GB1571752A - Method of rolling billets adapted to be rolled into bar sections - Google Patents

Description

(54) METHOD OF ROLLING BILLETS ADAPTED TO BE ROLLED INTO BAR SECTIONS (71) We, DONETSKY POLITEKH NICHES SKY INSTITUT, of ulitsa Artema, 58, Donetsk, and TSENTRALNY NAUCHNO-IS SLED OVATELSKY IN STITUT CHERNOI METALLURGII IMENI I.P. BARDINA, of 2 Baumanskaya ulitsa 9/23, Moscow, both Union of Soviet Socialist Republics, both Corporations organised and existing under the laws of the Union of Soviet Socialist Republics, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a method of rolling billets adapted to be rolled into bar sections. The invention is suitable for application in a combined process of continuous casting and rolling where billets are produced from ferrous and non-ferrous metaIs and alloys. The invention is also applicable in blooming mills, blooming-slabbing mills, continuous billet mills, and in the roughing groups of bar and rod mills.

The present invention provides a method of rolling billets adapted to be rolled into bar sections, in which billets transversely interconnected by bridges are formed from a slab in a plurality of grooves each defined by a plurality of transversely juxtaposed passes between two rolls, to thereby form a number of billets capable of being severed into individual billets by being displaced relative to one another in the direction of their longitudinal axes, the thickness of the bridges being from 0.005 to 0.1 times the height of the original slab.

Displacement of the billets relative to one another may be effected by way of imparting to adjacent billets rolling speeds differing from one another by a factor of at least 1.04.

Alternatively, billets may be displaced relative to one another by. subjecting one or more billets to rolling while preventing linear movement of one or more other billets adjacent thereto.

The method of the invention and various embodiments thereof make it possible to produce billets with good surface quality in the zone of separation, to enhance production efficiency of rolling mills, and lower the production costs of the billets rolled into small sections.

Prior to displacing the billets relative to one another in the direction of the longitudinal axes thereof, stress raisers are preferably formed in the bridges. This operation facilitates the separation of the billets one from another, as well as improving their quality.

It has been found effective to displace some of the billets relative to one another in direction of their longitudinal axes by rolling the adjacent billets with different degrees of reduction. In this case it is preferably for the cross-sectional areas of the adjacent billets to differ from one another by a factor of from 1.05 to 1.5, the billets of larger cross-section being alternated with those of the smaller cross-section. This simplifies the process of separating the interconnected billet individual billets as well as performing automation of the rolling process.

Preferably, the billets are formed so that the billets of square cross-section alternate with the billets of rhombic cross-section having equal horizontal diagonals, the vertical diagonals of the rhomboids exceeding in size respective diagonals of the squares by a factor of from 1.1 to 1.5, with the billets being one fewer than the number of passes in a multipass groove. This permits the grooves to be reduced in number and, consequently, the production cost of a billet to be cut.

The invention will be described further, by way of example only, with reference to the accompanying drawings, in which: Figure 1 schematically illustrates the process of rolling a slab in a three pass groove; Figure 2 is a view of interconnected billets prior to being separated; Figure 3 is a schematic view of the billets being displaced relative to one another in the direction of their longitudinal axes; Figure 4 schematically illustrates the process of rolling a slab in a four-pass groove having round passes; Figure 5 schematically illustrates the process of rolling a billet as the latter is concurrently separated into individual billets; Figure 6 schematically illustrates the process of rolling billets of rhombic cross section in a three-pass groove of square pass crosssection; Figure 7 schematically illustrates the process of separating billets by way of fixing in position part of the billets and subjecting the adjacent billets to rolling; Figure 8 schematically illustrates the pro cess of rolling billets, while stress raisers are formed in the bridges between the billets; Figure 9 schematically illustrates the process of rolling as billets of different crosssectional areas are concurrently separated; Figure 10 schematically illustrates the process of rolling a billet on a roughing mill with the number of passes in a multi-pass groove thereof exceeding by one the number of billets; and Figure 11 shows individual billets resultant from the longitudinal separation of a slab in multi-pass grooves.

Example 1.

A slab 3 is advanced repeatedly through the zone of deformation formed by rolls 1 and 2 (Figure 1). The rolls 1 and 2 form a multi pass groove 4. The multi-pass groove 4 con sists of three transversely aligned passes 5, 6s and 7, each in the form of a square.

