US2972472A - Heat transfer roll - Google Patents

Description

Feb. 21, 1961 J. R. KONOLD HEAT TRANSFER ROLL 2 Sheets-Sheet 1 Filed June 11, 1956 D m N o K AS D ATTORNEY .1- R. KONOLD HEAT TRANSFER ROLL Feb. 21, 1961 2 Sheets-Sheet 2 Filed June 11, 1956 l4 l3 IO l2 2 INVENTOR J. REYNOLDS KONOLD ATTORNEY HEAT TRANSFER ROLL J. Reynolds Konold, Netfsville, Pa., assignor to Annstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania This invention relates to a heat transfer roll having a hardened steel working surface. The invention will'be described in conjunction with a calender roll for working plastic material, such as linoleum, asphalt tile, vinyl plastic compositions, and the like, as a typical embodiment of the invention.

Calender rolls are frequently provided with heat transfer chambers; and brine, water, and steam are commonly used as heat transfer media in such rolls. In some rolls, a central cavity is provided and the heat transfer fluid is fed into one end of the cavity and discharged through the other end. With this type of roll, the temperature gradient from end to end of the roll at the working surface is not uniform. Also, the time required for transfer of heat through the massive wall of the roll from the central heat transfer fluid chamber to the working surface is long, and accurate temperature control under calendering conditions is not obtained.

In the manufacture of linoleum, vinyl plastics, and other surface coverings, particularly where the product is to be provided with a decorative graining in simulation of marble, wood, and the like, close control of the temperature of the working surface of the roll is of paramount importance.

' To meet this demand for a quickly responsive, accurately controllable heat transfer roll, two types have been provided. In one, a forging or casting is provided with drilled openings disposed parallel to the roll axis adjacent to the working surface. These openings are connected by ported end rings and drilled openings extend diagonally from the end rings into a heat transfer fluid chamber in the center of the roll. In a second type of heat transfer roll, a forged or cast roll body is provided with channels in its periphery and a metal sleeve is shrunken onto the body, closing the channels and forming heat transfer fluid conduits in the roll, connected by drilled passageways in the roll body leading to a central heat transfer fluid chamber.

It is quite diflicult to fabricate the first or drilled type roll and obtain a working surface of the desired hardness for adequate strength and wear resistance. With a forged or cast drill type calender roll, the surface must be hardened after fabrication of the roll, for the drilling and other machining operations cannot be effected economically in hardened steel. There is great danger of the roll cracking during quenching after heating in the hardening process and, of course, such cracks result in irreparable damage to the roll.

The second or sleeve type roll is prone to leak around the joint between the sleeve and the roll body, especially after repeated heating and cooling cycles. In some manufacturing operations, brine is used as the coolant in one operation, and in another operation steam is used to heat the working surface of the roll. Under these severe conditions, it is extremely difficult to fabricate a sleeve type roll which will not develop leaks.

Another difiiculty with a sleeve type roll is to provide United StatesPatent'O F a uniformly close fit between the sleeve and the roll body 2,972,472 Patented Feb. 21, 1961 at the lands between the channels which are milled into the body. If a close fit is not obtained, corrosion sets in at the lands and effective heat transfer from the body to the sleeve is prevented.

It is also diflicult to obtain a working surface of the desired hardness with either a drill type or sleeve type roll. Steels which will provide the desired hardness are too expensive to use in a drill type roll where the whole roll is formed as a single casting or forging. Also, with both types such steels are diflicult to machine and harden, particularly in the large, massive units, such as calender rolls.

Both the drill type roll and the sleeve type roll cannot be repaired readily at the working surface. For instance,

should a piece of tramp metal inadvertently get into the linoleum mix being calendered, it will damage the hardened roll surface, leaving a scar in the working face.

It is also impossible with both types of rolls to obtain desirable configurations and arrangements of heat transfer fluid channels for most effective heat transfer at the working surface. With drilled rolls, the designer is limited almost entirely to straight, cylindrical channels which extend axially of the roll from end to end. The designer is limited with the sleeve type roll to channels which may be successfully closed with the sleeve, With relatively extensive lands being necessary between the channels to provide support for the sleeve to prevent corrosion and possible leakage.

An object of the present invention is to provide a heat transfer roll which may be fabricated to provide a working surface of the desired hardness free of cracks or porosity. The hardness may be greater than attainable with either the drilled or sleeve type rolls now used.

Another object of the invention is to provide a heat transfer roll with a hardened steel working surface which may be repaired if damaged by tramp metal passing between a pair of calender rolls, for instance, and which may be rebuilt at the working surface when it becomes worn below the desired minimum diameter.

A further object of the invention is to provide a heat transfer roll which may be fabricated with an almost limitless arrangement of heat transfer fluid passageways adjacent to the working surface.

Another object of the invention is to provide a heat transfer roll with a hardened steel working surface which may be repeatedly heated and cooled or may be alternately subjected to steam and refrigerated brine without danger of leaks developing.

Other objects of the invention will be clear from the following description of an embodiment of the invention which will be described in conjunction with the attached drawings, in which:

Figure 1 is a plan view, partially in section, showing a calender roll embodying the invention;

Figure 2 is a partial sectional view to an enlarged scale, taken along the line II'II of Figure 1;

Figure 3 is a partial development view showing the roll structure of Figure 1 in one stage of fabrication;-and

Figures 4, 5, and 6 are partial sectional views showing intermediate stages of fabrication of the roll shown in Figures 1 and 2.

The roll of Figure 1 includes a forged or cast steel body 2, having a centrally disposed chamber 3 therein for the reception of heat transfer fluid, such as refrigerated brine, water, or steam. An inlet conduit 4 is received within the chamber 3 and is secured in position by a threaded bushing 5.

The chamber 3 is counterbored at 6 to provide an exhaust chamber for delivery of spent heat transfer fluid from the roll through a discharge conduit 7 fitted into the exhaust chamber. A plurality of inlet bores 8 extend radially from the nlet chamber 3 to the periphery cf the roll body 2. These may be formed by boring holes from the face of the roll body completely therethrough in an angular direction into the inlet chamber. In a roll such as illustrated-in the-drawing there may be 15 .suchinlet bores extending from the inlet chamber.

Similar exhaust bores. 91may be provided at theopposite end of the roll body, extending intotheexhaust chamber 6. These may be arranged; alternately .with the inlet bores, as shown in-Figure 3.

Channels 10 are milled or otherwisej formedrinthe roll body 2 and preferably extendvthroughout the major portion of the working surface ;.,of the'roll. These channels provide passageways for delivery of heat transfer .fluid from inlet bore 8, back andforth along the axial'length of the roll, and for discharge through an exhaust bore 9, as indicated by the arrows in Figure 3.

The nature of the heattransfer fluid chambers, bores, and channels may be varied,.depending,upon service conditions. The present-invention is notconcerned with any particular arrangement. The one shownin the drawings is of a type usedin ashell type calender roll.

In the fabrication of a rollin accordance with the invention, the channels 10 at the surface of the roll body 2 are closed by metal end plates 11 of semicircular configuration and by rectangular metal cover plates 12. Four of the end plates and three of the cover plates are shown in position in Figure 3.

The end'plates and coverplates are welded to the roll body 2, the cover plates beingsecu-red to the upstanding ribs 13 (Figure 4) separating adjacent channels 10. The area between the adjacent cover plates is filled with weld :metal, as indicated at 14. This welding firmly attaches .theend plates and cover plates to the roll body, closing fthe channels, 10.

In .the next step of fabrication of the unit, the weld metal which extends above the plates 11 and 12 is removed by turningor grinding. This provides a clean surface for the reception of a mild steel weld metal backing layer 15 which is built up on the roll, as shown in Figure 5. The machining operation also serves to provide a substantially true cylindrical surface on the whole of the outer surface of the roll body and the end plates and cover plates. This is desirable, EfOI' the layer 15 is preferably applied by an automatic welding machinexwhere the roll body is mounted for rotation and the welding head and metal feeding unit are slowly traversed along the axis of the body as the welding operation proceeds.

For best results, it is'desirable to have a substantially cylindrical surface to work against in this operation.

During welding, the roll body is preferably heated to a temperature in the order of 900 F. This may be accomplished by positioning the roll and the welding head in an enclosed heated chamber.

. The thickness of the layer 15 and the type of. weld metal used will depend upon the rolling pressures .en-

countered in use, the kind of heat transfer medium used,

of thislayer 16 may be varied as may the nature of the -.weld metal used, depending upon'conditions to been- -countered in service.

The. layer 16 is built upon the layer 15 by the deposit of weld metal thereuponin the same manner as layer 15 is applied, with the roll heated to about 900 F. The-roll is-next-hardene'd. jThis-is accomplished b --merely heat tempering the roll at a temperatureof about 950 'F. This heat treatment alsovserves to relieve the 'residual stressesinevitably encounteredin massive welding -=operatioi1s. If: a-workingsurface of lower hardness 4 is desired, the heat treating temperature may be increased above 950 F., as is well known by the metallurgist. A

second temper at 950 K may be effected and will further increase the hardness of the working surface.

The hard surface of layer 16 constituting the working surface of the roll is ground to the desired surface finish and contour, as indicated at 17 in Figure 2. The ends 18 may be chamfereixasindicated inFigure 1, and the appropriate crown may be applied to the roll surface.

