JPS5927675B2 - How to connect strips - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting leading and trailing strips by welding in a steel sheet processing line.

Conventionally, a known method for connecting strips of steel plates while passing through the line is to overlap the rear end of the leading strip and the tip of the trailing strip, and connect the overlapping portions by spot welding. .

In this method, spot welding is performed automatically or by the operator's touch at regular intervals over the entire length of the strip in the width direction, and the distribution of welding points is shown in FIG. 4, for example. In FIG. 4, 1 is a leading strip, 2 is a trailing strip, and the (x) mark 3 represents a welding point. By the way, the strips connected in this way are
As shown in an exaggerated manner in FIG. 1, line center a and centers b of leading strip 1 and trailing strip 2 do not exactly match, so if the line tensioner deviates, it is possible to A concentrated tensile force is applied to the connecting part at one end (the part A on the right in FIG. 1). In order to obtain sufficient welding strength to cope with this concentration of tensile force, conventionally the interval (pitch) between the welding points 3 has been narrowed to perform welding at multiple points. However, in addition to the above-mentioned welding strength, it is essential to connect the strips that the time required for welding is short. In other words, the welding strength needs to be maintained high to reliably prevent the line from stopping due to strip breakage, and on the other hand, the welding time must be maintained at a certain level or longer due to the relationship with other processes in the steel plate processing line. It is not desirable to make it long. For example, since it is not possible to stop an annealing line such as a continuous annealing furnace, the strip accumulator must be large in order to prevent the annealing line from stopping even during welding. This is because it requires a lot of effort. Therefore, in order to obtain sufficient welding strength, the conventional method of welding the strip at regular pitches at small intervals over the entire length of the strip in the width direction requires a long welding time, and there is room for improvement. The present invention has been made in view of the actual situation of the conventional strip connection method described above, and has made it possible to shorten the welding time without substantially impairing the welding strength. Focusing on the point where the welding is concentrated in The welding pitch is narrower than the welding pitch of the welding pitch, and the welding current is adjusted to
Alternatively, the welding heat input value is corrected by adjusting the length of the energization time.

Furthermore, in the present invention, a plurality of leading strips and trailing strips are used in the steel plate process line in order to maintain higher welding strength despite the influence of the ineffective shunting of the welding current as in the above invention. When connecting by dot welding, the welding pitch at the end of the strip in the width direction is made narrower than the welding pitch in the center, and after constant welding over the entire length in the width direction by the welding pitch in the center, , is characterized in that additional stroke welding is performed on each of the ends from the opposite direction to reduce ineffective shunting of the welding current. The distribution of welding points 3 shown in FIG. 3 shows an example of the welding point distribution according to the method of the present invention.
At both ends in the width direction of the strip, the welding pitches are narrower due to increased welding strokes compared to the regular welding at the center, and the welding strength at both ends of strips 1 and 2 due to these welding pitches is as shown in Figure 1. It is strong enough to withstand concentrated tensile force. Further, when forming the welding point 3 as shown in FIG. 3, even higher welding strength can be easily obtained by using the following welding method that takes into consideration the ineffective branching of the welding current. That is, in FIG. 5, 1 and 2 are strips to be welded, 4 and 5 are electrodes, 6 is a welding transformer, 7 and 8 are conductors connecting the welding transformer 6 and electrodes 4 and 5, and 31 is a weld that has already been welded. As a point nugget, during welding, not all of the 1w of welding current that reaches the electrode 5 contributes to the formation of the welding nugget 32, and some of the welding current 1w passes through the welding nugget 31 etc. and does not contribute to welding. Inactive shunt 1N is included.

