KR20100021273A - High carbon hot rolled steel coil and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A high carbon hot rolled steel sheet and a manufacturing method thereof are provided to minimize the repetition time of cold rolling and spheroidizing. CONSTITUTION: A manufacturing method of a high carbon hot rolled steel sheet comprises the steps of: producing a high carbon slab, re-heating the slab over 1200°C, rough-rolling the slab and finish hot rolling the rough-rolled slab in an austenite area over 830°C to obtain a sheet with the thickness of 1.8mm or less, cooling the sheet through shear control cooling in a water cooler, maintaining the cooling temperature for a specific time to induce perlite phase transformation, and winding the sheet at the temperature of 650°C or less.

Description

High carbon hot rolled steel sheet and its manufacturing method {HIGH CARBON HOT ROLLED STEEL COIL AND MANUFACTURING METHOD THEREOF}

The present invention relates to a high carbon hot rolled steel sheet. More specifically, the present invention relates to a high carbon hot rolled steel sheet having a fine pearlite structure and a manufacturing method thereof.

The high carbon steel sheet refers to steel sheet containing 0.3 wt% or more of carbon and its crystal structure having a pearlite crystal phase. The high carbon steel sheet has high strength and high hardness after the final process. As such, the high carbon steel sheet is used as a tool steel or a mechanical structural steel that requires high strength and hardness because it has high strength and high hardness.

An example of a high carbon steel sheet used as a tool steel is JS-SK85 steel, which is classified as a Japanese industrial standard. JS-SK85 steel is used for automobile parts, needles for needles, razor blades or stationery blades.

High carbon steel sheet is usually produced as an intermediate product called a hot rolled steel slab (slab) by a continuous hot rolling process. The hot rolled steel sheet is rolled to a predetermined thickness through the rough and finish rolling of the heated slab for hot rolling, and then cooled to an appropriate temperature in a run-out table (ROT) and rolled into a coil of roll type. Is prepared.

The hot rolled steel sheet is subjected to a pickling and spheroodizing process and then cold rolled to produce a cold rolled steel sheet. The cold rolled steel sheet is repeatedly subjected to the annealing process and the cold rolling process in order to produce a cold rolled steel sheet having a desired thickness. The cold rolled steel sheet is processed into a desired product through a process such as blanking or burring, and then processed into a final product through QT heat treatment (quenching and tempering).

The present invention is to provide a high carbon hot rolled steel sheet having a thin thickness and fine pearlite structure in order to minimize the repeated number of spherical annealing and cold rolling in a subsequent process.

Still another object of the present invention is to provide a method for producing a high carbon hot rolled steel sheet having a fine pearlite structure and improving the phase transformation rate in a water cooling zone so that the coil is not crushed.

According to an embodiment of the present invention for achieving the above object ⅰ) by weight% C: 0.60 ~ 1.20%, Si: 0.10 ~ 0.35%, Mn: 0.10 ~ 0.80%, greater than P: 0 and less than 0.03%, S : Greater than 0 and contain 0.03% or less, Ni: 0.25% or less (contains 0), Cr: 0.30% or less (contains 0), Cu: 0.25% or less (contains 0) Any one or more, the remainder is Fe, and other inevitable impurities are added, ii) the cementite width is greater than 0 and less than 0.2㎛, the interval between cementite and cementite is greater than 0 and less than 0.5㎛ Provided is a high carbon hot rolled steel sheet having a fine pearlite structure.

In addition, according to an embodiment of the present invention, the high carbon hot rolled steel sheet has a fraction of 90% or more of the fine pearlite structure.

The high carbon hot rolled steel sheet has a thickness of 1.8 mm or less, preferably 1.6 mm or less.

According to an embodiment of the present invention for achieving another object, i) by weight% C: 0.60 ~ 1.20%, Si: 0.10 ~ 0.35%, Mn: 0.10 ~ 0.80%, greater than P: 0 and less than 0.03% , S: greater than 0 and less than 0.03%, Ni: less than 0.25% (contains 0), Cr: less than 0.30% (contains 0), Cu: less than 0.25% (contains 0). Slab manufacturing step comprising any one or more of), the rest is Fe, and other inevitably added impurities ii) reheating step of reheating the slab to 1200 ℃ or more iii) crude slab Hot rolling step to produce a thin plate having a thickness of 1.8 mm or less by finishing rolling in an austenite region of 830 ° C. or higher ⅳ) Cooling step of cooling the thin plate by shear controlled cooling in a water cooling stand 대) In the cooling step Cooling temperature for the time required to proceed with pearlite phase transformation Cooling stop step to maintain and iii) provides a method for producing a high carbon hot rolled steel sheet comprising the step of winding the thin plate at 650 ℃ or less.

