Manufacturing method of mushroom head forge piece of miter gate bottom pivot of ship lock of large hydropower station

Abstract

The invention discloses a manufacturing method of a mushroom head forge piece of a miter gate bottom pivot of a ship lock of a large hydropower station, and relates to the technical field of heat treatment methods, and the manufacturing method comprises the following steps: S1, smelting: smelting the mushroom head forge piece by adopting an electric furnace, external refining and vacuum degassing smelting; s2, forging is conducted, specifically, the initial forging temperature is 1200 DEG C, and the final forging temperature is 850 DEG C; forging deformation: drawing out, chopping a riser and a water port, upsetting, drawing out, upsetting, drawing out, upsetting and forging a mushroom head by a die, and shaping; s3, heat treatment after forging is conducted, refined grains are annealed at 680 DEG C, and tempering is conducted at 600-620 DEG C; s4, rough machining; s5, performance heat treatment is conducted, specifically, quenching is conducted at 1020 DEG C, and tempering is conducted at 520-540 DEG C; and S6, machining is carried out, after sampling detection is completed after heat treatment, one-time rough turning is carried out on the spherical end and the large-plane end, hoisting bolt holes are machined, and finish turning is carried out. The manufactured mushroom head forge piece meets the requirements of high working strength, corrosion resistance and wear resistance of the bottom of the ship lock.

Description

Technical Field

[0001] This invention relates to the field of heat treatment methods, and in particular to a method for manufacturing a mushroom head forging for the bottom pivot of a miter gate in a large hydropower station ship lock. Background Technology

[0002] The diameter of the mushroom head forging of the bottom pivot of the miter gate of a large hydropower station ship lock is up to 1.2 meters. The single gate of the miter gate at the bottom of the lock weighs more than 1,000 tons. Due to its difficult maintenance and the fact that it needs to work at the bottom of the lock for a long time, it must have the characteristics of high strength, corrosion resistance and wear resistance.

[0003] Traditional manufacturing methods use high-carbon, high-chromium martensitic stainless steel, which has a long manufacturing cycle and is prone to cracking during the manufacturing process.

[0004] Developing a manufacturing method for the mushroom head forging of the bottom pivot of a large hydropower station lock, and improving the hardness and tensile strength of the mushroom head forging through chemical composition optimization, forging and heat treatment process optimization, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a method for manufacturing a mushroom head forging for the bottom pivot of a miter gate in a large hydropower station lock, thereby solving the problems listed in the background art.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] This invention discloses a method for manufacturing a mushroom head forging for the bottom pivot of a miter gate in a large hydropower station. The mushroom head forging has dimensions of φ1235*1095 and is made of 04Cr13Ni5Mo low-carbon martensitic stainless steel.

[0008] The chemical composition (wt%) of the mushroom-shaped forging is as follows: C: 0.020%–0.045%, Si: 0.30%–0.50%, Mn: 0.50%–0.80%, S≤0.005%, P≤0.015%, Cr: 12.50%–13.00%, Mo: 0.50%–0.60%, Ni: 4.20%–4.50%, N: 0.015%–0.030%, C+N: 0.035%–0.060%, Cu≤0.15%, Al: ≤0.010%, Nb: ≤0.015%, Ti: ≤0.005%, As: ≤0.010%, Sn: ≤0.010%, Sb: ≤0.003%, Pb≤0.010%, Bi≤0.003%.

[0009] The method for manufacturing the mushroom head forging includes the following steps:

[0010] S1, Smelting

[0011] The mushroom head forgings are smelted using an electric furnace + ladle refining + vacuum degassing process.

