JP6301986B2 - Vacuum insulation panel and method for manufacturing the same - Google Patents

Description

  The present invention relates to a vacuum heat insulating panel suitably used for a refrigerator, a cold storage, a heat insulating wall, a heat insulating wall of a house, or the like, for example.

In recent years, energy-saving products and energy-saving technologies are being developed in various industries due to the power shortage. Vacuum insulation panels have also been developed as an energy-saving measure, and are now widely used as insulation for refrigerators and vending machines as thin, high-performance insulation.
In addition, although examination of application as a heat insulating material for houses is underway, the current vacuum heat insulating panel has a structure in which a core material such as glass wool is heat sealed with an aluminum laminate film as shown in the left figure of FIG. The ones are common.

It is generally known that vacuum insulation panels with a structure heat-sealed with an aluminum laminate film will permeate moisture from the heat-seal part and deteriorate the insulation performance. As a countermeasure, a gas adsorbent such as activated carbon or zeolite is used as a core. Although the method of sealing together with the material is adopted, there is still a problem that the heat insulation performance is halved in 7 to 8 years.
For this reason, development of the vacuum heat insulation panel which can maintain heat insulation performance over a long term is desired.
Therefore, for example, as shown in the right figure of FIG. 1, various vacuum heat insulating panels have been proposed in which a core material such as glass wool is wrapped in a high metal outer packaging material made of gas barrier, vacuumed and then welded at the end. Yes.

  In the method of Patent Document 1, a groove for discharging the air inside the panel is provided in one of the metal outer packaging materials that wrap the core material, and a method is proposed in which vacuuming is performed by an exhaust port connected to the groove and sealing is performed by welding. Has been. In this method, preliminary sealing around the groove and the exhaust port is performed by seam welding, plasma welding, or the like before vacuuming is performed in advance, and after the preliminary sealing, vacuuming is performed from the exhaust port through the groove. A vacuum insulation panel is manufactured by flattening the periphery with a press or the like and then welding the flattened groove by the same welding method.

  Further, in the method of Patent Document 2, a core material having both a thick region and a thin region is inserted into a substantially flat space formed by upper and lower metal outer packaging materials whose outer peripheral portions are welded together. Using the steps generated in the thick and thin areas, the inner surfaces of the upper and lower wrapping materials are prevented from contacting each other, and evacuation is performed after the exhaust opening is sealed while the exhaust passage is secured and the exhaust opening is sealed. Vacuum insulation panels are manufactured by welding the front.

Patent Documents 1 and 2 both propose a vacuum heat insulation panel that uses a metal outer packaging material and prevents moisture permeation from the seal part by welding to maintain the heat insulation performance over a long period of time. . It is also disclosed that a stainless steel plate is used as the metal outer packaging material and seam welding is used for welding.

JP 2009-228803 A Japanese Patent Laid-Open No. 2001-311497

Patent Documents 1 and 2 propose a method of manufacturing a stainless steel vacuum heat insulation panel by seam welding using a stainless steel plate having a high gas barrier property as a metal outer packaging material. Seam welding is a method in which two metal materials are pressurized with an electrode and a current is passed therethrough to melt and join the metal materials. Even if there is a gap between the metal materials, it is possible to perform welding while crushing the gap by applying pressure with an electrode. At least one of the outer packaging materials used in the stainless steel vacuum heat insulation panel requires processing of the bulging portion for storing the core material, and is often produced by press work with high productivity. Stainless steel sheets, especially thin plates, are prone to wrinkles in the flange, and seam welding, which can be welded while crushing the wrinkles by pressing the electrodes, produces stainless steel vacuum insulation panels. This is considered to be one of the welding methods suitable for the above.

