WO2018016908A1 - Method for manufacturing hot-rolled coil, and method for shape-correction of hot-rolled coil - Google Patents

Abstract

Disclosed is an invention related to a method for manufacturing a hot-rolled coil and a method for shape-correction of a hot-rolled coil. In a specific embodiment, the method for manufacturing a hot-rolled coil comprises: a step for reheating slab steel including 0.18-0.56 wt% of carbon (C), 0.1-0.5 wt% of silicon (Si), 0.7-6.5 wt% of manganese (Mn), more than 0 wt% and at most 0.02 wt% of phosphorus (P), more than 0 wt% and at most 0.02 wt% of sulfur (S), more than 0 wt% and at most 0.3 wt% of chromium (Cr), more than 0 wt% and at most 0.004 wt% of boron (B), and 0.01-0.04 wt% of titanium (Ti), with the remainder being iron (Fe) and inevitable impurities; a step for forming a hot-rolled sheet by hot-rolling the slab steel under the conditions of a final hot-rolling temperature of 850°C-950°C; and a step for winding at a winding temperature of 700°C or greater by cooling the hot-rolled sheet.

Description

Hot rolled coil manufacturing method and shape correction method of hot rolled coil

The present invention relates to a hot rolled coil manufacturing method and a shape correction method of a hot rolled coil. More particularly, the present invention relates to a method for manufacturing a hot rolled coil for preventing shape defects and a method for correcting a shape of a hot rolled coil, which can prevent shape defects caused by its own weight during the manufacture of a hot rolled coil.

Recently, securing light weight is considered as an important factor in the development of automotive materials, which is intended to improve fuel efficiency, which is the final goal by replacing existing components with high strength materials. To this end, the material used as a structural material for vehicles is a direction for improving performance by adding alloying elements such as manganese (Mn), nickel (Ni), chromium (Cr), molybdenum (Mo) and titanium (Ti). It is being developed and secured and applied to steel materials through cold rolling and heat treatment processes.

Background art related to the present invention is disclosed in Republic of Korea Patent Publication No. 1995-0016913 (published on July 20, 1995, the name of the invention: telescope calibration apparatus of a rolling coil).

According to an embodiment of the present invention, there is provided a hot rolled coil manufacturing method excellent in the deformation preventing effect of the hot rolled coil.

According to an embodiment of the present invention, it is to provide a method for straightening the shape of the hot rolled coil that can prevent the degradation of the material and physical properties of the hot rolled coil.

According to an embodiment of the present invention, it is to provide a method for straightening the shape of the hot rolled coil that can prevent the surface defects of the hot rolled coil caused by the shape correction by applying an external force.

According to one embodiment of the present invention, there is provided a shape correction method of a hot rolled coil excellent in economy.

One aspect of the invention relates to a method for manufacturing a hot rolled coil. In one embodiment, the hot rolled coil manufacturing method is carbon (C): 0.18 to 0.56% by weight, silicon (Si): 0.1 to 0.5% by weight, manganese (Mn): 0.7 to 6.5% by weight, phosphorus (P): greater than 0 0.02 wt% or less, sulfur (S): more than 0 and 0.02 wt% or less, chromium (Cr): more than 0 and 0.3 wt% or less, boron (B): more than 0 and 0.004 wt% or less, titanium (Ti): 0.01 to 0.04 weight Reheating the slab steel containing% and remaining iron (Fe) and other unavoidable impurities; Hot rolling the slab steel at a finish rolling temperature of 850 ° C. to 950 ° C. to form a hot rolled sheet; And cooling the hot rolled sheet to wind up at a winding temperature of 700 ° C. or higher.

In one embodiment, the slab steel, carbon (C): 0.21 to 0.37% by weight, silicon (Si): 0.1 to 0.4% by weight, manganese (Mn): 1.1 to 1.5% by weight, phosphorus (P): greater than 0 0.02 Wt% or less, sulfur (S): more than 0 and 0.02 wt% or less, chromium (Cr): 0.1 to 0.3 wt%, boron (B): 0.001 to 0.004 wt%, titanium (Ti): 0.01 to 0.04 wt% and the balance Of iron (Fe) and other unavoidable impurities.

In one embodiment, the slab steel, carbon (C): 0.18 to 0.25% by weight, silicon (Si): 0.3 to 0.5% by weight, manganese (Mn): 2 to 6.5% by weight, phosphorus (P): greater than 0 0.02 Wt% or less, sulfur (S): more than 0 and 0.01 wt% or less, chromium (Cr): more than 0 and 0.1 wt% or less, boron (B): more than 0 and 0.001 wt% or less, titanium (Ti): 0.01 to 0.04 wt% And residual amounts of iron (Fe) and other unavoidable impurities.

