CN116329462A - Machining method of large Cr-Ni-Mo-V steel connecting shaft for nuclear power unit - Google Patents

Machining method of large Cr-Ni-Mo-V steel connecting shaft for nuclear power unit Download PDF

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CN116329462A
CN116329462A CN202310137028.9A CN202310137028A CN116329462A CN 116329462 A CN116329462 A CN 116329462A CN 202310137028 A CN202310137028 A CN 202310137028A CN 116329462 A CN116329462 A CN 116329462A
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forging
fire
blank
connecting shaft
equal
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CN116329462B (en
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宋国旺
彭彩霞
王旭颖
梁晓捷
牛玉温
陈民涛
张军峰
王志军
常春青
付兴
闫少波
吴超
任伟
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Taiyuan Heavy Industry Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
    • B21K1/00—Making machine elements
    • B21K1/06—Making machine elements axles or shafts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/02—Die forging; Trimming by making use of special dies ; Punching during forging
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/06—Methods for forging, hammering, or pressing; Special equipment or accessories therefor for performing particular operations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/06—Methods for forging, hammering, or pressing; Special equipment or accessories therefor for performing particular operations
    • B21J5/08—Upsetting
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/28—Normalising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/28—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for plain shafts
    • 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
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • 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
    • 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
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • 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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin

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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Forging (AREA)

Abstract

The invention discloses a method for processing a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit, which comprises a steel ingot smelting process, a forging process, a post-forging heat treatment process and a performance heat treatment process, wherein: in the steel ingot smelting process, smelting by adopting an EBT, LF, VD and VC process to prepare a Cr-Ni-Mo-V double-vacuum steel ingot; the forging process comprises a first fire forging, a second fire forging, a third fire forging and a fourth fire forging, wherein in the first fire forging, a steel ingot is pressed to be a handle, a drawing part is drawn out, two parts of the steel ingot are bloomed, a bottom part is pressed to be a clamp handle additionally, upsetting and WHF blank making are carried out in the second fire forging, upsetting and step blank making are carried out in the third fire forging, and combined tire film forming is carried out in the fourth fire forging; carrying out high-low temperature twice normalizing and hydrogen diffusion annealing in the post-forging heat treatment process; in the performance heat treatment process, normalizing and tempering are adopted for performance heat treatment. The processing method can ensure the internal structure and mechanical property of the forging, meet the requirements of flaw detection and composition, ensure higher dimensional accuracy, improve the processing efficiency and reduce the processing cost.

Description

Machining method of large Cr-Ni-Mo-V steel connecting shaft for nuclear power unit
Technical Field
The invention belongs to the technical field of forging, and particularly relates to a method for processing a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit.
Background
Cr-Ni-Mo-V steel is an alloy steel with high hardenability and good comprehensive mechanical properties, is commonly used for manufacturing large forgings with high strength and toughness, and is widely used for manufacturing bearing and transmission structural parts in power station equipment such as thermal power, nuclear power and the like, and large metallurgical, mining and transportation equipment. As a typical application of Cr-Ni-Mo-V steel, the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit is a main transmission part in secondary loop power generation equipment of the nuclear power station, has complex stress state, bears high rotating speed and high torque, and has bad working condition, thus the connecting shaft has the characteristics of high strength, high toughness, low brittle transition temperature, high fatigue fracture resistance, good comprehensive mechanical property and the like.
Based on the special working condition and the performance requirement, the forging process of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit is poor in structural performance in view of the special structure of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, and the flaw detection requirement for the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit is very strict.
In the prior art, the conventional forging processing method can only forge the surplus blocks and the surplus blocks with the enlarged areas into simple cylinders, and then the connecting shaft for the nuclear power unit is manufactured through a large number of mechanical processing, but the conventional process can cause that the fiber streamline inside the forge piece is cut off, so that the internal structure and the performance are difficult to meet the technical requirements, the flaw detection is not up to standard, and the product has low dimensional accuracy, high production cost and low processing efficiency.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a processing method of a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit, which comprises a steel ingot smelting process, a forging process, a post-forging heat treatment process and a performance heat treatment process, wherein:
in the steel ingot smelting process, smelting to prepare a Cr-Ni-Mo-V double-vacuum steel ingot by adopting an EBT+LF+VD+VC process, wherein the steel ingot comprises the following components in percentage by mass: c:0.24 to 0.26 percent of Mn:0.20 to 0.40 percent, less than or equal to 0.10 percent of Si, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, and Cr:1.50 to 2.00 percent of Ni:3.25 to 3.75 percent of Mo:0.30 to 0.60 percent, V:0.07 to 0.15 percent, less than or equal to 0.25 percent of Cu, less than or equal to 0.025 percent of Al, less than or equal to 0.025 percent of Sn and less than or equal to 0.0015 percent of Sb;
in the forging process, the forging temperature range is controlled to 1200-850 ℃, the forging ratio is controlled to 6, the forging process comprises first fire forging, second fire forging, third fire forging and fourth fire forging, in the first fire forging, a riser end of a steel ingot is pressed, drawn and cogged to form one piece of blank and one piece of bottom end blank with pliers, meanwhile, the bottom part is pressed on the bottom end of the steel ingot, in the second fire forging, two pieces of blanks are respectively upset and WHF to form blanks, in the third fire forging, two pieces of blanks are respectively upset and step blanks are respectively formed, in the fourth fire forging, the two pieces of blanks obtained through the third fire forging are respectively put into a combined tire film to form a combined tire film, and two connecting shaft forgings are obtained;
in the post-forging heat treatment process, the forged piece is air-cooled to 300 ℃ on the surface after forging, and is charged into a furnace to be subjected to high-low temperature twice normalizing and hydrogen diffusion annealing;
in the performance heat treatment process, normalizing and tempering are adopted for performance heat treatment.
Preferably, in the method for processing the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, the following steps are adopted:
in the first fire forging, the cogging elongation reduction is controlled to be 16-20%, and the size of a blank after the pressing round is determined according to the relation of the height-diameter ratio;
in the second fire forging, upsetting the blank to 50-60% of the original blank height during upsetting, performing WHF blank making by using a wide flat anvil, controlling the rolling reduction to be 20% of the pre-pressing blank height, controlling the anvil lapping amount to be 200mm, turning over by 90 degrees after one pass is pressed, staggering the half anvil, and pressing the next pass;
in the third fire forging, the blank is upset to 50-60% of the original blank height during upsetting, and the flat anvil is used for manufacturing the step blank, so that the reduction is controlled to be 15-20%.
In one embodiment, in the method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit, the post-forging heat treatment step includes:
high-temperature normalizing: heating the forging to 900-950 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 18-20 hours, and then air-cooling to 280-320 ℃;
low temperature normalizing: heating the forging to 860-900 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 18-20 hours, and then air-cooling to 180-230 ℃;
hydrogen diffusion annealing: heating the forging to 640-660 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 75-80 hours, and then cooling to less than or equal to 150 ℃.
In one embodiment, in the method for processing a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit, the performance heat treatment process includes:
normalizing: heating the forging to 860-900 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 13-15 hours, and then air-cooling to 200-300 ℃;
tempering: quenching and tempering comprise quenching treatment and tempering treatment, wherein in the quenching treatment, the temperature of the forging is raised to 820-860 ℃ at a temperature rise rate of less than or equal to 60 ℃/hour, the temperature is kept for 13-15 hours, and then water cooling is carried out to 200-300 ℃; in tempering treatment, the temperature of the forging is raised to 560-600 ℃ at a temperature rising speed of less than or equal to 60 ℃/hour, the temperature is kept for 28-30 hours, and then the forging is cooled to 200-300 ℃ at a speed limiting furnace of less than or equal to 50 ℃/hour.
