JP2888133B2 - Continuous casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates relates to a continuous Casting method, in particular, to prevent the clogging of the secondary cooling water sprinkler nozzle or strainer continuous casting equipment, possible to carry out uniform and stable watering over time It relates to a continuous casting method and.

[0002]

2. Description of the Related Art Continuous casting (continuous c)
asting) is a slab or billet of rolling material,
Alternatively, it is a method of continuously and directly manufacturing a product having a simple sectional shape such as a round bar from molten steel. Specifically, molten steel is poured into a water-cooled mold without a bottom to solidify the outer shell (the water used for cooling the water-cooled mold is referred to as “primary cooling water”). This is a method in which cooling water is sprayed directly onto the ingot and water-cooled and solidified (water sprayed for this water-cooled solidification is referred to as "secondary cooling water"), which is cut into required lengths to produce products. Widely used in both ferrous and non-ferrous metals.

[0003] In the step of water-cooled solidification using secondary cooling water in such a continuous casting facility, a number of rolls for drawing an ingot from a water-cooled mold and a number of rolls (normally disposed) are arranged between the rolls. Hundreds of small diameters (usually 1
Although a secondary cooling water spray nozzle is provided, there is a problem that the secondary cooling water spray nozzle is easily clogged, and it is difficult to secure uniform and stable water spray. In addition, the secondary cooling water is often filtered with a filter together with the return water of the cooling water in other parts of the continuous casting facility, then cooled in a cooling tower, and used for circulation. There is also a problem that the strainer provided in the cooling water system is blocked, and the flow rate of the cooling water is reduced due to the blocked strainer.

The cause of the blockage of the secondary cooling water spray nozzle and the strainer is contamination in the cooling water system due to the following factors.

In-system contamination due to precipitation of dissolved salts Continuous casting powder is used in the process, and fluorine and calcium, which are components in the powder, are mixed into spray water (secondary cooling water), hardness in industrial water. Due to the concentration of the components and the presence of dissolved iron in the secondary cooling water due to equipment material corrosion, scale precipitation containing iron oxide, calcium fluoride, and calcium carbonate as components is observed.

[0006] In-system contamination by suspended substances Mill scale, continuously cast powder contaminants, and machine oil are mixed as suspended substances. That is, as described above, the secondary cooling water is often filtered and reused by a filter, but even after the filtration treatment, these contaminants often remain as suspended substances. This causes contamination in the system.

[0007] In-system contamination by slime Since the system is mixed with machine oil and the like, slime is easily generated. The generated slime also functions to promote the adhesion of suspended substances in the system to release the sticky substance.

Conventionally, in order to prevent such in-system contamination, treatments for individually suppressing the causes of in-system contamination described above have been proposed. There are also measures such as a slime peeling treatment by adding a high concentration of a chlorine agent and a removal of inorganic deposits by acid washing.

[0009]

However, the conventional pollution control treatment has the following problems in reducing the degree of contamination.
Although a certain effect is observed, the contamination is not completely eliminated, and unprocessable stains remain. In addition, it is impossible to prevent the remaining dirt from accumulating with time and causing trouble such as nozzle blockage.

In particular, in the secondary cooling water sprinkling nozzle, the secondary cooling water supplied from one water supply pump is supplied to several hundred nozzles having a very small diameter of about 1 mm at the end. Therefore, in an ordinary open circulating cooling water system, contamination (tolerance of 10 mg / cm ² at an adhering rate) is allowed.
/ One month), since the nozzle structure is more likely to be clogged due to the structure of the equipment as the nozzle clogs, the problem of clogging of the nozzles and the like cannot be solved by processing in which dirt remains.

On the other hand, in a cleaning treatment using a chlorine agent or an acid, a cleaning effect appears in a short time (within one day), and a large amount of peeled material is immediately generated by the cleaning. There is a problem of blocking the nozzle.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem of blockage of the conventional secondary cooling water system strainer and water spray nozzle, while suppressing contamination in the secondary cooling water system of the continuous casting equipment.
Already an object of the present invention to provide a granulation method continuous casting it can be gradually peeled off dirt adhering.

[0013]

Means for Solving the Problems] Continuous Casting process of the present invention,
A scale inhibitor having a dissolving power with respect to calcium and / or iron, chloromethyl isothiazolone, methylene bis thiocyanate Ne - DOO, bromonitro propanediol - le, Luz <br/> lime such than benzisothiazoline or dichloro dithiolane Sprinkle the cooling water with the control agent into the ingot.
It is characterized by racing .

Hereinafter, the present invention will be described in detail.

[0015] The onset Oite bright, the scale inhibitor having a dissolving power with respect to calcium and / or iron, dissolving the already adsorbed calcium and / or iron scale is precipitated in the system And phosphonic acids such as hydroxyethylidene diphosphonic acid.

On the other hand, slime control agents include
Chloromethyl isothiazolone, methylene bis thiocyanate, bromonitro propanediol, benzo isothiazoline, or dichloro dithio run-used. These slime control agents gradually exert their effects after being adsorbed on the dirt components in the system.

In the present invention, the contents of the scale inhibitor and the slime control agent are expressed in terms of weight ratio,
Scale inhibitor: slime control agent = 50: 1 to 1
The ratio is preferably 1: 1, especially 20: 1 to 5: 1.

In the present invention, the scale inhibitor and the slime control agent are intermittently (for example, a fixed amount is periodically injected) into a secondary cooling water system for spraying an ingot .
Alternatively, by injecting continuously (for example, low-concentration drug injection is always performed), dissolution of scale by the scale inhibitor and slow cleaning (dispersion cleaning) of contamination in the system by the slow-acting slime control agent can be achieved. In addition, a good blocking prevention effect can be obtained without causing a blockage failure of a nozzle or the like due to the washed and peeled material.

In the present invention, the dose of the scale inhibitor and the slime control agent is usually 1 to 100 mg / l, preferably about 10 to 50 mg / l, for the total active ingredient concentration in the aqueous system. It is preferable to do so.

[0020]

As mentioned above, in the dirt component of the secondary cooling water system, dissolved salts are precipitated and inorganic crystallization substances adhered in a crystalline form, and organic substances due to slime are entrapped by these adhesion phenomena. There is a suspended substance (SS). The actual form of adhesion of these dirt components is based on inorganic crystallization,
The organic matter by the slime is the one that embraces the suspended substance and adheres and grows.

The strainer and the nozzle are clogged by the detachment cleaning of such deposits because the crystallized substance serving as a nucleus is coarse, the cleaning is rapidly performed in a short time, and the concentration of the detachment increases. It depends.

Therefore, as a measure for preventing clogging, the crystallized substance is reformed and decomposed into small lumps, and the adhered substance is gradually removed by washing without using a fast-acting slime remover such as a chlorine agent. It is possible.

In the present invention, calcium and / or calcium constituting the inorganic crystallization in the secondary cooling water system of the continuous casting facility are used.
Or by a scale inhibitor having a dissolving power for iron,
The inorganic crystallization is modified and broken down into small lumps.

At the same time, the above-mentioned specific slow-acting slime control agent, which gradually exerts a cleaning effect after being adsorbed on the dirt component, provides an appropriate cleaning effect for a long period of time without causing a sharp increase in the concentration of the washed-off material. Can be obtained.

On the other hand, as described above, the fast-acting slime control agent causes a blockage failure due to the generation of a large amount of washed-off materials in a short period of time, and also has a high reaction rate and a high consumption rate. However, the effect cannot be maintained.

[0026]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 A 100 mesh SUS304 cylindrical wire mesh was immersed in an actual secondary cooling water flow path of a continuous casting facility and allowed to flow for one month, thereby producing a test piece to which dirt adhered as described below. did. The test piece has a diameter of 20 mm and a length of 50 mm.
mm.

Test piece Amount of attached matter: 200 to 300 mg (calculated as an attaching speed: 10 to 15 mg / cm ² / one month) Composition of attached matter (% by weight): CaO = 18.0 Fe ₂ O ₃ = 47.8 Fluorine = 6 5.5 CO ₂ = 5.0 Acid-insoluble content = 8.2 Ignition loss = 15.7 The surface of the adhered substance was viscous, but CaCO ₃ and CaF ₂ adhered to the crystallization scale Was also confirmed.

Each 1 liter of the actual secondary cooling water was placed in a 1 liter beaker, and after suspending the test piece, the respective chemicals shown in Table 1 were added in the amounts shown in Table 1 and stirred with a stirrer for 10 days. did. The test water was changed daily and the drug was added only during the first and fifth day test water preparation. The quality of the test water is as follows.

Water quality of test water pH: 7.1-8.1 Electric conductivity: 500-800 μS / cm M alkalinity: 40-80 mg-CaCO ₃ / l Calcium hardness: 40-90 mg-CaCO ₃ / l SiO ₂ : 40~50mg-SiO ₂ / l total iron: 0.1~2.0mg-Fe / l fluorine: 30~55mg-F / l SS: 3~10mg / l number of bacteria: 1.4~3.6 × 10 ⁵ pieces / ml The weight of the test piece before and after the test was measured to calculate the stain removal rate, and the naked eye was observed to determine the effect of each drug. The results are shown in Table 1. The criterion for the determination was that the removal rate was less than 20% × 20 to 50% △, 51 to 84% 、,
85% or more.

[0031]

[Table 1]

As shown in Table 1, according to the present invention, the combined use of a scale inhibitor and a slow-acting slime control agent allows the adhered scale to be peeled off and the scale to be prevented from adhering with a good dispersion cleaning effect. Is evident.

Example 2 Based on the results obtained in Example 1, HEDP / Cl-MI
A treating agent having a T of 19: 1 (weight ratio) was prepared, and the following actual system test was performed using the treating agent.

* Purpose: Water supply pipe (SUS-304 material)
Confirmation of the effect of peeling and cleaning of the sediment scale. The scale composition and feedwater quality are as follows.

Scale (appearance: black-brown layered) composition (% by weight) CaO: 15.5 Fe ₂ O ₃ : 37.0 Fluorine: 9.5 CO ₂ : 4.6 Acid-insoluble matter: 10.8 Loss on ignition : 22.3 Feed water quality pH: 7.1-8.3 Electric conductivity: 500-800 μS / cm M alkalinity: 40-80 mg-CaCO ₃ / l Calcium hardness: 40-90 mg-CaCO ₃ / l SiO ₂ : 40~50mg-SiO ₂ / l total iron: 0.1~2.0mg-Fe / l fluorine: 30~55mg-F / l SS: 2~14mg / l cell count: 1.0 to 3.5 × 10 ⁵ pcs / ml * Chemical injection condition: Inject 20mg / l of treatment agent into water for 2 hours every 3 days * Test period: 45 days As a result, scale of 2mm thickness adhered in the past 5 years peeled off after 45 days Washed, in stainless steel piping It was so clean that the surface of the surface was clearly visible.

Throughout this test period, no phenomenon was observed that clogging of the strainer and the nozzle was promoted, and it was judged that the exfoliated material accompanying the dispersion washing was dispersed into fine particles and passed smoothly through the strainer and the nozzle. .

[0037]

As detailed above, according to the present invention, according to a continuous Casting method <br/> of the present invention, by effectively preventing the clogging of the strainer and watering nozzle in continuous casting equipment secondary cooling water system for a long time, Uniform and stable watering can be reliably performed.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/50 532 C02F 1/50 532H 532J 532K 540 540B 5/08 5/08

Claims (1)

(57) [Claims] 1. A and scale inhibitor having a dissolving power with respect to calcium and / or iron, chloromethyl isothiazolone, methylene bis thiocyanate Ne - DOO, bromonitro propanediol - le, such than benzisothiazoline or dichloro dithiolane Luz Cooling with lime control agent
Continuous Casting Method, characterized in that spray water on the ingot.