CN103934648B

CN103934648B - The preparation method of the end cap in the antivibration bar assembly of nuclear power generating sets steam generator

Info

Publication number: CN103934648B
Application number: CN201410189524.XA
Authority: CN
Inventors: 王国年; 姜建东; 束志华; 张勋
Original assignee: DANYANG LONGXIN METAL ALLOY Co Ltd
Current assignee: DANYANG LONGXIN METAL ALLOY Co Ltd
Priority date: 2012-08-20
Filing date: 2012-08-20
Publication date: 2016-05-04
Anticipated expiration: 2032-08-20
Also published as: CN103934649A; CN102794608B; CN103934644A; CN103934648A; CN103934649B; CN102794608A; CN103934644B

Abstract

A kind of preparation method of antivibration bar assembly of nuclear power generating sets steam generator, described antivibration bar assembly comprises: the antivibration bar of V-shape structure and be located at respectively two end caps at antivibration bar two ends, antivibration bar is selected 405 stainless steel materials, and end cap is selected 690 nickel-bass alloy materials; The preparation method of described antivibration bar assembly, comprising: the preparation of antivibration bar, the preparation of end cap, bend moulding, end cap assembling, upsetting pressure, inspection, clean and packaging process. The preparation method of described end cap, comprises following operation successively: induction furnace smelting, forging, hot rolling, heat treatment, end cap Vehicle Processing. The antivibration bar assembly of AP1000 unit steam generator of the present invention, simple in structure, product quality meets the accurate requirement of steam generator to antivibration bar in nuclear power station, safer when use. The preparation method of this antivibration bar, through strict preparation section, has ensured the technological requirement of the antivibration bar assembly to steam generator in nuclear power station, has ensured quality, has improved security.

Description

Preparation method of end cap in vibration-proof strip assembly of nuclear power unit steam generator

This application is a divisional application, the application number of the original application: 201210297066.2, filing date: 2012-8-20, the invention provides an anti-vibration strip assembly of a steam generator of an AP1000 nuclear power generating unit.

Technical Field

The invention relates to a preparation method of an end cap in an anti-vibration strip assembly of a steam generator of an AP1000 nuclear power unit.

Background

The U-shaped heat transfer pipe in the nuclear power station is the most critical link and the weakest link in the pressure boundary of a loop system. Once the heat transfer pipe vibrates and breaks, the steam generator must be replaced, which inevitably causes huge waste of manpower, financial resources and events, and also increases the danger of radioactive irradiation of the maintainers. Therefore, solving the steam generator pipe breakage accident is a key issue related to the safety of the nuclear power plant and making the nuclear power plant competitive and vital.

In order to eliminate the root cause of vibration as much as possible, an anti-vibration strip is generally required to be additionally arranged at the elbow of a U-shaped heat transfer pipe in the steam generator, and how to provide an anti-vibration strip assembly with good anti-vibration performance and a convenient, simple and high-precision preparation method is a technical problem in the field.

Disclosure of Invention

The invention aims to provide a vibration-proof strip assembly of a steam generator of an AP1000 nuclear power unit, which has good vibration-proof performance.

The invention discloses an anti-vibration strip assembly of an AP1000 unit steam generator, which comprises: the anti-vibration strip of V style of calligraphy structure and fix the two end caps of locating anti-vibration strip both ends respectively.

The anti-vibration strip is made of 405 stainless steel materials; the end cap is made of 690 nickel-based alloy materials, the U-shaped heat transfer pipe in the unit steam generator is also made of nickel-based alloy materials, and the U-shaped heat transfer pipe and the end cap can be conveniently welded and fixed. 690 nickel base alloy material has strong corrosion resistance simultaneously.

The end cap is fixed on the anti-vibration strip in an upsetting mode, and the end cap is prevented from being pulled off in the assembling and welding processes of the anti-vibration strip assembly and the U-shaped pipe. In practice, the center of the end cap, and the portions of the anti-vibration strip adjacent the ends of the end cap, are flattened.

The preparation method of the vibration-proof strip assembly sequentially comprises the following steps of:

A. bending and molding the anti-vibration bar: cutting the anti-vibration bar material by adding 50mm allowance according to the required size of the total length, bending the anti-vibration bar material at a set angle, placing the bent anti-vibration bar material on a plane grinding machine, and grinding a bent angle thickening area;

B. and (3) assembling the end cap: the surface of the end cap and an inner hole of the linear cutting are lightly scrubbed by alcohol, simultaneously, the stainless steel bar is cleaned by alcohol, and after the stainless steel bar is cleaned, burrs, bites, protruding metals or sharp corners are removed; the end of the stainless steel rod is then inserted into the inner bore of the cap end.

