JPS606273A - Manufacturing method of steel strip for continuous processing - Google Patents

Abstract

PURPOSE:To prevent thoroughly the trouble occuring in the rupture of a strip from the weld zone in the stage of joining hot rolled coils having different sheet gauges by pressing the rear end of the preceding coil and the front end of the succeeding coil to have a uniform sheet gauge then butt-welding the two ends. CONSTITUTION:The front end of, for example, a heavier-gauged succeeding coil 2 is pressed with a press machine 3 to have the sheet gauge equal to the sheet gauge of a lighter-gauged preceding coil 1. The joining ends of the coil 1 and the coil 2 are then butted by aligning the centers in the sheet gauge direction. The butt parts are thereafter welded by arc welding, resistance welding, laser welding, etc. The bead in the weld zone 4 is removed with a bead knife upon ending of welding. The unification of the sheet gauges may be accomplished as well by pressing together the two welding ends of the coils 1, 2 to the sheet gauge lighter than the original sheet gauges of the coils. The permissible range for the difference in the sheet gauge of the differently gauged coils to be welded is thus widened and the titled steel strip having desired weld strength is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a continuous processing steel strip by joining hot rolled coils of different thicknesses by welding.

In order to improve the efficiency of hot-rolled coils in post-processes such as pickling fins, a method is used in which the coils are welded together to increase the size of the coils. For example, in the case of pickling fins, a welding machine installed on the entry side welds the leading coil and trailing coil to make the line continuous.

The above welding work must be performed not only to prevent plate breakage during passing through the pickling line, but also to prevent plate breakage during cold rolling in the subsequent process.

For example, when welding coils with different plate thicknesses, a stepped weld will naturally occur, and sufficient welding will not be possible, resulting in problems in terms of strength. Therefore, the current practice is to set tolerance standards for plate thickness differences when welding coils, and only weld coils with different thicknesses that fall within this standard.

That is, in the case of coils with different plate thicknesses, as shown in Fig. 1, the leading coil (1') and the trailing coil (6) of different plate thickness are butted together, welded after forming a welding groove, and then welded with a bead knife. The bead at the welded part (4') was cut and removed. However, the leading coil (1') and trailing coil (2)
If the plate thickness difference is large and does not meet the above-mentioned acceptable standards, bead residue will occur even if the bead is cut with a bead knife after welding, and indentation flaws will occur due to the bead residue during cold pressing in the subsequent process. In addition, since step welding is used, if there is a large difference in plate thickness, welding cannot be performed sufficiently and the desired welding strength cannot be obtained, resulting in plate breakage at the welded part during pickling fin threading or cold rolling process. occurs. In order to prevent such troubles, conventionally, tolerance standards for plate thickness differences have been set, and parts that fall outside of these standards are avoided from being joined.

The currently set plate thickness difference tolerance standard is a maximum of 0.511r for coils with plate thickness 8 or higher! ! , for coils with a plate thickness of 8 mm or less, the maximum values are o and am. In other words,
Conventionally, welding of different thickness coils with a plate thickness of 3 mm or more is limited to those where the difference in plate thickness between the leading coil 7 and the following coil is within 0.5 f1, and welding of different thickness coils with a plate thickness of 3 mm or less is limited to Welding is limited to those where the difference in plate thickness between both coils is within 0.8f1. However, even if the plate thickness difference is within the above-mentioned allowable standards, steel strips for continuous processing manufactured using conventional methods have a step in the welded area between the leading coil and the trailing coil, resulting in poor strength. is not desirable.

This invention was made in view of the above-mentioned conventional situation, and aims to widen the allowable range of plate thickness difference between coils of different thickness to be welded, and to completely prevent troubles due to plate breakage from the welded part. This paper proposes a method for manufacturing steel strip for continuous processing.

The gist of this invention is to weld hot-rolled coils of different thicknesses to produce a steel strip for continuous processing, in which the thicknesses of the rear end of the leading coil and the tip of the trailing coil are made uniform by press working. The present invention provides a method for producing a continuous processing steel strip, characterized in that the steel strip is welded.

