Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/16—Controlling or regulating processes or operations

Definitions

• the present invention relates generally to systems and methods for providing steel strip to order, and more specifically to systems and methods for converting customer-specified steel strip requirements to process operating parameters for controlling a continuous strip casting process operable to produce the customer- specified steel strip product.
• FIG. 1 a flowchart is shown illustrating a flow of one conventional process 10 for producing a customer-ordered steel strip product, wherein the term "strip" as used herein is to be understood to mean a product of 5mm thickness or less.
• Process 10 begins at step 12 where the steel manufacturer receives the customer order, typically set forth in terms of mechanical and dimensional requirements for the steel strip product as well as a desired quantity. Thereafter at step 14, the steel manufacturer determines from the customer order the particular steel chemistry requirements for achieving the product's broad properties.
• the chemistry requirements are selected from a large recipe list of steel chemistries that is available (and in many cases dates back to ingot casting/hot rolling technology where chemistry was the prime determinant of properties).
• the steel manufacturer determines casting parameters corresponding to operating parameters and/or set points for a steel casting process that will be used to produce steel slabs from molten steel formed in accordance with the steel chemistry requirements.
• the steel manufacturer determines downstream slab processing requirements, initially focusing on achieving the customer's dimensional requirements such as thickness etc and then working through additional downstream processing steps that may be required to achieve the final product properties.
• Such downstream slab processing requirements may include, for example, any one or combination of (a) slab reheat parameters corresponding to hot mill furnace operating parameters and/or set points for a hot strip mill processing apparatus, (b) hot rolling parameters corresponding to mill rolling operating parameters and/or set points for the hot strip mill processing apparatus, (c) cold rolling parameters corresponding to pickling and cold rolling operating parameters and/or set points for a cold mill processing apparatus, and (d) heat treatment parameters corresponding to heat treatment operating parameters and/or set points for a heat treatment apparatus.
• process 10 advances to step 20 where the steel manufacturer produces a batch of molten steel in accordance with the chemistry requirements for the specified steel product and casts the steel product into slab stock in accordance with the casting parameters established at step 16.
• customer's orders (which can be as small as 5 tonnes) are batched until there are sufficient orders to fill one steelmaking heat - typically 100 to 300 tonnes depending on the specific steel plant design. This adds further delay to the time that a particular customer's order can be filled, thereby extending the total time for production well in excess of 10 weeks.
• process 10 advances from step 20 to step 22 where the slab stock is reheated and hot rolled at a hot strip mill apparatus, in accordance with the slab reheat and hot rolling parameters established at step 18, to produce steel coil stock of a predefined thickness.
• the coil stock is pickled and cold rolled at a cold mill in accordance with any pickling and cold rolling parameters established at step 18 to reduce the thickness of the coil stock to a customer- specified thickness.
• the coil stock is heat treated at a heat treatment apparatus in accordance with any heat treatment parameters established at step 18 to anneal the coil stock such that it meets the requirements of the customer's order.
• a primary drawback associated with the conventional steel strip production process just described is the lengthy time period; typically 10 or more weeks, required to produce the steel product that satisfies the customer order. What is therefore needed is an improved steel strip production process that is more responsive to customer needs by greatly reducing the time required to produce customer-specified steel strip product.
• a method of controlling a continuous strip steel casting process to produce a customer-specified steel product includes receiving an order for a steel product including customer- specified requirements relating to said product, mapping said customer-specified requirements to a number of process parameters for controlling a continuous strip steel casting process to produce said steel product, and displaying said number of process parameters on a process change report to an operator of said continuous strip steel casting process.
• a method of controlling a continuous strip steel casting process to produce a customer-specified steel product includes receiving an order for a steel product including customer- specified requirements relating to said product, mapping said customer-specified requirements to a number of process parameters for controlling a continuous strip steel casting process to produce said steel product, and controlling said continuous strip steel casting process based on said process parameters to produce said steel product.
• a method for controlling a continuous strip steel casting process to produce a customer-specified steel product includes controlling a continuous strip steel casting process based on a set of predefined process parameters to produce a first steel product, receiving an order for a second steel product including customer-specified requirements relating to said second steel product, mapping said customer-specified requirements to a set of new process parameters for controlling said continuous strip steel casting process to produce said second steel product, and substituting said set of new process parameters for said set of predefined process parameters without interrupting said continuous strip steel casting process such that said continuous strip steel casting process immediately switches from producing said first steel product to producing said second steel product.
• a method of providing custom-specified steel strip includes processing orders for steel strip of customer-specified requirements into a schedule for producing the ordered steel strip in a production run of a continuous strip caster casting steel strip of a single steel chemistry, operating the continuous strip caster during the production run to produce cast strip of the single steel chemistry, cooling the strip through the austenite to ferrite transformation temperature range, and selectively controlling the process parameters to produce strip having the customer-specified requirements.
