JP2014214374A - Method of producing hot rolled steel sheet and hot rolled steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a method of producing a hot rolled steel sheet by which generations of grain boundary oxide when the hot rolled steel sheet containing Si and Mn is wound, can be suppressed; and the hot rolled steel sheet.SOLUTION: There is provided the method of producing a hot rolled steel sheet having a C percentage content of 0.04 mass% to 0.2 mass%, an Si percentage content of 0.5 mass% to 3 mass%, a Mn content of 0.1 mass% to 3 mass%. The method of producing the hot rolled steel has a hot rolling step, a step of cooling the hot rolled steel sheet by spraying cooling water, a step of laminating a sugar compound on a surface of the hot rolled steel sheet, and a step of winding the cooled steel sheet. The laminating step is preferably conducted by applying a solution having the concentration of the sugar compound of 1 mass% to 55 mass% onto the surface of the hot rolled steel sheet. In the laminating step, the solution is preferably applied onto an inner face of the steel sheet in the winding step. The cooling water is the solution and the cooling step and the laminating step may be conducted at same time.

Description

  The present invention relates to a method for producing a hot-rolled steel sheet and a hot-rolled steel sheet.

  A hot-rolled steel plate (thin plate) having a small thickness is generally cooled after hot rolling and conveyed to the next process equipment in a state of being wound in a coil by a winder. In recent years, Si, Mn, and the like are added to steel sheets to improve the strength. Since the steel sheet with improved strength has a lower winding property, it is necessary to raise the temperature during winding more than before.

  However, when the temperature at the time of winding is increased, the oxygen supplied from the scale generated during hot rolling promotes oxidation of Si, Mn, etc., which is easier to oxidize than iron, and grain boundary oxidation at the winding takes place in the steel sheet. Proceed to the deep surface. As a result, after rewinding the wound steel sheet, the pickling time for removing the grain boundary oxide increases, resulting in a disadvantage that the productivity of a product made from this steel sheet is reduced.

  For such inconvenience, for example, as disclosed in JP-A-7-278662, a method for preventing the generation of scale on the surface of a steel sheet with a scale inhibitor has been proposed, but the generation of grain boundary oxides is suppressed. No method has been proposed. Therefore, a method for suppressing generation of grain boundary oxide after winding in a hot rolled steel sheet containing Si or Mn is desired.

JP-A-7-278662

  The present invention has been made in view of the circumstances as described above, and a method for producing a hot-rolled steel sheet and a hot-rolled steel sheet capable of suppressing generation of grain boundary oxides at the time of winding a hot-rolled steel sheet containing Si and Mn. The purpose is to provide.

The invention made to solve the above problems is
Hot-rolled steel sheet having a C content of 0.04 mass% to 0.2 mass%, an Si content of 0.5 mass% to 3 mass%, and an Mn content of 0.1 mass% to 3 mass% A manufacturing method of
Hot rolling process,
Cooling the hot-rolled steel sheet by blowing cooling water;
Laminating a sugar compound on the surface of a hot-rolled steel sheet;
And a step of winding the cooled steel plate.

  The method for producing a hot-rolled steel sheet has a step of laminating a sugar compound on the surface of a hot-rolled steel sheet with respect to a hot-rolled steel sheet containing a certain amount of Si and Mn. Can be reduced. As a result, the oxygen supply source that oxidizes Si and Mn can be removed from the surface of the hot-rolled steel sheet. Therefore, in the method for producing the hot-rolled steel sheet, a grain boundary oxide is generated in the hot-rolled steel sheet during winding. Can be suppressed. Moreover, according to the method for producing a hot-rolled steel sheet, the scale of the hot-rolled steel sheet is reduced by the sugar compound, so that the scale removing operation can be omitted.

  The sugar compound is glyceraldehyde, erythrose, threose, ribose, lyxose, xylose, arabinose, apiose, allose, talose, gulose, glucose, altrose, mannose, galactose, idose, dihydroxyacetone, erythrulose, ribulose, xylulose, psicose , Fructose, sorbose, tagatose, cedoheptulose, coriose, trehalose, isotrehalose, cordierbiose, sophorose, nigerose, laminaribiose, maltose, cellobiose, isomaltose, gentiobiose, lactose, sucrose, fructooligosaccharide, lactose oligosaccharide, Deoxyribose, fucose, rhamnose, glucuronic acid, galacturonic acid, glucosamine, Lactosamine, glycerin, xylitol, sorbitol, glucuronolactone, gluconolactone, starch, amylose, amylopectin, glycogen, cellulose, pectin, glucomannan, dextrin, fructan, glucan, xyloglucan, hyaluronic acid, heparin, carrageenan, agarose, or It should be chitin. By using such a sugar compound, it is possible to easily and reliably reduce the scale of the surface of the hot-rolled steel sheet.

