JPH1161466A - Production of stainless steel strip having excellent surface characteristic, and continuous annealing and pickling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stainless steel strips having excellent surface characteristics by interposing a pass material between the steel strips of different kinds, subjecting this pass material to annealing and pickling in compliance with treatment conditions of the succeeding steel strip and subjecting the pass material to descaling without using an acid downstream of the pickling stage. SOLUTION: A high-pressure water descaling device 13 is disposed downstream of a rinsing section. The nozzle header 31 of this descaling device 13 is provided with many injection nozzles 32. The high-pressure water of >=100 kgf/cm<2> is supplied from a high-pressure water pump 34 through high-pressure piping 33. At the time of changing over from an SUS 304 stainless steel to an SUS 430 stainless steel, SUS 304 is used for the path material between both. According to this process, the inevitable contamination by the unpickled oxide powder of line supporting rolls by the path material accompanying the steel kind change from the SUS 304 system to the SUS 430 system is prevented and the stainless steel strips having an excellent surface quality may be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous annealing pickling method and a continuous annealing pickling apparatus for a cold rolled stainless steel strip.

[0002]

2. Description of the Related Art Generally, a cold-rolled stainless steel strip is subjected to continuous annealing and pickling for the purpose of, for example, removing work hardening after cold rolling to obtain desired surface quality and mechanical properties. FIG.
Shows an example of a continuous annealing pickling apparatus used for this purpose. The processing flow of the stainless steel strip S will be described with reference to FIG. The steel strip S paid out from the pay-off reel 1 is sent to the annealing furnace 4 and the cooling zone 5 through the cleaning tank 2 and the entrance looper 3, and undergoes a predetermined heat treatment. afterwards,
A pickling tank 6 for dissolving and removing oxides generated in the annealing furnace 4,
After passing through 7 and 8, the acid solution is removed by the rinsing section 9 and then passes through the exit side looper 10, temper rolling is performed by the temper rolling mill 11, and then wound on the tension reel 12. Pickling tank 6,
The types of acids constituting 7, 8 are H ₂ SO ₄ , HNO ₃ ,
Various acids such as HF or salt bath and combinations thereof have been proposed and used. For example, in the Handbook of Stainless Steel (1973), pages 841-842, published by Nikkan Shimbun, the acids used for pickling include nitric acid, hydrofluoric acid, sulfuric acid, hydrochloric acid and phosphoric acid. It is used for pickling stainless steel, hydrochloric acid and hydrofluoric acid are often used as mixed acid with nitric acid, and continuous pickling method combined with electrolytic pickling is used in stainless steel strip manufacturing plants. It is described that it is often used, that it is desirable to perform the final nitric acid washing in addition to the passivation treatment in finish pickling, and that it is more difficult to pickle a Cr-based material than a Ni-Cr-based material. ing.

[0003] In continuous annealing pickling, it is common to treat both Ni-Cr stainless steel such as SUS304 stainless steel and Cr stainless steel such as SUS430 stainless steel having different properties in the same line. is there. In such a case, for example, a neutral salt (Na ₂ SO ₄ ) electrolytic tank, a nitric hydrofluoric acid (mixed acid) tank, and a nitric acid electrolytic tank are provided downstream of the annealing furnace, and the following treatment is performed.

SUS304 series: Annealing 1100-1150 ° C Pickling Neutral salt electrolysis, nitric hydrofluoric acid (mixed acid) pickling, nitric acid electrolytic pickling SUS430 series: Annealing 800-850 ° C Pickling Neutral salt electrolysis, nitric acid electrolytic pickling Therefore, the annealing temperature is changed for both, so that the entire bath is used in the SUS304 series, and the nitric hydrofluoric acid (mixed acid) pickling is bypassed in the SUS430 series.