In one embodiment, the slab steel, carbon (C): 0.5 to 0.56% by weight, silicon (Si): 0.1 to 0.3% by weight, manganese (Mn): 0.7 to 1% by weight, phosphorus (P): greater than 0 0.02 % By weight or less, sulfur (S): more than 0 and 0.01% by weight or less, chromium (Cr): 0.1 to 0.3% by weight, boron (B): more than 0 and 0.001% by weight or less, titanium (Ti): 0.01 to 0.02% by weight and May contain residual amounts of iron (Fe) and other unavoidable impurities.

Another aspect of the invention relates to a method for straightening the shape of a hot rolled coil. In one embodiment the shape correction method of the hot rolled coil comprises the steps of seating the hot rolled coil on the bottom hanger of the C-hook; Measuring the long diameter of the hot rolled coil by using an outer diameter measuring means provided on the C-hook; Adjusting the long diameter of the hot rolled coil to be perpendicular to the C-hook by using a driving roll provided in the lower hanger; And arranging and lifting the C-hook on which the hot rolled coil is mounted on a holder to correct the shape of the hot rolled coil by its own weight.

Another aspect of the present invention relates to a method for straightening a shape of a hot rolled coil. In one embodiment the shape correction method of the hot rolled coil comprises the steps of seating the hot rolled coil on the bottom hanger of the C-hook; Measuring the long diameter of the hot rolled coil by using an outer diameter measuring means provided on the C-hook; Adjusting the long diameter of the hot rolled coil to be perpendicular to the C-hook by using a driving roll provided in the lower hanger; And arranging and lifting the C-hook on which the hot rolled coil is mounted on a holder, thereby correcting the shape of the hot rolled coil by its own weight. The hot rolled coil includes carbon (C): 0.18 to 0.56 wt% , Silicon (Si): 0.1-0.5% by weight, manganese (Mn): 0.7-6.5% by weight, phosphorus (P): more than 0 and 0.02% by weight or less, sulfur (S): more than 0 and 0.02% by weight or less, chromium (Cr ): Reheat the slab steel containing more than 0 and 0.3% by weight or less, boron (B): more than 0 and 0.004% by weight, titanium (Ti): 0.01 to 0.04% by weight and residual iron (Fe) and other unavoidable impurities ; Hot-rolling the slab steel at a finish rolling temperature of 850 ° C. to 950 ° C. to form a hot rolled sheet; And cooling the hot rolled sheet material and winding the coil at a winding temperature of 700 ° C. or higher.

In one embodiment, the hot rolled coil is carbon (C): 0.21 to 0.37% by weight, silicon (Si): 0.1 to 0.4% by weight, manganese (Mn): 1.1 to 1.5% by weight, phosphorus (P): greater than 0 0.02 Wt% or less, sulfur (S): more than 0 and 0.02 wt% or less, chromium (Cr): 0.1 to 0.3 wt%, boron (B): 0.001 to 0.004 wt%, titanium (Ti): 0.01 to 0.04 wt% and the balance Of iron (Fe) and other unavoidable impurities.

In one embodiment, the hot rolled sheet may be cooled to be wound at a winding temperature of 700 ° C. to 900 ° C.

By applying the hot rolled coil manufactured by the method of manufacturing a hot rolled coil of the present invention, when the shape is corrected, the phase transformation of the steel is delayed during the hot rolling and cooling, thereby preventing the deterioration of the material and the properties of the hot rolled coil, and excellent in preventing deformation of the hot rolled coil. By using self-gravity and gravity calibration, surface defects such as scratching of hot rolled coils by external force calibration can be prevented, and the cost of calibration can be reduced, so that economic efficiency can be excellent.

1 shows a method for manufacturing a hot rolled coil according to an embodiment of the present invention.

Figure 2 shows a shape correction method of a hot rolled coil according to an embodiment of the present invention.

3 schematically illustrates a shape correction method of a hot rolled coil according to one embodiment of the present invention.

Figure 4 (a) is a photograph immediately after the winding of an embodiment hot rolled coil according to the present invention, Figure 4 (b) is a photograph after the air cooling of the hot rolled coil.

Figure 5 (a) is a photograph immediately after the winding of another embodiment hot rolled coil according to the present invention, Figure 5 (b) is a photograph after the air cooling of the hot rolled coil.

FIG. 6A is a photograph immediately after winding up a comparative example hot rolled coil according to the present invention, and FIG. 6B is a photograph after air cooling of the hot rolled coil.

