JP2009528168A - Low surface roughness cast strip and method and apparatus for manufacturing the same - Google Patents

Abstract

It has at least one microstructure selected from the group consisting of polygonal ferrite, acicular ferrite, Widmanstatten, bainite, and martensite, has a surface roughness of less than 1.5 microns Ra, and a scale thickness of about A thin cast strip that is less than 10 microns applies the oil / water mixture to the work roll of the hot rolling mill, and passes the thin cast strip through the hot rolling mill at a temperature of less than 1100 ° C. while the oil / water mixture is applied to the work roll; It is formed by wrapping a thin cast strip passing from a casting roll through a hot rolling mill in an atmosphere of less than 5% oxygen to form a thin cast strip.

Description

  The present invention relates to a cast strip produced by a twin roll caster and a method and apparatus for producing such a cast strip.

  In the twin roll casting machine, the molten metal is introduced between a pair of horizontal casting rolls that are cooled and rotated in the mutual direction, so that the metal shell is solidified on the moving roll surface, and the roll gap between the rolls is set. Together to produce a solidified strip product that is fed downward from the roll gap between the casting rolls.

  In this specification, the term “roll gap” is used to refer to the entire region where casting rolls are closest to each other. Molten metal is poured from a ladle through a metal feeding system that is arranged above the roll gap and is composed of a tundish and a core nozzle, and is supported by the roll casting surface above the roll gap and extends along the length of the roll gap. A molten metal casting pool can be formed. The casting pool is normally enclosed by a refractory side plate or side weir that is slidably engaged with the roll end face to dam the ends of the casting pool so as not to overflow.

  When steel strips are cast on a twin roll caster, the strip exits the roll gap at very high temperatures in the range of 1400 ° C or higher. When exposed to normal atmosphere, the strips undergo scaling very rapidly due to such high temperature oxidation. Accordingly, a sealed enclosure is provided below the casting roll to receive the hot strip. The enclosure through which the strip from the strip caster passes contains an atmosphere that prevents oxidation of the strip. An atmosphere that prevents oxidation can be created by injecting a non-oxidizing gas, such as a combustion exhaust gas, which can be an inert or reducing gas such as argon or nitrogen. Alternatively, the sealed portion may be sealed so that an atmosphere containing oxygen does not enter during operation of the strip casting machine. Next, as disclosed in Patent Document 1 and Patent Document 2, oxygen is extracted from the sealed enclosure portion that allows oxidation of the strip, thereby reducing the oxygen content of the atmosphere in the enclosure portion in the initial phase of casting.

It is known to form a thin strip by casting a cast strip produced on a twin roll caster after the strip has exited the caster and hot rolling on a hot rolling mill. It is generally understood that a combination of a rolling mill and a twin roll caster is necessary to provide the desired cross-sectional profile for the strip.
US Patent No. 5,762,126 US Patent No. 5,960,855

  However, when a strip cast at a standard casting speed of 80 m / min is hot-rolled by a hot rolling mill so that the strip is reduced by 16%, the surface roughness is relatively high at 6 to 8 microns Ra. It has been found that surface microcracks can occur. FIG. 1 is a photomicrograph showing typical surface roughness of such a cast and hot rolled strip from a hot rolling mill in the same line as a twin roll caster. The rolling direction is from left to right, and the photomicrograph shows significant lapping on the strip surface (20-30 μm depth). The reason for this surface roughness may be due to shearing at the strip surface due to the welding of the strip to the work roll surface, texture of the work roll surface being imprinted on the strip surface and / or other factors. Furthermore, microcracks on the surface of the cast strip have been considered a problem. Although it was possible to reduce microcracks by reducing the casting speed and heat consumption rate of the strip, it was uneconomical to reproduce these conditions during production.

  The microstructure of the hot strip mill product is nearly 100% equiaxed ferrite. However, when making a cast strip with a twin roll caster, what has been conventionally experienced is that the microstructure is coarse grains of polygonal ferrite, acicular ferrite and Widmanstatten, and the microstructure is 30-60. Typically,% is polygonal ferrite and 70 to 40% is Widmanstatten and acicular ferrite. For this microstructure, the typical surface roughness was 4-7 microns Ra.

