CN114918611A - Repairing method for bearing seat of hot rolling large-scale rolling mill - Google Patents
Repairing method for bearing seat of hot rolling large-scale rolling mill Download PDFInfo
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- CN114918611A CN114918611A CN202210554212.9A CN202210554212A CN114918611A CN 114918611 A CN114918611 A CN 114918611A CN 202210554212 A CN202210554212 A CN 202210554212A CN 114918611 A CN114918611 A CN 114918611A
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- 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
- C22C38/04—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
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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
- C22C38/44—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
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Abstract
The invention discloses a method for repairing a bearing seat of a hot rolling large-scale rolling mill, which comprises the following steps: cleaning, disassembling and polishing; detecting the screw thread; thirdly, size detection; rough turning and rough milling; fifthly, magnetic particle inspection; sixthly, laser cladding and gas shielded welding: the inner hole surface and the slide 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; removing stress and annealing; eighthly, half finish turning and half finish milling; ninthly toCarrying out color flaw detection; finish machining is carried out on the R;
repairing the screw thread;
cleaning an oil cavity and an oil duct;
and (5) final inspection. The large-scale rolling mill bearing seat obtained by the repairing method has better wear resistance, impact resistance and corrosion resistance, thereby prolonging the service life of the bearing seat and obviously reducing the spare part cost of a steel mill.
Description
Technical Field
The invention relates to the field of metallurgical equipment maintenance, and particularly provides a method for repairing a bearing seat (with the weight more than 2 tons) of a hot rolling large-scale rolling mill.
Background
The large-scale rolling mill bearing block is one of the core components of metallurgical rolling equipment and has the function of ensuring that a roller can normally and effectively rotate. The service condition of the rolling mill bearing seat is extremely poor, and the rolling mill bearing seat can bear high-strength impact force when a steel plate is bitten and extruded for a long time, so that the rolling mill bearing seat is required to have excellent comprehensive mechanical properties. In addition, cooling water in the rolling process is rapidly gasified when meeting red hot steel billets, and steam corrosion can be generated on a rolling mill bearing seat. Further, the scale on the surface of the billet is also peeled off and splashed on the surface of the rolling mill housing. In the past, the bearing seat of the rolling mill is easy to wear and corrode, and fatigue cracks are generated due to the extremely high impact force. The precision of the rolling mill bearing housing has a crucial influence on the service life of the bearing, the service life of the rolling mill housing, the stable operation of the rolling mill and the quality of the rolled steel billet.
Therefore, how to repair the large rolling mill bearing seat becomes a key point of research of various large steel mills. The bearing seat of the large-scale rolling mill has higher precision requirement, larger size and larger wall thickness difference, so that the bearing seat is easy to deform in the repairing process. The repair by the surfacing method alone can generate large deformation, and the dimensional accuracy and form and position tolerance can not be ensured. In addition, because the bearing seat of the large-scale rolling mill has a complex structure and generally has more positions to be repaired, 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 repair method for a rolling mill bearing pedestal, which mainly comprises four steps of detection, mechanical cleaning, preparation of laser cladding material for laser repair of the rolling mill bearing pedestal, mechanical processing and detection after repair. Although the method adopts a laser cladding mode to repair the rolling mill bearing seat, the used materials and process parameters are also given, the four steps of the repair method are not targeted, the method is almost suitable for repairing all products, and key points and differences in the repair process of the rolling mill bearing seat are omitted. In addition, the problems of high cost and low efficiency exist when only a laser cladding mode is adopted for repairing. Furthermore, the invention does not consider how to reduce the deformation in laser cladding.
In addition, in the existing laser cladding repair method, the slide plate surface of the rolling mill bearing seat is clad in a horizontal state, and the rolling mill bearing seat has a large volume, needs to be lifted up integrally by laser cladding equipment, and is time-consuming, labor-consuming and complex to operate; the inner hole is cladded by adopting a rotated spiral line, and the bearing seat is large in size, heavy in weight, high in cost and capable of rotating by adopting a vertical lathe.
