COIL AREA FOR IN-LINE TREATMENT OF ROLLED PRODUCTS

Abstract: Apparatus for the production and heat treatment of coiled elongated metal product of relatively small cross section, such as rods, bars and wire-rod material, comprising elements for the conduct of a variety of heat treatments on coiled product in a continuous manner through the use of a ring conveyor (334) with which the coilers of various process lines and a heat treating funace communicate. Methods for performing various heat treatments using the described apparatus are also disclosed.

Description: COIL AREA FOR IN-LINE TREATMENT OF ROLLED PRODUCTS Field of Invention This invention relates to the heat treatment of metal product. More particularly, the invention concerns the conduct of various heat treatments of elongated rolled metal products formed into coils, which heat treatments are conducted in facilities which are in-line with the metal product rolling and coiling apparatus. Prior Art Various systems are known for the heat treatment of wire rod and coiled bars. Systems in which heat treatment is conducted on the metal product in a heating chamber disposed in-line with the product rolling apparatus, however, have the heating chamber disposed upstream from the coiler and suffer the disadvantages that the process is slow and is limited to heat treatment operations which do not require the metal product to reside in the heating chamber excessive amounts of time. In order to perform heat treatment operations requiring longer duration in the heating chamber, it has been the practice to wind the rod or bar product into coils following the rolling operation, removing the wound coils from the coiling apparatus and transferring the coils to a heat treatment facility which is disposed remotely from the coiling apparatus. This latter procedure suffers from the disadvantages that, even in instances in which it is not necessary to cool the coils prior to transferring them, the coils undergo a significant heat loss during the time required for their removal from the coiler and transfer to the heating chamber that an expense is incurred in adding reheat to the metal product. The practice of transferring coils to a remotely located heating chamber for heat treatment is additionally costly due to the time, manual effort and need for transport facilities, such as carts and rails, for transferring the coils. It is to the amelioration of these problems therefore to which the present invention is directed. Summary of the Invention According to the invention there is provided an apparatus disposed downstream of the rolling mill and substantially contiguous therewith whereby a considerable variety of heat treatments can be conducted on stock which is immediately coiled and transferred in-line to facilities for conducting the heat treatment operations. Such heat treatments include workability-annealing, spheroidizing-annealing, solubilization for austenitic steels, recrystallization for ferritic steels, coil quenching and tempering; patenting, and slow air cooling. Specifically, according to a principle aspect of the invention there is provided apparatus for processing hot rolled steel stock of small sectional shape, such as bars and rods, comprising apparatus for processing hot rolled steel stock of small sectional shape comprising a conveyor having a closed path, a heating chamber disposed interiorly of the path and having an inlet opening and an outlet opening communicating with the conveyor path, coiling means adjacent the conveyor for winding the steel stock into coils, means for transferring wound coils to the conveyor, and means for moving said wound coils about the conveyor path including movement selectively through said heating chamber. The conveyor is arranged to receive stock coiled on a Garrett line or, alternatively, on a line wherein additional rolling can take place for the production of wire rod, or the like. For a better understanding of the invention, its operating advantages and the specific objectives obtained by its use, reference should be made to the accompanying drawings and description which relate to a preferred embodiment thereof. Brief Description of the Drawings Fig. 1 is a schematic representation illustrating an overall plant layout incorporating a finishing area for the in-line heat treatment of wire rod and bars according to the invention. Fig. 2 is a schematic layout of the finishing area for in-line heat treatment of bars and wire rod shown in Fig. 1. Description of the Preferred Embodiments of the Invention The disclosed invention is particularly directed to a plant 10 for the production of "long products", i.e. billets or blooms from about forty meters or more in length, used in the production of bars, wire, rod, rebar, or shaped beams or angles, and the like, in which the production machinery utilized is typically smaller in size than that used in the production of sheet material from slabs. As used herein, the