JPS6342697B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the invention of a continuous annealing steel strip cooling method, which can efficiently cool the steel strip when annealing and cooling the steel strip using continuous annealing equipment.
Moreover, the present invention aims to provide a method that can accurately control the temperature of the steel strip after cooling to the overaging treatment temperature. Industrial application field Cooling method of steel strip before overaging treatment in continuous annealing. Prior Art Methods for cooling a steel strip after annealing in continuous annealing include methods using gas, gas-liquid, liquid, liquid, and rolls. Publication, JP-A-50-90515 and JP-A-51-
There is a publication number 104417. That is, the method disclosed in Japanese Patent Application Laid-open No. 50-80208 adjusts the contact area of a roll through which a heating medium is passed through the heating and cooling of a steel strip in a heat treatment furnace.
No. 50-90515 discloses cooling by blowing gas from the opposite side of the indirect cooling roll. The method disclosed in Japanese Patent Application Laid-Open No. 104417/1983 also uses an internal cooling roll. Problems to be Solved by the Invention However, each of the above-mentioned conventional devices has its own problems. In other words, gas cooling generally has a slow cooling rate, and in the above cases, it is difficult to achieve the required rapid cooling of 50°C/sec to 2000°C/sec. Since this is necessary, equipment costs and operating costs are inevitably high. In this respect, rapid cooling is easy for products that use liquid, but in this case, the product is cooled to room temperature, and therefore requires reheating for subsequent heat treatment, which increases equipment costs and thermal energy. This has the disadvantage of high operating costs. On the other hand, in the case of roll cooling described in the above-mentioned patent publication, even though the mechanism of the cooling roll has been clarified to some extent, effective application techniques regarding the annealing treatment have not yet been elucidated. "Structure of the Invention" Means for Solving the Problems In cooling the steel strip after heating in continuous annealing treatment and before over-aging treatment after recrystallization, a plurality of internal cooling units are provided in the running direction of the steel strip. A method for cooling a steel strip in continuous annealing, characterized by cooling the steel strip to an overaging treatment temperature at a cooling rate of 50° C./sec or more by adjusting the contact time of the steel strip with a rolling roll. Function The heated and recrystallized steel strip is efficiently cooled by cooling rolls at a rate of 50°C/sec or more, and furthermore, by adjusting the contact time, it is cooled to the overaging treatment temperature. Therefore, it can be subjected to overaging treatment as it is or by slight reheating. EXAMPLE To explain the specific embodiment of the present invention shown in the attached drawings, a continuous annealing facility having the general structural relationship as shown in FIG. 1 is adopted as a specific apparatus for carrying out the method of the present invention. In other words, the strips S unwound and pulled out from one of the plurality of uncoilers 1a and 1b are continuously connected alternately with the strips from the other uncoiler by the shear 2-1 and the welding machine 2-2. The welding machine 2-2 is followed by a hot water washing tank 3 and an alkali washing tank 4.
A pre-treatment surface cleaning section is provided in which a spray hot water washing tank 5 is sequentially arranged. The furnace 10 has a heating zone 8 for recrystallization annealing, a soaking zone 9 and a cooling section 12, and thus recrystallization annealing and cooling are performed. The pickled material is further sent to the pickling tank 13 and thereafter. That is, the strip S goes from the pickling tank 13 to the neutralization tank 1.
4. After the surface is cleaned in a hot water washing tank 15 and a dryer 6-2, it enters the furnace again, passes through a reheating zone 16 for overaging treatment, an overaging treatment zone 17, a gas cooling zone 18 using atmospheric gas, and then enters the outlet looper. 19, and from this output side looper 19 it reaches a water cooling mechanism 20 and a drying mechanism 21. The strip S leaving the drying mechanism 21 passes through a temper rolling mill 22, a trim width change notch 23 when changing the trim width, a side trimmer 24, an oiler 25, an exit shear 26, and then is wound onto an exit take-up reel 27. As shown in the figure, it is configured to be taken. By the way, the cooling device used by the present inventors in the above-mentioned annealing equipment is as shown in FIGS. Rolls 11, 11 and 11a, 11a are provided, and a steel strip is wound around these rolls to allow them to pass, and each of the rolls 11, 11 has a bearing box 31 arranged at each end thereof as shown in FIG. installed, and those bearing boxes 31
It is movable with the rollers 11a and 11, and is moved up and down by a plurality of operating mechanisms 30, such as screw mechanisms or hydraulic mechanisms, disposed on both ends of each of the bearing boxes 31 described above. Water or other refrigerant is introduced into one or both. For example, the winding angle of the passing strip 5 with respect to the cooling roll is changed by the above-mentioned upper and lower rolls 11, 11, and the contact length thereof is changed, so that the strip S is kept under the same running speed condition. The cooling rate and temperature can be freely adjusted, and of course it is also possible to change the contact length for only one operating mechanism or one end of the roll, and the temperature after annealing and overaging treatment temperature for each can be adjusted. It is possible to immediately respond to fluctuating conditions between steel strips and send the steel strip to the next process at a predetermined temperature that matches each case. It can be cooled to a corresponding temperature, and after a slight reheating, it can be overaged. In the above-mentioned device, when cooling water is forcibly circulated in the cooling roll and the steel strip S is brought into contact with the cooling water, the thickness of the steel strip S is 0.6 mm in the temperature range of about 300 to 600 degrees Celsius. For example, a 1-second contact can cool around 180°C, a 2-second contact can cool around 260°C, and in the case of a 1.2 mm thick steel strip, a 1-second contact can cool it to around 90°C, and a 2-second contact can cool it to around 90°C. Cooling of around 140℃ can be obtained. Specifically, this is 150m/min.
A cooling roll with a diameter of 600 mm is used for the steel strip S being fed at a speed of
When cooling water is circulated throughout the strip 1a, the strip with a thickness of 0.8 mm and a temperature of about 580°C fed along the line described above after recrystallization annealing will have a temperature of 505° C. after passing through the first roll 11. ~515℃
It is further cooled to about 465 to 480°C by passing through the second roll 11a. Further, it passes through the third roll 11 to a temperature of 410 to 420°C, and passes through the fourth roll 11a to about 380°C, and is sent to the subsequent line as described above to be reheated in the reheating zone 16. An advantageous overaging treatment can be carried out which significantly reduces the reheating energy required in the process to obtain a desirable product. Specific production examples and comparative examples of products produced by the method of the present invention are explained below. The steel types specifically adopted by the present inventors are rimmed steel, killed steel, and high-strength steel, and their compositions are as shown in Table 1 below.

