USRE18378E - Franz wever - Google Patents

Description

'1 position to act on them. In these processes. the impurities and partially converted into Reiasued Mar. '8, 1932 UNITED ,sTA'ras PATENT rnanz wnvna, or nussnnnonr, erascauan'r, Assmnon, at new Assmmanu'rs, 'ro c. LORENZ ax'rmnonsnnnscnur, or BERLIN-murmur, AND smunns a msxn ax'nauonsnuscmr, or nannm-srnunnss'ran'r, emuumr,

rnocnss 1-03 mm: mnuoarron or mans OFFICE y no Drawing. Original 110. 1,145,4e4, dated February 4.1mm, Serial no. mass, med fl'anuary 18 1927,

and in Germany January, 1926. Application for reissue Med January 26, 1982. Serial No.

Processes have .long been known and in use in metallurgy for the removal of undesirable ingredients from metals and alloys by allowing slags of suitable chemical comgaseous volatile compounds, or are chemically united directly with the'slag, as for example by the addition of substances for which 'the undesirable ingredients possess a bi her afiinity than for the fundamental metal. he

undes rable ingredients are first converted into easily removable mtermedlate substances and are afterwards transferred to the slag.

The efliciency of these methods in the past has been mainly determined in practice by the fact that the dominant operations take place as heterogeneous reactions in two phases. only at the surface of contact between the bath of metal and the slag. 7 As, however, in furnaces of the well known types, the metal and the slag lie comparatively motionless one on top of the other, the rate of diffusion determines the progress of the reaction to a much higher extent than does the natural velocity of the various chemical'processes taking place. The differences in concentration within the bath and within the slag depend upon the velocity of diffusion. This velocity of diffusion is however frequently undesirably low. When the concentration and temperature are low,

- the velocity of diffusion is always very small,

the fluid mass by settlng the bath or the enso that the'last residues of impurities can be removed only very slowly, if at all. The resulting disadvantages are obvious and they quality of the product. Repeated attempts have been made on the one hand to cause vigorous stirring within affect the-economy of the processand the tire furnace in motion mechanicall or by artificially causing an evolution 0 gas, or

on the other hand, to increase the velocity of the reaction by raising the temperature.

These attempts have however only cessful in a few cases.

It is also known that in induction furnaces,

EBII S110- in consequence of the electromagnetic stirring force of the induced currents, movements are set 11P.'Wlthll1 the metal bath. These 6 p I h movements can only act imperfectly in the narrow annular hearth of low frequency induction furnaces, whereby they have no effect upon the metallurgical operations.

These low freguency induction. furnaces do not therefore ilfer greatly, in res ct to the velocity and completenessof the a reactions, from other types of furnace in w 'ch the bath is motionless. On theother hand,

theyare inferior in operation owing to the low' temperature. of the slag and have'therefore not met with such a demand as furnaces of the are types, which have been continually mproved.

The views held as to theeifects of move ment of the bath on the separation of suspended impurities still difier widely. Thus it is considered that electric steel-does not acquire the quality of crucible steel becauw the unavoidable movement of the bath prehave hitherto-been exclusively used for melting down or running down pure metals. Numerous examples can be given indicating that, even in cases where the use of impure charges and subse uent refining b means of suita le sla'gs wou d have been olivious, the

advantages of movement of the bath for re-- oses were never recognized, and therefore high grade pure raw materials were simply melted or run down without any regard to subsequently influencing-the degree of purity. I I The use of the well known high fre uency induction furnaces for refining work or the purpose indicated, namely, the removal of' undesirable ingredients from impure charges I by allowing slags of suitable chemical comosition to react with them, and if necessary y conversion of the impurities into more -idea of 0.04% of .total impurities,

easily removable intermediate substances, by the addition of substances for which the in-' edientspossess a greater aflinity than they 0' for the fundamental metal, is based'on the utilizing the motion of the bath for metallurgical purposes, also for improving the action of the slag and therefore the quality of the product obtained.

This.idea is based on the knowledge ob tainedfrom systematic experiments,v which show that the movement of the bath in high frequency induction furnaces of the kind herein mentioned has unexpected effects .which fundamentally alter metallurgical theory. These results involve an order of magnitude of velocity of movement in the bath and a completeness of the slag reactions hitherto unattained. The vigorous movement in the bath produces coagulation of the highly dispersed components formed in the bath of metal by reaction of the added substances with the impurities tobe removed, so

that if the composition of the slag be correct the impurities can be very rapidly and completely separated therein. Thus, for example, oxygen in an iron melt is very rapidly replaced by added manganese or silicon. The high frequency induction furnace thus, contrary to the much represented view as to the deleterious effect of movement in the'bath on the separation of the impurities distributed through it, is capable of yielding the highest degree of purity by means of the slag reactions effected and this purity is attainable, moreover, by reason of the more eflicient movement of the 'bath than in the types of electric furnaces hitherto used.

That the proposed method of refining metals constitutes anextremely important technical advance willbe more fullylillustrated by the examples hereafter set forth, which are limited to the production of steels. The object of these examples is to show that by the new method .of operating, not only is a considerable increase in the quality of known products obtained, but entirely new methods of production are rendered possible, which cannot be carried out in the apparatus hitherto used.

The increase in the speed of refining due to the vigorous movementof the bath in the induction furnace having no iron core, may first be utilized to remove those undesirable substancesin association with the iron, which have a higher aflinity for oxygen, much more 1 quickly and moi-e completely from the charge than is possible with the refining apparatus hitherto known. Thus it has been possible in carrying out the method of the present.

invention to obtain an iron with only'about consisting ofjbarbon, silicon, manganese, phosphorous and sulphur, and, therefore, considerably to surpass the hitherto known degree of purity.

The imprc vement obtained is still further ..of 0, and 1.45% of power in drawing was surprising. The .same steel could be rolled out in a tube rolling increased by the fact that, after the partial oxidation of the fundamental metal which is unavoidable in the refining. treatment, the oxide may be reduced muchlmore completely than hitherto. Owing to the vigorous stirring movement in the bath, the reaction between the oxygen combined with iron and the deoxidizing agents added takesplace very refining is stopped at the moment when the a main quantity of the oxygen has been reduced products have been transferred to and the the slag.

Thus steels produced with the very low carbon content of 0.01% were, notwithstanding the low content of deoxidizing agents (0.13% to 0.17% of Mn and 0.15% to 0.22% of Si) very free from red shortness. They could be used on .a manufacturing scalewith a very small pro ortion of waste for rods and fine sheets. sample treated cold at a high rate of speed was still completely satisfactory after being rolled down by 90% to 0.22 mm. Without any intermediate annealing. The testing of the. annealed sheet strips on the Erichsen apparatus gave depth values which were all considerably above the normal curve laiddown by Erichsen. A similar material containing 0.01% C, 0.46% Mn and 0.22% Si could be rolled into tubes in a perfectly satisfactory manner on a manufacturing scale in a Stiefel rolling mill.

Carbon steels produced according to the new process yielded, even in the preliminary experiments, quality numbers in multiple hardening which not only equalled the fig-' ures of selected commercial steels but in some respects. considerably surpassed them.

In like manner fused iron-chromium t1- loys could be further worked in all cases with a surprising V ease hitherto unattainable. Thus, for example, the expenditure of labour forv the hot rolling of a chromium iron containing 0.02% C and 12.67% Cr, was only two-thirds that required for a malleable iron rolled under similar conditions. In the case. of a chromium-nickel steel containing 1.1 of Cr, the small expenditure mill without difliculty, the amount of power required being about 10%' less than that required for a first class commercial product treated under exactly similar conditions.

