US1888132A - Method of casting steel ingots - Google Patents

Description

Patented Nov. 15, 1932 UNITED STATES PATENT OFFICE AUGUSTUS B. KINZEL, OF BEECHHURST, NEW YORK, ASSIGNOR '10 ELECTRO METALLURGICAL COMPANY, A CORPORATION OF WEST VIRGINIA METHOD OF CASTING STEEL INGOTS No Drawing.

This invention relates to a method of casting metals and is especially applicable to the casting of steel ingots.

It is well known that the natural laws 5 governing the solidification of liquid metal tend to prevent the formation of perfect ingots, and cause, among the more common defects, piping and blowholes within the ingot. The formation of pipes, or cavities in the upper central portion of the ingot,-causes considerable waste since the piped portion is, as a rule, cut oil and discarded prior to rolling in order to prevent subsequent defects in the metal. Blowholes may also cause trouble in subsequent working of the steel if the surf faces of the holes become oxidized and do not properly weld together. At the same time blowholes have the effect of reducing the size of the pipe and for this reason are often desired as ameans for increasing the yield of useful steel.

Where a'high yield of useful steel is desirable it has therefore become customary to form so-called rimmed or effervescent steel,

made by promoting in various ways the formation of blowholes, with corresponding reduction ofpiping within the ingot. It has been found impracticable, however, to rim steel with more than 0.30% carbon, and alloy steels, or those with even small amounts of silicon, cannot be rimmed in the usual manner. If quality rather than yield is of primary importance, it is customary to kill the steel previous to pouring. This consists in treating the molten-metal in such a manner that it is in a quiet state when ready to pour, and is substantially free from any gases which might be trapped within the ihgot and form gas pockets as the metal solidifies in the mold. In the latter case piping is appreciable but the portion of the ingot free from pipe contains little or no blowhole formation.

One of the primary objects of my invention is to provide a method of casting molten metal which, when applied to the formation of steel ingots, is capable of producing a steel having substantially the qualities of killed steel and the advantages in yield of the usual rimmed or effervescent steel.

able difliculty.

Application filed October 27, 1980. Serial No. 491,488.

Another object is to provide a simple means for causing a rimming effect to take place in the process of casting those steels which heretofore could only be rimmed with consider- A still further object is to provide a means for promoting the rimming effect, where yield is of primary importance, .in steels which have been only partially killed, or not killed at all.

Essentially my method consists in first killing the steel, and then, while the metal is still molten, introducing therein a nonoxidizing gas, which will be evolved while the metal is cooling in the mold, and produce arimming effect in the ingot. The usual form of steel ingot mold may be used, and the killing of the steel may be accomplished as desired, by treating in some well known manner, such, for example, as the addition of small amounts of silicon. The charging with gas may take place while the metal is in the ladle ready to pour, or very shortly after it has been introduced into the ingot mold and while still in a molten condition. In either case the amount of gas added, the temperature of the molten steel and the rate of cooling in the mold should be such that, as the metal solidifies, some of the gas is liberated and some is trapped within the ingot, causing a blowhole formation, and wholly or partly compensating for the shrinkage of the metal.

Thorough killing of the steel previous to pouring is usually desirable in order to prevent any oxygen or other gases dissolved in the metal from corroding the blowhole surfaces. By then charging the metal with a gas which is nonoxidizing under the existing conditions and which will not react with the metal to a deleterious extent, the usual rimming effect is obtained, but the blowholes formed have clean surfaces which will readily weld together on subsequent working of the steel. Hydrogen gas is preferred for this purpose as it is readily available, and may .be easily introduced into the metal in the ladle or the ingot mold in any suitable manner.

Other gases, such as argon, helium, and in 100 some instances nitrogen, ammonia or methane may be used.

The resulting ingots formed by this method may be forged and rolled in any of the usual ways to give a steel comparing favorably in quality with the ordinary killed steel. Furthermore the yield produced is substantially the same as that obtained by the older rimming processes. It is also practical by this means to cause rimming of alloy steels and other steels of such composition that, heretofore, they could not be rimmed at all, or could only be satisfactorily rimmed with considerable difficulty.

Where quality is not so important, but

economy is an essential factor, an increase in yield may be produced by introducing the non-oxidizing gas to the steel when it has been only partially killed, or not killed at all. This will promote the blowhole formation within the ingot, and while it may aid in decreasing the tendency of the blowhole surfaces to oxidize, it will not produce a finished steel of as good quality as that which has been previously thoroughly killed.

