JPH04200876A - Seam welding method for stainless steel strips - Google Patents

Abstract

PURPOSE:To join the stainless steel strips without welding failure by heating the joining interference so that its temperature attains below the melting point in excess of the recrystallization temperature and applying specified loads by rolling reduction rolls. CONSTITUTION:The stainless steel strips 1 and 2 are superposed on each other and subjected to seam welding and joining. At that time, the joining interference is heated so that welding heat input from seam welding electrode disks 6 attains below the melting point in excess of the recrystallization temperature. The loads of 0.5-1.5ton per 1mm thickness of the steel strips 1 and 2 in the vicinity of the melting point and 1.0-2.0ton per 1mm thickness in the vicinity of the recrystallization temperature, respectively are then applied by a couple of upper and lower rolling reduction rolls 8 and the superposed part of the stainless strips 1 and 2 are crushed. Consequently, the speed of a process line can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION <Utilization of Industry L> The present invention relates to a method for seam welding stainless steel strips in a process line.

<Prior art> Steel strip bushing 2 cess line and 1. For example, in a continuous annealing line, a continuous plating line, a continuous pickling line, a continuous rolling line, etc., the button 1 band coil is welded to L2 during the production process, and the plate is continuously threaded. , BuI'
The operating rate of the J.S. line is being increased. Seam welding, Francheband welding, laser welding, and the like are used to join such annual coils.

These bonding methods, Sea J, and welding methods have overlapping = 1
! The end of the steel strip is sandwiched between a pair of upper and lower copper electrode discs, and
Since it is a method of welding with intermittent energization, it is simpler than other methods and has a high speed of 2 to 20 mpm, so it is widely used in process lines.

However, when welding this seam (stainless steel/stainless steel) by the capacitive welding method, stainless steel has lower V1 conduction and higher electrical resistance than carbon steel, so welding method uses intermittent energization, in which current is applied for a short time. (Co-author: Nakate, Kazutaka, Kobayashi, Kaimoto [
Resistance 1jL Welding 1 January 23, 1980, Sanpo Publishing, P.
145) was widely adopted. This is because when continuously energizing seam welding is performed on stainless steel, a sound weld cannot be formed because the mechanical properties deteriorate due to crystallization/forceps formation due to the thermal influence of the base metal, and the melt drops.

<Problem to be solved by the invention> However, in the above method, the nugget (?
8) The shape of the solidified steel becomes intermittent, so in a continuous process line that undergoes repeated bending, stress concentration resides in the intermittent nugget formation area, which cannot withstand the load of threading, and the line Welds may break, requiring a long time to recover, and is a major cause of reduced equipment availability.

Furthermore, 1. Comparing the welding speed with intermittent energization and the welding speed with continuous energization on a 0 mm thick low carbon steel strip,
The former is 2.5mpm (the above-mentioned "Resistance Welding JP, 14
0), the latter is 20mpm (rBasic research on the joint formation phenomenon of high-speed seam welding (8th report) J Vo
l.

48.4, P., 222.1979, Journal of the Welding Society of Japan), and the seam welding method using intermittent energization could only perform welding at low speeds. In intermittent current seam welding of stainless steel, it is necessary to further slow down the welding speed.]
, the welding speed for Omm thickness is 1.8 mpm or less (see above [Resistance Welding JP, 14G)], and the continuous welding speed is 1.8 mpm or less (see [Resistance Welding JP, 14G)]. ] There was a drawback that it was necessary to reduce the sheet passing speed of the cess line.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-speed seam welding method for stainless steel strips by continuous energization, which improves the above-mentioned drawbacks.

<Means for Solving the Problems> In order to achieve the above object, the present invention, when stacking stainless steel strips and joining them by seam welding, reduces the welding heat input from the seam welding electrode disk to the joining interface of the stainless steel. is heated so that the temperature exceeds the recrystallization temperature and is below the melting point, and then 0.5 to 1.5 tons per 1 mm of the thickness of the stainless steel strip under thermal conditions near the melting temperature. 1.0-2. under heat input conditions near the recrystallization temperature.
This is a seam welding method for stainless steel strips, which is characterized in that a load jJj of 0 tons is rolled by a pair of upper and lower reduction rolls to crush the overlapped portions of stainless steel (1).

<Function> According to the present invention, since the current is applied continuously, there is no discontinuity in the formation of nuggets in the welding direction, which occurs with intermittent current application, and stress concentration does not occur. In addition, since the welding heat input is kept below the melting temperature of stainless steel, the temperature of the electrode contact surface can be kept low, preventing coarsening of crystal grains, and since the bonding interface is also below the melting temperature, the melt will not fall. Not alive.

