Composite high-temperature protective coating as well as preparation method and application thereof

Abstract

The invention relates to the technical field of steel rail production, in particular to a composite high-temperature protective coating as well as a preparation method and application thereof. The composite high-temperature protective coating comprises: 15 wt%-20 wt% of calcium carbonate micro powder; 35 wt%-40 wt% of silica sol; the content of the vanadium-containing tailings is 20 wt%-30 wt%; 10 wt%-15 wt% of alumina micro powder; 2 wt%-3 wt% of a dispersant; and the balance of deionized water. Double protection is achieved through decarburization inhibition and anti-adhesion design, the surface quality of the steel rail is improved, the depth of a decarburized layer is reduced, and the running safety of the steel rail is improved. Meanwhile, the anti-decarburization protective coating and the on-line spraying process are successfully developed by starting from the characteristics of steel types and utilizing the characteristics of vanadium-containing tailing resources, and are successfully applied to the production of high-quality steel rails.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rail production, and in particular to a composite high-temperature protective coating, a preparation method and application thereof. BACKGROUND

[0002] With the continuous development of high-speed railway technology in China, the comprehensive quality requirements of high-speed railway on rails are also continuously improved. In order to ensure the engineering quality of high-speed railway in China, the railway user puts forward the requirements including decarburization layer and surface quality, among which it is pointed out that the decarburization layer depth requirement is increased from ≤0.50mm to ≤0.30mm, which is increased by 40% on the basis of the original index. In the surface quality requirements, the depth of rail hot scratch, longitudinal line, rolling mark and the like formed under the hot state is ≤0.5mm.

[0003] The heating mode of rail steel of domestic rail production enterprises has been optimized from the initial push steel type to the step type heating. This mode significantly improves the production efficiency of the heating furnace while effectively reducing the decarburization layer depth of the rail, so that the decarburization layer depth of the rail is controlled within 0.50mm with high qualified rate. According to the production statistics, the decarburization layer depth of rails at home and abroad is mostly distributed between 0.30-0.50mm, and at present, there is no condition for industrial production of rails with decarburization layer depth ≤0.30mm. In the heating of the billet, the hot scratch, longitudinal line, rolling mark and the like defects are caused by the oxidation layer stacking of the heating furnace pad biting the billet, which seriously affects the surface quality of the rail.

[0004] When the rail is heated in the continuous heating furnace, there are two technical problems: one is the decarburization problem: the surface layer carbon element of high carbon rail is oxidized at high temperature (1100-1300℃), which leads to the decrease of surface hardness and the shortening of fatigue life. The second is the problem of oxide scale sticking: the surface iron oxide scale of the billet is sintered with the heating furnace pad at high temperature, which causes the rail surface to be bitten with lines, affecting the flatness and wheel-rail contact performance.

[0005] The existing technology adopts physical isolation (such as ceramic coating) or atmosphere control (nitrogen protection), but there are problems such as easy peeling of the coating, high energy consumption, and complex process. The existing patent only aims at single decarburization or oxide scale protection, and does not realize synergistic control. SUMMARY

[0006] Therefore, the technical problem to be solved by the present application is to provide a composite high-temperature protective coating, a preparation method and application thereof, which improves the surface quality of the rail, reduces the decarburization layer depth, and improves the running safety of the rail.

[0007] The present application provides a composite high-temperature protective coating, which comprises:

[0008]

[0009] the balance is deionized water.

[0010] Preferably, the particle size of the calcium carbonate micropowder is not more than 80 μm.

[0011] The particle size of the alumina micropowder is not more than 100 μm.

[0012] Preferably, the vanadium-containing tailings include:

[0013]

[0014] The total amount of the components is 100%.

[0015] Preferably, the silica sol is silica sol JN-30 or silica sol JN-40.

[0016] The dispersant is polyethylene glycol.

[0017] The application also provides a preparation method of the composite high-temperature protective coating described above, comprising the following steps:

[0018] The calcium carbonate micropowder, silica sol, vanadium-containing tailings, alumina micropowder, dispersant and deionized water are stirred and uniformly mixed to obtain the composite high-temperature protective coating.

[0019] The application also provides a method for improving the surface layer quality of a steel rail, comprising the following steps:

[0020] S1) After continuous casting, the steel billet is cooled to 60-120 °C, and the composite high-temperature protective coating is sprayed on the surface of the steel billet under high pressure;

[0021] The composite high-temperature protective coating is the composite high-temperature protective coating described above.

