JP3760821B2 - Steel strip joining method in continuous processing line - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of joining the end portions of a preceding steel strip and a succeeding steel strip by means of lap welding in a continuous processing line of the steel strip.
[0002]
[Prior art]
As a method of joining the end portions of the preceding steel strip and the succeeding steel strip in the continuous processing line of the steel strip, the end portions of the preceding steel strip and the succeeding steel strip are overlapped, and a pair of upper and lower traveling traveling in the plate width direction is performed. An overlap (seam) welding method is generally used in which welding is performed while pressing with an electrode ring.
[0003]
[Problems to be solved by the invention]
However, if overlap welding is performed between the ends of the preceding steel strip and the succeeding steel strip by this method, problems such as flaws on the surface of the welded portion and through holes in the welded portion may occur. In the worst case, the steel strip may break in the furnace.
[0004]
However, the cause of such welding defects has not been known for a long time, and appropriate measures could not be taken.
[0005]
Accordingly, an object of the present invention is to provide a method capable of obtaining a good weld in the lap welding for joining the end portions of the preceding steel strip and the succeeding steel strip.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have found the following facts.
[0007]
In other words, in the lap welding for joining the ends of the preceding steel strip and the succeeding steel strip in the continuous processing line of the steel strip, the electrode wheel rotating air motor of the lap welder is usually a constant rotation type, The rotational speed Ro is constant when the electrode wheel is unloaded (during idling), but during welding, the rotational speed decreases to R ₁ due to the pressurization of the steel strip. Further, when the electrode wheel is repeatedly used, the electrode wheel diameter gradually decreases, and the electrode wheel peripheral speed becomes smaller than the moving speed of the welding machine, that is, the welding speed. If an electrode ring with a reduced diameter is used in this way, the electrode wheel peripheral speed cannot follow the welding speed and slips, and as a result, hunting of the welding temperature occurs, causing the above-described abnormal welding. understood. Here, hunting of the welding temperature refers to a phenomenon in which the welding temperature fluctuates irregularly.
[0008]
As a result of further investigation based on such knowledge, the present inventors have determined that the rotation speed of the electrode wheel and the electrode so that the peripheral speed of the electrode wheel is always larger than the welding speed until the electrode wheel reaches the minimum usable diameter. It was found that setting the ring diameter can prevent the electrode ring and the steel strip from slipping and prevent welding temperature hunting.
[0009]
The present invention has been made on the basis of such findings. The feature of the present invention is that the end of the preceding steel strip and the following steel strip is obtained by a welding machine using a constant rotation type electrode wheel rotation motor in a continuous processing line of the steel strip. In the method of joining the parts by overlap welding , the rotation speed of the electrode wheel rotation motor is such that the electrode wheel peripheral speed during pressurization when using the smallest electrode wheel usable diameter is larger than the welding speed. Is a method for joining steel strips in a continuous processing line, characterized in that is set before welding.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show an embodiment of a method for joining steel strips according to the present invention. FIG. 1 shows joining of end portions of a preceding steel strip and a succeeding steel strip in a continuous processing line of the steel strip. FIG. 1 is an explanatory view showing a welding machine for welding and a welding situation by this welding machine, and FIG. 1 shows a superposed part 7 between end parts of a preceding steel strip 5 and a succeeding steel strip 6, that is, a welded part. As seen from the cross section of FIG. 7, the preceding steel strip 5 and the trailing steel strip 6 move in a direction perpendicular to the paper surface. FIG. 2 is a graph showing an example of the relationship between the peripheral speed of the electrode wheel and the temperature of the welded portion (deviation from the average welding temperature value of the overlapped portion).
[0011]
1 is a pair of upper and lower electrode rings (welding rolls) 1a, 1b and an upper electrode ring 1a sandwiching an overlapping portion 7 between end portions of a preceding steel strip 5 and a trailing steel strip 6. A drive motor (not shown), a pair of upper and lower swaging rolls 2a and 2b (planar rolls) positioned adjacent to the electrode wheels 1a and 1b, and the upper electrode wheel 1a and the upper swaging roll 2a are held. Air cylinders 3 and 4 for moving up and down, and a support frame 8 that holds the air cylinders 3 and 4 and is movable in the width direction of the steel strip.
[0012]
The upper and lower electrode wheels 1a and 1b are pressed by sandwiching the overlapping portion 7 between the ends of the preceding steel strip 5 and the trailing steel strip 6 from above and below, and rolling on the steel strip surface while energizing, The overlapping portion 7 between the end portions of the preceding steel strip 5 and the trailing steel strip 6 is welded.
[0013]
The upper and lower swaging rolls 2a and 2b follow the electrode wheels 1a and 1b, and roll while pressing the welded portion 7 from above and below to smooth the welded portion 7. Although the swaging rolls 2a and 2b of the present embodiment only rotate following the moving speed of the welding machine, the swaging rolls 2a and 2b may be driven by a drive motor.
[0014]
The support frame 8 is configured to be able to run in the width direction of the steel strips 5 and 6 by a lead screw method or a hydraulic cylinder method.
[0015]
FIG. 2 is a graph showing an example of the relationship between the peripheral speed of the electrode wheel and the temperature of the joint. Fig. 2 shows three cases (V _{1a to} V _1c , V _{1d to} V _1f ) for the peripheral speed V ₁ of the initial electrode ring for the initial electrode ring diameter of 200φ and 165φ, respectively. The result of investigating the temperature deviation which is the deviation from the welding temperature average value of the welded part at that time is shown.
[0016]
Pressurization of electrode wheels rotation speed R ₁ (rpm), when the electrode wheels diameter was D ₁ and (mm), setting the electrode wheel circumferential speed V ₁ (mpm) is _{V 1 = πR 1 D 1/} 1000
It is represented by In addition, the rotation speed of the electrode wheel is reduced by α times when the upper and lower electrodes are rotated by applying pressure (R ₁ ) due to the resistance due to the pressure compared to when rotating without load (Ro). . (R ₁ = α × Ro)
Further, the electrode wheel speed during welding R ₂ (rpm), when the electrode wheels diameter was D ₂ (mm), the electrode wheel peripheral speed V ₂ (mpm) is _{V 2 = πR 2 D 2/} 1000
It is represented by
[0017]
When the initial electrode ring circumferential speed V ₁ is larger than the moving speed (= welding speed) Vw of the welding machine, that is, when the electrode ring circumferential speed V ₁ > the welding speed Vw, the rotation speed R ₂ of the electrode ring decreases during welding. and, the electrode wheel circumferential speed V ₂ is synchronized with the welding speed Vw (a V ₂ = Vw) electrode wheels circumferential speed V ₂ is reduced to. That is, as shown by the arrow b in FIG. 2, the electrode wheel circumferential speed V ₂ decreases until it coincides with the welding speed Vw, but the temperature deviation at this time is small.
[0018]
On the other hand, if the initial electrode wheel peripheral speed V ₁ is smaller than the moving speed (= welding speed) Vw of the welding machine, that is, if the electrode wheel peripheral speed V ₁ <welding speed Vw, the rotation of the electrode wheel during welding The number R ₂ increases, and the electrode wheel peripheral speed V ₂ increases until the electrode wheel peripheral speed V ₂ synchronizes with the welding speed Vw (V ₂ = Vw). That is, as shown by the arrow a in FIG. 2, the electrode wheel peripheral speed V ₂ tends to increase until it coincides with the welding speed Vw, but the electrode wheel slips. When such slip occurs, hunting at the welding temperature as described above is likely to occur. Therefore, the temperature deviation is large at this time.
[0019]
On the other hand, the surface of the electrode wheel is polished at a certain rate in order to prevent fluctuations in the welding temperature due to surface roughness. For this reason, the electrode ring diameter gradually decreases and is replaced when the usable minimum diameter (Dmin) is reached. As the electrode ring diameter decreases, the electrode wheel peripheral speed naturally decreases even at the same rotation speed. As an example, as the motor rotation speed in FIG. 3 is set to 30 rpm before welding, the electrode ring peripheral speed decreases as the electrode ring diameter decreases. In this example, the electrode ring diameter is about 185 mm. Sometimes, the electrode wheel peripheral speed V ₂ <welding speed Vw, and the welding temperature tends to cause hunting.
