US2097709A - Method of making rolls - Google Patents

Description

Nov. 2, 1937. H. E. wALTERs METHOD OF MAKING ROLLS Filed Sept. 30, 1935 2 Sheets-Sheet l INVENTOR. #W7 Www' ATTORNEY;

Nov. 2, 1937. H E, WALTERS' 2,097,709

METHOD OF MAKING ROLLS Filed sept. so, 1955 A 2 sheets-'sheet 2 WIM/5555 INVENTOR.

mm B? W, M vm ATTORNEYC Patented Nov. 2, 1937 UNITED STATES PATENT OFFICE United Engineering Pittsburgh, Pa.,

& Foundry Company,

a corporation of Pennsylvania Application September 30, 1935, Serial No. 42,800 v 7 Claims.

This invention relates to an improved process for making cast metal rolls, as used in metal rolling mills.

It has long been desirable to produce `a cast metal roll, for example, to be employed in metal strip rolling operations, which roll is very resistant to scarring as caused by the ends of thev strip passing through the rolls or by other means.

Moreover, in recent years the severe drafts and speedier production methods as well as the work with wider and alloyed strip have made the advantages of a, hard-surfaced roll particularly attractive. It is the usual practice to employ hard-surfaced rolls in the strip finishing mills, but in addition the use of hard-surfaced rolls in the regular mills is also highly benecial.

Prior to my invention hard-surfaced rolls have been made by casting highly alloyed iron in a mold having a chilling surface adjacent the enlarged central portion of the roll. It has been found that this method produces a satisfactory surface on the enlarged central or working portion of the roll, but that the bearing necks and wabbler portions of the rolls are also of the same hard high alloy material. This means that in order to finish the roll after casting, the entire roll surface, including the central portion and the reduced neck portions, must be .ground down rather than turned down by edge tools in a roll lathe.

Grinding the roll surfaces, and particularly the bearing necks and wabbler portions, has added greatly to the cost of manufacture since grinding is necessarily slow and expensive where the fillets, shoulders and other irregularly shaped bearing necks or other roll portions must be brought to the proper dimension and nish. The grinding of the truly cylindrical central portion of the roll is not diicult, nor does it noticeably add to the cost of roll Vmanufacture over the cost of edge tool machining. Likewise, the enlarged central portionof the roll can usually be cast more closely to its finished size in that it contacts directly with an iron or other chill which is not the case with respect to the necks and wabblers.

I have also found that by former practices as above described sacrifice of strength and toughness in the roll must be made to obtain the'hard roll surface. The alloy metal is more brittle and less adapted to withstand wear and shock than is a softer but tougher metal.

It has likewise been proposed to form composite rolls of different metals by casting. Dilculties of separation after freezing and lack of segregation have been experienced, however.

It is accordingly the object of my invention to avoid and overcome the foregoing and other difculties of known rolls and methods of making them, and I provide a composite metal roll havlng an extremely hard working surface on its enlarged portion but with a core of relatively soft tough metal extending through the central portion and forming the necks and wabblers and bonded by casting with the hard working surface.

Another object of my invention is to provide a method of casting composite rolls from different metals so that the roll will be tough and longwearing in service and have a. hard chilled working surface.

Another object of the invention is to provide a method of making rolls which are very hard on their working surface but ingwln'ch the bearing necks and wabbler portionsare relatively soft and can be edge-tool machined to size after casting.

The foregoing and other objects of the invention are achieved by casting a composite roll with reduced neck portions by bottom-pouring the central portion and lower neck with a hard alloy metal. The metal is surface-chilled at the central portion of the roll, and while all but the chilled shell of the metal is still molten bottompouring is continued, but with a softermetal. This displaces the ymolten alloy metal completely from the inside of the chilled shell of alloy metal and the casting of the roll is completed by toppouring the upper bearing neck with the soft metal. The resulting composite` roll includes a large central portion having a relatively soft metal core extending through the central portion and forming reduced bearing necks with a chilled relatively hard alloy metal shellforming the surface of the central roll portion'and bonded to the core by casting.

In the drawings, Fig. 1 is a vertical crosssectional view of typical apparatus which may be employed to practice the invention; Fig. 2 is a side elevation of a roll embodying the features of 4and constructed in accordance with .the method of my invention; Fig. 3 is a transverse crosssectional View taken on line III-III of Fig. 2; Fig. 4 is a transverse cross-sectional view taken on line IV .IV of Fig. 2; and Fig. 5 is a transverse cross-sectional view taken on line V-V of Fig. 2.

