FI82716B - FOERFARANDE FOER AVLAEGSNANDE AV VAETE FRAON ETT METALLFOEREMAOL GENOM VAERMEBEHANDLING I ROTERUGN. - Google Patents

Description

1 82716

This invention relates to heat treatments in general and more particularly to a degassing method for removing hydrogen from purified metal.

When cobalt is refined by electrochemical electroplating in a cobalt-containing electrolyte, the resulting refined cobalt metal typically contains 10-10 ppm of hydrogen. A similar situation is with nickel processing. Often, however, these amounts of hydrogen are undesirable and the specifications require a maximum amount of hydrogen of about 1 ppm.

Dehydrogenation is usually performed in several ways. The metal can be heated in a vacuum, in an inert atmosphere, or in a reducing atmosphere. In addition, the environment must be carefully controlled to eliminate the possibility of undesired oxidation. Ultimately, a portion of the electrolytically produced cobalt or nickel is formed into squares or rounds. The squares 20 may be about 2.54 cm x 2.54 cm x 0.635 cm in size. The round pieces may be about 2.54 cm in diameter and about 0.635 cm thick.

The problem is encountered when squares and spins are heated in an oven to remove hydrogen. The chicken squares and wheels (which are not treated simultaneously) of the heating cycle ai-25 sinter together and form a substantially useless mass.

One method of overcoming this difficulty is to place the materials on low trays and then place the trays in the oven. Not only does this input method result in a very slow output rate, it is also very labor intensive. Another possible way is to use relatively low temperatures. Although sintering is not a problem, the time periods required are disadvantageously long. Accordingly, heating nickel and cobalt in conventional heat sources is not a practical method for industrial purposes. Chemical methods for removing hydrogen are unnecessarily expensive and complicated.

The invention relates to a method for removing hydrogen from a metal body. The invention is characterized in that 1) the body is placed in a bed furnace, 2) the bed furnace is heated to a temperature of 500-700 ° C, 3) the body is kept in a bed furnace for about 1½ to 12 h 10 to reduce the hydrogen content of the body to at least about 1 ppm, 4) .

Thanks to the invention, the combination of heat and rotation releases hydrogen from the body, and at the same time the citration of the materials together is prevented.

The figure shows a curve depicting the amount of hydrogen per hour at different temperatures.

As referred to above, time and temperature are the major variables that control the rates of hydrogen removal from cobalt and nickel. The figure shows the relationship between these two variables.

Electrolytically purified nickel and cobalt are usually made into 6.35 mm thick sheets and cut into 2.54 cm x 2.54 cm x 0.635 cm squares for sale 25 or galvanized into a 2.54 cm round button about 6.35 cm thick.

Some small experiments were performed in a tubular furnace to determine the relationship between furnace temperature and time required for hydrogen removal. Four heat-30 modes were selected - 500 ° C, 550 ° C, 600 ° C and 700eC. These isotherms are shown in the figure. In each case, a reducing atmosphere containing about 5% H 2 to 95% N 2 was used. At higher temperature ranges, data recording ceased after four hours. It is not a critical factor that the 35 higher temperature experiments started from slightly higher

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3,82716 from the hydrogen level.

The dehydration rate shown in the figure is for cobalt rollers 2.54 cm in diameter and 0.635 cm thick. It can be seen from the figure that heating the hydrogen-containing metal 5 for about 1.75 hours at 700 ° C, about 3 hours at 600 ° C, or about 11 hours at 500 ° C in a reducing atmosphere containing about 5% H 2 to 95% N 2 gives a metal desirably containing about 1 ppm hydrogen.

10 Accordingly, two large-scale tests were carried out on the basis of the above experiments, in which 2721 kg of cobalt rollers, each about 2.54 cm in diameter and about 0.635 cm thick, were placed in a stainless steel tank 95.6 cm in diameter and 15,104 cm high. . The average hydrogen content of the wheel was 15 ppm.

