JPS5941482A - Apparatus for removing scale of stainless steel strip - Google Patents

Abstract

PURPOSE:To remove scale without damaging the surface properties of a stainless steel strip, by further passing the stainless steel strip having oxide scale adhered to the surface thereof through a specific rolling machine, a scale breaker, a grinding brush and a pickling tank. CONSTITUTION:A stainless steel strip 1 having scale formed on the surface thereof by hot rolling or annealing treatment is at first passed through a rolling machine 2 capable of taking a draft of 2% or more. The rolled strip is subsequently passed through a scale breaker 3 to be subjected to three times or more of bending processings and surface stress of 10% or more in total is imparted thereto to perform the breakage and partial peeling of scale. Thus treated steel strip is passed through a pickling tank 4 having a pickling liquid comprising sulfuric acid alone or a mixed liquid of sulfuric acid and fluoric acid or nitric acid and fluoric acid received therein and subjected to surface treatment by a grinding brush 5 comprising wires containing grinding particles and rotating at a high speed to mechanically remove scale and the resulting steel strip is finally passed through a pickling tank 4a to perfectly dissolve and remove the residual scale.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scale removal device that can efficiently remove scales from stainless steel strips caused by hot rolling and annealing without causing surface defects.

In the case of steel/stainless steel, scaling occurs due to hot rolling and annealing.
・Since steel is thicker (and denser) than ordinary steel, even if you try to remove it by direct pickling, the penetration of the acid will be suppressed, and the dissolution of the base metal will also be restricted, resulting in an extremely low removal efficiency.For this reason, conventional methods When removing scale from stainless steel strips, mechanical pretreatment is applied before pickling to create two scales.
The crack allows acid to penetrate easily.

Conventionally, shot blasting was generally used as this mechanical pretreatment. However, even after cold rolling, it is completely erased, and remains as a serious surface defect called glitter (also called gold dust), which deteriorates the puff properties of the product. A method has been proposed to use a scale breaker-2, which applies strong bending strain to the steel and causes cracks on the scale.However, although this scale breaker solves the above drawbacks, it does not improve production efficiency. Since the scale removal method is inferior to shot blasting, the cost of scale removal increases, and the overall result is not necessarily satisfactory.Finally, the present invention is aimed at improving quality in view of the above-mentioned drawbacks of conventional scale removal methods. The present invention provides a descaling device that is productively satisfactory.

The apparatus of the present invention is shown in FIG. The scale is placed in tandem with a scale breaker 3 for pretreatment, and the scale is first crushed by a rolling mill 2, and then the crushed scale is destroyed and partially peeled off by a scale bunker 3. In the pickling process (in the case of scale breaker 3, 2
A grinding brush 5 and a grinding brush 5 are installed between the pickling tanks (4.4a...) and the pickling tanks (7) to increase the efficiency of scale removal.

Although the rolling mill 2 and the scale breaker 3t'i that constitute the pretreatment process of the present invention have a scale breaking action, the action of the scale brake 77 of both is not the same. In other words, the former has a large crushing action, so it can crush the scale finely, but the peeling action is small. On the other hand, the latter utilizes bending by rolls, so the crushing effect is small and the crushed pieces become thicker, but the peeling effect is large.

Therefore, although either one alone cannot exert a large scale-breaking effect, if the two are combined as in the present invention, the scale-breaking effect becomes large.

In addition, in order to increase the scale breaking effect using only rolling mill 2, it is necessary to increase the rolling reduction rate (・However, if the rolling reduction rate is increased too much, work hardening of the metal will occur,
In addition to the later hindrance to cold rolling, there is also a lot of scale encroachment (which causes damage to the metal and rolls).

Similarly, if you try to make the scale breaking action more convenient with only scale breaker 3, you have to make the bending strain thicker, so you have to increase the size to be able to handle thick gauges, which increases the equipment cost. If the surface distortion is large, the risk of fracture of the weld will be high. Therefore, if the construction is made as in the case of the present invention, the rolling reduction by the rolling mill will be a light reduction of 1, and the bending distortion will also be reduced. Need to make it bigger7
Z.

For this reason, the rolling mill 2 according to the present invention only needs to be capable of achieving a reduction rate of 2% or more, and the scale breaker 3 is not a large one, and the rolling reduction rate is 10% in total by bending three or more times. In the case of the present invention, two or more pickling tanks 4.4a...χ are arranged after the scale breaker 3, and there is a Grinding brushes 5 are further placed at these locations, but the reason for placing the grinding brushes 5 between the tanks is that if they are placed immediately after the school breaker, clogging will occur and the scale removal ability will be reduced. This is because once scale-broken items are pickled, the bonding force between the scale and the base metal is weakened, making removal easier.
The reason for arranging two or more of 4a is to facilitate scale removal by the grinding brush 5 as described above, and also to remove smut and passivate the base metal after removing scale.

The acid used in the pickling process 4.4a... may be simple sulfuric acid, a mixed acid of sulfuric acid and hydrofluoric acid, or a mixed acid of nitric acid and hydrofluoric acid, which have been conventionally used.

