JPH0679784B2 - Welding method for thin steel sheets - Google Patents

Description

The present invention relates to a method for welding thin steel sheets, in particular flash butt welding.

Thin steel sheets for automobiles, home appliances, etc. are made by cold rolling a coiled steel sheet, in which case the tail end of the steel sheet and the steel sheet tip of the next coil are flash butt welded for continuous pickling and rolling. The way to do is taken. The present invention relates to a welding method suitable for this type of welding.

[Conventional technology]

FIG. 5 shows an outline of flash butt welding of this kind of workpiece. 10A and 10B are steel plates to be welded, 11 and 12 are steel plates 10A
Is a die (electrode) for sandwiching the tail end and the tip of the steel plate 10B from above and below. 13 is a die holder on the fixed base side, and 14 is a die holder on the movable base side. 15 and 16 are clamp cylinders, which move the upper die holders 13 and 14 up and down to move the die (electrode) 11,
The steel plates 10A and 10B are clamped by 12 and energized and released. 17 is a gauge bar, 19 is a counterweight, and 18 is a cylinder for raising and lowering the gauge bar. Further, 20 is a moving cylinder of the moving table, 24 and 25 are transformers, and 26 is a voltage regulator.

Cylinder 18 lowers gauge bar 17, and gauge back cylinder 22 moves the moving table forward to move the gauge bar to moving table 2.
1, sandwiched between the fixed base 23.

When the tail end of the steel plate 10A reaches the position shown in the figure (there is a looper at the tip), the upper die holder is lowered by the cylinder 15 while pressing the tail end against the gauge bar 17, and the tail end is clamped by the electrode 11. Next, send the steel plate tip of the next coil to the position shown in the figure and press the tip against the gauge bar 17
The upper die holder is lowered by 16 and the tip is held by the electrode 12. After that, the moving table is slightly retracted by the gauge back cylinder 22, the gauge bar 17 is pulled up by the cylinder 18, and the moving table is moved forward by the gauge back cylinder 22 to restore the distance between the steel plates 10A and 10B to the thickness of the gauge bar.

This completes the setting of the steel plate, and next, a voltage is applied between the electrodes 11 and 12 through the path of the power supply AC, the auto transformer 24, and the welding transformer 25, the flash process is performed, and then the upset process is performed to perform the steel plate 10A, Flash butt welding 10B.
At the end of welding, the upper die holder is raised to release the steel plate sandwiched by the electrodes and start moving the steel plates 10A and 10B.

In flash butt welding, the steel plate 10B is fed so that the flash is maintained in the flash process, and is rapidly fed in the upset process to weld the steel plate 10B to the steel plate 10A.

The uniform acceleration method shown in FIG. 7 (a) is generally used for this feeding speed. The vertical axis of this figure is the amount of displacement of the moving table, that is, the steel plate, and the horizontal axis is time.

There are various types of steel plates, and good results cannot be obtained with conventional equal acceleration methods such as high-tensile steel. Therefore, the latter-stage acceleration method of FIG. 7 (b) and the latter-stage sudden acceleration method of FIG. 7 (c) have been developed, and good results have been obtained.

Figure 6 shows the amount of carbon and the equivalent amount of carbon (C + Si / 24 + Mn /
6) shows the weldable range of various steel plates (cold-rolled materials) using the parameters as parameters. C ₁ indicates the welding range of the conventional method and C ₂ indicates the welding range of the latter stage acceleration + oiling method (as indicated by the diagonal lines, C ₁ or less and C ₂ or less can be welded). Marks are various steel plates, for example S ₁
Is a Hi-Mn high-tensile material, and S ₂ is a Hi-Si high-tensile material.

There is a cam as a means for generating a desired amount of displacement of the steel plate displacement versus time curve, and this cam system is widely adopted. This outline is shown in FIG. The cam plate 29 operates the servo valve 28 to control the hydraulic pressure to the cylinder 20. Reference numeral 21 is the above-mentioned movable table, and 23 is a fixed table.

Flash butt welding has a method called a 3-C (constant current control) method. It uses an electro-hydraulic servo and also detects the welding current and moves the carriage forward / backward so that it equals the set value and preheats it. When the end surface of the object to be welded is sufficiently heated by this preheating, the process automatically proceeds to the flash process and then the upset process. FIG. 7 (d) shows the displacement amount-time characteristic in the 3-C method. PH is the preheat period, FL is the flash period, and US is the upset.

