US2187416A - Method of roll casting - Google Patents

Description

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F. C. T. DANIELS METHOD OF ROLL CASTING Filed June 21 Jan. 16, 1940.,

INVENTOIR 7 g aw! Wuz'a/ till atented Jan. 16, 1940 PATENT OFFICE DIETHOD F ROLL CASTING Fred 0. "1". Daniels, Bridgeville, Pa., assignor to Mackintosh-Hemphill Company,

tion 01' Delaware a corpora- Appiication June 21, 1939, Serial No. 280,339

4 Claims.

This invention relates to the casting of metalworking rolls.

The object of the invention is to provide a simple and satisfactory method of making castlron metal-working rolls having a relatively hard roll body and relatively soft and machinable necks. Various methods of effecting this same general purpose have previously been employed and my invention specifically considered is purposed to provide a method simpler than some of those previously employed and to give more satisiactory results than other prior methods for obtaining the same general effect.

, l orexample, one previously employed method has been to make rolls having a hardened body surlace or chill and necks which are softer and more readily machinable than the hardened surlace of the roll body, by washing out from the mold all of an initially poured hot metal, save that which is included in the hardened surface or chill depth of the. roll body. It is frequently, however, unnecessary or undesirable to make a roll having the interior of its body composed. of metal oi difierent composition than that of the body surface or chill. Also, the casting oi a roll by initially pouring a hard metal and washing out the still molten portion, after metal to the desired depth has been congealed against the surface of the chill, or surface of the body portion of the mold, is a procedure requiring accurate timing and delicacy of operation. This is particularly a fact since there is a tendency to wash out a portion of the initially congealed metal, and thus to give a chilled shell of unequal or unpredictable depth, in pouring the second metal touwash out all the uncongealed initial metal in the mold.

A procedure used, to make a roll having necks more machinable than the body portion of the roll, has been to bottom-pour a mold charge up to a level slightly above the body region of the mold; and, after a chill has formed against the surface oflthe body portion 01 the mold, enough cotter metal is added to fill the drag neck and wobbler portion of the mold, and the displaced metal is run oil at a level just above the body portion of the mold, initial metal being displaced upwardly by the softer metal poured into the lower, or drag, portion of the mold. In such procedure the tap hole, by which the surplus metal is drawn off, is then closed and the upper, or cope neck of the roll is individually poured. s last method involves running oif from the mold metal of the initial charge which is usually metal of high .alloy content and relatively expensive, in' a quantity equal to the weight of metal initially included in the drag neck, drag Wobbler of the roll, and the vertical runner of the mold.

The method of my invention is such that the entire weight of metal introduced into the mold at various stages in the roll casting operation is retained in the mold. There is no flow off of metal from the mold. In the practice of my 1 method, therefore, there is no scrap loss of the relatively expensive high alloy metal of which the hardened body of the roll is formed, and there is no danger of washing out metal which it is desired to include in the surface chill of the roll body. Only about one-half as much metal is required as an additive in the cope neck and sinkhead, as in a method in which the initially poured metal is inhibited from rising substantially in the neck cavity and sinkhead in 90 the cope portion of the mold.

The accompanying drawing, which is to be taken asa conventional representation of a mold assembly for roll casting, shows in vertical section a conventional structure in which my 25 method may advantageously be practiced. In the drawing there is shown in vertical section a vertically positioned roll casting mold. As illustrated, the mold comprises a central body portion formed as a body chill I, a sand drag 2 providing the mold for one roll neck and the Wobbler or coupling structure associated with it,

a sand cope 3 providing the mold for the other roll neck and its associated Wobbler or coupler structure, and a sinkhead 4 providing'an upward extension of the mold assembly. A vertical runner 5 communicates with the lower region of the lower or drag portion of the mold cavity by way of a gate 6 in the drag mold 2.

In conducting my method the mold cavity is, 0 by pouring through the vertical runner in the conventional manner, initially filled with metal to a level above the upper extent of the roll body cavity and below the upper level of that portion of the cavity within the mold cope which provides space for the metal of the roll neck and its associated parts. After waiting until centrifugal motion in the metal teemed into the mold has ceased and the metal has become quiet, I 50 pour in through the runner 5, and down gate 6 in the drag mold, a soft machinable iron in a weight suflicient to replace the original hard metal in the drag mold, and in the vertical runner and gate. This different metal ll pour with 1 5 duced by diluting the hard initially cast metal sufllcient rapidity bodily to displace the original metal upwardly in the mold, sothat in the upper region of the mold cavity the level of molten metal is to a corresponding extent raised. As the level of the initially poured metal rises in the mold cavity, none of that metal is run off.

