JPS6037201A - Rolling method for providing step difference to thick plate - Google Patents

Abstract

PURPOSE:To roll a rolling material into a plate having a large step difference without causing turbulence in its flatness by controlling the advancing and returning rollings of the material, in rolling a rolling material by leaving a part of the material by a prescribed length and rolling the other part into a thinner one through several passes of reversing rollings. CONSTITUTION:A steel plate 1 rolled into the sheet thickness t1 is rolled into the sheet thickness t1' by upper and lower work rolls 2, 3 having a roll gap S1 between them, and when the top of plate 1 is detected by a steel plate detector 4, the rotation of mill is stopped to leave a thick-plate part having thickness t1 by a length l1. Successively a return rolling is performed by reversing the mill to obtain a thin-plate part having sheet thickness t1''. Further, the 2nd pass rolling is performed to obtain a thin plate-thickness t2' part by regulating the roll gap to S2(S1>S2), and the mill is reversed when the detector 4 detects the top of plate 1 to obtain a thin plate-thickness t2 part. In this way, a plate with different thicknesses is obtained, which consists of a part having a prescribed length l1 and a sheet thickness t1 and a remaining part having a sheet thickness t2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of rolling a thick plate, and more particularly to a method of differential thickness rolling of a thick plate that provides a step in the longitudinal direction.

Traditionally, steel plates with different thicknesses were joined by welding, but recently, from the perspective of saving energy by omitting the welding process, plates with different thicknesses that do not require a joining process by welding have been manufactured. It's starting to look like this. In other words, in one steel plate, the thickness is t from the top of the steel plate to the length of eo, and the thickness of the remaining 42 minutes to the bottom is t2 (t, □〉t2). The idea is to use thick plates and omit the welding process.

Such differential thickness plates are usually manufactured by rolling, and after the steel plate is bitten into a rolling mill and advanced a predetermined distance, the rolling mill is reversed to form a thin section (thickness t
2) is manufactured by chewing it back. However, when producing thick plates with a large difference in thickness (t, -t2), the rolling load of the rolling mill is limited, so a large reduction cannot be achieved, and therefore one pass of reverse chewing is required. It was impossible to manufacture using this method, and even if it were manufactured in one pass, there was a possibility that the flatness would be disturbed, so it was a good idea.

Therefore, the inventors of the present invention have conducted various studies on a method that can solve these problems and roll any thickness difference, especially a large thickness difference, without disturbing the flatness. The present invention was conceived based on the knowledge that this is possible by carrying out the reverse rotation by using a copper plate tip detector and making the reversal timing (eo) constant at that time.

That is, in detail, the gist of the present invention is that after rolling a rolled material to a thickness of t□, the thick part is left at a predetermined length and the remaining part is rolled into a thin wall by several baths of reversible rolling. In the method for differential thickness rolling of a thick plate in which a desired step is provided in the longitudinal direction by obtaining a desired thickness t2 (t□〉t2) of the thin part, the thick part side of the rolled material is A rolled material detector is installed at a rear position separated from the rolling mill by a distance corresponding to obtaining the length of the thick section, and is used to detect the difference as the rolled material advances toward the rolling mill. The thin wall portion is forward rolled until the rear end of the thick wall portion is detected by the rolled material detector, and at the same time as the detection, bit back rolling is performed to roll the thin wall portion in the opposite direction, and these forward rolling and A method for differential thickness rolling of a thick plate, characterized in that bit back rolling is repeated until the thickness of the thin wall portion reaches a desired thickness t2.

The present invention will be explained in detail below using the drawings.

FIG. 1 shows an example of manufacturing a differential thickness plate using multiple passes. In the figure, 1 is a steel plate, 2.8 is an upper and lower work roll, and number is a steel plate detector.

First, after rolling the steel plate 1 to t□ according to the normal rolling schedule, it enters the first bus of differential thickness plate production ((al process) in the figure. At this time, the upper and lower work rolls 2, 8
The roll opening setting is 80, and the distance between the steel plate detector number and the rolled material is L□.

Then, when rolling is performed with this opening degree S0, a thin section with a thickness t1' is pulled out of the rolling machine (step (b)), and the steel plate detector 4
At the same time as detecting the top portion of the steel plate 1, the rotation speed of the rolling mill is reduced to zero ((C) step). From this K, a thick portion with a length l remains without being thinned.

Next, the rolling mill is reversed with the roll opening S
e) process).

Furthermore, the roll opening degree is set to 52 (S□〉S2) and a second pass of rolling is performed to chew out the thin wall portion at t2' (step f)), and the top part of the steel plate 1 is detected by the steel plate detector 4. By detecting this, the rolling mill can be reversed without changing the roll opening (g)
Step), a thin part with a plate thickness of t2 is obtained (Step (b)).

In this way, a differential thickness plate is manufactured which has a thin part with a thickness t2 and a length e2 and a thick part with a thickness t and a length σ□. Since the rolling mill is always reversed by the steel plate detector 4,
Multiple steps are not generated in the differential thickness portion of the differential thickness plate.

In the above embodiment, a case was explained in which one steel plate detector number was installed, but in the present invention, as shown in FIG. 2, a plurality of steel plate detectors 4.4' are installed.

It is also possible to perform differential thickness rolling by installing a roller.

This will be explained with reference to FIG. In the figure, 2 and 8 indicate 1 upper and lower work rolls, and 5 indicates a roller table.

