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Method and device for the deformation of semi-finished material in wire and rod form, close to the final dimensions, as well as a flat profile produced accordingly

Abstract: The invention relates to a method for shaping wire-shaped and rod-shaped starting materials by rolling, especially for rolling flat profiled elements consisting of a wire rod. The starting material is heated in a heating station at a desired temperature, shaped during at least one rolling process, and then cooled. According to the invention, once the starting material has been heated in the heating station, it is cooled in a cooling station to a pre-determinable rolling temperature; it is then shaped into a flat profiled element by rolling close to the gauge block, and then cooled and/or subjected to a subsequent treatment according to joining properties to be correspondingly adjusted. In this way, a series of different methods can be carried out by means of an installation for rolling starting materials with a patented structure, an austenite structure, a bainite structure or an undercooled austenite structure. ...

Agent: William Collard Collard & Roe, P.C. - Roslyn, NY, US
Inventors: Hans-Toni Junius, Heinz Hofinghoff, Norbert Brachthauser, Victor Blinov, Rudolf Kawalla
USPTO Applicaton #: #20080006350 - Class: 148559000 (USPTO) - 01/10/08 - Class 148
Related Terms: Austenite

Related Patent Categories: Metal Treatment, Process Of Modifying Or Maintaining Internal Physical Structure (i.e., Microstructure) Or Chemical Properties Of Metal, Process Of Reactive Coating Of Metal And Process Of Chemical-heat Removing (e.g., Flame-cutting, Etc.) Or Burning Of Metal, Heating Or Cooling Of Solid Metal
The Patent Description & Claims data below is from USPTO Patent Application 20080006350, Method and device for the deformation of semi-finished material in wire and rod form, close to the final dimensions, as well as a flat profile produced accordingly.

Austenite

[0001] The present invention relates to a method for the deformation of semi-finished material in wire and rod form, close to final dimensions, in accordance with the preamble of claim 1, to a device suitable for carrying out the method, in accordance with claim 26, as well as to a flat profile produced according to the method, in accordance with claim 38.

[0002] The production of relatively narrow and flat strips of steel materials, referred to hereinafter as flat profiles, can take place in different ways, depending on the material properties that are required, the dimensions of the flat profiles to be produced, and the purpose of use of the flat profiles. Flat profiles are usually understood to mean profile shapes in which the width of the cross-section is not greater than 10-20 times the thickness. Such flat profiles are used for functional components and, in many instances, also for wear components in technical devices, e.g. for springs or similar components in the automotive, aircraft, and space industry, in equipment construction, and in agricultural machine construction. Also, such flat profiles are used as the starting material for the production of saws, saw blades, bush chains for motorcycles and bicycles, rollers, roller bearings, ski edges, or also for piston rings. Frequently, these flat profiles are components subject to great mechanical stress, whose strength properties are of central significance, in addition to the adherence to required cross-sectional shapes and dimensions.

[0003] In the case of properties that are usually required, such flat profiles are frequently cut out of wide steel strips, by means of dividing them lengthwise, making it possible to use commercially available steel strips as the starting material, which can be brought to the appropriate dimensions by means of known hot-rolling and/or cold-rolling processes. Setting of the material properties is generally also not problematic in the case of such steel strips, since the material of the flat profiles does not change in comparison with that of the steel strips when it is divided lengthwise.

[0004] However, such flat profiles have the disadvantage of not demonstrating certain configurations of the edges of the flat profiles that are required or advantageous on the basis of the later use of the flat profiles, which configurations certainly have important advantages for the fitness for use and/or useful lifetime of the components produced from them. Thus, after the lengthwise division of steel strips from broad steel strips, an edge shaping must be worked on, as an extra step, by means of additional machining processes after the lengthwise division, and this causes additional costs.

[0005] Another possibility for the production of such flat profiles consists in drawing the materials, as wire, through appropriately formed drawing dies, which produce the required profile cross-sections and their precise geometry, as well as the edge configuration, automatically. Problems in connection with the drawing of corresponding flat profiles, which is otherwise wide-spread for wire production, are, for one thing, the relatively low drawing speeds that can be reached, due to the wear of the drawing molds that otherwise occurs, and for another, the cold-solidification of the materials that occurs when drawing corresponding materials, because of transformation, which can only be made retroactive again by means of complicated intermediate heat treatments of the drawn wires. As a result, such production of flat profiles is complicated and technically not without problems.

