JP2001046248A - Vacuum double container made of stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make fouling and odors hard to remain, and also, easy to remove, and improve both of the heat insulating property and the outer appearance by applying an electrolytic polishing treatment on the internal surface of an internal container, and also, specifying the surface roughness Rz of the treated surface. SOLUTION: For this vacuum double container made of stainless steel, an internal container 1 and an external container 2 made of stainless steel are doubly combined with a gap, and a vacuum heat-insulating space 3 is formed between the internal and external containers. Then, the internal surface of the internal container 1 is a smooth surface having a gentle uneven shape, on which, an electrolytic polishing treatment is applied without a blast treatment. In addition, the surface roughness Rz is set to be less than 0.4 μm, and the heights of the indented sections and the protruding sections when being microscopically seen are kept small, and contamination is hard to enter and hard to settle down. Also, even when contamination enters the indented sections, the contamination is easy to remove by washing with water or the like. Therefore, the vacuum double container is hard to stain, and odors do not remain as well. Also, as the smoothness of the internal container 1 increases, the outer appearance of the surface is improved, and the heat-insulating property by the vacuum double container structure made of stainless steel having a low heat conductivity is improved as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel vacuum double container, and mainly to a stainless steel vacuum double container used for food and drink insulated containers, for example, portable or stationary heat insulating bottles, electric pots, and lunch jars. It concerns a container.

2. Description of the Related Art Conventionally, a portable heat-insulating bottle using a stainless steel vacuum double container is made of SUS304 as the material of stainless steel, and the inner surface of the inner container is subjected to electric field polishing or blasting. Post-fluororesin coating has been performed. Electropolishing is performed using an electrolytic solution containing phosphoric acid and sulfuric acid as main components, and the inner surface of the treated inner container becomes a clean smooth surface from which dirt such as welding scale has been removed, and has good appearance and corrosion resistance. As it improves, it is used as it is. The fluororesin coating film serves as a decoration on the surface, has good releasability, and is easy to care for.

However, such a stainless steel vacuum double container is limited to green tea,
Many types of tea, such as black tea, oolong tea, coffee, water, sake, soup, and soft drinks, are put in and widely used.In normal use conditions that can be easily washed with a neutral detergent, scale, tea astringent, The adhesion of stains such as coloring cannot be completely prevented, and the residual odor has become a problem relatively early in the case of using different kinds of beverages. As a result, the present inventors conducted various experiments and conducted repeated studies, and as a result, it was found that the surface smoothness was not so much increased by any of the above surface treatments, that dirt and smell were easily attached and remained easily. did. Although the inner surface of the inner container is apparently finished to a smooth surface by the conventional electrolytic polishing, the surface roughness Rz is 4.0 μm or more, and when observed microscopically, as shown in FIGS. In addition, there are numerous crater-shaped or void-shaped recesses a on the inner container surface. For this reason, the fine particle component in the beverage enters the concave portion a and easily adheres to the concave portion a, and it is difficult to remove the fine particle component. The inner surface of the inner container coated with fluorocarbon resin has been considered to be less likely to adhere to dirt due to its releasability and water repellency.
Even in the early stage of use, it is not practically easy to prevent dirt and easy care. This is due to the fact that the odor is easily adsorbed as a property of the fluororesin, and the influence of irregularities formed on the surface of the inner container due to the blast treatment before coating. There are numerous void-like or crater-like concave portions b as shown in FIG. 6, and dirt easily adheres to the surface over time as in the case of the conventional electrolytically polished surface, and is difficult to remove.
SUMMARY OF THE INVENTION An object of the present invention is to provide a stainless steel vacuum double container which has been subjected to an electropolishing treatment, is less likely to leave dirt and odor, is easy to remove, and has excellent heat retention and appearance.

