JP2010089096A - Method of manufacturing austenitic stainless steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an austenitic stainless steel strip at high yield by rolling the entire length at high efficiency by suppressing the generation of work hardening in the unsteady area where a rolling speed is less than 50 m/min when manufacturing the austenitic stain steel strip by performing a plurality of passes of warm reverse rolling with a reversible rolling mill after beforehand heating a material to be rolled. <P>SOLUTION: The temperature of the material 2 to be rolled during rolling does not lower to less than 50°C by adjusting in at least one pass of a plurality of passes in the existing region of a coolant on the surface of the material 2 to be rolled during rolling in an unsteady area is performed with a tandem six-stage rolling mill 4 so that the coolant which flows by covering the whole surface in the width direction of the material to be rolled is not existed on the outlet side of the tandem six-stage rolling mill 4 and also the coolant is existed in only the range from a position where the material 2 to be rolled is brought into contact with work rolls 5a, 5b to a position where is within 500 mm in the opposite direction of the rolling direction on the inlet side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an austenitic stainless steel strip. Specifically, for example, in a rolling process using a reversible rolling mill, high-efficiency production is possible, and the unsteady region where the rolling speed decreases. It is related with the manufacturing method of the austenitic stainless steel strip which can prevent the quality defect and yield fall by this.

  Generally, stainless steel strips with high deformation resistance are subjected to continuous annealing pickling for the purpose of softening annealing and its oxidation and oxide scale removal by heat treatment in the atmosphere on the hot-rolled steel strip that is the material, In order to roll with high efficiency and high accuracy, usually, a reversible multiple rolling mill (for example, a series 6-high rolling mill) having a work roll having a small diameter of about 50 to 250 mm is used, and a rolling oil for stainless steel (for example, ester is used). Reverse rolling is performed while supplying the added naphthenic refined mineral oil) as a coolant, and thereafter, continuous annealing pickling or bright annealing and cold rolling are repeated.

  In particular, when an austenitic stainless steel having high strength at room temperature and excellent ductility is cold-rolled, a work-induced martensite phase is generated from a part of the austenite by rolling, so that the work hardening is remarkable. Therefore, it becomes difficult to ensure a large rolling rate in rolling, and productivity is lowered. This work hardening is particularly remarkable in the metastable austenitic steel represented by SUS304 and SUS301. On the other hand, it is known that the amount of the processing-induced martensite phase generated is greatly suppressed by increasing the processing temperature.

  For this reason, when rolling austenitic stainless steel strips, work hardening is suppressed by preheating the material to be rolled and rolling it warm before rolling, thereby significantly improving productivity. Can be achieved.

For example, in Patent Documents 1 to 3, a large rolling reduction is easily secured by suppressing work hardening by heating the material to be rolled prior to rolling by a rolling mill, thereby making stainless steel highly efficient. An invention relating to a rolling method is disclosed.
JP-A-57-188622 Japanese Unexamined Patent Publication No. 64-21013 Japanese Patent Laid-Open No. 01-210103

  When the invention disclosed in Patent Documents 1 to 3 is applied to reverse rolling by a reversible rolling mill to produce an austenitic stainless steel strip, the front side and the rear end side of the material to be rolled are accompanied by reverse rolling. Thus, an unsteady region where rolling is performed at a low speed inevitably appears.

  The leading end side and the trailing end side of the material to be rolled at low speed are excessively cooled because the time of contact with the coolant supplied at the time of rolling becomes longer than the portion excluding these, thereby inducing processing induction. A large amount of martensite phase is generated and work hardening is remarkable. For this reason, the rolling load on the front end side and the rear end side is increased, and the flatness such as off-gauge defects due to sheet thickness loss, ear waves and medium elongation is formed on the front end side and the rear end side of the austenitic stainless steel strip after rolling. In the worst case, narrowing is performed (the rolling mill is folded at the entry side of the rolling mill and is caught in the rolling gap, which places a load on the rolling mill. In the worst case, a fire accident occurs. And a phenomenon that leads to plate breakage), causing operational troubles, which may cause a significant decrease in productivity.