As the material grinding brush 5, it is preferable to use a roll type abrasive material in which a nylon wire with a thread diameter of LO to 2.5 mm is impregnated with abrasive grains of 11:60 to #l:240. A motor is directly connected to the roll shaft and rotated at a rotation speed of 800 to 1200 rpm to grind a stainless steel strip 1 with surface imperfections Φ.

Other desk-type cutters with similar effects can also be used as the X-grinding brush 5, but according to actual usage results, wire-fed cutters such as the one described above The things I do are excellent.

Table 1 shows the combinations with and without the use of the rolling mill, scale breaker, shot blast, pickling tank group, grinding brush, etc.
AT type scale removal equipment is shown. Among these, device/1
61 represents the configuration of the present invention.

Table 2 shows 5US43 for each scale removal device shown in Table 1.
0. After removing scale from the stainless steel hot rolled strip steel and 1. removing the rough Rz and school on the surface of the hot rolled steel strip in this case, cold rolling and annealing are further carried out. 1. Appearance of the strip surface as a final product. situation? It can be seen that the product using the uninvented device AI does not make the surface rough and the final product has a good appearance.

Table 1 (Note 1) ○: Used, ×: Not used.

(Note 2) Reduction rate of rolling mill is 2% or more.

(Note 3) Edge surface strain given by scale breaker 10
%that's all.

(Note 4) At: Nitric acid 10 for both h and /162 pickling tanks
% and hydrofluoric acid about 1.0%.

(Note 5) Grinding brush is #10 on wire with thread diameter 12■ψ.
A roll containing 0 abrasive grains (ψ-=300 fl
lin)'a? 1200 rpm rotation.

Table 2 (Note 1) The glitter quality was determined by pasting a viscous tag on the surface of the final steel strip, peeling it off, and examining the glitter-like defects 2 that remained behind. A and B are good, C and below are bad.

(Note 2) Puffability is determined using the same band steel method Ifi'v as above.
I polished it with paper and examined the finish. B or higher is good, C or lower is poor.

In addition, Figure 2 shows the various combinations ρ) and phrases 5 shown in the third precept.
When SUS 430 stainless steel hot-rolled strip is passed through various types of scale removal equipment, the pickling time required for scale removal in each equipment is determined. Devices/161 to 4 in Table 3 are the same as those in Table 1 above, with the addition of device iWi 5'aj.

Device/I65 is an addition to the device/I61 that was not invented, and is intended to clarify the difference in pickling time when there is no grinding brush between the pickling tanks of device/161. be. That is, according to Figure 2, the uninvented equipment @/
In the case of No. 161, the required pickling time is significantly longer than any of the other devices of /162-5.

The pickling time required for the uninvented device /I61 is 60 seconds, while that for the device /165, which only has no grinding brush during pickling, is 140 seconds, and the difference between the two is 86 seconds.
There are also seconds.

Incidentally, the conditions for the required pickling time and the equipment shown in Table 1 in Figure 2 are the same as (Note 1) to (Note 5) in Table 1.

Table 3 and Table 4 show three types of scale removal devices A66 to A68 in addition to the device of the present invention, in which the mechanical treatment process is carried out in the same way as the device of the present invention, but chemical acid When the washing and grinding brush processes are changed, no school removal performance is shown. In other words, 5LJS4
30 stainless steel hot-rolled strip steel was passed through the plate, the scale removal ability of the surface of the hot-rolled steel strip was determined at the rear of each device. We investigated the relationship between the arrangement of the pickling tank and the grinding brush, and scale removal performance, and found that after the mechanical treatment process, it is important to first immerse the surface in the pickling tank and then grind it with the grinding brush. This shows that placing the grinding brush between the pickling tanks is most desirable for scale removal.

Table 4? The conditions for each device in Table 4 are the same as (Note 1) to (Note 5) in No. iH-.

As described above, according to the apparatus of the present invention, scale can be removed efficiently and with high productivity, and the quality of the steel strip as a final product is improved due to its extremely excellent scale removal properties. Therefore, the manufacturing yield is greatly improved, which greatly contributes to reducing the cost of removing scale.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the device of the present invention;
FIG. 2 is a graph showing the pickling time required for various scale removal devices. 1... Stainless steel strip, 2... Rolling machine, 3... Scale breaker-14, 4a... Pickling tank, 5...
・Grinding brush patent applicant Nisshin Steel Co., Ltd. Hitachi Ltd. Agent Shindo Mitsuru 10th continuation @ Applicant Hitachi Ltd. 5-1 Marunouchi-chome, Chiyoda-ku, Tokyo

Claims (1)

[Claims] A rolling mill capable of achieving a reduction rate of 2% or more on stainless steel strip, and a rolling machine that is capable of rolling the stainless steel strip with a rolling reduction ratio of 2% or more. a scale breaker for pickling the steel strip processed by the breaker; and two or more pickling tanks for pickling the steel strip processed by the breaker (and a grinding brush installed at at least one location between the pickling tanks). A stainless steel band descaling device characterized in that it is provided with: