JP3624787B2 - Metal strip connection method by lap seam welding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for connecting metal strips by lap seam welding for processing a metal plate in a process line.
[0002]
[Prior art]
In general, lap seam welding is widely used as a welding method for connecting metal bands in process lines such as a continuous annealing line for metal bands and a continuous molten metal plating line.
For example, in the continuous annealing line, as shown in FIG. 5, the preceding metal strip 1 and the subsequent metal strip 2 are connected by lap seam welding with a lap seam welding device 20 disposed upstream of the continuous annealing furnace 30. Both metal strips 1 and 2 are annealed.
[0003]
An example of the lap seam welding apparatus 20 is shown in FIG. In FIG. 6, 1a is the tail end of the preceding metal strip, 2a is the tip of the trailing metal strip, 3 is the welded portion, 4a and 4b are the upper and lower disk electrodes, 5 is the welding power source, 6 is the transformer, H _1, H ₂ respectively preceding metal strip, the thickness of the trailing metal strip.
In lap seam welding, the tail end portion 1a of the preceding metal strip 1 and the tip end portion 2b of the following metal strip 2 are overlapped and pressurized from above and below, and the leading metal strip 1 is passed from the welding power source 5 through the transformer 6. The disc electrodes 4a and 4b are moved in the width direction of the preceding metal strip 1 and the succeeding metal strip 2 while passing a current through the disc electrodes 4a and 4b arranged above and below the succeeding metal strip 2, and sequentially welded. By forming the portion 3, the leading metal band 1 and the trailing metal band 2 are connected.
[0004]
The leading metal strip 1 and the trailing metal strip 2 are repeatedly bent in the continuous annealing line by the conveying rolls 70 in the continuous annealing furnace 30 and the looper 30a as shown in FIG.
By the way, in lap seam welding for connecting metal bands, the welding current, electrode pressurization, welding speed, and the like are determined by the thickness of both metal bands, the material of both metal bands, and the like.
[0005]
For example, in Japanese Patent Application Laid-Open No. 63-203285, as shown in FIG. 7, a range C surrounded by a curve A and a curve B is stored in a controller, and the steel strip overlap thickness at the time of welding, A welding determination method for steel strip connection welds in a process line for determining whether welding is good or bad is introduced to the controller.
However, when a metal strip is connected by lap seam welding and passed through a continuous annealing line, it may break from the connection depending on the connection conditions of the metal strip, even if the welding current and electrode pressure are appropriate. It was.
[0006]
For this reason, dangerous work such as removing a broken metal strip in a continuous process line is performed, it takes a long time to recover, the productivity is significantly reduced, and the continuous annealing furnace is again heated to a high temperature. Therefore, there was a problem that energy consumption increased.
[0007]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to eliminate the above-mentioned problems of the prior art, and the connection of metal bands by lap seam welding that does not break from the connection portion even when repeatedly bent by a transport roll in the process line. It is to provide a method.
[0008]
[Means for Solving the Problems]
The inventors of the present invention have observed the metal strip passing through the continuous annealing line in detail, and as a result, the metal strip just before the fracture has been bent in the vicinity of the connecting portion between the preceding metal strip 1 and the subsequent metal strip 2. The present invention was completed by discovering that this was caused by repeated bending by the conveying rolls in the process line.
[0009]
The present invention is a metal band connecting method for connecting a preceding metal band and a subsequent metal band, which are repeatedly bent by a plurality of conveying rolls in a process line, by lap seam welding, and the combination of the two metal bands is described below. A method for connecting metal strips by lap seam welding, wherein the parameter α represented by the formula (1) is 0.6 or more and 2.5 or less.
[0010]
α = (σ _ta · H _a · W _a ) / (σ _YPb · H _b · W _b ) (1)
σ _ta = σ _YPa · {(2 · r · σ _YPa ) / (H _a · E _a ) −1}
Σ _YP : Yield point of metal strip, H: Plate thickness of metal strip, W: Plate width of metal strip, r: Roll radius of the smallest diameter roll among a plurality of transport rolls, E: Young's modulus of metal strip , Subscript a; one of the preceding metal strip and the succeeding metal strip, subscript b; plate thickness H and plate width W, which has the larger product of the plate thickness H, plate width W, and yield point σ _YP the smaller the product of the yield point sigma _YP and is the other of the metal strip of the preceding metal strip and the following metal strip, the yield point of the metal strip, plate thickness, plate width, Young's modulus at connection Is the value of each metal band.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The cause of the breakage of the connection part in the continuous annealing line is that the vicinity of the connection part between the preceding metal band 1 and the subsequent metal band 2 is repeatedly bent by the looper 30a shown in FIG. 5 and the transport roll 70 in the continuous annealing furnace 30. Since it was found that bending accompanied by a local decrease in thickness occurred in the vicinity of the connection portion, a repeated bending test of the connection portion was performed as follows.
[0012]
FIG. 1A and FIG. 1B are a plan view and an XX sectional view of FIG. FIG. 2A to FIG. 2D are cross-sectional views illustrating a repeated bending method. FIG. 3 is a cross-sectional view showing a bent portion generated in the connection portion. FIG. 4 is a graph showing the relationship between the parameter α in the repeated bending test and the presence or absence of occurrence of a bent portion.
[0013]
Here, a is one side of the metal strip, ae is the end of the metal strip on one side, b is the other side of the metal strip, BE is the end of the metal strip on the other side, W _a is one side of the metal strip width, W _b is the other side of the metal band width, H _a one side of the metal strip thickness, H _b is the other side of the metal strip thickness, 3 welds, 4 welding line, 7 roll, r ₀ is a roll radius and 8 is a bent portion.
Moreover, a calculates _| requires the product of sheet _{| seat} thickness H (mm), sheet _{| seat} width W (mm), and yield point (sigma) _YP (Pa) about both metal bands of the preceding metal band 1 and the succeeding metal band 2, The metal band with the larger product is b, and b is the metal band with the smaller product.
[0014]
The repeated bending test piece of the connecting portion was obtained by changing the thickness, width and yield point of the preceding metal strip 1 and the trailing metal strip 2 in various ways, and using the lap seam welding apparatus shown in FIG. After the two metal bands are overlapped and the disc electrode is moved, the connecting portion is cut out. The vicinity of both width end portions of the connecting portion is cut and removed in a substantially arc shape.
[0015]
First, as shown in FIGS. 1 (a) and 1 (b), the repeated bending test piece of the connecting portion is placed between the point P on the peripheral surface of the roll 7 and the welded portion 3 as shown in FIGS. by positioning the and placed on a roll 7 of radius r _0. In the first bending, the metal bands a and b were bent along the peripheral surface of the roll 7 as shown in FIG. In the second bending, as shown in FIG. 2 (b), the metal bands a and b are arranged so that the metal band b is between the point P on the peripheral surface of the roll 7 and the welded portion 3. The metal strips a and b were bent along the roll surface as shown in FIG. Next, as shown in FIG. 2D, metal bands a and b were arranged. Thereafter, the bending was repeated a predetermined number of times as shown in FIGS. 2 (a) to 2 (d).
[0016]
And about each repeated bending test piece, as shown in FIG. 3, within a predetermined number of times, it was investigated whether bending occurred in the connection part vicinity.
A thin steel plate was used as the metal strip, the roll radius was 750 mm, the predetermined number of repeated bendings was the maximum number of bendings in an ordinary process line, and the test was performed at room temperature.
In addition, if the bending part does not occur after a predetermined number of repeated bendings, bending will not occur even if the number of bendings is further increased, while if the bending part occurs within the predetermined number of times, bending will occur. After being bent several times, it broke. Therefore, the test was stopped at the time when the bent portion was generated within the predetermined number of times.
[0017]
Based on the results of this repeated bending test, various studies were made on the relationship between the thickness of the metal strips a and b, the plate width, the yield point, the roll radius, and the presence or absence of occurrence of a bent portion, and is expressed by equation (2). It has been clarified that the occurrence of bending at the connecting portion can be arranged by the parameter α.
That is, as shown in FIG. 4, it has been found that bending can be prevented by connecting the combination of both metal bands so that the parameter α is 0.6 or more and 2.5 or less.
[0018]
α = (σ _ta · H _a · W _a ) / (σ _YPb · H _b · W _b ) (2)
In equation (2), the metal strip a on one side is obtained by calculating the product of the plate thickness, plate width, and yield point of the metal strip for each of the preceding metal strip 1 and the succeeding metal strip 2. The metal band having the larger product of the yield point and the other metal band b is the metal band having the smaller product. Also, σ _YPa and σ _YPb are the yield points of the metal bands a and b, W _a and W _b are the widths of the metal bands a and b, and H _a and H _b are the thicknesses of the metal bands a and b. Further, σ _ta is the tension expressed by the formula (3) necessary to bend the metal band a along the roll of radius r ₀ , and E _a is the Young's modulus (Pa) of the metal band a.
[0019]
σ _ta = σ _YPa · {(2 · r ₀ · σ _YPa ) / (H _a · E _a ) −1} ·· (3)
The parameter α used in the present invention described above is shown with H _a / H _b on the horizontal axis, but H _a · H _b , W _a / W _b , σ _YPa / σ _YPb, etc. are taken on the horizontal axis. Can also be shown.