In order to achieve the above object, a stainless steel vacuum double container according to the present invention comprises:
A stainless steel inner container and an outer container are double-coupled with a gap therebetween, a vacuum space is formed between the inner and outer containers, the inner surface of the inner container is subjected to electric field polishing treatment, and the surface roughness Rz is 4.0 μm. The main feature is that it is less than. In such a configuration, the inner surface of the inner container is a smooth surface having a gentle uneven shape subjected to electropolishing without blasting, and further, the surface roughness Rz is less than 4.0 μm, and the inner surface has a concave portion as viewed microscopically. Since the difference in the heights of the protrusions is kept small, dirt hardly enters and hardly deposits, and even if it enters the concave portion, it can be easily removed by washing with water or the like. Therefore,
It is hard to be stained and the smell is hard to remain. In addition, the appearance of the surface is improved by the degree that the microscopic smoothness of the surface of the inner container is improved, the reflectance of radiant heat is increased, and the inner container is made thinner by electropolishing, so that heat conduction can be suppressed. As a result, it becomes difficult for heat to escape to the outside, which leads to a further improvement in heat retention by a vacuum double container structure made of stainless steel having low heat conductivity. The smaller the surface roughness Rz, the smaller the difference between the heights of the concave and convex portions of the surface. If the surface roughness Rz of the inner surface of the inner container becomes 1.5 μm or less, the appearance becomes visually specular. In addition, the adhesion of the fine particles in the beverage can be almost certainly prevented, and the attached fine particles can be very easily removed by washing with water. further,
When the surface roughness Rz of the inner surface of the inner container is 0.7 μm or less, the adhesion of the fine particles in the beverage can be reliably prevented,
The surface condition is a substantially smooth surface with almost no irregularities and a perfect mirror surface. The stainless steel that is the material of the inner container is Md
When the value of 30 (° C.) is less than −50, stainless steel as a material of the inner container is susceptible to SUS3 in which work-induced martensite is liable to be generated by pipe expansion or drawing.
Even austenitic stainless steel such as 04,
Since the amount of work-induced martensite generated by processing such as forming the inner container by deep drawing and the roughening that the work-induced martensite brings to the surface of the inner container are suppressed, the subsequent electric field polishing As long as this is performed to the extent of the conventional art, the above condition of the surface roughness Rz of 0.4 μm or less is satisfied, and there is no particular difficulty in surface treatment, and a good yield can be obtained at a low cost. Stainless steel, which is the material of the inner container, has a nickel or nickel + copper content of 10%.
% Or more and 14% or less, the content of nickel or nickel + copper while preventing the content of nickel or nickel + copper from exceeding 14% and causing cracks during processing. Falls below 10% and Md30
(° C.) is also prevented from exceeding −50, and the surface condition required for the inner surface of the inner container can be stably obtained with a good yield. Such features include nickel or nickel + copper,
Is more than 11% and less than 13%. The stainless steel used for the inner container is SUS304L or SUS among austenitic stainless steels.
XM7 is particularly suitable for workability and surface finish. Further objects and features of the present invention will become apparent from the following detailed description and drawings. Each feature of the present invention can be used alone or in combination in various combinations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings together with the embodiments to provide an understanding of the present invention. This embodiment is an example of a case where the present invention is mainly applied to a portable heat-insulating bottle for beverages. However, it is not limited to this, it is hard to get dirty,
In addition, the present invention can be applied to various stainless steel vacuum double containers that want to easily remove dirt, and can be used in a stationary state, or in an electric pot equipped with a heating source, or in a thermal insulation container for food other than beverages. Good. As shown in FIG. 1, the vacuum double container of the present embodiment has an inner container 1 and an outer container 2.
Are double combined to form a vacuum insulation space between them. The inner container 1 and the outer container 2 are both SUS304, SUS304L, SUS made of austenitic stainless steel.
It is formed of XM or the like and is welded at the mouth 4. In FIG. 1, P indicates a welded joint of the mouth 4. Mouth 4
The inner container 1 has a screw thread 5 screwed to a not-shown mouth member, and the outer container 2 of the mouth portion 4 has a screw thread 6 screwed to a not-shown lid. Further, the outer container 2 at the bottom 7 has an opening 8 for evacuation, and the vacuum heat insulating space 3 is evacuated through the opening 8.