During the preheating period, the welding current is sampled for ₁ hour and then continued for t ₂
Time is not sampled, and this is repeated. When the moving table is moved forward and the tail end and the tip of the workpiece are brought into contact with each other, a short circuit current flows, which exceeds the set current, so the moving table is retracted, and when the current decreases, the moving table is moved forward. Repeat this. A short circuit occurs at the beginning of the preheating period, but eventually a flash occurs due to an increase in the end surface temperature of the workpiece, and the short circuit does not occur. In this state, the movable table, and hence the object to be welded, advances while generating flash (flash period), enters the upset process at a predetermined position, and finishes welding.

[Problems to be Solved by the Invention]

Conventionally, the cam plate is mainly used to control the feed of the work piece during the flush period and the upset period.However, various patterns of displacement-time characteristics of the work piece are desired depending on the material, size, etc. In order to deal with this, it is necessary to prepare cam plates of various shapes and replace them, which is very troublesome.

It is an object of the present invention to improve these points and to select a speed pattern very easily and thereby to control the feed of a work piece.

[Means for Solving the Problems]

As shown in FIG. 1, in the present invention, various speed patterns that become command speeds during the feed control period of the workpiece are stored in the semiconductor memory.
Remember in 30. Pattern I, pattern II, ... Pattern V are various speed patterns thereof, and these are a data group of each point (x _i , y _i ) ( _i = _{1, 2,} ...) Of the pattern. x corresponds to the time, y corresponds to the amount of displacement, and the number of points in each pattern is N seconds, for example, 20 seconds.

The number of points (x _i , y _i ) can be simply set to various numbers and the number of velocity patterns can be approximated to a step wave with desired accuracy. In this case, the time data x ₁ , x ₂ , ... Can be omitted, and the data y ₁ , y ₂ ,.

However, in the above method, the number of points (x _i , y _i ) becomes considerably large, and it is difficult to create data, and there are problems such as an increase in memory capacity. The points (x _i , y _i ) can be improved by interpolating between a small number of points discretely on the velocity pattern and interpolating between these points. Reference numeral 31 is a processing circuit (actually, processing means such as a processor) for performing the interpolation or the like.

The selecting means 32 selects any one of the speed patterns I to V on the memory 30 and inputs it to the processing circuit 31. 33 is a clock
A counter for counting CLK and outputting the current time t, 34 is a multiplication / division circuit for outputting x = Nt / T. 35 is a keyboard,
Each point (x _i , y _i ) data of patterns I to V is input and written in the memory 30.

Although the selection means 32 is shown as a changeover switch for selecting read data in the figure, the pattern selection is performed by the pattern I.
It is also possible to use the upper address bits that represent the storage locations of ~ V. Of course, also in this case, which upper address bit is to be generated is selected by a push button switch or the like.

Memory 30 can be non-volatile for battery support,
Alternatively, it is loaded from the external non-volatile memory each time a welding operation is performed. Further, the processing circuit 31 may also be provided with a memory so that the data of the selected pattern is loaded.

[Action]

In FIG. 1, the patterns I, II, and
One of the command speeds Y can be output. By using this as the servo valve control signal described above (FIG. 8), the feed control of the workpiece can be performed in accordance with the selected pattern. Incidentally, FIG. 8 (b) shows the system of the present invention in accordance with FIG. 8 (a), in which 38 is a servo amplifier and 37 is a potentiometer for position feedback.

The welding time T determined by the material, size, etc. of the object to be welded is input by a digital switch (not shown) or the like, the desired pattern is selected by the switch 32, the clock CLK is input when entering the flash process, and the memory 30 is read. . The counter 33 counts the clock CLK and outputs the present time (time from the start of the flash process to the present) t, and the multiplication / division circuit 34 outputs x = Nt / T. x gives the read timing of each data of the selected pattern. If the number of data in the pattern is small, the clock CL
The cycle of K is shorter than the read cycle of each data, and therefore the processing circuit 31 reads each data and interpolates between each data by the following processing.

In this example, the number of data in each pattern is 21, and x ₂₁ and y ₂₁ are the final data.