C. And (3) upsetting: (1) and (3) tensile force process evaluation: evaluating the pull-out force of the end cap after the assembly and the upsetting so that the position of the sleeve cap does not move under the minimum pull force; recording the end pulling-out force under different pressures, and selecting the most appropriate pressure as a pressure process parameter in the upsetting procedure; (2) upsetting: and (3) putting the end cap into an upsetting die, upsetting the central position of the end cap and the positions of the two ends of the adjacent end cap on the anti-vibration strip respectively by using a hydraulic machine, holding the pressure for 10 seconds after pressing down and positioning, and unloading. The upsetting positions on the anti-vibration strips are arranged at four positions, two positions are adjacent to the end cap end part respectively, and the upsetting positions are used for limiting the cap end and preventing the end cap from displacing on the anti-vibration strips.

The preparation method of the anti-vibration bar comprises the following steps in sequence:

a. smelting in an induction furnace: when the alloy material is smelted, a nickel plate, pure iron and metal chromium are placed at the bottom of the induction furnace, mixed and densely loaded, after 70% of the alloy material is melted, slag accounting for 2% of the total feeding weight is added for steelmaking, after the measured temperature of molten steel reaches the tapping temperature, the molten steel is poured into a steel ladle, and after the molten steel is calmed for 1-2 minutes, the molten steel is poured into a steel ingot bar, so that the purity and the structure uniformity of the alloy steel are effectively improved, the surface and the internal quality of a steel ingot are improved, and the performance of the alloy steel is improved.

The anti-vibration strip alloy material is required to be pure; the chemical components are accurate and uniform; and has a specified organizational state. The use of induction furnaces has a series of undisputed advantages. Because it has no pollution source existing in other equipment, the metallic material which is purest for carbon and other impurities can be obtained; the uniformity of the alloy is ensured due to the electric power for stirring the metal molten pool; ensuring that the required temperature of the metal is accurately obtained and maintained and that the temperature is uniformly distributed along the entire bath temperature; eliminating local overheating; because the melting speed is high and the metal burning loss is less, favorable conditions are created for accurately obtaining specified alloy components and the minimum element burning loss; it has a high flexibility in refining metals of different chemical composition than the forehearth.

b. Forging: heating the alloy material steel ingot smelted by the induction furnace at 1150-1220 ℃, preserving heat and forging into a billet with the size of 50 x 50 mm; and the blank is sent to the next hot rolling blank process after finishing and polishing the surface.

Forging is a processing method which utilizes forging machinery to apply pressure on a metal blank to enable the metal blank to generate plastic deformation so as to obtain a forging with certain mechanical property, certain shape and certain size, the defects of casting-state looseness and the like generated in the smelting process of metal can be eliminated through forging, the microstructure is optimized, and meanwhile, because a complete metal streamline is saved, the mechanical property of the forging is generally superior to that of a casting made of the same material. Important parts with high load and severe working conditions in related machines are mainly forged pieces except for plates, sections or welding pieces which are simple in shape and can be rolled. Forging is generally the first step of material processing called "cogging"

c. Hot rolling: the blank of the vibration-proof bar alloy material with the diameter of 50mm is heated and insulated at the temperature of 1050-.

The vibration-proof strip alloy material is forged and cogging into a 50X 50mm blank, and the blank is rolled into steel products with various geometric cross-section shapes by a heating mode. The section steel is divided into three types of section steel, namely a simple section, a complex section or a special section and a periodic section according to different section shapes.

(1) The hot rolling can obviously reduce energy consumption and cost. The metal plasticity is high during hot rolling, the deformation resistance is low, and the energy consumption of metal deformation is greatly reduced.

(2) Hot rolling can improve the processing technological properties of metals and alloys, i.e. crushing coarse grains in a casting state, obviously healing cracks, reducing or eliminating casting defects, converting an as-cast structure into a refined deformation structure and improving the processing properties of alloys.

(3) The anti-vibration strip alloy material is rolled by hot rolling large cast ingots and large reduction, so that the production efficiency is improved, and conditions are created for improving the rolling speed and realizing the continuity and automation of the rolling process.

