US3822574A

US3822574A - Ring-rolling mill

Info

Publication number: US3822574A
Application number: US00346886A
Authority: US
Inventors: A Krupin; V Izotov; O Burov; V Roschin; L Alekhin; V Lepin; F Vinogradov; V Gavrilov; A Chekanov
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-04-02
Filing date: 1973-04-02
Publication date: 1974-07-09
Anticipated expiration: 1991-07-09

Abstract

A rolling mill comprising a driven outside and a not-driven inside rolls adapted for radial reduction of the ring being rolled, and face rolls adapted for maintaining a constant dimension as to the height of the ring being rolled with the face rolls being made as conical rings and located so that their interiors accommodate the not-driven roll. The pivotal axes of the face rolls are arranged at an angle to that of the inside roll.

Description

United States Patent [191 Krupin et al.

3,822,574 July 9, 1974 1 RING-ROLLING MILL [22 Filed:

Inventors: Alexandr Vasilievich Krupin,

Apr. 2, 1973 Appl. No.: 346,886

'lllgl Inn lllllnl [52] US. CL...

[51] Int. Cl B2111 l/06 [58] Field of Search ,72/84, 101, 106, 107, 110

[56] References Cited UNITED STATES PATENTS 499,824 6/1893 DuBois 72/101 965,032 7/1910 Slick 72/84 2,062,415 12/1936 Harrison 72/107 3,461,701 8/1969 Marcovitch 72/1 10 Primary Examiner-Lowe1l A. Larson Attorney, Agent, or Firm-I-lolman & Stern 1 A rolling mill comprising a driven outside and a notdriven inside rolls adapted for radial reduction of the ring being rolled, and face rolls adapted for maintaining a constant dimension as to the height of the ring being rolled with the face rolls being made as conical rings and located so that their interiors accommodate the not-driven roll. The pivotal axes of the face rolls are arranged at an angle to that of the inside roll.

ABSTRACT 7 Claims, 6 Drawing Figures PATENTEU 91974 SHEET 1 0F 5 PATENTED JUL 9 7 sum 2 UF 5 mm FQN NM NR R NM mm m? EM NYE E Kw. w mmfiw? mm g wv MENTEDJUL 9W SHEET 5 OF 5 FIG!) 1 RING-ROLLING MILL BACKGROUND OF THE INVENTION The present invention relates to rolling mills for rolling metallic rings, preferably under vaccum.

Known from the Authors Certificate of the USSR No. 139650, Cl. 7f, I, is a ring-rolling mill for producing rolled rings comprising a housing mounting an outside driven roll and an inside not-driven roll set up on supports and adapted for radial reduction of the ring being rolled, with the inside not-driven roll allowed to move axially, face rolls adapted for maintaining a constant dimension as to the height of the ring being rolled and also installed on supports, a backup roll which serves for holding in place the ring during rolling being connected to the outside cylindrical driven roll and traversed in conjunction with the latter during the rolling operation, and a centering roller and devices for loading and unloading the rings to be rolled.

In this prior-art embodiment of the ring-rolling mill, the outside driven roll is mounted on a pivot arm, with one end of the arm being located on a swing support and the other end being coupled to a cam screwdown gear through a roller. When the wall of the ring being rolled issubject to radial reduction, the outside roll transfers together with the arm along a circumference with a center point arranged in the swing support.

. The face rolls of the mill are mounted in a separate stationary stand being located from the side in relation to the rolls adapted for radialreduction. The face rolls are brought together and separated with the help of an When rolling the rings, the outside roll traverses along the circumference which hinders the sealing of the supports of the outside roll and makes the tightness of the rolling mill less dependable. The face rolls are mounted on,the mill in a separate stand positioned stationary from the side of the rolls for radial reduction of the rings being rolled in such a manner that the axes of the face rolls form a constant angle in relation to the line of transfer of the center point of the ring being rolled.

Moreover, the face rolls arefitted with gears adapted for bringing them together and separation and with a device for their transfer in a radial direction relative to the center point of the ring being rolled.

Due to such a sophisticated kinematics of movement of the face rolls and their cumbersome stand, an'adequate tightness of the ring-rolling mill in various respects is also a problem, this complicating substantially the mill design and making it more metal-consuming.

