JP2001234252A - Steel strip carrying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel strip carrying method to prevent the quality degradation caused by the contact of a cooling gas jet nozzle. SOLUTION: When a steel strip is fed to a continuous annealing facility or a continuous galvanizing facility having a cooling zone provided with the cooling gas jet nozzle in a carrying process of the steel strip, the steel strip is supported by at least a pair of guide rolls to hold the steel strip by face and back sides thereof, and the unit tension to satisfy the inequality: T/9.8>=2.13×105×l1.2×t0.8×(W/1000)1.1/d1.8} is given to the steel strip in the cooling zone by bridle rolls disposed on the inlet and outlet sides of the cooling zone under the support by the guide rolls. In the inequality, T is the tension (N) in the steel strip, t is the thickness (mm) of the steel strip, W is the width (mm) of the steel strip, d is the gap (mm) between the nozzle and the steel strip, l is the maximum length (m) between the guide rolls between the guide roll and the bridle roll.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transporting a steel strip, and more particularly, to a method for continuously cooling a steel strip by using a cooling method using a gas jet nozzle or a cooling method using a combination of a cooling method using a gas jet nozzle and another cooling method. An object of the present invention is to effectively avoid deterioration in quality of a steel strip due to contact with a gas jet nozzle, which is likely to occur when the steel strip is fed to an annealing facility or a continuous hot-dip galvanizing facility for processing.

[0002]

2. Description of the Related Art Generally, a furnace portion of a continuous annealing facility or a continuous hot-dip galvanizing facility mainly includes a heating zone, a soaking zone and a plurality of cooling zones. Among them, various cooling systems have been applied to the cooling zone. The most common cooling method is a gas jet nozzle that cools a reducing atmosphere gas consisting of nitrogen and a few percent of hydrogen through a cooler and injects the cooling gas into a steel strip through a gas jet nozzle to cool it. The scheme is known.

[0003] In addition, a roll cooling method of introducing a cooling medium such as water into the inside to cool the inside, and a mist cooling method of spraying water into a steel strip in a mist state are also known. Among them, the cooling method using a gas jet nozzle is simpler in operation and relatively inexpensive compared with other cooling methods, and also enables uniform cooling of the steel strip and obtains a good shape. Moreover, since the steel strip surface is hardly oxidized by using a reducing gas, it has many advantages such as no need for post-treatment such as pickling, and has been widely applied so far.

[0004] In particular, when a cold-rolled steel sheet used for deep drawing is manufactured in a continuous annealing facility, it is possible to obtain characteristics excellent in ductility and aging by precipitating solid solution carbon. However, for this purpose, rapid cooling and subsequent overaging treatment are required, and in this case, the cooling rate during rapid cooling is particularly important due to the behavior of the solute carbon. It is generally said that an appropriate cooling rate employed in the treatment of this type of steel sheet is about 50 ° C./s to 100 ° C./s. However, this cooling rate can be obtained by a conventional cooling method using a gas jet nozzle. For this reason, various attempts have been made to increase the gas flow velocity, improve the structure of the nozzle, or reduce the distance between the nozzle and the steel strip.

[0005]

Even when a plenum chamber with an improved nozzle shape is applied, the gap between the steel strip and the nozzle tip must be reduced in order to obtain a high cooling rate. The distance from the band surface to the tip of the nozzle is set to 150mm or less.

In the case of continuous annealing equipment, the length of one pass of the rapid cooling section of the steel strip is generally about 15 m to 25 m, so that when the gas is blown at a high speed, the vibration and torsion of the steel strip are caused. At this time, there is a problem that the steel strip comes into contact with the tip of the nozzle, the surface of the steel strip is damaged, and the commercial value is lost.

FIG. 1 shows an example of a typical configuration of a cooling zone employing a cooling method using a gas jet nozzle. In FIG. 1, reference numeral 1 denotes a tropical zone, 2 denotes an overaged zone, and 3 denotes a tropical zone. A cooling zone disposed between the steel strip S and the overaging zone 2, a hearth roll 4, and a cooling plenum chamber 5 for blowing a cooling gas onto the steel strip S in a conveying process to cool the steel strip S.

In the cooling zone having the structure as shown in FIG. 1, rapid cooling is difficult because contact with the nozzle is inevitable.

As a prior art document relating to this point, for example, Japanese Patent Application Laid-Open No. 60-63326 proposes a device in which a steel strip is sandwiched from the front and back by a hearth roll. The technique is intended to simply prevent the occurrence of abrasions in other words, in other words, it has been devised on the assumption that the tension applied to the steel strip is within a normal range.

