JP3684942B2 - Cold rolled steel strip manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a cold-rolled steel strip manufactured through hot rolling, pickling, cold rolling, and a continuous heat treatment process, and particularly to a method for manufacturing a cold-rolled steel strip capable of controlling the width of the steel strip.
[0002]
[Prior art]
Currently, the cold-rolled steel strip is manufactured by the following method. First, in a hot rolling (hereinafter abbreviated as hot rolling) process, a slab heated in a heating furnace is rolled to a sheet thickness of approximately 1 to 5 mm through a rough rolling mill and a finishing rolling mill, and is appropriately cooled. The hot-rolled steel strip is manufactured by winding after performing. In the hot-rolled steel strip produced in this way, the oxide film generated on the surface during hot-rolled steel strip production is removed by pickling in the pickling-cold rolling process, and the hot-rolled steel strip is cold-rolled by a cold rolling mill. Rolling (hereinafter abbreviated as cold rolling) is performed to finish a cold rolled steel strip having a thickness of approximately 1 to 3 mm. However, because the cold-rolled steel strip at this stage is work-hardened by cold rolling and has poor workability, it is recrystallized and annealed by a heat treatment furnace in a continuous heat treatment (continuous annealing, continuous galvanizing, etc.) process, and further a heat treatment furnace By adjusting the pressure with a temper mill disposed on the outlet side, a cold-rolled steel strip having appropriate workability, property characteristics, and surface roughness is finished.
[0003]
In the manufacturing process of such a cold-rolled steel strip, various investigations have conventionally been made regarding the sheet thickness accuracy in the hot-rolling process and the cold-rolling process. Until recently, it was rarely considered.
[0004]
FIG. 3 shows an outline of the current plate width setting method. First, for the given slab width, in the hot rolling process, rough width control is performed by controlling the steel strip tension of the edger of the rough rolling mill and the finishing mill. However, the longitudinal plate width distribution of the normal hot-rolled steel strip is not uniform, and is broadened at the rear end of the steel strip as shown in FIG. 3, and is often narrowed at about 50 to 100 m immediately after the front end, The difference is as large as 10 mm.
[0005]
Next, in the pickling-cold rolling process, the hot-rolled steel strip is cold-rolled while being tensioned by a cold-rolling mill, so that sheet width shrinkage occurs. At that time, the above-described difference in plate width tends to further increase.
[0006]
Furthermore, in a heat treatment furnace in a continuous heat treatment step, for example, a continuous annealing step, at a recrystallization temperature of about 600 to 850 ° C., the cold-rolled steel strip is repeatedly bent by an in-furnace roll while being tensioned. Therefore, it extends in the longitudinal direction of the steel strip, and accordingly, the plate width is reduced and the plate thickness is reduced. When the pressure is adjusted in the outlet temper mill, the plate width shrinkage occurs depending on the pressure adjusting condition. At that time, the above-described difference in plate width tends to further increase. Thereafter, both ends of the steel strip are cut by an edge trimmer disposed on the outlet side so as to be aligned with a predetermined steel strip width.
[0007]
[Problems to be solved by the invention]
However, the above prior art has the following drawbacks.
(1) The steel strip width shrinkage amount in the cold rolling and / or continuous heat treatment process varies depending on the steel type, steel strip dimensions, operating conditions, etc., and is difficult to predict.
(2) If the steel strip width shrinkage in the cold rolling and / or continuous heat treatment process is less than expected (ie, if the steel strip width before edge trim is too wide: A in FIG. 3), discard as trim scraps As a result, the scraps at both ends of the steel strip increase and the yield decreases.
(3) If the steel strip width shrinkage in the cold rolling and / or continuous heat treatment process is greater than expected, especially if the steel strip width before the edge trim falls below the product width, the steel strip is shipped as a product. Can not do. If the steel strip width before edge trim does not fall below the product width, but the cut-off width at both ends of the steel strip is too small (C in FIG. 3), the edge trim operation cannot be performed. The minimum cut-off width at which this edge trim operation cannot be performed is called the minimum trim margin, and is usually about 5 mm on one side.
[0008]
Therefore, in order to perform the edge trim work without trouble while avoiding a decrease in yield, the minimum value of the steel strip width before the edge trim is “product width + 2 × minimum trim margin (this is referred to as a steel strip width target value). It is necessary to adjust the operating conditions in each process so that it becomes “(”) (B in FIG. 3), but this has not been realized yet.
[0009]
The present invention has been made in view of such circumstances, and provides a method for manufacturing a cold-rolled steel strip that can control the width of a steel strip before edge trim to prevent the occurrence of defective width and improve the yield. The purpose is to provide.
[0010]
Means to be Solved by the Invention
In order to solve the above problems, the present invention provides the following (1) to (6).
