JP2020533181A - Continuous hot rolling equipment and methods for difficult-to-join materials - Google Patents

Abstract

A method for continuous hot rolling of high-grade steel, which is a difficult-to-join material, is disclosed. According to the continuous hot rolling method for difficult-to-bond materials according to an embodiment of the present invention, a boron-based flux or a fluorine-based and boron-based mixed flux is applied to a bonding portion on which a plurality of rolled materials to be bonded are superimposed. Includes a step of applying the above to melt the scale on the surface and a step of superimposing and shearing both ends of a plurality of rolled materials.

Description

The present invention relates to a continuous hot rolling apparatus and method for difficult-to-bond materials that are difficult to join with each other.

Recently, continuous rolling techniques of various methods have been developed between a rough rolling mill and a finishing rolling mill by joining leading and trailing metal plates so that finish rolling can be continuously performed. Among them, the rear end portion of the preceding metal plate and the tip portion of the succeeding metal plate are superposed on the top and bottom, and the superposed portion of the metal plate is simultaneously sheared, thereby being generated in the shearing process. A technique for directly contacting and joining the sheared surfaces of a metal plate is widely known.
The above-mentioned direct contact joining technique is performed by shearing, so that joining can be performed easily and in a short time, the required space is small, and the temperature drop during finish rolling is small. It has many advantages as a continuous rolling technique.

However, when joining high-grade steel using the above-mentioned conventional joining technique, there arises a problem that it is difficult to secure the plate-passability of the high-grade steel due to a decrease in the joining strength ratio. Normally, in order to ensure the plate-through property of high-grade steel during continuous continuous rolling, the joint strength ratio needs to be 70% or more, but in the case of high-grade steel, a large amount of scale is formed on the surface due to the alloy component. This is because it is generated and is not often deleted by descaling work. For example, on the surface of high carbon steel, electromagnetic steel sheet, and stainless steel, which are a type of high-grade steel, Si-based scale or Cr-based scale is generated, but especially Si-based scale and Cr-based scale are difficult to remove and are difficult to remove on the surface. A large amount will remain.

An object of the present invention is to provide a continuous hot rolling apparatus and method for a difficult-to-join material, which can improve the rolling rate of a joint portion of the difficult-to-join material.

According to one aspect of the present invention, a reheating furnace that controls the temperature of the rolling material, a rough rolling machine that roughly rolls the rolling material that has passed through the reheating furnace, and a preceding rolling material that has passed through the rough rolling machine. A joining device that joins the rolling material and the rolling material of the following to each other, a finishing rolling machine that manufactures the rolling material that has passed through the joining device to a required thickness, and the front of the reheating furnace, or the rough rolling machine and the above. A continuous hot rolling apparatus for difficult-to-join materials can be provided, which includes a first coating apparatus which is arranged at any one of the joining devices and forms a surface coating layer on the rolled material to be joined.

A second coating apparatus located in front of the reheating furnace or any other location between the rough rolling mill and the joining apparatus to form a surface coating layer on the rolled material to be joined. Further can be included.

The surface coating layer can be composed of a boron-based flux or a mixed flux of a boron-based and a fluorine-based flux.

According to another aspect of the present invention, a coating step of forming a surface coating layer on one or more of the preceding rolled material and the succeeding rolled material to melt the scale and the surface coating layer are formed. It is possible to provide a continuous hot rolling method for a difficult-to-join material, which includes a step of superimposing a preceding rolled material and a succeeding rolled material including a portion and a joining step of shearing and deforming the superimposed rolled material.

The rolled material can be a high-grade steel slab or metal bar containing a large amount of any one or more selected from the group consisting of Si and Cr.

The high-grade steel slab or metal bar can be Si steel or high alloy steel as an electromagnetic steel plate material.

The surface coating layer can be formed with a width of 50 mm or more in the rolling traveling direction.

The surface coating layer can be formed over the entire width in a direction perpendicular to the rolling traveling direction.

The surface coating layer can be sparsely formed at predetermined intervals in a direction perpendicular to the rolling traveling direction.