The principles of my invention are applicable to the manufacture of cast metal rolls of various shapes and sizes and adapted for any desired use. However, the invention is particularly concerned with the production of cast metal rolls for use in rolling metal strip and the like, and accordingly the invention has been illustrated and will be de scribed as dealing with relatively large and heavystrip mill roll.

Referring to Fig. l of the drawings, the numeral I0 indicates generally a mold formed of cylindrical flasks II, I2, and I3 and a cylindrical chill I4 all secured together in vertical alignment by clamps I8. The cylindrical flasks II, I2, and I3 are filled with moldingsand or other refractory material 20 and 2I and are shaped with a. patthe manufacture of a a basin 28 at its upper end and the gate extends into the mold cavity 23 at its bottom and in a direction substantially tangential to the mold cavity so that metal poured in the mold swirls in a circle about the cavity. Tangential pouring itself is old and Well known and will not be described in greater detail.

An important feature of the invention is the provision in the mold just described of an overflow or drainage spout 3| lined with refractory 32 and provided with a closure plug 33. The overfiow spout 3| may extend over a ladle 35. to deposit any overflow metal in the ladle. The overiiow spout 3| is positioned in the mold slightly above the enlarged central portion of the roll which is defined by the chill I4.

In thepractice of my invention the mold is bottom-poured through the gate 26 ordinarily with a relatively hard high alloy metal such as, for example, one of a composition comprising 2.84% carbon, .28% silicon, .07% sulfur, .14% manganese, .41% chromium, .30% molybdenum, .38% phosphorus, 4.05% nickel, and the remainder iron. The bottom-pouring of the mold is continued until the metal overflows through the spout 3| into the ladle 35. The closure plug 33 of the spout 3| is in the open position at this time. Bottom-pouring is then discontinued and the relatively hard metal is allowed to set for a time sufficient to cause the surface chilling of the metal at the enlarged central portion of the roll by the cylindrical chill I4. The action of the chill is such that the metal immediately adjacent or close to the surface of the chill, such as identified by lthe numeral 40 in Fig. 1, is frozen without precipitation of any carbon in the form of graphite. The carbon is retained in combined form in the metal and aords a very hard chilled surface on the finished roll. The metal marked 4| in Fig. 1 immediately below the chilled roll metal is also frozen, rapid at some distance from the chill surface, carbon is precipitated out of solution or from its combined form and appears as graphite 48 in the metal. Actually instead of two distinct layers of metal 40 and 4| as shown in the drawings, the change from the chill surface I4 inwardly of the roll is a gradual one in which more and more carbon is in the free or uncombined state.

After the metal layers 40 and 4I have solidified against the cylindrical chill I4 and while the remainder of the hard alloy metal is in a molten state the bottom-pouring of the mold is renewed. However, the mold is now poured with a relatively soft metal as, for example, ordinary gray cast iron, a typical composition being: carbon 3.3%, silicon .9%, phosphorus .35%, sulfur .1%, manganese .3%, and the remainder largely iron. The addition of the hot soft metal at the bottom of the mold together with the swirling action imparted to the metal by the tangential bottom feed causes the hard alloy metal still in the molten state to be carried up to and out of the overflow spout 3| into the ladle 35. The bottom-pouring of the softer metal is continued until all of the hard metal alloy has been forced by displacement out of the mold with the softer metal taking its place. The rotary movement of the metal is' advantageous as a better washing and displacing action is obtained with a superior bond ultimately resultbut since the chilling action is not sol ing between the softer core metal and the harder chilled surface metal.

'I'he plug 33 in the overow spout 3| is now closed and with the metal in the mold up to about the dotted line 45 the remainder of the mold is top-poured with the relatively soft core or neckforming metal. The entire cast roll is then allowed to solidify in the usual manner and is ready for machining. The machining operations are quite simplified since the bearing neck and Wabbler portions of the roll are of relatively soft gray cast iron and these portions can be tool-machined in an ordinary roll lathe. .The enlarged central portion of the roll has an extremely hard surface which must be ground to size, but this can be readily accomplished by grinding since the surface is cylindrical.

