AU2001291504B2 - Method of providing steel strip to order - Google Patents

Abstract

A method of controlling a continuous steel strip casting process based on customer-specified requirements includes a general purpose computer in which product specifications of steel product ordered by a customer is entered. The computer is configured to automatically map the product specifications to process parameters/set points for controlling the continuous steel strip casting process in a manner to produce the customer ordered product, and in one embodiment produces a process change report detailing such process parameters/set points for operator use in physically implementing such process parameters/set points in the strip casting process. Alternatively, the computer may provide the process parameters/set points directly to the strip casting process for automatic control thereof in producing the customer ordered steel product. The process of the present invention is capable of substantially reducing the time between a customer request for a steel product and delivery thereof over that of conventional steel manufacturing processes.

Description

WO 02/26423 PCT/AU01/01227 METHOD OF PROVIDING STEEL STRIP TO ORDER Cross-Reference To Related Application This application claims priority to and the benefit of U.S. Provisional Application number 60/236,390 filed September 29, 2000.

Field Of The Invention: 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 customerspecified steel strip product.

BACKGROUND OF THE INVENTION The conventional steel industry process for fulfilling a customer's order for a steel product with particular mechanical and dimensional properties is complicated and time-consuming, and may typically require 10 or more weeks to accomplish.

Referring to FIG. 1, for example, 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 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 SUBSTITUTE SHEET (RULE 26) RO/AU WO 02/26423 PCT/AU01/01227 2 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). Thereafter at step 16, 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 1o requirements. At step 18, 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 slab reheat parameters corresponding to hot mill furnace operating parameters and/or set points for a hot strip mill processing apparatus, hot rolling parameters corresponding to mill rolling operating parameters and/or set points for the hot strip mill processing apparatus, cold rolling parameters corresponding to pickling and cold rolling operating parameters and/or set points for a cold mill 7o processing apparatus, and heat treatment parameters corresponding to heat treatment operating parameters and/or set points for a heat treatment apparatus.

From step 18, 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. Oftentimes, 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 weeks. In any case, process 10 advances from step 20 to step 22 where the slab WO 02/26423 PCT/AU01/01227 3 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. Thereafter at step 24, 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 customerspecified thickness. Finally, at step 26 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.

Conventional steel strip production of the type just described necessitates the production of many different steel grades (typically, in excess of 50) that are first cast into slabs and then processed through complex hot rolling schedules in hot strip mills that produce product in thicknesses as low as 1.5mm with yield strengths in the range 300 to 450MPa. If the customer requires thinner material or properties outside this range, subsequent processing involving pickle lines, cold reduction mills and annealing furnaces is required.

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.

N-D 4 SUMMARY OF THE INVENTION The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect, the present invention provides, a method for 0 controlling a continuous strip steel casting process to produce a plurality of customer-specified steel products with different mechanical properties, the method Sincluding: receiving an order for a first steel product including customer-specified requirements including Smechanical properties relating to said first steel CI product; mapping said customer-specified requirements to a set of predefined process parameters for controlling said continuous strip steel casting process to produce said first steel product; controlling a continuous strip steel casting process based on said set of predefined process parameters to produce a first steel product; receiving an order for a second steel product including customer-specified requirements including mechanical properties relating to said second steel product, wherein said mechanical properties are different from the mechanical properties of the first 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 switches from producing said first steel product to producing said second steel product.

In accordance with another aspect, the present invention provides a method of controlling a continuous H.\Leanne\Keep\BHP\2001291504 .doc 16/05/06 IN- O strip steel casting process to produce a customerspecified 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 Scontinuous strip steel casting process based on said process parameters to produce said steel product.

c SIn accordance with another aspect, the present CI invention provides a method of controlling a continuous strip steel casting process to produce a plurality of customer-specified steel products with different mechanical properties without changing steel composition fed to the strip casting process, the method including: receiving a plurality of orders for steel products including customer-specified requirements for different mechanical properties relating to said products; 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 producing said plurality of steel products with different mechanical properties following said mapped process parameters without changing the steel composition fed to the strip casting process.

In accordance with yet another aspect, the present invention provides 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 H \Leanne\Keep\HP\2001291504.doc 16/05/06 ID- 5A Saustenite to ferrite transformation temperature range, and selectively controlling the process parameters to produce strip having the customer-specified requirements.