  FIG. 6 shows a hot rolled annealing coil made of SUS301 having a plate thickness of 3.0 mm and a plate width of 660 mm, which has been heated to 180 ° C. in advance, by a 6-stage series rolling mill having main specifications shown in Table 1 to 0.4 mm. It is a graph which shows temporally an example of 11-13 pass rolling load, rolling temperature, and rolling speed when reverse rolling of 13 passes to thickness is performed warm.

  In the unsteady region where the rolling speed is reduced and surrounded by an ellipse in the graph of FIG. 6, the rolling load increases approximately twice compared to the steady region. For this reason, the entire length of the material to be rolled cannot be rolled, and unrolled parts longer than expected before rolling are generated on the front end side and rear end side of the austenitic stainless steel strip after rolling. .

  For this reason, in order to perform rolling stably over the entire length of the material to be rolled to improve productivity, work hardening in an unsteady region where the rolling speed is reduced must be suppressed. However, none of Patent Documents 1 to 3 discloses or suggests means for suppressing this work hardening, and such means is not known to those skilled in the art.

  The present invention manufactures an austenitic stainless steel strip by preheating a material to be rolled made of austenitic stainless steel in advance, and then performing warm reverse rolling with a reversible rolling mill such as a series six-high rolling mill. In this case, by suppressing the occurrence of work hardening in the unsteady region where the rolling speed is reduced, it is possible to perform stable and high-efficiency rolling over substantially the entire length of the material to be rolled, which enables austenite with a high yield. It is to provide a method for producing a stainless steel strip.

  In order to investigate the cause of the occurrence of work hardening in the unsteady region where the rolling speed is reduced when rolling a rolled material made of austenitic stainless steel that has been heated in advance, the present inventors have introduced a work-induced martensite phase. As a result of simulating the material temperature and rolling load while considering the generation of the material, the tip side and the rear end side of the material to be rolled made of austenitic stainless steel are both coolants in the unsteady region where the rolling speed decreases. It has been found that it is difficult to perform rolling in the temperature range necessary for suppressing the formation of the processing-induced martensite phase because it is in contact with the substrate for a long time and is thereby excessively cooled.

  The present invention suppresses the occurrence of the work hardening described above by preventing excessive cooling by the coolant even in the unsteady region, and thereby, also on the front end side and the rear end side of the material to be rolled made of austenitic stainless steel. Based on the knowledge that high-efficiency austenitic stainless steel strips can be produced without causing a decrease in yield due to poor quality or unrolling, etc. It was made.

  In the present invention, by using a reversible rolling machine on a rolled material made of austenitic stainless steel, the rolled material is subjected to reverse multiple-roll rolling in which the rolled material is heated to 50 ° C. or higher in advance. In the method for producing an austenitic stainless steel strip, the region where the coolant exists on the surface of the material to be rolled when rolling in an unsteady region where the rolling speed by the reversible rolling machine is reduced to less than 50 m / min is performed. The method for producing an austenitic stainless steel strip is characterized in that the temperature of the material to be rolled at the time of rolling is not lowered to less than 50 ° C. by adjusting in at least one of a plurality of passes.

  In other words, as its name suggests, coolant is used as a coolant to prevent seizure (or heat scratch) from occurring due to the temperature of the material being rolled up due to processing heat or the like. Although the adjustment of the amount has been performed only for the purpose of preventing the temperature rise of the material to be rolled, in the present invention, the amount of coolant supplied to the material to be rolled is caused by excessively lowering the temperature of the material to be rolled. Adjustment is made to suppress the occurrence of work hardening.

  In the method for producing an austenitic stainless steel strip according to the present invention, on the exit side of the reversible rolling mill at the time of rolling, there is no coolant flowing over the entire surface in the width direction of the material to be rolled. It is desirable to adjust the existence area. In this case, it is desirable to adjust the existence region by stopping the supply of coolant to the material to be rolled from the coolant supply device installed on the exit side of the reversible rolling mill.

