AU2003235800A1

AU2003235800A1 - Method and rolling stand for producing rods, bar stock or seamless tubes

Info

Publication number: AU2003235800A1
Application number: AU2003235800A
Authority: AU
Inventors: Manfred Leferink
Original assignee: SMS Meer GmbH
Current assignee: SMS Group GmbH
Priority date: 2002-01-09
Filing date: 2003-01-08
Publication date: 2003-07-24
Anticipated expiration: 2023-01-08
Also published as: BR0306683A; AU2003235800B2; PL369431A1; ES2243904T3; EP1463591B1; WO2003057383A1; PL203879B1; ATE296689T1; EP1463591A1; RU2274503C2; BR0306683B1; RU2004124048A

Abstract

The invention relates to a method for producing rods, bar stock or seamless tubes on a rolling stand for rolling hot metal material. Said rolling stand optionally comprises, when seen in the direction of rolling, a piercing-crossrolling mill, a multiple-stand stretch-rolling mill as the main stretching stage (4), a drawing mill (6), a finishing mill (10) and a rod rolling block (15) and devices, mounted upstream, intermediately or downstream thereof, such as a preheating furnace and a reheating furnace (11), roller tables (14) and a cooling bed (13). According to the inventive method, in the main stretching stage (4), a three-roller continuous rolling mill (3) is used both for rolling tubes and for massive rolling for producing bar stock, rods or the like. For massive rolling, the mandrel bar used for tube milling is brought out of the operative position and the provided bar stock rolls calibrated for a larger diameter reduction than used for tube milling are replaced by rolls calibrated for tube milling. A rolling mill suitable for carrying out the inventive method has, in the main stretching stage (4), a multi-stand three-roller continuous rolling mill (3) adapted to receive bar stock rolls or tube rolls and a device for removing the mandrel bar.

Description

CERTIFICATE OF TRANSLATION Wo o0 3 /os-7,91 4 I, Roland Meier, c/o Technisches Fach0bersetzungsbiro, Forsterweg 33, A-2136 Laa/Thaya, Austria, fully conversant with the English and German languages, am the translator of the documents attached and certify that the following is a true translation to the best of my knowledge and belief. Signature of translator Dated this Z day of 200q WO 03/057383 METHOD AND ROLLING STAND FOR PRODUCING RODS, BAR STOCK OR SEAMLESS TUBES The invention relates to a method and a rolling stand for producing rods, bar stock or seamless tubes on a rolling stand for rolling hot metal material. Said rolling stand optionally comprises, when seen in the direction of rolling, a piercing-rolling mill, a multiple-stand stretch-rolling mill as the main stretching stage, a drawing mill, a finishing mill and a rod rolling block and devices, mounted upstream, intermediately or downstream thereof, such as a preheating furnace and a reheating furnace, roller tables, separation devices and a cooling bed. In order to achieve better utilisation of the rolling stand, and in order to no longer require a rolling stand for producing tubes, which rolling stand differs from a rolling stand for producing rods, bar stock or the like, DE 199 35 647 Al discloses that rolling of rods, bar stock and the like as well as rolling of seamless tubes is carried out on the same rolling stand in two rolling lines, with part of the units of the plant being used both for rolling tubes (seamless tubes) and for massive rolling (rods, bar stock or the like). While in this way the number of units required in total can be reduced, for example because devices which are present in the rolling stand - such as furnaces, separation devices, the cooling bed and sections of the roller tables - can be universally used, nonetheless, behind the furnace which heats the rolling stock to rolling temperature and behind a transverse transport device arranged downstream of said furnace, a rolling line for rods or bar stock and a rolling line for tubes are required, i.e. two separate rolling lines beside each other and parallel to each other. It is only much later in the material flow, i.e. in the direction of rolling, that these two rolling lines are again brought together to form a common rolling line. It is thus the object of the invention to create a rolling method and a rolling stand of the type mentioned in the introduction which allow optimal operation with further reduced equipment expenditure. This object is met with a method according to the invention in that in the main stretching stage a three-roller continuous rolling mill is used both for rolling tubes and for massive rolling for producing bar stock, rods or the like, wherein for massive rolling, a mandrel bar used for tube rolling is brought out of the Confirmation copy -2 operative position and the provided bar stock rolls calibrated for a larger diameter reduction than used for tube rolling are replaced by rolls calibrated for tube rolling. "Continuous rolling mill", sometimes also referred to as "continuous tube rolling mill" refers to a rolling mill comprising several stands of rolls with a mandrel bar arranged on the inside, as has for example become known by DE Z "Berg- und H~ttenmannische Monatshefte" 130 (1985) vol. 7, pp. 205 to 211. While in the known rolling stand the massive line is arranged so as to be separate from the tube rolling line, according to the invention a single line can be used for both purposes. This results in a significant reduction not only in investment expenditure but also in operating and maintenance expenditure. The idea of the invention is based on rigorous exploitation of the three-roller technology, because it is recognised that despite conflicting requirements (during tube milling the external diameter is usually changed little so as to avoid process-inherent disadvantages, while very significant stretching results due to the central hole; while during massive rolling a large diameter-reduction has to be ensured in order to achieve the necessary stretch) universal rolling is possible. It is further recognised that, when compared to conventional piercing crossrolling mills comprising two-roller stands, the method according to the invention does not result in tensile strain but in compressive strain in the core zone of the material, so that there is a considerable reduction in the danger of internal faults occurring. The strain behaviour in the rolling stock during rolling in two-roller or three-roller crossrolling mills is described in detail in "Herstellung von Rohren", Verlag Stahleisen 1975, pp. 28 to 31. When changing from one type of rolling to the other, the invention provides for different rollers for tube rolling and for massive rolling, wherein, due to matched different calibration, the cross-section is different, but the external shape remains the same so that a simple changeover becomes possible. The concrete number of the three-roller arrangements or three-roller stands in the main stretching stage depends on the desired degree of stretch, wherein the pass reduction or the reduction distribution differs between rolling bar stock and rolling tubes. The measures which have to be arranged for this, and which depend on the ingot or hollow ingot and the respective materials properties, are well known.