As a specific implementation mode, the method for processing the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit is used for processing the flange with the outer diameter
Figure BDA0004086251520000031
And flange outer diameter->
Figure BDA0004086251520000032
Figure BDA0004086251520000033
Is a double flange middle short-sized concave-gear special-shaped connecting shaft, wherein:
in the steel ingot smelting process, preparing a Cr-Ni-Mo-V double-vacuum 97-ton steel ingot;
in the first fire forging of the forging process, according to the relation of the height-diameter ratio, the dimensions of two blanks after being pressed into circles are determined to be respectively
Figure BDA0004086251520000034
And->
Figure BDA0004086251520000035
In the second hot forging of the forging process,
Figure BDA0004086251520000036
upsetting the blank under the action of a 125MN press, performing WHF blank making by using a wide flat anvil with the length of 1700mm, pressing to the size of the blank, and cleaning surface cracks and indentations by using an oxygen lance;
in the third forging step, the forging by the third fire is performed
Figure BDA0004086251520000037
Upsetting the blank under the action of a 125MN press, forging a step blank by using a flat anvil with the length of 850mm, and uniformly heating the blank to 1240 ℃ in a third fire forging;
in the fourth forging step, the two blanks forged by the third forging step are respectively put into a combined tire mold to form the combined tire mold, and the combined tire mold is formed by
Figure BDA0004086251520000038
Blank preparation of flange outer diameter ∈>
Figure BDA0004086251520000039
Figure BDA00040862515200000310
Is made of->
Figure BDA00040862515200000311
Is prepared from the blank of flange with outer diameter +.>
Figure BDA00040862515200000312
Figure BDA00040862515200000313
Is a connecting shaft forging piece.
Preferably, in the method for processing the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, after the steel ingot smelting process is completed, the steel ingot is thermally sent to the forging process in a state that the surface temperature is not lower than 700 ℃ after solidification.
Preferably, in the method for processing the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, after forging by the fourth fire in the forging process, the forging is taken out from the combined tire film and then trimmed by a flat anvil of 850mm, and flanges at two ends of the connecting shaft are rounded.
Preferably, in the method for processing the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, the nonmetallic inclusion and the segregation in the solidification process are regulated and controlled in the steel ingot smelting process.
The processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit has the following advantages and beneficial effects:
the method for processing the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit adopts the profiling combined tire membrane to manufacture and process the connecting shaft, so that the profiling distribution of fiber streamlines is effectively improved, the internal structure and the mechanical property are ensured, and the product is ensured to have higher dimensional accuracy;
the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit can process steel ingots into a finished product of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit through a forging process, a post-forging heat treatment process and a performance heat treatment process, and does not need additional large-scale machining; meanwhile, the processing method can be carried out at one time to produce two connecting shaft forgings by using one steel ingot, so that the processing efficiency is effectively improved, and the processing cost is obviously reduced;
the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, disclosed by the invention, has the advantages that when steel ingots are smelted, the material components are strictly controlled internally, nonmetallic inclusion and segregation in the solidification process are regulated and controlled, so that the flaw detection and component and performance requirements are met;
the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit is four-fire forging, and the WHF method is adopted to prepare the blank, so that the cast structure is effectively crushed, the internal defects of the steel ingot are compacted, and the internal structure and the mechanical property can meet the requirements;
the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit carries out high-low temperature twice normalizing in the post-forging heat treatment process, carries out normalizing and tempering in the performance heat treatment process, effectively refines grains, improves internal tissues and meets the flaw detection requirement and the final mechanical performance requirement.
Drawings
For a clearer description of embodiments of the invention or of the solutions of the prior art, the drawings which are required to be used in the description of the embodiments or of the prior art will be briefly described, it being apparent that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained, without inventive effort, by a person skilled in the art from these drawings, in which:
FIG. 1 is a schematic flow chart of a method for processing a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit;
FIG. 2 is a schematic diagram of a steel ingot in the method for processing a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit;
FIG. 3 is a schematic view of a blank forged by a first fire in the method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit;
FIG. 4 is a schematic diagram of a blank forged by a second fire in the method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit;
FIG. 5 is a schematic view of a blank forged by a third fire in the method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit;
FIG. 6 is a schematic diagram of a fourth fire forged composite tire membrane in the method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit;
FIG. 7 is a schematic diagram of a forging piece made by the method for processing a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit;
FIG. 8 is a process diagram of a post-forging heat treatment process in the method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit of the present invention;
FIG. 9 is a process diagram of a performance heat treatment process in a method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments of the present invention and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The method for machining the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit according to the present invention is described in detail below with reference to FIGS. 1 to 9. Generally, the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit mainly comprises a steel ingot smelting process, a forging process, a post-forging heat treatment process and a performance heat treatment process.
