JP2009214163A - Method for joining metal strip coil, and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for joining metal strips where whether the joined part between metal strip coils is good can be determined with high reliability, and the improvement of productivity can be achieved, and to provide a device therefor. <P>SOLUTION: In the metal strip coil joining method where, before cold tandem rolling, the tail part of a preceding metal strip coil S1 and the tip part of the subsequent metal strip coil S2 are joined, so as to be a continuous coil, in a state where the part near the tail of the preceding metal strip coil S1 and the part near the tip of the subsequent metal strip coil S2 are clamped, external force or elongation obtained by multiplying prescribed tensile stress by the cross-sectional area of the joined part is applied to the joined part, and whether fracture is present in the joined part is detected, so as to determine whether the joined part is good. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a metal strip coil joining method and apparatus for joining a rear end portion of a preceding metal strip coil and a front end portion of a succeeding metal strip coil to form a continuous coil before cold rolling.

  For the purpose of improving productivity and reducing off-gauge, the cold tandem rolling mill is connected from a batch method (a method that rolls through and strips every coil) to a continuous method (joining coils upstream of the tandem rolling mill). The method has been shifted to a continuous rolling method. As a coil joining device for the continuous method, devices such as a flash butt welding method and a laser welding method have already been developed and put into practical use.

  In recent years, the demand for high-strength metal strip materials (hereinafter referred to as “HITEN”) used as automobile steel sheets has been increasing in order to improve collision safety and reduce vehicle weight. Since high tensile steel has more Si components than ordinary steel, a Si concentrated layer is easily formed during welding. Since this Si-enriched layer is not ductile, it has a characteristic that it easily breaks when subjected to plastic deformation by a cold tandem rolling mill. For this reason, a method is employed in which the thickened layer is upset, the thickened layer is pushed out to the outer surface of the strip, and the portion (beat portion) is trimmed. However, even if this method is used, welding may be insufficient, and as a result, there are frequent breaks in a cold tandem rolling mill (especially a rear stage stand).

  FIG. 3 is a schematic view showing an example of a conventional coil joining machine, and shows a case of a flash butt welding machine as a welding method. In FIG. 3, this coil welding machine is installed upstream of the cold tandem rolling mill. A looper is installed between the coil joining machine and the cold tandem rolling mill, and the trailing end of the preceding metal strip S1 and the leading end of the trailing metal strip S2 can be stopped for a short time. During this stop time, while welding with the coil welder, the rear end portion of the preceding metal strip S1 is clamped to the fixed base 1 with the electrode 3, and cut with a shear (not shown) to adjust the cutting shape. Moreover, the front-end | tip part of the succeeding metal strip S2 is clamped to the movement stand 2 with the electrode 4, and it cut | disconnects with a shear | shear (not shown), and arranges a cutting shape. Thereafter, the moving table 2 is brought close to the fixed table 1 side, and the rear end portion of the preceding metal strip S1 and the leading end portion of the following metal strip S2 are brought close to each other with a voltage applied between the electrodes of the fixed table 1 and the moving table 2. Then, it is pressed and bonded quickly at a predetermined upset cost while flashing. When the upset is completed, burrs are generated at the joint, and the burrs are removed by a trimmer (not shown). After that, release the clamp and judge the acceptance of the weld by visual inspection, or judge the acceptance of the joint with the conventional inspection technique described below, and if it passes, pass the plate, otherwise The joining operation and the inspection operation are repeated until the inspection result is acceptable.

As a method for solving the above-described welding failure, for example, a method of accurately detecting a difference in abutting amount at both end portions in the width direction of the metal strip of the joint portion, and comparing the set value with a set value (for example, a method of determining whether the joint portion is acceptable or not ( Patent Document 1) and a method of measuring the temperature distribution of the joint and determining whether the joint is acceptable from the temperature distribution (see, for example, Patent Document 2) are disclosed.
Japanese Patent Laid-Open No. 02-84278 JP 2005-342788 A

  However, none of the conventional methods for inspecting a joint is to inspect by directly applying a load to the joint and detecting the fracture or strength of the joint. For this reason, there is a case where a bonding failure is overlooked or a good bonding portion is determined as a bonding failure. A rejected product produced by such a low-reliability inspection method has led to a decrease in productivity. There is still room for improvement in the method of inspecting the metal strip coil joint, and thus in the method of joining the metal strip coil including the inspection method.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a metal strip joining method and apparatus capable of accurately determining whether or not a joining portion of a metal strip coil is highly reliable and improving productivity.

