US2060920A - Nonferrous metal - Google Patents

Description

Patented Nov. 17, 1936 lTED STATES PATENT OFFICE NONFERROUS METAL No Drawing. Application September 12, 1935,

Serial No. 40,342. 21, 1933 2 Claims.

This application is a continuation in part of our application Serial No. 752,184.

The invention relates to improvements in zinc alloys and to articles made therefrom such as 5 rolled sheets.

It is known to prepare binary alloys of zinc for special purposes. Moreover, good quality commercial brands of zinc, which contain lead and perhaps certain other elements such as cadmium are commonly used for the manufacture of engraving sheets. It is known that zinc in its cast state has a crystalline structure which makes it difficult to work and until such structure has been modified by heat treatment or other means, it is unsuitable for many industrial purposes. Further, zinc both in the pure state and also when mixed or alloyed with certain other elements such as lead can be rolled successfully only at temperatures not exceeding 200 C., and 20 after rolling either hot or cold it undergoes serious increase of grain size when heated to temperatures of 250 to 300 C.

According to the present invention alloys of zinc are prepared which contain at least 99% of zinc, and nickel and/or cobalt together with silicon in an amount not greater than is required to form a silicide. The proportion of the metallic element or elements is usually from 0.02 to 0.25 per cent (preferably 0.10 to 0.18 per cent) and that of silicon from 0.001 per cent upwards (preferably 0.001 to 0.03 per cent), provided that the ratio of silicon to the metallic element or elements must not exceed that corresponding to the chemical composition of the silicide or silicides of the particular element or'elements, but may be considerably less than this amount. The proportions are those in the finished alloy as some of the added ingredients may be lost in the dross. The purpose of the silicon is largely to act as a deoxidant and this purpose is fulfilled if the alloy contains any amount of residual silicon which is analytically detectable.

Small quantities of other elements may be present, notably lead (say 0.1 or 0.3%) which improves the etching and cutting properties of engraving sheets.

A deficiency of nickel may be met to some extent by an addition of lead; a preferred proportion of nickel is in the neighbourhood of 0.1 to 0.15 per cent with, say, 0.1 per cent of lead.

A suitable method of incorporating the ingredients is as followsz- The nickel and silicon are first alloyed to contain a suitable proportion of silicon, that is, not more than 20% of silicon and not less than 80% In Great Britain October of nickel. After alloying this metal is subdivided bypouring in a thin stream into water in the usual way. A proportion of this alloy is dissolved in molten zinc to make an alloy containing about 5% of nickel with a corresponding percentage of silicon. This rich alloy is used by adding to the molten zinc to give the proportion of nickel required in the casting, which is then ready for the hot rolling operation.

Alloys prepared according to the present invention possess very favourable qualities as compared with zinc itself or with the previously known alloys of zinc. Thus the new ternary alloys of zinc, nickel, and silicon cast well; they are readily worked hot, from temperatures of 350 C. or even higher, and are capable of undergoing severe cold working. The grain size after hot and/or cold working is not seriously increased by heating at temperatures as high as 350 to 380 C. The alloys possess both in the cast and in the worked state great ductility and a hardness which makes them suitable for many technical applications. As a result of these valuable properties the alloys are capable of being rolled direct from the cast ingots without preliminary heat-treatment, and at much higher temperatures than are customary with zinc or the usual alloys of zinc, and their high ductility enables them to be rolled into thin sheet strip or foil and to be drawn into wire. In fact, the presence of a small proportion of a metal silicide greatly assists mechanical working of the zinc alloy, in general.

The alloys possess numerous technical applications and they are particularly suitable, for example, for the manufacture of engraving sheets. Such engraving sheets are characterized by exceptional cleanliness, uniformity, and rapidity of etching, while their immunity from any development of a grain structure at temperatures encountered during the burning-in process considerably simplifies the latter operation. Sheets for use in lithography afford another illustration of their successful application in the arts. The alloys are also particularly suitable for extruding into rods or rolling and drawing into wire.

The zinc employed in the preparation of these alloys may be electrolytic zinc or commercial zinc; in general the former is preferred. In addition to the elements already enumerated, that is in addition to one or more of the metallic elements previously named and to the corresponding proportion of silicon, the alloys may contain, if desired for special reasons, small amounts of other elements such as aluminium or cadmium or lead.

A typical alloy which may be prepared according to the present invention contains 0.13 per cent of nickel, 0.01 per cent of silicon and 0.1 per cent of lead. The alloying elements may be added to the molten zinc before casting, but it is preferable to prepare initially an alloy of zinc, nickel, and silicon which is relatively rich in nickel and silicon and then incorporate this in the zinc. It has been found that the alloys are best prepared by melting in an electric induction furnace.

The function of the silicon appears to be twofold; it appears to efiect complete deoxidation of the alloy and so to allow of the production of sound dense castings free from porosity and from oxide inclusions; it is further believed that the residual silicon may be present in the form of 2,

metallic silicide such as NizSl or CozSi etc., and that it may exist in this combination as a disperse phase distributed throughout the mass of the alloy.

We declare that what we claim is:-

1. An alloy for engraving sheets capable of hot working from temperatures exceeding 350 C. and capable of reheating thereto without increase of grain size, containing 0.02% to 0.25% of a metal selected from the group consisting of nickel and cobalt, 0.001% to 0.03% of silicon, substantially 0.10% to 0.30% of lead, and the remainder completely deoxidized zinc.

2. An alloy as in claim 1, in which the content of nickel is 0.13%.

HENRY CHARLES ANSTEY. WILLIAM ERNEST ALKINS.