KR20140000550A - Continuous rolling apparatus and continuous rolling method of stainless steel - Google Patents

Abstract

The present invention relates to a continuous rolling apparatus for stainless steel includes: at least two rolling stands having a rolling roll each rolling stainless steel; a first rolling oil supplying unit supplying a first rolling oil to the rolling roll at the inlet and the outlet of the rolling stand; a second rolling oil supplying unit supplying a second rolling oil to the stainless steel at the inlet of the rolling stand; and a gas supplying unit supplying liquefied nitrogen gas to the inlet or the outlet of the rolling stand, wherein the first rolling oil has a viscosity lower than that of the second rolling oil.

Description

Continuous rolling device and continuous rolling method of stainless steel {CONTINUOUS ROLLING APPARATUS AND CONTINUOUS ROLLING METHOD OF STAINLESS STEEL}

The present invention relates to a continuous rolling device of stainless steel and a continuous rolling method of stainless steel, and more particularly, to enable the step-down and high-speed rolling for a variety of steel types and stainless steel of various sizes in the process of continuous rolling of tandem rolling stainless steel It relates to a continuous rolling device of stainless steel and a continuous rolling method of stainless steel capable of producing stainless steel with excellent surface quality with high productivity.

In general, stainless steel having a large deformation resistance is rolled by multipass reciprocating rolling using a small-diameter multi-roll rolling mill having a diameter of 40 mm to 120 mm, represented by a Zenny mill mill, and 7 mm ² / s to 10 mm when rolling the stainless steel. Mineral oil-based knit rolling oil or emulsion oil of ² / s (@ 40 ° C) is used as rolling oil. The rolling process using the other pass reciprocal rolling using the small-diameter multi-roll rolling mill may be suitable for the production of small quantities of various kinds, but in the case of the production of small quantities of small kinds, there is a problem of low productivity.

Therefore, various studies have been conducted to solve this problem, and one of them has been developed a continuous rolling process for rolling with high productivity in cold rolling of stainless steel, wherein the small diameter zigzag mill is arranged sequentially to roll the stainless steel. On the other hand, although rolling oil is used as emulsion oil having lubricity and cooling property to reduce high pressure of stainless steel at high speed, there is still a problem in realizing high gloss surface quality and high speed rolling simultaneously.

In addition, in order to continuously roll stainless steel, two to six Z-Hi mils of medium diameters of 130 mm to 150 mm in diameter are used instead of small diameter zenmemere mills in a row. A process of continuously rolling stainless steel using a tandem rolling mill, but using mineral oil-based knit oil as a rolling oil, has been developed. On the other hand, when continuously rolling stainless steel of Chong-high mill of Chongqing, the working roll diameter is larger than that of Zhenmime Mill, and the surface gloss of stainless steel is maintained due to the limitation on the number of rolling stands constituting the tandem rolling mill. The rolling reduction and rolling speed that can be applied in one pass are performed at a low level. In addition, there are restrictions on the type and size of stainless steel that can be rolled using a tandem rolling mill of stainless steel. In particular, in the case of the rolling speed, the conventional multi-pass reciprocating rolling mill has a degree of freedom to increase the rolling speed at high speed in the middle of rolling. On the other hand, the tandem rolling mill is determined by the rolling speed of the preceding rolling stand by the exit rolling speed of the final rolling stand, so the advantages of the tandem rolling mill for rolling at high speed are not properly exhibited. In fact, such a tandem rolling mill is used for steel grades of which surface quality is not very strict. At this time, the total reduction ratio is about 60% and the maximum rolling speed is about 250mpm.

In addition, in order to compensate for lubrication and cooling performance in the continuous rolling of stainless steel using a tandem rolling mill for spraying a large amount of the mineral oil-based low-viscosity rolling oil to increase the injection flow rate of the mineral oil-based low-viscosity rolling oil or between the rolling stand The cooling of the plate is performed, but the effect thereof is insignificant.

The present invention relates to a continuous rolling apparatus of stainless steel in the process of continuously rolling stainless steel, the continuous rolling at high speed and high pressure to improve productivity and at the same time improve the surface quality of stainless steel. The continuous rolling apparatus of stainless steel according to the present invention can roll stainless steel of various steel types and various sizes, and can improve the process efficiency of continuous rolling of stainless steel.

The present invention provides a continuous rolling apparatus of stainless steel capable of continuously rolling various steel grades and various sizes of stainless steel of the present invention devised to solve the above problems.

In addition, another object of the present invention is to provide a stainless steel that can produce a continuous rolling method of stainless steel that can be produced in a stainless steel having excellent surface quality with high productivity.

According to a feature of the present invention for achieving the object as described above, the present invention comprises two or more rolling stands each having a rolling roll for rolling stainless steel; A first rolling oil supply unit for supplying a first rolling oil to the rolling rolls at the entry and exit sides of the rolling stand; A second rolled oil supply unit supplying a second rolled oil to the stainless steel at an inlet side of the rolled stand; And a gas supply unit supplying liquefied nitrogen gas to the inlet or outlet side of the rolling stand, wherein the first rolled oil includes a continuous rolling device of stainless steel having a lower viscosity than the second rolled oil.

The rolling stand may include first to fourth rolling stands sequentially provided, the first rolling oil may be supplied to the entry and exit sides of the first to fourth rolling stands, and the second rolling oil may be provided to the first to fourth rolling stands. 4 Can be fed to the mouth side of the rolling stand.

