US1770433A - Alloy - Google Patents

Description

Patented July 15, 1930 .ATNT OFFIC WILLIAM ROBERT SALTRICK, OF PURLEY, ENGLAND, ASSIGNOR TO ROBERT WICKER- SHAM STIMSON, OF NEW YORK, N. Y. ii

ALLOY No Drawing. Application filed February 14, 1923, Serial IiTo. 619,015 and in Great Britain March 7, 1922.

This invention relates to the production of richly alloyed special steels, including special tool steels, and comprises a process of manufacture wherein any number of metals to be alloyed with the elements iron and any quantity of carbon, are obtained direct from their ores, and a suitable furnace, which is to supply'the heat units needed to accomplish the chemical reactions and maintain the metal-bath in a fluid state, is employed for the purpose of smelting materials consisting of: (a) any number of ores of non-ferrous metals and (b) silicon, in the form of an ironcontaining alloy, but in a quantity "which is insufficient to decompose all of the iron and reducible, non-ferrous, metallic oxids present in the, ore, and to which (a) suitable slagforming and slag-liquefying fluxes are added for the purpose of forming a liquid, calcareous slag. These reactive materials are fed to a furnace, containing a prepared steel bath, i. e., a protected, bath of refined mediumsoft, or extra-soft, steel, and smelted; and, from the location they naturally gravitate to above the metal bath and beneath the upper surface of the liquid, inert, non-metallicmatter, covering the metal-bath, i. e., the molten, non-oxidizing fluxes or the fluid slag that rapidly forms therewith, the alloying, metallic reaction-product sinks into the molten steel, without being altered from its original liquidity and sustaining the loss of heat that is unavoidable in any less direct method of being dissolved in, or diluted with, the element iron.

Richly alloyed special steels that may be made according to the invention comprise iron and any quantity of carbon and include any number of alloying metals, such as cobalt, chromium, molybdenum, tungsten, vanadium and the like,for examples, ironchromiu1nvanadium-carbon and iron-cobaltchromium alloys. .As regards their carboncontents, it may be said that they are frequently below 0.70% of the aggregate; and, in the case of some alloy steels, including iron-chromium-cobalt. alloys, the carboncontent may not exceed 0.10% of the aggreate.

a Usually, heretofore, these special alloy steels have been made either by melting down substantially pure alloy element, or

ferro-alloys of the alloy elements, with appropriate steel in crucibles, or by making such alloying additions to liquid steel in an electric furnace,suitable provision being made for recarburizing the alloy, when necessary. It is the object of my invention, therefore, to dispense with the separate production of any number of the alloying elements, or their ferro-alloys, and thus eflecting savings in heat, transportation charges and time. In my co-pending application, Serial No. 617,143, a process is described whereby an ore of an alloying metal is reduced above a prepared steel or ingot iron bath, a silicon alloy, containing iron with, or without, another reactive or fluxing metal being employed in the approximate quantity required to reduce the ore to metal; and, in order that heat units may not be wasted upon inert matter, only enough fluxes are added to produce an easily fusible and sufficiently liquid slag. Since the chemical reactions are not sufficiently exothermic as to'be self-maintaining, after having been brought to the reacting temperature and started, heat provided by a furnace is employed to accomplish the reactions and keep the metal-bath in a fluid condition. The special steels produced according to' this method, which provides for an oxidizing treatment, are very low in carbon, even when an electric arc furnace having carbon electrodes is used; but unless extreme care is exercised, the steels may contain more silicon than it is desirable to remove, and thus make them unfit for certain purposes.

'Now, I have found that when fluid slag, containing the reactive materials, also contains an excess of lime, so that uncombined C210 is present therein until the metal-bath has been sufliciently alloyed, the quantity of chromium that is precipitated into the, steel bath is greater than otherwise; also that when the ratio of silicon to reducible metallic oxids is diminished, so that a surplus of ore exists in the slag until the metal-bath is sufficiently alloyed, and when this latter condition is concurrent with the presence of tion of calcium carbide, on or in the calcareous slag, and to the indirect, as well as direct, reaction of carbon with metallic oxids present in the slag.