The advantages of the process just described as well as the superior product resulting will be evident from a consideration of Figs. 2 to 5. The reduced bearingnecks of the roll are shown in Figs. 3 and 5 and it will be seen that the sections as cast are relatively free from a chilling action and that the composition of the metal is substantially uniform from the surface of the roll inwardly to the axis. Due to the slow cooling of these portions of the roll, graphite, as represented by the marks 48, is precipitated quite uniformly throughout the bearing necks.

Sharply distinguishing from the bearing neck sections of Figs. 3 and 5, is the central roll section, shown in Fig. 4, in which the numeral 40 indicates the outer layer or shell of hard alloy metal which has been highly chilled by direct contact with the cylindrical chill I4 so that substantially all of the carbon in the metal is retained in the combined state. The metal layer or shell4l positioned internally of the layer 40 is also of the hard metal alloy, but some graphite has been precipitated into the metal as this portion of the roll has cooled somewhat slowly. The core of the roll which is of relatively soft metal is identied by the numeral 49 and graphite 48 is precipitated quite uniformly through the metal due to the slow cooling of this portion of the roll.

The bond between the hard alloy metal shell and the relatively soft core and neck metal is very satisfactory due to the thorough washing out of the original molten hard metal and the integral casting and cooling of the composite parts. The fact that the hard metal of the shell has a gradually changing combined carbon content further effects a substantial bonding action since there is n'ot so sharp a line of demarcation between the metals, particularly with respect to the combined carbon content. Moreover, as shown in the drawings, there is a mechanical interlocking of the hard metal and softer metal as occasioned by the slightly uneven freezing of the hard metal and the uneven displacement of the original molten hard metal by the softer molten metal.

A modification or alternative of the method just described comprises first bottom-pouring with the hard alloy metal and chilling and then continuing the bottom-pouring with a softer tougher metal, all as described heretofore. However, the bottom-pouring with the softer metal is stopped after the molten hard alloy metal is displaced from the lower bearing neck. The spout 3| is then plugged and the upper bearing neck is poured as before with the softer metal. This process produces a roll having a large central portion of hard alloy metal and reduced necks of tougher but machinable metal.

The location of the overflow spout 3| is particularly important since to place it at the top of the mold would seriously prejudice, if lnot prevent, the operation of my improved process as displacing and washing out the molten harder metal with a softer core metal would result in freezing of portions of the hard metal along the upper bearing neck and wabbler portions of the roll.' By placing the overflow spout immediately above the enlarged central portion'of the roll the molten harder metal can be readily removed from the mold to obtain the effective result above described.

By way of illustrating the advantages of my invention,.a typical scleroscope hardness reading on a known type of solid alloy roll castin a mold having a chill only at the enlarged central portion of the roll showed a reading of 80 4to 85 at the chilled central portion of the roll. The reading at the surface of the bearing necks cast against a refractory surface was 70 to 75. This reading in itself is a clear indication that grinding must be resorted to for finishing the roll.

As directly distinguished from the extreme hardness of both the central and neck portions of the roll just described is the composition of a f roll constructed in accordance with the principles of the present invention. More particularly,

a scleroscope hardness test made of a roll cast as heretofore described shows that the wabbler and bearing neck portions of the roll lare substantially soft, namely, about 40 to 50. This is the standard scleroscope reading of ordinary gray iron. Metal of this degree of hardness can read- 35 ily be tooled with usual machine tools in a lathe so that the machining of the roll necks is readily accomplished. The surface of the central portion of my improved roll is, however, extremely hard with, for example, the particular alloy metal recited, and the scleroscope reading is about 80 to 85. This surface is substantially cylindrical and can be cast close to finished size against a chill so that the central roll portion can be readily ground to size as will be understood.

I have found that there is very little change in the percentage of free carbon in a radially outward direction from the axis of the roll except in the chilled shell portion of the roll formed of hard alloy metal in which the gradual carbon or graphite segregation has been heretofore described. Various rolls constructed in accordance with my invention have been cut in two and samples of the metal takenI to accurately determine the exact composition of the metal at various points in the roll. The following table is illustrative of the metal compositions at a plurality of points in a typicalroll made with metals of the compositions above described with thepoints roll with reduced neck while insuring a very positive bond between the core and shell.