[0006] It is furthermore known to produce corresponding flat profiles by means of cold-rolling, in that a starting material structured as a round wire, for example, is gradually transformed into a flat profile by means of cold-rolling, by means of relatively slight reductions in cross-section, as a function of the deformation, in each instance. In this connection, it is also possible to guarantee the dimensions and the required edge configurations by means of appropriate guidance of the technology. However, as in the case of all cold-rolling methods, it is a disadvantage that the cold-rolled materials are subject to corresponding cold solidification, as in the case of drawing, and therefore also have to undergo intermediate treatment, analogous to the heat treatment that is necessary for drawing. Particularly in the case of great changes in cross-section, however, this frequently makes intermediate annealing of the materials necessary during the course of cold-rolling.

[0007] Therefore, an approach for the further development of rolling flat profiles from wire-like starting material has become known, in which hot-rolling is carried out instead of cold-rolling, according to EP 0 314 667 B2, in order to carry out the significant cross-section changes during transformation of the wire-like starting material in the hot state of the material, in which it is significantly easier to deform. For this purpose, the wire-like starting material is heated to a temperature of at most A.sub.1 or to the conversion temperature, into the .gamma. region of the alloy, and then rolled in a multiple frame. Subsequently, the rolled flat profile can then be cooled. A disadvantage of this method of procedure is that while it is possible to carry out the deformation relatively true to final dimensions, control of the material properties of the material is anything but simple-in the case of such process management. Also, the processing of steel materials is limited to only specific material classes.

[0008] It is therefore the task of the present invention to indicate a method for the deformation of semi-finished material in wire and rod form, close to final dimensions, which combines the advantages of the hot-forming of semi-finished material in wire and rod form with the adherence to the process management relevant for the material characteristic values, and thereby allows the production of a great number of different material and work piece properties, which can nevertheless be set in very uniform manner.

[0009] The solution for the task according to the invention is evident, with regard to the method for continuous tempering of strip steel, from the characterizing features of claim 1, with regard to the device suitable for carrying out the method, from the characterizing features of claim 26, as well as with regard to a flat profile produced in such a manner, from the characterizing features of claim 38, in interaction with the characteristics of the related preamble, in each instance. Further advantageous embodiments of the invention are evident from the dependent claims.

[0010] The invention according to claim 1 proceeds from a method for the deformation of semi-finished material in wire and rod form, by means of roller technology, particularly for rolling of flat profiles from rolled wire, in which heating of the semi-finished material to a desired temperature takes place in a heating station, the semi-finished material is deformed in at least one rolling process, and subsequently cooled. A method of this type is further developed in that after heating of the semi-finished material in the heating station, the semi-finished material is cooled to a rolling temperature, in a cooling station, deformed into a flat profile at this rolling temperature, close to the final dimensions, and subsequently is cooled and/or post-treated in accordance with the microstructure properties that are to be set. By means of the targeted cooling of the material to the desired rolling temperature before the rolling process is carried out, it can be achieved, despite the prior heating of the material to a temperature required to trigger the desired microstructure conversions, which is generally a higher temperature, that precisely the starting microstructure can be set, before rolling of the semi-finished material, which guarantees the desired microstructure properties of the flat profile, together with the change in the material due to rolling and any post-treatment that might follow the rolling. In this connection, a corresponding microstructure conversion is assured, by means of heating the semi-finished material to a temperature that guarantees reliable austenitization, for example, above the A.sub.3 temperature, which then sets a microstructure state, by means of targeted cooling of the semi-finished material to the temperature required for rolling, which essentially allows the starting basis for changing the microstructure of the flat profile to the finished cross-section, close to the final dimensions. Here, additional post-treatments such as cooling and hardening can also follow, which allow a further change in the microstructure properties. With this, a possibility has been found for combining deformation of flat profiles produced from steel materials, in the hot state, close to final dimensions, with a targeted adjustment of the microstructure with regard to characteristic material values, which minimizes the post-treatment of flat profiles produced in such a manner.

[0011] It is particularly advantageous if the heating of the semi-finished material takes place in the heating station to a temperature above the A.sub.3 temperature of the .gamma. mixed crystal (austenite). In this way, the most varied microstructures can be produced from the austenitized microstructure as the starting microstructure, before rolling of the semi-finished material, which correspond to the various properties of the steel material required for the typical uses of the flat profile, and thereby allow a broad area of use of flat profiles produced accordingly.

