JPH0578755A - Bright annealing furnace for stainless steel sheet - Google Patents

Abstract

PURPOSE:To provide a bright annealing furnace which can produce a treating material from an extremely thin sheet to a thick sheet in high efficiency by using a cooling means capable of obtaining the cooling distribution covering a heating furnace and a coating zone, a wide range of cooling capacity in the cooling process and smooth blasting flow. CONSTITUTION:By arranging the furnace deciding the cooling capacity, by which the yield stress in the treating material at the max. sheet temp. part in the bright annealing furnace is made to >=1.4 times of the used tension stress, and the cooling devices 7, 9 providing the cooling speed at <=30 deg.C/sec in the high temp. range from the furnace outlet to the position at 900 deg.C and also at <=35 deg.C/sec in the medium temp. range from 900 deg.C to 550 deg.C and having >=20 deg.C/sec cooling rate, and further, fluid pads 6, 12 for preventing shift of the sheet in the ranges at 900 deg.C and at 550 deg.C, the sheet thickness range from the extremely thin sheet to the thick sheet can be treated at the high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical type bright annealing furnace for thin stainless steel strip.

[0002]

2. Description of the Related Art In a conventional furnace, for example, Japanese Patent Publication No.
As disclosed in Japanese Patent No. 35848, as a method of preventing C warpage in a vertical bright annealing furnace, a furnace atmosphere gas in which a front surface and a back surface of a steel strip passing through the furnace have a temperature difference between the front surface and the back surface is used. The method of spraying is shown.

However, in the conventional method, in the production of an extremely thin material in a long furnace, C warpage occurs due to the dead weight of the strip, and throttling and bending occur in the cooling zone, so that the temperature inside the furnace is the normal operating temperature (1100 ° C.). It was necessary to operate at a lower temperature (1000 ° C.), and the capacity of the furnace could not be used effectively.
In addition, the cooling zone has a structure in which the cooling zone length is determined on the premise of rapid cooling (the maximum sheet thickness determines the cooling capacity), and the cooling rate cannot be controlled during the cooling process. The strip speed is regulated because the strip steel is susceptible to breakage due to the cooling and vertical wind flow and it is necessary to operate in a state close to natural cooling (slow cooling rate).

[0004]

As described above, in the production of the ultra-thin material in the vertical bright annealing furnace, squeezing and bending during the cooling process easily occur. Since the heating capacity and cooling capacity of the conventional furnace are determined by the maximum plate thickness, ultra-thin materials are overcooled during the cooling process and plate throttling and breakage occur, which is a quality problem and the processing speed is regulated. It was necessary and productivity was poor. INDUSTRIAL APPLICABILITY According to the present invention, by appropriately distributing the lengths of the heating zone and the cooling zone and having a wide range of cooling ability in the cooling process, it is possible to efficiently produce the processed materials from the extremely thin material to the thick material. It is intended to provide a bright annealing furnace for stainless steel strip.

[0005]

In order to achieve the above object, the vertical strip bright annealing furnace for stainless steel strip for thin products according to the present invention is a method for suppressing the warp in the furnace.
₁ (m) satisfies the following formula. σ _y / σ _t ≧ 11.4 σ _t = 7.93 × 10 ⁻³ × L ₁ + σ _h σ _y : Material yield stress at the maximum plate temperature σ _t : Allowable tensile stress at the maximum plate temperature σ _h : Plate transport tension

Further, as a method for preventing the plate from being drawn in the cooling zone, the heating zone outlet side temperature (T ₁ ° C) to 900 ° C and 90
The cooling length in each temperature range from 0 ° C to 550 ° C satisfies the following formula, so that the plate temperature 9
In the high temperature region up to 00 ° C, the cooling rate is 30 ° C / sec or less, 9
In the medium temperature range from 00 ℃ to 550 ℃, the cooling rate is 3 / s.
The cooling rate is 5 ° C. or less and 20 ° C. or more per second. L ₂ ≧ [(T ₁ −900) / 30] × V, L ₃ ≧ [(T ₁ −550) / 35] × V, L ₄ ≦ [(900−550) / 20] × V L ₂ : furnace Cooling length from outlet temperature (T ₁ ) to 900 ° C (m) L ₃ : Cooling length from furnace outlet temperature (T ₁ ) to 550 ° C (m) L ₄ : Cooling length from 900 ° C to 550 ° C (m ) V: Line speed (m / sec)

Furthermore, a heating device and a parallel flow type variable hot air cooling device are installed in a high temperature region of 900 ° C. from the heating zone exit side,
This is an apparatus for variable temperature air cooling and cooling equipment for both parallel flow and vertical flow, which has a wide range of cooling capacity in the medium temperature range from 900 ° C to 550 ° C. Moreover, in order to prevent the plate from swinging in the cooling zone,
The static pressure pad is installed in the medium temperature range from ℃ to 550 ℃.

[0008]

With this structure, the treatment material is about 110 in the heating zone.
In the cooling zone, the ultra-thin material is processed by the slow cooling method and the thick material is processed by the rapid cooling method to the normal temperature in the cooling zone to produce a stainless bright annealed product from the ultra-thin material to the thick material.

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic overall configuration diagram of a stainless steel bright annealing furnace of the present invention, and FIG. 2 is an explanatory diagram showing a structure of a cooling zone, and FIGS. 3 and 4 are drawing (creases in a transfer width direction generated when tensile strength is performed). ), And experimental data showing the limit of occurrence of bending (local bending of the plate).

