GB2070994A

GB2070994A - Variable crown roll

Info

Publication number: GB2070994A
Application number: GB8106822A
Authority: GB
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 1980-03-11
Filing date: 1981-03-04
Publication date: 1981-09-16
Also published as: SE8101377L; AU6768881A; GB2070994B; IN155422B; ES500278A0; LU83210A1; ES8206994A1; IT8167333A0; AU544037B2; BE887885A; IT1144158B; BR8101400A; FR2477913A1; FR2477913B1; DE3109316A1; SE441984B; CA1170087A; MX152302A; AR227776A1

Abstract

In a variable crown roll for a rolling mill, an annular cavity of a predetermined depth is formed between an arbor (1) and a sleeve (2), a pressure transmitting medium, e.g. oil or water, is forced into the cavity through a passage in the arbor, and the pressure of the medium is adjusted to control the value of crowning of the roll. The cavity has an inlet at one end and an outlet at the other, and is of a radial depth greater than the maximum expected deflection of the sleeve. <IMAGE>

Description

SPECIFICATION Variable crown roll The present invention relates to a variable crown roll of such construction that the value of crowning of the roll is controlled by adjusting the pressure of a medium.

The variable crown roll (hereinafter referred to merely as a VC roli) generally comprises an arbor and a sleeve which is shrinkage-fitted onto the arbor and includes an annular cavity of a predetermined width and depth formed between the arbor and the sleeve, into which a pressure transmitting medium such as oil, water, grease or the like (hereinafter referred to merely as a medium) is forced through a leading-in passage so as to control the value of the crowning of the roll by adjusting the pressure of the medium. The leading-in passage comprises an axial passage extending axially from an end to the other of the arbor and radial passages communicating from the axial passage to opposite ends of the cavity.

Heretofore, the VC roll was used for light rolling load mills such as skinpass rolling mills for hot rolled strip or sheets but not for mills, in which extraordinary load tends to occur, such as hot or cold tandem mills. If the VC roll is used in such mills, there is a possibility of rolling troubles or cracking in the sleeve due to the extraordinary load. In the conventional VC rolls, since the initial depth of the cavity (the depth of the cavity at the time of roll assembly) was relatively large, the inner surface of the central portion of the sleeve did not contact the peripheral surface of the arbor even when the sleeve was deflected radially inwardly by the extraordinary load occurred during rolling at the normal value of crowning of the roll.As a result, the stress occurring in the sleeve increased substantially in proportion to the load applied to the sleeve, leading eventually to cracking of the sleeve when exceeded the yield strength of the sleeve material. Accordingly, the old type VC roll could not be used in mills in which the extraordinary load might occur.

In the old type VC rolls, the initial depth of the cavity was formed relatively large as mentioned above for the reasons that the application of the VC roll was limited to small reduction rolling which eliminated the need for consideration of the sleeve cracking caused by the extraordinary load and that the forming of the cavity and the pouring of the medium thereinto were made easy.

Further, there was a problem of evacuation of air from the cavity of the VC roll when pouring the pressure transmitting medium into the cavity. Heretofore, when filling the VC roll cavity and passages with the medium, air was forced out of the cavity of the roll through the steps of suspending the VC roll by a crane vertically, opening the top end of the axial passage communicating with the cavity, introducing the medium into the axial passage through the lower end thereof forcing the air therein out of it, and placing a plug at the top end of the axial opening when the introduction of the medium was finished.

In the old type VC roll, in which the axial opening extended along the overall length of the roll, sufficient evacuation of the air was impossible since the medium reached the top end of the axial opening before the medium spread sufficiently over the cavity. Presence of air in the roll presented a few such problems as a slower response speed of the medium pressure due to compression of the air by elevating the pressure of the medium and a more intensive splashing of the medium due to the increase of the stored energy of the air when the cracking of the sleeve would have occurred.

Accordingly, an object of the present invention is to provide a variable crown roll which can be used in mills in which extraordinary loads tend to occur.

Another object of the present invention is to provide a variable crown roll from which air can be easily evacuated when the medium is poured thereinto.

A VC roll according to the present invention is of the construction in which an annular cavity having a predetermined depth is formed between an arbor and a sleeve, an end of the cavity is communicated with a medium leading-in passage, and the other end of the cavity is communicated with a medium leading-out passage.

The cavity is formed by caving either only one or both of the interface of the arbor and the sleeve. The depth of the cavity is predetermined to a nalue smaller than the value of maximum deflection of the sleeve due to an extraordinary load occurring during rolling with a normal value of roll crowning. Because of the construction described above, when the extraordinary load occurs, the inner surface of the sleeve defining the radially outer wall of the cavity is brought in contact in a portion thereof with the peripheral surface of the arbor defining the radially inner wall of the cavity whereby the extraordinary load is supported by the sleeve and the arbor, and consequently the stress arising in the sleeve is considerably suppressed.

