Spraying agent suitable for surface oxidation resistance and decarburization resistance of steel billet with silicon content of more than 0.5% and preparation method of spraying agent

Abstract

The invention relates to a spraying agent suitable for resisting oxidation and decarburization of the surface of a steel billet with the silicon content of 0.5% or above and a preparation method of the spraying agent, and belongs to the technical field of steel hot working surface protection. In order to solve the problems that an existing spraying agent is difficult to synergistically inhibit decarburization and oxidation of the surface of a steel billet with the silicon content of 0.5% or above, and the phosphorus removal and accumulation inhibition effect is poor, the invention provides an anti-oxidation and anti-decarburization spraying agent which comprises the following components: high-temperature-resistant coating kaolin, a binder, a solvent and an additive. According to the spraying agent provided by the invention, the anti-oxidation and anti-decarburization synergistic inhibition effect is remarkably improved, the burnout rate of a steel billet is reduced by 17.33%, and the thickness of a decarburized layer is strictly controlled within 0.3 mm. And meanwhile, the binding force between the oxide scale and the base body is reduced, and the high-pressure water descaling efficiency is improved to 98% or above. The spraying agent disclosed by the invention is remarkable in accumulated tumor inhibition effect, the accumulated tumor formation period is prolonged, the cleaning frequency and the solid waste generation amount are reduced, and dual optimization of energy conservation, consumption reduction and production efficiency is realized.

Description

Technical Field

[0001] This invention belongs to the field of steel hot working surface protection technology, and particularly relates to a spraying agent and its preparation method suitable for anti-oxidation and decarburization of steel billet surface with silicon content of more than 0.5%. Background Technology

[0002] In steel production, billet heating is a critical process before rolling. When billets are heated for extended periods at high temperatures, severe oxidation and decarburization easily occur on their surface, especially in alloy steels with a silicon content of 0.50% or higher. The oxidation and decarburization rate of these billets is 0.5-2 times that of low-silicon alloy steels. Silicon readily reacts with oxygen in the furnace at high temperatures to form SiO2. Although SiO2 initially forms a certain oxide layer, this layer has weak adhesion to the steel substrate and cannot effectively prevent subsequent oxygen penetration. Simultaneously, the presence of silicon accelerates the diffusion and loss of carbon from the billet surface, leading to an increased decarburized layer thickness, typically reaching 0.4-0.8 mm. This severely affects the mechanical properties of the steel, reducing surface strength and hardness, and shortening its service life.

[0003] Iron oxide scale forming on the surface of steel billets with a silicon content of 0.5% or higher is mainly composed of a composite of FeO, Fe2O3, and SiO2. It exhibits high density and adhesion, and its interfacial bonding with the steel matrix is ​​significantly higher than that of steel billets with low silicon content. High-pressure water descaling at 25 MPa is insufficient to completely remove this iron oxide scale. Residual scale will be pressed into the steel surface during subsequent rolling, forming defects such as pitting and scratches, thus reducing product surface quality. During heating, the iron oxide scale detached from the billet surface accumulates on the surfaces of components such as the heating furnace frame tracks and slide blocks. Due to the viscosity of SiO2 at high temperatures, the accumulated scale gradually sinterstalizes to form "tumors." These tumors not only damage the billet surface but also hinder smooth billet transport, even causing billet deviation and uneven heating, severely impacting production continuity and steel quality.

[0004] Existing protective coatings for steel billet surfaces are mostly designed for ordinary low-silicon alloy steel. They have poor synergy between decarburization prevention and oxidation resistance, making it difficult to simultaneously inhibit decarburization and oxidation on the surface of steel billets with a silicon content of 0.5% or higher. They also lack peeling aids for high-adhesion iron oxide scale, resulting in poor descaling effects and failing to solve the problem of nodule accumulation on furnace components. Summary of the Invention

[0005] To address the problem that existing protective sprays for steel billet surfaces are ineffective in synergistically inhibiting decarburization, oxidation, phosphorus removal, and nodule formation on steel billet surfaces with a silicon content of 0.5% or higher, this invention provides a spray for resisting oxidation and decarburization on the surface of steel billets with a silicon content of 0.5% or higher, and its preparation method.