When the welding time T is 20 seconds, x = t since N = 20 seconds in this example. This will read the memory 30, interpolate,
Pattern Y can be output for 20 seconds. Clock for example
If the CLK cycle is 0.1 seconds, x is 0.1, 0.2, 0 every 0.1 second.
It increases to 3, ……. If pattern I, II, ... is set to 20 seconds, x ₁ , x ₂ , x ₃ , ... can be set as 1,2,3, .. so that for every 10 x, x = x ₁ , x ＝ x ₂ ,…, and so on. It is at this point that there is read data y ₁ , y ₂ , ...
Since there is no y ₁ or y _{2 in the} middle, interpolation is performed.

When the welding time T is T = 15, x = 20t / 15, and the pattern with the time axis reduced to 15/20 can be output for 15 seconds.
The same applies hereinafter. Thus, pattern selection and welding time T
By inputting, it becomes possible to weld in a desired pattern and at a desired time.

The pattern can be easily modified or added by operating the keyboard 35. Further, the interpolation may be curved interpolation instead of linear interpolation.

〔Example〕

Some examples of velocity patterns are shown in FIG. Curve I is suitable for low alloy steels and patterns II, IV are suitable for high alloy steels. For high alloy steel, the latter rapid acceleration is good to prevent the oxidation of Si and Mn. Numerical examples are shown in the following table.

The pattern I is a post-acceleration type and is suitable for general materials. Pattern II is a rapid acceleration type in the latter stage, and it is thicker than 50kg and high-tensile (t3mm)
Suitable for, pattern IV is over 50kg high-tensile thin (t <3mm)
Suitable for Pattern III is uniform acceleration.

The pattern data (x _i , y _i ) in the memory 30 is shown in FIG.
x ₁₀ , y ₁₀ ), etc., where the horizontal axis is x and the vertical axis is y to represent the points on each pattern curve (the horizontal axis is divided into 20 and the y value for each x point is represented).

FIG. 3 shows the main part of the mobile platform speed control system. The processing circuit 31 is in the sequencer 40, and this output Y is input to the servo amplifier 38 via the adder / subtractor 41, the amplifier 42, the speed regulator 44, and the changeover switch 49. This welding device can also perform 3-C welding,
CT is a welding current detecting current transformer therefor, 48 is a preheating (sampling) cycle setting, 47 is a heating time setting, and 46 is a welding speed setting variable resistor. 43 is a display for displaying the position of the mobile platform.

FIG. 4 shows a welding device. As is the case with all figures,
The same parts as those in the other figures are denoted by the same reference numerals. 51 is an entrance looper, 52 is an exit looper, 53 is a guide roller, 54 is a guide rail, 55 is an upper electrode handle, 56 is a trimmer, 57
Is a transfer, and 58 is a vertical device.

〔The invention's effect〕

As described above, according to the present invention, feed control in flash butt welding can be performed with an arbitrary speed pattern and a desired welding time. The pattern selection is possible with a switch operation, it is extremely easy and quick. Further, since the pattern is displayed by the decimal point, it is easy to create / input the pattern data.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention, FIG. 2 is a graph showing various speed patterns, FIG. 3 is a block diagram of a feed control unit, FIG. 4 is a side view of a welding device, and FIG. 5 is a steel plate flash butt. FIG. 6 is an explanatory view of welding, FIG. 6 is a graph showing a weldable range, FIG. 7 is a graph showing various conventional speed patterns, and FIG. 8 is an explanatory view of a servo mechanism of a moving table. In FIG. 1, 30 is a memory, 31 is a processing means, and 35 is a keyboard.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Sakimoto 1 Kimitsu, Kimitsu-shi, Chiba Shin Nippon Steel Co., Ltd. Kimitsu Steel Co., Ltd. Within the Kimitsu Branch of Iron & Steel Industry Co., Ltd. (56) References JP-A-53-122645 (JP, A)

Claims (1)

[Claims] 1. A method of welding a work piece by sandwiching a rear end and a front end of the work piece with electrodes, and performing a flash process and an upset process by speed-controlling a moving table on which one of the electrodes is mounted. , Each point of various speed patterns such as the first half low speed and the second half high speed, which is composed of a plurality of data (x, y) for N seconds indicating the current time and the commanded speed at that time, is stored in the memory, One of the various speed patterns is selected by the selecting means, and the desired welding time is T and the current time is t, and the one speed pattern selected in the memory is read and obtained by the processing means at x = Nt / T. A plurality of data y are interpolated and output as an analog command speed, the output of the processing means is used as a command speed of the speed control device of the mobile base to control the speed of the mobile base, and a flash process is performed. To A characteristic method for welding thin steel sheets.