• the method further includes in-line hot rolling the cast strip prior to cooling the strip through the austenite to ferrite transformation temperature range.
• the customer-specified requirements may include a specified steel grade and/or a specified strip thickness
• the process parameters to produce the customer-specified steel product may include any one or combination of casting speed of the continuous strip casting process, as-cast steel thickness of the steel product, percentage of hot reduction of the steel product, cooling rate of the steel product, coiling temperature of the steel product, percentage of cold reduction of said steel product, annealing cycle type and annealing temperature.
• One object of the present invention is to provide an improved method of providing steel strip to meet customer's orders.
• Another object of the present invention is to minimize the turnaround time between receipt of a customer order for steel strip product and actual production of the steel strip product.
• FIG. 1 is a flowchart illustrating a conventional steel strip production process.
• FIG. 2 is a diagrammatic illustration of one preferred embodiment of a continuous steel strip casting apparatus, in accordance with the present invention.
• FIG. 3 is a diagrammatic illustration showing some of the details of the twin roll strip caster of the apparatus of FIG. 1.
• FIG. 4 is a block diagram illustration of a general purpose computer system operable to convert customer-specified steel strip requirements to process parameters for controlling the continuous steel strip casting apparatus of FIGS. 2 and 3.
• FIG. 5 is a flowchart illustrating one preferred embodiment of a process flow for controlling the continuous steel strip casting apparatus of FIGS. 2 and 3 using the general purpose computer of FIG. 4.
• casting steel strip continuously in a twin roll caster involves introducing molten steel between a pair of contra-rotated horizontal casting rolls which are internally water-cooled so that metal shells solidify on the moving rolls surfaces and are brought together at the nip between them to produce a solidified strip delivered downwardly from the nip between the rolls, the term "nip" being used to refer to the general region at which the rolls are closest together.
• the molten metal may be poured from a ladle into a smaller vessel from which it flows through a metal delivery nozzle located above the nip so as to direct it into the nip between the rolls, so forming a casting pool of molten metal supported on the casting surfaces of the rolls immediately above the nip and extending along the length of the nip.
• This casting pool is usually confined between side plates or dams held in sliding engagement with end surfaces of the rolls so as to dam the two ends of the casting pool against outflow, although alternative means such as electromagnetic barriers have also been proposed.
• the casting of steel strip in twin roll casters of this kind is for example described in U.S. Patent Nos. 5,184,668, 5,277,243 and 5,934,359, all of which are expressly incorporated herein by reference.
• Applicants have determined that it is possible to produce steel strip of a given composition that has a wide range of microstructures, and therefore a wide range of mechanical properties, by continuously casting the strip and thereafter selectively varying downstream strip processing parameters. For example, applicants have determined from work carried out on plain carbon steel, including plain carbon steel that has been silicon/manganese killed, that selecting cooling rates in the range of 0.1 °C/s to greater than 100°C/s through the austenite to ferrite transformation temperature range can produce steel strip that has yield strengths that range from 200MPa to greater than 550MPa.
• a production run of a continuous strip caster that is casting steel strip of a given composition can be controlled such that the cast strip can be selectively subjected to different cooling rates through the austenite to ferrite transformation temperature range, with the result that the strip can be produced so as to have any selection of a range of different microstructures and therefore mechanical properties.
• the following description of the preferred embodiment of the present invention is in the context of continuous casting steel strip using a twin roll caster.
• the present invention is not limited to the use of twin roll casters, however, and extends to other types of continuous strip casters.
• FIGS. 2 and 3 illustrate a twin roll caster denoted generally as 54 which produces a cast steel strip 56 that passes in a transit path 52 across a guide table 58 to a pinch roll stand 60 comprising pinch rolls 60A.
• the strip passes into a hot rolling mill 62 comprising a pair of reduction rolls 62A and backing rolls 62B by in which it is hot rolled to reduce its thickness.
• the rolled strip passes onto a run-out table 64 on which it may be force cooled by water jets 66 and through a pinch roll stand 70 comprising a pair of pinch rolls 70A and 70B, and thence to a coiler 68.
• twin roll caster 54 comprises a main machine frame 72 which supports a pair of parallel casting rolls 74 having a casting surfaces 74A and 74B. Molten metal is supplied during a casting operation from a ladle (not shown) to a tundish 80, through a refractory shroud 82 to a distributor 84 and thence through a metal delivery nozzle 86 into the nip 88 between the casting rolls 74.
• Molten metal thus delivered to the nip 88 forms a pool 92 above the nip 88 and this pool 92 is confined at the ends of the rolls by a pair of side closure dams or plates 90 which are applied to the ends of the rolls by a pair of thrusters (not shown) comprising hydraulic cylinder units connected to the side plate holders.
