PARK SANG HYUCK (KR)
LEE HWANG GU (KR)
HAN JEONG WHAN (KR)
PARK SANG HYUCK (KR)
LEE HWANG GU (KR)
| WO1996024701A1 | 1996-08-15 |
| DE4445007A1 | 1996-06-20 | |||
| DE4434425A1 | 1996-03-28 |
| 1. | A method for manufacturing kitchenware, comprising the steps of : (a) forming a main body of said kitchenware with a magnesium alloy; and (b) coating protective films onto a surface of said formed main body. |
| 2. | The manufacturing method defined in claim 1, wherein said step of coating said protective films comprises a step of anodizing said surface of said main body of said kitchenware. |
| 3. | The manufacturing method defined in claim 1, wherein said step of coating said protective films comprises the steps of anodizing said surface of said main body of said kitchenware and coating it once or more with Teflon. |
| 4. | The manufacturing method defined in claim 2 or 3, wherein said anodizing step comprises the steps of cleansing said main body of said kitchenware, immersing said main body into an aqueous solution containing fluoride ions, and anodic oxidizing said main body. |
| 5. | The manufacturing method defined in claim 4, wherein voltage applied in said anodic oxidizing step is higher than 150 Volts. |
| 6. | Kitchenware manufactured by the method according to any one of claims 1 to 3. |
| 7. | A method for manufacturing kitchenware, comprising the steps of : (a) melting magnesium alloy at a temperature of 600~750°C using flux; (b) degassing the molten alloy in step (a) using an inert gas; (c) stabilizing the molten alloy in step (b); (d) hot chamber diecasting said magnesium alloy; (e) heat treating the cast alloy at a temperature of 100~450°C for 30 minutes to 3 hours; and (f) coating protective films onto the surface of said kitchenware. |
| 8. | The method defined in claim 7, wherein step (f) comprises: (i) sand blasting said cast alloy from step (e) ; (ii) degreasing the cast alloy from step (i); (iii) cleansing the cast alloy with a weak alkaline solution at a temperature of about 80°C for several minutes; (iv) immersing the cast alloy in an aqueous solution containing fluoride ions to form magnesium fluoride, oxofluoride and magnesium oxide; and (v) applying a voltage in excess of 150 Volts to an aqueous solution containing silicate, carboxylate and alkaly hydroxide, under conditions such that the cast alloy becomes an anode. |
Description of the Related Art Conventional kitchenware has been made of stainless steel, cast iron, aluminum alloys or the like. For example, a conventional frying pan is shown in Fig. 1 and includes a main body 4 of the frying pan made of an aluminum-silicon alloy and a handle 7. The main body 4 of the frying pan is formed by melting the aluminum-silicon alloy containing 0.01-25.0% by weight Si at the molten temperature of the alloy, 600~700°C, followed by cold chamber die-casting.
Subsequently, the main body is sand blasted, and is finally coated with a metal spray layer 3, a first Teflon coating layer 1 and a second Teflon coating layer 2.
Conventional kitchenware made of stainless steel or cast iron materials are heavy for the user. Further inconvenience results when such utensils become even heavier as the weight of foodstuffs are added thereto during cooking. In particular, outdoor kitchenware such as saucepans for camping and hiking are particularly heavy for the user, as they need to be portable.
Aluminum has been used as an alternative, but aluminum is a nonessential mineral for the human body, and it is reported that aluminum may be toxic if assimilated into a cell. For example, toxicity of aluminum may be considered when symptoms of presenile dementia or Alzheimer's disease are observed. Further, it is reported that individuals having renal problems or suffering from renal calculus may have elevated levels of aluminum. Although a Teflon coating is formed over the surface of conventional kitchenware made of aluminum, cooked food may be exposed to aluminum since the aluminum leaches through the Teflon coating.
Therefore, using kitchenware made of aluminum may cause an accumulation of aluminum in the human body through the intake of food cooked in said kitchenware.
SUMMARY OF THE INVENTION The present invention proposes to solve the problems in conventional kitchenware. To this end, an object of the present invention is to provide light and safe kitchenware.
