JPH0215615B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention is a vertical BA furnace (bright annealing furnace), which is particularly suitable for heat treating stainless steel BA steel strips and high nickel alloy steel strips, and which can prevent width curvature of steel strips. Regarding type BA furnace. [Prior art] When a stainless BA steel strip or a high nickel alloy steel strip is heat treated in a vertical BA furnace, for example, solution treatment is performed, the width as shown in Figures 2-A and 2-B is applied. It is easy to cause curvature in the direction, that is, curvature in width. Both Fig. 2-A and Fig. 2-B are cross-sectional views taken in a direction perpendicular to the conveying direction of the steel plate.
The figure shows the case where the curve is at one place, and the figure 2-B shows the case where there is the curve at two places in the width W direction. By the way, high nickel alloys used for specific applications, for example, electronic materials, have extremely strict standards for flatness, and require a flatness correction process such as skin pass rolling and a leveler after BA treatment. Furthermore, if the width is significantly curved, the product will come into contact with members in the furnace while traveling or moving in the furnace, causing scratches and significantly degrading the surface quality of the product. The following factors are considered to be the cause of the above width curvature. (1) Thermal stress due to the temperature difference in the width direction that occurs during cooling. (2) Deformation that occurs because the high tension applied in the furnace is uneven in the width direction. On the other hand, when a horizontal BA furnace is used, this type of shape defect is rare. The reason for this is that in the horizontal BA furnace, deformation is prevented by the rolls installed in the furnace to reduce the amount of catenary caused by the weight of the material. However, when a furnace roll is provided, the following problems are likely to occur. (1) When rolls are installed in a heating furnace, contact with the rolls at high temperatures (furnace temperature of 900 to 1150°C) may cause scratches due to abrasion of the roll surface or scratches due to defects in the rotating parts, which may affect the quality of the product. and seriously impairs the aesthetic appearance. (2) When installing rolls in the heating furnace, the mechanism of the roll support part that can follow the thermal expansion of Matsufuru at high temperatures is complicated and the equipment cost is enormous. (3) At the exit of the heating furnace, due to the rapid temperature change of the material due to contact with the rolls, creases and wrinkles occur, which is a fatal defect especially in thin materials. Therefore, the vertical type heating furnace does not have rolls inside the heating furnace.
In order to prevent the above defects in BA furnaces, the following proposals have been made. (1) Perform precise control to maintain uniform cooling capacity across the width of the cooling zone. (2) Use low tension transport inside the furnace. [Problems to be solved by the invention] Even with the above-mentioned proposal for the conventional vertical BA furnace, problems such as increased equipment costs for precise control, meandering caused by low-tension conveyance, and roll slips cannot be solved. However, the width curvature phenomenon could not be resolved. [Means for Solving the Problems] The structure of the present invention for solving the above problems is as follows:
This is a vertical BA furnace as described in the claims. That is, this invention solves the above-mentioned problem of the vertical BA furnace by providing a restraint that can prevent material deformation between the top roll and the bottom fixed part (for example, felt seal or seal roll) of the vertical BA furnace. This is based on the discovery that this is due to no force acting on the rolls, and also the discovery of conditions for installing rolls in the furnace that do not cause defects in shape such as creases and wrinkles even when heated materials in the furnace come into contact with the rolls. . To explain specifically with reference to the drawings, as shown in Fig. 1, a steel strip is heat-treated in a vertical BA furnace in which a heating zone and a cooling zone are vertically provided by outer furnace rolls 4. 1 travels in the direction of the arrow to undergo heat treatment, and then descends by the outer furnace roll 4 and is sent to the next process. As shown in FIG. 3, three or more furnace rolls 3 are located in the cooling zone where the material temperature reaches 200 to 700°C. If the number of rolls is less than two, a winding movement path cannot be taken, and it is impossible to secure the curvature. The diameter D of this furnace roll 3 is selected so that D≧1.4Et/σ. However, t: Thickness of the plate (mm) E: Elastic modulus of the material when in contact with the roll (Kg/mm ² ) σ: Yield strength of the material when in contact with the roll (Kg/mm ² ). The tension acting on the steel plate 1 is set to 0.1 to 1.5 Kg/ ^mm2 , and at the same time, the values of the interval S between the furnace rolls and the amount of roll wrap L are such that the radius of curvature of the steel plate curved by the furnace rolls 3 is 1000 to 1000. It is set to be 15000mm. If the temperature at the location where the furnace roll is installed is higher than 700℃, the strength of the material will be low and deformation will easily occur.
Maintenance of the equipment is also difficult. If the tension exceeds 1.5Kg/ ^mm2 , the material may buckle in the furnace, causing creases and wrinkles, and the rolls in the furnace will be heavily worn, as well as surface defects (scratches, dents, etc.).
It also becomes more likely to occur. On the other hand, if the tension is less than 0.1 Kg/mm ² , there will be no shape correction effect, easily causing deflection and distortion, and directional stability will deteriorate. If the diameter D of the furnace rolls 3 is too small, the material is likely to deform due to bending, and if the diameter D is too large, the roll installation interval S and roll wrap amount L to obtain an appropriate radius of curvature will not fit into the furnace space. It becomes something that does not exist. After all, the relational expression described in the claims was derived experimentally. Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the threading material is SUS304 with a thickness of 0.25 mm and a width of
It was 650mm and the tension was 0.15Kg/ ^mm2 .

[Table] [Effects of the Invention] As explained above, according to the present invention, a defect-free metal strip can be obtained using a relatively simple device when heat treating a metal strip.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the outline of a vertical BA furnace, Figure 2
-A figure and 2-B figure are explanatory diagrams of width curvature, 3rd figure
The figure is an explanatory diagram of the roll installation interval and roll wrap amount. 1...Steel strip, 2...Horizontal surface plate, 3...Roll in the furnace, 4...Roll outside the furnace, C...Amount of width curvature, L...
Roll wrap amount, S...Roll installation interval, W...
Board width.

Claims (1)

[Claims] 1. A vertical BA furnace having a heating zone and a cooling zone, characterized in that the cooling zone has a plurality of rolls meeting the following conditions. (1) It is installed in a cooling zone where the material temperature is 200 to 700℃. (2) The number of rolls is 3 or more. (3) The furnace roll diameter (D) is a value that satisfies the following formula. D≧1.4Et/σ Where, t: Thickness of the plate through which it passes (mm) E: Elastic modulus of material when in contact with rolls (Kg/mm ² ) σ: Proof strength of material when in contact with rolls (Kg/mm ² ) (4 ) The tension range is 0.1-1.5Kg/ ^mm2 . (5) The distance between rolls in the furnace and the amount of roll wrap are such that the radius of curvature caused by the rolls is 1000 to 15000 mm.
It is set up to be.