In the manufacturing method of these austenitic stainless steel strips according to the present invention, on the entry side of the reversible rolling mill at the time of rolling, the material to be rolled is opposite to the rolling direction from the position where it comes into contact with the work roll of the reversible rolling mill. It is desirable to adjust the existence region so that the coolant exists only in a range up to a position within 500 mm in the direction. Such adjustment of the existence area is
(I) The amount of coolant supplied to the material to be rolled on the entry side of the reversible rolling mill, and sufficient lubrication performance when rolling the material to be rolled at a rolling speed of 50 m / min or more with this reversible rolling mill; Set lower than the amount of coolant required to obtain the cooling performance, or (ii) the work roll side of the reversible rolling mill by an oil draining device installed on the entry side of the reversible rolling mill This may be done by one or both of blocking the coolant flowing back from the tank.

  According to the present invention, it is possible to prevent the occurrence of work hardening in the unsteady region where the rolling speed is reduced, and thereby stably and highly efficiently over the entire length of the material to be rolled made of austenitic stainless steel. While being able to perform rolling, an austenitic stainless steel strip can be manufactured with high productivity without causing a decrease in yield due to poor quality or generation of unrolled parts.

Hereinafter, the best mode for carrying out the method for producing an austenitic stainless steel strip according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an explanatory view schematically showing a manufacturing process 1 of an austenitic stainless steel strip for carrying out the present invention.

In FIG. 1, the material 2 to be heated used in the present embodiment is an austenitic stainless steel strip.
This heated material 2 is at a temperature of 50 ° C. or higher and 300 ° C. or lower when reverse rolling is performed by a reversible rolling mill 4 described later. In the present embodiment, a coil of the material to be rolled 2 is inserted into the batch-type heating furnace 3, the material to be heated 2 is heated to a temperature of 50 ° C. or more and 300 ° C. or less in advance, and then the heating furnace 3 is heated. The temperature of the material 2 to be rolled during reverse rolling is set to a temperature of 50 ° C. or higher and 300 ° C. or lower by extracting from the above and using it for reverse rolling.

  However, in the present invention, it is not always necessary to heat the material 2 to be heated in this way. For example, the temperature of the material 2 to be rolled increases due to processing heat generated by reverse rolling using a reversible rolling mill 4 described later. When the temperature of 50 ° C. or higher and 300 ° C. or lower is maintained during rolling, it is not necessary to heat the material to be heated 2 in advance before rolling.

  The reason why the material to be rolled 2 is preliminarily heated to a range of 50 ° C. or higher and 300 ° C. or lower before rolling in this embodiment is to suppress the production amount of the work-induced martensite phase. When the heating temperature is lower than 50 ° C., the production of work-induced martensite phase due to rolling cannot be sufficiently suppressed, and work hardening cannot be suppressed to improve productivity. On the other hand, when the heating temperature exceeds 300 ° C., the austenitic stainless steel strip having a temperature exceeding 300 ° C. will be exposed to the atmosphere, and coloring and heat scratching due to the formation of an oxide film on the surface will occur. This is because the rolling quality and the appearance quality of the surface after rolling are deteriorated. From such a viewpoint, the heating temperature of the material 2 to be rolled is desirably 80 ° C. or higher and 250 ° C. or lower.

  The material to be rolled 2 is most easily heated by inserting it into the heating furnace 3 in the state of a coil as shown by a broken line in FIG. However, the present invention is not limited to this form, and any heating means that can heat the material to be heated 2 to a range of 50 ° C. or higher and 300 ° C. or lower may be used.

  In this way, the material to be rolled 2 is heated in the range of 50 ° C. or more and 300 ° C. or less, extracted from the heating furnace, set in the winding and unloading device 12 of the material to be rolled 2, and heated by the reversible rolling mill 4. An austenitic stainless steel strip is manufactured by performing reverse rolling of a plurality of passes (11 passes in this embodiment).

  In this embodiment, a series 6-high rolling mill 4 having the specifications shown in Table 1 is used as the reversible rolling mill. As is well known, the series 6-high rolling mill 4 includes a pair of upper and lower work rolls 5a and 5b, a pair of upper and lower intermediate rolls 6a and 6b, and a pair of upper and lower backup rolls 7a and 7b.

