JP2019034325A - Manufacturing method of ferritic stainless steel cold-rolled steel strip - Google Patents

Abstract

The present invention provides a method for producing a ferritic stainless steel cold-rolled steel strip having excellent surface gloss and suppressing uneven gloss. SOLUTION: For ferritic stainless hot rolled steel strip after pickling, in a pass other than the final pass, the roll diameter is 40 mm or more and 150 mm or less, and the arithmetic average roughness Ra of the surface is 0.20 μm or more and 0.45 μm Ra or less. In the final pass, the roll is rolled using a work roll having a roll diameter of 40 mm or more and 150 mm or less and a surface arithmetic average roughness Ra of 0.03 μm or more and 0.15 μm or less. A method for producing a ferritic stainless steel cold-rolled steel strip, characterized by performing temper rolling with an elongation of 0.3 to 2.0% after annealing. [Selection figure] None

Description

  The present invention relates to a method for producing a ferritic stainless steel cold-rolled steel strip.

  Ferritic stainless steel cold-rolled steel strip is often used for home appliances, kitchen products, Western dishes, etc., and surface gloss is an important characteristic. In particular, when a high-gloss cold-rolled steel strip with a high surface glossiness is used, gloss unevenness (difference in surface gloss) is more noticeable in the width direction of the cold-rolled steel strip, so that surface gloss is excellent and gloss unevenness It is an important subject to obtain a cold-rolled steel strip in which the above is suppressed.

  Ferritic stainless steel cold-rolled steel strips are usually hot-rolled slabs produced by continuous casting to produce hot-rolled steel strips, annealed (may be omitted in some cases), pickled, and then cold-rolled. It is manufactured by annealing, pickling (may be omitted in some cases), and temper rolling. Among these, gloss unevenness is a defect generated in the cold rolling process.

  Stainless cold-rolled steel strips that require surface gloss (high gloss) as described above are cold-rolled with a cold rolling mill having a work roll with a small roll diameter, such as a 20-stage Zenzimir mill or a 12-stage cluster mill. Generally, it is manufactured. This is because a work roll with a small roll diameter is preferable for obtaining excellent surface gloss with less drawing of rolling oil, and for rolling stainless steel with a large deformation resistance, it is better to use a work roll with a small roll diameter. By being advantageous.

  Conventionally, many techniques for improving the surface gloss of a ferritic stainless steel cold-rolled steel strip have been disclosed. In cold rolling, every roll or every 2 or 3 passes, the roll is rolled from a roll with a large surface roughness to a roll with a small surface roughness in order, and the roll is cold rolled with excellent surface gloss. A method of building steel strip has been implemented. However, in this case, there are problems that the number of times of exchanging the work rolls increases and it is necessary to prepare several kinds of work rolls having different surface roughness for each pass.

  For example, in Patent Document 1, in cold rolling, the first pass is rolled using a work roll of Ra = 0.4 to 1.6 μm, and the second and subsequent passes are Ra = 0.01 to 0.06 μm. A method for producing a high-gloss stainless steel cold-rolled steel sheet that is rolled using a work roll is disclosed.

  In Patent Document 2, after rolling using a work roll having a surface roughness Ra of 0.5 μm or more and 3.0 μm or less, using a work roll having a surface roughness Ra of 0.18 μm or less, the rolling reduction is 20%. Disclosed is a method for producing a cold-rolled stainless steel sheet having excellent surface properties, which is rolled as described above and further rolled at a reduction rate of 8% to less than 20% using a work roll having a surface roughness Ra of 0.18 μm or less. Has been.

  Further, in Patent Document 3, in a method for producing a ferritic stainless steel plate that is finished by performing bright annealing, a rolling roll having an average surface roughness of 0.030 μm or less is used at a rolling reduction of 15% or more in the final pass. After rolling, finish with a rolling roll having an average surface roughness of 0.020 μm or less in the final pass at a reduction rate of 10% or more, and even in temper rolling after bright annealing, the average surface roughness is 0.010 μm. The manufacturing method of the ferritic stainless steel plate excellent in the glossiness which uses the following rolling rolls is disclosed.

  Patent Document 4 discloses a surface that uses a roll that is subjected to Cr plating on the surface of the temper rolling roll during temper rolling and then polished to an average roughness Ra in the roll width direction of 0.003 μm or more and 0.010 μm or less. A method for producing a ferritic stainless steel cold-rolled steel strip excellent in gloss is disclosed. Patent Document 5 discloses a method for producing a stainless cold-rolled steel sheet that regulates the surface roughness of a hot-rolled steel strip by grinding the surface of the hot-rolled steel strip with a grinder to reduce uneven glossiness of the strip.

Japanese Patent No. 2642571 Japanese Patent Publication No. 64-3561 Japanese Patent No. 3241495 JP 2011-110594 A JP 2002-239604 A

  In the method disclosed in Patent Document 1, although a highly glossy surface is obtained, band-like gloss unevenness may occur in the width direction of the steel band, and the yield may be reduced. The method disclosed in Patent Document 2 relates to a technique for smoothing a steel strip in which heat streaks have been generated in advance, but heat streaks cause gloss unevenness, and strip-shaped gloss unevenness occurs. The surface of the manufactured steel strip was excellent in glossiness but sometimes had cloudy defects. The methods disclosed in Patent Documents 3 and 4 are techniques for creating surface gloss using a roll having a very small surface roughness. However, in general cylindrical polishing, a roll roughness of less than 0.030 μmRa is created. Is impossible, requires special polishing technology and Cr plating, is expensive, and is difficult to industrially operate. The method disclosed in Patent Document 5 has a problem that the manufacturing cost of the cold-rolled steel sheet is high and the productivity of the cold-rolled steel sheet is low because of using a grinder equipment, and the processing capacity is limited.

  Conventionally, in order to build surface gloss, it is advantageous to transfer a roll surface having a small surface roughness to the surface of the steel strip, and various techniques based on the idea have been presented. It was difficult to achieve a balance with gloss unevenness that became more noticeable as the gloss was improved. In addition, in order to suppress uneven glossiness, only methods with high manufacturing load have been presented, such as grinding the entire length and width of the steel strip uniformly at a high cost.

  This invention solves the above subjects, and it aims at providing the manufacturing method of the ferritic stainless steel cold-rolled steel strip excellent in surface glossiness, and the gloss nonuniformity being suppressed.

The present invention has the following configuration.
[1] For ferritic stainless hot rolled steel strip after pickling, in a pass other than the final pass, the roll diameter is 40 mm or more and 150 mm or less, and the arithmetic average roughness Ra of the surface is 0.20 μm or more and 0.45 μm or less. Rolled using a work roll, and in the final pass, the roll diameter is 40 mm or more and 150 mm or less, and the surface arithmetic average roughness Ra is cold rolled using a work roll of 0.03 μm or more and 0.15 μm or less, A method for producing a ferritic stainless steel cold-rolled steel strip, characterized by performing temper rolling with an elongation of 0.3 to 2.0% after annealing.

  According to the present invention, it is possible to manufacture a ferritic stainless steel cold-rolled steel strip that is excellent in surface gloss and that suppresses uneven gloss.

  According to the present invention, for example, shot blasting is performed before pickling, and even when a hot-rolled steel strip having a deep dent is cold-rolled as a material to be rolled, the surface gloss is excellent, and It becomes easy to manufacture a ferritic stainless steel cold-rolled steel strip in which uneven gloss is suppressed. Therefore, according to the present invention, it is possible to produce a ferritic stainless steel cold-rolled steel strip with higher productivity, lower cost, excellent surface gloss, and suppressed gloss unevenness.

  Details of the present invention will be described below.

  As a result of investigating the occurrence of gloss failure, considering the generation mechanism, and intensively studying the improvement method, the present inventors have completed the present invention.

First, as a result of investigating the occurrence of uneven gloss,
(I) A high ratio is generated in the first rolling pass of the cold rolling process.
(Ii) likely to occur when the rolling speed in the cold rolling process is high;
I found out.

  Furthermore, the present inventors have observed in detail the cold-rolled steel strip in which the uneven gloss has occurred, and investigated the cause of the uneven gloss. As a result, it was found that there was a difference in the amount of oil pits (number of oil pits) in the portion where the uneven gloss occurred compared to the other portion (normal portion). Here, the oil pit means that rolling oil is enclosed in a dent on the surface of a hot-rolled steel strip that is a material to be rolled during cold rolling, and the rolling oil remains in the dent on the surface of the steel strip even after the cold rolling process. Is a dent remaining in the sealed state. Ferritic stainless steel hot-rolled steel strips are difficult to descal, so it is common practice to perform shot blasting on the steel strip surface before pickling, and shot blasting is applied to the steel strip surface before cold rolling. There is a dent exceeding a depth of 1 μm which is a mark. This is the starting point, and oil pits are generated during cold rolling.

  Next, the first half pass of cold rolling and the mechanism of occurrence of gloss unevenness during high speed rolling were considered. That is, in the first half pass, which is the initial stage of the cold rolling process, there are many dents on the surface of the hot-rolled steel strip (rolled material), and there are also variations in surface properties (unevenness) in the width direction of the steel strip. The amount of oil pits remaining after hot rolling increased and gloss unevenness was likely to occur. On the other hand, as the rolling speed is increased, the amount of rolling oil drawn into the roll bite increases as the rolling speed increases, so that the rolling oil is easily enclosed in the recesses on the surface of the hot-rolled steel strip, and oil pits are easily generated. And even if it rolls to the produced | generated oil pit, the dent of a surface is hard to be reduced. For this reason, oil pits remaining after cold rolling increased, and it was considered that gloss unevenness was likely to be manifested. That is, if the oil pit generated during cold rolling can be reduced, it is considered that gloss unevenness is less likely to occur.

  As a method for reducing the oil pit, conventionally, a measure for reducing the amount of rolling oil drawn into the roll bite has been generally taken. For this purpose, for example, it has been effective to reduce the rolling speed or to lower the viscosity of the rolling oil. However, in the present invention, as a result of examining a method for more effectively removing (erasing) an oil pit exceeding a depth of 1 μm, for example, caused by shot blast marks, the following knowledge was obtained.

  That is, the oil pit is generated when the rolling oil is sealed in the recess on the surface of the steel strip. Therefore, in order to prevent the rolling oil from remaining encapsulated, a ridge is provided as an outlet for the rolling oil to flow out of the recess, and the rolling oil is allowed to flow out of this ridge to effectively deepen the oil even with a small number of rolling operations. We considered removing the pits. As a result, it has been found that it is effective to use the transfer marks on the rolling rolls as a method for forming the wrinkles.

  Conventionally, cold rolling with a work roll having a small surface roughness has been effective for producing a high-gloss cold-rolled steel strip. However, according to the present invention, a work roll having a large surface roughness is intentionally produced in order to reduce the oil pits remaining after cold rolling, and to produce a cold rolled steel strip having high gloss and suppressed gloss unevenness. It was revealed that it was effective to use this in combination with a work roll having a small surface roughness.

  Furthermore, the roll diameter and surface roughness of the work roll in each rolling pass in the cold rolling process were intensively studied, and the optimum range was determined as follows.

  First, the reason for limiting the roll diameter of the work roll will be described. In order to obtain a product with high gloss, the roll diameter of the work roll is preferably as small as possible. However, when the roll diameter is too small, the durability of the roll is deteriorated. Therefore, the range (diameter) of the roll diameter was set to a range of 40 to 150 mm. When the roll diameter is less than 40 mm, the durability is low, and troubles such as falling off of the roll surface (spoling) are likely to occur, and the number of rolling is increased and the wear of the roll becomes remarkable. When the roll diameter exceeds 150 mm, the amount of rolling oil drawn into the roll bite increases and the gloss deteriorates. The rolling method may be reverse rolling such as Sendzimir mill or cluster mill or unidirectional rolling represented by tandem mill.

  Next, the reason for limiting the surface roughness of the work roll in each rolling pass will be described. In the present invention, a work roll having a large surface roughness and a work roll having a small surface roughness are used in combination. Further, the operation of the two types of surface roughness work rolls in each rolling pass is performed as follows.

  First, a work roll having a large surface roughness (hereinafter sometimes referred to as a high roughness roll) is used in the first pass of cold rolling to prevent uneven gloss. By using a high roughness roll in the first pass of cold rolling, the occurrence rate of uneven glossiness is significantly reduced. On the other hand, if the first pass of the cold rolling is rolled with a roll having a small surface roughness, gloss unevenness occurs, and it becomes difficult to remove the gloss unevenness in a later pass.

  The surface roughness (arithmetic average roughness Ra) of the high roughness roll is 0.20 μmRa or more and 0.45 μmRa or less. Oil pits can be effectively removed when the surface roughness of the high roughness roll is within the above range. If the surface roughness of the high-roughness roll is less than 0.20 μmRa, the transfer marks on the polishing marks are shallow, and the transfer marks disappear before the oil is pushed out of the recess due to plastic deformation. As a result, gloss unevenness cannot be improved. Also, if the surface roughness of the high roughness roll is larger than 0.45 μmRa, a sufficient transfer mark is formed, but the transfer mark is too strong and the unevenness on the surface of the steel strip cannot be erased by a subsequent rolling pass, resulting in gloss. Gets worse. The surface roughness of the high roughness roll is more preferably 0.25 μmRa or more and 0.35 μmRa or less.

  Next, a roll having a small surface roughness (hereinafter sometimes referred to as a low roughness roll) is used in the final pass of cold rolling to improve gloss. By using the low roughness roll in the final pass of the cold rolling, the transfer marks of the high roughness roll disappear and the gloss is improved. Even if a low roughness roll is used before the final pass, if a roll having a surface roughness larger than that of the low roughness roll is used in the final pass, the transfer marks of the roll remain and the gloss deteriorates.

  The surface roughness (arithmetic average roughness Ra) of the low roughness roll is 0.03 μmRa or more and 0.15 μmRa or less. In order to finish the surface roughness of the low-roughness roll to be smaller than 0.03 μmRa, the surface is plated or requires a special polishing technique, so that it is industrially produced for use in a cold rolling roll. It is unrealistic on the line. Further, if the surface roughness of the low roughness roll exceeds 0.15 μmRa, it gives a transfer mark of the same level as the transfer mark given by the work roll having a rough surface roughness in the first half pass of the cold rolling process, I cannot expect the gloss improvement. From the viewpoint of polishing load and gloss of the final product, the surface roughness of the low roughness roll is more preferably 0.05 μmRa or more and 0.12 μmRa or less.

  Furthermore, when rolling 3 passes or more, passes other than the final pass are rolled with a high roughness roll. After rolling the first pass with a high roughness roll, if the low roughness roll is used in the second and subsequent passes, the smoothened plate surface will be further rolled, and rolling oil will accidentally occur on the surface of the steel strip. The creation of a new oil pit to be sealed is encouraged. Therefore, the low-roughness roll is used only for the final pass, and the previous passes are rolled with a high-roughness roll.

  The surface roughness of the high-roughness roll used from the first pass of cold rolling to the final front pass may be 0.20 μmRa or more and 0.45 μmRa or less. That is, as long as a high-roughness roll satisfying the surface roughness range is used, it is necessary to consider the surface roughness of the high-roughness roll used for the front and rear passes between the first pass and the final pass. There is no.

  Moreover, in this invention, surface roughness means the arithmetic mean roughness (Ra) prescribed | regulated to JISB0601-2001. In the present invention, the surface roughness of the roll means the surface roughness in the roll axial direction.

  Note that the polishing direction and the processing method are not particularly limited in building the surface roughness of the high roughness roll and the low roughness roll. For example, the same effect can be obtained even with circumferential polishing and dull roll. However, on the other hand, considering the wearability, roll polishing load, and occurrence of seizure, the most industrially effective polishing finish is in the cylindrical direction.

  Further, the rolling speed is not particularly limited, and a certain effect can be obtained, and the speed may be controlled within the range allowed by productivity.