Disclosure of Invention
The invention aims to solve the problem of providing a repairing method for a bearing seat of a hot rolling large-scale rolling mill, and the repaired bearing seat of the large-scale rolling mill has better wear resistance, impact resistance and corrosion resistance, thereby prolonging the service life of the bearing seat and obviously reducing the cost of spare parts of a steel mill. Meanwhile, the repairing method is simple to operate, high in production efficiency and low in production cost.
The invention relates to a method for repairing a bearing seat of a hot rolling large-scale rolling mill, which comprises the following steps:
cleaning, disassembling and polishing: cleaning the surface of the bearing seat and removing oil stains; dismantling the assembly parts such as the sliding plate, the pressure bearing pad, the pressing cylinder and the like on the bearing seat; manually polishing the rest surfaces except the assembly surface by using a polishing sheet to remove surface oxide skin;
secondly, detecting the screw thread: detecting whether the thread is intact by using a thread gauge, and marking and counting the damaged thread;
thirdly, size detection: detecting the size and cylindricity of an inner hole of the bearing seat, detecting the symmetrical size, the total length size and the planeness of the sliding plate surface, and detecting the sizes of other assembly surfaces;
fourthly, rough turning and rough milling: turning to remove the fatigue layer of the inner hole and ensuring that the cylindricity is within 0.1 mm; milling to remove the oxide skin on the surface of the slide plate, and ensuring that the symmetry is within 0.2mm, and milling the area with severe local corrosion is bright; milling a non-working surface on the outer side of the sliding plate surface to obtain a bright part which is used as a reference for semi-finishing and finishing;
magnetic powder inspection: performing magnetic powder inspection on all processing surfaces to ensure that the processing surfaces have no defects such as cracks;
sixthly, laser cladding and gas shielded welding: the inner hole surface and the slide plate surface are repaired by laser cladding, and the other assembly surfaces are repaired by gas shielded welding; during laser cladding, the undamaged threaded hole is covered by a stainless steel gasket with the thickness of 2mm in a spot welding manner, so that damage is prevented; the thickness and the layer number of the laser cladding and the gas shielded welding are determined according to the size after rough machining;
and stress relief annealing: heating the position of the gas shield welding surfacing to 400-500 ℃ by adopting a heating belt or induction heating mode, preserving heat for 2-4 h, and slowly cooling the asbestos wrap to room temperature;
eighthly, semi-finish turning and semi-finish milling: reserving a margin with a single side of 0.5mm according to the size required by a drawing, semi-finish turning an inner hole surface, and semi-finish milling other repair surfaces;
ninthly, dye-uptake inspection: performing dye check on all processing surfaces to ensure that the processing surfaces are free of defects;
finish machining red: finishing each repairing surface according to the dimension and form and position tolerance required by a drawing;
After flaw detection in the fifth step and the ninth step, if the flaw is detected, removing the flaw by adopting a manual polishing clamp repairing mode and a manual argon arc welding repairing mode; the welding wire adopted by argon arc welding is 316L stainless steel welding wire.
Wherein, the technological parameters of the laser cladding in the step sixthly are as follows: the diameter of a 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 conveying amount is 25-60 g/min. The thickness of the single layer is 0.8-1.8 mm.
In the step (sixthly), when the size of the inner hole surface or the slide plate surface exceeds 1mm, the laser cladding layer is divided into a bottoming layer and a cover surface layer; if the size out-of-tolerance is smaller than 1mm, the laser cladding layer is only provided with one covering layer.
Sixthly, performing laser cladding on the surface of the sliding plate in a vertical surface cladding mode; the inner hole laser cladding adopts a mode of symmetrical cladding by regions.
Wherein, the technological parameters of the gas shield welding in the step sixthly are as follows: the current is 220-260A, the voltage is 22-26V, the moving speed is 400-600mm/min, the air flow is 10-15L/min, and the single-layer thickness is 2.5-4 mm.
And sixthly, welding wires used for the medium-gas shield welding are low-carbon steel or low-carbon alloy steel welding wires.
The alloy material used for the bottom 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.