  On one side of the serial 6-high rolling mill 4 with respect to the pass line of the material 2 to be rolled, first coolant supply devices 8a and 8b for supplying coolant to the rolled material 2 and the serial 6-high rolling mill 4 First oil draining devices 9a and 9b are provided for blocking the coolant that flows back from the work rolls 5a and 5b. On the other hand, on the other side of the series 6-high rolling mill 4, second coolant supply devices 10 a and 10 b for supplying the coolant to the rolled material 2 and the material to be rolled out from the series 6-high rolling mill 4. Second oil draining devices 11a and 11b are provided for wiping (squeezing out) the coolant adhering to the surface of 2.

  In addition, all the code | symbol P in FIG. 1 shows the pump for supplying coolant to each coolant supply apparatus 8a, 8b, 10a, 10b. Moreover, in this Embodiment, it is more than the plate | board width of the to-be-rolled material 2 supported by the cylinder shown in figure so that raising / lowering is possible as each oil draining device 9a, 9b, 11a, 11b, and pressed against the surface of the to-be-rolled material 2 A tube wiper made of a hard rubber tube (diameter of about 20 mm) having a width of 1 mm was used. However, the present invention is not limited to this tube wiper, and may be replaced by a roll wiper of a type that is squeezed by sandwiching between two upper and lower metal rolls, for example.

  Furthermore, in order to perform reverse rolling, the winding and unloading devices 12 and 13 for the material 2 to be rolled are disposed on both sides of the series 6-high rolling mill 4 with respect to the pass line of the material 2 to be rolled. Reference numerals 14 and 15 are deflector rolls for keeping the pass line constant.

  In addition, in short, since this invention adjusts the area | region where the coolant exists in the surface of the to-be-rolled material 2 in order to suppress the excessive temperature fall of the to-be-rolled material 2 with the fall of a rolling speed, it is reversible. The type rolling mill may be any type of reversible rolling mill as long as it can perform desired rolling on the austenitic stainless steel strip, and is not limited to a specific type of reversible rolling mill. For example, in addition to the above-described series 6-high rolling mill, reverse rolling of austenitic stainless steel strips such as a series 4-high rolling mill, a Sendzimir Z-Hi rolling mill, a 20-stage Sendzimir rolling mill, a 12-stage cluster rolling mill, etc. Various known reversible rolling mills that can be used can be used.

  Moreover, in this Embodiment, as shown in FIG. 1, each coolant supply apparatus 8a, 8b, 10a, 10b is arrange | positioned closer to the serial 6-high rolling mill 4 rather than each oil removal apparatus 9a, 9b, 11a, 11b. Take the case of being done as an example. However, the manner of installation of the coolant supply devices 8a, 8b, 10a, and 10b and the oil draining devices 9a, 9b, 11a, and 11b, such as the arrangement positions and orientations, is not limited to the illustrated example, but six stages in series. If the region where the coolant exists on the surface of the material to be rolled 2 during rolling by the rolling mill 4 can be adjusted as will be described later, no limitation is required. For example, unlike the embodiment shown in FIG. 1, each oil draining device 9 a, 9 b, 11 a, 11 b is arranged closer to the series six-high rolling mill 4 than each coolant supply device 8 a, 8 b, 10 a, 10 b. May be.

  In the present embodiment, the region where the coolant is present on the surface of the material to be rolled 2 when rolling in the unsteady region by the series 6-high rolling mill 4 is performed in at least one pass of reverse rolling consisting of 11 passes. By adjusting, the austenitic stainless steel strip is manufactured while preventing the temperature of the material 2 to be rolled during rolling in the unsteady region from dropping below 50 ° C. Hereinafter, the reason for adjusting the existence area of the coolant in this way will be described.