Figure 7 is a graph comparing the phase transformation curve of the hot rolled coil according to the hot rolled coil manufacturing and shape correction time progress of the embodiment and the comparative example for the present invention.

Hereinafter, the present invention will be described in detail. In this case, when it is determined that the detailed description of the related known technology or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The terms to be described below are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators, and the definitions should be made based on the contents throughout the specification for describing the present invention.

Hot rolled coil manufacturing method

One aspect of the present invention relates to a hot rolled coil manufacturing method. 1 shows a method for manufacturing a hot rolled coil according to an embodiment of the present invention. In one embodiment the hot rolled coil manufacturing method (S10) slab steel reheating step; (S20) hot rolling step; And (S30) winding-up step. More specifically, the hot rolled coil manufacturing method is (S10) carbon (C): 0.18 to 0.56% by weight, silicon (Si): 0.1 to 0.5% by weight, manganese (Mn): 0.7 to 6.5% by weight, phosphorus (P) : More than 0 and 0.02% by weight or less, sulfur (S): more than 0 and 0.02% by weight or less, chromium (Cr): more than 0 and 0.3% by weight or less, boron (B): more than 0 and 0.004% by weight or less, titanium (Ti): 0.01 Reheating the slab steel containing -0.04 wt% and remaining iron (Fe) and other unavoidable impurities; (S20) hot rolling the slab steel at a finish rolling temperature: 850 ° C. to 950 ° C. to form a hot rolled sheet; And (S30) cooling the hot rolled sheet material and winding the coil at a winding temperature of 700 ° C. or higher.

Hereinafter, a method for manufacturing a hot rolled coil according to the present invention will be described in detail step by step.

(S10) slab steel reheating stage

The step is carbon (C): 0.18 to 0.56% by weight, silicon (Si): 0.1 to 0.5% by weight, manganese (Mn): 0.7 to 6.5% by weight, phosphorus (P): greater than 0 and 0.02% by weight or less, sulfur ( S): more than 0 and 0.02% by weight or less, chromium (Cr): more than 0 and 0.3% by weight or less, boron (B): more than 0 and 0.004% by weight or less, titanium (Ti): 0.01 to 0.04% by weight and the balance of iron (Fe) ) And other unavoidable impurities.

Hereinafter, the components included in the slab steel will be described in detail.

Carbon (C)

Carbon (C) is added to secure the strength. The carbon is included 0.18 to 0.56% by weight based on the total weight of the slab steel. If the carbon content is less than 0.18% by weight, it may be difficult to secure sufficient strength. In contrast, when the carbon content exceeds 0.56% by weight, toughness may occur.

Silicon (Si)

The silicon (Si) is added to enhance the function and solid solution of the deoxidizer to remove oxygen in the steel. In one embodiment the silicon is included in 0.1 to 0.5% by weight based on the total weight of the slab steel. When the silicon content is less than 0.1% by weight, the addition effect is insignificant, and when the content of the silicon is more than 0.5% by weight, the weldability is lowered and a red scale is generated during reheating and hot rolling to improve the surface quality. It can have a detrimental effect. In addition, it may adversely affect the plating property after welding.

Manganese (Mn)

The manganese (Mn) is an element that is effective in securing strength by improving hardenability of steel as a solid solution strengthening element. In addition, manganese is an austenite stabilizing element, which delays ferrite and pearlite transformation and contributes to grain refinement of ferrite.

In one embodiment the manganese is included 0.7 to 6.5% by weight relative to the total weight of the slab steel. When the content of the manganese is included in less than 0.7% by weight may have a solid solution strengthening effect. On the contrary, when the manganese content exceeds 6.5% by weight, weldability is greatly reduced. In addition, there is a problem of greatly reducing the ductility of the steel sheet by the generation of MnS inclusions and the generation of center segregation.

Phosphorus (P)

The phosphorus (P) is added to inhibit cementite formation and increase strength. However, phosphorus deteriorates weldability and causes a final material deviation by slab center segregation. Therefore, in the present invention, the content of phosphorus (P) is limited to more than 0 and 0.02% by weight or less of the total weight.

Sulfur (S)

Sulfur (S) is an element that inhibits the toughness and weldability of the steel, and combines with manganese to form MnS non-metallic inclusions to generate cracks during processing of the steel. Therefore, the content of sulfur (S) is limited to more than 0 and 0.02% by weight or less based on the total weight of the slab steel.

Chrome (Cr)

The chromium (Cr) is added for the purpose of improving the hardenability and strength of the steel. In one embodiment, the chromium is included in more than 0 0.3% by weight based on the total weight of the slab steel. When the chromium is included in an amount of more than 0.3 wt%, the toughness of the hot rolled coil may decrease.

Boron (B)

The boron (B) is added for the purpose of compensating quenchability by replacing molybdenum, which is an expensive quenchable element, and has a grain refinement effect by increasing austenite grain growth temperature.

In one embodiment the boron is greater than 0 and less than 0.004% by weight based on the total weight of the slab steel. Including the boron in excess of 0.004% by weight may increase the risk of inferior elongation.

Titanium (Ti)

The titanium (Ti) is added for the purpose of strengthening the hardenability by forming precipitates and improving materials. In addition, by forming a precipitated phase such as Ti (C, N) at a high temperature, it effectively contributes to the austenite grain refinement.

In one embodiment, the titanium is included 0.01 to 0.04% by weight based on the total weight of the slab steel. When the titanium is included in less than 0.01% by weight, the addition effect is insignificant, when it contains more than 0.04% by weight, poor performance occurs, it is difficult to secure the properties of the hot rolled coil, cracks may occur on the surface of the hot rolled coil.

The remainder other than the above components consists essentially of iron (Fe). Here, the remainder substantially made of iron (Fe) means that it may be included in the scope of the present invention to include other trace elements, including inevitable impurities, as long as the action effect of the present invention is not impeded.

In one embodiment, the slab steel may be applied to a medium carbon-based hot rolled coil. For example, the slab steel, carbon (C): 0.21 to 0.37% by weight, silicon (Si): 0.1 to 0.4% by weight, manganese (Mn): 1.1 to 1.5% by weight, phosphorus (P): greater than 0 0.02 weight % Or less, sulfur (S): more than 0 and 0.02% by weight or less, chromium (Cr): 0.1 to 0.3% by weight, boron (B): 0.001 to 0.004% by weight, titanium (Ti): 0.01 to 0.04% by weight and residual amount Iron and other unavoidable impurities.

In another embodiment the slab steel may be applied to high manganese hot rolled coils. For example, the slab steel, carbon (C): 0.18 to 0.25% by weight, silicon (Si): 0.3 to 0.5% by weight, manganese (Mn): 2 to 6.5% by weight, phosphorus (P): greater than 0 0.02 weight % Or less, sulfur (S): more than 0 and 0.01 wt% or less, chromium (Cr): more than 0 and 0.1 wt% or less, boron (B): more than 0 and 0.001 wt% or less, titanium (Ti): 0.01 to 0.04 wt% and May contain residual amounts of iron (Fe) and other unavoidable impurities.

In another embodiment, the slab steel may be applied to a high carbon hot rolled coil. For example, the slab steel, carbon (C): 0.5 to 0.56% by weight, silicon (Si): 0.1 to 0.3% by weight, manganese (Mn): 0.7 to 1% by weight, phosphorus (P): greater than 0 0.02 weight % Or less, sulfur (S): more than 0 and 0.01% by weight or less, chromium (Cr): 0.1 to 0.3% by weight, boron (B): more than 0 and 0.001% by weight or less, titanium (Ti): 0.01 to 0.02% by weight and residual amount Of iron (Fe) and other unavoidable impurities.

In one embodiment, the slab steel may be heated at slab reheating temperature (SRT): 1,150 ℃ ~ 1,250 ℃. At the slab reheating temperature, the homogenizing effect of the alloying elements may be excellent.

(S20) hot rolling step

The step is a step of hot rolling the slab steel at the finish rolling temperature: 850 ℃ ~ 950 ℃ condition to form a hot rolled sheet material. When hot rolling at the finish rolling temperature, the stiffness and formability of the hot rolled coil can be excellent at the same time, the workability at the time of winding, can be excellent in preventing the distortion of the hot rolled coil.

(S30) winding step

The step is the step of cooling the hot rolled sheet, the winding temperature: 700 ℃ or more. In one embodiment, the hot rolled sheet may be cooled by winding up to the winding temperature condition. In one embodiment, the cooling can be carried out using air cooling without pouring cooling water. When cooling under the above conditions, occurrence of duckbill defects in the hot rolled coil can be effectively reduced. Here, the duckbill defect may mean a shape distortion defect of the hot rolled coil. Specifically, the duckbill defect may refer to a shape deformation defect in which the hot rolled coil is crushed in the direction of gravity, among the shape defects occurring in the wound hot rolled coil, so that the inner and outer diameters of the coil change to an ellipse rather than a round shape.