It has at least one microstructure selected from the group consisting of polygonal ferrite, acicular ferrite, Widmanstatten, bainite and martensite, surface roughness less than 1.5 microns Ra, and scale thickness of about 10 microns. A thin cast strip is provided that is less than and is made from the following steps.
a) assembling a twin roll caster having laterally positioned caster rolls forming a roll gap therebetween and a hot rolling mill having a work roll and a backup roll adjacent to the twin roll caster;
b) forming a thin cast strip from the roll gap between the casting rolls of the twin roll caster;
c) Apply the oil / water mixture to the work roll of the hot rolling mill,
d) passing the thin cast strip through a hot rolling mill at a temperature below 1100 ° C. with the oil-water mixture applied to the work roll;
e) selected from the group consisting of polygonal ferrite, acicular ferrite, Widmanstatten, bainite and martensite, with a thin cast strip passing from a casting roll through a hot rolling mill in an atmosphere of less than 5% oxygen. A thin cast strip having at least one microstructure and having a surface roughness of less than 1.5 microns Ra and a scale thickness of less than 10 microns is formed.

Also provided is a thin cast steel strip made from the following steps and having a surface roughness reduced to less than 1.5 microns Ra.
a) assembling a strip casting machine comprising a pair of casting rolls with a gap between the rolls;
b) assembling a metal feed system, in which a casting pool can be formed between the casting rolls above the roll gap, and a side dam adjacent to the end of the roll gap surrounds the casting pool;
c) assembling a hot rolling mill with a work roll adjacent to the strip caster and having a working surface forming a gap for rolling the hot strip;
d) assembling a spray nozzle positioned adjacent to the work roll to provide an oil / water mixture to the work roll;
e) introducing molten steel between the pair of casting rolls to form a casting sump supported on the casting surface of the casting roll and enclosed by the first side weir;
f) rotating the casting rolls in opposite directions to form a solidified metal shell on the surface of the casting roll, casting a steel strip from the casting shell through a roll gap between the casting rolls;
g) spraying the oil-water mixture as the strip enters the hot rolling mill,
h) Rolling the cast strip between work rolls of a hot rolling mill to produce a cast strip having a surface roughness of less than 1.5 microns Ra.

Also provided is a thin cast steel strip made from the following steps and having a surface roughness reduced to less than 1.5 microns Ra.
a) assembling a strip casting machine comprising a pair of casting rolls with a gap between the rolls;
b) assembling a metal feed system that can form a casting pool between the casting rolls above the roll gap and surrounds the casting pool with a side dam adjacent to the end of the roll gap;
c) assembling a hot rolling mill having a backup roll and a work roll adjacent to the strip casting machine, the hot strip being rolled by the work surface forming a gap between the work rolls;
d) assembling a spray nozzle located upstream of the work roll and capable of spraying the oil-water mixture on the backup roll;
e) Molten steel is introduced between the pair of casting rolls to form a casting reservoir supported on the casting surface of the casting roll and enclosed by the first side dam. f) Casting by rotating the casting rolls in opposite directions. Forming a solidified metal shell on the roll surface, casting a steel strip from the solidified shell through a roll gap between the casting rolls;
g) spraying the oil-water mixture as the casting strip enters the hot rolling mill;
h) Rolling the cast strip between work rolls of a hot rolling mill to produce a cast strip having a surface roughness of less than 1.5 microns Ra.

  The thin cast strip may have a surface roughness of less than 1.0 micron Ra, or less than 0.7 micron Ra, or less than 0.5 micron Ra, or less than 0.4 micron Ra.

  The thin cast strip may have a scale thickness of less than 7 microns, or less than 4 microns. The cast strip can be passed through a hot rolling mill at a temperature below 1050 ° C. with the oil / water mixture applied to the work roll.

  The thin cast strip may have a scale thickness of less than 7 microns, or less than 4 microns.

  The oil-water mixture can be applied by spraying on work rolls.

  The oil / water mixture can be applied to a backup roll.

  The oil-water mixture is less than 5% oil and can form a thin cast strip with a low surface roughness of less than 1.5 microns Ra.