The treatment material 16 which is a stainless steel strip enters the furnace through the sealing device 1 and is heated to about 1100 ° C. in the heating zone 3. The furnace length is set to satisfy the condition of σ _y / σ _t ≧ 11.4 at the highest plate temperature part in order to suppress warpage in the furnace. Next, the treatment material 16 enters the cooling zone, and in the high temperature region, first, the ultrathin material is adjusted by the adjustment cooling device 5 for heating and cooling, which enables the use of the heater 4 or the parallel flow nozzle 8b, and the squeezing and bending shown in FIG. Gentle cooling is performed in order to keep the cooling rate of 30 ° C./sec or less, which is a generation limit condition. Thick materials are passed as they are while being left to cool.

Next, in the middle temperature region, the ultra-thin material uses the parallel flow nozzle 8a and the parallel flow cooling device 9 and the throttle shown in FIG.
The cooling rate is 35 ° C./sec or less, which is the critical condition for the occurrence of breakage, so that the cooling is slow. The thick material is rapidly cooled by using the vertical flow cooling device 7. In the low temperature region, both the ultrathin material and the thick material are rapidly cooled to room temperature by the secondary cooling zone (vertical flow) 13.

Between the controlled cooling device 5 and the primary cooling zone (for both parallel flow / vertical flow) 10, in order to prevent plate runout in the furnace, N
o. No. 1 vibration prevention static pressure pad 6 was installed, and at the inlet of the secondary cooling zone (vertical flow) 13, vibration was prevented in order to prevent vibration propagation during rapid cooling below 550 ° C. 2 A vibration prevention static pressure pad 12 is installed to prevent the processing material 16 from being broken.

The adjustment cooling device 5 has a heater 4 on the inner wall surface,
By disposing the plate thermometer 15 at the inlet / outlet and the parallel flow nozzle 8b at the upper part, a smooth counterflow is obtained, and the measurement result of the plate thermometer 15 is fed back to control the temperature of the cooling gas and the temperature of the heater. Control is performed to obtain a predetermined cooling rate.

The primary cooling zone 10 for both parallel flow / vertical flow comprises a vertical flow cooling device 7 in the lower part, a parallel flow cooling device 9 in the entire length, a parallel flow nozzle 8a in the upper part, and an adiabatic furnace wall 11.
The ultra-thin material is capable of preventing breakage of the treated material by making the entire cooling zone from the parallel flow nozzle 8a a smooth hot air counter flow. The thick material is rapidly cooled by the vertical flow cooling device 7.

Incidentally, No. 1 Vibration prevention pad 6 and No. 1 Two
The vibration prevention pad 12 is a static pressure type to minimize the influence of wind. In the secondary cooling zone (vertical flow) 13, the ultra-thin material and the thick material are cooled to room temperature under the same conditions as in the conventional method.

[0016]

EXAMPLES Table 1 shows that the present invention enables high-speed processing of stainless steel strip having a thickness of 0.2 mm or less, which could not be produced in a conventional furnace or was very slow even if it could be produced.

[0017]

[Table 1]

[0018]

As is apparent from the above description, in the conventional furnace, the productivity of the ultra-thin material was poor due to the problem of breakage of the treated material, but according to the present invention, the ultra-thin material can be widely used for thick materials. It has become possible to process the plate thickness range with high efficiency.

[Brief description of drawings]

FIG. 1 is a schematic overall configuration diagram of a stainless steel bright annealing furnace of the present invention.

FIG. 2 is an explanatory diagram showing a structure of a cooling device.

[Fig. 3] Cooling condition from start of cooling to 900 ° C (0.1 mm
It is a figure which shows the generation | occurrence | production state of t), a diaphragm, and a break.

[Fig. 4] Cooling conditions from the start of cooling to 550 ° C and restriction,
It is a figure which shows the generation | occurrence | production state of bending.

[Explanation of symbols]

 1 Sealing device 2 Muffle 3 Heating furnace 4 Heater 5 Adjustment cooling zone (combined heating and cooling) 6 No. 1 Vibration Prevention Pad 7 Vertical Flow Cooling Device 8a Primary Cooling Zone Parallel Flow Nozzle 8b Adjusting Cooling Zone Parallel Flow Nozzle 9 Parallel Flow Cooling Device 10 Primary Cooling Zone (for Parallel Flow / Vertical Flow) 11 Primary Cooling Zone Furnace Wall 12 No. 2 Vibration prevention pad 13 Secondary cooling zone (vertical flow) 14 Top roll 15 Plate thermometer 16 Treatment material

Claims (2)

[Claims] 1. A thin stainless steel strip bright annealing furnace having a thickness of 0.2 mm or less, the yield stress of the treated material at the highest plate temperature part in the heating zone is 11.4 times or more the used tensile stress, and the plate is applied from the heating zone exit side. A cooling facility having a cooling rate of 30 ° C. or less per second in a high temperature range up to 900 ° C., a cooling rate of 35 ° C. or less per second in a medium temperature range from 900 ° C. to 550 ° C., and a cooling rate of 20 ° C. or more per second A thin stainless steel strip bright annealing furnace characterized in that a plate shake preventing fluid pad is provided in the temperature range of 50 ° C and 550 ° C so that a wide range of plate thickness can be processed at high speed. 2. A variable cooling air cooling device for both vertical flow and parallel flow in the moderate cooling equipment equipped with a heating device and a parallel flow type hot air cooling device in the high temperature region up to a plate temperature of 900 ° C. 2. The stainless steel strip bright annealing furnace according to claim 1, further comprising facilities.