(4) The hot rolling process, which in fact belongs to an intermediate working process, is an important step in the formation of the finished blank.

d. First heat treatment (annealing heat treatment): and in order to ensure the surface quality of the anti-vibration bar alloy material, the hot-rolled bar is subjected to surface finishing and polishing again and then subjected to vacuum annealing treatment, and the phi 16 anti-vibration bar alloy material bar is heated and insulated at the temperature of 800 +/-10 ℃.

The annealing heat treatment includes complete annealing, incomplete annealing and stress relief annealing. The mechanical properties of the annealed material can be measured by a tensile test or a hardness test. The intermediate heat treatment is also called as a preliminary heat treatment, and is a heat treatment provided for eliminating the defect of the previous process or for making the subsequent process ready for processing. Is a metal heat treatment process in which the metal is slowly heated to a certain temperature, held for a sufficient time, and then cooled at a suitable rate.

Purpose of annealing

The method improves or eliminates various tissue defects and residual stress caused by the processes of casting, forging, rolling and welding of steel, and prevents the deformation and cracking of workpieces.

② softening the work to perform cutting processing.

Refining crystal grains and improving the structure to improve the mechanical property of the workpiece.

Fourthly, preparing the structure for final heat treatment (quenching and tempering).

e. Cold drawing: firstly, softening annealing treatment is carried out, and the temperature is kept at the temperature of 720-750 ℃ for 40 minutes; and (4) sequentially drawing by using a polycrystalline die according to the deformation requirement, polishing the surface microcracks, and performing next drawing after polishing until no defect exists.

Cold drawing is a production method for re-processing the anti-vibration bar alloy bar subjected to hot rolling in a cold state after softening and annealing so as to obtain various precise and high-precision products or intermediate products.

f. Second heat treatment: pulling the anti-vibration strip alloy bar stock to a finished product material, flatly paving the finished product material in a bell-type heat treatment furnace, and carrying out heat treatment in a hydrogen protection state, wherein the temperature is 788-815 ℃ during annealing heat preservation, and the heat preservation is carried out for more than 3 hours; then slowly cooling to below 610 ℃ at a cooling speed of no more than 28 ℃/hour, and then air-cooling to room temperature.

Heat treatment of metals is one of the important processes in mechanical manufacturing, and heat treatment generally does not change the shape and overall chemical composition of the workpiece, but imparts or improves the performance properties of the workpiece by changing the microstructure inside the workpiece, or changing the chemical composition of the surface of the workpiece, as compared to other machining processes. Its feature is to improve the intrinsic quality of the workpiece, which is not normally visible to the naked eye.

In order to make metal workpieces have required mechanical properties, physical properties and chemical properties, heat treatment processes are often indispensable except for reasonable selection of materials and various forming processes. Steel is the most widely used material in the mechanical industry, and the steel microstructure is complex and can be controlled by heat treatment, so the heat treatment of steel is the main content of metal heat treatment. In addition, aluminum, copper, magnesium, titanium and the like and alloys thereof can also be subjected to heat treatment to change the mechanical, physical and chemical properties of the aluminum, copper, magnesium, titanium and the like so as to obtain different service properties.

g. And (3) processing a finished product: and straightening and polishing the treated bar.

The correction of the shape defects of the metal plastic processing products is one of the important finishing processes, various shape defects such as bending, wave, buckling and the like of the section pipes are often generated in the production process or the subsequent cooling and transportation process of the cold-drawn materials, and the defects such as bending and the like can be eliminated under the action of external force through various straightening equipment, so that the products reach the qualified and ideal state.

(1) Coarse grinding: in addition to the smooth and flat surface, it is important to polish the product to minimize surface damage. Each polishing process must remove the deformation layer caused by the previous process (at least the deformation layer generated by the previous process is reduced to the depth of the deformation layer generated by the current process), rather than only removing the grinding marks of the previous process; meanwhile, the process itself should reduce the damage as much as possible so as to facilitate the next process. The depth of the deformed layer generated in the last polishing process is very shallow, so that the deformed layer can be removed in the next polishing process. Care should be taken to prevent excessive heating of the metal.

