CN111215830A - Method for repairing cracks of high-pressure medium-carbon cast steel oil cylinder body with thickness larger than 200mm - Google Patents
Method for repairing cracks of high-pressure medium-carbon cast steel oil cylinder body with thickness larger than 200mm Download PDFInfo
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- CN111215830A CN111215830A CN201911211972.4A CN201911211972A CN111215830A CN 111215830 A CN111215830 A CN 111215830A CN 201911211972 A CN201911211972 A CN 201911211972A CN 111215830 A CN111215830 A CN 111215830A
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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
- B23P6/04—Repairing fractures or cracked metal parts or products, e.g. castings
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/013—Arc cutting, gouging, scarfing or desurfacing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/04—Welding for other purposes than joining, e.g. built-up welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/32—Accessories
Abstract
The invention discloses a method for repairing cracks of a high-pressure medium-carbon cast steel oil cylinder body with the thickness of more than 200mm, and aims to repair cracks by adopting a layer-by-layer surfacing and reasonable step-by-step stress-relief welding repair scheme. The main oil cylinder of the rapid forging machine has cracks with the length of about 600 mm-1000 mm at different parts, and on-site proves that if the stress of the medium carbon steel casting with the thickness of about 200mm is relieved for the last time, the cracks can appear in the surfacing process, if the stress is relieved step by step, the stress level of a workpiece can be reduced, and the cracking caused by overlarge welding stress is avoided. The results of the invention show that: for medium carbon steel castings with the thickness of about 200mm, a welding repair scheme of layer-by-layer surfacing and step-by-step stress relief is adopted, so that a good repair effect can be obtained, and the production cost is reduced by repairing the old and utilizing the waste.
Description
Technical Field
The invention belongs to the field of high-pressure medium-carbon cast steel crack welding repair processes, and mainly relates to a method for repairing cracks of a high-pressure medium-carbon cast steel cylinder body with the thickness of more than 200 mm.
Background
The hydraulic system working pressure of 2000 tons of fast forging machine is 31.5MPa, the diameter of the main oil cylinder body of the fast forging machine is 1370mm, the length is 2250mm, the weight reaches 19 tons, the main oil cylinder is the main pressure oil cylinder of the fast forging machine, the oil cylinder is the core part of the press, the main oil cylinder of the fast forging machine has cracks with the length of about 600 mm-1000 mm at different positions, the machine is forced to stop, if the production stop loss is large, the loss can be reduced if a repairing method is adopted.
The ZG35 material of the rapid forging machine has high carbon content, the minimum wall thickness of the main oil cylinder body is 190mm, main cracks are near the boss of the intermediate flange, the maximum thickness reaches 290mm, double-side welding is difficult, welding performance is poor, a heat affected zone is easy to generate low-plasticity hardening structures, the larger the plate thickness is, the larger the hardening tendency is, the positive value in northeast winter is, the environment temperature is low, when the rigidity of a workpiece is higher, stress is increased, and when the workpiece is cooled to be below 300 ℃, cold cracks are easy to generate in the hardening zone. Because the carbon content of the base metal is higher, the base metal is melted into a molten pool in the welding process, so that the carbon content of the weld metal is increased, and because the contents of sulfur, phosphorus and the like of cast steel are more, the sulfur enters the weld, and is the main reason of causing the hot cracks of the weld. Under metallurgical conditions, sulfur and iron form Fe-FeS eutectic, the melting point of the eutectic is only 985 ℃, eutectic substances with low melting points are extruded and converged at the boundary of columnar crystals, the eutectic substances are weak parts due to contraction of a welding seam cooling process, the eutectic substances crack under the action of tensile stress to cause thermal cracks, the increase of carbon content aggravates the harmful effect of the sulfur, and particularly, the eutectic substances are more sensitive to arc closing and have large welding stress in winter at positive values.
The repair process belongs to the key technology in the field of repair and manufacture of large-thickness high-pressure cast steel spare parts, and no public data for repairing cracks by a segmented stress relief method is introduced at present.