The method for producing a high carbon hot rolled steel sheet has a cooling rate of 50 to 300 ° C / sec for cooling the thin plate in the cooling step.

In the manufacturing step of the thin plate by hot rolling, the thin plate manufactures a hot rolled steel sheet of 1.6 mm or less.

In addition, the shear control cooling to cool the thin plate in the cooling step is cooled to less than 650 ℃ and this cooling is completed within at least 3 seconds.

And in the cooling stop step of the manufacturing method of high-carbon hot-rolled steel sheet to complete the pearlite phase transformation of more than 90% and this phase transformation completion time is at least 6 seconds. In addition, this cooling stop step maintains the temperature at 550 ~ 660 ℃.

The method of manufacturing a high carbon hot rolled steel sheet according to an embodiment of the present invention has an effect of providing a technology capable of producing a large amount of thin plates having a thickness of 1.8 mm or less, preferably 1.6 mm or less.

The method for manufacturing a high carbon hot rolled steel sheet according to an embodiment of the present invention can be manufactured in a thin plate state having a thickness of 1.8 mm or less, preferably 1.6 mm or less, so as to recover spheroidizing annealing and cold rolling in a subsequent product manufacturing process. There is a technical effect to reduce the at least one or more times.

As such, the subsequent manufacturing process steps can be omitted, thereby reducing processing costs and shortening the manufacturing process time.

The high carbon hot rolled steel sheet manufactured according to the embodiment of the present invention has a fine pearlite structure, and thus has a technical effect of having durability and strength in the final product.

Hereinafter, embodiments of a high carbon hot rolled steel sheet and a method for manufacturing the same according to the present invention will be described in detail, but the present invention is not limited to the following examples. Therefore, those skilled in the art may implement the present invention in various other forms without departing from the technical spirit of the present invention.

In the present invention, the content of component elements means all weight percent unless otherwise specified.

Hereinafter, a high carbon hot rolled steel sheet according to an embodiment of the present invention will be described in detail.

High-carbon hot-rolled steel sheet according to an embodiment of the present invention by weight% C: 0.60 ~ 1.20%, Si: 0.10 ~ 0.35%, Mn: 0.10 ~ 0.80%, P: 0 greater than 0.03%, less than S: 0 Large, 0.03% or less, Ni: 0.25% or less (including 0), Cr: 0.30% or less (including 0), Cu: 0.25% or less (including 0), and residual Fe and other unavoidable impurities Is made of.

The reason for limiting the components in the high carbon hot rolled steel sheet according to an embodiment of the present invention will be described.

 [C: 0.60-1.20%]

Carbon C is a component that affects hardenability when the final product is heat treated (QT). If the C content is less than 0.6%, hardenability may decrease, which may cause the strength of the product to decrease and wear resistance may deteriorate. In addition, when C exceeds 1.20%, the final product may have poor workability and lower impact toughness. Therefore, the preferable content range of carbon C is 0.60 to 1.20%.

[Si: 0.10 ~ 0.35%]

Silicon Si is an element added for deoxidation. If the Si content is less than 0.10%, deoxidation is incomplete and oxidative inclusions remain in the product. Therefore, cold rolling of the hot rolled steel sheet to an ultra-thin thickness causes the surface to be torn and causes the fatigue strength of the final product to fall. If the Si content is more than 0.35%, red scale is generated on the surface of the hot-rolled steel sheet manufactured by regenerating the material causing red scale when the slab is reheated for the hot rolling process. It becomes the cause. Therefore, the preferable content range of Si is 0.10 to 0.35%.

[Mn: 0.10-0.80%]

Manganese Mn improves hardenability when the final product is heat treated (QT). In addition, the impact cloth generated as C increases the role of suppressing the temperature rise. If the content of Mn is less than 0.10%, the impact transition temperature is increased, the workability is reduced. In addition, when Mn is contained in excess of 0.80%, the product is thermally deformed during the heat treatment (QT) of the final product. Therefore, the preferable content range of Mn is 0.10 to 0.80%.

[P: 0.03% or less]

Phosphorus P causes precipitation of Fe ₃ P or the like on the fine austenite grain boundaries of the hot rolled steel sheet during the manufacturing process. When these precipitates are formed in the hot rolled steel sheet, the impact toughness of the product is deteriorated. Therefore, although P content is larger than 0, it is preferable to restrict | limit to 0.03 weight% or less.

