JPS6254505A - Manufacturing method of differential thickness steel plate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a differential thickness steel plate having thickness differences in the longitudinal direction obtained by hot rolling.

[Conventional technology]

As a method for producing such a stepped steel plate, for example, Japanese Patent Publication No. 50-36826 and Japanese Patent Publication No. 52-49781 are known.
It is disclosed in the publication No.

These described methods basically involve reversing the rolls during hot rolling of a single steel plate and rolling in the opposite direction without changing the roll gap.

[Problems to be Solved by the Invention] The method of obtaining a steel plate with a step with a different thickness W4 by reversing the intermediate roll can obtain a steel plate with a difference in thickness with a step in one step, and furthermore, the step part has an arc shape. Since they are connected by a connecting portion, it is possible to obtain a product having excellent mechanical properties without stress concentration, but there is a drawback that waves are generated during reverse rolling and the flatness is impaired.

An object of the present invention is to eliminate the above-mentioned drawbacks in manufacturing a stepped steel plate by reversing the process halfway, and to provide a method for manufacturing a stepped steel plate having high flatness.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a differential thickness steel plate having thickness differences in the longitudinal direction by hot rolling, in the middle of the rolling process after the material to be rolled is bitten.
The method is to continue rolling by changing the roll gap within a range that can maintain a rolling reaction force that can maintain flatness.

[Effect]

In hot rolling, the flatness of a rolled material is influenced by the rolling reaction force (hereinafter simply referred to as reaction force) against the plate thickness, and in order to obtain a rolled material with a flat surface, the flatness must be within the specific range shown in Figure 1. It is necessary to apply a reaction force to the plate thickness.

In other words, referring to Fig. 1, at a specific plate thickness, if the reaction force is smaller than the value (area B), waves, that is, medium waves, are generated on the surface of the central part of the rolled plate; If it is larger than (range C), waves are generated in the ear portion, that is, ear waves, and the reaction force that does not generate these waves, that is, maintains flatness, is within a specific range. This flatness maintenance range (area A) tends to expand as the plate thickness increases.

According to experiments conducted by the present inventors, the occurrence of flatness defects in the prior art is due to the fact that the rolling reaction force after halfway reversal is small because the rolls are reversed without changing the roll gap, and in the reverse rolling process, as shown in Figure 1. When the reaction force enters the medium wave generation area (area B) as shown by the y-y line, or the ear wave generation area occurs when the reaction force in the rolling process before reversal is large as shown by the z-z line. It turned out that this is based on the elucidation of the phenomenon that occurs when entering the medium wave generation area (Area B) from (Area C).

That is, the present invention achieves high flatness by changing the roll gap and the reaction force corresponding to the thickness of the rolled material within the flatness maintenance range (area A) shown in FIG. 1 during reversal in the middle of rolling. This is to obtain a steel plate with a difference in thickness.

When changing the roll gap, it is possible to create an open state in which no reaction force is generated at all, and also to perform 11) one-way rolling, (2) half-way reverse rolling, and (3) half-way reverse rolling multiple times. It can be applied to

〔Example〕

Next, the present invention will be explained in detail.

(1) This is a method that can be suitably applied when the difference between the thickness of the large thickness portion and the thickness of the small thickness portion of a unidirectionally rolled step rolled plate is relatively small.

In Fig. 2, (a) shows the control system in this unidirectional rolling, Fig. 2 (b) shows the change in the form of the rolled material, and Fig. 2 (c) shows the change in the form of the rolled material in Fig. 2 (b). It is a figure which shows the state of the rolling reaction force corresponding to.

In the control system shown in FIG. 2(a), the target thicknesses tl and t of the target small and large thickness parts of the rolled material are
2, the roll gap control data corresponding to the allowable reaction force is input from the process controller 1 to the operation command unit 2,
It is configured so that it can compare with the actually measured reaction force from the roll 3 and adjust the roll gap based on the comparison data. In this way, data from the recorder of the process controller 1 is compared with the reaction force from the rolls during rolling, and at a predetermined rolling position, a rolling reaction force that is within the flatness tolerance range shown in Figure 1 is determined. The roll gap is the thickness of the small thick part t
The configuration is such that the thickness t2 of the large thick portion can be changed from 1 to the thickness t2 of the large thick portion that has been input in advance to the data storage device.

During rolling, the rolling mill shown in FIG. 2(c) is driven to perform rolling according to the procedure shown in FIG. 2(b). First, a roll gap is set so that a material to be rolled having a thickness t shown in (■) has a preset thickness tl, and the material is bitten as shown in (■). After this biting, use a length measuring device such as a Mill Pulse to find the predetermined position shown in
When reaching VLr ) at Ll, the speed is decelerated, and upon receiving the comparison command signal at Ll, the roll gap is adjusted so that the plate thickness becomes t2, and the large thick portion shown in (2) is rolled.

As a result, it was possible to manufacture a thick steel plate with steps that had steps at predetermined positions and maintained high flatness.

(2) This is a method that can be suitably applied when the difference between the thickness of the large thickness portion and the thickness of the small thickness portion of a partially reverse-rolled differentially thick steel plate with steps is relatively large.

FIG. 3 shows, as in the case of unidirectional rolling (1) above shown in FIG. 2, (a) shows the control system in halfway reverse rolling, and (b) shows the change in shape of the same rolled material, (c) is (b)
It is a figure showing the state of the rolling reaction force corresponding to the shape change of the rolled material.

