A furnace roller self-abrasion coating for a horizontal continuous annealing furnace and a preparation method thereof

Abstract

The present application relates to the technical field of metal surface treatment, in particular to a kind of furnace roller self-abrasion coating for horizontal continuous annealing furnace and preparation method thereof, high-temperature alloy MCrAlY is used to bottom+ceramic coating (three kinds of ceramic mixed powder) working layer mode to carry out surface strengthening to the surface of horizontal continuous annealing furnace furnace roller, high-temperature alloy plays the transition effect of matrix and ceramic coating, improves coating bonding performance, the coating of working layer is mainly the oxide ceramic of ZrO2-Y2O3+BN+SiO2.ZrO2-Y2O3 plays the role of skeleton support;BN plays the role of lubrication and anti-adhesion;And the main role of SiO2 is to reduce the internal bonding strength of coating, so that the coating can timely peel off when small block neoplasm appears on the surface of roller piece to prevent neoplasm from continuing to adhere and grow.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal surface treatment, in particular to a self-abrasive coating for furnace roller of horizontal continuous annealing furnace and a preparation method thereof. BACKGROUND

[0002] A horizontal continuous annealing furnace is used in cold rolling and galvanizing line and silicon steel production line. The structure of the horizontal continuous annealing furnace is different from that of the vertical furnace of conventional galvanizing line and continuous annealing line. Due to the difference in function and space structure, the structure of the roller in the furnace is also different. The rollers in the horizontal continuous annealing furnace are mostly small-diameter and slender-shaft roller bodies. In theory, the surface of the roller is tangent to the strip steel. In practice, due to the influence of gravity and speed, the strip steel also has a certain degree of surface contact with the roller surface. The front section of the furnace is the non-oxidation section (NOF section), which adopts open flame heating. The annealing furnace is in an oxidizing atmosphere. While heating the steel strip, the steel strip surface residues and the steel strip surface will be oxidized, thereby forming various oxides mainly composed of FeO / Fe2O3 / Fe3O4. Under the double external forces of the gravity of the hot steel strip and the sliding friction generated by the horizontal relative motion of the furnace roller, combined with the strong affinity and mutual solubility of these iron oxides and the furnace roller material (mostly heat-resistant stainless steel), the oxides are easily adhered to the roller surface and chemically react with the base material of the furnace roller to form nodules that are difficult to remove. In addition, under the long-term high-temperature and frequent contact between the furnace roller and the strip steel, the nodules are continuously generated and grown. Since the purity of the atmosphere in the horizontal continuous annealing furnace is relatively poor and the cleanliness in the furnace is also poor, the problem of nodule accumulation on the furnace roller in the furnace is particularly serious. In general, the base of the furnace roller of the horizontal continuous annealing furnace is either uncoated or coated with a conventional coating, which has poor anti-nodule accumulation effect and low furnace roller service life. The production can only be maintained by frequently replacing the roller in a short period of time.

[0003] A certain domestic steel plant introduced the self-abrasive coating roller disclosed in Chinese patent application CN202011481777.6 in 2021. After more than one year of trial, the service life of the furnace roller was prolonged from 3 (uncoated) to 5 (conventional coating) months to more than 9 months, and the nodule problem was also significantly improved. However, the self-abrasive coating roller disclosed in CN202011481777.6 has the problem of local coating falling off. The falling-off part is easy to become a nodule attachment point due to the overall loss of the coating, thereby causing the furnace roller to fail.

[0004] The main problem of the self-abrasive coating roller disclosed in Chinese patent application CN202011481777.6 is that the ceramic phase content in the material ratio is relatively high. After long-term use, the furnace roller is subjected to heat and stress. When subjected to a large impact force, cracking and peeling (falling off) may occur at a certain local position, thereby causing the furnace roller to fail prematurely. SUMMARY

[0005] The purpose of the present application is to solve the problem of premature local failure of the self-abrasion coating roller at high temperature, thereby reducing the maintenance and replacement cost of the continuous annealing furnace caused by the problem of the furnace roller, and improving the performance of the production line capacity, a furnace roller self-abrasion coating (improved type) for a horizontal continuous annealing furnace and a preparation method thereof are provided.

