Blast furnace chute surface protective coating and preparation method thereof

Abstract

The invention provides a protective coating on the surface of a blast furnace chute and a preparation method of the protective coating. The protective coating is formed by covering the surface of a stainless steel substrate of the blast furnace chute with a chromium-doped mullite coating, and the chromium-doped mullite coating contains Cr, Fe and / or chromium oxide and iron oxide particles. According to the preparation method, a fiber laser and a synchronous powder feeding device are adopted for cladding the composite coating reinforced phase powder material on the to-be-treated surface of the blast furnace chute. The protective coating and a stainless steel base body of the blast furnace chute have good metallurgical bonding, the internal microscopic structure of the protective coating is compact and uniform in performance, and the high temperature resistance and the gas erosion resistance of the stainless steel chute are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of protective coating of stainless steel base material, and particularly relates to a blast furnace chute surface protective coating and a preparation method thereof. BACKGROUND

[0002] The blast furnace ironmaking is the main ironmaking mode in the steel industry at present, and has the advantages of high yield, stable production and low fuel consumption. With the large-scale of blast furnace and the improvement of mechanical automation, the requirements for blast furnace equipment are also increasing. The blast furnace chute is a main equipment responsible for material distribution in the blast furnace, and long-term high-temperature radiation, raw material wear and gas corrosion can cause deformation and even breakage of the stainless steel chute, which seriously affects the blast furnace material distribution, causes the fluctuation of furnace condition, and needs to be replaced by stopping the furnace, which seriously affects the stable operation of the blast furnace and the steel production, and causes a large amount of economic loss during the period.

[0003] In order to improve the high-temperature resistance and corrosion resistance of the blast furnace chute, an oxide coating is sprayed on the surface of the stainless steel, which can resist the impact of high-temperature gas and resist the corrosion of alkali metal gas in the gas to the stainless steel chute. However, the anti-oxidation coating prepared by most traditional coating preparation technologies often has a large number of cracks, pores and other micro defects, and the substrate and the coating are not well metallurgically combined, and are easy to fall off. As one of the additive manufacturing technologies, the laser cladding technology has the advantages of simple process, small heat-affected zone, high energy density and good metallurgical combination of the coating and the substrate compared with other coating technologies. Therefore, the laser cladding technology is used to spray a suitable oxide coating on the surface of the stainless steel substrate, which will greatly improve the high-temperature resistance and gas corrosion resistance of the stainless steel chute. This has great significance for improving the service life of the chute in the blast furnace environment. SUMMARY

[0004] The purpose of the present application is to provide a blast furnace chute surface protective coating and a preparation method thereof, which has the characteristics of heat resistance, wear resistance and corrosion resistance, greatly improves the high-temperature resistance and gas corrosion resistance of the stainless steel chute, and further improves the service life of the chute in the blast furnace environment.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a blast furnace chute surface protective coating, the protective coating is covered with a chromium-doped mullite coating on the surface of the stainless steel substrate of the blast furnace chute; the mullite oxide coating contains Cr, Fe and / or chromium oxide and iron oxide particles.

[0006] The protective coating has a thickness of 50-100 μm and is uniformly covered on the surface of the stainless steel substrate of the chute; the stainless steel substrate is 321 austenitic stainless steel (1Cr18Ni9Ti).

[0007] The main components of the protective coating according to the application are 49-95 wt.% mullite, 3-37 wt.% aluminum-chromium solid solution, 0-9 wt.% silicon oxide and 2-5 wt.% Cr, Fe and / or chromium oxide, iron oxide.

[0008] The protective coating according to the application has a microhardness of 580-950 HV measured by a Vickers hardness tester, a wear loss of 3-6 mg after a 60 min wear test and a friction coefficient of 0.66-0.74 after the wear test.

[0009] The application also provides a method for preparing a protective coating for a blast furnace chute surface, comprising the following steps: 1) pretreating the surface to be treated of the blast furnace chute; 2) preparing and mixing the composite coating reinforcing phase powder; 3) cladding the composite coating reinforcing phase powder material on the surface to be treated of the blast furnace chute by using a fiber laser and a synchronous powder feeding device.

[0010] In step 1) of the application, the pretreatment includes polishing and rust removal, alcohol cleaning and drying of the surface to be treated of the blast furnace chute; the surface of the stainless steel substrate of the blast furnace chute is polished by using 500-2000 mesh silicon carbide sandpaper, then the surface to be treated is cleaned by using an ethanol solution with a purity of 75-85%, and the surface to be treated is dried by using a hot air drying machine.