[0005]

The conventional continuous pickling of stainless steel has the following problems. In the continuous annealing and pickling apparatus for stainless steel, since both SUS304 stainless steel and SUS430 stainless steel are treated, the following problems occur. The annealing temperature of SUS304 stainless steel is 1100 to 1150 ° C, and SUS43
The annealing temperature of type 0 stainless steel is around 800 to 850 ° C. Nitric hydrofluoric acid (mixed acid) is often used for pickling SUS304 stainless steel, and it is said that mixed acid is essential. On the other hand, when nitrous hydrofluoric acid is used, the surface of the SUS430 stainless steel strip has a problem that the surface is severely eroded by the acid and the surface quality is impaired. Therefore, in order to switch between SUS304 stainless steel and SUS430 stainless steel during the operation to perform the annealing and pickling treatment, it is necessary to change the temperature setting of the annealing furnace and the pickling conditions.

[0006] A dummy material (referred to as a sheet passing material) that does not become a product when continuous annealing and pickling are performed by switching such different stainless steels is inserted between products.
During this time, it is common to adjust the furnace temperature and switch the pickling conditions. This passing material is made of SUS so that it can withstand high temperatures.
304 series stainless steel is used. Since this sheet passing material is also heated like a product, an oxide is generated on the surface.

[0007] When the next product in such a continuous annealing and pickling process is SUS430 stainless steel, it is necessary to remove nitric hydrofluoric acid from the acid bath or to make it unused.
As a result, the oxide formed on the surface of the sheet passing material is wound on a tension reel via a rinse section and an outlet looper without being pickled. As a result, each support roll in the outlet looper comes into contact with the surface of the sheet passing material covered with the oxide, and is contaminated with fine oxide powder. This oxide powder accumulates on the roll surface without being removed, and after being accumulated in a certain amount, is conversely transferred to the product surface,
It also caused the surface to be contaminated and to create pit-like defects on the surface.

It is an object of the present invention to provide a method for producing a stainless steel strip having excellent surface properties and a continuous annealing and pickling apparatus, in which such disadvantages are eliminated.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its technical means is to carry out continuous annealing and pickling of different kinds of stainless steel strips by using different kinds of steels. Passing a strip material between the strips, annealing and pickling the strip material in accordance with the processing conditions of the succeeding steel strip, and performing descaling without using an acid downstream of the pickling step on the strip material. This is a method for producing a stainless steel strip having excellent surface properties.

[0010] SUS304 stainless steel is used as the pass-through material, and the descaling without using the acid is such that the leading steel strip is SUS304 stainless steel and the succeeding steel strip is SUS304 stainless steel.
It may be performed for 430 series stainless steel. The apparatus of the present invention that can suitably carry out the method of the present invention is a continuous annealing pickling apparatus for a cold-rolled stainless steel strip,
A descaling device that does not use a chemical such as an acid is installed downstream of the pickling device.

It is preferable that the descaling apparatus is provided with a water spray nozzle having a nozzle pressure of 100 kg / cm ² or more on the upper and lower surfaces of the steel strip. Nozzle pressure 10
The reason why it is set to 0 kg / cm ² or more is that if it is less than 100 kg / cm ² , the cleaning effect is poor. A method of spraying an acid solution with a nozzle until the sheet material is switched to a product has been considered, but the acid solution adheres to the roll, which causes contamination of the product surface. I found something. In the case of descaling using high-pressure water, it was confirmed that there was no problem in quality even if the product surface was sprayed, and the present invention was completed.

[0012]

FIG. 1 is a flow sheet showing an embodiment of the present invention. In the embodiment shown in FIG. 1, reference numeral 6 denotes a neutral salt electrolytic cell, 7 denotes a nitric hydrofluoric acid tank, and 8 denotes a nitric acid tank. The present invention is applied to the rinsing section 9 of the conventional apparatus shown in FIG. 4, and specifically, a descaling apparatus 13 using high-pressure water is provided downstream of the rinsing section 9 as shown in FIGS. FIG. 2 shows details of the descaling device 13. A number of high-pressure water injection nozzles 32 were provided on the header 31, and high-pressure water of 100 kgf / cm ² or more was supplied from a high-pressure pump 34 through a high-pressure pipe 33. From SUS304 stainless steel to SUS430
The present invention was applied when switching to stainless steel. At this time, SUS304 is used as a passing material between SUS304 stainless steel and SUS430 stainless steel,
During the pickling, the nitric acid solution in the nitric acid tank 7 was extracted from the tank. The evaluation was made based on the amount of oxide on the surface of the threaded material in front of the temper rolling mill 11 and the result of a visual inspection of the support roll surface 100 times after changing the steel type. Table 1 shows the results.

