US1185252A - Manufacture of steel. - Google Patents

Description

- H. E. SHELDON.

MANUFACTUREOF STEEL. APPLICATION FILED MAR. 30, 1912.

Patented May 30,1916.

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HARQY. SHELDON, 0F PITTSBURGH, PENNSYLVANIA,

Mannrecrunn or STEEL.

Specification of Letters 2atent.

Patented May 3%, l llfia Application filed March 30, 1912. Serial No. 687,365.

I '0 all whom 2'25 may concern:

.Be it known that I, HARRY E. Simpson, a citizen of the United States, and resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in -the Manufacture of Steel; and I do hereby 'tleclarethe following to be a full, clear, and exact de scription thereof.

y invention relates to the manufacture of steel- 4 j As it-is Well known, steel has been made in' different Ways, such as by the Bessemer thereof, particularly in-the lower portion thereof, and that themolte n' steel supplied to thetmold during the casting of the metal, enters Within these recesses or cavities and mold so that it cannotbe stripped therefrom, thereby necessitating the destructlon of the mold. Another more mportant difficulty in this manufacture of the steel and arising from the use of the cast ironniolds,

has been the entering of the mold meta-l into the molten steel, rendering it relatively impure. Ihave discovered that this is due to a phenomenon akin to osmotic action. This action can'bedescribed as follows: The cast iron ingot molds are relatively high in carbon, and'inay be higher thanthe molten steel in manganese, phosphorus, sulfur and ,otherimpurities, and a large proportion of carbonin SHCllfiIlOldS appears as free carbon, not being chemically united with the iron. The molten steel cast therein is of course much purer than this cast iron, having only a relativelysmall content of carbon and probably a lower content of manganese and other impurities A chemically united with the iron of the steel I body. -When this steel is in a highly molten condi tion it is poured within the cold cast iron mold, and the molten steel which is composed of a more dilute alloy infuses itself upon solidification locks the ingot in the or immigrates into the cast iron, or higher alloy, and causes, or tends to cause, an increase in the size and the dilution of the higher alloy until both alloys are of the same composition, there being a sharp separation between the higher alley, or cast iron, and the lower alloy, or molten steel, which envelops it. During this infusion or immigration of the steel into the cast iron, glob ules or fragments of the cast iron separate therefrom and continue to be acted upon by the molten steel, or lower alloy, in the same fashion as above described with reference to the parent mass of the cast iron, or higher alloy, and in this way the globules or fragments are, as it were, dissolved wathm the molten steel, or lower alloy. If the infusion or immigration 'ofthe molten steel into the cast iron be checked at any stage previous to complete merger of the two metals or alloys, as by the solidification of the metal, therethe cast iron or higher the mold body,

maining globules or fragments, if any, of

alloy separated from will remaln as hard spots in the mass of steel, or lower alloy. I have found that such infusion or immigration of the molten steel acts upon the walls of the cast iron molds and is responsible for the attack of the former upon the latter, causing the recesses or cavities in the innenmold faces hereinbefore referred to, and'the appearance of hard spots in the sheets, plates or other products] made from the ingots. While creating this difficulty with the molds and shortening their average life, a. more serious difliculty is the change inthe character of the steel, as it is well known that a very sllght amount of such impurity dissolved within the steel of the ingot may, and often does, weaken the steel,or harden the same, affect its other physical characteristics, ac cording to the impurities contained in the cast iron of which the mold is formed and which is thus taken up by the molten steel. Even if the body of the mold is thus carried into the steel in small granules and fully dissolved therein, the resultant steel may be seriously contaminated in this Way, and as the object aimed at is to'form the solidified steel ingot of the exact composition pro-- duced in the furnace or converter, it is very important to overcome this difficulty and producethe steel free from such contamination. The difficulty isof course intensified where the portions of the mold body so brokenofi are notentifely dissolved Within the molten steel of the ingot, but form hard spots which may be present in the rails, bars, sheets, and form hidden weaknesses therein. I

My invention has for its object to produce a purer steel by practically overcoming this so-called osmotic action during the cooling and solidification of the ingot.

