JPH0765201B2 - Descaling composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention makes it easy to remove scale that has already been generated on the surface of a metal substrate by applying it to the surface of the metal substrate during or before the heat treatment. The present invention relates to a composition for removing scale.

[Problems of the Prior Art and Invention] Since a metal substrate such as a high temperature slab in continuous casting or a high temperature coil after hot rolling is usually exposed to an air atmosphere,
The surface of the substrate is extremely easily oxidized, and scales of metal oxide are generated. After cooling, the scale generated on the metal surface is removed by means such as pickling.For example, the scale generated when stainless steel is heated is dense and hard because it contains a lot of non-ferrous components, so it is very difficult to remove the scale. Is.

Therefore, in order to completely remove such scales, it takes a long time for the pickling treatment, which causes a problem that the production efficiency of metal products is significantly reduced.

[Means for Solving the Problems] The present invention is a composition containing a flux component having a specific melting temperature, a filler containing a specific alkali metal or alkaline earth metal compound or salt, and an attacking agent containing a specific compound or salt. To find a phenomenon in which the scale has a function of making the scale easy to remove by mechanical peeling and / or pickling by applying this to a high temperature slab or a metal substrate surface during or before heat treatment. It has been completed.

That is, the scale removing composition according to the present invention comprises (A) a flux component having a melting temperature of 1000 ° C. or lower, (B) an alkali metal or alkaline earth metal carbonate,
A filler comprising one or a combination of two or more selected from the group consisting of hydroxides and oxides, and (C) a halogen-containing compound, nitrate, nitrite, sulfate, sulfite and phosphate 1 composed and selected from the group
It comprises a scale attack agent composed of one kind or a combination of two or more kinds.

[Operation] Of the three components constituting the scale-removing composition of the present invention, first, regarding the flux component (A), when the composition is applied to a heat-treated metal substrate having a scale layer on the surface, The component (A) is rapidly melted by the heat of the substrate to form a glassy coating layer. When the component (A) is applied to a high temperature slab in continuous casting, a vitreous coating layer is formed as above. Further, when the composition is applied to the metal substrate before the heat treatment, the component (A) is melted in the next heat treatment step to form a glassy coating layer.

Further, the filler component (B) is dissolved in an acid to improve acid permeability when the metal substrate after heat treatment is pickled.
The acid acts as a penetrating medium, and the acid penetrates the scale layer through the coating layer of the composition of the present invention through this filler, and the coating layer and the scale are peeled and dissolved together with the scale to be removed.

Further, the scale attack agent component (C) is melted or decomposed by heating alone or in a molten flux,
Attacks the scale on the metal surface to weaken the scale layer,
The scale is captured in a form that is easily mechanically peeled or a form such as iron halide that is easily removed by pickling.

Thus, by applying the composition to the surface of the metal substrate having the scale layer, the scale can be easily removed mechanically by peeling and / or pickling, which greatly improves the production efficiency of metal products such as steel plates. Can be made.

[Preferred Embodiment of the Invention] (A) Flux component As the flux component in the composition for removing scale of the present invention, for example, SiO ₂ as a main component, Al ₂ O ₃ , Fe ₂ O ₃ , CaO, Mg
O, Na ₂ O, B ₂ O ₃ , TiO ₂ , P ₂ O ₅ , ZnO, BaO, glass compositions containing oxide components such as PbO, K, Na, Li, Ca, Mg, Mn, Examples thereof include phosphates and borates of metals such as Al and Fe, and boric acid, and those having a melting temperature of 1000 ° C. or less, particularly in the range of 400 to 800 ° C. are used.

If the melting temperature is higher than the above range, it becomes difficult to form a glassy coating layer when applied to the surface of the metal substrate during heat treatment, and the effect of the scale attack agent is reduced.

The slacks component (A) forms a vitreous coating layer by heat as described above, and its content is based on the three components of the filling component (B) and scale attack agent (C) described below. 15 to 95% by weight, preferably 18 to 95% by weight. When the content of the flux component is less than 15%, it becomes impossible to form a sufficient vitreous coating layer, and the effect of the scale attack agent decreases. Further, when the content of the flux component is more than 95%, excessive reaction between the flux component and the surface of the metal substrate easily causes corrosion of the surface of the metal substrate.

(B) Filler The filler used in the present invention comprises one kind or a combination of two or more kinds selected from the group consisting of oxides, hydroxides and oxides of alkali metals or alkaline earth metals. there are, for example, _{Na 2 CO 3, NaHCO 3,} K 2 CO 3, KHCO 3,
MgCO ₃ , CaCO ₃ , MgO, CaO, NaCH, Mg (OH) _{2 and the} like.

This filler is used to dissolve the acid during pickling to improve the permeability of the acid as described above, and is 3 to 3 on the basis of the three components (A) and (C). 68
It is used in proportions by weight, preferably 5 to 65% by weight.

When the amount of the filler used is more than this range, the pickling property is improved, but the effect of the scale attack agent is hindered.

(C) Scale Attack Agent The scale attack agent used in the present invention is as described above.
It is melted or decomposed by heat and attacks the metal surface scale to weaken the scale layer, making it a form that can be easily mechanically peeled or pickled to facilitate removal of the layer. Consists of one or a combination of two or more selected from the group consisting of a compound containing, nitrate, nitrite, nitrate, nitrite and phosphate. Halogen-containing compounds include NaCl, NaBr, CaCl ₂ , K ₂ SiF ₆ , KBF
₄ , Na ₃ AlF _5, etc. are exemplified, and as the nitrate, NaNO ₃ , KNO ₃ , Ca
Examples of (NO ₃ ) ₂ and Mg (NO ₃ ) ₂ are nitrites.
KNO ₂ , NaNO ₂ etc. are exemplified, and as the nitrate, K ₂ SO ₄ , KHSO ₄ ,
_{Na 2 SO 4, NaHSO 4,} CaSO 4, MgSO 4 , etc., and examples of the sulfite is exemplified _{K 2 SO 3, KHSO 3,} Na 2 SO 3, NaHSO 3 , and examples of the phosphoric acid compound P ₂ O ₄ , P ₂ O ₅ , H ₃ PO ₄ , KH ₂ PO _{4 and the} like are exemplified.

Scale attack agent component (C) comprises components (A) and (B)
It is used in a proportion of 2 to 80% by weight based on the three components. When the content of the scale attack agent is less than 2%, sufficient scale attack ability cannot be obtained, and the scale layer remains strong and cannot be removed by pickling for a long time. On the contrary, when the content of the scale attack agent exceeds 80%, not only the scale layer but also the metal surface under the scale layer is corroded.

Scale Removal Method Next, a scale removal method using the scale removal composition will be described.

The scale-removing composition of the present invention comprising each of the above-mentioned components is used by applying the scale-removing composition to the surface of the metal substrate on which scale has already been generated before or after the heat treatment. The composition can also be applied to high temperature slabs in continuous casting. The scale removing composition may be used in the same form as it is, or may be used as a paint prepared by dispersing the composition in an appropriate vehicle.

When the scale-removing composition of the present invention is applied to a heat-treated metal substrate having a scale layer on its surface, the flux component (A) is rapidly melted by the heat of the substrate to form a glassy coating layer. To be Further, the composition may be applied at room temperature to a metal substrate having a scale layer on the surface before heat treatment. In this case, the flux component (A) is melted in the next heat treatment step, and the glassy coating layer is also formed. Is formed.

The scale layer of the metal substrate is weakened by the action of the scale attack agent component (C) in the molten glassy coating layer thus formed, and is in the form of iron halide or the like, which is easily removed by pickling. Caught inside.

The vitreous coating layer of the composition which has captured the scale is cracked or cracked due to thermal expansion or the like with the metal substrate during the cooling process after the heat treatment and is easily mechanically peeled. Also,
The scale layer of the metal substrate after the heat treatment is weakened by the action of the scale attack agent component (A) as described above, and is in a form that is easily peeled off. Therefore, the metal substrate is bent or a brushing roll is applied to the substrate. The vitreous coating layer that has captured the scale can be peeled from the surface of the metal substrate by a mechanical scale peeling treatment such as applying.

After completion of the heat treatment, the metal substrate is usually subjected to pickling with a mineral acid such as HCl or H ₂ SO ₄ after the above mechanical scale peeling. By this pickling, the glassy coating layer is easily removed together with the scale. That is, when the above pickling treatment is carried out, the filler component (B) such as alkali metal carbonate incorporated in the glassy coating layer is attacked by the acid and is eluted into the liquid. As a result, the vitreous coating layer becomes brittle and mechanically fragile, and the acid penetrates into the vitreous coating layer from this elution trace. Further, as described above, the scale layer on the surface of the metal substrate is corroded by the scale attack agent component (C) to be mechanically weakened, and is converted into an easily pickled form such as iron halide. Along with the quality coating layer, it is peeled off and removed from the metal surface. However, pickling may not be performed when the glassy coating layer that has captured the scale is completely removed by the mechanical peeling. Further, the glassy coating layer that has captured the scale is removed only by pickling, and mechanical peeling may be omitted.