The ratio of this ineffective shunt current 1N to 1W of welding current is affected by factors such as the material of strips 1 and 2, plate thickness, and weld pitch, so when these factors change, welding conditions must be corrected. It is not possible to obtain the same welding strength. For example, using a three-phase low-frequency spot welding machine,
Welding pitch of 50j on stainless steel plate with m1 thickness without correction! When welding at one point and welding at only one point, the welding tensile shear strength of the former decreases by up to 50% of that of the latter due to the effect of ineffective shunting. Therefore, in the present invention, as a first method to prevent a decrease in welding strength due to this ineffective shunt flow, during multi-stroke welding in which the pitch of the welding point 3 is small, the ineffective shunt flow IN is larger than that in steady stroke welding. In this case, welding strip 1 can be welded by increasing the welding current 1W or by increasing the energization time per point.
, 2. Also, as a second method,
The order of forming the welding points 3 is as shown in Fig. 4.As in the conventional multi-thread welding method, the order of forming the multi-thread welding points in one direction over the entire length of the strips 1 and 2 in the width direction is maintained in advance at narrow intervals. Instead, as shown in Fig. 3, welding is carried out over the entire length in the width direction by regular strokes corresponding to the welding pitch at the center of strips 1 and 2, and then regular welding is performed at both ends of strips 1 and 2. Make sure to move the electrode in the opposite direction to the direction used during hammer welding. When this steady hammer welding is performed, the ineffective shunt current can be suppressed to a negligible level, and the welding strength can be maintained extremely high.
In other words, according to this method, it is only the additional strokes when the electrode moves in the opposite direction that are affected by the increase in the ineffective shunt flow, so that it is possible to obtain a higher end welding strength than in the conventional example. Of course, it is also possible to use the first and second methods together. 6th
FIG. 7 shows an example of an apparatus for carrying out the method of the present invention, and reference numerals 1 to 8 indicate the same components as those with the same reference numerals in FIG. 9 is a moving frame having wheels 10 and movable on rails 11; 12 and 13 are pressurizing devices for the electrodes 4 and 5 supported by the moving frame 9;
14 and 15 are electrode holders that can move the electrodes 4 and 5 up and down; 16 and 17 are phototube emitters and light receivers that detect both ends of the width of the strips 1 and 2; , 2 shows the exit side clamp and the entry side clamp that stop the movement of

In this device, during welding, pressure devices 12 and 13 apply pressure to the strips 1 and 2 located between the electrodes 4 and 5,
At the same time, a welding current flows between electrodes 4 and 5 to perform spot welding. On the other hand, when the movable frame 9 moves by the welding pitch and when the strips 1 and 2 move under line tension, the electrode holders 14 and 15
, 5 are released from strips 1 and 2. The clamps 18 and 19 on the exit and entry sides fix the strips 1 and 2 only during the welding process, and are opened when the strips 1 and 2 are moved. Further, the phototubes 16 and 17 detect both ends of the width of the strips 1 and 2 when the movable frame 9 moves, and regulate the ends of the movable frame 9. Therefore,
A predetermined distribution of welding points can be obtained by moving the moving frame 9 by a necessary welding pitch using one drive device of the moving frame 9 and performing welding at each moving point. This one-drive control of the moving frame 9 is carried out by known means such as storing the widths of the strips 1 and 2 and the pitches of the regular stroke welding and the additional stroke welding determined according to the widths in a memory section of the control device. This can be easily done using . Further, in order to correct the heat input in consideration of the ineffective shunt, it is sufficient to change the firing angle of the switch on the primary side of the welding transformer 6, for example, the ignitron. In addition to the spot welding described above, the present invention is also applicable to roll spot welding using a rotating electrode.

As described above, the method for connecting strips according to the present invention is to cope with the fact that the tensile force applied to the connection portion between the leading strip and the trailing strip is concentrated at one end in the width direction of the strip in the steel plate process line. By adopting a welding method in which only the welding pitch at both ends of the strip is smaller than the welding pitch at the center, and at the same time, by correcting the heat input value for welding at both ends, Alternatively, after steady stroke welding over the entire length of the plate width using the weld pitch in the center, additional stroke welding is performed at both ends from the opposite direction, thereby achieving high weld strength at both ends despite the influence of ineffective shunting. Compared to the conventional method of welding the entire width of the strip at a pitch corresponding to the welding pitch at both ends, welding time can be shortened and work efficiency can be improved. It is possible to improve the line speed, reduce the line accumulator, and increase the line speed.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an exaggerated connection state of a normal strip, FIG. 2 is a side view of FIG. 1, and FIG. Fig. 4 is a plan view showing an example of conventional welding point distribution, Fig. 5 is a connection diagram for explaining reactive current during spot welding, and Fig. 6 is an example of an apparatus for implementing the method of the present invention. The front view shown in Fig. 7 is
FIG. 6 is a right side view of FIG. 6; 1... Leading strip, 2... Trailing strip, 3... Welding point.

Claims (1)

[Claims] 1. When connecting a leading strip and a trailing strip by welding a plurality of dots in a steel plate process line, the welding pitch at the ends in the width direction of the strip is equal to the welding pitch at the center. In addition to making the welding pitch narrower, the welding heat input value should be corrected by adjusting the magnitude of the welding current or the length of the current application time to compensate for the ineffective shunt flow caused by the narrowing of the welding pitch. A strip connection method featuring: 2. When connecting a leading strip and a trailing strip by welding a plurality of dots in a steel plate process line, the welding pitch at the ends in the width direction of the strip is narrower than the welding pitch at the center, and the A strip connection characterized in that after constant stroke welding over the entire length in the width direction of the strip at a welding pitch in the center, additional stroke welding is performed at each end from the opposite direction to reduce ineffective shunting of welding current. Method.