US1916042A - Apparatus for treating ingots - Google Patents

Description

June 27, 1933. 1... c. EDGAR APPARATUS FOR TREATING INGOTS Filed May 20, 1932 Invenfor 0/5 C. 5064B Patented June 27, 1933 UNITED STATES LOUIS C. EDGAR, OF SWISSVAIJE, PENNSYLVANIA Arrnmrus FOR TREATING moors Application med Kay 20,

This invention relates toa method of and apparatus for treatin ingots in order to reduce or eliminate blowholes, segregation and piping found in ingots castin the usual manner.

The in ot molds. in common use are tall, box-like s apes made of cast iron and open at both ends, one end of which is smaller than the other to give the mold a slight taper.

The molds generally have a square or rectangular section rounding at the corners and when in use one end, usually the larger, is closed by a stool onwhich the mold stands in an upright position. As soon as the molten steel or metal is poured into the mold the metal next to the mold and stool solidifies at a rapid rate. During the process of making steel, there is evolved large quantities of gases, some of which pass out of the liquid mixture durin the refining process while in the furnace an ladle, while other gases are retained and do not pass out of the metal until solidification occurs. These latter gases are retained within the molten metal due to their density, and it is a known fact that the density of gas bubbles within a liquid increases as their size diminishes, due to the surface tension or sphere of molecular attraction of surrounding liquid. Therefore, as the liquid contains a great manyvery small gas bubbles, their density approaches the weight or density of the surrounding liquid wit the result that their buoyancy 15 very slight. It is the object 5 of this invention to remove the gases contained in the small bubbles or spheres within the molten metal prior to thesolidification of the ingot. A

When the process of solidification or crystallization starts the surface tension or sphere of molecular attraction is broken down and the gas pressure reduced, and the coalescing of these minute particles of gases form'the cavities or blowholes appearing in the ingot as 9. "art of the coalesced bubbles are trapped by t e rapidly solidifying mass of metal. The trapping action of the metal may be diminished by retarding the speed of solidification by mixing the relatively hot steel in the center of the ingot with'the cooler steel 1932. Serial 1%. sum s. I 7 against the walls of the molding stool as 'it is solidifyin This retarding action will give time for t e coalesced bubbles-to escape.

Steel, particularly liquid steel, is also characterized by the presence of gaseous impurities, which gases, frequently called occlud ed gases and comprising chiefly hydrogen, nitrogen, carbon monoxide and probably oxygen in the form of FeO, may pass out of he liquid mixture during the refining gzocess in the furnace or ladle, or some may retained and not pass out of the metal before solidification occurs.

The ver small proportion of impurities generally ound in steel of good quality has very little injurious efiect upon its physical 1 roperties so long as the steel is chemically omogeneous, i. e., so long as such impurities are uniformly distributed throughout the metallic mass. These impurities become extremely injurious, however, when they show a tendency to segregate or to collect in certain portions of the metallic mass. With suiiicient segregation thereresults a metal which is generally very brittle, weak and hard, and which has substantially little or no actual utility.

The present invention has for one of 1ts objects the treatment. of a castin during the solidification thereof "which wi minimize the objections due to the segregation of impurities. In its broader aspects, the invention contemplates the agitation of a mass of molten metal either during 'or after the teeming operations have been completed, from a point wholly within the casting, in such manner that the rapidity with which localized solidification occurs, such, for exam 1e, as that responsible for the initial-skin o rma- 7 tion, is retarded. In this manner there is afforded an opportunity for the escape of the gaseous impurities from the surface reg on of the casting, with a conse uent reduction in the possibility of forming low holes at or adj acent such region wherein surface oxidation readily occurs.

More specifically, my 1nvent1on contemplates agitation, by st rring, of the teemed metal in such manner as to not onl retard localized solidification, but to distur or (118- 0 rupt the viscous or retaining nature of the metal so that enclosures, inclusions and occlusions are not so readily obtained. At the same time, the stirring results in a substantially uniform distribution of the remaining impurities throughout the metallic mass, in such manner as to decrease to a minimum their deleterious effects.

Such stirring further produces desirable results in that it accomplishes a metal diffusion such that dendritic segregation is largely prevented, and a chemically homogeneous dendrite or dendritic structure is obtained.

Still further objects of this invention will be apparent from the detailed description contained in the following specification.

In the drawing:

Figure 1 is a side elevation of an apparatus used in carrying out the method of this application with the stirring mechanism shown in its foremost position in full lines.

Figure 2 is a front elevation taken at right angles to Figure 1.

Figure 3 is an enlarged detailed side elevation, part1 in section, showing the stirring rod loa ed into an ingot mold.