The covering surface layer comprises the following alloy materials 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 elevation cladding mode is that the surface of a sliding plate of the bearing seat is vertically placed, and a laser head and the sliding plate form an included angle of 60 degrees for cladding; the mode of regional symmetrical cladding is that the 360-degree circumference of the inner hole surface is divided into four blocks, namely, an upper left block, a lower left block, an upper right block and a lower right block, any one (a first block) of the four blocks is cladded, the other (a second block) which is centrosymmetric with the first block is cladded, any one (a third block) of the remaining two blocks is cladded, and the remaining (a fourth block) is cladded; the bearing seat direction needs to be adjusted during each cladding, so that the cladding area is positioned at the bottom.
The principle and the effect of the method for repairing the bearing seat of the hot rolling large-scale rolling mill are as follows: firstly, according to the characteristic that the wall thickness difference of a large-scale rolling mill bearing seat is large, the repairing method adopts a mode of laser cladding and gas shielded welding; positions with thinner wall thickness and easy deformation are all repaired in a laser cladding mode, so that the deformation can be reduced; the position with thicker wall thickness is repaired in a gas shield welding mode, so that the production efficiency is improved, and the repair cost is reduced; secondly, considering that the cladding multi-layer cover surface layer has the risk of cracking, the laser cladding adopts a mode of combining a prime coat and the cover surface layer, and the prime coat plays a transition role; the alloy components of the bottom layer need 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 strengthening and improving the high-temperature strength of the alloy; the cover layer needs to have better wear resistance, so that the content of Ni element is reduced, and the hardness of the alloy is improved; and 2-4% of Co element is added to obviously improve the wear resistance of the alloy; the alloy material is adopted for laser cladding, the hardness of a bottom layer is 20-25 HRC, and the hardness of a cover surface layer is 40-50 HRC, so that the repaired bearing seat slide plate surface and the repaired inner hole have good wear resistance, impact resistance and corrosion resistance; thirdly, the laser cladding process parameter design is to further improve the cladding efficiency on the premise of ensuring that the cladding layer has good metallurgical bonding; meanwhile, the heat input of laser cladding is further reduced so as to reduce the thermal deformation; fourthly, the slide plate surface is repaired by adopting vertical surface cladding, so that the operation is convenient and fast; the inner hole is symmetrically cladded in different areas, so that cladding deformation is reduced; during each cladding, only the bearing seat is rotated to enable the cladding area to be positioned at the bottom, and a vertical lathe is not required to rotate, so that the production cost is greatly reduced; fifthly, the gas shielded welding adopts low-carbon steel or low-carbon alloy steel welding wires, and the corrosion resistance of the repair surface is ensured by reducing the carbon content; after gas shield welding, local stress relief annealing is carried out in a heating belt or induction heating mode, so that the welding residual stress is reduced, the welding deformation is reduced, and the risk of generating cracks is reduced; compared with the integral annealing in a furnace, the method not only reduces the cost, but also prevents the deformation. Moreover, because the heat input of the laser cladding repair position is small, the generated residual stress and deformation are small, and annealing treatment is not needed; seventhly, allowance is reserved after semi-finishing, so that convenience is provided for subsequent flaw detection and defect removal, and deformation after machining is reduced; eighthly, the damaged thread is repaired in a mode of reaming → tapping → embedding the internal and external thread sleeves, the operation is simple, the production efficiency is improved, and the cost is reduced.
Compared with the prior art, the method for repairing the bearing seat of the large rolling mill improves the wear resistance, impact resistance and corrosion resistance of the repaired surface, and has small deformation in the repairing process, 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 efficiency and low in cost. The repairing method has pertinence, is particularly suitable for repairing the bearing seat of the large-scale rolling mill, and covers the aspects of the whole repairing process. The repairing method provides an idea for repairing the bearing seat of the large-scale rolling mill, and has reference significance.
Drawings
FIG. 1 is a flow chart of the repairing method for hot rolling a bearing seat of a large rolling mill according to the present invention;
FIG. 2 is a schematic view of a repaired rolling mill bearing housing in example 2;
FIG. 3 is a schematic diagram of a laser repair inner hole zoned symmetric cladding mode according to the present invention.