After hot rolling the plate containing the alloying component of the present invention, cooling control can be carried out so that the winding is completed above the temperature at which the phase transformation starts. When winding up at the winding temperature conditions, since the ferrite phase transformation starts after a certain time after the winding, due to the slow cooling effect (air cooling) of the coil after winding up, the time of phase transformation is rapidly increased, which may advantageously prevent the deformation. . That is, in one embodiment of the present invention, after winding, the process conditions for delaying the time when the ferrite phase transformation occurs as possible can be presented.

When the hot rolled sheet is wound at a coiling temperature of less than 700 ° C., the phase transformation of the hot rolled sheet proceeds during the cooling process, and additional phase transformation occurs when the hot rolled coil is formed, thereby expanding the coil volume, and then decreasing the temperature as the hot rolled coil is By contracting and deforming the shape into an elliptical shape due to its own weight, the duckbill defect may occur. In one embodiment, the hot rolled sheet may be cooled to be wound at a winding temperature of 700 ° C. to 900 ° C. For example, winding temperature: It can wind up at 730 degreeC-820 degreeC. The manufactured hot rolled coil may include ferrite and bainite microstructures.

Shape correction method of hot rolled coil

Another aspect of the invention relates to a method for straightening the shape of a hot rolled coil. Figure 2 shows a shape correction method of a hot rolled coil according to an embodiment of the present invention. Referring to Figure 2, the shape correction method of the hot rolled coil (S101) hot rolled coil seating step; (S102) hot rolled coil long diameter measuring step; (S103) hot rolled coil position adjustment step; And (S104) lifting step.

3 schematically illustrates a shape correction method of a hot rolled coil according to one embodiment of the present invention. Referring to FIG. 3, the shape correction method of the hot rolled coil may include: mounting the hot rolled coil on a bottom hanger of the C-hook; (S102) measuring the long diameter of the hot rolled coil using the outer diameter measuring means provided on the upper portion of the C-hook; (S103) adjusting the long diameter of the hot rolled coil to be perpendicular to the C-hook by using the driving roll provided in the lower hanger; And (S104) arranging and lifting the C-hook on which the hot rolled coil is mounted on a holder, thereby correcting the shape of the hot rolled coil by its own weight.

For example, the hot rolled coil 100 is seated on the lower hanger 201 of the C-hook 200 as shown in FIG. 3 (a), and is provided on the upper part of the C-hook 202 as shown in FIG. 3 (b). The long diameter of the hot rolled coil 100 is measured using the outer diameter measuring means 210. Next, using the driving roll 220 provided in the lower hanger 201 as shown in FIG. 3 (c), the long diameter of the hot rolled coil 100 is adjusted to be perpendicular to the C-hook, and FIG. 3. By placing and lifting the C-hook 200 on which the hot rolled coil is seated, as shown in (e), on the holder 300, the shape of the hot rolled coil crushed in an elliptical shape as shown in FIG. have.

The hot rolled coil is carbon (C): 0.18 to 0.56% by weight, silicon (Si): 0.1 to 0.5% by weight, manganese (Mn): 0.7 to 6.5% by weight, phosphorus (P): more than 0 and 0.02% by weight or less, Sulfur (S): more than 0 and 0.02 wt% or less, Chromium (Cr): more than 0 and 0.3 wt% or less, boron (B): more than 0 and 0.004 wt% or less, titanium (Ti): 0.01 to 0.04 wt% and the balance of iron Reheating the slab steel containing (Fe) and other unavoidable impurities; Hot-rolling the slab steel at a finish rolling temperature of 850 ° C. to 950 ° C. to form a hot rolled sheet; And cooling the hot rolled sheet material and winding the coil at a winding temperature of 700 ° C. or higher. In one embodiment, the hot rolled coil may be manufactured by cooling the hot rolled sheet and wound at a coiling temperature of 700 ° C. to 900 ° C. The manufactured hot rolled coil may include ferrite and bainite microstructures.

Since the hot rolled coil manufacturing method may be performed using the same slab steel as the hot rolled coil manufacturing method described above, a detailed description thereof will be omitted.

In one embodiment, the hot rolled coil may be a medium carbon-based hot rolled material. Carbon (C): 0.21 to 0.37 wt%, Silicon (Si): 0.1 to 0.4 wt%, Manganese (Mn): 1.1 to 1.5 wt%, Phosphorus (P): more than 0 and 0.02 wt% or less, Sulfur (S): More than 0 and 0.02% by weight or less, chromium (Cr): 0.1 to 0.3% by weight, boron (B): 0.001 to 0.004% by weight, titanium (Ti): 0.01 to 0.04% by weight and the balance of iron (Fe) and other unavoidable impurities It may include.

