JP5208274B2 - Lubrication rolling method under high pressure - Google Patents

Abstract

In the disclosed method of cold rolling an acid-washed stainless steel plate, a lubricant is used having a viscosity of 140 cst or higher at 40C, and with one rolling stand, rolling is performed with a 30% or greater rolling reduction rate at least.

Description

  The present invention relates to a rolling method for rolling a stainless steel plate at a high pressure ratio without causing heat scratch and slip.

  Conventionally, when a high-strength steel sheet is manufactured using a tandem rolling mill having a plurality of rolling stands, it is directed to perform high-pressure rolling in order to improve productivity. In order to perform high-pressure rolling with a tandem rolling mill, it is necessary to increase the rolling reduction at each rolling stand.

  However, when the rolling reduction is increased, the amount of lubricating oil flowing between the rolling roll and the steel sheet decreases, the oil film between the rolling roll and the steel sheet becomes thin, and the contact pressure between the rolling roll and the steel sheet increases. Heat scratches are likely to occur. In particular, heat scratching occurs in high-pressure rolling of stainless steel plates.

The heat scratch is a seizure flaw that occurs when the interface temperature between the rolling roll and the steel sheet rises and the oil film of the lubricating oil breaks, resulting in direct contact between the rolling roll and the steel sheet.
Since a steel sheet with traces of heat scratches on the surface cannot be shipped, the yield is naturally reduced. Moreover, since the rolling roll in which the trace of a heat scratch remains must be replaced | exchanged immediately, productivity falls remarkably.

  Therefore, various methods for preventing the occurrence of heat scratch have been proposed so far (see, for example, Patent Documents 1 to 7).

  Patent Document 1 discloses a rolling method in which a rolling mill that easily generates heat scratches is designated in advance, and the operating conditions related to the rolling mill are controlled so that heat scratches do not occur.

  Patent Documents 2 to 4 disclose a rolling method that adjusts the amount, concentration, components, and the like of the lubricating oil (lubricating oil) supplied to the material to be rolled and the work roll so that heat scratches do not occur. .

  Patent Documents 5 and 7 disclose a rolling method that controls the tension between rolling mills to suppress the generation of heat scratches.

Patent Document 6 discloses a rolling method in which shot blasting or shot peening is performed on the surface of a material to be rolled after pickling in order to reduce the rolling load at the first rolling stand.
However, in any rolling method, there is a limit to the increase in the rolling reduction at each rolling stand.

  In tandem rolling, it is difficult to increase the total rolling reduction, and in order to roll a steel plate to a desired thickness, rolling may be further performed following tandem rolling.

  In particular, when trying to tandemly roll a stainless steel plate with high efficiency, the stainless steel plate must be rolled at a high pressure reduction rate that is higher than the conventional value. .

  In order to suppress the occurrence of heat scratching and realize rolling under high pressure, it is usually one measure to increase the viscosity of the lubricating oil and increase the film thickness (see Patent Documents 8 to 12).

  However, simply increasing the film thickness of the lubricating oil decreases the coefficient of friction between the rolling roll and the steel sheet, resulting in excessive lubrication and slipping, resulting in unstable rolling (see Patent Documents 9 and 10).

  Patent Documents 11 and 12 disclose that, in the cold rolling method, high viscosity rolling oil (100 to 300 cSt at 40 ° C.) is used, but the stainless steel plate easily reacts with Cr contained in the rolling roll. Since heat scratches are likely to occur, rolling at a high pressure reduction rate has not been industrially performed.

  Patent Documents 11 and 12 do not disclose a method of rolling without generating heat scratches and slips at a high pressure reduction rate.

  Patent Document 13 discloses that in a tandem rolling mill, the rolling reduction at each rolling stand is 30 to 35% from the viewpoint of improving productivity.

  However, Patent Document 13 does not disclose the viscosity of the rolling oil that realizes rolling under high pressure. With a rolling oil having a viscosity of several tens of cSt, which is usually used in ordinary steel, heat scratches and slips are not generated. It is extremely difficult to roll so as not to occur.

  In tandem rolling, the higher the pressure is, the narrower the range of rolling conditions under which heat scratches and slips do not occur and the rolling becomes difficult, so the rolling reduction per rolling mill must be limited.

  In order to produce a steel plate with a desired thickness, in the case of a tandem rolling mill, many rolling mills are arranged, and in the case of a reverse rolling mill, the number of rolling is increased. Such a measure does not improve productivity.

  In order to increase productivity in cold rolling, it has been necessary to develop a rolling technique that does not generate heat scratches and slips at a high pressure reduction rate.

JP 2007-307620 A JP 2007-253178 A JP 2007-237230 A Japanese Patent Laid-Open No. 2006-267339 JP 2006-198661 A JP 2005-177774 A JP 2001-179306 A JP 05-043888 A Japanese Patent Application Laid-Open No. 07-251209 JP 2000-317510 A Japanese Patent Laid-Open No. 05-253604 Japanese Patent Application Laid-Open No. 08-024908 Japanese Patent Laid-Open No. 06-091306

  Between the rolling roll and the steel plate, a lubrication state in which fluid lubrication in which an oil film of lubricating oil is present and boundary lubrication in which metals directly contact each other is mixed is formed.