First, in the manufacturing process shown in FIG. 1, when rolling is performed on the material 2 made of austenitic stainless steel using the serial 6-high rolling mill 4, the entry side and the exit side of the serial 6-high rolling mill 4 are used. The region of the coolant on the surface of the material 2 to be rolled in (the range in which a sufficient amount of coolant exists for cooling the material 2 to be rolled) will be described.
(A) When the material 2 to be rolled is fed from left to right as indicated by white arrows in FIG. 1, rolling is performed on the surface of the material 2 to be rolled of the work rolls 5 a and 5 b of the series six-high rolling mill 4. Regardless of the speed, the coolant exists while flowing over the section S1 (the length of the section S1 in the present embodiment: about 1.2 m) from the work rolls 5a and 5b to the oil draining devices 11a and 11b. Conversely, when the material 2 to be rolled is sent from right to left in FIG. 1, the surface of the material 2 to be rolled on the exit side of the work rolls 5 a and 5 b of the series six-high rolling mill 4 is independent of the rolling speed. The coolant is present while flowing over the section S2 (in the present embodiment, the length of the section S2: about 1.2 m) from the work rolls 5a and 5b to the oil draining devices 9a and 9b.
(B) On the other hand, on the surface of the material to be rolled 2 on the entry side of the work rolls 5a and 5b of the series six-high rolling mill 4, the region where the coolant exists varies depending on the rolling speed.

  When the material to be rolled 2 is sent from left to right in FIG. 1, the coolant supplied from the first coolant supply devices 8 a and 8 b reaches the work rolls 5 a and 5 b at a low rolling speed of 100 m / min or less. When the rolling speed is, for example, 10 m / min while flowing backward from the installation position of the work rolls 5a and 5b toward the left in FIG. 1, the installation position of the work rolls 5a and 5b. Exists in a section S3 having a length of about 1.0 m. On the other hand, when the rolling speed exceeds 100 m / min, such a reverse flow of the coolant does not occur, and the coolant is supplied from the first coolant supply devices 8a and 8b and the work roll is moved from the position where it collides with the material 2 to be rolled. It exists in section S4 to the installation position of 5a, 5b.

  When the coolant during rolling by the in-line 6-high rolling mill 4 is generally present on the surface of the material 2 as described above, the region where the coolant is present on the surface of the material 2 is adjusted. The extent to which the rolling load fluctuates due to the change was determined by the simulation described above. The calculation conditions for this simulation are summarized in Table 2.

  As shown in Table 2, in this simulation, for the steady region, the rolling speed is 100 m / min for all passes, and the coolant existence region is the time of rolling in the steady region for the material to be rolled made of the austenitic stainless steel described above. As a reference, specifically, an input supply distance of 200 m and an output supply distance of 1200 mm were used as references.

Moreover, regarding the unsteady region, the rolling speed was set to 10 m / min for all passes, and the coolant existing region was set to 5 levels of cases 1 to 5 listed below.
Case 1: Reference existence area (incoming distance: 1000 m, outgoing distance: 1200 mm)
Case 2: Presence area obtained by placing the oil removal device on the exit side close to the work rolls 5a and 5b from the work roll 5a, 5b (entrance distance: 1000m, exit side distance: 400mm)
Case 3: Presence region obtained by stopping the outlet side coolant supply device (entrance distance: 1000 m, outlet distance: 0 mm)
Case 4: An existing region (entrance distance: 400 m, outlet side) obtained by stopping the outlet side coolant supply device and reducing the supply amount of the inlet side coolant supply device to be lower than that of case 1 to reduce the coolant backward flow distance. (Distance: 0mm)
Case 5: Presence region obtained by restricting the backflow of the coolant by restricting the supply amount of the coolant supply device on the inlet side further than that on the case 4 (entry side distance: 200 m, outlet side distance: 0 mm)
In this simulation, the region where the coolant exists is the same for all 11 passes.

  FIG. 2 (a) is a graph collectively showing the cases 1 to 5 in the unsteady region and the rolling temperature in the steady region (roll bite inlet temperature; ° C.), obtained by this simulation, in each pass. FIG. 2B is a graph collectively showing the cases 1 to 5 in the unsteady region and the rolling load (ton) in the steady region in each pass obtained by this simulation.

  As shown in FIGS. 2 (a) and 2 (b), in comparison with the steady region, in case 1 in which the region where the reference condition exists is set, the rolling temperature is greatly lowered and the rolling load is greatly increased. In particular, it can be seen that the rolling load of 9 to 11 passes in the latter stage is almost doubled.

On the other hand, it can be seen that in cases 2 and 3 in which the region where the outlet side coolant is present is made small, the temperature drop is suppressed, and the increase in the rolling load is also reduced accordingly.
Further, in cases 4 and 5 in which the existence region of the coolant on the inlet side is further reduced, it can be seen that a significant temperature reduction preventing effect can be obtained and the rolling load can be suppressed to approximately the same level as the steady region.