  The laminating step may be performed by applying an aqueous solution having a sugar compound concentration of 1% by mass to 55% by mass. Thus, by using the aqueous solution containing a saccharide compound, the saccharide compound can be easily and uniformly laminated on the steel sheet surface.

  In the lamination step, the aqueous solution may be applied to the inner surface of the steel plate in the winding step. By applying the sugar compound aqueous solution to the inner surface of the steel sheet in this way, the coated surface is sandwiched between the steel sheets immediately after the application of the sugar compound aqueous solution, so that the sugar compound can be reliably fixed on the surface of the hot rolled steel sheet. As a result, the scale can be reduced more reliably.

  The cooling water may be the aqueous solution, and the cooling step and the laminating step may be performed simultaneously. Thus, the manufacturing method of the said hot rolled sheet steel can be used using the conventional installation by using sugar compound aqueous solution as cooling water. Moreover, since it is not necessary to provide the sugar compound lamination step separately, the productivity of the method for producing the hot-rolled steel sheet can be further improved.

  The Al content of the hot-rolled steel sheet is preferably more than 0% by mass and 0.06% by mass or less, the Cr content is preferably more than 0% by mass and 2% by mass or less, and the Ti content is more than 0% by mass. 1% by mass or less is preferable, Ni content is preferably more than 0% by mass and 2% by mass or less, Cu content is preferably more than 0% by mass and 2% by mass or less, and Mo content is more than 0% by mass and more than 2% by mass. Nb content is preferably more than 0% by mass and less than 1% by mass, V content is preferably more than 0% by mass and less than 1% by mass, and W content is more than 0% by mass and more than 0.3% by mass. % Or less is preferable, and the B content is preferably more than 0% by mass and 0.01% by mass or less. Moreover, it is preferable that the said hot-rolled steel plate contains at least 1 sort (s) among Ca, Mg, or rare earth elements more than 0 mass% and 0.03 mass% or less. By making each content rate of said each composition into the said range, the mechanical property, workability, etc. of the hot-rolled steel plate obtained with the manufacturing method of the said hot-rolled steel plate can further be improved.

Further, another invention made to solve the above problems is as follows:
A hot-rolled steel sheet wound up in a coil shape,
It has a reduced iron layer on at least one surface, and a sugar compound or a carbide derived from the sugar compound adheres to at least a part of the outer surface of the reduced iron layer.

  The hot-rolled steel sheet has a reduced iron layer on at least one surface, and a sugar compound or a carbide derived from the sugar compound adheres to at least a part of the outer surface of the reduced iron layer. The generated scale is reduced, thereby suppressing the generation of grain boundary oxides. Therefore, the hot-rolled steel sheet can reduce the pickling time after rewinding from the coil shape.

  The manufacturing method of the said hot-rolled steel plate can suppress generation | occurrence | production of the grain boundary oxide at the time of winding of the hot-rolled steel plate containing Si and Mn. Therefore, the hot-rolled steel sheet obtained by the method for producing the hot-rolled steel sheet can reduce the processing cost.

The flowchart which shows the manufacturing method of the hot rolled sheet steel of one Embodiment of this invention. Schematic explanatory drawing which shows the coating method of the sugar compound aqueous solution in the manufacturing method of the hot-rolled steel sheet of FIG. The flowchart which shows the manufacturing method of the hot-rolled steel plate of embodiment different from the manufacturing method of the hot-rolled steel plate of FIG.

  Hereinafter, an embodiment of a method for producing a hot-rolled steel sheet according to the present invention will be described in detail with reference to the drawings.

<First embodiment>
The method for manufacturing a hot-rolled steel sheet shown in FIG. 1 includes the following steps.
(1) Hot rolling process S1 for obtaining a steel sheet by hot rolling a slab
(2) Cooling step S2 for cooling the hot-rolled steel sheet by blowing cooling water
(3) Sugar compound lamination step S3 for laminating a sugar compound on the surface of a hot-rolled steel sheet
(4) Winding step S4 for winding the cooled steel plate

(Hot rolling process S1)
In the hot rolling step S1, the slab is heated and rolled to form a steel plate.

