US1887453A - Method of producing cast-iron of high qualities of strength in alpha cupola furnace - Google Patents

Description

Nov. 8, 1932. K 'EMMEL l METHOD op PRoDUcING cAsT IRON op HIGH QUALITIES oF STRENGTH 1N A cupo-LA FURNACE Filed March 6, 1928 Patented Nov. 8, 1932 UNITED STATES PATENT ori-wlan KARL Emmi., or MULHmM-BUHB, amm

IETHOD F PRODUCING CAST- IRON 0F HIGH QUALITIES 0F STRENGTH IN' A. CUPOLA. FURNACE Application led March 6, 13928, Serial No.

Thorough experiments have proved that a smelting made according to the 'process for the production of iron castings with a low carbon content and of particularly high qualities, as described in the specication of my prior Patent No. 1,683,714, has the property of maintaining said hi h qualities of strength even if it is subjecte to a subsequent carbonization.

The invention is based upon this fact, and its object is, as a furtherimprovement or modification of the process afore-mentioned, to produce iron castings which beside their high qualities of strength have a particular favorable capability of being conveniently worked.

The improved method forming the subject matter of the present invention consists in, first, producing, according to the process aforementioned, a superheated smelting of a total carbon content of about 2-3% from acharge whereof thev iron portion consists of at least 50% of iron low in carbon while the remainder of the iron contents consists of iron rich in carbon and of suitable admixtures and wherein the quantity of coke employed amounts to between 9 and 13% of the total charge that is submitted to a varying blast pressure of between 400 and 80() mms. water gauge pressure,l and, subsequently, carbonizing said smelting low in carbon to a higher carbon content, for instance 3.4-3.6%.

Beside the favorable capability of working the product obtained, which does not in any way impair the high qualities of strength of the same, the further advantage is attained that the subsequent carbonization reduces the solidification point of the smelting and fav orably influence the casting capability of the latter.

The improvedv method can, invention, for instance, within'the same cupola furnace, in which the' melting of the charge was done, by the subsequent carbonization of the superheated smelting low in carbon being produced in the lower art ofthe cupola furnace by the heat-l ing co e of the latter. The degree of carbonization can be controlled by a' regulation of the carbonization time or of the height of the bath in the receiver of the cupola furaccording to the also be carried out 259,609, and in Germany march 15, 1927.

nace, or by a change of the height of the meltod may be satisfactorily practiced, isI illus-.

trated by way of example. The shell or wall of the furnace is indicated at 10, upper and lower tuyres at 11 and 12 respectively, and tapping holes at 13 and 14. The body of coke is shown to occupy the lower end of the smelting chamber, below the tuyres, and the charge of iron and carbon the bulk of the remainder of the space available. The relationships of the diameter of the combustion space to the distances of the tuyres 4from the bottom, respectively, are set forth, the lower set of tuyres being preferably located at a distance above the bot-tom equal to three fourths of the diameter of the combustion space, and the upper tuyres being one and one fourth diameters above the bottom. These dimensions are, of course, approximate.

I am aware that it has already been proposed for instance in the U. S. Patent 1,336,256 (Muntz and Roubien) to work a cupola furnace with a deep lower part in such a way that, first, the heating coke is brought-to incandescence by an upwardly directed blast and, then, the casting scraps are molten, which smelting is to form at the rear of the tap-hole at the bottom of the furnace a liquid cast-lron layer of slow solidification due to its less high carbon content. Only then, the remaining charge or burden consisting mainly of steel scraps is to melt down.\ The result of said proposal would be-like in the last-mentioned mode of carrying out the improved method forming the subject matter of the present invention-Aa carbonization of theVv steel smelting inthe lower part of the furnace, which result has, however, been neither foreseen nor stated as a consequence of said proposal, for otherwise'v the precaution against solidification at the rear of the tap-ho e is not understood. Furthermore, said proposal of` the Patent 1,336,256 did not aim at the superheating of the smelting or at the production of a smelting of articularly favorable casting capability. his is also contradicted by the fear in said proposal of a solidification ofthe smelting already in the furnace itself. Said known proposal had for its only object to cheapen the charge principally desi ed for an adjoining Bessemer process, wit out the perception of the high value, of the idea upon which the present invention is based, for the\ production of iron castings of high qualities of strength, and so on.

The present invention has for its Object, to produce in a simple cupola furnace such castings of specially high values, which possess besides high resistance values still specially favorable capability for treatment. It conslsts in utilizing the high superheating -which in the cupola furnace 1s due to the stee containing smelting, to obtain a good distribution of the carbon at subsequent carbonization without the necessit7 to use, as hitherto, several devices for sme ting and carbonizing, only one single device and only one single smelting operation being re uired. Thisis obtained by arranging the evice specially for the lsubsequent carbonizing by suitably spacing the tuyres from the bottom plate of the furnace and by roviding a suitable number of rows of tuyeres and further by conducting the operation of the furnace in such a manner, that a very high temperature of the smelting is attained.

