US1132611A - Method of making chilled rolls with steel centers. - Google Patents

Description

J. T. OSLER.

METHOD OF MAKING OHILLED ROLLS WITH STEEL CENTERS.

APPLICATION FILED DEG.18.1913.

Patented Mai'.23,1915.

INVENTQR M gheny and State of Pennsylvania,

vented a new and useful Improvement in Methods of Making their strength.

4 JAY 'r. OSLEB, or conaoroms,PENNSYLVANIA.

To all whomz't may concern:

Be it known that I, JAY T; Osman, resident of Coraopolis, in the county of Allehave invery few cast iron or high carbon steel rolls would be used, lower carbon steel or alloy steel rolls being preferable from the standpoint of strength. Cast iron mill rolls, however, are subjected to frequent variations in temperature, and the diflerences in expansion and contraction of the metal near the surface and along the core of the roll are are very hard and crack.

7 billet in'a mold and then pouring mol frequently sufiicient to rupture or crack the body of the roll- This is particularly true in the case of chilled cast iron rolls, which are more liable to break or form chilled heated steel ten It has been proposed to cast iron rolls by first placing a cast iron around the same in such a manner -'ever,- 1t has been impossible to with each other at as to secure a weld between the steel core and cast iron body. In such methods, howbring the heated billet and. molten iron into contact the same temperature. or even at the best working temperature. The

core cools rapidly while beingcarried from 4 to the mold and while I and thelatter is maintained the heating furnace being introduced thereinto and is usually considerably cooler than the molten iron when the latter is poured into the mold. Consequently,

heat from the molten cast iron and quickly the center rapidly absorbs cools thesame. This rapid cooling-produces allotropie changes in the structure. of the cast iron and it-becomes brittle and is liable to rupture under the. heavy loads and varying temperature conditions .encountered in use.

The present the production ing a body formed of one metal, say, cast invention has for its object iron, either chilled or unchilled, and a core v Specification of Letters Patent.

.ferred to the portable .roll body is in of a composite mill roll hav- I METHOD OF MAKING CHILL-ED ROLLS WITH STEEL CENTEBJ S.

or center welded'thereto and formed of another metal of reater strength and toughness, for examp e, steel, whereby the roll as a whole is stronger and not so liable .to break and also has a surface which has the desired wearing quality and will take a good finish. Another object of the invention is the production of a composite roll having a core or center which at all times is under initial tension or stress, whereby in use of the roll the heat tends to equalize the tension or stress throughout the roll but never entirely relieves the same, which reduces the net destructive stresses set up by the varying temperatures to which the roll is subjected dur ing the rolling operation.

Patented Mar. 23, 1915. Application filed December 18, 1913'. Serial No. 807,469.

Another object of the invention isto pro- I vide a method of forming a composite roll which can be carried out in such manner that the heated steel core and the molten cast iron for the body can "be brought into contact with each other at substantially the same temperature, whereby both the core and body will weld and cool under the same conditions and will not transmit heat one to the other, thereby producing a roll of maximum strength and durability.

According to the present inventionthe mold is arranged to receive or to cooperate with a billet heating furnace. which may be portable by a crane or fixed to the mold.

. This furnace is arranged to hold the core or center for the roll and said core may be heated in an ordinary furnace, and-transcarried therein to the mold, or it may be heated entirely in the portable furnace.

The portable furnace is placed in position on the mold with the heated core therein temperature say about 2200 degrees Fahrenheit, until the molten iron for forming the the proper condition for pouring. The molten metal is heated slightly above the temperature of the heated core, say 2400 degrees Fahrenheit. and is then underteemed into the mold. When the proper quantity of molten metal has been run in, the heated core or center is lowered into the. molten metal, preferably, although not necessarily, passing devices-to free the billet from scale and provide it with clean surfaces so that it will readily unite or weld with the molten metal.

heating furnace and at the proper through cleaning Preferably, also, centering devices are prosided so that when the core seats in the mold it need not be again moved, but will be perfectly central in the mold cavity and surrounded on all sides with an equal thickness of molten metal. From the time of pouring the molten metal into the mold to the introduction of the heated core thereinto the molten metal gradually cools down until at thetime the core seats the core and the molten metal will be at substantially the same temperature, of the core--about 2200 degrees. The core is preferably made somewhatdonger than actually necessary so that it sinks clear to the bottom of the mold by its own weight and will not be liable to float in the molten iron. The extra length at the ends of the horizontal I neck sand portions 2, which are suitably.

, bottom center the same,

.- unite with the core may afterward be cut ed to trim. the

roll down to proper shape and size.

. The invention will be more readily understood by reference to the description herein- 7 after,

taken in connection with the accompanving drawings, wherein- Figure 1 represents a sectional elevation of suitable apparatus for carrying out the method; Fig. 2 is a detail view on a larger scale, of the centering devices; Fig. is a section on the line 3-3, Fig. 2; and Fig. 4 is a sectional view of the finished roll.