The flux forming the surface coating layer can be composed of a boron-based flux or a mixed flux of a boron-based and a fluorine-based flux.

The flux can be a powdery solid or a liquid liquid or a gaseous gas or a mixed form thereof.

The flux can be applied to the joint site by a spray method or a drop method by gravity.

Between the coating step and the superimposing step, a step of reheating and rough rolling the rolled material on which the surface coating layer is formed at a temperature of 1100 to 1300 for 1 to 5 hours can be further included. ..

The continuous hot rolling apparatus and method for a difficult-to-join material according to the present invention applies a flux for removing oxides to the surface of a planned joining portion of a rolled material before or during the execution of hot rolling. It is possible to remove the scale on the surface and increase the strength of the joint during shear joining of the continuously hot-rolled material, secure a joint strength ratio of 70% or more, and improve the rolling through rate of the joint. Can be done.

It is a conceptual diagram of the continuous hot rolling apparatus of a difficult-to-join material which concerns on one Embodiment of this invention. It is a joining machine which concerns on one Embodiment of this invention. It is a perspective view for demonstrating the continuous hot rolling method of the conventional high-grade steel. It is a perspective view for demonstrating the continuous hot rolling method of high-grade steel which concerns on one Embodiment of this invention. It is a perspective view for demonstrating the flux coating surface which concerns on one Embodiment of this invention. It is a perspective view for demonstrating the flux coating surface which concerns on one Embodiment of this invention. It is a perspective view for demonstrating the flux coating surface which concerns on one Embodiment of this invention. It is a graph for demonstrating the bonding strength ratio by the continuous hot rolling method of the difficult-bonding material which concerns on one Embodiment of this invention. It is a graph for demonstrating the bonding strength ratio by the continuous hot rolling method of the difficult-bonding material which concerns on one Embodiment of this invention. It is a graph for demonstrating the bonding strength ratio by the continuous hot rolling method of the difficult-bonding material which concerns on one Embodiment of this invention. It is a graph for demonstrating the cracking rate of the joint part by the continuous hot rolling method of the difficult-to-join material which concerns on 13th Example of this invention. It is a graph for demonstrating the bonding strength ratio of the high alloy steel by the continuous hot rolling method of the difficult-bonding material which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are presented in order to fully convey the ideas of the present invention to a person having ordinary knowledge in the technical field to which the present invention belongs. The present invention is not limited to the embodiments presented here, and can be embodied in other embodiments. In the drawings, the parts not related to the description may be omitted for clarifying the present invention, and the sizes of the components may be exaggerated to help understanding.

FIG. 1 is a diagram for explaining a continuous hot rolling apparatus for a difficult-to-join material according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a joining machine according to an embodiment of the present invention. Hereinafter, a continuous hot rolling apparatus for a difficult-to-bond material according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the continuous hot rolling apparatus for difficult-to-bond materials according to the present invention includes a reheating furnace 10 for heating the material from the upstream side, and a rough rolling mill 20 composed of a plurality of rolling mills. , A coil box 30, a joining device 40, a finishing rolling mill 50 composed of a plurality of rolling mills, and a down coiler 60. In the following, the difficult-to-join material will be described by taking high-grade steel, which is difficult to join due to scale generation, as an example.

The rough rolling mill 20 rolls a slab of high-grade steel, which is a difficult-to-join material, to produce a metal bar of high-grade steel, and the manufactured metal bar is wound into a coil by a coiler of a coil box 30. At this time, the coil box 30 also plays a role of adjusting the difference in speed between the metal bars traveling on the rough rolling 20 and the finishing rolling mill 50.

After the tip of the rolling material 2 of the trailing line taken out from the coil box 30 is cut by the crop shear, the surface of the planned joining portion of the metal bar to be joined is descaled by the partial descaling device 70, and the joining device is used. It is superposed on the rear end of the preceding rolled material 1 by the superimposing device 41 of 40.

The tip of the trailing rolling material 2 and the trailing end of the preceding rolling material 1 are joined by the joining machine 100 of the joining device 40, and the crop of the joined portion is cut by the crop processing device 80. The metal bar 200 joined by the joining device 40 is transferred to the finish rolling mill 50.