• the upper surface of pool 92 (generally referred to as the "meniscus" level) may rise above the lower end of the delivery nozzle 86 so that the lower end of the delivery nozzle 86 is immersed within this pool 92.
• Casting rolls 74 are water cooled so that shells solidify on the moving roll surfaces and are brought together at the nip 88 between them to produce the solidified strip 56 which is delivered downwardly from the nip 88 between the rolls 74.
• the twin roll caster 54 may be of the kind which is illustrated and described in some detail in U.S. Patent Nos. 5,184,668 and 5,277,243 or U.S. Patent No. 5,488,988, the disclosures of which are each expressly incorporated herein by reference.
• customer orders for steel strip are entered into a general purpose computer system, such as computer system 150 of FIG.
• general purpose computer system 150 includes a general purpose computer 152 that may be a conventional desktop personal computer (PC), laptop or notebook computer, or other known general purposed computer configured to operate in a manner to be described subsequently.
• Computer system 150 includes a conventional keyboard 154 electrically connected to computer 152 for entering information relating to the customer's order therein, and may include any one or combination of output devices.
• computer 152 may be electrically connected to a printer 156, wherein computer 152 may be configured to print a set of process parameters in the form of a process change report or similar report, wherein the process change report sets forth the process parameters and/or set points for controlling a continuous steel strip casting process, such as continuous steel strip casting process 50 illustrated in FIGS. 2 and 3, in a manner to produce the customer ordered steel strip product.
• a continuous steel strip casting process such as continuous steel strip casting process 50 illustrated in FIGS. 2 and 3
• an operator of the continuous steel strip casting process such as process 50, views the process change report and makes corresponding physical changes to the continuous steel strip casting process to thereby produce the customer ordered steel strip product.
• Computer 152 may alternatively or additionally be electrically connected to a conventional monitor 158, wherein computer 152 may be configured to display a set of process parameters in the form of a process change report orsimilar report, wherein the process change report sets forth the process parameters and/or set points for controlling a continuous steel strip casting process, such as continuous steel strip casting process 50 illustrated in FIGS. 2 and 3, in a manner to produce the customer ordered steel strip product.
• An operator of the continuous steel strip casting process, such as process 50 may view the process change report displayed on the monitor 158, in addition to or in place of a printed report, and make corresponding physical changes to the continuous steel strip casting process to thereby produce the customer ordered steel strip product.
• Computer 152 is also electrically connected to a conventional storage media unit 160, wherein computer 152 is configured to store information to, and retrieve information from, storage unit 160 in a known manner.
• computer 152 is configured to download a set of process parameters in the form of a process change report or similar report to a storage media 162 via storage unit 160, wherein the process change report sets forth the process parameters and/or set points for controlling a continuous steel strip casting process, such as continuous steel strip casting process 50 illustrated in FIGS. 2 and 3, in a manner to produce the customer ordered steel strip product.
• Storage media unit 160 and storage media 162 may be implemented as any known storage media unit and storage media combination. Examples include, but are not limited to, a magnetic disk read/write unit 160 and magnetic diskette 162, CD ROM read/write unit 160 and CD ROM disk 162, and the like.
• the continuous steel strip casting process such as continuous steel strip casting process 50 illustrated in FIGS.
• computer system 150 may be configured to provide the process change report directly (electronically) to process 50 via a suitable communication link 164 as shown in phantom in FIG. 4.
• computer 152 may be configured in such an embodiment to download the process change report to storage media 162, wherein an operator loads the storage media 162 containing the process change report into a storage media unit (not shown) similar to. storage media unit 160 resident within process 50 as illustrated in FIG. 4 by dashed line 166.
• the continuous steel strip casting process such as process 50, is responsive to the process change report to automatically make corresponding process changes and/or apparatus set point changes.
• the strip casting process apparatus is responsive to such changes to immediately switch from producing the steel strip product that it is currently producing to producing steel strip product according to the new process parameter/process set point information.
• Process 200 begins with an initial step 202 of receiving a customer order for a steel strip product having specified mechanical properties or product specifications.
• the product specifications include a desired grade of the steel product, a desired strip thickness and total strip quantity, although the present invention contemplates requiring additional or alternative information relating to the customer ordered product.
• the product specifications are entered into computer 152 via any known mechanism therefore.
• an operator may key the information into computer 152 via keyboard 154, or if the information is provided by the customer on a storage media such as a diskette, an operator may simply upload the information into the computer via storage media unit 160.
• the present invention contemplates entering the product specifications into computer 152 in accordance with other known techniques not detailed in the attached drawings, wherein such other known techniques may include, but are not limited to, transferal of the product specifications via a telephone modem connection between computer 152 and a customer computer, transferal of the product specifications via an internet connection, or the like.
• process 200 advances from step 204 to step 206 where computer 152 is operable to compute the process parameters and/or process set points for controlling a continuous steel strip casting process, such as process 50, in a manner to produce the customer ordered steel product, based on the product specifications entered into computer 152 at step 204.
