KR101778179B1 - Method for preventing curve of hot rolling material - Google Patents

Abstract

The present invention discloses a method of preventing deformation of a hot-rolled material. According to an embodiment of the present invention, in an advanced steel continuous hot rolling method in which both ends of a plurality of bonding materials are overlapped and subjected to shear deformation and joining, included are: forming a surface modification layer by cladding using a modifying material having a content of Si and Cr smaller than that of the bonding material at one or more joining sites of both ends where the bonding material is overlapped; and performing shear deformation by overlapping both ends of the plurality of bonding materials, wherein the bonding material and the modifying material have a high temperature tensile strength in the range of 1:0.8 to 1:1.2.

Description

METHOD FOR PREVENTING CURVE OF HOT ROLLING MATERIAL [0001]

The present invention relates to a method for minimizing strain during hot rolling, and more particularly, to a method for minimizing excessive bending that occurs during hot rolling of a material having a surface-modified surface.

In recent years, continuous continuous rolling techniques have been developed in which finishing rolling can be continuously performed by joining a line and a trailing metal plate between a rough rolling mill and a finishing rolling mill.

For example, a technique has been known in which the front end portion of the leading metal plate is overlapped with the front end portion of the trailing metal plate, and the overlapped portions of the metal plate are simultaneously sheared so that the front end surface of the metal plate produced in the shearing process is directly contacted.

This technique has many merits as a continuous continuous rolling technique such as simple joining by shearing, short joining, short space requirement, and low temperature drop during rolling.

However, in the case of joining high-grade steel using the above-mentioned conventional joining technique, there is a problem that it is difficult to secure the ductability of the high-grade steel due to the lowered bonding strength ratio.

Normally, the joint strength ratio should be 70% or more in order to ensure the ductability of high-grade steel during continuous continuous rolling.

However, in the case of high-grade steel, a large amount of scale is generated on the surface due to the alloy component, and it is not removed well by descaling work. For example, Si-based scale or Cr-based scale is produced on the surface of high carbon steel, electric steel sheet and stainless steel, which is one kind of high-grade steel. Especially, Si-based scale and Cr-based scale are difficult to remove and remain in large amounts on the surface.

When such a high-grade steel is subjected to the shear joining by the above joining technique, a large amount of scale is mixed into the joining surface and the joining strength ratio is lowered, thereby failing to secure the ducting property in the continuous rolling of high-grade steel.

Therefore, it is necessary to develop a material joining technique that can improve the joining strength ratio of the high-grade steel joining portion and ensure the ducting quality of the high-grade steel.

Korean Patent Publication No. 10-2012-0075308 (published Jul. 6, 2012)

Embodiments of the present invention provide a method of preventing deformation of a hot rolled material by modifying the surface of a high-grade steel in a slab state prior to hot rolling so as to increase the joint strength at the time of shearing the continuous hot rolled material, do.

A method for preventing deformation of a hot rolled material by superimposing both ends of a plurality of bonded materials according to an embodiment of the present invention to shear deformation to join the bonded material is characterized in that at least one of the two ends of the bonded material is overlapped, Forming a surface modification layer using a modified material having a content smaller than that of the bonded material, and shear deformation by superimposing both ends of the plurality of bonded materials, wherein the modified material has a high temperature tensile strength Lt; RTI ID = 0.0 > 80% < / RTI >

Also, according to an embodiment of the present invention, the bonding material may be a high-grade steel slab including at least one selected from the group consisting of Si and Cr.

According to an embodiment of the present invention, the bonding material may be an electrical steel sheet containing Si in an amount of 1 wt% or more.

Also, according to an embodiment of the present invention, the modified material may contain 5 wt% or more of Al.

Also, according to an embodiment of the present invention, the modified material may have a ferrite phase in an entire temperature range from a high temperature region where hot rolling is performed to a cold room temperature region.