At ■ in Fig. 3(b), the finish rolling of the large thickness part t2 is completed, and the roller is rotated in the normal direction by ■ to ■ so that the reaction force can be maintained within the flatness maintenance range (area A) in Fig. 1. t
Control data for a rolling schedule of tl with □ and mid-way reversal are input from the process controller 1 shown in FIG. 3(a) to the operation command unit 2. Then, when the rolling roll reaches a predetermined point ■ from the biting position ■, that is, the distance VL from the biting position, the roll rotation speed is reduced to the lower limit of the mill function, and then the reverse rotation is started at the point 1. At the same time as the rolls are reversed, the roll gap value is set at the time of reversal, and rolling is continued as shown in (■) to cause the roll to start biting from the biting side.

The advantage of this method is that by changing the gear and pull during reversal to the gear and pull during engagement, the reaction force changes during engagement and reverse can be brought closer to the anti-cover turn that yields a good shape. , it becomes possible to easily manufacture a steel plate with a large difference in thickness.

(3) Multiple reverse rolling This example is a method in which the above (2) intermediate reverse rolling is performed multiple times during the pass, and when setting the rolling schedule, the flatness shown in Figure 1 is The roll gap is set so that the reaction force can be maintained within the maintenance range (area A).

In Figure 4, as in Figures 2 and 3, (a) shows the control system, (b) shows changes in the shape of the rolled material, and (c) corresponds to the changes in the shape of the rolled material in (b). It is a figure showing the state of rolling reaction force.

In rolling, the rolled plate (■) is bitten into the middle thickness part t1 shown in (■), and then rolled from the biting position to VL at (■).

When it reaches , it decelerates, reverses at position Ll, and moves at t2 shown in ■.
form a section. Subsequently, when it reaches VL2 from the reverse rotation position, it is decelerated, and at the L2 position, the rotation is reversed to form the t3 section shown in (■). Furthermore, when it reaches L3 from the above-mentioned reverse rotation position, it decelerates, and after opening the roll gap at the L3 position, it begins to bite. Moreover, by further repeating the above roll reversal,
A steel plate with a large difference in thickness can be obtained.

The advantage of this method is that a differential thickness steel plate can be obtained in which the intermediate part in the longitudinal direction of the rolling direction is thinner than the other parts.

〔Example〕

Next, specific examples of each of these rolling methods (1) to (3) are as follows. For each side, the rolling pass schedule before the start pass of differential thickness rolling is omitted, and the size unit and roll gap unit are square ■, and the reaction force unit is ton.
, (normal) appended to the path error indicates a normal rotation pass, and (reverse) indicates a reverse rotation pass.

In addition, FIGS. 5(a) to 5(c) show the slab immediately before the start of differential thickness rolling on each side and the target size pattern of finish rolling.

Further, FIG. 6 shows the position within the shape maintenance allowable range of each pass rolling reaction force of each slab rolling section R-X in each specific example.

This figure 6 shows the rolling target thickness of 10 to 17 dragon 7 width 280
The shape maintenance permissible reaction force range of each pass of differential thickness rolling when the value is 0■■ is shown in relation to the thickness of each pass.

(B) Specific example of unidirectional rolling [Size pattern Fig. 5 (a)] Slab size immediately before starting differential thickness rolling Thickness x width x length: 14.8 x 2800 x 2000
0 Finish rolling target size R thickness/S thickness X width x R length/S length: 12.0/12.3 x 2800 x 12000/
12,000, which was extremely good.

(b) Specific example of mid-turn reverse rolling [Size pattern Fig. 5 (b)] Immediately before the start of differential thickness rolling Slab size Thickness x Width x Length: 14.8 x 2800 x 2400
0 Finish rolling target size T thickness/U thickness x width x T length/U length: 12.0/12.3 X2800X14000/140
00 (c) Specific example of reverse rolling multiple times midway [Size pattern Fig. 5 (C)] Immediately before the start of differential thickness rolling Slab size Thickness x Width x Length: 21. OX 2800 x 28000
Finish rolling target sizing thickness / U thickness / χ thickness X width × v length / Ka length / X length: 17.0 /
12.0/21. Ox 2800 x 12000/1
2000/12000 [Effects of the Invention] According to the present invention, it is possible to obtain a stepped steel plate having excellent flatness without surface waves, and in particular, it contributes to the popularization of the production of stepped steel plates by halfway reversal. It is.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a region where flatness is maintained in relation to plate thickness and rolling reaction force, and FIGS. 2 to 6 are diagrams showing embodiments of the present invention. 1: Process controller 2 2 Operation command unit 3: Roll

Claims (1)

[Scope of Claims] 1. In a method for manufacturing a steel plate having a thickness difference in the longitudinal direction due to hot rolling, the flatness of the roll gap can be maintained in the middle of the rolling process after the material to be rolled is bitten. A method for producing a differential thickness steel plate, characterized in that rolling is continued by changing the rolling reaction force within a range that can maintain the same rolling reaction force. 2. The method for manufacturing a differential thickness steel plate according to claim 1, characterized in that the roll gap is changed during unidirectional rolling. 3. The method for manufacturing a differential thickness steel plate according to claim 1, characterized in that the roll gap is changed at the same time as the rotational direction of the rolls is reversed. 4. The method for producing a differential thickness steel plate according to claim 3, characterized in that the rotational direction of the rolls is reversed at a plurality of locations on the rolled plate.