Detailed Description
For better understanding of the present invention, the method for repairing a bearing housing of a hot rolling large rolling mill according to the present invention will be described in further detail with reference to examples.
Example 1
Supporting roller bearing frame on 3000mm medium plate production line of some steel mill, specification: 2850mm x 2110mm (length and height), 20 tons in weight and the material ZG35SiMn, and the repairing method comprises the following steps:
cleaning, disassembling and polishing: cleaning the surface of the bearing seat and removing oil stains on the surface; dismantling the assembly parts such as the sliding plate, the pressing cylinder and the like on the bearing seat; manually polishing the rest surfaces except the assembly surface by using a polishing sheet to remove surface oxide skin;
secondly, detecting the screw thread: detecting whether the thread is intact by using a thread gauge, and marking and counting the damaged thread;
thirdly, size detection: detecting the size and cylindricity of the inner hole surface of the bearing pedestal, detecting the symmetrical size, total length size and planeness of the slide plate surface, and detecting the size of the assembling surface of the pressing cylinder;
rough turning and rough milling: turning to remove the fatigue layer of the inner hole and ensuring that the cylindricity is within 0.1 mm; milling to remove the oxide skin on the surface of the slide plate, and ensuring that the symmetry is within 0.2mm, and milling the area with severe local corrosion is bright; milling a part of a non-working surface on the outer side of the surface of the sliding plate to be bright and serving as a reference for semi-finishing and finishing;
magnetic particle inspection: performing magnetic powder inspection on all the processing surfaces, and if defects exist, removing the defects in a manual argon arc welding repair mode after manual grinding and clamping repair so as to ensure that the processing surfaces have no defects such as cracks; the welding wire used for argon arc welding is 316L stainless steel welding wire;
sixthly, laser cladding and gas shielded welding: the inner hole surface and the slide plate surface are repaired in a laser cladding mode, and the pressing cylinder joint surface is repaired in a gas shielded welding mode; before laser cladding, spot welding a sealing cover on the undamaged threaded hole by adopting a stainless steel gasket with the thickness of 2mm to prevent damage caused during laser cladding; after the inner hole surface is roughly processed, the single edge is out of tolerance by 1.6mm, the laser cladding is '0.8 mm bottoming layer +1.6mm covering surface layer', and the cladding is carried out according to the sequence of (1) → (two) > in the figure 3; the single edge of the sliding plate surface is out of tolerance by 1.6mm, the laser cladding is '0.8 mm priming coat +1.6mm cover coat', and the facade cladding is adopted; the joint surface of the compaction cylinder has larger cracks due to the long-term maintenance, the single-side out-of-tolerance is 7.8mm after the removal, and three layers of ER50-6 welding wires are overlaid by gas shielded welding, wherein each layer is 3.3 mm.
The alloy material used for the bottom layer in laser cladding comprises, by mass, 16.5% of Cr, 2% of Mo, 12% of Ni, 0.3% of Mn, 0.05% of C, 1.2% of Si and the balance of Fe, and the process parameters are as follows: the diameter of a 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 covering surface layer is made of alloy materials with 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 a 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 3.3 mm.
And stress relief annealing: local stress relief annealing is needed on the assembly surface of the compaction cylinder, the assembly surface is heated to 500 ℃ by adopting an induction heating mode, the temperature is kept for 2 hours, and the asbestos is wrapped and slowly cooled to the room temperature;
eighthly, half finish turning and half finish milling: reserving a margin with a single side of 0.5mm according to the size of a finished product, semi-finish turning an inner hole surface, and semi-finish milling other repairing surfaces;
ninthly, coloring flaw detection: performing dye penetrant inspection on the inner hole surface, the slide plate surface and the pressing cylinder joint surface, and if defects are found, performing argon arc welding repair by using a 316L stainless steel welding wire after manual polishing and clamping repair to ensure that the machined surface is free of defects;
finish machining at R: finishing each repairing surface according to the dimension and form and position tolerance required by a drawing;
The alloy composition design of the bottom layer in the embodiment mainly considers that the matrix material is ZG35SiMn, and the laser cladding has a certain dilution rate: in order to ensure the ductility and the corrosion resistance of the bottom layer, high contents of Ni, Cr and Mo elements and low contents of C, Mn elements are required to be selected; the covering layer mainly considers that the position is abraded seriously, and in order to improve the wear resistance, higher content of Co element and C, Cr element are selected.