[0022] S2) Preheating to 800-1000 °C to form a glassy protective layer, and then soaking at 1200-1250 °C to obtain a decarburization-resistant protective coating layer;

[0023] S3) The steel billet obtained in step S2) is subjected to surface dephosphorization.

[0024] Preferably, the steel billet is a steel rail billet; in the steel billet, the carbon content is 0.65wt%-0.82wt%, the silicon content is 0.15wt%-0.80wt%, the manganese content is 0.70wt%-1.20wt%, the chromium content is ≤0.40wt%, and the vanadium content is ≤0.12wt%.

[0025] Preferably, the temperature of the high-pressure spraying is 60-120 °C, the coating atomization pressure is 0.6-0.8 MPa, and the thickness of the high-pressure spraying is 3-5 mm.

[0026] Preferably, the preheating time at 800-1000 °C is 15-25 min.

[0027] The time for soaking at 1200-1250 DEG C is 25-60 min.

[0028] Preferably, the surface phosphorus-removed billet temperature is 1200-1250 DEG C, the working pressure of phosphorus-removed water is 18-25 MPa, and the spraying angle of phosphorus-removed water is 22 DEG -32 DEG.

[0029] The application develops a composite high-temperature protective coating containing nano calcium carbonate, and realizes double protection through the following mechanisms: 1) decarburization inhibition: the coating forms a dense SiO2-CaO composite glassy layer on the surface of the billet, blocks the diffusion of oxygen, and reduces the decarburization rate; 2) anti-sticking design: the high-temperature decomposition of calcium carbonate (CaCO3→CaO+CO2↑) produces a porous structure, which cooperates with alumina fibers to form a "lotus leaf effect", so that the oxide skin is isolated from the pad. The surface quality of the steel rail is improved, the decarburization layer depth is reduced, and the running safety of the steel rail is improved. At the same time, starting from the characteristics of the steel grade, the application successfully develops a decarburization prevention protective coating and an online spraying process by utilizing the resource characteristics of vanadium-containing tailings, and successfully applies it to high-quality steel rail production, so that the decarburization layer depth of high-quality steel rail is ≤0.30 mm, and the surface quality (the proportion of no lines) is ≥95%. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The sampling position of the decarburization layer and the microstructure sample. DETAILED DESCRIPTION

[0031] The technical solutions of the application will be described clearly and completely below in combination with the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0032] The application provides a composite high-temperature protective coating, which comprises:

[0033]

[0034]

[0035] The balance is deionized water.

[0036] In some embodiments of the application, the particle size of the calcium carbonate micro powder is not more than 80 μm. The content of the calcium carbonate micro powder is 15 wt%, 20 wt%, 16 wt%, or 18 wt%. The calcium carbonate micro powder functions to prevent adhesion and promote the generation of a porous structure during high-temperature heating.

[0037] In some embodiments of the present application, the silica sol is silica sol JN-30 or silica sol JN-40. The silica sol is a binder, and at the same time, the silica sol is a SiO2 source. The content of the silica sol is 35wt%, 36wt%, 37wt%, 40wt%.

[0038] In some embodiments of the present application, the vanadium-containing tailings include:

[0039]

[0040] The sum of the amounts of the components is 100%.

[0041] In some embodiments of the present application, the content of TFe in the vanadium-containing tailings is 44wt%; the content of V2O5 in the vanadium-containing tailings is 18wt%; the content of TiO2 in the vanadium-containing tailings is 8wt%; the content of SiO2 in the vanadium-containing tailings is 14wt%; the content of MnO in the vanadium-containing tailings is 8wt%; the content of CaO in the vanadium-containing tailings is 3wt%; the content of MgO in the vanadium-containing tailings is 3wt%; and the content of Al2O3 in the vanadium-containing tailings is 2wt%.

[0042] The content of the vanadium-containing tailings is 20wt%, 22wt%, 23wt%, 21wt%, 25wt%.

[0043] The vanadium-containing tailings are obtained by oxidation and blowing during the vanadium extraction of vanadium-containing molten iron in the process of smelting vanadium-titanium magnetite in Panzhihua, or are obtained by wet vanadium extraction of vanadium-containing iron concentrate to obtain vanadium oxide-containing residues.

[0044] The vanadium-containing tailings serve to enhance heat resistance.