By narrowing the gap between the rolls 1 and 2, the slab 3 is gradually reduced in thickness until three billets 8, 9, and 10, interconnected by bridges, are obtained (see Figure 2). The rolls 1 and 2 (Figure 2) are designed so that, with the thickness of the bridges being 0.005 to 0.1 times the height of the original slab 3, the billets 8, 9, and 10 (Figure 2) assume the shape and dimensions conforming to the finished billets adapted to be rolled into small sections.

After the bridges between the billets 8, 9, 10 (Figure 3) have been reduced to the prescribed thickness, the billets are displaced relative to one another in the direction of their longitudinal axes. The billets 8 and 10 are preferably displaced in one direction (shown in Figure 3 by arrows), whereas the billet 9 is displaced in the opposite direction. The displacement of the billets 8, 9, 10 relative to one another can be carried out on a hori- zontal press, after the billets 8, 9, and 10 have been cut to lengths.

Thus, the displacement of the billets 8, 9, 10 gives rise to shearing stress which acts in the zone of the bridges between the billets to cause their separation from one another.

The shearing deformation acting in the direction of longitudinal axes of the billets 8, 9, 10 provides for the production of billets for rolling into small sections on bar and rod mills, having high surface quality at their zones of separation.

It is possible to effect the displacement of billets by imparting to adjacent billets rolling speeds which will differ from one another by a factor of at least 1.04.

Example 2.

A slab 3, preheated to rolling temperature, is advanced through rolls 11 and 12 (Figure 4). The rolls 11 and 12 are formed with a multi-pass groove 13. The multi-pass groove 13 consists of four transversely aligned ovalshaped passes 14, 15, 16, and 17. Where a single stand two-high reversing mill is used, four billets 18, 19, 20, 21 (Figure 5) are formed as the gap between the rolls 11 and 12 is reduced from stage to stage. The billets 18, 19, 20, 21 are interconnected by bridges.

If a continuous mill train system is used, then each successive groove will have to he smaller in height than the preceding one. By rolling the slab 3 (Figure 4) in a plurality of stages, four interconnected billets 18, 19, 20, 21 (Figure 5) are gradually formed. After the thickness of the bridges between the billets 18, 19, 20, 21 has become 0.005 to 0.1 times the height of the original slab 3, the interconnected billets are advanced into a multi-pass groove 22 wherein the billets are reduced in thickness to one and the same value. The speed of rolling of the billets 18 and 20 is equal to the rotation speed of the rolls 11 and 12. The speed of rolling of the billets 19 and 21 is reduced by applying a braking force to the end portions of these billets.

It has been experimentally found that stable conditions for the separation of billets are created with the ratio of rolling speeds imparted to adjacent billets being not less than, 1.04 to 1.

The rolling of adjacent billets at different speeds causes their separation from one another, with the surface quality at their zones of separation remaining satisfactory.

Example 3.

Where blooming mills are used for rolling, it is advisable to displace the billets relative to one another in the direction of their longitudinal axes by way of rolling some of the billets and preventing from linear movement a billet or billets adjacent thereto.

In this case, for example, several billets 23, 24, and 25 (Figure 6) are formed from a slab, which billets are interconnected by bridges. The thickness of the bridges is 0.005 to 0.1 times the height of the original slab.

Thereafter, the interconnected billets 23, 24, and 25 are subjected to rolling in a groove 26, reducing the billets in thickness to one and the same value. The billet 24 is fixed in position after the exit ends of the billets 23, 24, and 25 pass beyond the plane of the axes of rolls 27 and 28 (Figure 7). The fixing of the billet 24 in position is effected, for example, with the aid of a retracting stop 29 provided on the downstream end of the roll mill stand.

The procedure of rolling one billet while holding in position an adjacent billet is essentially similar to the procedure of rolling the billets at different rolling speeds, since in both cases there is a difference in rolling speeds imparted to adjacent billets to cause their mutual displacement and ultimate separation from one another.

To ensure faultless separation of the billets, the force with which the billets are advanced between the rolls should exceed that required for displacing the billets along their longitudinal axes.

Example 4.

It has been found effective to form, in the process of rolling, stress raisers in the bridges between the billets prior to displacing them relative to one another in the direction of their longitudinal axes. Billets 30, 31, and 32 are formed in multi-pass grooves until the thickness of the bridges therebetween is 0.005 to 0.1 times the height of the original slab.