The selection of the process parameters of laser cladding and gas shielded welding in the embodiment is mainly determined according to the single-layer thickness and the repair efficiency: thicker thickness allows for greater heat input parameters, and faster speeds and greater heat input to be selected for efficiency.
Example 2
A production line lower supporting roll bearing seat is produced to 3000mm middle plate of a certain steel mill, specification: 2070mm x 2110mm, weight 14 ton/piece, material ZG35SiMn, the repairing method includes the following steps:
cleaning, disassembling and polishing: cleaning the surface of the bearing seat and removing oil stains on the surface; dismantling the assembly parts such as the sliding plate, the pressure bearing pad and the like on the bearing seat; manually polishing the rest surfaces except the assembly surface by using a polishing sheet to remove surface oxide skin;
secondly, detecting the screw thread: detecting whether the thread is intact by using a thread gauge, and marking and counting the damaged thread;
thirdly, size detection: detecting the size and cylindricity of the inner hole surface of the bearing seat, detecting the symmetrical size, the total length size and the planeness of the sliding plate surface, and detecting the size of the assembly surface of the pressure bearing pad;
rough turning and rough milling: turning to remove the fatigue layer on the surface of the inner hole and ensuring the cylindricity to be within 0.1 mm; milling to remove the oxide skin of the slide plate surface, and ensuring that the symmetry is within 0.2mm, and milling the area with severe local corrosion is bright; milling a part of a non-working surface on the outer side of the surface of the sliding plate to be bright and serving as a reference for semi-finish machining and finish machining;
magnetic particle inspection: performing magnetic powder inspection on all the processing surfaces, and if defects exist, removing the defects by using a 316L welding wire argon arc welding repair mode after manual grinding and clamping repair so as to ensure that the processing surfaces have no defects such as cracks;
sixthly, laser cladding and gas shielded welding: the inner hole surface and the slide plate surface are repaired in a laser cladding mode, and the assembly surface of the pressure-bearing pad is repaired in a gas shielded welding mode; before laser cladding, spot-welding and capping undamaged threaded holes by adopting stainless steel gaskets with the thickness of 2mm, and preventing damage caused during laser cladding; after the inner hole surface is roughly processed, the single edge is out of tolerance by 0.8mm, the laser cladding is a 1.6mm covering surface layer, and cladding is carried out according to the sequence of → → II in the figure 3; the single edge of the sliding plate surface is out of tolerance by 1.4mm, the laser cladding is '0.8 mm priming coat +1.4mm cover coat', and the facade cladding is adopted; the assembly surface of the pressure bearing pad is worn seriously due to the long-term repair, the single edge is out of tolerance of 9.5mm after polishing, and three layers of ER50-6 welding wires are overlaid by gas shielded welding, wherein each layer is 3.8 mm.
The laser cladding bottom coating comprises alloy materials, by mass, 17% of Cr, 2% of Mo, 12.5% of Ni, 0.3% of Mn, 0.04% of C, 1.2% of Si and the balance of Fe, wherein the alloy materials comprise the following chemical components; the covering surface layer is made of alloy materials with the following chemical components in percentage by mass: 17.5% of Cr, 2% of Mo, 4.5% of Ni, 3.5% of Co, 0.5% of Mn, 0.1% of C, 1.2% of Si and the balance of Fe. The inner hole surface cover surface layer laser cladding process parameters are as follows: the diameter of a 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 laser cladding of the bottom layer of the sliding plate surface are as follows: the diameter of a 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 surface layer are as follows: the diameter of a 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: the current is 260A, the voltage is 26V, the moving speed is 480mm/min, the air flow is 15L/min, and the single-layer thickness is 3.8 mm.
Stress relief annealing: local stress relief annealing is needed on the assembly surface of the pressure bearing pad; heating to 400 ℃ by adopting a heating belt mode, preserving heat for 4h, and slowly cooling to room temperature by wrapping asbestos;
eighthly, semi-finish turning and semi-finish milling: reserving a margin with a single side of 0.5mm according to the size of a finished product, semi-finish turning an inner hole surface, and semi-finish milling other repairing surfaces;
ninthly, coloring flaw detection: performing dye check on the inner hole surface, the slide plate surface and the pressure bearing pad assembly surface, if defects are found, manually polishing and repairing by pliers, and performing argon arc welding repair by using a 316L stainless steel welding wire to finally ensure that the processed surface is free of defects;
finish machining at R: finishing each repairing surface according to the dimension and form and position tolerance required by a drawing;
The design basis of the alloy components of the bottom layer and the cover layer in the embodiment comprises that the base material is ZG35SiMn, and certain dilution rate exists in laser cladding and the performance requirement of the cladding layer.
In the embodiment, the selection of the process parameters of laser cladding and gas shielded welding is mainly determined according to the single-layer thickness and the repair efficiency. Larger heat input parameters can be selected for larger thicknesses, and a higher speed and thus a larger heat input are also required for improving efficiency.
Example 3
A850 production line R1 rolling mill working roll lower bearing seat of a certain steel mill has the following specification: 1194mm multiplied by 1330mm, the weight of 4 tons per piece, the material ZG310-570, the repairing method comprises the following steps:
cleaning, disassembling and polishing: cleaning the surface of the bearing seat and removing oil stains on the surface; dismantling the assembly parts such as the sliding plate, the pressure bearing pad and the like on the bearing seat; manually polishing the rest surfaces except the assembly surface by using a polishing sheet to remove surface oxide skin;
secondly, detecting the screw thread: detecting whether the thread is intact by using a thread gauge, and marking and counting the damaged thread;
thirdly, size detection: detecting the size and cylindricity of the inner hole surface of the bearing pedestal, detecting the symmetrical size, total length size and planeness of the slide plate surface, and detecting the size of the assembly surface of the pressure bearing pad;
fourthly, rough turning and rough milling: turning to remove the fatigue layer on the surface of the inner hole and ensuring the cylindricity to be within 0.1 mm; milling to remove the oxide skin of the slide plate surface, and ensuring that the symmetry is within 0.2mm, and milling the area with severe local corrosion is bright; milling a part of a non-working surface on the outer side of the surface of the sliding plate to be bright and serving as a reference for semi-finishing and finishing;
magnetic particle inspection: performing magnetic powder inspection on all the processing surfaces, and if defects exist, removing the defects by adopting a 316L welding wire argon arc welding repair mode after manual polishing and clamping repair so as to ensure that the processing surfaces have no defects such as cracks;
sixthly, laser cladding and gas shielded welding: the inner hole surface and the slide plate surface are repaired in a laser cladding mode, and the assembly surface of the pressure-bearing pad is repaired in a gas shielded welding mode; before laser cladding, spot welding a sealing cover on the undamaged threaded hole by adopting a stainless steel gasket with the thickness of 2mm to prevent damage caused during laser cladding; after the inner hole surface is roughly processed, the single edge is out of tolerance by 1.0mm, laser cladding is 1.8mm of a covering surface layer, and cladding is carried out according to the sequence of → (r) → r) ((r) () in the figure 3; the single edge of the slide plate surface is out of tolerance by 1.2mm, the laser cladding is '0.8 mm bottoming layer +1.2mm covering layer', and the vertical surface cladding is adopted; after the assembly surface of the pressure bearing pad is polished, the single-side out-of-tolerance is 4.5mm, and two layers of ER50-6 welding wires are overlaid by gas shielded welding, wherein each layer is 3.3 mm.