[0006] The technical solution of this invention:

[0007] A spraying agent suitable for resisting oxidation and decarburization on the surface of steel billets with a silicon content of 0.5% or higher, comprising the following components by weight percentage:

[0008] The high-temperature resistant coating comprises 50-60%, binder 10-20%, solvent 20%, and additives 10%. The high-temperature resistant coating is kaolin, the binder is a mixture of water glass and aluminum dihydrogen phosphate, the solvent is water, and the additives are chromium oxide and titanium dioxide.

[0009] Furthermore, the mass ratio of the water glass to aluminum dihydrogen phosphate is 8:1.

[0010] Furthermore, the mass ratio of chromium oxide to titanium dioxide is 3:1.

[0011] Furthermore, the spraying agent, after being stirred evenly and allowed to stand for 5 minutes, is loaded into the spraying machine and sprayed onto the surface of the steel billet. After the spraying is completed, the steel billet is directly put into the high-temperature furnace.

[0012] Furthermore, when the spraying agent is applied to the surface of the steel billet, the temperature of the steel billet is ≤50℃.

[0013] Furthermore, the thickness of the coating obtained by spraying is 0.1~0.2mm.

[0014] A method for preparing a spraying agent suitable for resisting oxidation and decarburization on the surface of steel billets with a silicon content of 0.5% or higher includes the following steps:

[0015] Step 1: Place the solvent in a container, pour the adhesive into the container containing the solvent, and stir for a certain period of time to obtain mixed system A;

[0016] Step 2: Pour the high-temperature resistant coating into the mixture A. Stir constantly and evenly during the pouring process. After pouring it in completely, stir for a certain period of time to obtain the mixture B.

[0017] Step 3: Pour the additive into the mixture B and stir continuously until evenly mixed to obtain the spraying agent.

[0018] Furthermore, the stirring time in step one is 3 to 5 minutes.

[0019] Furthermore, the stirring time in step two is 10-15 minutes.

[0020] Furthermore, the stirring time in step three is 10-15 minutes.

[0021] The beneficial effects of this invention are:

[0022] The spraying agent provided by this invention achieves a significant improvement in the synergistic inhibition effect of anti-oxidation and anti-decarburization. The spraying agent forms a dense protective layer on the surface of the steel billet through components such as silicon dioxide and aluminum oxide, effectively inhibiting the oxidation and decarburization reactions during heating of steel billets with a silicon content of 0.5% or higher. Experimental data shows that after using the spraying agent, the billet burn-off rate decreased from 1.50% to 1.24%, a reduction of 17.33%; the average thickness of the decarburized layer decreased from 0.40 mm to 0.28 mm, a reduction of 30%, and the thickness of the decarburized layer was strictly controlled within 0.3 mm. This protective layer also reduces the adhesion between the iron oxide scale and the substrate, increasing the high-pressure water descaling efficiency to over 98%, leaving no iron oxide scale residue on the surface, and avoiding rolling defects. Furthermore, the heating process of the spraying agent does not release harmful gases, meeting environmental protection production requirements, and simultaneously reducing phosphorus pollutants in the descaling wastewater, improving the overall efficiency of the descaling process.

[0023] The spraying agent provided by this invention can inhibit the sintering of iron oxide scale, reduce its adhesion to the furnace frame, steel rails, and slide blocks, extending the nodule formation cycle to twice the original length, reducing the frequency of cleaning internal furnace components by 30%, and simultaneously reducing solid waste generation by 30%. This effect significantly reduces the frequency of furnace shutdowns for cleaning iron oxide scale at the furnace bottom, and reduces the intensity of manual cleaning. Simultaneously, the improved process stability resulting from nodule inhibition increases the yield by 0.26% and reduces the overall power consumption per ton of steel billet by 12.4 kWh, achieving a dual optimization of energy saving and production efficiency. Attached Figure Description

[0024] Figure 1 A photograph showing the descaling effect of the spray agent of this invention on a steel billet;

[0025] Figure 2 This is a photograph of the descaling effect on a steel billet without the use of spraying agent. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention. In the following embodiments, the process equipment or apparatus not specifically specified are all conventional equipment or apparatus in the art. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available; unless otherwise specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0027] Example 1

[0028] This embodiment provides a spraying agent suitable for anti-oxidation and decarburization of steel billet surfaces with a silicon content of 0.5% or higher, comprising the following components by weight percentage:

[0029] The high-temperature resistant coating consists of 50% kaolin, 20% a mixture of water glass and aluminum dihydrogen phosphate as a binder, 20% water as a solvent, and 10% chromium oxide and titanium dioxide as additives. The mass ratio of water glass to aluminum dihydrogen phosphate in the binder is 8:1, and the mass ratio of chromium oxide to titanium dioxide in the additives is 3:1.