However, there is a problem when manufacturing a vacuum heat insulation panel by seam welding. As described above, at least one of the outer packaging materials requires processing of the bulging portion for storing the core material, and is often processed into a rectangular tube shape by pressing. When a packaging material pressed into a rectangular tube shape is used, particularly when the corner R of the processed portion is small, it is difficult to weld the entire periphery of the peripheral portion by this one seam welding, so FIG. As shown in a), it is necessary to divide into a plurality of welds so that the welding lines intersect each other. In this method, the weld lines always intersect and a lap portion is generated. As shown in FIG. 2B, the nugget is regularly and stably formed in a cross section of a normal non-intersecting weld line. On the other hand, since the cross section of the lap part is welded twice at the same location, the nugget is affected at the intersection of the two lines as shown in FIGS. 2 (c) and 2 (d). If it grows excessively and an nugget-unformed site is formed in the vicinity of the intersection, a blowhole or a welded portion is generated, the frequency of occurrence of defective welds increases and productivity decreases. In addition, the material metal plate is distorted by the influence of welding heat, and as shown in FIG. 2 (e), a gap is generated between the two metal outer packaging materials with the wavy flange portion. Even in seam welding where welding is performed while crushing the gap, the phenomenon that the contact area between the electrode and the outer packaging material decreases is unavoidable, and spatter is generated during welding as the current density increases, and the core material inserted inside However, there is a problem that the thermal insulation performance is deteriorated due to damage by sputtering. These phenomena become more prominent as the plate thickness is thinner and the weld line length is longer.

  The present invention has been devised to solve such problems, and suppresses the occurrence of welding thermal distortion and spatter, and stably produces a high-performance vacuum insulation panel that does not change its performance over a long period of time. The purpose is to provide.

  In order to achieve the object, the vacuum heat insulation panel of the present invention comprises a heat-insulating core material and two outer metal plates covering the periphery thereof, and the inside of the two outer metal plates covering the core material is A vacuum heat insulating panel in which the outer peripheral metal plate is joined by welding in a vacuum state, and the welded joint is solid-phase joined in total length, and the thickness reduction rate of the joined part is 10%. It is the vacuum heat insulation panel characterized by the following.

Further, the two enveloping metal plates are a vacuum heat insulating panel characterized by being a duplex stainless steel plate having a duplex structure composed of two or more of a ferrite phase, a martensite phase or an austenite phase.

Furthermore, the manufacturing method of the vacuum heat insulation panel of the present invention is characterized in that the inside of two outer metal plates is set to a pressure of 1 Pa or less, and the peripheral edge portion of the outer metal plate is joined by seam welding by pulse energization. It is a manufacturing method.

  According to the present invention, since two outer metal plates are welded by solid phase bonding, welding is performed under a low heat input condition where no nugget is formed. Therefore, even if a stainless steel vacuum insulation panel is manufactured continuously using seam welding as in the prior art, the above-described welding failure occurs at the weld lap, deformation due to thermal strain, and spattering to the core material. It is possible to prevent damage and to stably provide a high-performance vacuum insulation panel that does not deteriorate in performance over a long period of time.

Schematic explaining the structure of the vacuum insulation panel Diagram explaining problems in manufacturing vacuum insulation panels by seam welding Exploded view of vacuum insulation panel Diagram explaining the difference between melt bonding and solid phase bonding A pulse energization mode during seam welding in the method of the present invention will be described. The figure explaining the state of intermittent nugget formation under pulse energization conditions The figure which shows the schematic structure of the apparatus used for preparation of the vacuum heat insulation panel in an Example. The figure explaining the joining form in an Example

  Hereinafter, the embodiment of the manufacturing method of a vacuum heat insulation panel is described. For example, as shown in FIG. 3, the vacuum heat insulation panel manufactured by the manufacturing method according to this embodiment wraps the core material 1 with an outer packaging material 2 made of stainless steel plate, and the inside of the outer packaging material 2 that wraps the core material 1. The space 3 is in a vacuum state.

  The core material 1 supports the outer packaging material 2 from the inside so that the outer packaging material 2 of the vacuum heat insulating panel 10 after manufacture is not crushed by atmospheric pressure. An inorganic fiber is used for the core material 1. Examples of the inorganic fiber include glass wool and ceramic fiber. It is desirable to use a core material that does not contain any binder. This is because if a core material containing a binder is used, outgas is generated from the core material over time, and the heat insulation performance may deteriorate over time. Moreover, it is better to use the thing which heat-processed the core material beforehand and removed the water | moisture content. This is because the moisture adhering to the core after the production is gasified and contributes to performance deterioration.

