JPS61103603A - Manufacture of thick steel plate having plural step differences in thickness - Google Patents

Abstract

PURPOSE:To obtain a thick steel plate having plural step differences, highly reliable for strength, by reversing rolling the intermediate section of thin wall into a prescribed thickness after rolling a stock into the sheet thickness of thick-sheet section of a different-thickness steel plate. CONSTITUTION:A thick plate of thickness (t1) is obtained by finishing rolling a stock of steel slab after forming rolling and broadside rolling the stock by heating it. Next, a roll opening is constricted at the time when a rolling roll arrives at a point A of the stock, and the stock is gradually subjected to rolling reduction so that the stock attains the thickness (t2) when the roll arrives at a point B. Further, the rolling, that the thickness (t2) is obtained at a point C, is continued while maintain a rolling force, and the rotating direction of roll is reversed at the point C, to roll the stock in the opposite direction. When the roll arrives at the point B after reversing the rolling direction, the stock is rolled by, for instance, an automatic plate thickness control system so that the thickness is (t2) from the point B to the point A. Next, when the roll arrives at the point A, the roll is reversely rotated again to release the constriction of roll opening thereafter.

Description

[Detailed Description of the Invention] (Industrial Application Field) The technical contents described in this specification regarding the manufacturing method of a thick steel plate having a plurality of steps in the longitudinal direction of the steel plate are applicable to shipbuilding shell plates or other welding materials. This paper presents the results of a development in which a thick body plate having a thickness thinner in the middle section of a plurality of sections divided in the longitudinal direction than in the remaining sections is obtained by a hot rolling method.

Different-thickness steel plates with steps in the longitudinal direction, that is, different thicknesses, include copper plates that are thinner at one end and thicker at the other end, thicker in the center and thinner at both ends, and in recent years, steel plates for shipbuilding. For example, steel plates that are thicker at both ends and thinner in the center are desired as materials for welded structures such as steel sheets due to demands for strength and shortening of the tempering process.

(Prior art) Conventionally, steel plates that are thick at both ends and thin in the center are made by joining Wi plates of each thickness by welding, or by joining the thicker part and the thinner part of the steel plate with one end thicker and the other end thinner. It was made by joining equal steel plates by welding (the name of the document is unknown and cannot be cited).

Such welded joints leave concerns about the strength of structural materials.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for manufacturing a thick steel plate having a plurality of steps in the direction of the edge.

(Means for Solving the Problems) This invention provides a method for manufacturing a thick steel plate having a plurality of sections divided in the longitudinal direction, the middle section being thinner than the remaining sections, and having a plurality of thickness steps. 1 is a method for manufacturing a thick steel plate having a plurality of thickness steps, which comprises the steps of rolling the material to the residual section, and reverse rolling the intermediate section to make it thinner. Is there a difference in thickness? Have thick steel plate? The manufacturing process is illustrated. Note that the example in FIG. 1 describes a case where a steel plate having a width wider than the slab width is manufactured.

First, FIG. 1 (al) is a thick plate with a thickness of t obtained by heating a steel slab as a raw material, forming and rolling, tentering, and then finishing rolling.

Next, when the rolling roll reaches point A of the steel plate, the roll opening degree is tightened, and when the roll reaches point B, the plate thickness becomes t,
Rolling is performed by gradually applying reduction so that

Roughly until the 0 point, rolling is continued to maintain the rolling force to obtain the plate thickness t2, and at the 0 point, the rotation of the rolls is reversed to perform reverse biting.

Then, when the roll reaches point B after reversal, rolling is performed using, for example, an automatic plate thickness control system (AGO) so that the plate thickness from point B to point A is t2.

In other words, at point 0, the roll is reversed and the plate thickness is A.

The load is locked on so that the plate thickness becomes constant (t2) between 0 and 0. The rolling load at this time can be determined as follows when controlling the plate thickness using a gauge meter.

The gauge meter method detects the rolling force and controls the plate thickness, and the plate thickness hL is .

hL=F L /M + SL, given by +of S.

However, hL: Plate thickness at the time of rolling down (==t21SL: Whirl opening degree at the time of rolling down FL: Load ofs at the time of rolling down Nioh7 set amount M: Mill (spring) constant, so the load FL is FL = (hL-SL , −ofs l ·M.

Next, when the seal reaches point A, the rotation of the roll is reversed again, and then the narrowing of the roll opening is released.

In addition, if the plate thickness t2 cannot be obtained even by rolling the rolls back and forth once due to the limit of the mill capacity, the plate thickness t2 can be obtained by repeating the reversal between points A and 0. (Example) The method of this invention is used to manufacture a thick steel plate with a width of aoooom, in which the thick parts at both ends are 25M in thickness and 8500 in length, and the thin part in the center sandwiched between the thick parts is 20 in thickness and 60001 LI11 in length. was carried out.

First, it was heated to 1150°C. Thickness 24Qg+a, width 1
After forming and rolling a steel slurry 7"E-1 with a length of 60 Qm and a length of 4800 m in the usual manner, it was rolled 900 times to make the width 3QQQsm, and then turned 90 degrees again to form a 980"
Finish rolling was performed at C to produce a thick plate with a thickness of 25 ins.

Next, the roll opening degree is narrowed down at the point where the rolling roll reaches 8500j+s from one end (point A in Figure 1 (a)'') and 145008 from the one end (point 0 in Figure 1 (t)l). Rolling was carried out so that the plate thickness was 22 mm.
At this point, the rolls are reversed and bitten back to continue rolling and reduce the plate thickness to 2Q.
It was set as a+a. The temperature of the steel plate at this time was 940°C.
The rolling load gradually increased from 1800 to 4700 tOn. When rolling the plate to a thickness of 3 Q m t, an AGO was used to apply the required rolling load to each part each time.

Thereafter, after rolling 6,000 rolls from the position where the reel was reversed, the roll was reversed again and released. At this time, the finishing temperature of the thin portion was 850''C.

(Effects) As explained above, according to the present invention, unlike conventional differential thickness steel plates having a thick wall portion only on one end side, a steel plate can be produced by omitting the step of welding a thick wall portion of another steel plate to a thin wall portion. A thick steel plate having multiple thickness steps in the longitudinal direction can be manufactured. In addition, since the thick and thin parts of this rusted steel plate are integrally formed, it has the advantage of high reliability in terms of strength.

[Brief explanation of drawings]

FIG. 1 [a] to C1 are explanatory diagrams showing the rolling process of differential thickness steel plates.

Claims (1)

[Claims] 1. When manufacturing a thick steel plate that has a plurality of sections divided in the longitudinal direction, the middle section is thinner than the remaining section, and has a plurality of thickness steps, the material is separated from the remaining section. A method for producing a thick steel plate having a plurality of thickness steps, which comprises: rolling the steel plate to a thicker thickness; and rolling the intermediate section to a thinner thickness. 2. The method for producing a thick steel plate having a plurality of thickness steps according to item 1, wherein the step of rolling the material to the thickness of the remaining section includes preliminary forming rolling and tentering rolling.