00 Preferably the method further includes in-line hot rolling the cast strip prior to cooling the strip through the austenite to ferrite transformation temperature range.

In each of the foregoing methods according to the present invention, the customer-specified requirements may Sinclude a specified steel grade and/or a specified strip C1 thickness, and 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.

These and other objects of the present invention will become more apparent from the following description of the preferred embodiment.

H,\Leanne\Keep\BP\20OJ291504.doc 16/05/06 WO 02/26423 PCT/AU01/01227 6 BRIEF DESCRIPTION OF THE DRAWINGS 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.

WO 02/26423 PCT/AU01/01227 7 DESCRIPTION OF THE PREFERRED EMBODIMENT For the purposes of promoting an understanding of the principles of the invention, reference will now be made to a preferred embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that, no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated embodiment, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

The present invention is based on producing steel strip in a continuous strip caster. Applicants have carried out extensive research and development work in the field of casting steel strip in a continuous strip caster in the form of a twin roll caster. In general terms, 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 zo 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 darns 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 WO 02/26423 PCT/AU01/01227 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 1 00°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. One example of the flexibility of continuous strip casting that has thus been recognized by applicants is that a production run of a continuous strip caster that is casting steel strip of a given composition can be to 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.

Applicants have discovered, generally, that by selectively varying downstream strip processing parameters in a continuous strip steel casting process, considerable flexibility in terms of operating a continuous strip caster to meet production (i.e.

customer) requirements can be realized. This means that orders placed by customers for steel strip of a given dimensional specification and a range of different mechanical properties can be produced from a single steel chemistry in a single production run. In o addition, this means that adjustments to a production run can be made while the production run is underway. This has been recognized by applicants as being an important advantage of continuous strip casting in terms of meeting customer demands for urgent orders.

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.

Referring to FIG. 2, a continuous strip steel casting apparatus/process is illustrated as successive parts of a production line whereby steel strip can be produced in accordance with the present invention. FIGS. 2 and 3 illustrate a twin roll WO 02/26423 PCT/AU01/01227 9 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 Immediately after exiting the pinch roll stand 60, 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 comprising a pair of pinch rolls 70A and 70B, and thence to a coiler 68.

Referring now to FIG. 3, 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 lo 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 [s 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 o 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.

In accordance with the present invention, customer orders for steel strip are entered into a general purpose computer system, such as computer system 150 of FIG.

4, and processed in a manner to be more fully described hereinafter to determine process parameters and/or process set points for controlling a continuous steel strip casting process such as continuous steel strip casting process 50 just described with io respect to FIGS. 2 and 3 to thereby satisfy the customer's order. Referring to FIG. 4, WO 02/26423 PCT/AU01/01227 general purpose computer system 150 includes a general purpose computer 152 that may be a conventional desktop personal computer 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.

For example, 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. In one embodiment of the present invention, 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 o'similar report, wherein zo 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. In one embodiment of the WO 02/26423 PCT/AU01/01227 11 present invention, 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. An operator of the continuous steel strip casting process, such as process 50, may then access the contents of the storage media via conventional techniques to view the process change report and make corresponding physical changes to the continuous steel strip casting process to thereby 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.

In an alternative embodiment, the continuous steel strip casting process, such as continuous steel strip casting process 50 illustrated in FIGS. 2 and 3, is a computercontrolled process, and in this case 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. Alternatively still, 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. In either case, 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. It is to be understood, however, that regardless of how process and/or set point changes are made to the continuous steel strip casting process, 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 WO 02/26423 PCT/AU01/01227 12 point information.

Referring now to FIG. 5, a flowchart is shown illustrating one preferred embodiment of a process 200 for controlling a continuous strip steel casting process, such as process 50 illustrated and described with respect to FIGS. 2 and 3, to produce a customer-specified steel product. 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. In one embodiment, 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 lo information relating to the customer ordered product. Thereafter at step 204, the product specifications are entered into computer 152 via any known mechanism therefore. For example, 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. Alternatively, 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.