  The outer packaging material 2 is composed of two outer packaging plates 2A and 2B. For these outer cover plates 2A and 2B, stainless steel plates having a surface roughness Ra of 0.2 μm or less are used. Moisture is adsorbed on the surface of the stainless steel plate, and the lower the surface roughness Ra, the smaller the amount of moisture brought into the inner space of the outer packaging material. It is because it can prevent. In addition, when the stainless steel plate is solid-phase bonded in the welding process described later, the smaller the surface irregularity, the so-called Ra, the better the solid-phase bonding property. The two outer packaging plates 2A and 2B have the same shape and size at the peripheral edge. A bulging portion 4 is formed on at least one outer packaging plate 2B, and the peripheral sides of the two outer packaging plates 2A and 2B are aligned and overlapped to form a concave side surface of the bulging portion 4 of one outer packaging plate 2B. An internal space 3 is formed between the other outer packaging plate 2A. The core material 1 is accommodated in the internal space 3. The two outer cover plates 2A and 2B illustrated in the drawings are rectangular when viewed from the thickness direction.

Next, a method for manufacturing a vacuum heat insulation panel using the above-described outer packaging material and core material will be described. The vacuum heat insulation panel of the present invention is manufactured by performing evacuation in vacuum and joining the four peripheral edges of the outer packaging material by seam welding after evacuation as shown in FIG. However, under the seam welding conditions in which normal nuggets are continuously formed as described above, it is difficult to avoid poor welding at the lap where the welding lines intersect, and deformation and spatter are generated due to welding thermal strain. It is difficult to avoid damage to the core material. Furthermore, when seam welding is performed in a vacuum, the heat generated by the welding cannot be discharged to the outside, and heat is accumulated. As a result, the function of the manufacturing apparatus is degraded, and continuous operation for a long time cannot be performed. There is also a possibility of end. For this reason, it is difficult to stably manufacture a vacuum heat insulating panel capable of maintaining heat insulating performance over a long period of time under seam welding conditions in which a normal nugget is formed.
Therefore, the present inventors can avoid welding defects and various problems as described above because welding with low heat input is possible if jointing by solid phase joining using seam welding in a vacuum is possible. The present invention was reached in the process of earnestly examining the method of solid phase bonding using seam welding.

In the seam welding method, an electric current is passed in a state where the metal materials to be joined are pressed and held to generate resistance heat, and the heat is joined by the heat. Under general seam welding conditions, a nugget is continuously formed as shown in FIG. 4A, and a large depression is generated on the surface of the weld due to pressurization. Under such conditions, welding can be performed without any particular problem with one-time welding, but at locations where welding is performed twice, such as a lap, the welding current may be shunted due to the effects of the nuggets and depressions described above. It is considered that poor welding occurs due to local flow. Therefore, as shown in FIG. 4 (b), if the joining condition is low heat input (solid phase joining) so that the nugget is not formed and the generation of the depression on the plate surface is reduced, the above-described problem may occur. It was thought that the vacuum insulation panel could be manufactured stably. Therefore, an investigation was made as to whether there are solid-phase bonding conditions that can provide strength and airtightness comparable to those of melt-bonding conditions in which ordinary nuggets are formed.
As a result of repeating various preliminary experiments, even if it is a vacuum insulation panel that is solid-phase bonded by seam welding, if it is sufficiently solid-phase bonded, it has the same strength as melt bonding and can maintain airtightness It was confirmed. Details will be described below.

  First, the inventor performs a seam welding test in a vacuum of 1 Pa or less, makes welding speed constant by continuous energization, changes welding conditions such as pressure, electrode shape, and welding current, and generates a dent in the weld. The thickness reduction rate before welding was calculated, and the correlation of the nugget formation state was investigated. As a result, there is a correlation between the plate thickness reduction rate and the formation of the nugget under any conditions. Under conditions where the amount of depression is large and the plate thickness reduction rate exceeds 10% of the total plate thickness before welding, the material is used during welding. When the space between the plates is heated to the melting point or higher and the nugget is formed over the entire length of the weld and is in the normal melt-bonded state, and further, when the amount of dents is small and the plate thickness reduction rate is 10% or less, the first half of welding is solid. It became clear that there was a condition of fusion bonding in the second half of welding in phase bonding. The ratio between the solid-phase joint and the fusion joint is affected by the welding speed, the magnitude of the welding current, and the length of the weld.For example, the higher the welding current, the longer the total weld length, the higher the fusion joint ratio. In continuous energization, it has been found that it is difficult to make the entire length of the welded portion solid-phase bonded regardless of the conditions. As a cause of this, even in the case of solid-state diffusion bonding immediately after the start of welding in continuous energization, the temperature of the material rises and the amount of heat input increases due to the preheating effect of the welding performed earlier as the second half of welding. It is considered that it is difficult to uniformly heat the entire length of the weld at a temperature below the melting point.