Moreover, the rolling oil used for cold rolling is not specifically limited, It can select arbitrarily from an emulsion, neat oil, etc. Further, the base oil is not limited and can be arbitrarily selected from mineral oil, ester oil, water-soluble polymer and the like. However, for the need to eliminate high gloss and gloss unevenness, low-viscosity neat oil is recommended because it is the easiest to reduce the amount of oil drawn, and unevenness in the roll width direction of the pull-in amount is recommended. In addition, as a viscosity (kinematic viscosity in 50 degreeC) of low-viscosity neat oil, 4-20 mm < ² > / s is preferable.

  After the cold rolling, annealing is further performed and temper rolling is performed to produce a ferritic stainless steel cold rolled steel strip.

  As an example, after performing cold rolling so that the sheet thickness is 0.5 to 2.0 mm in the cold rolling, annealing (cold rolling sheet annealing) is performed at a temperature of 700 to 1100 ° C. And after annealing, temper rolling with an elongation of 0.3 to 2.0% is performed to produce a ferritic stainless steel cold-rolled steel strip. By performing temper rolling in the range of the elongation rate, a ferritic stainless steel cold-rolled steel strip having more excellent surface gloss can be produced. If the elongation is less than 0.3%, excellent surface gloss cannot be obtained, and if the elongation exceeds 2.0%, heat scratches are likely to occur.

  Further, in the temper rolling, it is preferable to perform rolling of one pass or more using a roll having a roll diameter (diameter) of 400 mm or more and 1000 mm or less. Moreover, you may perform pickling as needed before the temper rolling after the said annealing. Preferably, when annealing is performed in an oxidizing atmosphere, pickling is performed, and when annealing in a reducing atmosphere (bright annealing) is performed, temper rolling is performed without performing pickling.

  Moreover, the steel type to which the production method of the present invention is applied is not particularly limited. Examples of the steel types include SUS410L, SUS430, SUS430LX, SUS430J1L, SUS434, SUS436L, SUS436J1L, SUS436J1L, SUS443J1, SUS444, SUS445J2, and SUS445J2 defined in Japanese Industrial Standard JIS G 4305.

  Moreover, the manufacturing method of the to-be-rolled material (ferritic stainless steel hot-rolled steel strip) which performs the cold rolling of this invention is not specifically limited. As an example, after heating a steel slab having a predetermined composition to 1100 to 1300 ° C., the finishing temperature is 700 to 1100 ° C., the winding temperature is 400 to 850 ° C., and the plate thickness is 2.0 to 5.0 mm. After hot rolling, it is pickled and manufactured. After the hot rolling, annealing (hot rolled sheet annealing) may be performed at a temperature of 800 to 1100 ° C. Further, shot blasting may be performed before the pickling. According to the manufacturing method of the present invention, oil pits caused by deep dents by shot blasting can also be removed.

In addition, the ferritic stainless steel cold-rolled steel strip manufacturing equipment for carrying out the manufacturing method of the present invention has a high roughness with a roll diameter of 40 mm to 150 mm and an arithmetic average roughness Ra of 0.20 μm to 0.45 μm. A work roll having a low roughness with a roll diameter of 40 mm or more and 150 mm or less, and an arithmetic average roughness Ra of 0.03 μm or more and 0.15 μm or less on the surface. A cold rolling mill that rolls with a work roll having a low roughness, and a cold rolled steel strip that has been rolled with the cold rolling mill. And a temper rolling mill for performing temper rolling at a%. The cold rolling mill may be a reverse rolling mill or a tandem rolling mill. In the case of a reverse rolling mill, after rolling the first pass to the last pass with a high-roughness work roll, replacing the work roll and rolling the final pass with a low-roughness work roll Good.
Moreover, an annealing apparatus may be provided between the cold rolling mill and the temper rolling mill in the conveying direction of the steel strip. Furthermore, a pickling apparatus may be provided downstream of the annealing apparatus.

  Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

  SUS430 steel defined in Japanese Industrial Standard JIS G 4305 (component composition (mass%) of steel used in this example is C: 0.03-0.05%, Si: 0.2-0.5%, Mn: 0.4-0.7%, P: 0.02 to 0.04%, Cr: 16.0 to 16.7%, N: 0.04 to 0.05%) were melted in a converter and further decarburized with VOD. The obtained molten steel was made into a slab by a continuous casting method. Subsequently, a slab having a mass of 12 to 18 t was heated at 1150 ° C. for 1 hour and hot-rolled at a finishing temperature of 900 to 1100 ° C. to obtain a ferritic stainless hot rolled steel strip having a thickness of 3.0 mmt and a width of 980 to 1020 mmw. Manufactured. The manufactured hot-rolled steel strip was subjected to hot-rolled sheet annealing at 830 ° C. for 8 hours in a batch furnace, then shot blasted and pickled (descaled). The pickling was first pickled with sulfuric acid and then pickled with a mixed acid of nitric acid and hydrofluoric acid.

  The hot-rolled steel strip that had been subjected to pickling as described above was cold-rolled with a 12-stage cluster type reverse rolling mill. Cold rolling uses a cold die steel work roll having a roll diameter (diameter) of 90 to 110 mm, and a mineral oil (kinematic viscosity at 50 ° C .: 8 cSt) controlled to 40 ° C. or more and 60 ° C. or less and a test material. (Hot rolled steel strip) was performed while being circulated.

  At that time, the surface roughness (arithmetic mean roughness Ra) of the work roll in each cold rolling pass was changed as shown in Table 1, and 10 0.8 mmt coils were manufactured. In addition, as for the work roll used for the cold rolling in a present Example, all surface roughness was adjusted by the grinding | polishing finishing along the circumferential direction. Moreover, the surface roughness of the work roll shown in Table 1 is measured before rolling the steel strip in each pass. Even when the same work roll was continuously used for two or more passes, the surface roughness of the work roll was measured every time before rolling in each pass. In the first pass, rolling was performed at 80 to 100 mpm because the plate thickness of the specimen was thick and the shape was unstable in the first pass, and rolling was performed at a maximum speed of 250 mpm after the second pass.

  The steel strip after cold rolling is annealed at 830 ° C. for 5 minutes under an oxygen concentration of 4-7 vol% (cold rolled plate annealing), and then subjected to neutral salt electrolytic pickling and nitric acid electrolytic pickling. And descaling. Finally, temper rolling is performed without lubrication in a 2-stand temper rolling mill with a roll diameter of 700 mm in an elongation range of 0.8 to 1.2%, and ferritic stainless cold-rolled steel strips of 10 coils each are formed. Manufactured.

<Evaluation of surface gloss>
Samples (from the longitudinal part of the ferritic stainless steel cold-rolled steel strip (coil) after temper rolling from the longitudinal part of the tip (position 5 m from the forefront), the center, and the tail end (position 5 m from the end) About 1000 mm wide × 300 mm long in the longitudinal direction) is collected, and the glossiness (Gs20 °) at the center of the widthwise direction of each sample is measured in the rolling direction (incident light when measuring glossiness is parallel to the rolling direction). ) And the width direction (incident light when measuring glossiness is parallel to the width direction), respectively, and the average value is the representative value, and the average value of the representative values of the three samples is the glossiness of each coil. did. The glossiness was measured using a gloss meter (UGV-6P) manufactured by Suga Test Instruments.
The surface gloss was judged as rejected (x) when the glossiness of the coil was less than 850, passed (◯) when the coil glossiness was less than 850 and less than 1000, and passed and particularly excellent when it was 1000 or more (◎).

<Evaluation of uneven gloss>
Samples (from the longitudinal part of the ferritic stainless steel cold-rolled steel strip (coil) after temper rolling from the longitudinal part of the tip (position 5 m from the forefront), the center, and the tail end (position 5 m from the end) Gloss (Gs20 °) at 10 positions at regular intervals in the width direction excluding the region from both width ends of each sample to 15 mm is rolled. Five points were measured in each direction (incident light when measuring glossiness was parallel to the rolling direction), and the average value was used as the representative value of the position. In the same sample, if the difference between the maximum value and the minimum value of the representative value at each position is 50 points or more, it is determined that uneven gloss has occurred, and the difference is less than 50 points. The product was judged to have no gloss unevenness.
Judgment of gloss unevenness passes (○) when it is judged that gloss unevenness does not occur in any of the samples taken from the three longitudinal positions of the coil, and gloss of even one of the samples is glossy. A case where it was determined that unevenness occurred was regarded as a failure (x).

