Method for maintaining oxidation film of roller

Abstract

The invention belongs to the field of rolling mill production and roller surface strengthening, and particularly relates to a method for keeping a roller oxidation film for a long time and inhibiting short-time falling. A layer of alloy uniform in thickness is formed on the surface of the roller through pretreatment of the oxidation film on the surface of the roller, the surface performance hardness and roughness of the alloy are consistent with use requirements, abrasion of a rolling mill to the roller due to high temperature and high rolling force can be reduced, meanwhile, an anti-abrasion oxidation film can be formed in the later period, the rolling requirement of high-quality products is met, and the service life of the roller is prolonged. Alloy close to a roller base body is selected and tightly combined to a roller body through laser spraying, alloy elements contained in the alloy elements can be effectively fused into the roller body, forming and maintaining of an oxidation film of the roller body are facilitated, in the continuous and repeated forming process of the oxidation film, the oxidation film can be restrained from being rapidly peeled off and effectively combined with the roller body, and therefore the service life of the roller body is prolonged. The oxidation film is always kept in dynamic balance, the high-quality surface of the roller is achieved, roller abrasion is reduced, and batch production of high-surface products is achieved.

Description

Technical Field

[0001] The present invention belongs to the fields of rolling mill production and roll surface strengthening, and specifically relates to a method for long-term retention of the roll oxide film and suppression of short-term shedding. Background Art

[0002] High-speed steel rolls are high-carbon high-alloy steels containing a large amount of elements such as tungsten, molybdenum, chromium, and vanadium, and have characteristics such as high hardness, high wear resistance, and high hot hardness. The eutectic carbides distributed on the matrix are mostly of the Fe3C type or M7C3 type. The oxide film formed on the roll surface during the rolling process can reduce the friction coefficient between the roll and the rolled material, improve the surface quality, and extend the roll life.

[0003] Due to the influence of factors such as the rolling force of the rolling mill, alternating shear force, friction force, cooling water, high temperature, and scale, the oxide film will become thicker, the surface will become rough, and the bonding strength with the matrix will decrease. Eventually, the oxide film will be damaged and shed, affecting the surface quality. If it is stopped for use and repaired, the performance of the high-speed steel will be reduced.

[0004] Currently, the methods for extending the high-speed steel oxide film mainly include reducing the rolling load to generate shear force, increasing the roll cooling water to slow down the thickening of the oxide film, and using rolling lubrication to reduce the friction force. However, the current situation of oxide film shedding has not been significantly improved.

[0005] For example, a method for extending the service life of superalloys by prefabricating an oxide film disclosed in CN114717626A and a device and process for prefabricating an oxide film on the surface of a hot rolling roll by laser forming disclosed in CN114622154A. Both of these patents prefabricate an oxide film on the surface, which only plays a protective role at the initial stage of roll use. However, under the action of high temperature and high rolling force during hot rolling, the prefabricated oxide film will be worn out relatively quickly in a short period, without considering the continuous shedding, formation, and effective bonding of the oxide film with the roll matrix, and thus cannot solve the problem of maintaining the roll oxide film well. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: the problem that the existing roll oxide film wears out relatively quickly in a short period and cannot be retained for a long time.

[0007] To solve the above technical problem, the inventors obtained the technical solution of the present invention through practice and summary. The present invention adopts the following technical solution:

[0008] A method for maintaining a roll oxide film, comprising:

[0009] Step 1, purifying the roll surface;

[0010] Step 2, dehumidifying the roll surface;

[0011] Step 3, roughening the roll surface: Carry out sandblasting operations on the forward helix and reverse helix of the roll surface to form a roughened structure on the roll surface. The sandblasting distance is between 120 and 150 mm, the sandblasting angle is between 75° and 90°, the air pressure is 0.6 - 0.7 Mpa, and the surface roughness of the workpiece after sandblasting reaches Ra: 6.5 - 8 μm;

[0012] Step 4, laser spraying: Before powder feeding for spraying, preheat the spraying surface, and control the preheating temperature at 50°C - 60°C;

[0013] Immediately, alloy powder one and alloy powder two are evenly sprayed on the roughened roll surface through a laser powder spraying device in sequence to obtain coating one and coating two, and the total thickness of the coating is not less than 0.2 mm;

[0014] The chemical composition is C 1.5 / 2.5%, Si 0.4 / 0.8%, Mn 0.4 / 1.0%, Cr 4 / 7%, Ni 0.3 / 1.2%, Mo 2.0 / 6.0%, Nb ≤ 2%, S ≤ 0.06%, P ≤ 0.08%; the metallographic structure is martensite, cementite, carbide and a small amount of retained austenite; the surface finish requirement is greater than 0.8 Ra; the hardness is 75 - 85 hsc.