The present invention has been made to solve the above problems, and the gist of the invention is as follows.
(1) A metal strip coil after hot rolling or a metal strip coil after hot rolling / pickling is subjected to a rear end portion of a preceding metal strip coil and a front end portion of a subsequent metal strip coil before cold tandem rolling. In the metal strip coil joining method for joining to a continuous coil, 0.2% of the preceding metal strip is clamped after joining the back end of the preceding metal strip coil and the end of the succeeding metal strip coil after joining. Compare the external force obtained by multiplying the proof stress by the thickness and width of the preceding metal strip and the external force obtained by multiplying the 0.2% proof strength of the subsequent metal strip by the thickness and width of the subsequent metal strip. A metal strip coil joining method characterized by providing 0.2 to 5.0% elongation, detecting the presence or absence of breakage of the joint, and judging whether or not the joint is acceptable.
(2) The metal strip coil after hot rolling or the metal strip coil after hot rolling / pickling is subjected to the rear end portion of the preceding metal strip coil and the front end portion of the subsequent metal strip coil before cold tandem rolling. In the metal strip coil joining method for joining to a continuous coil, a portion near the rear end of the preceding metal strip coil and a portion near the front end of the succeeding metal strip coil are clamped after joining, and 0 is applied to the joint portion of the continuous coil. A metal strip coil characterized by continuously detecting elongation and load while applying elongation until reaching an elongation of 2 to 5.0%, and judging whether the joint is acceptable or not based on an incremental tendency of the load with respect to elongation. Joining method.
(3) The metal strip coil after hot rolling or the metal strip coil after hot rolling / pickling is subjected to a rear end portion of the preceding metal strip coil and a front end portion of the subsequent metal strip coil before cold tandem rolling. In the metal strip coil joining method, the preceding metal strip is joined to the joining portion of the continuous coil in a state of being clamped after joining the rear end of the preceding metal strip coil and the front end of the succeeding metal strip coil. The external force obtained by multiplying the 0.2% proof stress of the preceding metal strip by the plate thickness and the plate width and the external force obtained by multiplying the 0.2% proof stress of the succeeding metal strip by the plate thickness and the plate width of the succeeding metal strip It is characterized by continuously detecting the load and elongation while applying a load until the lower external force is reached, and judging whether the joint is acceptable or not from the incremental tendency of the elongation with respect to the load. Genus strip coil bonding methods.
(4) The metal strip coil joining method according to (1), (2) or (3), wherein when the joining part is accepted or rejected, the joining defective part is removed and rejoining is performed.
(5) The metal strip coil after hot rolling or the metal strip coil after hot rolling and pickling is disposed upstream of the cold tandem rolling mill, and the rear end of the preceding metal strip coil and the trailing metal strip coil In the metal strip coil joining apparatus which joins with a front-end | tip part and makes it a continuous coil, it joins in the state which clamped after the back end of the preceding metal strip coil after joining, and the front end side of a succeeding metal strip coil after joining The external force obtained by multiplying the 0.2% proof stress of the preceding metal strip by the plate thickness and width of the preceding metal strip, and the external force obtained by multiplying the 0.2% proof stress of the succeeding metal strip by the plate thickness and plate width of the subsequent metal strip. A load applying means for applying a lower external force or elongation of 0.2 to 5.0%, a load applying means, a load applying control means for controlling the external force or elongation, and a joint portion. A metal strip coil joining apparatus comprising: a break detecting means for detecting a broken state of a joint portion of the metal strip in a state where the external force or elongation is applied; and a detection result display means for displaying the broken state. .
(6) The metal strip coil after hot rolling or the metal strip coil after hot rolling and pickling is disposed upstream of the cold tandem rolling mill, and the rear end of the preceding metal strip coil and the trailing metal strip coil In a metal strip coil joining apparatus that joins at a tip portion to form a continuous coil, a load applying unit that applies elongation to the joined portion of the continuous coil until reaching an elongation of 0.2 to 5.0%, and the elongation. A load application control means for controlling, an elongation / load detection means for continuously detecting the elongation and the load during the application of the elongation, and a detection result display means for displaying an incremental tendency of the load with respect to the elongation. A metal strip coil joining device.
(7) Located upstream of the cold tandem rolling mill, the metal strip coil after hot rolling or the metal strip coil after hot rolling and pickling is used for the rear end of the preceding metal strip coil and the trailing metal strip coil. In the metal strip coil joining apparatus which joins with a front-end | tip part and makes it a continuous coil, 0.2% proof stress of a preceding metal strip multiplied by board thickness and board width of a preceding metal strip, and 0.2% of a succeeding metal strip A load applying means for comparing the external force obtained by multiplying the plate strength and the plate width of the trailing metal strip by the% proof stress and applying elongation until reaching the load of the lower external force, and a load applying control means for controlling the load; A metal comprising load / elongation detection means for continuously detecting the load and elongation during the application of the load, and detection result display means for displaying an incremental tendency of the elongation with respect to the load. Trip coil bonding apparatus.

