JP4927320B2 - Manufacturing method of bright annealed austenitic stainless steel strip - Google Patents

Description

  The present invention relates to a method for producing a bright annealed austenitic stainless steel strip.

  Unlike normal steel sheets, which are normally used after being plated or painted, stainless steel sheets are used for building materials that are not plated or painted, so-called solid materials. Be seen. Cold-rolled stainless steel sheet is generally obtained by hot rolling a slab obtained by casting after melting, annealing and pickling the stainless steel strip obtained by hot rolling, and further polishing the surface to cold Manufactured by rolling and final finish annealing.

  In the manufacturing process of a stainless steel sheet, annealing a hot-rolled stainless steel strip is intended to alleviate work hardening by hot rolling and reduce a rolling load in the subsequent cold rolling. However, in the cooling process after annealing a hot-rolled stainless steel strip, especially an austenitic stainless steel strip, carbides precipitate at the grain boundaries when passing through a specific temperature range, and this grain boundary carbides However, since it is eroded by the pickling solution in the pickling process after annealing, fine recesses are formed on the surface of the austenitic stainless steel strip. If it is cold-rolled without removing this recess, the surface quality of the austenitic stainless steel strip will be degraded.

  Therefore, in particular, in the austenitic stainless steel strip having a bright anneal (bright annealing: abbreviated as BA) finish in which a final finish annealing is performed in a non-oxidizing atmosphere and a surface property such as a mirror surface is required, It was essential to polish the surface before rolling and remove the recess formed by annealing pickling. However, polishing the surface of the stainless steel strip causes problems such as a decrease in thickness, that is, a decrease in yield due to polishing loss, and a decrease in production efficiency due to an increase in the number of processes.

  As a prior art for solving such problems, a method of manufacturing a stainless steel strip having excellent surface properties that can omit the surface polishing step in the stainless steel strip manufacturing process has been proposed (see Patent Document 1). .

  In this prior art, a stainless steel strip after hot rolling is wound at a material temperature of 650 ° C. or less, descaling is performed without annealing, and then a predetermined thickness is obtained by cold rolling, followed by final annealing. It is. That is, by cooling the stainless steel strip after hot rolling and winding it at a temperature of 650 ° C. or less, precipitation of grain boundary carbides during the cooling process during winding is prevented, and annealing of the hot rolled steel strip is performed. The absence of precipitation prevents precipitation of grain boundary carbides in the cooling process after annealing. By preventing the precipitation of grain boundary carbides in this way, it is possible to prevent grain boundary erosion from being caused by the pickling liquid during pickling, which is a descaling treatment on the surface of the hot-rolled steel strip. Since a recess due to grain boundary erosion is not formed on the surface of the stainless steel strip, a stainless steel strip having excellent surface properties can be obtained through subsequent cold rolling and final finish annealing.

  However, according to the investigation by the present inventors, the technique disclosed in Patent Document 1 has the following problems. That is, in the production of austenitic stainless steel strips, particularly in the production of BA-finished austenitic stainless steel strips that require mirror-like surface gloss, simply suppressing the precipitation of grain boundary carbides provides excellent surface properties. It is difficult to produce a stainless steel strip stably. In order to stably produce a stainless steel strip having excellent surface properties, the present inventors suppress the precipitation of grain boundary carbides and transfer the rolling roll surface to the stainless steel strip surface during cold rolling. The inventors have obtained the knowledge that it is important to keep the rate high, and have reached the present invention.

JP 59-163003

  An object of the present invention is to provide a method for producing a bright annealed austenitic stainless steel strip that can stably produce a steel strip having excellent surface properties.

The present invention includes a step of hot rolling an austenitic stainless steel strip,
By winding austenitic stainless steel strip having a finished thickness of 5.5 mm after hot rolling at 470 ° C. or more and 570 ° C. or less, the 0.2% proof stress becomes 400 N / mm ² or more. The winding process to
After descaling without annealing heat treatment, cold rolling the austenitic stainless steel strip,
A step of bright annealing heat treatment of austenitic stainless steel strip after cold rolling is a method for producing a bright annealing finish austenitic stainless steel strip, characterized in including it.