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According to an embodiment of the present invention, the Si content of the surface modification layer is 1.5 wt% or less, and the Si content in the region within 6 mm from the surface layer of the surface modification layer may be 0.5 wt% or less.

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Also, according to an embodiment of the present invention, the surface modification layer may be formed over the whole vertical direction of rolling of the bonded material.

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According to an embodiment of the present invention, the surface modification layer may be formed to have a pattern in a direction perpendicular to the rolling direction of the bonded material.

According to an embodiment of the present invention, the modified material may be a strip.

Further, according to an embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, which comprises performing flux cored arc welding (FCAW) or metal cored arc welding (MCAW) on the joint and placing the reformed material on the weld have.

Further, according to an embodiment of the present invention, the welding can be performed one pass.

According to an embodiment of the present invention, there is also provided a method of manufacturing a semiconductor device, comprising: applying a dissolution material, which is obtained by vacuum-dissolving a powder containing an alloy component of the modified material, to the junction region; and disposing the modified material on the dissolution material .

Also, according to one embodiment of the present invention, the dissolving material is applied to the joint portion by a spraying method, and the modified material may be strip cladded continuously on the dissolving material to be applied.

According to an embodiment of the present invention, the bonding material having the surface modification layer may be reheated and rough-rolled at a temperature of 1,100 to 1,300 ° C for 1 to 5 hours.

The embodiments of the present invention can improve the strength of the joint portion in the front end joining of the continuous hot rolled material by modifying the surface of the high-grade steel in the slab state before hot rolling, thereby securing a bonding strength ratio of 70% or more, It is possible to minimize a bending deformation phenomenon at the time of hot rolling and to prevent a progress fault during rolling, and it is possible to improve the rate of rolling of joints.

1 is a view for explaining an advanced steel continuous hot rolling facility according to an embodiment of the present invention.
2 is a view for explaining an adapter according to an embodiment of the present invention.
FIGS. 3 to 6 are photographs of the surface scales of the high-grade steel slabs before surface modification according to an embodiment of the present invention.
7 is a perspective view for explaining a conventional advanced steel continuous hot rolling method.
8 is a perspective view for explaining a method of preventing deformation of hot rolled material according to an embodiment of the present invention.
9 to 11 are perspective views illustrating a surface modification layer according to an embodiment of the present invention.
12 is a perspective view illustrating a method of forming a surface modified layer of a high grade steel slab according to an embodiment of the present invention.
13 is a cross-sectional view of a high-grade steel having a surface modification layer after rough rolling.
FIG. 14 is a cross-sectional view of a high-grade steel having a surface modification layer according to an embodiment of the present invention after rough rolling; FIG.
15 is a graph for explaining the high temperature tensile strength according to the Al content of a general steel.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present invention to a person having ordinary skill in the art to which the present invention belongs. The present invention is not limited to the embodiments shown herein but may be embodied in other forms. For the sake of clarity, the drawings are not drawn to scale, and the size of the elements may be slightly exaggerated to facilitate understanding.

1 is a view for explaining an advanced steel continuous hot rolling facility according to an embodiment of the present invention. 2 is a view for explaining an adapter according to an embodiment of the present invention.

1 and 2, an advanced steel continuous hot rolling process according to an embodiment of the present invention will be described.

1, the hot rolling apparatus according to the present invention includes a reheating furnace 10, a roughing mill 20, a coil box 30, a joining apparatus 40, a plurality of rolling mills, A rolling mill 50, and a down coiler 60.

A metal bar of a high-grade steel produced by rolling a high-grade steel slab in the rough rolling mill 10 is wound into a coil state in the coil box 30. Such a coil box 30 adjusts the speed difference between the roughing mill 20 and the metal bar running in the finishing mill 50.

After the tip of the trailing metal bar 2 unwound from the coil box 30 is cut by the crush shear, the surface of the portion to be joined of the metal bar to be joined is descaled by the partial descaling device 70, 40 are overlapped on the rear end of the preceding metal bar 1 in the superposition device 41.

