JP3197502B2 - Continuous hot rolling of steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous hot rolling method for steel sheets, and more particularly, to joining several to several tens of steel pieces, such as sheet bars, slabs, billets, and blooms, to form a continuous hot rolling. The present invention relates to a continuous hot rolling method for rolling a steel sheet into a steel sheet.

[0002]

2. Description of the Related Art Conventionally, in a hot rolling line for a billet, a billet to be rolled has been heated, rough-rolled and finish-rolled one by one to finish a hot-rolled sheet having a desired thickness. In the rolling method, there is a problem that the following troubles occur with the meandering of the rolled material. (1) As shown in FIG. 2, there is a “poor tip biting” in which the rolled material 2 bites into the rolling rolls 1a, 1b of the finishing mill in a meandering state and the tip sticks to the side guides 3a, 3b on the exit side. And the line stops. In FIG. 2, 4 is a looper and 5 is a looper.
Is a threading abnormal portion at the longitudinal end caused by meandering, and here is a portion where the leading end bites poorly.

(2) As shown in FIG. 3, when the rolled material 2 comes off from the rolling rolls 1a and 1b of the finishing mill, it comes into a meandering state and the tail end is narrowed by the entrance side guides 3a and 3b. (Referred to as “squeezing when the tail end is removed”), a surface flaw is attached to the tail end of the rolled material 2, and defective product quality occurs. Further, as a result of rolling this narrowed portion, flaws also occur on the surface of the rolling roll, and the roll flaws are transferred to the subsequent rolled material, resulting in poor product quality. In addition, the passing plate abnormal part 5 is a narrowing part at the time of tail end missing.

(3) While the rolled material 2 travels on the hot run table on the exit side of the finish rolling mill, the leading end or the tail end of the rolled material may be broken and overlapped (referred to as “doubled”). If it is wound up in a coiler in this state, this portion becomes defective and is cut off in the next step, resulting in a decrease in yield. For this reason, recently, the rolling method of joining the leading end of the preceding material and the leading end of the following material of the billet to be rolled prior to finish rolling, and continuously supplying this to the hot rolling line to perform rolling is known. It has been adopted.

For example, Japanese Patent Application Laid-Open No. 7-241601 discloses a winding / rewinding device 6 for winding and rewinding a billet after rough rolling, as shown in FIG. A leveler 7 for correcting the winding and warping of the billet unwound by the unwinding device, a guide 9 for preventing the displacement of the billet in the width direction, and removing a shape defect portion at the leading and trailing ends of the billet. Mobile joining device 10 for joining the crop shear 8 by heating, heating and pressing the rear end and the front end of the steel slab
And a ridge removal device (burr removal device) 11 for removing the ridge of the slab after joining, and a hot finish rolling mill (finish rolling) for continuously rolling the slab after the removal of the ridge. Machine)
There is disclosed a continuous hot rolling facility for billets in which 14 are sequentially arranged. In FIG. 4, reference numeral 10a denotes an input side clamping and pressing device, 10b denotes an output side clamping and pressing device, 12 denotes a rotary blade, 13 denotes a cooling (water cooling) header, 15 denotes a coiler, 16 denotes a hot run table, and L denotes a joining device. There are 10 running paths.

[0006]

By the way, the number of continuous steel strips to be joined and rolled is not infinite at the present stage. This is because there are the following constraints. (1) As the number of continuous rolls increases, the surface roughness of the rolling roll increases due to thermal fatigue, which is transferred to the surface of the product, and the surface quality of the product deteriorates.

(2) The control data for rolling (such as the product dimensions, the setting conditions of each equipment, the rolling schedule, etc. for achieving the target of mechanical quality) is enormous, and the data amount increases as the number of continuous rolls increases. Due to the increase, the computer load increases and the computer storage capacity becomes insufficient. Due to these constraints, at this stage, the maximum number of rolls that can be continuously rolled is reduced to about 15 rolls.