Here, the joining device 40 is a facility for joining the rear end of the preceding rolled material 1 and the tip of the trailing rolled material 2 in a running state, and is capable of shear joining within a short time. It may be a time joining device. In order to shear-join the rolled materials 1 and 2 in the running state, the joining machine 40 is movable according to the running of the metal bar, and the joining machine 40 is shaken according to the running of the metal bar. Equipment to move may be added.

For example, in the joining machine 100 of the joining device 40, as will be described later, a state in which the rear end of the preceding rolled material 1 and the tip of the succeeding rolled material 2 are superimposed is clamped. A pair of shearing knives are provided for shearing while press-fitting and shearing from both sides.

The metal bar 200 transferred to the finish rolling mill 50 is sequentially hot-rolled by a plurality of rolling mills to be produced to a required thickness, and then wound up by a down coiler 60.

The levelers 90 and 91 can have the first leveler 90 and the second leveler 91 installed on the outlet side of the coil box 30 and the joining device 40, respectively, and are selectively selected according to the material to be hot-rolled and the conditions of hot-rolling. Can be placed in.

The coating apparatus includes a first coating apparatus (not shown) provided in front of the reheating furnace 10 and a second coating apparatus 300 provided between the rough rolling mill 20 and the joining apparatus 40, both of which are provided. The surface coating layer 3 can be formed on the rolled material to be joined by being arranged at one or more of the above locations.

The rolled materials 1 and 2 can be high-grade steel slabs or metal bars containing a large amount of any one or more selected from the group consisting of Si and Cr. For example, the rolled materials 1 and 2 can be high carbon steel, high alloy steel, silicon (Si steel) for electromagnetic steel sheets, or stainless steel.

The surface coating layer 3 is formed in a slab state by using a flux coating device before reheating using the reheating furnace 10, or rough rolling by the rough rolling mill 20 and finish rolling by the finish rolling mill 50. In the intermediate step of, the flux coating device 300 can be used to form a metal bar. Moreover, the surface coating layer 3 can be formed on each of the metal bars in the process between the slab before reheating and the rough rolling and the finish rolling. At this time, the width of the surface coating layer 3 can be formed to be the entire width of the rolled materials 1 and 2 with a width of 50 mm at both ends in the rolling direction of the rolled materials 1 and 2. That is, the surface coating layer 3 can be formed with a length of about the width of the rolled materials 1 and 2 and a width of 50 mm.

As shown in FIG. 2, the joining machine 100 according to the embodiment of the present invention roughly includes an assembly 120 of upper knives, an assembly 130 of lower knives, and a housing 110 that movably supports them. Including.

The assembly 120 of the upper knives includes an upper knife 121, an upper clamp 122, and an upper support device 123, all of which can be integrally configured. Correspondingly, the lower knife assembly 130 placed below the upper knife assembly 120 consists of a lower knife 131, a lower clamp 132, and a lower support device 133, all of which are Can be configured as one.

The assembly 120 of the upper knives and the assembly 130 of the lower knives are guided by the housing 110 and can be movably supported in the thickness direction of the preceding rolled material 1 and the succeeding rolled material 2. Further, the assembly 120 of the upper knives and the assembly 130 of the lower knives can be configured so as to be able to approach and separate from each other by a link mechanism (not shown).

The operation of such a joining machine 100 will be briefly described. First, in the joining machine 100, the leading end 2'of the trailing rolled material 2 is guided on the trailing end 1'of the leading rolled material 1 of the high-grade steel. Then, the overlapped portion of the tip end 2'and the rear end end 1'is sandwiched between the protrusions 124 and 134 of the upper knife 121 and the lower knife 131. That is, the protrusions 124 and 134 of the upper knife and the lower knife come into contact with the surfaces of the tip 2'and the rear 1'.

Then, the upper clamp 122 and the lower clamp 132 come into contact with the overlapped portion of the rear end 1'of the preceding rolled material 1 and the tip 2'of the trailing rolled material 2. Here, the upper clamp 122 can be supported by a predetermined pressure by the upper support device 123, and the lower clamp 132 can be supported by a predetermined pressure by the lower support device 133.

