Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
  • B21B3/02—Rolling special iron alloys, e.g. stainless steel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
  • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
  • B21B1/24—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process
  • B21B1/28—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process by cold-rolling, e.g. Steckel cold mill
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
  • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
  • B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
  • B21B45/04—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing
  • B21B45/06—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing of strip material

Definitions

• the invention relates to the manufacture of stainless steel strips. More specifically, it relates to an installation for producing such strips bringing together all the stages of this production, from casting to cold rolling.
• stainless steel strips intended to be delivered to customers in the form of cold-rolled coils are produced according to the following diagram:
• Annealing and pickling after cold rolling can be replaced by bright annealing, depending on the condition and surface appearance desired for the strip. These operations are carried out on installations which are, for the most part, separated from each other, which requires multiple operations for packaging the products, such as intermediate windings, and for transferring the coils from one installation to another. .
• EP 0 695 808 presents an example.
• This last document also mentions the possibility of carrying out these transformation steps not on strips produced from hot-rolled slabs, but on strips produced by an installation for direct continuous casting of thin strips a few mm thick from of liquid metal, for example by pouring the liquid metal between two cylinders with horizontal axes, internally cooled.
• This casting can possibly be followed by a light hot rolling, carried out in line with the casting or on a completely separate installation, with the aim in particular of limiting the surface roughness of the strip and of promoting the recrystallization of the metal to avoid the appearance 2 of the phenomenon known as “ragging” or “roping” during the subsequent transformations of the strip.
• An annealing furnace can also be arranged after the hot rolling mill, and before the installation for winding the strip.
• the production line for cold-rolled stainless steel strips is long and costly in investment. It is also costly in energy, due to the multiple operations of transporting the intermediate products (slabs and coils) between installations which are not always located on the same industrial site, and reheating of these products which are necessary before several of the operations. cited to bring them from room temperature to the desired treatment temperature. In addition, the storage of these intermediate products while awaiting their processing requires space and immobilizes metal.
• the object of the invention is to propose a method of manufacturing cold-rolled stainless steel strips which regularly ensures a very good surface quality of said strips, as well as a manufacturing installation adapted to this method.
• the invention relates to a process for manufacturing thin strips of stainless steel according to which successively and continuously is carried out on a single processing line:
• the invention also relates to an installation for the production of cold rolled stainless steel strips, successively comprising:
• an installation for final shaping of the strip such as a hardening rolling mill; - a tape winding installation; all these installations being arranged on the same continuous line, and at least some of them being separated by a tape accumulator.
• the installation also includes a hot rolling mill placed after the installation of continuous casting.
• This hot rolling mill can be followed by an annealing installation.
• the casting installation can be of the “casting between two cylinders” type.
• the invention consists in continuously carrying out, on a single manufacturing line, all the stages of manufacturing a strip of cold-rolled stainless steel produced from a thin strip cast directly at from liquid metal, from casting to finishing operations and packaging of the strip in the form of a reel ready to be sent to the customer.
• the inventors have realized that the residual scale encrustations and surface cracks, which are too often found on cold rolled strips obtained by conventional discontinuous installations, are considerably reduced if all the intermediate windings normally required are eliminated. undergo the tape before being transferred from one workshop to another. Indeed, re-reeling can only be done by subjecting the strip to a tension which, in the case of particularly fragile shades, can be sufficient to damage it, during the winding itself or during the time that the cooled strip, therefore not very malleable, passes in the form of a coil. On the other hand, the stay of the strip in the form of coils tightened one on the other contributes to deeply embedding in its surface layers the residual scale which may remain on its surface if the latter has been imperfectly cleaned before winding. The elimination of all the intermediate windings permitted by the method and the entirely continuous line according to the invention therefore gives the possibility of eliminating important causes of deterioration of the surface quality of the strips.
• each winding considerably deforms the beginning and the end of the strip making up the coil. It therefore makes these parts unusable, and in addition, they could damage the parts of the installation that they would pass through during the next treatment. he 4 is therefore essential to remove them.
• the elimination of the intermediate windings in the method according to the invention therefore reduces the quantity of metal made unusable during the sheet-making process, as well as the necessary number of shear installations at the start and end of the strips.
• the treatment line according to the invention can be relatively compact, and in any case it occupies less floor space than the set of discontinuous installations (and often very distant geographically) for which it replaces.
• the first possibility is to aim at obtaining cold-rolled strips having a surface quality very regularly superior to that of the usual strips.
• the same descaling tools are kept on the line, in particular before cold rolling, as those used on conventional installations. These tools most often include in succession:
• one or more mechanical descaling tools which may comprise, alone or in cascade, a shot blasting installation, a brushing installation, an installation for spraying a pressurized fluid, the function of these latter two tools being 5 essentially to complete the removal on the one hand of the scale residues torn off by the pellets and on the other hand of the pellets which would remain on the surface of the strip;
• a chemical and / or electrolytic pickling installation which may include one or more similar or different baths, the composition of which is to be chosen according to usual parameters such as the grade of the steel (which partly determines the composition and the behavior of scale), the type of surface finish desired for the strip, the duration desired for the treatment; if the temperature of the strip at its exit from mechanical descaling is relatively high (this may be the case in particular if it has undergone a hot rolling followed by an intermediate annealing), it may be necessary to cool the strip before entering pickling baths.
• the second possibility of using the process according to the invention consists in being satisfied with a regular surface quality of the strip which is simply comparable to that obtained by traditional processes from the point of view of scale inlays, but in obtaining it by using only a simplified descaling installation, therefore less costly to build and operate.
• the single appended figure schematically shows an example of installation according to the invention. It firstly comprises an installation 1 for continuous casting of thin strips, itself composed of a pocket 2 containing the liquid steel to be cast, of a distributor 3 collecting a jet 4 of liquid steel, and supplying by a jet 5 of liquid steel an ingot mold composed of two cylinders 6, 6 'with horizontal axes, internally cooled and rotated in opposite directions. Their cylindrical side surfaces define a space 6 of casting whose smallest width corresponds to the thickness of the strip to be cast and which is closed laterally by plates 7 of refractory material applied against the ends of the cylinders 6, 6 '.
• the liquid steel solidifies in the mold in the form of a thin strip 8 of stainless steel, the thickness of which is of the order of 1 to 10 mm for this type of casting machine, and which is continuously extracted of the mold by pinching rollers not shown.