With welding heat input using a welding electrode disc, no nuggets are formed because the joint interface does not reach the melting temperature, but since the pressure is applied with a reduction roll while the temperature of the joint interface is maintained above the recrystallization temperature, the joint interface does not reach the melting temperature. The overlapped portions are joined by the generation and growth of recrystallization nuclei. At this time, the thickness of the stainless steel strip was 1 mm under heat input conditions close to the melting temperature.
If the weld is less than 0.5 ton, recrystallization will not occur over the entire overlap and the joint cross section will become discontinuous, and if it is more than 15 ton, the weld will be crushed and a sound weld will not be formed. Furthermore, under heat input conditions near the recrystallization temperature, if it is less than 1.0 tons, recrystallization is difficult to form over the entire overlap margin, and if it is more than 2.0 tons, the welded part will be crushed and a sound welded part will not be formed.

<Embodiment> FIG. 1 is a side view of a welding apparatus showing an embodiment of the present invention. When joining the upper stainless steel strip 1 and the lower stainless steel strip 2, which are threaded in the direction of arrow 5 in FIG. Then, electricity is applied continuously while applying pressure using the electrode pressurizing device 7 installed in the scissor welding device frame 10. The welding current (welding heat input) at this time is set in a temperature range such that the temperature of the overlapped joint interface is higher than the recrystallization temperature of the stainless steel and lower than the melting point, and is controlled so as not to exceed the melting point.

These temperatures can be easily determined by conducting preliminary experiments for each steel type without applying the reduction roll 8.

Next, while the joint interface between the steel strips j and 2 is in the above-mentioned temperature range, the reduction roll 8 is used and the reduction roll pressure device 1) 15.
2) Apply a load of iJ to crush and join the overlapping portions. Figure 2 shows the relationship between the welding result of the welding strip A'1 of the joints 1 to 78 and the welding results of the aforementioned operation (1).The vertical axis shows the pressure I. This welding current (welding heat) is taken.As is clear from Fig. 2, below 9 kA, which is the fire heat below the recrystallization temperature, the recrystallization 4L formation in the overlap is discontinuous, and the melting point The heat input exceeds 1
If it is over 8kA, the loss will be large and the melting will be severe.

) t, ta, pressure 1-' c When the pressure is zero,
Continuous IIt crystals were not formed, and from 1.2 kA to 1
6. Applying 0.5 tons of roll pressure with 5kAO heat input. 2, I can be recrystallized and then processed. Under conditions where the heat input is high (15bn or more) and the pressurizing force is high, crushing occurs. In other words, after the joint was heated by electricity from the welding electrode disc 6 to a temperature exceeding the recrystallization temperature and below the melting point, pressure was applied to the appropriate jaw using a G-roller roll, so that the welding strip was wide (!1 range) due to recrystallization. A good result was obtained with continuous bonding!? surface.

In addition, the above-mentioned example rl! Although the case of electrical heating using an electrode disc will be described, the present invention is not limited to heating using a heating element, but heating may be performed using a gas flame or high frequency.

<Effects of the Invention> In the present invention, since the bonding is carried out by continuous energization and continuous pressure reduction, continuous and uniform bonding can be achieved from 2 to 2, and a lK! Because it is heated to r degrees,
Mother + 3 \ heat shadow 1, hoof father q yong (・J drop and ゛? It can be joined without any problems.

In addition, since welding can be performed even with low heat, there is an effect that the wear of the welding electrode disk, which is a problem in stainless steel welding, is extremely reduced.

Furthermore, since welding is not done when pressure is applied with a welding electrode, high-speed welding of 2"20mpm is possible even when joining stainless steel strips, and it is always effective to increase the speed of one cessline.

[Brief explanation of the drawing]

Fig. 1 is a side view of a sheet and welding device showing an embodiment of the present invention, and Fig. 2 is a side view of a sheet and welding device according to an embodiment of the present invention. It doesn't show the relationship between the 8th tangent results, which is a shame. 1...Upper stainless steel m band, 2...Lower stainless steel band, 3...Unjointed part, 4...Joint part, 5...Welding direction, 6...Hyperstatic contact electrode disk, 7 . . . Electrode pressure device, 8. Roll down roll, 9. Roll down 1-1-roll pressure device, 10. Welding device frame. Special agreement applicant: Kawasaki Steel Corporation]

Claims (1)

[Claims] When stacking stainless steel strips and joining them by seam welding, the welding heat input from the seam welding electrode disc is heated so that the temperature at the joint interface of the stainless steel exceeds the recrystallization temperature and is below the melting point. Then, under heat input conditions near the melting temperature, 0 per mm of stainless steel strip thickness is applied.
．． The overlapping portion of the stainless steel strips is pressed by applying a load of 5 to 1.5 tons or 1.0 to 2.0 tons with a pair of upper and lower reduction rolls under heat input conditions near the recrystallization temperature. A seam welding method for stainless steel strips characterized by collapsing them.