In the steel ingot smelting process, an EBT+LF+VD+VC (namely electric furnace+ladle refining+vacuum degassing refining+vacuum pouring) process is adopted to smelt and prepare the high-purity homogeneous Cr-Ni-Mo-V double-vacuum steel ingot, and the schematic diagram of the steel ingot is shown in figure 2. In the steel ingot smelting process, nonmetallic inclusion affecting the flaw detection and performance of a product and segregation in the solidification process are regulated and controlled, and the mass percentages of steel ingot components in the steel ingot smelting process are controlled as follows: c:0.24 to 0.26 percent of Mn:0.20 to 0.40 percent, less than or equal to 0.10 percent of Si, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, and Cr:1.50 to 2.00 percent of Ni:3.25 to 3.75 percent of Mo:0.30 to 0.60 percent, V:0.07 to 0.15 percent, less than or equal to 0.25 percent of Cu, less than or equal to 0.025 percent of Al, less than or equal to 0.025 percent of Sn and less than or equal to 0.0015 percent of Sb.
In the forging process, the forging temperature range is controlled to be 1200-850 ℃, and in the temperature range, the material has lower deformation resistance and better shaping, and is suitable for forging large deformation and shaping; the forging ratio is controlled to be 6, and the microstructure refinement and the forging penetration densification collaborative deformation method under the multi-working-path are utilized, so that the micro void defects in the steel ingot can be effectively compacted, the coarse as-cast dendrite microstructure is crushed, and the flaw detection qualification rate and the comprehensive mechanical performance of the forging are improved. The forging process comprises a first fire forging, a second fire forging, a third fire forging and a fourth fire forging, and concretely comprises the following steps:
a. first fire forging: the riser end of the steel ingot is pressed, drawn and bloomed to form a first blank with a clamp at the riser end and a first blank at the bottom end, meanwhile, the bottom part is additionally pressed with the clamp at the bottom end of the steel ingot, and the schematic diagram of the first fire forged blank is shown in fig. 3. For large double-vacuum steel ingots, a pressing clamp handle of a cutting part of a deposition cone at the bottom of the steel ingot and a pressing clamp handle of a riser part of the steel ingot are utilized, and particularly when the pressing clamp handle of the riser part of the steel ingot is used, the upper ingot body is about 100mm, and the part with the accumulated inclusions at the shoulder of the riser is completely forged and pressed on the clamping clamp handle, so that the parts are prevented from being brought into a forge piece. The pliers are consistent with the axis of the steel ingot, and are used for preparing the subsequent drawing and chopping procedures. In the first fire forging, the cogging elongation reduction is controlled to be 16-20%, and the dimensions of two blanks after the round pressing are determined to be respectively as follows according to the relation of the height-diameter ratio of 2-2.2
Figure BDA0004086251520000051
And->
Figure BDA0004086251520000052
b. Second fire forging: the two blanks are respectively upset and forged by WHF method (wide anvil forced press forging)Fabrication) of a blank, a schematic view of a second hot forged blank is shown in fig. 4. In the second fire forging, use is made of
Figure BDA0004086251520000053
The blank is upsetted to 50 to 60 percent of the height of the original blank under the action of a 125MN press; performing WHF drawing by using a wide flat anvil with the width of 1700mm from top to bottom, controlling the rolling reduction to be 20% of the height of the blank before rolling, controlling the anvil lapping amount to be 200mm, turning over by 90 degrees after one pass is finished, staggering the half anvil, and rolling down the next pass; after the billet is pressed to the cogging size, an oxygen gun is used for cleaning surface defects such as surface cracks, indentations and the like.
c. Third fire forging: the two blanks are respectively upsetted, step blanks are manufactured, and a schematic diagram of the blank forged by the third fire is shown in fig. 5. In the third fire forging, use is made of
Figure BDA0004086251520000061
The blank is upsetted to 50 to 60 percent of the height of the original blank under the action of a 125MN press; and forging the step blank by using a flat anvil with the upper and lower parts of 850mm, wherein the rolling reduction is controlled to be 15-20%. In the third fire forging, attention is required to: the forging is uniformly heated to 1240 ℃; the step blank is concentric, and the size of the part which is inserted into the combined fetal membrane is matched with the fetal membrane.