The gas supply unit may supply the liquefied nitrogen gas to the entry or exit side of the fourth rolling stand.

The liquefied nitrogen gas may be supplied only to the exit side of the fourth rolling stand.

The continuous rolling apparatus of the stainless steel may further include a return tank for collecting the first rolled oil supplied and used to the rolling stand, and a filtration unit for filtering the first rolled oil collected in the return tank.

The first rolled oil may be passed through the filtration unit and recovered to the first rolled oil supply unit, and then supplied to the entry and exit sides of the rolling stand for reuse.

The first rolling oil may have a viscosity of 10 mm ² / s to 18 mm ² / s (@ 40 ° C.), and the second rolling oil may have a viscosity of 25 mm ² / s to 40 mm ² / s (@ 40 ° C.).

The first rolling oil may be supplied between the rolling roll and stainless steel, and the second rolling oil may be supplied to the surface of the stainless steel before the first rolling oil before the stainless steel passes through the rolling roll.

The supply pressure of the second rolled oil may be 10 kg / cm ² to 20 kg / cm ² , and the injection flow rate of the second rolled oil may be 100 cc / min to 500 cc / min.

According to another embodiment of the present invention, the present invention is a method for cold-rolling stainless steel with two or more rolling stands provided with rolling rolls, respectively, and sequentially passing the stainless steel through two or more rolling stands. A first continuous rolling step of feeding and rolling the first and second rolling oils having different viscosities; And a second continuous rolling step of passing the first and second rolling oils through the two or more rolling stands through the stainless steel that has undergone the first continuous rolling step, and re-rolling the second and second rolling oils. The final rolling stand for finally rolling the stainless steel in the rolling step includes a continuous rolling method of stainless steel supplied with liquefied nitrogen gas.

The first rolling oil may have a lower viscosity than the second rolling oil.

In the first continuous rolling step or the second continuous rolling step, the first rolling oil may be supplied to the entry and exit sides of the rolling stand, and the second rolling oil may be supplied to the entrance side of the rolling stand.

In the second continuous rolling step, the liquefied nitrogen gas may be supplied to the entry or exit side of the rolling stand.

The rolling stand includes first to fourth rolling stands sequentially arranged, and in the first continuous rolling step, the first and second rolling oils are respectively supplied to the first to fourth rolling stands. In the second continuous rolling step, the second rolling oil may be supplied to the first to fourth rolling stands, respectively, but in the final rolling stand, liquefied nitrogen gas may be supplied instead of the second rolling oil and the first rolling oil.

The first rolling oil may be supplied between the rolling roll and stainless steel, and the second rolling oil may be supplied to the surface of the stainless steel before the first rolling oil before the stainless steel passes through the rolling roll.

The rolling roll includes a G-high mill having a diameter of 130 mm to 150 mm, the viscosity of the first rolling oil is 10 mm ² / s to 18 mm ² / s (@ 40 ℃), the viscosity of the second rolling oil is 25 mm ² / s to 40 mm ² / s (@ 40 ° C.).

The supply amount of the liquefied nitrogen gas may be a pressure of 3kg / cm ² , the injection flow rate may be 0.01Nm ³ / hr to 0.03Nm ³ / hr.

The first rolled oil supplied to and used in the rolling stand in the first continuous rolling step or the second continuous rolling step may be collected in a return tank and then filtered through a filtration unit.

The first rolled oil filtered through the filtration unit may be supplied to the inlet and the outlet of the rolling stand for reuse.

According to the present invention as described above, it is possible to provide a continuous rolling device of stainless steel capable of continuously rolling a variety of steel grades and stainless steel of various sizes.

In addition, according to the present invention can provide a stainless steel capable of producing a continuous rolling method of stainless steel that can produce a stainless steel with excellent surface quality with high productivity.

1 is a view schematically showing a continuous rolling apparatus of stainless steel according to a preferred embodiment of the present invention.
Figure 2 is a graph showing the rolling load steel according to the injection flow rate of the second rolling oil.
3 is a graph showing the exit temperature of stainless steel according to the injection flow rate of liquefied nitrogen gas.

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

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with 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 schematically showing a continuous rolling apparatus of stainless steel according to a preferred embodiment of the present invention.

Continuous rolling apparatus 100 according to a preferred embodiment of the present invention comprises two or more rolling stands 110 each having a rolling roll 111 for rolling stainless steel (s); A first rolled oil supply part 120 for supplying a first rolled oil (a) to the rolling rolls 111 at the entry and exit sides of the rolling stand 110; A second rolled oil supply unit 130 for supplying a second rolled oil (b) to the stainless steel (s) at an inlet side of the rolled stand 110; And a gas supply unit 160 for supplying liquefied nitrogen gas to the entry or exit side of the rolling stand 110, wherein the first rolling oil (a) may have a lower viscosity than the second rolling oil (b). . For example, the continuous rolling device 100 may include a device for cold rolling stainless steel (s).