[0045] In some embodiments of the present application, the particle size of the alumina micropowder is not more than 100μm. The content of the alumina micropowder is 13wt%, 12wt%, 10wt%, 15wt%. The alumina micropowder can enhance heat resistance.

[0046] In some embodiments of the present application, the dispersant is polyethylene glycol. Particle agglomeration can be prevented. The content of the dispersant is 2wt%, 3wt%.

[0047] The present application also provides a preparation method of the composite high-temperature protective coating, comprising the following steps:

[0048] The calcium carbonate micropowder, silica sol, vanadium-containing tailings, alumina micropowder, dispersant and deionized water are stirred and uniformly mixed to obtain the composite high-temperature protective coating.

[0049] The present application provides a method for improving the surface layer quality of a steel rail, comprising the following steps:

[0050] S1) after continuous casting, cooling to 60-120℃, high-pressure spraying of the composite high-temperature protective coating on the surface of the billet;

[0051] The composite high-temperature protective coating is the composite high-temperature protective coating described above.

[0052] S2) heating to 800-1000℃ for preheating to form a glassy protective layer, and then soaking at 1200-1250℃ to obtain a decarburization-preventing protective coating layer;

[0053] S3) removing phosphorus on the surface of the billet obtained in step S2).

[0054] Regarding step S1):

[0055] After continuous casting, cooling to 60-120℃, high-pressure spraying of the composite high-temperature protective coating on the surface of the billet;

[0056] The composite high-temperature protective coating is the composite high-temperature protective coating described above.

[0057] In some embodiments of the present application, the billet is a rail billet.

[0058] In some embodiments of the present application, the cooling is natural air cooling. The temperature after cooling is 60℃, 80℃, 100℃, 120℃.

[0059] In some embodiments of the present application, the temperature for high-pressure spraying is 60-120℃, such as 60℃, 80℃, 100℃, 120℃; the pressure for coating atomization is 0.6-0.8MPa, such as 0.6MPa, 0.7MPa, 0.8MPa; the thickness for high-pressure spraying is 3-5mm, such as 3mm, 5mm, 4mm.

[0060] Regarding step S2):

[0061] Heating to 800-1000℃ for preheating to form a glassy protective layer, and then soaking at 1200-1250℃ to obtain a decarburization-preventing protective coating layer.

[0062] In some embodiments of the present application, the heating is furnace heating, and the rate of heating is 5-10℃ / s, such as 8℃ / s.

[0063] In some embodiments of the present application, the time for preheating at 800-1000℃ is 15-25min. Specifically, the temperature for preheating is 800℃, 850℃, 950℃, 1000℃, and the time is 15min, 20min, 25min, 22min, 23min.

[0064] In some embodiments of the present application, the soaking time at 1200-1250℃ is 25-60 minutes. Specifically, the soaking temperature is 1200℃, 1210℃, 1250℃, 1230℃, 1240℃, and the time is 25 minutes, 30 minutes, 60 minutes, 45 minutes, or 50 minutes.

[0065] In some embodiments of the present application, the preheating and soaking are both performed in a walking beam furnace. After the soaking is completed, the billet is discharged. The temperature of the discharged billet is 1200-1250℃, such as 1200℃, 1210℃, 1250℃, 1230℃, or 1240℃.

[0066] Regarding step S3):

[0067] The billet obtained in step S2) is subjected to surface phosphorus removal.

[0068] In some embodiments of the present application, the surface phosphorus removal is high-pressure water surface phosphorus removal. The temperature of the billet subjected to the surface phosphorus removal is 1200-1250℃, such as 1200℃, 1210℃, 1250℃, 1230℃, or 1240℃; the working pressure of the phosphorus removal water is 18-25 MPa, such as 18 MPa, 19 MPa, 25 MPa, 20 MPa, or 22 MPa; and the spray angle of the phosphorus removal water is 22°-32°, such as 22°, 23°, 32°, 25°, or 28°.

[0069] The raw material used in the present application is not particularly limited and can be a commercially available one.

[0070] The present application breaks through the traditional single protection idea and realizes the combination of the paint anti-sticking function and decarburization protection by material system innovation, i.e., using CaCO3 decomposition kinetics (ΔG = -178 kJ / mol @ 1200℃) to control the interface reaction and constructing a "hard layer (SiO2) + buffer layer (CaO porous body)" composite structure, thus simplifying the process flow.