 [S: 0.03% or less]

Sulfur S forms fine precipitates MnS and CuS during the manufacturing process. When these precipitates are formed inside the hot-rolled steel sheet, the growth of grains is suppressed, which worsens the hardenability of the final product. Therefore, it is desirable to manage S as low as possible and limit its content to 0.03 wt% or less.

High-carbon hot-rolled steel sheet according to an embodiment of the present invention is Fe and other unavoidable impurities in addition to the above element components.

One embodiment of the present invention may include at least one element of Ni, Cr, Cu in addition to the above components. These elements may be incorporated as impurities, but such elements are included to improve hardenability in the final heat treatment process. However, when these elements contain more than 0.25% of Ni, more than 0.30% of Cr, and more than 0.25% of Cu, the inclusion effect saturates and the cost increases. Cr has an effect of suppressing surface oxidation and decarburization by forming a Cr oxide layer on the surface of the slab when the slab is reheated in a hot rolling process. In view of the points described above, the content of these elements is controlled to be Ni: 0.25% or less (including 0), Cr: 0.30% or less (including 0) and Cu: 0.25% or less (including 0).

Hereinafter, a method of manufacturing a high carbon hot rolled steel sheet according to the embodiment described above will be described.

First, in weight percent C: 0.60 to 1.20%, Si: 0.10 to 0.35%, Mn: 0.10 to 0.80%, P: 0, greater than 0.03%, S: 0, greater than 0.03%, Ni: 0.25% or less ( High carbon steel slab comprising Cr: 0.30% or less (including 0), Cu: 0.25% or less (including 0) and residual Fe and other unavoidably added impurities.

The steel slab thus prepared is reheated to a temperature of 1200 ° C. or lower, and then hot rolled in an austenite region of 830 ° C. or higher.

In the hot rolling, the heated slab is rolled in a thin sheet state so that the thickness thereof becomes 1.8 mm or less, preferably 1.6 mm or less, in a state in which rough rolling and finish rolling are completed.

The reason for hot rolling the slab to a thin sheet state is as follows.

In order to produce the final product with the hot rolled steel sheet, it is first manufactured as a cold rolled steel sheet in an intermediate state. However, in order to manufacture such a cold rolled steel sheet, the hot rolled steel sheet is repeatedly spheroidized annealing process and cold rolling process several times to produce a cold rolled steel sheet having a desired thickness (for example, 0.6 mm or less). Therefore, the thicker the thickness of the provided hot rolled steel sheet, the greater the number of spheroidizing annealing and cold rolling processes can be performed repeatedly.

In addition, the high carbon steel according to one embodiment of the present invention has a carbon content of 0.60 to 1.20 wt%. High carbon steel is characterized by high strength but low impact toughness due to high carbon content. Therefore, the hot rolled vacancy steel is subjected to spheroidization annealing before cold rolling. The vacancy steel is cold rolled after spheroidizing annealing. In this case, when cold rolling is performed to reduce the vacancy steel to 70% or more, the spheroidized cementite is separated from the matrix to form fine voids in the product. Such voids cause deterioration of durability and strength of the final product. Therefore, in case of vacancy steel, the rolling reduction is limited to 60 ~ 70% when cold rolling is performed once.

For this reason, when the hot rolled steel sheet is cold rolled, if the thickness of the hot rolled steel sheet becomes thick, the cold rolled sheet may be repeatedly cold rolled several times and rolled to a desired thickness.

Therefore, when the thickness of the hot rolled steel sheet is manufactured to 1.8mm or less, preferably 1.6mm or less, as in the embodiment of the present invention, at least one spherical annealing process and cold rolling may be omitted in the subsequent cold rolling process.

As described above, when the hot rolled steel sheet is provided, a manufacturing process step may be omitted in a subsequent process, thereby reducing processing cost and shortening manufacturing process time during product production.

The thin plate subjected to the finish hot rolling to the thickness as described above is cooled to an appropriate temperature in a run-out table (ROT) and then wound in a rolled coil.

The thin plate cooled in the water cooler allows the pearlite phase transformation to be more than 90% complete before winding up in the winder.