According to this invention, which-comprehends the manufacture of alloy steels that are high in carbon, as well as those that are substantially free therefrom, one. or more ores, beneficiated ores, or oxygen-containing compounds, such as, roasted sulphide ores, mattes and speisses, are reduced above a prepared medium-soft or-extra-soft, ordinary or alloy steel or ingot iron bath that is contained in a non-carbonaceous lined furnace, which supplies heat requisite to the melt.- As the reducing element I employ silicon, an element which may be readily oxidated and removed from the liquid steel with little loss of alloy elements; and, to diminish the quantity of silicon that would normally find its way into the metal-bath, i. e., according to'the chemical equations of the deoxidizing reactions, I employ less silicon than is required to deoxidize the reducible metallic oxids, and flux the reactive materials with a considerable quantity of lime and fluorspar, thereby forming a calcareous, oxidizing slag. For the purpose of decreasing the natural tendency of the reducing element to separate from the ore and rise to the upper surface of the slag, where it burns or is vaporized, it is used in the form of an iron-containing alloy, which may also contain other metals, for examples, ferro-silicon and ferro-calcium silicide. When objectionable quantitiesof oxidizable impurities are found to have entered the metal-bath they are removed by means of an oxidizing treatment, such, for example, as employing an air blast; when required the composition ,of the metal-bath is adjusted by metallic alloying additions and recarburation; and, finally, the metal-bath is treated with any of the known deoxidizing and scavenging additions and finishing slags. j

The steel bath may be prepared in any of the well known ways whereby a liquid, softsteel is provided that is suitable for the purpose in view. Thus it will be purified, if necessary to remove objectionable quantities of the various metalloids; it may be deoxidized before adding an alloy element; and, as is also customary, it will be covered with a non-oxidizing layer of basic fluxes, such as, lime and fluorspar, to protect it from the oxidizing atmosphere that is introduced when the reactive materials are being fed to the furnace. I have found that the steel bath should contain less than 0.30% of carbon, otherwise metallic oxids, present in the slag, cause the'metal-bath to boil to an extentthat interferes with the operation of the process.

Any convenient kind of high-temperature furnace may be used to supply and apply the heat required during any or all steps of the process, provided it has a non-carbonaceous hearth and lining. I prefer to use a tilting, direct are electric furnace having a basic lining, such as of magnesite, dolomite, magnesia, and the like, and having the usual carbon or graphite, electrodes.

Because of using more lime and using metalliferous material in excess of the requisite quantity, the present process requires more independent thermal energy than the process disclosed in my co-pending application, Serial No. 617,143; nevertheless the ore-reduction and bath-alloying step isfacilitated in every way without increasing the temperature of the slag and metal-bath so high as to cause serious metallic vaporization losses. In addition to applying sufiicient independout, i. e. furnace developed heat, it is preferred to use a reducing agent, for this purpose, that is rich in silicon; also, when permissible, about ten per cent of the silicon may be replaced with powdered aluminum. It is also a feature of the invention that, when the analysis of the final metal permits, carbonaceous matter, which may be calcium carbid, may be employed in part, or exclusively, to reduce some of the metalliferous materials, such, for example, as tungsten concentrates. The following example of a preferred method of operation will explain to those skilled in the art how the invention is performed,it being understood that no limitations are implied, also that specific materials, the manner in which they. are used and the mechanical equipment may be abbreviated, augmented, or otherwise. selected, as is expedient according to known practice, in the production of richly alloyed special steels.

