KR20140070101A - Cold rolling method of stainless steel - Google Patents

Abstract

The present invention relates to a method for continuously cold-rolling stainless steel using a tandem rolling mill comprising four or more rolling stands prepared in order. The cold-rolling is conducted while changing the velocity of rolling from slow cold-rolling to rapid cold-rolling. During the slow cold-rolling, a first oil supply quantity (Q1) of rolling oil is supplied by a final rolling stand, and a second oil supply quantity (Q2) of rolling oil is supplied by the final rolling stand during the rapid cold-rolling. The second oil supply quantity (Q2) satisfies formula 1, 1 : Q2 = (1/2*Q1) to (3/4*Q1).

Description

[0001] The present invention relates to a cold rolling method of stainless steel,

The present invention relates to a method of cold-rolling a stainless steel, and more particularly, to a method of cold-rolling a stainless steel using a tandem rolling mill comprising a rolling stand continuously provided, And more particularly, to a cold rolling method of a stainless steel which can be manufactured.

Generally, in the case of continuous rolling of a stainless steel having a large deformation resistance, rolling is performed while passing a plurality of reciprocating passes by using a rolling mill composed of multiple rolls having a small diameter of about 40 mm to 100 mm and represented by Zenjima Mill, Mineral kneaded rolling oil having a viscosity of 7 mm ² / s to 10 mm ² / s (@ 40 ° C) was used. As described above, the rolling method in which a plurality of reciprocating passes are carried out with a rolling machine using a small-diameter multiple roll is suitable for small-scale production of a large variety of products such as stainless steel, electric steel, high carbon steel, titanium steel, However, in the case of mass production of a small number of small pieces, such a rolling method has been problematic because productivity is very low.

On the other hand, various methods have been studied in order to improve the low productivity of the round-trip pass rolling method using the conventional small diameter multi-roll in the stainless steel cold rolling process requiring excellent surface quality. One of them is a method of sequentially cold-rolling a small-diameter Zen-zhi miller, but the number of rolling mills due to such spatial limitations of the rolling mill is limited, and therefore, the rolling reduction and the rolling speed are also limited . Therefore, in order to solve this problem, the emulsion oil having oil activity and cooling property is applied by a rolling mill. However, it has been difficult to secure the surface quality of a predetermined stainless steel and the productivity is low due to restrictions on high speed rolling.

 As another process for continuous rolling of stainless steel, two to six large-diameter rolls having a working roll diameter of 130 mm to 150 mm, which are Z-Hi mills, are continuously disposed in place of Zen- A technique of cold rolling stainless steel using a knife oil has been developed. On the other hand, in the cold rolling method of a stainless steel using such paper-and-hight mill, the working roll diameter is larger than that of Zenjimi, and the predetermined surface quality and productivity can be secured It was difficult.

The present invention is directed to solving the above-mentioned problems, and relates to a cold rolling method of a stainless steel having high productivity and at the same time ensuring excellent surface quality of the stainless steel.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cold rolling method of stainless steel having excellent surface quality and high productivity.

Another object of the present invention is to provide a cold rolling method of a stainless steel having a high surface quality without deteriorating productivity by controlling the rolling conditions of each rolling stand using a sequentially provided tandem rolling mill.

According to an aspect of the present invention, there is provided a method of continuously cold-rolling a stainless steel with a tandem rolling mill comprising four or more rolling stands sequentially provided, Wherein the rolling is performed while changing the rolling speed from the rolling to the high speed cold rolling, the rolling oil is supplied to the final rolling stand from the low speed cold rolling to the first feed rate (Q1), and in the high speed cold rolling, (Q2), and the second supply flow rate (Q2) satisfies the following formula (1): " (1) "

Equation 1: Q2 = (1/2 * Q1) to (3/4 * Q1)

The rolling speed in the low-speed cold rolling may be less than 150 mpm, and the rolling speed in the high-speed cold rolling may be in the range of 150 to 400 mpm.

In the high-speed cold rolling, rolling oil is supplied to the second rolling stand as the third supply flow rate Q3, and the third supply flow rate Q3 can satisfy the following expression (2).

Equation 2: Q3 = Q1 + Q2

Wherein the rolling stand comprises first to fourth rolling stands which are sequentially provided, and in the low-speed cold rolling, the rolling oil is supplied to the first to fourth rolling stands as a first supply flow rate (Q1) The rolling oil can be supplied to the first and third rolling stands as the first supply flow rate Q1 and the rolling oil can be supplied as the second supply flow rate Q2.

In the high-speed cold rolling, rolling oil is supplied to the second rolling stand at a third supply flow rate (Q3), and the third supply flow rate (Q3) can satisfy the following formula (2).

Equation 2: Q3 = Q1 + Q2

The rolling stand may be equipped with a Z-Hi mill, which is a heavy-duty roll having an operating roll diameter of 130 mm to 150 mm.

INDUSTRIAL APPLICABILITY According to the present invention as described above, it is possible to provide a cold rolling method of a stainless steel having excellent surface quality and high productivity.

In addition, according to the present invention, it is possible to provide a cold rolling method of a stainless steel having a high surface quality without lowering productivity by controlling the rolling conditions of each rolling stand using a sequentially provided tandem rolling mill.

1 is a view illustrating a cold rolling mill for performing a cold rolling method of a stainless steel according to an embodiment of the present invention.
Fig. 2 is a graph showing gloss rolls according to supply flow rates according to rolling oil at respective rolling speeds.

The details of other embodiments are included in the detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below, but may be embodied in various forms. In the following description, it is assumed that a part is connected to another part, But also includes a case in which other elements are electrically connected to each other in the middle thereof. In the drawings, parts not relating to the present invention are omitted for clarity of description, and like parts are denoted by the same reference numerals throughout the specification.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

1 is a view illustrating a cold rolling mill for performing a cold rolling method of a stainless steel according to an embodiment of the present invention.

A cold rolling method of a stainless steel according to a preferred embodiment of the present invention is a method of continuously cold rolling a stainless steel with a tandem rolling machine comprising four or more rolling stands which are sequentially provided, wherein the cold rolling is a cold rolling And the rolling oil is supplied to the final rolling stand as the first supply flow rate Q1. In the high-speed cold rolling, the rolling oil is fed to the final rolling stand as the second supply flow rate Q2 And the second supply flow rate Q2 satisfies the following formula (1).

Equation 1: Q2 = (1/2 * Q1) to (3/4 * Q1)

Referring to FIG. 1, a method of cold-rolling a stainless steel according to the present embodiment may be performed by a tandem rolling machine 100 comprising four or more rolling stands 110 sequentially provided. The number of the rolling stands 110 may be four or more. In the following description, the four rolling stands 110 will be described for convenience of explanation, but the present invention is not limited thereto.

The tandem rolling mill 100 comprises first to fourth rolling stands 110a, 110b, 110c and 110d which are sequentially provided, and the first to fourth rolling stands 110a, 110b, 110c and 110d are made of stainless steel And a rolling roll 111 for rolling the steel s. The stainless steel s is rewound on one side of the reel 10 and passes through the first to fourth rolling stands 110a, 110b, 110c and 110d and then is wound on the reel 10 on the other side winding. A welder 20 and a looper 30 are provided at the front end of the first rolling stand 110a to continuously weld the stainless steel s so as to facilitate continuous rolling of the stainless steel s, 1 rolling stand 110a.

The rolling roll 111 and the rolling oil supply unit 120 for supplying the rolling oil s as the stainless steel s are provided at the entrance and exit sides of the first to fourth rolling stands 110a, 110b, 110c, . The rolling oil supply unit 120 is connected to the rolling oil tank 121 in which the rolling oil a is stored and the rolling oil tank 121 in the first to fourth rolling stands 110a, 110b, 110c, The rolling oil transfer line 123 may be provided. The rolling oil transfer line 123 is composed of four first to fourth rolling oil transfer lines 123a, 123b, 123c and 123d to be connected to the first to fourth rolling stands 110a, 110b, 110c and 110d, respectively. And a rolling oil pump 122 is provided in each of the first to fourth rolling oil transfer lines 123a, 123b, 123c and 123d to control the injection flow rate and the like of the rolling oil a. For example, the rolling oil pump 122 may be a variable displacement type injection pump. The rolling oil spraying part 124 is provided at one end of each of the first to fourth rolling oil transfer lines 123a to 123d so that the first to fourth rolling stands 110a, 110b, 110c and 110d The rolling oil (a) can be supplied to the inside and the outside of the rolling roll 111, respectively. The first to fourth rolling oil transfer lines 123a, 123b, 123c and 123d are each provided with a valve 125 to control the flow rate of the rolling oil a.