  The amount of lubricating oil flowing between the rolling rolls and the steel sheet is shown in Fig. 1 (Third Edition Steel Handbook III (1) Rolling Foundation / Steel [Maruzen Co., Ltd., June 30, 1980, Second Printing, Issued] ], Page 92), it decreases as the rolling reduction increases, and the oil film between the rolling roll and the steel sheet becomes thinner.

  That is, as the rolling reduction increases, the contact pressure between the rolling roll and the steel sheet increases, and the lubrication oil balances with the pressure of the oil film caused by the shear force trying to draw the lubricating oil between the rolling roll and the steel sheet. The oil film becomes thinner.

  When the lubricating oil film thickness is reduced, the boundary lubrication region is widened, and the pressure at which the metals are in direct contact with each other increases, so that a seizure phenomenon (heat scratch) between the rolling roll and the steel sheet is likely to occur.

  Usually, in order to increase the film thickness of the lubricating oil, the viscosity of the lubricating oil is increased to increase the shear force, but simply increasing the film thickness results in a coefficient of friction between the rolling roll and the steel plate as described above. Lowering, excessive lubrication, slipping, and unstable rolling.

  Eventually, in rolling, the higher the pressure, the narrower the range of rolling conditions under which heat scratches and slips do not occur, making rolling difficult. That is, the rolling reduction per rolling mill is limited, and productivity is not improved.

  Therefore, the present invention increases the rolling reduction ratio of the rolling stand in cold rolling, does not generate heat scratches and slips, and continuously anneals steel sheets after pickling, particularly stainless steel sheets, without re-rolling. It is an object to provide a high-strength steel sheet (for example, having a tensile strength of 300 MPa or more) that can be used as it is with good productivity, and to provide a rolling method that solves the problem.

  In order to solve the above-mentioned problems, the present inventors diligently studied the quantitative relationship between the rolling reduction and lubrication.

  As described above, between the rolling roll and the steel plate, a lubrication state is formed in which fluid lubrication in which a lubricating oil film is interposed and boundary lubrication in which metals are in direct contact with each other are formed. Boundary lubrication with which they are in direct contact is greater than fluid lubrication via lubricating oil.

  Therefore, normally, when the rolling reduction is increased, the ratio of boundary lubrication increases and the friction coefficient increases.

  In order to confirm the quantitative relationship between the reduction ratio and lubrication, the present inventors investigated the correlation between the reduction ratio and the friction coefficient by changing the viscosity of the lubricating oil. The result is shown in FIG. The viscosity is a viscosity measured with a Canon-Fenske viscometer based on JIS K 2283.

  From FIG. 2, (x) when using a lubricating oil with a viscosity of 130 cSt at 40 ° C., the friction coefficient increases with an increase in the rolling reduction, but (y) when using a lubricating oil with a viscosity of 140 cSt at 40 ° C., Even if the rolling reduction exceeds about 30%, the change in the friction coefficient is small. (Z) When a lubricating oil having a viscosity of 150 cSt at 40 ° C. is used, if the rolling reduction exceeds about 30%, the friction is reversed. It can be seen that the coefficient is small.

  The above phenomena (y) and (z) are phenomena that cannot be explained by conventional rolling theory. That is, the present inventors have found that the above phenomena (y) and (z) appear when the viscosity of the lubricating oil used in rolling is increased.

Furthermore, the present inventors have found that using a lubricant of higher viscosity 140cSt at 40 ° C., when rolling at a reduction rate of 30 percent, in addition to the heat scratch, slip also does not occur, it has been found that can be stably rolled.

  This invention was made | formed based on the said knowledge, and the summary is as follows.

(1) In a method of cold rolling a pickled stainless steel plate with a dandem rolling mill equipped with a plurality of rolling stands, a high viscosity lubricating oil of 140 cSt or more is used at 40 ° C., and the rolling stand has a diameter of 150 mm or more and 600 mm or less. using the work rolls, the plurality of rolling stands, the rolling speed at the entrance side of the first rolling stand and 66m / min or more, at least 1 group rolling stands except the last rolling stands, pressure under 30% A high-pressure lubricated rolling method characterized by rolling at 35 % or less and rolling at a rolling reduction of 18 to less than 26% at the final rolling stand .
However, the viscosity is a viscosity measured with a Canon-Fenske viscometer based on JIS K 2283.

  (2) The cold rolling under high pressure as described in (1) above, wherein the cold rolling is performed with a dandem rolling mill having four or more rolling stands.

(3) In the tandem rolling performed by the dandem rolling mill, at least two rolling stands excluding the final rolling stand are rolled at a rolling reduction of more than 30% and not more than 35 %. The high-pressure lubricated rolling method described.

(4) The high-pressure lubricated rolling method according to (2), wherein in the tandem rolling, rolling is performed at a reduction ratio of more than 30% and not more than 35 % at the first rolling stand.

(5) In the tandem rolling, the high-pressure lubricated rolling method according to (3), wherein rolling is performed at a rolling reduction ratio of more than 30% and not more than 35 % at the first rolling stand.

  (6) The high-pressure lubricated rolling method according to (3), wherein in the tandem rolling, rolling at a rolling reduction of 33% or less is performed at a rolling stand immediately before the final rolling stand.

  (7) In the tandem rolling, the high-pressure lubricated rolling method according to (4), wherein rolling is performed at a rolling reduction of 33% or less at a rolling stand immediately before the final rolling stand.