The initial metal, which is of a harder composition, and is the metal of which the roll body to be composed, then extends from a level just below the lower level of the body cavity to a level lying approximately at the upper end of the cavity for the cope neck and wobbler. As this would give a roll having one soft and machinable neck and one neck of the same hard metal as the roll body, I pour into it through the sinkhead a dilutant metal of softer composition. During the time of all the previous steps the original metal is being congealed by the body mold chill and has now solidified to some 2" to 6" in depth, so

much so, that it is undisturbed by the addition body cavity of the mold.

If the metal which has been poured to form the drag neck is of a sufliciently soft composition, it may be used to dilute the metal of the cope neck. Commonly I add this metal in a weight equal to the weight of metal lying in the neck cavity of the cope mold. If desired, the sinkhead may be made of sumcient capacity to accommodate a weight of metal greater than that included in each of the roll necks, and the dilutant metal may be added in the upper mold region in a weight greater than that of the metal initlally standing therein. It is, however, unnecessary in this mixing step to overflow any of the metal at any stage poured into the mold. As exemplary of this simplest procedure in accordancewith my method. I may use for the initial charge, and for the additive charge, metals corresponding generally to the following formulae:

Si S P Mn C Ni Cr Initial charge 1.04 048 093 0.46 3. 42 4.18 1. 96 Additive charge 1.62 .004 .085 0.68 3.86

In the finished roll the'roll body will have, save in blending zones at the junction of the body and in equal proportions of the initially cast metal and of the additive metal, will have approximately the following composition:

greater diversity between the roll necks, but in which the cope neck of the roll is nonetheless readily machinable:

When the metal of the additive charge is mixed in an equal weight with the initially cast metal lying in the cope mold, the resultant composition of the cope neck will be-- Si S P Mn 0 Ni Cr Mo As above explained, this composition is without difllculty machinable.

In some instances it is desirable to effect a low graphite content in the roll necks. In such case the additive metal will be of a sort which is in itself machinable, but which is not capable, when added in any reasonable quantity, of use as a dilutant to provide a machinable cope neck when mixed with the initially cast metal of which the roll body is composed. Inv such case, the additive Under such circumstances, I employ one of two variant procedures in rendering the cope neck machinable;

One such procedure, assumes that there is available a melt of softer metal than that poured for the drag, such as the metal given above, as exemplary of a composition for machinable roll necks, and corresponding approximately to the formula:

Si s r Mn 0 If added in a weight equal to that of the metal previously standing in the cope portion of the mold,and assuming that the initial metal responds to the formula for the roll body metal first above given, the dilution would give in the cope neck a final composition corresponding approximately to the formula:

81 s r Mn 0 I Ni Or 4 si s P Ma 0 Ni Cr It will be recognized by those skilled in the art of roll making that this latter composition, prowith the softer additive metal, is sufficiently soft to be readily machinable. As explained, a somewhat softer cope neck may be obtained, without varying the compositions of the metals, by adding the dilutant metal of the additive composition to the cope mold in a weight somewhat exceeding the weight of the initial hard metal therein. The following is another exemplary set of formulae, illustrating a case in which there is If, however, no satisfactory second dilutant metal is readily available, I follow an alternative procedure. This procedure consists in pouring initially so that the molten metal stands in the mold at a level slightly above the body cavity of the mold. An additive metal of moderate graphite-forming tendency is then poured to replace the initial metal in the drag mold, displacing metal upwardly of the mold to fill the cavity for the cope neck. At this stage, and before making any further addition I stir finely divided ferrosilicon into theinitial metal standing in the cope til till

til

dill

ill)

till

cavity. If, for example, the initial metal and the additive metal respond to the formula:

Si I S 1 1H1] C Ni Or 1. 04 048 093 46 3. 42 4. l8 1. 96 1.10 I .066 .095 .60 3.72

I may add sufficient ferro-silicon, to give, as a resultant a composition having a higher silicon content, for example I usually add sufficient ferro-silicon to bring the metal of the upper roll neck into approximate correspondence with the formula:

Si S P M11 C Ni 1 Cr than that of the metal with which it is mixed,

rather than in a weight equal to or greater than the weight of the initial metal, if the nature of the compositions renders such proportioning desirable.