Formed in a roughing groove 33 (Figure 8) at the places of bridges between the billets 30, 31, 32 are stress raisers 34 and 35. The stress raisers 34 and 35 are formed over the entire length of the bridges, assuming the form of, for example, V-shaped indentations.

After the stress raisers 34 and 35 have been formed, the billets 30, 31, 32 are displaced relative to one another in the direction of their longitudinal axes. The formation of the stress raisers facilitates the separation of the billets 30, 31, 32 from one another, and provides for better surface quality at their zones of separation.

Example 5.

In a number of cases, for example in continuous mills, billets are preferably separated from one another by rolling the adjacent billets with various degrees of reduction. In several passes a siab is formed into three billets 36, 37, 38 (Figure 9). The billets 36, 37, 38 are interconnected by bridges with the thickness thereof being 0.005 to 0.1 times the height of the original slab. The billets 36 and 38 are rhombic in cross-section; the billet 37 is square in cross-section. The cross-sectional areas of the billets 36 and 38 are equal and are from 1.05 to 1.5 times the cross-sectional area of the billet 37.

The billets 36, 37,. 38 are thereafter subjected to finishing rolling in a groove 39, with the degree of deformation applied in the course of reducing the billets 36 and 38 being sufficient to give them the same crosssection as the billet 37. Preferably, linear reduction ob the billets 36 and 38 effected in the square-shaped passes of the groove 39 causes linear shear deformation to appear in the zone od the bridges wherein the separation of the billets into individual billets occurs.

Example 6.

Where roughing mills are used with a limited number of grooves in their rolls it is advantageous that, prior to obtaining a prescribed thickness of the bridges in the process of rolling billets, individual billets should be formed of square and rhombic cross-section having equal horizontal diagonals, the vertical diagonals of the rhombs exceeding in size respective diagonals d the squares by 1.1 to 1.5 times; the number of billets is less by one than the number of passes in a multi-pass groove.

Rolled in a multi-pass groove 40 (Figure 10) in the form of alternating rhombs and squares is a slab 3. Billets 41, 42, and 43 are formed in the process of rolling. Horizontal diagonals of the billets 41, 42, 43 are equal, whereas vertical diagonals of the billets 41 and 43 are 1.2 to 1.5 times larger than respective diagonal ob the billet 42. Thence, after the prescribed thickness of the bridges has been obtained, the interconnected billets 41, 42, 43 are displaced by one pass along the axes of the rolls, while the rhomb-shaped billets 41 and 43 are rolled in the square passes of the roll groove 40. In the course of rolling the billets 41 and 43 are reduced with the degree of deformation of 1.2 to 1.5, and due to substantial shear deformation the billets 41, 42 and 43 are separated from one another into individual billets 41, 42, 43 (Figure 11).

AtHAT WE CLAIM IS: 1. A method of rolling billets adapted to be rolled into bar sections, in which billets transversely interconnected by bridges are