Specifically, the slab is first heated at 900 ° C. or more and 1200 ° C. or less in a heating furnace, and the primary scale generated at this time is removed by a descaler. Next, this heated slab is roughly rolled while maintaining the temperature at 900 ° C. or higher and 1200 ° C. or lower, and then the secondary scale generated on the surface is removed with a descaler. Further, a hot rolled steel sheet is obtained by finish rolling the roughly rolled slab at 800 ° C. or higher and 1100 ° C. or lower. If the heating temperature in each step is less than the above lower limit, depending on the production conditions such as the size of the hot rolled steel sheet, the rolling speed, the capacity of the rolling equipment, hot rolling of the steel sheet may not be completed until the slab becomes low temperature There is. Further, when the heating temperature exceeds the above upper limit, Fe ₃ O ₄ is rapidly growing crack and peeling occurred, there is a possibility that the decarburization depth of the hot-rolled steel sheet is increased.

  As the rough rolling mill used for the rough rolling and the finish rolling mill used for the finish rolling, a known multi-stage rolling mill can be used.

  If the slab which is the raw material of the hot-rolled steel sheet obtained by the manufacturing method of the hot-rolled steel sheet includes steel whose main component is iron and can manufacture a hot-rolled steel sheet containing the composition described below, There is no particular limitation.

  As a minimum of C content of a hot-rolled steel plate obtained with the manufacturing method of the hot-rolled steel plate, it is 0.04 mass%, 0.05 mass% is more preferred, and 0.06 mass% is still more preferred. There exists a possibility that the intensity | strength of a hot-rolled steel plate may run short that C content rate of a hot-rolled steel plate is less than the said minimum. On the other hand, the upper limit of the C content of the hot-rolled steel sheet is 0.20% by mass, more preferably 0.18% by mass, and still more preferably 0.16% by mass. If the C content of the hot-rolled steel sheet exceeds the above upper limit, the cold workability of the hot-rolled steel sheet may be reduced. By setting the C content of the hot-rolled steel sheet within the above range, the strength of the hot-rolled steel sheet can be appropriately ensured.

  As a minimum of Si content of a hot-rolled steel plate obtained with the manufacturing method of the hot-rolled steel plate, it is 0.5 mass%, 0.6 mass% is more preferred, and 0.7 mass% is still more preferred. There exists a possibility that the intensity | strength of a hot-rolled steel plate may run short that the Si content rate of a hot-rolled steel plate is less than the said minimum. On the other hand, the upper limit of the Si content of the hot-rolled steel sheet is 3% by mass, more preferably 2.5% by mass, and still more preferably 2% by mass. If the Si content of the hot-rolled steel sheet exceeds the above upper limit, the ductility of the hot-rolled steel sheet may be impaired. By setting the Si content of the hot-rolled steel sheet within the above range, the ductility and workability of the hot-rolled steel sheet can be secured in a well-balanced manner.

  As a minimum of Mn content of a hot-rolled steel plate obtained with the manufacturing method of the said hot-rolled steel plate, it is 0.1 mass%, 0.2 mass% is more preferred, and 0.3 mass% is still more preferred. If the Mn content of the hot-rolled steel sheet is less than the lower limit, the hot-rolled steel sheet may have insufficient strength and toughness. On the other hand, the upper limit of the Mn content of the hot-rolled steel sheet is 3% by mass, more preferably 2.5% by mass, and still more preferably 2% by mass. If the Mn content of the hot-rolled steel sheet exceeds the above upper limit, the ductility of the hot-rolled steel sheet may be impaired. By setting the Mn content of the hot-rolled steel sheet within the above range, the strength and toughness of the hot-rolled steel sheet can be appropriately increased.

  The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet preferably contains Al from the viewpoint of increasing strength. When the hot-rolled steel sheet contains Al, a deoxidizing effect is exhibited, and austenite crystal grains can be prevented from becoming coarse during normalizing heating. As a minimum of Al content rate of a hot-rolled steel plate, more than 0 mass% is preferred, 0.001 mass% is more preferred, and 0.005 mass% is still more preferred. Moreover, as an upper limit of Al content rate of a hot-rolled steel plate, 0.06 mass% is preferable, 0.05 mass% is more preferable, and 0.04 mass% is further more preferable. If the Al content of the hot-rolled steel sheet exceeds the above upper limit, not only will the cost increase, but the crystal grains may become unstable.

  The hot-rolled steel sheet obtained by the method for producing the hot-rolled steel sheet preferably contains Cr from the viewpoint of increasing the strength. As a minimum of Cr content of a hot-rolled steel plate, 0.01 mass% is preferred, 0.05 mass% is more preferred, and 0.1 mass% is still more preferred. Moreover, as an upper limit of Cr content rate of a hot-rolled steel plate, 2 mass% is preferable, 1.5 mass% is more preferable, and 1 mass% is further more preferable. If the Cr content of the hot-rolled steel sheet exceeds the above upper limit, the ductility of the hot-rolled steel sheet may be impaired.