Magnesium alloys have a specific gravity of about 1.8, and are considerably lighter as their specific gravity is about 63% of the specific gravity of aluminum alloys which is about 2.87. Magnesium alloys have unique strengths, and consequently have attracted considerable attention as parts for aircraft. Furthermore, magnesium is an essential mineral that is necessary for activity of enzymes and electrolytes in the bio-function in the human body. Magnesium contributes to control of cellular osmotic pressure, body temperature control, and improvement in muscle stimulation. In addition, magnesium plays an important role in the excretion of non-physiological calcium and the absorption of physiological calcium.
However, magnesium alloy is easily oxidizable, and its corrosion resistance becomes an issue. Due to such problems, the art has taught away from attempts to employ magnesium alloy in kitchenware.
According to an aspect of the present invention for achieving the above object, there is provided a method for manufacturing kitchenware, which comprises the steps of forming a main body of the kitchenware with a magnesium alloy and coating protective films onto a surface of the formed main body.
A magnesium alloy that is appropriate for the manufacturing method includes ASTM AZ91D alloy. This alloy contains approximately 9.0% aluminum, 0.7% zinc, and 0.13% manganese. The magnesium alloy may further contain calcium to improve high temperature strength. In addition to the aforementioned ASTM AZ91D alloy, various magnesium alloys can be used in the embodiments of the present invention.
The step of forming the main body of the kitchenware comprises the steps of melting the magnesium alloy in a protective atmosphere, degassing the molten magnesium alloy, and casting the molten magnesium alloy as the main body.
Alternatively, the step of forming the main body may be performed by a step of sheet metal forming the main body.
The step of coating the protective films comprises the steps of pretreating the surface of the main body of the kitchenware and forming the protective films onto the surface of the main body of the kitchenware. The step of forming the protective films may comprise the steps of anodizing the surface of the main body and coating it once or more with Teflon. The Teflon coating may be replaced with
other proper coatings, or the Teflon coating formed only on the outer surface of the main body may be replaced with other coatings such as ceramic coating.
According to another aspect of the present invention, there is provided kitchenware manufactured by the aforementioned manufacturing method.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view of a conventional frying pan.
Fig. 2 is a sectional view of a frying pan manufactured in accordance with a first embodiment of the present invention., Fig. 3 is a sectional view of a frying pan manufactured in accordance with a second embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS I The present invention will now be described in detail with reference to the accompanying drawings.
Fig. 2 is a sectional view of a frying pan according to an embodiment of the present invention. Taking high temperature strength, formability, etc. into consideration, ASTM AZ91D is used as a material for main body 5 of the frying pan. Magnesium alloys have the advantages of high specific strength and high specific elastic modulus, excellent formability, and latent heat of melting is low.
The magnesium alloy is cast into the main body 5 of the frying pan through a die- casting process. In order to prevent the magnesium from being oxidized when melting, the magnesium alloy is melted in an atmosphere where temperature of molten metal is controlled within a range of 600~750°C using flux. At this time, in order to remove hydrogen gas remaining within the molten metal, a degassing process is performed for 30 minutes using an inert gas, and a stabilizing process is then performed for 5-40 minutes. And then, the magnesium alloy is cast into the main body 5 of the frying pan through a vacuum cold chamber die-casting process.
In order to additionally remove the remaining gas, the main body 5 of the frying pan cast in the magnesium alloy can be heat treated at a temperature of 100~450°C for 30 minutes to 3 hours.
In order to further improve the high temperature strength, 0.01-20.0% calcium may be added to the magnesium alloy which has been used as a material
for the main body 5 of the frying pan.
The kinds of the magnesium alloy, heat treatment conditions, etc. are being presented herein by way of example. Other materials for the kitchenware and alternative heat treatment conditions for embodying the present invention may become apparent to those skilled in the art after having the benefit of this disclosure.
SF6 gas, HFC-132A, argon gas, or the like can be used as atmosphere for preventing the magnesium from being oxidized as it melts. As SF6 gas is costly, a mixture gas containing air (40-90% by weight), argon gas (10-40% by weight), nitrogen gas (10~30% by weight), and chloride gas (1-10% by weight) can be used.