Disclosure of Invention
The invention discloses a method for repairing cracks of a high-pressure medium-carbon cast steel oil cylinder body with the thickness of more than 200mm, and aims to repair cracks by adopting a reasonable step-by-step stress-relief welding repair scheme.
The repair process of the invention comprises the following steps:
⑴ preparation before welding:
⑴ the U-shaped groove is cut on the outer wall of the cylinder body by a carbon arc gouging, the folded matter and the carburant layer of the carbon arc gouging are cleaned by an angle grinder, and the folded matter and the carburant layer are not cleaned by flame, thereby avoiding hardening cracks.
⑵ adopts alkaline low-hydrogen type welding rod E4316, J426 (diameter phi 4, phi 5) to perform direct current reverse connection, the welding rod is dried at 350-400 ℃ for 2h, and is placed in a heat-preserving container to be taken at any time, and the ER506 welding wire is welded under the protection of carbon dioxide.
⑶ preventing oxidation of cylinder bolt hole in furnace, plugging with asbestos felt, heating to 400 deg.C in heating furnace, maintaining for 4 hr, wrapping the part not to be welded with asbestos felt, and welding as soon as possible, wherein the preheating temperature before welding is not lower than 300 deg.C and the interlayer temperature is not lower than 300 deg.C.
⑷ in order to prevent the temperature from dropping too fast, a self-made flame heater is placed in the oil cylinder, and the repaired part is always baked during the welding process.
⑵ the welding process has the key points:
⑴ the first welding (the target of each welding thickness is 70-90 mm) uses E4316, J426 phi 4 and phi 5, welds on the ground side, spot welds the lining board on the groove bottom, build up welds on both sides, and finally seals the weld, the current (I) is 140-160A short arc welding and rapid welding, reduces the fusion ratio, the interlayer temperature is not lower than 300 ℃, strictly removes slag, and removes the welding stress with air hammer.
⑵ in order to improve the repair efficiency and facilitate slag removal at the flat welding position, the second and third welding times (the welding thickness is 70-90 mm each time) adopt carbon dioxide gas protection flat welding and ER506 welding wire, during the heat treatment of the workpiece, a flat welding working platform is prepared in advance, protective heat insulation work is done after the workpiece is taken out of the furnace, and flat welding is carried out on the platform.
⑶ welding to a thickness of 70 mm-90 mm each time, performing heat treatment once, keeping the temperature at 650 ℃ for 4h, and discharging at 400 ℃.
⑷ after the final welding of the outer wall, the whole heat treatment is immediately carried out, the furnace is immediately put into, the welding stress is eliminated, the temperature is kept for 4h at 650 ℃, the furnace is taken out at 150 ℃ along with the furnace cooling, and the slow cooling is carried out by covering with asbestos felt.
⑸ back gouging welding process comprises cooling cylinder to 150 deg.C, spreading heat-insulating felt inside, welding at a thickness of about 30mm, welding oil cylinder with E4316 and J426, removing slag, inspecting the surface of the welded seam, and heating to dark red at 150mm side of the welded seam by local flame stress relief heat treatment, and cooling for 30 min.
⑶ post-weld treatment
⑴, cooling to below 100 deg.C, grinding, coloring, and inspecting for flaws such as crack, undercut, air hole, and inclusion, after inspecting for flaws such as slag inclusion, undercut, and air hole, cleaning with angle grinder, heating to 100 deg.C, and welding for repair until defects are detected.
⑵ grinding to meet the specified size requirement.
The innovation points of the repair process of the invention are as follows:
the welding repair process of combining manual electric arc welding and carbon dioxide gas shielded welding, overlaying layer by layer and eliminating stress step by step is adopted, cracks of 1000mm long and 190-290 mm thick of the main oil cylinder body of the 2000-ton quick forging machine are repaired, defects of cracks, air holes, slag inclusion and the like do not exist in the repaired part, and the stress is basically eliminated.
Special care needs to be taken during the repair process: when the cracks are treated, cold machining is adopted to remove the cracks as much as possible, dye penetrant inspection is carried out before welding, the cracks are thoroughly cleaned, and the back gouging welding process is adopted on the inner wall of the direct stress surface of the cylinder body, which is the most critical step.
The results of the invention show that: for medium carbon steel castings with the thickness of about 200mm, a welding repair scheme of layer-by-layer surfacing and step-by-step stress relief is adopted, so that a good repair effect can be obtained, and the production cost is reduced by repairing the old and utilizing the waste.
Drawings
FIG. 1 is a cylinder body process annealing stress relief curve for repairing a master cylinder of a 2000-ton quick forging machine;
FIG. 2 is a graph of the overall annealing stress relief curve of a cylinder body repaired by a master cylinder of a 2000-ton quick forging machine;
FIG. 3 is a schematic view of a primary crack in the master cylinder body;
fig. 4 is a schematic view of a secondary crack of the master cylinder body.
Icon: 1-first crack length 820mm, 2-second crack length 1060 mm.
Detailed Description
The present invention is described in detail with reference to the accompanying drawings and examples.
Example 1
The method has the advantages that the crack repairing examples with the length of about 600 mm-1000 mm appear at different parts of the main oil cylinder of the rapid forging machine, and the fact that if stress is eliminated for the last time, cracks appear in the surfacing welding process of medium carbon steel castings with the thickness of about 200mm is proved, if step-by-step stress elimination is adopted, the stress level of workpieces can be reduced, and cracking caused by overlarge welding stress is avoided.
1. And (3) removing the cracks by adopting a cold machining method as much as possible when the cracks are treated, drilling an upper crack stop hole at a position 5-8 mm before the tips of the cracks before flame cutting hot machining if cold machining conditions are not met, wherein the hot cutting method can not be used blindly, otherwise, the cracks grow at the highest speed, and the cracks cannot be controlled and are discarded.
2. The dye check before welding, which confirms to clear up cracks, is the most critical first step for completing the repair, and because the inner wall of the oil cylinder is the surface which is stressed most directly, the inside must be smooth, no stress concentration exists, and the back gouging process is the most critical step for ending.
3. The method has the advantages that stress concentration can be caused to small defects of the high-pressure oil cylinder, cracks such as casting shrinkage cavities, round corners of processing steps, flame cutting marks and scratches during maintenance and the like are caused, and the stress concentration is caused by the defects of the sharp corners by paying certain attention during design, manufacture or maintenance.
Claims (2)
1. The method for repairing the cracks of the high-pressure medium carbon cast steel oil cylinder body with the thickness larger than 200mm is characterized in that the repair method adopts a welding repair scheme of layer-by-layer surfacing and step-by-step stress relief.
2. The method for repairing the cracks of the high-pressure medium-carbon cast steel oil cylinder body with the thickness of more than 200mm according to claim 1, characterized by comprising the following specific steps of layer-by-layer surfacing and step-by-step stress relief:
⑴ preparation before welding:
⑴ cutting a U-shaped groove on the outer wall of the cylinder body by a carbon arc gouging, cleaning folded objects and a carburant layer of the carbon arc gouging by an angle grinder, and avoiding hardening cracks by flame cleaning for thousands of times;
⑵ adopting alkaline low-hydrogen welding rods E4316 and J426 with diameter phi 4 and phi 5 for direct current reverse connection, drying the welding rods at 350-400 ℃ for 2h, placing the welding rods in a heat-preserving container for use and taking;
⑶ preventing oxidation of oil cylinder bolt hole in furnace, plugging with asbestos felt, heating in heating furnace to 400 deg.C, maintaining for 4h, wrapping the part not to be welded with asbestos felt, and performing tissue welding as soon as possible, wherein the preheating temperature before welding is not lower than 300 deg.C, and the interlayer temperature is not lower than 300 deg.C;
⑷ in order to prevent the temperature from dropping too fast, a self-made flame heater is placed in the oil cylinder, and the repaired part is always baked in the welding process;
⑵ the welding process has the key points:
⑴ the target thickness of each welding is 70 mm-90 mm;
⑵ welding at ground side with E4316, J426 phi 4 and phi 5 for the first time, spot welding lining plate on the bottom of groove, overlaying welding at two sides, and final sealing welding with current (I) of 140-160A short arc welding and rapid welding to reduce fusion ratio, wherein the interlayer temperature is not lower than 300 deg.C, removing slag strictly, and eliminating welding stress with air hammer;
⑶ in order to improve the repair efficiency and the flat welding position to facilitate slag removal, the second and third welding uses carbon dioxide gas protection flat welding, ER506 welding wire, during the heat treatment of the workpiece, preparing a flat welding working platform in advance, taking out of the furnace, doing protective heat insulation work, and welding on the platform in a flat position;
⑷ welding to the target thickness, performing heat treatment once, keeping the temperature at 650 deg.C for 4h, and discharging at 400 deg.C;
⑸ after the final outer wall welding, the whole heat treatment welding is immediately carried out in the furnace, the welding stress is eliminated, the temperature is kept for 4h at 650 ℃, the furnace is discharged at 150 ℃ along with the furnace cooling, and the slow cooling is carried out by covering with asbestos felt;
⑹ back gouging welding process, which comprises cooling the cylinder to 150 deg.C, spreading heat-insulating felt inside, welding at a thickness of about 30mm, welding the weld seam inside the cylinder by E4316 and J426, removing slag strictly between layers, inspecting the weld seam surface after welding, and eliminating slag, air holes, and incomplete fusion, etc., heating the weld seam to dark red at 150mm side by local flame stress relief heat treatment, and cooling for 30 min;
⑶ post-weld treatment
⑴, cooling to below 100 deg.C, grinding, coloring, and inspecting defects such as crack, undercut, air hole, and inclusion, after inspecting, if some defects such as slag inclusion, undercut, and air hole are found, cleaning with angle grinder, heating to 100 deg.C, and welding and repairing until no defect is detected;
⑵ grinding to meet the specified size requirement.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911211972.4A CN111215830A (en) | 2019-12-02 | 2019-12-02 | Method for repairing cracks of high-pressure medium-carbon cast steel oil cylinder body with thickness larger than 200mm |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911211972.4A CN111215830A (en) | 2019-12-02 | 2019-12-02 | Method for repairing cracks of high-pressure medium-carbon cast steel oil cylinder body with thickness larger than 200mm |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI753773B (en) * | 2021-02-18 | 2022-01-21 | 興達海洋基礎股份有限公司 | Method for repairing weld cracks |
| CN115138951A (en) * | 2022-08-01 | 2022-10-04 | 南京钢铁股份有限公司 | Online repairing method for cracking of large hydraulic cylinder |
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2019
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| CN1031726A (en) * | 1988-08-22 | 1989-03-15 | 潘相尧 | The method of plating iron reparing deep bore cylinder casing and device |
| US5373630A (en) * | 1993-12-13 | 1994-12-20 | Mk Rail Corporation | Cylinder conversion fabrication of crankcases for two-cycle V-type locomotive diesel engines |
| US5657526A (en) * | 1995-12-15 | 1997-08-19 | Yatcko; Michael J. | Split riding ring for rotary cylinders |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI753773B (en) * | 2021-02-18 | 2022-01-21 | 興達海洋基礎股份有限公司 | Method for repairing weld cracks |
| CN115138951A (en) * | 2022-08-01 | 2022-10-04 | 南京钢铁股份有限公司 | Online repairing method for cracking of large hydraulic cylinder |
| CN115138951B (en) * | 2022-08-01 | 2023-12-15 | 南京钢铁股份有限公司 | Online repairing method for large hydraulic cylinder cracks |
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Application publication date: 20200602 |