  Comprehensive evaluation is that the surface gloss determination result and the gloss unevenness determination result are both passed (◯), and at least one of the surface gloss determination result and the gloss unevenness determination result is rejected. What was there was determined to be rejected (x). And the ratio [(the number of coils in which the comprehensive evaluation was determined to be passed / the number of manufactured coils) × 100] of the coils in which the comprehensive evaluation was determined to be the pass was defined as the pass rate. Table 1 shows each determination result and pass rate.

  In Table 1, No. A1 to A10 are coils manufactured by the manufacturing method of the present invention. No. In all the coils A1 to A10, the surface gloss passed and no gloss unevenness occurred. As a result, the pass rate was 100%.

  No. B1 to B10 are coils manufactured by rolling paths other than the final path (first to seventh paths) with a roll having a surface roughness smaller than 0.20 μmRa, which is smaller than the high roughness roll of the present invention. It is. According to the conventional idea, it has been said that the surface gloss is better as the roll having a smaller surface roughness is used. However, the non-uniform remaining of shot blast marks is promoted, and the surface gloss is rejected with 3 coils. The gloss unevenness was rejected in half of the manufactured coils. As a result, the pass rate was 40%.

  No. C1 to C10 are coils manufactured by rolling the first pass with a roll having a surface roughness of less than 0.20 μmRa, which is smaller than the high roughness roll of the present invention. By rolling the first pass with a roll having a surface roughness smaller than that of the high roughness roll of the present invention, deep dents already formed in the base material (rolled material) by shot blasting tend to remain. Even if a roll with a surface roughness of 0.20 μm Ra or more is used in the passes after the first pass (second pass to seventh pass), the oil pits cannot be completely removed, and gloss unevenness is rejected with 7 coils. It was. As a result, the pass rate was 30%.

  No. D1 to D10 are coils manufactured by rolling the final pass with a roll having a surface roughness larger than that of the low roughness roll of the present invention. Since the same concept as the present invention example up to the last pass, the occurrence rate of gloss unevenness was as low as 30%, but on the other hand, the effect of smoothing the transfer marks of the roll polishing eyes in the final pass was small, and any coil The surface gloss was also unacceptable. As a result, the pass rate was 0%.

  No. E1 to E10 are rolling in the final front pass (seventh pass) and the front pass (sixth pass) with a roll having a surface roughness of less than 0.20 μmRa which is smaller than the high roughness roll of the present invention. It is a coil manufactured as described above. While smoothing has the effect of improving the surface gloss, by using a roll with low surface roughness at an early stage, it does not start from shot blast marks, but accidentally occurs by enclosing rolling oil on the surface of the steel strip. There is an adverse effect that promotes the generation and survival of oil pits. For this reason, some of the manufactured coils failed in the surface gloss due to the remaining oil pits, and some had a new gloss unevenness in the last pass or the final pass, resulting in a failure in the gloss unevenness. As a result, the pass rate was 0%.

  From the above, according to the production method of the present invention, it was confirmed that a ferritic stainless steel sheet excellent in surface gloss and suppressed in occurrence of gloss unevenness can be efficiently produced.

Claims (1)

For ferritic stainless steel hot rolled steel strip after pickling,
Rolls other than the final pass are rolled using a work roll having a roll diameter of 40 mm to 150 mm and an arithmetic average roughness Ra of 0.20 μm to 0.45 μm. In the final pass, the roll diameter is 40 mm to 150 mm. Hereinafter, the surface arithmetic mean roughness Ra is cold-rolled to roll using a work roll of 0.03 μm to 0.15 μm,
After annealing,
A method for producing a ferritic stainless steel cold-rolled steel strip, characterized by performing temper rolling with an elongation of 0.3 to 2.0%.