It has at least one microstructure selected from the group consisting of polygonal ferrite, acicular ferrite, Widmanstatten, bainite, and martensite, has a surface roughness of less than 1.5 microns Ra, and a scale thickness of about A method of producing a thin cast strip that is less than 10 microns is provided, which method comprises the following steps.
a) assembling a twin roll caster having laterally positioned caster rolls forming a roll gap therebetween and a hot rolling mill having a work roll and a backup roll adjacent to the twin roll caster;
b) forming a thin cast strip from the roll gap between the casting rolls of the twin roll caster;
c) Apply the oil / water mixture to the work roll of the hot rolling mill,
d) passing the thin cast strip through a hot rolling mill at a temperature below 1100 ° C. while the oil / water mixture is applied to the work roll;
e) At least selected from the group consisting of polygonal ferrite, acicular ferrite, Widmanstatten, bainite and martensite, wrapped in a cast cast roll through a hot rolling mill with a thin cast strip in an atmosphere of less than 5% oxygen. A thin cast strip having a single microstructure, a surface roughness of less than 1.5 microns Ra and a scale thickness of less than 10 microns is formed.

Also provided is a method for producing a thin cast steel strip having a surface roughness reduced to less than 1.5 microns Ra, the method comprising the following steps.
a) assembling a strip casting machine comprising a pair of casting rolls with a gap between the rolls;
b) assembling a metal feed system that can form a casting pool between the casting rolls above the roll gap and surrounds the casting pool with a side dam adjacent to the end of the roll gap;
c) assembling a hot rolling mill having a work roll adjacent to the strip caster and the hot strip being rolled by a working surface forming a gap therebetween;
d) assembling a spray nozzle positioned adjacent to the work roll and capable of providing an oil / water mixture to the work roll;
e) introducing molten steel between the pair of casting rolls to form a casting sump supported by the casting surface of the casting roll and enclosed by the first side weir;
f) forming a solidified metal shell on the surface of the casting roll by rotating the casting roll in a mutual direction, and casting a steel strip from the solidified shell through a roll gap between the casting rolls;
g) spraying the oil-water mixture as the strip enters the hot rolling mill,
h) rolling the cast strip between work rolls of a hot rolling mill to produce a cast strip having a surface roughness of less than 1 micron Ra

There is also provided a method for producing a thin cast steel strip having a surface roughness reduced to less than 1.5 microns Ra, the method comprising the following steps.
a) assembling a strip casting machine comprising a pair of casting rolls with a gap between the rolls;
b) assembling a metal feed system that can form a casting pool between the casting rolls above the roll gap and surrounds the casting pool with a side dam adjacent to the end of the roll gap;
c) assembling a hot rolling mill having a backup roll and a work roll adjacent to the strip caster, wherein the hot strip is rolled by a work surface forming a gap between the work rolls;
d) assembling a spray nozzle positioned upstream of the work roll and capable of spraying the oil / water mixture onto the backup roll;
e) introducing molten steel between the pair of casting rolls to form a casting sump supported by the casting surface of the casting roll and enclosed by the first side weir;
f) rotating the casting rolls in the mutual direction to form a solidified metal shell on the surface of the casting roll, and casting a steel strip from the solidified shell through a roll gap between the casting rolls;
g) spraying the oil-water mixture as the casting strip enters the hot rolling mill;
h) Rolling the cast strip between work rolls of a hot rolling mill to produce a cast strip having a surface roughness of less than 1.5 microns Ra.

  The method can consist of applying an oil / water mixture by spraying it onto a work roll with an oil / water mixture, for example a spray nozzle.

  The spray rate through the nozzle may be 10-30 gallons / minute.

  The oil / water mixture may be applied to the work roll by applying the oil / water mixture to a backup roll.

  The method may comprise producing a cast strip at a speed of about 80 m / min.

  The rolling temperature may be less than 110O ° C, or less than 1050 ° C, or less than 900 ° C.

  The exemplary casting and rolling equipment comprises a twin roll caster, generally designated by reference numeral 11, in which a thin cast steel strip 12 produced passes through a transition path and passes across a guide table 13 to pinch rolls. The stand 14 is reached. After exiting the pinch roll stand 14, the thin cast strip 12 enters a hot rolling mill 15 comprised of a backup roll 16 and upper and lower work rolls 16A, 16B, and the strip thickness is reduced. The strip 12 exiting the rolling mill 15 can be forcedly cooled by a water jet 18 over a runout table 17 and then passed through a pinch roll stand 20 composed of a pair of pinch rolls 2OA. To 19.