'I'he gist of my invention resides in the discovery that I may make a roll with necks of metal more machinable than the metal forming the body of the roll by replacement in one roll neck, and may effect dilution without removal of any of. the initial metal in the other roll neck. This is in marked distinction to previous methods for attaining the same purpose which have included as a. matter of supposed necessity a step in which initially-poured metal is run off from the upper neck cavity of the mold as the level of metal in the mold rises by displacement of the initial metal with a different metal in the lower neck cavity of the mold. By dilution in the upper neck cavity of the mold in distinction to replacement of metal therein, I insure the formation of a perfect bond between the roll body and the upper roll neck, while obtaining in the upper roll neck as well as in the lower roll neck a composition and quality of the metal which is within the bounds of what the art considers to be a readily machinable metal. This I have found I can do, while obtaining a roll body adequately hard for many conditions of use, by a simple apportionment in the composition of the initiallypoured metal and of the additive metal. Since the additive metal of the lower roll neck serves upwardly to displace the metal initially standing in the mold there is no washing efiect resultant from that action; and'the addition in the upper neck cavity. of the mold being eiTecte-d by mixing in distinction to replacement, washing in the metal of the roll body; is not caused by this latter addition. The economy of my method of making a roll having readily machinable necks and relatively hard body over methods in which all of the uncongealed initial metal is washed from the mold, and methods in which initial metal is run oif from the upper neck cavity in the mold and replaced with a different metal, is obvious to those skilled in the art.

I It may be explained that as used herein, the terms lower roll, neck and upper roll neck refer to the position of those necks in a vertical mold contoured for roll casting; and that where the terms neck and neck cavity are used without qualification, they are to be taken as designating not only the roll neck proper, but

the structure associated therewith to provide wobblers, couplings, and the like. Where I have spoken herein of metal as being machinable or readily machinable, both of these terms are used to define an ease of machinability which those skilled in the art consider to lie within the bounds of economical commercial practice, and I do not herein intend by either of those terms to make distinction from an umn-achinable nature of absolute sort.

I claim as my invention:

1. In making a cast-iron roll having a body of one composition and necks of different and more readily machinable composition, the steps of pouring into a vertically positioned mold contoured for the casting of rolls metal of a sort not readily machinable to be included in the roll body to a level slightly above the body cavity of the mold and below the upper end of the upper neck cavity of the mold, by pouring rapidly a diiferent metal of more readily machinable sort into the lower neck cavity of the mold displacing the initial metal upwardly in the mold and replacing it in the lower neck cavity of the I mold with the difierent metal while retaining all the initially poured metal in the mold, and mixing with the initially poured metal in the upper neck cavity of the mold a different metal of more machinable sort in quantity and composition adequate in admixture with the initial metal to give a machinable upper roll neck.

2. In making a cast-iron roll having a body,

of one composition and necks of diiferent and more readily machinable composition, the steps of pouring into a vertically positioned'mold contoured for the casting of rolls metal of a sort not readily machinable to be included in the roll body to a level slightly above the body cavity of the mold and below the upper end of the upper neck cavity of the mold, by pouring rapidly a different metal of more readily machinable sort into the lower neck cavity of the mold displacing the initial metal upwardly in the mold and replacing it in the lower neck cavityof the mold with the difierent metal while retaining all the initially poured metal in the mold, mixing with the initially poured metal in the upper neck cavity of the mold a different metal of more machinable sort, and supplementing the efiect of the additive metal in producing a machinable upper roll neck by adding to the mixed metal in the upper neck cavity a graphitizing composition adequate in conjunction with the additive metal to give a machinable upper roll neck.

3. In making a cast-iron roll having a body of one composition and necks of different and more readily machinable composition, the steps of pouring into a vertically positioned mold contoured for the casting of 'rolls to a level slightly above the body cavity of the mold and below the upper end of the upper neck cavity therein a relatively unmachinab le metal for inclusion in the roll body, by pouring rapidly a different metal of more readily machinable sort into the lower neck cavity of the mold displacing the initial metal upwardly in the mold and replacing it in the lower neck cavity of the mold with the additive metal while retaining all the initially poured metal in the mold, and mixing with the initially poured metal in the upper neck cavity of the mold additive metal of the same composition as that secondarily poured to form the lower mold neck in quantity adequate in admixture with the initial metal to give a machinable upper roll neck.

4. In making a cast-iron roll having a body of one composition and necks of different and more readily machinable composition, the steps of pouring into a vertically positioned mold contoured for the casting of rolls to a level slightly above the body cavity of the mold and below the upper end of the upper neck cavity therein a relatively unmachinable metal for inclusion in the roll body, by pouring rapidly a different metal of more readily machinable sort into the lower neck cavity of the mold displacing the initial metal upwardly in the mold and replacing it in the lower neck cavity of the mold with the additive metal while retaining all the initially poured metal in the mold, mixing with the initially poured metal in the upper neck cavity of the mold additive metal of thesame composition as that secondarily poured to form the lower mold neck, and supplementing the effect of the additive metal in producing a machinable upper roll neck by adding to the mixed metal in the upper neck cavity a graphitizing composition adequate in conjunction with the additive metal to give a 5 machinable upper roll neck.

FRED C. T. DANIELS.

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