That is, as shown in FIG. 1, when the steel plate detector 4 is installed at a distance of L□ from the rolling mill, this steel plate detector 4
When the top part of the steel plate l is detected at , and the rotation speed of the rolling mill is reduced to zero, a thick part (non-thin part) with a length of e remains, and the length between the top part of the steel plate and the rolling mill is e. . is equal to Lo, but (
(See Figure 1 (C)), when manufacturing a plate with a difference in thickness go such that L The top portion of the steel plate 1 will be detected by the only steel plate detector 4 before the time when Sag□ is left. In such a case, add an arbitrary amount of extra length to the top of the steel plate 1 to substantially extend the edge of the steel plate to be detected, and then go.

LX equal to any steel plate detector (4, 4
', /) can detect the extra long end of the steel plate. On the other hand, when manufacturing a differential thickness plate with an internal length el such that L□<eo, the extra length can be added and detected using steel plate detectors 4/ and 4#. can. Of course,
If eo is shorter than L□, L□', or L-,
If the top part of the steel plate is detected by a steel plate detector separated by a distance longer than eo, and the rotation speed of the rolling mill is reduced to zero after detection, taking into account the traveling distance of 10 steel plates, add extra length. There's no need. In this way, by installing a plurality of steel plate detectors, at least e can be obtained with or without extra length. >Ll, it is possible to design the material to achieve the maximum yield, and therefore the desired length e
Differential thickness plates with a thick wall part of □ can be manufactured as ordered.

Furthermore, regarding the length of the thin part (thickness t2), the length of e2 can be changed by installing multiple steel plate detectors, so that the length is appropriate for e2, which is the order dimension of the differential thickness plate. The material can be designed to improve the yield rate.

In this way, it is possible to design a material with a large needle thickness difference and a high yield.

Next, a description will be given of what kind of rolling schedule should be adopted for one or more buses.

Figure 8 shows a rolled material with a plate thickness of t□ rolled at a roll opening degree of S,
The relationship between the rolling load and the plate thickness is shown when a thin section with a plate thickness of t is obtained.

In the figure, when a rolled material with a thickness t0 is rolled at a rolling position (roll opening degree) S, the plastic constant Q (inclination AB
) and the mill constant M (inclination Be) of the rolling mill. Furthermore, this rolled material is rolled again at the same rolling position S (
When the sheet is chewed back), a rolling load F2 determined by the same constants Q and M is generated, and the sheet thickness at the exit side becomes t2.

In addition, XY in the same figure is a constant crown ratio curve, which is a condition for improving the shape of the rolled material, and is determined by the entrance side plate thickness, exit side plate thickness, roll crown, rolling load, etc. Assuming that the rolling load at the pass where tl is F□, the curve that makes the shape good is approximated by a straight line passing through R and descending to the left.

When manufacturing a differential thickness plate with good flatness in one pass under the relationship shown in Figure 8, if F2/ exceeds the load limit, the differential thickness plate will be produced in one pass. Of course, it is impossible to roll.Furthermore, even if F, / is below the load limit, if F2 is a much larger value than Fo, the rolling schedule will deviate from the constant crown ratio rule. Therefore, ear waves occur and good flatness cannot be obtained.

On the other hand, when manufacturing a differential thickness plate in a plurality of passes, for example, two passes, as in the present invention, it is possible if the rolling schedule is set as shown in FIG.

In other words, when a rolled material with a thickness of t□ is rolled in the first pass with the reduction position of 8□, the thickness of the plate becomes t,! When this is chewed back and rolled, the plate thickness becomes t, //.

Next, in the second pass, when the rolling position is changed to S and bite rolling is performed, the plate thickness becomes t21, and when this is bite-back rolled, the plate thickness becomes tg. In this 2) scrap method, each rolling load Fil
Fz, F8', F8 are constant crown ratio plane lines
Y can be selected close to Y, and plates with different thicknesses can be manufactured without large disturbances in flatness while following the constant crown ratio law.

As described above, according to the present invention, the bit-back rolling can always be performed at the same bit-back position, which improves the product yield, and since reversible rolling is performed in multiple buses, the flatness of rolling with large steps is not disturbed. It has remarkable effects, such as being able to perform it without causing any problems.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing the differential thickness plate manufacturing process a (a) to (h) using multiple buses according to an uninvented embodiment, and the shape of the differential thickness plate product, and FIG. is an explanatory diagram showing an embodiment in the case where a plurality of steel plate detectors are installed in the present invention, and FIGS. 8 and 4 are diagrams showing the relationship between rolling load and plate thickness when manufacturing differential thickness plates. , FIG. 8 shows the case using l-path, and FIG. 4 shows the case using z-nox. l... Steel plate 2... Upper work roll 8... Lower work roll 4... Steel plate detector 6... Table roller.

Claims (1)

[Claims] L After rolling the rolled material to a thickness of tl, the thick part is left at a predetermined length and the remaining part is rolled into a thin wall by several passes of reversible rolling, so that the thickness of the thin part becomes the desired thickness t2. (to>t2
) in a method for differential thickness rolling of a thick plate that imparts a desired step difference in the longitudinal direction by obtaining a distance from the rolling mill corresponding to obtaining the length of the thick part on the thick part side of the rolled material. A rolled material detector is installed at the rear position separated by
As the rolled material advances toward the rolling mill, the thin-walled portion is rolled forward until the rolled material detector detects the rear end of the thick-walled portion, and at the same time as the detection, the thin-walled portion is then rolled in the opposite direction. A method for differential thickness rolling of a thick plate, characterized in that rolling is performed by bit back rolling, and these forward rolling and bit back rolling are repeated until the thickness of the thin wall portion reaches a desired thickness t.