  The present invention applies to metal strips such as steel, stainless steel, and titanium. As a joining method, welding (laser, flash bat, ultrasonic), pressure welding (vibration welding), or the like is used.

  Since the present invention directly detects the joint strength including breakage, the coil joint is inspected with high reliability. For example, even a high-grade material that is difficult to weld, such as high tension, does not miss the welding failure of the coil joint. As a result, plate breakage during cold tandem rolling is eliminated, and productivity can be improved.

  FIG. 1 is a schematic diagram showing an example of a coil joining machine according to the present invention, and shows a case of a flash butt welder as a welding method. In FIG. 1, this coil welding machine is installed upstream of a cold tandem rolling mill, and a looper (not shown) is installed between the welding machine and the cold tandem rolling mill. The trailing end of the preceding metal strip S1 and the leading end of the trailing metal strip S2 can be stopped for a short time. During this stop time, during welding with the welding machine, the rear end portion of the preceding metal strip S1 is clamped to the fixed base 1 with the electrode 3, and cut with a shear (not shown) to adjust the cutting shape. Moreover, the front-end | tip part of the trailing metal strip S2 is clamped to the moving stand 2 with the electrode 4, and it cut | disconnects with a shear, and arranges a cutting shape. Thereafter, the moving table 2 is brought close to the fixed table 1 side, and the voltage is applied between the electrodes 3 and 4 of the fixed table 1 and the moving table 2, and the leading end of the preceding metal strip S1 and the leading end of the trailing metal strip S2 are applied. And pressurizing quickly and joining at a predetermined upset cost while flashing the flash. When the upset is completed, burrs are generated in the welded portion (joined portion), and the burrs are removed with a trimmer (not shown).

  After welding, an external force obtained by multiplying the 0.2% proof stress of the preceding material or the following material by the cross-sectional area of the welded portion is applied by the hydraulic cylinder 5 attached to the fixed base 1. The applied external force is detected by the load cell 8 attached to the movable table 2, and the stroke of the hydraulic cylinder 5 is controlled by the load application control means 10 so as to be a predetermined external force. The load application control means 10 is preset with an external force to be loaded. In the state where an external force is applied to the welded portion, the light source 6 installed at the lower part of the welded portion is illuminated over the entire width of the welded portion. Light leaking from the welded portion is detected using a light receiver (light sensor) 7 installed on the upper portion of the welded portion. The detection result is displayed on the detection result display means (monitor) 12. The state of the welded portion displayed on the detection result display means 10 is visually observed to determine whether there is an abnormality in the welded portion. If leakage light is detected, the weld is determined to be rejected. It is also possible to input a signal from the light receiver 7 to a computer (not shown), determine the presence or absence of leakage light with the computer, and automatically determine whether the welded part is acceptable.

  The applied external force reaches at least the plastic deformation stress of the steel sheet of either the preceding material or the following material. Thereby, when there is poor welding, a gap is generated due to a difference in deformation amount between a portion where plastic deformation occurs and a portion where plastic deformation does not occur. Since the leakage of light from this gap is detected, the applied external force is 0.2% of the preceding metal strip multiplied by the plate thickness and the plate width of the preceding metal strip, and 0.2% of the following metal strip. It is desirable that the external force is lower than the external force obtained by multiplying the proof stress by the plate thickness and the plate width of the subsequent metal strip. The error of 0.2% proof stress is not particularly problematic as long as it is within ± 10% in view of general work hardening of metals, and more preferably within about ± 5%.