The face rolls have a constant angle at which their axes are located relative to the line of transfer of the center point of the ring being rolled when the latter changes its geometric dimensions in the course of rolling which results in different linear speeds of the face rolls and the ring being rolled on their contact surface and in the development of additional frictional forces which may overstrain the ring in the rolling plane, cause additional loads on the backup roll and disturb the tightness of the ring-rolling mill. This is attributable to the fact that as the ring is growing, the'plane of axes of the face rolls does not pass through the center point of the ring being rolled.

Location of the face roll stand on the housing requires the use of an additional gear for removing the rolled rings from deformation focus, the gear being made as a driven arm, which in turn necessitates additional seals and more intricate construction of the rolling mill.

The above-listed design features of the known ringrolling mill impede the creation of vacuum in this mill.

Furthermore, the prior-art ringrolling mill suffers from a number of other-disadvantages.

The face rolls of the mill are articulated with one an other and on being brought together traverse along a radius coming into contact with the lateral surface of the rings being rolled and featuring different heights at different angles. On account of this, the rings of various geometric dimensions require the face rolls with different' cone angles. I

Moreover, the ring-rolling mill of the known construction is suitable only for rolling the rings with a certain minimum height.

SUMMARY OF THE INVENTION .mum height without replacing the face rolls.

. These and other objects are accomplished by the provision of a ring-rolling mill comprising a housing mounting an outside driven roll and inside not-driven roll set up on supports and adapted to provide radial. reduction of the ring being rolled, with the not-driven roll being allowed to transfer axially, face rolls adapted .for maintaining a constant dimensions as to the height.

According to the invention the face rolls are made as conical rings mounted in such a manner that their interiors accommodate'the inside not-driven roll with the pivotal axis of the face rolls being located at an acute angle to that of the inside roll.

The ring-rollingmill is expedient to be made so that its face rolls be mounted with their supports on the mill housing which would make it possible to roll the rings of various geometric dimensions and to extend the diversity of the rings being rolled.

It is also expedient to install the face rolls with their supports resting on those of the inside roll which would offer a reduction in both the dimensions of theface rolls and their metal requirements.

It is also sound practice tomake the facerolls with their supports swivelling relative to the pivotal axis of the inside roll, a feature which will enable a decrease BRIEF DESCRIPTION OF THE DRAWINGS The invention is further exemplified by a detailed description of a specific embodiment thereof, to be had in compliance with the accompanying drawings, wherein:

FIG. 1 represents a general view of the ring-rolling mill, according to the present invention;

FIG. 2 is section view taken along the line IIII of FIG. 1;

FIG. 3 is section view taken along the line IllIII of FIG. 2;

FIG. 4'is a view of unit A of'FIG. 2;

FIG. 5 is'a view of unit A of FIG; 2 with the face roll supports arranged on those of the inside roll; and

FIG. 6 is a view of an arrangement of contact surfaces of the face rolls and the lateral surface of the ring being rolled.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A ring-rolling mill represented in FIGS. 1 through 6 comprises a tight loading device 1 which consists of a tight hatch 2 through which the rings 3 being rolled are charged, and a feed barrel 4 with cells 5 for the rings to be rolled.

The feed barrel 4 is rotatable about an axis (the direction of rotation being indicated by an arrow) for discharging the rings 3 being rolled into a trough-shaped guide 6.

The loading device 1 is connected to a heating vacuum furnace 8 with the help of a cutoff gate-type device 7.

With the aid of the cutoff device 7, the loading device 1 can be connected or disconnected from the furnace 8.

The vacuum heating furnace 8 is designed for heating the rings 3 being rolled up to a predetermined temperature prior to rolling, and is provided with a troughshaped guide 9 which serves to direct the rings to be rolledto the heater 10 of the furnace 8 wherein it is centered and caught by a retainer 11.

The heating furnace 8 is bolted through a tight guide branch 12 to a cutoff gate-type device 13 which is also bolted to a housing 14 forming a vacuum chamber 14a.

The cutoff device 13 is intended for connecting or disconnecting the furnace 8 to the chamber 14a.

After the cutoff device 13, in the direction of motion of thering 3 being rolled, there is mounted a troughshaped guide 15 which can swing in a vertical plane about the common axis with the support 16 installed on the wall of the housing 14.

In order to make the loading device 1 and furnace 8 adequately tight the cutoff devices 7 and 13 as well as the branch 12 are fitted with tight cups 17, 18, 19, 20 and 21.

Mounted on supports 23 (FIG. 2) in the tight housing 14 is an outside cylindrical driven roll 22 rotating in bearings 24 furnished with tight cups 25 to enable adequate sealing of the housing 14.

