US2203179A - Process for the manufacture of hematite cast iron - Google Patents

Description

' R.. P.ERRIN une 4,1940.

I PROCESS FOR THE MANUFACTURE OF HEMATITE CAST IRON Filed March 14, 1958 Iv entom- Patented June 4, 1 940 sif Q. I I I 2,203,179

PROCESS FOR THE HEMATITE MANUFACTURE OF CAST IRON Ren Perrin, Paris, France, assignor to Societe dlllectr'ochimie, dElectromettalurgie et des Acieries Electriques dUginc, Paris, France, a

corporation of France Application March-14, 1938, Serial No. 195,842

' In France March 16, 1937 4 Claims.

lt has already been proposed to make hematite cast iron by means of the Thomas converter starting from cast iron containing phosphorus by first transforming this cast iron into a dephos-' phorised steel and by then recarburising this steel by addition ofcarbon. The recarburation may be effected either in the converter itself or by successive turning down of the converter with very short blowings or in a ladle by transfer.

in the same process it has been proposed to add to the metal during the reoarburation addi tions of materials producing evolution of heat in order to increase the solubility of the carbon.

By the present invention I have discovered the means of effecting this recarburation in conditions such that:

l. The solution of the carbon is extremely rapid.

2. The addition of materials giving off heat to obtain an increase of the solubility of the carbon is in no way necessary.

3. The operation is very losses are very small.

4. The operation leads to high yields of the 5 recarburising material and moreover yields which are extremely regular from one operation to another.

5. The final composition of the cast iron obtained is extremely regular from one operation to another. a

In order to arrive at these results I propose to submit the material to be recarburised-generally extra mild steel coming from the converter-and the recarburising materialfor example coke or charcoal-to successive energetic intermixings 1 repeated at short intervals in an apparatus formed for example of two chambers arranged so as to permit with rapid frequency the contents of one of the chambers to be poured into the other and reciprocally with a force suilicient to bring, during the pourings thus effected, thecarboniferous elements below the surface of the metal producing strong eddies. 1

Such an apparatus may be formed in particular simple and the heat of two chambers opposing mouth to mouth and l ment, the liquid steel and'the'carbon which it is desired to react are introduced into the apparatusand this is subjected to a series of successive oscillations or rotations which project the steel and carbon from one chamber into the other i reciprocally. The ratio between the volume of each chamber and the charge of metal and solid reacting substance which is introduced therein for treatment is so chosen that the height of fall of the said charge from one chamber into the other is sufiicient for the carboniferous substance'to be entrained into the body of the metal and to produce strong eddies.

It is important however to explain how these successive pourings should be effected for the success of the operation. If it is presumed that one of the chambers of the apparatus contains liquid steel upon which for example pieces of coke have been dropped and that the metal from this chamber is poured slowly into the other chamber, of the apparatus, the coke having a density much u less than that of the metal will remain at the, surface of the bath and only a very slow reaction and solution will be produced.

If on the contrary the metal is poured with force, strong eddies will be produced, the whole or a large part of the coke is entrained into the body of the metal and experiment then shows that the'speed of the reactions and of the solution increases to a very considerable extent as well as the regularity of the results obtained.

It is this phenomenon of entrainment of the coke into the body of the metal which is to be v sought, this entrainment is moreover also facilitated by the eddies which are produced by theshock of the molten metal against the walls.

It is important in all cases that the pouring. of the metal with the carboniferoussubstance should be sufiiciently strong for there to be penetration of the pieces of the carburising material into thebody of the metal which condition is the more diflicult to produce the'greater the difference between the density of this material and that of the metal. This result may be obtained in the most simple way for example in the type of. apparatus described below. At each oscillamolten metal and the recarburising material will give rise to considerable evolution of carbon I monoxide particularly at the beginning of the operation in the case when one starts from an extra mild Thomas steel which is strongly oxidised. In this case precautions should be taken so that the rapidity of the reaction is not such that it leads to an explosion or even to expulsion of metal out of the apparatus.

Apart from the fact that the apparatus should be open to permit the outlet of the gases as they are formed, two means may be employed to regulate the rapidity of the reaction.

1. The successive pourings may be slowed down. But in this case the pouring must remain sufficiently strong for there to be penetration of the carboniferous material into the body of the molten metal which condition is essential for rapid reaction.

2. The quantities of carboniferous material may be introduced periodically by fractions in regulated proportions (at each pouring for example) or even in a less divided form. It is important not to use too fine powder which may be partially taken away by the gases which are evolved.

The adjustment will be effected for each particular treatment by previous tests.

It will be observed when operating under the conditions described above that in a very short time even when starting from an extra mild steel a cast iron'having the desired carbon content will be obtained.

