JPS5948681B2 - How to roll thick plates - Google Patents

Description

[Detailed description of the invention] The present invention forcibly cools a rolled plate material during rolling.
The present invention relates to an improvement in a method for rolling a thick plate that is rolled while controlling the temperature, and particularly relates to a method for rolling a thick plate in which the impact when the rolled plate material is bitten is alleviated.

Normally, thick plates are made into finished products from slabs through a forming pass, tentering pass, thickness reduction pass, and shaping pass. So-called control trolling, in which the heating temperature, temperature during rolling, and rolling reduction rate are controlled, is sometimes performed.

In this control trolling, a so-called temperature adjustment pass is usually performed once or several times in which the steel plate is forcibly cooled to a predetermined temperature by means such as air cooling, shower cooling, or descaling spray during the thickness reduction pass.

However, when such forced cooling is performed, the ends of the steel plate are supercooled to a greater degree than other parts, and in particular, the longitudinal ends of the steel plate, the top and bottom, are supercooled due to supercooling. It is known that the deformation resistance is greater than that of the middle portion, and therefore the plate thickness is also increased.

That is, the temperature and plate thickness distribution in the longitudinal direction of the steel plate in control trolling are, for example, as shown in FIG.
In some cases, the plate thickness deviation ΔH2 reached 0°C and 1 mm.

In addition, in FIG. 1, effects caused by skid marks and the like are omitted for the sake of simplification.

When the top and bottom parts of a steel plate are thicker than the middle part, the impact load on the rolling rolls at the biting part and the torque of the rolls become excessive during rolling. The impact on the mechanical system becomes excessive, making it difficult to ensure its safety, and excessive torque at the time of jamming causes problems such as tripping of the power supply.

Therefore, in order to avoid these inconveniences, it is necessary to reduce the amount of reduction per pass, which reduces efficiency, and furthermore, even if such measures are taken, the top and bottom of the product may be excessively large. There was also the inconvenience that the quality problem of thickening could not be avoided.

To solve the above problem, in order to prevent the top and bottom from becoming too thick, the roll gap is set small to allow the rolled plate material to bite, and after passing through the supercooled section, it is returned to the original roll gap and rolled. There is a so-called jamming repair method that has been put into practical use, but although this method can prevent overthickness of the top and bottom, it actually increases the risk of shock to mechanical systems such as rolling mills and power tripping. The problem is that the amount increases.

The present invention was made to solve the above-mentioned conventional problems, and it is possible to prevent the top and bottom from becoming too thick, and also to avoid the risk of shock to the mechanical system and the risk of power supply lip. The purpose is to provide a method for rolling thick plates.

The present invention provides a thick plate rolling method in which a rolled plate material is forcibly cooled during rolling and rolled while adjusting the temperature, at least in passes after the first temperature adjustment pass and before the final two to three passes. In at least one of the passes, the rolled plate material is rolled with a gap between the rolls rather than in other parts while the part passes through the rolls, thereby achieving the above object.

Note that rolling according to the method of the present invention is limited to passes that do not affect the plate thickness accuracy after the final pass due to the dimensional accuracy of the plate thickness.

According to the inventor's experiments, although it depends on the plate thickness, supercooling conditions of the top and bottom, etc., even if the method of the present invention is applied up to the final 2 to 3 passes, there is no problem in terms of accuracy. There wasn't.

In addition, the final 2 to 3 passes are included in the so-called shape pass for adjusting flatness and plate thickness, and the amount of reduction is generally small, so the biting shock is also smaller than in the previous passes, so we purposely decided not to There is no need to apply the method of invention.

Further, since the bite shock increases as the top and bottom subcooling increases, it is desirable to apply the method of the present invention in passes after the first temperature adjustment pass.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows the steps after the first temperature adjustment pass and before the final two to three passes in the process of rolling a thick plate according to the present invention.
FIG. 3 is a schematic side view showing the side shape of the steel plate on the exit side of the i-pass and (i+1) pass.