[0011] In step 2) of the application, Al2O3 and SiO2 powders with a particle size of 40-60 μm and Cr2O3 powder with a particle size of 20-40 μm are used as the ceramic reinforcing phase of the composite coating, and the ceramic powders are composed of Al2O3: 50.4-72 wt.%, SiO2: 19.6-28 wt.% and Cr2O3: 0-30 wt.% respectively; 321 austenitic stainless steel (1Cr18Ni9Ti) powder with a particle size of 50-100 μm is used as the stainless steel matrix phase of the composite coating; 90 wt.% of the ceramic reinforcing phase powder is mixed with 10 wt.% of the stainless steel matrix phase powder to prepare the composite coating reinforcing phase powder before cladding, the mixing time is 55-60 min, and the composite coating reinforcing phase powder is dried in a drying oven at 150-160 °C for 5-6 hours after mixing.

[0012] In step 3) of the application, the cladding parameters are as follows: the laser power is 2000-2200 W, the spot diameter is 3-5 mm, the scanning speed is 5-6 mm / s, the powder feeding rate is 12-14 g / min, and the scanning path spacing is 2±0.1 mm.

[0013] The beneficial effects produced by the above technical scheme are as follows: 1. The present application coats a layer of heat-resistant, wear-resistant and gas-erosion-resistant chromium-doped mullite coating on the surface of the stainless steel base body of the blast furnace chute by using laser cladding technology. The chromium-doped mullite coating has good metallurgical bonding with the stainless steel base body of the blast furnace chute, and the internal microstructure is dense and uniform, which greatly improves the high-temperature resistance and gas-erosion resistance of the stainless steel chute. 2. The present application forms a chromium-doped mullite coating on the surface of the coating by adjusting the Cr2O3 content in the coating reinforcement phase powder. The appropriate amount of Cr2O3 can significantly improve the strength of the protective coating, which is due to the formation of chromium-doped mullite phase. 3. The present application can effectively prevent the blast furnace chute from directly contacting with corrosive gas by preparing a protective coating on the surface of the stainless steel base body, and the oxide has the characteristics of high-temperature resistance, which can effectively increase the service life of the stainless steel chute. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a process flow diagram of the method of the present application. Figure 2 It is a cross-sectional SEM micrograph of the thermal barrier coating on the surface of the stainless steel chute. Figure 3 It is a low-power photograph of the force surface after wear resistance test of the protective coating on the surface of the stainless steel chute of Example 1. Figure 4 It is a trend graph of the friction coefficient of the protective coating on the surface of the stainless steel chute of Example 1 with time. Figure 5 It is a low-power photograph of the force surface after wear resistance test of the protective coating on the surface of the stainless steel chute of Example 2. Figure 6 It is a trend graph of the friction coefficient of the protective coating on the surface of the stainless steel chute of Example 2 with time. Figure 7 It is a low-power photograph of the force surface after wear resistance test of the protective coating on the surface of the stainless steel chute of Example 3. Figure 8 It is a trend graph of the friction coefficient of the protective coating on the surface of the stainless steel chute of Example 3 with time. Figure 9 It is a low-power photograph of the force surface after wear resistance test of the protective coating on the surface of the stainless steel chute of Example 4. Figure 10 It is a trend graph of the friction coefficient of the protective coating on the surface of the stainless steel chute of Example 4 with time. DETAILED DESCRIPTION

[0015] The present application will be further described in detail below with reference to the embodiments and drawings. Example 1

[0016] A method for preparing a protective coating on the surface of a blast furnace chute comprises the following steps: 1) Pre-treat the surface of the blast furnace chute to be treated; The pretreatment includes grinding and rust removal, alcohol cleaning and drying of the surface to be treated of the blast furnace chute; polishing the stainless steel base surface of the blast furnace chute with 1200 mesh silicon carbide sandpaper, then cleaning the surface to be treated with 75% purity ethanol solution, and drying the surface to be treated with a hot air dryer.