The laser cladding bottom coating comprises alloy materials, by mass, 17% of Cr, 2.5% of Mo, 13% of Ni, 0.5% of Mn, 0.02% of C, 1.0% of Si and the balance of Fe; the covering layer is made of alloy materials comprising the following chemical components in percentage by mass: 18% of Cr, 2% of Mo, 4% of Ni, 3% of Co, 0.5% of Mn, 0.08% of C, 1.0% of Si and the balance of Fe. The inner hole surface cover surface layer laser cladding process parameters are as follows: the diameter of a 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 laser cladding of the bottom layer of the sliding plate surface are as follows: the diameter of a 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 cover layer are as follows: the diameter of a 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: the current is 260A, the voltage is 26V, the moving speed is 550mm/min, the air flow is 15L/min, and the single-layer thickness is 3.3 mm.
And stress relief annealing: local stress relief annealing is needed on the assembly surface of the pressure bearing pad; heating to 450 ℃ by adopting a heating belt mode, preserving heat for 3h, and slowly cooling the asbestos package to room temperature;
eighthly, half finish turning and half finish milling: reserving a margin with a single side of 0.5mm according to the size of a finished product, semi-finish turning an inner hole surface, and semi-finish milling other repairing surfaces;
ninthly, dye-uptake inspection: performing dye check on the inner hole surface, the slide plate surface and the pressure bearing pad assembly surface, if defects are found, manually polishing and repairing by pliers, and performing argon arc welding repair by using a 316L stainless steel welding wire to finally ensure that the processed surface is free of defects;
finish machining at R: finishing each repairing surface according to the dimension and form and position tolerance required by a drawing;
The alloy components of the bottom layer and the cover layer in the embodiment are designed according to the base material ZG310-570, the base material ZG contains 0.5% of carbon element, 0.6% of Si element and 0.9% of Mn element, and considering that certain dilution rate exists in laser cladding, in order to ensure the performance requirement of the cladding layer, the content of C element in the cladding layer is low, and the content of other elements is high.
The selection of the process parameters of laser cladding and gas shielded welding in the embodiment is mainly determined according to the single-layer thickness and the repair efficiency. Larger heat input parameters can be selected for larger thicknesses, and a higher speed and thus a larger heat input are also required for improving efficiency.
In order to verify the performance of the large-scale rolling mill bearing seat repaired by the method, the corresponding test block is manufactured by adopting the laser cladding material and the process of the sliding plate surfaces of the embodiments 1, 2 and 3, and meanwhile, the reference block is manufactured by adopting the new bearing seat ZG310-570 material in the embodiment 3 to carry out quenching and tempering heat treatment. The hardness, the wear resistance and the corrosion resistance are compared and researched. Wherein, the hardness test is carried out by adopting a handheld Leeb hardness tester; the wear resistance is tested by adopting a self-made simple friction wear testing machine and is represented by the wear loss per unit time; the corrosion resistance was compared by immersion corrosion testing.
The test results are shown in table 1:
TABLE 1 comparison of the Properties of different test blocks
| Sample number | hardness/HRC | Loss on abrasion/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 the table 1, the hardness, the wear resistance and the corrosion resistance of the large-scale rolling mill bearing seat repaired by the material and the method are all superior to those of a new bearing seat under the same condition. That is to say, the method of the invention is adopted to repair the bearing seat of the rolling mill, which not only simply recovers the size, but also further improves the performance of the bearing seat, and further prolongs the service life of the bearing seat. The service life of the bearing seat is 1.5-2 times of that of a new bearing seat after the bearing seat is used online in a steel mill. In addition, the method has the advantages of simple process, higher efficiency and low comprehensive cost.
The concept of laser cladding and gas shielded welding in the repair method can be suitable for repairing parts with large wall thickness difference, and is not limited to the rolling mill bearing seat provided by the invention.