  The pair of laterally positioned casting rolls 22 supported by the main machine frame constituting the twin roll casting machine 11 has a casting surface 22A that forms a roll gap therebetween. During the casting operation, the molten metal is fed from a ladle (not shown) to the tundish 23, into a tundish 25 (also called a distribution vessel or transition piece) that can be removed via a refractory shroud, and further to the roll gap. It leads to a metal feed nozzle 28 (also called a core nozzle) between the upper casting rolls 22.

  Molten steel is introduced into the tundish 25 which can be removed from the tundish 23 through the refractory shroud outlet. The tundish 23 includes a stopper rod and a slide gate valve (not shown), and selectively opens and closes the shroud outlet to effectively control the molten metal flow from the tundish 23 to the casting machine. Molten metal flows from the removable tundish 25 to the outlet and optionally to the feed nozzle 28.

  Accordingly, the molten metal fed to the casting roll 22 forms a casting reservoir supported by the casting roll surface 22A above the roll gap. A pair of side dams or side plates that enclose the casting pool at the roll ends are applied to the roll ends by a pair of thrusters (not shown) constituted by a hydraulic cylinder unit connected to the side dams. The upper surface of the casting pool (commonly referred to as the “meniscus” level) may be above the lower end of the feeding nozzle 28 so that the lower end of the feeding nozzle is immersed in the casting pool.

  The casting roll 22 is internally water-cooled by a coolant supply source (not shown) and is rotationally driven in a mutual direction by a driving device (not shown), so that the shell is solidified on the surface of the moving casting roll. They are joined together at the roll gap to produce a thin cast strip 12, which is fed downward from the roll gap between the cast rolls.

  Below the twin roll casting machine 11, the cast steel strip 12 passes through the sealed enclosure 10 to the guide table 13, and the guide table guides the strip to the pinch roll stand 14, and then the sealed enclosure. Get out of 10. The seal of the enclosure 10 may not be perfect, but should be appropriate to allow control of the atmosphere within the enclosure and the access of oxygen to the cast strip within the enclosure as described below. After exiting the sealed enclosure 10, the strip can pass through a further sealed enclosure containing a hot rolling mill 15 after the pinch roll stand 14.

  The enclosure portion 10 is formed by connecting a plurality of separate wall portions with various seal connecting portions to form a continuous enclosure portion wall. These connecting portions are constituted by a first wall portion 41 surrounding the casting roll 22 in a twin roll casting machine, an opening extending below the first wall portion 41, and an upper edge portion of the scrap box container 40. It is the wall enclosure part 42 which carries out seal engagement. The seal 43 between the scrap box container 40 and the enclosure wall 42 can be formed by a knife / sand seal around the opening of the enclosure wall 42, and the seal can be established / released by the vertical movement of the scrap box container 40 relative to the enclosure wall 42. . The seal 43 is formed by raising the scrap box container 40 and allowing a knife flange to enter the groove sand to establish a seal.

  The seal 43 can be released by lowering the scrap box container 40 from the operating position to move it to a scrap discharge position (not shown) away from the casting machine. Since the scrap box container 40 is attached to a carriage 45 with wheels 46 and travels on the rail 47, the scrap box container can be moved to the scrap discharge position. A pair of powered screw jacks 51 provided on the carriage 45 is moved from a lowered position where the scrap box container 40 is separated from the enclosure wall 42 to an elevated position where the knife flange enters the sand and forms a seal 43 therebetween. And is operable.

  The sealed enclosure portion 10 can be further configured by a third wall portion 61 disposed around the guide table 13 and connected to the frame of the pinch roll stand 14 including the pair of pinch rolls 50. The 3rd wall part 61 distribute | arranged to the enclosure part 10 is sealed with a sliding seal.

  Most of the enclosure part wall parts 41, 42, 61 may be lined with refractory bricks. Further, the scrap box container 40 may be lined with a refractory brick or an irregular refractory lining. In this way, the entire enclosure 10 is sealed prior to the casting operation, thereby limiting oxygen access to the thin cast strip 12 as the strip goes from the casting roll 22 through the pinch roll stand 14 to the hot rolling mill 15. To do.