Thus, according to the present invention, scale removal by pickling or mechanical scale removal can be effectively and quickly performed.

[Effects of the Invention] According to the present invention, it becomes possible to quickly and effectively remove the scale generated on the metal substrate that is heat-treated at a high temperature by mechanical peeling and / or pickling.

By applying the composition for removing scale according to the present invention to a metal substrate which is difficult to remove scale such as heat treatment of stainless steel, the pickling time can be shortened and the production efficiency can be greatly improved.

[Examples] Next, the excellent effects of the present invention will be demonstrated by Examples.

Preparation of Samples Three kinds of glass compositions a, b and c having the compositions shown in Table 1 were used to prepare 9 kinds of samples (No. 1 to No. 9) shown in Table 2.

Test piece dimensions A test piece made of SUS430 stainless steel plate (4 mm x 50 mm x 100 mm) was used.

8 wt% HCl was used as the acid for the pickling treatment.

Example 1 1 g of powder obtained by crushing the No. 1 formulation shown in Table 2 using a ball mill was applied to the surface of a test piece and heated at 700 ° C. for 30 minutes. Then, the test piece was cooled and subjected to acid treatment at 80 ° C. for 30 seconds, and the glassy coating layer formed was peeled from the test piece together with the scale, and a surface without the scale appeared.

Comparative Example 1 1 g of powder obtained by crushing the compound of No. 2 was applied to a test piece,
Heated at 750 ° C for 20 minutes. The glassy coating layer formed was in a semi-molten state. Then, after cooling, an acid treatment was carried out in the same manner as in Example 1. The glassy coating layer was dissolved in acid,
Almost the scale layer remained.

Comparative Example 2 1 g of powder obtained by grinding the compound of No. 3 was applied to a test piece,
Heated at 800 ° C. for 20 minutes. The glassy coating layer formed was in a semi-molten state. Then, after cooling, an acid treatment was carried out in the same manner as in Example 1. The glassy coating layer was dissolved in acid,
The scale layer remained intact.

Example 2 First, a test piece was heated at 900 ° C. for 30 minutes, and in this state, 0.8 to 1.0 g of the powder obtained from the compound of No. 4 was applied to the surface scale layer by a powder gun, and was left in the air as it was. Cooled to room temperature. When the surface of the test piece was observed after cooling, the glassy coating layer formed was peeled from the test piece along with the scale, and the scale was completely removed.

Comparative Example 3 1 g of powder obtained by crushing the compound of No. 5 was applied to a test piece,
Heated at 700 ° C. for 30 minutes. Then, when acid treatment was carried out in the same manner as in Example 1, most of the glassy coating layer was dissolved in acid, but the scale layer was not removed.

Comparative Example 4 1 g of powder obtained by crushing the compound of No. 6 was applied to a test piece,
Heated at 900 ° C. for 30 minutes. The glassy coating layer formed was in a semi-molten state. Then, the test piece was mechanically bent to peel off the glassy coating layer, and the surface of the test piece was observed. As a result, it was found that the steel sheet material was corroded although there was no scale.

Example 3 No. 7 was coated with 1 g of the powder obtained by crushing the composition,
Heated at 700 ° C. for 30 minutes. When the surface of this test piece was observed after cooling, the formed glassy coating layer was partly peeled off. When the coating layer was removed using slurwool, a surface with less scale appeared.

Example 4 1 g of powder obtained by crushing the compound of No. 8 was applied to a test piece,
Heated at 650 ° C for 1 hour. Then, after cooling, the same acid treatment as in Example 1 was carried out. As a result, the glassy coating layer formed was peeled from the test piece along with scale, and a surface without scale appeared.

Example 5 1 g of powder obtained by crushing the compound of No. 9 was applied to a test piece,
Heated at 700 ° C. for 30 minutes. Then, after cooling and acid treatment in the same manner as in Example 1, the glassy coating layer formed was dissolved in acid and a surface with less scale appeared.

Claims (2)

[Claims] 1. (A) a flux component having a melting temperature of 1000 ° C. or lower; (B) an alkali metal or alkaline earth metal carbonate;
A filler comprising one or a combination of two or more selected from the group consisting of hydroxides and oxides, and (C) a halogen-containing compound, nitrate, nitrite, sulfate, sulfite and phosphate. Contain a scale attack agent consisting of one kind or a combination of two or more kinds selected from the constituted group, the content of the flux component is 15 to 95% by weight, and the content of the filler is 3 to 68, based on 3 components. A scale-removing composition having a weight percentage of 2 to 80 wt% and a scale attack agent content. 2. A method for removing metal scale, comprising applying the composition for removing scale according to claim 1 to a metal substrate during and before heat treatment.