  The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet preferably contains Ti as a deoxidizer. As a minimum of Ti content of a hot-rolled steel plate, more than 0 mass% is preferred, 0.01 mass% is more preferred, and 0.02 mass% is still more preferred. Moreover, as an upper limit of Ti content rate of a hot-rolled steel plate, 0.1 mass% is preferable, 0.05 mass% is more preferable, and 0.01 mass% is further more preferable. If the Ti content of the hot-rolled steel sheet exceeds the above upper limit, the toughness of the hot-rolled steel sheet may be reduced.

  The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet preferably contains Ni from the viewpoint of improving hardenability. When the hot-rolled steel sheet contains Ni, the effect of the annealing in the continuous annealing line (CAL) and the increase in the martensite ratio at the time of cooling and the refinement of the martensite lath structure occur, and the continuous galvanizing line (CGL) The hardenability during the two-phase region reheating / cooling process during annealing is improved. As a result, the final composite structure after cooling can be made suitable for processing, and various molding processability can be improved. As a minimum of Ni content of a hot-rolled steel plate, more than 0 mass% is preferred, 0.1 mass% is more preferred, and 0.2 mass% is still more preferred. Moreover, as an upper limit of Ni content rate of a hot-rolled steel plate, 2 mass% is preferable, 1.5 mass% is more preferable, and 1 mass% is further more preferable. When the Ni content of the hot-rolled steel sheet exceeds the above upper limit, the manufacturing cost of the hot-rolled steel sheet becomes unnecessarily large.

  The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet preferably contains Cu from the viewpoint of improving hardenability. When the hot-rolled steel sheet contains Cu, various formability can be improved by the same action as Ni described above. As a minimum of Cu content rate of a hot-rolled steel plate, more than 0 mass% is preferred, 0.1 mass% is more preferred, and 0.2 mass% is still more preferred. Moreover, as an upper limit of Cu content rate of a hot-rolled steel plate, 2 mass% is preferable, 1.5 mass% is more preferable, and 10 mass% is further more preferable. When the Cu content of the hot-rolled steel sheet exceeds the above upper limit, the manufacturing cost of the hot-rolled steel sheet becomes unnecessarily large.

  The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet preferably contains Mo from the viewpoint of enhancing hardenability and strength. When the hot-rolled steel sheet contains Mo, various formability can be improved by the same action as Ni and Cu described above. Further, solid solution strengthening can be achieved without impairing the plating property. As a minimum of Mo content of a hot-rolled steel plate, more than 0 mass% is preferred, 0.1 mass% is more preferred, and 0.2 mass% is still more preferred. Moreover, as an upper limit of Mo content rate of a hot-rolled steel plate, 2 mass% is preferable, 1.5 mass% is more preferable, and 1 mass% is further more preferable. When the Mo content of the hot-rolled steel sheet exceeds the above upper limit, the manufacturing cost of the hot-rolled steel sheet becomes unnecessarily large.

  The hot-rolled steel sheet obtained by the method for producing the hot-rolled steel sheet preferably contains Nb from the viewpoint of increasing strength. When the hot-rolled steel sheet contains Nb, the structure is refined and the strength can be improved without impairing the toughness. As a minimum of Nb content of a hot-rolled steel plate, more than 0 mass% is preferred, 0.001 mass% is more preferred, and 0.005 mass% is still more preferred. Moreover, as an upper limit of Nb content rate of a hot-rolled steel plate, 1 mass% is preferable, 0.5 mass% is more preferable, and 0.1 mass% is further more preferable. If the Nb content of the hot-rolled steel sheet exceeds the above upper limit, carbides are generated excessively, so that the martensite volume fraction decreases or martensite precipitates, which may reduce the balance between strength and workability. .

  The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet preferably contains V from the viewpoint of increasing strength. As a minimum of V content of a hot-rolled steel plate, more than 0 mass% is preferred, 0.001 mass% is more preferred, and 0.005 mass% is still more preferred. Moreover, as an upper limit of V content rate of a hot-rolled steel plate, 1 mass% is preferable, 0.5 mass% is more preferable, and 0.1 mass% is further more preferable. If the V content of the hot-rolled steel sheet exceeds the above upper limit, not only will the cost be increased, but the yield point (yield ratio) may be increased to reduce the workability of the hot-rolled steel sheet.