The front end of the trailing metal bar 2 and the rear end of the preceding metal bar 1 are joined at the joinder 100 of the joining device 40 and the cropping of the joining portion is cut by the crop processing device 80. The metal bar 200 joined by the joining device 40 and brought into a continuous state is conveyed to the finishing mill 50.

Here, the joining device 40 is a device for joining the rear end of the preceding metal bar 1 and the front end of the following metal bar 2 in a running state, and is a short-time joining device capable of shear joining in a short time.

In order to perform the front end joining of the metal bars 1 and 2 in the traveling state, the adapter 100 can move according to the running of the metal bar, and the adapter 100 can swing Can be additionally installed.

For example, the adapter 100 of the bonding apparatus 40 is provided with an overlapping portion in which the rear end of the leading metal bar 1 and the leading end of the trailing metal bar 2 are overlapped with each other And a pair of shearing blades which are press-fitted and sheared while being sheared.

The metal bar 200 transferred to the finishing mill 50 is hot-rolled sequentially through a plurality of mills to a required thickness and then wound on the down coiler 60.

The hot rolling equipment according to the present invention may further include a leveler (90, 91) provided at the outlet side of the coil box (30) and the joining device (40) As shown in FIG.

Referring to FIG. 2, the adapter 100 according to an embodiment of the present invention mainly includes an upper blade assembly 120, a lower blade assembly 130, and a housing 110 for movably supporting the upper blade assembly 120, the lower blade assembly 130, and the like.

Here, the upper blade assembly 120 includes an upper blade 121, an upper clamp 122, and an upper supporting device 123, all of which are integrally formed. The lower blade assembly 130 disposed at the lower portion of the upper blade assembly 120 includes a lower blade 131, a lower clamp 132, and a lower support device 133, Consists of.

The upper blade aggregate 120 and the lower blade aggregate 130 are guided by a post portion (not shown) of the housing 110 and are moved in the thickness direction of the leading metal bar 1 and the trailing metal bar 2 Can be supported. The upper blade aggregate 120 and the lower blade aggregate 130 may be configured to be accessible and transferred by a link mechanism (not shown).

The leading end 2 'of the trailing metal bar 2 is guided in the overlapped state on the rear end 1' of the leading steel bar 1 of the advanced steel into the adapter 100 according to the present invention.

Then, the front end 2 'of the trailing metal bar 2 is overlapped on the rear end 1' of the advanced steel bar 1, and the overlapping portion of the front end 2 'and the rear end 1' And is sandwiched between the projections 124 and 134 of the blade 121 and the lower blade 131. [ That is, the projections 124 and 134 of the upper blade and the lower blade come into contact with the surfaces of the tip 2 'and the rear end 1'.

The upper clamp 122 and the lower clamp 132 come into contact with each other at a position where the rear end 1 'of the leading metal bar 1 and the leading end 2' of the trailing metal bar 2 overlap each other. Here, the upper clamp 122 is supported by the upper support device 123 by hydraulic pressure, and the lower clamp 132 is supported by the lower support device 133 by hydraulic pressure.

In this state, when the upper blade 121 and the lower blade 131 shear the leading metal bar 1 and the trailing metal bar 2, the leading edge of the leading metal bar 1 and the trailing metal bar 2 And the end faces are shear-jointed to each other by the plastic flow deformation, thereby forming the metal bar 200 integrally joined continuously.

When the end portion of the advanced steel is completed in this way, the upper crop of the trailing metal bar 2 is cut and the rear end of the preceding metal bar 1 is positioned on the joint portion of the continuous metal bar 200 1 ') is cut. When the metal bars 200 are connected to each other, the upper blade 121 and the lower blade 131 are retracted until they have a predetermined distance from each other.

