JPH11290903A - Hot rolling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain lubrication effect and to remarkably reduce the coefficient of friction at the time of rolling by jetting a lubricant after executing dewatering of both work rolls and back-up rolls, joining the rear end of a hot preceding material to the tip of the hot succeeding material and executing hot finish rolling. SOLUTION: By connecting the rear end of the hot preceding material heated in a heating furnace to the tip of the hot succeeding material, endless rolling is executed. In the hot finish rolling, lubricated rolling is executed by jetting a lubricant from lubricant supply nozzles 3 to the work rolls 1 and back-up rolls 2 for rolling a rolled stock 13 and also cooling is executed jetting cooling water from cooling water supply nozzles 4 to the work rolls 1. In this way, by directly sticking the lubricant to the work rolls 1 and also transferring the lubricant from the back-up rolls 2, the lubricant is sufficiently stuck to the work rolls 1 and highly lubricated rolling is enabled. At this time, it is preferable to remove sticking water from the lubricant sticking surfaces by providing a de-watering wipers 10, 11, 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolling method for stably producing thin steel sheets.

[0002]

2. Description of the Related Art In recent years, a method has been started in which a rear end of a preceding rolled material is connected to a leading end of a succeeding rolled material on the entry side of a rolling mill and hot rolling is continuously performed. In this method, unlike the conventional hot rolling, since there is no bite in each rolled material, there is an advantage that high lubrication rolling can be performed. Here, high lubrication rolling means rolling in which the coefficient of friction during rolling is 0.15 or less.

[0003] The lubrication method in the current hot rolling including the method of connecting the rear end of the preceding rolled material and the leading end of the succeeding rolled material at the entry side of the rolling mill and performing continuous hot rolling is as follows. A method using water injection is employed. Here, the water injection method is a method in which a lubricant is mixed into a pipe of cooling water, the lubricant is made into an emulsion form from a nozzle arranged toward a rolling roll, and the oil is supplied. At this time, a drainer is generally provided on the entrance side and the exit side of the work roll in order to scatter the cooling water on the rolled material and to efficiently attach the lubricant to the surface of the roll.

As a method of injecting a lubricant, tribology in plastic working (Corona Co., Ltd., Showa 63)
(Published in 1998), there is a method of spraying on work rolls and a method of spraying on backup rolls. However, the rolls for spraying lubricant have problems due to the specifications of the rolling mill or the spatial arrangement space. Etc., and not based on an inevitable reason in consideration of the lubrication effect. Also, in a finishing rolling mill consisting of a plurality of rolling mills arranged in tandem, the amount of lubricant supplied to each stand is determined by the amount of lubricant contained in the amount of cooling water since there is no guideline for extracting a sufficient lubricating effect. It is controlled at a determined concentration, and at present, rolling is performed at a concentration that does not cause rolling slip.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem. In a hot finish rolling step, a rear end of a preceding high-temperature material is connected to a front end of a following high-temperature material. When performing endless rolling, the lubricant to be injected most efficiently to obtain the lubricating effect and the width of the rolled material and the amount of lubricant supplied to each stand are controlled according to the rolling speed and high lubrication rolling. Hot-rolling method for producing a hot-rolled steel sheet for deep drawing according to the present invention.

[0006]

The gist of the present invention is as follows. (1) In the hot finish rolling step, lubricant is supplied to each of the work roll and the backup roll when performing the endless rolling by connecting the trailing end of the preceding hot material and the leading end of the following hot material. Hot rolling method. (2) The hot rolling method according to the above (1), wherein the lubricant supply amount is controlled in accordance with the width of the rolled material and the rolling speed. (3) The hot rolling method according to the above (2), wherein a drainer wiper is used on the rolled material entering side of the lower backup roll.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have shown in FIG. 1 in order to verify on which roll of a rolling mill the lubricant is most effective to maximize the lubrication effect. Using a hot coil rolling mill, the lubricating effect was investigated by variously changing the rolls for injecting the lubricant. FIG. 2 shows the arrangement of the rolling roll 1, the lubrication nozzle 3, the cooling nozzle 4, and the drainers 10, 11 at this time. As a result, it has been found that the lubricant supply method of injecting the lubricant to both the work roll 1 and the backup roll 2 has the largest lubrication effect.