( 8 ) The high pressure lubricated rolling method according to any one of (2) to (7), wherein in the dandem rolling, rolling with a total rolling reduction of more than 70% is performed.

( 9 ) In the tandem rolling, the rolling speed in the final rolling stand is 250 m / min or more, and the high-pressure lubricated rolling method according to any one of (2) to (7) above.

( 10 ) In a method of cold rolling a pickled stainless steel plate with a reverse rolling mill, a high viscosity lubricating oil of 140 cSt or higher is used at 40 ° C., and the reverse rolling mill uses a work roll having a diameter of 150 mm or more and 600 mm or less. Of the multiple rolling passes of reverse rolling, the rolling speed at the entrance side of the first rolling pass is set to 66 m / min or more, and at least one rolling pass excluding the final rolling pass, the reduction rate exceeds 30%, 35 % High-pressure lubricated rolling method, wherein rolling is performed at a reduction rate of 18 to less than 26% in the final rolling pass.
However, the viscosity is a viscosity measured with a Canon-Fenske viscometer based on JIS K 2283.

(11) In the reverse rolling performed in the reverse rolling mill, at least two rolling passes but the last rolling pass, reduction of 30 percent, according to above, wherein the performing rolling below 35% (10) Lubricating rolling method under high pressure.

( 12 ) In the reverse rolling, the high-pressure lubricated rolling method according to ( 10 ), wherein rolling is performed at a rolling reduction of more than 30% and not more than 35 % in the first rolling pass.

( 13 ) The high-pressure lubricated rolling method as described in ( 11 ) above, wherein in the reverse rolling, rolling is performed at a rolling reduction of more than 30% and not more than 35 % in the first rolling pass.

( 14 ) In the reverse rolling, the rolling is performed at a rolling reduction of 33% or more and 35% or less in a rolling pass immediately before a final rolling pass, and any one of ( 10 ) to ( 13 ), Lubricating rolling method under high pressure.

( 15 ) The high-pressure lubricated rolling method according to any one of ( 10 ) to ( 13 ), wherein the reverse rolling is performed with a total rolling reduction exceeding 70%.

( 16 ) The high pressure lubricated rolling method as described in ( 14 ) above, wherein in the reverse rolling, rolling with a total rolling reduction of more than 70% is performed.

( 17 ) The high-pressure lubricated rolling method according to any one of ( 10 ) to ( 13 ), wherein in the reverse rolling, a rolling speed in a final rolling pass is 250 m / min or more.

( 18 ) In the reverse rolling, the rolling speed in the final rolling pass is 250 m / min or more, and the high-pressure lubricated rolling method as described in ( 14 ) above.

( 19 ) In the reverse rolling, the rolling speed in the final rolling pass is 250 m / min or more, and the high-pressure lubricated rolling method as described in ( 15 ) above.

( 20 ) In the reverse rolling, the rolling speed in the final rolling pass is 250 m / min or more, and the high-pressure lubricated rolling method as described in ( 16) above.

  ADVANTAGE OF THE INVENTION According to this invention, the stainless steel plate of the desired final board thickness which does not generate | occur | produce a slip and does not have a heat scratch with a tandem rolling mill or a reverse rolling mill can be rolled with sufficient productivity.

It is a figure which shows the relationship between the quantity (g / m < ² >) of lubricating oil which flows in between a rolling roll and a steel plate, and rolling speed | rate (m / min) when changing a rolling reduction (3rd edition steel manual III (1) Rolled foundation / steel plate [Maruzen Co., Ltd., June 30, 1980, second edition, issue], page 92). It is a figure which shows the correlation of a rolling reduction (%) and a friction coefficient when changing the viscosity (cSt) of lubricating oil. The result of quantitative investigation of the shape of the indentation generated on the collision surface by dropping and colliding a steel ball on a flat anvil coated with lubricating oil (Volume 66 of the Japan Society of Mechanical Engineers) 645 (2000-5), P1687-1693, "Study on indentation shape of sphere and flat plate caused by impact through oil", see FIG.

(A) is when a steel ball made of SUS304 having a hardness of HV307 is dropped and collided with an anvil made of SUJ2 having a hardness of HV710, coated with a high-viscosity oil (S100) having a viscosity of 99.5 mm ² / s at 40 ° C. The deformation shape of the steel ball is shown.

(B) is when a steel ball made of SUS304 having a hardness of HV307 is dropped and collided with an anvil made of SUJ2 having a hardness of HV710, which is coated with a high viscosity oil (TN220) having a viscosity of 203.4 mm ² / s at 40 ° C. The deformation shape of the steel ball is shown.

The present invention is characterized in that in a method of cold rolling a pickled stainless steel plate, a high viscosity lubricating oil is used and rolling is performed at a rolling reduction of more than 30% and 40% or less with at least one rolling stand. To do.

  First, the knowledge that forms the basis of the present invention will be described.

  As described above, the present inventors have found that the following phenomena (y) and (z) appear when the viscosity of the lubricating oil used is increased.

  (Y) When a lubricating oil having a viscosity of 140 cSt at 40 ° C. is used, even if the rolling reduction exceeds about 30%, the change in the friction coefficient is small.

  (Z) In the case of a lubricating oil having a viscosity of 150 cSt at 40 ° C., when the rolling reduction exceeds about 30%, the friction coefficient decreases.

  The present inventors consider the mechanism by which the phenomena (y) and (z) are expressed as follows.

  Conventionally, it is known that an oil pit generated by the containment of lubricating oil is observed on the surface of a cold-rolled steel sheet (Third Edition Steel Handbook III (1) Rolling Foundation / Steel [Maruzen Co., Ltd., June 30, 1980, Second Print, Issue], page 92, left column).

  The oil pit occurrence phenomenon indicates that during cold rolling, a high pressure was generated between the rolling roll and the steel sheet so that the lubricating oil was contained and the steel sheet surface was deformed.

  The occurrence of the above phenomenon is supported by the research results of quantitatively investigating the shape of the indentation generated on the collision surface by dropping a steel ball on a flat anvil coated with lubricating oil (anvil) ( The Japan Society of Mechanical Engineers Proceedings (C), Vol. 66, No. 645 (2000-5), P1687-1693, “Study on Indentation Shapes of Balls and Flat Plates Generated by Impact through Oil”).

FIG. 3 shows a part of the research results. In FIG. 3 (a), a SUS304 steel ball of hardness HV307 is applied to an anvil (anvil) made of SUJ2 having a hardness of HV710 and coated with a high viscosity oil (S100) having a viscosity of 99.5 mm ² / s at 40 ° C. The deformation shape of a steel ball when dropped and collided is shown.

In FIG. 3 (b), a SUS304 steel ball of hardness HV307 is applied to an anvil made of SUJ2 having a hardness of HV710 (TN220) coated with a high viscosity oil (TN220) having a viscosity of 203.4 mm ² / s at 40 ° C. The deformation shape of the steel ball when dropped is shown.

  As shown in FIG. 3, the steel ball has a shape in which the center of the collision portion of the steel ball is recessed due to the oil contained in the collision. This dent shape has a larger oil viscosity (TN220> S100). From this, it can be seen that high-viscosity oil is contained between the steel ball and the anvil and generates a high pressure.

Based on the result shown in FIG. 3, the phenomenon of (z) is considered as follows.
In other words, rolling using high-viscosity lubricating oil under high pressure makes the lubricating oil containment phenomenon prominent, and a very high pressure is generated in the part where the lubricating oil is contained, and rolling is supported by fluid lubrication. The ratio of the load becomes relatively larger than the ratio of the rolling load supported by the boundary lubrication, and as a result, the overall friction coefficient is lowered.

  On the other hand, the absolute value of the rolling load supported by boundary lubrication does not change so much or increases slightly even if the rolling reduction is increased, so that no slip occurs during rolling.

  The phenomena (y) and (z) shown in FIG. 2 are epoch-making findings that overturn the conventional technical common sense related to the rolling technology.

  The present inventors consider that the above knowledge can be applied to cold rolling of a stainless steel plate after pickling. In a tandem rolling mill having a five-rolling stand configuration, a high-viscosity lubricating oil is used and the first rolling stand is reduced. The reduction ratio was set to 31.3%, the rolling reduction ratio of the second rolling stand was set to 30.3%, a steel plate having a thickness of 2.700 mm after pickling and a steel plate having a thickness of 0.572 mm at a rolling speed of 303 mpm. Rolled into. The total rolling reduction was 78.8%.

  During rolling, no slip occurred, and there was no heat scratch in the rolled stainless steel plate. However, in order to make the plate thickness of the steel plate desired (for example, less than 0.540 mm), cold rolling was performed again. It is necessary to apply.

  In order to roll to a desired plate thickness (for example, less than 0.540 mm) only by tandem rolling, a steel plate having a plate thickness of 2.700 mm must be rolled at a total reduction of 80% or more.

  In order to perform rolling with a total rolling reduction of 80% or more by tandem rolling, it is necessary to set the rolling reduction at each rolling stand beyond the conventional rolling reduction.

  When the rolling reduction rate in each individual rolling stand is set to exceed the conventional rolling reduction rate, there is a concern that heat scratching may occur, but the present inventors have a high viscosity (for example, in a tandem rolling mill having a 5 rolling stand configuration) , 40 ° C: 140 cSt or more), aiming to roll a 2.70 mm thick 17% Cr stainless steel plate to a thickness of less than 0.58 mm, adjusting the rolling reduction of each rolling stand and rolling did.

  Table 1 shows rolling conditions and rolling results. The viscosity is a viscosity measured with a Canon-Fenske viscometer based on JIS K 2283. The work roll diameter is 500 mm.

  In rolling example a (comparative example), a low-viscosity (40 ° C .: 40 cSt) lubricating oil was used, the rolling reduction of each rolling stand was less than 30% (low pressure reduction rate), and rolling was performed at a total reduction rate of 77.0%. It is an example.

  Although there is no problem in the rolling itself, the final plate thickness is 0.62 mm, which exceeds 0.60 mm. Therefore, it is necessary to perform rolling again to a desired plate thickness. The rolling example a (comparative example) is “low viscosity + low pressure” rolling, and is a rolling example with low efficiency as a whole of the cold rolling operation.

  Rolling example b (comparative example) is an example in which a low viscosity (40 ° C .: 40 cSt) lubricating oil was used and rolled at a total rolling reduction of 78.6%. The second rolling stand (No. 2std in the table) performs high-pressure rolling with a reduction ratio of 32%, and heat scratches are generated due to “low viscosity + high pressure”.

