CN114918611B - Repairing method for bearing seat of hot-rolled large-scale rolling mill - Google Patents
Repairing method for bearing seat of hot-rolled large-scale rolling mill Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P6/00—Restoring or reconditioning objects
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C24/00—Coating starting from inorganic powder
- C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
- C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
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Abstract
The invention discloses a repairing method for a bearing seat of a hot-rolled large-scale rolling mill, which comprises the following steps: (1) cleaning, disassembling and polishing; (2) detecting screw threads; (3) size detection; (4) rough turning and rough milling; (5) magnetic powder flaw detection; (6) laser cladding and gas shielded welding: the inner hole surface and the sliding plate surface are repaired by laser cladding, and the other assembly surfaces are repaired by gas shielded welding; the thickness and the layer number of the laser cladding and the gas shield welding are determined according to the size after rough machining; (7) stress relief annealing; (8) semi-finish turning and semi-finish milling; (9) dye check; finish machining;repairing the screw thread;cleaning an oil cavity and an oil duct;and (5) final inspection. The large-sized rolling mill bearing seat obtained by the repairing method has good wear resistance, impact resistance and corrosion resistance, so that the service life of the bearing seat is prolonged, and the spare part cost of a steel mill is obviously reduced.
Description
Technical Field
The invention relates to the field of maintenance of metallurgical equipment, and particularly provides a method for repairing a bearing seat (weight of more than 2 tons) of a hot-rolled large-sized rolling mill.
Background
The large-scale rolling mill bearing is one of core components of metallurgical rolling equipment, and the function of the large-scale rolling mill bearing is to ensure that a roller can normally and effectively rotate. The rolling mill bearing seat has extremely bad service conditions and can bear high-strength impact force during steel plate biting and extrusion for a long time, so that the rolling mill bearing seat is required to have excellent comprehensive mechanical properties. In addition, the cooling water in the rolling process is quickly gasified when encountering red hot steel billets, and water vapor corrosion can be generated on a rolling mill bearing seat. In addition, the scale on the surface of the billet is peeled off and splashed on the surface of the rolling mill bearing seat. For a long time, the bearing seat of the rolling mill is easy to wear and corrode, and the fatigue crack can be generated due to the extremely large impact force. The accuracy of the rolling mill bearing housing has a crucial influence on the service life of the bearing, the service life of the rolling mill stand, the stable operation of the rolling mill and the quality of the rolled billet.
Therefore, how to repair a large mill bearing block has become an important point of research in various large steelworks. Because the precision requirement of the large-scale rolling mill bearing is higher, the size is larger, the wall thickness difference is larger, and the deformation is easy to generate in the repairing process. The repairing by the build-up welding method alone can generate larger deformation, and the dimensional accuracy and the form and position tolerance can not be ensured. In addition, because the large-scale rolling mill is complex in structure and usually needs more repair positions, a whole set of repair process which is simple in process, strong in operability and capable of covering all repair processes is particularly needed.
CN108048836a discloses a laser repairing method for a rolling mill bearing seat, which mainly comprises four steps of detection, mechanical cleaning, preparing a laser cladding material for performing laser repairing, mechanical processing and detecting after repairing of the rolling mill bearing seat. The invention adopts a laser cladding mode to repair the rolling mill bearing seat and also provides the used materials and technological parameters, but the four steps of the repairing method are not targeted, the repairing method is almost suitable for repairing all products, and some key points and differences in the repairing process of the rolling mill bearing seat are ignored. Moreover, the repair by only adopting the laser cladding method has the problems of high cost and low efficiency. Furthermore, the invention does not consider how to reduce distortion in laser cladding.
In addition, in the existing laser cladding repair method, cladding is carried out on the slide plate surface of the rolling mill bearing seat in a horizontal state, the volume of the rolling mill bearing seat is larger, the whole laser cladding equipment is required to be lifted, the time and the labor are consumed, and the operation is complex; the inner hole is clad by adopting a spiral line after rotation, and the bearing seat has huge volume and heavy weight, and needs to be rotated by adopting a vertical lathe, so that the cost is high.
Disclosure of Invention
The invention aims to solve the problem of providing a repairing method for a bearing seat of a hot-rolled large-sized rolling mill, which has better wear resistance, impact resistance and corrosion resistance after repairing the bearing seat of the large-sized rolling mill, thereby prolonging the service life of the bearing seat and obviously reducing the spare part cost of a steel mill. Meanwhile, the repairing method is simple to operate, high in production efficiency and low in production cost.