  In another embodiment of the metal strip coil joining method of the present invention, after upsetting and removal of burrs, an elongation of 0.2 to 5.0% occurs in the hydraulic cylinder 5 having a position detecting function attached to the fixed base 1. Control cylinder position. At that time, whether or not the welded portion is acceptable is determined using the light source 6 installed at the lower portion of the welded portion and the light receiver 7 installed at the upper portion of the welded portion in the same manner as the above method. In the case where there is a bonding failure, when the elongation of 0.2% or more is given, the light emitted from the light source 6 and leaked from the bonding failure portion can be detected by the light receiver 7. On the other hand, imparting an elongation of 5% or more is not preferable because it requires a large amount of equipment.

  In still another embodiment of the metal strip coil joining method of the present invention, a load application control device is provided so that a predetermined elongation occurs in the hydraulic cylinder 5 having a stroke detecting function attached to the fixed base 1 after the upset and the burr removal. 10 to control the stroke. At the same time, the load applied by the load cell 8 attached to the movable table 2 is continuously detected. The detected elongation and load are displayed on the detection result display device 12 as an elongation-load diagram. In the elongation-load diagram, the incremental tendency of the load with respect to the elongation is visually observed to determine whether the weld is acceptable or not. When the load decreases rapidly with respect to elongation, it is considered that a crack has occurred in the welded portion, and the welded portion is determined to be rejected. In contrast to the above method, it is also possible to detect the elongation with respect to the load and determine whether or not the welded portion is acceptable from the incremental tendency of the elongation with respect to the load. The detected values of elongation and load are input to a computer (not shown), and the rate of change of load with respect to elongation is obtained by the computer. Then, the pass / fail of the welded portion may be automatically determined by comparing the obtained rate of change with a preset threshold value.

  Here, a reliability experiment of the bonding strength will be described. As a test coil, Hiten (a 980 MPa class product) having a plate thickness of 1.0 mm and a plate width of 1240 mm was used. After coil welding, a predetermined elongation rate (here, 3%) or a predetermined stress (here, 490 MPa (external force is 607.6 kN) was applied. The welding method was flash butt welding, and the welding conditions were changed. (1) Intentionally leaving the Si-enriched layer in the weld zone with a small amount of upset and breaking reliably (b) Do not know whether or not to break under normal joining conditions, (c) Larger upset amount In order to prevent oxidation during welding, the entire welded portion is sealed with an inert gas, and the upset time is lengthened so that it hardly breaks. Using the installed light receiver 7, the quality of the welded part was examined under 100 conditions.

  Under the welding conditions (a) for reliably breaking, when elongation or stress was applied, a defective portion was detected at a fracture joint with a probability of 81%. (B) Under welding conditions where it was not known whether or not to break, when elongation or stress was applied, a defective portion was detected at a fracture or joint at a probability of 38%. In addition, (c) Under the welding conditions that hardly break, when elongation or stress was applied, there was no defective portion in the fracture or joint.

FIG. 2 shows the relationship between time and external force change when elongation is applied to a predetermined value at a constant speed after coil joining. In this case, since the elongation is applied at a constant speed, the horizontal axis is proportional to the elongation. The test coil was Hiten (980 MPa class product) with a plate thickness of 1.0 mm and a plate width of 1240 mm. As the conditions of the shape of the test coil, flat (steepness 0.5% or less: symbol ◯) and end elongation (steepness 2.5 to 3.0%: symbols ●, □) were used. The predetermined elongation was 3%.
In FIG. 2, ○ and ● are welded under the condition (c), and □ is welded under the condition (b).