[0020]
Therefore, in the method of the present invention, even when the electrode ring diameter becomes the minimum usable diameter (Dmin) as in the case where the motor rotation speed in FIG. 3 is set to 35 rpm before welding, the rotation speed of the motor is taken into consideration. The electrode wheel peripheral speed V ₁ dmin is set to be larger than the welding speed Vw (15 mpm in this example). That is, the electrode wheel rotation speed and the minimum electrode wheel usable diameter (Dmin) are set before welding so that the electrode wheel peripheral speed and the welding speed satisfy the following expression (1).
Vw <V ₁ dmin (= π × R ₁ × Dmin = π × α × Ro × Dmin) (1)
Here, Vw: moving speed of welding machine (= welding speed), V ₁ dmin: peripheral speed at the minimum diameter that can be used for electrode wheel, α: rate of decrease of electrode wheel rotation speed due to pressurization, Ro: at no load rotation Electrode wheel rotation speed, R ₁ : electrode wheel rotation speed during pressurization (= α × Ro), Dmin: minimum usable diameter of electrode ring [0021]
【Example】
The example which applied this invention to the entrance side welding machine of the continuous annealing equipment is described. The entrance side welding machine of the continuous annealing equipment of a present Example has a structure as shown in FIG.
[0022]
The initial electrode ring diameter is 200 mmφ, and when the diameter decreases to 165 mmφ, the use is stopped and replaced with a new one. In addition, a dresser that polishes the electrode wheel that is rough every time it is welded online is included. The upper electrode wheel is pressed downward by an air cylinder, and the upper swaging roll is similarly pressed downward by an air cylinder.
[0023]
4 and 5 show steel strip width direction welding temperature charts of a comparative example and an example of the present invention, respectively. The steel strip used was 950 mm in width and 0.4 mm in thickness for both the preceding steel strip and the trailing steel strip. The welding temperature deviation is the standard deviation of the welding temperature fluctuation in the plate width direction. And Here, the welding temperature is a temperature measured at a location a few centimeters (usually about 2 cm) behind the welding point on the overlap welding line between the ends of the preceding steel strip and the succeeding steel strip.
[0024]
FIG. 4 shows a steel strip width direction welding temperature chart of a comparative example. When the welding speed is 15 mpm and the initial electrode ring diameter is 200, the rotation speed of the electrode ring with no load is set to 25 rpm. The speed was set lower than the welding speed, welding temperature hunting (indicated by an arrow in the figure) occurred, and the welding temperature deviation was 32 ° C. On the other hand, in the present invention example, when the welding speed is 15 mpm and the minimum usable diameter of the electrode wheel is φ165, the peripheral speed of the electrode wheel is always higher than the welding speed by setting the rotation speed of the electrode wheel at no load to 35 rpm. As shown in FIG. 5, the welding temperature deviation was 16 ° C., and hunting of the welding temperature as shown in FIG. 4 could be prevented.
[0025]
【The invention's effect】
As described above, according to the present invention, at the time of lap welding for joining the end portions of the preceding steel strip and the subsequent steel strip in the continuous processing line of the steel strip, without generating hunting of the welding temperature, Steel strips can be stably welded together.
[Brief description of the drawings]
FIG. 1 shows an embodiment of a method for joining steel strips according to the present invention, and a lap welder for joining the ends of a preceding steel strip and a succeeding steel strip in a continuous treatment line of the steel strip, FIG. 2 shows an embodiment of a method for joining steel strips according to the present invention, and shows the circumferential speed of the electrode wheel and the temperature of the welded portion (welding of the overlapped portion). FIG. 3 is a graph showing an example of the relationship between the electrode ring diameter and the electrode wheel peripheral speed according to the present invention. FIG. 4 is a steel strip width direction of the comparative example. Welding temperature chart [Fig. 5] Steel strip width direction welding temperature chart of the present invention example [Explanation of symbols]
1a Upper electrode wheel 1b Lower electrode wheel 2a Upper swaging roll 2b Lower swaging roll 3 Air cylinder 4 Air cylinder 5 Leading steel strip 6 Subsequent steel strip 7 Overlapping part 8 Support frame

Claims (1)

The smallest electrode wheel usable diameter in the method of joining the ends of the preceding steel strip and the succeeding steel strip by overlap welding with a welding machine using a constant rotation type electrode wheel rotation motor in a continuous treatment line of steel strip Joining steel strips in a continuous processing line, characterized in that the rotational speed of the electrode wheel rotation motor is set before welding so that the circumferential speed of the electrode wheel during pressurization is higher than the welding speed. Method.

Images