[0012] S2, Forging

[0013] Forging temperature: initial forging temperature: 1200℃, final forging temperature: 850℃;

[0014] Forging deformation: drawing, removing the sprue, upsetting, drawing, upsetting, drawing, die upsetting, forging mushroom head, shaping;

[0015] S3, Post-forging heat treatment

[0016] Grain refinement annealing at 680℃;

[0017] Tempering at 600℃~620℃;

[0018] S4, rough machining;

[0019] S5, Performance Heat Treatment

[0020] Quenching at 1020℃ + tempering at 520℃~540℃;

[0021] S6, Machining

[0022] After heat treatment and sampling and testing, rough turning, machining of lifting bolt holes, and finish turning are performed on both the spherical end and the large flat end.

[0023] Preferably, the S3 post-forging heat treatment step specifically includes air cooling to 150°C followed by furnace cooling, holding at 120°C ± 10°C for no less than 12 hours after furnace cooling to 150°C ± 10°C, and holding at 680°C ± 10°C for no less than 50 hours at a heating rate of no more than 100°C / h.

[0024] When air-cooling from 680℃±10℃ to 150℃ furnace-cooling, and continuously cooling to 100±10℃, the holding time shall not be less than 12 hours. When heating from 100±10℃ to 620℃±10℃ at a heating rate not exceeding 100℃ / h, the holding time shall not be less than 90 hours. Then, air-cool from 620℃±10℃.

[0025] Preferably, the S5 performance heat treatment step specifically includes holding at 350℃±10℃ for no less than 5 hours; after holding, raising the temperature to 750℃±10℃ at a rate of no more than 60℃ / h, and holding for no less than 10 hours.

[0026] After the heat preservation is completed, the temperature is increased from 750℃±10℃ to 1020℃±10℃ at a heating rate of 80℃~120℃ / h, and kept at this temperature for 27.0~29.0 hours. Then, the temperature is water-cooled from 1020℃±10℃ to 350℃, air-cooled to 80℃, and kept at 100℃±10℃ for 10 hours.

[0027] After the heat preservation time is over, the temperature is increased to 520℃±10℃ at a rate of no more than 60℃ / h, and then kept at that temperature for 72.0~73.0 hours before being air-cooled to room temperature.

[0028] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0029] This invention discloses a method for manufacturing a mushroom head forging for the bottom pivot of a miter gate in a large hydropower station lock. By optimizing the chemical composition, forging process, and heat treatment of commonly used 04Cr13Ni5Mo low-carbon martensitic stainless steel, a mushroom head forging with a hardness ≥300HB and a tensile strength exceeding 950Mpa was successfully obtained. This forging has the characteristics of high strength, corrosion resistance, and wear resistance, and can work at the bottom of the lock for a long time. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the post-forging heat treatment process for a manufacturing method of a mushroom head forging for the bottom pivot of a miter gate in a large hydropower station, according to the present invention.

[0032] Figure 2 This is a schematic diagram illustrating the manufacturing method and heat treatment process of a mushroom head forging for the bottom pivot of a large hydropower station ship lock according to the present invention. Detailed Implementation

[0033] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] like Figure 1-2 As shown, a method for manufacturing a mushroom head forging for the bottom pivot of a miter gate in a large hydropower station is disclosed. The mushroom head forging has dimensions of φ1235*1095 and is made of 04Cr13Ni5Mo low-carbon martensitic stainless steel.

[0035] The chemical composition (wt%) of the mushroom-shaped forging is as follows: C: 0.020%–0.045%, Si: 0.30%–0.50%, Mn: 0.50%–0.80%, S≤0.005%, P≤0.015%, Cr: 12.50%–13.00%, Mo: 0.50%–0.60%, Ni: 4.20%–4.50%, N: 0.015%–0.030%, C+N: 0.035%–0.060%, Cu≤0.15%, Al: ≤0.010%, Nb: ≤0.015%, Ti: ≤0.005%, As: ≤0.010%, Sn: ≤0.010%, Sb: ≤0.003%, Pb≤0.010%, Bi≤0.003%.

[0036] The method for manufacturing the mushroom head forging includes the following steps:

[0037] S1, Smelting

[0038] The mushroom head forgings are smelted using an electric furnace + ladle refining + vacuum degassing process.