[0015] The components of alloy powder one, by 100 parts, include 6 - 18 parts of Fe, 4.0 - 9.0 parts of Cr, 1.0 - 5.0 parts of Mo, 4.0 - 8.0 parts of Co, 1.0 - 2.5 parts of Nb, 1.0 - 2.5 parts of Mn, 0.2 - 0.5 parts of Cs, 0.5 - 1.2 parts of C, 3.0 - 4.2 parts of B, and the balance is Ni and unavoidable impurities, where: 0.04 ≤ (C + Nb + B + Mn) / (Cr + Mo + Fe + Ni) ≤ 0.19, 0.02 ≤ (Cr + Co + Mo) / (Ni + Fe + Mn) ≤ 0.16, 0.06 ≤ (Cs + C) / (Cr + Mo + Fe) ≤ 0.41;

[0016] The components of alloy powder two, by 100 parts, include: 15 - 25 parts of Cr, 5 - 15 parts of Ni, 2 - 4 parts of Mn, 0.2 - 0.8 parts of C, 1.0 - 3.0 parts of Mo, and the balance is Co and unavoidable impurities, where: 0.65 ≤ (Cr + C) / (Ni + Mo + Mn) ≤ 3.45;

[0017] Step 5, post-spraying treatment

[0018] Immediately after the spraying surface, use an oilstone to polish the spraying surface, and the hardness of the roll body is not less than 73 HSC.

[0019] Preferred local solution: By weight per 100 parts, a component of the alloy powder includes 6 - 10 parts of Fe, 5.0 - 8.0 parts of Cr, 3.0 - 5.0 parts of Mo, 6.0 - 8.0 parts of Co, 1.5 - 2.5 parts of Nb, 1.5 - 2.5 parts of Mn, 0.2 - 0.5 parts of Cs, 0.5 - 0.8 parts of C, 3.5 - 4.2 parts of B, and the balance is Ni and inevitable impurities, where: 0.05 ≤ (C + Nb + B + Mn) / (Cr + Mo + Fe + Ni) ≤ 0.12, 0.04 ≤ (Cr + Co + Mo) / (Ni + Fe + Mn) ≤ 0.08, 0.08 ≤ (Cs + C) / (Cr + Mo + Fe) ≤ 0.32;

[0020] Preferred local solution: By weight per 100 parts, a second component of the alloy powder includes: 15 - 25 parts of Cr, 5 - 15 parts of Ni, 2 - 4 parts of Mn, 0.2 - 0.8 parts of C, 1.0 - 3.0 parts of Mo, and the balance is Co and inevitable impurities, where: 0.75 ≤ (Cr + C) / (Ni + Mo + Mn) ≤ 1.52.

[0021] Preferred local solution: The laser powder spraying equipment includes:

[0022] A clamping mechanism, at the bottom of which a moving component is provided. The clamping mechanism includes a clamping fixture, a top column, a driving main shaft and a support roller. The clamping fixture and the top column fix the rolling mill from both ends. The support roller is used to support one end of the rolling mill away from the clamping fixture, and the driving main shaft drives the clamping fixture to make a rotary motion;

[0023] A powder spraying mechanism, which includes an enclosure. Both ends of the enclosure are provided with inlets and outlets. The clamping mechanism can enter the enclosure through the inlets and outlets. At the inlets and outlets, a closing door and a component for driving the closing door to open the inlets and outlets are installed. At the top of the enclosure, a laser spraying part is installed, and the laser spraying part melts and sprays alloy powder one and alloy powder two on the surface of the straightening roller;

[0024] A preheating mechanism, which includes a preheating frame. The preheating frame is arranged obliquely downward and a preheating ring body is provided at its free end. A heating coil is embedded inside the preheating ring body. After the heating coil is powered on, the surface of the roller is preheated to 50°C - 60°C.

[0025] Preferred local solution: The laser spraying part includes a central laser beam tube and a powder feeding frame rotatably installed outside the bottom of the central laser beam tube. A plurality of powder feeding tubes distributed circumferentially are installed on the powder feeding frame. The powder outlet of the powder feeding tube is arranged obliquely downward and gradually approaches the central laser beam tube. A powder leveling cover is connected to the top of the powder feeding tube;

[0026] A gear ring is installed on the outer side of the powder leveling cover, and an annular sealing plate is fixed on the outer side of the central laser beam tube. The annular sealing plate is used to block the top of the powder leveling cover and rotates relative to the powder leveling cover. A powder receiving pipe and a micro motor are installed on the annular sealing plate, and a driving gear is installed at the output end of the micro motor. The driving gear meshes with the gear ring.

[0027] In a preferred embodiment, a protective gas pipe is independently arranged on the outer side of the powder feeding pipe. The gas port of the protective gas pipe is arranged obliquely downward and gradually approaches the central laser beam tube, and the inclination angle of the protective gas pipe is greater than or equal to the inclination angle of the powder feeding pipe.

[0028] The top of the protective gas pipe is connected with a gas leveling cover. The gas leveling cover is arranged on the outer side of the powder leveling cover, and a toothed ring is arranged on the inner wall. The toothed ring meshes with the driving gear. The top of the gas leveling cover and the annular sealing plate are rotationally arranged, and an air receiving pipe communicated with the gas leveling cover is also arranged on the annular sealing plate.

[0029] In a preferred embodiment, a support body is installed on the powder feeding rack. The support body passes through the gap between the powder feeding pipes, and an isolation cover is installed at the free end. The isolation cover collects the protective gas and guides it outward.