[0008] The mechanism of lubrication in hot rolling is that the lubricant adhering to the rolling rolls burns while being drawn into the roll bite, and at the same time performs lubrication. Lubricants boil and burn, so they are not drawn into the roll bite from the oil pool formed between the roll bite entrance and the rolled material as in cold rolling, forming an oil film and lubricating. . Therefore, in hot rolling, it is important how the lubricant is attached to the roll surface in order to maximize the effect of the lubricant. In the method of spraying only to the work roll 1, the time from the time when it is attached to the roll to the time when it is drawn into the roll bite is very short, it is difficult to sufficiently adhere only by the pressure at the time of spraying, and the drainage is insufficient. In such a case, it is difficult to obtain a sufficient lubricating effect due to a decrease in the adhesion efficiency of the lubricant.

On the other hand, in the method in which the lubricant is sprayed only on the backup roll 2, the lubricant sprayed and adhered to the backup roll 2 is transferred to the surface of the work roll 1 by rolling with the work roll 1. The contact pressure between the work roll 1 and the backup roll 2 is usually 200 to 2
At a very high pressure of about 50 kgf / mm ^2, the lubricant transferred under such a high pressure has a very strong adhesive force, and has a greater lubricating effect than when it is sprayed onto the work roll 1.

On the other hand, when the lubricant is sprayed on both the work roll 1 and the backup roll 2, the lubricant adhered to the surface of the work roll 1 is further sprayed on the work roll side by the transfer effect described above. At this time, since the lubricant is present on the surface of the work roll 1, the lubrication injected on the work roll 1 side is smaller than the lubrication method using only the work roll 1 without the lubricant on the surface of the work roll 1. The lubricant has a high affinity with the agent, and as a result, the lubricant sufficiently adheres to the surface of the work roll 1 to maximize the lubrication effect.

Next, the lubricant supply amount will be described. Generally, the supply amount of the lubricant in the hot rolling is controlled by the concentration, and the value is empirically determined so that the rolling slip does not occur. As described above, considering the lubrication mechanism in hot rolling, since the lubricant is injected in the form of an emulsion, the amount of the lubricant injected in the emulsion per unit time contributes to lubrication. . Therefore, since the rolling speed increases as the finishing stage stands, it is necessary to increase the amount of lubricant to be supplied per unit time according to the rolling speed. Therefore, at each stand, a lubricant must be supplied according to the width of the rolled material passing through and the rolling speed. The lubricant supply amount required at this time is the lubricant supply amount per minute (cc / min) / (rolled material width (m) × rolling speed (m / min) (unit: cc / m ² ) The actual amount of lubricant (unit: cc / m ² ) required depends on the type of lubricant, supply method, roll material, etc., and should be determined in advance through laboratory experiments or actual machine experiments. It should be left.

If the lower backup roll 2 does not have the drainer wiper 12, the cooling water of the lower work roll 1 scatters on the backup roll 2. In the state where the cooling water adheres to the rolling roll surface, the adhesion efficiency is very poor even if the lubricant is supplied. Therefore, it is very difficult to remove the cooling water scattered on the roll surface with the drain wiper 12 before supplying the lubricant. Will be important.

[0013]

(Embodiment 1) As Embodiment 1 of the present invention, FIG.
In the case where the roll for injecting the lubricant was sprayed onto the work roll alone, the backup roll alone, and both the work roll and the backup roll under the rolling conditions shown in Tables 1 and 2 using the hot coil rolling mill shown in The lubrication effect when the lubricant supply amount was changed was investigated. The coefficient of friction is 1
Proceedings of the 29th Joint Lecture on Plastic Working 997 139
Using the rolling analysis model described in (1), the advance rate and the rolling load determined in the experiment were determined so as to match the analysis results. A drainer wiper was provided on the lower backup roll so that the cooling water of the work roll did not scatter before the lubricant was injected.