  As described above, in rolling an austenitic stainless steel strip, as the name suggests, coolant is used to prevent the temperature of the material to be rolled 2 from rising due to processing heat or the like and causing seizure (or heat scratching). The coolant is used as a coolant, and so far, adjustment of the coolant supply amount has been performed only for the purpose of preventing an excessive temperature rise of the material 2 to be rolled.

  On the other hand, in this Embodiment, the fall of the temperature of the to-be-rolled material 2 is prevented by adjusting the presence area of the coolant in the surface of the to-be-rolled material 2 so that it may differ from a normal existing area, thereby Suppresses the occurrence of work hardening during rolling in the unsteady region.

In the present embodiment, such adjustment of the coolant existing region is performed during rolling in an unsteady region where the rolling speed is reduced to less than 50 m / min. The reason for this will be explained.
In order to determine the range of the rolling speed at which the occurrence of work hardening can be substantially eliminated by adjusting the existence region of such coolant, the above simulation model based on the calculation conditions shown in Table 2 is used. The simulation calculation was performed with the coolant supply conditions corresponding to the case 1 described above, the rolling speed of all passes being the same, and the rolling speed being changed to 10 to 100 mpm. Here, the upper limit of the studied rolling speed is set to 100 m / min because, as described above, at a high rolling speed exceeding 100 m / min, the influence of coolant cooling on the rolling temperature is small.

  FIG. 3 is a graph showing the influence of the rolling speed on the rolling load in the final pass, FIG. 3 (a) shows the relationship between the rolling speed and the rolling load in the final pass, and FIG. Rate of increase in rolling load in the final pass ({(rolling load in the final pass at each rolling speed−rolling load in the final pass at a rolling speed of 100 m / min) / (rolling load in the final pass at a rolling speed of 100 m / min)} × 100 (%)).

  As shown in FIG. 3 (a), the rolling load increases as the rolling speed decreases, but based on the rolling load of the final pass at a rolling speed of 100 m / min, as shown in FIG. 3 (b), When the rolling speed is 50 m / min, the rolling load increases by 10% or more, and when the rolling speed is 10 m / min, the rolling load increases by 30% or more.

  Based on the past operation results, it is empirically determined that rolling is possible if the rate of increase in rolling load in the unsteady region of the final pass is within 20% of the steady region. As shown in 3 (b), in the region where the rolling speed is less than 30 m / min, the increase rate of the rolling load with respect to the steady region (rolling speed 100 m / min) exceeds 20%, so it is necessary to adjust the supply amount of the coolant. There is. Furthermore, in consideration of the time required for changing the coolant supply amount in actual operation, it is desirable to set the region where the rolling speed is 50 m / min or less as an unsteady region and adjust the region where the coolant exists.

  Next, a method for adjusting the coolant supply amount will be described. As described above, the narrower the region in which the coolant exists, the lower the temperature of the material 2 to be rolled can be prevented. From the coolant supply device installed on the outlet side of the series 6-high rolling mill 4 to the material 2 to be rolled. By stopping the supply of the coolant, it is desirable not to supply the outlet-side coolant that has little influence on the rollability of the material to be rolled 2 at the unsteady portion.

  On the other hand, if the supply of the coolant on the inlet side is completely stopped, the lubricity in rolling of the material 2 to be rolled is adversely affected, so that at least the surface of the work rolls 5a and 5b does not run out of oil. Of the required amount of coolant.

  Thus, based on the calculation conditions shown in Table 2, the rolling speed of all passes is set to a low speed of 10 m / min, and the coolant supply region in the inlet side coolant is determined in a state where supply of the outlet side coolant is stopped. The simulation was performed by changing the length of 2 in the range of 100 to 1000 mm.

  FIG. 4 is a graph showing the influence of the coolant cooling distance on the entry side (entrance coolant cooling distance; mm) on the rolling load of the final pass, and FIG. FIG. 4B shows the relationship between the inlet coolant cooling distance and the rate of increase in rolling load in the final pass. Here, the rate of increase in rolling load in the final pass is {(rolling load in the final pass in rolling in which the inlet side coolant cooling distance is changed at a rolling rate of 10 m / min) / (rolling rate of 100 m / min (in Table 2). The rolling load of the final pass in the steady region))-1} × 100 (%).