  According to the present invention, since the austenitic stainless steel strip after hot rolling is wound at 470 ° C. or more and 570 ° C. or less, it is possible to prevent the precipitation of carbides on the grain boundaries of the austenitic stainless steel. Precipitation of grain boundary carbides is prevented and pickling after hot rolling but before cold rolling is not performed, so that surface property deterioration due to erosion of grain boundary carbides can be prevented.

Moreover, it can finish so that 0.2% yield strength may be set to 400 N / mm < ² > or more by winding up in the said temperature range. Since the 0.2% yield strength of the hot-rolled austenitic stainless steel strip becomes high, the rolling load for rolling to a predetermined thickness increases when the steel strip is cold-rolled. This reduces the thickness of the oil film formed between the cold rolling roll and the surface of the austenitic stainless steel strip, so that the transfer rate of the cold rolling roll surface to the austenitic stainless steel strip surface is increased.

  Thus, it becomes possible to stably manufacture an austenitic stainless steel strip having excellent surface properties by subjecting the cold-rolled austenitic stainless steel strip to bright annealing (BA) heat treatment.

Moreover, since the finishing thickness of the austenitic stainless steel strip after hot rolling is 5.5 mm, the coiling temperature is regulated within the above range without reducing the rolling work efficiency. It is possible to stably and efficiently manufacture an austenitic stainless steel strip having an excellent surface property that is finished to have a 0.2% yield strength without depositing carbides.

  FIG. 1 is a flowchart illustrating a method for producing a bright annealed austenitic stainless steel strip that is an embodiment of the present invention. With reference to the flowchart shown in FIG. 1, the manufacturing method of a bright-annealed finish austenitic stainless steel strip is demonstrated.

  At the start of step s0, austenitic stainless steel, for example, SUS304 specified in Japanese Industrial Standard (JIS) G4305 is melted with a predetermined component composition and formed into a slab by a continuous casting apparatus. It is in the state heated by.

  In step s1, the slab extracted from the heating furnace is hot-rolled. Although the finishing thickness in hot rolling is not limited, it is preferably 5.5 mm or less. In step s2, the hot-rolled austenitic stainless steel strip is wound at a winding temperature of 470 to 570 ° C.

  FIG. 2 is a system diagram showing a simplified configuration of the hot rolling apparatus 1. The hot rolling apparatus 1 includes two first and second rough rolling stands R1 and R2 for rough rolling the slab 2, and seven first to seventh finishes for finish rolling the rough rolled hot rolled steel strip 3a. Rolling stands F1, F2, F3, F4, F5, F6, F7 and a hot rolling steel strip 3b provided on the downstream side in the rolling direction of the hot rolling steel strip 3a indicated by the arrow 4 of the seventh finishing stand F7 Water-cooling means 5 for water-cooling, a take-up reel 6 for taking up the hot-rolled hot-rolled steel strip 3b, and a temperature detection means for detecting the temperature of the hot-rolled steel strip 3b taken up by the take-up reel 6 7 and the like. The first and second rough rolling stands R1 and R2 and the first to seventh finishing rolling stands F1 to F7 are provided in this order from the upstream side in the rolling direction indicated by the arrow 4 to the downstream side.

  The first rough rolling stand R1 includes a pair of rolling rolls 11a and 11b provided on the upper and lower sides of the hot rolled steel strip 3a, and backup rolls 12a and 12b provided on the outside in contact with the rolling rolls 11a and 11b, respectively. The housing 13 is rotatably supported. Although the rolling rolls 11a and 11b are connected to driving means including an electric motor and a control device for rotating them, these are not shown. In addition, illustration of a drive means is abbreviate | omitted also in the finishing rolling stands F1-F7. Since 2nd rough rolling stand R2 is comprised the same as 1st rough rolling stand R1, description is abbreviate | omitted. A slab 2 having a thickness of about 200 mm is roughly rolled by the first and second rough rolling stands R1 and R2 to form a hot-rolled steel strip 3a having a thickness of several tens of millimeters, and is conveyed to a finishing rolling stand.

