherein the inside of the cooling cylinder is cooled by a cooling gas passing through a gap between the outer cylinder and the inner cylinder provided outside the inner cylinder through which the welded pipe is inserted. 3. The welded pipe projecting from the cooling cylinder,
3. The method according to claim 1, wherein an inert cooling gas is directly injected for recooling.