  In this simulation, since the rolling speed is set to an extremely low speed of 10 m / min, although an increase in load of about 10% can be seen even in the condition where the inlet side coolant is 100 mm, the inlet side coolant supply distance is If it is 500 mm or less, even if it is rolling at a very low speed of 10 m / min, the increase rate of a rolling load can be suppressed to 20% or less.

  For this reason, for example, (i) the amount of coolant supplied to the material to be rolled 2 on the entry side of the series six-high rolling mill 4 is the same as that of the inlet side coolant. 4 is set lower than the supply amount of coolant necessary to obtain sufficient lubrication performance and cooling performance when rolling at a rolling speed of 50 m / min or more, or (ii) series 6-high rolling mill 4 On the entry side of the series 6-high rolling mill 4 by damming the coolant that flows backward from the work rolls 5a, 5b side of the series 6-high rolling mill 4 by the oil draining device installed on the entrance side It is desirable to adjust so that the backflow distance of the coolant is suppressed to 500 mm or less.

  Such a stop of the supply of the coolant on the outlet side of the series six-high rolling mill 4 and the adjustment of the coolant existing area on the inlet side of the series six-high rolling mill 4 need not be performed simultaneously in all passes. Instead, one or both of them may be appropriately performed in at least one pass of all passes in accordance with a schedule of rolling passes to be actually performed and a result of rolling load.

  In this way, according to the present embodiment, the austenitic stainless steel strip is obtained by subjecting the material to be rolled 2 made of austenitic stainless steel to the 11-pass reverse rolling in a warm manner by the series 6-high rolling mill 4. At the time of manufacturing, at least one pass of the coolant existing region on the surface of the material 2 to be rolled when rolling by the series 6-high rolling mill 4 is performed in the unsteady region where the rolling speed is reduced to 50 m / min or less. In order to prevent the temperature of the material to be rolled during rolling from dropping below 50 ° C., the work hardening can be suppressed and the productivity can be improved. Stable rolling can be performed also on the side and rear end sides.

Further, the present invention will be described more specifically with reference to examples.
After the material 2 to be rolled made of SUS301 is heated to 200 ° C. in advance, the manufacturing process 1 shown in FIG. 1 including the 6-stage in-line 6-high rolling mill 4 having the main specifications shown in Table 1 results in 9 passes. An austenitic stainless steel strip was produced by reverse rolling. The production conditions are summarized in Table 3.

In the example of the present invention in Table 3, the coolant on the outlet side stopped the coolant supply in the unsteady region by manually operating the opening / closing valve of the coolant supply device immediately before the rolling speed decreased to 50 m / min or less. . On the other hand, the inlet side coolant adversely affects the lubricity of rolling when it stops completely. Therefore, by adjusting the opening of the open / close valve immediately before the rolling speed drops to 50 m / min or less, The coolant backflow distance to the side was adjusted. At this time, in the unsteady region, when the supply pressure of the inlet-side coolant is a normal 1.6 kg / cm ² , the reverse flow distance of the coolant was about 1.0 m. By manually reducing the pressure to 0.5 kg / cm ² , the backflow distance of the coolant was suppressed to about 300 mm.

Further, the comparative example in Table 3 is different in thickness and width from the inventive example, but warm rolling was performed under the same conditions as in the steady region without changing the coolant supply amount even in the unsteady region.
FIG. 5 is a graph showing the results of warm rolling (rolling load in the steady region and unsteady region for each pass), FIG. 5 (a) shows an example of the present invention, and FIG. 5 (b) is a comparison. An example is shown.

  As shown in FIG. 5 (b), in the comparative example, the coolant was not adjusted in the unsteady portion, so the rolling load in the unsteady region increased as the rolling pass progressed, and the 9th pass As a result, a large unpressed part was left.

  On the other hand, as shown in FIG. 5 (a), in the example of the present invention, the coolant of the unsteady part was adjusted, so the rolling load slightly increased compared to the steady part, but was suppressed to substantially the same level. Thus, stable warm rolling could be performed without leaving an unpressed part over the entire length of the material 2 to be rolled.