[0030] The top of the isolation cover is of a conical structure, and the bottom is of a waist-shaped structure.

[0031] In a preferred embodiment, the powder outlet of the powder feeding pipe is arranged obliquely downward and gradually deviates from the axis of the central laser beam tube.

[0032] In a preferred embodiment, the laser spraying in the step specifically includes:

[0033] Step 41: Lift the rolling mill onto the clamping fixture and the supporting roller, and fix the rolling mill from both ends through the clamping fixture and the top column.

[0034] Step 42: The moving component moves the clamping mechanism into the closed cover through the inlet and outlet, and the closing door closes the inlet and outlet.

[0035] Step 43: Drive the main shaft to drive the clamping fixture to drive the rolling mill to rotate. At the same time, the heating coil is energized, and the roller surface is preheated to 50°C - 60°C through the preheating ring body.

[0036] Step 44: Turn on the laser spraying part, the moving component drives the clamping mechanism to move horizontally. The laser spraying part immediately sprays alloy powder on the preheated roller surface. The laser beam shoots out from the central laser beam tube. The micro motor drives the driving gear to rotate, and then drives the powder feeding pipe and the protective gas pipe to rotate at different speeds through the gear ring. Under the action of the high-speed gas, the alloy powder is ejected from the powder outlet, forms a vortex and converges in the laser beam and absorbs energy to melt, and then collides with the laser-irradiated roller surface in a vortex manner and quickly combines to form a coating on the roller surface. At the same time, the protective gas pipe forms a vortex protection air flow cover on the outer side of the powder feeding pipe.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The object of the present invention is to pre-treat the oxide film on the surface of the roll to form a layer of alloy with uniform thickness on the surface of the roll, whose surface properties such as hardness and roughness are consistent with the usage requirements, which can reduce the wear of the roll caused by high temperature and high rolling force of the rolling mill. At the same time, an anti-wear oxide film can be formed in the later stage to meet the rolling requirements of high-quality products and extend the service life of the roll. By selecting an alloy close to the roll substrate and tightly bonding it to the roll body through laser spraying, the alloy elements can effectively fuse into the roll body, which helps the formation and maintenance of the oxide film on the roll body. During the continuous formation of the oxide film, its rapid peeling can be inhibited and it can effectively bond with the roll body, so that the oxide film is always in dynamic equilibrium, achieving a high-quality surface of the roll, reducing roll wear and mass production of high-surface-quality products.

[0039] The inventor made targeted optimization treatments for the specific ratios of components. By reasonably introducing elements such as Nb, Mn, Co, Cs, and B, and optimizing the ratios of Cr, Fe, Mo, C, and Ni, since the melting point of the alloy was reduced by reasonably introducing B, Cs, etc., the cladding temperature was reduced from 1290°C - 1350°C of traditional nickel-based alloys to 1050°C - 1100°C, which promoted the formation of the alloy coating and helped improve the purity of the alloy, and a more uniform and dense coating was obtained. The introduction of Cs was beneficial to enhancing the bonding force between the coating and the substrate, improving the adhesion and durability of the coating. The introduction of B was beneficial to increasing the hardness of the alloy. Since elements such as Ni, Cr, Mo, and Fe could form solid solutions or intermetallic compounds, and form hard phases with C and B to ensure high hardness and wear resistance of the coating; since elements such as C and B were important components for forming hard phases, however, too many hard phases would lead to an increase in the brittleness of the coating and reduce its impact resistance, but it couldn't be too low either, otherwise there would be a problem of insufficient hardness. Nb could form stable compounds with C and B that could enhance the hardness and wear resistance of the coating and play a role in solid solution strengthening in the alloy. At the same time, Mn could dissolve in ferrite to form a substitutional solid solution. The formation of this solid solution would increase the lattice distortion, thereby hindering the movement of dislocations and increasing the strength and hardness of the alloy. This was helpful for the alloy to resist deformation when subjected to external forces. Therefore, controlling the ratio of (C + Nb + Mn + B) / (Cr + Mo + Fe + Ni) between 0.04 and 0.19 could balance the high-temperature resistance, high rolling force, thermal and cold deformation stresses, and anti-shedding performance of the coating, ensuring its good comprehensive performance. At the same time, since elements such as Cr, Mo, and Co could form hard compounds, improving the hardness and high-temperature corrosion resistance of the coating; while elements such as Ni, Fe, and Mn could improve the toughness and fatigue resistance of the coating. By controlling the ratio of (Cr + Mo + Co) / (Ni + Fe + Mn) between 0.02 and 0.16, the high-temperature corrosion resistance and overall mechanical properties of the coating could be further optimized. Cr, Mo, and Fe were important components for forming the BCC phase structure. Secondly, the introduction of Cs was beneficial to promoting the formation of the BCC phase structure. C mainly formed carbides with Cr, Mo, and Fe to ensure the hardness and wear resistance of the coating. Therefore, by controlling the ratio of (Cs + C) / (Cr + Mo + Fe) between 0.06 and 0.41, controlling this ratio could ensure the appropriate distribution of Cs and C elements in the coating, enabling good coordination between the hard phases (such as carbides, BCC phase structure, etc.) and the substrate (such as solid solution) in the coating, avoiding cracks or spalling during the impact process, and also avoiding the adverse effects caused by excessive addition, such as increased brittleness of the coating and reduced interfacial bonding strength, ensuring good metallurgical bonding between the coating and the substrate and helping to improve the impact resistance of the entire coating.By specifically designing new components of alloy powder two and reasonably optimizing its ratio, Cr and C are the main components of the hard phase and solid solution in the alloy, and Ni, Mo, and V are the main components for improving the alloy. By optimizing and controlling their ratio to be between 0.65 and 3.45, the hardness, wear resistance, and toughness of the alloy coating can be balanced, ensuring the high hardness, high wear resistance, high temperature corrosion resistance, and impact resistance of the coating, reducing the brittleness of grain boundaries, increasing the bonding strength, and making it less likely to generate fatigue cracks and thermal cracks. Secondly, alloy powder two is a cobalt-based alloy, and elements such as Cr, Ni, V, Co, and Mo can form a metallurgical bond with the coating one metal, which can improve the wetting behavior between alloy powder two and coating one and promote the formation of metallurgical bonding.