The mold may be arranged for casting either chilled or unchilled rolls, and in the drawings is arranged for casting chilled rolls. It comprises the body chill 1 and clamped together and rest upon a base or bottom 3, the lower sand portion 2 being preferably formed with a conical depression to receive the pointed end of the core or billet. The molten metal is introduced into the mold through'a spout 4 which enters the of the mold. Supported upon the upper end of the mold is a casing 5 within which is located the centering rig for centering the core in the mold cavity. This centering rig comprises two superposed sets of pivoted arms 6, having counterweights 7 at their outer ends, and having their inner ends arranged to contact-the core and center it as it is lowered into the mold. Each set preferably comprises three or more cantering fingers,

and the fingers of the two sets are in staggered relation with each other, as shown in Fig. 3. The centering fingers may be arranged to completely sur-- round the core,

as fully described in my companion application for apparatus for erewith', Serial and clean its surface as it passes through so that it will readily and completely weld or ody. The upper end of the casing 5 is it may be moved into that is, the temperature Th rectly in the portable furnace 10.

molten metal for forming the preferably closed by a shield 9, which is in the form of a sliding gate arranged so that position to close the lower end of the heating furnace, as hereinafter described, or withdrawn therefrom when it is desired to lower the core into the mold.

The heating furnace is represented at 10, and preferably comprises a cylindrical casing or jacket 11 with a lining 11 of refractory material, such as fire brick or the like.

e furnace is heated by means of any suitable number of burners 12, arranged in any manner. The lower end of the furnace rests upon the-top of the casing 5 and is closed by thegate 9 before referred to. The upper end of the furnace is preferably provided with any suitable means, such as the trunnions 14:, by means of which it may be lifted and transported from place to place.

In use of the apparatus a core 15 is slowly heated up to the proper temperature. This may be done in an ordinary furnace, or di- In the former case the core is first heated in the ordinary furnace to about the proper temperature and is then removed and placed in the portable furnace 10, which is then carried to and placed in position on top of the mold in the position shown in Fig. the billet is finally heated to the proper temperature. In the second case the core is placed directly in the portable furnace, while in position on the mold, and is there heated to the proper temperature. It will, of course, be understood that the core 15 may be made of any suitable material, but preferably is of soft or mild steel, possessing the proper degree of toughness and resiliency to withstand'heavy strains without breaking. The body 16 of the roll is formed of cast iron, which is heated in any suitable v furnace or cupola to a little higher tempera ture than the core or center 15, say to about 2400 degrees. "When in the proper condition. the molten metal is poured into the spout 4; and underteemed into the mold. llt immediately begins to transmit its heat to the chill 1 and to chill on its outer surface. Gate 9 is now withdrawn to open up the lower end of the heating furnace 10. Center or core 15 is now lowered into the mold. Its lower end is conical or pointed, as at 17, and first strikes the inner ends of the upper set of arms 6 which swing outwardly on their pivots and hold thecore in central po" sition. They also preliminarily scrape the core and free it from scale. The second set of arms next encounters the core andase 'sists in cleaning and centering the same. The core sinks until its pointed center seats in the conical depression in the sand portion 2 with the core in a central or axial posi tion in the mold cavity. lln

sinking the forces it up practically the same temperature as the' core. Both the core and body then begin to cool at substantially the same rate. The chill l-produces a hard chilled surface on the body of the roll and the high temperature produces an intimate weld or union between the body and core.

1 It will, of course, be understood that the co eificients of expansion of cast-iron and steel are slightly difl'erent. Consequently, in cooling, the iron body 16 contracts a little less than the core, thereby placing the core under an initial tensile stress, which becomes more and more fixed and pronounced as the roll cools down. Similarly, the iron body 16 is placed under slight longitudinal compression, due to the same difference in contraction. When the roll has completely cooled the extra lengths at the ends of the core are cut off and the roll is turned down to final shape.

At normal temperatures the roll is in a condition of internal strain, with the core under tensile stress. In use of the roll the surface or body heats up first and thereby expands and increases the stress on the core, which, however, is made of steel and is well able to withstand tensile stresses. As the heat soaks into the roll and temperature conditions become more uniform the greater co-eflicient of expansion of the steel core over the iron body relieves some of the strain, but the strain is never entirely relieved because the roll is never heated up to the temperature at which it was cast. The

hotter the roll' becomes, however, the nearer it approaches a condition of no internal strain. In cooling the surfaceor body of the roll cools first, but as the internal strain has never been entirely relieved contraction of the body does not place the body under tension or the core under compression, but merely relieves a little more of the internal strain. As cooling goes on the core begins to shrink until when normal conditions are finally reached the original internal stresses are again set up.

The composite roll described has the metal disposed therein in the best possible manner to withstand the bad efl'ects of expansion and contraction produced by the varying temperature conditions encountered in use. It is consequently very durable and is not liable to develop flaws, cracks or breaks, and,

moreover, has a cast iron surface which will take a very good finish.

What I claim is 1. The method of forming rolls in a mold, consisting in first pouring into said mold cast iron to form theroll body and then lowering into the cast iron a heated mild steel core to form the roll center, and allowing said core and body to cool.

2. The method of forming composite rolls in a mold, consisting in heating a steel core to form the roll center, pouring into saidv mold molten iron at a temperature above that of the heated steel core, lowering the core into the molten cast iron, and allowing the core and cast iron to cool and weld together.

3. The method of forming composite rolls in a mold, consisting in heating a core to form the roll center, heating molten cast iron to form the body to a temperature slightly above that of the heated core, pouring said molten metal into the mold, lowering the heated core into the molten metal, and allowing the same to cool.

In testimony whereof, I have hereunto set my hand.

JAY 'r. OSLER.

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