JP2000051907A - Hot pressure-welding method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sure bonding strength with small press capacity at the time of superimposing and pressure-welding high-temp. steel. SOLUTION: This method is a method by which, after descating the high- temp. rolled steel using rotary cutting tools in reducing-flame atmosphere, at the time of continued hot rolling, the steel is superimposed and pressure-welded in the reducing-flame atmosphere and the volume to be cut for descaling or the area of the superimposed part is adjusted. When the length of superimposition at the time of pressure welding is made to L0 and the length of the joining after pressure welding is made to L, the rolled steel is pressed so that L/L0 becomes >=1.5, the inclined angle θ of removing allowance by cutting is made to 0-45 deg., the max. depth d1 of the removing allowance by cutting is made in the range of 10-40% of the thickness of the rolled steel, the removing allowance L1 by cutting is made larger than the length L0 of superimposition, the joint part of the rolled steel and the corner parts which are brought into contact with a pressure-welding tool are chamfered, the surface of the pressure-welding tool is made to <=2 μm in surface roughness Ra and a device for spraying a lubricant is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for hot pressing used for continuous hot rolling, and more particularly, to a method for overlapping and pressing high-temperature steel materials to be subjected to continuous hot rolling. TECHNICAL FIELD The present invention relates to a hot-welding method and apparatus for improving the surface roughness of a form of a joint and a welding tool in order to ensure reliable welding and reduce a welding load.

[0002]

2. Description of the Related Art In an ironworks, continuous production processes are being vigorously promoted for the purpose of energy saving, improvement of product yield, improvement of productivity, and the like. Among them, continuation of a hot rolling process for producing a hot-rolled steel sheet (hot coil) is one of the important issues.

In conventional hot rolling, heated slabs are sequentially supplied one by one to a rough rolling mill and a finishing rolling mill, and intermittently rolled. In this way, intermittent rolling, in which the material to be rolled is rolled one by one, is not only in itself inefficient, but in particular, in the case of rolling in which the material to be rolled becomes thinner, its tip deforms and guides. Often, the roll is squeezed when it hits the roll or the trailing end passes through the rolling mill, causing damage to the roll. When such troubles occur, it is necessary to stop the rolling line to perform repairs and roll replacement, and to prevent such troubles, the rolling speed must be reduced. It will be significantly reduced.

On the other hand, intermittent rolling is not preferable in terms of the quality and yield of hot-rolled steel. At the leading end and the trailing end of the material to be rolled, the balance of the rolling speed is more unbalanced than at the center, and it is difficult to control the rolling temperature within an appropriate range, and it is easy to cause dimension deviation. Further, at the leading end of the material to be rolled, the central portion in the plate width direction protrudes in the rolling direction to reduce the plate width, and at the rear end, a phenomenon occurs in which the center of the plate width is conversely recessed, that is, a fish tile. Further, when the leading end portion is bitten by the rolling roll or when the winding is started by the down coiler, a situation in which the width of the steel sheet becomes narrow with the sudden increase in the tension also occurs. Due to the above-mentioned phenomenon, the leading end and the trailing end of the intermittently rolled steel sheet are not stable in quality and lower the product yield.

In recent years, in order to solve the above-mentioned problem of intermittent rolling, in a process between a rough rolling mill and a finishing rolling mill, a steel material which has been coarsely rolled in advance (hereinafter referred to as “preceding steel material”) has been used. A method has been implemented in which a finish rolling is continuously performed by joining a steel material that has been roughly rolled after a preceding steel material (hereinafter, referred to as “following steel material”).

FIG. 1 is a view for explaining a method in which a preceding steel material and a succeeding steel material are joined between a rough rolling mill and a finishing rolling mill to continuously perform finish rolling. The steel slab 9 is rolled by the rough rolling mill 1 to become a rolled steel material S, which is once wound into a coil in the intermediate coiler 2. Then, it is rewound before being sent to the finishing mill group 6, the winding habit of the coil is corrected by the leveler 3, and the defective portion at the end is cut by the crop shear 4. Then, after the rear end of the preceding steel S1 and the front end of the succeeding steel S2 are pressed against each other in the traveling hot-welding apparatus 5, finish rolling is performed by the finishing mill group 6 and wound up by the down coiler 8. . Then, it is cut by the high-speed shear 7 to form a hot-rolled steel sheet coil. At this time, the joining of the preceding steel material S1 and the succeeding steel material S2 may be performed by an overlap method or a butt method depending on the shape of the steel material joint. However, the overlap welding method is often used.