The upper and lower cuts cut according to the shear joining of the metal bar are removed by the crop processor 80 shown in FIG. 1, and the continuous metal bar 200 is fed to the finishing mill 50.

When the joining portion of the metal bar passes through the finishing mill 50, strong compressive stress and bending at the time of finishing rolling, and external force such as bending or tensile between the stands of the finishing mill act on the joining portion, do.

At this time, it is necessary to maintain the bonding strength to such an extent that the joint of the high-grade steel metal bar can pass through the finishing mill 50 without breaking.

FIGS. 3 to 6 are photographs of the surface scales of the high-grade steel slabs before surface modification according to an embodiment of the present invention. 7 is a perspective view for explaining a conventional advanced steel continuous hot rolling method.

However, in the case of high-grade steels, a large amount of scale is generated on the surface when reheating is performed before hot rolling by alloying components, and these scales are hardly removed even by descaling work. Especially, Si- and Cr- It is formed into an internal scale and its removal is difficult, resulting in a large amount remaining on the surface.

FIG. 3 is a photograph of a scale existing on the surface of a high carbon steel S45C, FIG. 4 is a photograph of a scale existing on the surface of an electric steel sheet containing 2.0% of Si, And FIG. 6 is a photograph of the scale on the STS 409 steel surface.

3 to 5, it can be seen that a large amount of Si-based scale is formed on the surface of the base material because the content of Si is large in comparison with general steel or the like in the case of high carbon steel to electric steel sheet. In the case of the stainless steel according to FIG. 6, the content of Cr is large in comparison with that of general steel, and a large amount of Cr scale is formed on the surface of the base material.

That is, in the case of high-grade steels having a high content of Si and Cr such as high carbon steel, electric steel plate or stainless steel, Si-based scale or Cr-based scale is formed on the surface. Such scale is difficult to remove even by descaling work, Lt; / RTI > In addition, in the case of Si-based scale, Si is penetrated into the base material and fayalite (Fe ₂ SiO ₄ ) is formed, and descaling is further lowered. At this time, fayalite (Fe ₂ SiO ₄ ) increases as the content of Si increases do.

The inner scale or fayalite (Fe ₂ SiO ₄ ) formed on the surface of the reheated slab is concentrated between the interface of the base material and the outer scale through rough rolling. Therefore, when the steel slab having such a scale is subjected to the shear joining as shown in Fig. 7, there is a problem that a large amount of scale is mixed into the joining surface to lower the joining strength ratio of the joining portion.

8 is a perspective view for explaining a method of preventing deformation of hot rolled material according to an embodiment of the present invention.

Referring to FIG. 8, a method for preventing deformation of a hot rolled material by overlapping both ends of a plurality of bonded materials 1 and 2 according to an embodiment of the present invention, A step of forming a surface modification layer (3) by using a modified material in which the content of Si and Cr is smaller than that of the bonded material at any one or more of the overlapping ends, So as to shear deformation.

The bonding material (1, 2) contains at least one selected from the group consisting of Si and Cr in a large amount. For example, the high-grade steel slab may be an electrical steel sheet containing at least 1% by weight of Si, and preferably a grain-oriented electrical steel sheet containing at least 3% by weight of Si.

The modified material includes, by weight%, Si: not more than 0.2%, Cr: not more than 0.2%, and the balance of Fe. The modified material may further contain 0.3% or less of C, 1.6% or less of Mn, 0.3% or less of Cu, 0.04% or less of P, and 0.04% or less of S in weight percent.

The Si content and the Cr content of the surface modification layer 3 are 1.5 wt% or less. The Si content and the Cr content in the region within 6 mm from the surface layer of the surface modification layer 3 are 0.5% by weight or less.

Si and Cr are less contained in the modified material for forming the surface modification layer 3 than the bonded materials 1 and 2. However, Si and Cr contained in the bonded materials 1 and 2 may be slightly diffused into the surface modification layer 3 while reheating the slab before performing shear deformation. However, even when the diffusion of Si and Cr is considered, the Si and Cr contents in the surface layer region of the surface modification layer 3 in the reheated slab can be minimized, thereby minimizing the surface residual scale and improving the joint strength .

For example, the thickness of the surface modification layer 3 may be 5 to 20 mm.

When the thickness of the surface modification layer 3 is less than 5 mm, Si or Cr due to reheating diffuses to the surface layer region of the surface modification layer 3, and it is difficult to sufficiently secure the bonding strength. However, when the thickness of the surface modification layer 3 is more than 20 mm, problems such as an increase in cost and a change in a component of a local final product may occur. More preferably, the thickness of the surface modification layer 3 may be 6 to 10 mm.

The width of the surface modification layer 3 may be 50 to 500 mm from both ends in the rolling direction of the bonded materials 1 and 2.

When the width of the surface modification layer 3 is less than 50 mm, it is difficult for the front surface of the leading metal bar 90 and the trailing metal bar 60 to sufficiently overlap each other. When the width of the surface modification layer 3 is more than 500 mm Problems such as an increase in cost and a change in the composition of a local final product may occur. More preferably, the width of the surface modification layer 3 may be 100 to 500 mm.

9 to 11 are perspective views illustrating a surface modification layer according to an embodiment of the present invention.

Referring to FIG. 9, the surface modifying layer 3A may be formed over the whole vertical direction of the bonding material 1, 2. For example, the surface modification layer 3A may be formed over the entire width of the bonding material 1, 2.

Referring to FIGS. 10 and 11, the surface modification layers 3B and 3C may be formed so as to have a pattern perpendicular to the rolling direction of the bonded materials 1 and 2. For example, the surface modification layers 3B and 3C may be formed so as to have a pattern in the width direction of the bonded materials 1 and 2.

For example, the surface modification layer 3B may be formed only on both edge portions in the width direction of the bonding materials 1 and 2, and accordingly, the cost of forming the surface modification layer 3B may be more Can be saved. Alternatively, the surface modification layer 3C may be formed in at least two regions in the width direction of the bonding materials 1 and 2 to have an intermittent pattern, It is possible to further reduce the cost due to the formation.

Referring to FIG. 9, in the step of forming the surface modification layer 3 of the advanced steel continuous hot rolling method according to an embodiment of the present invention, the surface modification layer 3 is formed using the modified material .

At this time, for example, the modified material may be ordinary steel or low carbon steel. For example, the modified material may use various types of materials, but preferably a thin strip material may be used.

More specifically, according to the method of forming the surface modifying layer 3 according to the first embodiment of the present invention, a flux cored arc welding (FCAW) or a metal cored arc welding (MCAW) is performed on the joint portion And placing the modified material on the welded portion.

In the case of performing the welding, for example, 80% Ar and 20% CO ₂ are used as the protective gas, and a current of 250 to 400 A, a voltage of 25 to 35 V, an input heat of 8 to 12 kJ / / min. < / RTI > At this time, the welding wire may contain iron powder as a flux, or iron powder may be used as the iron powder.

For example, the welding can be performed in one pass.

After the welding is performed, a modified material is disposed on the welded portion, and the bonded material (1) having the surface modified layer (3) is subjected to reheating and rough rolling for 1 to 5 hours at a temperature of 1,100 to 1,300 ° C can do.

Si and Cr are less contained in the modified material for forming the surface modification layer 3 than the bonded materials 1 and 2. However, Si and Cr contained in the bonded materials 1 and 2 may be slightly diffused into the surface modification layer 3 while reheating the slab before performing shear deformation. However, even when the diffusion of Si and Cr is considered, the Si and Cr contents in the surface layer region of the surface modification layer 3 in the reheated slab can be minimized, thereby minimizing the surface residual scale and improving the joint strength .

12 is a perspective view illustrating a method of forming a surface modified layer of a high grade steel slab according to an embodiment of the present invention.