  The first finishing rolling stand F1 is configured in the same manner as the first rough rolling stand R1, and is in contact with the rolling rolls 14a and 14b and the rolling rolls 14a and 14b, which are provided in pairs above and below the hot rolling steel strip 3a, respectively. Further, backup rolls 15 a and 15 b provided on the outer side are rotatably supported by the housing 16. Since the second and third finishing rolling stands F2 and F3 are configured in the same manner as the first finishing rolling stand F1, description thereof will be omitted.

  The fourth finish rolling stand F4 includes a pair of upper and lower rolling rolls 17a and 17b across the hot-rolled steel strip 3a, and intermediate rolls 18a and 18b provided on the outside in contact with the rolling rolls 17a and 17b, respectively. Backup rolls 19a and 19b provided on the outer sides in contact with the intermediate rolls 18a and 18b are rotatably supported by the housing 20, respectively. Since the fifth to seventh finishing rolling stands F5 to F7 are configured in the same manner as the fourth finishing rolling stand F4, description thereof is omitted.

  The hot-rolled steel strip 3a having a thickness of several tens of mm is rolled by the first to seventh finish rolling stands F1 to F7 to become the hot-rolled steel strip 3b having the finished thickness, and is water-cooled by the water cooling means 5. The winding temperature is adjusted and the winding reel 6 is wound. The finished thickness of the hot-rolled steel strip 3b is preferably 5.5 mm or less. When the thickness exceeds 5.5 mm, there is a possibility that problems such as inconsistency with the capability of the cold rolling apparatus and a decrease in production efficiency due to an increase in the number of rolling passes may occur in the subsequent cold rolling.

  The water-cooling means 5 includes a spray nozzle 21 disposed so as to face the hot-rolled steel strip 3b on the downstream side in the rolling direction of the seventh finishing stand F7, that is, the outlet side of the seventh finishing stand F7. The water supply source 22 for supplying water, the injection nozzle 21 and the water supply source 22 are connected, the water supply pipe 23 serving as a water flow path, and the water supply pipe between the injection nozzle 21 and the water supply source 22 And a flow rate adjusting valve 24 provided in the passage 23. In the present embodiment, the water supply source 22 is realized by a pumped-up industrial water piping system. However, without being limited to this, the water supply source may be composed of a water storage tank and a feed pump. The flow rate adjusting valve 24 provided in the water supply pipe 23 adjusts the amount of water jetted from the jet nozzle 21 toward the hot-rolled steel strip 3b by adjusting the opening thereof, and the hot-rolled steel strip. The winding temperature of 3b can be adjusted.

  The temperature detection means 7 measures the temperature of the hot-rolled steel strip 3b wound on the take-up reel 6, for example, a non-contact thermometer 25 such as a radiation thermometer, and a temperature detection result by the non-contact thermometer 25. And display means 26 such as a liquid crystal display.

  The coiling temperature of the hot-rolled steel strip 3b was prepared by experimenting in advance with various changes in the finished thickness of the hot-rolled steel strip 3b and the amount of water sprayed by the jet nozzle 21 to create actual heat data. At the time of hot rolling, a desired coiling temperature can be realized by selectively setting the amount of jet water corresponding to the finished thickness of the hot rolled steel strip 3b. The operator of the hot rolling apparatus 1 recognizes the winding temperature of the hot rolled steel strip 3b displayed on the display means 26, and then adjusts the opening degree of the flow rate adjusting valve 24 to The winding temperature of the rolled steel strip 3b can be finely adjusted.