[0008] Therefore, the frequency of occurrence of the above-described problems of poor biting of the rolled material in the finish rolling mill and narrowing or doubling when the tail end comes off is greatly reduced as compared with the conventional intermittent method. However, the first hot end of the continuous hot rolling (the leading end of the rolled material consisting of a continuum of joined steel slabs) and the last end of the last hot roll (the rolled material consisting of a continuum of joined steel slabs) For tail end), this problem has not been solved.

Accordingly, the present invention provides a method for narrowing the leading end and the tail end of a rolled material consisting of a continuous body of joined billets, which is poor in biting at the front end and when the tail end comes off. It is an object of the present invention to provide a continuous hot rolling method for a steel sheet which does not cause burrs or doubling.

[0010]

SUMMARY OF THE INVENTION The present invention according to claim 1, by hot rolling line, the product tensile strength of 400MPa less than
When the steel slabs are joined and finish rolling is performed continuously, rolling is started with the first cutting edge of the continuous rolling to a finished plate thickness of 1.2 mm or more, and after the coiler is wound or near the joining point that follows. Finished thickness using running thickness change function 1.2
mm, and before the tail end of the final product leaves the finishing stand, the finished plate thickness is returned to 1.2 mm or more by using the running thickness change function near the junction. <br/> Is a continuous hot rolling method for a steel sheet.

[0011] According to a second aspect of the invention, by hot rolling line, joining the steel pieces product tensile strength is on 400MPa or more, upon continuously finish rolling, the continuous rolling first run of the outermost Start rolling at the end with a finished plate thickness of 1.4 mm or more, and use the inter-running thickness change function to reduce the finished plate thickness to less than 1.4 mm after winding the coiler or near the joining point. before part leaving the final stand finishing is, joined
Finished thickness is 1.4mm near the point using the running thickness change function
A continuous hot rolling method for a steel sheet, characterized by returning to the above.

According to a third aspect of the present invention, in a hot rolling line, the product tensile strength of the first continuous rolling and the final rolling is determined.
A billet of less than 400MPa and a finished plate thickness of 1.2mm or more,
In the middle, the product tensile strength is 400MPa or more and the finished plate thickness
Incorporating and joining steel slabs of less than 1.4 mm ,
For the joint where the change occurs, the running thickness near the joint
A continuous hot rolling method for a steel sheet, characterized by performing continuous rolling using a change function . According to a fourth aspect of the present invention, in the hot rolling line, the first and the last continuous rolling are made into a steel slab having a product tensile strength of 400 MPa or more and a finished plate thickness of 1.4 mm or more, and a product in the middle. A steel slab with a tensile strength of less than 400 MPa and a finished plate thickness of less than 1.2 mm is assembled and joined.
A continuous hot rolling method for a steel sheet, characterized in that the steel sheet is continuously rolled by using a running thickness changing function at a side thereof.

[0013] According to a fifth aspect of the invention, by hot rolling line, the product tensile strength joining steel pieces becomes less than 400 MPa, upon continuously finish rolling, the continuous rolling first run of the outermost Start rolling at the end with a finished plate thickness of 1.6 mm or more, and use the running thickness change function to reduce the finished plate thickness to less than 1.6 mm after winding the coiler or near the joining point. before part leaving the final stand finishing is, joined
Near the point, using the thickness change function during running, the finished thickness is 1.6mm
A continuous hot rolling method for a steel sheet, characterized by returning to the above.

According to a sixth aspect of the present invention, in the hot rolling line, the product tensile strength of the first continuous rolling and the final rolling is determined.
A billet of less than 400MPa and a finished plate thickness of 1.6mm or more,
In the middle, the product tensile strength is 400MPa or more and the finished plate thickness
Incorporating and joining steel slabs of less than 1.4 mm ,
For the joint where the change occurs, the running thickness near the joint
A continuous hot rolling method for a steel sheet, characterized by performing continuous rolling using a change function .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A hot rolling line to which the present invention is applied is one in which hot rolling equipment as shown in FIG. 1 is arranged, for example, and a finishing mill 14 is composed of a plurality of stands. In addition, each stand is equipped with a normal running thickness change function. The means of the present invention described in claims 1 to 4 is
In such a hot rolling line, the steel slabs are sequentially joined, and a method of setting a continuous hot rolling order when the continuous body is continuously subjected to finish rolling as a rolled material is defined. In other words, at least the first and final billets that are joined to form a continuous rolled material are made of a material that is less likely to be jammed at the tip and that does not squeeze at the end of the tail end, or at least the first tip of the first billet. For the tail end of the final book, set the thickness of the finished plate to prevent poor biting at the tip and squeezing when the tail end is pulled out. It is intended to be incorporated.