The container was sealed and placed in a retort oven and heated. In the first test, the outdoor temperature of the wheels did not exceed 550 ° C, and the internal temperature was 600 ° C, for 5 hours. In the second test, the outdoor temperature of the spindles was at most below 550 ° C and the internal temperature was 500 ° C, for 11 hours. In both tests, a flow of 5% H 2 to 95% N 2 through the tank was maintained during the heating and cooling cycle. In Test 1, the average hydrogen content of the cobalt wheels was 0.3 ppm, while in Test 2 it was 0.6 ppm. Thus, the desired hydrogen content was achieved in both tests. Unfortunately, in both tests, with the exception of some rollers on or near the tank surface, all cobalt rollers were sintered together. This method of dehydrogenating cobalt rollers is thus not practical for industrial purposes.

It was found that nickel or cobalt wheels (about 2.54 cm in diameter, about 0.635 cm thick) or squares (2.54 cm x 2.54 cm x 0.635 cm) could be fed and unloaded continuously from an externally heated rotary kiln, in which is a 5% H2 to 95% N2 atmosphere. The rotational movement of a nickel or co-load of nickel or 4 82716 bolts in the furnace prevents the rotors from sintering together under such temperature conditions that a hydrogen content of less than 1 ppm can be routinely achieved.

5 Example

A rotary kiln with an inner diameter of about 35.6 cm was raised and fed with cobalt spindles (diameter 2.54 cm, thickness 0.635 cm) containing 20 ppm hydrogen. The feed rate was 2 kg / min for cobalt rollers. 10 The furnace tube had a slope of zero degrees and a rotation speed of 1.2 rpm.

The electric heaters outside the furnace tube were adjusted so that the temperature of the furnace metal tube was 600 ° C uniform over the entire length. A 10% H2 to 90% 15 N2 reducing gas mixture was introduced into the furnace at 31 liters per minute. N2 scrubbing gas was also used with supply and discharge valves.

The blast furnace was operated under these conditions five days a week, twenty-four hours a day for 20 to three months. At no time did the metal of the product melt or sinter together. Under these conditions, the average residence time of the metal in the furnace was determined to be about six hours. The average hydrogen content of the product was 0.4 ppm.

25 It appears that the material components of the environment in the furnace are not critical to the process. An experiment using 50% H 2 50% N 2 resulted in suitably degassed bodies. Rather, the critical parameters appear to be temperature and time.

Based on the above, this method can be performed at a temperature in the range of about 500 ° C to about 700 ° C. The total residence time should be between about one and a half hours and about twelve hours. From an energy point of view, it may be more advantageous to carry out the process in about six hours at a temperature of 35 (or longer) and about 600 ° C (or lower).

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5 82716 mass). The degassing rate increases as the temperature rises. However, more energy is needed to maintain higher temperatures. Accordingly, slightly lower temperatures and slightly longer processing times may prove to be necessary.

Normal commercial gas sources often include small amounts of contaminants such as water vapor and / or oxygen. If the final body must have a clear appearance, the chances of oxidation must be reduced. Accordingly, hydrogen is added to counteract the oxidizing effects of these impurities. However, oxidation itself does not appear to preclude the effectiveness of this degassing method.

Although specific embodiments of the invention have been described in accordance with the teachings of the Regulation, those skilled in the art will appreciate that changes may be made in the form of the claimed invention and that certain features of the invention may sometimes be advantageously used without correspondingly using other features.

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Claims (7)

A process for removing hydrogen from a metal article, characterized in that 1) the article is placed in a rotary kiln, 2. the rotary kiln is heated to a temperature of 500-700 °, 3. the object is poured into the rotary kiln for a period of 1 % -12 h to reduce the hydrogen content of the article to a value of at least about 1 ppm, 4. the article is rotated, and 5. the article is removed from the rotary furnace. 2. A method according to claim 1, characterized in that a reducing gas is present in the rotary furnace. Method according to claim 2, characterized in that the gas contains nitrogen. Process according to claim 2, characterized in that the gas contains hydrogen. 20 5. A process according to claim 4, characterized in that the gas contains about 50% by weight of hydrogen. Method according to claim 1, characterized in that the article contains cobalt. 25 7. A method according to claim 1, characterized in that the article contains nickel.