  Rolling example c is an example in which a lubricating oil having a high viscosity (40 ° C .: 150 cSt) was used and rolled at a total rolling reduction of 78.6%. The second rolling stand (No. 2std) is rolling under high pressure with a reduction ratio of 32%, but because it uses a high-viscosity lubricating oil, there is no problem in rolling, and the plate thickness is up to 0.58 mm. Rolled.

The rolling example d is an example in which a lubricating oil having a high viscosity (40 ° C .: 150 cSt) is used and rolled at a total rolling reduction of 79.2%. In the second rolling stand (No.2std) and the third rolling stand (No.3std), it is performed under high pressure rolling reduction ratio exceeds 30%, because it uses a lubricating oil of high viscosity, the rolling There is no problem, and the sheet is rolled to a thickness of 0.56 mm.

  The rolling example e is an example in which a lubricating oil having a high viscosity (40 ° C .: 150 cSt) is used and rolled at a total rolling reduction of 78.8%. The first rolling stand (No. 1std) is rolling under high pressure with a reduction ratio of 32%, but because it uses a high-viscosity lubricating oil, there is no problem with rolling and the plate thickness is up to 0.57 mm. Rolled.

  In addition, even if wrinkles occur in the high-pressure rolling at the former stage, the degree of wrinkles can be reduced by rolling at the latter stage, so it is preferable to perform the high-pressure rolling at the previous stage.

  The rolling example f is an example in which a high viscosity (40 ° C .: 150 cSt) lubricating oil is used and rolled at a total rolling reduction of 79.8%. The fourth rolling stand (No. 4std) was rolled under high pressure with a reduction ratio of 35%, and extremely mild heat scratches were produced, but because a highly viscous lubricant was used, the plate thickness was 0.54 mm. Rolling is done.

  In addition, it is practically not problematic to perform rolling under high pressure in a rolling stand (No. 4std) preceding the final rolling stand (No. 5std).

  The rolling example g is an example in which a lubricating oil having a high viscosity (40 ° C .: 150 cSt) is used and rolled at a total rolling reduction of 79.9%. Since the second rolling stand (No.2std) was rolled under a high pressure of 32%, the final rolling stand (No.5std) was reduced to less than 30% and the total rolling reduction was optimized. No rolling occurs, and rolling is performed to a plate thickness of 0.54 mm by using a high viscosity lubricating oil.

The rolling example h is an example in which a lubricating oil having a high viscosity (40 ° C .: 150 cSt) is used and rolled at a total rolling reduction of 82.8%. The first to fourth rolling stands (No. 1std to No. 4std) perform high-pressure rolling with a reduction ratio of more than 30%, but use of high-viscosity lubricating oil causes problems in rolling. In other words, the sheet is rolled to a thickness of 0.46 mm.

  Rolling i (Reference Example) is an example in which a lubricating oil having a high viscosity (40 ° C .: 150 cSt) is used, the rolling reduction of each rolling stand is less than 30% (low pressure reduction), and rolling is performed at a total reduction of 77.0%. It is. Although there is no problem in rolling, the final plate thickness is 0.62 mm, and it is necessary to cold-roll again to the desired plate thickness.

  Even when a high-viscosity lubricating oil is used, if the rolling reduction is low (high viscosity + under low pressure), this is an example of rolling with low efficiency as a whole of the cold rolling operation.

  As described above, the rolling examples c to h are invention examples that can be efficiently rolled to a desired plate thickness with “high viscosity + high pressure”.

Thus, the present inventors have a reduction ratio for the first rolling stand (No.1std) and the second rolling stand (No.2std) was set to 30 percent, reduction of the third stand (No.3std) It was found that even when the rate was set to a reduction rate close to 30%, no slip occurred during rolling, and no heat scratch occurred in the steel sheet after rolling.

  This is the knowledge forming the basis of the present invention.

The heat scratch is a seizure flaw that occurs when the interface temperature between the rolling roll and the steel sheet rises, the oil film of the lubricating oil breaks, and the rolling roll and the steel sheet come into direct contact with each other, so the rolling speed is 100 to 150 mpm. , even if rolling at a reduction ratio of 30 super 35%, the heat scratch is not generated on the surface of the steel sheet, the use of the lubricating oil of high viscosity, under the rolling speed and the reduction ratio, the oil film of the lubricating oil is broken It means not to.

  In the case of stainless steel, since the rolling roll contains about 5% of Cr, if the rolling reduction exceeds 40%, heat scratches are generated on the steel plate surface. In the case of steels other than stainless steel, heat scratches do not occur on the surface of the steel sheet up to a rolling reduction of 45%.

  Based on the above test results, the present inventors examined the setting of the rolling reduction for further rolling the stainless steel plate to 0.48 mm or less.

  The rolling reduction of the first rolling stand, the rolling reduction of the second rolling stand, and the rolling reduction of the third rolling stand are 31.6%, 31.3%, and 30.7%, respectively, in anticipation of safety. In the fourth rolling stand, the rolling reduction was changed from 27.0% to 33% in increments of 1%, and a stainless steel plate having a thickness of 2.70 mm was rolled to a thickness of 0.476 mm.

  Moreover, in the 4th rolling stand, when the reduction rate was 33%, the rolling speed was increased from 250 mpm to 400 mpm, and the influence on the quality due to the lubrication change and the plate temperature increase was observed. The total rolling reduction is 82.4%.