The invention discloses a repairing method for a bearing seat of a hot-rolled large-scale rolling mill, which comprises the following steps of:
(1) cleaning, dismantling and polishing: cleaning the surface of a bearing seat and removing greasy dirt; removing assembly parts such as a sliding plate, a pressure bearing pad, a compression cylinder and the like on the bearing seat; polishing the rest surfaces except the assembly surface by adopting a polishing sheet, and removing surface oxide skin;
(2) and (3) thread detection: detecting whether the thread is intact or not by using a thread gauge, and marking and counting damaged threads;
(3) size detection: detecting the size and cylindricity of an inner hole of a bearing seat, detecting the symmetrical size, the total length size and the flatness of a sliding plate surface, and detecting the sizes of other assembly surfaces;
(4) rough turning and rough milling: turning to remove an inner hole fatigue layer, wherein cylindricity is ensured to be within 0.1 mm; milling to remove the oxide skin on the slide plate surface, ensuring that the symmetry is within 0.2mm, and milling the area with serious local rust is bright; the milling part of the non-working surface on the outer side of the sliding plate surface is bright and is used as a reference in semi-finishing and finishing;
(5) magnetic powder inspection: performing magnetic powder inspection on all the processing surfaces to ensure that the processing surfaces have no defects such as cracks and the like;
(6) laser cladding and gas shielded welding: the inner hole surface and the sliding plate surface are repaired by laser cladding, and the other assembly surfaces are repaired by gas shielded welding; when in laser cladding, the undamaged threaded holes are covered by spot welding with stainless steel gaskets with the thickness of 2mm, so that damage is prevented; the thickness and the layer number of the laser cladding and the gas shield welding are determined according to the size after rough machining;
(7) stress relief annealing: for the position of gas shield welding overlaying welding, heating to 400-500 ℃ by adopting a heating belt or induction heating mode, preserving heat for 2-4 hours, and slowly cooling the asbestos package to room temperature;
(8) semi-finish turning and semi-finish milling: reserving a single-side 0.5mm allowance according to the required size of a drawing, semi-finish turning an inner hole surface, and semi-finish milling other repair surfaces;
(9) dye check: performing dye check on all the processing surfaces to ensure that the processing surfaces are defect-free;
and (3) finish machining: finish machining each repair surface according to the size and form and position tolerance required by the drawing;
and (3) thread repairing: only the thread of the sliding thread, and adopting a tap to return the thread again; the damaged screw thread is repaired by adopting the modes of reaming, tapping and embedding the internal and external screw thread sleeves;
oil cavity and oil duct cleaning: polishing and cleaning the oil cavity and the oil duct, and spraying oil-resistant primer;
and (3) final inspection: and finally, checking the repaired finished bearing seat.
After flaw detection in the step (5) and the step (9), if the flaw is found, manual polishing and clamping and manual argon arc repair are adopted for removal; the welding wire adopted by the argon arc welding is 316L stainless steel welding wire.
Wherein, the technological parameters of laser cladding in the step (6) are as follows: the diameter of the light spot is 5mm, the laser power is 2.5-3.5 kW, the scanning speed is 15-25 mm/s, the lap joint rate is 40-50%, and the powder feeding amount is 25-60 g/min. The thickness of the single layer is 0.8-1.8 mm.
In the step (6), when the size of the inner hole surface or the sliding plate surface exceeds 1mm, the laser cladding layer is divided into a bottom layer and a cover surface layer; if the size out-of-tolerance is less than 1mm, only one covering layer is used for the laser cladding layer.
Wherein, in the step (6), the slide plate surface laser cladding adopts a vertical surface cladding mode; the inner hole laser cladding adopts a mode of regional symmetrical cladding.
Wherein, the technological parameters of gas shielded welding in the step (6) are as follows: 220-260A current, 22-26V voltage, 400-600mm/min moving speed, 10-15L/min air flow and 2.5-4mm single-layer thickness.
Wherein the welding wire used in the gas shield welding in the step (6) is a low carbon steel or low carbon alloy steel welding wire.
Wherein, the alloy material used for the priming layer comprises the following chemical components in percentage by mass: 15-17% Cr, 1-2.5% Mo, 10-13% Ni, <0.6% Mn, <0.1% C, 0.8-1.5% Si, and the balance Fe.
Wherein, the alloy material used for the cover layer comprises the following chemical components in percentage by mass: 15-18% Cr, 1-2% Mo, 3-5% Ni, 2-4% Co, <0.8% Mn, 0.05-0.15% C, 0.6-1.2% Si and the balance Fe.
The vertical face cladding mode is to vertically place the sliding plate surface of the bearing seat, and the laser head and the sliding plate surface form an included angle of 60 degrees for cladding; the zoned symmetrical cladding mode is to divide the 360-degree circumference of the inner hole surface into four blocks of upper left, lower left, upper right and lower right, cladding any block (first block) firstly, cladding the other block (second block) which is symmetrical with the first block as a center, cladding any block (third block) of the two rest blocks, and cladding the rest block (fourth block); the direction of the bearing seat is adjusted for each cladding, so that the cladding area is positioned at the bottom.
The principle and effect of the method for repairing the bearing seat of the hot-rolling large-scale rolling mill are as follows: 1. according to the characteristic of large wall thickness difference of the large-scale rolling mill, the repairing method adopts a mode of laser cladding and gas shielded welding; the positions with thinner wall thickness and easy deformation are all repaired by adopting a laser cladding mode, so that the deformation can be reduced; repairing the position with thicker wall thickness by adopting a gas shielded welding mode, improving the production efficiency and reducing the repairing cost; 2. considering the risk of cracking of the cladding multilayer covering layer, the laser cladding adopts a mode of combining a prime layer and a covering layer, and the prime layer plays a transitional role; the alloy component of the priming layer needs to consider that the cladding layer needs to have certain toughness, so that 10-13% of Ni element improves the plasticity of the alloy, 15-17% of Cr element improves the corrosion resistance of the alloy, and 1-2.5% of Mo element is used for forming solid solution reinforcement, thereby improving the high-temperature strength of the alloy; the covering layer needs to have better wear resistance, so that the content of Ni element is reduced, and the hardness of the alloy is improved; 2-4% Co element is added to obviously improve the wear resistance of the alloy; the alloy material is adopted for laser cladding, the hardness of the base layer is 20-25 HRC, and the hardness of the cover layer is 40-50 HRC, so that the repaired bearing seat slide plate surface and inner hole have good wear resistance, impact resistance and corrosion resistance; 3. the design of the technological parameters of laser cladding is to further improve the cladding efficiency on the premise of ensuring that the cladding layer has good metallurgical bonding; at the same time, the heat input of laser cladding is further reduced to reduce thermal deformation; 4. the slide plate surface is repaired by cladding the vertical surface, so that the operation is convenient; the inner hole adopts regional symmetrical cladding, so that cladding deformation is reduced; the bearing seat is rotated to enable the cladding area to be positioned at the bottom during each cladding, and a vertical lathe is not required to be used for rotation, so that the production cost is greatly reduced; 5. the gas shield welding adopts a low-carbon steel or low-carbon alloy steel welding wire, and the corrosion resistance of the repairing surface is ensured by reducing the carbon content; 6. after gas shielded welding, local stress relief annealing is carried out by adopting a heating belt or induction heating mode, so that welding residual stress is reduced, welding deformation is reduced, and the risk of generating cracks is reduced; compared with the integral furnace-entering annealing mode, the method reduces the cost and prevents deformation. The laser cladding repair position has smaller heat input, so that the generated residual stress and deformation are smaller, and annealing treatment is not needed; 7. the allowance is left after semi-finishing, so that convenience is provided for defect removal in subsequent flaw detection, and deformation after processing is reduced; 8. the damaged threads are repaired by means of reaming, tapping and embedding the internal and external thread sleeves, so that the operation is simple, the production efficiency is improved, and the cost is reduced.
Compared with the prior art, the repairing method of the large-sized rolling mill bearing improves the wear resistance, impact resistance and corrosion resistance of the repairing surface, and the deformation generated in the repairing process is small, so that the service life of the bearing seat is prolonged, and the spare part cost of a steel mill is obviously reduced. Meanwhile, the repairing method is simple to operate, high in efficiency and low in cost. The repairing method provided by the invention has pertinence, is particularly suitable for repairing the bearing seat of the large-sized rolling mill, and covers the aspects of the whole repairing process. The repairing method provides thought for repairing the bearing seat of the large-scale rolling mill and has reference significance.
Drawings
FIG. 1 is a flow chart of a repair method for a hot rolling large mill bearing of the present invention;
FIG. 2 is a schematic view of a mill housing being repaired in example 2;
FIG. 3 is a schematic diagram of the laser repair of the present invention in a split zone symmetric cladding mode.
Detailed Description
In order to better understand the present invention, the method for repairing a hot rolling large mill bearing housing according to the present invention will be described in further detail with reference to examples.
Example 1
Bearing block of supporting roller on production line of 3000mm middle plate in certain steel mill, specification: 2850mm×2110mm (length×height), 20 tons/piece, material ZG35SiMn, repair method comprising the steps of:
(1) cleaning, dismantling and polishing: cleaning the surface of the bearing seat and removing oil stains on the surface; removing assembly parts such as a sliding plate, a compression cylinder and the like on the bearing seat; polishing the rest surfaces except the assembly surface by adopting a polishing sheet, and removing surface oxide skin;
(2) and (3) thread detection: detecting whether the thread is intact or not by using a thread gauge, and marking and counting damaged threads;
(3) size detection: detecting the size and cylindricity of an inner hole surface of a bearing seat, detecting the symmetrical size, the total length size and the flatness of a slide plate surface, and detecting the size of an assembly surface of a compression cylinder;
(4) rough turning and rough milling: turning to remove an inner hole fatigue layer, wherein cylindricity is ensured to be within 0.1 mm; milling to remove the oxide skin on the slide plate surface, ensuring that the symmetry is within 0.2mm, and milling the area with serious local rust is bright; the milling part of the non-working surface on the outer side of the sliding plate surface is bright and is used as a reference in semi-finishing and finishing;
(5) magnetic powder inspection: performing magnetic powder inspection on all the processing surfaces, if defects are found, manually polishing and clamping, and removing the defects by using a manual argon arc welding repair mode to ensure that the processing surfaces have no defects such as cracks; the welding wire used in argon arc welding is 316L stainless steel welding wire;
(6) laser cladding and gas shielded welding: repairing the inner hole surface and the sliding plate surface by adopting a laser cladding mode, and repairing the bonding surface of the compression cylinder by adopting an air-shielded welding mode; before laser cladding, a stainless steel gasket with the thickness of 2mm is adopted to spot-weld and cover the undamaged threaded hole, so that damage caused by laser cladding is prevented; after the inner hole surface is rough machined, the single side is out of tolerance by 1.6mm, the laser cladding is a 0.8mm bottom layer plus 1.6mm cover layer, and the cladding is carried out according to the sequence of (1) to (2) to (3) to (4) in the figure 3; the unilateral out-of-tolerance of the surface of the sliding plate is 1.6mm, the laser cladding is 0.8mm priming layer plus 1.6mm covering layer, and elevation cladding is adopted; the joint surface of the pressing cylinder has larger cracks due to the annual repair, the unilateral exceeding 7.8mm after the elimination, and three layers of ER50-6 welding wires are stacked and welded by gas shielded welding, and each layer is 3.3mm.
The alloy material used for the priming layer in the laser cladding comprises the following chemical components in percentage by mass of 16.5% Cr, 2% Mo, 12% Ni, 0.3% Mn, 0.05% C, 1.2% Si and the balance Fe, and the technological parameters are as follows: the diameter of the light spot is 5mm, the laser power is 2.5kW, the scanning speed is 20mm/s, the lap joint rate is 40%, and the powder feeding amount is 36-38 g/min; the alloy material used for the cover layer comprises the following chemical components in percentage by mass: 17% of Cr, 2% of Mo, 4% of Ni, 4% of Co, 0.5% of Mn, 0.12% of C, 1.2% of Si and the balance of Fe, and the laser cladding process parameters are as follows: the diameter of the light spot is 5mm, the laser power is 3.5kW, the scanning speed is 18mm/s, the lap joint rate is 50%, and the powder feeding amount is 55-57 g/min; the technological parameters of gas shield welding are as follows: the current is 250A, the voltage is 25V, the moving speed is 500mm/min, the air flow is 15L/min, and the single-layer thickness is 3.3mm.
(7) Stress relief annealing: the assembly surface of the pressing cylinder is required to be locally stress-relieved and annealed, and is heated to 500 ℃ by adopting an induction heating mode, and is kept for 2 hours, and the asbestos wrapping is slowly cooled to room temperature;
(8) semi-finish turning and semi-finish milling: reserving a allowance of 0.5mm on a single side according to the size of a finished product, semi-finish turning an inner hole surface, and semi-finish milling other repair surfaces;
(9) dye check: performing dye check on the inner hole surface, the sliding plate surface and the pressing cylinder joint surface, if defects are found, manually polishing and clamping, and then performing argon arc repair by using a 316L stainless steel welding wire to ensure that the processed surface is defect-free;
and (3) finish machining: finish machining each repair surface according to the size and form and position tolerance required by the drawing;
and (3) thread repairing: according to the statistical result of the step (2), if only the thread of the sliding thread is adopted, the thread is returned again by adopting the tap; if the damaged screw thread is damaged, the method of reaming, tapping and embedding an internal and external screw thread sleeve is adopted for repairing;
oil cavity and oil duct cleaning: manually polishing and cleaning the oil cavity and the oil duct, not keeping sundries, and re-spraying and brushing the oil cavity and the oil duct for resistingOil priming paint;
and (3) final inspection: and finally checking the repaired finished bearing seat according to the drawing and the technical requirements.
In the embodiment, the design of the components of the underlying layer alloy mainly considers that the matrix material is ZG35SiMn, and a certain dilution rate exists in laser cladding: in order to ensure the toughness and corrosion resistance of the priming paint, the elements Ni, cr and Mo with higher content and the elements C, mn with lower content are needed to be selected; the cover layer mainly considers that the abrasion of the position is serious, and in order to improve the abrasion resistance, co element and C, cr element with higher content are selected.
In this embodiment, the selection of the technological parameters of laser cladding and gas shield welding is mainly determined according to the thickness of a single layer and the repair efficiency: the thicker thickness allows for a larger heat input parameter, and also requires a faster speed for efficiency, and therefore a larger heat input.
Example 2
Bearing block of lower supporting roller of 3000mm middle plate production line of certain steel mill, specification: 2070mm x 2110mm, 14 tons/piece weight, ZG35SiMn material, repair method includes the following steps:
(1) cleaning, dismantling and polishing: cleaning the surface of the bearing seat and removing oil stains on the surface; removing assembly parts such as a sliding plate, a pressure bearing pad and the like on the bearing seat; polishing the rest surfaces except the assembly surface by adopting a polishing sheet, and removing surface oxide skin;
(2) and (3) thread detection: detecting whether the thread is intact or not by using a thread gauge, and marking and counting damaged threads;
(3) size detection: detecting the size and cylindricity of an inner hole surface of a bearing seat, detecting the symmetrical size, the total length size and the flatness of a slide plate surface, and detecting the size of an assembly surface of a pressure bearing pad;
(4) rough turning and rough milling: turning to remove a fatigue layer of the inner hole surface, wherein the cylindricity is ensured to be within 0.1 mm; milling to remove the oxide skin on the slide plate surface, ensuring that the symmetry is within 0.2mm, and milling the area with serious local rust is bright; the milling part of the non-working surface on the outer side of the sliding plate surface is bright and is used as a reference during semi-finishing and finishing;
(5) magnetic powder inspection: performing magnetic powder inspection on all the processing surfaces, if defects are found, manually polishing and clamping, and removing the defects by using a 316L welding wire argon arc welding repair mode to ensure that the processing surfaces have no defects such as cracks;
(6) laser cladding and gas shielded welding: repairing the inner hole surface and the sliding plate surface by adopting a laser cladding mode, and repairing the assembly surface of the pressure bearing pad by adopting an air-shielded welding mode; before laser cladding, a stainless steel gasket with the thickness of 2mm is adopted to spot-weld and cover the undamaged threaded hole, so that damage caused by laser cladding is prevented; after the inner hole surface is roughly machined, the single side is out of tolerance by 0.8mm, the laser cladding is performed to form a cover layer with the thickness of 1.6mm, and the cladding is performed according to the sequence from (4) to (3) to (1) to (2) in the figure 3; the unilateral out-of-tolerance of the surface of the sliding plate is 1.4mm, the laser cladding is 0.8mm priming layer plus 1.4mm covering layer, and elevation cladding is adopted; the assembly surface of the pressure bearing pad is damaged in a long time, the abrasion is particularly serious, the unilateral deviation after polishing is 9.5mm, and three layers of ER50-6 welding wires are stacked and welded by gas shielded welding, wherein each layer is 3.8mm.
Wherein, the alloy material used for the laser cladding priming layer comprises the chemical components by mass percent of 17 percent Cr, 2 percent Mo, 12.5 percent Ni, 0.3 percent Mn, 0.04 percent C, 1.2 percent Si and the balance of Fe; the alloy material used for the cover layer comprises the following chemical components in percentage by mass: 17.5% Cr, 2% Mo, 4.5% Ni, 3.5% Co, 0.5% Mn, 0.1% C, 1.2% Si, and the balance Fe. Wherein, the technological parameters of hole face covering layer laser cladding are: the diameter of the light spot is 5mm, the laser power is 3.5kW, the scanning speed is 17mm/s, the lap joint rate is 45%, and the powder feeding amount is 56-58 g/min; the technological parameters of the laser cladding of the bottom layer of the slide plate surface are as follows: the diameter of the light spot is 5mm, the laser power is 2.5kW, the scanning speed is 20mm/s, the lap joint rate is 40%, the powder feeding amount is 36-38 g/min, and the technological parameters of laser cladding of the cover layer are as follows: the diameter of the light spot is 5mm, the laser power is 3.5kW, the scanning speed is 20mm/s, the lap joint rate is 50%, and the powder feeding amount is 54-56 g/min; the technological parameters of gas shield welding are as follows: current 260A, voltage 26V, moving speed 480mm/min, air flow 15L/min, single layer thickness 3.8mm.
(7) Stress relief annealing: the assembly surface of the pressure bearing pad is subjected to local stress relief annealing; heating to 400 ℃ by adopting a heating belt mode, preserving heat for 4 hours, and slowly cooling the asbestos package to room temperature;
(8) semi-finish turning and semi-finish milling: reserving a allowance of 0.5mm on a single side according to the size of a finished product, semi-finish turning an inner hole surface, and semi-finish milling other repair surfaces;
(9) dye check: performing dye check on the inner hole surface, the sliding plate surface and the bearing pad assembly surface, if defects are found, manually polishing and clamping, and then performing argon arc repair by using a 316L stainless steel welding wire to finally ensure that the machined surface is defect-free;
and (3) finish machining: finish machining each repair surface according to the size and form and position tolerance required by the drawing;
and (3) thread repairing: according to the statistical result of the step (2), if only the thread of the sliding thread is adopted, the thread is returned again by adopting the tap; if the damaged screw thread is damaged, the method of reaming, tapping and embedding an internal and external screw thread sleeve is adopted for repairing;
oil cavity and oil duct cleaning: manually polishing and cleaning the oil cavity and the oil duct, and re-spraying oil-resistant primer;
and (3) final inspection: and finally checking the repaired finished bearing seat according to the drawing and the technical requirements.
In this embodiment, the design of the alloy components of the base layer and the cover layer includes that the base material is ZG35SiMn, and the laser cladding has a certain dilution rate and the performance requirement of the cladding layer.
In this embodiment, the selection of the technological parameters of laser cladding and gas shield welding is mainly determined according to the thickness of the single layer and the repair efficiency. The thicker thickness allows for a larger heat input parameter, and also requires a faster speed for efficiency, and therefore a larger heat input.
Example 3
Working roll lower bearing seat of R1 rolling mill of production line of 850 of a certain steel mill, specification: 1194mm multiplied by 1330mm, the weight of the material ZG310-570 is 4 tons/piece, and the repairing method comprises the following steps:
(1) cleaning, dismantling and polishing: cleaning the surface of the bearing seat and removing oil stains on the surface; removing assembly parts such as a sliding plate, a pressure bearing pad and the like on the bearing seat; polishing the rest surfaces except the assembly surface by adopting a polishing sheet, and removing surface oxide skin;
(2) and (3) thread detection: detecting whether the thread is intact or not by using a thread gauge, and marking and counting damaged threads;
(3) size detection: detecting the size and cylindricity of an inner hole surface of a bearing seat, detecting the symmetrical size, the total length size and the flatness of a slide plate surface, and detecting the size of an assembly surface of a pressure bearing pad;
(4) rough turning and rough milling: turning to remove a fatigue layer of the inner hole surface, wherein the cylindricity is ensured to be within 0.1 mm; milling to remove the oxide skin on the slide plate surface, ensuring that the symmetry is within 0.2mm, and milling the area with serious local rust is bright; the milling part of the non-working surface on the outer side of the sliding plate surface is bright and is used as a reference in semi-finishing and finishing;
(5) magnetic powder inspection: performing magnetic powder inspection on all the processing surfaces, and if defects are found, removing the defects by adopting a mode of argon arc repair of a 316L welding wire after manual grinding pliers repair, so as to ensure that the processing surfaces have no defects such as cracks;
(6) laser cladding and gas shielded welding: repairing the inner hole surface and the sliding plate surface by adopting a laser cladding mode, and repairing the assembly surface of the pressure bearing pad by adopting an air-shielded welding mode; before laser cladding, a stainless steel gasket with the thickness of 2mm is adopted to spot-weld and cover the undamaged threaded hole, so that damage caused by laser cladding is prevented; after the inner hole surface is roughly machined, the single side is out of tolerance by 1.0mm, the laser cladding is performed to form a cover layer of 1.8mm, and cladding is performed according to the sequence from (2) to (1) to (4) to (3) in the figure 3; the unilateral out-of-tolerance of the surface of the sliding plate is 1.2mm, the laser cladding is '0.8 mm bottom layer plus 1.2mm cover layer', and elevation cladding is adopted; after the assembly surface of the pressure bearing pad is polished, the single side exceeds the tolerance by 4.5mm, and two layers of ER50-6 welding wires are welded by gas shielded welding in a pile, wherein each layer is 3.3mm.
Wherein, the alloy material used for the laser cladding priming layer comprises the chemical components by mass percent of 17 percent Cr, 2.5 percent Mo, 13 percent Ni, 0.5 percent Mn, 0.02 percent C, 1.0 percent Si and the balance of Fe; the alloy material used for the cover layer comprises the following chemical components in percentage by mass: 18% Cr, 2% Mo, 4% Ni, 3% Co, 0.5% Mn, 0.08% C, 1.0% Si, and the balance Fe. Wherein, the technological parameters of hole face covering layer laser cladding are: the diameter of the light spot is 5mm, the laser power is 3.4kW, the scanning speed is 15mm/s, the lap joint rate is 50%, and the powder feeding amount is 52-54 g/min; the technological parameters of the laser cladding of the bottom layer of the slide plate surface are as follows: the diameter of the light spot is 5mm, the laser power is 3kW, the scanning speed is 25mm/s, the lap joint rate is 40%, the powder feeding amount is 46-48 g/min, and the technological parameters of laser cladding of the covering layer are as follows: the diameter of the light spot is 5mm, the laser power is 3.5kW, the scanning speed is 20mm/s, the lap joint rate is 40%, and the powder feeding amount is 56-58 g/min; the technological parameters of gas shield welding are as follows: current 260A, voltage 26V, moving speed 550mm/min, air flow 15L/min, and single layer thickness 3.3mm.
(7) Stress relief annealing: the assembly surface of the pressure bearing pad is subjected to local stress relief annealing; heating to 450 ℃ by adopting a heating belt mode, preserving heat for 3 hours, and slowly cooling the asbestos coating to room temperature;
(8) semi-finish turning and semi-finish milling: reserving a allowance of 0.5mm on a single side according to the size of a finished product, semi-finish turning an inner hole surface, and semi-finish milling other repair surfaces;
(9) dye check: performing dye check on the inner hole surface, the sliding plate surface and the bearing pad assembly surface, if defects are found, manually polishing and clamping, and then performing argon arc repair by using a 316L stainless steel welding wire to finally ensure that the machined surface is defect-free;
and (3) finish machining: finish machining each repair surface according to the size and form and position tolerance required by the drawing;
and (3) thread repairing: according to the statistical result of the step (2), if only the thread of the sliding thread is adopted, the thread is returned again by adopting the tap; if the damaged screw thread is damaged, the method of reaming, tapping and embedding an internal and external screw thread sleeve is adopted for repairing;
oil cavity and oil duct cleaning: manually polishing and cleaning the oil cavity and the oil duct, and re-spraying oil-resistant primer;
and (3) final inspection: and finally checking the repaired finished bearing seat according to the drawing and the technical requirements.
In the embodiment, the design basis of the alloy components of the bottom layer and the cover layer is ZG310-570, which contains 0.5% of carbon element, 0.6% of Si element and 0.9% of Mn element, and the laser cladding has a certain dilution rate, so that the C element content of the cladding is lower and the content of the rest elements is higher in order to ensure the performance requirement of the cladding.
In this embodiment, the selection of the technological parameters of laser cladding and gas shield welding is mainly determined according to the thickness of the single layer and the repair efficiency. The thicker thickness allows for a larger heat input parameter, and also requires a faster speed for efficiency, and therefore a larger heat input.
In order to verify the performance of the large-sized rolling mill bearing repaired by the method, corresponding test blocks are manufactured by adopting the laser cladding materials and the process of the slide surfaces of the embodiments 1, 2 and 3, and meanwhile, the new bearing seat ZG310-570 material of the embodiment 3 is adopted for tempering heat treatment to manufacture the comparison test block. Comparative researches are carried out on hardness, wear resistance and corrosion resistance. Wherein, the hardness test is to detect by using a hand-held type Lee hardness tester; the abrasion resistance is tested by adopting a self-made simple friction and abrasion tester, and is characterized by abrasion weight loss in unit time; the corrosion resistance is compared by a soaking corrosion test.
The test results are shown in table 1:
table 1 comparison of the properties of the different test blocks
| Sample numbering | hardness/HRC | Weight loss on wear/g | Corrosion weight loss/g |
| Example 1 | 45～50 | 0.00376 | 0.125 |
| Example 2 | 43～48 | 0.00412 | 0.139 |
| Example 3 | 43～48 | 0.00397 | 0.127 |
| Comparative example | 23～30 | 0.01533 | 0.302 |
As can be seen from Table 1, the hardness, wear resistance and corrosion resistance of the large mill bearing housing repaired by the material and the method of the invention are all superior to those of the new bearing housing under the same condition. That is, the method of the invention is adopted to repair the rolling mill bearing seat, which not only is simple in size recovery, but also further improves the performance of the bearing seat, thereby prolonging the service life of the bearing seat. The service life of the steel mill is 1.5-2 times of that of a new bearing seat after being used on line. In addition, the method has the advantages of simple process, higher efficiency and low comprehensive cost.
The thought of laser cladding and gas shield welding in the repairing method can be suitable for repairing parts with larger wall thickness difference, and is not limited to the rolling mill bearing seat.
Claims (7)
1. The repairing method for the bearing seat of the hot-rolled large-scale rolling mill is characterized by comprising the following steps of:
(1) cleaning, dismantling and polishing: cleaning the surface of a bearing seat and removing greasy dirt; removing assembly parts such as a sliding plate, a pressure bearing pad, a compression cylinder and the like on the bearing seat; polishing the rest surfaces except the assembly surface by adopting a polishing sheet, and removing surface oxide skin;
(2) and (3) thread detection: detecting whether the thread is intact or not by using a thread gauge, and marking and counting damaged threads;
(3) size detection: detecting the size and cylindricity of an inner hole of a bearing seat, detecting the symmetrical size, the total length size and the flatness of a sliding plate surface, and detecting the sizes of other assembly surfaces;
(4) rough turning and rough milling: turning to remove an inner hole fatigue layer, wherein cylindricity is ensured to be within 0.1 mm; milling to remove the oxide skin on the slide plate surface, ensuring that the symmetry is within 0.2mm, and milling the area with serious local rust is bright; the milling part of the non-working surface on the outer side of the sliding plate surface is bright and is used as a reference in semi-finishing and finishing;
(5) magnetic powder inspection: performing magnetic powder inspection on all the processing surfaces to ensure that the processing surfaces have no defects such as cracks and the like;
(6) laser cladding and gas shielded welding: the inner hole surface and the sliding plate surface are repaired by laser cladding, and the other assembly surfaces are repaired by gas shielded welding; when in laser cladding, the undamaged threaded holes are covered by spot welding with stainless steel gaskets with the thickness of 2mm, so that damage is prevented; the thickness and the layer number of the laser cladding and the gas shield welding are determined according to the size after rough machining;
(7) stress relief annealing: heating the gas shield surfacing position to 400-500 ℃ by adopting a heating belt or induction heating mode, preserving heat for 2-4 hours, and slowly cooling the asbestos package to room temperature;
(8) semi-finish turning and semi-finish milling: reserving a single-side 0.5mm allowance according to the required size of a drawing, semi-finish turning an inner hole surface, and semi-finish milling other repair surfaces;
(9) dye check: performing dye check on all the processing surfaces to ensure that the processing surfaces are defect-free;
and (3) finish machining: finish machining each repair surface according to the size and form and position tolerance required by the drawing;
⑪ thread repair: only the thread of the sliding thread, and adopting a tap to return the thread again; the damaged screw thread is repaired by adopting the modes of reaming, tapping and embedding the internal and external screw thread sleeves;
⑫ oil cavity and oil duct cleaning: polishing and cleaning the oil cavity and the oil duct, and spraying oil-resistant primer;
⑬ final inspection: carrying out final inspection on the repaired finished bearing seat;
after flaw detection in the step (5) and the step (9), if the defect is found, removing by adopting a manual polishing clamp repairing and manual argon arc welding repair mode; the welding wire adopted by argon arc welding is a 316L stainless steel welding wire; the technological parameters of laser cladding in the step (6) are as follows: the diameter of the light spot is 5mm, the laser power is 2.5-3.5 kW, the scanning speed is 15-25 mm/s, the lap joint rate is 40-50%, and the powder feeding amount is 25-60 g/min; the thickness of the single layer is 0.8-1.8 mm; the technological parameters of gas shield welding are as follows: 220-260A current, 22-26V voltage, 400-600mm/min moving speed, 10-15L/min air flow and 2.5-4mm single-layer thickness.
2. A repair method according to claim 1, characterized in that: in the step (6), when the dimension of the inner hole surface or the sliding plate surface exceeds 1mm, the laser cladding layer is divided into a bottom layer and a cover layer; if the size out-of-tolerance is less than 1mm, only one covering layer is used for the laser cladding layer.
3. A repair method according to claim 1, characterized in that: in the step (6), the slide plate surface is subjected to laser cladding in a vertical surface cladding mode; the inner hole laser cladding adopts a mode of regional symmetrical cladding.
4. A repair method according to claim 1, characterized in that: and (3) welding wires used in the gas shield welding in the step (6) are low-carbon steel or low-carbon alloy steel welding wires.
5. A repair method according to claim 2, characterized in that: the alloy material used for the priming layer comprises the following chemical components in percentage by mass: 15-17% Cr, 1-2.5% Mo, 10-13% Ni, <0.6% Mn, <0.1% C, 0.8-1.5% Si, and the balance Fe.
6. A repair method according to claim 2, characterized in that: the alloy material used for the cover layer comprises the following chemical components in percentage by mass: 15-18% Cr, 1-2% Mo, 3-5% Ni, 2-4% Co, <0.8% Mn, 0.05-0.15% C, 0.6-1.2% Si, and the balance Fe.
7. A repair method according to claim 3, wherein: the vertical face cladding mode is to vertically place the sliding plate surface of the bearing seat, and the laser head and the sliding plate surface form an included angle of 60 degrees for cladding; the zoned symmetrical cladding mode is to divide the 360-degree circumference of the inner hole surface into four blocks of upper left, lower left, upper right and lower right, cladding any block (first block) firstly, cladding the other block (second block) which is symmetrical with the first block as a center, cladding any block (third block) of the two rest blocks, and cladding the rest block (fourth block); the direction of the bearing seat is adjusted for each cladding, so that the cladding area is positioned at the bottom.
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