It is joined to the opening 8 by soldering or other methods in an airtight manner.
Is sealed so that the vacuum state is maintained. The sealing of the opening 8 is performed by using a sealing material without the cover plate 9.
It can be performed only by melt-filling and then solidifying. In particular, in the present embodiment, the inner surface 1a of the inner container 1 is subjected to the electric field polishing treatment, and the surface roughness Rz is set to less than 4.0 μm. The surface roughness Rz is, as is well known, "JI
It shows the "ten-point average roughness" defined in "SB 0601". Those configured in this way,
Since the inner surface 1a of the inner container 1 is subjected to the electropolishing treatment without the blast treatment, the inner surface 1a has a smooth surface having a gentle uneven shape. In addition, the surface roughness Rz is reduced to less than 4.0 μm by the electric field polishing treatment, and the difference between the height of the concave and the convex when viewed microscopically is suppressed to a small value. Therefore, the inner surface 1 of the inner container 1
a does not have a large concave portion caused by the conventional electric field polishing or the surface treatment of the fluororesin coating, it is difficult for dirt to enter and hard to deposit, and even if it enters the concave portion, it is easily removed by washing with water or the like. Also, it does not work to adsorb odors such as fluororesin. As a result, it becomes difficult to stain over a long period of time, and the smell hardly remains. In addition, inner container 1
The appearance of the surface improves as much as the microscopic smoothness of the inner surface 1a surface improves, the reflectance of radiant heat increases, and the inner container 1 is thinned by the high polishing effect of electric field polishing to suppress heat conduction. In addition to the fact that the heat is hard to escape to the outside, it is possible to further improve the heat retention by the stainless steel vacuum double container structure having low heat conductivity. The high polishing effect by electropolishing also contributes to the weight reduction of the vacuum double container. The smaller the surface roughness Rz, the smaller the difference between the heights of the concave and convex portions of the surface. If the surface roughness Rz of the inner surface 1a of the inner container 1 becomes 1.5 μm or less, an appearance state that can be visually regarded as a mirror surface Thus, adhesion of the fine particles in the beverage can be almost certainly prevented, and the attached fine particles can be very easily removed by washing with water. Furthermore, when the surface roughness Rz of the inner surface 1a of the inner container 1 is 0.7 μm or less, the adhesion of the fine particles in the beverage can be surely prevented, and the surface state is a substantially smooth surface with almost no irregularities and a perfect mirror surface. Becomes In a study by the present inventors to satisfy the above-described surface roughness by electropolishing, the surface roughness of the inner surface 1a of the inner container 1 before the electropolishing treatment has a large effect, and this is considered to be a predetermined surface roughness. The surface roughness Rz of less than 4.0 μm required by conventional electric field polishing when suppressed below
And found that it can be obtained stably. In particular, inner container 1
By setting the value of Md30 (° C.) for the stainless steel as the material, the inner surface 1a of the inner container 1 before the electropolishing was easily and stably operated so that the surface roughness of the inner surface 1a was within a necessary range. This is based on the Md30 (° C.) method for determining the degree of occurrence of the work-induced martensite by determining the degree of occurrence of the work-induced martensite by roughening the surface of the inner container 1 by the work-induced martensite generated at the time of expanding or drawing austenitic stainless steel. Therefore, this is an operation for suppressing the generation amount of the work-induced martensite to a predetermined amount or less. Md30 (° C.) = 551-462 (C + N) −9.2
(Si) -8.1 (Mn) -13.7 (Cr) -29
Operate according to (Ni + Cu) -18.5 (Mo) -68 (Nb). According to experiments by the present inventors, Md3
By setting the conditions so that the value of 0 (° C.) is less than −50, the stainless steel as the material of the inner container 1 is
SUS304, SUS304S, SU in which work-induced martensite is likely to be generated by pipe expansion or drawing