The starting materials to be utilised for recarburation may be coke, charcoal, anthracite or any other carboniferous material capable of dissolving in the metal. They will be chosen as free from sulphur as possible.

Although the addition of substances giving ofi heat is not necessary to effect the dissolution of the carbon substances may if desired be introduced' such as silicon or manganese or'other alloying elements with the object of bringing th cast iron to the desired composition.

The process of the invention is capable of being applied in advantageous conditions in an apparatus such as that shown schematically by way of example in the accompanying drawing.

The apparatus comprises two chambers I and 2, relatively deep, connected to one .another by their mouth and communicating with a -medial aperture 3 open to the atmosphere. These two chambers areeonstituted by a metallic casing 4 provided with a refractory lining 5., The whole is mounted upon a, shaft 6 capable of turning in support bearings 'I. and receives an alternating oscillatory movement by means of a driving mechanism of suitable known typewhich is not shown. This, movement brings turn by turn the.

chambers l and 2 into a position respectively high or low and with a strong inclination which causes Example of operation Into the apparatus 3 metric tons of extra mild strongly oxidised steel were introduced.

phorus content 0.010%. 65 kgs. of coke with a low sulphur content were added.

The carbon content of this steel was 0.05%, the phos-'" To the apparatus a series of oscillations were imparted. An intense ebullition occurreddue to the action of the coke on ,the oxides present in the metal. The ebullition slowed down as the oscillations continued. After six oscillations 65 kgs. of coke were added.

At the end of 12 oscillations in all the operation was terminated. The cast iron obtained contained: C=3.5%; P=0.012%; S=0.025%.

The melting .point of the final metal being notably lower than that of the initial metal, 8.6-1

cording to the invention the heat which has become availablein consequence of the difierences in temperature in question may be utilised to increase finally without expenditure of external heat or without necessarily having to develop internal heat, the weight of the initial metal and.

Due to the fact that the metallic bath is at a temperature above its melting point and due likewise to the speed of the successive pourings, the

elements thus added dissolve rapidly in the bath even if they are introduced cold, and this without the bath cooling below the temperature which should be maintained for its subsequent use.

. There is obtained finally by recovery of the excess heat which otherwise would be lost a weight of metal above that of the initial metal increased by that of the solid reacting material which haspassed into the: metal, for example if I the manufacture of cast ironiis concernedwa weight of cast iron above that of the initial steel increased by that of the carbon which has passed into the cast iron.

The proportionof the pieces or fragments of metal or of scrap or of alloying elements which it is possibleto incorporate thus in the bath of. metal is considerable and may reach practically I 5% and evenmore of the initial weight ofcthe metal, but it is naturally limited: by the quantity of excess heat available in the cycle. It dependsalso on thestate of division in which are the.

materials to be melted, for example fine scrap metal or scrap iron or turnings will be'capable of dissolving very rapidly. This proportion may readily be determined in each case by-calcula- .tion or .even better by experiment. -The importance of such metallic additions in the special apparatus employed, resides .in the particularly economical utilisation which is thus made of these materials and of the excess heat, which materialsare utilised normally by fusion in the electric. or Mar tin furnace, that'isto say with expenditure of external heat.

What I claim is:

l. Theprocess of making .cast iron, which comprises subjecting molten mild steel and solid re:

carburizing material simultaneously to a series of successive'rapid pouring's which are effected with a force suflicient to insure during these pourings an intimate and turbulent mixture of the metal and recarburizing material, and during or at the end of the carburizing reaction adding solid metallic or alloying elements which are caused to dissolve by means ofthe heat rendered available by reason of the difference of the melting point of the initial metal and that of the recarburized metal.

oi' s'uccessive rapid pourings which are effected with a force sufllcient to insure during these pourings an intimate and turbulent mixture of the metal. and recarburizing material, and dis- I solving solid metallic or alloying elements in the bath which has been at least partially carburized and without the supply of external heat to the bath.

3. The process of making cast iron, which comprlsessubjecting molten mild steel and solid recarburizing material simultaneously to a series of successive rapid pouringswhich are eflected with a force sumcient to insure during these pourin'gs an intimate and turbulent mixture of the metal t 3 ments in the bath which has been at least partially carburized and without the supply of external heat to the bath.

4. v'I'he process 0! making cast iron, which comprises subiecting molten mild steel and solid recarburizingmaterial simultaneously to a series of successive rapid pourings which are effected with a force sufllcient to insure during these pourings an intimate'and turbulent mixture of the metal and recarburizing material, and continuing the pourings until the carbon content of the bath is raised by an amount of the order of at least 3.0%

and dissolving solid metallic or alloying elements in the bath which has been at least partially carburized and without the supply of external heat] to the bath, the mild steel being substantially free from sulphur and the carburizing reaction being carried out in the absence of added oxidizing agents. v

RENE rmmm.

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