The possibilities of development resulting from the new process are indicated by the following examples The manufacture of thechromium alloys and nickel alloys required for various purposes and containing small quantities of car-' on isat the present time only possible with very great expense, as chronnum and nickel pairin of the quality of thematerial, is not possibl e. Practical experiments have conclusively demonstrated that a new method of working can be developed on the principle of the vigorous stirring of the bath of metal in the ironless induction furnace, which permits the demands made on the degree of purity of the raw materialto be considerably reduced. Thus, in a practical example, a low carbon iron-chromium alloy was produced by first alloying a ferro-chromium containing 4.8%

C and 64.9% Cr with a bath of iron, and subs sequently removing the carbon by refining with hammer sla Immediately after the addition of the c romium, themelted mass contained 1.04% C and 14.5% Gr; while after refining, the carbon had dropped to 0.16% and the chromium to 13.42%. -The product could be worked on a manufacturing scale in a satisfactory way and rolled into tubes in a Stiefel rolling mill, and therefore it is, notwithstanding the refining treatment, perfectly free from red shortness even under severe conditions. This proves that the chromiumnickel alloys which are highly sensitive to oxygen can be subjected in ironless induction furnaces to a refining treatment without the chromium being greatly burnedaway, the metallurgical properties of this furnace ensuring at the same time a thorough deoxidation'with a suitable methodofworking.

9 In the metallurgy of pure nickel, the refining of impure charges by means of slags of suitable composition has not so far been found to be possible. The reason for this is that by the means hitherto available for the purpose, the slow-and incomplete progress'of the metallurgical reactions between the slag and the bath rendered it impossible to be sure to preventthe bath from becoming supersaturated with oxygen or to properly-reduce the oxide formed. In view of the high sensitiveness of-nickel, this resulted in the prop- The metallurgical treatment of nickel is limited for this reason to the remelting of a. very pure intermediate product without any appreciable effects on its composition.

crude nickel to be purified inetallurgically,

conseq-uently-greatly decreasing the total cost of production and treatment. The new pr0cass is more fully described in the following example. i y a I In remelting a very pure-Mond nickel by themethod of working customary to the present day in the metallurgy of nickel, the following analysis was obtained: 98.86% Ni+ (,0 0.04% Si, 0.013% C, 0.72% Fe, 0.15% Mn, 0.052% Mg, 0.29% 5, 0.142% Cu.

In refining according to the invention, on the contrary, a highly impure nickel containing both carbon and sulphur was melted in an ironless induction furnace and treated subsequently by the developed process. This consists in first carrying out a vigorous refining by the aid of an oxidizing lime and fluorspar slag and the addition of nickel oxide. In this treatment all the elements hav-- ing a higher alfinityfor oxygen than has the fundamental metal are highly oxidized and combined with the slag. In addition the ex-- "cess of oxygen which is present as nickel oxide, under a thick layer of lime and fluorspar .slag, is combined by the addition of manrnelted pure nickel is thus greatly surpassed.

The nickel refined in an induction furnace having no iron core can be satisfactorily forged and rolled. v

I claim 1. Process for refining metals and alloys carried out in a high frequency induction furnace consisting in treating the metal with a slag which under the conditions of temperature and vigorous stirring in which the treating is carried out in the said furnacehas a greater aflinity for impurity than the fundamental metal and in vigorously stirring the metal and slag under 'conditions usual in a high frequency induction furnace.

2. In process specified in claim 1 the addi tion to the melt of a slag forming substance that is adapted under the conditions of vigor ous stirring imparted to have a greater ailinmetal. 7

3. In process specified in claim 1 the addi-- erties of the material being badly impaired. 1 non to the'fur-nace chug? of deoxldlzmg agent. 4. Process for treating "a metal or alloy "carried out in, a high frequency. induction furnace consisting in refining the metal with an oxidizing slag which, under the conditions of temperature and vigorous stirring in which the refining is carried out inthe said furnace, has a greater tendency to oxidize the impurity than to oxidize the fundamental metal and in vigorously stirring the metal and oxidizing slag under the conditions 11 ity for impurity than for the fundamental I usual in a high frequency induction furnace. 5. Process for treating a metal or alloy i I carried ,out in a high frequency induction furnace consisting in refining the metal with an oxidizing slag which, under the conditions of tem erature and vigorous stirring in which the re ning is carried out in the said furv nace, has a greater tendency-to oxidize the impurity than to oxidize the fundamental 1Q metal, in vigorously stirring the metal and oxidizin slag under the conditions usual in a high requency induction furnace and'in deoxidizing the metal by adding a deoxidizing agent. i I FRANZ WEVER.