It consists inmelting and refining the steel and then pouring it into an ingot mold having a steel inner face and permitting it to solidify in contact with such face; it being found that as the chemical content of the stcelmold .does not diller greatly from the chemical content of the molten steel, and the carbon content of the steel from which the mold was formed is chemically united with the iron, this osmotic action is practically overcome and thus the molten steel cast within the teel molds is kept pure and free fromimpui'ties taken up from the mold body and the formation. of the solidified ingot as pure as the metal produced in the furnace or converter and free from contamination from the mold can be insured; while the life of't'he mold itself is greatly extended and the cost of manufacture of the steel is thus reduced.

ingot molds are The special form of mold hereinafter described is not claimed in this application since it forms the subject matter of applicants co -pending application, No. (587,366, filed March 30, 1912.

In the accompanying drawings ligure 1 shows an ingot mold; and Fig. 2 shows the same in vertical section illustrating one manner of pouring the metal.

For the practice of the invention the formed of cast steel, for example, either Bessemer or openhearth steel, being formed in the ordinary way of forming steel castings. They can be formed in the steelvmaking plant where they are to be used and are thus easily formed of the same or approximately the same carbon co. tent as the steel produced in the plant. I prefer to employ in the molds a steel which is practically the same as the molten steel ingots to be cast therein, for; example, say, having its impurities within ten or twenty points of like impurities in the molten steel, However, from my experience in the practice of the invention, it is believed that this osmotic action can be practically prevented if the content of either of the main impurities, carbon or manganese, shall not differ from the like elements in the molds by more than two per cent. That is, if the steel to be cast contains, for example, .20

percent. of carbon the steel er the mold should not be of a higher carbon content than, say 220 pen cent, and its arbon content may extend :Itll the way practically, nothing.

..: In the practice .,of v the invention the steel from this to messes -lined in converters, received in a casting ladle and cast in the steel ingot molds 5. Or, in the open hearth plant, the steel may be refined in furnaces and received in a ladle and cast by bottom casting in the cluster of molds, the metal passing down through the central runner 9 and being distributed by side runners 10 into the steel ingot molds 5, the molds being of the -ordinary shape as employed with the cast iron'mold.

The metal enters the molds, at an extrei'nely high heat, probably from 2700 to 3000 F., and is permitted to cool therein in contact with the steel inner face thereof illl until properly solidified ready for with- A metal or. impurity from the body of the steel mold into the molten steel and therefore the ingot is solidified, passing from the -molten to the solid state, practically as produced in the converter or furnace, and a much purer ingot is obtained, one'free from the impurities formed by the alloying of the metal. of the mold body with the metal of the ingot, such as where it is actually dissolved therein, as above described, while hard spots in the ingot from undissolved portions of the mold body entering into the same are prevented, and hidden weaknesses of the ingot or the metal produced therefrom arising from contamination in the formation of the ingot are entirely avoided.

As set forth in a companion application of even date herewith, Serial No. 687,366, the life of the ingot molds is largely extended, practical use showing that they outlast the cast iron molds many times. The limit of wear has not yet been fully ascertained.

What I claim is:

1. The herein described method of manufacturing and casting steel c'onsisting in melting and refining the crudemetal to produce the steel, and casting the molten steel into an ingot within an ingot mold having a steel inner face, such steel inner face of the ingot mold being approximately of the same carbon content as that of the molten steel cast within the mold.

2. The herein described method of manufacturing and casting steel, consisting in melting and refining the crude metal to produce the steel, and casting the molten steel into an ingot Within an ingot mold having {1' steel inner face, the proportiqn of any S one of the main alloying elements of the steel forming the inner face of the mold not )eing more than two per cent. abpve the content of like alloying element of the molten steel east within the mold.

In testimony whereofI the said HARRY E. HELDON havevhereunto set my hand. 7 HARRY E. SHELDON. Witnesses ROBERT 0. TOWN, JOHN F. W LL.

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