[0071] The present application focuses on the technical research on reducing the depth of the decarburized layer of the rail steel and improving the surface quality of the rail steel, and breaks through the production process of the low-decarburized layer high-surface-quality rail steel, thus realizing industrialized production.

[0072] In order to quickly and economically realize the industrial production of the low-decarburized layer and improve the surface quality of the rail steel, the present application successfully develops a decarburization protection paint and an online spraying process by using the resource characteristics of vanadium-containing tailings, and successfully applies the same to the production of high-quality rail steel, so that the depth of the decarburized layer of the high-quality rail steel is ≤0.30 mm, and the qualified rate of the surface quality (the proportion of no lines) is ≥95%.

[0073] In order to further illustrate the present application, a composite high-temperature protective coating, a preparation method and application thereof provided by the present application are described in detail below in combination with examples, but it should not be understood as limiting the protection scope of the present application.

[0074] In the examples and comparative examples, steel rail billets are used.

[0075] Example 1

[0076] 1) Preparation of the composite high-temperature protective coating:

[0077] The calcium carbonate powder, silica sol, vanadium-containing tailings, alumina powder, dispersant and deionized water are stirred and uniformly mixed to obtain the composite high-temperature protective coating.

[0078] The particle size of the calcium carbonate powder is not more than 80 μm.

[0079] The silica sol is silica sol JN-30.

[0080] The vanadium-containing tailings include:

[0081]

[0082] The particle size of the alumina powder is not more than 100 μm.

[0083] The dispersant is polyethylene glycol.

[0084] The component content of the composite high-temperature protective coating is shown in Table 1.

[0085] 2) After the steel rail billet is continuously cast, it is naturally air-cooled to 60 ℃, and the composite high-temperature protective coating is high-pressure sprayed on the surface of the billet; the temperature of the high-pressure spraying is 60 ℃, the coating atomization pressure is 0.6 MPa, and the thickness of the high-pressure spraying is 3 mm; the related parameters of the high-pressure spraying are shown in Table 2.

[0086] The composite high-temperature protective coating is the composite high-temperature protective coating described above;

[0087] 3) In a step-by-step heating furnace, the furnace is heated (the heating rate is 8 ℃ / s) to 800 ℃ for preheating for 15 min to form a glassy protective layer, and then is soaked at 1200 ℃ for 25 min to obtain a decarburization-resistant protective coating layer, and the billet is discharged. The preheating and soaking temperatures and times are shown in Table 3. The temperature of the billet discharged is 1200 ℃.

[0088] 4) The billet obtained in step 3) is subjected to surface dephosphorization, the temperature of the surface dephosphorized billet is 1200 ℃, the working pressure of the dephosphorizing water is 18 MPa, and the injection angle of the dephosphorizing water is 22°. The parameters of the surface dephosphorization are shown in Table 4.

[0089] Example 2

[0090] 1) Preparation of the composite high-temperature protective coating:

[0091] The calcium carbonate powder, silica sol, vanadium-containing tailings, alumina powder, dispersant and deionized water were stirred and uniformly mixed to obtain the composite high-temperature protective coating.

[0092] The components of each raw material were the same as in Example 1, and the contents of each raw material component were as shown in Table 1.

[0093] 2) After continuous casting of the rail steel billet, the billet was naturally air-cooled to 80℃, and the composite high-temperature protective coating was high-pressure sprayed on the surface of the billet; the temperature of the high-pressure spraying was 80℃, the coating atomization pressure was 0.7 MPa, and the thickness of the high-pressure spraying was 3 mm; the related parameters of the high-pressure spraying were as shown in Table 2.

[0094] The composite high-temperature protective coating was the composite high-temperature protective coating described above;

[0095] 3) In a step-by-step heating furnace, the billet was preheated to 850℃ at a heating rate of 8℃ / s for 20 min to form a glassy protective layer, and then was soaked at 1210℃ for 30 min to obtain a decarburization-resistant protective coating layer, and the billet was discharged. The preheating and soaking temperatures and times were as shown in Table 3. The temperature of the billet when discharged was 1210℃.

[0096] 4) The billet obtained in step 3) was subjected to surface dephosphorization, the temperature of the surface dephosphorized billet was 1210℃, the working pressure of the dephosphorizing water was 19 MPa, and the spray angle of the dephosphorizing water was 23°. The parameters of the surface dephosphorization were as shown in Table 4.