That is, in order to avoid step welding, the present invention is a method of welding the welding ends of the leading coil and trailing coil by press working to a uniform plate thickness before welding. In this case, to align the thickness of the welded ends, you can either press only the thicker coil to match the thinner coil, or the welded ends of both the leading and trailing coils. Any method may be used in which the parts are pressed together and made to have a thickness thinner than that of both coils. Note that press working was adopted as a method for making the thickness of the front and rear ends of the coil uniform, taking into account work efficiency, equipment availability, precision, etc. That is, the press processing can be performed automatically using an existing press machine, and the desired dimensional accuracy can be ensured. Furthermore, the press machine does not require a large installation space and can be easily installed in front of an existing continuous wine welding machine.

Next, an embodiment of the present invention will be described based on FIGS. 2 and 8.

Figure 2 shows the case where only the thicker plate coil is pressed and welded to match the thinner coil. First, the trailing coil (2) of the thicker plate is welded. The thinner preceding coil (1) is rolled down with a press machine (3).
Make the plate thickness uniform. Next, the joining ends of the leading coil (1) and the trailing coil (2) are butted together with their centers aligned in the thickness direction. After that, the butt portions are welded.

Since there is no difference in level between the butt parts, sufficient welding can be performed. Note that welding methods include flash butt welding, seam welding, laser welding, CO, gas welding, arc welding, and the like. When welding is completed, the bead of the welded portion (4) is cut and removed with a bead knife. In this case as well, since the joint ends have the same plate thickness, no bead remains will occur (
Can be removed by cutting.

In addition, Figure 8 shows an example of a case where both the leading coil (1-2) 4- and the trailing coil (2-2), which have different plate thicknesses, are press-formed at the same time to make the bonded ends uniform in plate thickness. In this case, the press machine ( 3) Both coils are pressurized simultaneously (or separately) to obtain a desired uniform plate thickness, and then welded.

In addition, in both cases of FIG. 2 and FIG. 3, the pressing part may be heated to facilitate press forming. Further, the length of the rolled part is not particularly limited, but it is preferably 100 m or less.

Since the steel strip for continuous processing obtained in this manner has no steps in the welded portion, there is almost no possibility that the plate will break at the welded portion during pickling fin passing or during the cold rolling process. Further, since no bead remains in the welded portion, there is no occurrence of indentation flaws caused by the bead remains during cold pressing.

Examples of this invention are shown below.

〔Example〕

A pickled hot-rolled coil for cold-rolled steel sheets that complies with JIS G3141, and has a plate thickness of 3. The leading coil of Qmm x plate width of 900 mm and the trailing coil of plate thickness of 4.0 fl x plate width of 900 mm are butted together, and in this state a 200 ton hydraulic press 7
Pressure is applied to the joining ends of both coils at the same time to obtain a uniform plate thickness of 2.
．． After forming into 8 mm, it is joined by normal seam welding,
The weld bead was removed using a bead knife to finish the work. In order to finish the steel strip of different thickness produced in this way to a thickness of 0.8mm, it was passed through a cold rolling machine at a wine speed of 1000.
Although the sheet was rolled at a rate of m/min, there was no sheet breakage at the welded portion. Furthermore, no indentation flaws due to bead residue were observed.

As is clear from the above examples, according to the method of this invention, hot rolled coils with different plate thicknesses can be welded with the same plate thickness, so the tolerance range for plate thickness differences can be greatly expanded. Moreover, it is possible to produce a steel strip for continuous processing having a desired welding strength, and it is possible to completely prevent plate breakage troubles during pickling and cold rolling processes. Therefore, hot-rolled coils can be made larger than ever before, making a significant contribution to improving the productivity of steel sheets.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a conventional manufacturing method of steel strip for continuous processing, Fig. 2 is a process diagram showing one embodiment of the present invention, and Fig. 8 is a process diagram showing another embodiment of the invention. It is. 1.1-2... Leading coil, 2.2-2... Trailing coil, 3... Plaine machine, 4... Welding part. Applicant: Sumitomo Metal Industries, Ltd. Figure 2 Before press Figure 3 Before press ↓ Before welding after derene 438-

Claims (1)

[Claims] In a method of manufacturing steel strip for continuous processing by welding the leading and trailing ends of hot-rolled coils with different thicknesses, the thickness of the trailing end of the leading coil and the tip of the trailing coil is made uniform by plenoid processing. A method for manufacturing a copper strip for continuous processing, which comprises the steps of: