GB2206180A

GB2206180A - A cast roll shell for a press or calender roll and a process and apparatus for its manufacture

Info

Publication number: GB2206180A
Application number: GB08812164A
Authority: GB
Inventors: Christian Schiel
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1987-06-24
Filing date: 1988-05-23
Publication date: 1988-12-29
Also published as: FI882212A; GB8812164D0; DE3720832A1; FI882212A0

Description

0 k x 2206180 A cast roll shell for a press or calender roll and a process

and apparatus for its manufacture The present invention relates to a cast tubular roll shell of the type comprising a relatively thick-walled roll, for use in apparatus for the treatment of web-shaped material such as a press or calender roll.

The invention also relates to a process and apparatus for the manufacture of such a roll shell.

The preferred area of application of such rolls, which are generally slender and kelatively thick-walled (length approximately 3-10 metres, external diameter approximately 0.4-1.2 metres and wall thickness approximately 0.07-0.15 metres), are paper manufacturing machines.

In this case it may be used, e.g. as a so-called deflection-correcting roll (see EP-PS 0043119), i.e. a press roll, the deflection of which can be controlled and which, with a counter roll, forms a press nip through which a web of material, e.g. a paper web, passes. With this deflectioncorrecting roll, hydraulic supporting appliances are provided inside the roll to transfer the compression force from the roll shell to a stationary bending support. Components of these hydraulic supporting appliances may be, e.g. stationary longitudinal seals opposite one another and/or stationary pressure shoes, which in operation slide on the interior shell surface.

A roll shell of the said type may also be a component of a calender roll heated or cooled on its inner A X - 2 shell surface by means of a heat carrier medium (see US-PS 4,639,990). In this case a stationary cylindrical chamber relative to the roll shell is provided and the annular nip between the roll shell and cylindrical chamber is divided into a plurality. of heat transfer chambers individually acted upon by heat transfer medium at different temperatures by means of sealing rings sliding on the inner shell surface of the roll shell. In addition to the radial sealing rings, stationary longitudinal bars may also be provided.

With respect to the present invention, a roll shell of the last-named type, i.e. a roll shell heated or cooled from inside, but without said sealing rings and longitudinal bars, is of course also of -interest (see US-PS 4,503,626). Finally simple press rolls, i.e. rolls without devices for supplying fluid into the interior, are also possible.

In most of the applications discussed above, t-he inner shell surface is exposed to both mechanical and chemical loads --- via the heat transfer medium. Consequently, one object of the present invention consists, among other things, in providing a roll shell ofthe type referred to above, in which the inner shell surface is leakproof and non-porous, or is provided with a hard-wearing layer, or a different surface protection. However, another object of the. present invention is additionally to provide the roll shell with surface protection for the outer shell surface or, if necessary with surface protection for the outer surface only.

i 1 According to one aspect of this invention, a. cast tubular roll shell of the type discussed above is characterised in that the roll body is cast on to an inner steel pipe and/or an outer steel pipe in a material locking manner to provide shelded inner and/or outer shell surface.

The result is a seamless case pipe, with an integrally cast or fused roll body, e.g. of cast iron, which is exceptionally fluid-tight and corrosionresistant.

The production of seamless cast pipes and tubular roll shells is already known per se.

From DE-PS 477 287 is known a process for the manufacture of rolls having great surface hardness, in which the metal intended to form the hard surface, is put into an upright mould and depending on the desired-layer thickness, is forced to solidify. Subsequently, the metal forming the core is then poured in. The tubular roll shell itself is then formed by boring out the centre -of the cast cylindrical body. The result is a roll with an inner shell surface which is qualitatively perfect as it has no shrink holes; however, the consumption of material and expenditure for subsequent treatment is very high.

It is also known to cast roll shells in a mould wth a sand core. In this process the expenditure for material and treatment is low - apart from the fact that the sand core can be used only once; however, the amount of waste involved is relatively high as the sand core, which is by necessity very slender because of the dimensions of the roll shell, is frequently destroyed during casting. Also the quality of the inner shell surface is only relatively fair as shrink holes cannot be excluded during casting.

A centrifugal casting process is also known for the manufacture. of seamless pipes or other cylindrical hollow bodies. In this, cast iron is cast in rapidly rotating moulds and spun under the effect of centrifugal force on to the inner wall. With this coreless manufacturing process, the risk of waste is in effect slight, but the manufacturing plant is relatively expensive.

Known too is the so-called composite casting process, in which parts of a workpiece produced from steel or cast iron are cast around with another metal, in particular light metal. Before casting around the steel or grey cast iron parts, these are immersed in an aluminium bath so that a thin coating of an iron-aluminimm compound is formed as an adhesive base for the metal to be applied. Therefore, for this a processing-intensive preliminary treatment of the steel, or grey cast iron parts to be cast around is required; also the bond between the steel or grey cast iron parts and the cast-around metal is not as stable as would be required for the applications discussed hereinbefore.

On the basis of these known manufacturing processest the object of the invention discussed hereinbefore, and its solution, can produce an absolutely close-grained structure with a wear and n Ir k 1 corrosion-resistant shielding, which can be relatively simply applied. moreover, by not using a sand core, the risk of the production of waste is largely eliminated.

Further development, or special refinement features of this.invention are set out in sub-claims 2 to 7

Claims

According to' Claim 8, a roll shell in accordance with Claims 1 to 7 is provided in which the inner steel pipe is subsequently drilled or bored out. Another object of this invention is to provide a process for the manufacture of a roll shell according to Claims 1 to 8. According to another aspect of the invention, this object is achieved in that the outer shell surface of the roll body is encased (or forced in) during the casting process so that this outer shell surface cannot expand radially as a result of being heated by the casting material of the roll body, at least not noticeably. Further development features of this process are set out in Claims 10 to 15. A further object of this invention is to provide apparatus for the manufacture of a roll shell according to Claims 1 to 8 and for carrying out a process for manufacturing such a roll shell according to Claims 9 to 15. According to a further aspect of this invention this further object is achieved in that the apparatus has an annular body which is positioned on a baseplate and which has an internal diameter corresponding to the is j is external diameter of the roll body or the external diameter of the outer steel pipe and which, with respect to the dimensions of the roll shell, is so inherently stable that during the casting process it remains constant, at least approximately, with respect to its internal diameter. Further development features of this apparatus are set out in Claims 16 to 23. The invention is explained in more detail below by means of the drawings, in which:- Figure 1 is an axial section through a roll shell having inner and outer shielding; Figure 2 is a sectional view of the mould for casting a roll shell having inner and outer shielding; Figure 3 is a sectional view of the inner steel pipe having a compression device for supporting its inner shell surface; Figure 4 is a sectional view of the inner steel pipe along the line A-A as shown in Figure 3. In Figure.1 is shown a roll shell 1, comprising inner and outer steel pipes 2 and 3, which define a coaxial annular space. This annular space is filled by casting to provide a roll body 4, so that the final result is a roll shell 1 which, when viewed in section through its wall as shown, is formed from" the inside to the outside by the inner steel pipe 2, roll body 4 and outer steel pipe 3. The wall of the roll shell 1 consequently consists of three layers. According to more simple exemplified embodiments, the finished roll shell may however also have a wall with finished roll shell may however also have a wall with two layers only, depending on the specific application, e.g. comprising a cast roll body and inner steel pipe, or a roll body and outer steel pipe. These exempliefied embodiments are of interest if, e.g. only the inner shell surface of the roll shell, or only its outer shell surface require a special surface quality which shields the cast material of the shell. With regard to the requirements for the surface quality of the inner shell surface of the roll shell, reference is made to the examples of application mentioned at the beginning. With respect to the surface quality of the outer shell surface of the roll shell, it is pointed out that for a good and homogenouse adhesion of a layer of e.g. rubber or plastic applied subsequently to the roll shell, it may be important to keep its surface free from shrink holes. An essential and common feature of the possible exemplified embodiments of the roll shell is that at the boundaries between the inner and the outer steel pipe on the one hand and the roll body on the other hand, a material-locking, close bond of the abutting material walls is guaranteed. This is achieved by integrally casting or pouring in the roll body to or between steel pipes arranged concentrically with respect to one another. The wall strength of the inner steel pipe 2 is approximately 0.15 to 0.5 times that of roll body 4; the wall strength of outer steel pipe 3 is approximately 0.03 1 to 0.25 times that of roll body 4. The materials of the steel pipes are chosen, as appropriate, for the specific application. Both the inner and the outer steel pipe may for this purpose be manufactured from material having special properties, e.g. stainless steel. For the outer steel pipe, quenched and subsequently tempered steel, or casehardened steel, may be used. The roll body itself is cast from cast iron (GG), or from spheroidal graphite cast iron (GGG). In this respect the coordination of the melting points of the cast iron on the one hand, and of the steel used on the other hand, are of parmount importance. At the same time, it is understood that it must be impossible for the steel pipes to melt, or for the inner steel pipe to lose its cylindrical shape during the casting process. For the sake of completeness, with respect to the roll shell according to Figure 1, attention is also dra-w'n to the following: The inner shell surface of roll shell 1 formed by the inner steel pipe 2 may be rough, stripped or honed; the same applies to the outer shell surace. The surface condition, in particular the depth of pits, is chosen according to the respective applications intended. On the two f ront surf aces of the outer shell 1 there are also provided tapped holes 5, distributed over the circumference, via which roll journals or caps can be screwed on. The roll shell according to Figure 1 will be 1 explained in more detail below by means of the installation shown in Figure 2, and the manufacturing process used with this installation. Figure 2 shows the casting installation as such. The inner steel pipe 2 stands vertically on a base plate 10. Along its outer shell line are provided several spacer pins 11, distributed over the circumference, which are all at the same respective distance from the shell surface, like thorns. The length of these spacer pins 11 is chosen to correspond to the thickness of the roll body (4 in Figure 1) or to the internal diameter of outer steel pipe 3. This outer steel pipe 3 is placed coaxially or concentrically over inner steel pipe 2 and is centred by means of the spacer pins 11. The annular space between the steel pipes 2,3 standing on base plate 10 may be closed by means of a tightly welded-on steel circular plate 12 so that the coaxial double cylinder consisting of the inner and oute7r steel pipe 2,3 forms a rigid unit. This double cylinder is inserted into a ring body standing equally pn base plate 10, which according to the exemplified embodiment shown in Figure 2, consists'of two ring body parts 13, 14 roughly of equal length, which are fixed tightly to one another via screws passing through flanges 15,16. on their abutting end faces, the two body parts 13, 14 have complementary spigots and sockets so as to provide a form-locked unit. The two body parts 13, 14 also have, on their inner shell surface, a fireproof insulating casing 17, 18 respectively, for restricting the is transfer of heat from the outer steel pipe 3 to the ring body (13,14). On to the f ree upper f ront surf ace of the inner steel pipe 2, a sheet metal dome 19 in the shape of a truncated cone is located, which protects the interior of the inner steel pipe 2 against the unintentional pouring in of cast iron during the actual casting operation. The cast iron for shaping or forming the roll body between the inner and outer steel pipes 2, 3 is f ed into the annular space between these pipes, depending on the type of casting, by means of casting ladles 20,21. In a refinement of the previously described configuration, a spray pipe 22 is provided, which extends axially within the inner steel pipe 2. This'spray pipe is mounted at the lower end in a socket 23 supported on base plate 10 and, at its upper end, in a socket 24 fixed on the upper surf ace of sheet-metal dome 19 so as to be rotatable in the direction of arrow X. The spray pipe -12 has flat-section spray nozzles 25 distributed over its length, with which-water sprays 26 can be directed against the inner shell surface of inner steel pipe 2. With this installation, i.e. by means of this spraying of water, the temperature of the inner steel pipe 2 may be controlled and regulat ed even if the wall thickness is slight, with the result that this inner steel pipe 2 does not become too soft, in particular not until the cast material has hardened. Instead of spray pipes having flat-section spray nozzles 25, a nozzle tip may be provided which sprays the 1 1 inner shell surf ace of the inner steel pipe 2 over the entire circumference, i.e. over 3600. In this case, the nozzle tip is moved upwards at the rate of climb of the level of the cast iron in the annular space between inner and outer steel pipes 2 and 3. In addition to the spraying of water, as a measure against an inpermissible softening of inner steel pipe 2, (and thus against an unintentional and likewise inpermissible deformation of the inner steel pipe) excess pressure may also be established within the inner steel pipe in the manner of and autoclave. For this purpose, the socket 24 of spray pipe 22 f ixed on dome 19 is sealed and, on dome 19, itself there is