[0012] Another embodiment of the method according to the invention provides that the heating of the semi-finished material takes place in the heating station to a temperature in the range of the .alpha./.gamma. mixed crystal (ferrite/austenite). In this way, an advantageous starting microstructure can be set for the subsequent rolling, particularly for steels low in carbon.

[0013] It is also possible, in another embodiment, that the heating of the semi-finished material takes place in the heating station to a temperature just below the A.sub.1 point. In this way, other different processes of the microstructure conversion can be triggered during the rolling of the semi-finished material, which leads to another spectrum of the microstructure configuration of the rolled and possibly post-treated flat profile.

[0014] It is significantly advantageous for carrying out the method if round wire or oval wire is used as the semi-finished material. In this connection, round wire should be understood to be not only wire having a circular cross-section, which can be produced by means of rolling technology or drawing technology, for example, but rather in general, wire having any cross-section that is suitable for deformation into a flat profile by means of rolling technology. In this connection, corresponding oval wires have an oval cross-section. In this connection, the free spreading of the round wire or oval wire during roller processing is generally utilized in order to bring about required property changes with regard to the geometry of the flat profile, on the one hand, and, on the other hand, in order to bring about the required microstructure properties and, with them, the material properties of the finished flat profile. Such round wire or oval wire is a commercially available semi-finished material, and can be purchased commercially in many different compositions and alloys, thereby making the costs for such round wire or oval wire relatively advantageous.

[0015] It is possible, in this connection, that the round wire or oval wire runs through the process as a semi-finished material that can be wound up. In this way, essentially continuous processing of the round wire or oval wire, which is usually delivered on rings, is possible, which wire can be processed further as a wound-up coil of the finished flat profile, also as a finished material that can be wound up. In another embodiment, however, it is also possible that the round wire or oval wire runs through the process as a rod-like semi-finished material, whereby the rod-like semi-finished material also yields rod-like flat profiles, accordingly.

[0016] It is advantageous if unalloyed or low-alloyed carbon steels are used as the semi-finished material. Such unalloyed or low-alloyed carbon steels form the starting material for the production of many different components, and offer a broad palette of areas of use for flat profiles produced according to the invention.

[0017] It is possible, in this connection, that the heating of the semi-finished material in the heating station takes place to a temperature above the A.sub.3 point. Such a temperature of the semi-finished material clearly lies in the range of austenite for the steels usually used in this connection, so that the microstructure changes that occur during austenitization form the basis for a number of usual changes in the material properties, with regard to the material properties of the flat profiles that are to be achieved.

[0018] A first embodiment of the method according to the invention can be seen in that cooling in the cooling station cools the semi-finished material, before rolling, to a temperature for setting an austenite microstructure, of only slightly above the A.sub.3 temperature of about 800.degree. C. In this way, the rolling process itself is still carried out with the characterization of the microstructure of the semi-finished material as an austenite microstructure, which makes it possible for diffusion processes to still take place in correspondingly simple manner, and influencing of the intended microstructure changes can be carried out in controlled manner.

[0019] For this purpose, in another advantageous embodiment of this characterization of the method, cooling of the austenite microstructure for conversion to a sorbite microstructure is carried out immediately after rolling of the flat profile, in the temperature range of the austenite microstructure. This sorbite microstructure is configured with very fine lamellae, and offers the best prerequisites for certain areas of use of such flat profiles.

[0020] Another embodiment of the method according to the invention can be seen in that cooling in the cooling station cools the semi-finished material, before rolling, to a temperature for setting a patenting microstructure, for example for a steel C75, between 400-550.degree. C. Such a patenting microstructure is formed from a fine-striped perlite, and is particularly suitable for further cold-drawing of corresponding flat profiles, for example, or also for areas of use of the flat profiles in which great tensile strengths must be combined with good impact strength of the materials. A correspondingly slow cooling of the patenting microstructure from the perlite stage usually follows the rolling, in this connection. The formation of a patenting microstructure (the same holds true also for the bainite microstructure and austenite microstructure indicated in the following), takes place, in the case of every material that is relevant here, because of its composition, at a different temperature, but this is known and characteristic for each material. The connections between the microstructure characterizations and the temperatures and kinds of process management of the different materials, in each instance, can be read off from the so-called time/temperature conversion graphs (so-called TTC graphs), in this connection. Therefore, in the following, the temperature for setting a patenting microstructure (or a bainite microstructure or an austenite microstructure, respectively) is understood to be a temperature that, although it is different for every material relevant here, is clear when a corresponding material is indicated, for which concrete values are also given, purely as an example, for a steel C75. For the remainder, a person skilled in the art knows what temperatures he/she must set for setting a patenting microstructure or a bainite microstructure or an austenite microstructure, respectively, for every material that is relevant here.