Referring more particularly to the drawing, the numeral 2 designates an in ot mold of standard design supported on t e usual stool 2 which closes the bottom of the mold. The agitating shaft or rod, which is revolved in the molten metal within the mold, is designated by the numeral 3 and comprises a central metal stem member 3* which is enclosed within the sectional refractory casing 3 composed of stopper brick. The lower end of the stem 3" is added, as at 3, to support the casing member or brick 3 and the lower brick is closed by a refractory filling 3.to protect the stem 3 from the molten metal of the ingot. The upper portion of the stem 3 is keyed in a suitable bearing 3' journaled in a bearing opening in a carriage member 6. A suitable motor 5 is mounted on the carriage 6 and has a drive connection to the upper end of the stem 3 through a coupling 5 and gears 4.

The carriage 6 is mounted for vertical movement on a supporting column 10 of H or I cross-section, and is provided with flanged wheels 8 and 9 for movement on the column 10. The column 10 is mounted for ivotal movementabout its vertical axis by aring members 10' and 10"-at its bottom and to ends, respectively. A suitable hoisting ca le is anchored to the carriage 6 at a point 7, and is adapted to be connectedto a standard form of hoisting mechanism 12 for raising and lowering the carriageon the column 10. The hoisting mechanism 12 is provided with control ropes or cables 12 which extend downwardly within reach of an operator 'on the floor.

The' pouring platform from which the metal is poured into the ingot molds is designated at 20. A suitable lock is provided, composed of overlapping angles 21 and 22 which are mounted on the carriage 6 and the floor 20, respectively,-and a pin 11 is provided for locking the carriage 6 in alined position with'the ingot mold into which the rod 3 is adapted to be rolled.

Suitable stop lugs 25 and 26 are provided on the column 10 to limit the movement of the carriage 6 in both down and up positions, and suitable limit switches will be provided as is usual on the standard hoisting mechanism 12 for stopping the hoisting mechanism prior to the engagement of the carriage 6 with the stops or lugs 25 and 26.

In carrying out the method of this invention the ingot mold 2 will be positioned to receive the metal from the ladle in the usual manner. As soon as the mold is filled with the molten metal, solidification commences at that part of the metal in contact with the mold and stool. Therefore, as soon as possible after the mold has been filled the carriage 6 will be rolled into position with the rod 3 immersed in the molten metal, and the motor 5 will be started to revolve the rod 3 and thereby agitate the molten metal in the mold. This agitation of the molten metal willdiminish the speed of solidification and transmit mechanical action to the bubbles of gases within the metal so as to aid in coalescing the bubbles and assist said bubbles to escape prior to the solidification of the metal.

Experience has'shown that the agitation of the molten metal prevents the formation of the tube-like cavities that extend at right angles to the skin wall of the ingot and toward the center, and other defects which are due to retained gases in the ingot cast in the usual manner and Without agitation.

To those skilled in the art, it will be apparent that the a itating or stirring mechanism above descri ed may be readily brought into the desired cooperative relation to a mold so as to permit the desired agitation or stirring whenever desired.

The stirring mechanism may be positioned within themold during the teeming operation so as to be eifective on the metal substantially as soon as it is received by the mold, or it may be inserted into the metal immediately upon the conclusion of the teeming process. In many cases, since it is desirable to institute the agitation as soon as possible, the first mentioned procedure will be practiced so as to insure the prevention of localized solidification and the desired escape and distribution ofimpurities as well as the desired metal diffusion.-

As the. solidification progresses, the agitating mechanism may be progressively raised until it is ultimately withdrawn from the.

moldatsuch time as it has served its full purpose.

. While I have shown and described one specific embodiment of my invention and spec1fic steps of the method it will be understood that I do not wish to be limited thereto, since various modifications may be made without departing from the $00 e of my invention, as defined in the appen ed claims. a

I claim:

1. Apparatus for stirring molten ingots, including the combination of a movable carriage, means for moving said carriage vertically, a stirring rod depending from said carriage and including a metal stem covered by brick elements, and means on said carriage for imparting stirring movement to said rod.

2. Apparatus for stirring molten ingots, including the combination of an upright column, a carriage fixed to said column for vertical movement, means for vertically moving said carriage, a rotative stirring rod depending from said carriage andincluding a metal stem covered with brick elements, and means on said carriage for imparting stirring movement to said rod.

3. Apparatus for stirring molten ingots including the combination of an upright rotative column, a carriage fixed to said column for vertical movement, means for vertically moving said carriage, a rotative stirring rod depending from said carriage and including a metal stem covered with brick elements and means on said carriage for imparting a stirring movement to said rod.

In testimony whereof, I have hereunto set m hand.

y LOUIS C. EDGAR.

Images