The metalliferous materials to be reduced, which may consist of ores, concentrates, mattes and speisses, are beneficiated, according to their natures, to form oxygen ous metallic compounds and remove sulphur, arsenic, gangue and the like; after which they, and the reducing agents, are crushed to pass through a 20 to 30 mesh screen, intimately mixed together and either sintered or briquetted with the aid of a bindingagent, which may be silicate of soda. Obviously, metalliferous materials of more than one alloy element may be included in a briquet, but it is preferred to make and use a variety of briquets each containing one alloy element only; also solid ore and reducing agent may be brought into contact with each other within the layer of molten fluxes or the fluid slag that is rapidly-forming therewith, i. e., they may be fed to the furnace separately and in anyorder, but it has been found that the reactions are accelerated and steadier whenthese materials are bound together and in a state of intimate admixture. The reducible metallic oxids, in the metalliferous materials, are calculated and employed so that they will be present in the briquets in a ratio that will provide an excess of about ten per cent over the requisite quantities, as indicated by the chemical equations; and lime, or preferably lime and fluorspar, is added in quantities sufiicient to produce a fluid, decidedly limy slag. The latter condition, as is well known, is easily recognizable because of having a chalky, insteadof vitreous, consistency or structure. In the be inning only enough of the above described riquets are fed and smelted to form a slag, with the layer of liquid non-oxidizing fluxes that protects the steel bath, which will be deep enough to either cover or to envelop the next charge of briquets; and this minimum depth of slag is maintained as long as briguets are to be smelted. After the slag is ormed I find it advantageous to feed enough briquets, at a time, to add approximately 2% to 5% of an alloy element to the metalbath, and, preceding each charge the bathtemperature is increased, the furnace is tilted, and the unnecessary accumulation of slag is poured ofi, also lime and about one-tenth its weight of fluorspar are fed to the furnace before and after the briquets. During this step of the process the bath is rabbled, samples are taken and to avoid wast ing the electrodes, they are preferably elevated and kept away from the oxidizing slag, also the furnace is manipulated so that it applies independent heat, to the charge, in increased or decreased amounts,as required to accomplish rapid reactions without unnecessarily vaporizing metals. When an analysis of the bath shows that its alloy element, or elements, is or are, present as desired, fiuorspar, with or without borax, is added to further liquefy the slag and release particles of metal that may be held in suspension therein; the bath-temperature is increasedabout -100 6.; the slag is largely poured ofi, and,

if the metal-bath contains too much silicon, a farm-manganese addition is made and the bath is given an oxidizing treatment, as by a blowing operation in the same or any other furnace, or a reaction chamber. And, finally, finishing additions are made, the bath is recarburized, if necessary, and the richly alloyed steel is treated, tapped and teemed in the usual befitting manner to produce sound in ots.

It should be mentioned that when final specifications require the removal of silicon and I resort to a blowing operation therefor, I may allow for a concurrent loss of alloy elements by adding the elements in excess of the maximum tolerances specified, but owing to the absence of any substantial quantity of carbon at the time the molten alloy -may be blown, the blowing operation does hearth furnaces.

What I claim is: 1. In the manufacture of special steels, of

- all kinds and all degrees of alloying enrichment, by any furnace method that makes use of an operation wherein and whereby both smelting and direct alloying actions take place, also wherein the metal to be alloyed, which comprises the element iron, and a separate metallic reducing agent, which contains silicon, and a reducible metal-yielding material, are at any time used simultaneously: the step of employing, durin the operation, a greater quantity of metalli erous mattercomprising an oxid of an alloying elementthan is re uired according to chemical equations of t e reactions, whereby silicon is transformed into silica, to oxidate the quantity of silicon used in the form ofa reducin agent, the amount of such oxid material being sufficient to keep silicon substantially out of the metal bath.

2. In the manufacture of special tool steels, rust resisting steels and the other alloy steels that are malleable at a steel working temper- 'ature, by any furnace process that makes use of an operation wherein and whereby both smeltin and direct alloying actions take place, a so wherein the followin materials are, at any time, employed simu tane- 'ouslyz (a)-a metal to be alloyed, comprising the element iron; (b)--a separate metallic reducing agent containing silicon also an number, any kinds and any variety of (c -non-metalliferous fiuxing materials and (d)-materials to be reduced that comprise an oxid of an alloying element: the step of employing, during the operation, any

quantity of siliconin the form of a sep-- arate reducing agent-which is less than the qlillantity specifically required according to c emical. e nations of the reaction, whereby Si is trans ormed into SiO to completely reduce all oxids that become part of the to-' tal furnace charge which are oxide of the metals composing the final alloy, the amount of such oxid material being sufiicient to keep silicon substantiallyout .of'the metal bath.