[0021] Another embodiment of the method according to the invention can be seen in that cooling in the cooling station cools the semi-finished material, before rolling, to a temperature for setting a bainite microstructure, for example for a steel C75, between 275-370.degree. C. In this connection, the semi-finished material, in contrast to the setting of a patenting microstructure, is cooled even further, until rolling of the semi-finished material is carried out in a microstructure state of the intermediate stage microstructure bainite, in which diffusion processes are prevented, to a great extent, because of the low temperature, and .alpha. lattice regions form due to folding of austenite regions in the material. This is where fine-grained cementite precipitates, with the advantageous effects for the microstructure properties.

[0022] An alternative embodiment of the method according to the invention can be seen in that cooling in the cooling station cools the semi-finished material, before rolling, to a temperature for setting an undercooled austenite microstructure, for example for a steel C75, between 220-280.degree. C. By means of correspondingly rapid cooling of the microstructure from the austenite, conversion processes that occur otherwise are delayed, or cannot occur at all, or not to a significant extent, so that rolling of such a rapidly cooled, undercooled austenite microstructure offers the possibility of carrying out the conversion to a martensite microstructure with the known, needle-like hardening microstructure, thereby making it possible to produce corresponding high-strength materials with which, in a further embodiment, for example, an annealing treatment, with cooling of the flat profile before it is wound up, can be carried out immediately afterward, for example. By means of the annealing treatment, the material is changed once again with regard to hardness and impact strength, and thereby achieves great hardness, while continuing to have good mechanical strength properties.

[0023] However, in the case of rolling of the semi-finished material as undercooled austenite, it is possible that after rolling of the flat profile, directly following, a tempering treatment is carried out, without quenching the undercooled austenite microstructure, but with an annealing treatment, possibly for the formation of a bainite microstructure, and an annealing treatment with cooling of the flat profile before it is wound up. In this connection, instead of the martensite formation described above, the intermediate stage microstructure bainite is produced, which has the advantageous properties also already above.

[0024] Furthermore, it would also be possible, without producing undercooled austenite, to roll directly in the austenite phase, as already described above, to quench after rolling of the flat profile, in the temperature range of the austenite microstructure, in order to form martensite, but directly afterward, to carry out an annealing treatment and cooling of the flat profile before it is wound up. In this way, an annealed martensite microstructure is produced, which also has the advantages already mentioned.

[0025] It is advantageous in connection with all these different kinds of process management if the semi-finished material is held at least at the temperature set in the cooling station, after cooling of the semi-finished material, during the rolling process. In this way, the microstructure does not change during rolling, or does not change greatly, so that rolling alone does not trigger any changes in microstructure. For this purpose, depending on the configuration of the rolling process, it might be necessary either to remove heat from the rolling zone, in view of the deformation work introduced into the semi-finished material in this connection, and the temperature change in the semi-finished material that occurs thereby, for example at high degrees of deformation, or, for example in the case of slight deformations, to hold the semi-finished material at the desired temperature by means of providing heat, for example by means of tempering the rollers.

[0026] Furthermore, it is possible that depending on the selection of the process management to be carried out, the semi-finished material is subjected to further cooling, particularly rapid cooling, after the deformation by means of roller technology to produce a flat profile close to the final dimensions. For this purpose, the material, which is already present as a flat profile, can be subjected to water cooling, for example, or to similar known cooling methods.

[0027] It can furthermore be practical if the rapid cooling cools the rolled flat profile at least below the temperature limit for the occurrence of oxidation processes at the surface of the flat profile, and thereby ensures that oxidation processes or the like can no longer occur, or can no longer occur to an impermissible extent.