  Initially, the strip can remove all oxygen from the enclosure 10 by forming a heavy scale at the initial portion of the strip. However, the sealed enclosure 10 limits the oxygen entry from the ambient atmosphere into the enclosure and reduces the amount of oxygen that the strip can take up. Therefore, after the initial start-up period, the oxygen content of the enclosure 10 remains exhausted, limiting the amount of oxygen that can be used for strip 12 oxidation. In this way, scale formation is controlled to a thickness of less than 10 microns without the need to continuously deliver reducing or non-oxidizing gas to the enclosure. Of course, reducing or non-oxidizing gas may be supplied through the enclosure wall. However, to avoid heavy scaling during the start-up period, the enclosure 10 can be cleaned immediately before the start of casting to lower the initial oxygen level in the enclosure 10 thereby oxidizing the strip passing through the enclosure. As a result of the interaction with the oxygen to be produced, the time until the oxygen level in the enclosure is stabilized is reduced. For example, as an example, the sealed portion can be conveniently cleaned with nitrogen gas or the like. By reducing the initial oxygen content to a level as low as 5%, it has been found that even during the initial start-up phase, the strip scaling at the exit from the enclosure 10 is limited to about 10-17 microns. . In embodiments of the invention, the scale thickness of the thin cast steel strip may be less than about 10 microns in continuous casting, or the scale thickness may be less than 7 microns or less than 4 microns.

  At the beginning of the casting operation, a short length of incomplete strip is produced until the casting condition is stabilized. When continuous casting is established, the casting roll 22 is slightly spaced and then re-matched, and the strip tip is as described in Australian Patent 646,981 and US Pat. No. 5,287,912, Cut off to form a clean head end of the subsequent thin cast strip 12. The incomplete material falls into a scrap box container 40 located below the casting machine 11, and at this time, as shown in FIG. 3, a swivel apron 38 usually hanging from the pivot 39 to one side of the casting machine is used. Swing across the outlet to guide the clean head end of the thin cast strip 12 to the guide table 13 and the strip is fed to the pinch roll stand 14. Then, the apron 38 is returned to the drooping position as shown in FIG. 3 so that the strip 12 can be drooped into the loop 36 on the lower side of the casting machine as shown in FIG. 2 and FIG. Go to. A series of strip support rolls 37 constituting the guide table 13 support the strips up to the pinch roll stand 14. The rolls 37 are arranged in a line and extend downward and curved downward from the pinch roll stand 14 to the lower side of the casting machine, and smoothly receive and guide the strip from the loop 36. The twin roll casting machine is of the type shown and described in detail in US Pat. Nos. 5,184,668 and 5,277,243, or US Pat. No. 5,488,988. Good. Reference may be made to these patents for structural details that do not form part of the invention.

  The pair of pinch rolls 50 constituting the pinch roll stand 14 responds to the tension applied by the hot rolling mill 15. Therefore, the strip can hang down in the form of a loop 36 from the casting roll 22 through the guide table 13 to the pinch roll stand 14, and the pinch roll 50 is between the loop that hangs freely and the tension applied to the strip downstream in the processing line. Provides a tension barrier. The pinch roll 50 also stabilizes the position of the strip on the feed table 13 and feeds the strip to the hot rolling mill 15.

  The thin cast strip 12 is sent from the pinch roll stand 14 to a hot rolling mill 15 composed of an upper work roll 16A and a lower roll 16B. As shown in FIG. 4, the preferred embodiment of the present invention consists of spraying the oil / water mixture onto the downstream surface of the backup roll 16. The oil sump 100 is provided with a heater 101 to maintain the oil at approximately 50 ° C., but heating is not essential. The heated oil is transferred to the static mixer 104 by the constant displacement pump 102 via the oil transfer line 103, where the heated oil is mixed with water.

  Water is supplied from a water source 110 to a water strip cooling header 111 and a rolling mill roll supply line 112. The first portion of water is supplied to the spray header 18 to cool the hot strip 12 after exiting the hot rolling mill 15 with the supply of cooling water. Typically, the water pressure is reduced through pressure regulator 113 to about 40 pounds per square inch. About 10-30 gallons / minute of water is fed to each static mixer 104 and mixed with about 4 gallons / hour of heated oil.