In any case, 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. In accordance with the present invention, 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, WO 02/26423 PCT/AU01/01227 13 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): ASTM Grade Grade 33 Grade 40 Grade 50 Grade 65 Grade 80 YS (ksi) 33 to 43 40 to 50 50 to 60 65 to 75 80 to 90 Elong 30 to 25 to 20 to 15 to 10 to And the residual level indicators L, M and H are defined by the relationships Low 0.35 Med 0.8 and High =1.2 Table I Hot band product Caster process set points specifications CUSTOMER ORDER Thickness ASTM Level of Casting As-cast hot ROT cooling (mm) grade residuals Speed thickness reduction curve (Cu+Sn+ (m/min) (mm) Mo+Ni+ Cooling Coiling Cr) Rate* Temp (oC) 0.04" Grade 33 Cannot be produced with the current chemistry mm) 0.04" Grade 40 -L 80 1.6 38 700 mm) 0.04" Grade 50 L 80 1.6 38 150 mm) M 80 1.6 38 700 0.04" Grade 65 L 80 1.6 38 200 WO 02/26423 PCT/AU01/01227 mm) M 80 1.6 38 150 H 80 1.6 38 650 0.04" Grade 80 M 80 1.6 38 200 mm) L 80 1.6 38 250 0.047" Grade 33 Cannot be produced with the current chemistry (1.2 mm) 0.047" Grade 40 L 80 1.6 25.0 700 (1.2 mm) 0.047" Grade 50 L 80 1.6 25.0 150 (1.2 mm) M 80 1.6 25.0 700 L 45 1.9 37 650 0.047" Grade 65 L 80 1.6 25.0 200 (1.2 mm) M 80 1.6 25.0 150 H 80 1.6 25.0 650 0.047" Grade 80 H 80 1.6 25.0 200 (1.2 mm) M 80 1.6 25.0 250 0.055" Grade Cannot be produced with the current chemistry 33 0.055" Grade 40 L 80 1.6 12.5 700 (1.4mm) 0.055" Grade 50 L 80 1.6 12.5 (1.4mm) M 80 1.6 12.5 650 L 45 1.9 26.0 650 0.055" Grade 65 L 80 1.6 12.5 100 (1.4mm) 0.055" Grade 80 L B0 1.6 12.5 150 (1.4mm) H 80 1.6 12.5 650 0.063" Grade 33 Cannot be produced with the current chemistry (1.6 mm) 0.063" Grade 40 L 80 1.6 0.0 700 (1.6 mm) 0.063" Grade 50 L 80 1.6 0.0 (1.6 mm) M 80. 1.6 0.0 650 0.063" Grade 65 L 80 1.6 0.0 100 (1.6 mm) 0.063" Grade 80 L 80 1.6 0.0 150 (1.6 mm) H 80 1.6 0.0 650 0.075" Grade 33 Cannot be produced with the current chemistry (1.9 mm) 0.075" Grade 40 L 45 1.9 0.0 700 (1.9 mm) 0.075" Grade 50 M 45 1.9 0.0 650 (1.9 mm) 0.075" Grade 65 H 45 1.9 0.0 650 (1.9 mm) I I I I I WO 02/26423 PCT/AU01/01227 0.075" Grade 80 Unlikely to produce as the transformation will occur before (1.9 mm) the ROT cooling rate in the 800 5000 C temperature range A general set of rules for hot band products used to generate the Table I values are summarized in Table II below, wherein the term "chemistry" refers to the level of residuals in the steel product, and wherein the Low, Med and High levels are summarized above.

Table II Chemistry %HR Cooling rate Yield strength MPa Low <15 150 550 Low 25-40 250 550 Med 25-40 200 550 High 0-50 30* 550 Low <15 100 475 Low 25-40 200 475 Med 25-40 150 475 High 0-50 30* 475 Low <15 60 400 Low 25-40 150 400 Med 25-40 30* 400 Low 0-50 30* 350 standard cooling rate to achieve coiling temperatures around 650 700°C From data gathered from actual runs, it was determined that 1.2% of residuals resulted in an increase in yield strength of approximately 120 Mpa, and it is therefore assumed that a 0.1% increase in residuals results in a corresponding 10 Mpa increase in yield strength.

From Table I, it should now be apparent that 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.

WO 02/26423 PCT/AU01/01227 16 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 andc 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): ASTM Grade Grade 33 Grade 40 Grade 50 Grade 65 Grade 80 YS (ksi) 33 to 43 40 to 50 50 to 60 65 to 75 80 to 90 Elona 30 to 30 to 25 to 10 to 2 min.