Rotation of the outside roll 22 is effected by means of an electric motor 26 through a step-down reducing gear 27 and a spindle 28 which is connected to the reducing gear and electric motor by movable articulated joints 28a and is capable of transmitting the rotary motion to the outside roll 22 when the latter traverses vertically.

To enable radial reduction of the ring 3 to be rolled which is arranged on an inside roll 29., the supports 23 with the outside roll 22 are allowed to traverse in a vertical plane (without disturbing the tightness of the housing 14) along tight cups 30 which are installed in erection lids 31 fastened to the housing 14 through the use of tight cups 32.

The lids 31 are intended for erecting the outside roll 22 inside the housing 14. The cups 30 serve for sealing the housing 14 when the ring 3 being rolled is subject to radial reduction by the outside roll 22, and the cups 32 are designed to make the housing-14 tight when erecting the M531.

Vertical transfer of the outside roll 22 is performed by means of two pressure cams 33. through rollers 34 set up on the supports 23.

External surfaces of the pressure cams 33 which are brought into contact with the rollers 34 have a design profile which ensures vertical transfer of the outside -roll 22 in accordance with a certain law, by which virtue one revolution of the cams 33 provides for a predetermined reduction of the ring 3.

The cams are brought into rotation by an electric motor 35 through a step-down reducing gear 36.

The interior of the ring 3 being rolled incorporates an inside not-driven cylindrical roll 29 fitted with supports 37a and 37b and with an anti-friction bearing 38. These supports are sealed by tight cups 39. The two supports of the inside roll are similar in design, differing only in that the support 37a houses the inside roll 29 and the support 37b houses a loose shaft 40 with a seat 41 for the inside roll 29. Both supports can traverse horizontally along tight cups 43 by way of hydraulic cylinders 42a and 42b.

Tightness of the housing 14 during the rotation of the inside roll 29 and loose shaft 40 is provided by the cups 39, with the cups 43 ensuring tightness of the housing 14 during horizontal transfer of the supports 37a and 37b.

The inside roll 29 is brought into the interior of the ring 3 being rolled prior to rolling and taken out of it after the rolling operation by means of the hydraulic cylinder 42a. I

The hydraulic cylinder 42b is intended for traversing the support 37b only in case the height of the ring 3 being rolled is changed.

In order to provide for the required length of stroke of pistons 44, the hydraulic cylinders 42a and 42b are fitted with adjusting nuts 44a fastened to connecting rods 45a and 45b outside cylinder casings 46a and 46b.

To prevent spreading during radial reduction of the ring 3 being rolled by the outside roll 22 and inside roll 29, the ring-rolling mill is equipped with face rolls 47a or 47b (FIGS. 4-5).

The face rolls 470 or 47b are not driven and are mounted on supports 48a or 48b in anti-friction bearings (radial and thrust bearings on each support).

The face rolls 47a made as conical rings are installed on their ring-shaped supports 48a whose shape determines the arrangement of pivotal axes I-l and II-II of the face rolls relative to that of the inside roll 29. The inside roll 29 is disposed in the interiors of the face rolls 47a.

The supports 48a mounting the face rolls 47a are fitted with cylindrical projections 49 entering appropriate cylindrical guide slots 49a provided on the housing 14. Rotation of the supports .in relation to the pivotal axis of the inside roll 29 is prevented by bolts (not shown in the drawing). 6

Pivotal axes I-I and lI-II of the face rolls are arranged at an acute angle or to the pivotal axis of the inside roll 29.

The above arrangement of the face rolls allows rolling rings of different geometric dimensions and extending the range of the rings being rolled on the mill.

The supports 48b (FIG. 5) mounting'the face rolls 47b are fitted with cylindrical projections 49 entering appropriate cylindrical guide slots 4% provided on the supports 37a and 37b of the inside roll 29. Rotation of The supports 48a and 48b with the face rolls 47a and 47! can be mounted in the slots 49a and 49b at any angle relative to the pivotal axis of the inside roll 29. However, the above-described arrangement of the face rolls is particularly useful for the rings, to be rolled, having small dimensions, the outside diameters of the face rolls being restricted in that case by those of the supports 37a and 37b which offers a reduction in the overall dimensions of the face rolls and in their metal requirements.

Whatever the arrangement of the supports of the face rolls, generatrices 50 of the conical surfaces of the face rolls 47a or 47b brought into contact with the lateral surfaces of the ring 3 being rolled are located in parallel with'each other in the same plane with pivotal axes 'l-I and llll of the face rolls.