[0017] 2) Preparation and mixing of composite coating reinforcement phase powder; Al2O3 and SiO2 powders with a particle size of 40 μm are used as the ceramic reinforcement phase of the composite coating. The composition of the ceramic powders is Al2O 3： 72wt.% and SiO2: 28wt.%; 321 austenitic stainless steel powder with a particle size of 60 μm was used as the stainless steel matrix phase of the composite coating. Before cladding, 90 wt.% of ceramic reinforcement phase powder and 10 wt.% of stainless steel matrix phase powder were mixed by mass percentage to prepare the composite coating reinforcement phase powder. The mixing time was 55 min. After mixing, the composite coating reinforcement phase powder was dried in a drying oven at 150°C for 5 hours.

[0018] 3) A fiber laser and synchronous powder feeding device were used to clad the composite coating reinforcement phase powder material onto the surface to be treated on the blast furnace chute. Cladding parameters were: laser power of 2000W, spot diameter of 5mm, scanning speed of 5.2mm / s, powder feeding rate of 12g / min, and scanning path spacing of 2±0.1mm.

[0019] The obtained protective coating on the surface of the blast furnace chute mainly includes a chromium-doped mullite coating. The main components of the protective coating are 95wt.% mullite, 3wt.% aluminum-chromium solid solution and 2wt.% Cr, Fe and / or chromium oxide, iron oxide, in terms of mass percentage.

[0020] The protective coating, 50 μm thick, evenly covers the surface of the chute's stainless steel substrate (321 austenitic stainless steel 1Cr18Ni9Ti). The microhardness of the cladding coating cross-section, measured using a Vickers hardness tester, was 807 HV. After a 60-minute wear test, the coating's wear loss was 4 mg, and the coefficient of friction after the wear test was 0.662. Example 2

[0021] A method for preparing a protective coating on the surface of a blast furnace chute comprises the following steps: 1) Pre-treat the surface of the blast furnace chute to be treated; The pretreatment includes polishing and rust removal of the surface of the blast furnace chute to be treated, alcohol cleaning and drying; 500 mesh silicon carbide sandpaper is used to polish the surface of the stainless steel substrate of the blast furnace chute, then an ethanol solution with a purity of 78% is used to clean the surface to be treated, and a hot air drying machine is used to dry the surface to be treated.

[0022] 2) Preparation of composite coating reinforcing phase powder and powder mixing; Al2O3 and SiO2 powders with a particle size of 60 μm and Cr2O3 powder with a particle size of 40 μm are used as ceramic reinforcing phases of the composite coating, and the compositions of the ceramic powders are Al2O3: 64.8 wt.%, SiO2: 25.2 wt.% and Cr2O3: 10 wt.% respectively; 321 austenitic stainless steel powder with a particle size of 50 μm is used as the stainless steel substrate phase of the composite coating; 90 wt.% of the ceramic reinforcing phase powder is mixed with 10 wt.% of the stainless steel substrate phase powder before cladding to prepare the composite coating reinforcing phase powder, the mixing time is 56 min, and the composite coating reinforcing phase powder is dried in a drying box at 160°C for 5.5 hours after mixing.

[0023] 3) The composite coating reinforcing phase powder material is cladded on the surface to be treated of the blast furnace chute by using a fiber laser and a synchronous powder feeding device. The cladding parameters are: the laser power is 2200 W, the spot diameter is 3.5 mm, the scanning speed is 5.6 mm / s, the powder feeding rate is 14 g / min, and the scanning path interval is 2±0.1 mm.

[0024] The obtained blast furnace chute surface protective coating mainly includes a chromium-doped mullite coating, and the main components of the protective coating are 82 wt.% of chromium-doped mullite, 12 wt.% of aluminum-chromium solid solution, 3.0 wt.% of silicon oxide, and 3 wt.% of Cr, Fe and / or chromium oxide, iron oxide.

[0025] The thickness of the protective coating is 80 μm, which uniformly covers the surface of the stainless steel substrate of the chute (the stainless steel substrate is 321 austenitic stainless steel 1Cr18Ni9Ti).

[0026] The microhardness of the cross section of the protective coating is measured by using a Vickers hardness tester, which is 950 HV. The wear loss of the surface coating after 60 min of wear resistance test is 3 mg, and the friction coefficient of the coating after wear resistance test is 0.660. Example 3

[0027] A preparation method of a blast furnace chute surface protective coating, comprising the following steps: 1) pretreating the surface to be treated of the blast furnace chute; The pretreatment includes grinding and rust removal, alcohol cleaning and drying of the surface to be treated of the blast furnace chute; polishing the stainless steel base surface of the blast furnace chute with 1500 mesh silicon carbide sandpaper, then cleaning the surface to be treated with 85% purity ethanol solution, and drying the surface to be treated with a hot air dryer.

[0028] 2) Preparation and mixing of composite coating reinforcement phase powder; Al2O3 and SiO2 powders with a particle size of 45 μm and Cr2O3 powder with a particle size of 40 μm are used as the ceramic reinforcement phase of the composite coating. The compositions of the ceramic powders are Al2O3: 57.6 wt.%, SiO2: 22.4 wt.% and Cr2O3: 20 wt.% respectively. 321 austenitic stainless steel powder with a particle size of 100 μm was used as the stainless steel matrix phase of the composite coating. Before cladding, 90 wt.% of ceramic reinforcement phase powder and 10 wt.% of stainless steel matrix phase powder were mixed by mass percentage to prepare the composite coating reinforcement phase powder. The mixing time was 58 min. After mixing, the composite coating reinforcement phase powder was dried in a drying oven at 158 ​​° C for 5.2 hours.

[0029] 3) A fiber laser and synchronous powder feeding device were used to clad the composite coating reinforcement phase powder material onto the surface to be treated on the blast furnace chute. Cladding parameters were: laser power of 2100W, spot diameter of 3mm, scanning speed of 6mm / s, powder feed rate of 13g / min, and scanning path spacing of 2±0.1mm.

[0030] The obtained protective coating on the surface of the blast furnace chute mainly includes a chromium-doped mullite coating. The main components of the protective coating are 66.0wt.% of chromium-doped mullite, 24wt.% of aluminum-chromium solid solution, 6.0wt.% of silicon oxide and 4wt.% of Cr, Fe and / or chromium oxide, and iron oxide.

[0031] The protective coating has a thickness of 100 μm and is evenly covered on the surface of the stainless steel substrate of the chute (the stainless steel substrate is 321 austenitic stainless steel 1Cr18Ni9Ti).

[0032] The microhardness of the protective coating cross section was measured by a Vickers hardness tester and was 675HV. The wear loss of the surface coating after a 60-min wear test was 5 mg, and the friction coefficient of the coating after the wear test was 0.668. Example 4

[0033] A method for preparing a protective coating on the surface of a blast furnace chute comprises the following steps: 1) Pre-treat the surface of the blast furnace chute to be treated; The pretreatment includes polishing and rust removal, alcohol cleaning and drying of the surface to be treated of the blast furnace chute; the surface of the stainless steel substrate of the blast furnace chute is polished with 2000 mesh silicon carbide sandpaper, then the surface to be treated is cleaned with 75% pure ethanol solution, and the surface to be treated is dried with a hot air drying machine.

[0034] 2) Preparation of composite coating reinforcing phase powder and powder mixing; Al2O3 and SiO2 powders with a particle size of 55 μm and Cr2O3 powder with a particle size of 20 μm are used as ceramic reinforcing phases of the composite coating, and the compositions of the ceramic powders are respectively Al2O3: 50.4wt.%, SiO2: 19.6wt.% and Cr2O3: 30wt.%; 321 austenitic stainless steel powder with a particle size of 80 μm is used as the stainless steel substrate phase of the composite coating; 90wt.% of the ceramic reinforcing phase powder is mixed with 10wt.% of the stainless steel substrate phase powder to prepare the composite coating reinforcing phase powder before cladding, the mixing time is 60 min, and the composite coating reinforcing phase powder is dried in a drying box at 155°C for 6 hours after mixing.

[0035] 3) The composite coating reinforcing phase powder material is cladded on the surface to be treated of the blast furnace chute by using a fiber laser and a synchronous powder feeding device. The cladding parameters are as follows: the laser power is 2000W, the spot diameter is 4mm, the scanning speed is 5mm / s, the powder feeding rate is 12g / min, and the scanning path interval is 2±0.1mm.

[0036] The obtained surface protective coating of the blast furnace chute mainly includes a chromium-doped mullite coating, and the main components of the protective coating are 49.0wt.% of chromium-doped mullite, 37wt.% of aluminum-chromium solid solution, 9.0wt.% of silicon oxide, and 5wt.% of Cr, Fe and / or chromium oxide, iron oxide.