The tandem rolling mill 100 includes a return tank 140 for collecting the rolling oil a used in the first to fourth rolling stands 110a, 110b, 110c and 110d, And may further include a filtration unit 150 for filtrating the rolling oil (a). The rolling oil a may be filtered through the filtration unit 150 and then recovered to the rolling oil supply unit 110 for reuse.

The control unit 130 may include a flow meter 131, a directional control valve 132, and a check valve 132. The control unit 130 may include a control unit 130, 133). The flow rate of the rolling oil a flowing through the second and fourth rolling oil transfer lines 123b and 124d is checked through the flow meter 131 and the flow rate of the rolling oil a flowing through the direction control valve 132 and the check valve 133 is checked. The rolling oil (a) supplied to the fourth rolling stands 110b and 110d can be redistributed.

The rolling stand 110 may be equipped with a Z-Hi mill having an operating roll diameter of 130 mm to 150 mm. The rolling oil (a) is a mineral oil-based rolling oil having a viscosity of 13 mm ² / 20 mm ² / s (@ 40 ° C), a flash point of at least 250 ° C, and a saponification of 40 mg KOH / mg.

Generally, in the cold rolling method of stainless steel, the surface quality of the stainless steel is controlled to use a plurality of round-trip reciprocating mills. However, when such a round mill is used, productivity has been low. On the other hand, in the case of using a tandem rolling mill composed of a plurality of rolling stands to solve the productivity problem, the productivity can be improved, but it is difficult to secure the surface quality of the stainless steel. In the case of a reciprocating rolling mill, there is a degree of freedom in controlling the rolling speed, such as raising the rolling speed at a high speed in an intermediate pass, while in the case of a tandem rolling mill, the rolling speed of the preceding rolling stand is determined by the exit rolling speed of the final rolling stand . Also, the surface quality of the stainless steels is largely determined in the final rolling stand, and the rolling speed in the final rolling stand of the tandem rolling mill can not be made high in order to ensure a certain surface quality and, therefore, in the entire rolling stand of the Tandem rolling mill The rolling speed of the steel sheet can not be made high. That is, even if a tandem rolling mill is used, the tandem rolling mill can not be used at high speed, although high-speed rolling is possible due to the restriction of surface quality of stainless steel. When the tandem rolling mill is actually used, only the steels having a hard surface quality such as an austenitic 304 steel or a ferritic 409 steel are used. The total rolling reduction is about 60% and the maximum rolling speed is 250 mpm .

In the cold rolling method of stainless steel according to this embodiment, the stainless steel is cold-rolled using a tandem rolling mill, and high-speed rolling is performed to improve the productivity and ensure the surface quality of the stainless steel.

The cold rolling of stainless steel has the greatest effect on the surface quality of the stainless steel in the final rolling pass in the final rolling stand. Therefore, conventionally, in the case of reciprocating rolling using a small-diameter mill, separate finishing rolling such as rolling at a lower rolling speed is performed by changing the roll in the final pass. On the other hand, in the case of a tandem rolling machine in which a plurality of rolling mills are sequentially passed through in one direction, the rolling speed of the final rolling stand determines the total rolling speed. Thus, There is a problem that the productivity of cold rolling is significantly lowered in mill work.

In the case of rolling in a reciprocating pass using multiple rolls of a small diameter, stainless steel is rolled at a high speed and a low pressure lowering rate in a roughly intermediate pass to sequentially reduce the thickness gauge and gradually perform surface planarization. The flow rate of the rolling oil flowing into the roll bite is increased so that the oil pit is not greatly reduced as the film thickness increases, and the surface gloss is not greatly improved. Therefore, in order to increase the surface gloss, the roll is replaced with a new roll in the final pass, and finish rolling is performed with low speed rolling. On the other hand, in the case of using a tandem mill using a heavy-duty roll having an operating roll diameter of 130 mm to 150 mm, the rolling speed at the front-end rolling stand is sequentially reduced in accordance with the rolling speed in the final rolling stand of the tandem rolling mill. Therefore, even if the lubrication state by the rolling oil in the roll bite of each rolling stand is shifted to the boundary lubrication region and as a result the rolling speed at the final rolling stand is performed at high speed, the rolling speed at the rolling stand of the front end is low Heat streak occurs due to severe rubbing conditions, and continuous high-speed rolling is impossible.

That is, according to the present embodiment, in the case of continuously cold-rolling stainless steel with four to six rolling stands of paper-hi-mill, rolling conditions in the shear rolling stand are the most severe and heatstreaks occur frequently, It was confirmed that the heat stroke was hardly generated due to the low rolling reduction rate in the rear stage rolling stand, for example, the final rolling stand.

The cold rolling according to this embodiment can be carried out while changing the rolling speed, for example, while changing the rolling speed from low-speed cold rolling to high-speed cold rolling. In this case, the rolling oil injected into the final rolling stand can be controlled differently in the low-speed cold rolling and the high-speed cold rolling. In the low-speed cold rolling, the rolling oil is supplied to the final rolling stand as the first supply flow rate Q1, In the rolling, the rolling oil is supplied to the final rolling stand as the second supply flow rate (Q2), and the second supply flow rate (Q2) satisfies the following formula (1).

Equation 1: Q2 = (1/2 * Q1) to (3/4 * Q1)

Further, the rolling speed in the low-speed cold rolling may be less than 150 mpm, and the rolling speed in the high-speed cold rolling may be 150 to 400 mpm.

In this embodiment, when a stainless steel is rolled by a taming rolling machine comprising a plurality of rolling stands having a paper-high mill, a large amount of a mineral oil such as a neat oil or the like for securing the surface gloss of the stainless steel May be used as the rolling oil. On the other hand, when the mineral oil knitted oil is used as the rolling oil, the lubricating and cooling properties are significantly lowered unlike the emulsion jetting system. That is, in the case of rolling using rolling oil having good lubricating and cooling properties, it is possible to easily secure a thickness gauge under high pressure and high speed rolling, however, there is a problem of lowering surface gloss of stainless steel, When rolling with low rolling oil, it causes fatal surface defects such as heat stroke, so that it is difficult to carry out high-pressure rolling and high-speed rolling.

An embodiment according to the present invention is a method of continuously cold-rolling a stainless steel by using a Tamil rolling mill comprising a plurality of rolling stands using a light type knitted oil as a rolling oil and having a paper-high mill, The present invention relates to a cold rolling method of a stainless steel capable of achieving high productivity by enabling high-pressure and high-speed rolling while maintaining surface gloss quality.

The continuous cold rolling by the tandem rolling mill increases the rolling speed as the thickness is decreased in such a manner that the thickness is sequentially decreased from the raw material before machining to the thickness of the final material or the thickness of the intermediate material. As a result, once the thickness and speed at the final rolling stand are determined, the thickness and rolling speed at the preceding rolling stand relative to the final rolling stand are determined accordingly, and successive rolling passes are automatically performed according to the determined schedule.

In the case of continuously rolling a stainless steel with a tandem rolling machine comprising a rolling stand having a paper-heavy mill roll and a paper mill, the maximum rolling speed in the final rolling stand is not more than 250 mpm, and when the rolling speed is not more than about 150 mpm In the rolling stand, the lubrication area in the working roll roll bite is rolled in the boundary lubrication area, and the rolling conditions become more severe as it goes from the final rolling stand to the shearing stand, which easily causes heatstreaks and the like.

As a result of continuous cold rolling of the stainless steel according to the present embodiment, heatstreaks easily occur in the second to third rolling stands, except for the first rolling stand, of the shear rolling stands. Especially, in the second rolling stand, It was confirmed that the occurrence of leakage was the most serious. Therefore, it was confirmed that the surface quality of the stainless steel can be secured by suppressing the occurrence of heatstreak in the shearing-rolling stand excluding the final rolling stand (for example, the nth rolling stand) during high-speed rolling.

That is, in order to achieve cold rolling while securing the surface gloss of the stainless steel, the amount of lubricating oil flowing into the roll bite is minimized in the finish rolling, and the thickness of the oil film caused by the rolling oil between the roll (work) It is preferable to roll the roll to aim at faithful transfer of roll roughness. When the rolling speed is increased, the thickness of the oil film flowing into the roll bite is increased, and therefore the oil film thickness of the oil film is increased, the oil pit fraction is increased and the surface gloss of the stainless steel is remarkably lowered.