[0030] High-temperature resistant coatings made of kaolin are rich in silicon dioxide, aluminum oxide, etc., and have a high melting point and good chemical and thermal stability. They can form a high-temperature resistant protective layer on the surface of steel billets, effectively blocking the diffusion of oxygen and carbon, and playing a role in anti-oxidation and decarburization prevention.

[0031] The water glass in the binder can firmly bond the components together and make the coating firmly adhere to the surface of the steel billet, improving the overall strength and stability of the coating; aluminum dihydrogen phosphate can react with fillers such as aluminum oxide at high temperature to form high-temperature resistant ceramic phases such as aluminum phosphate, which enhances the bonding strength.

[0032] Chromium oxide in the additive has good antioxidant properties and is not easily oxidized in high-temperature environments. It can protect the steel billet from reacting with oxygen at high temperatures and improve the bonding force between the coating and the steel billet, thereby increasing the adhesion of the coating and preventing it from peeling off. Titanium dioxide can inhibit the sintering of iron oxide scale, reduce the adhesion between iron oxide scale and furnace frame components, and prevent accumulation.

[0033] The preparation method of the anti-oxidation and decarburization spray agent on the surface of steel billets in this embodiment includes the following steps:

[0034] Step 1: Place the solvent in a container, pour the adhesive into the container containing the solvent, and stir for 3-5 minutes to obtain mixture A;

[0035] Step 2: Pour the high-temperature resistant coating into the mixture A. During the pouring process, stir continuously and evenly to prevent the high-temperature resistant spray agent from clumping in the solvent. After pouring completely, stir for another 10-15 minutes to obtain the mixture B.

[0036] Step 3: Pour the additive into the mixture system B and stir continuously and evenly for 10-15 minutes until the mixture is uniform, and the anti-oxidation and decarburization spray agent for the steel billet surface is obtained.

[0037] After the spraying agent is stirred and allowed to stand for 5 minutes, it is quickly loaded into the spraying machine and sprayed onto the surface of the 38MnVS6 steel billet. The billet temperature is ≤50℃ during spraying. One layer is sprayed, and the thickness of the resulting coating is 0.1~0.2mm. After the billet is sprayed with the spraying agent, it is directly put into the high-temperature furnace. The high-temperature furnace temperature is ≤850℃, the maximum heating temperature is 1150-1200℃, and the total heating time is 260 minutes.

[0038] The chemical composition of the 38MnVS6 steel used in this embodiment, by weight percentage, includes: C: 0.36-0.40%, Si: 0.50-0.75%, Mn: 1.30-1.50%, P≤0.025%, S: 0.020-0.040%, Cr: 0.10-0.20%, Ni: 0.06-0.10%, V: 0.08-0.13%, Al: 0.010-0.025%, Ti: 0.01-0.03%, with the remainder being Fe and unavoidable impurities.

[0039] The heated 38MnVS6 steel billet was subjected to high-pressure water descaling, achieving a descaling rate of 98% at a descaling pressure of 21MPa. Figure 1 and Figure 2 As shown, the steel billet surface treated with the spray agent has no residual iron oxide scale, thus avoiding the generation of surface defects during the rolling process.

[0040] Example 2

[0041] This embodiment provides a spraying agent suitable for anti-oxidation and decarburization of steel billet surfaces with a silicon content of 0.5% or higher, comprising the following components by weight percentage:

[0042] The high-temperature resistant coating consists of 60% kaolin, 10% a mixture of water glass and aluminum dihydrogen phosphate as a binder, 20% water as a solvent, and 10% chromium oxide and titanium dioxide as additives. The mass ratio of water glass to aluminum dihydrogen phosphate in the binder is 8:1, and the mass ratio of chromium oxide to titanium dioxide in the additives is 3:1.