The coiling temperature of the hot-rolled steel strip 3 b is adjusted to 470 to 570 ° C. by being water cooled by the water cooling means 5. Even if it is cooled to less than 470 ° C., a 0.2% proof stress of 400 N / mm ² or more is achieved, so there is no problem in terms of material. However, from the viewpoint of suppressing the deterioration of the shape of the hot-rolled steel strip 3b due to excessive cooling and maintaining good workability, it is preferably set to 470 ° C. or higher. When the temperature exceeds 570 ° C., grain boundary carbides precipitate, so that a solution heat treatment of the carbides is necessary, and the desired 0.2% yield strength cannot be obtained. Therefore, the coiling temperature was set to 470 to 570 ° C.

By winding in the said temperature range, the hot rolled steel strip 3b which has 0.2% yield strength of 400 N / mm < ² > or more is obtained. When the 0.2% proof stress is less than 400 N / mm ² , the transfer rate on the surface of the cold rolling roll in the subsequent cold rolling is low, and excellent surface properties cannot be obtained. Therefore, the 0.2% yield strength of the hot-rolled steel strip 3b is set to 400 N / mm ² or more.

  Returning to FIG. 1, in step s3, the hot-rolled steel strip 3b is subjected to a pickling process which is a descaling process without being subjected to an annealing heat treatment. FIG. 3 is a system diagram showing a simplified configuration of the pickling apparatus 30. The pickling device 30 is generally pickled by immersing the rewinding reel 31 for rewinding the hot rolled steel strip 3b wound in a coil shape and the hot rolled steel strip 3b in the pickling solution. The pickling tank 32, the hot-rolled steel strip 3b after the pickling was washed with water to remove the pickling solution, the dryer 34 for drying the hot-rolled steel strip 3b after the water-washing, and dried. The hot-rolled steel strip 3b includes a take-up reel 35. The pickling apparatus 30 is appropriately provided with deflector rolls 36 and 37 for conveying the hot rolled steel strip 3b. As the pickling liquid supplied to the hot-rolled steel strip 3b in the pickling tank 32, a known one, for example, a mixed acid of hydrofluoric acid and nitric acid is used.

  The hot-rolled steel strip 3b is wound in the above-mentioned temperature range and no grain boundary carbide is precipitated, so an annealing heat treatment, which is a solid solution heat treatment of the carbide, is not required, and the 0.2% yield strength is reduced. In order to prevent, the pickling treatment is performed without performing the annealing heat treatment.

  Returning to FIG. 1, in step s4, the hot-rolled steel strip 3b after pickling is subjected to surface polishing. The surface polishing step is not an essential step in the method for producing a BA-finished austenitic stainless steel strip of the present invention. However, the thickness of the oxide scale formed by slab heating in the hot rolling process is not uniform on the surface of the slab, and thus is not uniform on the surface of the hot rolled steel strip 3b after hot rolling. Accordingly, the surface of the hot-rolled steel strip 3b after being descaled by pickling generally has irregularities. Since the unevenness remaining on the surface of the hot-rolled steel strip 3b after descaling also causes the surface properties to deteriorate, it is preferably removed by surface polishing.

  FIG. 4 is a system diagram showing the configuration of the surface polishing apparatus 40 in a simplified manner. The surface polishing apparatus 40 includes a rewind reel 41 for rewinding the hot rolled steel strip 3b, first to fifth polishing stands P1, P2, P3, P4, P5 for polishing the surface of the hot rolled steel strip 3b, A take-up reel 42 for winding the hot-rolled steel strip 3b after polishing, and pinch rolls 43 and 44 provided on the entry side and the exit side of the first to fifth polishing stands P1 to P5, respectively. The first to fifth polishing stands P <b> 1 to P <b> 5 are provided in this order from the upstream side toward the downstream side in the conveyance direction of the hot-rolled steel strip 3 b indicated by an arrow 45.