[0006] In order to achieve the above-mentioned purpose, the present application discloses a furnace roller self-abrasion coating for a horizontal continuous annealing furnace, comprising the following steps:

[0007] S1, roller blank making: the roller body is made of centrifugal casting heat-resistant alloy, the shaft head is made of forged piece, then assembled and welded, the roller body and the shaft head are machined to the drawing, and the whole roller surface is ground to the surface roughness Ra0.8 by using hard grinding wheel;

[0008] S2, roller preheating: the roller is preheated in the trolley type heating furnace with the furnace temperature rising;

[0009] S3, roller surface roughening: the roller is clamped on the sand blasting machine tool, the sand blasting tank is filled with 30# white corundum sand, the roller is put into the sand blasting room with the tooling for sand blasting and roughening, and the surface roughness reaches Ra6-8;

[0010] S4, supersonic spraying: the roller is clamped on the spraying equipment tooling, the dried base powder is filled into the supersonic spraying equipment powder hopper, the mechanical hand is installed with the supersonic spraying gun, the supersonic flame spraying is started, each spraying is two times, the next spraying is carried out after 5 minutes, the total spraying is 4 times, after each spraying, the roller surface needs to be scraped and removed by using the blade, the high points of local particle aggregation are removed, the spreading and bonding quality between layers is improved, finally the spraying layer thickness is 70-90 microns, and the surface roughness after spraying is Ra5-7;

[0011] S5, plasma spraying: switch to the plasma spraying equipment, fill the dried working layer powder into the powder hopper, connect the hydrogen and argon, switch the plasma spraying interface, and carry out plasma spraying on the roller surface, the working layer thickness after plasma spraying is controlled within 180-200 microns, and the surface roughness after spraying is Ra6-8;

[0012] S6, abrasive belt polishing: the roller is put on the machine tool, the special polishing machine is used with diamond abrasive belt, and after the surface is bright and smooth and the lines are uniform, the polishing is finished;

[0013] S7, oil removal and alkali washing: the roller is soaked in 30wt% NaOH solution for more than 2 hours, until no bubbles are generated on the surface of the roller, then the roller is washed in clean water for more than three times, and is dried at room temperature or dried by heating;

[0014] S8, hole sealing treatment: the roller surface is brushed with special high-temperature hole sealing agent, the roller is put into the heat treatment furnace after brushing, the hole sealing material is penetrated into the coating pores and solidified to seal the coating pores, and the furnace power is turned off and the furnace is cooled to room temperature.

[0015] In the step S2, the furnace is heated to 200 DEG C, and the furnace is kept for 2 hours, and the furnace is discharged, and the roller surface temperature is detected to be less than or equal to 100 DEG C.

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

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

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

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

[0020] In the step S6, the polishing and grinding machine is set as follows: the driving current is 0.5-0.9 A, the frequency is set to be 35-45 Hz, the abrasive belt is in contact with the roller surface at a pressure of 0.8 MPa, the roller rotates on the machine tool at a rotating speed of 30-50 rpm, the polishing and grinding machine advances at a speed of 20-30 mm / revolution, the roller is uniformly polished and ground to be reduced in diameter by 15-25 mu in the radial direction, and the surface roughness is to be Ra2.0-4.0.

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

[0022] The application further discloses the self-abrasion coating of the furnace roller for the horizontal continuous annealing furnace prepared by the preparation method.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] 1. The application is to make a high-temperature-resistant and stable ceramic coating (a variety of oxide composite ceramic coating) on the surface of the furnace roller, which is a surface strengthening method for the surface of the horizontal continuous annealing furnace roller, and the working layer of the ceramic coating (a powder mixed with three kinds of ceramics) is made of high-temperature alloy MCrAlY bottom + ceramic coating. The high-temperature alloy plays a transition role between the matrix and the ceramic coating, improves the coating bonding performance, and the working layer of the coating is mainly ZrO2-Y2O3+BN+SiO2 oxide ceramic. Among them, ZrO2-Y2O3 plays a skeleton supporting role; BN plays a lubricating and anti-sticking role; and SiO2 mainly plays a role in reducing the internal bonding strength of the coating, so that when small lumps of lumps appear on the surface of the roller, the coating can timely peel off to prevent the lumps from continuing to adhere and grow. Through the composite coating method and the working layer material design, the surface of the horizontal continuous annealing furnace roller is strengthened, the high-temperature resistance and anti-lump performance are improved, and the maintenance and replacement cost caused by the problem of the continuous annealing furnace is reduced, and the production line capacity is improved.

[0025] 2. The application adjusts 0-50% ZrO2-Y2O3+30-50% Al2O3 ceramic phase to 50-70% ZrO2-Y2O3, reduces the content of ceramic phase; introduces 10-40% Al wrapped BN and increases the micron or submicron micropores in the coating through subsequent alkali treatment. In this way, when the coating is subjected to a larger impact force, the microcracks generated in the coating will be passivated in the micropores, and only the micro area will peel off instead of the whole block. In addition, the introduction of BN makes the coating have a lubricating effect during the process of the strip, which offsets the loss of wear resistance caused by the reduction of ceramic phase, thereby comprehensively improving the service life of the coating. It is worth mentioning that the content of Al wrapped 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 wrapped BN is required; when the overall roughness of the strip is small, a coating with a low content of Al wrapped BN is required), and the content of ZrO2-Y2O3 needs to be matched, so as to obtain the optimal comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The process route and flow of the application;

[0027] Figure 2 The lump situation of the conventional coating roller after service;

[0028] Figure 3 The roller surface condition after 1 year of use of the comparative example;

[0029] Figure 4 The roller surface condition after 1.5 years of use of the embodiment. DETAILED DESCRIPTION

[0030] The above and other technical features and advantages of the application will be described in more detail below in conjunction with the accompanying drawings.

[0031] Example 1

[0032] To prepare a composite coating on a small diameter Φ150 roll, the following process steps need to be strictly implemented:

[0033] 1. Roll blank production: The roll body is made of centrifugally cast heat-resistant alloy, the shaft head is made of a forged piece, then assembled and welded, the roll body and shaft head are machined to the drawing, and the entire roll surface is ground to a surface roughness Ra 0.8 using a hard grinding wheel.

[0034] 2. Roll surface inspection: Check the roll surface for defects such as pinholes, shrinkage holes, cracks, etc. If there are defects, use welding material equivalent to the roll body material to perform spot welding, and then perform repair and polishing after spot welding.

[0035] 3. Roll preheating: The roll is preheated in a roller type heating furnace, the furnace temperature is raised to 200°C, and the roll is kept at this temperature for 2 hours before being taken out of the furnace. The roll surface temperature is ≤100°C after being taken out of the furnace.

[0036] 4. Sand blasting: The roll is clamped in a sand blasting machine, the sand blasting tank is filled with 30# white corundum sand, and the roll is sandblasted with the workpiece into the sandblasting room. The surface roughness is Ra 6-8. The process parameters for sandblasting are shown in Table 1.

[0037] Table 1 Process parameters for sandblasting

[0038]

[0039] 5. Supersonic spraying: The roll is clamped to the workpiece of the spraying equipment, the dried base powder (MCrAlY) is filled into the supersonic spraying equipment powder hopper, the mechanical hand is installed with a supersonic spraying gun, and the supersonic flame spraying is started according to the parameters in the table below. Each spraying is performed twice, with an interval of 5 minutes for the next spraying. A total of 4 times (4 passes) of spraying are performed. After each spraying, the roll surface is scraped and the local particle aggregation high points are removed with a blade to improve the spreading and bonding quality between layers. The final spraying layer thickness is 70-90 μm, and the surface roughness after spraying is Ra 5-7.

[0040]

[0041] 6. Plasma spraying: switch to the plasma spraying equipment, fill the dried working layer powder (60% ZrO2-Y2O3, 25% Al-coated BN, and the rest SiO2) into the powder hopper, connect the related gas sources (hydrogen and argon), switch the plasma spraying interface, and perform plasma spraying on the roll surface. A total of 12 times (12 passes) of spraying are performed. The plasma sprayed working layer thickness is controlled at 180-200 μm, and the surface roughness after spraying is Ra 6-8.

[0042]

[0043] 7. Polishing: the roller is placed on a machine, and a special polishing machine with diamond abrasive belt is used. The polishing machine is set at 0.5-0.9 A driving current, and the frequency is set at 35-45 Hz. The abrasive belt is in contact with the roller surface at a pressure of 0.8 MPa. The roller rotates on the machine at a speed of 30-50 rpm. The polishing machine advances at a speed of 20-30 mm / revolution. The roller is uniformly polished until the diameter is reduced by 15-25 μm in the radial direction, and the surface roughness is Ra 2.0-4.0. After the surface is smooth and the lines are uniform, the polishing is completed.

[0044] 8. Alkali washing: the roller is soaked in 30 wt% NaOH solution for more than 2 h until no bubbles are generated on the surface of the roller. The roller is washed in clean water for more than three times, and is dried at room temperature or by heating.

[0045] 9. Hole sealing treatment: the roller surface is coated with a special high-temperature hole sealing agent (zirconium silicate type). After coating, the roller is heated in a heat treatment furnace (temperature is raised to 500°C, and the roller is kept at this temperature for 2 h). The hole sealing material penetrates into the pores of the coating and solidifies to seal the pores. The power of the furnace is turned off, and the roller is cooled to room temperature. The hole sealing treatment can improve the high-temperature resistance and the resistance to nodular accumulation of the roller surface.

[0046] In this example, the content of ZrO2-Y2O3 and BN in the coating is balanced. The roller diameter is detected by using a micrometer, the surface roughness is detected by using a surface roughness meter, and the hardness of the outermost coating of the roller surface is detected by using a sprayed test block. After the detection is qualified, the roller is assembled and used.

[0047] Example 2

[0048] The working layer powder is adjusted as follows: 70% ZrO2-Y2O3, 10% Al-coated BN, and the rest is SiO2.

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

[0050] This example is suitable for production lines and working sections with small overall roughness of the strip.

[0051] Example 3

[0052] The working layer powder is adjusted as follows: 50% ZrO2-Y2O3, 40% Al-coated BN, and the rest is SiO2.

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

[0054] This example is suitable for production lines and working sections with large overall roughness of the strip.

[0055] Comparative Example

[0056] A self-wearing 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 operating conditions at a steel plant in China. The comparative example showed localized spalling and fixed-point nodules after 9-12 months of continuous use, leading to premature failure of the coating roller; while Example 1 showed improvement after 1.5 years of continuous use (e.g., ...). Figure 3 As shown, the coating wear is more uniform, the overall wear level is lower than that of the comparative example, localized flaking is completely avoided, there is virtually no accumulation of nodules, and the roller surface is relatively smoother. Based on the current usage condition of the roller, Example 1 can be used continuously for more than 2 years. Therefore, Example 1 has a service life that is more than twice that of the comparative example, and the improvement effect is very significant. It not only reduces maintenance and replacement costs and increases production line capacity, but also significantly improves the surface quality of the steel plate.

[0058] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A method for preparing a self-wearing coating for furnace rolls in a horizontal continuous annealing furnace, characterized in that, Includes the following steps: S1, Roll blank manufacturing: The roll body is made of centrifugally cast heat-resistant alloy, and the shaft head is made of forging. Then, they are assembled and welded, the roll body and shaft head are machined to the drawing, and the entire roll surface is ground with a hard grinding wheel to a surface roughness of Ra0.