The stainless steel continuous rolling device 100 may be provided with two or more rolling stands 110 or less than six, in the present embodiment, the rolling stand 110 is described as four, but is not limited thereto. The rolling stand 110 may include first to fourth rolling stands 110a, 110b, 110c, and 110d sequentially provided, and the first to fourth rolling stands 110a, 110b, 110c, and 110d. Each of the rolling rolls 111 is provided with continuous rolling at a predetermined rolling rate and a rolling speed of the stainless steel s passing through the first to fourth rolling stands 110a, 110b, 110c, and 110d. The rolling roll 111 may be provided on the upper and lower portions of the stainless steel s, respectively, to roll the stainless steel s. For example, the rolling roll 111 may have a diameter of f130 to 150 mm. May comprise wheat. One or more reels 10 may be provided to wind or rewind the stainless steel s with the rolling stand 110 interposed therebetween. In addition, the front end of the first rolling stand 110 is provided with a welder 20 and the looper 30 may be to facilitate the continuous rolling of the stainless steel (s).

The first rolling oil supply unit 120 supplies a first rolling oil (a) to the rolling roll 111 at the entry and exit sides of the rolling stand 110, and the second rolling oil supply unit 130 is a second rolling oil ( b) can be supplied to the stainless steel (s) at the inlet side of the rolling stand (110). The first rolling oil supply unit 120 is connected to the first rolling oil tank 121 and the first rolling oil tank 121 in which the first rolling oil (a) is stored to roll the first rolling oil (a) to the rolling stand 110. The first rolling oil transfer line 123 may be provided to supply to the. The first rolling oil feed line 123 may be composed of four first rolling oil feed lines 123a, 123b, 123c, and 123d so as to be connected to the first to fourth rolling stands 110a, 110b, 110c, and 110d, respectively. have. Each of the first rolling oil transfer lines 123 is provided with a first rolling oil pump 122 to control the injection flow rate of the first rolling oil (a). In addition, one end of the first rolling oil feed line 123 is provided with a first rolling oil spraying unit 124, the first rolling oil spraying unit 124 is the first to fourth rolling stand (110a, 110b, 110c) , 110d), the first rolling oil a can be supplied to the entry and exit sides of the rolling roll 111, respectively.

The continuous rolling device 100 of the stainless steel is a return tank 140, the first rolling oil (a) is supplied and used to the rolling stand 110, and the first rolling oil collected in the return tank 140 ( It may further include a filtration unit 150 for filtering a). The first rolled oil (a) is recovered through the filtration unit 150 to the first rolled oil supply unit 110 and then supplied to the entry and exit sides of the rolling stand 110 to be reused. After the first rolling oil (a) supplied in a large amount is collected into the return tank 140, the contamination is removed through the filtration unit 150, and the process cost can be reduced by reusing the first rolling oil (a). . The first rolling oil (a) has a lower viscosity than the second rolling oil (b), whereas the first rolling oil (a) is used in large quantities, whereas the second rolling oil (b) is used in small amounts. Therefore, some second rolling oil (b) may be mixed in the first rolling oil (a) collected in the rolling stand 110 to reuse the first rolling oil (a), but the second rolling oil (b) Since the residual amount after use is extremely small, it hardly affects the physical properties and the like of the first rolled oil (a).

The second rolled oil supply unit 130 may be provided with a second rolled oil tank 131 for storing the second rolled oil (b) and a second rolled oil feed line 133 serving as a moving passage of the second rolled oil (b). have. Second rolling oil transfer line 133 connected to the inlet side of the first to fourth rolling stand (110a, 110b, 110c, 110d) may be provided. The second rolling oil feed line 133 is connected to the outlet side of the first to fourth rolling stands 110a, 110b, 110c, and 110d, and the second to fourth rolling stands 110a, 110b, 110c, and 110d of the first and fourth rolling stands 110a, 110b, 110c, and 110d. The second rolling oil (b) can be supplied to the stainless steel (s) from the outside. At this time, one end of the second rolling oil feed line 133 is provided with a second rolling oil spraying unit 134 to supply both the second rolling oil (b) to the upper surface and the lower surface of the stainless steel (s). In addition, the second rolling oil transfer line 133 may be provided with a second rolling oil pump 132 to control the injection flow rate of the second rolling oil (b).

The amount of the first rolling oil (a) used in the continuous rolling apparatus 100 of stainless steel may be greater than the amount of the second rolling oil (b) used. The first rolling oil (a) may include a low viscosity mineral oil-based rolling oil, the entry and exit of the first to fourth rolling stand (110a, 110b, 110c, 110d) in a large amount of the first rolling oil (a) In the rolling roll 111 may be injected between the stainless steel (s). On the other hand, the second rolling oil (b) may be sprayed with a small amount of high viscosity mineral oil-based rolling oil, the first rolling oil (a) is injected from the first to fourth rolling stand (110a, 110b, 110c, 110d) Before it can be sprayed on the surface of the stainless steel (s) at the mouth of each rolling stand. At this time, the first rolling oil (a) is injected in a large amount, the second rolling oil (b) may be injected in a small amount according to the rolling load.

The continuous rolling device 100 of stainless steel may further include a gas supply unit 160 for supplying liquefied nitrogen gas to the entry or exit side of the rolling stand 110. The gas supply unit 160 may supply the liquefied nitrogen gas to the entry or exit side of the fourth rolling stand 110d. The gas supply unit 160 may be connected to a gas tank 161 storing the liquefied nitrogen gas and a gas transfer line 163 connected to the gas tank 161 to supply the liquefied nitrogen gas to the rolling stand 110. Can be. In addition, the gas transfer line 163 may be provided with a gas pump 162 for controlling the injection flow rate of the liquefied nitrogen gas.