  The first polishing stand P1 is disposed above the contact roll 46 on the same side as the contact roll 46 with respect to the hot roll steel strip 3b, and the contact roll 46 and the billy roll 47 provided so as to face each other across the hot roll steel strip 3b. The idle roll 48 provided separately, the endless polishing belt 49 provided so as to be wound around the contact roll 46 and the idle roll 48, and the rolls 46, 47, 48 described above are rotatably supported. And a housing 50. The surface polishing apparatus 40 further operates a driving means for driving the contact roll 46, a pressing means for pressing the billy roll 47 against the hot-rolled steel strip 3b and the contact roll 46, and a driving means and a pressing means. Although not shown, the operation control means is omitted. Since the second to fifth polishing stands P2 to P5 are configured in the same manner as the first polishing stand P1, description thereof will be omitted.

  Although the first to fifth polishing stands P1 to P5 are configured identically, the roughness count of the polishing belt is not limited to the same, and for example, the first polishing stand P1 to the fifth polishing stand are used. For P5, the ones with successively larger counts (roughness) may be used. In step s4, the front and back surfaces of the hot-rolled steel strip 3b are polished by 10 to several tens of μm by the surface polishing apparatus 40. Polishing the back surface of the hot-rolled steel strip 3b is wound up by the take-up reel 42 so that the polished surface (front surface) of the hot-rolled steel strip 3b is inside, and the wound hot-rolled steel strip 3b is wound again. It can be performed by mounting on the return reel 41 and rewinding so that the outer surface becomes the polished surface.

  Returning to FIG. 1, in step s5, the hot-rolled steel strip 3b whose surface has been polished is cold-rolled into a cold-rolled steel strip 3c having a thickness of 2.0 mm, for example. FIG. 5 is a diagram showing a simplified configuration of the cold rolling apparatus 51. In this embodiment, a reverse-type Sendzimir mill 51 is used for cold rolling. The Sendzimir mill 51 is composed of a pair of rolling rolls 55a and 55b that are provided with a cold rolling steel strip 3c constituting a rolling stand 54 and a rewinding reel 52 and a take-up reel 53 (in the case of general terms, an alphabetic suffix). ) And three pairs of intermediate rolls 56a, 56b, 56c, 56d, 56e, 56f provided on the outside in contact with the rolling rolls 55a, 55b. ), Four pairs of backup rolls 57a, 57b, 57c, 57d, 57e, 57f, 57g, and 57h that are further provided on the outer side in contact with the intermediate roll 56 (in the case of generic names, the alphabetic suffixes are omitted) ), A housing 58 on which these rolls 55, 56, 57 are rotatably supported, and a cold rolled steel strip 3c. And a deflector roll 59 and 60 of the conveyor. Since the Sendzimir mill 51 performs reverse rolling, when the rolling direction changes, the rewind reel functions as a take-up reel and the take-up reel functions as a rewind reel. The Sendzimir mill 51 includes a driving unit that rotationally drives the roll, a control unit that controls the operation of the driving unit, and the like.

  In cold rolling, for the purpose of reducing the rolling load and preventing the occurrence of surface flaws due to slippage between the rolling roll 55 and the cold rolled steel strip 3c, a lubricating oil called rolling oil is used for the cold rolled steel strip 3c. Supplied on the surface. The lubricating oil supplied to the surface of the cold rolled steel strip 3c reaches between the rolling roll 55 and the cold rolled steel strip 3c, and forms a thin film, so-called oil film there.

This oil film thickness can be quantitatively determined by the oil film equivalent td, which is an index related to the yield strength of the cold rolled steel strip 3c, which is the material to be rolled. The oil film equivalent td is given by the following equation (1).
td = η · (U0 + U1) / (α · Pm) (1)
Where η: static viscosity of the lubricating oil
U0: peripheral speed of rolling roll
U1: Rolling entry speed of the material to be rolled
α: Biting angle of the material to be rolled with respect to the rolling roll
Pm: Two-dimensional yield stress of the material to be rolled [= 2 / √ (3) × 0.2% yield strength]

  As is clear from equation (1), when the 0.2% yield strength of the material to be rolled increases, the oil film equivalent td decreases, that is, the oil film thickness decreases. In this way, when the yield strength of the material to be rolled increases, the oil film thickness decreases, because the rolling load necessary for rolling at the same rolling rate increases as the yield strength of the material to be rolled increases. The oil film thickness is reduced.

