US1040517A

US1040517A - Process for casting molten metal in molds.

Info

Publication number: US1040517A
Application number: US50217009A
Authority: US
Inventors: Clay Crawford
Original assignee: Individual
Current assignee: Individual
Priority date: 1909-06-14
Filing date: 1909-06-14
Publication date: 1912-10-08
Anticipated expiration: 1929-10-08

Description

C. CRAWFORD. PROCESS FOB. CASTING MOLTEN METAL IN MOLDS. APPLICATION mum JUNE-14, 1900.

1,040,,5 1 7, Patented Oct. 8, 1912.

VI/IIII/Il/M SATES T TWICE.- k

CLAY cnnwroan, or TOLEDO, OHIO, ASSIGNOR To 0. s. BRIGHAM, or TOLEDO, c1110.

-IROCESS FOR CASTING MOLTEN METAL IN MOLDS.

Patented Oct. 8, 1912.

To all whom it may concern:

Be it known that I, CLAY CRAWFORD, a

I citizen of the United States, residing at 815 West Woodrufl avenue, in the city of Toledo, county'of Lucas, and State of Ohio,

have invented new and useful Improvements in Processes for Casting Molten Metal in Molds, of which the following is a specification.

This invention relates to the process of casting molten metal in molds and has for its object: First. The separation and elimi nation of the contained slags, segregates and gases,'which cause flaws and other defects. Second. Also to break up the axes and planes of cleavage in the forming crystals, which weaken the resulting casting. Third. To form and retain to the end of'the solidifying period a feeding head to reduce or prevent piping, or a honeycombed core along the central axis of the casting.

I shall describe ,my'invention with refer-' ence to the accompanying drawing of a machine for casting steel ingots by this process.

The machine used herein for illustration is the subject of an application for a patent now pending, filed October 21st, 1907, Number 398,498, but which can be used for many other forms of castings.

It consists of a mold mounted on a table, supported on the top end of a vertical shaft, with means to rotate the mold about its ver tical axis, with a constantly varying speed of rotation, cooperating simultaneously, with means to accelerate the cooling of the lower portion of the mold and casting, and to retard the cooling of the upper portion.

Among engineers it is a well known fact that metal castings, especially of steel, are not perfectly homogeneous and their reliability and value is much reduced by these defects. During all the time the liquid metal is cooling there are processes going on by which the carbon, phosphorus, slags and sulfur are being segregated, and the segregates concentrated in the central portion of the mass, and being lighter than the molten metal, most of them rise to the upper portion or surface of the core of molten metal.

In the manufacture of steel as now conducted, a portion of the upper end of the ingots are cut oil and scrapped, causing a great loss of material, but even then the central portion of what is left is not uniform with the outside portion, and contains slags,

segregates, blowholes, and holes caused by the solidification of an outside shell and the shrinkage of the inner portion as it cools, leaving a honeycombed core. Bolling or hammering while the ing'ot is highly heated partially remedies some of these defects but not wholly so.

The process by which I reduce or elimihate-the defects in the cast shapes to which it is applicable, is to oscillate or rotate with a constantly varying speed of rotation, the mold about its vertical axis, and at the same time regulate the cooling of the molten metal, so that the solidification shall proceed progressively from the bottom and sides of the mold and ending at the center of the upper surface. This leaves an avenue open for the escape of impurities, as they concentrate in the center and rise to the surface, if not prevented by the upper ortion solidifying. This also gives a ceding head to supply metal to correct the shrink= age due to solidification. The rotation of the mold about its vertical axis, with a constantly varying speed of rotation, causes every particleof the liquid metal to slide over the surface of every adjacent particle, which agitation separates the impurities and they rise to the upper surface of the core of liquid metal, and they can afterward be separated by cutting them off the upper end of the ingot. about its vertical axis to get the same effect as rotation with a constantly varying rota tive velocity. A box shaped mold may be mounted on rollers and oscillated or shaken in a horizontal plane with the cooling of the top portion retarded, and the coolingo'f .the bottom portion accelerated, to get the same effect as by rotation with a constantly varying rotative velocity. In other words, the process in its broadest aspect may be said to consist in agitating a body of molten metal during the cooling of the same.- Such agitation causing the unfrozenor molten metal to move or slide over the surface of that portion of the metalwhich has already solidified. More specifically, the process in eludes the production of the agitating movement by moving the metal to be cast with varying or unequal velocities in equal intervals of time.

It is a law of the molecular aggregation of crystalline solids that when their particles consolidate" under the influence of heat and The mold may he oscillated motion, their crystals arrange andgroup themselves with their principal axes in lines perpendicular tothe cooling surfaces of the solids. In castings of rectangular section 5 these axes meet at points equidistant from the cooling surfaces, and are there imperfectly connected and form a core or seam, which will contain a varying amount of slag or other impurities, which form a cleavage lane that is easy to rupture, and which it is impossible to remoye by subsequent working with rolls or hammers. This form of crystallization is nicely shown in a cake of artificial ice. In molds of circular cross section there is aptto be. a flow of impurities to the center of theingot, forming a vertical cpre or pipe. My process of constantly slidmg the liquid metal over the surfacesof the solidified metal breaks up the axes of crystallization, and at the same time separates the impurities, which rise to the surface and gives much stronger castings,1 free from coarse planes of cleavage, and better adapt ed to after-treatment with rolls and her. :mference should be had to the accom- .panylng drawings forming'a part .of this specification in which Figure 1 is a front elevation of the mechanlsm for rotating the mold; 2 is an end elevation of the mechanism for rotating the mold and Fig. 3 is a front'elevation, partly in section, of the mold and apparatus forrotating the same. 1 Referring to'the accompanying drawing, 1 is the frame of the machine, 2 is a hollow, vertical shaft, supported by frame 1, and having secured on its upper end a table 3, which hasv a flange extending from its outer circumference; resting-on table 3 is' a plate 15, which formsa bottom for the ingot mold 16., A portion oft-he upper end of the ingot mold may be enlarged and lined with a belt' 17 cf a non-conductor of heat to prevent rad ation of heat and retard the cooling of

theliquid metal

19, and 18 is a covering of a non-conductor of'heat on the upper surface of the molten metalto prevent the radiation the cooling process. .1