8. S2, Roller preheating: The rollers are preheated in the trolley-type heating furnace and the temperature rises with the furnace. S3, Roller surface roughening: The roller is clamped on the sandblasting machine, the sandblasting can is filled with 30# white corundum sand, and the roller is sandblasted and roughened in the sandblasting room with the tooling until the surface roughness reaches Ra6-8. S4, Supersonic Spraying: The roller is clamped onto the spraying equipment fixture, the dried primer powder is filled into the powder hopper of the supersonic spraying equipment, the robot arm is installed with the supersonic spray gun, and the supersonic flame spraying is started. Two coats are sprayed each time, with a 5-minute interval before the next coat is sprayed. A total of 4 coats are sprayed. After each coat, the roller surface needs to be scraped with a blade to remove local high points of particle aggregation, and to improve the spreading and bonding quality between layers. The final coating thickness is 70µm-90µm, and the surface roughness after spraying is Ra5-7. S5, Plasma Spraying: Switch to the plasma spraying equipment, load the dried working layer powder into the powder hopper, turn on the hydrogen and argon gas, switch the plasma spraying interface, and perform plasma spraying on 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: Roller on machine tool, using a special polishing machine with diamond belt, polishing ends after checking that the surface is bright and smooth and the texture is uniform; S7, Degreasing and Alkaline Washing: Immerse the rollers in a 30wt% NaOH solution for more than 2 hours until no more bubbles emerge from the surface of the rollers. Then wash the rollers in clean water more than three times and air dry or oven dry at room temperature. S8, Sealing treatment: Apply a special high-temperature sealing agent to the roller surface. After application, the roller is heated and kept warm in a heat treatment furnace to promote the sealing material to penetrate into the coating pores and cure, thus sealing the coating pores. Then, turn off the furnace power and let the furnace cool to room temperature. In step S4, the supersonic spraying process parameters are: kerosene flow rate of 19-21 L / h, oxygen flow rate of 860-890 NLPM, carrier gas flow rate of 4.0-6.0 NLPM, and powder feeding speed of 75-85 g / min. In step S5, the plasma spraying process parameters are: argon flow rate of 45.0-65.0 NLPM, hydrogen flow rate of 10.0-13.0, carrier gas flow rate of 4.0-6.0 NLPM, current of 550-600 A, and total power of 35.0-42.0 kW. In step S5, the powder used in plasma spraying is a mixed ceramic powder, with the following main components and proportions: 50-70% ZrO2-Y2O3, 10-40% Al-coated BN, and the remainder being SiO2.

2. The method for preparing a self-wearing coating for furnace rolls in a horizontal continuous annealing furnace as described in claim 1, characterized in that, In step S2, the furnace is heated to 200°C and kept at that temperature for 2 hours before being removed from the furnace. The temperature of the roller surface is then checked and found to be ≤100°C.

3. The method for preparing a self-wearing coating for furnace rolls in a horizontal continuous annealing furnace as described in claim 1, characterized in that, In step S4, the primer powder used in supersonic spraying is MCrAlY powder.

4. The method for preparing a self-wearing coating for furnace rolls in a horizontal continuous annealing furnace as described in claim 1, characterized in that, In step S4, the supersonic spraying process parameters are: rotation speed of 150~180 rpm, pitch speed of 4.0~6.0 mm / Pitch, surface linear velocity of 1175-1415 L / h, and spraying distance of 330-350 mm.

5. The method for preparing a self-wearing coating for furnace rolls in a horizontal continuous annealing furnace as described in claim 1, characterized in that, In step S5, the plasma spraying process parameters are: spraying distance of 110-130 mm, rotation speed of 96-120 rpm, and pitch of 3.0-5.0 mm / pitch.

6. The method for preparing a self-wearing coating for furnace rolls in a horizontal continuous annealing furnace as described in claim 1, characterized in that, In step S6, the polishing machine is set with the following parameters: 0.5-0.9A drive current, frequency set at 35-45Hz, sanding belt pressed against the roller surface with 0.8MPa pressure, roller rotating on the machine tool at 30-50rpm, and the polishing machine's forward speed at 20-30mm / revolution. The polishing is carried out uniformly until the roller's radius is reduced by 15-25µm, and the surface roughness reaches Ra2.0-4.

0.

7. The method for preparing a self-wearing coating for furnace rolls in a horizontal continuous annealing furnace as described in claim 1, characterized in that, In step S8, the special high-temperature sealing agent is zirconium silicate-based.

8. A self-wearing coating for furnace rolls in a horizontal continuous annealing furnace, prepared by the method described in any one of claims 1 to 7.

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