  FIG. 6 is a diagram showing the relationship between the cold rolling rate of the cold rolled steel strip by the method of the present invention and the 0.2% proof stress. In FIG. 6, a line 61 connecting the black squares with a solid line is a method of the present invention, that is, a hot rolled steel strip 3b of SUS304 hot rolled to a thickness of 5.5 mm is wound at 470 to 570 ° C. and annealed. The relationship between the cold rolling (cold rolling) rate at the time of cold-rolling after pickling and surface polishing without performing and 0.2% yield strength is shown. In FIG. 6, a line 62 connecting the white squares with a solid line is data exemplified for comparison with the present invention. A hot rolled steel strip of SUS304 hot rolled to a thickness of 5.5 mm is obtained by water cooling. The figure shows the relationship between the cold rolling rate and the 0.2% proof stress in the case of cold rolling after pickling and surface polishing after winding and annealing heat treatment without adjusting the winding temperature.

  The cold rolling rate 0% of the line 61 indicates a 0.2% proof stress before cold rolling of the hot rolled steel strip 3b which is wound at 470 to 570 ° C. and not annealed. A cold rolling rate of 0% in the line 62 indicates a 0.2% proof stress before cold rolling of a hot rolled steel strip that has been wound and annealed without adjusting the temperature.

The 0.2% proof stress at a cold rolling rate of 0% of the hot rolled steel strip 3b according to the method of the present invention is 470 N / mm ² . On the other hand, the 0.2% yield strength of the hot-rolled steel strip subjected to the annealing heat treatment at a cold rolling rate of 0% is 270 N / mm ^2, which is 200 N / mm as compared with the hot-rolled steel strip 3 b according to the method of the present invention. mm ^{2 is} also low. Furthermore, looking at the transition of 0.2% proof stress accompanying the increase in the cold rolling rate, the line 61 which is data relating to the hot rolled steel strip 3b according to the method of the present invention, and the hot rolled steel strip subjected to annealing heat treatment The 0.2% proof stress value does not intersect with the line 62, which is data relating to the above, and the 0.2% proof stress value does not overlap with each other at any cold rolling rate.

That is, the hot-rolled steel strip 3b by the method of the present invention that has been hot-rolled so that the 0.2% proof stress is 400 N / mm ² or more is always 0. 0 compared with the hot-rolled steel strip that has been annealed. Cold-rolled with a high 2% yield strength. As described above, since the higher 0.2% proof stress of the material to be rolled during cold rolling can be rolled with a thin oil film thickness, the surface of the rolling roll 55 is the material to be rolled. It is possible to transfer at a high transfer rate to the surface of the hot rolled steel strip 3b (= cold rolled steel strip 3c). Since the surface of the rolling roll 55 of the cold rolling apparatus 51 is polished and polished, by increasing the transfer rate of the surface of the rolling roll 55 relative to the surface of the cold rolled steel strip 3c, the cold rolled steel strip The surface of 3c can be brought close to the surface property of the rolling roll 55, and the surface property can be made excellent.

  Returning to FIG. 1, in step s6, the cold-rolled steel strip 3c is subjected to bright annealing (BA) heat treatment. FIG. 7 is a system diagram showing a simplified configuration of the BA heat treatment apparatus 65. In the BA heat treatment apparatus 65, the cold rolled steel strip 3c unwound from the rewind reel 66 is cleaned by a degreasing cleaning apparatus 67, and in the BA furnace 68 after cleaning, for example, non-oxidative mixing of nitrogen gas and hydrogen gas Heat treated in atmosphere. After the BA heat treatment, the surface is cooled to a temperature at which the surface is not oxidized to the atmosphere and wound on the take-up reel 69. The cold-rolled steel strip 3c unwound from the rewind reel 66 is subjected to a transfer direction change, a driving force application, a tension application, etc. by rolls 70, 71, 72 provided at various places in the transfer path, and a degreasing cleaning device. 67 and BA furnace 68 are passed through.