In another embodiment, the hot rolled coil may be a high manganese-based hot rolled material. Carbon (C): 0.18 to 0.25 wt%, Silicon (Si): 0.3 to 0.5 wt%, Manganese (Mn): 2 to 6.5 wt%, Phosphorus (P): more than 0 and 0.02 wt% or less, Sulfur (S): Greater than 0 and 0.01% by weight or less, chromium (Cr): greater than 0 and 0.1% by weight or less, boron (B): greater than 0 and 0.001% by weight or less, titanium (Ti): 0.01 to 0.04% by weight and the balance of iron (Fe and other unavoidable It may contain impurities.

In another embodiment, the hot rolled coil may be a high carbon based hot rolled material. Carbon (C): 0.5-0.56 wt%, Silicon (Si): 0.1-0.3 wt%, Manganese (Mn): 0.7-1 wt%, Phosphorus (P): more than 0 and 0.02 wt% or less, Sulfur (S): More than 0 and 0.01% by weight or less, chromium (Cr): 0.1 to 0.3% by weight, boron (B): more than 0 and 0.001% by weight or less, titanium (Ti): 0.01 to 0.02% by weight and the balance of iron (Fe) and other unavoidable It may contain impurities.

By applying the hot rolled coil manufactured by the method of manufacturing a hot rolled coil of the present invention, when the shape is corrected, the phase transformation of the steel is delayed during the hot rolling and cooling, thereby preventing the deterioration of the material and the properties of the hot rolled coil, and excellent in preventing deformation of the hot rolled coil. By using self-gravity and gravity calibration, it is possible to prevent surface defects such as scratching of hot rolled coils by external force calibration, and to reduce calibration costs by excluding calibration equipment by external force. Can be.

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, this is presented as a preferred example of the present invention and in no sense can be construed as limiting the present invention.

Examples and Comparative Examples

Example 1

As a medium carbon-based material, carbon (C): 0.23 wt%, silicon (Si): 0.2 wt%, manganese (Mn): 1.2 wt%, phosphorus (P): 0.015 wt%, sulfur (S): 0.01 wt% , Reheating the slab steel at 1200 ° C. comprising chromium (Cr): 0.2% by weight, boron (B): 0.003% by weight, titanium (Ti): 0.02% by weight and residual iron (Fe) and other unavoidable impurities, The slab steel was hot rolled at a finish rolling temperature of 880 ° C. to form a hot rolled sheet. Then, the hot rolled sheet was cooled and wound at a coiling temperature of 700 ° C. to produce a hot rolled coil.

Example 2

As a high manganese-based material, carbon (C): 0.2 wt%, silicon (Si): 0.4 wt%, manganese (Mn): 6 wt%, phosphorus (P): 0.015 wt%, sulfur (S): 0.01 wt% , Reheating the slab steel at 1200 ° C. containing 0.05% by weight of chromium (Cr), 0.001% by weight of boron (B), 0.02% by weight of titanium (Ti) and the balance of iron (Fe) and other unavoidable impurities The slab steel was hot rolled at a finish rolling temperature of 940 ° C. to form a hot rolled sheet. Then, the hot rolled sheet was cooled and wound at a coiling temperature of 700 ° C. to produce a hot rolled coil.

Example 3

As a high carbon material, carbon (C): 0.55% by weight, silicon (Si): 0.2% by weight, manganese (Mn): 0.8% by weight, phosphorus (P): 0.015% by weight, sulfur (S): 0.01% by weight, Reheating the slab steel containing chromium (Cr): 0.2% by weight, boron (B): 0.001% by weight, titanium (Ti): 0.01% by weight and residual iron (Fe) and other unavoidable impurities at 1200 ° C., The slab steel was hot rolled at a finish rolling temperature of 890 ° C. to form a hot rolled sheet. Then, the hot rolled sheet was cooled and wound at a coiling temperature of 730 ° C. to produce a hot rolled coil.

Comparative Example 1

A hot rolled coil was manufactured in the same manner as in Example 1 except that the hot rolled sheet was wound at a winding temperature of 560 ° C.

Comparative Example 2

A hot rolled coil was manufactured in the same manner as in Example 1, except that the hot rolled sheet was wound at a winding temperature of 600 ° C.

Comparative Example 3

A hot rolled coil was manufactured in the same manner as in Example 1, except that the hot rolled sheet was wound at a winding temperature of 620 ° C.