word, "billet", shall include blooms or slabs, or other strand forms produced by a continuous caster and useful in the production of the aforementioned intended product. Fig. 1 of the drawings shows a schematic representation of an overall plant layout suitable for the practice of the present invention. The described plant comprises a casting/mill entry area A, a rolling mill/stands store area B, a finishing area C for the in-line heat treatment of product; and a finishing area D for the in-line heat treatment of wire rod and bars according to the invention. A description of the finishing area for the in-line heat treatment of wire rod and bars is presented hereinafter. With particular reference to Fig. 2, there is shown a coil forming and heat treating facility 310 disposed in-line and downstream of the rolling mill 14 and, preferably, emanating from the mill line downstream of the reduction and sizing block 216. Desirably, larger diameter rod having diameters of from about 10 to about 60 mm, which has been rolled in the rolling mill 14 and sized in the reduction and sizing block 216, is directed by well known product diverting apparatus into a Garrett line 312 of known construction in which the product is cut into pieces of predetermined length by shear 313 and then is wound into one or more coils on coilers 314. Alternatively, a second line 316 is particularly adapted for the production of smaller size products, such as wire rod having diameters between about 4 mm and about 25 mm. As shown in the drawings, the second line 316 desirably contains, in a consecutive in-line relationship, a crop shear 318, a finishing block 320, water cooling line 322, high speed shear 324 and twin module block 326, which are all operative in the production of smaller diameter wire rod. The second line terminates in coiling apparatus including laying head 328 for forming wire rod spirals, and a roller cooling conveyor 330 along which the spirals are conducted to a coiler 332. A ring conveyor 334 defining an essentially closed annular path is located at the ends of the respective rod producing lines 312 and 316 with the coilers 314 and 332 at the ends of the respective lines being closely spaced with respect to each other along one peripheral side of the conveyor. Other work processing stations, including an inspection and testing station 336, a coil compacting and strapping station 338 and a weighing and discharging station 340, are disposed at spaced locations about the perimeter of the conveyor 334. The ring conveyor 334, which may be of the walking beam or roller table type, permits coils to be conducted to the respective stations around the conveyor and, following discharge of the coils, permits the trestles (not shown) upon which the coils are conveyed and from which they are removed upon discharge, to be returned to positions for receiving coils from coiler 332. (Trestles are not used for coils wound on coiler 314.) This invention contemplates the conduct of in-line heat treatments to the coils conducted by the conveyor 334. Accordingly, as shown, an elongated annealing furnace 340 is arranged to receive coils to be treated from the conveyor 334. The furnace 340 preferably has a U-shaped construction being formed of two legs 342 and 344, each of which has an end 346 and 348, respectively, opening onto the conveyor 334. Preferably, end 346, here shown as defining the inlet to the furnace 340, is located substantially directly opposite the coiler 332 whereby coils formed on the coiler can be passed directly into the furnace leg 342. Advantageously, the furnace 340 may be heated by burners supplied from a fuel source or by induction or other electric heating means. The heat to each leg 342 or 344 of the furnace 340 is independently controlled and, if desired, only one furnace leg can be heated to the exclusion of the other leg. Other elements which are utilized in the heat treating procedures of the described apparatus include a first quench tank 350 disposed immediately adjacent the coiler 314 of the Garrett line 312. A second quench tank 352 is disposed intermediate the ends of the furnace 340, here shown as being adjacent the nexus 354 between the two furnace legs 342 and 344. Fans 356 are disposed adjacent one peripheral side of the conveyor 334 whereby coils carried by the conveyor can be cooled by forced air cooling. In the disclosed arrangement a conveyor offset 358 is optionally provided for conducting coils to a cold finishing facility 360 in which the coils may undergo such processing as pickling, phosphatizing and/or lubricating, or the like. Coils, after processing in this facility are passed to a coil compacting and strapping device 362 prior to discharge from the facility. The operation of the herein described in-line small section steel stock coiling and heat treating facility for conducting various forms of heat treatment are as follows. For workability annealing coils of stock, which stock has undergone