20 is metal that has solidified. around the sides and-bottom of the mold. I 21 are: pipes thatmay be used to throw t5 jets from holes 22 offa' cooling fluid. "(as' a mistiof air and water) on the lowers-and:-

ou'ter surface'of the mold, tejiacpeleratefthe cool of the metalzfm tha't'ipbrtion of; the

. These j ts are controlled the an, m be pp l-p cesivel from he I of: heat from the upper-surface of the liquid the Bxtmme metal, and retard the solidification of the surface of them etal to the very last end of Y tousoli.

process is to keep the to o surface of the mo ten metal. This 'rotat p merging "1% into the outer surface .dilftti l'iilg mo d as theyrise. furnish radiating surface for .the pose-of accelerating the cooling of the contained metal at its lower end.

Instead of lining 17 ,"a belt of a non-.con-

ductor of heat may be used .to cover the outer surface of theupper end of the mold to obtain the same results as those obtained by lining 17. 1

On the vertical shaft 2 is a beveled gear 4 meshing into gear 5 on shaft 7, supported by bearings 6; on shaft 7 is crank 8, having a pin 9, on which is box 10, sliding in a slot in crank 11, on the endof shaft 13, which is turned by a belt on pulley 14. The shafts 7 and 13 are parallel, but not in the same line,

13 being shown a little higher than 7 and as they rotate with a mean angular velocity the angular velocity ratio at each instant 1s varying in the position shown the angular velocity of gear 4 would be at a minimum,

and with the cranks pointing downward it would be at its maximum velocity.

The mode of operation is to.-rotate the table and mold with a constantly varying speed of rotation, then fill the mold with molten metal from a ladle in the usual manner, then cover the upper surface of the molten metal with a non-conductor of heat,

as 'air-slaked lime, to prevent the radiation of heat as much as possible, then, if necessary, apply the cooling fluid from the lowest ring of jets and progressively at intervals to the upper ring of jets as may be needed to cool the metal progressively from the bottom upward. The efiect of this process of re-' tarding the cooling of the upper end of the casting and the accelerating the cooling of its lower end soon forms the shell 20 of solidified steel next the bottomsides of the mold, with the sides of the shell 20 decreasing gradually in thickness toward the top ,port1on,' aiid during the process .of cooling there will be a core 19 inverted conoidal shape, which will con-' stantly decrease in size as the cooling proceeds until it finally disappears at the center of'thetop-of the casting. The center of top surface being the last point One of'the most important oints of my the molten of molten metal of I metal liquidto the end 0 the solidifying stage, and thus 'to furnish a feeder to up the space left in the interior of the casting due to the shrinka e ofthecontained cooling metal, this liqui core also furnishes an outlet for the contained slags, segregates and gases to esca e out through the upper of the mold with a constantly va spec of rotation keeps every parti' e of the ac htrffilhe ho and anger e" it. Also the agitation brings t e particles one another is-caused by the resistance of their inertia to a change in their rotative velocity about the axis of rotation, and by their friction on the surface of the solidified metal and on each other. This sliding and agitation, separates the slugs and nodular segregates and also the occluded gases, and as they'are lighter than the molten metal, they arise to its surface and se arate from of oxid of iron in the molten metal into con tact with the carbon and it is'reduced to metallic iron.

. hammering or rolling. I

When castings are allowed to solidify on their upper surface while the interior is molten, shrinkage causes a honeycombed core in the interior, which in effect are 'flaws and cannot be eliminated by subsequent eliminate this 'center by, eeping the upmold around its vertical axis. A

Changes may be made in some of the minor details while the essential features are retained, and thespirit of th invention embodied.

Having described my invention and its gene'ralmethod of operation what I claim is 2-- 1. The process of casting, which consists in introducing the metal into a mold, causing the metalto cool more rapidly in one "part of the mold than in the others and im ltaneously causing the particles of the eatly reduce or unsolidified metal to move with respect to each other and to the solidified metal during the cooling.

2. The process of casting, which consists in introducing the metal'into a mold, coolin the'mold rogressively from one end toward the opposite end thereof and simultaneously causing the particles of the unsolidified metal to move with respect to each other and to the solidified metal during the cooling.

3. The process of casting which consists in rotatin a body of molten metal within-a mold, t roughout a succession'of time 'periods, the velocity of rotation of the mold varyin during each time period.

4. T e process of casting, which consists in introducing the metal into a mold, subje'cting the mold to rotary motion so that the same moves with unequal velocities in equal intervals of time and simultaneously cooling one portion of the mold more rapidly thanthe other portions.

5. The process of casting, which c nsists in moving the body of metal with un ual velocities in equal intervals of time and simultaneously preventing the radiation of heat from a certain ortion of the metal and cooling another portion of the metal.

6. The process of casting, which consists in introducing the metal into a mold, rotating the mold with unequal velocities in equal intervals of time and preventing the radiation (13f heat from the exposed surface of the meta CLAY CRAWFORD.

Witnesses GHABpEs SPRAGUE, Gannon. KING.