The following will serve to show one practical application of the method of my invention.

A heat of 0.70% carbon steel was made in an electric furnace. Manganese and silicon were added in the furnace, so that, on pouring a test ladle into small ingots, shrinkage and piping took place. The metal was then treated in the bull ladle with hydrogen from a cylinder of the compressed gas. This was effected by means of a long iron pipe with a flexible connection to the cylinder. The hydrogen was turned on, ignited at the end of the pipe, and then the pipe was plunged under the surface of the'metal in the ladle. Since the heat of the molten metal slowly melted the end of the pipe, it was necessary to progressively push the pipe downward into the metal. In this manner approximately 50 cu. ft. of gas was passed into the ladle of steel, the steel weighing approximately one ton. A round bottom, square ingot mold, with the large end up, was prepared to receive the metal by Warming with a kerosene torch to simulate standard practice. The metal was poured into this mold. and at first rested quietly therein. After a few seconds, gas evolution started, and considerable gas a escaped from the top. At the same time, a

slight freezing from the sides was noted, and from this point on the steel rose in the mold, so that its level in the mold was about six inches higher at the end of this part of the freezing than it was when poured. Gas con tinued to be evolved for a short period through a horn formed on the ingot. The ingot was then cut longitudinally, machined for surface inspection, and a complete run of blowholes was observed, the surfaces of which were perfectly bright and unoxidized. The absence of pipe was very noticeable.

While I have described my invention as applied to the making of steel ingots, it will be evident that the method might also be used in producing other forms of steel castings, where blowholes are not objectionable, and economy is of prime importance. Various modifications in the nature of the gas charged into the molten metal, and the manner of introducing it, may also be made without departlng from the spirit of my invention. For example it may, under certain conditions, be suitable to add a solid material to the steel, which will react, with no deleterious effect on the metal, to cause evolution of sufficient as in the mold to produce the rimming effect.

I claim: 1. A method of casting metal to produce a rimming effect, which comprises charging a non-oxidizing gas into the molten metal, and

solidifying the metal in a mold by cooling at such a rate that enough of the non-oxidizing gas is trapped in the metal to at least partly compensate for its shrinkage.

2. A method of casting metal to produce a rimming effect, which comprises treating the molten metal to prevent liberation and trapping of oxidizing gases on freezing, charging a nonoxidizing gas into the metal, and then solidifying the metal in a mold by cooling at such a rate that enough of the non-oxidizmg gas is trapped within the metal to at least partly compensate for its shrinkage.

3. A method of casting steel ingots to produce a rimming effect which comprises pouring the molten metal into an ingot mold, charging a non-oxidizing gas into the molten metal during the period from just prior to pouring to just before the metal solidifies in the mold and solidifying the metal in the mold by cooling.

4. A method of casting steel ingots to produce arimming effect, which comprises producing killed steel, dissolving a non-oxidizing as in the molten metal, and then solidifying the metal in ingot molds by coolmg.

5. A method of casting steel ingots to produce a rimming effect which comprises producing killed steel, dissolving a non-oxidizing gas in the molten metal, and then solidifying the metal in a mold by cooling at such a rate that enough of the non-oxdizing gas is trapped within the metal to at least partly compensate for its shrinkage.

. 6. A method of casting steel ingots to produce a rimming effect, which comprises producing killed steel, dissolving hydrogen gas in the molten metal, and then solidifying the metal in ingot molds by cooling.

7. A method of casting steel ingots to produce a rimming effect, which comprises producing killed steel, pourin the steel mto an ingot mold, charging hydrogen gas into the molten steel in the mold and solidifying the metal in the mold by cooling.

8. A method of casting steel ingots to produce a rimming effect which comprises treating the-molten metal to produce killed or quiet steel, dissolving hydrogen gas in the molten metal, and then solidifying the metal in an ingot mold by cooling at such a rate that enough of the hydrogen is trapped within the ingot to at least partly compensate for the shrinkage of the metal.

9. A method of casting steel ingots to produce a rimming effect, which comprises producing killed steel, pouring the steel into an ingot mold, charging hydrogen gas into the molten steel at a time just prior to pouring and solidifying the metal in the mold by cooling.

In testimony whereof, I afiix my signature.

AUGUSTUS B. KINZEL.