Materials that are likely to cause poor biting at the front end and squeeze when the tail end comes off are specifically the following materials. (1) A material with a thin finished plate. Low carbon steel (C: 100wtp
pm to less than 0.4 wt%), extremely low carbon steel (C: 100 wtppm or less)
For general ordinary steel with a product tensile strength of less than 400 MPa, such as, a material with a finished plate thickness of less than 1.2 mm.

(2) A hard material, that is, a material whose rolling reaction force and required rolling power are large and which easily meander. This also means that for special materials with a tensile strength of the product of 400 MPa or more, the finished plate thickness is less than 1.4 mm. In fact,
When these materials are rolled by conventional intermittent rolling, FIG.
As shown in FIG. 7 to FIG. 7, as the plate thickness becomes thinner, the leading end biting failure (see FIG. 4 and FIG. 6) and the squeezing when the tail end comes off (FIG.
(See FIG. 7). When comparing between materials,
Special materials (see Figs. 6 and 7) with a tensile strength of 400MPa or more compared to general ordinary steels (see Figs. 4 and 5), such as low carbon steel and ultra low carbon steel However, poor biting at the tip and squeezing when the tail end came off easily occurred.

Therefore, when these materials are hot-continuously rolled, at least the first roll and the final roll of the continuous rolling include:
In FIGS. 4 to 7, it is assumed that the occurrence rate of the biting defect at the leading end and the squeezing at the trailing end of the tail end is less than 0% is not applied. Instead, these materials are used in the first and last continuous rolling. It was applied to the middle between the rolls and rolled.

Similarly, the present invention as set forth in claims 5 to 6 is intended to provide at least the first and last rolls of continuous rolling that are set to a finish plate thickness that does not easily include double rubbing. Materials that are liable to cause double embedment are specifically as follows. The material is relatively hard and the finish thickness is small. It is a general plain steel with a product tensile strength less than 400MPa, such as low carbon steel (C: 100wtppm or more, less than 0.4wt%), and the finish thickness. Material less than 1.6mm. In fact, when rolling these materials by the conventional rolling method,
As shown in FIGS. 8 and 9, the thinner the plate, the more likely it is for the leading end and the tail end to contain doubles.

Therefore, when these materials are continuously hot-rolled, the first and last continuous rollings are not applied with a material which is liable to cause double rubbing, but are applied in the middle of the rolling. It was done. During the continuous rolling, in the place where the sheet thickness needs to be changed, while maintaining the state where the volume speed of the rolled material is equally distributed to each stand of the finishing mill 14, the upper and lower roll gaps and the rotation speed of the rolls during the rolling. The so-called running thickness changing method of changing the thickness is adopted. The timing of changing the running thickness is after the coiler winding, where the rolling material from the final stand of the finish rolling mill 14 to the coiler 15 is under tension and the threading is stabilized, or at the turn of the product order The vicinity of a certain junction is preferred.

By doing so, there is no occurrence of poor biting of the first end of the continuous hot rolling and squeezing or double squeezing at the end of the tail end of the last hot rolling. Can be rolled smoothly. In addition, if the thickness of the rolled material is excessively thin, the temperature drop during rolling increases and the mechanical quality deteriorates. In the present invention, about 0.8 mm is a practical lower limit of the finished plate thickness for any material.

[0022]

【Example】

(Embodiment 1) In accordance with the present invention, in a hot rolling line having the equipment row shown in FIG. 1 (the finishing mill 14 is composed of 7 stands), the row of hot continuous rolling is set as follows. Then, continuous rolling was performed to obtain an example.