According to the method of forming the surface modification layer 3 according to the second embodiment of the present invention, a step of applying a dissolution material 4, which is obtained by dissolving a powder containing an alloy component of the modified material, And disposing the modified material on the dissolution material (4).

Then, the bonding material 1 on which the surface modifying layer 3 is formed may be subjected to reheating and rough rolling at a temperature of 1,100 to 1,300 ° C for 1 to 5 hours.

The dissolving material (4) may be applied as a solution in which the modified material is dissolved, more preferably a powder containing an alloy component of the modified material in a semi-molten state. For example, the dissolving material 4 may be applied to the joint portion in a spray manner. At this time, the modified material may be strip cladded continuously on the dissolving material 4 to be applied. That is, the strip can be clad-bonded onto the bonding material 1 at the same time as the dissolving material 4 is applied.

13 is a cross-sectional view of a high-grade steel having a surface modification layer after rough rolling. FIG. 14 is a cross-sectional view of a high-grade steel having a surface modification layer according to an embodiment of the present invention after rough rolling; FIG.

Referring to FIG. 13, when the surface modification layer is formed by cladding a general steel on a bonding material of a high-grade steel and reheating and rough rolling are performed, bending deformation occurs as the slab is hot-rolled.

This is due to the difference between the high temperature tensile strength and the elongation ratio between the high grade steel and the general steel. For example, in the case of the high strength steel sheet, the ferrite phase of the body center cubic structure (BCC) There is a difference in the degree of rolling due to the difference in the austenite phase due to the hot rolling. As a result, a bending deformation occurs in the hot rolling of the slab.

Referring to FIG. 14, according to a method of joining a continuous high-strength continuous hot rolled steel sheet according to an embodiment of the present invention, a material having a high temperature tensile strength similar to that of the bonded material and the modified material can be used. When they have similar high temperature tensile strengths, they exhibit similar elongation to each other, so that bending deformation due to different elongation rates can be prevented as the rolling progresses in a similar range in hot rolling.

Accordingly, the bonded material and the modified material have a high temperature tensile strength in the range of 1: 0.8 to 1: 1.2. That is, the modified material has a high temperature tensile strength in the range of 80 to 120% based on the high temperature tensile strength of the bonded material.

When the ratio of the high temperature tensile strength of the bonded material and the modified material is in the range of 1: 0.8 to 1: 1.2 or more, a bending deformation at the end portion of more than 10 mm occurs in the hot rolling due to the difference of the high temperature tensile strength For example, when the bonding material is 8 MPa and the modifying material is 40 MPa, a bending strain of about 60 mm is generated at the end of the roughing after reheating, which causes a progressive failure in rolling.

It is more advantageous to minimize the difference in high temperature tensile strength between the bonded material and the modified material, and preferably, the bonded material and the modified material may be used as a material having high tensile strength at the same time.

As described above, the difference in high-temperature tensile strength is due to the difference in the austenite phase in the case of an ordinary steel though it has a ferrite phase in the case of an electric steel sheet. Therefore, when a general steel structure is converted into a ferrite phase, Can be advantageous to reduce.

For example, a ferrite stabilizing element may be added to a conventional general steel material, and examples of the ferrite stabilizing element include Cr and Al. If Cr is added in an excessive amount, for example, when Cr is added in an amount of 0.2 wt% or more, Cr may be diluted in the surface layer of the surface modification layer 3 and the bonding strength ratio of the bonding portion may be lowered. do.

15 is a graph for explaining the high temperature tensile strength according to the Al content of a general steel.

Referring to FIG. 15, when Al is an element stabilizing on a ferrite phase, the ferrite phase of the modified material is increased by increasing the content thereof. When the content of Al is 5 wt%, the tensile strength at 950 ° C is 24.2 MPa . When the content of Al is 7 wt%, the tensile strength at 950 ° C is 21.7 MPa. Therefore, when the content of Al is 5 wt% or more, the tensile strength at 950 ° C is 25 MPa or less.