In addition to the vacuum cold chamber die-casting process, a cold chamber die-casting process, a vacuum hot chamber die-casting process, a hot chamber die- casting process, a squeeze casting process, a metal casting process, a sand casting process, a centrifugal casting process, etc. can be used for casting the magnesium alloy into the main body 5 of the frying pan. Although the main body 5 has been shown as formed through the die-casting process in the above embodiment of the present invention, the magnesium alloy material may be formed through other forming processes such as press forming or sheet metal forming process in order to embody the present invention.
The main body 5 of the frying pan formed by the above process is completed by coating the protective films onto a surface of the main body. As shown in Fig. 2, the protective films according to the embodiment of the present invention comprise a metal spraying layer 3, a first Teflon coating layer 1 and a second Teflon coating layer 2. The coating layers can be formed as follows. Prior to the process of coating the protective films, the main body 5 of the frying pan is sand blasted, then treated with acid pickling in a solution containing 1-10% by weight HCl in order to remove oxides from the surfaces, and dried at a temperature of 50~250°C for 2 hours, as a pretreatment process for facilitating the coating process. After the pretreatment process has been completed, the main body is plasma spray treated with stainless steel in order to form the metal spraying layer 3.
The spray-treated main body 5 of the frying pan is first coated with Teflon, and then dried at a temperature of 150~350°C for 10 minutes to 1 hour. The main body 5 is second coated with Teflon, and then dried at a temperature of 200~480°C for 10 minutes to 1 hour. Thus, the first and second Teflon coating layers 1 and 2 are formed.
At least one metal selected from the group, stainless steel, titanium, copper or manganese can be used for forming the metal spray layer 3. Although the main body 5 of the frying pan has been coated twice with Teflon in the present
embodiment, the Teflon coating may be formed once or more than two times.
Fig. 3 is a sectional view of a frying pan according to another embodiment of the present invention. Except for the process of coating main body 5'of the frying pan with protective films, the other processes of the present embodiment are identical to those of the previous embodiment. The protective films of the frying pan in Fig. 3 are formed by an anodizing process onto a surface of the main body 5' of the frying pan that has been formed by the process of forming the main body (as above), and then Teflon is coated onto the protective films. To this end, as a pretreatment process prior to the process of coating the protective films, the main body 5'of the frying pan is sand blasted, cleansing treated with alkaline on the main body in order to remove oxides from the surfaces, and the main body is finally dried at a temperature of 50°C or above for several hours. In order to anodize the magnesium, the surface of the main body 5'of the frying pan is first degreased and cleansed at a temperature of about 50°C for about 10 minutes. It is then cleansed with weak alkaline at a temperature of about 80°C for several minutes in order to remove fine corrosion layer. The main body 5 of the frying pan is finally immersed in an aqueous solution containing fluoride ions at a temperature of about 90°C to form magnesium fluoride, oxofluoride and magnesium oxide. Subsequently, voltage of above 150 Volts is applied to an aqueous solution containing silicate, carboxylate and alkaly hydroxide, under conditions such that main body 5'of the frying pan made of magnesium alloy becomes an anode and stainless steel coated tank becomes a cathode. Thus, a porous oxidizing layer, i. e. an anodizing layer 6 is formed. Thereafter, the first Teflon coating layer 1 is formed by performing the steps of Teflon coating and baking.
Preferably, a process for protecting the inner metallic layer by forming the anodizing layer 6, and then sealing internal pores and unevenness on the surface of the anodizing layer with resin material, may be further performed. In addition, although the Teflon coating has been made once in the embodiment of the present invention, the Teflon coating can be made twice or more. Furthermore, the Teflon coating may be replaced with other protective coatings, or the Teflon coating formed only on the outer surface of the main body may be replaced with other protective coatings such as ceramic coating, without departing from the scope or spirit of the present invention.
INDUSTRIAL APPLICABILITY According to the present invention, the kitchenware made of the magnesium alloy is considerably lighter than conventional kitchenware made of stainless steel, casting material, or even aluminum alloys or the like. For example,
as the specific gravity of magnesium alloy is lower by 33% or more, when compared with the specific gravity of aluminum alloy, the weight of the kitchenware itself can be reduced by about 33% or more.
Further, according to the present invention, productivity of the kitchenware can be improved since the magnesium alloy has excellent castability and high solidification rate.
Additionally, the life of the metal molds can be prolonged since the magnesium alloy has low reactivity with iron. Accordingly, the unit cost of production can be reduced.