The thickness reduction rate is obtained by the following equation with reference to FIG.
Plate thickness reduction rate (%) = (plate thickness before welding-plate thickness after welding) / plate thickness before welding x 100

The plate thickness before welding and the plate thickness after welding were both measured using a micrometer. The plate thickness before welding is the sum of the plate thicknesses of the flange portions before the two outer metal materials are welded. Further, as shown in FIG. 8 (c), the post-weld plate thickness is determined by the formation of a depression at the positions D1 to D2 across the lap portion where the welding line A and the welding line D intersect. The thickness of the portion where the thickness was the smallest was determined. The thickness of the thinnest portion was obtained for four lap portions, and the average value thereof was defined as the post-welding plate thickness.

Therefore, it was investigated whether there was a condition capable of solid-phase joining the entire length of the welded portion by welding under pulsed energization conditions (FIG. 5) in which current is intermittently supplied instead of welding with continuous energization. As a result, in the previous continuous energization, when the plate thickness reduction rate exceeded 10%, the nugget was completely formed continuously, whereas in the current pulse energization condition, the plate thickness reduction rate was 15%. It has been found that the nugget cannot be continuously formed unless it exceeds. Further, it has been found that when the plate thickness reduction rate is between 11 and 15%, melt bonding and solid phase bonding are mixed and formed at regular intervals as shown in FIG. Furthermore, under the conditions where the plate thickness reduction rate was 10% or less, no nugget was formed under any conditions. However, when a peel test of the welded part was performed under these conditions, the nugget was not in a certain current range. Although the nugget was not formed, the base material was broken, and it was confirmed that there was a solid-phase bonded region having sufficient strength.

Next, in order to investigate the influence of the degree of vacuum on the solid phase bonding, the degree of vacuum was changed between 100 and 0.001 Pa, and the same experiment was performed. As a result, the bonding state varied under conditions exceeding 1 Pa. Although it was observed, it was found that there was a region capable of solid phase diffusion bonding in a certain current range under the condition of a vacuum degree of 1 Pa or less. Moreover, it was confirmed that the higher the degree of vacuum, the wider the current range of the solid phase diffusion bonding conditions tends to be. However, in order to achieve a high vacuum, the evacuation time becomes longer and the productivity decreases. The degree is considered to be preferably in the range of 0.1 to 1 Pa for practical use.
From the above results, the welding speed is kept constant in a high vacuum of 1 Pa or less, and the welding current is intermittently adjusted so that the plate thickness reduction rate after welding falls within 10% of the total plate thickness before welding. Thus, it has been found that the entire length of the weld can be solid-phase bonded.

  By adopting the present invention, even if a stainless steel vacuum insulation panel is manufactured continuously using seam welding in a vacuum, welding is performed under low heat input conditions where no nugget is formed. Even in the region where the crosses, the nugget is not formed at the time of the first seam welding and there are few dents. Therefore, even if the second seam welding is performed, the welding current is not diverted and no welding failure occurs. Further, even if continuous welding is performed in a vacuum, the deterioration of the flatness of the flange due to welding thermal distortion and the deterioration of the function of the manufacturing apparatus due to the accumulation of heat do not occur. For this reason, it is possible to stably provide a stainless steel vacuum insulation panel having high performance and no performance change.

For the upper and lower enveloping metal plates covering the core material, stainless steel plates having a surface roughness of 0.05 μm and having a two-phase structure of ferrite + austenite phases having the components shown in Table 1 were used. The dimensions of the upper and lower outer metal plates are 220 mm × 220 mm × plate thickness 0.1 mm, and the outer dimensions match. In addition, one outer metal plate was provided with a bulging portion of 190 mm × 190 mm × 5.0 mm by press molding for accommodating the core material. The core material used was glass wool with a basis weight of about 1200 g / m ² , and the core material used was pre-heated for 3 hours in an air atmosphere furnace at a temperature of 400 ° C. Then, the core material was filled without gaps on the inner surface side of the bulging portion of one outer metal plate, and was overlapped with the other outer metal plate. Since the peripheral portions of the overlapped outer metal plates are not joined, there is a gap between the upper and lower outer metal plates over the entire circumference, which becomes an opening when evacuating in a vacuum chamber described later. .