However, in recent years, materials (steel strips) have become thinner and wider, and from the viewpoint of preventing buckling of these materials, the necessity of lowering the in-furnace operation tension has increased, while the width of such materials (steel strips) has increased. The need to increase the cooling rate in the cooling method using gas jet nozzles and gas jet nozzles requires that the tension in the furnace operation be increased in order to prevent the generation of abrasions. is there.

In order to cope with the above-mentioned conventional problems, it is effective to shorten the roll interval. However, the shortening of the roll interval causes a decrease in the cooling capacity due to a reduction in the length of the cooling plenum chamber equipment. Become.

When a plenum chamber is added to increase the cooling capacity, the cooling time is prolonged. Therefore, there is a disadvantage that the cooling rate to be increased is originally reduced, and moreover, a large number of guide rolls need to be provided. Therefore, there is a problem that the equipment cost is increased, and there are still many problems to be solved in equipment having a rapid cooling zone employing a cooling method using a gas jet nozzle.

An object of the present invention is to propose a new transporting method which can solve the conventional problems as described above.

[0014]

According to the present invention, in order to solve the above-mentioned problems, bridle rolls are arranged before and after a rapid cooling zone of a continuous annealing facility or a continuous galvanizing facility,
In addition, when the steel strip is transported at an appropriate steel strip tension value or more that is determined by the relationship between the strip width of the steel strip, the gap between the nozzle and the steel strip, and the length between the guide rolls (or the length between the guide roll and the bridle roll). Is what you do.

That is, according to the present invention, in the process of transferring a steel strip in a continuous line, the steel strip is provided with a cooling zone using a cooling system using a gas jet nozzle or a cooling system using a cooling system using a gas jet nozzle in combination with another cooling system. In sending to annealing equipment or continuous hot-dip galvanizing equipment,
In the cooling zone of the equipment, the steel strip is supported by at least a pair of guide rolls sandwiching the steel strip between the front and back, and under the support of the steel strip by the guide rolls, bridle rolls arranged on the inlet side and the outlet side of the cooling zone. A method of conveying a steel strip, wherein a tension equal to or greater than a tension value calculated from the following equation is applied to a steel strip passing through a cooling zone.

[0016]

(Equation 2) T: Steel strip tension (N) t: Steel strip thickness (mm) W: Steel strip width (mm) d: Clearance between nozzle and steel strip (mm) l: Length between guide rolls or guide rolls Longest length between the and the bridle roll (m)

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to the drawings. FIG. 2 shows an example of rapid cooling equipment of continuous annealing equipment suitable for continuous annealing treatment of a steel strip. In FIG. 2, reference numeral 6 denotes a rapid cooling zone, and 7 denotes a rapid cooling zone.
And 8 is an overage treatment zone located downstream of the rapid cooling zone 6.

Reference numeral 9 denotes a bridle roll disposed on the entrance side of the rapid cooling zone 6, and reference numeral 10 denotes a bridle roll disposed on the exit side of the rapid cooling zone 6. Is applied to the steel strip S passing therethrough.

Reference numeral 11 denotes a guide roll for sandwiching the steel strip S between the front and back sides in the rapid cooling zone 6. In this example, the guide roll 11 is formed of a first guide roll 11a and a second guide roll 11a.
Of the guide roll 11b. Also, 12
Is a plenum chamber for rapid cooling of the steel strip.
In this example, three gaps are set along the transport direction of the steel strip S, and the gap up to the surface of the steel strip S is set to d.

[0020] In place shown above掲図2, the distance from the bridle rolls 9 up to the first guide roll 11a and l _1, the distance from the first guide roll 11a up to the second guide roll 11b l _2, and further when the distance from the second guide roll 11b up to the bridle roll 10 was set to l _3, deflection caused by the vibration of l _1, l _2, l steel strip S the greater the distance between the mutual ₃ It is conceptually easily understood that the smaller the gap d between the steel strip S and the nozzle, the more likely the contact between the steel strip S and the nozzle occurs.

Further, with respect to the plate width W of the steel strip S, the larger the width is, the more likely the gas jet is twisted due to the slight non-uniformity of the gas jet in the width direction. By increasing the tension, it is possible to suppress torsion accompanying the run-out of the steel strip S.