In the continuous rolling apparatus of the stainless steel according to the present embodiment, the liquefied nitrogen gas may be supplied to the final rolling stand for finally rolling the stainless steel, for example, the fourth rolling stand 110d. A first valve 125 is provided in the first rolling oil transfer line 123d for supplying the first rolling oil a to the fourth rolling stand 110d, and the liquefied nitrogen gas is supplied to the fourth rolling stand 110b. The second gas supply line 163 may be provided with a second valve 165. Therefore, when the stainless steel s passes through the fourth rolling stand 110d, a first gap is formed between the rolling roll 111 and the stainless steel s at the entry or exit side of the fourth rolling stand 110d. Rolled oil (a) or liquefied nitrogen gas may be supplied, or the first rolled oil (a) and liquefied nitrogen gas may be supplied simultaneously.

The liquefied nitrogen gas may be preferably supplied only to the outlet side of the fourth rolling stand 110d. For example, in the process of rolling the stainless steel s in the rolling stand 110, both the first and second rolling oils (a, b) may be used, and the first and second rolling oils (a, b) May remain on the surface of the stainless steel (s) after the continuous rolling is finished. Therefore, the first and second rolling oil remaining on the surface of the stainless steel (s) by supplying liquefied nitrogen gas to the final rolling stand such as the fourth rolling stand 110d to be finally rolled of the stainless steel (s) ( a, b) can be removed. This, it is possible to further improve the surface quality of the stainless steel (s), it is possible to efficiently proceed to the subsequent process, such as continuous annealing rinse line and temper rolling.

For example, the viscosity of the first rolling oil (a) is 10mm ² / s to 18mm ² / s (@ 40 ℃), the viscosity of the second rolling oil (b) is 25mm ² / s to 40mm ² / s (@ 40 ° C). The first and second rolled oils (a, b), it is preferable to use the same base oil in order to prevent the change of the property caused by the mixing of two oils having different characteristics. The viscosity of the first rolling oil (a) may be lower than that of the second rolling oil (b), and may affect the surface gloss of the stainless steel (s) when rolling the stainless steel (s). When the viscosity of the first rolling oil (a) is less than 10 mm ² / s, the rolling efficiency of the stainless steel (s) can be reduced, and when the viscosity of the first rolling oil (a) is more than 18 mm ² / s While increasing the rolling efficiency, it is difficult to secure the surface gloss of the stainless steel (s). In addition, when the viscosity of the second rolling oil (b) is less than 25mm ² / s, the lubricity is not sufficiently increased, thereby preventing high pressure and high speed rolling. On the other hand, if the viscosity of the second rolling oil (b) is more than 40mm ² / s, the viscosity is too high may cause heat strips, etc. on the surface of the stainless steel (s) may cause surface quality degradation of the stainless steel (s). .

The rolling flow rate of the first rolling oil (a) is 1000 lpm / stand to 5000 lpm / stand, the supply flow rate may be 2000 lpm / stand to 4000 lpm / stand. The first rolling oil (a) is supplied in large quantities to each of the rolling stands 110, and apart from the second rolling oil (b), the stainless steel (s) is previously stainless steel before the stainless steel (s) enters the rolling roll (111). A small amount can be applied to the entire surface of (s). The second rolling oil (b) may increase the lubricity at high pressure rolling and high speed rolling at high viscosity. Therefore, it is preferable that the second rolling oil (b) is supplied to the rolling stand having a relatively high reduction ratio in the rolling stand.

Figure 2 is a graph showing the rolling load steel according to the injection flow rate of the second rolling oil.

The first rolling oil may be supplied between the rolling roll and stainless steel, and the second rolling oil may be supplied to the surface of the stainless steel before the first rolling oil before the stainless steel passes through the rolling roll. For example, the supply pressure of the second rolling oil is 10kg / cm ² to 20kg / cm ² , the injection flow rate of the second rolling oil is preferably 100cc / min / rolling stand to 500 cc / min / rolling stand. Supply pressure of the second rolling oil is 10kg / cm ² If less than, the first provided on the surface of the stainless steel between each rolling stand It may be difficult to remove the oil film by the rolling oil and attach the second rolling oil to the surface of the stainless steel. On the other hand, if the supply pressure of the second rolling oil exceeds 20kg / cm ² , since the injection amount of the second rolling oil is increased and the adhesion effect of the second rolling oil is already saturated, the second rolling oil is wasted unnecessarily to reduce the production cost Can be increased. In addition, the injection flow rate of the second rolling oil If it is less than 100 cc / min / rolling stand, the effect of reducing the rolling load by the second rolling oil is insignificant, and when the injection flow rate of the second rolling oil is more than 500 cc / min / rolling stand, the rolling load by the second rolling oil Compared with the reduction effect, since the second rolling oil consumed is increased, unnecessary waste may be caused.

Normal. In continuous rolling, stainless steel can be supplied in large quantities at the entrance and exit of the rolling roll by using mineral oil-based rolling oil of low viscosity. At this time, the low viscosity mineral oil-based rolling oil may be supplied in order to ensure a high gloss surface quality of stainless steel. On the other hand, the rolling roll of the rolling stand according to the present embodiment may include a g-high mill having an operating roll diameter of 130 mm to 150 mm, and the diameter of the rolling roll is generally used for the Jenji mill mill used for continuous rolling of stainless steel. Larger than the diameter of the small diameter roll, the rolling load may be large due to the limitation of the number of the rolling stand. Therefore, even if a large amount of injection of the first rolling oil, which is a mineral oil-based rolling oil, the reduction ratio per rolling stand cannot be high, and high-speed rolling is very difficult due to plastic working and frictional heating. In the case of stainless steel, the total reduction ratio is up to 60%, and the rolling speed is up to 250mpm, which almost limits the continuous rolling. Accordingly, in order to roll the stainless steel to the final thickness, a tandem rolling continuous rolling mill may be repeatedly performed two or three times, thereby significantly reducing the productivity of the stainless steel. That is, the conventional tandem rolling continuous rolling mill was able to apply stainless steel only to a limited steel grade and limited size, there is a disadvantage that high pressure and high-speed rolling is difficult even if applied.