The high strength steel sheet of the present invention contains at least 1% by weight of Si and has tensile strength of about 25 MPa or less at 950 ° C. For example, in the case of an electrical steel sheet containing 3% by weight Si, Lt; / RTI > shows a tensile strength of 20.9 MPa. As the content of Si increases, the tensile strength at high temperature tends to decrease.

For example, the modified material may comprise at least 5 wt% Al. Accordingly, the high temperature tensile strength of the modified material may be 25 MPa or less.

Al is a ferrite phase stabilizing element. Since the modified material contains 5 wt% or more of Al, it can have a ferrite phase in the entire temperature range, thereby reducing the difference in high temperature tensile strength with the bonding material.

The bonding material and the modified material according to an embodiment of the present invention can appropriately select the content range of Al of the modified material according to the Si content and the high temperature tensile strength of the bonded material and adjust the high temperature tensile strength It is preferable that the bonding material and the modified material have a high temperature tensile strength in the range of 1: 0.8 to 1: 1.2.

Accordingly, after the cladding surface modification layer is formed on the bonded material according to the embodiment of the present invention, when the reheating and rough rolling are performed, the bending deformation of the end portion is less than 10 mm and the hot rolling It is possible to prevent the occurrence of a progression of time.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example  One

80% Ar and 20% Si were welded using welding wire containing flux of 80% of iron powder and 20% of fluorite powder to the shear joint of the electric steel slab including 3.0% Si of 250 mm in thickness, 1,000 mm in width and 10,000 mm in length. CO ₂ was used as a protective gas, and flux cored arc welding (FCAW) was performed one pass at a welding rate of 480 mm / min at a current of 280 A, a voltage of 30 V, and an input heat quantity of 10.5 kJ / cm. Then, on the welded portion Al: 7%, Si: 0.2 % or less, Cr: 0.2% or less, C: 0.3% or less, Mn: 1.6% or less, Cu: 0.3% or less, P: 0.04% or less, S: 0.04% And the remainder of Fe was placed on the high carbon steel slab, and the high carbon steel slab was subjected to reheating and rough rolling at a temperature of 1,250 DEG C for one hour. Shear joints were then performed and hot rolled coils were produced with a total reduction of 90%.

Example  2

A melting material obtained by vacuum melting a metal powder containing 80% of iron powder and 20% of fluorite powder was applied to the front end joint portion of an electric steel plate slab including 3.0% of Si having a thickness of 250 mm, a width of 1,000 mm and a length of 10,000 mm by spraying At the same time, Al: 7% , Si: not more than 0.2%, Cr: not more than 0.2%, C: not more than 0.3%, Mn: not more than 1.6%, Cu: not more than 0.3%, P: not more than 0.04%, S: The ordinary steel sheet strip containing the remaining Fe was strip-clad continuously. Then, the high-carbon steel slab was subjected to reheating and rough rolling at a temperature of 1,250 DEG C for one hour. Shear joints were then performed and hot rolled coils were produced with a total reduction of 90%.

Example  3

A hot-rolled coil was produced in the same manner as in Example 1, except that the general steel sheet strip contained Al: 5% .

Comparative Example  One

A hot-rolled coil was produced in the same manner as in Example 1, except that the general steel sheet strip did not contain Al .

Comparative Example  2

A hot-rolled coil was produced in the same manner as in Example 2, except that the general steel sheet strip did not contain Al .

Comparative Example  3

A hot-rolled coil was produced in the same manner as in Example 1, except that the general steel sheet strip contained Al: 3% .

Comparative Example  4

A hot-rolled coil was produced in the same manner as in Example 1, except that the general steel sheet strip contained Al: 4% .