Due to the above embodiment of the unit of the face rolls 47a or 47b the contact5la or 51b or 51c (FIG. 6)

dependent on the points of contact of the generatrices 50 of the face rolls 47a or 47b with the lateral surface of the ring 3 being rolled, can be located at any point of the lateral surface of the ring to be rolled depending on its final diameter.

The possibility of changing the above contact point offers a considerable reduction in the force arising at the point of contact of the face rolls and the ring being rolled (due to a difference in their linear speeds) during rolling and being transmitted by the ring being rolled to the backup roll 52 (FIG. 3) intended to maintain in conjunction with the master form 53 a regular geometric shape of the ring being rolled.

The backup roll 52 is mounted on an arm 54 rotatable about an axis located in the supports of the arm 55. The latter is rigidly fixed to the supports 23 of the outside cylindrical driven roll 22.

During rolling the backup roll 52 contacts the external surface of the ring 3 being rolled, with its roller bearing 56 resting on a preset design shaped surface of the master form 53 which, when being rolled by the rollerbearing 56 during center point along the vertical line parallel to the plane, wherein the pivotal axes of the inside and outside rolls are located and which is situated on the side of an unloading device, by which virtue the ring will roll down by gravity into the unloading device after the rolling operation.

The master form 53 is fastened to a flange 57 set up on the wall of the housing 14 by way of tight cups (not shown in the drawing).

An oblique upper wall of the housing 14 (FIG. 3) mounts a hydraulic cylinder 58. The connecting rod 59 of the cylinder is mounted through tight cups (not shown in the drawing) inside the housing 14 and termi nates with a centering roller 60.

Outside the housing the connecting rod 59 of the hy draulic cylinder 58 is coupled to dowels 61 fixed rigidly to the hydraulic cylinder 58. The dowels 61 serve to adjust the transfer of the centering roller 60. The latter is designed to securethe center point of the ring 3 being rolled in relation to the pivotal axis of the inside roll 29 so that it (the inside roll) can be: readily brought into the interior of the ring 3 to be rolled.

The wall of the tight housing 14 is fitted with an outlet 62 for discharging the rolled rings 3 from the housing into a tight unloading device 63.

To enable the rolled ring 3 to enter the outlet 62, a chute 64 is secured inside the housing 14 to direct the finished ring 3. The tight housing 14 is connected to the unloading device 63 with the help of an tight gate-type cutoff device 65. The latter serves to connect or disconnect the housing 14 from the unloading device 63.

Inside the unloading device 63, there is a movable staging 66 with cells for therolled rings 3. The unloading device 63 is fitted with a tight hatch 67 through which the rolled rings are removed from the ringrolling mill. V

In the lower part of the tight housing 14, provision is made for 'a connecting pipe 68 adapted to couple the housing with a vacuum pump (not shown in the draw ing). v y

y The ring-rolling mill of the invention operates as follows.

The rings 3 to be rolled are loaded through an open hatch 2 into cells 5 of the feed barrel 4 accommodated in the tight loading device 1.

After that the tight hatch 2 is closed and a vacuum pump connected to the connecting pipe 68 of the tight housing 14 is started.

As soon as the requisite vacuum is created inside the ring-rolling mill, the feed barrel 4 rotates in the direction of the arrow.

The ring 3 being rolled rolls by gravity into the trough-shaped guide 6 proceeding through an open cutoff gate-type device 7 along the guide 9 into the furnace 8.

In the furnace 8, the ring 3 being rolled is centered relative to the heater 10 being kept in the furnace by means of a retainer 11.

The retainer 11 on being lowered releases with the aid of a leverage system (not shown in the drawing) the ring 3 heated to an appropriate temperature, whereafter it continues to roll by gravity along the trough shaped guide 90, tight guide branch 12, through the open cutoff device 13, down the trough-shaped guide onto the outside cylindrical driven roll 22 brought into rotation by an electric motor 26 (the direction of rotation is indicated by an arrow). It is retained on the roll 22 by means of the backup roll 52 and centering roller 60 lowered with the help of the connecting rod 50 of the hydraulic cylinder 58 and brought into contact with the external surface of the ring 3 being rolled. In this case the interior of the ring being rolled is made fast by the centering roller 60 in relation to the pivotal axis of the inside roll 29.