Table III Cold rolled product Hot band Cold rolling/annealing parameters specifications specifications CUSTOMER ORDER Cold Cold Hot band Hot band cold Annealing Annealing rolled rolled thickness ASTM reduction cycle temperature Thickness ASTM (mm) grade (mm) grade 0.008" Grade 33 1.0-1.6 Grade 40 80-88 Batch Lab data* (0.2 mm) Annealing see (BA) footnote 0.008" Grade 40 1.0-1.6 Grade 40 80-88 Batch/Con 1250-1350 (0.2 mm) -tinuous Annealing

(CA)

0.008" Grade 50 1.4-1.6 Grade 50 86-88 CA 1250-1350 (0.2 mm) 0.008" Grade (0.2 mm) 0.008" Grade 80 Grade 40 80-88 N/A N/A (0.2 mm) 0.016" Grade 33 1.0- 1.6 Grade 40 60-75 BA (0.4 WO 02/26423 PCT/AU01/01227 0.016" Grade 40 1.0-1.6 Grade 40 60-75 BA/CA 1250-1350 (0.4 mm) 0.016" Grade 50 1.4-1.6 Grade 50 70-75 CA 1250-1350 (0.4 mm) 0.016" Grade (0.4 mm) 0.016" Grade 80 Grade 40 60-75 N/A N/A (0.4 mm) 0.024" Grade 33 1.4-1.6 Grade 40 57-63 BA (0.6 mm) 0.024" Grade 40 1.4-1.6 Grade 40 57-63 CA 1250-1350 (0.6 mm) 0.024" Grade 50 Grade 50 57-68 CA 1250-1350 (0.6 mm) 0.024" Grade (0.6 mm) 0.024" Grade 80 Grade 40 40-63 N/A N/A (0.6 mm) 0.032" Grade 33 1.4-1.6 Grade 40 43-50 BA (0.8mm) 0.032" Grade 40 Grade 40 50-58 BA (0.8mm) 0.032" Grade (0.8mm) 0.032" Grade 65 1.0 Grade 40 20 N/A N/A (0.8mm) 0.032" Grade 80 Grade 40 33-50 N/A N/A (0.8mm) 0.040" Grade 33 1.9 Grade 40 47 BA mm) 1 0.040" Grade 40 1.9 Grade 40 47 BA mm) 0.040" Grade mm) 0.040" Grade 65 1.3 Grade 40 23 N/A N/A mm) 0.040" Grade 80 Grade 40 38-48 N/A N/A mm) I I I Lab data on batch annealing slow heating to 1275°F (took around 33 hours) followed. by slow cooling from 1275°Fto 750°F (took around 8 hours). Material yield strength after annealing was quite low (23 ksi), there accordingly exists an opportunity to optimize batch annealing for Grade 33.

WO 02/26423 PCT/AU01/01227 18 thinner gauge hot band preferred, as less cold reduction will give better elongation.

thicker gauge hot band preferred to get higher yield strength with good elongation after annealing.

A general set of rules for cold rolled material used to generate the Table III values are: need greater than 35-40 CR to get Grade (ii) for continuous annealing, need at least 50% cold reduction, and (iii) for batch annealing, need at least 40% cold reduction.

From Table III, it should now be apparent that 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; batch or batch/continuous, and annealing temperature.

Referring again to FIG. 5, process 200 advances from step 206 to step 208 where computer 152 is operable in one embodiment of the present invention to display z0 the process parameters on a process change report to a continuous strip casting operator. It will be appreciated that step 208 is typically included only when computer 152 is not operable to automatically control the continuous steel strip casting process as described hereinabove, and may otherwise be omitted from process 200. If included, 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. In this embodiment, dashed-line box 210 outlines the steps of process 200 that are executed by computer 152. Additionally, as described hereinabove, the present invention contemplates embodiments wherein computer 152 is operable to receive the customer order electronically, and dashed-line box 210 may be extended in such embodiments to include step 202.

WO 02/26423 PCT/AU01/01227 19 Following step,208, process 200 advances to step 212 where 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 processparameters computed at step 206 to thereby produce the customer-specified steel product. In embodiments of process including step 208, 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. In embodiments wherein computer 152 is configured to provide the process parameters/set points directly (electronically) to the continuous steel strip casting process, step 208 may be omitted an step 206 may advance directly to step 212. In such embodiments, 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.

In accordance with the present invention, computer system 150 is operable to map the customer-specified product specifications to a production run schedule for a steel of a selected composition. Typically, a production run schedule for a given steel chemistry may extend for at least several days during which steel strip is continuously zo cast by the twin roll caster 54. Depending upon the number of orders and ordered quantities, 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 5500C) 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.

io By adjusting the cooling rate within the range of 0.1°C/s and in excess of WO 02/26423 PCT/AU01/01227 100°C/s it is possible to produce cast having microstructures including: predominantly polygonal ferrite; (ii) a mixture of polygonal ferrite and low temperature transformation products,-such as a acicular ferrite, Widmanstatten ferrite, and bainite; and (iii) predominantly low temperature transformation products.

In the case of plain carbon steels, such a range of microstructures can produce yield strengths in the range of 200MPa to in excess of 700MPa. After the production run schedule has been established, the twin roll caster 54 can be operated to produce 0to 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. Thus, in the method of the present invention: 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 ?o 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.

While the invention has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as illustrative and not restrictive in character, it being understood that only preferred embodiments thereof have been IN 21 shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.

00 It is to be understood that, if any prior art publication is referred to herein, such reference does not Sconstitute an admission that the publication forms a part I of the common general knowledge in the art, in Australia or any other country.

H\Leanne\eep\BHP\2001291504.doc 16/05/06

Claims (45)

1. A method for 6ontrolling a continuous strip steel casting process to produce a plurality of customer- specified steel products with different mechanical properties, the method including: receiving an order for a first steel product including customer-specified requirements including mechanical properties relating to said first steel product; mapping said customer-specified requirements to a set of predefined process parameters for controlling said continuous strip steel casting process to produce said first steel product; controlling a continuous strip steel casting process based on said set of predefined process parameters to produce a first steel product; receiving an order for a second steel product including customer-specified requirements including mechanical properties relating to said second steel product, wherein said mechanical properties are different from the mechanical properties of the first 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 switches from producing said first steel product to producing said second steel product.

2. The method of claim 1 wherein said customer- specified requirements include thickness of said steel products. AMENDED SHEET IPEAIAU Pc/ /AU 01 ci i1 23

3. The method of claim 1 or claim 2 wherein said customer-specified requirements include grade of said steel products.

4. The method of any one of the preceding claims wherein said set of new process parameters include a casting speed of said continuous strip steel casting process.

5. The method of any one of the preceding claims wherein said set of new process parameters include an as- cast thickness of said steel product.

6. The method of any one of the preceding claims wherein said set of new process parameters include a percentage of hot reduction of said steel product.

7. wherein cooling

8. wherein coiling The method of any one of the preceding claims said set of new process parameters include a rate of said steel product. The method of any one of the preceding claims said set of new process parameters include a temperature of said steel product.

9. The method of any one wherein said set of new process percentage of cold reduction of

10. The method of any one wherein said set of new process annealing cycle type. of the preceding claims parameters include a said steel product. of the preceding claims parameters include an

11. The method of claim 10 wherein said set of new process parameters include an annealing temperature,

12. A method of providing custom-specified steel AMENDED SHEET IPEAIAU P /IAu 0 1o l1 a=zisWeA 11 teaMboLr lool 24 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 for producing cast strip and cooling the strip to produce strip having the customer-specified requirements.

13. The method of claim 12 further includes in-line hot rolling the cast strip prior to cooling the strip through the austenite to ferrite transformation temperature range.

14. The method of claim 12 or claim 13 wherein said customer-specified requirements include thickness of said steel strip.

15. The method of any one of claims 12 to 14 wherein said customer-specified requirements include grade of said steel strip.

16. The method of any one of claims 12 to 15 wherein said process parameters include a casting speed of said continuous strip steel casting process.

17. The method of any one of claims 12 to 16 wherein said process parameters include an as-cast thickness of said steel strip.

18. The method of any one of claims 12 to 17 wherein AMENDED SHEET IPEAIAU Pcs /AU cu/01d1-- -aa~r 236o7 said process parameters include a percentage of hot reduction of said steel strip.

19. The method Of any one of claims 12 to 18 wherein -9 said process parameters include a cooling rate of said steel strip. ao. The method of any one of claims 12 to i9 wherein said process parameters include a coiling temperature of said steel strip.

21. The method of any one of claims 12 to 20 wherein said process parameters include a percentage of cold reduction of said steel strip.