Comparative Example 4

A hot rolled coil was manufactured in the same manner as in Example 1 except that the hot rolled sheet was wound at a winding temperature of 650 ° C .;

Figure 4 (a) is a photograph immediately after the winding of the first embodiment hot rolled coil according to the present invention, Figure 4 (b) is a photograph after the air cooling of the hot rolled coil, Figure 5 (a) is implemented according to the present invention Example 1 is a picture immediately after the winding of the hot rolled coil, FIG. 5B is a picture after the air cooling of the hot rolled coil, and FIG. 6A is a picture immediately after the winding of the comparative example hot rolled coil according to the present invention. (b) is a photograph after air cooling of the hot rolled coil. Referring to FIGS. 4A and 4B, in Example 1, a duckbill defect was not observed immediately after winding of the hot rolled coil, but during the air cooling, a duckbill defect was observed. However, it was confirmed that the degree of duckbill defects is smaller than that of the comparative example. Referring to FIGS. 5A and 5B, in Example 2, a duckbill defect was not observed immediately after winding of the hot rolled coil and after air cooling, respectively. Referring to (a) and (b) of FIG. 6, in the comparative example, the duckbill defect was observed immediately after the coiling of the hot rolled coil, and the degree of the duckbill defect was increased as the air cooling progressed.

Hot rolled coil shape correction

Shape correction was performed about the hot rolled coils of the said Examples 1-3 and Comparative Examples 1-4. The hot rolled coil was seated on the bottom hanger of the C-hook, and the long diameter of the hot rolled coil was measured by using an outer diameter measuring means provided at the upper part of the C-hook. Subsequently, by using the driving roll provided on the lower hanger, the long diameter of the hot rolled coil is adjusted to be perpendicular to the C-hook, and the C-hook on which the hot rolled coil is seated is placed on a holder and lifted, The shape of the hot rolled coil was corrected by its own weight.

For Examples 1 to 3 and Comparative Examples 1 to 4, the inner diameter of the coil and whether or not the duckbill defect was improved after the shape correction were observed, and the results are shown in Table 1 below.

division	Coiling temperature [℃]	Coil Inner Diameter [mm]	Whether or not correcting duckbill defects by shape correction
Example 1	700	740	correction
Example 2	730	760	correction
Example 3	730	740	correction
Comparative Example 1	560	700	Uncalibrated
Comparative Example 2	600	710	Uncalibrated
Comparative Example 3	620	680	Uncalibrated
Comparative Example 4	650	720	Uncalibrated

Referring to FIG. 1, in the case of Examples 1 to 3, the duckbill defect did not occur after the calibration, but in Comparative Examples 1 to 4 outside the winding temperature of the present invention, the duckbill defect of the coil was not properly corrected even after the calibration. It was found out.

7 is a graph comparing the phase transformation curves of the hot rolled coils according to the production of the hot rolled coils of Example 1 and Comparative Example 1 and the progress of shape correction time. Referring to FIG. 7, in Example 1 of the present invention, after applying a specific alloy component system and winding at a temperature (700 ° C.) or more above a phase transformation temperature, the phase transformation into ferrite is wound up to manufacture a hot rolled coil. Since the process proceeds after a certain time has elapsed, the time required for phase transformation to increase due to the slow cooling effect (air cooling) of the coil after winding was found to be advantageous for shape correction. On the other hand, in the case of Comparative Example 1 wound below the hot-rolled sheet phase transformation temperature, the ferrite phase transformation occurs earlier than Example 1, it was difficult to secure the phase transformation start time of the present invention, it was found that it is disadvantageous in shape correction.

In addition, according to the method of manufacturing and shape correction of the hot rolled coil of the present invention, by improving the generation of the duckbill of the hot rolled coil, further work such as internal cut-off, work time delay, equipment damage, etc. caused by the duckbill coil in the post-correction correction process By reducing the efficiency, the efficiency of the work, the quality of the material, and the scrapping rate of the scraped products were reduced.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (9)

1. Carbon (C): 0.18 to 0.56% by weight, Silicon (Si): 0.1 to 0.5% by weight, manganese (Mn): 0.7 to 6.5% by weight, phosphorus (P): greater than 0 and 0.02% by weight or less, sulfur (S): More than 0 and 0.02% by weight or less, chromium (Cr): more than 0 and 0.3% by weight or less, boron (B): more than 0 and 0.004% by weight or less, titanium (Ti): 0.01 to 0.04% by weight and the remaining iron (Fe) and others Reheating the slab steel containing unavoidable impurities;

   Hot rolling the slab steel at a finish rolling temperature of 850 ° C. to 950 ° C. to form a hot rolled sheet; And

   Cooling the hot rolled sheet, winding temperature: winding at 700 ℃ or more; hot rolled coil manufacturing method comprising a.
2. The method of claim 1,

   The slab steel, carbon (C): 0.21 to 0.37% by weight, silicon (Si): 0.1 to 0.4% by weight, manganese (Mn): 1.1 to 1.5% by weight, phosphorus (P): more than 0 and 0.02% by weight or less, Sulfur (S): more than 0 and 0.02% by weight or less, Chromium (Cr): 0.1 to 0.3% by weight, boron (B): 0.001 to 0.004% by weight, titanium (Ti): 0.01 to 0.04% by weight and the balance of iron (Fe) ) And other unavoidable impurities.
3. The method of claim 1,

   The slab steel, carbon (C): 0.18 to 0.25% by weight, silicon (Si): 0.3 to 0.5% by weight, manganese (Mn): 2 to 6.5% by weight, phosphorus (P): more than 0 and 0.02% by weight or less, Sulfur (S): more than 0 and 0.01 wt% or less, Chromium (Cr): more than 0 and 0.1 wt% or less, boron (B): more than 0 and 0.001 wt% or less, titanium (Ti): 0.01 to 0.04 wt% and the balance of iron A method for producing a hot rolled coil, comprising (Fe) and other unavoidable impurities.
4. The method of claim 1,

   The slab steel, carbon (C): 0.5 to 0.56% by weight, silicon (Si): 0.1 to 0.3% by weight, manganese (Mn): 0.7 to 1% by weight, phosphorus (P): more than 0 and 0.02% by weight or less, Sulfur (S): more than 0 and 0.01 wt% or less, Chromium (Cr): 0.1 to 0.3 wt% and boron (B): more than 0 and 0.001 wt% or less, titanium (Ti): 0.01 to 0.02 wt% and the balance of iron ( Fe) and other inevitable impurities containing hot rolled coil manufacturing method.
5. The method of claim 1,

   Cooling the hot rolled sheet material, the hot rolled coil manufacturing method characterized in that the winding temperature at 700 ℃ ~ 900 ℃.
6. Placing the hot rolled coil in the bottom hanger of the C-hook;

   Measuring the long diameter of the hot rolled coil by using an outer diameter measuring means provided on the C-hook;

   Adjusting the long diameter of the hot rolled coil to be perpendicular to the C-hook by using a driving roll provided in the lower hanger; And

   And arranging and lifting the C-hook on which the hot rolled coil is seated on a holder, thereby correcting the shape of the hot rolled coil by its own weight.

   Shape correction method of hot rolled coil.
7. Placing the hot rolled coil in the bottom hanger of the C-hook;

   Measuring the long diameter of the hot rolled coil by using an outer diameter measuring means provided on the C-hook;

   Adjusting the long diameter of the hot rolled coil to be perpendicular to the C-hook by using a driving roll provided in the lower hanger; And

   And arranging and lifting the C-hook on which the hot rolled coil is mounted on a holder, thereby correcting the shape of the hot rolled coil by its own weight.

   The hot rolled coil is carbon (C): 0.18 to 0.56% by weight, silicon (Si): 0.1 to 0.5% by weight, manganese (Mn): 0.7 to 6.5% by weight, phosphorus (P): more than 0 and 0.02% by weight or less, Sulfur (S): more than 0 and 0.02 wt% or less, Chromium (Cr): more than 0 and 0.3 wt% or less, boron (B): more than 0 and 0.004 wt% or less, titanium (Ti): 0.01 to 0.04 wt% and the balance of iron Reheating the slab steel containing (Fe) and other unavoidable impurities;

   Hot-rolling the slab steel at a finish rolling temperature of 850 ° C. to 950 ° C. to form a hot rolled sheet; And

   Cooling the hot rolled sheet, winding temperature: winding at 700 ℃ or more; shape correction method of the hot rolled coil characterized in that it is produced.
8. The method of claim 7, wherein

   The hot rolled coil is carbon (C): 0.21 to 0.37% by weight, silicon (Si): 0.1 to 0.4% by weight, manganese (Mn): 1.1 to 1.5% by weight, phosphorus (P): greater than 0 and 0.02% by weight or less, Sulfur (S): more than 0 and 0.02% by weight or less, Chromium (Cr): 0.1 to 0.3% by weight, boron (B): 0.001 to 0.004% by weight, titanium (Ti): 0.01 to 0.04% by weight and the balance of iron (Fe) ) And other unavoidable impurities.
9. The method of claim 7, wherein

   The hot rolled sheet is cooled and wound at a winding temperature of 700 ° C to 900 ° C.

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