When the degree of perlite phase transformation is 90% or less before the thin plate cooled in the water cooling zone is wound, the phase transformation is performed in perlite in the state where the hot rolled steel sheet is wound. Then, the temperature of the winding coil is increased by the transformation heat, and when the temperature is increased, the pearlite structure is coarse. Subsequent processing with the coarse pearlite structure results in residual cementite in the product after annealing. As such, the presence of residual cementite causes stress to concentrate on the cementite structure in the product processing process, causing the product to break or not perform heat treatment smoothly. In addition, if the thin sheet cooled in the water cooling zone is not transformed into pearlite before being wound, but is transformed into pearlite in the wound state, the volume fraction of the crystal structure is changed so that the hot rolled steel sheet wound in the coil state has its shape It will crush down and change to an elliptical shape. Such a crushed coil is called a duckbill coil. Like this, when the duckbill coil is generated, it is difficult to operate in the subsequent correction process or pickling process, which causes a decrease in productivity or error rate.

And the high carbon hot rolled steel sheet according to an embodiment of the present invention will be described why the transformation heat generation during the hot rolling process.

In the case of high carbon steel, as the C content increases, the curve nose of the CCT curve shifts to the right. Therefore, the start time of phase transformation from austenite to pearlite is delayed, and the end time is also delayed. In addition, as the C content increases, the transformation calorific value according to the difference in heat capacity increases.

Therefore, for the reasons described above, it is preferable that the thin plate that has been finished hot rolling is completed at least 90% of the phase transformation from austenite to pearlite before being wound into a coil state.

To this end, it is preferable that the thin plate after finishing hot rolling is rapidly cooled at the initial stage of entering the water cooling stage. The cooling rate at this time is preferably 50 ~ 300 ℃ / sec.

Therefore, it is desirable that the thin plate entered into the water cooling zone be cooled rapidly and cooled to a cooling stop temperature of 650 ° C. or less. The thin plate cooled below 650 ℃ in the water cooling stage passes through the water cooling stage and completes the pearlite phase transformation more than 90% while maintaining the cooling temperature, and then winds up below 650 ℃.

High carbon steels require more than 9 seconds to complete phase transformation in the water cooling zone. However, when the thickness is thinned by hot rolling, the speed at which the mail is increased can be increased, and when rolling to a thickness of 1.8 mm or less, it is not easy to secure time to complete phase transformation sufficiently. Therefore, in one embodiment of the present invention, in order to minimize the time taken for the hot-rolled steel sheet to complete the phase transformation, it is rapidly cooled to 50-300 ° C./sec at the initial entry into the water cooling zone and cooled to the cooling stop temperature. At this time, it is preferable to control the time required within 3sec. In addition, the hot rolled steel sheet cooled while moving in the water cooling zone completes the phase transformation while reducing the amount of transformation calorific value through the slow cooling at the cooling stop temperature of 550 ~ 660 ℃ temperature range. At this time, the time required is preferably maintained for 6 seconds or more.

When hot rolling is performed under the above water cooling zone shear control cooling conditions, the manufactured hot rolled steel sheet has a fine pearlite structure.

The manufactured hot rolled steel sheet preferably has a cementite width of 0.2 μm or less and a cementite and cementite gap of 0.5 μm or less. Such a crystal structure will eventually have a fine pearlite structure, the final hot rolled steel sheet has a phase ratio of fine pearlite 90% or more.

The manufactured hot rolled steel sheet is subjected to a pickling and spheroodizing process, and then cold rolled to produce a cold rolled steel sheet. The cold rolled steel sheet is repeatedly subjected to the annealing process and the cold rolling process in order to produce a cold rolled steel sheet having a desired thickness. The cold rolled steel sheet is processed into a desired product through a process such as blanking or burring, and then processed into a final product through QT heat treatment (quenching and tempering).

When processing the final product, the structure of the hot rolled steel sheet should be controlled by fine pearlite, which can suppress cementite residue in the final product, increase the strength of the final product, and improve the wear resistance and fatigue resistance. Can be granted.

<Example>

The composition of the steel sheet used in the experiment is shown in Table 1.

TABLE 1

A slab having the composition shown in Table 1 was prepared, and the slab was then reheated to 1200 ° C. for hot rolling.

The sheet thickness of the hot rolled steel sheet by hot rolling was set to 1.8 to 1.4 mm in both the comparative example and the example.

All the comparative examples in Table 1 did not perform shear controlled cooling in the water cooling zone after finishing hot rolling, and all of the examples performed shear controlled cooling.

And it wound up at the winding temperature shown in Table 2. Table 2 shows the HrC hardness test values and the microscopic tissue observation results of the hot rolled steel sheets after hot rolling and winding.