d. Fourth fire forging: and (3) forming a combined tire membrane, namely respectively placing the two blanks forged by the third fire into the combined tire membrane, and finally forming the forge piece to finally obtain two connecting shaft forge pieces, wherein the forming schematic diagram of the fourth fire forged combined tire membrane is shown in fig. 6, and the schematic diagram of the finally formed forge piece is shown in fig. 7.
In the post-forging heat treatment process, the forged piece is cooled to 300 ℃ on the surface after forging, and is charged into a furnace for twice normalizing and hydrogen diffusion annealing at high and low temperatures, so that the phenomenon of cutting off the structure after forging and inheritance mixed crystal is met, the grain refinement is realized, the internal structure is improved, and the flaw detection requirement is met. Specifically, as shown in fig. 8, the post-forging heat treatment process includes:
high-temperature normalizing: heating the forging to 900-950 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 18-20 hours, and then air-cooling to 280-320 ℃;
low temperature normalizing: heating the forging to 860-900 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 18-20 hours, and then air-cooling to 180-230 ℃;
hydrogen diffusion annealing: heating the forging to 640-660 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 75-80 hours, and then cooling to less than or equal to 150 ℃.
In the performance heat treatment process, the performance heat treatment is carried out by adopting normalizing and tempering in consideration of the structural inheritance characteristics and the final performance requirements of the Cr-Ni-Mo-V material large-section forging so as to meet the final mechanical performance requirements. Specifically, as shown in fig. 9, the performance heat treatment process includes:
normalizing: heating the forging to 860-900 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 13-15 hours, and then air-cooling to 200-300 ℃;
tempering: quenching and tempering comprise quenching treatment and tempering treatment, wherein in the quenching treatment, the temperature of the forging is raised to 820-860 ℃ at a temperature rise rate of less than or equal to 60 ℃/hour, the temperature is kept for 13-15 hours, and then water cooling is carried out to 200-300 ℃; in tempering treatment, the temperature of the forging is raised to 560-600 ℃ at a temperature rising speed of less than or equal to 60 ℃/hour, the temperature is kept for 28-30 hours, and then the forging is cooled to 200-300 ℃ at a speed limiting furnace of less than or equal to 50 ℃/hour.
By the method for processing the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, the two large Cr-Ni-Mo-V steel connecting shaft finished products for the nuclear power unit can be processed and manufactured by adopting one steel ingot through the steel ingot smelting process, the forging process, the post-forging heat treatment process and the performance heat treatment process.
Preferably, after the steel ingot smelting process is completed, the steel ingot is thermally sent to the forging process in a state that the surface temperature is not lower than 700 ℃ after solidification.
Preferably, after the fourth fire forging of the forging process, the forging is removed from the combined tire mold, and then trimmed with a 850mm flat anvil, and the flanges at the two ends of the connecting shaft are rounded.
As a specific application example of the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, the method for preparing Cr-Ni-Mo-V double-alloy steel is prepared by adopting a vacuum carbon deoxidization smelting ingot casting method in the steel ingot smelting processVacuum 97 ton steel ingot, cogging forming sizes are respectively
Figure BDA0004086251520000071
And->
Figure BDA0004086251520000072
After the two blanks are respectively forged, the two blanks are respectively molded by a combined tire film to obtain a double-flange middle short-size concave-profile special-shaped forging piece, namely ++>
Figure BDA0004086251520000073
The dimension of the forging corresponding to the blank of (2) is the flange outer diameter +.>
Figure BDA0004086251520000074
Figure BDA0004086251520000075
The dimension of the forging corresponding to the blank of (2) is the flange outer diameter +.>
Figure BDA0004086251520000076
Figure BDA0004086251520000077
The method is used in 1000MW nuclear power units of a nuclear power project. Therefore, by utilizing the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, two connecting shaft products can be produced by one steel ingot.