In such a state, when the upper knife 121 and the lower knife 131 shear the leading rolled material 1 and the trailing rolled material 2, the sheared surfaces of the preceding rolled material 1 and the trailing rolled material 2 are respectively. However, they are shear-bonded to each other by plastic flow deformation to form a metal bar 200 that is integrally continuously bonded.

In this way, when the shear joint to the end of the high-grade steel is completed, the upper crop in which the tip 2'of the rolling material 2 in the subsequent row is cut is located at the joint portion of the continuous metal bar 200, and the leading crop is located. The lower crop where the rear end 1'of the rolled material 1 is cut is located. Then, when the metal bars 200 are joined to each other, the upper knife 121 and the lower knife 131 retract until a certain separation distance is provided.

The upper crop and the lower crop cut by shear joining of the metal bars are removed by the cropping apparatus 80 as shown in FIG. 1, and the continuous metal bars 200 are transferred to the finish rolling mill 50. It will be. Here, when the joint portion of the metal bar passes through the finish rolling mill 50, strong compressive stress and bending during finish rolling, and external forces such as bending or tension act between each stand of the finish rolling mill. Therefore, the joint portion 100 will be placed under harsh process conditions. At this time, the joint portion of the metal bar of the high-grade steel is not broken, and it is necessary to maintain the joint strength sufficient to allow the finish rolling mill 50 to pass through.

FIG. 3 is a perspective view for explaining a conventional continuous hot rolling method for high-grade steel, and FIG. 4 is a perspective view for explaining a continuous hot rolling method for high-grade steel according to an embodiment of the present invention. It is a figure.

First, as shown in FIG. 3, in the case of high-grade steel, when reheating is performed before hot rolling due to the alloy component, a large amount of scale is generated on the surface, and these are also removed by the descaling operation. It gets harder. In particular, Si-based and Cr-based scales are formed on the surface of the base material on an internal scale, which is difficult to remove and remains on the surface in a large amount.

That is, high-grade steels having a high content of Si and Cr, such as high carbon steels, electromagnetic steel sheets, and stainless steels, have Si-based scales or Cr-based scales formed on the surface, but these scales are descaled. Since it is difficult to remove it, a lot of it remains on the surface. Moreover, in the case of the Si-based scale, since Si penetrates into the base material to form a fialite (Fe ₂ SiO ₄ ), the descalability is further lowered, but at this time, the more the Si content increases. The scaleite (Fe ₂ SiO ₄ ) will also increase.

The internal scale or fairite (Fe ₂ SiO ₄ ) formed on the surface of the reheated slab will be concentrated between the base metal and the interface of the external scale while passing through rough rolling. .. Therefore, as shown in FIG. 3, a high-grade steel slab having such a scale formed has a problem that a large amount of scale is mixed in the joint surface and the joint strength ratio of the joint is lowered when shear joint is performed. There is.

On the other hand, the continuous hot rolling method for difficult-to-join materials, which is shown in FIG. 4 and is joined by superimposing and shearing the ends of the plurality of rolled materials 1 and 2 on both sides according to the embodiment of the present invention. A coating step of forming a surface coating layer on the rolled material and melting the scale, a superimposition step of superimposing the preceding rolling material and the succeeding rolling material including the portion where the surface coating layer is formed, and superposed rolling. The joining process of shearing and deforming the material can be carried out in sequence.

Therefore, in the present invention, in the coating step, a surface coating layer is applied by using a boron-based or fluorine-based mixed boron-based flux at one or more of the joint sites at both ends on which the rolled materials 1 and 2 are superimposed. By forming No. 3, it is possible to remove the scale on the surface of the planned joining portion of the rolled material and increase the strength of the joining portion at the time of shear joining of the continuously hot rolled material. At this time, the scale can be generated by including a large amount of any one or more of the rolled materials 1 and 2 selected from the group consisting of Si and Cr.