provided a relief pressure valve 27 which is activated if the internal pressure in the interior of the inner steel pipe 2 exceeds specified value. The pressure itself is automatically built up as result of steam developed during the casting process; however, it is also possible to produce the internal pressure in the interior of inner steel pipe 2 in advance of, or at the beginning of, the casting process, via an external compressed air connection 28 on the dome 19. To seal, or stabilise, the interior of inner steel pipe 2, it is welded at its ends to bases 29,30, which in addition can be mutually braced axially by means of tension rods (not shown). The upper base 30 may alternatively or in addition be braced by dome 19. In the casting installation - described with reference to Figure 2, the material for roll shell 4 is 1 is continually poured in by means of casting ladles 20,21 until the level C of the cast iron has reached the upper edge of the annular space formed from inner and outer steel pipes 2 and 3. After the cast iron has hardened and the end faces have been faced, the roll shell 1 according to Figure 1 is finished. This roll shell has an. inner and outer shell surface free of shrink holes; the steel pipes forming these inner and outer shell surfaces are also connected in a close and material -locking way to the cast-iron shell body so that there are no cracks at all at the interfaces between the steel and cast iron. This is achieved by means of the above-specified process and apparatus for carrying out -this process respectively in that during the casting process a occurs at the interfaces between the steel and cast iron because of the radial expansion of inner steel pipe 2 (as a result of being heated by the liquid cast iron) and the secure clamping within the ring- body parts 13,14 so that radial expansion of the outer shell surface of the roll body connected thereto is prevented. The radial expansion of the inner steel pipe is controlled and regulated so that this pipe expands radially outwards during the hardening of the cast iron by such large amounts that the shrink holes which would otherwise occur when the cast iron hardens are avoided. The reduction in volume resulting during the hardening of the cast iron is compensated by the radial expansion of inner steel pipe 2. so-called "sealed loading' i k 13 - is The result is not only a throughly homogenous roll body, but there is also a complete "welded joinC and material-locking respectively. It is precisely this satisfactory and permanent bond at the interface between the steel and cast iron that enables a roll shell produced in accordance with the process described above to be particularly suitable for bending loads and rolling stresses. Referring now to Figure 3, constructive details of the apparatus for manufacturing the roll shell are explained. Figure 3 shows an axial section through an inner steel pipe 2 standing on base plate 10 in the casting position. Into this steel pipe 2 a compression device in the form of a compression member 35 is coaxially introduced from above. This compression member 35 comprises a rod along which two guide blade disks 36 are spaced. On their outer circumferences the disks prets against conical sides of several longitudinal ribs 37. These longitudinal ribs 37 abut the inner shell surface of inner steel pipe 2 with the paraxial sides opposite the conical sides and thus press against this inner shell surface. If several longitudinal ribs.37 uniformly distributed over the circumference (see Figure 4) press against the circumferential shell surface, the inner steel pipe 2 is adequately strengthened. Further longitudinal ribs 38 are provided above longitudinal ribs 37 and they respectively align with one another. These further longitudinal ribs 38 are also coni-cally constructed on their sides turned towards compression member 35 and, with their second side, they also paraxially abut the inner shell surface of inner steel pipe 2. Two further spaced guide blade disks 39 radially support these further longitudinal ribs 38. These two further guide blade disks 39 are movably mounted on the rod of compression member 35 and are prevented f rom rotating by means of a pin 41 engaging in a notch 40 on compression member 35, so that ribs 38 are prevented from being rotated with respect to the ribs 37. The compression member 35 is inserted into the interior of inner steel pipe 2 at the beginning of, or before the casting process. In this case, the lower guide blade disks 36 abut the longitudinal ribs 37 on the side of the base so that they are pressed with the weight of compression member 35 and of guide blade disks 36 against the inner shell surface of inner steel pipe 2. Further, the longitudinal ribs 38 are pressed via a spring 2 supported on the uppermost guide blade disk 39 against the inner shell surface, which latter is thus supported over its length and around its circumference by the ribs 37 and 38. With the radial expansion of inner steel pipe 2 as a result of the casting process, longitudinal ribs 37,38 accordingly follow outwards (radially). Compression member 35 drops accordingly. During or after the hardening of the cast iron, i.e. as the roll shell cools, compression member 35 however has to be raised before the inner steel pipe 2 contracts as it cools.

1 1 1 is To prevent the inner steel pipe 2 deforming, if it has been forgotten, e. g. to withdraw compression member 35 punctually, the longitudinal ribs 37, 38 are specially mitred on their edges on the side of the compression member.

Along line A-A of Figure 3 as shown in Figure 4 six longitudinal ribs 37 are fixed or supported in guide blade disk 36. This support is provided by cast iron flanges 43 fixed at right angles to the plane of the longitudinal ribs 37 in guide blade disk 36, and behind said flanges seen from longitudinal ribs 37 - there is a free space 44. If compression member 35 is not punctually withdrawn from the interior of inner steel pipe 2, longitudinal ribs 37 press against the cast"iron flanges 43 until they break - since they are not supported at their rear face. Consequently, inner steel pipe 2 can again contract as the cast iron cools.

The above description of the roll shell, the process for its manufacture and apparatus for carrying out the process has been described above for a roll shell having inner and outer shielding. if only outer shielding is desired, the inner steel pipe which is necessary for reasons relating to casting, has to be drilled out or bored after casting.

Despite this subsequent operation, the economy of this manufacturing process is ensured. Finally, with respect to the known processes, the boring of the core from the solid block is omitted and, moreover, the amount of waste is extremely small in comparison with a manufacturing process having a sand core.

Finally, it is noted that the roll shell of the type described above can quite generally always be used if the inner, the outer, or both shell surfaces are to receive special surface heat treatment.

j -1 i CLAIMS 1 1. A cast tubular roll shell comprising a relatively thick-walled roll for use in apparatus for the treatment of web-shaped material, such as a press or calender roll, characterised in that the body (4) of the roll shell is cast on to an inner steel pipe (2) and/or an o uter steel pipe (3) in a material-locking manner to provide a shielded inner and/or outer shell surface.

2. A roll shell according to Claim 1, characterised in that the roll body (4) is cast in a material-locking manner between two coaxially aligned steel pipes (2,3) to provide shielded inner and outer shell surfaces.

3. A roll shell according to Claim 1 or 2, characterised in that the wall strength of the inner steel pipe (2) relative to that of the roll body (4) is approximately 15% to 50%.

4. A roll shell according to any one of Claims 1 to 3, characterised in that the wall strength of the outer steel pipe (3) relative to that of the roll body (4) is approximately 3% to 25%.

5. A roll shell according to any one of Claims 1 to 4, characterised in that the material of the roll body is cast iron, more particularly spheroidal graphite cast iron.

6. A roll shell according to any one of Claims 1 to 5, characterised in that the material of the inner steel pipe (2) is stainless steel.

J k 18 -

7. A: roll shell according to any one of Claims 1 to 6, characterised in that the material of the outer steel pipe (3) is stainless steel and/or heat-treatable steel.