[0097] Example 3

[0098] 1) Preparation of the composite high-temperature protective coating:

[0099] The calcium carbonate powder, silica sol, vanadium-containing tailings, alumina powder, dispersant and deionized water were stirred and uniformly mixed to obtain the composite high-temperature protective coating.

[0100] The components of each raw material were the same as in Example 1, and the contents of each raw material component were as shown in Table 1.

[0101] 2) After continuous casting of the rail steel billet, the billet was naturally air-cooled to 100℃, and the composite high-temperature protective coating was high-pressure sprayed on the surface of the billet; the temperature of the high-pressure spraying was 100℃, the coating atomization pressure was 0.8 MPa, and the thickness of the high-pressure spraying was 5 mm; the related parameters of the high-pressure spraying were as shown in Table 2.

[0102] The composite high-temperature protective coating was the composite high-temperature protective coating described above;

[0103] 3) in the step-by-step heating furnace, preheating (the rate of temperature rise is 8°C / s) to 950°C for 25 min, forming a glassy protective layer, then soaking at 1250°C for 60 min, obtaining a decarburization-resistant protective coating, and the billet is discharged. The preheating and soaking temperature and time are shown in Table 3. The temperature of the billet discharged is 1250°C.

[0104] 4) the billet obtained in step 3) is subjected to surface phosphorus removal, the temperature of the surface phosphorus removal billet is 1250°C, the working pressure of the phosphorus removal water is 25 MPa, and the injection angle of the phosphorus removal water is 32°. The surface phosphorus removal parameters are shown in Table 4.

[0105] Example 4

[0106] 1) Preparation of the composite high-temperature protective coating:

[0107] The calcium carbonate micro powder, silica sol, vanadium-containing tailings, alumina micro powder, dispersant and deionized water are stirred and uniformly mixed to obtain the composite high-temperature protective coating.

[0108] The components of each raw material are the same as in Example 1, and the content of each raw material component is shown in Table 1.

[0109] 2) After continuous casting of the rail steel billet, the billet is naturally air-cooled to 120°C, and the composite high-temperature protective coating is sprayed on the surface of the billet at high pressure; the temperature of the high-pressure spraying is 120°C, the coating atomization pressure is 0.6 MPa, and the thickness of the high-pressure spraying is 4 mm; the related parameters of the high-pressure spraying are shown in Table 2.

[0110] The composite high-temperature protective coating is the composite high-temperature protective coating described above;

[0111] 3) in the step-by-step heating furnace, preheating (the rate of temperature rise is 8°C / s) to 1000°C for 22 min, forming a glassy protective layer, then soaking at 1230°C for 45 min, obtaining a decarburization-resistant protective coating, and the billet is discharged. The preheating and soaking temperature and time are shown in Table 3. The temperature of the billet discharged is 1230°C.

[0112] 4) the billet obtained in step 3) is subjected to surface phosphorus removal, the temperature of the surface phosphorus removal billet is 1230°C, the working pressure of the phosphorus removal water is 20 MPa, and the injection angle of the phosphorus removal water is 25°. The surface phosphorus removal parameters are shown in Table 4.

[0113] Example 5

[0114] 1) Preparation of the composite high-temperature protective coating:

[0115] The calcium carbonate micro powder, silica sol, vanadium-containing tailings, alumina micro powder, dispersant and deionized water are stirred and uniformly mixed to obtain the composite high-temperature protective coating.

[0116] The content of each raw material component is shown in Table 1.

[0117] 2) After continuous casting of the rail steel billet, the billet is naturally air-cooled to 100℃, and the composite high-temperature protective coating is high-pressure sprayed on the surface of the billet; the high-pressure spraying temperature is 100℃, the coating atomization pressure is 0.7MPa, and the high-pressure spraying thickness is 3mm; the related parameters of high-pressure spraying are shown in Table 2.

[0118] The composite high-temperature protective coating is the composite high-temperature protective coating described above;

[0119] 3) In a step-by-step heating furnace, the billet is preheated to 950℃ at a heating rate of 8℃ / s for 23min to form a glassy protective layer, and then is soaked at 1240℃ for 50min to obtain a decarburization-resistant protective coating layer, and the billet is discharged. The preheating and soaking temperature and time are shown in Table 3. The temperature of the billet discharged is 1240℃.

[0120] 4) The billet obtained in step 3) is subjected to surface dephosphorization, the surface dephosphorization temperature of the billet is 1240℃, the working pressure of dephosphorization water is 22MPa, and the spray angle of dephosphorization water is 28°. The parameters of surface dephosphorization are shown in Table 4.

[0121] Comparative Example 1

[0122] 1) Preparation of the composite high-temperature protective coating:

[0123] The calcium carbonate powder, silica sol, vanadium-containing tailings, alumina powder, dispersant and deionized water are stirred and uniformly mixed to obtain the composite high-temperature protective coating.

[0124] The components of the silica sol, vanadium-containing tailings, alumina powder and dispersant are the same as those in Example 1.

[0125] The content of each raw material component is shown in Table 1.

[0126] 2) After continuous casting of the rail steel billet, the billet is naturally air-cooled to 50℃, and the composite high-temperature protective coating is high-pressure sprayed on the surface of the billet; the high-pressure spraying temperature is 50℃, the coating atomization pressure is 0.5MPa, and the high-pressure spraying thickness is 1mm; the related parameters of high-pressure spraying are shown in Table 2.

[0127] The composite high-temperature protective coating is the composite high-temperature protective coating described above;

[0128] 3) In the step-by-step heating furnace, preheat to 700℃ (the rate of temperature rise is 8℃ / s) for 10 min to form a glassy protective layer, then heat to 1150℃ for 15 min to obtain a decarburization-resistant protective coating, and the billet is discharged. The preheating and soaking temperatures and times are shown in Table 3. The temperature of the billet discharged is 1190℃.

[0129] 4) The billet obtained in step 3) is subjected to surface phosphorus removal, the temperature of the surface phosphorus removal billet is 1190℃, the working pressure of the phosphorus removal water is 17 MPa, and the spray angle of the phosphorus removal water is 20°. The parameters of the surface phosphorus removal are shown in Table 4.

[0130] Comparative Example 2

[0131] 1) Preparation of the composite high-temperature protective coating:

[0132] The calcium carbonate micro powder, silica sol, vanadium-containing tailings, alumina micro powder, dispersant and deionized water are stirred and uniformly mixed to obtain a composite high-temperature protective coating.

[0133] The components of each raw material are the same as in Example 1, and the contents of each raw material component are shown in Table 1.

[0134] 2) After continuous casting of the rail steel billet, the billet is naturally air-cooled to 130℃, and the composite high-temperature protective coating is high-pressure sprayed on the surface of the billet; the temperature of the high-pressure spraying is 130℃, the coating atomization pressure is 0.4 MPa, and the thickness of the high-pressure spraying is 1 mm; the related parameters of the high-pressure spraying are shown in Table 2.

[0135] The composite high-temperature protective coating is the composite high-temperature protective coating described above;

[0136] 3) In the step-by-step heating furnace, preheat to 750℃ (the rate of temperature rise is 8℃ / s) for 14 min to form a glassy protective layer, then heat to 1180℃ for 20 min to obtain a decarburization-resistant protective coating, and the billet is discharged. The preheating and soaking temperatures and times are shown in Table 3. The temperature of the billet discharged is 1260℃.

[0137] 4) The billet obtained in step 3) is subjected to surface phosphorus removal, the temperature of the surface phosphorus removal billet is 1260℃, the working pressure of the phosphorus removal water is 16 MPa, and the spray angle of the phosphorus removal water is 21°. The parameters of the surface phosphorus removal are shown in Table 4.

[0138] Comparative Example 3

[0139] 1) Preparation of the composite high-temperature protective coating:

[0140] The calcium carbonate micro powder, silica sol, vanadium-containing tailings, alumina micro powder, dispersant and deionized water are stirred and uniformly mixed to obtain a composite high-temperature protective coating.

[0141] The components of each raw material are the same as in Example 1, and the content of each raw material component is shown in Table 1.

[0142] 2) After continuous casting of the rail billet, the billet is naturally air-cooled to 150°C, and a composite high-temperature protective coating is high-pressure sprayed on the surface of the billet; the high-pressure spraying temperature is 150°C, the coating atomization pressure is 0.3 MPa, and the high-pressure spraying thickness is 2 mm; the related parameters of high-pressure spraying are shown in Table 2.