  Then, the mixed oil and water are provided to the downstream surface of the backup roll 16 (the moving direction of the thin cast steel strip 12 is indicated by an arrow 120) via the oil water nozzle 71. Alternatively, the oil / water mixture may be provided to the casting strip 12 in the roll gap region, or may be provided to the upstream surface of the backup roll 16 or the work rolls 16A and 16B.

  The temperature of the thin cast steel strip 12 in the hot rolling mill 15 is preferably less than 1100 ° C, more preferably less than 1050 ° C, and most preferably less than 900 ° C. Also preferably, the temperature of the thin cast steel strip in the hot rolling mill 15 is greater than 400 ° C.

  The static mixer 104 is a standard type, conventionally obtained device. Other types of mixers may be used as long as the oil and water can be mixed well.

  In one embodiment, the oil / water mixture is fed to the backup roll 16 at a rate of 5-30 gallons / minute, 40 pounds per square inch. In this example, the oil / water mixture is typically delivered to the backup roll at about 10-20 gallons / minute, with 15 gallons / minute being a reasonable setting. The oil / water mixture may have an oil content of less than 5%, and in one embodiment consists of 4 parts oil and 600 to 1800 parts water by volume. The oil may be less than 2% or less than 1% of the mixture. Oil is typically provided to be mixed with less than 15 gallons / hour of water.

  FIG. 5 shows the average surface roughness (Ra) in microns of a steel strip 12, which is a thin cast strip made using the present invention. As can be seen from FIG. 5, the average surface roughness is significantly lower, about 0.66 to about 1.5 microns with the addition of the oil / water mixture as described above.

  In one embodiment, the present invention produces a thin cast steel strip at a rate of about 80 m / min using oil water as described above.

  Although the invention has been described with reference to specific embodiments, those skilled in the art will recognize that various modifications can be made and equivalents can be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular condition or material to the teachings of the invention without departing from the scope of the invention. Accordingly, the invention is not limited to the specific embodiments disclosed, but is intended to include all embodiments within the scope of the appended claims.

2 is a photomicrograph showing typical surface roughness of a cast strip after hot rolling. 1 is a schematic diagram showing a thin strip casting plant having a hot rolling mill that controls the shape of the cast strip. FIG. It is an expanded sectional side view of the casting machine of the thin strip casting plant of FIG. It is the schematic which shows the system which adds an oil-water mixture to the roll of a hot rolling mill. FIG. 4 is a graph showing the average surface roughness of a thin cast steel strip, sequence 2613, made using the present invention.

Claims (28)