8. A roll shell according to any one of Claims 2 to 7, characterised in that the inner steel pipe (2) is drilled or bored out after casting to leave an outer shielded shell surface only.

9. A process for the manufacture of a roll shell according to any one of Claims 1 to 8, characterised in that the outer shell surf ace of the roll body (4) is encased during the casting process so that the radial expansion of said shell body in inhibited.

10. A process according to Claim 9, characterised in that prior to casting, the steel pipes (2,3) are coaxially aligned with respect to one another and are centred relative to one another by means of spacer members, in particular spacer pins (11).

11. A process according to Claim 9 or 10-, characterised in that during the casting process excess pressure is established in the interior of inner steel pipe (2).

12. A process according to Claim 11, characterised in that the excess pressure is only established in the part of inner steel pipe (2) first filled.

13. A process according to any' one of Claims 10 to 12, characterised in that during the casting process the inner shell surface of inner steel pipe (2) is acted upon by at least four adjacent longitudinal ribs (37, 38) if necessary with additional supporting forces.

z 1 1

14. A,process according to any one of Claims 9 to 13, characterised in that the inner steel pipe (2) is temporarily cooled from inside during the casting process.

15. A process according to any one o.f Claims 9 to 14i characterised in that the. inner steel pipe (2) is temporarily cooled during the hardening phase of the roll body (4).

16. Apparatus for manufacturing a roll shell according to any one of Claims 1 to 8, characterised in that a ring body (13,14) is provided which is positioned on a base plate (10) and which has an internal diameter corresponding to the external diameter of the roll shell (1) or outer steel pipe (3) and with respect to the dimensions of the roll shell is so inherently stable that during the casting process it remains constant, at least approximately, with respect to its internal diameter.

17. Apparatus for manufacturing a roll shell according to any one of Claims 1 to 8, characterised in that a ring body (13,14) positioned on the front side on a base plate (10) is provided, the internal diameter of which corresponds to the external diameter of the outer steel pipe (3) and is dimensioned so that the outer shell surface of the roll body (4) can only expand to a limited extent during the casting process.

18. Apparatus. according to Claim 16 or 17, characterised in that the annular body (13,14) has insulation (17) on the inner wall.

19. Apparatus according to any one of Claims 16 to 18, characterised in that the ring body consists of at - least two ring body parts (13,14) abutting one another in a form-locked manner as a single unit, and if necessary connected to one another by means of a flange connection (15,16).

20. Apparatus according to any one of Claims 16 to 19, characterised in that a front side of the inner steel pipe (2) is closed with a base (29, 30), and in that a compressed air connection (28) is provided, via which excess pressure can be established in the interior of said inner steel pipe.

21. Apparatus according to any one of Claims 16 to 20, characterised in that a compression member (35) is inserted coaxially into the inner steel pipe (2), in that the compression member (35) has at least four"longitudinal ribs (37, 38) directed radially towards the inner shell surface of inner steel pipe (2), in that the compression member (35) and the longitudinal ribs (37,38) are connected to one another so that the longitudinal rib; (37,38) are pressed radially against the inner shell surface of inner- steel pipe (2) during the casting process, and in that the compression member (35) is suspended so that it can be withdrawn after the casting has hardened and before the final cooling.

22. Apparatus according to Claim 21, characterised in that several longitudinal ribs (37,38) are disposed above one another along compression member (35).

23. Apparatus according to Claim 21 or 22, characterised in that the longitudinal ribs (37,38) are connected to the compression member (35) via guide blade disks (36), and in that they abut cast iron flanges (43) open at the rear with the side farther from the compression member.

24. A cast tubular roll shell, substantially as hereinbefore described with reference to the accompanying drawings.

25. A process or apparatus for manufacturing a roll shell substantially as hereinbefore described with reference to the accompanying drawings.

Published 1988 at 'llie Patent Office, State House, 66171 Righ Holborn, London WC1R 4TP. F4arther copies may be obtained from The Patent Or[ice, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con--- 1187.