The linished-rollanay include' clean-cutopenings 19, closed with plugs 20,-" disposed fiush'with the end su'rface of the roll. A suitable end plug 2 1 may be secured to the roll byrnachineiscrews-ll,lclosingthe inlet chamber. As a typical embodiment of the invention, the roll may have a working surface '17 about 24" in diameter and about 86" in axial length. The channels 10 may be about 1%" wide and about deep and about long. The end plates 11-,and cover plates 12 may be made ofsoft, steel=% 'fthick.or thicker. The softsteel backing layer-15 maybe about 1" thick and may have aharduessof about ,15 Rockwell C. The facing layer 16 maybe about Ms" thick and of an alloy steel having a Shore C" hardness of 72 to 75 as welded, a hardness of 92 to 94. after the first temper at 950 F., and after a second temperat 950 F., a hardness of 95 to 102, free of cracks and porosity. I v

The alloy of the facing layer 16 may be varied to-pro vide ,the'desired physical properties in the working surface of the roll. A typical example is an alloy of the fol In the treatment of the roll to effect hardening,aadequate stress relaxation will be effected to avoid checking or cracking or other deleterious actions in service.

It will be understood, of course, that the foregoing specifications are typical illustrations of a roll suitable for calendering linoleum, using refrigerated brine asva coolant. Other types of rolls for other services may be made in-accordance with the invention, and the dimensions, types of metal used, and othervariable factors will be modified to meet the requirements of the particular service conditions to which the roll will be subjected.

From the foregoing, it will be clear that with' aroll constructed in accordance with the present invention, all

of the advantages of a one-piece roll structure can be achieved. In addition, the designs of the cooling channelsare unlimited, and many which are desirable and are not attainable in a one-piece construction can now be had. The hazards involved in heat treating of ametal shell or solid type roll are avoided, for in the present roll structure a high alloy content weld metal is used and quenching to obtain hardness is not necessary. Allother advantage of the present construction is the fact that, when the roll is worn to the allowable limits, it'may be recoated with hard weld metalto the desired thickness and then reground to the surface contour and finish desired. Leakage is completely eliminated. Damaged areas in the working surface may be repaired bypreheating the roll, filling in the damaged area with weld 'metal the sameas the layer 16, heatingto 950F.:-or

other desired hardening temperature, and grinding tto the desired surfacefinish.

' While theinvention has been described in' conjunction =with acalender roll forforming sheet surface coverings,

it is obviousthatthe invention -:will be usefulinother fields where heat transferrollsare used.

'I'cl'aim: 1 1 a 1 i-In a'-=-heat I transfer -=roll including a steer -mandi:el

having a substantially cylindrical face with heat transfer fluid channels provided therein and sheet steel covers disposed over said channels to form a roll body with fluid sealed heat transfer fluid passages therein, the com bination of a backing layer consisting essentially of a fused-on homogeneous deposit of soft steel weld metal filling the areas between said covers and extending completely over said roll body and a facing layer bonded to saidbacking layer, the outer surface of said facing layer constituting essentially the whole working surface of said roll and consisting essentially of a fused-on homogeneous deposit of alloy steel weld metal.

2. In a heat transfer roll including a forged steel mandrel having heat transfer fluid channels provided in the face thereof and separated by lands disposed therebetween and steel cover plates disposed over the channels and welded to the lands to provide a roll body with fluid sealed heat transfer fluid passages therein and a substantially cylindrical surface, thecombination of a backing layer consisting essentially of a fused-on homogeneous deposit of soft steel weld metal filling the areas between adjacent cover' plates and extending completely over said roll body and a facing layer the outer surface of which constitutes essentially the Whole working surface of said roll, said facing layer consisting essentially of a fused-on homogeneous deposit of alloy steel weld metal temper hardened extending over said backing layer.

3. In a heat transfer roll including a metal mandrel having a substantially cylindrical face with heat transfer fluid channels provided therein and sheet metal covers disposed over said channels to form a roll body with fluid sealed heat transfer'fluid passages therein, the combination of a facing layer the outer surface of which constitutes essentially the whole working surface of said roll, said facing layer consisting essentially of a homogeneously fused-on deposit of alloy steel weld metal filling the areas between adjacent metal covers and extending completely over said roll body. 4. A heat transfer roll comprising, in combination, a metal mandrel having a substantially cylindrical face with heat transfer fluid channels provided in the face thereof and separated by lands disposed therebetween, sheet metal cover plates disposed over said channels and welded to the lands and forming a roll body with fluid sealed heat transfer fluid passages therein and a fused-0n facing layer of homogeneous deposits of alloy steel weld metal filling the areas between the cover plates and extending completely over said roll body and forming a generally cylindrical form.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 2,972,472 February 21 1961 J. Reynolds Konold It is hereby certifiedthat error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 10, for "clean-cut" read clean-out Signed and sealed this 4th day of July 1961.

(SEAL) kttest:

ERNEST W. SWIDER DAVID L. LADD Lttesting Officer Commissioner of Patents

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