JPH0352778A - Method for welding steel strips - Google Patents

Abstract

PURPOSE:To form a satisfactory nugget and to improve strength of a weld zone in a method to weld a preceding steel strip to a succeeding strip by providing a stage to crush a predetermined weld zone between the preceding steel strip and the succeeding steel strip by a depressing roll after finishing a lap allowance adjusting stage. CONSTITUTION:A width fitting stage between the preceding steel strip and the succeeding steel strip, a cutting stage of predetermined welding ends, a strip fitting stage, the lap allowance adjusting stage and a welding stage are provided. In advance of the welding stage, the predetermined weld zone between the preceding steel strip and the succeeding strip is depressed by the depressing roll (swaging roll). The predetermined weld zone is preheated by utilizing working heat generated by depressing work and the nugget is formed satisfactorily at the time of welding and lap welding of the steel strips having thickness larger than specified thickness and the steel strips having a scale coating film is made possible. By this method, strength of the weld zone is increased and both the steel strips having specified thickness referred to as thick material and the steel strips having thickness smaller than specified thickness referred to as thin material can be easily welded without any trouble.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for welding steel strips, and particularly to lap welding of thick steel strips or steel strips having a scale coating.

[Conventional technology]

Conventionally, the thick plate was 2. Since lap welding of steel strips exceeding 0 wn or steel strips having a scale coating is difficult, spot welding is used for the former, and butt welding called flash butt welding is used for the latter.

In this case, in spot welding, the length in the longitudinal direction of the steel strip at the welded overlapping part is about 100 mm, so a pool of cleaning solution or pickling solution will occur in that part, resulting in staining of the steel strip and spot welding. Not only is there the problem of damage to the rolls in the line due to the convex portions, but there are also other problems such as point welding, which takes a long welding time and is difficult to automate.

Furthermore, since the flash butt welding method involves butt welding of steel strips, there is a problem in that welding becomes difficult when the plate thickness is reduced to about 2.0+ nm.

In order to solve this problem, two types of overlapping welding machines, usually called Matsushi seam welders, for thin steel strips and flash butt welding machines for thick steel strips were installed on the entry side of the continuous processing line. Although some business establishments have installed such facilities, there is a problem in that these facilities require a large amount of capital.

[Problem to be solved by the invention]

An object of the present invention is to solve the problems of the various conventional welding methods for steel strips, and to perform effective lap welding of steel strips in a simple manner without requiring a large amount of capital. is to provide.

[Means to solve the problem]

The gist of the present invention is as follows.

That is, in a steel strip welding method comprising the steps of adjusting the widths of the preceding steel strip and the following steel strip, cutting the ends to be welded, joining the sheets, adjusting the overlap margin, and welding, the overlap margin is This method of welding steel strips comprises the step of crushing the welding portions of the preceding and following steel strips with a reduction roll after the adjustment step.

A flowchart of the welding process according to the present invention is shown in FIG. In other words, as shown in Fig. 1, the conventional method of welding immediately after the overlap adjustment process is eliminated, and after the overlap adjustment process is completed, the welding portions of the leading steel strip and the following steel strip are welded using a reduction roll. A new process of crushing with an edging roll has been added.

[Effect]

-3- Prior to the welding process, the parts to be welded of the preceding steel strip and the following steel strip are rolled down with a reduction roll (swaging roll), and the process heat generated by the rolling process is used to preheat the parts. . The welding shape becomes better, and
This enables lap welding of steel plates with a thickness of 2.0 mm or more and steel plates with scale coatings.

〔Example〕

Example 1 Plate thickness 5. When welding the own SUS304 steel strip and the low-alloy steel strip with a scale coating, work according to the welding flow shown in Figure 1, and after the overlap adjustment process is completed, the press 〇 placed in front of the electrode ring of the Matsushi seam welder. Pressure was applied before welding using a steel tube, and then welding was performed.

By the above welding method of the present invention, the plate thickness is further increased to 1.0 to 5.0.
Welding was performed on SUS304 steel strips with a thickness of mm, but the welding speed (m/
The change in welding current (KA) due to the difference in plate thickness is shown in curve B in Figure 2.

In addition, the welding cycle time (time from stopping the welding line to restarting the line for welding) due to changes in plate thickness from 1.0 to 5.0 mm+ is as shown in Figure 3, and is extremely short from 1 to 5.0 mm+.
It's 2 minutes.

Example 2 A case in which a threaded material of low alloy steel with a scale coating of 4.5 mm in thickness was subjected to reduction processing using a reduction roll before welding according to the present invention, and a case in which no reduction was performed before welding by the conventional method. , micrograph of weld structure and tensile strength of weld (T
．． S. ) were tested for comparison.

FIG. 4 shows a weld structure according to the conventional method, and FIG. 5 shows a weld structure according to the present invention, both of which are micrographs magnified 20 times. As is clear from the comparison between FIGS. 4 and 5, a much better nugget is formed in the case of the present invention shown in FIG.

Furthermore, in the tensile test, the welded area by the conventional method shown in Figure 4 was 32 kg/mm, whereas the welded area by the method of the present invention shown in Figure 5 was 66 kg/mm.
/trtn'', and was found to have approximately twice the strength of the conventional method.

〔Effect of the invention〕

The present invention provides a method for welding steel strips, particularly the current situation where lap welding of steel strips with a thickness of 2.0 m+ or more or steel strips with a scale coating has conventionally been extremely difficult or required a large amount of equipment cost. In view of this, we were able to achieve the following excellent effects by simply adding a new, extremely simple process of compressing with a pressure roll before the welding process and utilizing the heat from the process.

(b) In the above-mentioned lap welding of steel strips, the present invention uses an extremely simple method of simply rolling down the steel strips with a roll-down roll before the welding process, so that a good nugget is formed in the welded area, and the strength of the welded area is higher than that of the conventional welded area. We were able to obtain an extremely excellent welded area that was approximately twice that of the previous one.

(Explanation) There is no need to install a stack seam welding machine or flashbutt welding machine, which requires a large amount of equipment cost.

(c) The present invention has a thickness of 2.0 to 5, which is called a so-called thick one.
．． 2. Omm thick steel strip and thin steel strip. OLI
It can be easily applied to any steel strip of II1 or below without any trouble, and is particularly effective for steel strips with scale coating, which has been extremely difficult in the past, and its range of application is extremely wide.

[Brief explanation of drawings]

Fig. 1 is a welding flow diagram showing the welding process of steel strip according to the present invention, and Fig. 2 is a welding speed (m/min) and welding current (KA )
FIG. 3 is a diagram showing changes in cycle time (Sec) as a function of changes in steel strip thickness in the embodiments of the present invention. FIGS. 4 and 5 are diagrams showing changes in the welding method according to the present invention. and 20x microphotographs comparing the differences in the metal structure of the cross section of a welded part obtained by the conventional method, which does not include a reduction process before welding. This is the welded part.

Claims (1)

[Claims] (1) In a steel strip welding method comprising the steps of adjusting the widths of the preceding steel strip and the following steel strip, cutting the edges to be welded, joining the sheets, adjusting the overlap margin, and welding, the overlap A method for welding steel strips, comprising the step of crushing the welding portions of the preceding and following steel strips with a reduction roll after the completion of the margin adjustment step.