JPH084568B2 - Manufacturing method of metal thermos - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a metal thermos bottle in which at least an outer bottle is made of titanium or a titanium alloy.

"Prior Art" Conventionally, various metal thermos having a double structure in which a space between an inner bottle and an outer bottle is evacuated is provided.

When manufacturing this type of metal thermos, an exhaust port for exhausting the gas in the void is provided in the bottom of the outer bottle in advance,
A plurality of solid brazing filler metals are arranged around the exhaust port at the bottom of the outer bottle at intervals, and vacuum heat treatment is performed with the sealing plate supported via these solid brazing filler metals, and the solid brazing filler metals are bonded to each other. The solid brazing material is melted and the exhaust port is vacuum-sealed while exhausting the gas in the gap through the gap.

In such a metal thermos, stainless steel or carbon steel is often used as a constituent material because of the ease of manufacturing method, etc., and in particular, stainless steel has corrosion resistance, low thermal conductivity, and weldability. It is used because it is excellent. However, since stainless steel and carbon steel have a large specific gravity, there is a drawback that the weight becomes heavy when used as a constituent material of a metal thermos.

Therefore, conventionally, as a lighter metal thermos,
Various materials using aluminum or an aluminum alloy as a constituent material have been proposed, but they have the drawbacks of insufficient corrosion resistance, high thermal conductivity and insufficient heat retention. Under these circumstances, recently, titanium and titanium alloys have attracted attention as materials satisfying all the conditions required in terms of thermal conductivity, corrosion resistance, specific gravity, etc., and as a metal thermos using such materials, It has been considered that at least the outer bottle is made of titanium or titanium alloy.

"Problems to be solved by the invention" However, when titanium or titanium alloy is used as a constituent material of a metal thermos, titanium is a very expensive material, and thus the price of the metal thermos is very high. There is a problem of becoming. For this reason, it is necessary to reduce the wall thickness in order to reduce the amount of titanium used as much as possible, but especially when the wall thickness of the outer bottle is reduced, there is a problem that the strength decreases. In addition, when a metal thermos bottle with a thin outer wall is manufactured and the outer surface of the obtained metal thermos is subjected to a new treatment to improve the strength, the productivity will decrease and the manufacturing cost will decrease. However, there was a problem that it would be higher.

The present invention has been made in view of the above problems, and an object thereof is to efficiently manufacture a lightweight metal thermos bottle having high strength.

"Means for Solving Problems" The present invention relates to a metal thermos bottle in which at least the outer bottle is made of a metal inner / outer bottle made of titanium or a titanium alloy, and a vacuum is provided between the inner and outer bottles. The outer plate and the outer bottle are joined at the mouth to form a double structure, and the sealing plate is supported by a solid brazing material provided with a gap around the exhaust port provided at the bottom of the outer bottle. By heating in a furnace in a vacuum state inside, the sealing plate is brought into close contact with the bottom portion, the exhaust port is sealed, and the space between the inner bottle and the outer bottle is vacuum-sealed. In the manufacturing method, the sealing plate is closely adhered to the bottom portion and after closing the exhaust port, the furnace is cooled while being kept in a vacuum state, and the temperature in the furnace is equal to or lower than the solidification temperature of the solid brazing material. When it is cooled down to this temperature, nitrogen gas is introduced into the furnace and the above titanium or Alternatively, a nitride film is formed on the outer surface of the titanium alloy.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2.

The metal thermos bottle manufactured in this embodiment has a double-layer structure in which an inner bottle 1 made of a metal such as titanium or a titanium alloy and an outer bottle 2 at least the body of which is made of titanium or a titanium alloy are joined at the mouth. The structure,
An exhaust port 3 is formed at the bottom of the outer bottle 2, and the exhaust port 3
A sealing plate 4 is joined to the periphery of the above so as to close the exhaust port 3 from the outside, and a nitride film 5 is formed on the outer surface of the outer bottle 2.

When manufacturing such a metal thermos,
The mouth portion of the inner bottle 1 and the mouth portion of the outer bottle 2 are joined by welding to make the inner bottle 1 and the outer bottle 2 have a double structure, and then exposed to at least the outer surface of the outer bottle 2. Polish the part to be used (the part that will be the exterior of the metal thermos). After doing this, the exhaust port 3 at the bottom of the outer bottle 2 is directed upward, and a plurality of solid brazing materials 6 are arranged around the exhaust port 3 on the bottom of the outer bottle 2 at intervals. The sealing plate 4 is placed on 6. After assembling the assembly shown in FIG. 1 in this manner, the assembly is placed in the furnace in this state, and then the interior of the furnace is evacuated. After this, the inside of the furnace is heated to 800 ° C. or higher and 1100 ° C. or lower to subject the assembly to heat treatment. By doing so, the gas in the gap 7 between the inner bottle 1 and the outer bottle 2 is exhausted from the gap between the solid brazing filler metals 6 and the solid brazing filler metal 6 is melted.
For this reason, the sealing plate 4 is lowered by its own weight and closes the exhaust port 3 so as to be in close contact with the bottom portion of the outer bottle 2 to seal the void portion 7 while maintaining a vacuum. After the sealing plate 4 is thus brought into close contact with the bottom of the outer bottle 2, the inside of the furnace is cooled while being kept in a vacuum state, and the temperature inside the furnace is cooled to the solidification temperature of the solid brazing material 6 or lower. At this time, nitrogen gas is introduced into this furnace. Here, the outer bottle 2 is degassed from the gas adhering to the surface thereof and released from the hydrogen gas contained therein by the heat treatment of the constituent titanium material in vacuum. At the same time, the oxide film formed on the surface of the outer bottle 2 is activated by being dissociated. Therefore, when nitrogen gas is introduced into the outer bottle 2 at a high temperature, the outer surface of the outer bottle 2 made of titanium or titanium alloy suddenly reacts with nitrogen, and the outer surface of the outer bottle 2 is nitrided.
Are formed and the outer surface is cured.