  About the stainless steel plate obtained by rolling, the presence or absence of the heat scratch was investigated. In any steel sheet, no heat scratch occurred. The fourth rolling stand was rolled under severe conditions with a rolling reduction of 33% and a rolling speed of 400 mpm, but no heat scratch was generated on the steel plate surface.

  Based on the above investigation results, the present inventors use a high-viscosity lubricating oil (for example, 140 cSt or more at 40 ° C.) in a tandem rolling mill having a five-rolling stand configuration, except for the final rolling stand, and rolling down on the four-rolling stand. It has been found that if the rate is set to the 30% range, the stainless steel plate can be rolled to a desired final thickness only by tandem rolling, without generating heat scratches on the steel plate surface.

  This point is also the knowledge forming the basis of the present invention.

According to the above knowledge, in cold rolling of a stainless steel plate after pickling, high-viscosity lubricating oil is used, and at least one rolling stand is subjected to high-pressure lubricating rolling at a rolling reduction of more than 30% and 40% or less. For example, the steel plate can be stably rolled to a desired final plate thickness without generating heat scratches on the steel plate surface.

  In high-pressure lubricated rolling, the higher the strength of the steel sheet to be rolled, the more remarkable the effect of suppressing the occurrence of heat scratches. Moreover, since the pressure of the lubricating oil contained between a rolling roll and a steel plate rises, so that a rolling speed becomes high, the said effect becomes more remarkable.

  The high-viscosity lubricating oil used in the high-pressure lubrication rolling method only needs to have a viscosity that exceeds the viscosity of the lubricating oil used in ordinary cold rolling, but the viscosity (based on JIS K 2283 is a Canon-Fenske viscometer). If a high-viscosity lubricating oil having a measured viscosity of 140 cSt or higher at 40 ° C. is used, the effect of suppressing the occurrence of heat scratch can be reliably obtained.

  Up to now, high-pressure lubricated rolling has been described based on a tandem rolling mill having five rolling stands, but the number of rolling stands is not limited to five.

  The number of rolling stands may be set as appropriate so that lubrication rolling under high pressure can be performed, but in order to perform stable rolling without generating heat scratch, a dandem rolling mill having four or more rolling stands is used. preferable.

When rolling (tandem rolling) using a dandem rolling mill equipped with four or more rolling stands, at least two rolling stands excluding the final rolling stand, rolling at a rolling reduction of more than 30% and not more than 40% Preferably it is done.

Rolling with a rolling reduction of more than 30% and not more than 40% may be performed in the first rolling stand, or may be performed in a rolling stand after the second rolling stand (excluding the final rolling stand). That is, rolling with a rolling reduction of more than 30% and 40% or less may be performed in a rolling stand excluding the final rolling stand.

  Rolling over a rolling reduction of 33% may be performed at the rolling stand immediately before the final rolling stand, but if the selection of the lubricating oil is not appropriate, the possibility of heat scratching increases, so the final rolling stand The rolling reduction at the rolling stand immediately before is preferably 33% or less.

  In the final rolling stand, it is preferable to perform rolling at a rolling reduction of less than 25 to 30% so that heat scratches do not occur.

  The total rolling reduction in dandem rolling is preferably more than 70%. If the total rolling reduction is 70% or less, the desired final thickness may not be achieved, and cold rolling may be required again.

  Although the rolling speed is adjusted in consideration of the reduction ratio, if the rolling speed at the final rolling stand is less than 150 m / min, the oil film pressure of the lubricating oil is low, and there is a possibility that minute heat scratches may occur. 150 m / min or more is preferable.

  Further, the rolling speed in the final rolling stand is preferably 250 m / min or more from the viewpoint of productivity of high-pressure lubricated rolling.

In order to secure a rolling reduction of more than 30% and 40% or less with a rolling stand, it is preferable to use a work roll having a diameter of 150 mm or more and 600 mm or less. If the diameter is less than 150 mm, the strength of the work roll cannot be secured, and breakage may occur during rolling.

Moreover, since the r value of a steel plate becomes high when the work roll diameter is large, when rolling a steel sheet that requires workability, it is desirable that the work roll diameter is large. On the other hand, when the diameter exceeds 600 mm, it becomes difficult to secure a rolling reduction of more than 30% and 40% or less .

  The high-pressure lubricated rolling may be performed by a reverse rolling mill that sequentially repeats rolling with a single rolling mill.

In reverse rolling performed by a reverse rolling mill, it is preferable to perform rolling at a rolling reduction of more than 30% and not more than 40% in at least two rolling passes excluding the final rolling pass.

Rolling with a rolling reduction of more than 30% and not more than 40% may be performed in the first rolling pass, or may be performed in the rolling pass after the second pass (excluding the final rolling pass). That is, rolling with a rolling reduction of more than 30% and 40% or less may be performed in a rolling pass excluding the final rolling pass.

  Rolling over a rolling reduction of 33% may be performed immediately before the final rolling pass. However, if the selection of the lubricating oil is not appropriate, the possibility of heat scratching increases, so the final rolling pass. The rolling reduction in the rolling pass immediately before is preferably 33% or less.

  In the final rolling pass, it is preferable to perform rolling at a rolling reduction of less than 25 to 30% so that heat scratches do not occur.

  The total rolling reduction in reverse rolling is preferably more than 70%. If the total rolling reduction is 70% or less, the desired final plate thickness may not be reached with the required number of passes, and rolling may be required again.

  The rolling speed is adjusted in consideration of the rolling reduction in each rolling pass. However, if the rolling speed in the final rolling pass is less than 150 m / min, the oil film pressure of the lubricating oil is low, and micro heat scratches may occur. Therefore, 150 m / min or more is preferable.

  Further, the rolling speed in the final rolling pass is preferably 250 m / min or more from the viewpoint of the productivity of high-pressure lubricated rolling.

In order to ensure a rolling reduction of more than 30% and 40% or less in the rolling pass, it is preferable to use a work roll having a diameter of 150 mm or more and 600 mm or less. If the diameter is less than 150 mm, the strength of the work roll cannot be ensured, and the work roll may break during rolling.

Moreover, since the r value of a steel plate becomes high when the work roll diameter is large, when rolling a steel sheet that requires workability, it is desirable that the work roll diameter is large. On the other hand, when the diameter exceeds 600 mm, it becomes difficult to secure a rolling reduction of more than 30% and 40% or less .

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
A tandem rolling mill equipped with 5 rolling stands, using a high-viscosity lubricating oil with a viscosity of 150 cSt at 40 ° C., selecting a rolling stand as appropriate, and setting the rolling reduction to more than 30% and not more than 40% , The washed stainless steel plate was rolled. The rolling conditions and rolling results are as shown in the invention examples in Table 1.

  The viscosity is a viscosity measured with a Canon-Fenske viscometer based on JIS K 2283.

  The work roll diameter is 500 mm. Although not shown in Table 1, when the work roll diameter was 620 mm, the rolling load exceeded the specification of the mill, and the necessary reduction ratio could not be realized. When the work roll diameter was 140 mm, the roll surface was broken and could not be rolled.

  In rolling example c, high-pressure rolling was performed at a rolling reduction rate of 32% on the second rolling stand (No. 2std). The total rolling reduction is 78.6%. There was no problem in rolling, and the sheet thickness could be rolled to 0.58 mm.

  In rolling example d, high-pressure rolling with a rolling reduction of more than 30% was performed in the second rolling stand (No. 2std) and the third rolling stand (No. 3std). The total rolling reduction is 79.2%. There was no problem in rolling, and the sheet thickness could be rolled to 0.56 mm.

  In rolling example e, high-pressure rolling with a rolling reduction of 32% was performed on the first rolling stand (No. 1std). The total rolling reduction is 78.8%. There was no problem in rolling, and the sheet thickness could be rolled to 0.57 mm.

  In addition, even if wrinkles occur in the high-pressure rolling at the former stage, the degree of wrinkles can be reduced by rolling at the latter stage, so it is preferable to perform the high-pressure rolling at the previous stage.

  In rolling example f, high pressure rolling with a rolling reduction of 35% was performed on the fourth rolling stand (No. 4std). The total rolling reduction is 79.8%. Although extremely mild heat scratches occurred, the sheet could be rolled to a thickness of 0.54 mm.

  In addition, it is practically not problematic to perform rolling under high pressure in a rolling stand (No. 4std) preceding the final rolling stand (No. 5std).

  In rolling example g, high-pressure rolling was performed at a rolling reduction of 32% on the second rolling stand (No. 2std). The total rolling reduction is 79.9%. The final rolling stand (No. 5std) was rolled with a reduction ratio of 22%, and the total reduction ratio was optimized. There was no chattering and the sheet thickness could be rolled to 0.54 mm.

In rolling example h, high-pressure rolling with a rolling reduction of more than 30% was performed using the first to fourth rolling stands (No. 1std to No. 4std). The total rolling reduction is 82.8%. There was no problem in rolling, and the sheet thickness could be rolled to 0.46 mm.

  As described above, the rolling examples c to h are rolling examples that can be efficiently rolled to a desired plate thickness (less than 0.60 mm) with “high viscosity + high pressure”.

(Comparative example)
In Table 1, rolling example a and rolling example b are comparative examples. In rolling example a, a low-viscosity (40 ° C .: 40 cSt) lubricating oil was used, and each rolling stand was subjected to low-pressure rolling with a rolling reduction of less than 30%. The total rolling reduction is 77.0%. There was no problem in the rolling itself, and the sheet thickness could be rolled to 0.62 mm.

  However, since the final thickness is more than 0.60 mm, it is necessary to perform rolling again to a desired thickness (less than 0.60 mm). The rolling example “a” is “low viscosity + low pressure” rolling, and is a rolling example having low efficiency as a whole of the cold rolling operation.

In rolling example b, low-viscosity (40 ° C .: 40 cSt) lubricating oil was used, and high-pressure rolling was performed at a rolling reduction of 32% using a second rolling stand (No. 2std in the table). The total rolling reduction is 78.6%.
Rolling example b was a rolling example in which heat scratches occurred due to “low viscosity + under high pressure” although the sheet thickness could be rolled to 0.58 mm.

(Reference example)
In rolling example i, high-viscosity (40 ° C .: 150 cSt) lubricating oil was used, and rolling under low pressure with a rolling reduction of less than 30% was performed at each rolling stand. The total rolling reduction is 77.0%. There was no problem in rolling, and the sheet thickness could be rolled to 0.62 mm.