[0039] S2, Forging

[0040] Forging temperature: initial forging temperature: 1200℃, final forging temperature: 850℃;

[0041] Forging deformation: drawing, removing the sprue, upsetting, drawing, upsetting, drawing, die upsetting, forging mushroom head, shaping;

[0042] By using open die forging to forge the mushroom-shaped sphere, material can be saved while ensuring that the forging flow line is parallel to the final use state, thus guaranteeing the full utilization of the material's various properties.

[0043] S3, Post-forging heat treatment

[0044] Annealing at 680℃ refines the grains and austenitizes them at the lower limit in the two-phase region. This not only fully eliminates forging stress in the forgings, but also effectively refines the grains and prevents the surface and core of large forgings from reaching the temperature at different times, which would otherwise cause grain growth on the surface of the forgings.

[0045] Temper at 600℃~620℃, the hardness after tempering is ≤260HB, which fully reduces the hardness of the forging and facilitates machining.

[0046] S4. Rough machining: Rough machining of the sample drawing, retaining a part of the flat surface at one end of the mushroom head to facilitate machining and clamping;

[0047] S5, Performance Heat Treatment

[0048] Quenching at 1020℃ + tempering at 520℃~540℃, mist cooling is selected for quenching: This is because 04Cr13Ni5Mo material has good hardenability, and even air cooling can obtain sufficient martensite structure in the core of the forging. In order to prevent cracking caused by rapid cooling of the forging, water cooling was not selected. At the same time, in order to avoid too much residual austenite in the material caused by complete air cooling, air cooling or mist cooling is selected to accelerate the cooling of the forging.

[0049] Air cooling after tempering: Although the content of harmful elements in the material is strictly controlled, in order to further ensure that the product does not produce second-type temper brittleness, the workpiece is cooled appropriately after tempering, which can ensure that the forging has excellent toughness.

[0050] S6, Machining

[0051] Because the mushroom-shaped end of the forging head is spherical at one end, there is a problem with it being unable to be clamped after turning over during machining. Therefore, while saving material through profile forging, a platform is left at the spherical end of the mushroom-shaped forging head to facilitate machining and clamping.

[0052] After heat treatment and sampling and testing, rough turning, machining of lifting bolt holes, and finish turning are performed on both the spherical end and the large flat end.

[0053] As attached Figure 1 As shown, the S3 post-forging heat treatment step specifically includes air cooling to 150℃ and furnace cooling, furnace cooling to 120℃±10℃ and holding for no less than 12 hours, and heating to 680℃±10℃ at a heating rate of no more than 100℃ / h and holding for no less than 50 hours.

[0054] When air-cooling from 680℃±10℃ to 150℃ furnace-cooling and continuously cooling to 100±10℃, the holding time shall not be less than 12 hours; when heating from 100±10℃ to 620℃±10℃ at a heating rate not greater than 100℃ / h, the holding time shall not be less than 90 hours; and when air-cooling from 620℃±10℃.

[0055] Furthermore, when loading the furnace, the forging body should be externally connected to a thermocouple. During the furnace cooling process, the furnace fan should be turned on and the seal should not be tightened. When the furnace cools to the holding temperature, the seal should be tightened. The time interval between air cooling and loading of the two forgings should be as large as possible to avoid mutual interference in heat dissipation. The surface quality of the forged workpiece should be recorded in detail. Large surface cracks and folds and other defects should be reported in a timely manner.

[0056] like Figure 2 As shown, the S5 heat treatment step specifically includes holding at 350℃±10℃ for no less than 5 hours; after holding, raising the temperature to 750℃±10℃ at a rate of no more than 60℃ / h, and holding for no less than 10 hours.

[0057] After the heat preservation is completed, the temperature is increased from 750℃±10℃ to 1020℃±10℃ at a heating rate of 80℃~120℃ / h, and kept at this temperature for 27.0~29.0 hours. Then, the temperature is water-cooled from 1020℃±10℃ to 350℃, air-cooled to 80℃, and kept at 100℃±10℃ for 10 hours.