[0040] In the laser spraying process of the present invention, the rolling mill is fixed by a clamping mechanism and rotates under the drive of the driving main shaft. The heating coil at the end of the preheating rack is energized to preheat the roll surface to 50°C - 60°C. After preheating, the rolling mill rotates under the action of the driving main shaft and then laser spraying is carried out immediately. The laser spraying of this scheme is different from traditional laser spraying in that the alloy powder converges in a vortex in the laser beam, and the alloy powder is in a vortex shape in the laser beam, and then collides with the roll surface in a vortex manner to form a coating. The coating has better uniformity, and can disperse the thermal shock of the laser beam and alloy particles on the roll surface, reducing the risk of thermal stress concentration; at the same time, the protective gas forms a vortex-shaped protective air flow cover on the outside to protect its interior. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is the production process diagram of the present invention;

[0042] Figure 2 is the overall structure schematic diagram of the present invention;

[0043] Figure 3 is the structure diagram of the laser spraying part of the present invention;

[0044] Figure 4 is the bottom view of the laser spraying part of the present invention;

[0045] Figure 5 is the structural relationship diagram of the support body and the isolation cover in the present invention;

[0046] Figure 6 is the overall structure diagram of the preheating mechanism in the present invention;

[0047] Figure 7 is the front view of the clamping mechanism in the present invention;

[0048] Figure 8 is the internal structure diagram of the powder spraying mechanism in the present invention.

[0049] In the figure: 10, clamping mechanism; 11, clamping fixture; 12, ejector pin; 13, support roller; 14, moving component; 20, powder spraying mechanism; 21, closed cover; 22, closed door; 23, laser spraying part; 231, central laser beam tube; 232, powder feeding rack; 2321, support body; 2322, isolation cover; 233, powder feeding pipe; 234, powder leveling cover; 235, gear ring; 236, ring sealing plate; 2361, powder receiving pipe; 2362, protective gas pipe; 2363, gas leveling cover; 2364, tooth ring; 2365, gas receiving pipe; 237, micro motor; 238, driving gear; 30, heat preservation mechanism; 31, preheating rack; 32, preheating ring body; 33, heating coil. Detailed implementation mode

[0050] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0051] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0052] Embodiment 1

[0053] Step 1, purify the surface of the rolling mill roll;

[0054] Step 2, dehumidify the roll surface;

[0055] Step 3, roughen the roll surface: perform sandblasting operations on the forward helix and reverse helix of the roll surface to form a roughened structure on the roll surface. The sandblasting distance is between 120 and 150 mm, the sandblasting angle is between 75° and 90°, the air pressure is 0.6 - 0.7 Mpa, and the surface roughness of the workpiece after sandblasting reaches Ra: 6.5 - 8 um;

[0056] Step 4, laser spraying: preheat the spraying surface before powder feeding for spraying, and control the preheating temperature at 50°C - 60°C;

[0057] Immediately, alloy powder one and alloy powder two are evenly sprayed on the roughened roll surface of the rolling mill through a laser powder spraying device in sequence to obtain coating one and coating two, and the total thickness of the coating is not less than 0.2 mm;

[0058] One component of the alloy powder, by weight per hundred parts, includes 6 parts of Fe, 5 parts of Cr, 1 part of Mo, 4 parts of Co, 1 part of Nb, 1 part of Mn, 0.2 part of Cs, 0.5 part of C, 3.5 parts of B, and the balance is Ni and unavoidable impurities, where: 0.05 ≤ (C + Nb + B + Mn) / (Cr + Mo + Fe + Ni) ≤ 0.12, 0.04 ≤ (Cr + Co + Mo) / (Ni + Fe + Mn) ≤ 0.08, 0.08 ≤ (Cs + C) / (Cr + Mo + Fe) ≤ 0.32;

[0059] Two components of the alloy powder, by weight per hundred parts, include: 15 parts of Cr, 12 parts of Ni, 2 parts of Mn, 0.4 part of C, 2 parts of Mo, and the balance is Co and unavoidable impurities, where: 0.75 ≤ (Cr + C) / (Ni + Mo + Mn) ≤ 1.52;

[0060] Step 5, post-treatment after spraying

[0061] Immediately after the surface to be sprayed, the sprayed surface is polished with an oilstone, and the hardness of the roll body is not less than 73 HSC.

