Metal treatment – Compositions – Heat treating
Patent
1983-10-27
1985-07-30
Skiff, Peter K.
Metal treatment
Compositions
Heat treating
148 132, 148434, 165DIG8, C22F 108
Patent
active
045319804
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a corrosion resisting copper alloy and more particularly to a corrosion resistant copper alloy specially suitable for use with a heat exchanger and the invention also relates to heat exchangers using such an alloy. Such heat exchangers may be intended to be used under severe corrosive conditions and may, for example, be heat exchangers for heating cooling water for automobile engines or heat exchangers intended for industrial use.
In general, heat exchangers used for cooling water for use in connection with automobile engines, which are generally termed "radiators", are composed of a brass material which comprises 65 percent copper by weight and 35 percent zinc by weight. It is to be appreciated that when an automobile is in use the heat exchanger may be affected directly by harmful elements contained in exhaust gas emanating from the automobile, or other automobiles running on the same road, and also such a heat exchanger may be affected by salinity when the automobile is used near the sea shore, or when used on roads that have been treated with salt to prevent or minimize icing on the roads. Additionally the heat exchanger is always in contact with the heat exchanging medium circulating therein, and such a heat exchanging medium may be corrosive, particularly if the heat exchanging medium contains anti-freeze components. Thus heat exchangers of the type under the discussion are frequently used under severely corrosive conditions, with the heat exchanger being corrosively attacked both from the inside and from the outside.
A heat exchanger such as an automobile radiator operates by circulating a heat exchanging medium through a large number of tubes, and during the circulation of the heat exchanging medium heat is conducted to heat radiating fins which are in thermal contact with the tubes. Therefore, in order to ensure that there is sufficiently good heat conduction between the interior of the tubes and the fins it is preferred to make the tubes with walls that are as thin as possible. It is also preferable to make the heat exchanger as light as possible, again by making the walls of the tubes as thin as possible. Not only does this facilitate handling of the heat exchanger but also minimizes the amount of material used in making the heat exchanger, and this minimizes the costs of the materials utilized.
However, since a heat exchanger made of brass will corrode (by means of the so-called dezincifying corrosion) under the above mentioned severe corrosive conditions, there is a minimum practical thickness for the tube walls when the tubes are made of conventional brass and thus there is a minimum practical limit to the improvements of heat conductivity and the saving of material cost that can be effected by minimizing the thickness of the tube walls.
OBJECT OF THE INVENTION
The present invention seeks to provide a material which has a very high corrosion resistance whilst still having good thermal conductivity which will thus facilitate the manufacture of heat exchangers having tubes with thinner walls than heretofore. It is also an object of the invention to provide a method of making such a material. It is also an object of the invention to provide such a heat exchanger.
SUMMARY OF THE INVENTION
This invention provides a copper alloy exhibiting corrosion resisting properties which consists essentially of 25 to 38 percent zinc by weight of the alloy, 0.005 to 0.04 percent phosphorus by weight of said alloy, the balance of said alloy being copper, the recrystallized grain size of said alloy being within the range of 2.mu. to 10.mu. inclusive.
In an advantageous alloy in accordance with the invention the phosphorus is in a substantially uniform solid solution within the recrystallized grains of the alloy. This may be accomplished by recrystallizing the alloy at a temperature of between 450.degree. and 600.degree. C. for a period of time between 5 seconds and 5 minutes to produce grains of the required size.
This invention also provides a h
REFERENCES:
patent: 2131437 (1938-09-01), Jennison
patent: 2224095 (1940-12-01), Barry
patent: 2261975 (1941-11-01), Crampton
patent: 3615922 (1971-10-01), Alyea
Naether et al., "Structure and Softening of Brass During Accelerated Recrystallization", Metals Technology, Aug. 1980, pp. 345-347.
Hasegawa Yoshiharu
Miura Tatsuo
Ohta Kazuhiro
Yoneyama Takao
Granges Metallverken AB
Skiff Peter K.
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