The surface coating layer 3 is formed in a slab state by using a first coating apparatus (not shown) before reheating using the reheating furnace 10 of FIG. 1, or is subjected to rough rolling and finish rolling. In the intermediate stage, the metal bar can be formed by using the second coating device 300. Moreover, each surface coating layer 3 can be formed on the slab before reheating and the metal bar in the process between the rough rolling and the finish rolling. At this time, the width of the surface coating layer 3 can be formed with a width of 50 mm from both ends in the rolling direction of the rolling materials 1 and 2.

On the other hand, if the width of the surface coating layer 3 is less than 50 mm, the strength of the joint between the preceding rolled material 1 and the succeeding rolled material 2 may be insufficient, so the width of the surface coating layer 3 Can also be formed at 100-500 mm.

5a, 5b and 5c are perspective views for explaining the surface coating layer according to the embodiment of the present invention. First, referring to FIG. 5a, the surface coating layer 3A can be formed over the entire vertical direction of rolling of the rolling materials 1 and 2. In other words, the surface coating layer 3A can be formed over the entire width direction of the rolled materials 1 and 2.

Then, referring to FIGS. 5b and 5c, the surface coating layers 3B and 3C can be provided so as to be vertically spaced at predetermined intervals in the rolling direction of the rolling materials 1 and 2. For example, the surface coating layers 3B and 3C can have a specific pattern in the width direction of the rolled materials 1 and 2. As shown in FIG. 5b, the surface coating layer 3B can be formed only on both edge portions (end portions) in the width direction of the rolled materials 1 and 2, thereby further reducing the cost for forming the surface coating layer 3B. it can. In comparison, as shown in FIG. 5c, the surface coating layer 3C can be sparsely formed in two or more regions in the width direction of the rolled materials 1 and 2 at predetermined intervals, thereby forming the surface coating layer 3C. The cost of rolling can be further reduced.

Moreover, the flux of the surface coating layer 3 can be a powdery solid or a liquid liquid or a gaseous gas or a mixed form of these forms. In the method of shearing the continuous hot-rolled material of high-grade steel, the method of forming the surface coating layer 3 can include a method of spraying flux on the joint portion or a method of dropping by gravity.

On the other hand, one embodiment of the present invention can include the first to 14th examples depending on the method and timing of forming the surface coating layer 3. For example, according to the method for forming the surface coating layer 3 according to the first embodiment, the surface coating layer 3 can be formed at the joint portion in front of the reheating furnace 10. After that, the rolled material 1 on which the surface coating layer 3 is formed can be reheated and roughly rolled at a temperature of 1100 to 1300 for 1 to 5 hours.

According to the method for forming the surface coating layer 3 according to the second embodiment, the surface coating layer is formed at the joint portion between the rough rolling and the finish rolling. Then, according to the method for forming the surface coating layer 3 according to the third embodiment, the joining portion is between the step of forming the surface coating layer 3 at the joining portion in front of the reheating furnace and the rough rolling and the finish rolling. Includes a step of forming a surface coating layer.

Hereinafter, the present invention will be described in more detail with reference to Examples 1 to 14.

(Example 1 (3.4% Si electromagnetic steel sheet: flux is applied to the slab before reheating))
Borax, which is a boron-based flux, is applied to the sheared joints of 3.4% Si electromagnetic steel sheets with a thickness of 250 mm, a width of 1200 mm, and a length of 10000 mm to a total width of 500 mm in the length direction and 1000 mm in the width direction. Applied to the area. The coating amount per unit area was 0.6 kg / m ² . The slab was reheated at a temperature of 1200 ° C. for 3 hours and then roughly rolled. Then, shear joint was performed and the strength of the joint was evaluated.

(Example 2 (3.4% Si electromagnetic steel sheet: flux is applied to the metal bar after rough rolling))
Borax, which is a boron-based flux, was applied to a coating area of 2000 mm in the length direction and 1200 mm in the width direction at the sheared joint portion of the metal bar of the 3.4% Si electromagnetic steel plate after the rough rolling. The coating amount per unit area was 0.6 kg / m ² . Then, shear joint was performed and the strength of the joint was evaluated.

