Pipes and tubular conduits – Miscellaneous
Reexamination Certificate
1994-05-27
2001-03-20
Flanigan, Allen (Department: 3743)
Pipes and tubular conduits
Miscellaneous
C165S134100, C165S133000, C420S493000, C420S499000
Reexamination Certificate
active
06202703
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an corrosion resistant copper alloy tube which is used as a refrigerant copper alloy tube or a heat exchanger copper alloy tube and a fin-tube heat exchanger which is used for an air-conditioner, particularly relates to an corrosion resistant copper tube and a fin-tube heat exchanger having improved corrosion resistant property against an ant-nest type corrosion.
2. Description of Prior Art
A tube which was made of copper deoxidized by phosphorous has been widely used for the conventional refrigerant tube or the conventional heat exchanger tube generally due to its better bending and brazing properties.
In these tubes, however, organic materials such as lubricant oil or process oil and organic solvents unavoidably remaining on the surface of the fins and tubes after the tubing and fabrication processes may decompose during the repeated deposit and evaporation of water due to a coolant and during the exposure to peculiar temperature/moisture and air-exchange environment created as a nature of its construction to form carboxylic acids which cause peculiar corrosion showing local ant-nest type corrosion on the surface of the tube.
Thus, a large amount of lubricant oil has been used in the fabrication process of the heat exchanger, however considering recent environmental problems there is a trend to avoid the degreassing wash by organic solvents and rather to use volatile lubricant oil instead of such organic solvents. In this case, even though the base oil itself is volatile, such lubricant oil still contains some oil additives which may remain on the surface of the copper tube.
Therefore, there is an increasing risk for the ant-nest type corrosion in future according to more usage of volatile lubricant oil, compared to the case the degrase wash was performed using organic solvents. Reflecting such circumstance, measurements for the ant-nest type corrosion are attracting the attention of the industry as one of serious problems. Further, increase of remaining organic materials on the surface of the copper alloy tube is creating another problem of poor conjunction of tube during the brazing which is used as a major method for the tube connection. Therefore, development of a copper alloy tube having superior corrosion resistant and brazing properties than the conventional phosphorous deoxidized copper tube is desired as a tube material for the refrigerant tube or the heat exchanger tube.
Further, the fin-tube heat exchanger used for an air-conditioner is generally fabricated using aluminum or aluminum alloy plate fins provided with tube insertion holes and copper tubes. Inside the insertion hole, a tube-type fin collar is provided. Many of said fins are placed in parallel and the copper tube is inserted into said fin collar so as to connect each fin. Then, this tube extended and fixed on the fins. And the heating medium is allowed to flow through the inside of said tube and its heat is transmitted to and radiated from said fins. In this fin-tube heat exchanger, said plate fins are made from aluminum or aluminum alloy due to its thermal conductivity and cost, and, for said tube, the copper tube is widely used from the stand points of its thermal conductivity and corrosion resistant properties. For this copper tube, a pure copper called as phosphorous dioxided copper is mainly used.
However, in these conventional fin-tube heat exchanger, organic materials such as lubricant oil and organic solvents used in the processes of blanking and extending of the tube unavoidably remain on the surface of the tubes, and these organic materials are affected by repeated deposit and evaporation of water during storage of fins and tubes or usage as the heat exchanger. These organic materials are also exposed to the peculiar temperature/humidity and air-exchange environment during usage of the heat exchanger. Under such conditions, these organic materials decomposed to form carboxylic acids which cause the peculiar local corrosion showing the ant-nest type corrosion, resulting in leakage of the tube frequently.
In addition, as aforementioned, although a large amount of lubricant oil has been used during fabrication process of the fin-tube heat exchanger, considering recent environmental problems there is a trend to avoid the degreassing wash by organic solvents and rather to use volatile lubricant oil instead of such organic solvents. Even though the base oil itself is volatile, such lubricant oil still contains some oil additives which may remain on the surface of the copper tube. Therefore, the amount of organic materials remaining on the surface of raw materials is in trend towards increase compared to the case of degreassing wash by organic solvents and the risk for the ant-nest type corrosion is higher than the past.
Under such circumstance, measurements for the ant-nest type corrosion of the fin-tube heat exchanger are attracting the attention of the industry as one of serious problems, and development of a fin-tube heat exchanger having superior corrosion resistant property against the ant-nest type corrosion is desired.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an corrosion resistant copper alloy tube having better corrosion resistant property against the ant-nest type corrosion even though exposed to the phenomenon specific to the refrigerant tube or the heat exchanger tube; that is, repeated deposit and evaporation of water, and used under the peculiar environmental conditions of temperature/humidity and air-exchange, and having better brazing property so that capable of increasing its integrity and life span as the refrigerant tube or the heat exchanger tube.
The another object of the present invention is to provide a fin-tube heat exchanger having better corrosion resistant property against the ant-nest type corrosion even though affected by the phenomenon specific to the fin-tube heat exchanger; that is, repeated deposit/evaporation of water, and used under the peculiar environmental conditions of temperature/humidity and air-exchange so that carboxylic acids are formed, and capable of increasing its integrity and life span.
A corrosion resistant copper alloy tube according to the present invention consists essentially of 0.05 to 1.5 wt. % of Mn, 100 ppm or less of oxygen, and Cu and inevitable impurities.
The corrosion resistant copper alloy tube according to the present invention shows better corrosion resistant property against the ant-nest type corrosion which specifically may occur in the conventional refrigerant tube or the heat exchanger tube made of phosphorous deoxidized copper; that is, the ant-nest type corrosion which may occur under the conditions of affecting repeated deposit and evaporation of water and peculiar environmental conditions of temperature/humidity and air-exchange, and shows better brazing property. Therefore, it is capable of increasing its integrity, applicability and life span as the refrigerant tube or the heat exchanger tube. Thus, the present invention is very useful.
A corrosion resistant copper alloy tube for a heat exchanger according to the present invention, comprises a main tube body including a copper alloy tube and an oxide film formed on the surface of said main tube body in the thickness of from 30 to 3000 Å by oxidizing the surface of the main tube body. Said copper alloy consist essentially of at least one additive element at 1.7 to 3.0 wt. % in total, the volume ratio of oxide thereof to Cu base metal (ratio of molecular volume of oxide to atomic volume of Cu base metal) being within 1.7 to 3.0, and Cu and inevitable impurities. The additive element or elements remaining in said copper alloy is solid solubilized into Cu base metal. The differential natural electric potential between said oxide film and phosphorous deoxidized copper in 0.1 v. % of formic acid solution is within the range of from 0.2 V to −0.2 V.
In the conventional heat exchanger copper tube made of phosphorous deoxidized copper, the corrosion re
Kuroda Taro
Minamoto Kenju
Miyafuji Motohisa
Ohkubo Mitsuhiro
Ozaki Ryoichi
Flanigan Allen
Kabushiki Kaisha Kobe Seiko Sho
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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