It has at least one microstructure selected from the group consisting of polygonal ferrite, acicular ferrite, Widmanstatten, bainite and martensite, has a surface roughness of less than 1.5 microns Ra and a scale thickness of less than 10 microns. A thin cast strip of
a) assembling a twin roll caster having laterally positioned caster rolls forming a roll gap therebetween and a hot rolling mill having a work roll and a backup roll adjacent to the twin roll caster;
b) forming a thin cast strip from the roll gap between the casting rolls of the twin roll caster;
c) Apply the oil / water mixture to the work roll of the hot rolling mill,
d) passing the thin cast strip through a hot rolling mill at a temperature below 1100 ° C. with the oil-water mixture applied to the work roll;
e) selected from the group consisting of polygonal ferrite, acicular ferrite, Widmanstatten, bainite and martensite, with a thin cast strip passing from a casting roll through a hot rolling mill in an atmosphere of less than 5% oxygen. A thin cast strip made of steps of forming a thin cast strip having at least one microstructure and having a surface roughness of less than 1.5 microns Ra and a scale thickness of less than 10 microns. The thin cast strip according to claim 1, wherein the thin cast strip is passed through a hot rolling mill at a temperature of less than 1050C while the oil-water mixture is applied to the work roll. 3. A thin cast strip according to claim 1 or claim 2 having a surface roughness of less than 1.0 micron Ra. The thin cast strip of claim 3 having a surface roughness of less than 0.7 microns Ra. 5. A thin cast strip according to claim 4 having a surface roughness of less than 0.5 microns Ra. 6. A thin cast strip according to any of claims 1 to 5, wherein the scale thickness is less than 7 microns. The thin cast strip of claim 6, wherein the scale thickness is less than 4 microns. A thin cast strip according to any of the preceding claims, wherein the mixture of oil and water is applied by spraying on a work roll. The thin cast strip according to any one of claims 1 to 8, wherein the oil / water mixture is applied to the work roll by applying the oil / water mixture to a backup roll. 10. A thin cast strip according to any of claims 1 to 9, wherein the oil-water mixture has an oil content of less than 5% and a low surface roughness of less than 1.5 microns Ra. a) assembling a strip casting machine comprising a pair of casting rolls with a gap between the rolls;
b) assembling a metal feed system that can form a casting pool between the casting rolls above the roll gap, and a side dam adjacent to the end of the roll gap surrounds the casting pool;
c) assembling a hot rolling mill with a work roll adjacent to the strip caster and having a working surface forming a gap for rolling the hot strip;
d) assembling a spray nozzle positioned adjacent to the work roll to provide an oil / water mixture to the work roll;
e) introducing molten steel between the pair of casting rolls to form a casting sump supported on the casting surface of the casting roll and enclosed by the first side weir;
f) rotating the casting rolls in opposite directions to form a solidified metal shell on the surface of the casting roll, casting a steel strip from the casting shell through a roll gap between the casting rolls;
g) spraying the oil-water mixture as the strip enters the hot rolling mill,
h) rolling the cast strip between the work rolls of a hot rolling mill to produce a cast strip having a surface roughness of less than 1.5 microns Ra;
A thin cast steel strip with a surface roughness reduced to less than 1.5 microns Ra. 12. A thin cast steel strip with reduced surface roughness as claimed in claim 11, wherein the production rate of the cast strip is about 80 m / min. The thin cast steel strip with reduced surface roughness according to claim 11 or 12, wherein the rolling temperature is less than 900 ° C. 14. A thin cast steel strip with reduced surface roughness according to any one of claims 11 to 13, wherein the spray rate by the nozzle is 10 to 30 gallons / minute. 15. A thin cast steel strip with reduced surface roughness as claimed in any one of claims 11 to 14, wherein the surface roughness is less than 0.7 microns Ra. The thin cast steel strip with reduced surface roughness according to claim 15, wherein the surface roughness is less than 0.4 microns Ra. a) assembling a strip casting machine comprising a pair of casting rolls with a gap between the rolls;
b) assembling a metal feed system that can form a casting pool between the casting rolls above the roll gap and surrounds the casting pool with a side dam adjacent to the end of the roll gap;
c) assembling a hot rolling mill having a backup roll and a work roll adjacent to the strip casting machine, the hot strip being rolled by the work surface forming a gap between the work rolls;
d) assembling a spray nozzle located upstream of the work roll and capable of spraying the oil-water mixture on the backup roll;
e) Molten steel is introduced between the pair of casting rolls to form a casting reservoir supported on the casting surface of the casting roll and enclosed by the first side dam. f) Casting by rotating the casting rolls in opposite directions. Forming a solidified metal shell on the roll surface, casting a steel strip from the solidified shell through the roll gap between the casting rolls,
g) spraying the oil-water mixture as the casting strip enters the hot rolling mill;
h) rolling the cast strip between the work rolls of a hot rolling mill to produce a cast strip having a surface roughness of less than 1.5 microns Ra;
