US1266928A - Open-hearth steel process. - Google Patents

Description

iny iria urns rarnir orisibn CHARLEShH. ELLIOTT AND ELMER T. MCCLEARY, OLE YOUNGSTOWN, OHIO, ASSIGNORS T0 THE YOUNGSTOW'NSHEET & TUBE COMPANY, OF YOUNGSTOWN, OHIO, A CORPORA- TION OF OHIO.

OPEN-H'EARTH STEEL PROCESS.

No .Drawing.

To all whom it may concern:

Be it known that we, Cnannns H. Emao'r'r and ELM-En T. MOCLEARY, citizens of the United States, residing at Youngstown, in the county of Mahon-ing and the State of Ohio, have inyented a new and useful Open- IIearth Steel Process-of which the following is a full, clear, andexact description.

Heretotore in the manufacture of steel by the open hearth process, particularly in the case of higher carbon steels, such as steel having from .2 per cent and upward 'of-carbon, it has been common practice to take a test sample, or preliminary test, from the bath at or near the end of the heat and analyze this "in the laboratory in order to ascertain Whether or not the steel is in proper condition for pouring. This analysis occupies usually about thirty inmates and during that time the carbon is being reduced in the bath so that when the analysis has been obtained it no longer represents the composition of the bath. Testing by tracture of a solidified sample has always been used, but this is uncertain and causes many mistakes. c

Furthermore, where "recarburizing is carried out by adding pig iron to the bath at the end of the heat,..this addition causes a violent ebullition which makes it uncertain as to how much of the carbon which is added to the bath is takenup by the steelbath and how much is lost by theexcessive throwing off of gases. Consequently, it is ditiicult, if not impossible, to obtain a specific desired carbon content in the steel where l'ecal'burizing is carried out by additions to the bath in the furnace.

We have discovered a method of overcoming these difliculties and we will now explain the two phases of the process as follows:

First: 'To overcome the decrease of the carbon content of the bath during the analysis oi the test sample, we add approximately suflicient silicon to the bath to prevent the oxidation of the carbon content during the period of analysis. For example, when the preliminary test sample is taken, we feed into the bath suflicient silicon pig iron to supply the silicon to be burned during the ordinary period of analysis. As is well known, silicon will be attacked and burned before the carbon is attacked, and consequently when sutlicient silicon is supplied to the bath to last "through the analysis period Specification of Letters Patent.

Patented MayZll, 191%.

Application filed JuIy'ZO, 1917. Serial No. 181,887.

the carbon will not be attacked through this periochbut will remain constant.

F or example, in a hundred ton bath in the open hearth, we add under a hundred pounds and preferably about fifty pounds of silicon pig iron per ton of steel. The pig. iron which we are employing has about the following metaliloid analysis:

Silicon 8 per cent.

Carbon 4 per cent.

Phosphorus .250 per cent.

Sulfur .015 per cent.

Manganese .80 :per cent.

The silicon may, of course, be added in other forms, such as ferrosilieon, in any case the silicon being added to approximately the correct amount to receive the oxidation during the analysis period and be burnt out at the end of this period while preventing the carbon from being attacked through such period.

In any case the analysis of the n'iaterial containing the silicon should, of course, be known so that approximately the correct amount of silicon may be added for this purpose.

The silicon addition is in such small proportion to the total bath that the carbon and other metalloids in the addition do not materially affect the metalloid contents of the bath other than as to silicon.

In case the test analysis requires more than the normal time of aboutthirty minutes, additional silicon may be added to prevent the attacking of the carbon. In case the preliminary analysis shows that the bath requires further refining, this may be carried on, another test sample taken out and analyzed and a further addition of silicon may be sufficient to prevent attacking the carbon during this new period, and so on, repeating the process until the desired analysis is reached.

If the analysis shows that the carbon content of the bath is too low, recarburizers may be added either in the furnace or ladle after tapping the heat. In any case, the operator has substantially exact knowledge of the carbon content of the bath, at the time of tapping the steel.