This is known to be due to the dynamic pressure effect of the rolling oil in the mixed lubrication region. On the other hand, in the tandem rolling mill using the chongqing roll mill paper-high mill, the rolling reduction added to each rolling stand is larger than that of the small diameter roll mill and the rolling speed is relatively low. This is because the fluid lubrication effect can not be expected by the rolling speed. Therefore, in the shear rolling stand excluding the final rolling stand, rolling is generally performed in the boundary lubrication region, and the rolling in the second rolling stand of the shearing stand is liable to generate heatstroke under high pressure and low speed rolling. That is, when stainless steel is continuously cold-rolled by using a tandem rolling machine using a heavy-duty roll, since the lubrication mode in the final rolling stand and the lubrication mode in the shearing rolling stand are different from each other, In the rolling stand, heat stroke occurs, and in the rear stage rolling stand, the surface gloss is lowered due to the increase of the oil film.

In this embodiment, when the stainless steel is continuously cold-rolled by a tandem rolling machine comprising a plurality of rolling stands with a heavy-duty roll having such a problem, the cold rolling of the shearing rolling stand and the rear stage rolling stand (for example, Rolling stand) can be individually controlled to obtain high-productivity cold-rolled steel strip of stainless steel having high-gloss surface quality.

As the rolling speed increases, the boundary lubrication area further increases, which ultimately leads to film breakage, which leads to temperature rise and heatstreak. That is, high-speed rolling is indispensable in order to secure high productivity in continuous cold rolling, but the occurrence of heatstreaks due to the high-speed rolling causes fatal defects in the surface quality of the stainless steel, and the damaged rolls must be replaced with the stainless steel And the replacement of the rolls causes a serious decrease in productivity.

In this embodiment, in order to prevent the generation of heatstreaks, the rolling oil in the final rolling stand is supplied at the first feed flow rate Q1 in the low-speed cold rolling while the continuous stainless steel is continuously cold-rolled at a high speed, The rolling oil can be supplied to the second supply flow rate Q2 by controlling the rolling oil differently from the first supply flow rate Q1. The second supply flow rate Q2 may be reduced by 0.5 to 0.75 times the first supply flow rate Q1. That is, in the case of the high-speed cold rolling in the final rolling stand, the surface lightness of the stainless steel can be improved by reducing the lubricating oil.

When the stainless steel is continuously cold-rolled by a tandem rolling mill comprising a plurality of rolling stands with a heavy-duty roll-finishing mill and a high mill, the load on each of the rolling stands is very severe, so that heat stroke occurs during high-speed cold rolling, Low-speed cold rolling is performed because the surface quality of the steel is lowered. In such low-speed cold rolling, if the rolling speed in the final rolling stand is determined, the rolling speed in the preceding rolling stand is uniformly determined according to the intended rolling thickness of the stainless steel. Further, the thickness of the stainless steel may also affect the rolling speed, because the thickness of the stainless steel on the side of the front end rolling stand is relatively thicker than that on the rear end rolling stand side (because the thickness decreases as the rolling progresses) The rolling speed increases as you move from the stand side to the later and downstream stage. When the rolling speed of the final rolling stand is 150 mpm or more in the continuous cold rolling of stainless steel, the rolling speed in the entire rolling stand is increased and the dynamic pressure effect can not be expected at all. Therefore, the frictional coefficient is very large, Since the cold rolling is performed in the lubrication region, the rolling load is increased by the plastic working and the friction heat generation, and the rise of the plate temperature in the roll bite causes a very weak generation of heat stroke. The increase in the rolling oil introduced into the roll bite by the transition from the boundary lubrication area to the mixed fluid lubrication in the final rolling stand may increase the film thickness and degrade the gloss. Therefore, in the present embodiment, the supply flow rate of the rolling oil in the final rolling stand can be controlled in the high-speed cold rolling of 150 mpm or more to improve the surface gloss of the stainless steel. For example, in low-speed cold rolling, rolling oil may be supplied to the final rolling stand at a first supply flow rate Q1, while in high-speed cold rolling, rolling oil may be supplied to the final rolling stand at a second supply flow rate Q2. At this time, the second supply flow rate Q2 may be 1/2 to 3/4 of the first supply flow rate Q1.

Further, in the high-speed cold rolling, the rolling oil is supplied to the second rolling stand as the third supply flow rate Q3, and the third supply flow rate Q3 can satisfy the following expression (2).