[0037] The thickness of the protective coating is 72 μm, which uniformly covers the surface of the stainless steel substrate of the chute (the stainless steel substrate is 321 austenitic stainless steel 1Cr18Ni9Ti).

[0038] The microhardness of the cross section of the protective coating is measured by using a Vickers hardness tester, and the hardness is 580HV. The wear loss of the surface coating after 60 min of wear resistance test is 6mg, and the friction coefficient of the coating after wear resistance test is 0.74.

[0039] The wear resistance of the coating is tested by using a wear tester, the test force is 200N, the reciprocating frequency is 4HZ, and the test time is 60min. The wear loss of the surface coating of examples 1-4 is 4mg, 3mg, 5mg and 6mg, respectively. Figures 3-10The surface high-magnification pictures and the friction coefficient change trend graph with time during the wear test of examples 1-4 after the wear test. The protective coating obtained by the present application has good wear resistance The above examples are only used to illustrate but not limit the technical solutions of the present application. Although the present application is described in detail with reference to the above examples, those skilled in the art should understand that the present application can still be modified or equivalently replaced without departing from the spirit and scope of the present application, and any modification or partial replacement should be covered in the scope of the claims of the present application.

Claims

1. A blast furnace spout surface protective coating, characterized by, The protective coating is a chromium-doped mullite coating covering the surface of a stainless steel substrate of a blast furnace chute; the mullite oxide coating contains Cr, Fe and / or chromium oxide and iron oxide particles.

2. A blast furnace spout surface protection coating according to claim 1, characterised in that, The protective coating has a thickness of 50-100 μm and uniformly covers the surface of the stainless steel substrate of the chute; the stainless steel substrate is 321 austenitic stainless steel.

3. A blast furnace spout surface protection coating according to claim 1, characterised in that, The main components of the protective coating include 49-95 wt.% mullite, 3-37 wt.% aluminum-chromium solid solution, 0-9 wt.% silicon oxide, and 2-5 wt.% Cr, Fe and / or chromium oxide and iron oxide.

4. A protective coating for a surface of a trough of a blast furnace according to claim 1, characterized in that, The protective coating has a microhardness of 580-950 HV measured by a Vickers hardness tester, a wear loss of 3-6 mg after a 60 min wear test, and a friction coefficient of 0.66-0.74 after the wear test.

5. A method for the production of a blast furnace chute surface protection coating according to any one of claims 1 to 4, characterized in that The preparation method comprises the following steps: 1) pretreating the surface of the blast furnace chute to be treated; 2) preparing and mixing the composite coating reinforcing phase powder; 3) using a fiber laser and a synchronous powder feeding device to melt the composite coating reinforcing phase powder on the surface of the blast furnace chute to be treated.

6. A method of preparing a surface protective coating for a blast furnace chute according to claim 5, characterized in that, In step 1), the pretreatment includes polishing and rust removal, alcohol cleaning and drying of the surface of the blast furnace chute to be treated; the surface of the stainless steel substrate of the blast furnace chute is polished using 500-2000 mesh silicon carbide sandpaper, then the surface to be treated is cleaned using an ethanol solution with a purity of 75-85%, and the surface to be treated is dried using a hot air drying machine.

7. A method of preparing a surface protective coating for a blast furnace chute according to claim 5, characterized in that, In step 2), Al2O3 and SiO2 powders with a particle size of 40-60 μm and Cr2O3 powder with a particle size of 20-40 μm are used as the ceramic reinforcing phase of the composite coating; the ceramic powders are composed of Al2O3: 50.4-72 wt.%, SiO2: 19.6-28 wt.% and Cr2O3: 0-30 wt.% respectively; 321 austenitic stainless steel powder with a particle size of 50-100 μm is used as the stainless steel substrate phase of the composite coating; 90 wt.% of the ceramic reinforcing phase powder is mixed with 10 wt.% of the stainless steel substrate phase powder to prepare the composite coating reinforcing phase powder before melting, the mixing time is 55-60 min, and the composite coating reinforcing phase powder is dried in a drying oven at 150-160 °C for 5-6 hours.

8. The method of claim 5, wherein the method further comprises the step of applying a protective coating to the surface of the trough. In step 3), the parameters of the melting are as follows: the laser power is 2000-2200 W, the spot diameter is 3-5 mm, the scanning speed is 5-6 mm / s, the powder feeding rate is 12-14 g / min, and the scanning path spacing is 2±0.1 mm.

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