US1349733A - Method of treating steel ingots - Google Patents

Description

C: H. READ.

METHOD OF TREATING STEEL INGOTS.

APPLICATION FILED AUG. 5, I916.

Patented Aug. 17, 1920.

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' C. H. READ.

METHOD OF TREATING STEEL INGOTS.

APPLICATION FILED AUG,5. 1916.

1,349,733. Patented Aug. 17, 1920.

2 SHEETSSHEET 2.

CHARLES :a. READ, or PITTSBURGH, PENNSYLVANIA.

METHOD OF TREATING STEEL INGOTS.

Application filed August 5, 1916. SeriabNo. 113,296.

To all whom it mag concern: i

Be it known that 1, CHARLES H. READ, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Method of TreatingSteel lngots, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming part of this specificatlon, in which:

Figure l is a perspective view showing,

sets of kneading dies arranged to carry out my new process.

Fig. 2 is a sectional elevation more clearly the die members.

Fig. is a diagrammatic side elevation showing a set of kneading rolls for carry- .ing out my invention, and i Fig. t is a diagrammatic plan view of the same. p 1

My invention relates to the treatment of steel ingots to make them more homogeneous and reduce or remove segregations, blowholes, piping, etc.

\Vhen steel is poured into an ingot mold, it is not a homogeneous body of iron containing chemically combined alloys and im purities. It is a conglomerate, comprising a liquid bath oi -iron carbids having dissolved therein the alloys and impurities, this bath containing particles of relatively pure iron. The meltmg point of pure iron is much higher than that of iron carbid and hence the car-bids remain liquid after the iron has set. Indeed it is doubtful if these small particles of iron are ever actually i'ully liquefied. \Vhile these iron particles remain in the fluid carbid bath, gases are generated and thrown ofl'; these gases con sisting mainly, it not wholly, of carbonmonoxid. \Vhen the mold is filled. the molten steel is subject to the following influences and reactions: p

1. The mold being relatively cold chill showing the surface of the ingot and forms its skin,"

this varying in thickness according to the size of the ingot, the thickness of the walls of the mold, heat at which it is poured, etc. Thisskin being in contact with the liquid interior will remain hot and in a tough malleable condition for some tune, dur ng which it can be worked to a certain extent without rupture even though the interior is still liquid. 1 p

2. As the steel cools, it contracts at the Specification of Letters Patent. i Patented Aug.

rate of of an inch to the foot and the interior mass of the ingot is subject to this compressive force and reduced in bulk, The greater part oi this shrinkage takes place in the cooling iiroma liquid state to that of a bright red. V

so rapid that some of the fluid carbids are caught in the massand held: until they in turn cool and set; and the gases given oil atthe moment of congealiug are also, caught and held :inthe skin, thus leading to surface blow-holes.

4. During and after the setting of the skin the cooling of the interior mass goes on with the result thatthe iron part.ii.-les chill and set first in the form of dendrites (spicules); these spiculac extending inward until they finally reach the center where they remain for some time in a pasty mass owing to a slower rate oi cooling. The gases liberated by the formation of the dendrites flow along the lines oi least resistance, which are toward the center, because this central portion remains fluid the longest. In this central liquid. portion the gases tend to rise, but as cooling oi the mass proceeds they are trapped and held, thus causing serious blow-holes. y

5. The dendrites formed in the cooling mass extend in all directions and resemble a mass of mixed fibers. As they cool they shrink somewhat, but the shrinkage of the whole mass so much greater that the fluid carbids are under constant pressure and flow toward the center, :arrying with them the alloys and impurities such as manganese, Slllfiflll, phosphorus, etc, thus causing segregation. These alloys and impurities do not all pass to the center, as portions of themare trapped by the cooling dendrites and are held in place. .l'lowever, segregation always occurs to a sufficient extent to seriously affect the qualityot the steel in the interior, especially toward the upper portions. i i

6. As the liberated gases move toward the still fluid center and rise, they leave a serious void which is only filled by the upper liquid contents dropping into these spaces. This filling of the spaces is not complete, however, owing to thecooling oi the outer walls of theingot and hence the solidifying parts form around the sides of a cavity or pipe occupying usually the upper half or third of the ingot. This hollow or pipe The cooling and setting oi? the skin is that if a liquid is placed in the center of a mass of dough and the dough is then kneaded, the liquid will be worked outwardly through the plastic mass and disseminated through it -wi-th comparative uniformity.

Bysimilarly kneading a steel ingot after the skin isset and while the interior is still liquid or at least plastic, I can work. the still liquid carbids outward among the dendritic interstices and thus disseminate the impurities and alloys more uniformly through the mass and at the same time cause a better release of the gases from the mass or their dissemination through it. This action also, of course, reduces or closes up the pipe.-due to the kneading of the mass and its consequent reduction in size, and also to the release or dissemination of the gases.

In carrying out my process, I apply successive local pressures to different successive portions of the ingot, preferably successively from different sides, thus giving a true kneading action. This is preferably carried out by one or-a series of kneading dies, preferably arranged in opposite pairs, one pair working on two opposite portions of the ingot and the next pair working at right angles thereto or over opposite portions of the ingot. The ingot may be fed along through these pairs of dies which are given a relatively slow gentle pressing movement as distinguished from a hammer-like blow, or the distorting force ofa forging operation.