Even with austenitic stainless steel such as S304L and SUSXM7, the amount of work-induced martensite generated by processing such as forming the inner container 1 by deep drawing, and the amount of the work-induced martensite on the surface of the inner container 1 The surface roughness Rz of 0.4 μm or less is satisfied as long as the subsequent electropolishing is performed to the extent of the prior art, since the surface roughening or matte finish caused by the above is suppressed. There was no particular difficulty in the surface treatment, and the yield was good and the cost was low. By adding something in the operation of Md30 (° C), the value of Md30 (° C) decreases. When a large amount of Ni as a main element is added, the value of Md30 (° C.) tends to decrease. Further, since Cu has the same coefficient as Ni, it shows the same tendency. FIG. 2 shows the relationship between Ni and the value of Md30 (° C.), and FIG. 4 shows the relationship between Ni + Cu and the value of Md30 (° C.). On the other hand, components other than Ni and Cu originally have a small content, so that it is difficult to change the content%, and if changed, the workability and durability are affected, so that it is difficult to operate. For example, when the content of C is increased, intergranular corrosion is likely to occur, which makes the alloy unsuitable for practical use. In addition, since the content of Ni excessively increases the workability, it is preferable that the Ni content is set to about the maximum value of SUS304L. As an example, the stainless steel as the material of the inner container 1 has a content of nickel or nickel + copper of 10%.
As described above, when the content is 14% or less, the content of nickel or nickel + copper is prevented while preventing the content of nickel or nickel + copper from exceeding 14% and causing cracks during processing. Md30 below 10%
(° C.) is also prevented from exceeding −50, and the surface condition required for the inner surface of the inner container can be stably obtained with a good yield. Such features include nickel or nickel + copper,
Is more than 11% and less than 13%. Copper has a solid solution limit of 4 for stainless steel.
-5%, but Md30
It is effective for use in manipulating the value of (° C.). As an example, 1
8.2Cr-11.3Ni-Low C high NiSUS304
When set to L, the value of Md30 (° C) is -70,
SUSXM7 of 18.2Cr-8.9Ni-3.2Cu
, The value of Md30 (° C.) is -100, which is preferable. (Embodiment 1) The vacuum double container as described above is manufactured in the process shown in FIG. This will be described below. High Ni above
An inner container body 1b, an inner container bottom 1c, an outer container body 2b, and an outer container bottom 2c made of SUS304L are constituent members. The inner container body 1b and the inner container bottom 1c are welded in advance and assembled to form an inner container 1. The inner container 1 is also pre-plated with copper. Such an inner container 1 and the outer container body 2b are double-combined and welded and joined at the mouth 4 to be integrated with the quasi-double container A. Such a quasi-double container A is welded and joined to the outer container bottom 2c to form a double container B. The double container B is formed as a vacuum double container C by sealing the opening 8 in a state where the vacuum heat insulating space 3 is evacuated by vacuum evacuation through the opening 8 in a vacuum heating furnace. In the state of the vacuum double container C, the inner surface 1a of the inner container 1 is mirror-processed by electric field polishing. This mirror processing is shown in FIG.
As shown in FIG. 3, the electrode 11 is inserted into the inner container 1 in a state where the vacuum dual container C is immersed in the electrolytic solution 12 up to a position near the upper part of the shoulder 10 with the mouth portion 4 facing down. The surface of the outer container 2 at the entire inner surface 1a of the inner container 1, the mouth portion 4, and the shoulder portion 10 is subjected to the electrolytic polishing in a state where the electrolytic solution 12 is ejected from the tip.
Note that the electrolytic polishing uses an electrolytic solution 12 mainly composed of phosphoric acid. After the mirror processing, the vacuum double container C is inspected for its heat retaining performance, and the outer surface of the body is polished or painted as necessary. In the first embodiment, Md30 (° C.) is reduced while preventing the Ni or Ni + Cu content from exceeding 14% from generating cracks during processing.
Inner container 1 due to significantly lower than 70 and -50
The surface condition required for the inner surface 1a can be stably obtained with a high yield. As shown in FIG. 2C, the entire inner surface 1a of the inner container 1 and the surface on which the outer container 2 has been subjected to the electropolishing by the electropolishing are surface states that can be visually regarded as mirror surfaces. Became. The surface roughness Rz at this time is 0.1
It was about 3 μm. (Example 2) This is different from Example 1 in that a vacuum double container C made of the above SUSXM7 material having a value of Md30 (° C) of -100 is used. The other configurations are not particularly changed, and overlapping illustrations and descriptions are omitted. In the present embodiment, the entire inner surface 1a of the inner container 1 and the surface of the outer container 2 on which the electropolishing is performed by the electropolishing are shown in FIG.
As shown in FIG. 5, the inner surface state of the inner container 1 was a smooth surface with almost no irregularities and a perfect mirror surface, and the surface roughness Rz was about 0.25 μm. Table 1 below
Are the inner surface of the inner container for each of the surface treated by the conventional electropolishing (conventional example 1), the surface treated by the conventional fluororesin coating (conventional example 2), and the embodiments 1 and 2. Shows the results of measuring the surface roughness of the sample. In addition, the surface roughness Rz, the surface roughness Rmax
Are "center line average roughness" and "maximum height" defined in "JIS B 0601", respectively.