(Example 3 (3.4% Si electromagnetic steel sheet: flux is applied to the slab before reheating + flux is applied to the metal bar after rough rolling))
Borax, which is a boron-based flux, is applied to the sheared joints of 3.4% Si electromagnetic steel sheets with a thickness of 250 mm, a width of 1200 mm, and a length of 10000 mm to a coating area of 500 mm in the length direction and 1000 mm in the width direction. It was applied. The coating amount per unit area was 0.6 kg / m ² . The slab was reheated at a temperature of 1200 ° C. for 3 hours and then roughly rolled. Borax, which is a boron-based flux, was applied to a coating area of 2000 mm in the length direction and 1200 mm in the width direction at the sheared joint portion of the metal bar of the 3.4 Si electromagnetic steel plate after the rough rolling. The coating amount per unit area was 0.6 kg / m ² . Then, shear joint was performed and the strength of the joint was evaluated.

(Examples 4 to 6 (3.4% Si electromagnetic steel sheet: coated with a mixed flux of 40% fluorine-based + 60% boron-based))
Shear bonding was performed in the same manner as in Examples 1 to 3 except that a mixed flux of 40% fluorine + 60% boron was used instead of borax, which is a boron-based flux, and the strength of the joint was formed. Was evaluated.

(Example 7 (Electromagnetic steel sheet of 3.2% Si: Borax, which is a boron-based flux, is applied))
Shear joint is performed in the same manner as in Example 2 except that the electromagnetic steel sheet containing 3.2% Si is used instead of the electrical steel sheet containing 3.4% Si, and the strength of the joint is increased. evaluated.

(Example 8 (3.2% Si electromagnetic steel sheet: coated with a mixed flux of 40% fluorine-based + 60% boron-based))
Shear joint was performed and the strength of the joint was evaluated in the same manner as in Example 7, except that a mixed flux of 40% fluorine + 60% boron was used instead of borax, which is a boron-based flux. did.

(Example 9 (3.2% Si electromagnetic steel sheet: coated with a mixed flux of 20% fluorine-based + 80% boron-based))
Shear joint was performed and the strength of the joint was evaluated in the same manner as in Example 7, except that a mixed flux of 20% fluorine + 80% boron was used instead of borax, which is a boron-based flux. did.

(Example 10 (coating amount per unit area 1.2 kg / m ² ))
Shear bonding is performed in the same manner as in Example 2 except that the coating amount per unit area of 1.2 kg / m ² is applied instead of the coating amount of 0.6 kg / m ² per unit area. The strength of the part was evaluated.

(Example 11 (coating amount per unit area 0.3 kg / m ² ))
Instead of coating weight 0.6 kg / m ² per unit area, with the exception that the application of the coating amount of 0.3 kg / m ² per unit area, in the same manner as in Example 2, performs shearing bonding, bonding The strength of the part was evaluated.

(Example 12 (coating amount per unit area 0.15 kg / m ² ))
Shear bonding is performed and joined in the same manner as in Example 2, except that the coating amount of 0.15 kg / m ² per unit area is applied instead of the coating amount of 0.6 kg / m ² per unit area. The strength of the part was evaluated.

(Example 13 (evaluation of crack rate of joint))
Shear joint was performed in the same manner as in Example 2, and then the joint was finish-rolled to evaluate the crack ratio of the joint.
(Example 14 (evaluated with high alloy steel))

(Comparative Example 1)
A slab of an electromagnetic steel sheet containing 3.4% of Si having a thickness of 250 mm, a width of 1000 mm and a length of 10000 mm was reheated and roughly rolled at a temperature of 1200 for 3 hours. Then, shear joint was performed and the strength of the joint was evaluated.

(Comparative Example 2)
A slab of an electromagnetic steel sheet containing 3.2% of Si having a thickness of 250 mm, a width of 1000 mm and a length of 10000 mm was reheated and roughly rolled at a temperature of 1200 for 3 hours. Then, shear joint was performed and the strength of the joint was evaluated.

(Comparative Example 3)
Shear joint was performed in the same manner as in Comparative Example 1, and then the joint was finish-rolled to evaluate the crack ratio of the joint. With reference to this, it can be seen that fracture occurs at the joint immediately after joining due to the Si-based scale of the surface layer during shear joining of high-grade steel.

(Comparative Example 4)
Evaluated with high alloy steel

Here, the joint strength ratio indicates a value obtained by dividing the strength of the joint portion by the strength of the base material as a result of the tensile test. The crack rate of the joint portion indicates a value obtained by dividing the size of the crack at the joint portion by the width of the entire material.

6 to 8 are graphs for explaining the joint strength ratio of the high-grade steel by the continuous hot rolling method of the high-grade steel according to the embodiment of the present invention.
FIG. 6 is a graph comparing the bonding strength ratios of Example 1, Example 2, and Example 3 of electrical steel sheets containing Si of 3.4% or more and Comparative Example 1. These show the bonding strength ratio of materials that have been shear-bonded using a coating layer in which a boron-based flux is applied to a rolled material. The bonding strength ratio of the shear-bonded material is improved as compared with the shear-bonded material according to the conventional comparative example 1, that is, without applying flux, and shows an average bonding strength ratio of 90% or more. ..

When applied to the surface of the slab before reheating, or when applied to the surface of the metal bar after rough rolling, or when applied to the surface of the slab before reheating and secondary coating on the surface of the metal bar after rough rolling. All show high bonding strength ratios. In particular, the highest bonding strength ratio is exhibited when the coating is applied to the surface of the slab before reheating and the secondary coating is applied to the surface of the metal bar after rough rolling.

FIG. 7 is a graph comparing the bonding strength ratios of the electromagnetic steel sheets of Example 2 and Example 5 containing Si of 3.4% or more and Comparative Example 1. These show the bonding strength ratio of materials that have been shear-bonded using a coating layer in which a boron-based flux or a mixed flux of fluorine-based and boron-based is applied to a rolled material in the state of a metal bar after rough rolling. It is a thing. With reference to this, the bonding strength ratio is relatively higher when a single boron-based flux is applied than when a mixed flux of a fluorine-based and boron-based flux is applied.

FIG. 8 is a graph comparing the bonding strength ratios of the electromagnetic steel sheets containing 3.2% or more of Si with Example 7, Example 8 and Example 9 and Comparative Example 2. These show the bonding strength ratio of materials that have been shear-bonded using a coating layer in which a boron-based flux or a mixed flux of fluorine-based and boron-based is applied to a rolled material in the state of a metal bar after rough rolling. It is a thing. The highest bonding strength ratio is shown when a single boron-based flux is applied than when a mixed flux of fluorine-based and boron-based is applied.

FIG. 9 is a graph comparing the cracking rate of the joint portion between Example 13 and Comparative Example 3 of an electromagnetic steel sheet containing 3.4% or more of Si. These show the cracking rate of the joint after finish rolling of the material shear-bonded using the coating layer in which a boron-based flux is applied to the rolled material, and the cracking rate of the joint when the flux is not used. It is a thing. It can be seen that the crack rate of the joint portion is 100% after the fracture occurs at the joint portion immediately after the joint due to the Si-based scale of the surface layer at the time of shear bonding of the conventional high-grade steel.

FIG. 10 is a graph comparing the bonding strength ratio between Example 14 of a high alloy steel containing 0.2% or more of Si and 0.3% or more of Cr and Comparative Example 4. These show the bonding strength ratio of the material that has been shear-bonded by using a coating layer in which a boron-based flux is applied to the rolled material in the state of a metal bar after rough rolling. The bonding strength ratio when flux is applied shows a higher bonding strength ratio than before. With reference to this, it can be seen that the flux affects not only the Si-based scale but also the Cr-based scale.

Therefore, referring to each of the above-described examples, the continuous hot rolling method for difficult-to-bond materials according to the present invention rolls a flux for removing oxides before or during hot rolling. It can be applied to the surface of the planned joint part of the material to remove the surface scale, increase the strength of the joint during shear bonding of the continuously hot-rolled material, and secure a joint strength ratio of 70% or more to secure the joint. It is possible to improve the passing rate of rolling.