According to the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, disclosed by the invention, the problems of high-purity homogeneous manufacturing of the forge piece are innovatively solved by applying the nonmetallic inclusion regulation and control in the steel in the smelting process and reducing the internal control smelting chemical components of the segregation method in the solidification process; the method for manufacturing and processing and controlling mixed crystal caused by tissue inheritance by adopting the profiling combined fetal membrane solves the problems of forging forming and flaw detection; the method solves the problems of product structure and mechanical performance by adopting a strengthening and toughening green heat treatment method, and the large Cr-Ni-Mo-V steel connecting shaft forging for the nuclear power unit manufactured by the method for processing the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit is qualified at one time.
In summary, compared with the prior art, the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit has the following advantages and beneficial effects:
the method for processing the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit adopts the profiling combined tire membrane to manufacture and process the connecting shaft, so that the profiling distribution of fiber streamlines is effectively improved, the internal structure and the mechanical property are ensured, and the product is ensured to have higher dimensional accuracy;
the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit can process steel ingots into a finished product of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit through a forging process, a post-forging heat treatment process and a performance heat treatment process, and does not need additional large-scale machining; meanwhile, the machining method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit can be implemented at one time, so that two connecting shaft forgings can be produced by using one steel ingot, the machining efficiency is effectively improved, and the machining cost is remarkably reduced;
the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit, disclosed by the invention, has the advantages that when steel ingots are smelted, the material components are strictly controlled internally, nonmetallic inclusion and segregation in the solidification process are regulated and controlled, so that the flaw detection and component and performance requirements are met;
the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit is four-fire forging, and the WHF method is adopted to prepare the blank, so that the cast structure is effectively crushed, the internal defects of the steel ingot are compacted, and the internal structure and the mechanical property can meet the requirements;
the processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit carries out high-low temperature twice normalizing in the post-forging heat treatment process, carries out normalizing and tempering in the performance heat treatment process, effectively refines grains, improves internal tissues and meets the flaw detection requirement and the final mechanical performance requirement.
It should be noted that the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (8)

1. The processing method of the large Cr-Ni-Mo-V steel connecting shaft for the nuclear power unit is characterized by comprising a steel ingot smelting process, a forging process, a post-forging heat treatment process and a performance heat treatment process, wherein:
in the steel ingot smelting process, smelting to prepare a Cr-Ni-Mo-V double-vacuum steel ingot by adopting an EBT+LF+VD+VC process, wherein the steel ingot comprises the following components in percentage by mass: c:0.24 to 0.26 percent of Mn:0.20 to 0.40 percent, less than or equal to 0.10 percent of Si, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, and Cr:1.50 to 2.00 percent of Ni:3.25 to 3.75 percent of Mo:0.30 to 0.60 percent, V:0.07 to 0.15 percent, less than or equal to 0.25 percent of Cu, less than or equal to 0.025 percent of Al, less than or equal to 0.025 percent of Sn and less than or equal to 0.0015 percent of Sb;
in the forging process, the forging temperature range is controlled to 1200-850 ℃, the forging ratio is controlled to 6, the forging process comprises first fire forging, second fire forging, third fire forging and fourth fire forging, in the first fire forging, a riser end of a steel ingot is pressed, drawn and cogged to form one piece of blank and one piece of bottom end blank with pliers, meanwhile, the bottom part is pressed on the bottom end of the steel ingot, in the second fire forging, two pieces of blanks are respectively upset and WHF to form blanks, in the third fire forging, two pieces of blanks are respectively upset and step blanks are respectively formed, in the fourth fire forging, the two pieces of blanks obtained through the third fire forging are respectively put into a combined tire film to form a combined tire film, and two connecting shaft forgings are obtained;
in the post-forging heat treatment process, the forged piece is air-cooled to 300 ℃ on the surface after forging, and is charged into a furnace to be subjected to high-low temperature twice normalizing and hydrogen diffusion annealing;
in the performance heat treatment process, normalizing and tempering are adopted for performance heat treatment.