[Table 1]

According to the present invention, as is apparent from the above description, dirt and smell such as water scale and tea astringent hardly remain, and dirt and smell can be easily removed by ordinary washing such as washing with water. It is possible to provide a vacuum double container made of stainless steel which has excellent properties and aesthetic appearance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a vacuum double container of Example 1 according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing a cross-sectional shape of an inner surface of an inner container, comparing Conventional Examples 1 and 2 and Examples 1 and 2 of the present invention with (a) to (d).

FIG. 3 is a graph showing a relationship between Ni and Md30 (° C.).

FIG. 4 is a graph showing a relationship between Ni + Cu and Md30 (° C.).

FIG. 5 is an enlarged view of the inner surface of the inner container of Conventional Example 1 at a magnification of 200 times.

FIG. 6 is a diagram showing the inner surface of the inner container of Conventional Example 2 at a magnification of 500 times.

FIG. 7 is a diagram showing the inner surface of the inner container of Example 2 enlarged 200 times.

FIG. 8 is a flowchart showing a process of forming the vacuum double container of the first embodiment.

FIG. 9 is a conceptual diagram of an electric field polishing process adopted in Examples 1 and 2.

[Explanation of symbols]

 1 inner container 2 outer container 3 vacuum insulation space

Claims (9)

[Claims] A stainless steel inner container and an outer container are double-coupled to each other with a gap provided therebetween, and a vacuum space is provided between the inner and outer containers. Polished and its surface roughness R
A stainless steel vacuum double container, wherein z is less than 4.0 μm. 2. The stainless steel vacuum double container according to claim 1, wherein the surface roughness Rz is 1.5 μm or less. 3. The stainless steel vacuum double container according to claim 1, wherein the surface roughness Rz is 0.7 μm or less. 4. The stainless steel used for the inner container is made of Md.
The value of 30 (° C) is less than -50.
The stainless steel vacuum double container according to any one of the above. 5. The stainless steel vacuum double container according to claim 1, wherein the stainless steel as the material of the inner container has a nickel content of 10% or more and 14% or less. . 6. The stainless steel vacuum double container according to claim 1, wherein the stainless steel as the material of the inner container has a nickel content of 11% or more and 13% or less. . 7. The stainless steel vacuum cylinder according to claim 1, wherein the stainless steel as the material of the inner container has a nickel + copper content of 10% or more and 14% or less. Heavy container. 8. The stainless steel vacuum cylinder according to claim 1, wherein the stainless steel as a material of the inner container has a nickel + copper content of 11% or more and 13% or less. Heavy container. 9. The stainless steel as the material of the inner container is SU
The stainless steel vacuum double container according to any one of claims 1 to 8, which is S304L or SUSXM7.