TABLE 2

As shown in Table 2, all of the comparative examples without shear controlled cooling in the water cooling zone had lower HrC hardness values than the examples, and all of the structures showed coarse pearlite. In contrast, the HrC hardness value was higher than that of the comparative example, and all of the structures showed fine pearlite.

Next, FIGS. 1 to 4 show the crystallographic images after hot rolling and the crystallographic images after spheroidizing annealing for the specimens of Comparative Example 1 and Example 1. FIG.

Comparative Example 1 shown in FIG. 1 was wound up after passing through a water cooling stand without shear-controlled cooling after finishing hot rolling.

In the manufacturing process conditions of Comparative Example 1, because the slow cooling was performed without shear controlled cooling in the water cooling zone, it was not possible to secure sufficient time for phase transformation in the water cooling zone. In this case, the phase transformation rate before winding was 50% or less, and the crystal structure showed coarse pearlite structure at a level observable by an optical microscope (X500). In this case, the coiling temperature is 600 ~ 650 ℃ section, but after winding the temperature rises to 650 ℃ or more by the transformation heat, the shape of the wound coil is in the shape of a duckbill.

The hot rolled steel sheet of Comparative Example 1 thus prepared was subjected to a pickling process and spheroidized annealing. The micrograph of the product in which spheroidization annealing is completed is shown in FIG.

In Comparative Example 1 shown in FIG. 2, the hot rolled steel sheet having a thickness of 1.6 mm was subjected to a pickling process, and spheroidized annealing was maintained for 30 hours or more in a 650 to 720 degree section. After cold rolling once, it is made of 0.8mm thick cold rolled steel sheet, and then recrystallized annealing is observed tissue under a microscope. As shown in FIG. 2, the points represented in black are undissolved cementite, which adversely affects heat treatment defects and fatigue properties of the final product.

In Example 1 shown in Figure 3 was subjected to the final hot rolling at a temperature of 880 ℃ or more, and then started cooling at a rate of 50 ℃ / sec or more in front of the water cooling stage and quenched to 580 ℃ cooling stop temperature. Then, while maintaining the temperature to complete the pearlite transformation more than 90% while passing through the water cooling stand and then wound up to 650 ℃ or less.

The hot rolled steel sheet of Example 1 manufactured as described above was hot rolled to a thickness of 1.6 mm and subjected to a pickling process and a spheroidizing annealing process for maintaining at least 30 hours in a 650 to 720 degree section. The specimen was subjected to cold rolling once, then cold rolled to a thickness of 0.8 mm, and then recrystallized and annealed.

4 is a micrograph of Example 1 after recrystallization annealing in this manner. As shown in FIG. 4, in the embodiment of shear controlled cooling in the water cooling zone, cementite is uniformly dispersed, thereby improving heat treatment of the final product and improving fatigue characteristics.

The above has described the crystallographic photographs of Comparative Example 1 and Example 1, but the specimens prepared according to other comparative examples and other examples also showed similar structures.

In summary, the hot rolled steel sheet prepared according to the embodiment has a fine pearlite structure as shown in FIG. 3, while the hot rolled steel sheet manufactured according to the comparative example has a coarse pearlite structure as shown in FIG. 1.

As described above, when the hot rolled steel sheet is directly rolled in a thin sheet state of 1.8 mm or less, the comparative example manufactured by the conventional hot rolling method exhibits torsion due to thermal deformation in the coil state because the crystal structure shows coarse pearlite structure. have.

However, even if the hot rolled steel sheet is directly rolled in a thin state of 1.8 mm or less, when shear-controlled cooling is performed in the water cooling zone as in the embodiment, the crystal structure shows a fine pearlite structure, and the transformation is over 90%. Since the coil was wound in a state, no twisting of the coil appeared.

In addition, the results of spheroidizing annealing the hot-rolled steel sheets of Comparative Examples and Examples thus prepared by the subsequent processes were similar to the structures shown in FIGS. 2 and 4.

As shown in FIG. 2, in the product according to the comparative example, a large number of cementite in an undissolved state was found, whereas in the product according to the example, no cementite in such an undissolved state was found.

Therefore, the product according to the embodiment did not cause breakage due to stress concentration in the processing process of the final product and did not generate defective products even by heat treatment.

As described above, a high carbon hot rolled steel sheet and a method of manufacturing the same have been described with reference to preferred embodiments of the present invention, but those skilled in the art will not depart from the spirit and scope of the present invention as set forth in the claims below. It will be understood that various modifications and variations can be made within the scope of the invention.