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. The rolling of adjacent billets at different speeds causes their separation from one another, with the surface quality at their zones of separation remaining satisfactory. Example 3. Where blooming mills are used for rolling, it is advisable to displace the billets relative to one another in the direction of their longitudinal axes by way of rolling some of the billets and preventing from linear movement a billet or billets adjacent thereto. In this case, for example, several billets 23, 24, and 25 (Figure 6) are formed from a slab, which billets are interconnected by bridges. The thickness of the bridges is 0.005 to 0.1 times the height of the original slab. Thereafter, the interconnected billets 23, 24, and 25 are subjected to rolling in a groove 26, reducing the billets in thickness to one and the same value. The billet 24 is fixed in position after the exit ends of the billets 23, 24, and 25 pass beyond the plane of the axes of rolls 27 and 28 (Figure 7). The fixing of the billet 24 in position is effected, for example, with the aid of a retracting stop 29 provided on the downstream end of the roll mill stand. The procedure of rolling one billet while holding in position an adjacent billet is essentially similar to the procedure of rolling the billets at different rolling speeds, since in both cases there is a difference in rolling speeds imparted to adjacent billets to cause their mutual displacement and ultimate separation from one another. To ensure faultless separation of the billets, the force with which the billets are advanced between the rolls should exceed that required for displacing the billets along their longitudinal axes. Example 4. It has been found effective to form, in the process of rolling, stress raisers in the bridges between the billets prior to displacing them relative to one another in the direction of their longitudinal axes. Billets 30, 31, and 32 are formed in multi-pass grooves until the thickness of the bridges therebetween is 0.005 to 0.1 times the height of the original slab. Formed in a roughing groove 33 (Figure 8) at the places of bridges between the billets 30, 31, 32 are stress raisers 34 and 35. The stress raisers 34 and 35 are formed over the entire length of the bridges, assuming the form of, for example, V-shaped indentations. After the stress raisers 34 and 35 have been formed, the billets 30, 31, 32 are displaced relative to one another in the direction of their longitudinal axes. The formation of the stress raisers facilitates the separation of the billets 30, 31, 32 from one another, and provides for better surface quality at their zones of separation. Example 5. In a number of cases, for example in continuous mills, billets are preferably separated from one another by rolling the adjacent billets with various degrees of reduction. In several passes a siab is formed into three billets 36, 37, 38 (Figure 9). The billets 36, 37, 38 are interconnected by bridges with the thickness thereof being 0.005 to 0.1 times the height of the original slab. The billets 36 and 38 are rhombic in cross-section; the billet 37 is square in cross-section. The cross-sectional areas of the billets 36 and 38 are equal and are from 1.05 to 1.5 times the cross-sectional area of the billet 37. The billets 36, 37,. 38 are thereafter subjected to finishing rolling in a groove 39, with the degree of deformation applied in the course of reducing the billets 36 and 38 being sufficient to give them the same crosssection as the billet 37. Preferably, linear reduction ob the billets 36 and 38 effected in the square-shaped passes of the groove 39 causes linear shear deformation to appear in the zone od the bridges wherein the separation of the billets into individual billets occurs. Example 6. Where roughing mills are used with a limited number of grooves in their rolls it is advantageous that, prior to obtaining a prescribed thickness of the bridges in the process of rolling billets, individual billets should be formed of square and rhombic cross-section having equal horizontal diagonals, the vertical diagonals of the rhombs exceeding in size respective diagonals d the squares by 1.1 to 1.5 times; the number of billets is less by one than the number of passes in a multi-pass groove. Rolled in a multi-pass groove 40 (Figure 10) in the form of alternating rhombs and squares is a slab 3. Billets 41, 42, and 43 are formed in the process of rolling. Horizontal diagonals of the billets 41, 42, 43 are equal, whereas vertical diagonals of the billets 41 and 43 are 1.2 to 1.5 times larger than respective diagonal ob the billet 42. Thence, after the prescribed thickness of the bridges has been obtained, the interconnected billets 41, 42, 43 are displaced by one pass along the axes of the rolls, while the rhomb-shaped billets 41 and 43 are rolled in the square passes of the roll groove 40. In the course of rolling the billets 41 and 43 are reduced with the degree of deformation of 1.2 to 1.5, and due to substantial shear deformation the billets 41, 42 and 43 are separated from one another into individual billets 41, 42, 43 (Figure 11). AtHAT WE CLAIM IS:

1. A method of rolling billets adapted to be rolled into bar sections, in which billets transversely interconnected by bridges are

formed from a slab in a plurality of grooves each defined by a plurality of transversely juxtaposed passes between two rolls, to thereby form a-number of billets capable of being severed into individual billets by being dis placed relative to one another in the direction of their longitudinal axes, the thickness of the bridges being from 0.005 to 0.1 times the height of the original slab.

2. A method as claimed in claim 1, wherein adjacent billets are subsequently displaced relative to one another by imparting to the said billets rolling speeds differing from each other by a factor of at least 1.04.

3. A method as claimed in claim 1, wherein adjacent billets are subsequently displaced relative to each other by subjecting one billet to rolling while preventing linear movement of the other.

4. A method as claimed in claim 1, wherein stress raisers are formed in the bridges.

5. A method as claimed in claim 1, wherein adjacent billets are subsequentlv disolaced relative to each other in the direction of their longitudinal axes by rolling the adjacent billets with different degrees of reduction.

6. A method as claimed in claim 5, wherein the cross-sectional area of the interconnected adjacent billets differ from each other by a factor of from 1.05 to 1.5.

7. A method as claimed in claim 6, wherein, -before relative displacement, billets of square cross-section alternate with billets of rhombic cross-section having equal horizontal diagonals, the vertical diagonals of the rhomboids exceeding in size respective diagonals of the squares by a factor of from 1.1 to 1.5, the number of billets being one fewer than the number of passes in a multi-pass groove.

8. A method of rolling billets adapted to be rolled into bar sections, substantially as described in any of the Examples.