[0062] Example 2

[0063] Differing from Example 1, one component of the alloy powder, by weight per hundred parts, includes 8 parts of Fe, 8 parts of Cr, 3 parts of Mo, 6 parts of Co, 1.5 parts of Nb, 1.5 parts of Mn, 0.4 part of Cs, 0.6 part of C, 3.5 parts of B, and the balance is Ni and unavoidable impurities, where: 0.05 ≤ (C + Nb + B + Mn) / (Cr + Mo + Fe + Ni) ≤ 0.12, 0.04 ≤ (Cr + Co + Mo) / (Ni + Fe + Mn) ≤ 0.08, 0.08 ≤ (Cs + C) / (Cr + Mo + Fe) ≤ 0.32;

[0064] Two components of the alloy powder, by weight per hundred parts, include: 20 parts of Cr, 15 parts of Ni, 4 parts of Mn, 0.4 part of C, 4 parts of Mo, and the balance is Co and unavoidable impurities, where: 0.75 ≤ (Cr + C) / (Ni + Mo + Mn) ≤ 1.52.

[0065] Example 3

[0066] Different from Example 1, one component of the alloy powder, by weight, includes 10 parts of Fe, 8 parts of Cr, 5 parts of Mo, 8 parts of Co, 2.5 parts of Nb, 1.8 parts of Mn, 0.5 part of Cs, 0.8 part of C, 4 parts of B, and the balance is Ni and inevitable impurities, where: 0.05 ≤ (C + Nb + B + Mn) / (Cr + Mo + Fe + Ni) ≤ 0.12, 0.04 ≤ (Cr + Co + Mo) / (Ni + Fe + Mn) ≤ 0.08, 0.08 ≤ (Cs + C) / (Cr + Mo + Fe) ≤ 0.32;

[0067] The second component of the alloy powder, by weight, includes: 18 parts of Cr, 13 parts of Ni, 3 parts of Mn, 0.6 part of C, 3 parts of Mo, and the balance is Co and inevitable impurities, where: 0.75 ≤ (Cr + C) / (Ni + Mo + Mn) ≤ 1.52.

[0068] Through surface oxide film pretreatment, the present invention forms a stable oxide film on the surface of the high-speed steel roll, which can improve the surface quality of the oxide film, increase the proportion of the primary oxide film, increase the number of times the high-speed steel is put into operation, speed up the rolling rhythm, improve production capacity, reduce energy consumption and the quality block rate, and has considerable economic benefits.

[0069] List the data and effects of oxide film pretreatment.

[0070] The first round of use was from November 2 to December 6, 2024, and the second round of use was from December 15, 2024 to March 5. The test results are as follows:

[0071] 1) The number of times the high-speed steel roll is put into operation is increased from 1.4 times to 4 times, the rolling volume per millimeter is increased by 1.44 times, and the roll consumption is reduced by 54.5%;

[0072] 2) The primary oxide film of the oxide film taken off the machine reaches 2 times, and the pickled plate is increased from 1 rolling plan to 3 rolling plans, making it easier to arrange the rolling plan;

[0073] 3) The oxide film retention ability of the roll surface taken off the machine is good, without local peeling. For steel types such as pickled plates with high surface quality and thin specifications, the rolling process is stable, there is no peeling of the oxide film, no sticking of the roll, the surface quality of the plate is excellent, and the quality block rate and waste and defect reduction are reduced;

[0074] 4) Regarding the effectiveness of rolling high-surface-quality plates and pickled plates (high-strength thin specifications), it is currently being promoted on the hot-rolled thin plate line.

[0075]

[0076]

[0077] Example 4

[0078] Based on Embodiment 1, the following improvements are made: As Figures 2 to 8 shown, the laser powder spraying device includes:

[0079] A clamping mechanism 10, a moving component 14 is arranged at the bottom of the clamping mechanism 10. The clamping mechanism 10 includes a clamping fixture 11, a top column 12, a driving main shaft and a support roller 13. The clamping fixture 11 and the top column 12 fix the rolling mill from both ends. The support roller 13 is used to support one end of the rolling mill away from the clamping fixture 11, and the driving main shaft drives the clamping fixture 11 to perform a rotary motion;

[0080] A powder spraying mechanism 20, the powder spraying mechanism 20 includes an enclosure 21. Both ends of the enclosure 21 are provided with inlets and outlets. The clamping mechanism 10 can enter the enclosure 21 through the inlets and outlets. A closing door 22 is installed at the inlets and outlets and drives the closing door 22 to open the inlets and outlets. A laser spraying part 23 is installed on the top of the enclosure 21. The laser spraying part 23 melts and sprays alloy powder one and alloy powder two on the surface of the straightening roller;

[0081] A preheating mechanism 30, the preheating mechanism 30 includes a preheating frame 31. The preheating frame 31 is arranged obliquely downward and a preheating ring body 32 is arranged at the free end. A heating coil 33 is embedded inside the preheating ring body 32. After the heating coil 33 is powered on, the surface of the roller is preheated to 50°C to 60°C.