Equation 2: Q3 = Q1 + Q2

As described above, in this embodiment, the cold rolling conditions in the second rolling stand are the most severe compared to the other rolling stands, and it is confirmed that the occurrence of heatstreak also shows the highest frequency in the second rolling stand. Therefore, in the case of continuous high-speed cold rolling, since the work roll in the second rolling stand is operated in the boundary lubrication region, the load can be greatest and heat stroke can occur. Therefore, in the second rolling stand, it is preferable that the rolling oil is sufficiently supplied in order to reduce frictional heat generation. At this time, by increasing the amount of the rolling oil supplied to the second rolling stand by the reduction amount of the rolling oil supplied from the high-speed cold rolling to the final rolling stand, it is possible to prevent the occurrence of heat stroke in the second rolling stand. That is, in the cold rolling method of the stainless steel according to the present invention, the rolling oil is supplied to the second rolling stand at the first supply flow rate Q1 in the case of low-speed cold rolling, and when the rolling speed is increased by high- Can be supplied to the third supply flow rate Q3. The third supply flow rate Q3 may be 1.5 times to 1.75 times the first supply flow rate Q1 in an amount larger than the first supply flow rate Q1.

That is, in another embodiment of the present invention, when the rolling speed is changed from low-speed cold rolling to high-speed cold rolling when the stainless steel is continuously cold-rolled by using a tandem rolling machine comprising four or more rolling stands, The present invention relates to a cold rolling method for a stainless steel which can simultaneously control a supply flow rate of a rolling oil supplied to a rolling mill. For example, when the rolling stand includes the first to fourth rolling stands sequentially, the low-speed cold rolling may supply the rolling oil to the first to fourth rolling stands to the first supply flow rate Q1, In the high-speed cold rolling, the rolling oil may be supplied to the first and third rolling stands as the first supply flow rate Q1 while the fourth rolling stand may be supplied with the rolling oil as the second supply flow rate Q2. Further, in the high-speed cold rolling, the rolling oil can be supplied to the second rolling stand at the third supply flow rate Q3. At this time, the second supply flow rate Q2 satisfies the following equation (1), and the third supply flow rate Q3 can satisfy the following equation (2).

Equation 1: Q2 = (1/2 * Q1) to (3/4 * Q1)

Equation 2: Q3 = Q1 + Q2

The rolling oil supplied to the rolling stand through which the stainless steel passes immediately before passing through the final rolling stand may be supplied to the first supply flow rate Q1. For example, in the low-speed cold rolling and the high-speed cold rolling, the rolling oil to the first and third rolling stands can be supplied as the first supply flow rate Q1. In the fourth rolling stand as the final rolling stand, Is supplied as the feed flow rate Q1 and can be supplied to the second feed flow rate Q2 in the high speed cold rolling and is supplied to the first feed flow rate Q1 in the low speed cold rolling in the second rolling stand, May be supplied at the supply flow rate Q3. At this time, the reduction amount of the rolling oil of the second supply flow rate Q2 to the first supply flow rate Q1 may correspond to the increase amount of the rolling oil of the third supply flow rate Q3.

Further, according to another embodiment of the present invention, the supply flow rate of the rolling oil in the final rolling stand (nth rolling stand, n > = 4) in the high-speed cold rolling is set to the rolling stand immediately before the final rolling stand (n-1) th rolling stand, n? 4). For example, when the rolling oil supplied to the (n-1) th rolling stand in the low-speed cold rolling is the first supply flow rate, the rolling oil supplied to the (n-1) th rolling stand in the high- While the supply amount of the rolling oil to the (n) th rolling stand, which is the final rolling stand, is supplied at the second supply flow rate, and the second supply flow rate may be 0.5 to 0.75 times the first supply flow rate.

Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the scope of the present invention is not limited by the following examples.

The stainless steel steels were continuously cold-rolled using the tandem mill of Fig. 1 described above. The tandem rolling mill is composed of first to fourth rolling stands equipped with a Z-Hi mill, which is a heavy-duty roll having an operating roll diameter of 130 to 150 mm, and STS430 hot-rolled annealing pickling coil (3.0 tx 1290 mm x coil) The first to fourth rolling stands were successively passed through to perform continuous cold rolling. In this case, a mineral oil knitted oil was used as the rolling oil, and the viscosity of the rolling oil was 13 mm ² / s to 20 mm ² / s (at 40 ° C.), the flash point was 250 ° C. or higher and the saponification was 40 mg KOH / mg . Table 1 below shows rolling conditions and results according to Comparative Examples and Examples.

Remarks Thickness (mm) Output thickness (mm) Reduction rate (%) Rolling speed (mpm) The rolling oil supply flow rate (lpm) of the fourth rolling stand The rolling oil supply flow rate (lpm) of the second rolling stand Glossiness
(@ 20 ℃) Hitstreak Comparative Example 1 3.0 1.2 60 100 4000 4000 195 Not occurring Example 1 3.0 1.2 60 100 3000 4000 230 Not occurring Example 2 3.0 1.2 60 100 2000 4000 270 Not occurring Comparative Example 2 3.0 1.2 60 150 4000 4000 x Occur Example 3 3.0 1.2 60 150 3000 4000 220 Not occurring Example 4 3.0 1.2 60 150 2000 4000 260 Not occurring Comparative Example 3 3.0 1.2 60 200 4000 4000 x Occur Example 5 3.0 1.2 60 200 3000 4000 200 Not occurring Example 6 3.0 1.2 60 200 2000 4000 240 Not occurring Comparative Example 4 3.0 1.2 60 250 4000 4000 x Occur Example 7 3.0 1.2 60 250 3000 5000 200 Not occurring Example 8 3.0 1.2 60 250 2000 6000 220 Not occurring

It is preferable that the surface of the stainless steel has a glossiness of 200 to 275 (at 20 DEG C). When the glossiness is less than 200, it is difficult to use as a product. When the glossiness is more than 275, there is a risk of occurrence of fire during operation and surface defects may be caused by friction with the roll bite. Therefore, in this embodiment and the comparative example, the gloss of the stainless steel during continuous cold rolling was from 200 to 275 (@ 20 DEG C). The supply flow rate of the rolling oil to the first to third rolling stands not shown in Table 1 was constantly set at 4000 lpm.

In Comparative Examples 1 to 4, the supply flow rate of the rolling oil supplied to the second and fourth rolling stands was kept constant without being controlled. It was the same as the supply flow rate of the rolling oil supplied to the first and third rolling stands Respectively. On the other hand, in Examples 1 to 8, the supply flow rate to the first to third rolling stands was kept constant at 4000 lpm, while the supply flow rate of the rolling oil was controlled for the second and fourth rolling stands as shown in Table 1.

In Comparative Example 1, only the low-speed cold rolling was carried out at a rolling speed of 100 mpm, so no heatstreak occurred. On the other hand, since only one pass was performed, the gloss was 195, which did not reach the target reference gloss. On the other hand, in the case of Examples 1 and 2, the supply flow rate of the rolling oil to the second rolling stand was reduced to 3000 lpm and 2000 lpm, respectively, and the gloss values were 230 and 270, respectively, within the range of the surface gloss of the target stainless steel And it was confirmed that it had a higher gloss than Comparative Example 1. That is, when comparing Comparative Example 1 with Examples 1 and 2, it is possible to improve the surface gloss of the stainless steel by reducing the supply flow rate of the rolling oil supplied to the fourth rolling stand when rolling under the same conditions such as the same reduction rate and rolling speed It can be confirmed that That is, it was confirmed that the same effect as in the case of the high-speed cold rolling can be obtained even in the case of low-speed cold rolling (less than 150 mpm).

Comparative Example 2 and Examples 3 and 4 are the results of continuous cold rolling at a rolling speed of 150 mpm, i.e., high-speed cold rolling. In the case of Comparative Example 2, the supply flow rate of the rolling oil in the fourth rolling stand was kept constant at 4000 lpm, and in Examples 3 and 4, the supply flow rate of the rolling oil in the fourth rolling stand was reduced to 300 lpm and 2000 lpm, respectively. As a result, it was confirmed that the heatstreak defect occurred on the surface of the stainless steel in the case of the comparative example 2, and in the cases of the examples 3 and 4, no heatstreak occurred and the gloss was also 220 and 260 And the range of gloss was satisfied.

Comparative Example 3, Examples 5 and 6 are the results of performing high-speed cold rolling at a rolling speed of 200 mpm. In the case of Comparative Example 3, the supply flow rate of the rolling oil in the fourth rolling stand was kept constant at 4000 lpm, while in Examples 5 and 6, the supply flow rate of the rolling oil in the fourth rolling stand was reduced to 3000 lpm and 2000 lpm, respectively. As a result, it was confirmed that in Comparative Example 3, heat stroke occurred, but in Examples 5 and 6, 200 and 240, respectively, had predetermined gloss.

That is, when the above Comparative Examples 2 and 3 and Examples 3 to 6 are compared together, in the case of high-speed cold rolling of 150 mpm or more, the supply flow rate of the rolling oil in the fourth rolling stand is reduced to prevent the occurrence of heatstreak , It is confirmed that excellent surface quality can be obtained. Further, it has been confirmed that by increasing the rolling speed at high speed, the surface quality can be maintained and high productivity can be ensured.