[0014]

[Table 1]

[0015]

[Table 2]

FIG. 3 shows the relationship between the coefficient of friction and the amount of lubricant supplied when the rolling roll for spraying the lubricant is changed. FIG.
As is clear from the graphs, in any case, the coefficient of friction decreases with an increase in the supply amount of the lubricant. Also,
The greatest lubrication effect is obtained when a lubricant is sprayed on both the work roll and the backup roll.

(Embodiment 2) Next, as Embodiment 2 of the present invention, using a finishing hot rolling mill in which seven rolling mills are arranged in tandem under the conditions of Table 3, the width of the rolled material The supply amount of the lubricant was adjusted as shown in Table 4 according to the rolling speed and the rolling speed, and the lubricating effect was investigated. The lubricant used at this time was the same as that used in Example 1, and was based on the supply amount of 5 cc / m ² at which the lubricating effect was remarkably observed. In addition, a drainer wiper was also provided on the lower backup roll, and the test was performed.
Table 5 shows the results obtained by calculating the coefficient of friction at this time in the same manner as in Example 1.

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

From Table 5, it can be seen that Invention Example 1 has a very low coefficient of friction at each stand when the supply amount of the lubricant is increased according to the rolling speed. Invention Example 2
In the case where the lubricant supply amount of the F4 to F7 stands was further increased from that of Inventive Example 1, although the friction coefficient was slightly reduced, the lubricating effect was almost saturated. Comparative Example 1 was a case where the lubricant was supplied without adjusting the lubricant supply amount of the F5 to F7 stands to the increase in the rolling speed, but the friction coefficient of the stand did not decrease. Comparative Example 2 is a case where the supply amount of the lubricant was not made to correspond to the rolling speed for all the stands. It can be seen that the friction coefficient was at a high level in all the stands.

Example 3 As Example 3, under the conditions of Tables 6 and 7, the lubrication effect of the lower backup roll on the presence or absence of a drainer wiper was investigated. FIG.
Is the result of calculating the friction coefficient at this time. Based on the coefficient of friction when the lower backup roll is provided with a drainer wiper, the coefficient of friction when the drainer is not provided is about 1.4 times higher, and the lubricating effect is reduced. From this result, it can be seen that unless the drainer wiper is installed on the lower backup roll, the effect is not seen even if the lubricant is injected. Therefore, it is important to install a drainer on the lower backup roll in order to effectively bring out the lubrication effect.

[0023]

[Table 6]

[0024]

[Table 7]

[0025]

By using the hot rolling method according to the present invention, the coefficient of friction during rolling can be greatly reduced. Units are expected to decrease, and significant cost reductions will be possible.

[Brief description of the drawings]

FIG. 1 is a schematic view of a rolling mill showing an embodiment of the present invention.

FIG. 2 is a view showing a nozzle arrangement of a roll portion in the present invention.

FIG. 3 is a diagram illustrating a relationship between a friction coefficient and a lubricant supply amount when a roll that injects lubricant is changed.

FIG. 4 is a result of comparing a friction coefficient between a case where a drainer wiper is provided and a case where a drainer wiper is not provided for a lower backup roll.

[Explanation of symbols]

 1 Work Roll 2 Backup Roll 3 Lubricant Supply Nozzle 4 Cooling Water Supply Nozzle 5 Load Cell 6 Pulse Generator 7 Heating Furnace 8 Winding Machine 9 Cooling Zone 10 Work Roll Inlet Drain Wiper 11 Work Roll Out Drain Wiper 12 Lower Backup Roll Drainer wiper 13 Rolled material

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Inoue 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division

Claims (3)

[Claims] In the hot finish rolling step, when a rear end of a preceding high-temperature material is connected to a front end of a following high-temperature material to perform endless rolling, a lubricant is added to each of a work roll and a backup roll. And a hot rolling method. 2. The hot rolling method according to claim 1, wherein the lubricant supply amount is controlled according to the width of the rolled material and the rolling speed. 3. The hot rolling method according to claim 2, wherein a drainer wiper is used on the rolled material input side of the lower backup roll.