Note 1st low carbon steel Finished plate thickness 1.2mm Width 1000mm 2nd Low carbon steel Finished plate thickness 1.0mm Width 1000mm 3rd Low carbon steel Finished plate thickness 0.8mm Width 1000mm 4th Low carbon steel Finished plate thickness 0.8mm 5th low carbon steel Finished plate thickness 0.8mm Width 1000mm 6th low carbon steel Finished plate thickness 0.8mm Width 1000mm 7th low carbon steel Finished plate thickness 0.8mm Width 1000mm 8th Low carbon steel Finished plate thickness 0.8mm Width 1000mm 9th Low carbon steel Finish plate thickness 0.8mm Width 1000mm 10th Low carbon steel Finish plate thickness 0.8mm Width 1000mm 11th Low carbon steel Finish plate thickness 0.8mm Width 1000mm 12th Low carbon steel Finish plate thickness 0.8mm Width 1000mm 13th 14th low carbon steel finish plate thickness 0.8mm width 1000mm 14th low carbon steel finish plate thickness 1.0mm width 1000mm 15th low carbon steel finish plate thickness 1.2mm width 1000mm
No squeezing occurred at the tail end of the fifteenth line at the end of the tail end, the board could be passed very well without breakage at the intermediate joint, and no surface quality defect occurred in the product. (Embodiment 2) According to the present invention, in a hot rolling line having the equipment row shown in FIG. 1 (the finishing mill 14 is composed of 7 stands), the row of hot continuous rolling is set as follows. Then, continuous rolling was performed to obtain an example.

Note 1st low-carbon steel Finished plate thickness 1.6mm Width 1000mm 2nd Low-carbon steel Finished plate thickness 1.2mm Width 1000mm 3rd Low-carbon steel Finished plate thickness 1.2mm Width 1000mm 4th Low-carbon steel Finished plate thickness 1.2mm 5th low-carbon steel Finished plate thickness 1.2mm Width 1000mm 6th Low-carbon steel Finished plate thickness 1.2mm Width 1000mm 7th Low-carbon steel Finished plate thickness 1.2mm Width 1000mm 8th Low-carbon steel Finished plate thickness 1.2mm Width 1000mm 9th Low carbon steel Finished plate thickness 1.2mm Width 1000mm 10th Low carbon steel Finished plate thickness 1.2mm Width 1000mm 11th Low carbon steel Finished plate thickness 1.2mm Width 1000mm 12th Low carbon steel Finished plate thickness 1.2mm Width 1000mm 13th Low carbon steel Finished plate thickness 1.2mm Width 1000mm 14th Low carbon steel Finished plate thickness 1.2mm Width 1000mm 15th Low carbon steel Finished plate thickness 1.6mm Width 1000mm Very good threading without tail end folding and rewinding The surface quality of the product did not deteriorate.

[0025]

According to the present invention, it is possible to smoothly carry out the whole hot rolling without the problem of poor biting at the front end, squeezing when the tail end comes off, and winding at the end of the tail end. It has an excellent effect that it can be rolled.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an example of a hot rolling line in which the present invention is implemented.

FIG. 2 is an explanatory diagram of a state of occurrence of a tip biting failure.

FIG. 3 is an explanatory diagram of a squeezing state at the time of tail-end loss.

FIG. 4 is a diagram showing the incidence of biting failure at the tip with respect to the finished plate thickness of a product for a material having a tensile strength of less than 400 MPa.

FIG. 5 is a graph showing the rate of occurrence of squeezing when the tail end is pulled out with respect to the finished plate thickness of a product for a material having a tensile strength of less than 400 MPa.

FIG. 6 is a diagram showing the incidence rate of biting failure at the tip with respect to the finished plate thickness of a product for a material having a tensile strength of 400 MPa or more.

FIG. 7 is a graph showing the occurrence ratio of squeezing at the tail end with respect to the finished plate thickness of a product for a material having a tensile strength of 400 MPa or more.

FIG. 8 is a diagram showing the rate of occurrence of winding in a state in which the front end is doubled with respect to a finished plate thickness of a product for a material having a tensile strength of less than 400 MPa.

FIG. 9 is a diagram showing the rate of occurrence of winding in a state where the tail end is included with respect to a finished plate thickness of a product for a material having a tensile strength of less than 400 MPa.

[Explanation of symbols]

 1a, 1b Roll for rolling 2 Rolled material 3a, 3b Side guide 4 Looper 5 Abnormal part of plate passing at longitudinal end 6 Winding / unwinding device 7 Leveler 8 Crop shear 9 Guide 10 Joining device 10a Input side clamping and pressing device 10b Discharge side clamping and pressing device 11 Ridge removal device (burr removal device) 12 Rotary blade 13 Cooling (water cooling) header 14 Hot finishing rolling mill group (finishing rolling mill) 15 Coirer 16 Hot run table

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Futa Goto 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Inside the Chiba Works (72) Inventor Akio Adachi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Chiba Works, Ltd. (56) References “Kawasaki Steel Technical Report”, Vol. 28, No. 4 (1996), pp. 224-230, "IRON AND STEEL ENGINEER", Vol. 74, No. 2 (Feb. 1997), pp. 41-47 edited by the Iron and Steel Institute of Japan, “History of Rolling Technology Development and Recent Progress” (March 5, 1985), p. 182 (58). .Cl. ⁷ , DB name) B21B 1/26 B21B 15/00 B21B 37/18 B21B 37/72

Claims (6)

(57) [Claims] 1. The product tensile strength in a hot rolling line
Joining 400MPa less than become billet upon continuously finish rolling, the first run of the finishing cutting edge portion thickness 1.2mm the continuous rolling
Rolling is started as above, and after finishing winding the coiler or near the joining point, use the thickness change function during running to make the finished plate thickness less than 1.2 mm, and before the tail end of the last roll leaves the final stand. In the vicinity of the joint,
A continuous hot rolling method for steel sheets, characterized in that the finished sheet thickness is returned to 1.2 mm or more by using a steel sheet. 2. The product tensile strength in a hot rolling line
Joining 400MPa or more on become billet upon continuously finish rolling, the first run of the finishing cutting edge portion thickness 1.4mm the continuous rolling
Rolling is started as above, and after finishing winding the coiler or near the joining point, use the running thickness change function to make the finished plate thickness less than 1.4 mm. In the vicinity of the joint,
A continuous hot rolling method for a steel sheet, wherein the finished sheet thickness is returned to 1.4 mm or more by using a steel sheet. 3. In a hot rolling line, the first and last continuous rolling are made into a steel slab having a product tensile strength of less than 400 MPa and a finished plate thickness of 1.2 mm or more. joined by incorporating a steel piece to be higher than or equal finish thickness less than 1.4 mm 400 MPa, junction changes finish thickness occurs Nitsu
And a continuous hot rolling method for a steel sheet, wherein a continuous rolling is performed near a joining point by using a function of changing a running thickness . 4. In a hot rolling line, the first and last continuous rolling are made into a slab having a product tensile strength of 400 MPa or more and a finished plate thickness of 1.4 mm or more, and the product tensile strength is intermediate between them. joined incorporate slab containing less than a and finish thickness less than 1.2 mm 400 MPa, junction changes finish thickness occurs Nitsu
And a continuous hot rolling method for a steel sheet, wherein a continuous rolling is performed near a joining point by using a function of changing a running thickness . 5. The product tensile strength in a hot rolling line
Joining 400MPa less than become billet upon continuously finish rolling, the first run of the finishing cutting edge portion thickness 1.6mm the continuous rolling
Rolling is started as above, and after finishing winding the coiler or near the joining point, use the running thickness change function to make the finished plate thickness less than 1.6 mm, and leave the tail end of the final sheet before leaving the finishing stand. In the vicinity of the joint,
A continuous hot rolling method for a steel sheet, wherein the thickness of the finished sheet is returned to 1.6 mm or more by using a steel sheet. 6. In the hot rolling line, the first and the last continuous rolling are made into a slab having a product tensile strength of less than 400 MPa and a finished plate thickness of 1.6 mm or more, and the product tensile strength is intermediate between them. joined by incorporating a steel piece to be higher than or equal finish thickness less than 1.4 mm 400 MPa, junction changes finish thickness occurs Nitsu
And a continuous hot rolling method for a steel sheet, wherein a continuous rolling is performed near a joining point by using a function of changing a running thickness .