  Returning to FIG. 1, in step s <b> 7, the BA-rolled cold-rolled steel strip 3 c is temper-rolled by the temper rolling device 75. FIG. 8 is a diagram showing a simplified configuration of the temper rolling apparatus 75. The cold-rolled steel strip 3c unwound from the rewind reel 76 is temper-rolled at a reduction rate of several percent by a pair of temper rolling rolls 78a and 78b provided in the temper rolling stand 77. This temper rolling is performed for the purpose of further improving the surface quality of the cold-rolled steel strip 3c subjected to BA heat treatment. After temper rolling, the process proceeds to the end of step s8 shown in FIG. 1, and the production of a series of BA-finished austenitic stainless steel strips is completed.

(Example)
Examples of the present invention will be described below.

[Example]
First, a bright annealed austenitic stainless steel strip according to an embodiment of the present invention manufactured according to the flowchart shown in FIG. 1 will be described. An austenitic stainless steel having a chemical composition corresponding to SUS304 of JIS-G4305 was melted and a slab having a thickness of 200 mm was produced by continuous casting. The slab was hot-rolled to a final thickness of 5.5 mm by the hot rolling device 1 and adjusted to a winding temperature by water cooling, and wound at a temperature of 520 ° C. The 0.2% yield strength of the hot-rolled steel strip obtained as described above was determined by a tensile test and found to be 470 N / mm ² .

  The hot-rolled steel strip was descaled by the pickling device 30 without annealing, and then the front and back surfaces were polished by the surface polishing device 40. The hot-rolled steel strip after polishing was cold-rolled by a total of 8 passes by the cold-rolling device 51 to produce a cold-rolled steel strip having a thickness of 1.90 mm. Table 1 shows the conditions such as the cold rolling rate of each rolling pass in the cold rolling.

  The obtained cold-rolled steel strip having a thickness of 1.90 mm was passed through a BA heat treatment apparatus 65 and subjected to BA treatment at a heating temperature of 1060 ° C. in a mixed atmosphere of nitrogen gas and hydrogen gas. The cold-rolled steel strip after the BA treatment was temper-rolled with a temper rolling device 75 at a reduction rate of 0.6% to produce the bright annealed austenitic stainless steel strip of the example.

[Comparative example]
Next, the bright annealed austenitic stainless steel strip of the comparative example will be described. A slab was produced in the same manner as in the example, and the slab was hot-rolled to a finished thickness of 5.5 mm by the hot rolling device 1, but wound at a temperature of 800 ° C. without adjusting the winding temperature. . The 0.2% yield strength of the hot-rolled steel strip thus obtained was determined by a tensile test,
450 N / mm ² .

  The hot-rolled steel strip was annealed at a heating temperature of 1060 ° C. in the air atmosphere and then descaled by pickling. The hot-rolled steel strip after the descaling treatment was polished on the front and back surfaces by the surface polishing apparatus 40 in the same manner as in the example. The hot-rolled steel strip after polishing was cold-rolled by a total of 8 passes by the cold-rolling device 51 to produce a cold-rolled steel strip having a thickness of 1.90 mm. Table 2 shows the conditions such as the cold rolling rate of each rolling pass in the cold rolling. The obtained cold-rolled steel strip was subjected to BA heat treatment and temper rolling in the same manner as in the Example to produce a bright annealed austenitic stainless steel strip of Comparative Example.

  The surface properties of the bright annealed austenitic stainless steel strips of Examples and Comparative Examples were evaluated by glossiness. For the glossiness, the surface glossiness specified in JIS Z8741: 1997 was measured at an incident reflection angle of 20 degrees. A higher glossiness was evaluated as having superior surface properties.

