JP3211652B2 - Roll thinning prevention agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a roll-thinning inhibitor,
In particular, the present invention relates to an agent for preventing wall thinning of a roll in a system that comes into contact with a high-temperature object and water, such as a continuous casting process of a metal and a hot rolling process.

[0002]

2. Description of the Related Art Rolls used in a continuous casting process of a metal such as steel, a hot rolling process, and the like include:
A material having high corrosion resistance such as an iron-chromium alloy is used.
Since a high-temperature object at 0 to 1200 ° C. and a low-temperature water such as cooling water are alternately contacted, a metal oxide is generated on the roll surface. The oxide dissolves in water or peels off due to physical friction, causing the roll to lose its thickness, and the roll needs to be replaced in a short time. The degree of wall thinning is also affected by the quality of the cooling water, and in particular, fluorine compounds and low pH caused by powder are factors that promote wall thinning, and particularly in a system using the cooling water in a highly concentrated state, the wall thinning is remarkable.

[0003] Generally, in continuous casting and hot rolling processes,
The direct cooling water is managed in an open circulation system. However, in order to prevent the above-mentioned wall thinning of the roll, 1.2-1.5
It is operated at a low concentration ratio of about 2 times to prevent a decrease in pH and an increase in fluorine concentration. However, even if the operation is performed at such a low concentration ratio, the prevention of wall thinning is not perfect, and the cost of water treatment increases.

[0004] In order to enhance the corrosion protection of the incidental equipment, an alkali agent such as sodium hydroxide or an anticorrosive such as a phosphate may be added to the cooling water system. In addition to the necessity, even if the above-mentioned chemicals can prevent the incidental equipment from being corroded, the effect of preventing the roll from being reduced in thickness cannot be said to be sufficient. As a roughening inhibitor for hot rolling rolls,
Silicates and borates are known (see, for example,
-108900), but they also do not always have a sufficient effect on rolls in a continuous casting process.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems by using a continuous casting process, a hot rolling process, etc. even when using cooling water having a low pH and a high fluorine concentration. Prevents thinning of rolls used in systems that come into contact with high-temperature objects and low-temperature water alternately, prolongs the life of the rolls, reduces roll repair costs, and enables the use of high-concentration cooling water. To provide a roll-thinning inhibitor capable of reducing the cost of water treatment and reducing the use of chemicals.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a hot object and C
a a water-soluble silicate (as SiO ₂ ) per 1 part by weight of a polymer of an unsaturated carboxylic acid or a salt thereof, wherein
A roll-thinning inhibitor comprising 100 parts by weight.

In the present invention, the rolls to be reduced in thickness are:
Rolls used in systems that come into contact with hot objects and water, such as the continuous casting or hot rolling process of steel and other metals. As such a roll, a roll made of an iron-chromium alloy such as an iron-chromium alloy (for example, 13 chromium steel, 18 chromium steel, etc.) and an iron-chromium-nickel alloy (for example, 18 chromium-8 nickel steel, etc.) is generally used. However, it may be made of another material.

The water that comes into contact with the roll is water containing Ca hardness, and may be a one-time cooling water, but a circulating cooling water such as an open circulation cooling water is preferred. In the case of open circulation type cooling water, the concentration ratio can be 1 to 5 times, preferably about 1 to 3 times. The water has a Ca hardness (water-soluble calcium salt) of 5 mg / l or more, preferably 10 mg / l.
Those present in mg / l are preferred.

The unsaturated carboxylic acid polymer or salt thereof, which is one of the components of the roll thinning inhibitor of the present invention, includes:
For example, homopolymers of unsaturated carboxylic acids having a polymerizable unsaturated bond such as (meth) acrylic acid, maleic acid, and itaconic acid, copolymers thereof, and copolymers thereof with other monomers copolymerizable therewith. Polymers or water-soluble salts such as sodium salts thereof are exemplified.

The other copolymerizable monomers include the following:
For example, vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, alkyl (meth) acrylate,
-Hydroxyethyl (meth) acrylate, isobutylene, etc., which are copolymerized at 50 mol% or less.

The above polymer has a number average molecular weight of 200 to 2
It is preferably from 000, preferably from 300 to 15,000, more preferably from 500 to 10,000.
The polymerization method is not particularly limited, and a general method such as aqueous solution polymerization can be employed.

The other component, water-soluble silicate, is M ₂ O.
It is a water-soluble salt represented by xSiO ₂ (where M is a monovalent metal), and particularly preferred is sodium silicate represented by Na ₂ O · xSiO ₂ . As sodium silicate,
Disodium monosilicate, disodium disilicate,
Na ₂ O / SiO ₂ (molar ratio) such as disodium tetrasilicate and tetrasodium monosilicate is (（) to
(2/1).

The unsaturated carboxylic acid (salt) and the silicate can be used alone or in combination of two or more.
The mixing ratio of both is 0.005 parts by weight of water-soluble silicate (as SiO ₂ ) to 1 part by weight of unsaturated carboxylic acid (salt).
To 100 parts by weight, preferably 0.01 to 20 parts by weight.

The roll-thinning inhibitor of the present invention may contain, in addition to the above two components, other additives such as other anticorrosives, other water treatment agents, and stabilizers. The roll thinning inhibitor of the present invention has a total weight of the polymer (salt) of unsaturated carboxylic acid and water-soluble silicate (as SiO ₂ ) of 5 to 500 m.
g / l, preferably 10 to 200 mg / l, can be used by adding to cooling water. In this case, the components are added to water separately or in a mixed state, dissolved and used.

When the water containing the roll-thinning inhibitor of the present invention is used as cooling water and brought into contact with a roll in a continuous casting or hot-rolling process, the formation of metal oxides is suppressed, and the thickness of the roll is prevented. You. Although the mechanism is not clear, it is assumed that a dense film mainly composed of calcium and silica is formed on the roll surface, and this film suppresses the diffusion of oxygen.

Therefore, it is important that Ca hardness is present in water, but there is no problem since ordinary cooling water has 10 mg / l or more. Especially when operating at a high concentration ratio,
Since Ca hardness is increased by concentration, it is not necessary to add Ca from the outside, but it can be added when the concentration is low.

[0017]

As described above, according to the present invention, a polymer (salt) of an unsaturated carboxylic acid and a water-soluble silicate are used as components to form a high-temperature object such as a continuous casting process and a hot rolling process. In addition to reducing the wall thickness of the rolls used in the contact system alternately with water and low-temperature water, prolonging the life of the rolls and reducing the repair cost of the rolls, and enabling the use of cooling water with a high concentration ratio, enables water treatment. A roll-thinning agent capable of reducing costs and using less drug is obtained.

[0018]

Embodiments of the present invention will be described below. Examples 1 to 20 pH 4, fluoride ion concentration 30 mg / l, Ca hardness 1
To the cooling water of 0 mg / l, the composition, the mixing ratio and the addition amount of the wall thinning inhibitor shown in Table 1 were added. On the other hand, 30mm x 50mm
A test piece made of × 3 mm 18Cr-8Ni steel was 700
After repeating the cycle of heating at 5 ° C. for 5 minutes, immersion in the cooling water and cooling, 20 times, pickling with 20% by weight of nitric acid and measuring the weight, the loss dissolved and removed as a metal oxide film was obtained. The amount was determined.

The unsaturated carboxylic acid polymers (salts) used are as follows. Mn indicates a number average molecular weight. A: sodium polyacrylate (Mn4000) B: polymaleic acid (Mn500) C: maleic acid / isobutylene copolymer (molar ratio 50 /
50: Mn 10,000) D: terpolymer of acrylic acid, 2-hydroxyethyl methacrylate and methyl acrylate (molar ratio: 83/16 /
1, Mn3,000) E: Acrylic acid-2-hydroxy-3-allyloxypropanesulfonic acid copolymer (80/20 molar ratio, Mn4
000)

The water-soluble silicate is as follows. Disodium monosilicate (Na ₂ O / SiO ₂ = 1 /
1) Disodium disilicate (Na ₂ O / SiO ₂ = 1/2) Disodium tetrasilicate (Na ₂ O / SiO ₂ = 1 /
4) Tetrasodium monosilicate (Na ₂ O / SiO ₂ = 2)
/ 1)

Comparative Examples 1 to 6 In Comparative Example 1, when the Ca hardness was 0 mg / l, in Comparative Example 2, the compounding ratio was out of the range, in Comparative Example 3, when no additive was added, and in Comparative Examples 4 to 6, each component was used alone. A similar test was performed for the case of addition.

Table 1 shows the results of each example. In Table 1,
The type of the unsaturated carboxylic acid (salt) is indicated by the above symbol, the type of the silicate is indicated by the above Na ₂ O / SiO ₂ molar ratio, and the compounding ratio is the weight ratio of the polymer (salt) and the value in terms of SiO _2. The amount of addition indicates the total weight of the polymer (salt) + SiO ₂ conversion value, and the loss of the test piece is expressed in mg per 100 cm ² of the surface area.

From the results shown in Table 1, it can be seen that the results of the examples show an excellent effect of preventing wall thinning as compared with the comparative examples.

[0024]

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-108900 (JP, A) JP-A-8-39109 (JP, A) JP-A-8-41486 (JP, A) 288916 (JP, A) JP-A-8-67895 (JP, A) JP-A-7-178523 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 28/02 B22D 11 / 124 B22D 11/128 340 F16C 13/00

Claims (1)

(57) [Claims] A roll-thinning inhibitor for a roll which comes into contact with a high-temperature object and water containing Ca hardness, wherein a water-soluble silicate (SiO 2) is added to 1 part by weight of an unsaturated carboxylic acid polymer or a salt thereof. ₂ as) 0.005 to
A roll-thinning inhibitor comprising parts by weight.