Next, the heat treatment cycle in the method for manufacturing the metal thermos bottle will be described in detail.

FIG. 3 is a diagram showing an example of a heating cycle in the method for manufacturing a metal thermos bottle, in which the solid line represents the temperature inside the furnace and the broken line represents the degree of vacuum inside the furnace.

In this heating cycle, first, the inside of the furnace containing the above assembly is evacuated to 1 × 10 ⁻⁴ Torr, and then heating is started to raise the temperature inside the furnace to 900 ° C. Then, the inside of the furnace
The solid brazing material 6 is melted by keeping the assembly at a temperature of 00 ° C. and soaking the assembly so that the sealing plate 4 is brought into close contact with the periphery of the exhaust port 3. After doing so, the solid brazing filler metal 6 is solidified by vacuum cooling, and nitrogen gas is introduced into the furnace when the temperature in the furnace reaches 800 ° C., whereby the pressure in the furnace is reduced to 50
Hold it at 0 Torr. In this way, the outer bottle 2
After nitriding the outer surface of the furnace, turn the fan to rapidly cool the inside of the furnace, and when the temperature has dropped sufficiently, the inside of the furnace is heated to atmospheric pressure (76
Return to 0 Torr) and take out the metal thermos from the furnace.

FIG. 4 is a diagram showing another example of the heating cycle in the method for manufacturing a metal thermos. In this heating cycle, after heating, it is the same as the above example until the vacuum is gradually changed, but when the temperature in the furnace drops to 800 ° C, nitrogen gas is introduced and heating is stopped to allow natural cooling. Then, nitriding treatment is performed in this state.

The thickness and hardness of the nitrided film 5 formed by such a heating cycle can be controlled by the time and temperature of reaction with nitrogen gas. For example, when a metal thermos bottle with a wall thickness of 0.4 mm is subjected to nitrogen treatment at 800 ° C. for 30 minutes by the heating cycle shown in FIG. 3, the hardness of the outer bottle 2 is , As shown in FIG.
The outer surface has a Vickers hardness (Hv) of about 1000, which decreases according to the depth from the outer surface and approaches the original hardness (Hv≈150) of the base material of the outer bottle 2.

In this method of manufacturing a metal thermos bottle, at least the portion exposed on the outer surface of the outer bottle 2 is subjected to polishing finish in advance. After that, gloss can be obtained by further performing final polishing.

“Effect of the Invention” According to the method for manufacturing a metal thermos bottle of the present invention, the outer surface of the outer bottle is subjected to the nitriding treatment. Therefore, a nitrided film is formed on the outer surface of the outer bottle, whereby It is possible to manufacture a metal thermos bottle that is hard to be scratched by hardening the outer surface of the outer bottle and is hard to dent even when dropped. Moreover,
By hardening the outer surface of the outer bottle to increase the strength of the outer bottle, it is possible to obtain sufficient strength even if the outer bottle is thinned, which reduces the amount of extremely expensive titanium used. Therefore, the manufacturing cost of the metal thermos can be reduced.

Further, according to the method for manufacturing a metal thermos bottle, since the nitriding treatment is performed at the time of cooling after the heat treatment, it is possible to increase the hardness of the outer surface without newly providing a surface treatment step, and to make a metal of high strength. The thermos can be manufactured without lowering the productivity.

Of course, the same effect can be obtained when titanium or titanium alloy is used for both the inner bottle and the outer bottle.

[Brief description of drawings]

1 to 5 are views showing an embodiment of the present invention, and FIG. 1 is a sectional view of a metal thermos bottle before heat treatment,
2 is a cross-sectional view of a metal thermos bottle after heat treatment, FIG. 3 is a graph showing an example of a heating cycle, FIG. 4 is a graph showing another example of a heating cycle, and FIG. 5 is a hardness distribution of an outer bottle. It is a graph which shows. 1 ... inner bottle, 2 ... outer bottle, 3 ... exhaust port, 4 ... sealing plate, 5 ... nitrided film, 6 ... solid brazing material, 7 ... void part.

Claims (1)

[Claims] 1. An inner bottle and an outer bottle are joined together at their mouths to manufacture a metal thermos bottle in which at least the outer bottle is made of a metal inner and outer bottle made of titanium or titanium alloy, and a vacuum is provided between the inner and outer bottles. In addition to having a double structure, the sealing plate is supported by a solid brazing material provided with a gap around the exhaust port provided at the bottom of the outer bottle, and the sealing plate is supported in a furnace with a vacuum inside. In the method for manufacturing a metal thermos bottle, in which the sealing plate is brought into close contact with the bottom portion by heating to seal the exhaust port to vacuum-seal the gap between the inner bottle and the outer bottle, the sealing plate is After sealing the exhaust port in close contact with the bottom part, the furnace is cooled while keeping it in a vacuum state, and when the temperature in the furnace is cooled to the solidification temperature of the solid brazing material or less, the furnace is cooled. Nitrogen gas is introduced to nitride the outer surface of the titanium or titanium alloy. Metal thermos manufacturing method, which comprises forming a film.