(1) When manufacturing a cold-rolled steel strip through hot rolling, pickling, cold rolling, and a continuous heat treatment step, measure at least the minimum value of the steel strip width distribution in the longitudinal direction of the steel strip after hot rolling, Adjusting the operating conditions of the cold rolling and / or continuous heat treatment process based on the value, the measured steel strip width on the outgoing side of the continuous heat treatment process approaches the steel band width target value and does not fall below that value. A method for producing a cold-rolled steel strip, characterized by adjusting the steel strip width.
[0011]
(2) In the manufacturing method of (1), the steel strip width adjusting method in the cold rolling step is performed by adjusting the steel strip rolling force of each stand and the steel strip tension between each stand. A method for producing a cold-rolled steel strip.
[0012]
(3) In the manufacturing method of (1) or (2), the steel strip width adjusting method in the continuous heat treatment step is steel strip tension, heat treatment temperature, steel strip reduction of a pressure regulator arranged on the continuous heat treatment apparatus outlet side. A method for producing a cold-rolled steel strip, wherein the method is performed by adjusting at least one of a force and a tension on an inlet / outlet side of a pressure regulator.
[0013]
(4) The steel strip width measured value on the outgoing side of the continuous heat treatment process is brought close to the steel strip width target value by any of the methods (1), (2), and (3), and the steel strip width should not fall below that value. When the band width cannot be adjusted, the steel band width measured value on the outgoing side of the continuous heat treatment process is brought close to the steel band width target value even if the steel band width shrinkage in the cold rolling and continuous heat treatment process is taken into consideration. Production of cold-rolled steel strip characterized by adjusting the minimum value of steel strip width distribution in the longitudinal direction of the steel strip during hot rolling by changing the operating conditions of the hot rolling process so as not to fall below the value Method.
[0014]
(5) In carrying out any one of the methods (1) to (4), at least (a) the hot rolling device outlet side or the cold rolling device inlet side, (b) the cold rolling device outlet side or the continuous heat treatment A steel strip width meter is disposed on the furnace entrance side of the apparatus, (c) the furnace exit side and pressure regulator input side of the continuous heat treatment apparatus, and (d) the steel strip width meter on the pressure regulator output side of the continuous heat treatment apparatus. A method for producing a steel strip.
[0015]
(6) In the manufacturing method of (5), each steel strip width meter has a function which corrects the amount of thermal expansion by steel strip temperature, The manufacturing method of the cold-rolled steel strip characterized by the above-mentioned.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a schematic view showing a manufacturing process and equipment of a cold-rolled steel strip to which the present invention is applied, and FIG.
As shown in FIG. 1, the method for producing a cold-rolled steel strip includes three major steps: a hot-rolling step, a pickling-cold-rolling step, and a continuous heat treatment step. First, in the hot rolling step, the slab 31 heated in the heating furnace 1 is passed through the roughing mill 2 and the finishing mill 4 to be rolled to a thickness of approximately 1 to 5 mm, and appropriate cooling is performed on the runout table 5. The hot rolled steel strip 32 is manufactured by winding with the downcoiler 6 after performing. Reference numeral 3 is an edger (width killer).
[0017]
The hot-rolled steel strip 32 thus manufactured is sent to the pickling-cold rolling process. In this process, the hot-rolled steel strip 32 is first unwound from the payoff reel 7 and sent to the pickling tank 10 through the entry looper 9, where pickling is performed, and oxidation generated on the surface during the production of the hot-rolled steel strip. After the film is removed, it is sent to the cold rolling mill 12 through the delivery looper 11, where it is cold-rolled and finished into a cold-rolled steel strip 33 having a thickness of approximately 1 to 3 mm, and a tension reel (winding machine) ) 14. Reference numeral 8 is a welder (welding machine), and 13 is a shear (cutting machine).
[0018]
The cold-rolled steel strip 33 at this stage undergoes work hardening due to cold rolling and has poor workability, and therefore is subjected to a continuous heat treatment step. In this process, the cold-rolled steel strip 33 is first unwound from the payoff reel 15, and after the rolling oil is removed by the washing machine 17, it is sent to the annealing furnace 19 through the entry looper 18, where recrystallization and annealing treatment are performed. Then, after passing through the delivery looper 20, pressure adjustment is performed by a temper mill 21 disposed on the heat treatment furnace outlet side, whereby a cold-rolled steel strip 34 having appropriate workability, property characteristics, and surface roughness is obtained. Finished. Then, both ends of the cold-rolled steel strip 34 are cut by the edge trimmer 22 so as to be aligned with a predetermined steel strip width, and wound by a tension reel (winding machine) 24. Reference numeral 16 is a welder (welding machine), and 23 is a shear (cutting machine).