[0082] The rolling mill is hoisted onto the support roller 13, clamped at both ends by the clamping fixture 11 and the top column 12, and then enters the enclosure 21 through the inlets and outlets by the moving component 14. When it reaches the predetermined position, the heating coil 33 is powered on and locally heats the surface of the roller until it is heated to 50°C to 60°C. After preheating, immediately the laser spraying part 23 sprays alloy powder on the surface of the roller, which can avoid the appearance of brittle layers at the bonding interface; the laser spraying part 23 melts and sprays alloy powder one and alloy powder two on the surface of the roller, and successively forms a first coating and a second coating on the outside of the straightening roller.

[0083] Embodiment 5

[0084] Based on Embodiment 4, the following improvements are made: As Figures 2 to 8 shown, the laser spraying part 23 includes a central laser beam tube 231 and a powder feeding frame 232 rotatably installed on the outside of the bottom of the central laser beam tube 231. A plurality of powder feeding tubes 233 distributed circumferentially are installed on the powder feeding frame 232. The powder outlet of the powder feeding tube 233 is arranged obliquely downward and gradually approaches the central laser beam tube 231. The top of the powder feeding tube 233 is connected with a powder leveling cover 234;

[0085] A gear ring 235 is installed outside the powder leveling cover 234. An annular sealing plate 236 is fixed outside the central laser beam tube 231. The annular sealing plate 236 is used to block the top of the powder leveling cover 234 and rotates relative to the powder leveling cover 234. A powder receiving pipe 2361 and a micro motor 237 are installed on the annular sealing plate 236. A driving gear 238 is installed at the output end of the micro motor 237, and the driving gear 238 meshes with the gear ring 235.

[0086] A protective gas pipe 2362 is independently arranged outside the powder feeding pipe 233. The gas port of the protective gas pipe 2362 is arranged obliquely downward and gradually approaches the central laser beam tube 231, and the inclination angle of the protective gas pipe 2362 is greater than or equal to the inclination angle of the powder feeding pipe 233.

[0087] The top of the protective gas pipe 2362 is connected with an air leveling cover 2363. The air leveling cover 2363 is arranged outside the powder leveling cover 234 and a toothed ring 2364 is arranged on the inner wall. The toothed ring 2364 meshes with the driving gear 238. The top of the air leveling cover 2363 and the annular sealing plate 236 are rotationally arranged, and an air receiving pipe 2365 communicated with the air leveling cover 2363 is also arranged on the annular sealing plate 236.

[0088] The air receiving pipe 2365 is externally connected with an inert gas tank. The powder receiving pipe 233 is externally connected with an alloy powder tank one (containing alloy powder one) and an alloy powder tank two (containing alloy powder two) through electromagnetic valves. The alloy powder is sprayed into the laser beam emitted by the central laser beam tube 231 through the powder feeding pipe 233 by high-speed gas. While feeding the powder, the micro motor 237 drives the driving gear 238 to rotate, and then drives the air leveling cover 2363 and the powder leveling cover 2362 to rotate simultaneously. The alloy powder in the laser beam absorbs energy through laser radiation and melts, and collides with the roller surface in a vortex state. Since the alloy powder forms a vortex path in the laser beam and can obtain higher energy, the laser power can be appropriately reduced under the condition of ensuring complete melting of the alloy powder. At the same time, since the alloy powder will spin after absorbing energy in the laser beam, when it collides with the roller surface in a vortex manner, the uniformity of the alloy coating will be better, the problem of micro cracks in the coating can be overcome, the thickness consistency is high, and the thermal shock of the laser beam and the alloy liquid to the roller surface will be dispersed, reducing the risk of thermal stress concentration, and the quality of the alloy coating is better.

[0089] In order to prevent the protective gas from easily destroying the vortex posture of the alloy liquid in the laser beam during laser spraying, a support 2321 is installed on the powder feeding frame 232. The support 2321 passes through the gap between the powder feeding pipes 233, and an isolation cover 2322 is installed at the free end. The isolation cover 2322 collects and outwardly diverts the protective gas to form. The top of the isolation cover 2322 is a conical structure and the bottom is a waist-shaped structure. The protective gas emitted from the protective gas pipe 2362 shoots towards the conical structure and is vortex-covered outward through the waist-shaped structure after diversion, using the isolation cover 2322 to protect the posture of the alloy liquid.

[0090] In one way, the powder outlet of the powder delivery pipe 233 faces the axis of the central laser beam pipe 231, and in this way, it can be in a vortex posture in the laser beam.

[0091] In another way, while the powder outlet of the powder delivery pipe 233 is arranged obliquely downward, it gradually deviates from the axis of the central laser beam pipe 231, and the deviation distance is 1-5 mm. This distance can be adjusted according to actual spraying conditions. In this way, it can accelerate the vortex posture in the laser beam and increase the vortex coverage area of the alloy liquid.