Surface layer ~ 6mm area Si content Surface layer ~ 6mm area Cr content Bond strength ratio (%) During the tensile test, Example 1 0.33 0.04 86 Base material Example 2 0.35 0.08 89 Base material Example 3 0.32 0.05 90 Base material Comparative Example 1 0.31 0.08 86 Base material Comparative Example 2 0.29 0.05 87 Base material Comparative Example 3 0.37 0.08 82 Base material Comparative Example 4 0.35 0.10 84 Base material

950 占 폚 Tensile Strength (MPa) End bending deformation (mm) Bonded material Modified material Example 1 20.9 21.7 4 Example 2 20.9 21.7 3 Example 3 20.9 24.2 10 Comparative Example 1 20.9 32.5 62 Comparative Example 2 20.9 32.5 59 Comparative Example 3 20.9 29.7 48 Comparative Example 4 20.9 30.5 32

Here, the bonding strength ratio represents a value obtained by dividing the bonding strength by the base metal strength as a result of a tensile test.

That is, referring to Table 1 and Table 2, when the general steel sheet strip is clad to the surface of the electrical steel sheet to form the surface modification layer, sufficient bonding strength ratio desired in the present invention can be satisfied. However, in the case of ordinary steels, when the high-strength steel sheet and the high-temperature tensile strength are different from each other and the bending deformation of the end portion exceeds 10 mm, if the high-temperature and high- The bending strain was less than 10 mm, and it was found that the range satisfying the range that does not cause the progress disorder in the hot rolling was satisfied.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited thereto. Those skilled in the art will readily obviate modifications and variations within the spirit and scope of the appended claims. It will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

Claims (18)

A method of preventing deformation of a hot rolled material in which both ends of a plurality of bonded materials are overlapped and subjected to shearing deformation,
Forming a surface modification layer using a modified material having a content of Si and Cr smaller than that of the bonded material at one or more junctions at both ends where the junction material is overlapped; And
And shear deformation by superimposing both ends of a plurality of bonded materials,
Wherein the surface modification layer is formed to a thickness of 5 to 20 mm and a width of 50 mm or more from both ends in the rolling direction of the bonded material,
Wherein the modifying material has a high temperature tensile strength in the range of 80 to 120% based on the high temperature tensile strength of the bonded material. The method according to claim 1,
Wherein the bonding material is a high-grade steel slab containing at least one selected from the group consisting of Si and Cr. 3. The method of claim 2,
Wherein the bonded material is an electrical steel sheet containing 1% by weight or more of Si. The method of claim 3,
Wherein the modified material comprises at least 5 wt% Al. delete 5. The method of claim 4,
Wherein the modified material has a ferrite phase in an entire temperature range from a high temperature region where hot rolling is performed to a cold room temperature region after cooling. delete delete The method according to claim 1,
The Si content of the surface modification layer is 1.5 wt% (excluding 0)
Wherein the Si content in the region within 6 mm from the surface layer of the surface modification layer is 0.5% by weight (excluding 0). delete The method according to claim 1,
Wherein the surface modification layer is formed over the entire vertical direction of rolling of the bonded material. The method according to claim 1,
Wherein the surface modification layer is formed to have a pattern in a direction perpendicular to the rolling direction of the bonded material. The method according to claim 1,
Wherein said modifying material is a strip. The method according to claim 1,
Performing flux cored arc welding (FCAW) or metal cored arc welding (MCAW) on the joint; And
And disposing a modified material on the welded portion. 15. The method of claim 14,
Wherein the welding is performed one pass. The method according to claim 1,
Applying a dissolution material obtained by dissolving a powder containing an alloy component of the modifying material to a bonding site; And
And disposing the modified material on the dissolution material. 17. The method of claim 16,
The dissolving material is applied to the joint by spraying,
Wherein the modifying material is continuously strip cladded on the dissolving material to be coated. The method according to claim 1,
And reheating and rough rolling the bonded material having the surface modification layer at a temperature of 1,100 to 1,300 ° C for 1 to 5 hours.

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