• the strip 8 then preferably passes through an enclosure 9 inside which an atmosphere is kept as little oxidizing as possible by means of inerting with a neutral gas such as argon or nitrogen, or by a reducing gas such as hydrogen, in order to limit the formation of scale on its surface.
• the walls of the enclosure 9 also make it possible to return the radiation which results therefrom to the strip 8, and thus to limit the heat losses of the strip 8.
• the latter then passes, in known manner, through a hot rolling mill 10 whose function is to reduce its thickness, to close its possible internal porosities and to cause recrystallization of the grains which is favorable, in particular, to avoid the appearance of crumpling on the stretched products which will subsequently be produced from the strip 8. Then, again known manner, the strip 8 passes through an annealing oven 11 if it is desired to carry out such a heat treatment.
• the part of the installation which has just been described corresponds to the usual description of an installation for the continuous casting of thin strips and of treatment installations which can conventionally be directly connected to it.
• the casting installation may be of a different type from a casting between rolls, for example a casting between running strips, or on a single cylinder, and produce strips slightly thicker or thinner than the 1 to 10 mm previously mentioned.
• the presence of the hot rolling mill 10 is only optional, as is that of the annealing furnace 11, the presence and use of which is not necessarily linked to that of the hot rolling mill 10.
• it is possible to install on the production line other devices such as additional ovens and coolers.
• the strip 8 then passes into a first strip accumulator 12, which separates the “heat-treatment” part from the next part of the line, in which the descaling of the strip 8 is carried out.
• This accumulator 12 makes it possible to make independent from one another the running speeds of the strip 8 in these two parts of the line, as well as continuing to supply metal to one of the two parts when the other is temporarily stopped.
• the strip 8 penetrates into an oxide breaker 13, of a type known in itself, to crack and weaken the layer of scale which may have formed on the surface of the strip 8 despite the precautions taken. It then passes through a shot blasting machine 14, where the scale is disintegrated by the projection of metal or ceramic balls on the surface of the strip 8. The latter is then preferably freed of its scale residues, or even also balls which have could be embedded in it, by a 7 brushing installation 15 to which can, for example, be added or substituted an installation where a fluid under pressure is projected onto the strip.
• the cleaning of the surface of the strip 8 is completed by the passage of the strip 8 inside one or more tanks 16, 17 containing pickling baths (chemical and / or electrolytic), the natures are conditioned in a known manner by the composition of the strip 8, the desirable duration of the stay of the strip 8 in the baths 16, 17, the type of surface finish desired for the strip 8 etc.
• the first pickling tank 16 is preceded by an installation for cooling the strip 8.
• these tanks are equipped with means allowing the strip 8 to penetrate therein or not according to the precise needs of the moment.
• a rinsing installation 18 and a drying installation 19 then eliminate from the surface of the strip 8 the remaining traces of the pickling baths.
• the “cold rolling” part of the installation according to the invention comprises a single rolling mill of the conventional type with three cages ensuring that the strip 8 is brought to its almost final thickness, it being understood that this configuration n is in no way limiting.
• the rolling mill 21 is preceded by a shear 22 by means of which, when the rolls of the rolling mill 21 change, the strip 8 is cut so as to interrupt the feeding of the rolling mill 21.
• the rolling mill 21 is, in known manner, followed by a degreasing installation 23 and a drying facility 24.
• the “cold rolling” section of the installation can include a second cold rolling mill if the strip enters this section at a relatively high temperature, in particular if no no pickling installation.
• the strip 8 then passes into a third accumulator 25 which separates the part
• the “annealing-pickling” part of the line first comprises an annealing oven 26 of conventional type, which is followed by a cooler 27. then the 8 strip 8 penetrates into pickling tanks 28, 29 of chemical and / or electrolytic type, containing baths of compositions known in themselves. Preferably, these tanks 28, 29 are each equipped with means making it possible for the strip 8 to pass through or avoid them at the operators' choice. There is shown in the single figure two pickling baths, but of course, as required, they can be more or less numerous.
• the annealing-pickling treatments carried out at this location of the installation according to the invention are not particularly distinguished from the treatments that it is usual to carry out on conventional installations for manufacturing cold-rolled strips.
• the strip 8 then passes through a rinsing installation 30 and a drying installation 31.
• the annealing oven 26 may comprise, at its inlet, an induction heating device. This provides a large instantaneous heating power which makes it possible to quickly bring the strip 8 to its nominal treatment temperature. This power is, moreover, easily adjustable, which gives the possibility of easily varying the residence time of the strip 8 in the annealing furnace 26 necessary for the execution of the desired metallurgical treatment, by varying the quantity of energy supplied to the strip 8 in the induction device. This gives us an additional degree of freedom in the management of the entire line.
• the “annealing-pickling” part that we have just described can be replaced by a bright annealing installation, depending on the type of products that one wishes to manufacture.
• the strip 8 then passes into a fourth accumulator 32 which separates the “annealing-pickling” part of the hardening rolling mill 33 and makes their operations independent.
• the hardener rolling mill (or “skin-pass”) 33 which can be supplemented by a leveler under tension 34, conventionally has the function of giving the strip its final metallurgical structure and surface condition, which goes hand in hand with a very slight reduction in thickness. Again, that of the installation according to the invention is not distinguished from those which it is conventional to use on the cold rolling lines of the prior art.
• the strip 8 then passes into a fifth accumulator 35 which separates the hardening rolling mill 33 from the “winding” part of the line, and makes it possible to adjust the speed and the winding tension of the strip 8 independently of the running speed of the strip. in the hardener rolling mill 33.
• the strip preferably passes through a shears of edges 36, which cuts the edges of the strip not having a metallurgical quality sufficient to be exploited. It is then packaged on a winder 37, preceded by a shear 38 which cuts the strip 8 when the winder 37 is about to be completely filled. Only one winder 37 has been shown, but it is understood that there must be at least two, so as to be able to orient the strip towards the empty winder as soon as the other is filled, as it is the case on traditional cold rolling lines. 9
• the installation according to the invention with a second cold rolling mill, arranged for example after the annealing-pickling section, if it is considered preferable to reduce the thickness of the strip 8 in several separate steps.
• This second cold rolling mill can itself be followed by another annealing-pickling section.
• the installation according to the invention is to be completed by any ancillary apparatus which it is usual to find on independent installations according to the prior art and which we would not have mentioned in this description, such only devices for controlling the quality of the surface and the flatness of the products.
• a second continuous casting installation possibly equipped with its own hot rolling mill and / or its own annealing furnace
• a splicing installation making it possible to connect the start of the strip to be cast by one of the continuous casting installations at the end of the strip cast by the other continuous casting installation. This connection could be made, for example, just upstream of the "descaling" part of the installation.
• the composition, the other metallurgical characteristics and the final thickness which it is desired to give to the strip 8 are chosen, and the operating parameters are granted. of the different parts of the installation according to the metallurgical requirements to be respected and the respective productivities to be imposed on the various elements of the installation.
• the reference stage according to which the operating parameters of the installation must be adjusted is the stay of the strip 8 in the annealing furnace 26. This is the duration to be imposed on this stay, calculated for a strip 8 of thickness given at this stage of manufacture, which will condition in particular:

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Metal Rolling (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Heat Treatment Of Steel (AREA)
• Finishing Walls (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

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• 1998
  • 1998-02-25 FR FR9802264A patent/FR2775205B1/fr not_active Expired - Fee Related
• 1999
  • 1999-02-22 ID IDW20001622A patent/ID28239A/id unknown
  • 1999-02-22 CN CN99803325A patent/CN1291922A/zh active Pending
  • 1999-02-22 US US09/623,015 patent/US6478899B1/en not_active Expired - Fee Related
  • 1999-02-22 DE DE69903001T patent/DE69903001D1/de not_active Expired - Lifetime
  • 1999-02-22 EP EP99904921A patent/EP1058588B1/de not_active Expired - Lifetime
  • 1999-02-22 KR KR1020007009411A patent/KR20010041309A/ko not_active Application Discontinuation
  • 1999-02-22 CA CA002320942A patent/CA2320942A1/fr not_active Abandoned
  • 1999-02-22 AT AT99904921T patent/ATE224246T1/de not_active IP Right Cessation
  • 1999-02-22 JP JP2000533239A patent/JP2002504434A/ja active Pending
  • 1999-02-22 AU AU25258/99A patent/AU2525899A/en not_active Abandoned
  • 1999-02-22 WO PCT/FR1999/000388 patent/WO1999043451A1/fr not_active Application Discontinuation
  • 1999-02-22 BR BR9908239-0A patent/BR9908239A/pt unknown
  • 1999-02-24 ZA ZA9901471A patent/ZA991471B/xx unknown
  • 1999-05-03 TW TW088102717A patent/TW431916B/zh not_active IP Right Cessation

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