  By the above examples, according to the present invention, it is possible to suppress the occurrence of work hardening in the unsteady region, and thereby, also at the front end side and the rear end side of the material 2 to be rolled made of austenitic stainless steel. It can be seen that stable rolling can be performed.

FIG. 1 is an explanatory view schematically showing a manufacturing process of an austenitic stainless steel strip for carrying out the present invention. FIG. 2A is a graph that collectively shows the cases 1 to 5 in the unsteady region and the rolling temperature in the steady region obtained in the simulation, and FIG. It is the graph which shows each case 1-5 of the unsteady area in each pass, and the rolling load in a steady area collectively. FIG. 3 is a graph showing the influence of the rolling speed on the rolling load in the final pass, FIG. 3 (a) shows the relationship between the rolling speed and the rolling load in the final pass, and FIG. The relationship with the increase rate of the rolling load of the last pass is shown. FIG. 4 is a graph showing the influence of the coolant cooling distance on the entry side (entrance coolant cooling distance; mm) on the rolling load of the final pass, and FIG. FIG. 4B shows the relationship between the inlet coolant cooling distance and the rate of increase in rolling load in the final pass. FIG. 5 is a graph showing the results of warm rolling in the examples. FIG. 5 (a) shows an example of the present invention, and FIG. 5 (b) shows a comparative example. FIG. 6 shows a hot rolled annealing coil made of SUS301 having a plate thickness of 3.0 mm and a plate width of 660 mm that has been heated to 180 ° C. in advance by a series 6-high rolling mill having the main specifications shown in Table 1. It is a graph which shows temporally an example of 11-13 pass rolling load, rolling temperature, and rolling speed when reverse rolling of 13 passes to thickness is performed warm.

Explanation of symbols

1 Manufacturing process of austenitic stainless steel strip 2 Material to be heated 3 Batch furnace 4 In-line 6-high rolling mill (reversible rolling mill)
5a, 5b Work rolls 6a, 6b Intermediate rolls 7a, 7b Backup rolls 8a, 8b First coolant supply devices 9a, 9b First oil release devices 10a, 10b Second coolant supply devices 11a, 11b Second oil release Device 12, 13 Winding and dispensing device

Claims (5)

  Austenitic stainless steel is obtained by subjecting a material to be rolled made of austenitic stainless steel to reverse rolling in a plurality of passes in which the material to be rolled is heated to 50 ° C. or higher in advance using a reversible rolling mill. In the method for producing a strip, the region where the coolant exists on the surface of the material to be rolled when rolling in an unsteady region where the rolling speed by the reversible rolling mill is reduced to less than 50 m / min is performed. A method for producing an austenitic stainless steel strip, wherein the temperature of the material to be rolled during rolling is not lowered to less than 50 ° C. by adjusting in at least one pass.   The exit region of the reversible rolling mill at the time of rolling is adjusted to the existence region so that there is no coolant flowing over the entire surface in the width direction of the material to be rolled. A method for producing an austenitic stainless steel strip.   The austenitic stainless steel strip according to claim 2, wherein the existence region is adjusted by stopping the supply of coolant to the material to be rolled from a coolant supply device installed on the outlet side of the reversible rolling mill. Production method.   On the entry side of the reversible rolling mill during the rolling, only the range from the position where the material to be rolled contacts the work roll of the reversible rolling mill to a position within 500 mm in the direction opposite to the rolling direction. The method for producing an austenitic stainless steel strip according to any one of claims 1 to 3, wherein the existence region is adjusted so that the coolant is present in the coolant.   The amount of coolant supplied to the material to be rolled on the entry side of the reversible rolling mill is sufficiently lubricated and cooled when the rolled material is rolled at a rolling speed of 50 m / min or more by the reversible rolling mill. Set lower than the supply amount of coolant necessary to obtain performance, and / or the work roll side of the reversible rolling mill by an oil draining device installed on the inlet side of the reversible rolling mill The method for producing an austenitic stainless steel strip according to claim 4, wherein the existence region is adjusted by damming a coolant that flows backward.

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