[0019]
Although the above is a general process, in this embodiment, the steel strip width meter is arrange | positioned in the appropriate location of each process. That is, (1) a position 41 on the exit side of the hot rolling apparatus or a position 42 on the entry side of the cold rolling apparatus, (2) a position 43 on the exit side of the cold rolling apparatus or the entrance side of the annealing furnace of the continuous heat treatment apparatus (in front of the furnace) The width of the steel strip at the position 44 of (3) the annealing furnace outlet side of the continuous heat treatment apparatus and the position 45 of the temper mill (pressure regulator) entry side, and (4) the position 46 of the temper mill (pressure regulator) outlet side of the continuous heat treatment apparatus. A meter is provided. It is desirable that each steel strip width meter has a function of correcting the thermal expansion due to the steel strip temperature at that position.
[0020]
In the present invention, as shown in FIG. 2, after the continuous casting process (STEP 1) and the hot rolling process (STEP 2) are completed, a hot strip steel strip 32 is used by using a steel strip width meter existing at the position 41 or 42. At least the minimum value of the longitudinal width distribution is measured (STEP 3).
[0021]
Next, in the pickling-cold rolling step and the continuous heat treatment step, the steel strip width shrinkage when the cold rolled and heat treatment is performed on the hot rolled steel strip 32 under normal operating conditions is predicted (STEP 4). .
[0022]
This STEP 4 is performed as follows using a cold rolling and continuous heat treatment condition determining calculator.
First, based on the minimum value of the longitudinal width distribution of the hot-rolled steel strip 32 measured in STEP 3 described above, the steel strip width shrinkage amount under the pickling-cold rolling process reference conditions is predicted (STEP 4-1). Further, based on this value and the minimum value of the width distribution in the longitudinal direction of the cold-rolled steel strip 33 measured in STEP 6 described later, the steel strip width shrinkage prediction (STEP 4-2) is performed under the continuous heat treatment process reference conditions.
[0023]
The steel strip width change behavior during cold rolling and pressure regulation can be predicted from the rolling theory, and the steel strip width change behavior in the furnace during continuous heat treatment can be predicted from the repeated bending theory, especially in the continuous heat treatment furnace. As methods for predicting the amount of shrinkage, techniques described in JP-A-8-127820, JP-A-11-29825, and the like are known.
[0024]
Based on the prediction results of STEP4-1 and STEP4-2, the steel strip width minimum value immediately before the edge trimmer 22 on the continuous heat treatment apparatus exit side is predicted (STEP4-3).
[0025]
It is determined whether or not the prediction result matches “product width + 2 × minimum trim margin (steel band width target value)” (STEP 4-4). If they match, the cold rolling and continuous heat treatment processes are performed under the reference conditions. A command is issued to execute (STEP 4-5).
[0026]
On the other hand, when a prediction result exceeds a steel strip width target value (A of FIG. 3), operation of a pickling-cold rolling process and a continuous heat treatment process is performed using at least one of the following methods (1) to (3). The conditions are changed within a predetermined range (STEP 4-6).
[0027]
(1) Lowering the steel strip rolling force of each stand within a predetermined range while increasing the tension between the stands within the predetermined range in the cold rolling process (increasing the amount of width shrinkage while ensuring a predetermined plate thickness).
(2) Increase the furnace tension in the continuous heat treatment step within a predetermined range. And / or raising the heat treatment temperature within a predetermined range (increasing the amount of width shrinkage).
(3) Lowering the steel strip rolling force within a predetermined range while increasing the inlet / outlet tension of the temper mill 21 in a predetermined range in the continuous heat treatment step (increasing the amount of width shrinkage while ensuring a predetermined elongation rate)
[0028]
Conversely, when the predicted result is below the steel strip width target value (C in FIG. 3), at least one of the following methods (4) to (6) is used, and the pickling-cold rolling step and the continuous heat treatment step are performed. The operating conditions are changed within a predetermined range (STEP 4-6).
[0029]
(4) Raising the steel strip rolling force of each stand within a predetermined range while lowering the tension between the stands within the predetermined range in the cold rolling process (decreasing the width shrinkage while ensuring a predetermined plate thickness).
(5) Reducing the furnace tension in the continuous heat treatment step within a predetermined range. And / or lowering the heat treatment temperature within a predetermined range (reducing the width shrinkage).
(6) Increasing the steel strip rolling force within a predetermined range while decreasing the entry / exit tension of the temper mill 21 within a predetermined range in the continuous heat treatment step (decreasing the width shrinkage while ensuring a predetermined elongation rate)
[0030]
In both cases where the prediction result exceeds and falls below the steel strip width target value, the steel strip width minimum value immediately before the continuous heat treatment process exit edge trimmer 22 is predicted based on these changed conditions (STEP4- 7) It is determined whether or not there is an operating condition in which the predicted value matches the steel strip width target value represented by product width + 2 × minimum trim margin (STEP 4-8).