FIG. 2 is a view for explaining an example of the steps of the overlap pressing operation using a hot bonding machine. First, at the time of joining steel materials, the rear end of the preceding steel material S1
When it comes to the position (10), fix the steel material with the clamp device 11,
The table roller 13 provided on the gantry 12 is raised by the lifting cylinder 14 and is pushed up to a position where it can be cut by the cylindrical rotary cutting tool 15. Next, when the trailing steel S2 is advanced and its tip comes to the position of the press-contact tool 16 (position overlapping the rear end of the preceding steel), the trailing steel is fixed by the clamp device 11. Thereafter, the burner 17 is burned to move the rotary cutting tool 15 in the direction indicated by the arrow as a reducing flame atmosphere around the ends of the leading steel S1 and the trailing steel S2,
The end of each steel material is cut and descaling is performed. After cutting is completed, the rotating tool is retracted and the gantry 12
Is lowered simultaneously with the press-contact press 10 to overlap and press-contact. At the time of this pressing, the hot pressing device 5 runs in the rolling direction at the same speed as the preceding steel S1 and the following steel S2 by the running rollers 18.

[0008]

SUMMARY OF THE INVENTION In order to secure reliable joining at the time of superposition welding, which is a prerequisite for continuous finish rolling,
Conventionally, various proposals have been made regarding a descaling method of a joint portion of a steel material, a type of a rotary cutting tool, and an overlapping shape.

First, Japanese Patent Application Laid-Open No. 6-312277 discloses a method in which a joint portion of a high-temperature steel material is descaled in a reducing atmosphere, and then the joined portions are overlapped and pressed to each other. In order to secure the joint strength of steel,
Cut the joining surface in parallel by cutting the overlap margin by 10
% Or more. However, no consideration is given to the reduction of the press-contact load of the joining device, and the press capability of the device must be enormous.

Next, regarding the type improvement of the rotary cutting tool,
In Japanese Patent Application Laid-Open No. 9-216003, a cylindrical cutter is improved into a drum-shaped and saw-tooth-shaped shape, and when cutting a joint of steel materials, by changing a cutting amount in a width direction of the steel material,
A method for reducing the pressure load is disclosed. But,
According to the method of this disclosure, the shape of the cylindrical cutter becomes complicated, and the cutting amount varies depending on the cutting position in the width direction of the steel material, and the durability of the blade is different. Therefore, there is a problem that the management of the cutting blade becomes complicated. is there.

[0011] Further, several proposals have been made regarding the overlapping shape of the joints. For example, in Japanese Patent Application Laid-Open No. 8-252606, one or both of the ends of a steel material to be rolled are cut into concave arcs in the width direction and overlapped, and the overlap margin is reduced from both ends toward the center of the width. And a method of reducing the pressure contact load by bonding to a joint. Also, in Japanese Patent Application Laid-Open No. 8-252611, the tip of a steel material is cut in an arc shape in the width direction and overlapped, and the overlap margin is reduced toward the center of the width. There has been proposed a method of reducing the pressure contact load by joining the members so that they are completely separated from each other and apart from each other. However, in these proposed methods, the shape of the cutting tool becomes complicated, and when this joined steel material is rolled, excessive tension is applied to the central portion of the width, which may cause an opening at the central portion of the width or further breakage. is there.

As described above, in the conventional superposition welding of high-temperature steel materials in continuous finish rolling, reduction of the welding load is not considered at all, and the press capability of the apparatus must be enormous. Absent. Further, in the method of reducing the press-contact load, there are problems that the management of the cutting tool becomes extremely complicated and the strength of the joint is not ensured.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made to reduce the pressing load when a high-temperature steel material is press-welded by performing descaling of a bonding surface in a reducing flame atmosphere or a non-oxidizing atmosphere. The purpose is to make it possible to cope with even a small press capacity and to reduce the size of the hot bonding apparatus.

[0014]

Means for Solving the Problems In order to achieve the above object, the inventors of the present invention cut a joint surface of a high-temperature steel material in a reducing flame atmosphere or a non-oxidizing atmosphere with a rotary tool and superposedly press-welded. At this time, as a result of various studies on factors affecting the reduction in the press-contact load, it was found that the area of the overlap portion and the volume of the overlap portion affected the press-load. Here, the pressure contact load is understood as the maximum pressure contact load (kg / mm) with respect to the overlap length of the joint.