For pouring the pressure transmitting medium (for example, oil, water or grease) into the VC roll according to the present invention, the roll is placed aslant or upright with the medium leading-in passage held downward and the medium leading-out passage upward, the medium is poured into the roll through the leading-in passage while evacuating air in the cavity and the passages, and the outlet of the leading-out passage is plugged after the completion of the pouring of the medium.

The invention will be better understood from the following description taken in connection with the accompanying drawings, in which: Figure 1 is a longitudinal sectional view of a VC roll showing an embodiment of the present invention: Figure 2 is a longitudinal sectional view of a VC roll showing another embodiment of the present invention; Figure 3 is a partial cross-sectional view taken along the line Ill-Ill of Fig. 2; Figure 4 is a longitudinal sectional view of a VC roll showing another embodiment of the present invention; Figure 5 is a partial cross-sectional view taken along the line V-V of Fig. 4; Figure 6 is a longitudinal sectional view of a VC roll showing a still further embodiment of the present invention; Figure 7 is a partial cross-sectional view taken along the line VII-VII of Fig. 6;; Figures 8 and 9 are partial longitudinal sectional views of a VC roll showing different stages of the sleeve deformation; Figure 10 is a diagram showing the relationship between the rolling load and the increase in stress in the sleeve at the different stages of the sleeve deformation; and Figure ii is a diagram similar to Fig. 1 0. showing an embodiment of the present invention.

With reference to the drawings and more particularly to Fig. 1 thereof, there is illustrated an embodiment of the VC roll according to the present invention, comprising an arbor 1 and a sleeve 2 shrinkage-fitted to the arbor 1 with an annular cavity 3 having a predetermined depth defined therebetween. An end of the cavity 3 is communicated with an axial medium leading-in passage 5 at an end of the arbor 1 through a radial passage 4 in the arbor 1, while the other end of the cavity 3 is communicated with a medium leading-out passage 7 provided axially at.

the other end of the arbor 1 through a radial passage 6 in the arbor 1.

A conventional rotary joint 52 is attached at an inlet 51 of the medium leading-in passage 5.

The pressure transmitting medium such as water, oil ur grease is forced through the rotary joint 52 into the medium leading-in passage 5, radial passage 4. cavity 3, radial passage 6. and an axial medium leading-out passage 7. While the medium is forced into the VC roll, air in the passages and in the cavity is evacuated through an outlet 71. When the medium has reached the outlet 71, the outlet 71 is tightly closed with a conventional plug 72.

Another embodiment of the VC roll according to the present invention is shown in Figs. 2 and 3, in which a medium leading-out passage 7a is provided in the sleeve 2 and is communicated directly with an end of the cavity 3 without any radial passage.

A further embodiment of the VC roll according to the present invention is shown in Figs. 4 and 5. in which a medium leading-out passage 7b is provided in the arbor 1 in the vicinity of its periphery and is communicated directly with an end of the cavity 3 without any radial passage.

A still further embodiment of the VC roll according to the present invention is shown in Figs.

6 and 7, in which a portion of the medium leading-out passage 7a is provided in the sleeve 2 while the other portion of the medium leading-out passage 7b is provided in the arbor 1 in the vicinity of its periphery. and the two passages are communicated with each other and an end of the passage 7b is communicated with an end of the cavity 3.

In the VC roll according to the present invention having the construction in which, as described above, the axial opening is eliminated and the passages are so formed that the medium passes from one end of the arbor to the opposite end of the sleeve through the cavity, it is made possibie to reduce the quantity of the medium heretofore existed in the arbor and to evacuate the air easily and surely, to thereby increase the response speed and to decrease the stored energy.

Determination of initial depth d of the cavity 3 will now be described with reference to Figs. 8 to 11. Generally, in the VC roll assembled, the opposite surfaces in the cavity 3 are parallel to each other as shown in Fig. 8. In a modified form, however, the sleeve 2 has the V-shaped inner surface inclined toward the middle of the sleeve so that the depth d of the cavity gradually increases or decreases. Accordingly, the depth dwill be considered herein on the basis of the depth at the middle of the sleeve.

In Fly 8 solid lines A show the sleeve 2 under the condition of the medium pressure PM = 0 kg, Un! (gauge pressure) and rolling load P = O kg. Broken lines B show the sleeve 2 under the condition in which the medium pressure PM is a certain pressure (0-500 kg/cm2) for providing a normal value of crowning and the rolling pressure P is a certain load P for performing normal rolling. Two-dot lines C show the sleeve 2 at the moment when an extraordinary load Pc suddenly occurs whereby a portion of the inner surface of the sleeve 2 contacts a portion of the periphery of the arbor 1 in the cavity 3.

Then in Fig. 9. solid lines D show the sleeve 2 under the condition in which the extraordinary load P. has increased to PE, In the condition shown by the solid lines D, the most part of the inner surface of the sleeve 2 contacts the peripheral surface of the arbor 1 in the cavity 3.

In Fig. 9, two-dot lines D' show the sleeve 2 under the condition in which the initial depth d of the cavity 3 is so sufficiently large that the sleeve 2 freely deflects, whereby the inner surface of the sleeve 2 is kept separate from the peripheral surface of the arbor 1 in the cavity 3. In this state, the value of the maximum deflection of the sleeve 2 (from the initial state A) is denoted by S.