[0043] The preparation method of the anti-oxidation and decarburization spray agent on the surface of steel billets in this embodiment includes the following steps:

[0044] Step 1: Place the solvent in a container, pour the adhesive into the container containing the solvent, and stir for 3-5 minutes to obtain mixture A;

[0045] Step 2: Pour the high-temperature resistant coating into the mixture A. During the pouring process, stir continuously and evenly to prevent the high-temperature resistant spray agent from clumping in the solvent. After pouring completely, stir for another 10-15 minutes to obtain the mixture B.

[0046] Step 3: Pour the additive into the mixture system B and stir continuously and evenly for 10-15 minutes until the mixture is uniform, and the anti-oxidation and decarburization spray agent for the steel billet surface is obtained.

[0047] After the spraying agent is stirred and allowed to stand for 5 minutes, it is quickly loaded into the spraying machine and sprayed onto the surface of the 38MnVS6 steel billet. The billet temperature is ≤50℃ during spraying. One layer is sprayed, and the thickness of the resulting coating is 0.1~0.2mm. After the billet is sprayed with the spraying agent, it is directly put into the high-temperature furnace. The high-temperature furnace temperature is ≤850℃, the maximum heating temperature is 1150-1200℃, and the total heating time is 260 minutes.

[0048] Example 3

[0049] This embodiment provides a spraying agent suitable for anti-oxidation and decarburization of steel billet surfaces with a silicon content of 0.5% or higher, comprising the following components by weight percentage:

[0050] The high-temperature resistant coating consists of 55% kaolin, 15% a mixture of water glass and aluminum dihydrogen phosphate as a binder, 20% water as a solvent, and 10% chromium oxide and titanium dioxide as additives. The mass ratio of water glass to aluminum dihydrogen phosphate in the binder is 8:1, and the mass ratio of chromium oxide to titanium dioxide in the additives is 3:1.

[0051] The preparation method of the anti-oxidation and decarburization spray agent on the surface of steel billets in this embodiment includes the following steps:

[0052] Step 1: Place the solvent in a container, pour the adhesive into the container containing the solvent, and stir for 3-5 minutes to obtain mixture A;

[0053] Step 2: Pour the high-temperature resistant coating into the mixture A. During the pouring process, stir continuously and evenly to prevent the high-temperature resistant spray agent from clumping in the solvent. After pouring completely, stir for another 10-15 minutes to obtain the mixture B.

[0054] Step 3: Pour the additive into the mixture system B and stir continuously and evenly for 10-15 minutes until the mixture is uniform, and the anti-oxidation and decarburization spray agent for the steel billet surface is obtained.

[0055] After the spraying agent is stirred and allowed to stand for 5 minutes, it is quickly loaded into the spraying machine and sprayed onto the surface of the 38MnVS6 steel billet. The billet temperature is ≤50℃ during spraying. One layer is sprayed, and the thickness of the resulting coating is 0.1~0.2mm. After the billet is sprayed with the spraying agent, it is directly put into the high-temperature furnace. The high-temperature furnace temperature is ≤850℃, the maximum heating temperature is 1150-1200℃, and the total heating time is 260 minutes.

[0056] Example 4

[0057] This embodiment provides a spraying agent suitable for anti-oxidation and decarburization of steel billet surfaces with a silicon content of 0.5% or higher, comprising the following components by weight percentage:

[0058] The high-temperature resistant coating consists of 58% kaolin, 12% a mixture of water glass and aluminum dihydrogen phosphate as a binder, 20% water as a solvent, and 10% chromium oxide and titanium dioxide as additives. The mass ratio of water glass to aluminum dihydrogen phosphate in the binder is 8:1, and the mass ratio of chromium oxide to titanium dioxide in the additives is 3:1.

[0059] The preparation method of the anti-oxidation and decarburization spray agent on the surface of steel billets in this embodiment includes the following steps:

[0060] Step 1: Place the solvent in a container, pour the adhesive into the container containing the solvent, and stir for 3-5 minutes to obtain mixture A;

[0061] Step 2: Pour the high-temperature resistant coating into the mixture A. During the pouring process, stir continuously and evenly to prevent the high-temperature resistant spray agent from clumping in the solvent. After pouring completely, stir for another 10-15 minutes to obtain the mixture B.