As described above, exemplary embodiments of the present invention have been described, but the present invention is not limited thereto, and any person who has ordinary knowledge in the technical field will describe the concept of claims described below. It can be understood that various changes and modifications are possible within the range that does not deviate from the range.

Claims (13)

A reheating furnace that regulates the temperature of the rolled material,
A rough rolling machine that roughly rolls the rolling material that has passed through the reheating furnace,
A joining device that joins the preceding rolling material and the succeeding rolling material that have passed through the rough rolling mill to each other.
A finishing rolling mill that manufactures the rolling material that has passed through the joining device to the required thickness, and
Includes a first coating apparatus that is located in front of the reheating furnace or either between the rough rolling mill and the joining apparatus to form a surface coating layer on the rolled material to be joined. Continuous hot rolling equipment for difficult-to-join materials. In the continuous hot rolling apparatus for difficult-to-bond materials according to claim 1,
A second coating apparatus located in front of the reheating furnace or at any other location between the rough rolling mill and the joining apparatus to form a surface coating layer on the rolled material to be joined. Including, continuous hot rolling equipment for difficult-to-join materials. In the continuous hot rolling apparatus for difficult-to-bond materials according to claim 1 or 2.
The surface coating layer is a continuous hot rolling apparatus for difficult-to-bond materials, which is composed of a boron-based flux or a mixed flux of a boron-based and a fluorine-based material. A continuous hot rolling method in which rolling materials are joined and continuously rolled.
A coating process in which a surface coating layer is formed on the rolled material to melt the scale,
A step of superimposing the preceding rolled material and the succeeding rolled material, including the portion where the surface coating layer is formed,
A continuous hot rolling method for difficult-to-join materials, including a joining step of shear-deforming the superimposed rolled material. In the continuous hot rolling method for a difficult-to-join material according to claim 4,
A method for continuous hot rolling of a difficult-to-join material, wherein the rolling material is a high-grade steel slab or metal bar containing a large amount of any one or more selected from the group consisting of Si and Cr. In the continuous hot rolling method for a difficult-to-join material according to claim 5,
A method for continuous hot rolling of a difficult-to-join material, wherein the high-grade steel slab or metal bar is Si steel or high alloy steel of an electromagnetic steel plate material. In the continuous hot rolling method for a difficult-to-join material according to claim 4,
A method for continuous hot rolling of a difficult-to-bond material, wherein the surface coating layer is formed with a width of 50 mm or more in the rolling traveling direction. In the continuous hot rolling method for a difficult-to-join material according to claim 4,
A method for continuous hot rolling of a difficult-to-bond material, in which the surface coating layer is formed over the entire width in a direction perpendicular to the rolling traveling direction. In the continuous hot rolling method for a difficult-to-join material according to claim 4,
A method for continuous hot rolling of a difficult-to-bond material, in which the surface coating layer is sparsely formed at predetermined intervals in a direction perpendicular to the rolling traveling direction. In the continuous hot rolling method for a difficult-to-join material according to claim 4,
The flux forming the surface coating layer is a method for continuous hot rolling of high-grade steel, which is composed of a boron-based flux or a mixed flux of boron-based and fluorine-based. In the continuous hot rolling method for a difficult-to-join material according to claim 10,
A method for continuous hot rolling of a difficult-to-bond material, wherein the flux is a powdery solid or liquid liquid or a gaseous gas or a mixed form of these forms. In the continuous hot rolling method for a difficult-to-join material according to claim 10,
The flux is a continuous hot rolling method of a difficult-to-join material, which is applied to the joint portion by a spray method or a drop method by gravity. In the continuous hot rolling method for a difficult-to-join material according to claim 4,
Between the coating process and the superimposing process
A method for continuous hot rolling of a difficult-to-bond material, further comprising a step of reheating and rough rolling the rolled material on which the surface coating layer is formed at a temperature of 1100 to 1300 for 1 to 5 hours.

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