That is, thick plates are generally reverse rolled, and the biting part in the i pass becomes the biting part in the (i+1) pass, but in this example, the biting part in the steel plate 1 in the i pass becomes the biting part 2. The roll gap when passes through roll 3 is
By pinching the part that has already passed through, the punching process makes the thickness of the part 2 thinner.

The length of the part 2 for cutting out to reduce the plate thickness is necessary and sufficient if it is the length of the supercooled part, and this length can be predicted by calculating the plate length or using a hot lump detector. .

However, these methods involve some errors, so it is realistic to set the range of the roll gap (1 in Figure 3) as the length of the supercooling section 2 plus an allowance. Although it varies depending on the size of the steel plate and control trolling conditions, a practical length is approximately 500 to 2000 mm.

It is desirable that the cutout is as large as the rolling load and torque allow, but the roll gap should be set to 0.1 to 0.8 mm. It is practical to pinch it.

The amount of the roll gap is determined in the longitudinal direction of the steel plate, especially I
・The temperature is determined by measuring the temperature of the knob and bottom part and calculating from the relationship between the pre-determined temperature and the deformation resistance of the steel plate.

Note that the broken line portion in FIG. 2 shows the side shape of the steel plate when the conventional rolling method is used.

Example: Made of material equivalent to API standard API5LX-X60, slab dimensions are 200 (thickness) Xi, 620 (width) x 2,850
(Length) mm, rolling dimensions are 12.7X2.800X2
Tables 1 and 2 show rolling schedules and results when rolling was performed by the conventional rolling method and the present invention under conditions of 4,000 mm and a heating temperature of 1,150°C.

Table 1 shows the reduction schedule from the middle of the thickness reduction pass.

As a result of rolling according to the schedule as described above, the thickness of the punched portion is rolled to be 0.1 to 0.8 mm thinner than the thickness of the middle portion between the 14th pass and the 23rd pass.

Furthermore, the amount of transparency of the top and bottom in the finished thickness was 0.6 mm in the conventional method, but it was 0.1 mm in the case of the present invention, and the effect of reducing the transparency was also confirmed.

In addition, in the above experiment, the length from the end to the part where the roll opening starts to become thinner, that is, l in Fig. 3, is 10.
00 to 1500 mm.

Table 2 shows the ratio of rolling loads at the middle part and the biting part in the above experiment.

As is clear from Table 2, it can be seen that the biting shock is reduced in the case of the method of the present invention.

Since the biting shock increases as the supercooling of the top and bottom increases, it is desirable to apply the method of the present invention in passes after the first temperature adjustment pass, but it is preferable to apply the method of the present invention in passes after the first temperature adjustment pass. May be applied to paths other than .

In the method for rolling a thick plate as described above, the present invention is such that the biting of the rolled plate material is performed while the part passes through the rolls, and rolling is performed with the roll gap in place rather than in other parts. Compared to the rolling method described above, this method has excellent effects in that the biting shock is alleviated and the visibility of the plate thickness at the top and bottom portions is reduced.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the temperature and plate thickness distribution in the longitudinal direction of the steel plate in plate rolling with forced cooling, and Fig. 2 is a diagram showing the side shape of the steel plate on the roll exit side in the thick plate rolling method according to the present invention. FIG. 3 is a schematic side view showing the side shape of a steel plate during rolling by the same method. 1... Steel plate, 2... Biting part, 3...
·····roll.

Claims (1)

[Claims] 1. In a thick plate rolling method in which a rolled plate material is forcibly cooled during rolling and rolled while adjusting the temperature, at least the second or third pass after the first temperature adjustment pass is used.
In at least one pass before the pass,
A method for rolling a thick plate, characterized in that rolling of a rolled plate material is carried out by rolling with a roll gap in place rather than in other parts while the part passes through the rolls.