[0062] Step 3: Pour the additive into the mixture system B and stir continuously and evenly for 10-15 minutes until the mixture is uniform, and the anti-oxidation and decarburization spray agent for the steel billet surface is obtained.

[0063] After the spraying agent is stirred and allowed to stand for 5 minutes, it is quickly loaded into the spraying machine and sprayed onto the surface of the 38MnVS6 steel billet. The billet temperature is ≤50℃ during spraying. One layer is sprayed, and the thickness of the resulting coating is 0.1~0.2mm. After the billet is sprayed with the spraying agent, it is directly put into the high-temperature furnace. The high-temperature furnace temperature is ≤850℃, the maximum heating temperature is 1150-1200℃, and the total heating time is 260 minutes.

[0064] Comparative Example 1

[0065] This comparative example provides a spraying agent for resisting oxidation and decarburization on the surface of steel billets, comprising the following components in weight percentage:

[0066] The high-temperature resistant coating consists of 60% kaolin, 10% water glass as a binder, 20% water as a solvent, and 10% chromium oxide and titanium dioxide as additives, wherein the mass ratio of chromium oxide to titanium dioxide in the additives is 3:1.

[0067] The preparation method of the anti-oxidation and decarburization spray agent on the surface of steel billets in this embodiment includes the following steps:

[0068] Step 1: Place the solvent in a container, pour the adhesive into the container containing the solvent, and stir for 3-5 minutes to obtain mixture A;

[0069] Step 2: Pour the high-temperature resistant coating into the mixture A. During the pouring process, stir continuously and evenly to prevent the high-temperature resistant spray agent from clumping in the solvent. After pouring completely, stir for another 10-15 minutes to obtain the mixture B.

[0070] Step 3: Pour the additive into the mixture system B and stir continuously and evenly for 10-15 minutes until the mixture is uniform, and the anti-oxidation and decarburization spray agent for the steel billet surface is obtained.

[0071] After the spraying agent is stirred and allowed to stand for 5 minutes, it is quickly loaded into the spraying machine and sprayed onto the surface of the 38MnVS6 steel billet. The billet temperature is ≤50℃ during spraying. One layer is sprayed, and the thickness of the resulting coating is 0.1~0.2mm. After the billet is sprayed with the spraying agent, it is directly put into the high-temperature furnace. The high-temperature furnace temperature is ≤850℃, the maximum heating temperature is 1150-1200℃, and the total heating time is 260 minutes.

[0072] Comparative Example 2

[0073] This comparative example provides a spraying agent for resisting oxidation and decarburization on the surface of steel billets, comprising the following components in weight percentage:

[0074] The high-temperature resistant coating consists of 60% kaolin, 10% a mixture of water glass and aluminum dihydrogen phosphate as a binder, 20% water as a solvent, and 10% chromium oxide as an additive. The mass ratio of water glass to aluminum dihydrogen phosphate in the binder is 8:1.

[0075] The preparation method of the anti-oxidation and decarburization spray agent on the surface of steel billets in this embodiment includes the following steps:

[0076] Step 1: Place the solvent in a container, pour the adhesive into the container containing the solvent, and stir for 3-5 minutes to obtain mixture A;

[0077] Step 2: Pour the high-temperature resistant coating into the mixture A. During the pouring process, stir continuously and evenly to prevent the high-temperature resistant spray agent from clumping in the solvent. After pouring completely, stir for another 10-15 minutes to obtain the mixture B.

[0078] Step 3: Pour the additive into the mixture system B and stir continuously and evenly for 10-15 minutes until the mixture is uniform, and the anti-oxidation and decarburization spray agent for the steel billet surface is obtained.

[0079] After the spraying agent is stirred and allowed to stand for 5 minutes, it is quickly loaded into the spraying machine and sprayed onto the surface of the 38MnVS6 steel billet. The billet temperature is ≤50℃ during spraying. One layer is sprayed, and the thickness of the resulting coating is 0.1~0.2mm. After the billet is sprayed with the spraying agent, it is directly put into the high-temperature furnace. The high-temperature furnace temperature is ≤850℃, the maximum heating temperature is 1150-1200℃, and the total heating time is 260 minutes.