[0028] It is advantageous if the cooling of the semi-finished material takes place after it passes through the heating station and before rolling, in a tempered metal bath. Such tempered metal baths are fundamentally known and tested, and offer the possibility of tempering metal strips that pass through them in targeted and precise manner, and also of holding them at a pre-determined temperature, in order to allow corresponding equalization processes to take place, without the surfaces of the metal strips being exposed to impermissible oxidation.

[0029] Here, in a further embodiment, it can also be thought to keep the semi-finished material in the tempered metal bath for a period of time that can be pre-determined, to cool the semi-finished material after it has passed through the heating station, in particular, to allow it to pass through the tempered metal bath during a period of time that can be pre-determined, in order to allow the equalization processes that have already been mentioned to take place, for tempering the entire cross-section of the semi-finished material.

[0030] It is furthermore advantageous if heating of the semi-finished material takes place by means of inductive heating and/or conductive heating and/or by means of liquid metal baths. Of course, other heating methods, not mentioned in detail here, are possible; these are known and usual in metallurgy.

[0031] An improvement in the surface of the flat profile can be achieved if the heating of the semi-finished material is carried out under the influence of inert gas. In this way, oxidation processes that already occur when the semi-finished material is heated are prevented; of course these then cannot propagate through the entire process management and therefore also cannot bring about subsequent deviations from dimensions or surface defects.

[0032] It is furthermore possible that a uniformization device for temperature equalization within the heated semi-finished material is run through between heating station and cooling station, whereby in a further embodiment, the uniformization of the temperature within the heated semi-finished material can be carried out after it has passed through the heating station, under the influence of inert gas.

[0033] According to claim 26, the invention furthermore relates to a device for carrying out the method according to claim 1, in which the device has, in the pass-through direction of the semi-finished material, a winding/take-off device for unwinding the semi-finished material, which can be wound up, or a feed device for the semi-finished material in rod form, a heating station, a cooling station for setting a rolling temperature, a rolling station, a cooling segment, and a winding/take-off device for winding up the flat profile that can be wound up, or a removal device for the flat profile in rod form. This basic configuration of the device allows the fundamental method variants to be carried out, in which targeted cooling of the semi-finished material is carried out, after it has been heated, to a temperature that allows rolling of the semi-finished material with a microstructure either as an austenite microstructure, as a patenting microstructure, as a bainite microstructure, or as an undercooled austenite. In this connection, the corresponding microstructure can be set as a function of the gradient of cooling and of the cooling time. Additional post-treatments or also intermediate processes can be carried out by means of the interposition or post-position of corresponding additional device components, such as heat treatment processes that follow rolling, for example, such as in the case of annealing or also tempering processes, such as holding the semi-finished material at a specific temperature over a defined time span, in order to be able to allow equalization processes to take place within the material.

[0034] It is advantageous if the rolling station has at least one rolling device, preferably several rolling devices switched one behind the other. In this way, gentle deformation of the semi-finished material during rolling can be achieved in targeted manner, by means of the targeted configuration and also the arrangement of several rolling devices one behind the other.

[0035] It is furthermore possible that a temperature monitoring device for detecting the temperature of the semi-finished material before and/or after rolling is disposed in the region of the at least one rolling device, with which temperature changes that are impermissible with regard to the microstructure formation, for example, can be recognized during rolling, and can be corrected by means of targeted heat introduction into the rollers, for example possibly by means of tempering the rollers.

[0036] For targeted heating of the semi-finished material, it is advantageous if contact rollers through which current flows are disposed in the intake region of the device for the semi-finished material, for heating the semi-finished material by means of conductive heating. Such conductive heating of the semi-finished material, which is fundamentally known, allows heating that can be controlled well, and therefore a microstructure conversion of the semi-finished material that can be controlled well.

[0037] Particularly advantageous cooling of the semi-finished material can be implemented if the cooling station has a tempered metal bath for setting a rolling temperature. Such a tempered metal bath, for example a metal bath composed of a lead/bismuth alloy, is already used in many ways and is therefore known and tested, in terms of its behavior. In this way, reliable tempering of the semi-finished material can be guaranteed, even at relatively longer pass-through times of the semi-finished material through such a metal bath, while simultaneously preventing oxidation processes on the surface of the semi-finished material.