-3 An advantageous embodiment of the method according to the invention provides for a three-roller piercing-rolling mill to be used, whose piercing rollers, for the purpose of massive rolling, with the piercing mandrel removed, are exchanged for the provided bar stock rolls calibrated for a diameter reduction. In a piercing-rolling mill, the three-roller piercing-rolling mill according to the invention then makes possible, with the piercing mandrel brought out of the operative position, the production of different bar stock diameters in the sense of a prereduction, i.e. a proportional cross-sectional reduction related to the total reduction of all rolling mills involved. Thus, the piercing-crossrolling mill, too, fulfils a universal function. According to the invention, a rolling stand for implementing the method in the main stretching stage comprises a multiple-stand three-roller continuous rolling mill for accommodating bar stock rolls or tube rolls, and a device for bringing the mandrel bar out of the operative position. The continuous rolling mill or the main stretching stage accommodates in one frame either one or the other roll stands or roller sets, each comprising three rollers. For changeover, respective stands can be provided beside the continuous rolling mill, wherein said stands then, after the previous stands have been withdrawn, are brought from the frame into the operating position. As an alternative, a cassette design or the exchange of the rollers only, while the roll-stand housings remain in the frame, is also possible. During changeover of the three-roller continuous rolling mill to carry out massive rolling, the mandrel bar can be moved out of the operative position, in the simplest case with the assistance of the mandrel bar holding device. This also applies to the piercing mandrel of the piercing-rolling mill, which in the case of tube rolling is optionally arranged upstream of the main stretching stage, with said piercing-rolling mill according to one embodiment of the invention also being a universally useable three-roller piercing-rolling mill. A preferred embodiment of the invention provides for a speed control device to be associated with the three-roller continuous rolling mill of the main stretching stage. In this way advantageously the different rolling speeds required for tube rolling and bar stock rolling can be implemented. If advantageously the drawing mill arranged behind the main stretching stage comprises two roll-stand units, spaced apart from each other, with end shears that can be slid into place arranged in-between, then, during massive rolling, -4 bad ends can simply be cut off before rolling is continued. In contrast to this, the shears are not used during tube rolling. Advantageously, the drawing mill is followed by a reheating furnace. From there, the heat-treated steel bar stock or for example alloyed or unalloyed steel tubes reach the finishing mill. This can be a sizing mill, a reducing mill, a stretch reducing mill or a combination of these units. If a bar stock is to be rolled to form rods, according to the invention a roller table which leads to the rod block is arranged behind the cooling bed. Further details of the invention result from the drawing, which in a sole figure diagrammatically shows a rolling stand according to the invention in top view. The universal rolling stand shown in the diagram processes in one line (in other words, different from the situation shown in the drawing, the mill part shown in the lower half of the figure follows in linear arrangement from the upper half of the drawing as shown by the meandering line) supplied feed stock (an ingot) either to produce seamless tubes or to produce bar stock, rods or some similar massive rolled stock. The figure shows a furnace 1 comprising a charging device 2 for the feed stock to be rolled, i.e. the ingots e.g. made from a continuous-cast material. In the furnace, the ingots are heated to rolling temperature. In the embodiment shown, from that location a heated ingot to be used is fed to a piercing-crossrolling mill which is a three-roller piercing-rolling mill 3, where the ingot is guided by a feed channel and, by rolling onto a mandrel bar which comprises a piercing mandrel, is formed to a hollow ingot in preparation for subsequent rolling to form a seamless tube. Such a piercing-rolling mill 3 in three-roller design is known for the production of tubes. If instead of rolling tubes, either bar stock or rods is/are to be rolled, massive reduction of the ingot and compression of the microstructure takes place in the three-roller piercing-rolling mill 3 while the piercing mandrel is held back from, or brought out of, the rolling line. From the three-roller piercing-rolling mill 3, charging of the hollow ingots or of the massive ingots takes place into the downstream rolling devices. They comprise a main stretching stage 4 which in this embodiment is a six-stand -5 three-roller continuous rolling mill 5. However, other roll-stand numbers are also possible. The continuous rolling mill 5 is followed by a drawing mill 6 which in this embodiment comprises two roll-stand units 6a, 6b, arranged so as to be spaced apart from each other. Slide-in end shears 8, 9 are provided both between the multiple-stand three-roller continuous rolling mill 5 and the drawing mill 6, and between the two roll-stand units 6a, 6b of the drawing mill 6. During tube milling, a hollow ingot is stretched in the six-stand three-roller continuous rolling mill 5, and after withdrawal of the mandrel bar, an action which is carried out by a mandrel bar holding device which moves to and fro, said hollow ingot is reduced as a tube billet in the two roll-stand units 6a, 6b of the drawing mill 6. In contrast to this, during massive rolling, the six-stand three roller continuous rolling mill 5 and the drawing mill 6 reduce the bar stock by reducing its diameter. Before the reduced tube billet or the reduced bar stock is finish-rolled in a sizing mill or a stretch reducing mill 10 to form a tube or bar, the rolled stock is heated to the required temperature in a reheating furnace 11. A cropping saw 12, which is arranged at the delivery end of the sizing mill or stretch reducing mill 10, divides the finished tube or the finish-rolled bar stock into the desired lengths. The finished lengths are then transferred to a cooling bed 13. However, if the bar stock is to be rolled into rods, the bar stock is fed to a rod block 15 by way of an extension in the cooling bed roller table 14. The described universal rolling stand thus makes it possible to roll both seamless tubes and bar stock or rods in one line. To this effect, during massive rolling in the six-stand three-roller continuous rolling mill 5, first the rolls calibrated for tube rolling are replaced by rolls which are calibrated for massive rolling, and the mandrel bar is brought out of the operative position, e.g. in that the mandrel bar holding device is moved to its withdrawn home position.