  The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet preferably contains W from the viewpoint of increasing the strength. When the hot-rolled steel sheet contains W, the strength of the hot-rolled steel sheet can be increased by strengthening precipitates, strengthening fine grains by suppressing the growth of ferrite crystal grains, and strengthening transition by suppressing recrystallization. As a minimum of W content of a hot-rolled steel plate, more than 0 mass% is preferred, 0.001 mass% is more preferred, and 0.005 mass% is still more preferred. Moreover, as an upper limit of W content rate, 0.3 mass% is preferable, 0.2 mass% is more preferable, 0.1 mass% is further more preferable. If the W content of the hot-rolled steel sheet exceeds the above upper limit, carbonitride precipitation may be excessive, and the formability of the hot-rolled steel sheet may be reduced.

  The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet preferably contains B from the viewpoint of improving hardenability. As a minimum of B content of a hot-rolled steel plate, more than 0 mass% is preferred, 0.0001 mass% is more preferred, and 0.0002 mass% is still more preferred. Moreover, as an upper limit of B content rate of a hot-rolled steel plate, 0.01 mass% is preferable, 0.005 mass% is more preferable, 0.001 mass% is further more preferable. If the B content of the hot-rolled steel sheet exceeds the above upper limit, the plateability of the hot-rolled steel sheet may be reduced.

  The upper limit of the P content of inevitable impurities in the hot-rolled steel sheet obtained by the method for producing the hot-rolled steel sheet is preferably 0.02% by mass, more preferably 0.01% by mass, and further 0.001% by mass. preferable. If the P content of the hot-rolled steel sheet exceeds the above upper limit, the ductility may be reduced or the plating property may be reduced. Further, P may be contained in a small amount because it acts to delay precipitation of cementite and suppress transformation, and the lower limit of the P content of the hot-rolled steel sheet is preferably more than 0% by mass, preferably 0.0001% by mass Is more preferable.

  The upper limit of the S content of inevitable impurities in the hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet is preferably 0.004% by weight, more preferably 0.002% by weight, and further 0.001% by weight. preferable. If the S content of the hot-rolled steel sheet exceeds the above upper limit, sulfide inclusion MnS is formed and segregates during hot rolling, which may reduce the brittleness of the hot-rolled steel sheet. Moreover, as a minimum of S content rate of a hot-rolled steel plate, although it does not specifically limit, 0 mass% is preferable.

  The upper limit of the N content of the hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet is preferably 0.03% by mass, more preferably 0.01% by mass, still more preferably 0.001% by mass, and 0001 mass% is particularly preferred. When the N content of the hot-rolled steel sheet exceeds the above upper limit, coarse nitrides are formed, and workability such as bending of the hot-rolled steel sheet and diameter expansion of the holes may be reduced, and blowholes are likely to occur during welding. There is a fear. Moreover, as a minimum of N content rate of a hot-rolled steel plate, although it does not specifically limit, 0 mass% is preferable.

  The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet preferably contains at least one of Ca, Mg, and rare earth elements as a deoxidizer. The lower limit of the content of one of Ca, Mg, and rare earth elements in the hot-rolled steel sheet is preferably more than 0% by mass, more preferably 0.002% by mass, and still more preferably 0.003% by mass. Moreover, as an upper limit of one content rate among Ca, Mg, or rare earth elements of a hot-rolled steel sheet, 0.03 mass% is preferable, 0.02 mass% is more preferable, and 0.01 mass% is further more preferable. . If the content of one of Ca, Mg, or rare earth elements in the hot-rolled steel sheet exceeds the above upper limit, the formability of the hot-rolled steel sheet may be reduced. In addition, a hot-rolled steel plate may contain 2 or more types among Ca, Mg, and rare earth elements. In this case, the content of each element is preferably within the above range.

  Moreover, it does not specifically limit as a metal structure of the hot-rolled steel plate obtained with the manufacturing method of the said hot-rolled steel plate, The volume content rate of pro-eutectoid ferrite, pearlite, bainite, and a martensite can each be adjusted arbitrarily.

(Cooling step S2)
In the cooling step S2, cooling water is sprayed on the hot-rolled steel sheet to cool it. As this cooling method, for example, a method in which cooling water is sprayed onto the surface of the steel sheet with a plurality of sprays can be used. Moreover, as cooling temperature, 400 degreeC or more and 700 degrees C or less are preferable.

(Sugar compound lamination step S3)
In the sugar compound laminating step S3, a sugar compound aqueous solution is applied by spraying or spraying to the inner surface of the cooled steel sheet winding step S4, and the sugar compound is laminated.

