Process for cooling a metal wire obtained from a liquid jet

In order to cool the jet coming from a crucible and then the wire as it starts solidifying, there is used a gaseous cooling fluid mixture having a base of gaseous hydrogen and at least one other component which is a compound of hydrogen capable of an endothermic chemical reaction in contact with the jet (wire) and of a chemical composition such that the product or products of this reaction have a high molecular content (mol %) of free hydrogen.

This invention relates to processes for manufacturing a wire of metal or 
metal alloy in an installation comprising essentially a crucible 
containing the molten metal or metal alloy, a die arranged in a wall of 
the crucible, an enclosure containing a pressurizing fluid acting on the 
metal or metal alloy in the crucible and a cooling enclosure following the 
die and containing a gaseous cooling fluid mixture, the wire being 
obtained by projecting a jet of the metal or metal alloy, under the effect 
of the pressurizing fluid, through the die into the gaseous cooling fluid 
mixture contained in the cooling enclosure, wherein the liquid jet is 
cooled and transformed into solid wire. 
U.S. Pat. No. 3,543,831 describes the cooling of a metal jet coming from a 
die by means of a suspension of liquid or solid particles. The particles 
are capable of reacting chemically in contact with the hot jet. The 
chemical reaction upon the contact of the particles with the jet may be of 
the endothermic type in the case of solid particles, they being intended 
to form a solid coating on the wire. 
U.S. Pat. Nos. 4,149,584 and 4,153,099 describe an enclosure and a cooling 
fluid in which a fluid having a base of hydrogen and water vapor forming a 
mist is used. The droplets of water of the mist by coming into contact 
with the jet (wire) contribute by evaporation to the cooling of the 
latter. 
The object of the present invention is to improve the rate of the heat 
exchange in the cooling enclosure between the jet (wire) and the gaseous 
cooling fluid mixture having a base of gaseous hydrogen and at least one 
other component. 
The method of cooling employed in processes for the manufacture of wire of 
metal or metal alloy of the type described above, employing a gaseous 
cooling fluid mixture having a base of gaseous hydrogen and at least one 
other component contained in the cooling enclosure is characterized in 
accordance with the invention by the use of a gaseous cooling fluid 
mixture in which the other component is a compound of hydrogen capable of 
an endothermic chemical reaction in contact with the jet (wire) and of a 
chemical composition such that the product or products of this reaction 
have a high molecular content (mol %) of free hydrogen. 
The invention thus constitutes a combination between the cooling effect due 
to the endothermic chemical reaction of the other component and the 
cooling effect due to the enrichment of the gaseous cooling fluid mixture 
in hydrogen by the large amounts of free hydrogen resulting from the 
reaction of the other component. Gaseous hydrogen has a thermal 
conductivity which is far greater than that of other gases, such as 
helium, argon, carbon dioxide and nitrogen. Furthermore, the specific heat 
per unit of mass of hydrogen is large. 
The expression "jet (wire)" means that the gaseous cooling fluid mixture 
acts first of all on the jet but may also act on the wire, as long as the 
temperature of the wire permits the maintaining of the endothermic 
chemical reaction. 
It is also possible to use as the other component an oxygen donor, 
particularly within the scope of the processes for the manufacture of 
steel wires in accordance with U.S. Pat. Nos. 3,933,441 and 3,861,452, the 
steel projected into the gaseous cooling fluid mixture having a content of 
silicon and possibly of manganese such that the oxidation product upon the 
contact of the jet with the gaseous cooling fluid mixture is silica. The 
silica sheathing thus produced stabilizes the jet and permits the 
manufacture of continuous wires. 
Instead of using a single other component in the gaseous cooling fluid 
mixture containing hydrogen which dissociates within the course of an 
endothermic chemical reaction liberating free hydrogen when it comes into 
contact with the jet (wire), one may use two other components which react 
endothermically with each other in contact with the jet (wire), liberating 
free hydrogen.

Examples of gaseous cooling fluid mixtures which can be used within the 
scope of the process claimed are given below: 
EXAMPLE 1 
In this example, the other component of the gaseous cooling fluid mixture 
in accordance with the invention undergoes an endothermic chemical 
dissociation reaction when, in contact with the jet, it reaches its 
dissociation temperature. The component itself as well as the products 
resulting from its dissociation are chemically inert with respect to the 
jet (wire) of metal or metal alloy. A gaseous cooling fluid mixture of 50 
mol % ammonia (NH.sub.3) and 50 mol % hydrogen (H.sub.2) is used. The 
liquid ammonia under pressure in a cylinder is autovaporized by expansion 
in a number of atomizers which discharge into the cooling enclosure. The 
boiling point of ammonia at a pressure of one atmosphere is equal to 
-33.3.degree. C. 
The ammonia coming into contact with a jet of liquid steel of a diameter of 
1 mm dissociates endothermically in accordance with the equation: 
EQU 2NH.sub.3 .fwdarw.N.sub.2 +3H.sub.2 
the products of the dissociation containing 75 mol % of free hydrogen. 
The endothermic dissociation and the free hydrogen contributed by the 
dissociation absorb large amounts of heat. 
The thermal transfer is increased by about 30% as compared with a gaseous 
cooling fluid mixture of water vapor and hydrogen. 
EXAMPLE 2 
In this example, there are two other components in the gaseous cooling 
fluid mixture in accordance with the invention which undergo an 
endothermic chemical reaction between themselves when, in contact with the 
jet, the temperature for this reaction is reached. 
A first other component is water vapor, incorporated in H.sub.2 by 
saturating the latter by passage through an ordinary humidifier which 
makes it possible to reach saturation with water at 70.degree. C.; this 
gaseous mixture contains 69 mol % of hydrogen and is injected into the 
cooling enclosure. The second other component is propane (boiling point at 
one atmosphere; -42.6.degree. C.) injected into the cooling enclosure. 50 
mol % of the first other component (water vapor) are mixed with 50 mol % 
of the second other component (propane), the liquefied propane under 
pressure in a cylinder being auto-vaporized by expansion in a number of 
atomizers discharging into the cooling enclosure. 
The propane (C.sub.3 H.sub.8) coming into contact with the jet (wire) of 
stainless steel of 1.75 mm in diameter participates, as well as the water 
vapor, in the endothermic chemical reaction in accordance with the 
equation. 
EQU C.sub.3 H.sub.8 +3H.sub.2 O.fwdarw.3CO+7H.sub.2 
the products of the reaction containing 70 mol % free hydrogen. 
The thermal transfer is improved by about 50% as compared with a gaseous 
cooling fluid mixture of water vapor and hydrogen. 
It is to be noted that the carbon monoxide (CO) liberated during the said 
reaction contains oxygen. It can therefore be used as oxygen donor of the 
gaseous cooling fluid mixture for the production of silicon steel wire by 
the processes described in U.S. Pat. Nos. 3,861,452 and 3,933,441 which 
have been mentioned above. 
In place of propane, one can use other hydrocarbons which have a boiling 
point less than ambient temperature, are of low cost and are readily 
available on the market in liquid and compressed state, such as ethane, 
butane, isobutane, propadiene and butadiene. 
EXAMPLE 3 
A gaseous cooling fluid mixture containing 45 mol % of hydrogen (H.sub.2) 
and 55 mol % of the following two other components is used: 
1st other component: 45 mol % of propane (C.sub.3 H.sub.8) injected at 
several points close to the jet (wire) after expansion in an orifice with 
auto-vaporization of the propane coming from a liquefied gas cylinder 
under pressure. 
2nd other components: 10 mol % of water vapor (H.sub.2 O) injected at 
several points close to the jet (wire) after expansion in an orifice with 
auto-vaporization of the water heated to 200.degree. C. under a pressure 
of 17 atmospheres. 
After endothermic chemical reaction between the water vapor (steam) and 
propane in contact with the jet (wire) in accordance with the equation 
EQU C.sub.3 H.sub.8 +3H.sub.2 O.fwdarw.3CO+7H.sub.2, 
the products of the reaction contain 70 mol % of free hydrogen. 
The heat transfer is improved 53% as compared with a gaseous cooling fluid 
mixture of water vapor and hydrogen. 
In these three examples, the gaseous cooling fluid mixture in accordance 
with the invention has a specific weight greater than that of a gaseous 
cooling fluid mixture of hydrogen and water vapor: The gaseous cooling 
fluid mixture of Example 1 has a specific weight which is 4.75 times 
greater, the gaseous cooling fluid mixture of Example 2 has a specific 
weight which is 11.5 times greater, and the gaseous cooling fluid mixture 
of Example 3 has a specific weight which is 10.4 times greater than that 
of a gaseous cooling fluid mixture of hydrogen and water vapor. To use a 
gaseous cooling fluid mixture of a specific weight greater than that of a 
gaseous cooling fluid mixture of hydrogen and water vapor is of interest, 
particularly in installations in which a gasous cooling fluid mixture is 
also used to support the jet (wire) and/or stabilize it. 
In general, the gaseous cooling fluid mixture in accordance with the 
invention is at a pressure close to ambient pressure. 
Furthermore, it is advantageous to use a gaseous cooling fluid mixture 
having a base of as large an amount as possible of hydrogen, preferably at 
least 30 mol % not exceeding 80 mol % of the initial composition of the 
gaseous cooling fluid mixture, as well as one or more other components, 
the product or products of the endothermic chemical reaction of which in 
contact with the jet (wire) contain as large an amount as possible of free 
hydrogen, preferably at least 50 mol %. By "initial composition" there is 
understood the composition of the gaseous cooling fluid mixture before the 
contact with the jet (wire) and before the endothermic chemical reaction 
which this contact initiates. By "reaction products" there are understood 
the products appearing on the right-hand side of the chemical equations 
symbolizing the endothermic chemical reaction.