US1053454A - Process of improving the quality of malleable iron and steel. - Google Patents

Description

30 once successor in Drawing.

OFFICE.-

' o'rro Tasmania, or a assidi'ton zro ELEKTIBDSTAHL a. M. s. E,

, ormsqssm nasrsu, cannery.

I autism or minim IRON AND STEEL.

To allwlwmiitma concern r d Be it known t at I, O'rroTHALt-Jfim, a subject of the German Emperor, residing at Remscheid, in Germany, have invented a new and useful Process of Improving the Quality of Malleable il-on and Steel, of which the follow' I is-a specification.

' My invguti'on" re ates to 'a' process for treating, maileablpi.

I re" culiar crysta silt very ingzp a uw l t or substantially identical wan-,u grain-which has always been observedcruciblel steel and which apparently gives to-such steel its great tenacity.

process consists substantially in the treatment of liquid malleable iron orsteel in the manner hereinbelow stated and more particularly claimed in the appended claims.

3 My process may be operated in a hearth-' furnace (using this term to distinguish from the crucible or pot) and more particularly in an electric arc furnace, also on either an acid hearth or a basic hearth, whether the heat be furnished by gas, by electricity,

or in any other suitable manner.

The characteristic steps of my process, as o erated in practice, consist in adding to t e slag, or'providing'therein for the presa metallic oxid capable, under the conditions of melting practice, of giving oxygen to the bath of liquid malleable iron or'st'eel which is-covered by the slag; and also to add carbon to such bath. For inl stance, when working on an acid hearth with acid slag, I add to the slag a quantity of iron ore, and simultaneously provide for the presence of carbon in the bath by" inserting carbon therein. This carbon is pref- 'erably in the form of the solid oookedmixture of iron, carbon, and tar, known as carburite, which is particularly described in German Letters Patent No. 151,610, dated the carbon during the process substantially- April 25, 1902. By using this carbu'rite no i 5 Pspecific. process, but it may be stated that I the manner above described. While I prefer to commence with a liquid bath of metal which has been carburized to that content of carbon which is required for the finished metal, it is not essential that this be done, as I may, during the operation of my process and parallel thereto, carburize the metalto a higher degree of carbon.

It 15 not possible to state any definite proportion of iron ore to the amount of metal in the liquid bath as this amount will have to be determined in each case by the partlcular circumstances thereof. However, the amount of iron ore should not be so great as to provide an excess of oxygen which will thereafter remain inthe bath and or to contain blow holes? The iron ore should, of course, be sufiicientin quantity to insure the satisfactory erformance of the process. Generally, it Wlll be found that the iron ore should be somewhere between of carbon is to be added to "the bath as this stances of the case, or instance upon the amount of carbon already in the metal and product. I may, for instance when working with liquid metal carburized to the content of carbon desired in the finished metal, for example to v one per cent. of carbon, place therein from nine (9) to fifteen (15) kilograms ofcarbon in the form of carburite, but I may also add a larger quantity of carbon and withdraw the excess when samples taken from the bath show the required carbon content and the desired grain. I do not limit myself to the exact proportions or specifi ingredients of the slag used in this may use 30-35% sand, 3035% of lime and, to increase fusibility, 510% manganese ore, and add'to this mixture 25-30% of iron'ore. I may treat a bath of refinediron or steel in a basic furnace with a basic slag in a similar manner. The slag which I may use, without, however, limiting myself to any particular materials or proportions,may be composed of from about 40-50% lime the amount of carbon desired inthe finished and 2025% fluorspar which may be par- Patented Feb. 18, 1913.

cause the resulting metal to be' red-short I one and two and a half per cent. of the weight of the liquid metal. It'will also'not be possible to state exactly what. proportion proportion depends u on the many circuma bath of five thousand (5 000) kilograms of .25- 'working this process a parentlyjjustify the,

v above by othesis, and

that is to say, a slag free from oxid of iron,,

for the purpose of eliminating sulfur. The

' urified metal may be transferred to an acid earth and therein subjected to the acid treatment above described; or it may be left in the basic furnace and therein subjected tot-he basic treatment as described above.

As the exact course of the reactions in a process of this kind, particularly at the high temperatures involved, is most diflicult, if not impossible, to determine, I am not able to state positively what chemical changes take place in-the metal bath when treated as above described. In submitting the following theory as to the reactions I desire to be understood as utting forward no more than a hypothesis, y which I desire in no way to-be bound. The amounts of the various ingredients actually employed by me in have received much aid there rom in. determining what amounts to employ under various conditions and circumstances. I In the iron bath there are present, during the process, iron, carbid of iron and oxygen at a high temperature without acting upon one another. The reason for this inaction will be hereinafter explained. If the process is worked on a basic hearth, the slag will contain calcium oxid as well as iron ore (Fe O or Fe o and carbon, which is preferably added in the form of carburite, will be present both in the slag and in the bath. The calcium'oxid reacts with the carbon, or with the carbid of iron of the bath, to form calcium carbid.

The calcium carbid reacts with the iron of the bath and the oxygen dissolved therein to form calcium oxid, the carbon in nascent condition uniting with the iron to form carbid of iron.

0 CaC,+5Fe-|(Fe+0) #CaO-f-2Fe O. I In the above formula (Fe-l-O) represents iron holding oxygen in solution.

Itis my theory that the peculiar grain which is characteristic of crucible steel is due, not only to the action of nascent silicon so on iron as is commonly believed, but to a large extent to the resence in the iron or steel of molecules 0 ---carbid of iron'formed by the union of nascent carbon with iron. This would explain the necessity of rovid- '55 ing carbon in combination with anot erele ment of such a nature that at the temperatures in question, the aflinities are such as to permit the carbon andthe iron to unite.