  The method of spraying or spraying the sugar compound aqueous solution is not particularly limited. For example, as shown in FIG. 2, immediately before the cooled steel plate 1 is wound around the coil 2, it is inside when the steel plate 1 is wound by the spray 4. A method of spraying or spraying on the surface can be used. In this case, the sugar compound aqueous solution is supplied to the spray 4 by a pump 5 from a storage tank (not shown). Moreover, it is preferable to perform the position which injects or sprays sugar compound aqueous solution between the coil 2 and the roll 3 just before that in order to prevent scattering and dripping of sugar compound aqueous solution.

  The sugar compound contained in the aqueous sugar compound solution is not particularly limited, but glyceraldehyde, erythrose, threose, ribose, lyxose, xylose, arabinose, apiose, allose, talose, gulose, glucose, altrose, mannose, galactose, idose , Dihydroxyacetone, erythrulose, ribulose, xylulose, psicose, fructose, sorbose, tagatose, cedoheptulose, coliose, trehalose, isotrehalose, cordobiose, sophorose, nigerose, laminaribiose, maltose, cellobiose, isomaltose, gentiobiose, lactose Fructooligosaccharide, galactooligosaccharide, dairy oligosaccharide, deoxyribose, fucose, rhamno , Glucuronic acid, galacturonic acid, glucosamine, galactosamine, glycerin, xylitol, sorbitol, glucuronolactone, gluconolactone, starch, amylose, amylopectin, glycogen, cellulose, pectin, glucomannan, dextrin, fructan, glucan, xyloglucan, hyaluron Acid, heparin, carrageenan, agarose or chitin are preferred. Moreover, you may use the said sugar compound in mixture. Among these, glucose, fructose, sucrose, or starch which is excellent in handling property and low cost is preferable.

  The lower limit of the sugar compound concentration in the sugar compound aqueous solution is preferably 1% by mass, more preferably 5% by mass, and even more preferably 10% by mass. When the concentration of the sugar compound is less than the above lower limit, the scale reduction effect on the steel sheet surface is not sufficiently exhibited, and the effect of suppressing grain boundary oxidation may be insufficient. On the other hand, the upper limit of the concentration of the sugar compound is preferably 55% by mass, and more preferably 50% by mass. If the concentration of the sugar compound exceeds the above upper limit, it may be difficult to handle the aqueous sugar compound solution, and the cost of the aqueous sugar compound solution may be unnecessarily high.

  Additives such as aggregating agents, thickeners, preservatives and the like other than sugar compounds can be appropriately added to the sugar compound aqueous solution.

(Winding process S4)
In winding process S4, the steel plate which laminated | stacked the sugar compound after cooling is wound up with a winder. As this winder, a known winder for thin steel plates can be used.

  By winding the steel plate, the sugar compound aqueous solution is sandwiched and held between the steel plates. As a result, it is possible to reliably suppress generation of grain boundary oxidation on the steel sheet surface.

(advantage)
The method for producing a hot-rolled steel sheet has a step of laminating a sugar compound on the surface of a hot-rolled steel sheet with respect to a hot-rolled steel sheet containing a certain amount of Si and Mn. Can be reduced. As a result, the oxygen supply source that oxidizes Si and Mn can be removed from the surface of the hot-rolled steel sheet. Therefore, in the method for producing the hot-rolled steel sheet, a grain boundary oxide is generated in the hot-rolled steel sheet during winding. Can be suppressed. Moreover, according to the method for producing a hot-rolled steel sheet, the scale of the hot-rolled steel sheet is reduced by the sugar compound, so that the scale removing operation can be omitted.

  Furthermore, the method for producing the hot-rolled steel sheet is applied by spraying or spraying the sugar compound aqueous solution on the inner surface when winding the steel sheet, so that the coated surface is sandwiched between the hot-rolled steel sheets immediately after application of the sugar compound aqueous solution, The sugar compound can be uniformly fixed on the surface of the hot-rolled steel sheet. As a result, the scale can be reduced more uniformly.

(Hot rolled steel sheet)
The hot-rolled steel sheet obtained by the method for producing a hot-rolled steel sheet is wound in a coil shape, has a reduced iron layer on at least one surface, and a sugar compound or a sugar compound on at least a part of the outer surface of the reduced iron layer Carbide derived from is attached. This reduced iron layer has a scale reduced by a sugar compound. Moreover, the carbide | carbonized_material derived from the sugar compound adhering to the outer surface of this reduced iron layer is a thing in which the sugar compound burned incompletely.

  The lower limit of the average thickness of the reduced iron layer is preferably 1 μm, more preferably 2 μm, and even more preferably 3 μm. If the average thickness of the reduced iron layer is less than the lower limit, the scale may not be sufficiently reduced. On the other hand, the upper limit of the average thickness of the reduced iron layer is preferably 20 μm, more preferably 18 μm, and even more preferably 15 μm. When the average thickness of the reduced iron layer exceeds the above upper limit, the quality of the hot rolled steel sheet may be deteriorated.