 In addition, in continuous rolling of stainless steel using a continuous rolling mill having a conventional G-high mill as a rolling roll, the rolling oil is a mineral oil-based knit oil instead of using an emulsion rolling oil of carbon steel to secure the surface gloss of stainless steel. Inferior lubricity and coolability. Therefore, the continuous rolling of the stainless steel using the continuous rolling mill has a fundamental problem that high pressure and high-speed rolling is difficult, unlike carbon steel. That is, when rolling using emulsion rolling oil having good lubricity and cooling property, stainless steel can be easily rolled to enable high pressure and high speed rolling, but a new problem of surface gloss reduction of stainless steel occurs. On the other hand, in the case of using mineral oil-based knit oil in order to secure the surface gloss of stainless steel, it is difficult to secure a stainless steel of a predetermined thickness under high pressure and high-speed rolling, and even if secured, a plurality of rolling must be performed, thereby decreasing productivity.

According to the present invention, when continuously rolling stainless steel using a tandem rolling continuous rolling mill using a high-high mill as a rolling roll, the surface type of the stainless steel is secured using a rolling oil of mineral oil type knit oil and at the same time under high pressure and high speed. It includes a continuous mill of stainless steel employing a novel rolling oil spray system to enable rolling.

The following is a continuous rolling method of stainless steel according to another aspect of the present invention, each of which is provided with a rolling roll, and a method of cold rolling stainless steel with two or more rolling stands sequentially provided. A first continuous rolling step of passing the stand and supplying and rolling the first and second rolling oils having different viscosities; And a second continuous rolling step of passing the first and second rolling oils through the two or more rolling stands through the stainless steel that has undergone the first continuous rolling step, and re-rolling the second and second rolling oils. Liquid nitrogen gas may be supplied to the final rolling stand for finally rolling the stainless steel in the rolling step. For example, the first rolled oil may have a lower viscosity than the second rolled oil.

In the first continuous rolling step or the second continuous rolling step, the first rolling oil may be supplied to the entry and exit sides of the rolling stand, and the second rolling oil may be supplied to the entry side of the rolling stand. In the second continuous rolling step, the liquefied nitrogen gas may be supplied to the entry or exit side of the rolling stand. 2 to 6 of the rolling stands may be sequentially arranged. Hereinafter, the rolling stand will be described as four rolling stands for convenience of explanation, but the present invention is not limited thereto.

The rolling stand includes first to fourth rolling stands sequentially arranged, and in the first continuous rolling step, the first and second rolling oils are respectively supplied to the first to fourth rolling stands. In the second continuous rolling step, the second rolling oil may be supplied to the first to fourth rolling stands, respectively, but in the final rolling stand, liquefied nitrogen gas may be supplied instead of the second rolling oil and the first rolling oil. In this case, the first rolling oil may be supplied between the rolling roll and the stainless steel, and the second rolling oil may be supplied to the surface of the stainless steel before the first rolling oil before the stainless steel passes through the rolling roll. The rolling roll includes a G-high mill having a diameter of 130 mm to 150 mm, the viscosity of the first rolling oil is 10 mm ² / s to 18 mm ² / s (@ 40 ℃), the viscosity of the second rolling oil is 25 mm ² / s to 40 mm ² / s (@ 40 ° C.).

In general, in case of continuous rolling of stainless steel, due to the limited number of rolling stands, it is difficult to obtain a sufficient reduction ratio in one rolling, or it is difficult to realize a predetermined surface gloss, and high-speed rolling is difficult. There is a problem that the advantages of the tandem rolling continuous rolling method using a plurality of rolling stands cannot be sufficiently exhibited, and therefore, many restrictions are imposed on the steel grade and size during rolling. Specifically, when the tandem rolling continuous rolling method is used, cold rolling of carbon steel is performed at a rolling rate of over 70% and rolling speed of 1500mpm, whereas in cold rolling of stainless steel, emulsion oil is used as rolling oil in one rolling. The reduction rate of 67% and the rolling speed of 600mpm, the reduction rate of 60% and the rolling speed of 250mpm are known to be limited when the mineral oil-based knit oil is used as the rolling oil.

In the process of continuously rolling, for example, cold rolling stainless steel according to the present embodiment, the continuous rolling method of the stainless steel by using a tandem rolling continuous rolling method consisting of a plurality of rolling stands is the first continuous rolling step and the second time It can be made in a continuous rolling step. That is, the first continuous rolling step of one rolling through the first to fourth rolling stand and the first continuous rolling step of two rolling through the first to fourth rolling stand again. have. In the first continuous rolling step, it is possible to first secure and roll about the intermediate thickness of the target thickness of the stainless steel, and in the second continuous rolling step, it may be rolled to secure the final rolling thickness of the stainless steel.

The first continuous rolling step may be rolled up to approximately the middle thickness of the final target thickness of stainless steel, but the maximum rolling speed may be 250 mpm using the first and second rolling oils together. In addition, in the second continuous rolling step, the stainless steel is rolled to a final target thickness, wherein the first and second rolling oils are used together, and the final rolling stand may be rolled using only the second rolling oil.

3 is a graph showing the exit temperature of stainless steel according to the injection flow rate of liquefied nitrogen gas.

Referring to FIG. 3, in the continuous rolling method of stainless steel according to the present embodiment, in the final rolling stand, the supply of the first rolling oil may be turned off, and liquefied nitrogen gas may be supplied instead. The liquefied nitrogen gas may be injected between the rolling roll and the stainless steel, and may cool the surface of the stainless steel. 3 is a graph measuring the surface temperature of the stainless steel according to the injection flow rate of the liquefied nitrogen gas when the supply amount of the liquefied nitrogen gas is a pressure of 3kg / cm ² . The surface temperature of the stainless steel is the temperature measured at the exit side where the stainless steel passes through the fourth rolling stand.

The supply amount of the liquefied nitrogen gas may be a pressure of 3kg / cm ² , the injection flow rate may be 0.01Nm ³ / hr to 0.03Nm ³ / hr. For example, when the injection flow rate of the liquefied nitrogen gas is less than 0.01 Nm ³ / hr, the cooling effect of the liquefied nitrogen gas is insufficient and the surface of the stainless steel is not sufficiently cooled, so that the surface gloss of the stainless steel is too high or exceeds the target value. If the liquefied nitrogen gas injection flow rate is more than 0.03Nm ³ / hr, the cooling effect by the liquefied nitrogen gas is too much to be a problem, and the residual material on the surface of the stainless steel The viscosity of the 1st and 2nd rolling oil may fall and lubricity at the time of rolling may fall, and it may cause surface defects.

The first rolled oil supplied to and used in the rolling stand in the first continuous rolling step or the second continuous rolling step may be collected in a return tank and then filtered through a filtration unit. The first rolled oil filtered through the filtration unit may be supplied to the inlet and the outlet of the rolling stand for reuse. In the present embodiment, the first rolled oil may be recovered and reused after being used to continuously roll stainless steel. The first rolled oil is used in a large amount, while the second rolled oil is used in a small amount compared to the first rolled oil. In addition, since the first and second rolling oils use similar base oils, they do not cause a change in properties even when they are mixed, and since the second rolling oils are trace amounts, they do not affect the characteristics of the first rolling oils. Therefore, the production cost can be reduced by recovering and reusing the first rolled oil.

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 first to fourth rolling stands are arranged in sequence, the first to fourth rolling stand using a tandem rolling continuous rolling mill equipped with a rolling roll G-high mill having a diameter of f130 ~ 150mm respectively The stainless steel was rolled under the conditions described in. Table 1 and Table 2 show a comparative example, Table 3 and Table 4 shows an example. At this time, the stainless steel of Comparative Examples and Examples of Tables 1 to 4 used a hot-rolled annealing secoil of STS430 that is 3.0t × 1290mm.

Table 1 and Table 2 relates to Comparative Example 1 and Comparative Example 2, respectively, in the case of Comparative Examples 1 and 2 were continuously rolled stainless steel using only the first rolling oil, Tables 3 and 4 below are each Examples 1 and 2, in the case of Examples 1 and 2, the first and second rolling oils are used together, and in the fourth rolling stand of the final second continuous rolling step, the first rolling oil is liquefied instead of being supplied. Nitrogen gas was supplied to cold-roll stainless steel.

 The first rolling oil is a mineral oil-based rolling oil, having a viscosity of 7 cSt to 15 cSt, saponification of 20 mg KOH / g to 40 mg KOH / g, and a flash point of 150 ° C. The second rolling oil is a mineral oil-based rolling oil of the same base oil as the first rolling oil, having a viscosity of 20 cSt to 30 cSt, saponification of 20 mgKOH / g to 40 mgKOH / g, and a flash point of 150 ° C. In each table, one pass means that the stainless steel passes through the first rolling stand, and two passes through four passes mean that each passes through the second rolling stand and the fourth rolling stand. In addition, the stainless steel subjected to the first continuous rolling step by passing through the first to fourth rolling stands once was again passed through the first to fourth rolling stands to perform the second continuous rolling step. . In Tables 1 to 4, primary rolling means the first continuous rolling step, and secondary rolling means the second continuous rolling step.

The Examples and Comparative Examples pass through the first to fourth rolling stands sequentially provided, in the case of the Comparative Example was continuous rolling using only the first rolling oil, in the case of the Example using both the first and second rolling oil . In this case, the second rolling oil is injected to the inlet side of the first and second rolling stand, but the first rolling oil is injected to the inlet and the outlet side of the first to fourth rolling stand. The liquefied nitrogen gas was supplied in place of the second rolling oil to the final rolling stand in the second continuous rolling step.