[0013]

[Table 1]

Based on the results shown in Table 1, the nozzle header 14
Was determined to be 100 kg / cm ² or more. A large number of spray nozzles 32 were attached to the nozzle header 31 so that the spray water could hit the entire width of the steel strip S. Although structurally is generally similar to the spray nozzle pressure 2 to 10 kg / cm ² to be used for the purpose of cleaning or the like, for securing the pressure resistance, the thickness depending on the material properties using 100 kg / cm ² It was selected to withstand the above pressure, processed and used.

[0015]

According to the present invention, the surface of a sheet passing material as a dummy material is washed with a high-pressure water spray of 100 kg / cm ² or more, so that SUS304 stainless steel can be used.
It is possible to prevent inevitable contamination due to unpickled oxide powder of the line support roll with the passing material due to the change of the steel type to 430 series stainless steel or the like, so that a stainless steel strip with excellent surface quality can be manufactured. Became.

Further, since the space between the pickling section and the tension reel can be kept clean at all times, deterioration of the surface of the line support roll can be prevented, and the effect of extending the life can be obtained.

[Brief description of the drawings]

FIG. 1 is a flow sheet of an example.

2A is an elevation view and FIG. 2B is a side view showing an example of application to a stainless steel continuous annealing and pickling facility.

FIG. 3 is an overall flow sheet to which the present invention is applied.

FIG. 4 is a conventional overall flow sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Payoff reel 2 Cleaning tank 3 Inlet looper 4 Annealing furnace 5 Cooling zone 6 Pickling tank (neutral salt electrolytic tank) 7 Pickling tank (nitric acid hydrofluoric acid tank) 8 Pickling tank (nitric acid tank) 9 Rinse part 10 Out Side looper 11 Temper rolling mill 12 Tension reel 13 Descaling device 31 Nozzle header 32 Injection nozzle 34 High pressure water pump 35 High pressure pipe

 ──────────────────────────────────────────────────の Continued on the front page (72) Takashi Sato, Inventor, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Inside the Chiba Works of Steel Corporation (72) Inventor Yukihiro Baba 1, Kawasakicho, Chuo-ku, Chiba-shi, Chiba Kawasaki Inside the Chiba Works

Claims (4)

[Claims] 1. A method for continuously annealing and pickling different stainless steel strips, wherein a sheet passing material is interposed between the different kinds of steel strips, and the sheet passing material is annealed in accordance with the processing conditions of the succeeding steel strip. A method for producing a stainless steel strip having excellent surface properties, wherein the sheet passing material is subjected to descaling without using an acid downstream of the pickling while being pickled. 2. The passing plate material is made of SUS304 stainless steel. In the descaling without using the acid, the leading steel strip is SUS304 stainless steel and the succeeding steel strip is SUS43 stainless steel.
2. The method for producing a stainless steel strip having excellent surface properties according to claim 1, wherein the method is carried out when using a type 0 stainless steel. 3. A continuous annealing and pickling apparatus for a cold-rolled stainless steel strip, wherein a descaling apparatus which does not use a chemical is installed downstream of the pickling apparatus. Annealing pickling equipment. 4. The stainless steel having excellent surface properties according to claim 3, wherein said descaling device is provided with a water spray nozzle having a nozzle pressure of 100 kg / cm ² or more on upper and lower surfaces of a steel strip. Continuous annealing pickling equipment for steel strip.