• computer 152 is programmed with one or more sets of rules relating the product specifications entered into computer 152 at step 204 to a set of process parameters/set points for controlling the continuous steel strip casting process in a manner to produce the customer ordered steel product.
• the one or more sets of rules may be implemented as any one or combination of one or more tables, one or more graphs, one or more equations, and the like.
• An example of one illustrative set of rules is set forth below in Tables I, II and III.
• Table I details a set of rules mapping product specifications relating to steel products that may be ordered by any customer to hot brand product processing parameters/set points for the continuous steel strip casting process 50 shown and described herein. As they relate to table I, ASTM-specified steel grades for hot brand products are associated with the following yield strengths (YS) and percent elongations (% Elong):
• the process parameters required to produce a customer-specified hot band steel product may include any one or combination of casting speed of the continuous strip casting process, as-cast steel thickness of the steel product, percentage of hot reduction of the steel product, cooling rate of the steel product and coiling temperature of the steel product.
• Table III details a set of rules mapping product specifications relating to steel products that may be ordered by any customer to cold rolled product processing parameters/set points for the continuous steel strip casting process 50 shown and- described herein. As they relate to table III, the ASTM-specified steel grades for cold rolled products are associated with the following yield strengths (YS) and percent elongations (% Elong):
• the process parameters required to produce a customer-specified cold rolled steel product may include any of the hot . band process parameters for producing hot band products, and additionally one any or combination of percentage of cold reduction, annealing type; e.g., batch or batch/continuous, and annealing temperature.
• process 200 advances from step 206 to step 208 where computer 152 is operable in one embodiment of the present invention to display the process parameters on a process change report to a continuous strip casting operator.
• step 208 is typically included only when computer 152 is not operable to automatically control the continuous steel strip casting process 50 as described hereinabove, and may otherwise be omitted from process 200.
• computer 152 may be configured to display the process change report via any one or more of the output devices described hereinabove with respect to FIG. 4.
• dashed-line box 210 outlines the steps of process 200 that are executed by computer 152.
• step 212 the continuous strip casting process, such as continuous strip casting process 50 illustrated and described with respect to FIGS. 2 and 3, is controlled as a function of the process- parameters computed at step 206 to thereby produce the customer-specified steel product.
• step 212 is generally not executed by computer 152 but is instead carried out by an operator of the continuous steel strip casting process. The operator executes step 212 in such embodiments by physically implementing the process parameters/set points set forth in the process change report.
• step 208 may be omitted an step 206 may advance directly to step 212.
• computer 152 may be configured to automatically implement the process parameters/set points computed at step 206 in the continuous steel strip casting process, and these cases dashed-line box 210 extends to include step 212.
• computer system 150 is operable to map the customer-specified product specifications to a production run schedule for a steel of a selected composition.
• a production run schedule for a given steel chemistry may extend for at least several days during which steel strip is continuously cast by the twin roll caster 54.
• an entire production run may be concerned with producing steel strip having one particular set of mechanical properties or for producing steel strip. of different selected mechanical properties along the length of the strip.
• the production run schedule takes into account parameters such as casting speed, hot rolling temperature range, amount of hot reduction, and cooling rates through the austenite to ferrite transformation temperature range (typically 900 to 550°C) to produce final microstructures in the cast strip that provide the strip with the required mechanical properties and the consequential materials handling issues associated with changing the cooling rates of the strip.
• the cooling rate within the range of 0.1 °C/s and in excess of 100°C/s it is possible to produce cast having microstructures including: (i) predominantly polygonal ferrite;
• such a range of microstructures can produce yield strengths in the range of 200MPa to in excess of 700MPa.
• the twin roll caster 54 can be operated to produce cast strip in accordance with the production schedule and the strip can be delivered to customers as required.
• One advantageous feature of the method of the present invention is that it is possible to adjust a production run schedule during the course of a production run to accommodate production on an urgent basis of a strip order of required mechanical properties.
• a single steel chemistry is used to produce a wide range of mechanical properties - thus customer's orders no longer need to be delayed until a heat/batch is assembled;
• strip casting in conjunction with control of rolling temperature, degree of hot reduction and the final product cooling rate can enable the achievement of the customer's dimensional specification and required mechanical properties simultaneously within one production line typically less than 70 meters in length;
• properties can be changed in real time by modifying appropriate set points on key process control loops in a central control, computer and thus the time from receipt of customer order to product dispatch can be as little as 8 hours as opposed to conventional steel production method that takes 14 to 30 days; and the very short order to delivery time enables the concept of a "virtual warehouse " via the application of e-commerce.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Factory Administration (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Coating With Molten Metal (AREA)
• Metal Rolling (AREA)
• Continuous Casting (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)

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