22. The method of any on eof claims 12 to 21 wherein said process parameters include an annealing cycle type.

23. The method of claim 22 wherein said process parameters include an annealing temperature.

24. A method of controlling a continuous strip steel casting process to produce a plurality of customer- specified Pteel products with different mechanical properties without changing steel composition fed to the strip casting process, the method including: receiving a plurality of orders for steel products including customer-s-pedified requiremtents for different mechanical properties relating to said products; mapping said customer-specified requirements to a number of process parameters for controllinlg a continuous strip steel casting process to produce said steel product; and producing said plurality of steel products with different mechanical properties following said mapped process parameters without changing the steel composition fed to the strip casting process. AMENDED SHEET IPEAIAUi Pi s/g Ol/Oill -26 The method of claim 24 including the further step of: displaying said number Of process parameters on a process change report to an operator Of said continuous strip steel casting process-

26. The method of claima 25 further including controlling said continuous strip steel casting process based on said process parameters displayed on said process change report to produce said steel product.

27. The method of any of claims 24 to 26 wherein said plurality of customer-specified requirements for different mechanical properties include different grades of said steel products,

28. The method of any one of claims 24 to 27 wherein said number of process parameters includes casting speed of said continuous strip steel casting process.

29. The method of any one of claims 24 to 28 wherein said number of process parameters includes percentage of hot reduction of said steel products. The method of any one of claims 24 to 29 wherein said number of process parameters includes cooling rate of said steel products.

31. The method of any one of claims 24 to 30 wherein said number of process parameters includes hot rolling temperature of said steel products.

32. The method of any one of claims 24 to 31 wherein said number of process parameters includes coiling temperature of said steel products. AMENDED SHEET IPEAI AIJ ID- 27- S33. The method of any one of claims 24 to 32 wherein said number of process parameters includes percentage of cold reduction of said steel product. 00

34. The method of any one of claims 24 to 33 wherein said number of process parameters includes annealing cycle type. A method of controlling a continuous strip steel casting process to produce a customer-specified steel Sproduct, the method comprising: receiving an order for a CI 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.

36. The method of claim 35 wherein said customer-specified requirements include thickness of said steel product.

37. The method of claim 35 or 36 wherein said customer- specified requirements include grade of said steel product.

38. The method of any one of claims 35 to 37 wherein said number of process parameters includes casting speed of said continuous strip steel casting process.

39. The method of any one of claims 35 to 38 wherein said number of process parameters includes as-cast thickness of said steel product.

40. The method of any one of claims 35 to 39 wherein said number of process parameters includes percentage of hot reduction of said steel product. H\Leanne\Keep\BHP\2001291504.doc 16/05/06 28

41. The method of any one of claims 35 to 40 wherein said number of process parameters includes cooling rate of said steel product. 00

42. The method of any one of claims 35 to 41 wherein said number of process parameters includes hot rolling V)temperature of said steel product.

43. A method of controlling a continuous strip steel Scasting process to produce a customer-specified steel CI product, the method comprising: receiving an order for a steel product including customer-specified requirements relating to said product; and mapping said customer- specified requirements to a number of process parameters for controlling a continuous strip steel casting process to produce said steel product.

44. The method of claim 43 further including controlling said continuous strip steel casting process based on a process parameters displayed on a process change report to produce said steel product. The method of claim 43 or 44 wherein said customer- specified requirements include thickness of said steel product.

46. The method of any one of claims 43 to 45 wherein said customer-specified requirements include grade of said steel product.

47. The method of any one of claims 43 to 46 wherein said number of process parameters includes casting speed of said continuous strip steel casting process.

48. The method of any one of claims 43 to 47 wherein said number of process parameters includes as-cast thickness of Hs\Leanne\Keep\BHP\2001291504.doc 16/05/06 -29 O said steel product.

49. The method of any one of claims 43 to 48 wherein said number of process parameters includes percentage of hot reduction of said steel product. The method of any one of claims 43 to 49 wherein said Vt number of process parameters includes cooling rate of said steel product. S51. The method of any one of claims 43 to 50 wherein said C( number of process parameters includes the hot rolling temperature of said steel product.

52. A method of controlling a continuous strip steel casting process to produce a plurality of customer specified steel products, the method being substantially as described herein with reference to Figures 2 to

53. A method of providing custom-specified steel strip substantially as described herein with reference to Figures 2 to Dated this 16th day of May 2006 BHP STEEL (JLA) PTY LTD and ISHIKAWAJIMA-HARIMA HEAVY INDUSTRIES COMPANY LIMITED By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H.\Leanne\Keep\BHP\2001291504.doc 16/05/06