The vacuum insulation panel was manufactured using an apparatus in which a seam welder was installed in the vacuum chamber shown in FIG. This apparatus is provided with a work table for fixing the work in the chamber, and has a structure capable of rotating the work (material to be welded) 360 ° and adjusting the position. The upper and lower outer metal plates with the core material described above were fixed to the work table, and vacuuming was performed until the degree of vacuum in the chamber became 1 Pa or less. At this time, since the vacuuming is performed through the openings on all four sides at the edge of the outer metal plate, the air inside the panel is forcibly and efficiently exhausted, and the degree of vacuum in the vacuum chamber is almost the same. Presumed to be the same. After reaching the target degree of vacuum, the envelope metal plate was welded and sealed on all four sides one by one by seam welding to complete a stainless steel vacuum insulation panel.

The seam welding machine used at this time was a single-phase AC type, and the upper electrode was disk-shaped, the lower electrode was rod-shaped and the upper electrode was welded while rotating over the lower electrode. For the upper and lower electrodes, electrodes having the same tip shape and a width of 4 mm and a curvature of 40 R are used. The welding conditions are a pressurizing force: 150 N, a welding speed: 1 m / min, an energization time on / off: 2/1 ms, The welding current was changed and the thickness reduction rate of the welded part and the joining state (unjoined or melted joint or solid-phase joint / strength / sputtering presence / absence) were investigated. The plate thickness reduction rate was calculated by measuring the total plate thickness before and after welding with a micrometer as described above. As for the joined state, a sample was cut out from a part of the seam welded lap portion, and the joined state was judged by cross-sectional observation and a peel test. The experimental results will be described below.

Table 2 shows the experimental results. Under the conditions of a welding current of 0.6 kA and 0.8 kA at which the sheet thickness reduction rate corresponding to the product of the present invention is 10% or less, the base material has sufficient strength to break despite the fact that the nugget is not formed. It was confirmed that solid-phase bonding was performed. Moreover, no spatter was generated and no damage to the core material was observed. On the other hand, under conditions where the plate thickness reduction rate not exceeding the present invention exceeds 10%, the welding current is 1.0 kA or more, all of which have sufficient strength, but a nugget is formed and melt-bonded. It was confirmed. In addition, spatter was generated inside, and in the vicinity where spatter was generated, traces of damage to the core material were observed.

Then, performance evaluation was implemented about the vacuum heat insulation panel made as an experiment on the conditions whose welding current is 0.6 kA, 0.8 kA, and 1.0 kA. The performance of the vacuum heat insulation panel was evaluated by measuring the heat conductivity under the condition that the average temperature at the center of the vacuum heat insulation panel was 25 ° C. using a thermal conductivity measuring device HC-074 / 200 manufactured by Eiko Seiki Co., Ltd. As a result, the conditions (welding current: 0.6 kA, 0.8 kA) at which the sheet thickness reduction rate corresponding to the product of the present invention is 10% or less are both thermal conductivity 2.5 mW / m · K. It was. Moreover, the condition (welding current: 1.0 kA) where the plate thickness reduction rate evaluated for performance exceeds 10% as a comparison is that the thermal conductivity is 3.3 mW / m · K, and the core material is damaged. It is presumed that the performance slightly deteriorated.
As described above, in the case of the product of the present invention as described above, it was confirmed that a product with good performance was obtained without spattering because the entire welding length was joined by solid phase joining.

Claims (2)

A core material having a heat insulating property, made from two of the outer cover metal plate covering the periphery, the periphery of the interior of the outer hull metal plate two covering the core material is a vacuum state the outer hull metal plates welded a vacuum insulation panel which is joined by the joining portion by welding is a full-length solid-phase bonding, and there the sheet thickness reduction rate of the junction Ru der 10% or less in vacuum insulation panel manufacturing method of And
A method for manufacturing a vacuum heat insulating panel, wherein the inside of the two outer metal plates is set to a pressure of 1 Pa or less, the welding speed is constant, and the peripheral portions of the two outer metal plates are joined by seam welding by pulse energization . The outer hull metal plate metal structure ferrite phase, Ru dual phase stainless steel der having a duplex structure comprising two or more of the martensite phase, or austenite phase, the production of vacuum insulation panel according to 請 Motomeko 1 Way .

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