A thin cast steel strip with a surface roughness reduced to less than 1.5 microns Ra. The thin cast steel strip with reduced surface roughness of less than 1.5 microns Ra according to claim 17, wherein the production rate of the cast strip is about 80m / min. 19. A thin cast steel strip having a surface roughness reduced to less than 1.5 microns Ra according to claim 17 or claim 18, wherein the rolling temperature is less than 110O <0> C. 20. A thin cast steel strip having a surface roughness reduced to less than 1.5 microns Ra according to any of claims 17 to 19, wherein the rolling temperature is less than 1050 ° C. The rolling temperature is less than 900 ° C. 21. A thin cast steel strip having a surface roughness of claim 20 reduced to less than 1.5 microns Ra. 23. A thin cast steel strip having a surface roughness reduced to less than 1.5 microns Ra according to any of claims 17 to 21, wherein the spray rate by the nozzle is 10 to 30 gallons / minute. 23. A thin cast steel strip having a surface roughness reduced to less than 1.5 microns Ra according to any of claims 17 to 22, wherein the surface roughness is less than 0.7 microns Ra. 24. Thin cast steel strip with reduced surface roughness according to any of claims 17 to 23, wherein the oil content of the oil-water mixture is less than 5%. 25. A thin cast steel strip having a surface roughness reduced to less than 1.5 microns Ra according to any of claims 17 to 24, wherein the surface scale thickness of the thin cast steel strip is less than about 7 microns. It has at least one microstructure selected from the group consisting of polygonal ferrite, acicular ferrite, Widmanstatten, bainite and martensite, has a surface roughness of less than 1.5 microns Ra and a scale thickness of about 10 microns. A method for producing a thin cast strip of less than
a) assembling a twin roll caster having laterally positioned caster rolls forming a roll gap therebetween and a hot rolling mill having a work roll and a backup roll adjacent to the twin roll caster;
b) forming a thin cast strip from the roll gap between the casting rolls of the twin roll caster;
c) Apply the oil / water mixture to the work roll of the hot rolling mill,
d) passing the thin cast strip through a hot rolling mill at a temperature below 1100 ° C. while the oil / water mixture is applied to the work roll;
e) At least selected from the group consisting of polygonal ferrite, acicular ferrite, Widmanstatten, bainite and martensite, wrapped in a cast cast roll through a hot rolling mill with a thin cast strip in an atmosphere of less than 5% oxygen. Forming a thin cast strip having a microstructure, a surface roughness of less than 1.5 microns Ra and a scale thickness of less than 10 microns;
A method that consists of these stages. A method for producing a thin cast steel strip having a surface roughness reduced to less than 1.5 microns Ra comprising:
a) assembling a strip casting machine comprising a pair of casting rolls with a gap between the rolls;
b) assembling a metal feed system that can form a casting pool between the casting rolls above the roll gap and surrounds the casting pool with a side weir adjacent to the end of the roll gap;
c) assembling a hot rolling mill having a work roll adjacent to the strip caster and the hot strip being rolled by a working surface forming a gap therebetween;
d) assembling a spray nozzle positioned adjacent to the work roll and capable of providing an oil / water mixture to the work roll;
e) introducing molten steel between the pair of casting rolls to form a casting sump supported by the casting surface of the casting roll and enclosed by the first side weir;
f) forming a solidified metal shell on the surface of the casting roll by rotating the casting roll in a mutual direction, and casting a steel strip from the solidified shell through a roll gap between the casting rolls;
g) spraying the oil-water mixture as the strip enters the hot rolling mill,
h) rolling the cast strip between work rolls of a hot rolling mill to produce a cast strip having a surface roughness of less than 1 micron Ra;
A method that consists of these stages. A method for producing a thin cast steel strip having a surface roughness reduced to less than 1.5 microns Ra comprising:
a) assembling a strip casting machine comprising a pair of casting rolls with a gap between the rolls;
b) assembling a metal feed system that can form a casting pool between the casting rolls above the roll gap and surrounds the casting pool with a side dam adjacent to the end of the roll gap;
c) assembling a hot rolling mill having a backup roll and a work roll adjacent to the strip casting machine, the hot strip being rolled by the work surface forming a gap between the work rolls;
d) assembling a spray nozzle positioned upstream of the work roll and capable of spraying the oil / water mixture onto the backup roll;
e) introducing molten steel between the pair of casting rolls to form a casting sump supported by the casting surface of the casting roll and enclosed by the first side weir;
f) rotating the casting rolls in the mutual direction to form a solidified metal shell on the surface of the casting roll, and casting a steel strip from the solidified shell through a roll gap between the casting rolls;
g) spraying the oil-water mixture as the casting strip enters the hot rolling mill;
h) rolling the cast strip between work rolls of a hot rolling mill to produce a cast strip having a surface roughness of less than 1.5 microns Ra;
A method that consists of these stages.