division pass Mouth thickness (mm) Exit thickness (mm) Rolling reduction (%) Total Pressure Drop (%) Rolling speed (mpm) Exit temperature (℃) First rolling oil Second rolling oil Liquefied nitrogen gas injection Heat strip Primary rolling One 3.0 2.0 33.3 25.0 111 U radish radish 2 2.0 1.5 25.0 46.7 156 U radish radish 3 1.5 1.15 23.3 60.0 208 U radish radish 4 1.15 0.9 21.7 66.7 250 116 U radish radish Occur Secondary rolling One 0.9 0.75 16.7 16.7 266 U radish radish 2 0.75 0.64 14.7 28.9 312 U radish radish 3 0.64 0.55 14.1 38.9 363 U radish radish 4 0.55 0.50 9.1 44.4 400 105 U radish radish Occur

division pass Mouth thickness (mm) Exit thickness (mm) Rolling reduction (%) Total Pressure Drop (%) Rolling speed (mpm) Exit temperature (℃) First rolling oil Second rolling oil Liquefied nitrogen gas injection Heat strip Primary rolling One 3.0 2.25 25.0 25.0 133 U radish radish 2 2.25 1.75 22.0 41.7 171 U radish radish 3 1.75 1.4 20.0 53.3 214 U radish radish 4 1.40 1.2 14.3 60.0 250 112 U radish radish Occur Secondary rolling One 1.2 0.9 25.0 25.0 222 U radish radish 2 0.9 0.7 22.2 41.7 285 U radish radish 3 0.7 0.57 18.6 52.5 350 U radish radish 4 0.57 0.50 12.2 58.3 400 107 U radish radish Occur

division pass Mouth thickness (mm) Exit thickness (mm) Rolling reduction (%) Total Pressure Drop (%) Rolling speed (mpm) Exit temperature (℃) First rolling oil Second rolling oil Liquefied nitrogen gas injection Heat strip Primary rolling One 3.0 2.0 33.3 25.0 111 U U radish 2 2.0 1.5 25.0 46.7 156 U U radish 3 1.5 1.15 23.3 60.0 208 U U radish 4 1.15 0.9 21.7 66.7 250 100 U U radish Not occurring Secondary rolling One 0.9 0.75 16.7 16.7 266 U U radish 2 0.75 0.64 14.7 28.9 312 U U radish 3 0.64 0.55 14.1 38.9 363 U U radish 4 0.55 0.50 9.1 44.4 400 90 radish U U Not occurring

division pass Mouth thickness (mm) Exit thickness (mm) Rolling reduction (%) Total Pressure Drop (%) Rolling speed (mpm) Exit temperature (℃) First rolling oil Second rolling oil Liquefied nitrogen gas injection Heat strip Primary rolling One 3.0 2.25 25.0 25.0 133 U U radish 2 2.25 1.75 22.0 41.7 171 U U radish 3 1.75 1.4 20.0 53.3 214 U U radish 4 1.40 1.2 14.3 60.0 250 95 U U radish Not occurring Secondary rolling One 1.2 0.9 25.0 25.0 222 U U radish 2 0.9 0.7 22.2 41.7 285 U U radish 3 0.7 0.57 18.6 52.5 350 U U radish 4 0.57 0.50 12.2 58.3 400 95 radish U U Not occurring

Since it is difficult to manufacture a stainless steel having a thickness of 0.5t or less by primary rolling using a tandem rolling continuous mill to have a high gloss surface quality, cold rolling is performed once and twice. At this time, the primary rolling is rolled to approximately the middle thickness of the final target thickness, and in the secondary rolling is rolled to have the final target thickness of the stainless steel. In Comparative Examples 1 and 2, no liquefied nitrogen gas was used. In Examples 1 and 2, liquefied nitrogen was supplied in four passes, which are the final rolling stands of the secondary rolling. At this time, Comparative Examples 1 and 2 and Examples 1 and 2 were carried out with the same rolling rate and rolling speed, and in the first rolling, the rolling speed was performed at a maximum speed of 250 mpm, whereas in the second rolling, the rolling speed was 400 mpm. The rolling of the stainless steel was carried out.

Examining Tables 1 to 4 above, in Comparative Examples 1 and 2 of Tables 1 and 2, heat streaks occur in both the first continuous rolling step and the second continuous rolling step, and In Examples 1 and 2 it was confirmed that the heat crack does not occur in both the first continuous rolling step and the second continuous rolling step. In addition, in Examples 1 and 2 it was confirmed that the surface quality of the stainless steel after the secondary rolling has excellent gloss.

In the comparative examples 1 and 2, when working stainless steel at high speed by secondary rolling, the oil film thickness drawn into a roll bite increases and the surface gloss of this stainless steel falls remarkably. On the other hand, in Examples 1 and 2, the first and second rolling oils are used at the same time, and in addition, the final rolling stand can improve the surface gloss of the stainless steel while maintaining lubrication by supplying liquefied nitrogen gas instead of the first rolling oil. Specifically, in Examples 1 and 2, using the first and second rolling oil remaining on the surface of the stainless steel when rolling in the preceding rolling stand of the final rolling stand, the stainless steel is fast-rolled with a minimum amount of oil film. Friction heat can be controlled by cooling the surface and the rolling roll of the stainless steel by the liquefied nitrogen gas. Therefore, it is possible to stably manufacture stainless steel with improved surface gloss by preventing surface defects such as heat streak caused by oil film breakage. In addition, since it is possible to minimize the increase in the oil film thickness caused by the high-speed rolling in the final rolling stand, it is possible to produce stainless steel with a high surface quality without deteriorating the gloss of stainless steel even under high-speed rolling conditions.