FIG. 3 shows the area (X
XW) and the volume (X × W × H) of the overlapping portion. According to the study of the present inventors, it is possible to reduce the pressing load by reducing the area and the volume of the overlapping portion illustrated in FIG. 3 as much as possible. However, the area and the volume of the overlapping portion are as follows. There are certain restrictions in order to ensure an appropriate joining strength in the finishing rolling step after joining.

The present invention has been completed on the basis of the above findings, and includes the following (1) hot pressing method and (2) hot pressing apparatus.

(1) In performing continuous hot rolling by joining the ends of two rolled steel materials, the hot rolled steel material is descaled using a rotary cutting tool in a reducing flame atmosphere, and then reduced in a reducing flame atmosphere. A method of performing pressure welding by superimposing in the same, adjusting the cutting amount for descaling or the area of the superimposed portion, and setting the overlap length at the time of pressure welding to L ₀ , and the joining length after the pressure welding to L In this case, the hot pressing is performed so that L / L ₀ becomes 1.5 or more.

In the descaling by the hot pressing method described above, the inclination angle θ of the cutting allowance by cutting is 0 to 45 °, and the maximum depth d ₁ of the cutting allowance by cutting is 10 to 40% of the thickness of the rolled steel material. the range, for larger more desirable than cash L ₁ length L ₀ superposing is taken up by the cutting. In addition, it is desirable to chamfer a corner portion that comes into contact with the joining portion of the rolled steel material and the pressure welding tool (see FIGS. 5 to 7 described later).

(2) At the time of continuous hot rolling by joining the ends of two rolled steel materials, the hot rolled steel material is descaled using a rotary cutting tool in a reducing flame atmosphere, and then reduced in a reducing flame atmosphere. An apparatus for performing pressure welding by superimposing inside the apparatus, wherein the surface of the pressure welding tool has a surface roughness Ra of 2 μm or less, and a device for spraying a lubricant is provided.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention is characterized in that the pressure-contact load is reduced by minimizing the area and volume of the overlapped portion during pressure-contact. However, in order to secure the bonding strength in the finish rolling step, when the overlap length during pressure welding is L ₀ and the bonding length after pressure welding is L, the ratio L / L ₀ is 1.5 or more. It is necessary to make pressure contact so that

FIG. 4 is a diagram for explaining a length L ₀ and the joining length L superposition of longitudinal pressure, the length L ₀ superimposed upon FIG (a) is pressed, (b) the pressure The subsequent joint length L is shown. When L / L ₀ is less than 1.5 when pressing the rear end of the preceding steel S1 and the front end of the following steel S2, the bonding strength in finish rolling cannot be secured, and the joint is opened during rolling. Or break. Desirable range of L / L ₀ is 1.5 to 2.5
It is.

FIG. 5 is a view for explaining an inclined cutting method for cutting a joint surface of a steel material while tilting a cylindrical rotary cutting tool. In order to reduce the volume of the overlapped portion, it is preferable to perform the inclined cutting with the rotary cutting tool 15 to secure the cutting angle θ of the overlapped portion for cutting. In this case, to be larger than the algebraic L ₁ superposition length L ₀ taken by cutting, the inclination angle is 0-45 °. To greater than cash L ₁ length L ₀ superposed taken by cutting, extend the end of the steel material to be rolled at the time of pressing, because the length L ₀ superimposed spreads. Also, the inclination angle θ due to cutting is 0 °
If it is less than 1, the scale before joining cannot be completely removed, and a joining failure occurs.If the inclination angle θ exceeds 45 °, the rolling reduction is insufficient and the joining strength is reduced. There is a risk.

FIG. 6 is a view for explaining a parallel cutting method for cutting a joint surface of a steel material while moving a cylindrical rotary cutting tool in parallel. In the present invention, be either of the inclined cutting method or parallel cuts method, by deeply cutting the cutting depth d ₁ of the overlapping portion by cutting, to reduce the volume of the overlapping portion is desirable. Specifically, the maximum depth d ₁ of the machining allowance by cutting 10 to 40% of the thickness of rolled steel. To the lower limit of the maximum depth d ₁ of the machining allowance 10% of the steel thickness, while avoiding the occurrence of defective bonding was completely descaling before bonding, in order to perform sufficiently the sag elimination of the end portions On the other hand, the reason why the upper limit is set to 40% of the thickness of the steel material is to secure a sufficient amount of reduction and prevent a decrease in bonding strength.

Further, in the present invention, as shown in FIG.
It is desirable to chamfer the corners that come into contact with the joining portion of the rolled steel material and the pressure welding tool, so that the volume of the overlapped portion during the pressure welding can be reduced. Chamfer depth shown in Fig. 7
d ₂ is be processed up to 80% of the maximum steel thickness, machining margin is appropriately selected depending rolling conditions after bonding. For the chamfering, a commonly used method such as cutting or pressing is used.

FIG. 8 is a diagram showing the relationship between the surface roughness Ra of the pressure welding tool used for welding and the pressure welding load. As is clear from FIG. 8, any overlapping length (20 to 40 m
m), the pressure contact load can be reduced by lowering the surface roughness Ra. In the present invention, the surface roughness Ra of the pressing tool is set to 2 μm or less in order to sufficiently reduce the pressing load. At this time, it is desirable that the surface hardness of the press-welding tool is Hs50 or more in order to make it difficult for the surface eaves to be generated during the press-welding. Further, as long as the condition of the surface roughness Ra is satisfied, the surface of the pressure welding tool may be plated or sprayed with Ni, Cr, or the like to finish the surface. Further, a lubricant is applied to the surface of the pressure welding tool in order to prevent seizure during the pressure welding. In the hot welding machine shown in FIG.
Is applied from the lubrication application hole 19. Lubricants used in this case, oil or graphite of MoS ₂ system is employed.

Normally, the pressure welding load is almost proportional to the heating temperature of the joint. However, if the heating is performed at a predetermined temperature or more, it becomes difficult to control the heating time and the temperature during rolling. ° C. Further, as a method of heating the joint, means such as high-frequency induction heating, direct current heating, and laser heating are used.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, various means described above can be combined to reduce the pressing load required for pressing a steel material. In the following, the effect of each means on the reduction of the pressure welding load was investigated.

Each dimension has a thickness of 30 mm, a width of 300 mm, and a length of 100
A 0 mm carbon steel sheet (C: 0.1%, Si: 0.5%, Mn: 1.2%) was heated to a predetermined temperature, and a bonding test was performed using the hot bonding machine shown in FIG. The direct flame reducing flame when joining steel materials uses a burner of the mixing method in the nozzle, blows out the mixed gas from the ring-shaped slit nozzle to form a reducing flame, arranges the burners in the width direction of the plate and joins the cutting part and the joint It was applied to the surface to prevent oxidation. The cutting of the high-temperature steel material was performed by using a rotary cutting tool under the conditions described later and retracting the cutting device after the cutting to press-contact. The overlap length at the time of pressure welding was set to 25 mm, the amount of reduction was reduced to the original thickness, and the pressure was pressed using a 300-ton press.

After joining the steel materials, three finishing mills are arranged side by side at a steel material temperature of 1000 ° C., and a reduction ratio of 40%, 35% and 30% and a rolling tension between the rolling mills are about 2.0 kgf / mm ² and 3.Ok
The steel sheet was rolled with gf / mm ² and finished to a steel sheet having a thickness of 8.2 mm. During this time, tests were performed under various conditions shown below, and the results are shown in Table 1.

[0030]

[Table 1]

First, the effect of the inclination angle of the allowance for cutting on the pressure welding load was investigated. The rotary cutting tool used had an outer diameter of 300 mm, a rotation speed of 1500 rpm, a feed rate of 500 mm / sec, a cutting width of high-temperature steel material of 30 mm, and a cutting temperature of 1050 ° C.
As shown in FIG. 5, the inclination angle of the rotary cutting tool was changed by moving the rotary cutting tool in the range of 0 to 30 °. It can be seen that the press-contact load decreases as the inclination angle increases.

Next, as shown in FIG. 7, the influence of the presence or absence of the chamfer on the pressure contact load was examined by chamfering by machining, but it is clear that the provision of the chamfer reduces the pressure contact load. Became. Similarly, the surface roughness of the crimping tool
The influence was investigated by changing Ra, and it was found that by reducing the surface roughness Ra, the pressure contact load was also reduced.

The influence of the pressing temperature on the pressing load is remarkable, and the pressing load can be reduced by heating to 1200 ° C. Under any of the test conditions, L / L _0, which is the ratio of the overlap length at the time of pressure welding to the bonding length after the pressure welding, satisfied the value of 1.5 or more specified in the present invention. Therefore, in either pressure tests 1-16, after pressing a trailing steel and each preceding steel adds a rolling tension subjected to finish rolling 2.0kgf / mm ² ~3.Okgf / mm ² by rolling However, it could be rolled well without breaking.