According to the present invention, the relationship between the distances l _{1 to} l ₃ and the gap d and the conditions of the steel strip S such as the width W and the thickness t of the steel strip S can be changed even if these values change. The relationship in which S and the nozzle do not come into contact with each other is found from various experiments using actual process lines and the accumulated process production results so far, and the relationship is expressed by the following equation.

[0023]

(Equation 3) T: Steel strip tension (N) t: Steel strip thickness (mm) W: Steel strip width (mm) d: Clearance between nozzle and steel strip (mm) l: Length between guide rolls or guide rolls Longest length between the and the bridle roll (m)

When the steel strip S is conveyed and the tension value calculated by the above equation (1) is applied, rapid cooling becomes possible without causing contact between the steel strip and the nozzle. However, if the tension of the steel strip S is excessively increased in the high-temperature range, there is a concern that the width of the steel strip S may be reduced in quality and abnormal grain growth may be caused. In order to avoid this, it is necessary to increase the number of bridging rolls between the cooling zone and the solitary zone, which leads to an increase in equipment length and equipment costs.Therefore, the upper limit of the unit tension is 39.2 MPa in the present invention. Probable value.

[0025]

EXAMPLE A steel strip having a thickness of 1.0 mm and a width of 1400 mm is conveyed by using equipment having a configuration as shown in FIG. 2 in which the gap d between the steel strip and the nozzle is set to 100 mm. Per case
The interval l was determined by opening and closing the guide rolls to create four conditions, and the presence or absence of scratches when the tension of the steel strip was variously changed was examined.

FIG. 3 shows the results. When the tension value calculated by the formula (1) defined in the present invention was applied, no scratch was generated. In this embodiment, the gap d is
The study was conducted on a steel strip with a thickness of 100 mm, a thickness of 1.0 mm and a width of 1400 mm.The present invention provides an appropriate tension value even if the equipment and conditions change even with other dimensions of the steel strip. You can do it.

Table 1 shows an example of an embodiment of a thin and wide material other than the above embodiment.

[0028]

[Table 1]

As shown in Table 1, in particular, when the plate thickness is 0.
Conventionally, buckling and flaws were unavoidable in steel strips with a sheet width of 1450 mm at 4 mm.However, when the tension is adjusted according to the present invention, such steel strips can be stably passed without any surface flaws. It was confirmed that the plate was formed.

[0030]

According to the present invention, an appropriate tension value is calculated and set according to the structure of the equipment and the conditions of the steel strip, so that abrasion caused by contact with the nozzle on the surface of the steel strip can be avoided.
Product yield loss can be reduced.

Further, in the present invention, when constructing a new facility, it can be utilized for the layout of the rapid cooling zone and the design of the motor power, so that proper facility design becomes possible.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration of a cooling zone to which a conventional general cooling method using a gas jet nozzle is applied.

FIG. 2 is a diagram schematically showing a configuration of a device suitable for use in carrying out the present invention.

FIG. 3 is a graph showing a relationship between a tension T of a steel strip and a distance l between rolls.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 Soaking tropical zone 2 Overage treatment zone 3 Cooling zone 4 Hearth roll 5 Cooling plenum chamber 6 Rapid cooling zone 7 Soaking zone 8 Overaging treatment zone 9 Inlet bridle roll 10 Outlet bridle roll 11 Guide roll 12 Plenum chamber S Steel strip

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yuji Shimoyama 2-3-2 Uchisaiwaicho, Chiyoda-ku, Tokyo F-term in Kawasaki Steel Corporation (reference) 4K043 AA01 BB06 CB03 DA05 EA06 FA05 FA13 GA06 HA04

Claims (1)

[Claims] 1. In a process of transporting a steel strip in a continuous line,
In feeding the steel strip to a continuous annealing facility or a continuous hot-dip galvanizing facility having a cooling zone using a cooling method using a gas jet nozzle or a cooling method using a gas jet nozzle and another cooling method, a cooling zone for the equipment is used. The steel strip is supported by at least a pair of guide rolls sandwiching the steel strip between its front and back sides, and passes through the cooling zone by bridle rolls arranged on the inlet side and the outlet side of the cooling zone under the support of the steel strip by the guide rolls. A method of conveying a steel strip, wherein a tension equal to or greater than a tension value calculated by the following equation is applied to the steel strip to be formed. (Equation 1) T: Steel strip tension (N) t: Steel strip thickness (mm) W: Steel strip width (mm) d: Clearance between nozzle and steel strip (mm) l: Length between guide rolls or guide rolls Longest length between the and the bridle roll (m)