3. In the manufacture of special steel by a process as set forth in clalm 1, the step of extracting an alloy element from its oxid within molten slag covering the metal to be allowed.

4. In the manufacture of special steel by a process as set forth in claim 1, the step of producing a basic slag, in any stage of the process. I

5. In the manufacture of special steel by a process as set forth in claim 1, the step of producing a slag containing free lime, in any stage of the process.

6. In the manufacture of special steel by a process as set forth in claim 1, the steps of adding metalliferous matter, comprising an oxid of an alloying element, to slag covering liquid steel of any kind that has not been mechanically enriched with silicon; and, thereafter, heating the slag, reducing the metallic oxid-in the presence of fluxing materials-by means of a metallic reducing agent containing silicon, which reducing agent is also added to the slag, and allowing the metallic product to sink directly into the li uid steel.

In the manufacture of special steel by a process as set forth in claim 1, the steps of: adding a metallic reducing agent containing silicon, to slag covering liquid steel of any kind that has not been mechanically enriched with silicon, the addition being made in any manner that permits the metallic reducing agent to come into contact, whilst within the slag, with metalliferous matter comprising an oxid of an alloying element; and thereafter causing chemical reactions to take place between the reagentsin the presence of fluxing materials-and allowing the metallic product to sink into the underlying steel.

8. In the manufacture of special steel by a process as set forth in claim 1, the step of employing a reducing agent which approximately consists of the elements silicon and 11011.

9. In the manufacture of special steel by a process as set forth in claim 1, the step of employing a reducing agent which comprises silicon and calcium.

10. In the manufacture of special steel by a process as set forth in claim 1, the step of replacing a portion of the silicon-containing reducing agent with powdered aluminum.

resisting steels and irons and other steels. wherein more than the chemically prescribed quantity of metalliferous matter-comprissilicon-containing metallic reducing agent, are associated and smelted above liquid metal comprising the element iron; which comprehends preparing a suitable bath of appropriate ferrous metal to be alloyed in a furnace, and thereafter adding the above mentioned reactive agents to, also applying heat to, molten slag lying upon the liquid metal, the amount of metalliferous matter being sufficient to keep silicon substantially out of the metal bath. 3

14. A process of manufacturing ferrous alloys, as set forth in claim 13, wherein chemical reactions, resulting in the extraction of an alloy element, occur in fused slag lying upon the metal to be alloyed.

15. A process of manufacturing ferrous alloys, as set forth in claim 13, wherein any surplus of metalloidal impurities contained in the alloyed metal, is removed by means ofv an oxidizing, gaseous blast.

16. In the manufacture of richly alloyed special steels by a process wherein metal yielding material and a silicon-containing re ducing agent are added to a slag layer lying above liquid metal comprising the element iron, the step of employing a surplus quantity of metal yielding material comprising an oxid of an alloying element to react with silicon, the amount of metal yielding material being sufficient to keep silicon substantially out of the liquid metal.

17. In the manufacture of richly alloyed special steel wherein metal-yielding material and a silicon-containing reducing agent are caused to react in a slag layer lying above liquid metal comprising the element iron, the step of employing a surplus quantity of metal-yielding material comprising an oxid of an alloying element to react with silicon, the amount of metal yielding material being sufficient to keep silicon substantially out of the liquid metal.

18. The process for the manufacture of corrosion resisting steels and irons and other steels which comprises reducing chromite by exotherimc reaction wtih a silicon-reducer in presence of excess of chromite over the quantity chemically equivalent to the reducing agent, the amount of chromite being sufficient to keep silicon substantially out of the desired final metal. 11. In the manufacture of special steel by WILLIAM ROBERT SALTRICK.

" ing an oxid of an alloying elementand a Inn