  However, since the final thickness is more than 0.60 mm, it is necessary to perform rolling again to a desired thickness (less than 0.60 mm).

  Rolling example i is a rolling example in which even if a high-viscosity lubricating oil is used, if the rolling reduction at each rolling stand is low (“high viscosity + low pressure”), the efficiency of the entire cold rolling operation is low.

  In reverse rolling in which rolling is performed to the final plate thickness in 5 passes, it is clear that the same results can be obtained if the rolling conditions shown in the invention examples in Table 1 are adopted as rolling conditions for each pass.

  As described above, according to the present invention, a stainless steel plate having a desired final plate thickness that does not cause a slip during rolling and has no heat scratch can be rolled with high productivity in a tandem rolling mill or a reverse rolling mill. . Therefore, this invention has a high possibility of utilization in the steel plate manufacturing technology of the steel industry.

Claims (20)

In the method of cold rolling a pickled stainless steel plate with a dandem rolling mill equipped with a plurality of rolling stands, a high viscosity lubricating oil of 140 cSt or higher is used at 40 ° C., and the rolling stand is a work roll having a diameter of 150 mm or more and 600 mm or less. the use, of a plurality of rolling stands, the rolling speed at the entrance side of the first rolling stand and 66m / min or more, at least 1 group rolling stands except the last rolling stands, pressure under rate of 30 percent, 35 %, And rolling at a rolling reduction of 18 to less than 26% at the final rolling stand .
However, the viscosity is a viscosity measured with a Canon-Fenske viscometer based on JIS K 2283.   The high-pressure lubricated rolling method according to claim 1, wherein the cold rolling is performed by a dandem rolling mill having four or more rolling stands. The tandem rolling performed by the dandem rolling mill is performed under high pressure according to claim 2, wherein rolling is performed at a rolling reduction of more than 30% and not more than 35 % in at least two rolling stands excluding the final rolling stand. Lubrication rolling method. 3. The high pressure lubricated rolling method according to claim 2, wherein in the tandem rolling, rolling at a reduction ratio of more than 30% and not more than 35 % is performed at an initial rolling stand. 4. The high-pressure lubricated rolling method according to claim 3, wherein in the tandem rolling, rolling is performed at a rolling reduction of more than 30% and not more than 35 % at an initial rolling stand.   The high-pressure lubricated rolling method according to claim 3, wherein in the tandem rolling, rolling at a rolling reduction of 33% or less is performed at a rolling stand immediately before a final rolling stand.   5. The high-pressure lubricated rolling method according to claim 4, wherein in the tandem rolling, rolling at a rolling reduction of 33% or less is performed at a rolling stand immediately before a final rolling stand.   The high-pressure lubricated rolling method according to any one of claims 2 to 7, wherein in the dandem rolling, rolling with a total rolling reduction exceeding 70% is performed.   In the said tandem rolling, the rolling speed in the last rolling stand is 250 m / min or more, The high pressure lubricated rolling method of any one of Claims 2-7 characterized by the above-mentioned. In the method of cold rolling a pickled stainless steel plate with a reverse rolling mill, a high viscosity lubricating oil of 140 cSt or higher is used at 40 ° C., and the reverse rolling mill is a reverse rolling using a work roll having a diameter of 150 mm or more and 600 mm or less. Among the plurality of rolling passes, the rolling speed on the entry side of the first rolling pass is set to 66 m / min or more, and at least one rolling pass excluding the final rolling pass, the rolling reduction is more than 30% and 35% or less. A high pressure lubricated rolling method characterized by performing rolling and rolling at a rolling reduction of 18 to less than 26% in a final rolling pass.
However, the viscosity is a viscosity measured with a Canon-Fenske viscometer based on JIS K 2283. 11. The high pressure lubrication according to claim 10 , wherein in the reverse rolling performed by the reverse rolling mill, rolling at a rolling reduction of more than 30% and not more than 35 % is performed in at least two rolling passes excluding the final rolling pass. Rolling method. 11. The high-pressure lubricated rolling method according to claim 10 , wherein in the reverse rolling, rolling is performed at a rolling reduction of more than 30% and not more than 35 % in a first rolling pass. 12. The high-pressure lubricated rolling method according to claim 11 , wherein in the reverse rolling, rolling is performed at a rolling reduction of more than 30% and not more than 35 % in the first rolling pass. 14. The high pressure lubrication according to claim 10 , wherein in the reverse rolling, rolling is performed at a rolling reduction rate of 33% or more and 35% or less in a rolling pass immediately before a final rolling pass. Rolling method. The high-pressure lubricated rolling method according to any one of claims 10 to 13 , wherein the reverse rolling is performed with a total rolling reduction exceeding 70%. 15. The high pressure lubricated rolling method according to claim 14 , wherein the reverse rolling is performed with a total rolling reduction exceeding 70%. 14. The high-pressure lubricated rolling method according to claim 10 , wherein in the reverse rolling, a rolling speed in a final rolling pass is 250 m / min or more. In the reverse rolling, the rolling speed in a final rolling pass is 250 m / min or more, and the high-pressure lubricated rolling method according to claim 14 . In the reverse rolling, the rolling speed in the final rolling pass is 250 m / min or more, and the high pressure lubricated rolling method according to claim 15 . In the reverse rolling, the rolling speed in the final rolling pass is 250 m / min or more, and the high-pressure lubricated rolling method according to claim 16 .

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