In Comparative Examples 4 and 7 and 8, the rolling speed was increased to 250 mpm, and the results of the rapid cold rolling were shown. In the case of Comparative Example 4, the flow rates of the rolling oil supplied to the second and fourth rolling stands were made constant, but in Examples 7 and 8, the flow rates of the rolling oil supplied to the second and fourth rolling stands were changed. Specifically, in Examples 7 and 8, the supply flow rate of the rolling oil was reduced to 3000 lpm and 2000 lpm respectively by the fourth rolling stand, and the supply flow rate of the rolling oil to the second rolling stand was reduced by the amount of decrease in the rolling oil supply flow rate of the fourth rolling stand Respectively. As a result, it was confirmed that in Comparative Example 4, heatstreaks occurred and the surface quality of the stainless steel was greatly reduced. On the other hand, in Examples 7 and 8, excellent surface quality could be secured despite the high rolling speed. At the same time, by supplying a reduced amount of the rolling oil supplied to the fourth rolling stand to the second rolling stand, a predetermined surface quality can be ensured with high productivity while keeping the supply amount of the total rolling oil constant.

Fig. 2 is a graph showing gloss rolls according to supply flow rates according to rolling oil at respective rolling speeds.

In FIG. 2, "a" represents a case where the rolling speed is 100 mpm, "b" represents the case where the rolling speed is 150 mpm, "c" represents the case where the rolling speed is 200 mpm, and the surface gloss of the stainless steel with respect to the supply amount of the rolling oil to the fourth rolling stand The result is. Referring to FIG. 2, it can be seen that as the rolling speed increases, the influence of the glossiness on the flow rate of the rolling oil in the fourth rolling stand gradually increases. In the case of the low rolling speed a, the rolling oil supply flow rate satisfies the predetermined gloss range of the stainless steel at 2000 lpm to 4000 lpm, while the predetermined gloss of the stainless steel at the rolling oil supply flow rate of 4000 lpm at the high rolling speed b and c, And it was confirmed that it could not be obtained. That is, it was confirmed that, in the case of continuous cold rolling using a tandem rolling machine, the surface quality of the stainless steel can be secured by reducing the supply flow rate of the rolling oil to the fourth rolling stand during high-speed cold rolling.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalents thereof are included in the scope of the present invention Should be interpreted.

100: continuous rolling mill 110: rolling stand
120: rolling oil supply unit 130:
140: return tank 150:

Claims (6)

A method for continuously cold rolling a stainless steel with a tandem rolling mill comprising four or more rolling stands sequentially provided,
The cold rolling is performed while changing the rolling speed from low-speed cold rolling to high-speed cold rolling,
The rolling oil is supplied to the final rolling stand as the first supply flow rate Q1 in the low speed cold rolling and the rolling oil is supplied as the second supply flow rate Q2 to the final rolling stand in the high speed cold rolling, Q2) satisfies the following formula (1): " (1) "
Equation 1: Q2 = (1/2 * Q1) to (3/4 * Q1) The method according to claim 1,
Wherein the rolling speed in the low-speed cold rolling is less than 150 mpm, and the rolling speed in the high-speed cold rolling is in a range from 150 to 400 mpm. 3. The method of claim 2,
Wherein in the high-speed cold rolling, the rolling oil is supplied to the second rolling stand at a third supply flow rate (Q3), and the third supply flow rate (Q3) satisfies the following formula (2).
Equation 2: Q3 = Q1 + Q2 3. The method of claim 2,
Wherein the rolling stand comprises first to fourth rolling stands which are sequentially provided, and in the low-speed cold rolling, the rolling oil is supplied to the first to fourth rolling stands as a first supply flow rate (Q1) , The rolling oil is supplied to the first and third rolling stands as the first supply flow rate (Q1), while the fourth rolling stand is supplied with the rolling oil as the second supply flow rate (Q2). 5. The method of claim 4,
Wherein in the high-speed cold rolling, the rolling oil is supplied to the second rolling stand at a third supply flow rate (Q3), and the third supply flow rate (Q3) satisfies the following formula (2).
Equation 2: Q3 = Q1 + Q2 The method according to claim 1,
Wherein the rolling stand is provided with a Z-Hi mill, which is a heavy-duty roll having an operating roll diameter of 130 mm to 150 mm.

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