US2168129A - Method of making alloys of copper and nickel - Google Patents

Description

Patented Aug. 1, 1939 PATENT [OFFICE METHOD OF MAKING ALLOYS OF COPPER AND NICKEL Frank Leverick, Blaby, near Leicester, England,

assignor to Follsain Syndicate minster, London, England Limited, West- 1 No Drawing. Application February 18, 1936, Se-

rial No. 64,582. In Great Britain February 20,

1 Claim. (01. 75-135) In making alloys comprising nickel by melting and casting them into shapes, it is usual to put the simple ingredients into the melting crucible and then to raise the temperature of the whole 5 until all the ingredients melt, giving a liquid metal alloy which can be poured into a mould. This temperature is usually considerably above the melting point of the alloy to be formed.

In such a procedure it is found that there are difficulties.

1. Ingredients liable to volatilise are lost to. a large extent.

2. Ingredients liable to oxidise are not after oxidation in suitable form for forming alloys.

3. Non-metallic inclusions are liable to occur in the casting due to impurities melting at the high temperature necessary.

4. There is a liability to segregation.

All metals have a low limit of temperature below which they will not alloy with other metals.

In a complex alloy the lowest temperature at which the alloy can form is the highest low limit of the seperate metals. 'The lowest temperature in any given case occurs when one of the ingreclients of a duplex alloy is presented to the other ingredient in the nascent or more chemically active state.

It has been hitherto proposed to protect ingredients liable to oxidise or volatilise by either surrounding each portion of such ingredients with a slag, or by breaking down some carbide of the ingredient by an alternating contact and reaction of the carbide with a special slag in the bath, or in the special case of beryllium, by contacting the beryllium with a special slag free from certain specified matters. In none of these cases, however, is there any notice taken of the condition of the ingredients of the melt at operating temperatures.

I have found by experiment that there is a restricted temperature range within which alloying best takes place, and the loss of components is least. I have found that the best way of alloying when some components of the alloy were oxidisable or volatilisable was to present such components to others in the vapour form, and preferably freshly evolved i. e. in the nascent state. If so presented, when the temperature was suitable a quick alloy without serious loss and at a lower temperature than is possible by other means was formed. I have found that the best way to evolve the oxidisable or volatilisable components in suitable form was to link them with some other substance to form a chemical compound, usually complex which would not dissociate until the temperature was suitable.

The object of my invention is to provide means to evolve one or more of the ingredients of'the melt in the. nascent state when the other ingredient-or ingredients is, or are, at a suitable tempeiature toform the alloy.

The invention consists in adding to the ingredients of the melt which ingredients are mixed in any conventional manner, known to metallurgists, an operator which will form with the alloying materials or one or more thereof, a compound which is stable up to a temperature, in degrees centigrade, which is at least '75 per cent. of the temperature at which another or others of the ingredients will form an alloy with said alloying material but will dissociate at a higher temperature below that at which said ingredient or ingredients melt. Dissociation must also take place as close to the restricted temperature range (found by experiment) as possible. While I do not want to be restricted to them, I have successfully used as operators the followingz-potassum sulphate; alum (potassium aluminium sulphate and potassium iron sulphate) silver cyanide, sodium and calcium phosphates, potassium dichromate, lead chromate.

Ihave found that there are few simple compounds that will fully satisfy all the conditions because they usually have a dissociation rate that is too slow, or in other words after they have reached the lower limit of range of temperature above stated they are not fully dissociated by the time the upper limit is reached. I therefore add also to the melt an organic substance, which has the effect of quickening the dissociation rate. I call this the activator. The effect of the activator is to form a more complicated salt of the ingoing material. Activators are always organic, that is to say they contain carbon, hydrogen and oxygen. While not wishing to be restricted to the use of the following the most successful examples I have found are alcohol, glycerin, and liquids containing the sugars. Once dissociation has started, the complex salt formed by the effect of the activator evolves the oxidisable and volatilisable components at a high rate. The eifect of the activator is, therefore, to increase the rate at which dissociation of the compound takes place within the temperature range described.

By this means, then, the oxidisable and volatilisable components are kept in a form in which they may be termed latent until the temperature has reached the correct point, when they are released quickly, and in the nascent or more chemically active condition. The alloy, therefore, is formed and as the melt is at the most efiective alloying temperature (but may be below the melting point of one or more of the separate ingredients) the alloy forms rapidly, at a lower temperature than is usual for the alloy being formed. Because of the said lower temperature, such undesirables as slag, or gangue are not melted, and are easily skimmed off.

The invention consists in mixing with. one or more of those ingredients of the alloy comprising nickel, which are liable to oxidise or volatilise, or otherwise to be impaired in the melt,-two or more substances, one of which is a metallic salt and another or the other of which is alcohol for instance methylated spirit.

Although the mechanism: of; the reaction. isv not fully understood, I am led by my experiments to believe that the added substances reactvwith one or more ingredients of the melt at some temperature lower than the melting point of'the alloy to form a chemical compound'whose temperature of dissociation is below but approximates to the melting point of thealloyxto. be formed. When dissociation is fairly advancedor. is complete, the ingredient or ingredients of the meltwhich have formed part of the chemical compound are then in the nascent vapour state and combine easily and rapidly with theother ingredient or ingredients of the melt which then, as a whole fuses at a temperature substantially lower than that at which the same alloy is formed by known processes. Because of the said lower temperature, such undesirables as slag or gangue are not melted, and are easily skimmed off.

I have successfully made the following alloys by this process.

An alloy containing copper and nickel by the use of calcium nitrate and methylated spirit; or lime with potassium or sodium nitrate with methylated spirit.

Although I do not wish to be bound to specific cases, the following practical example will show the method more clearly. Suppose an alloy is required consisting of copper and nickel, a suitable operator will be lime and nitre, in equal quantities in total weight about 3 to 5 per cent. of the nickel. To this is added the activator, methylated spirit, just sufficient to make the lime and nitre into a paste. The nickel, lime, nitre and methylated spirit are then mixed and added to the copper, which is already in the cold melting crucible. Then heat is applied and the melt proceeds normally but will take place at a comparatively low temperature for this alloy and more quickly than usual.

I claim:

A method of preparing an alloy of copper and nickel which comprises preparation of a paste of lime and niter and methylated spirit, mixing this paste with the nickel, adding this product tothe copperv and heating the mixture until the metals fuse and form an alloy.

FRANK LEVERICK.