Claims

1. A method for producing rods, bar stock or seamless tubes on a rolling stand for rolling hot metal material, which rolling stand optionally comprises, when seen in the direction of rolling, a piercing-rolling mill, a multiple-stand stretch-rolling mill as the main stretching stage, a drawing mill, a finishing mill and a rod rolling block and devices, mounted upstream, intermediately or downstream thereof, such as a preheating furnace and a reheating furnace, roller tables, and a cooling bed, characterised in that in the main stretching stage (4) a three-roller continuous rolling mill (3) is used both for piercing when rolling tubes and for massive rolling for producing bar stock, rods or the like, wherein for massive rolling, a mandrel bar used for tube milling is brought out of the operative position and the provided bar stock rolls calibrated for a larger diameter reduction than used for tube milling are replaced by rolls calibrated for tube milling.

2. The method according to claim 1, characterised in that for a piercing-rolling mill which is mounted upstream of the main stretching stage (4), too, a three-roller continuous rolling mill (3) is used, whose piercing rollers, for the purpose of massive rolling, with the piercing mandrel removed, are exchanged for provided bar stock rolls calibrated for a diameter reduction usual when rolling bar stock.

3. A rolling stand for rolling hot metal material to form rods, bar stock or seamless tubes, which rolling stand optionally comprises, when seen in the direction of rolling, a piercing-rolling mill, a multiple-stand stretch rolling mill as the main stretching stage, a drawing mill, a finishing mill and a rod rolling block and devices, mounted upstream, intermediately or downstream thereof, such as a preheating furnace and a reheating furnace, roller tables, and a cooling bed, -2 characterised in that the main stretching stage (4) comprises a multiple-stand three-roller continuous rolling mill (5) for accommodating bar stock rolls or tube rolls, and a device (7) for removing the mandrel bar.

4. The rolling stand according to claim 3, characterised in that the piercing-rolling mill (3) mounted upstream of the main stretching stage (4) is a two-roller piercing-rolling mill or a three-roller piercing rolling mill for accommodating bar stock rolls or piercing rolls, and comprises a device for removing the mandrel bar.

5. The rolling stand according to claim 3 or 4, characterised in that a speed control device is associated with the three-roller continuous rolling mill (5) of the main stretching stage (4), which speed control device controls the roller speeds that are commonly required both in tube rolling and in bar stock rolling.

6. The rolling stand according to any one of claims 3 to 5, characterised in that the drawing mill (6) comprises two roll-stand units (6a, 6b), spaced apart from each other, with end shears (9) that can be slid into place in between.

7. The rolling stand according to any one of claims 3 to 6, characterised by -3 a reheating furnace (11) which is arranged downstream of the drawing mill (6).

8. The rolling stand according to any one of claims 3 to 7, characterised by a sizing mill and/or stretch reducing mill, arranged behind the reheating furnace (11), as a finishing mill (10) for tubes and bar stock.

9. The rolling stand according to any one of claims 3 to 8, characterised by an extension of the roller table (14), which extension is arranged behind the cooling bed (13) and leads to the rod block (15).