[0080] A group of 38MnVS6 steel billets without any surface protective agent were set up and heat-treated using the same method. The burn-off and oxidation decarburization depth of Examples 1-4, Comparative Examples 1-2 and the uncoated steel billets were investigated. The results are shown in Tables 1 and 2.

[0081] Table 1

[0082]

[0083] As shown in Table 1, the burn loss of the steel billet coated with the spray agent was 1.24%, while that of the comparative steel billet was 1.50%. The burn loss of the steel billet coated with the spray agent was reduced by 17.33% compared with that without the spray agent.

[0084] Table 2

[0085]

[0086] As shown in Table 2, the decarburization layer of the steel after using the spraying agent was 0.24-0.30 mm, with an average of 0.28 mm; the decarburization layer of the steel without the spraying agent was 0.38-0.43 mm, with an average of 0.40 mm. The test results show that the decarburization layer depth of the steel using the spraying agent was significantly reduced, with an average depth 30% lower than that of the steel without the spraying agent.

Claims

1. A spraying agent suitable for resisting oxidation and decarburization on the surface of steel billets with a silicon content of 0.5% or higher, characterized in that, It contains the following components in weight percentage: The high-temperature resistant coating comprises 50-60%, binder 10-20%, solvent 20%, and additives 10%. The high-temperature resistant coating is kaolin, the binder is a mixture of water glass and aluminum dihydrogen phosphate, the solvent is water, and the additives are chromium oxide and titanium dioxide.

2. The spraying agent according to claim 1, suitable for anti-oxidation and decarburization of steel billet surface with silicon content of 0.5% or more, is characterized in that, The mass ratio of water glass to aluminum dihydrogen phosphate is 8:

1.

3. A spraying agent for resisting oxidation and decarburization on the surface of steel billets with a silicon content of 0.5% or higher, as described in claim 1 or 2, characterized in that... The mass ratio of chromium oxide to titanium dioxide is 3:

1.

4. The spraying agent according to claim 3, suitable for anti-oxidation and decarburization of steel billet surface with silicon content of 0.5% or more, is characterized in that, After stirring and letting stand for 5 minutes, the coating agent is loaded into the spraying machine and sprayed onto the surface of the steel billet. After spraying, the steel billet is directly put into the high-temperature furnace.

5. The spraying agent according to claim 4, suitable for anti-oxidation and decarburization of steel billet surface with silicon content of 0.5% or more, is characterized in that, When the spraying agent is applied to the surface of the steel billet, the temperature of the steel billet is ≤50℃.

6. The spraying agent according to claim 5, suitable for anti-oxidation and decarburization of steel billet surface with silicon content of 0.5% or more, is characterized in that, The thickness of the coating obtained by spraying is 0.1~0.2mm.

7. A method for preparing a spraying agent as described in any one of claims 1-6, suitable for resisting oxidation and decarburization on the surface of steel billets with a silicon content of 0.5% or higher, characterized in that, Includes the following steps: Step 1: Place the solvent in a container, pour the adhesive into the container containing the solvent, and stir for a certain period of time to obtain mixed system A; Step 2: Pour the high-temperature resistant coating into the mixture A. Stir constantly and evenly during the pouring process. After pouring it in completely, stir for a certain period of time to obtain the mixture B. Step 3: Pour the additive into the mixture B and stir continuously until evenly mixed to obtain the spraying agent.

8. The method for preparing the spraying agent for resisting oxidation and decarburization on the surface of steel billets with a silicon content of 0.5% or higher, as described in claim 7, is characterized in that... The stirring time in step one is 3 to 5 minutes.

9. The preparation method of the spraying agent for anti-oxidation and decarburization of steel billet surface with silicon content of 0.5% or more as described in claim 8, characterized in that, The stirring time in step two is 10-15 minutes.

10. The method for preparing the spraying agent for resisting oxidation and decarburization on the surface of steel billets with a silicon content of 0.5% or higher, as described in claim 9, is characterized in that... The stirring time in step three is 10-15 minutes.

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