[0058] After the heat preservation time is over, the temperature is increased to 520℃±10℃ at a rate not exceeding 60℃ / h, and then kept at that temperature for 72.0~73.0 hours, followed by air cooling to room temperature.

[0059] For body sampling, refer to HB=300-330, check the appearance of the workpiece, the black skin on the surface needs to be polished to the bottom, the edges and corners need to be blunted, the joints of the steps need to be rounded, the mist cooling should ensure that 2-3 fans blow air in opposite directions to increase the cooling rate, and try to ensure that the forging is cooled evenly around the circumference.

[0060] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0061] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for manufacturing a mushroom head forging for the bottom pivot of a miter gate in a large hydropower station lock, characterized in that: The mushroom head forging has dimensions of φ1235*1095 and is made of 04Cr13Ni5Mo low-carbon martensitic stainless steel. The chemical composition (wt%) of the mushroom head forging is: C: 0.020%–0.045%, Si: 0.30%–0.50%, Mn: 0.50%–0.80%, S≤0.005%, P≤0.015%, Cr: 12.50%–13.00%, Mo: 0.50%–0.60%, Ni: 4.20%–4.50%, N: 0.015%–0.030%, C+N: 0.035%–0.060%, Cu≤0.15%, Al:≤0.010%, Nb:≤0.015%, Ti:≤0.005%, As:≤0.010%, Sn:≤0.010%, Sb:≤0.003%, Pb≤0.010%, Bi≤0.003%. The method for manufacturing the mushroom head forging includes the following steps: S1, Smelting The mushroom head forgings are smelted using an electric furnace + ladle refining + vacuum degassing process. S2, Forging Forging temperature: initial forging temperature: 1200℃, final forging temperature: 850℃; Forging deformation: drawing, removing the sprue, upsetting, drawing, upsetting, drawing, die upsetting, forging mushroom head, shaping; S3, Post-forging heat treatment Grain refinement annealing at 680℃; Tempering at 600℃~620℃; S4, rough machining; S5, Performance Heat Treatment Quenching at 1020℃ + tempering at 520℃~540℃; S6, Machining After heat treatment and sampling and testing, rough turning, machining of lifting bolt holes, and finish turning are performed on both the spherical end and the large flat end.

2. The manufacturing method of the mushroom head forging for the bottom pivot of a miter gate in a large hydropower station ship lock according to claim 1, characterized in that: The S3 post-forging heat treatment step specifically includes air cooling to 150℃ and furnace cooling, furnace cooling to 120℃±10℃ and holding for no less than 12 hours, and heating to 680℃±10℃ at a heating rate of no more than 100℃ / h and holding for no less than 50 hours. When air-cooling from 680℃±10℃ to 150℃ furnace-cooling, and continuously cooling to 100±10℃, the holding time shall not be less than 12 hours. When heating from 100±10℃ to 620℃±10℃ at a heating rate not exceeding 100℃ / h, the holding time shall not be less than 90 hours. Then, air-cool from 620℃±10℃.

3. The manufacturing method of the mushroom head forging for the bottom pivot of a miter gate in a large hydropower station ship lock according to claim 1, characterized in that: The S5 heat treatment step specifically includes holding at 350℃±10℃ for no less than 5 hours; after holding, raising the temperature to 750℃±10℃ at a rate of no more than 60℃ / h, and holding for no less than 10 hours. After the heat preservation is completed, the temperature is increased from 750℃±10℃ to 1020℃±10℃ at a heating rate of 80℃~120℃ / h, and kept at this temperature for 27.0~29.0 hours. Then, the temperature is water-cooled from 1020℃±10℃ to 350℃, air-cooled to 80℃, and kept at 100℃±10℃ for 10 hours. After the heat preservation time is over, the temperature is increased to 520℃±10℃ at a rate of no more than 60℃ / h, and then kept at that temperature for 72.0~73.0 hours before being air-cooled to room temperature.

Images