2. The method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit according to claim 1, wherein the method comprises the following steps:
in the first fire forging, the cogging elongation reduction is controlled to be 16-20%, and the size of a blank after the pressing round is determined according to the relation of the height-diameter ratio;
in the second fire forging, upsetting the blank to 50-60% of the original blank height during upsetting, performing WHF blank making by using a wide flat anvil, controlling the rolling reduction to be 20% of the pre-pressing blank height, controlling the anvil lapping amount to be 200mm, turning over by 90 degrees after one pass is pressed, staggering the half anvil, and pressing the next pass;
in the third fire forging, the blank is upset to 50-60% of the original blank height during upsetting, and the flat anvil is used for manufacturing the step blank, so that the reduction is controlled to be 15-20%.
3. The method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit according to claim 1, wherein the post-forging heat treatment process includes:
high-temperature normalizing: heating the forging to 900-950 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 18-20 hours, and then air-cooling to 280-320 ℃;
low temperature normalizing: heating the forging to 860-900 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 18-20 hours, and then air-cooling to 180-230 ℃;
hydrogen diffusion annealing: heating the forging to 640-660 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 75-80 hours, and then cooling to less than or equal to 150 ℃.
4. The method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit according to claim 3, wherein the performance heat treatment process comprises:
normalizing: heating the forging to 860-900 ℃ at a heating rate of less than or equal to 60 ℃/hour, preserving heat for 13-15 hours, and then air-cooling to 200-300 ℃;
tempering: quenching and tempering comprise quenching treatment and tempering treatment, wherein in the quenching treatment, the temperature of the forging is raised to 820-860 ℃ at a temperature rise rate of less than or equal to 60 ℃/hour, the temperature is kept for 13-15 hours, and then water cooling is carried out to 200-300 ℃; in tempering treatment, the temperature of the forging is raised to 560-600 ℃ at a temperature rising speed of less than or equal to 60 ℃/hour, the temperature is kept for 28-30 hours, and then the forging is cooled to 200-300 ℃ at a speed limiting furnace of less than or equal to 50 ℃/hour.
5. The method for manufacturing a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit according to claim 1, wherein the machining size is
Figure FDA00040862515100000211
And->
Figure FDA0004086251510000022
The special-shaped connecting shaft is characterized in that:
in the steel ingot smelting process, preparing a Cr-Ni-Mo-V double-vacuum 97-ton steel ingot;
in the first fire forging of the forging process, according to the relation of the height-diameter ratio, the dimensions of two blanks after being pressed into circles are determined to be respectively
Figure FDA0004086251510000023
And->
Figure FDA0004086251510000024
In the second hot forging in the forging step, use is made of
Figure FDA0004086251510000025
Upsetting the blank under the action of a 125MN press, performing WHF blank making by using a wide flat anvil with the length of 1700mm, pressing to the size of the blank, and cleaning surface cracks and indentations by using an oxygen lance;
in the third forging step, the forging by the third fire is performed
Figure FDA0004086251510000026
Upsetting the blank under the action of a 125MN press, forging a step blank by using a flat anvil with the length of 850mm, and uniformly heating the blank to 1240 ℃ in a third fire forging;
in the fourth forging step, the forging by the third forging step is performedThe two blanks are respectively put into a combined tire membrane to form the combined tire membrane, and the combined tire membrane is formed by
Figure FDA0004086251510000027
Blank preparation->
Figure FDA0004086251510000028
Is made of->
Figure FDA0004086251510000029
Is made of blank->
Figure FDA00040862515100000210
Is a connecting shaft forging piece.
6. The method for manufacturing a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit according to any one of claims 1 to 5, wherein after the completion of the ingot smelting process, the ingot is thermally transferred to the forging process in a state where the surface temperature is not lower than 700 ℃ after solidification.
7. The method for manufacturing a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit according to any one of claims 1 to 5, wherein after the fourth forging in the forging process, the forging is removed from the combined tire mold and then trimmed by a flat anvil of 850mm, and flanges at both ends of the connecting shaft are rounded.
8. The method for machining a large Cr-Ni-Mo-V steel connecting shaft for a nuclear power unit according to any one of claims 1 to 5, wherein the segregation during nonmetallic inclusion and solidification is controlled in the ingot smelting process.
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