At an inner diameter of the furnace of 900 mm there has been obtained, for instance at a distance of 450 mm. of the tuyres from the bottom plate of the furnace, 2,8 to 3,1% of carbon content o f the cast iron. If however the first row of tuyres is spaced 600 mm from the furnace bottom, the cast iron shows a percentage of carbon from 3 to 3,4%. r This shows that a subsequent carbonizing of the superheated smelting, obtained by the smelting, process with high steel charge, is the more possible the eater the distance of the nozzles from the ace bottom is selected.

The layer of the hottest workin ofthe furnace is situated about 30 cms. a ove the tuyres and, if -there are several rows of 'tuyres, higher plus the -distance between the several Vrows of tuyres. Y There have been.

proposed therefore two means for the subsequent carbonizing, i. e. first theincreasing of the distance between the furnace bottom and the first row of tufyres and secondly increasing the heigiltl;l o the layer of the hottest furnace wor g above the tuyres b arranging severa rows of tuyres. e producing develops in such a manner that first in the specially thick layer of the ,hottest furnace working above the tuyres the steel charge is heated to the highest 'ble temperature, and this excessively heatedv smelting is then su uently thoroughlyY carbonized underneath t e tuyres 1n the comparatively high layer of IilJin coke. This ce in the furnace between the irnace u bottomandthetu'yresisilledwithcokeina manner known per se. The molten iron takes up the carbon from this coke.

According1 to the smelting process of the invention, t e object of placing the layer of the hottest furnace working at a higher lever is, to obtain the highestpossible superheating in' order to subsequently carbonize thorou hly this highly heated smelting with the ai of a high layer of filling coke. From the high super eatlng of the smelting results a quite specially fine distribution of the carbon in the smelting so that a product can be obtained, which is equal to the best cast ironproducts known at present,

The improved method can, for instance, be put into practice in such a way that the smeltin of lowcarbon content attained above the tuyeres and heated to steel melting temperature is passed through and carbomzed in the coke-filled smelting receiver prior to its admission to the forehearth. Also in this case the degree of carbonization of the smelting can be controlled by a regulation of the bath in the smelting receiver. With a long stay of the smelting in the lower part of the furnace serving as a carbonization chamber, or with a slow passage of the smeltin therethrough, 'the latter will receive a hig er carbon content a larger velocity.

The height of the carbonizing smeltingreceiver, or the height of the bath respectively, can be regulated with a maintenance ofthe height of the tuyres, by illin -in the bottom end of the lower part of the rnace with suitable substances, such as sand, firebricks, or the like for making the bottom of the furnace of di erent heights.

The subsequent carbonization of the smelting low in carbon and thus taking indeed advantage of the maximum temperatures in the furnace, can also take place substantially or in addition to the afor-mentioned provisions by performing the melting process of the charged low-carbon iron, for a comparatively high layer of hi hest temperature, above as well as within t e uppermost artial layer thereof, and that in such a Way or the smeltthan with a shorter stay and withl ing produced has occasion to be heated to, or Y at least approximately to ature in the furnace. Additionally thereto, the superheated smelting low in carbon thus formed has then in the lower partial'layers said highest temperhand, by a systematic utilization of the ef.- 13o eated metal through a body o fects of such a zone of hottest furnace working a, controllable subsequent carbonization of a superheated smeltinglow in carbon can be obtained, and how, on the other hand, the final carbon content of the product leaving the furnace can be directly influenced by a regulation of height of said layer or zone of hottest furnace working.

It may be noted that a regulation of the height of such a layer or zone of hottest furnace working can also be attained with the aid of one single row of tuyres, by changing the quantity of blast supplied per unit of time, if required, with a simultaneous charge of the pressure of the blast. Then, by an increased supply of blast with a maintenance of the usual quantities of coke, an heightening of said layer or zone can be obtained with the stated action upon an increase of the carbon content of the smelting finally produced.

Thorough experiments have unobjectionally proved the effective applicability of the new rules upon which the improved method is based. The details of the latter depend, of course, upon the dimensions and the construction ofthe cupola furnace used and can be easily determined for each individual case by a series of'trials.

What I claim, is: v

1. The method of operating a cupola furnace in the production of cast iron which consists in introducing into the furnace chamber a charge of iron and coke, at least 50% of the iron so introduced being in the form of steel or wrought iron of low carbon.

content and the coke comprising not more than about 13% of the total char e, submitting the charge, after ignition of t e coke, to the actionof an air blast under water gauge pressure 'ofbetween 400 and 800 mm. to effect smelting of the metallic charge, whereby amolten metal of relatively low carbon content but extremely high temperature is produced, and thereafter passing this supercrease the carbon content thereof.

2. The method set forth in claim 1 which includes the step of regulating thedegree of carbonization below the tu res by va the height of the tuyres a ove the ttom.`

In testimony' whereof I have hereunto set my hand: v

KARL EMMEL.

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