[0038] It is possible, in this connection, that the tempered metal bath is disposed ahead of and/or behind the rolling station. Depending on the process management, rolling directly out of the austenite phase is possible, with appropriate coordination of the heating temperature in the heating station, so that the metal bath then takes over the tempering of the rolled flat profile, for the formation of bainite intermediate stage microstructure. In other cases, the metal bath is used for targeted cooling of the semi-finished material to the rolling temperature, and must, of course, be disposed ahead of the rolling station then. In this connection, in another embodiment, the tempered metal bath can have a winding device and/or deflection device, over which the semi-finished material is guided during the dwell time in the tempered metal bath. The winding device or deflection device can also take over a buffer function for subsequent device stations, in this connection.

[0039] For specific variants of the process management, it is advantageous if water cooling cools the flat profile in the cooling segment, at high temperature gradients. In this way, microstructures achieved after rolling are essentially frozen by means of the rapid cooling, and are maintained even at lower temperatures.

[0040] Within the framework of the post-treatment of rolled flat profiles, it is advantageous if another conductive heating station is provided for heating the flat profile for tempering that takes place after rolling, in which station heating then can take place, again, under the influence of inert gas, for example. Also, another cooling segment can be provided, for example, for cooling the flat profile within the framework of tempering that follows rolling.

[0041] According to claim 38, the invention furthermore describes a flat profile produced according to the method according to claim 1. It is advantageous if such a flat profile has an essentially rectangular cross-section or a cross-section close to a rectangle, whereby the most varied configurations of the edge region can be set, depending on the later use of the flat profile.

[0042] It is advantageous if typical carbon steels, particularly carbon steels having a carbon content between 0.10 and 1.35%, particularly also C 10 to Ck 101/125 Cr1, can be processed. In this connection, such flat profiles can preferably be processed in dimensions between a thickness of 0.5-5 mm and a width of 4-25 mm.

[0043] A particularly preferred embodiment of the device according to the invention, for carrying out the method according to claim 1, is shown in the drawing.

[0044] This shows:

[0045] FIG. 1--a schematic representation of the fundamental structure of a device for carrying out a method for hot-rolling rolled wires, with the major device components,

[0046] FIG. 2--a continuous time/temperature conversion graph for carrying out the method according to FIG. 1,

[0047] FIG. 3--a schematic representation of the fundamental structure of a device according to claim 26, for carrying out the method according to the invention, with cooling of the semi-finished material before rolling, for the production of patenting microstructure, bainite microstructure, or an undercooled austenite microstructure,

[0048] FIG. 4--an isothermal time/temperature conversion graph for carrying out the method according to FIG. 3, with indication of the process management, in each instance, for the production of patenting microstructure, bainite microstructure, or an undercooled austenite microstructure,

[0049] FIG. 5--a modified device according to FIG. 3, for heat treatment of an undercooled austenite microstructure, carried out after rolling,

[0050] FIG. 6--a modified device according to FIG. 3, for heat treatment of an austenite microstructure, carried out after rolling, without a cooling device ahead of the rolling,

[0051] FIG. 7--a modified device according to FIG. 3, with cooling device ahead of the rolling station, and devices for heat treatment carried out after the rolling,

[0052] FIG. 8--a modified device according to FIG. 7, with cooling device after the rolling station, and devices for heat treatment carried out after the rolling.

[0053] FIG. 1 shows in a very schematic representation, the structure of a device for carrying out a method for hot-rolling rolled wire into flat profiles. This is a device for carrying out a method, without any special devices for cooling the semi-finished material before rolling.

[0054] In this connection, a flat profile 18 is understood to be steel material whose width corresponds to maximally 10 to 20 times its thickness, and that is usually used as the design basis for components mainly subject to mechanical stress, such as springs, piston rings, or the like, as well as also work pieces subject to great stress, such as saw blades and others. The dimensions of such flat profiles are rather slight, in contrast to rolled strip that is produced otherwise, and typically lies in the range of up to 30 millimeters in width and 5 millimeters in thickness. The semi-finished material 17 is usually passed to the system 1 as round rolled wire, but of course can have other cross-sections, as the starting material for rolling in a rolling device 7.

[0055] At system 1, the semi-finished material 17 is conveyed into a device 5 for conductive heating of the semi-finished material 17, from a reel having a coil run-off 2, by way of a caterpillar take-off 3 and a directional device 4, whereby the conductive device 5 has contact rollers 16 through which current flows, which cause heating of the semi-finished material 17 by way of coupling of the current into the semi-finished material 17, along the conductive device 5. This heating takes place predominantly in an inert gas channel 6, which prevents oxidation products from occurring on the surface of the semi-finished material 17 during heating. Subsequent to the second pair of contact rollers 16, a channel 12, which is also channel-like and possibly flooded with inert gas, is provided as an equalization zone, within which the semi-finished material 17 heats up uniformly, also in the interior region, by means of equalization processes, and thereby a uniform temperature progression has been established within the semi-finished material 17 before it enters into the rolling device 7. Within this equalization zone 12, the temperature of the semi-finished material 17 drops from the end temperature that occurs during heating between the contact rollers 16, of 1020.degree. Celsius, for example, to a lower temperature, so that cooling of the semi-finished material 17 to a temperature just slightly above the A.sub.3 temperature, for example, occurs within the equalization zone 12. At this temperature, which is monitored by means of a temperature measurement 8 implemented, possibly by means of a radiation pyrometer, ahead of or behind the rolling device 7, for example, the semi-finished material 17 enters into the rolling device 7, and is rolled into a flat profile 18 there, in one or more passes (in simplified manner, only one rolling device 7 is shown, but several such rolling devices 7 can also be set one behind the other), which profile is then cooled by means of a cooling segment 9, with two rapid coolers 10 here, for example, and applied to a pay-on reel 11 by way of a caterpillar take-off 3, and wound into a coil there. The semi-finished material 17 therefore passes through the system 1 in the run-through direction 19, and is passed to the system 1 as a wound-up coil, for example of a round rolled wire, and completed as a wound-up coil of a flat profile 18.

[0056] Such a roller line 1 carries out a method that takes place in accordance with the temperature management along the line 13, according to FIG. 2, in a representation for a steel C 75 for the production of bainite, in a continuous time/temperature conversion graph. In this connection, the semi-finished material 17 is rolled at a temperature just slightly below 800.degree. Celsius, and then cooled along the line 13. The sorbite microstructure that is formed in this connection ensures the corresponding properties of the flat profile 18 produced in this manner. A disadvantage of this method of procedure is that it is relatively complicated to regulate the temperature of the semi-finished material 17, because cooling occurs only in the equalization zone 12, and furthermore, the temperature cannot be reduced to values that would be practical for other kinds of process management.

[0057] Therefore a further development of the system 1 shown in FIG. 1 is proposed, in that according to FIG. 3, the system 1 is modified in such a manner that a cooling device 14, consisting of a metal bath, for example a lead/bismuth bath, is set ahead of the rolling device 7, for example, in which targeted cooling of the semi-finished material 17 before it enters into the rolling device 7 is carried out, so that the microstructure of the semi-finished material 17 corresponds to precisely defined conditions before it enters into the rolling device 7, and therefore the deformation of the semi-finished material 17 to produce the flat profile 18, if applicable in combination with subsequent treatment processes that will be described further below, results in the desired microstructure of the flat profile 18 as well as the required cross-sectional dimensions and cross-sectional shapes. For the remainder, the system 1 of FIG. 3 essentially corresponds to the system 1 of FIG. 1, so that in the following, only the differences that exist will be discussed in greater detail.

[0058] In this connection, heating in the conductive device 5 can take place in two or more stages, whereby a number of contact rollers 16 are disposed behind one another, so that heating can be carried out in multiple stages, possibly even using different current intensities and therefore different temperature gradients during heating. In general, this results in heating of the semi-finished material 17 that can be controlled significantly better, and furthermore, corresponding equalization processes already occur during passage through the conductive device 5, so that at the end of its passage through the conductive device 5, the semi-finished material 17 is present very uniformly, for example at the indicated temperature of 1020.degree. Celsius.

[0059] The metal bath 14 has a winding device 15 for passage of the semi-finished material 17, in the form of rollers having a diameter of one meter, for example, onto which the semi-finished material 17 is wound several times, and therefore remains within the metal bath 14, while passing through the metal bath 14, for a period of time that can be pre-determined. In this connection, the metal bath 14 is tempered in such a manner that the desired starting temperature for rolling of the semi-finished material 17 in the rolling device 7 occurs within the semi-finished material 17, and therefore precisely the microstructure that is required for rolling within the rolling device 7, in order to achieve the subsequent final microstructure, can form within the semi-finished material 17. In order to prevent impermissible surface changes of the semi-finished material 17 after it exits from the conductive device 5 and while it passes through the metal bath 14, inert gas channels 6 are also disposed ahead of and behind the metal bath, so that the semi-finished material 17 is heated and tempered almost completely under an inert gas atmosphere.

