Electric heating – Metal heating – Nonatmospheric environment at hot spot
Patent
1992-09-11
1994-11-22
Shaw, Clifford C.
Electric heating
Metal heating
Nonatmospheric environment at hot spot
252372, B23K 916
Patent
active
053671376
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method of producing a protective gas consisting of 0.0010-0.100 percent by volume of nitric oxide, 0-90 percent by volume helium, 0-5 percent by volume hydrogen, 0-50 percent by volume carbon dioxide and the remainder argon, and also to a condensed gas mixture for the production of said protective gas.
In electric gas-arc welding processes there is often used a protective gas in the form of a gas mixture consisting of or comprising argon and nitric oxide. The protective gas mixture or protective gas may also include carbon dioxide, helium and/or hydrogen. To large consumers of protective gases, these gases containing nitric oxide, there is at present delivered a gas pre-mixture, a master gas, consisting of a nitric oxide in argon under high pressure, this gas being delivered in conventional steel bottles. The proportion of nitric oxide present is normally from 1-5 percent by volume, for instance 1.8 percent by volume. The desired protective gas is then produced by mixing the various gases with the gas pre-mixture to the composition desired. The amount of nitric oxide present in the final protective gas is normally at most 0.030 percent by volume.
Since nitric oxide is a poisonous gas, it is desirable to use lower proportions of nitric oxide in the master gas than those used hitherto. This results in higher transportation costs, since it is necessary to transport to the consumer more gas bottles containing master gas at unchanged protective gas consumption.
Another drawback with the master gas is that when preparing a protective gas it is necessary to supply additional argon in order to reach the desired final concentration of argon in the protective gas produced.
OBJECTS OF THE INVENTION
Accordingly, one object of the present invention is to provide a condensed gas mixture of nitric oxide in argon with a lower proportion of nitric oxide than has hitherto been used in the master gas without increasing the transportation costs as a result hereof and without occasioning excessive switching between gas sources (nitric oxide containing gas).
Another object of the present invention is to provide a condensed gas mixture of nitric oxide and argon for the production of a protective gas which does not require the additional admixture of pure argon.
Still another object of the invention is to provide a gas mixture of nitric oxide and argon in liquid form in order to considerably reduce the number of gas-mixture deliveries to the consumer.
A further object of the invention is to provide a method for producing a protective gas which in addition to containing nitric oxide and argon also contains helium, carbon dioxide and/or hydrogen, by using simpler mixing apparatus.
SUMMARY OF THE INVENTION
These objects are achieved with a condensed gas mixture which comprises condensed argon in which 0.0010-0.100 percent by volume, calculated on gas phase, of nitric oxide is dissolved. Argon is a liquid between about -185.9 and -189.2 degrees Celsius at atmospheric pressure, whereas nitric oxide, NO, has a freezing point at about. -164 degrees Celsius.
It has now surprisingly been found that nitric oxide can be dissolved in liquid argon at atmospheric pressure in an amount of at least up to 0.1 percent by volume calculated on gas phase, and that the vaporized gas mixture has essentially the same composition as the liquid phase.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described in more detail with reference to an exemplifying embodiment thereof illustrated in the accompanying drawing, the single FIGURE of which is a graph in which the nitric oxide concentration, in ppm, is plotted as a function of time during which removals of gas mixtures takes place.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A pressure container which accommodates about 800 kg liquid argon was filled with liquid argon, whereafter nitric oxide was dissolved in the argon until the nitrogen monoxide concentration had risen to about 300 ppm. This dissolution can be ac
REFERENCES:
patent: 3526740 (1970-09-01), Brinkmann et al.
patent: 4292493 (1981-09-01), Selander et al.
Hammarlund Nils
Persson Kjell-Arne
Sipek Ladislav
AGA Aktiebolag
Shaw Clifford C.
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