In addition, in the second rolling in Comparative Examples 1 and 2, the exit surface temperature of the stainless steel after 4 passes exceeded 100 ° C, whereas in Examples 1 and 2, the exit surface temperature of the stainless steel was 100 by using liquefied nitrogen gas. It can control by the temperature below ° C.

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: first rolling oil supply unit 130: second rolling oil supply unit
140: return tank 150: filtration unit
160: gas supply unit

Claims (19)

Two or more rolling stands each having a rolling roll for rolling stainless steel;
A first rolling oil supply unit for supplying a first rolling oil to the rolling rolls at the entry and exit sides of the rolling stand;
A second rolled oil supply unit supplying a second rolled oil to the stainless steel at an inlet side of the rolled stand; And
And a gas supply unit supplying liquefied nitrogen gas to the entry or exit side of the rolling stand.
The first rolling oil is a continuous rolling apparatus of stainless steel having a lower viscosity than the second rolling oil. The method of claim 1,
The rolling stand may include first to fourth rolling stands sequentially provided, the first rolling oil may be supplied to the entry and exit sides of the first to fourth rolling stands, and the second rolling oil may be provided to the first to fourth rolling stands. 4, a continuous rolling device of stainless steel, characterized in that supplied to the inlet side of the rolling stand. 3. The method of claim 2,
The gas supply unit is a continuous rolling device of stainless steel, characterized in that for supplying the liquefied nitrogen gas to the entry or exit side of the fourth rolling stand. 3. The method of claim 2,
The liquefied nitrogen gas is a continuous rolling device of stainless steel, characterized in that supplied only to the exit side of the fourth rolling stand. The method of claim 1,
The continuous rolling device of the stainless steel further comprises a return tank for collecting the first rolled oil used and supplied to the rolling stand, and a filtration unit for filtering the first rolled oil collected in the return tank. Device. The method of claim 5,
The first rolled oil is passed through the filtration unit and recovered to the first rolled oil supply unit, the continuous rolling device of stainless steel, characterized in that supplied to the entry and exit side of the rolling stand is reused. The method of claim 1,
The viscosity of the first rolling oil is 10mm ² / s to 18mm ² / s (@ 40 ℃), the viscosity of the second rolling oil is 25mm ² / s to 40mm ² / s (@ 40 ℃) characterized in that Continuous rolling device of steel. The method of claim 7, wherein
The first rolling oil is supplied between the rolling roll and the stainless steel, and the second rolling oil is supplied to the surface of the stainless steel before the first rolling oil before the stainless steel passes through the rolling roll, continuous rolling device of stainless steel . 9. The method of claim 8,
The supply pressure of the second rolling oil is 10kg / cm ² to 20kg / cm ² , the continuous rolling device of stainless steel, characterized in that the injection flow rate of the second rolling oil is 100cc / min to 500cc / min. In the method of cold rolling stainless steel with two or more rolling stands which are provided with rolling rolls sequentially, respectively,
A first continuous rolling step of passing the stainless steel through two or more rolling stands to supply and roll the first and second rolling oils having different viscosities; And
And a second continuous rolling step of passing the first and second rolling oils through the two or more rolling stands through the stainless steel that has passed through the first continuous rolling step, and re-rolling the second and second rolling oils.
Continuous rolling method of the stainless steel is supplied with liquefied nitrogen gas to the final rolling stand for finally rolling the stainless steel in the second continuous rolling step. The method of claim 10,
The first rolling oil has a lower viscosity than the second rolling oil, characterized in that the continuous rolling method of stainless steel. 12. The method of claim 11,
In the first continuous rolling step or the second continuous rolling step, the first rolling oil is supplied to the entry and exit side of the rolling stand, and the second rolling oil is supplied to the entry side of the rolling stand. Continuous rolling method. The method of claim 12,
The liquefied nitrogen gas in the second continuous rolling step is a continuous rolling method of stainless steel, characterized in that supplied to the entry or exit side of the rolling stand. 12. The method of claim 11,
The rolling stand includes first to fourth rolling stands sequentially arranged, and in the first continuous rolling step, the first and second rolling oils are respectively supplied to the first to fourth rolling stands. In the second continuous rolling step, the second rolling oil is supplied to the first to fourth rolling stands, respectively, but in the final rolling stand, liquefied nitrogen gas is supplied instead of the second rolling oil and the first rolling oil. Continuous rolling method. 12. The method of claim 11,
The first rolling oil is supplied between the rolling roll and stainless steel, and the second rolling oil is supplied to the surface of the stainless steel before the first rolling oil before the stainless steel passes through the rolling roll. . 12. The method of claim 11,
The rolling roll includes a G-high mill having a diameter of 130 mm to 150 mm, the viscosity of the first rolling oil is 10 mm ² / s to 18 mm ² / s (@ 40 ℃), the viscosity of the second rolling oil is 25 mm ² Continuous rolling method of stainless steel, characterized in that / s to 40mm ² / s (@ 40 ℃). 12. The method of claim 11,
The supply amount of the liquefied nitrogen gas has a pressure of 3kg / cm ² , the injection flow rate is 0.01Nm ³ / hr to 0.03Nm ³ / hr continuous rolling method of stainless steel. 12. The method of claim 11,
The first rolling oil supplied to the rolling stand used in the first continuous rolling step or the second continuous rolling step is collected in a return tank and then filtered through a filtration unit. 19. The method of claim 18,
The first rolling oil filtered through the filtration unit is supplied to the inlet and outlet side of the rolling stand to be reused continuous stainless steel.

Images