Furnace roller self-abrasion coating for horizontal continuous annealing furnace and preparation method of furnace roller self-abrasion coating

Abstract

The invention relates to the technical field of metal surface treatment, in particular to a furnace roller self-abrasion coating for a horizontal continuous annealing furnace and a preparation method of the furnace roller self-abrasion coating. The surface of a furnace roller of the horizontal continuous annealing furnace is subjected to surface strengthening in a working layer mode of a high-temperature alloy MCrAlY bottoming and a ceramic coating (powder formed by mixing three kinds of ceramics); the high-temperature alloy plays a role in transition between the matrix and the ceramic coating, the bonding performance of the coating is improved, and the coating of the working layer is mainly oxide ceramic of ZrO2-Y2O3 + BN + SiO2. Wherein the ZrO2-Y2O3 plays a role in supporting a framework; the BN plays a role in lubrication and adhesion prevention; siO2 is mainly used for reducing the internal bonding strength of the coating, so that the coating can be timely stripped to prevent the accumulated lumps from continuing to adhere and grow when small accumulated lumps appear on the surface of the roller piece.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment, and in particular to a furnace roller self-abrasion coating for a horizontal continuous annealing furnace and a preparation method thereof. Background Art

[0002] There is a horizontal continuous annealing furnace for cold-rolled galvanizing lines and silicon steel production lines. Its structure is different from the vertical furnace of conventional galvanizing lines and continuous annealing lines. Due to the different functions and spatial structures, the structure of the rollers in the furnace is also different. The rollers in the horizontal continuous annealing furnace are mostly small-diameter, slender shaft-type rollers. In theory, the surface of the roller is in tangential contact with the strip steel. In reality, due to the influence of gravity, speed, etc., the strip steel and the roller surface will also have a certain degree of surface contact. The front section of the furnace is a non-oxidizing section (NOF section), which uses open flame heating. The annealing furnace is an oxidizing atmosphere. While heating the steel strip, the residue on the surface of the steel strip and the surface of the steel strip will be oxidized, thereby forming a variety of oxides mainly composed of FeO / Fe2O3 / Fe3O4. Under the dual external forces of the hot steel strip's own gravity and the sliding friction generated by the horizontal relative movement with the furnace roller, and the strong affinity and mutual solubility of these iron oxides with the furnace roller material (mostly heat-resistant stainless steel), they are easy to adhere to the roller surface and react chemically with the base material of the furnace roller to form nodules that are difficult to remove. In addition, under long-term high temperature and frequent contact between the furnace roller and the strip, nodules are constantly generated and grow. The problem of nodules on the furnace rollers in the horizontal continuous annealing furnace is particularly serious because the atmosphere purity in the furnace is relatively poor and the cleanliness in the furnace is also poor. Under normal circumstances, the furnace roller base of the horizontal continuous annealing furnace is uncoated or with conventional coating, with poor anti-nodule effect and low furnace roller life. Production can only be maintained by frequent short-term roller replacement.

[0003] A domestic steel mill began to introduce the self-abrasive coating roller disclosed in Chinese invention patent application CN202011481777.6 in 2021. After more than a year of trial use, it was found that the service life of the furnace roller was extended from the previous 3 (uncoated) to 5 (conventional coating) months to more than 9 months, and the nodule problem was also significantly improved. However, the coating of the self-abrasive coating roller disclosed in CN202011481777.6 will fall off in local areas. The falling parts are easy to become nodule attachment points due to the overall loss of coating, which leads to failure of the furnace roller.

[0004] The main problem in the use of the self-abrasive coated roller disclosed in Chinese invention patent application CN202011481777.6 is that the ceramic phase content in the material ratio is relatively high. The furnace roller is subjected to heat and stress after long-term use. When it is subjected to a large impact force, cracks and peeling (block falling) are easily accumulated in a certain local position, resulting in premature failure of the furnace roller. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of premature local failure of self-abrasive coating rollers at high temperatures, thereby reducing the maintenance and replacement costs of continuous annealing furnaces due to furnace roller problems and improving the performance of production line capacity. A self-abrasive coating (improved type) for furnace rollers of a horizontal continuous annealing furnace and a preparation method thereof are provided.

[0006] In order to achieve the above object, the present invention discloses a self-abrasive coating for a furnace roller of a horizontal continuous annealing furnace, comprising the following steps:

[0007] S1, Roller blank production: The roller body is made of centrifugally cast heat-resistant alloy, the shaft head is made of forgings, and then assembled and welded, the roller body and shaft head are machined to achieve the drawing, and then the entire roller surface is ground with a hard grinding wheel to a surface roughness of Ra0.8;

[0008] S2, roller preheating: the roller is preheated in a trolley-type heating furnace and preheated as the furnace heats up;

[0009] S3, roller surface roughening: clamp the roller on the sandblasting machine, fill the sandblasting tank with 30# white corundum sand, and put the roller into the sandblasting room with the tooling for sandblasting roughening until the surface roughness reaches Ra6-8;

[0010] S4, supersonic spraying: clamp the roller to the spraying equipment fixture, fill the dried primer powder into the powder hopper of the supersonic spraying equipment, install the supersonic spray gun on the manipulator, start the supersonic flame spraying, spray twice each time, and spray the next time after 5 minutes, a total of 4 times. After each spraying, use a blade to scrape the roller surface and remove the high points where local particles are concentrated to improve the spreading and bonding quality between layers. Finally, the spray layer thickness is 70μm-90μm, and the surface roughness after spraying is Ra5-7;

[0011] S5, plasma spraying: switch to plasma spraying equipment, fill the dried working layer powder into the powder hopper, connect hydrogen and argon, switch the plasma spraying interface, and plasma spray the roller surface. The thickness of the plasma spraying working layer is controlled at 180-200μm, and the surface roughness after spraying is Ra6-8;

[0012] S6, belt polishing: The roller is placed on a machine tool, and a special polishing machine with a diamond abrasive belt is used to check that the surface is bright and flat, and the texture is even, and then the polishing is completed;

[0013] S7, degreasing alkali washing: soak the roller in 30wt% NaOH solution for more than 2h, until bubbles no longer appear on the surface of the roller, wash the roller in clean water for more than three times, and air-dry at room temperature or in an oven;

[0014] S8, Sealing treatment: Apply special high-temperature sealing agent to the roller surface. After coating, the roller is placed in a heat treatment furnace for heating and insulation to promote the sealing material to penetrate into the pores of the coating and solidify, thus sealing the pores of the coating. Turn off the power of the furnace and cool it to room temperature.

[0015] In the step S2, the temperature is raised to 200°C in the furnace, kept at this temperature for 2 hours and then taken out of the furnace. The temperature of the roller surface is detected to be ≤100°C after being taken out of the furnace.

[0016] In the step S4, the primer powder in the supersonic spraying is MCrAlY powder.

[0017] In step S4, the supersonic spraying process parameters are: rotation speed of 150-180rpm, step speed of 4.0-6.0mm / Pitch, surface linear velocity of 1175-1415L / h, kerosene flow rate of 19-21L / h, oxygen flow rate of 860-890NLPM, carrier gas flow rate of 4.0-6.0NLPM, powder feeding speed of 75-85g / min, and spraying distance of 330-350mm.

[0018] In step S5, the powder in plasma spraying is a mixed ceramic powder, and the main components and proportions are as follows: 50-70% ZrO2-Y2O3, 10-40% Al-encapsulated BN, and the rest is SiO2.

[0019] In step S5, the plasma spraying process parameters are: argon flow rate is 45.0-65.0NLPM, hydrogen flow rate is 10.0-13.0, carrier gas flow rate is 4.0-6.0NLPM, current is 550-600A, total power is 35.0-42.0kW, spraying distance is 110-130mm, rotation speed is 96-120rpm, and step distance is 3.0-5.0mm / pitch.

[0020] In step S6, the polishing machine is set with the following parameters: 0.5-0.9A driving current, frequency set at 35-45Hz, the abrasive belt contacts the roller surface with a pressure of 0.8MPa, the roller rotates at a speed of 30-50rpm on the machine, the forward speed of the polishing machine is 20-30mm / revolution, and the roller is polished evenly until the roller is reduced in radius by 15-25μm and the surface roughness reaches Ra2.0-4.0.

[0021] In the step S8, the special high-temperature sealing agent is a zirconium silicate system.

[0022] The invention also discloses a furnace roller self-abrasion coating for a horizontal continuous annealing furnace, which is prepared by the preparation method.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. The present invention manufactures a high-temperature resistant, anti-tumor and stable performance ceramic coating (a ceramic coating of a composite of multiple oxides) on the surface of the furnace roller. The surface of the furnace roller of the horizontal continuous annealing furnace is strengthened by a high-temperature alloy MCrAlY primer + ceramic coating (powder mixed from three ceramics) working layer. The high-temperature alloy plays a transitional role between the substrate and the ceramic coating, improving the coating bonding performance. The coating of the working layer is mainly an oxide ceramic of ZrO2-Y2O3+BN+SiO2. Among them, ZrO2-Y2O3 plays a skeleton support role; BN plays a lubricating and anti-sticking role; and SiO2 mainly plays a role in reducing the bonding strength inside the coating, so that when a small tumor appears on the surface of the roller, the coating can be peeled off in time to prevent the tumor from continuing to adhere and grow. The surface of the furnace roller of the horizontal continuous annealing furnace is strengthened by a composite coating method and a working layer material design, and its high temperature resistance and anti-tumor performance are improved, thereby reducing the maintenance and replacement costs of the continuous annealing furnace caused by furnace roller problems and improving the production line capacity.

[0025] 2. The present invention adjusts 0-50% ZrO2-Y2O3+30-50% Al2O3 ceramic phase to 50-70% ZrO2-Y2O3, reducing the ceramic phase content; introduces 10-40% Al-encapsulated BN and increases the micron-level or submicron-level micropores in the coating through subsequent alkali treatment, so that when the coating is subjected to a large impact force, the microcracks generated inside the coating will be passivated in the micropores, and will only peel off in the micro area instead of falling off as a whole; in addition, the introduction of BN makes the coating have a lubricating effect in the strip process, offsetting the loss of wear resistance caused by the reduction of the ceramic phase, thereby comprehensively improving the service life of the coating. It is worth mentioning that the content of Al-encapsulated BN needs to be selected according to the actual situation of the production line (when the overall roughness of the strip is large, a coating with a high content of Al-encapsulated BN needs to be used; when the overall roughness of the strip is small, a coating with a low content of Al-encapsulated BN needs to be used), and the content of ZrO2-Y2O3 needs to match it, so as to obtain the best comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The process route and process of the present invention;

[0027] Figure 2 The condition of tumor accumulation after the conventional coating roller is put into service;

[0028] Figure 3 This is the roller surface condition after one year of use for the comparative example;

[0029] Figure 4 This is the roller surface condition after 1.5 years of use in the example. DETAILED DESCRIPTION

[0030] The above and other technical features and advantages of the present invention are described in more detail below in conjunction with the accompanying drawings.

[0031] Embodiment 1:

[0032] In order to prepare the composite coating on the roller with a small diameter of Φ150, the following process steps need to be strictly followed:

[0033] 1. Roller blank production: The roller body is made of centrifugally cast heat-resistant alloy, and the shaft head is made of forgings. Then they are assembled and welded, the roller body and the shaft head are machined to the drawing, and then the entire roller surface is ground with a hard grinding wheel to a surface roughness of Ra0.8.

[0034] 2. Roller surface inspection: Check whether there are pinholes, shrinkage holes, cracks and other defects on the roller surface. If there are defects, use welding materials of the same material as the roller body and use argon arc welding to spot weld them. After spot welding, repair and polish them.

[0035] 3. Roller preheating: The roller is preheated in a trolley-type heating furnace, and the temperature is raised to 200°C with the furnace. It is kept warm for 2 hours and then taken out of the furnace. The roller surface temperature is tested to be ≤100°C after being taken out of the furnace.

[0036] 4. Sandblasting: The roller is clamped on the sandblasting machine, and the sandblasting tank is filled with 30# white corundum sand. The roller is brought into the sandblasting room with the tooling for sandblasting and roughening until the surface roughness reaches Ra6-8. The process parameters of sandblasting and roughening are shown in Table 1.

[0037] Table 1 Process parameters of sandblasting

[0038]

[0039] 5. Supersonic spraying: The roller is clamped on the spraying equipment fixture, and the dried primer powder (MCrAlY) is loaded into the powder hopper of the supersonic spraying equipment. The manipulator installs the supersonic spray gun, and starts supersonic flame spraying according to the parameters in the table below. Spray twice each time, and spray the next time after 5 minutes. A total of 4 times (4 times) are sprayed. After each spraying, the roller surface needs to be scraped with a blade to remove the high points of local particle aggregation and improve the spreading and bonding quality between layers. Finally, the spray layer thickness is 70μm-90μm, and the surface roughness after spraying is Ra5-7.

[0040]

[0041] 6. Plasma spraying: Switch to the plasma spraying equipment, load the dried working layer powder (60% ZrO2-Y2O3, 25% Al-encapsulated BN, and the rest SiO2) into the powder hopper, connect the relevant gas sources (hydrogen, argon), switch the plasma spraying interface, and plasma spray the roller surface. Spray a total of 12 times (12 times). The thickness of the plasma spraying working layer is controlled at 180-200μm, and the surface roughness after spraying is Ra6-8.

[0042]

[0043] 7. Polishing: The roller is placed on a machine tool, and a special polishing machine with a diamond abrasive belt is used. The setting parameters of the polishing machine are: 0.5-0.9A driving current, frequency set at 35-45Hz, the abrasive belt contacts the roller surface with a pressure of 0.8MPa, the roller rotates at a speed of 30-50rpm on the machine tool, and the forward speed of the polishing machine is 20-30mm / revolution. The roller is polished evenly until the radius of the roller is reduced by 15-25μm, and the surface roughness is Ra 2.0~4.0. After checking that the surface is bright and flat and the texture is uniform, the polishing is completed.

[0044] 8. Degreasing and alkaline washing: Soak the roller in 30wt% NaOH solution for more than 2 hours until no bubbles appear on the surface of the roller, then wash the roller in clean water for more than three times and air-dry or bake at room temperature.

[0045] 9. Sealing treatment: Apply special high-temperature sealing agent (zirconium silicate system) to the roller surface. After coating, the roller is placed in a heat treatment furnace for heating and insulation (heating to 500℃ and insulation for 2 hours) to promote the sealing material to penetrate into the pores of the coating and solidify, sealing the pores of the coating. Turn off the power of the furnace and cool it to room temperature. The sealing treatment can improve the high temperature resistance of the roller surface and improve the roller surface anti-nodule resistance.

[0046] The contents of ZrO2-Y2O3 and Al-enclosed BN in the coating composition of this embodiment are relatively balanced. In this embodiment, an outside micrometer is used to detect the roller diameter, a surface roughness meter is used to detect the roller surface roughness, and the microhardness of the sprayed test block is tested to characterize the hardness of the outermost coating on the roller surface. After passing the test, the roller is assembled and put into use.

[0047] Embodiment 2:

[0048] The working layer powder is adjusted to: 70% ZrO2-Y2O3, 10% Al-encapsulated BN, and the rest is SiO2;

[0049] The remaining steps are the same as in Example 1.

[0050] This embodiment is suitable for production lines and working sections with relatively small strip roughness.

[0051] Embodiment 3:

[0052] The working layer powder is adjusted to: 50% ZrO2-Y2O3, 40% Al-encapsulated BN, and the rest is SiO2;

[0053] The remaining steps are the same as in Example 1.

[0054] This embodiment is suitable for production lines and working sections with relatively large overall strip roughness.

[0055] Comparative Example:

[0056] A self-abrasive coated roller prepared according to the method disclosed in Chinese invention patent application CN202011481777.6.

[0057] Example 1 and the comparative example were tested under the same working conditions in a domestic steel plant. After 9 to 12 months of continuous use, the comparative example partially fell off and fixed point accumulation occurred, resulting in premature failure of the coating roller; while Example 1 failed after 1.5 years of continuous use (such as Figure 3 The coating wear is more uniform, the overall wear degree is lower than that of the comparative example, the local block drop phenomenon is completely avoided, there is basically no nodule accumulation, and the roller surface is relatively smoother. According to the current use of the roller, Example 1 can be used continuously for more than 2 years. Therefore, the service life of Example 1 is more than 2 times that of the comparative example, and the improvement effect is very significant, which not only reduces the maintenance and replacement costs, improves the production line capacity, but also significantly improves the surface quality of the steel plate.

[0058] The above description is only a preferred embodiment of the present invention, which is only illustrative and not restrictive of the present invention. Those skilled in the art understand that many changes, modifications, and even equivalences may be made to the present invention within the spirit and scope defined by the claims of the present invention, but all of them will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a self-abrasive coating for a furnace roller of a horizontal continuous annealing furnace, characterized in that: The following steps are involved: S1, Roller blank production: The roller body is made of centrifugally cast heat-resistant alloy, the shaft head is made of forgings, and then assembled and welded, the roller body and shaft head are machined to achieve the drawing, and then the entire roller surface is ground with a hard grinding wheel to a surface roughness of Ra0.8; S2, roller preheating: the roller is preheated in a trolley-type heating furnace and preheated as the furnace heats up; S3, roller surface roughening: clamp the roller on the sandblasting machine, fill the sandblasting tank with 30# white corundum sand, and put the roller into the sandblasting room with the tooling for sandblasting roughening until the surface roughness reaches Ra6-8; S4, supersonic spraying: clamp the roller to the spraying equipment fixture, fill the dried primer powder into the powder hopper of the supersonic spraying equipment, install the supersonic spray gun on the manipulator, start the supersonic flame spraying, spray twice each time, and spray the next time after 5 minutes, a total of 4 times. After each spraying, use a blade to scrape the roller surface and remove the high points where local particles are concentrated to improve the spreading and bonding quality between layers. Finally, the spray layer thickness is 70μm-90μm, and the surface roughness after spraying is Ra5-7; S5, plasma spraying: switch to plasma spraying equipment, fill the dried working layer powder into the powder hopper, connect hydrogen and argon, switch the plasma spraying interface, and plasma spray the roller surface. The thickness of the plasma spraying working layer is controlled at 180-200μm, and the surface roughness after spraying is Ra6-8; S6, belt polishing: The roller is placed on a machine tool, and a special polishing machine with a diamond abrasive belt is used to check that the surface is bright and flat, and the texture is even, and then the polishing is completed; S7, degreasing alkali washing: soak the roller in 30wt% NaOH solution for more than 2h, until bubbles no longer appear on the surface of the roller, wash the roller in clean water for more than three times, and air-dry at room temperature or in an oven; S8, Sealing treatment: Apply special high-temperature sealing agent to the roller surface. After coating, the roller is placed in a heat treatment furnace for heating and insulation to promote the sealing material to penetrate into the pores of the coating and solidify, thus sealing the pores of the coating. Turn off the power of the furnace and cool it to room temperature.

2. The method for preparing a self-abrasive coating for a furnace roller of a horizontal continuous annealing furnace according to claim 1, characterized in that: In the step S2, the temperature is raised to 200°C in the furnace, kept at this temperature for 2 hours and then taken out of the furnace. The temperature of the roller surface is detected to be ≤100°C after being taken out of the furnace.

3. The method for preparing a self-abrasive coating for a furnace roller of a horizontal continuous annealing furnace according to claim 1, characterized in that: In the step S4, the primer powder in the supersonic spraying is MCrAlY powder.

4. The method for preparing a self-abrasive coating for a furnace roller of a horizontal continuous annealing furnace according to claim 1, characterized in that: In step S4, the supersonic spraying process parameters are: rotation speed of 150-180rpm, step speed of 4.0-6.0mm / Pitch, surface linear velocity of 1175-1415L / h, kerosene flow rate of 19-21L / h, oxygen flow rate of 860-890NLPM, carrier gas flow rate of 4.0-6.0NLPM, powder feeding speed of 75-85g / min, and spraying distance of 330-350mm.

5. The method for preparing a self-abrasive coating for a furnace roller of a horizontal continuous annealing furnace according to claim 1, characterized in that: In step S5, the powder in plasma spraying is a mixed ceramic powder, and the main components and proportions are as follows: 50-70% ZrO2-Y2O3, 10-40% Al-encapsulated BN, and the rest is SiO2.

6. The method for preparing a self-abrasive coating for a furnace roller of a horizontal continuous annealing furnace according to claim 1, characterized in that: In step S5, the plasma spraying process parameters are: argon flow rate is 45.0-65.0NLPM, hydrogen flow rate is 10.0-13.0, carrier gas flow rate is 4.0-6.0NLPM, current is 550-600A, total power is 35.0-42.0kW, spraying distance is 110-130mm, rotation speed is 96-120rpm, and step distance is 3.0-5.0mm / pitch.

7. The method for preparing a self-abrasive coating for a furnace roller of a horizontal continuous annealing furnace according to claim 1, characterized in that: In step S6, the polishing machine is set with the following parameters: 0.5-0.9A driving current, frequency set at 35-45Hz, the abrasive belt contacts the roller surface with a pressure of 0.8MPa, the roller rotates at a speed of 30-50rpm on the machine, the forward speed of the polishing machine is 20-30mm / revolution, and the roller is polished evenly until the roller is reduced in radius by 15-25μm and the surface roughness reaches Ra2.0-4.

0.

8. The method for preparing a self-abrasive coating for a furnace roller of a horizontal continuous annealing furnace according to claim 1, characterized in that: In the step S8, the special high-temperature sealing agent is a zirconium silicate system.

9. A self-abrasive coating for furnace rollers used in a horizontal continuous annealing furnace, prepared by the preparation method according to any one of claims 1 to 8.

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