Following that, the inside roll 29 is brought by the hydraulic cylinder 42a through the interior of the ring 3 being rolled into a seat 41 of the loose shaft 40. The face rolls 47a or 47b are brought into contact with the ring 3 being rolled whereupon the centering roller 60 is taken aside with the help of the hydraulic cylinder 58 and the electric motor 35 is energized to bring into rotation the pressure cams 33.

The latter acting on the rollers 34 makes the supports 23 with the outside roll 22 to move upwards. The outside roll performs radial reduction of the ring being rolled and the backup roll 52 contacting the external surface of the ring 3 being rolled rests with its support 56 of the master form 53 and traversing along the master form ensures the retention of the regular geometric,

shape of the ring being rolled.

As the ring 3 being rolled achieves the predetermined final diameter, a signal is sent with the aid of a pickup (not shown in the drawing) for reversal of the cams 33 whereupon the outside roll 22 returns into its initial position. The inside roll 29 is brought out of the interior of the rolled ring 3 by the hydraulic cylinder 42a, the face roll 47a or 47b being moved aside from the roll. The hydraulic cylinder 42b moves aside the face roll 470 or 47b.

' As the center of gravity of the rolled ring 3 is displaced to the side of the unloading device 63 relative to the plane in which the pivotal axes of the inside and outside rolls are located the rolled ring rolls down along the chute 64 through the aperture 62 and open cutoff device 65 into the cell of the staging 66 of the unloading device 63.

Allthe rings 3 contained in the loading device 1 are rolled on the mill of the invention in a similar way.

After that the cutoff device 65 detaches the unloading device 63 from the chamber 14a of the housing 14. The tight hatch 67 is open and the rolled rings 3 are removed from the unloading device 63.

Then the tight hatch 67 is closed again and the unloading device 63 is connected via a connecting pipe (not shown in the drawing) to a vacuum pump which evacuates air to create the desired vacuum.

Following that the cutoff device 65 reconnects the unloading device 63 to the vacuum chamber 14a.

For rolling the next lot of the rings 3 the loading device 1 is disconnected by the cutoff device 7 from the furnace 8. Then the hatch 2 is open to charge the rings being rolled into the loading device 1.

After that the hatch 2 is closed, and the loading device 1 is connected through a connecting pipe (not shown in the drawing) to a vacuum pump which evacuates air to create the desired vacuum.

Then, the cutoff device 7 reconnects the loading device 1 to the furnace 8 and the entire cycle of rolling the rings 3 on the ring-rolling mill is reiterated as here- I inbefore described.

What we claim is:

l. A ring-rolling mill comprising: a housing mounting an outside driven roll (22) set up on supports (23) to allow its concurrent rotation and vertical transfer; an inside not-driven roll (29) also installed on supports (37a and 37b) to allow its axial motion to be brought through the interior of the ring (3) being rolled prior to its rolling and taken out of it after the rolling process and adapted to perform in conjunction with said outside driven roll (22) radial reduction of the ring (3) being rolled; face rolls (47a or 47b) adapted for maintaining a constant dimension as to the height of the ring being rolled and made as conical rings mounted on supports (48a or 48b) in such a manner that their interiors accommodate said inside not-driven roll (29), the supports (48a or 48b) of said face rolls being made as rings whose shape determines an acute angle (a) at which the pivotal axes (I-I and IllI) of the rolls (47a or 47b) are located relative to the pivotal axis of said inside not-driven roll (29); means for holding in place the ring being rolled during the rolling operation and maintaining regular geometric shape of the ring being rolled; means forsecuring the center point of the ring being rolled relative to the pivotal axis of said inside roll (29) so that this inside roll can be easily brought into the interior of the ring being rolled; a loading device (1) for charging the rings being rolled and an unloading device (63) for removing the rolled rings; means for bringing said inside roll (29) inside the ring being rolled prior to rolling and taking it out after the rolling operation; and a first drive means (26) for rotation and a second drive means (35) for vertical transfer of said outside roll (22) during rolling.

2. A ring-rolling mill as claimed in claim 1, wherein said means for holding the ring in place during rolling and for maintaining regular geometric shape of the ring being rolled comprises a backup roll (52) with a roller bearing (56) and a master form (53) with said backup roll (52) being connected to said outside driven roll (22) traversing in conjunction with said backup roll in the course of rolling, connecting during the rolling operation the external surface of the ring being rolled and simultaneously resting with its roller bearing (56) on the predetermined design shaped surface of said master form (53) which, with said roller bearing (56) rolling along it during rolling, ensures as upward motion of the ring center point along a vertical line parallel to the plane where the pivotal axes of said inside not-driven roll (29) and said outside driven roll (22) are located, with the shaped surface being disposed on the side of said unloading device (63) by which virtue the finished ring can roll be gravity after rolling into said unloading device.