  In the hot-rolled steel sheet, generation of grain boundary oxide is suppressed by the sugar compound as described above. Therefore, the hot-rolled steel sheet can reduce the pickling time after being rewound from the coil shape, and can improve the productivity of products using the hot-rolled steel sheet as a raw material.

<Second embodiment>
The manufacturing method of the hot-rolled steel sheet shown in FIG. 2 has the following processes.
(1) Hot rolling step S11 for obtaining a steel sheet by hot rolling a slab
(2) Cooling and sugar compound laminating step S12 for cooling the steel sheet hot-rolled by spraying the sugar compound aqueous solution and simultaneously laminating the sugar compound on the surface of the steel sheet.
(3) Winding step S13 for winding the cooled steel plate

(Hot rolling process S11)
Since hot rolling process S11 is the same as hot rolling process S1 of the manufacturing method of the hot-rolled steel sheet of the first embodiment, description thereof is omitted.

(Cooling and sugar compound lamination step S12)
In the cooling and sugar compound laminating step S12, cooling is performed by spraying cooling water using a sugar compound aqueous solution on the steel sheet hot-rolled in the hot rolling step S11.

  This sugar compound aqueous solution can be the same as that used in the sugar compound lamination step S3 of the method for producing a hot-rolled steel sheet of the first embodiment. Also, the cooling water spraying method using the sugar compound aqueous solution can be the same as the cooling step S2 of the method of manufacturing the hot-rolled steel sheet of the first embodiment.

(Winding process S13)
The winding step S13 can be the same as the winding step S4 in the method for manufacturing a hot-rolled steel sheet according to the first embodiment. Also in the manufacturing method of the hot-rolled steel sheet of the present embodiment, the sugar compound aqueous solution sprayed in the cooling and sugar compound lamination step S12 is sandwiched and held by winding the steel sheet. As a result, scale removal can be performed reliably.

(advantage)
The manufacturing method of the hot-rolled steel sheet, like the hot-rolled steel sheet manufacturing method of the first embodiment, suppresses the generation of grain boundary oxide on the hot-rolled steel sheet during winding by the scale reducing action of the sugar compound. can do. Moreover, according to the manufacturing method of the said hot-rolled steel plate, since the sugar compound aqueous solution is used as cooling water, it is not necessary to provide the sugar compound lamination equipment and the lamination process separately. As a result, equipment costs can be reduced and productivity can be improved.

<Other embodiments>
The manufacturing method of the hot-rolled steel sheet of the present invention is not limited to the above embodiment. In each of the above embodiments, the sugar compound is applied to the surface of the steel sheet in the form of an aqueous solution, but the sugar compound may be applied in the form of powder (granular). As a method for applying the powdered sugar compound, spraying can be used.

  Moreover, in said 1st embodiment, although sugar compound aqueous solution was apply | coated to the surface which becomes inner side at the time of winding of a steel plate, you may apply | coat to the surface on the opposite side (surface which becomes outer side at the time of winding). However, if a sugar compound aqueous solution is applied to the outer surface during winding, the sugar compound aqueous solution may not stay on the steel sheet surface by dripping or the like before winding. It is preferable to apply to the surface.

  In addition, when apply | coating using sugar compound aqueous solution, you may use the method of apply | coating aqueous solution directly on the surface of a steel plate with a roller or a brush. However, since the steel plate is hot and heat resistance is required, a method of applying indirectly by spraying or the like is preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
A slab having the composition A shown in Table 1 was heated at 1200 ° C. for 30 minutes, and the primary scale was removed with a high-pressure water descaler. Thereafter, the slab was roughly rolled at 1100 ° C., and the secondary scale produced by the rough rolling was removed with a high-pressure water descaler. Next, the slab was finish-rolled at 1000 ° C., cooled to 630 ° C. by blowing cooling water, and wound around a coil to obtain a hot-rolled steel sheet. When the hot-rolled steel sheet is wound around the coil after cooling, nothing is applied to the first half part, and in the second half part, an aqueous solution containing 10% by mass of sucrose is applied to the inner surface after winding of the steel sheet by spray injection. did.

  After winding the steel sheet, the steel sheet was allowed to cool naturally, and a sample was taken from a portion where the sugar compound aqueous solution was applied (second half portion) and a portion where the sugar compound aqueous solution was not applied (first half portion). This sample was subjected to resin polishing so that grain boundary oxidation could be observed from the cross section, and the maximum depth of grain boundary oxidation was measured using a scanning electron microscope (SEM).