  FIG. 9 is a diagram showing the glossiness measurement results. FIG. 9 shows the results of measuring the glossiness of the bright annealed austenitic stainless steel strips of the examples and comparative examples, and the vertical bars in the figure represent the glossiness variations measured for a plurality of samples, Black squares written so as to overlap the bars represent the arithmetic average value of the glossiness measured for a plurality of samples.

  Since the average glossiness of the examples is clearly improved as compared with the comparative examples, it can be seen that the bright annealed austenitic stainless steel strip of the present invention is excellent in surface properties. In the example in which the coiling temperature was adjusted to increase the 0.2% yield strength, as is clear from the comparison of the rolling loads in Tables 1 and 2, the 0.2% yield strength was obtained in all rolling passes. The rolling load is larger than that of the comparative example having a low thickness. Thus, in the embodiment with a high 0.2% proof stress, the rolling load increases with a correlation with the proof stress, so the oil film thickness during cold rolling becomes thin, and the surface of the cold rolled steel strip on the surface of the rolling roll The transfer rate with respect to the surface becomes higher and the surface properties are improved.

  As described above, in the present embodiment, the austenitic stainless steel strip is SUS304, but is not limited thereto, and may be SUS304L, SUS316, SUS321, or the like.

  Moreover, although a hot rolling apparatus is the structure which consists of rough rolling stands R1 and R2 and finish rolling stands F1-F7, it is not limited to this, It is equipped with more rolling stands, and slab is finished to finish thickness at a stretch. It may be configured to be rolled.

  Further, the cold rolling apparatus is a reverse-type Sendzimir mill 51, but is not limited thereto, and a plurality of rolling stands are provided in the rolling direction, and a tandem type capable of rolling a plurality of passes at once. It may be a cold rolling device, and a rolling stand provided with a pair of rolling rolls and a backup roll or a rolling stand provided with a pair of rolling rolls, an intermediate roll and a backup roll, respectively, or in the rolling direction A configuration may be employed in which a plurality are provided.

  Further, the pickling apparatus, the surface polishing apparatus, the BA heat treatment apparatus, and the temper rolling apparatus are not limited to the configuration disclosed in the present embodiment, and various modifications are allowed within the scope of the object of the present invention. .

It is a flowchart explaining the manufacturing method of the bright annealing finish austenitic stainless steel strip which is one aspect | mode of implementation of this invention. It is a systematic diagram which simplifies and shows the composition of hot rolling device 1. It is a systematic diagram which simplifies and shows the structure of the pickling apparatus 30. It is a systematic diagram which simplifies and shows the structure of the surface polishing apparatus. It is a figure which simplifies and shows the structure of the cold rolling apparatus 51. It is a figure which shows the relationship between the cold rolling rate of the cold rolled steel strip by the method of this invention, and 0.2% yield strength. It is a systematic diagram showing a simplified configuration of the BA heat treatment apparatus 65. It is a figure which simplifies and shows the structure of the temper rolling apparatus 75. FIG. It is a figure which shows a glossiness measurement result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hot rolling apparatus 2 Slab 3a, 3b Hot rolled steel strip 3c Cold rolled steel strip 5 Water cooling means 7 Temperature detection means 30 Pickling apparatus 40 Surface polishing apparatus 51 Cold rolling apparatus 65 BA heat treatment apparatus 75 Temper rolling apparatus

Claims (1)

Hot rolling the austenitic stainless steel strip,
By winding austenitic stainless steel strip having a finished thickness of 5.5 mm after hot rolling at 470 ° C. or more and 570 ° C. or less, the 0.2% proof stress becomes 400 N / mm ² or more. The winding process to
After descaling without annealing heat treatment, cold rolling the austenitic stainless steel strip,
Method for producing a bright annealing finish austenitic stainless steel strip, characterized in including that the step of bright annealing heat treatment of austenitic stainless steel strip after cold rolling.

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