[0031]
If there is an operating condition that matches the steel strip width target value, a command is issued to subject the hot-rolled steel strip 32 to a pickling-cold rolling step and a continuous heat treatment step (STEP 4-9). .
[0032]
If the steel strip width minimum value immediately before the edge trimmer 22 exceeds or falls below the steel strip width target value even using the above method, the difference between the two is calculated, and only the difference in the hot rolling process is calculated from the next production. The operating conditions of the hot rolling process are changed so that the minimum value of the steel strip width becomes smaller or larger (STEP 4-10).
[0033]
Based on such a calculation result, a pickling-cold rolling process (STEP 5) is performed, and a continuous heat treatment process (STEP 7) is performed. And at least the minimum value of the longitudinal width distribution of the cold-rolled steel strip 33 is measured using a steel strip width meter existing at the position 43 or 44 during these steps (STEP 6), and this result is also as described above. Used for the above arithmetic processing.
[0034]
By manufacturing the cold-rolled steel strip as described above, the amount of edge trim to be cut by the edge trimmer 22 can be appropriately controlled, so that the edge trim work can be performed without any trouble while suppressing the yield reduction. Is possible.
[0035]
In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, prediction of steel strip width change behavior during cold rolling and pressure regulation, steel strip width change behavior in the furnace during continuous heat treatment, prediction method of steel band width shrinkage amount in continuous heat treatment furnace, etc. Not limited to this, various conventionally used techniques can be employed. Moreover, although the case where continuous annealing was implemented as a continuous heat treatment process was shown in the said embodiment, it is not restricted to this, Other processes, such as continuous galvanization, may be sufficient.
[0036]
【The invention's effect】
As described above, according to the present invention, the steel strip width before the edge trim can be appropriately controlled, so that it is possible to prevent the occurrence of a width defect and improve the yield.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a manufacturing process and equipment for a cold-rolled steel strip to which the present invention is applied.
FIG. 2 is a diagram showing a flow of the present invention.
FIG. 3 is a diagram showing an outline of a current plate width setting method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Slab heating furnace 2; Coarse rolling mill 4; Finish rolling mill 5; Runout table 6; Downcoiler 10; Pickling tank 12; Cold rolling mill 19;
22; Edge trimmer 32; Hot-rolled steel strip 33; Cold-rolled steel strip (before heat treatment)
34; Hot-rolled steel strip 41, 42, 43, 44, 45, 46;

Claims (6)

When manufacturing a cold-rolled steel strip through hot rolling, pickling, cold rolling, and continuous heat treatment, measure at least the minimum value of the steel strip width distribution in the longitudinal direction of the steel strip after hot rolling, By adjusting the operating conditions of the cold rolling and / or continuous heat treatment process based on this, the steel strip width actual value on the outgoing side of the continuous heat treatment process is brought close to the steel band width target value, and not less than that value. A method for producing a cold-rolled steel strip, wherein the width is adjusted. The steel strip width adjusting method in the cold rolling process is performed by adjusting the steel strip rolling force of each stand and the steel strip tension between the stands. Production method. The steel strip width adjusting method in the continuous heat treatment process adjusts at least one of the steel strip tension, the heat treatment temperature, the steel strip rolling force of the pressure regulator disposed on the outlet side of the continuous heat treatment apparatus, and the tension on the inlet / outlet side of the pressure regulator. The method for producing a cold-rolled steel strip according to claim 1 or 2, wherein the method is performed. The steel strip width is adjusted so that the actual measured value of the steel strip width on the outgoing side of the continuous heat treatment process is brought close to the target value of the steel strip width by the method of any one of the first, second, and third aspects, and not less than that value. If adjustment is not possible, the steel strip width measured on the outgoing side of the continuous heat treatment process should be brought close to the target value of the steel strip width and below that value even if the steel strip width shrinkage in the cold rolling and continuous heat treatment processes is taken into account. A method for producing a cold-rolled steel strip, characterized in that the minimum value of the steel strip width distribution in the longitudinal direction of the steel strip at the time of hot rolling is adjusted by changing the operating conditions of the hot rolling process so as not to occur. In carrying out the method according to any one of claims 1 to 4, at least (a) a hot rolling device outlet side or a cold rolling device inlet side, (b) a cold rolling device outlet side or a furnace of a continuous heat treatment device Cold rolled steel strip, characterized in that a steel strip width meter is disposed on the inlet side, (c) the furnace outlet side of the continuous heat treatment device and the pressure regulator inlet side, and (d) the pressure regulator outlet side of the continuous heat treatment device. Manufacturing method. 6. The method of manufacturing a cold-rolled steel strip according to claim 5, wherein each steel strip width meter has a function of correcting a thermal expansion due to a steel strip temperature.

Images