low temperature rolling using water cooling line 322 and twin module block 326 of the second line, the coils are introduced to the annealing furnace 340 immediately after being coiled on coiler 332. The coils are held in the furnace 340 for up to about two hours and at temperatures of from about 600°C to about 850°C. The low temperature rolling of the stock before passing it to the furnace 340 significantly reduces the length of holding time for the coils in the furnace. For workability annealing of the rod stock conducted along the Garrett line 312, the stock undergoes low temperature rolling using controlling temperature device 212 and reduction and sizing block 216 and, after winding into coils upon coiler 314 at the end of the Garrett line, the coils are conducted along the adjacent side of the ring conveyor 334 to the annealing furnace 340 for heating under conditions similar to those previously described. For spheroidizing annealing the rolled stock, following thermomechanical or thermocontrolled rolling within a temperature range of from about 750°C to about 850°C, the stock is wound into coils and immediately passed to the coil annealing furnace 340 for a period of from about one to about two hours for heating at temperatures within the range of from about 680°C to about 720°C wherein spheroidizing occurs. After thermal treatment the coils are returned to conveyor 334 for final air cooling. For solubilization annealing for austenitic stainless steels, the stock, which has undergone normal rolling in the rolling mill 14, is coiled by coilers 314 at the end of the Garrett line 312 at a temperature of about 900°C and immediately passed along conveyor 330 to the coil annealing furnace 340 for heating to about 1000°C and for the time, between about thirty and sixty minutes, to achieve solution annealing. Typically this procedure will be formed in one leg 342 of the furnace 340 whereupon the coils, after achieving solution annealing, are quenched in the quench tank 352 and thence returned to the conveyor to be conducted to a point of final processing. For recrystallization of ferritic steels the process is similar to that performed for solubilization annealing of austenitic stainless steels, except that the coils are heated only to within the range of from about 700°C to about 800°C in the coil annealing furnace 340 before quenching in quench tank 352. When quenching and tempering is to be conducted on larger diameter rod material, the stock, after undergoing conventional rolling or thermocontrolled rolling in the section including the rolling mill 210, the controlling temperature device 212 and the reduction and sizing block 216 is coiled at a temperature of about 800°C on the coilers 314 of the Garrett line 312. Immediately after coiling, the coils are quenched in quench tank 350 to a temperature of about 100°C. Thereafter, the coils are conducted by conveyor 334 to the coil annealing furnace 340 to be heated to the tempering temperature of between about 700°C and 500°C for a period of one to two hours. The coils are thereafter air cooled on the conveyor 334 before being passed for further processing or to discharge. It is contemplated that patenting of the wire rod produced on the second line 316 can be performed by thermomechanically rolling the stock at about 850°C and thereafter subjecting it to forced air cooling by fans placed in the roller cooling conveyor 330 prior to coiling. It should be appreciated that following all of the foregoing forms of heat treatment, the coils are returned to conveyor 334 for transport to areas of further processing, as for example via conveyor offset 358 to the cold finishing facility 360 and final packaging by the compacting and strapping device 362 prior to shipment or storage. It will be understood that various changes in the details, materials and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

Claims: CLAIMS 1. Apparatus for processing hot rolled steel stock of small sectional shape, comprising: ■ a conveyor (334) having a closed path; ■ a coil heating chamber (340) disposed in correspondence of said path and having an inlet opening (346) and an outlet opening (348) communicating with said conveyor path (334); ■ coiling means (314, 332) adjacent said conveyor for winding said steel stock into coils; ■ means for transferring wound coils to said conveyor; and ■ means for moving said wound coils about said conveyor path including movement selectively through said coil heating chamber (340). ■ a quenching tank (352) adjacent said coil heating chamber (340) for quenching product heated therein. 2. Apparatus according to claim 1 , in which said coil heating chamber (340) is an elongated chamber and said quenching tank (352) is disposed intermediate the ends thereof. 3. Apparatus according to claim 2, in which said coil heating chamber has two legs (342, 344); means for controlling the heat output in each leg independently of the other; and said quenching tank is disposed intermediate said legs of said coil heating chamber. 