[Table] The heating and recrystallization of each steel as described above is
Rimmed steel and killed steel were tested at 700°C for 30 seconds, and high-strength steel was tested at 750°C for 60 seconds. However, for cooling after this heating and recrystallization until overaging treatment, cooling with a gas jet at an average cooling rate of 15°C and cooling with water at an average cooling rate of 1000°C are performed for rimmed steel, examples for killed steel, etc. and high tensile strength steel, and according to the present invention, the material was once cooled to 580°C in the gas jet section 12a before being fed to the cooling section 12 in FIG. 1, and then fed to each roll 11, 11a. , in the first roll
510℃, 470℃ for the second roll, 415℃ for the third roll,
For example, if the material is cooled to about 380℃ using the fourth roll,
,. The following Table 2 summarizes the subsequent over-aging treatment conditions for the steel strips described above and the properties of each steel strip obtained thereby, and the steel strips according to the present invention was confirmed to have favorable properties.

【table】

[Table] According to the present invention as explained above, efficient steel strip cooling is achieved by applying a progressively novel cooling method using cooling rolls to continuous annealing, and the temperature of the steel strip after cooling is It is possible to appropriately control the temperature within the desired range within a relatively short time and under conditions where there is no or at least very little thermal energy loss due to reheating, etc., and furthermore, compared to conventional methods. This invention has advantages such as low equipment costs and low operating costs, and is a highly effective invention industrially.

[Brief explanation of drawings]

The drawings illustrate embodiments of the invention,
FIG. 1 is an explanatory diagram of an example of continuous annealing equipment to which the present invention is applied, FIG. 2 is a side view of the cooling roll portion thereof, and FIG. 3 is a plan view thereof. However, in these drawings, 8 is a heating zone, and 9 is a heating zone.
10 is a soaking zone, 10 is a furnace, 11 and 11a are cooling rolls, 12 is a cooling section, S is a steel strip, 17 is an overaging treatment zone, 30 is an operating mechanism, and 31 is a bearing box.

Claims (1)

[Claims] 1. Adjusting the contact time of the steel strip with a plurality of internal cooling rolls arranged in the running direction of the steel strip when cooling the steel strip after heating and recrystallization in continuous annealing treatment and before over-aging treatment. A steel strip cooling method in continuous annealing characterized by cooling to an overaging treatment temperature at a cooling rate of 50°C/second or more.