[0092] In step 4, the laser spraying specifically includes:

[0093] Step 41: Hoist the rolling mill onto the clamping fixture 11 and the support roller 13, and fix the rolling mill from both ends through the clamping fixture 11 and the jack 12.

[0094] Step 42: The moving component 14 moves the clamping mechanism 10 into the closed cover 21 through the inlet and outlet, and the closing door 22 closes the inlet and outlet.

[0095] Step 43: Drive the main shaft to drive the clamping fixture 11 to drive the rolling mill to rotate. At the same time, the heating coil 33 is powered on, and the roll surface is preheated to 50°C - 60°C through the preheating ring 32.

[0096] Step 44: The laser spraying part 23 is turned on, and the moving component 14 drives the clamping mechanism 10 to move horizontally. Immediately, the laser spraying part 23 sprays alloy powder on the preheated roll surface. The laser beam is emitted from the central laser beam pipe 231. The micro motor 237 drives the driving gear 238 to rotate, and then drives the powder delivery pipe 233 and the protective gas pipe 2362 to rotate differentially through the gear ring 235. Under the action of high-speed gas, the alloy powder is ejected from the powder outlet, converges in a vortex in the laser beam and absorbs energy to melt, and then collides with the laser-irradiated roll surface in a vortex manner and quickly combines to form a coating on the roll surface. At the same time, the protective gas pipe 2362 forms a vortex protection air flow cover outside the powder delivery pipe 233.

[0097] As mentioned above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. The substitution can be the substitution of part of the structure, device, and method steps, or a complete technical solution. Any equivalent substitution or change made according to the technical solution and inventive concept of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for maintaining a roller oxide film, characterized in that: include: Step 1, roller surface cleaning; Step 2, dehumidifying the roller surface; Step 3, roller surface roughening: the roller surface is subjected to forward spiral and reverse spiral sandblasting to form a roughened structure on the roller surface. The sandblasting distance is between 120 and 150 mm, the sandblasting angle is between 75° and 90°, the air pressure is 0.6-0.7 MPa, and the surface roughness of the workpiece after sandblasting reaches Ra: 6.5-8 um; Step 4, laser spraying: preheat the spraying surface before powder is sprayed, and the preheating temperature is controlled at 50°C to 60°C; Then, alloy powder 1 and alloy powder 2 are uniformly sprayed on the roughened roller surface of the roller by laser powder spraying equipment to obtain coating 1 and coating 2, and the total thickness of the coating is not less than 0.2 mm; The alloy powder comprises, by percentage, 6 to 18 parts of Fe, 4.0 to 9.0 parts of Cr, 1.0 to 5.0 parts of Mo, 4.0 to 8.0 parts of Co, 1.0 to 2.5 parts of Nb, 1.0 to 2.5 parts of Mn, 0.2 to 0.5 parts of Cs, 0.5 to 1.2 parts of C, 3.0 to 4.2 parts of B, and the balance is Ni and unavoidable impurities, wherein: 0.04≤(C+Nb+B+Mn) / (Cr+Mo+Fe+Ni)≤0.19, 0.02≤(Cr+Co+Mo) / (Ni+Fe+Mn)≤0.16, 0.06≤(Cs+C) / (Cr+Mo+Fe)≤0.41; The two components of the alloy powder include, by percentage, 15 to 25 parts of Cr, 5 to 15 parts of Ni, 2 to 4 parts of Mn, 0.2 to 0.8 parts of C, 1.0 to 3.0 parts of Mo, and the balance is Co and unavoidable impurities, wherein: 0.65≤(Cr+C) / (Ni+Mo+Mn)≤3.45; Step 5, Post-spraying treatment After the surface is sprayed, it is polished with an oil stone. The hardness of the roller body should not be less than 73HSC.

2. A method for maintaining a roller oxide film according to claim 1, characterized in that: One component of the alloy powder includes, by percentage, 6 to 10 parts of Fe, 5.0 to 8.0 parts of Cr, 3.0 to 5.0 parts of Mo, 6.0 to 8.0 parts of Co, 1.5 to 2.5 parts of Nb, 1.5 to 2.5 parts of Mn, 0.2 to 0.5 parts of Cs, 0.5 to 0.8 parts of C, 3.5 to 4.2 parts of B, and the balance is Ni and unavoidable impurities, wherein: 0.05≤(C+Nb+B+Mn) / (Cr+Mo+Fe+Ni)≤0.12, 0.04≤(Cr+Co+Mo) / (Ni+Fe+Mn)≤0.08, 0.08≤(Cs+C) / (Cr+Mo+Fe)≤0.

32.

3. A method for maintaining a roller oxide film according to claim 1, characterized in that: The two components of the alloy powder include, by percentage, 15 to 25 parts of Cr, 5 to 15 parts of Ni, 2 to 4 parts of Mn, 0.2 to 0.8 parts of C, 1.0 to 3.0 parts of Mo, and the remainder is Co and unavoidable impurities, wherein: 0.75≤(Cr+C) / (Ni+Mo+Mn)≤1.

52.