[0060] After rolling in the rolling device 7, the flat profile 18 is cooled by way of a rapid cooler 10, by means of water cooling or the like, and wound up as already described for FIG. 1.

[0061] In FIG. 4, various possible method sequences along the line 13', 13'', 13''' are shown in an isothermal time/temperature conversion graph, for a steel C 75, which indicate the different final microstructures of the flat profile 18 after rolling in the rolling device 7. If, for example, the temperature of the semi-finished material is reduced, within the cooling device 14, to a value of about 500.degree. Celsius, and rolling then takes place, a so-called patenting microstructure can be adjusted in the case of this steel, according to the line 13', which allows particularly great impact strength at very high tensile strength values. If, in contrast, cooling in the cooling device 14 takes place even further, to values of about 350.degree. Celsius, then a so-called intermediate stage microstructure in the form of a bainite microstructure will occur during rolling, according to the line 13''. A particularly interesting possibility for the production of flat profiles 18 consists in carrying out cooling in the cooling device 14 so quickly that one comes into the range below 300 degrees Celsius, of undercooled austenite, for rolling in the rolling device 7, according to the line 13''', and then one can carry out martensite hardening of this undercooled austenite, by means of a corresponding post-treatment.

[0062] Thus, the placement of a cooling device 14 ahead of the rolling in the rolling device 7 creates the possibility of processing a very different type of materials into flat profiles 18 on a system 1, and, in this connection, of being able to conduct the optimal process management according to the lines 13', 13'', 13''' in FIG. 4, in this connection.

[0063] A modification of the system for rolling undercooled austenite as the microstructure of the semi-finished material 18, described for FIG. 3, is shown in FIG. 5, in which what was said above for FIG. 3 applies, except for the rollers in the rolling device 7. After the rapid cooling 10 after rolling in the rolling device 7, another conductive device 5' is disposed, which serves for renewed heating of the flat profile 18 for tempering of the microstructure of the flat profile 18, whereby again, heating takes place conductively, and cooling takes place in a subsequent rapid-cooling device 10. In this way, extensive control of the properties of the semi-finished material 17 rolled as undercooled austenite can be achieved.

[0064] FIG. 6 shows another modification of the system 1, in which the rolling takes place without a separate cooling device, according to line 3 in FIG. 4, and only after a certain cooling in the equalization zone 12, and therefore the rolling is carried out, in the rolling device 7, in the austenite range of the microstructure of the semi-finished material 17. This flat profile 18, rolled and cooled in the cooling device 10 in such a manner, is then annealed in a conductive device 5', by means of tempering operations already described above with regard to FIG. 5, and thereby its properties are changed once again.

[0065] According to FIG. 7 and 8, another two variants of system 1 according to FIG. 5 are shown, in which the cooling device 14 is disposed once in front of and once behind the rolling device 7, so that the temperature management of the semi-finished material 17 can be changed further, in the region of the rolling device 7, in targeted manner, for example also after rolling in the rolling device 17, by means of tempering of the flat profile 18 that has been formed. In this connection, the cooling device 14 according to FIG. 8 serves, for example, for correspondingly slow or targeted tempering of the flat profile 18 after rolling, in order to bring about a targeted change in the microstructure of the flat profile 18 that is present after rolling, without directly bringing about overly rapid cooling of the flat profile 18.

REFERENCE SYMBOL LIST

[0066] 1--roller line/system [0067] 2--coil run-off [0068] 3--caterpillar take-off [0069] 4--directional device [0070] 5, 5'--conductive heating [0071] 6--inert gas channel [0072] 7--rolling device [0073] 8--temperature measurement [0074] 9--cooling segment [0075] 10--water cooling [0076] 11--pay-on reel [0077] 12--equalization zone [0078] 13-13'''--temperature management for method variants [0079] 14--cooling station/metal bath [0080] 15--winding device [0081] 16--contact rollers [0082] 17--semi-finished material [0083] 18--flat profile [0084] 19--run-through direction, semi-finished material

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