1 is a 1.6 mm thick hot rolled steel sheet wound by slow cooling after finishing hot rolling according to a comparative example of the present invention, and its crystal structure is a micrograph showing coarse pearlite structure.

FIG. 2 is a micrograph showing the crystal structure of the hot rolled steel sheet of FIG. 1 subjected to spheroidization annealing, in which undissolved cementite in the form of black lines remains.

FIG. 3 is a micrograph showing a fine pearlite structure as a hot rolled steel sheet having a thickness of 1.6 mm obtained by quenching after finishing hot rolling and completing a pearlite transformation of 90% or more according to an embodiment of the present invention.

FIG. 4 is a micrograph showing unstructured cementite as showing crystal structure in a state of spheroidizing annealing the hot rolled steel sheet of FIG. 2.

Claims (13)

By weight% C: 0.60 ~ 1.20%, Si: 0.10 ~ 0.35%, Mn: 0.10 ~ 0.80%, greater than P: 0, 0.03% or less, S: greater than 0, containing 0.03% or less, Ni: 0.25% or less (Contains 0), Cr: 0.30% or less (contains 0), Cu: 0.25% or less (contains 0), the remainder is Fe, and inevitably added A high carbon hot rolled steel sheet having a fine pearlite structure having an impurity, and having a cementite width of greater than 0 and less than or equal to 0.2 µm, and a distance between cementite and cementite greater than 0 and less than or equal to 0.5 µm. The method of claim 1, The high carbon hot rolled steel sheet is a high carbon hot rolled steel sheet having a fraction of 90% or more of the fine pearlite structure. The method according to claim 1 or 2, The high carbon hot rolled steel sheet is a high carbon hot rolled steel sheet having a thickness of 1.8mm or less. The method according to claim 1 or 2, The high carbon hot rolled steel sheet is a high carbon hot rolled steel sheet having a thickness of 1.6mm or less. By weight% C: 0.60 ~ 1.20%, Si: 0.10 ~ 0.35%, Mn: 0.10 ~ 0.80%, greater than P: 0, 0.03% or less, S: greater than 0, containing 0.03% or less, Ni: 0.25% or less (Contains 0), Cr: 0.30% or less (contains 0), Cu: 0.25% or less (contains 0), the remainder is Fe, and inevitably added Slab manufacturing step of manufacturing a high carbon slab made of impurities; Reheating step of reheating the slab to 1200 ℃ or more; Hot rolling the slab and then performing a hot rolling finish in an austenite region of 830 ° C. or higher to manufacture a thin plate having a thickness of 1.8 mm or less; A cooling step of cooling the thin plate by shear controlled cooling in a water cooling stand; A cooling stop step of maintaining a cooling temperature for a time necessary to proceed with the pearlite phase transformation in the cooling step; and Winding step of winding the thin plate at less than 650 ℃; Method for producing a high carbon hot rolled steel sheet comprising a. The method of claim 5, Shear control cooling to cool the thin plate in the cooling step is a method of manufacturing a high carbon hot rolled steel sheet having a cooling rate of 50 ~ 300 ℃ / sec. The method of claim 6, In the manufacturing step of the thin plate by the hot rolling, the thin plate is 1.6mm or less manufacturing method of high carbon hot rolled steel sheet. The method of claim 7, wherein Shear control cooling to cool the thin plate in the cooling step is a method of manufacturing a high carbon hot rolled steel sheet to be cooled to less than 650 ℃. The method of claim 8, Cooling to cool to less than 650 ℃ in the cooling step is a method of producing a high carbon hot rolled steel sheet within at least 3 seconds. The method according to any one of claims 5 to 9, The method of manufacturing a high carbon hot rolled steel sheet in which the pearlite phase transformation is completed by 90% or more in the cooling stop step. The method of claim 10, The cooling stop step is a method of manufacturing a high carbon hot rolled steel sheet to maintain the temperature at 550 ~ 660 ℃. The method of claim 11, The method of manufacturing a high carbon hot rolled steel sheet in which the time for maintaining the pearlite phase transformation in the cooling stop step is completed for 90% or more. The method of claim 10, The hot-rolled steel sheet manufactured by the method of manufacturing the high-carbon hot-rolled steel sheet has a cementite width of greater than 0 and less than or equal to 0.2 μm, and a spacing of cementite and cementite is greater than 0 and has a fine pearlite structure having a fine pearlite structure of less than or equal to 0.5 μm. Manufacturing method.

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