In carrying out our process, we preferably recarburize the steel to bring it up to the desired carbon content by adding carbon to the steel in the ladle after tapping; for example, in the form of ferromanganese,

, Copies of this patent may be obtained for spiegeleisen, or any other desired form. The carbon may, however, be added in the bath in the form of ferromanganese or otherwise Within the'scope of our invention.

Under-the second phase of the invention, we employ a silicon addition in case recarburizing is carried out by adding pig iron or spiegel to the bath at the end of the heat in order to prevent the excessive ebullition or kick of the metal. In this case, when the bath has been brought to the proper carbon content, using the other phase of our method or not, as desired, suflicient silicon pig or silicon carrying material is added to kill the bath and reduce or stop the boil or ebullition. The addition of the recarburizer is then made to the bath, the silicon of the addition burning out between the silicon addition and the addition of the recarburizer. In this case the bath may be carried down to a low carbon content, for example, .1 per cent. and is then raised to the desired content by bath addition.

'Here the silicon addition prevents the violent and sudden ebullition of the bath which would throw out a large and varying amount of carbon addition, and enables the per cent. of carbon addition passing into the metal to be accurately determined.

In other words, under the first phase of our process, we hold in the bath the carbon already present, during the analysis period; while in the second phase We hold in the carbon then added to the bath in the carbon carrying addition.

In the second phase the addition may be in the form of molten pig iron from the mixer or molten spiegel added to the bath at the end of the heat before tapping, the silicon addition being made just before this bath addition to prevent excessive ebullition when the bath addition is made.

The advantages of our invention will be obvious to those skilled in the art, since the operations are made more accurate and worked to specification more successfully. Off heats may be prevented, or may be remedied by our methods.

Under the first phase, the preliminary analysis may be made just before, or just after the silicon addition. If the preliminary analysis is made after the addition, the silicon analysis will, of course, be unnecessary, as the silicon of the addition will be burned out during the taking of the analysis.

The amount of silicon pig added will, of course, vary with the amount of the bath and its condition. The silicon addition also serves to aid in deoxidizing the material and effecting a saving in the amount of ferromanganese, spiegeleisen or ferro-silicon in case they are used. The silicon-dioxid which will be formed also aids in cleansing the steel and having a better physical condition. The temperature of the bath will also be raised by the oxidation of the silicon, thus aiding in eliminating the sulfur.

The process also enables us to tap all heats at a substantially uniform temperature since the rise in temperature is governed by the amount of silicon added, a larger amount being added for a low temperature bath, and less for a higher temperature heat.

Under the second phase the killing of the metal aids in avoiding the formation of puddle holes in the bottom of the furnace, which cause much expense, labor and delay.

Variations may be made in the amount of silicon addition, the kind of addition used, and other changes may be made without departing from our invention.

We claim:

1. In the manufacture of open hearth steel, the steps consisting of testing the bath composition at near the end of the heat and adding silicon in conjunction therewith to retain the carbon of the bath during the testing period.

2. In the manufacture of open hearth steel, the steps consisting of adding silicon to the bath in the open hearth furnace near the end of the heat, and then recarburizmg the metal, the silicon serving to hold the carbon in the bath.

3. In the manufacture of open hearth steel, the steps consisting of making a preliminary metalloid analysis of the bath and adding in conjunction with said analysis a proper amount of silicon to hold the carbon content of the bath substantially uniform during the period of analysis.

4- In the manufacture of open hearth steel, the steps consisting of making a preliminary metalloid analysis of the bath and adding in conjunction with said analysis a proper amount of silicon to hold the carbon content of the bath substantially uniform during the period of analysis, and then recarburizing to raise the carbon content of the metal.

5. In the manufacture of open hearth steel, the steps consisting of making a preliminary metalloid analysis of the bath and adding in conjunction with said analysis a proper amount of silicon to hold the carbon content of the bath substantially uniform during the period of analysis tapping out the metal and then recarburizmg the metal in the ladle.

In testimony whereof, we have hereunto set our hands.

CHARLES H. ELLIOTT. ELMER T. MCCLEARY.

five-cents each, by addressing the Commissioner of Patents, Washington, D. G.