4. Apparatus according to claim 1 , including ancillary product processing means disposed at mutually spaced locations about said conveyor path. 5. Apparatus according to claim 4, in which said ancillary product processing means includes a coil compacting and strapping machine (336). 6. Apparatus according to claim 4, in which said ancillary product process means includes a coil weighing and discharging station (338). 7. Apparatus according to claim 5, in which said ancillary product process means include means for forced air cooling of said coils. 8. Apparatus according to claim 1 , including means upstream of said coiling means for finishing said hot rolled steel stock. 9. Apparatus according to claim 8, in which said stock finishing means comprises a first rod finishing line for rolling a billet to a wire rod size. 10. Apparatus according to claim 8, in which said stock finishing means comprises a second rod finishing line defined by a Garrett line. 11. Apparatus according to claim 8, in which said stock finishing means comprises: ■ a first rod finishing line for rolling a billet to a wire rod size; ■ a second rod finishing line defined by a Garrett line; and ■ means for diverting hot rolled stock to one of said first finishing line and said second finishing line. 12. Apparatus according to claim 11 , in which said coiling means from said first finishing line and said coiling means from said second finishing line are closely adjacent each other. 13. Apparatus according to claim 9, in which said first finishing line includes a finishing block, a cooling line, a high speed shear, a twin module block, wire coil laying means and a cooling conveyor. 14. Apparatus according to claim 9 in which said coiling means for said first finishing line is disposed opposite said conveyor from said inlet to said heating chamber. 15. Apparatus according to claim 10, in which said Garrett line includes a quenching tank for quenching coils delivered to said conveyor. 16. Apparatus according to claim 1 , in which said conveyor is a trestle conveyor. 17. Apparatus according to claim 1 , further including means to direct coils to a post heat-treatment means selected from the group consisting of coil pickling means, phosphatizing means and lubricating means; and means downstream of said post heat-treatment means for compacting and strapping said heat-treated coils. 18. A method of heat treating alloy structural steels by workability-annealing, straightening-annealing and slow cooling by operation of the apparatus of claim 1 , including the steps of: ■ treating rolled stock, before coiling, in a low temperature rolling device; ■ heating said coil heating chamber to a temperature between about 600°C and about 850°C; ■ conveying coils from one of said finishing lines to said coil heating chamber; and ■ holding said coils in said coil heating chamber for up to about two hours. 19. A method of heat treating austenitic stainless steels by solubilization annealing by operation of the apparatus of claim 14 comprising the step of quenching coils in said quenching means in said Garrett line. 20. A method of heat treating austenitic stainless steels by solubilization annealing by operation of the apparatus of claim 1 comprising the steps of heating coils in said coil heating chamber to a temperature above 1000°C; ■ holding said coils at said temperature for a time effective to obtain solution annealing; and ■ quenching said heated coil in said quench tank. 21. A method of heat treating steel coils by quenching and tempering by operation of the apparatus of claim 14 comprising the steps of quenching the coils in said quenching tank; and tempering the quenched coils in the coil heating chamber. 22. A method of heat treating steel coils by quenching and tempering by operation of the apparatus of claim 14 comprising the steps of quenching the coils in the quenching tank to a temperature of about 100°C; ■ transferring said coils to said coil heating chamber and heating said coils to a tempering temperature of between about 700°C and 500°C; ■ holding said coils at said temperature in said coil heating chamber from about one to about two hours; and ■ thereafter holding said coils on said conveyor for natural cooling. 23. A method of heat treating steel coils by spheroidizing annealing, including the steps of: ■ treating the rolled stock, before cooling, in a thermocontrolled rolling device to a temperature of between about 750°C and about 850°C; ■ heating a heating chamber to a temperature of between about 680°C and about 720°C; conveying coils from a finishing line to said coil heating chamber and holding said coils in said coil heating chamber for a period of one to two hours.

Inventors: BENEDETTI GIANPIETRO, BENEDETTI, GIANPIETRO
Applicants: DANIELI TECHNOLOGY INC, DANIELI TECHNOLOGY, INC.
Application year: 2000
Main classification: C21D9
IPC codes: C21D8, C21D9