Claims (10)
1. A repairing method for a bearing seat of a hot rolling large-scale rolling mill is characterized by comprising the following steps:
cleaning, disassembling and polishing: cleaning the surface of the bearing seat and removing oil stains; dismantling the assembly parts such as the sliding plate, the pressure bearing pad, the pressing cylinder and the like on the bearing seat; manually polishing the rest surfaces except the assembly surface by using a polishing sheet to remove surface oxide skin;
detecting the screw thread: detecting whether the thread is intact by using a thread gauge, and marking and counting the damaged thread;
thirdly, size detection: detecting the size and cylindricity of an inner hole of the bearing seat, detecting the symmetrical size, the total length size and the planeness of the sliding plate surface, and detecting the sizes of other assembly surfaces;
fourthly, rough turning and rough milling: turning to remove the fatigue layer of the inner hole and ensuring that the cylindricity is within 0.1 mm; milling to remove the oxide skin of the slide plate surface, and ensuring that the symmetry is within 0.2mm, and milling the area with severe local corrosion is bright; milling a part of a non-working surface on the outer side of the surface of the sliding plate to be bright and serving as a reference for semi-finishing and finishing;
magnetic particle inspection: performing magnetic powder inspection on all the processing surfaces to ensure that the processing surfaces have no defects such as cracks;
sixthly, laser cladding and gas shielded welding: the inner hole surface and the slide plate surface are repaired by laser cladding, and the other assembly surfaces are repaired by gas shielded welding; during laser cladding, the undamaged threaded holes are covered by adopting stainless steel gaskets with the thickness of 2mm in a spot welding mode, 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;
and stress relief annealing: heating the position of gas shield welding surfacing to 400-500 ℃ by adopting a heating belt or induction heating mode, preserving heat for 2-4 h, and slowly cooling the asbestos package to room temperature;
eighthly, half finish turning and half finish milling: reserving a margin with a single side of 0.5mm according to the size required by a drawing, semi-finish turning an inner hole surface, and semi-finish milling other repair surfaces;
ninthly, dye-uptake inspection: performing dye check on all processing surfaces to ensure that the processing surfaces are free of defects;
finish machining red: finishing each repairing surface according to the dimension and form and position tolerance required by a drawing;
2. The repair method according to claim 1, characterized in that: fifthly, after the flaw detection, if the flaw is found, removing the flaw by adopting a manual polishing clamp repairing mode and a manual argon arc welding repairing mode; the welding wire adopted by argon arc welding is 316L stainless steel welding wire.
3. The repair method according to claim 1, characterized in that: the technological parameters of laser cladding in the step VI are as follows: the diameter of a 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 conveying amount is 25-60 g/min. The thickness of the single layer is 0.8-1.8 mm.
4. The repair method according to claim 1, characterized in that: sixthly, when the size of the inner hole surface or the slide plate surface exceeds 1mm, dividing the laser cladding layer into a bottoming layer and a cover surface layer; if the size out-of-tolerance is less than 1mm, the laser cladding layer is only provided with one covering layer.
5. The repair method according to claim 1, characterized in that: sixthly, adopting a vertical surface cladding mode for the laser cladding of the surface of the sliding plate; the inner hole laser cladding adopts a mode of symmetrical cladding by regions.
6. The repair method according to claim 1, characterized in that: the technological parameters of the medium gas shield welding are as follows: the current 220-260A, the voltage 22-26V, the moving speed 400-600mm/min, the air flow 10-15L/min and the single-layer thickness 2.5-4 mm.
7. The repair method according to claim 1, characterized in that: and sixthly, welding wires used for gas shielded welding are low-carbon steel or low-carbon alloy steel welding wires.
8. The repair method according to claim 4, characterized in that: the bottom layer comprises the following alloy materials 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.
9. The repair method according to claim 4, characterized in that: the covering surface layer is made of alloy materials with 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.
10. The repair method according to claim 5, characterized in that: the vertical face cladding mode means that the surface of the sliding plate of the bearing seat is vertically placed, and a laser head and the surface of the sliding plate form an included angle of 60 degrees for cladding; the mode of regional symmetrical cladding is that the 360-degree circumference of the inner hole surface is divided into four blocks, namely an upper left block, a lower left block, an upper right block and a lower right block, any one block (a first block) is clad first, the other block (a second block) which is centrosymmetric with the first block is clad, any one block (a third block) of the rest two blocks is clad, and the rest block (a fourth block) is clad finally; the bearing seat direction needs to be adjusted during each cladding, so that the cladding area is positioned at the bottom.
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