4. A method for maintaining a roller oxide film according to claim 1, characterized in that: The laser powder spraying equipment comprises: A clamping mechanism (10), wherein a moving assembly (14) is arranged at the bottom of the clamping mechanism (10), and the clamping mechanism (10) comprises a clamping fixture (11), a top column (12), a driving spindle and a supporting roller (13), wherein the clamping fixture (11) and the top column (12) fix the roller from both ends, the supporting roller (13) is used to support an end of the roller away from the clamping fixture (11), and the driving spindle drives the clamping fixture (11) to rotate; A powder spraying mechanism (20), the powder spraying mechanism (20) comprising a closed cover (21), both ends of the closed cover (21) are provided with an inlet and an outlet, the clamping mechanism (10) can enter the closed cover (21) through the inlet and an inlet, a closed door (22) is installed at the inlet and an inlet and an inlet are driven to open the closed door (22), a laser spraying component (23) is installed on the top of the closed cover (21), and the laser spraying component (23) melts and sprays alloy powder 1 and alloy powder 2 on the roller surface of the straightening roller; The preheating mechanism (30) comprises a preheating frame (31), the preheating frame (31) is arranged obliquely downward and a preheating ring (32) is arranged at the free end, a heating coil (33) is embedded inside the preheating ring (32), and the heating coil (33) preheats the roller surface to 50°C to 60°C after being energized.

5. A method for maintaining a roller oxide film according to claim 4, characterized in that: The laser spraying part (23) comprises a central laser beam tube (231) and a powder delivery rack (232) rotatably mounted on the outer side of the bottom of the central laser beam tube (231), a plurality of powder delivery tubes (233) distributed in a circumferential direction are mounted on the powder delivery rack (232), a powder outlet of the powder delivery tube (233) is arranged obliquely downward and gradually approaches the central laser beam tube (231), and a powder distribution cover (234) is connected to the top of the powder delivery tube (233); A gear ring (235) is installed on the outer side of the powder uniforming cover (234), and a ring sealing plate (236) is fixed on the outer side of the central laser beam tube (231). The ring sealing plate (236) is used to seal the top of the powder uniforming cover (234) and rotate relative to the powder uniforming cover (234). A powder receiving pipe (2361) and a micro motor (237) are installed on the ring sealing plate (236). A driving gear (238) is installed on the output end of the micro motor (237), and the driving gear (238) and the gear ring (235) are meshed.

6. A method for maintaining a roller oxide film according to claim 5, characterized in that: A protective gas pipe (2362) is independently arranged on the outer side of the powder delivery pipe (233), the gas port of the protective gas pipe (2362) is arranged obliquely downward and gradually approaches the central laser beam pipe (231), and the inclination angle of the protective gas pipe (2362) is greater than or equal to the inclination angle of the powder delivery pipe (233); The top of the protective gas pipe (2362) is connected to a uniform gas cover (2363), the uniform gas cover (2363) is arranged on the outer side of the powder uniform cover (234) and the inner wall is provided with a gear ring (2364), the gear ring (2364) and the driving gear (238) are meshed, the top of the uniform gas cover (2363) and the ring sealing plate (236) are rotatably arranged, and the ring sealing plate (236) is also provided with a gas connection pipe (2365) connected to the uniform gas cover (2363).

7. A method for maintaining a roller oxide film according to claim 6, characterized in that: The powder delivery rack (232) is provided with a support body (2321), the support body (2321) passes through the gap between the powder delivery pipes (233) and an isolation cover (2322) is provided at the free end thereof, and the isolation cover (2322) collects the protective gas and guides it outwards to form; The top of the isolation cover (2322) is a conical structure, and the bottom is a waist-shaped structure.

8. A method for maintaining a roller oxide film according to claim 7, characterized in that: The powder outlet of the powder delivery pipe (233) is arranged obliquely downward and gradually deviates from the axis of the central laser beam tube (231).

9. A method for maintaining a roller oxide film according to claim 7, characterized in that: In step 4, laser spraying specifically includes: Step 41, hoisting the roller onto the clamping fixture (11) and the support roller (13), and fixing the roller from both ends via the clamping fixture (11) and the top column (12); Step 42, the moving assembly (14) moves the clamping mechanism (10) into the closed cover (21) through the inlet and outlet, and the closed door (22) closes the inlet and outlet; Step 43, the driving spindle drives the clamping fixture (11) to drive the roller to rotate, and at the same time the heating coil (33) is energized to preheat the roller surface to 50°C to 60°C through the preheating ring (32); Step 44, the laser spraying part (23) is turned on, the moving component (14) drives the clamping mechanism (10) to move horizontally, and the laser spraying part (23) then sprays the alloy powder on the preheated roller surface. The laser beam is emitted from the central laser beam tube (231), and the micro motor (237) drives the driving gear (238) to rotate, and then drives the powder feeding pipe (233) and the protective gas pipe (2362) to rotate at the same time through the gear ring (235). Under the action of high-speed gas, the alloy powder is ejected from the powder feeding port, gathered in the laser beam in a vortex and absorbed energy to melt, and then collides with the roller surface irradiated by the laser in a vortex manner and quickly combines to form a coating on the roller surface. At the same time, the protective gas pipe (2362) forms a vortex protective airflow cover on the outside of the powder feeding pipe (233).

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