The CO reduced by reactions A'or B probably umtes in .part with iron according to. the following formula;

in which case again nascent carbon unites with the iron.

I As the liquid metal at these temperatures will hold in solution only small quantities of oxy en, and part of the oxygen, in the form 0 CO is lost by rising out of the bath, it is clear that to obtain enough nascent carbon the oxygen at least must continuously be replaced. This is done by adding the Fe O, or Fe O to the slag, which substances decompose at the high temperature .into

' This is the (Fe-l-O) referred to in reaction (C). It is the oxygen thus dissolved in the iron which appears at these high temperatures, to be a necessary active ingredient in my process.

As much of the carbon is lost in the form i of CO (formulas A and B), theicarbon must be replaced and this is done by addingthe carbon as above described. If reaction}. A takes place, as I believe, thenthepres ence of the added carbon undoubtedly L XL hastens the formation of calcium carbid and thus speeds and cheapens the process.

hearth the course of the reactions is prob ably analogous to those above the lining or that which is present inthe slag, or both takes .thetlplace'of the CaO.- While it is known (R50) is reduced, by carbid of iron; iris also known that ,OXXgEIlYdlSSQlVGd in iron "will not react on carbid-of iron. The at finity of iron andcarbon increases as the temperature rises; carbid of iron being an endothermic body The. afiinity of iron for oxygen, and of carbon for oxygen, decreases as the temperature rises, protoxid of iron and carbon monoxid being. exothermic bodies. At a temperature which has not yet been exactlydetermined,the aflinityltheat I tension) of the carbid of ironjovertakes j that of protoxid of iron and ofcarbon monoxid; this temperature is, however, less than that at which my process isavor edf Therefore, oxygen, iron and. carbid of iron,

can exist side byside, undisturbed, under thetemperature conditions ofmy process.

At the temperature of my process the afiinity above reactions ,0 and D.

given, except that 810,, either that which is present in" at protoxid =of iron" ram vWhen the process is operated on. an acid When I speak in the claims of heating I the metal I mean that the metal is heated to a tem erature at which the result described w1l1 be attained, that is to say, as I understand the matter, to a temperature at which the oxygen dissolved in the iron will not decompose carbid of iron. When I speak in the. claims of malleable iron, I refer to liquid iron which does not contain more than substantially 2% of carbon.

I claim: I

1. The herein described process of im-. proving the quality of malleable iron or steel by causing a metallic oxid and carbon to react at the same time thereon in a hearth furnace at a temperature at which oxygen dissolved in the iron will not decompose carbid of iron.

2. The herein described process of improving the quality of malleable iron or steel which coinprises covering it in a hearth furnace with a slag containing a metallic oxid capable of supplying the metal with dissolved oxygen, heating the metal and adding carbon thereto, so that the dissolved oxygen and carbon may be simultaneously active within the metal substantially as and for the purpose described.

3. The herein described process of improving the quality of malleable iron or steel which comprises covering it in a hearth furnace with a slag containing iron ore -capable of supplying the metal with dissolved oxygen, heating the metal and adding carbon thereto so that the dissolved oxygen and carbon may be simultaneously active within the metal substantially as and for the purpose described.

4. The herein described process of improving the quality of malleable iron or steel which comprises coverin it in a hearth furnace with a slag containing a metallic oxid capable of supplying the metal with dissolved oxygen, heating the metal and adding carburite thereto, so that the dissolved oxygen and carbon may be simultaneously active within the metal substantially as and for the purpose described.

5. The herein described process of improving the quality of malleable iron or steel which comprises carburizing the same, then covering it in a hearth furnace with a slag containing a metallic oxid capable of supplying the metal with dissolved oxygen, heating the metal and adding carbon thereto so that the dissolved oxygen and carbon may be simultaneously active within themetal substantially as and for the purpose described.

6. The herein described process of improving the quality of malleable iron or steel proving the quality of malleable iron or steel which comprises carburizing the same, then coverin it in a hearth furnace with a slag containlng a metallic oxid capable of supplying the metal with dissolved oxygen, heating the metal and adding carburite thereto so that the dissolved oxygen and car bon may be simultaneously active within the metal substantially as and for the purpose described.

8. The herein described process of improving the quality of malleable iron or steel which comprises covering the iron in a basic hearth furnace with a non-oxygenous sulfur removing slag, heating the metal so i until the sulfur is eliminated, then removing the slag and with it the sulfur, then covering the metal on, a hearth with a slag containing metallic oxid capable of supplying the metal with dissolved oxygen, heating the metal and adding carbon thereto so that the dissolved oxygen and carbon may be simultaneously active within the metal substantially as and for the purpose described.

9. The herein described process of improving the quality of malleable iron or steel which consists in covering the metal in an acid hearth furnace with a suitable slag and with iron ore capable of supplying the metal with dissolved oxygen, heating the metal and simultaneously adding carbon so that this oxygen and carbon may be simultaneously active within the metal, substantially as and for the purpose described.

10. The herein described process of improving the quality of iron or steel which consists in covering the metal in an acid hearth furnace with an acid slag consisting of lime, sand and manganese ore, and with .iron ore capable of supplying the metal with