The kneading dies may be of any desirable width, say, for example, four inches wide on their hearing faces and are preferably recessed to fit two sides of the ingot, thus giving a diamond shaped opening between them, to give the kneading effect on four sides.

In the drawings, I show two pairs of such sequent passes, to be determined by the size and heat of the ingot, and its chemical constitution. Thus, in these later passes I may make a reduction of three-fourths of an inch to one inch, or as much as one and onefourth to one and one-half inches. These successive kneading pressures are imparted to successively different portions of the ingot either by feeding the ingot through two or more pairs of the dies or by providing a gang of the dies which work successively on the different portions of the ingot, the ingot remaining in place. In this kneading, the pressure must he applied locally, and must leave the adjoining portion free from pressures at that instant. The liquid or pasty carbids will move outwardly a short distance under each pressure and a portion will tend to return to their original place as the pressure is removed, to again be forced outwardly as the result of the continued successive pressing operations.

In Figs. 3 and -1- I show another form of apparatus for carrying out my invention. In this form of apparatus, three kneading rolls 5 are provided, the axes of these rolls being set at an angle to the axis of the ingot A, and the rolls preferably being longitudinally corrugated or otherwise formed to knead the ingot. The ingot may be set on a stand (3, resting on the upper end of a hydraulic plunger 7 of a hydraulic cylinder 8. hen the ingot has thus been set vertically in the stand, the rolls are rotated in the same direction through any suitable connections, and the plunger 7 is gradually lowered, allowing the ingot to be moved through the pass between the three kneading rolls. During this passage the kneading operation is obtainedin the same general way as with the dies.

The operation of this latter not the same as axial rolling, nor is it the same as the squeezing of a puddle hall. The projections on the rolls act to knead the metal in somewhat the same way as the dies of Figs. 1 and 2, without any material disturbance of the central portion of the ingot, as would be the case in a squeezing operation. It will be noted that, as distinguished from actual rolling, there are a succession of pressing actions given to the ingot during its passing through the kneading rolls, by reason of the projections on the rolls acting successively upon the surface of the ingot, whereas in actual rolling apparatus is there would be a continuous pressure.

Of course with the second form of apparatus the ingot is in the same condition that it is with the first form of apparatus; that is, the interior has not completely set, but is at least plastic.

The basic idea involved in my process is that of disseminating a liquid contained in the center of a porous mass, throughout the said mass, by a kneading operatioirand this, I believe to be entirely new in the art. The

ingot may be turned from side to side or rotated in a half circle around its major axis while being kneaded, and a kneadin operation is preferably started at the smaller end, although it may be started at either end or simultaneously at both ends and work to ward the center.

My operation is not to be confused with ordinary forging processes which are carried out upon solid masses of steel and have for their object a changing of shape and the further solidifying and refining of the steel after it has completely set and become solid throughout.

The advantages of my invention will'be obvious to those skilled in the art,since a simple and comparatively cheap method is afforded for reducing piping and blow-holes and at the same time thoroughly re'disseminating the alloys and impurities through the mass. The enormous loss now present in steel manufacture due to discarding bad ingots, cutting off the upper parts of ingots, etc, is greatly reduced or done away with.

If desirable, the top of the ingot may be especially chilled to prevent the interior liquid portion from bursting out, or the upper end may be forced against a bearing or movable plunger to sustain the skin of this upper part during the kneading. It is, of course, necessary that the kneading ope ation be carried out carefully in such a way as to not break the skin and cause the ingot to bleed.

Many changes may be made in the form of apparatus used without departing from my invention.

I claim:

1. The method of treating ingots, consisting in removing them from the casting molds and applying successive localized pressures to different successive portions thereof from opposite sides in successive passes before the interior is completely set and while a portion thereof is still in a liquid condition, to thereby disseminate the central liquid portion of the ingot throughout the mass of the ingot and distribute the segregated impurities.

2.. The method of treating ingots, consisting in removing them from the casting molds before the interior is completely set and while a portion thereof is still in liquid condition, and then applying successive localized pressures to different successive portions thereof to thereby disseminate the central liquid portion of the ingot throughout the mass of the ingot and distribute the segregated impurities, substantially as described.

The method of treating ingots, which consists in removing them from the casting molds and subjecting the ingot before its interior portions are set to a succession of sets of compressing actions, each set of such actions being applied progressively from end to end of the ingot and each set of such actions effecting a further reduction in the size of the ingot while a portion thereof is still in a liquid condition to thereby disseminate the central liquid portion of the ingot throughout the mass of the ingot and distribute the segregated impurities.

4. The herein described method of treating ingots, consisting in removing them from the casting molds and subjecting the ingot to a succession of localized compressing actions applied progressively throughout the length of the ingot to thereby Work the still liquid car-bids contained in the cent'al portion of the mass of the ingot outward among the dondritic interstices and thus disseminating the impurities and alloys more uniformly throughout the mass, and at the same time cause a better release or dissemination of the confined gases, and successively repeating such compressing actions during the cooling of the ingot.

The method of forming an ingot having substantially uniform dissemination of alloys and impurities throughout the en tire body thereof, which consists in casting the ingot, permitting the same to cool until the skin is set and the interior is in a lastic condition, and then applying successive localized pressures to different successive portions of the ingot from successive SldGS thereof, substantially as described.

In testimony whereof I have hereunto set my hand.

CHARLES H. READ. Witnesses:

A. F. TIBBEITS, H. M. Conwm.

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