It should be understood that various metals other than those specifically described-above can vbe employed in the manufacture of a roll in accordance with my invention. Primarily, however, the invention teaches the use of a hard high alloy metal for forming the chilled surface of a roll with a softer buttougher and more machinable metal being used as a core and to form the necks and wabbler portions of the roll.

Whilein accordance with the patent statutes one form of my invention and one manner of practicing my invention have been illustrated and described in detail, vit should be appreciated that the invention is not limited thereto or thereby but is defined in the appended claims.'

1I claim:

1. That method of casting a composite metal portions which comprises bottom-pouring the central portion land lower neck with a hard high alloy metal, allowing the metal to stand until its outer cylindrical portion solidies, bottom-pouring the roll with a softer metal to displace out of the mold at least part-of the centrally positioned molten alloy metal but to leave the chilled alloy metal, removing the displaced metal from the mold just above the central portion of the roll, and completing the casting of the roll by top-pouring the upper neck with the softer metal. y

2. In the manufacture of a necked metal roll for strip mills and the like, those steps which comprise bottom-pouring with a tangential flow a roll mold having its axis substantially vertical, said bottom-pouring being continued until the mold is filled to a point just above the central roll portion, surface chilling the central portion of the roll to fonn a cylindrical shell of solidified metal, continuing the bottom-pouring but with a different metal to force at least part ofthe still molten portion of the first metal out of the lower neck and central roll portion, withdrawing from the mold the first metal as displaced from the central portion of the roll, and top-pouring the upper neck of the roll with the diierent metal.

3. In the manufacture of a` necked metal roll being marked by circles identified by the letters-401' Strip mills and the like, those steps which Ato Gin Fig.4:

Composition of metal throughout roll Position A B C l) E F G Carbon 2. 84 3. 43 3. 50 3. 32 3. 38 3. 38 3. 37 Silicon 28 91 86 93 94 .93 90 Sulfur 076 108 100 104 104 .106 101 Molybdenum 30 `lot det erminec Manganese 14 335 335 335 315 32 335 Chromium 41 17 19 .19 21 21 .19 Phosphorus-.. 38 33 36 34 37 35 35 Nickel 4. 05 73 73 73 72 73 f 71 my4- metal has taken place as shown, for example, by

comprise bottom-pouring a roll mold having its axis substantially vertical, said bottom-pouring being continued until the mold is filled to a point above the central roll portion, chilling the central portion of the roll to form a cylindrical shell of solidied metal, continuing the bottom-pouring but with a different metal to force the still molten portion of the first metal at least out or the lower neck, withdrawing the first metal as displaced from the mold at a paint immediately above the central portion of the roll, closing the withdrawing port, and top-pouring the upper neck of the roll with the different metal.

4. That method of casting a roll with a large central portion and reduced bearing necks which comprises casting the central portion of the roll against a chill and while the metal radially inside of the chilled surface metal is stili molten displacing the molten metal by a swirling iiow of a core forming molten metal. removing the displaced metal directly as it leaves the central portion of the roll, and completing the casting of the roll by pouring the remainder of the roll with the core forming metal with the pouring being in substantially the opposite direction to the displaced metal flow.

5. That method of casting a roll with a largecentral portion and reduced bearing necks which comprises casting the central portion of the roll against a chill and while the metal radially inside of the chilled surface metal isstill 'molten displacing the molten metal by a swirling ow oi a core forming molten metal, removing the displaced metal directly as it leaves the central portion of the roll, and completing the casting of the roll.

6. That method oi casting a roll with a large central portion and reduced bearing necks which v comprises casting the central portion of the roll,

chilling the roll surface, and while the metal radially inside of the chilled surface metal is still molten displacing the molten metal by a core forming molten metal, and removing the displaced metal from the mold directly as it leaves the central portion of the roll. i

7. That method of casting a composite met roll having a working portion and neck portions which comprises bottom-pouring the working portion and lower neck portion with one metal. allowing the metal to stand until the outer part of the working portion of the roll solidies, bottom-pouring the roll with a second metal to displace at least part oi the molten rst metal but to leave the solidified outer part oi' the rst metal. removing the displaced rst metal from the'mold `iust above the working portion of the roll, and completing the casting of the roll by pouring with the second metal the upper neck portion at a point above the working portion of the roll.

HARRY E. WALTERB.

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