[0143] The composite high-temperature protective coating is the composite high-temperature protective coating described above;

[0144] 3) In a step-by-step heating furnace, the billet is preheated to 1000°C at a rate of 8°C / s for 30 min to form a glassy protective layer, and then is soaked at 1280°C for 20 min to obtain a decarburization-resistant protective coating layer, and the billet is discharged. The preheating and soaking temperature and time are shown in Table 3. The temperature of the billet discharged is 1255°C.

[0145] 4) The billet obtained in step 3) is subjected to surface dephosphorization, the surface dephosphorization temperature of the billet is 1255°C, the working pressure of dephosphorization water is 17 MPa, and the spray angle of dephosphorization water is 21°. The parameters of surface dephosphorization are shown in Table 4.

[0146] Table 1 Component content of composite high-temperature protective coating

[0147]

[0148] Table 2 Related parameters of high-pressure spraying

[0149]

[0150] Table 3 Preheating and soaking temperature and time

[0151]

[0152]

[0153] Table 4 Parameters of surface dephosphorization

[0154]

[0155] According to the requirements of the standard TB / T 2344 "43kg / m~75kg / m Rail Order Technical Conditions", the Figure 1 The decarburized layer and metallographic sample are processed and tested at the tensile sample sampling position. Figure 1 The decarburized layer and metallographic sample are processed and tested at the tensile sample sampling position.

[0156] The decarburized layer depth and line depth data statistics are shown in Table 5.

[0157] Table 5 Decarburized layer depth and line depth data statistics

[0158]

[0159]

[0160] As can be seen from Table 5, the rail decarburized layer depth is ≤0.30 mm, the surface quality (the proportion of no line) qualified rate is ≥95% by using the calcium carbonate modified high temperature protective coating, the rail decarburized layer depth is shallower, the proportion of line is lower, and it is more beneficial to improve the surface quality of the rail.

[0161] The present application improves the surface quality of the rail, reduces the decarburized layer depth, and improves the running safety of the rail.

[0162] The above examples are only used to help understand the method of the present application and its core idea. Various modifications of these examples will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other examples without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these examples shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A composite high-temperature protective coating, comprising: a balance of deionized water.

2. The composite high temperature protective coating of claim 1, wherein, The particle size of the calcium carbonate micro-powder is not more than 80 μm; The particle size of the alumina micro-powder is not more than 100 μm.

3. The composite high temperature protective coating of claim 1, wherein, The vanadium-containing tailings include: The total amount of the components is 100%.

4. The composite high temperature protective coating of claim 1, wherein, The silica sol is silica sol JN-30 or silica sol JN-40; The dispersant is polyethylene glycol. 5.A method for preparing the composite high-temperature protective coating according to any one of claims 1 to 4, comprising the following steps: stirring and mixing the calcium carbonate micro-powder, the silica sol, the vanadium-containing tailings, the alumina micro-powder, the dispersant, and the deionized water to obtain the composite high-temperature protective coating. 6.A method for improving the surface layer quality of a steel rail, comprising the following steps: S1) after continuous casting of a billet, cooling the billet to 60-120 ℃, and high-pressure spraying the composite high-temperature protective coating on the surface of the billet; The composite high-temperature protective coating is the composite high-temperature protective coating according to any one of claims 1 to 4; S2) preheating to 800-1000 ℃ to form a glassy protective layer, and then soaking at 1200-1250 ℃ to obtain a decarburization-preventing protective coating layer; S3) removing phosphorus from the surface of the billet obtained in step S2).

7. The method of claim 6, wherein, The billet is a steel rail billet; in the billet, the carbon content is 0.65wt%-0.82wt%, the silicon content is 0.15wt%-0.80wt%, the manganese content is 0.70wt%-1.20wt%, the chromium content is ≤0.40wt%, and the vanadium content is ≤0.12wt%.

8. The method of claim 6, wherein, The temperature for high-pressure spraying is 60-120 ℃, the coating atomization pressure is 0.6-0.8 MPa, and the thickness of the high-pressure spraying is 3-5 mm.

9. The method of claim 6, wherein, The preheating time at 800-1000 ℃ is 15-25 min; The soaking time at 1200-1250 ℃ is 25-60 min.

10. The method of claim 6, wherein, The temperature of the billet after surface phosphorus removal is 1200-1250 ℃, the working pressure of the phosphorus removal water is 18-25 MPa, and the injection angle of the phosphorus removal water is 22°-32°.

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