[0034]

According to the method and apparatus for hot pressing of the present invention, a reliable joining strength can be obtained when high-temperature steel materials are overlapped and pressed, and a small pressing capacity can be achieved by reducing the pressing load. This makes it possible to reduce the size of the hot bonding apparatus.

[Brief description of the drawings]

FIG. 1 is a view for explaining a method of joining a leading steel material and a succeeding steel material between a rough rolling mill and a finishing rolling mill to continuously perform finish rolling.

FIG. 2 is a diagram illustrating an example of a process of a superposition pressure welding operation using a hot bonding machine.

FIG. 3 is a diagram illustrating an area (X × W) of a superimposed portion and a volume (X × W × H) of the superimposed portion at the time of pressing.

FIG. 4 is a diagram for explaining a superposition length L ₀ and a bonding length L before and after pressure welding, and FIG. 4A shows a superposition length L during pressure welding.
₀ , and (b) shows the joining length L after the pressure welding.

FIG. 5 is a diagram illustrating an inclined cutting method for cutting a joint surface of a steel material while inclining a cylindrical rotary cutting tool.

FIG. 6 is a diagram illustrating a parallel cutting method for cutting a joint surface of a steel material while moving a cylindrical rotary cutting tool in parallel.

FIG. 7 is a view for explaining a method of chamfering a joint portion of a rolled steel material and a corner portion which comes into contact with a pressure welding tool.

FIG. 8 is a diagram showing the relationship between the surface roughness Ra of a pressure welding tool used for welding and a pressure welding load.

[Explanation of symbols]

1. Rough rolling mill 2. Intermediate coiler 3. Leveler 4. Crop shear 5. Hot pressure welding device 6. Finish rolling mill 7. High speed shear 8. Down coiler 9. Slab 10． Pressing press 11． Clamping device 12. Mount 13. Table roller 14. Lifting cylinder 15． Cylindrical rotary cutting tool 16. Pressure welding tool 17． Burner 18. Running roller 19. Lubrication application hole S. Steel S1. Lead steel S2. Subsequent steel materials L. Join length L ₀ . Superposition length L ₁ . Allowance for cutting

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiro Fukushima 4-5-33, Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd. (72) Inventor Norio Iwanami Shinnaka, Isogo-ku, Yokohama-shi, Kanagawa No. 1 Haramachi Ishikawa Shima-Harima Heavy Industries, Ltd. Yokohama Engineering Center (72) Inventor Nobuhiro Tasoe No. 1-19, Mori, Koto-ku, Tokyo Ishikawajima-Harima Heavy Industries, Ltd.Koto Office (72) Inventor Shiro Nagata Yokohama, Kanagawa No. 1 Shin-Nakahara-cho, Isogo-ku, Ishikawa Shima-Harima Heavy Industries, Ltd. Yokohama Engineering Center F term (reference) 4E002 AD02 AD04 BD05 BD10 4E067 BB02 DA04 DB04 EC01

Claims (4)

[Claims] In a continuous hot rolling process by joining the ends of two rolled steel materials, a hot rolled steel material is descaled using a rotary cutting tool in a reducing flame atmosphere, and then is heated in a reducing flame atmosphere. It is a method of performing pressure welding by overlapping with each other, adjusting the cutting amount for descaling, or the area of the overlapping portion, and setting the overlapping length at the time of pressing to L ₀ , and the joining length after the pressure welding to L. A hot-welding method characterized by performing L / L ₀ welding to 1.5 or more in such a case. 2. The descaling method according to claim 1, wherein the inclination angle of the machining allowance is 0 to 45 °, the maximum depth of the machining allowance is 10 to 40% of the thickness of the rolled steel material, hot pressing method according to claim 1, characterized in that larger than the length L ₀ superposing said algebraic. 3. The hot pressure welding method according to claim 1, wherein the descaling is performed by chamfering a joint portion of the rolled steel material and a corner portion that comes into contact with the pressing tool. 4. When continuous hot rolling is performed by joining the ends of two rolled steel materials, the hot rolled steel material is descaled using a rotary cutting tool in a reducing flame atmosphere, and then is heated in a reducing flame atmosphere. A hot-welding apparatus comprising: a device for superimposing and performing pressure-welding, wherein the surface of the pressure-welding tool has a surface roughness Ra of 2 μm or less and a device for spraying a lubricant.