FIG. 2 shows the relationship between time and load on a monitor, and shows what the operator has checked to see if there is a change in this sudden load change. Although the initial rise of the load increment differs depending on the plate shape in all three conditions, the subsequent load increment is not affected by the plate shape. Under the condition of (b), the condition of the symbol □ having a weld failure that does not lead to breakage is observed, and a change is observed in the subsequent load increment, and the load is partially reduced. Since this partial decrease may not be found unless an elongation of 0.2% or more is given, it is desirable to give an elongation of 0.2% or more. Further, if the test coil has a plate shape with a steepness of 2% or more, the occurrence of this load reduction phenomenon may be delayed. In this case, it is desirable to give an elongation of preferably 0.5% or more. It is more preferable to give an elongation of 3%. On the other hand, imparting an elongation of 5% or more is not preferable because it requires a large amount of equipment.
Furthermore, the test coils having different plate shapes were also tested under the same elongation imparting conditions and other welding conditions. As a result, a defective part was detected with a probability of 100% in the fractured joint under the welding conditions (A) of the one that surely fractured. Moreover, although it was not known whether it fractured or not, a good part was detected with a 90% probability at the joint under the welding conditions (b). In addition, in the welding conditions (c) that hardly break, there were no defective portions in the joint.

  A test was performed using the coil welding machine shown in FIG. 1 as a temper rolling mill. This welding machine was installed on the cold tandem rolling mill inlet side. A looper is installed between the welding machine and the cold tandem rolling mill, and the metal strip can be stopped for a maximum of 40 seconds in the welding machine at 250 m / min when the cold tandem rolling speed is reduced. The materials used in the experiment were the heat of high-tensile steel sheets of C: 0.08%, Si: 1.3%, Mn: 1.7%, P: 0.01%, S: 0.02% by mass%. Metal strip after hot rolling and pickling. The plate thickness of the material is 3.0 mm and the plate width is 1240 mm. The cold tandem rolling mill consists of 5 stands, all of which are quadruple rolling mills. The cold rolling rate is about 67%, and the 5 stand outlet side plate thickness is 1 mm. The tension between the stands is 147 to 245 MPa, and is set to increase as going to the subsequent stage.

  As an example of the prior art, a case where 300 coils (single weight 16 tons) are continuously performed using the welding machine shown in FIG. 3 and a case where the welding machine shown in FIG. Comparison was made by the number of breaks when 300 coils (single weight 16 tons) were rolled. The presence or absence of breakage was determined visually.

  In the case of the present invention, after coil joining, elongation is applied at a constant speed to a desired value (5%), the relationship between time and load is displayed on the monitor, and the operator determines whether there is a change in this rapid load increment variation. Then, the pass / fail of the joint was judged. When it was judged that the joining was poor, the rolling speed of the cold tandem rolling mill was immediately reduced to secure the re-welding time.

  In the case of the prior art, among the 300 coils, no welding defect was visually detected, but 63 were broken on the final stand entering side. At that time, the rolling mill for about 15 minutes was stopped for each work break, such as reworking the work roll, and an off gauge was generated by 20 m. On the other hand, in the present invention, 65 of the 300 coils detected poor welding, but the plate breakage and off gauge were zero by re-welding to remove the poor welding. However, because of the slowdown, productivity decreased slightly. When this productivity was evaluated when the operation of the rolling mill was stopped, the total amounted to 10 minutes.

  In the prior art, it was not possible to sufficiently prevent plate breakage due to poor welding, and it was forced to reduce productivity due to off-gauge generation and frequent mill change due to frequent roll replacement. The plate breakage disappeared and productivity was improved.

It is a schematic diagram which shows the structure of the metal strip coil joining apparatus of this invention. In this invention, it is a diagram explaining the method to detect the intensity | strength of a junction part from the increase tendency of the load with respect to elongation. It is a schematic diagram which shows the structure of the conventional metal strip coil joining apparatus.

Explanation of symbols

S1 Lead metal strip S2 Trailing metal strip 1 Fixed base 2 Moving base 3, 4 Electrode 5 Cylinder 6 Light source 7 Light receiver 8 Load cell 10 Load application control means 12 Detection result display means

Claims (7)