(Examples 2-78)
The hot-rolled steel sheet was wound around a coil and allowed to cool naturally in the same procedure as in Example 1 except that the slabs having the compositions shown in Tables 1, 2 and 3 were used, the type of sugar compound and the aqueous solution concentration. Thereafter, in the same manner as in Example 1, samples were taken from the portion where the sugar compound aqueous solution was applied (second half portion) and the portion where the sugar compound aqueous solution was not applied (first half portion), and grain boundary oxidation was performed using a scanning electron microscope (SEM). The maximum depth of was measured.

  The measurement results of the maximum depth of grain boundary oxidation in Examples 1 to 78 are shown in Tables 2 and 3.

  As shown in Table 2 and Table 3, in the hot-rolled steel sheets of Examples 1 to 78, the portion where the saccharide compound aqueous solution was applied (the latter half of the coil) was compared with the portion where the saccharide compound aqueous solution was not applied (the first half of the coil). The grain boundary oxidation depth is small. Further, depending on the type and concentration of the sugar compound, the grain boundary oxidation depth was 10 μm or less, and a remarkable improvement effect was seen. The grain boundary oxidation depth must be 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less.

  The production method of a hot-rolled steel sheet and the hot-rolled steel sheet of the present invention can suppress the generation of grain boundary oxides when winding a hot-rolled steel sheet containing Si and Mn.

1 Steel plate 2 Coil 3 Roll 4 Spray 5 Pump

Claims (7)

Hot-rolled steel sheet having a C content of 0.04 mass% to 0.2 mass%, an Si content of 0.5 mass% to 3 mass%, and an Mn content of 0.1 mass% to 3 mass% A manufacturing method of
Hot rolling process,
Cooling the hot-rolled steel sheet by blowing cooling water;
Laminating a sugar compound on the surface of a hot-rolled steel sheet;
And a step of winding the cooled steel plate.   The sugar compound is glyceraldehyde, erythrose, threose, ribose, lyxose, xylose, arabinose, apiose, allose, talose, gulose, glucose, altrose, mannose, galactose, idose, dihydroxyacetone, erythrulose, ribulose, xylulose, psicose , Fructose, sorbose, tagatose, cedoheptulose, coriose, trehalose, isotrehalose, cordierbiose, sophorose, nigerose, laminaribiose, maltose, cellobiose, isomaltose, gentiobiose, lactose, sucrose, fructooligosaccharide, lactose oligosaccharide, Deoxyribose, fucose, rhamnose, glucuronic acid, galacturonic acid, glucosamine, Lactosamine, glycerin, xylitol, sorbitol, glucuronolactone, gluconolactone, starch, amylose, amylopectin, glycogen, cellulose, pectin, glucomannan, dextrin, fructan, glucan, xyloglucan, hyaluronic acid, heparin, carrageenan, agarose, or The method for producing a hot-rolled steel sheet according to claim 1, which is chitin.   The method for producing a hot-rolled steel sheet according to claim 1 or 2, wherein the laminating step is performed by applying an aqueous solution having a sugar compound concentration of 1% by mass to 55% by mass.   The method for producing a hot-rolled steel sheet according to claim 3, wherein in the laminating step, the aqueous solution is applied to an inner surface of the steel plate in the winding step.   The method for producing a hot-rolled steel sheet according to claim 3, wherein the cooling water is the aqueous solution, and the cooling step and the laminating step are performed simultaneously.   The Al content of the hot-rolled steel sheet is more than 0% by mass and 0.06% by mass or less, the Cr content is more than 0% by mass and 2% by mass or less, the Ti content is more than 0% by mass and 0.1% by mass or less, and Ni is contained. The rate is more than 0% by mass and 2% by mass or less, the Cu content is more than 0% by mass and 2% by mass or less, the Mo content is more than 0% by mass and 2% by mass or less, the Nb content is more than 0% by mass and 1% by mass or less, The V content is more than 0% by mass and less than 1% by mass, the W content is more than 0% by mass and not more than 0.3% by mass, the B content is more than 0% by mass and less than 0.01% by mass. The method for producing a hot-rolled steel sheet according to any one of claims 1 to 5, wherein at least one of Ca, Mg, and rare earth elements is contained in an amount of more than 0% by mass and 0.03% by mass or less. A hot-rolled steel sheet wound up in a coil shape,
A hot-rolled steel sheet having a reduced iron layer on at least one surface, wherein a sugar compound or a carbide derived from the sugar compound is attached to at least a part of an outer surface of the reduced iron layer.

Images