In the present invention, the initial depth d of the cavity 3 is determined smaller than the value of the maximum deflection S. In practical application, the initial depth d is determined preferably to 0-2.0 mm in consideration to the response property of the medium.

Fig. 10 shows graphically the relationship between the rolling load and the stress induced thereby at the conditions of the sleeve 2 mentioned above regarding Figs. 8 and 9. In the diagram of Fig. 10, the horizontal axis denotes the rolling load P(kg) and the vertical axis denotes an increase in stress lSa(kg/cm2) in the sleeve 2 from the initial state A of the sleeve.

As shown in Fig. 10, in the condition represented by a line segment AB, the sleeve 2 is in the normal rolling range and deflects within the limits of the expansion. In the condition represented by a line segment BC, the sleeve 2 deflects freely within the range of the initial depth d of the cavity 3. Further, in the condition represented by the line segment CD, the sleeve 2 contacts the arbor 1 and the deflection of the sleeve is limited thereby. At the condition represented by the point D, the maximum increase in stress A of the sleeve 2 decreases considerably from D' in the old type VC roll to D.

Accordingly, in the VC roll according to the present invention, when extraordinary load, for instance caused by drawing out, occurs during rolling operation, the stress arising in the sleeve can be considerably reduced by letting the sleeve to be supported by the arbor which contacts the sleeve within the cavity. Accordingly, the VC roll according to the present invention can be used even in mills in which extraordinary load tends to occur.

It is difficult to determine the value of deflection Sof the sleeve accurately. However, the value Scan be estimated theoretically on the basis of the following conception, the value of maximum deflection 5may be a sum of bending deflection (YB) due to a rolling load, shearing deflection (Ys), and flattening (wax) of the roll sleeve (d = YB + Ys + 6,). Each term is calculated as follows.

i. Bending deflection (YB) and shearing deflection (Ys) These two terms are determined by solving an equation of strength of materials assuming that a typical roll model is uniformly loaded.

ii. Flattening (8x) of roll sleeve Assuming that a concentrated load F is applied to the middle portion of the peripheral surface of a sleeve having mean radius R, thickness t, and length L, the flattening b(X) is expressed by the' following formula: 0.1 35FR2 6(X) = ~ e - lXx (cosy, + sins,) (1) Et3 where, E: Young's modulus ss = 0.31 25/R assuming that a load q per unit length of the sleeve is uniform over a very small length Ax.

When the load is not concentrated, F is replaced by q.A in the formula (1). Assuming that a force q' acts against a depression by the load q from the inside in the shrinkage-fitted portion of the sleeve. the value b(X) is obtained determining the value of q' in such a manner that each of the integrated values of the formula (1) by q.a, and q'.A is zero at the shrinkage-fitted end, C and C' Fig. 11 shows graphically an example of the relationship between the rolling load (ton) and the increase in the stress Aa (kg/mm2) of the inner surface of the sleeve of the VC roll which is used as a back up roll in a 4 high mill. Dimension of the rolls used was as follows: Work Roll Diameter 700 mm X Drum length 2032 mm XAverage bearing distance 3124 mm X Overall length 5435.

Back Up Roll Diameter 1382 mm X Drum Length 2032 mm X Average bearing distance 3124 mm X Overall length 5435.

Width of the rolled material was 1000 mm.

While we have shown and described specific embodiments of our invention, it will be understood that these embodiments are merely for the purpose of illustration and explanation and that various other forms may be devised within the scope of our invention, as defined in the

Claims

claims. CLAIMS

1. A variable crown roll comprising: an arbor; a sleeve shrinkage-fitted on said arbor; an annual cavity defined between said arbor and said sleeve and having a predetermined depth; a medium leading-in passage provided at an end of said arbor and communicated with an end of said carvity; and a medium ieading-out passage communicated with the other end of said cavity; the depth of said cavity being predetermined to a value smaller than the value of maximum deflection of said sleeve due to an extraordinary load which occurs during rolling under a normal value of roll crowning.

2. A variable crown roll as set forth in claim 1. in which said medium leading-out passage is provided in an axial portion at the other end of said arbor and communicated with the other end of said cavity through radial passages.

3. A variable crown roll as set forth in claim 1, in which said medium leading-out passage is provided in the said arbor just under the periphery of the other end of said arbor and communicated directly with the other end of said cavity

4. A variable crown roll as set forth in claim 1, in which said medium leading-out passage is provided in the said sleeve and communicated directly with one end of said cavity.

5. A variable crown roll as set forth in claim 1, in which a first portion of said medum leading-out passage is provided in the said arbor just under the periphery of the arbor, a second portion of said passage is provided at one end of said sleeve, said first and second portions are communicated with each other, and said first portion is communicated with the other end of said cavity.

6. A variable crown roll substantially as herein described with reference to and as illustrated in Fig. 1 or Fig. 2, 3 or Fig. 4, 5 or Fig. 6, 7, and Figs. 8 to 11.