In the repeated bending test of the connecting portion described above, a thin steel plate is used as the metal strip, the roll radius is 750 mm, the predetermined number of repeated bendings is the maximum number of bendings in a normal process line, and the test is performed at room temperature. Is based on semi-theory, so it is not limited to repeated bending test conditions. For example, the connection method of this application is effective even when the temperature rises in the process line through plate and the characteristic value of the metal strip such as the yield point changes. It can be applied to the connection of metal bands by lap seam welding such as continuous annealing lines, continuous molten metal plating lines, continuous electroplating lines, etc. of various metals.
[0020]
At that time, r ₀ in the formula (3) is the roll radius of the smallest roll among the plurality of transport rolls.
[0021]
【Example】
The present invention was applied to the continuous annealing line shown in FIG. In the continuous annealing line, the thin steel strip is rewound with the payoff reel 10, the tail end portion of the leading metal strip 1 and the tip end portion of the trailing metal strip 2 are cut with a shear, and both ends of the connecting portion in the width direction are cut with the notch 20 b. After cutting and removing the portion, the tail end portion of the preceding metal strip 1 and the tip end portion of the following metal strip 2 were connected by the lap seam welder 20, and the thin steel strip was annealed in the continuous annealing furnace 30 having the looper 30a. .
[0022]
The thin steel strip is repeatedly bent and conveyed by a plurality of conveying rolls 7 in the looper 30a and a plurality of conveying rolls 7 in the continuous annealing furnace 30, but the roll radius is changed to a plurality of conveying rolls in the continuous annealing furnace 30. 7 and the roll radius of the smallest roll among the plurality of transport rolls 7 in the looper 30a, and the combination of both metal bands is such that the parameter α represented by the formula (1) is not less than 0.6 and not more than 2.5. After connecting the metal bands 1 and 2, the thin steel sheet can be continuously annealed without breaking once.
[0023]
One year or more has already passed since the present invention was applied to the continuous annealing line.
[0024]
【The invention's effect】
According to this invention, even if it receives repeated bending with the conveyance roll in a process line, it can plate in the process line without fracture | rupture from the connection part connected by the lap seam welding.
For this reason, productivity is greatly improved, and it contributes greatly to energy saving, and there is no restoration work such as removing a broken metal band, and safety can be ensured.
[Brief description of the drawings]
FIGS. 1A and 1B are a plan view showing the arrangement of repeated bending test pieces and a cross-sectional view taken along line XX in FIG. 1A, respectively.
FIG. 2A to FIG. 2D are cross-sectional views showing a repeated bending process, respectively.
FIG. 3 is a cross-sectional view showing a bent portion in a repeated bending test.
FIG. 4 is a graph showing a relationship between a parameter α and whether or not a bent portion is generated in a repeated bending test.
FIG. 5 is a layout diagram of a continuous annealing line to which the present invention is applied.
FIG. 6 is a configuration diagram of an example of a lap seam welder.
FIG. 7 is a graph showing an example of lap seam welding conditions.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Leading metal band 2 Subsequent metal band 1a Tail edge part 2a of preceding metal band Tip part H of trailing metal band ₁ Thickness of preceding metal band H ₂ Thickness of trailing metal band 3 Welding part 4 Welding line 5 Welding power source 6 Transformer 7 Transport roll (roll)
8 bent part a one side metal band ae one side metal band end b other side metal band be other side metal band end H _a one side metal band thickness H _b other side metal band end Thickness W _a Width of one side metal band W _b Width of other side metal band r Conveying roll radius (roll radius of the smallest diameter roll among a plurality of conveying rolls in the process line)
10 payoff reel 20 lap seam welder 20a shear 20b notch 30 continuous annealing furnace 30a looper

Claims (1)

A metal band connecting method for connecting a preceding metal band and a subsequent metal band, which are repeatedly bent by a plurality of conveying rolls in a process line, by lap seam welding, and a combination of the two metal bands is represented by the following formula: The metal band connecting method by lap seam welding, characterized in that the parameter α is 0.6 or more and 2.5 or less.
α = (σ _ta · H _a · W _a ) / (σ _YPb · H _b · W _b )
σ _ta = σ _YPa · {(2 · r · σ _YPa ) / (H _a · E _a ) −1}
σ _YP : Yield point of metal strip, H: Plate thickness of metal strip, W: Plate width of metal strip, r: Roll radius of smallest roll among a plurality of transport rolls, E: Young's modulus of metal strip, subscript a ; towards the product of the thickness H and the plate width W and yield point sigma _YP is large, one of the metal strip of the preceding metal strip and the following metal strip, the subscript b; the thickness H and the plate width W yield point The other metal band of the preceding metal band and the trailing metal band with the smaller product of σ _YP

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