3. A ring-rolling mill as claimed in claim 1, wherein said means for securing the center point of the ring being rolled in relation to the pivotal axis of said inside roll (29) comprises a centering roller mounted inside said housing l4) and a hydraulic cylinder having a connecting rod, said centering roller being mounted on said connecting rod, said hydraulic cylinder (58) being arranged outside said housing and adapted to adjust the transfer of said centering roller (60).

4. A ring-rolling mill as claimed in claim 1, wherein said means for bringing said inside roll (29) inside the ring being rolled .prior to rolling and for taking it out 9 after the rolling operation comprises a hydraulic cylinder (42a) fitted with adjusting nuts (44a) which is adapted to control the stroke of a piston (44) and is mounted on a connecting rod (45a).

5. A ring-rolling mill as claimed in claim 1, wherein said face rolls (47a) are installed with their supports (48a) on said housing (14) which renders possible the rolling of rings having different geometric dimensions and allows extending the diversity of the rings being rolled.

6. A ring-rolling mill as claimed in claim 1, wherein said face rolls (47b) are installed with their supports (48b) on the supports (37a) and (37b) of said inside roll (29) which offers a reduction in both the dimensions of the face rolls and their metal requirements.

7. A ring-rolling mill as claimed in claim 1, wherein said face rolls (47a or 47b) together with their supports (48a or 48b) are made rotatable relative to the pivotal axis of said inside roll (29) which permits decreasing the mismatch of linear speed of said face rolls and the ring being rolled on their contact surface, the load act ing on said backup roll (52) and providing a more reliable tightness of the mill.

Claims

1. A ring-rolling mill comprising: a housing mounting an outside driven roll (22) set up on supports (23) to allow its concurrent rotation and vertical transfer; an inside not-driven roll (29) also installed on supports (37a and 37b) to allow its axial motion to be brought through the interior of the ring (3) being rolled prior to its rolling and taken out of it after the rolling process and adapted to perform in conjunction with said outside driven roll (22) radial reduction of the ring (3) being rolled; face rolls (47a or 47b) adapted for maintaining a constant dimension as to the height of the ring being rolled and made as conical rings mounted on supports (48a or 48b) in such a manner that their interiors accommodate said inside not-driven roll (29), the supports (48a or 48b) of said face rolls being made as rings whose shape determines an acute angle ( Alpha ) at which the pivotal axes (I-I and II-II) of the rolls (47a or 47b) are located relative to the pivotal axis of said inside not-driven roll (29); means for holding in place the ring being rolled during the rolling operation and maintaining regular geometric shape of the ring being rolled; means for securing the center point of the ring being rolled relative to the pivotal axis of said inside roll (29) so that this inside roll can be easily brought into the interior of the ring being rolled; a loading device (1) for charging the rings being rolled and an unloading device (63) for removing the rolled rings; means for bringing said inside roll (29) inside the ring being rolled prior to rolling and taking it out after the rolling operation; and a first drive means (26) for rotation and a second drive means (35) for vertical transfer of said outside roll (22) during rolling.

3. A ring-rolling mill as claimed in claim 1, wherein said means for securing the center point of the ring being rolled in relation to the pivotal axis of said inside roll (29) comprises a centering roller (60) mounted inside said housing (14) and a hydraulic cylinder having a connecting rod, said centering roller being mounted on said connecting rod, said hydraulic cylinder (58) being arranged outside said housing and adapted to adjust the transfer of said centering roller (60).

4. A ring-rolling mill as claimed in claim 1, wherein said means for bringing said inside roll (29) inside the ring being rolled prior to rolling and for taking it out after the rolling operation comprises a hydraulic cylinder (42a) fitted with adjusting nuts (44a) which is adapted to control the stroke of a piston (44) and is mounted on a connecting rod (45a).

7. A ring-rolling mill as claimed in claim 1, wherein said face rolls (47a or 47b) together with their supports (48a or 48b) are made rotatable relative to the pivotal axis of said inside roll (29) which permits decreasing the mismatch of linear speed of said face rolls and the ring being rolled on their contact surface, the load acting on said backup roll (52) and providing a more reliable tightness of the mill.