  The metal strip coil after hot rolling or the metal strip coil after hot rolling and pickling is joined at the rear end of the preceding metal strip coil and the front end of the subsequent metal strip coil before cold tandem rolling. In the metal strip coil joining method using a continuous coil, 0.2% of the preceding metal strip is joined to the joining portion in a state where the back end of the preceding metal strip coil and the end of the following metal strip coil are clamped after joining. Compare the external force obtained by multiplying the proof stress by the thickness and width of the preceding metal strip and the external force obtained by multiplying the 0.2% proof strength of the subsequent metal strip by the thickness and width of the subsequent metal strip. A metal strip coil joining method characterized by providing 0.2 to 5.0% elongation, detecting the presence or absence of breakage of the joint, and judging whether or not the joint is acceptable.   The metal strip coil after hot rolling or the metal strip coil after hot rolling and pickling is joined at the rear end of the preceding metal strip coil and the front end of the subsequent metal strip coil before cold tandem rolling. In the metal strip coil joining method for forming a continuous coil, 0.2 to the joined portion of the continuous coil is clamped after joining the rear end of the preceding metal strip coil and the front end of the succeeding metal strip coil. A metal strip coil joining method characterized by continuously detecting elongation and load while imparting elongation until reaching 5.0% elongation, and judging whether or not the joint is acceptable from the incremental tendency of the load relative to elongation.   The metal strip coil after hot rolling or the metal strip coil after hot rolling and pickling is joined at the rear end of the preceding metal strip coil and the front end of the subsequent metal strip coil before cold tandem rolling. In the metal strip coil joining method of forming a continuous coil, the leading metal strip coil is joined to the joining portion of the continuous coil in a state where the back end of the preceding metal strip coil and the end of the following metal strip coil are clamped after joining. The external force obtained by multiplying the 0.2% proof stress by the thickness and width of the preceding metal strip is lower than the external force obtained by multiplying the 0.2% proof strength of the succeeding metal strip by the thickness and width of the subsequent metal strip. The load is characterized by continuously detecting the load and elongation while applying the load until reaching the external force, and judging whether the joint is acceptable or not based on the incremental tendency of the elongation with respect to the load. Strip coil bonding methods.   4. The metal strip coil joining method according to claim 1, wherein when the joining part is accepted or rejected, the joining defective part is removed and rejoining is performed.   Located upstream of the cold tandem rolling mill, the metal strip coil after hot rolling or the metal strip coil after hot rolling and pickling is connected to the rear end of the preceding metal strip coil and the front end of the subsequent metal strip coil. In the metal strip coil joining apparatus joined to form a continuous coil, the preceding metal strip coil is joined to the joining portion in a state where the back end of the preceding metal strip coil and the front end of the succeeding metal strip coil are joined and clamped after joining. Comparison of the external force obtained by multiplying the 0.2% proof stress of the strip by the thickness and width of the preceding metal strip and the external force obtained by multiplying the 0.2% proof strength of the succeeding metal strip by the thickness and width of the subsequent metal strip Load applying means for applying a lower external force or elongation of 0.2 to 5.0%, load applying control means for controlling the external force or elongation, and applying the external force or elongation to the joint. Given by a fracture detection means for detecting the rupture state of the joint portion of the metal strip in state, the detection result display means and the metal strip coil bonding apparatus characterized by comprising the displaying the break state.   Located upstream of the cold tandem rolling mill, the metal strip coil after hot rolling or the metal strip coil after hot rolling and pickling is connected to the rear end of the preceding metal strip coil and the front end of the subsequent metal strip coil. In the metal strip coil joining apparatus joined to form a continuous coil, a load applying means for applying elongation until the elongation of the continuous coil reaches 0.2 to 5.0%, and a load for controlling the elongation It is characterized by comprising an application control means, an elongation / load detection means for continuously detecting the elongation and the load during the application of the elongation, and a detection result display means for displaying an incremental tendency of the load with respect to the elongation. Metal strip coil joining device.   Located upstream of the cold tandem rolling mill, the metal strip coil after hot rolling or the metal strip coil after hot rolling and pickling is connected to the rear end of the preceding metal strip coil and the front end of the subsequent metal strip coil. In the metal strip coil joining device, which is joined to form a continuous coil, the 0.2% proof stress of the preceding metal strip is multiplied by the thickness and width of the preceding metal strip, and the 0.2% proof stress of the succeeding metal strip. Comparing the external force obtained by multiplying the plate thickness and the plate width of the trailing metal strip and applying the load until the lower external force is reached, the load applying control unit for controlling the load, and during applying the load And a detection result display means for displaying an incremental tendency of the elongation with respect to the load. Le bonding apparatus.

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