(2) Fine grinding: the purpose of fine grinding is to eliminate the deep grinding marks left during rough grinding and lay a foundation for the next polishing. The finish grinding is usually performed on sandpaper, which is divided into water-repellent sandpaper and metallographic sandpaper. The water sand paper is generally SiC abrasive which is insoluble in water, the abrasive of the metallographic sand paper comprises artificial corundum, silicon carbide, iron oxide and the like, the abrasive is extremely hard, has polygonal edges and good cutting performance, can be subjected to manual wet grinding or mechanical wet grinding by using water as a lubricant during fine grinding, can be polished after being polished by four kinds of water sand paper with the granularity of 240, 320, 400 and 600, and can be used for polishing softer metals after being polished by using finer metallographic sand paper. The sand paper is inclined downwards outwards (seen from the direction of an operator), when the sand paper is adhered to flat glass for grinding, the ground surface of a test sample is flat and then is arranged on the sand paper, the test sample is linearly pushed forwards and backwards to leave the sand paper, the operation is repeated until all old grinding marks disappear, new grinding mark edges with uniform directions are obtained on the whole ground surface, before each sand paper is replaced, the sand grains on the sample and hands are washed off by water and wiped, and then the test sample is ground on secondary sand paper by rotating 90 degrees. When in use, flowing water continuously flows through the surface of the abrasive paper, and most of abrasive dust and fallen abrasive particles are washed away in time. Thus, the sharp edges of the abrasive grains are always in contact with the surface of the sample during the whole polishing operation, and the good grinding effect is kept. Another advantage of wet milling is that the cooling effect of the water reduces the frictional heat generated on the sample surface during milling, avoiding microstructural changes. The whole polishing process can be completed on the same equipment.

The preparation method of the end cap sequentially comprises the following steps: smelting in an induction furnace, forging, hot rolling, heat treatment and end cap turning; (action, purpose or technical Effect of each step should be supplemented)

Smelting in the induction furnace: when the alloy material is smelted, a nickel plate, pure iron and metal chromium are placed at the bottom of the induction furnace, mixed and densely loaded, after 70% of the alloy material is melted, slag accounting for 2% of the total feeding weight is added for steelmaking, after the temperature of molten steel reaches the tapping temperature, the molten steel is poured into a steel ladle, and after the temperature is kept for 1-2 minutes, the molten steel is cast into steel ingots.

Forging, namely heating the steel ingot of the anti-vibration strip alloy material smelted by the induction furnace at 1150-1220 ℃, preserving heat and forging the steel ingot into a billet with the size of 50 x 50 mm; and the blank is sent to the next hot rolling blank process after finishing and polishing the surface.

Hot rolling: the shakeproof bar alloy material 50 x 50mm blank is heated at 1200 +/-10 ℃ and is subjected to heat preservation and hot rolling to be rolled into a bar with the diameter of 13 x 25 mm.

The heat treatment comprises the following steps: (1) solution treatment: spreading the hot-rolled end cap material 13 × 25mm in a bell-type hydrogen protection furnace for solution treatment; (2) aging treatment: and (5) placing the bar subjected to the solution treatment in a hydrogen protection furnace for aging treatment.

The solution treatment is to dissolve carbides and gamma 'in the matrix to obtain a uniform supersaturated solid solution, so that the carbides, gamma' and other strengthening phases with fine particles and uniform distribution are precipitated again during aging, and the stress generated by cold and hot working is eliminated, so that the alloy is recrystallized. Secondly, the solution treatment is to obtain proper grain size so as to ensure the high-temperature creep resistance of the alloy. The temperature range of the solution treatment is about 980-1250 ℃, and the temperature range is selected mainly according to the precipitation and dissolution rules of the main strengthening phases in each alloy and the use requirements so as to ensure the necessary precipitation conditions and a certain grain size of the main strengthening phases. For the alloy used at high temperature for a long time, the alloy is required to have better high-temperature durability and creep property, and a higher solid solution temperature is selected to obtain larger grain size; for alloys which are used at medium temperature and require good room temperature hardness, yield strength, tensile strength, impact toughness and fatigue strength, a lower solid solution temperature can be adopted to ensure a smaller grain size. During high-temperature solution treatment, various precipitated phases are gradually dissolved, and simultaneously, crystal grains grow up; at low temperature solution treatment, not only the main strengthening phase is dissolved, but also some phases may precipitate. For alloys with low supersaturation, a faster cooling rate is generally selected; for alloys with high supersaturation, cooling in air is typical.

Aging treatment: the heat treatment process is that after the alloy workpiece is treated by solution treatment, cold plastic deformation or casting and forged, the alloy workpiece is placed at a higher temperature or kept at room temperature, and the performance, the shape and the size of the alloy workpiece are changed along with the time. An aging treatment process in which a workpiece is heated to a high temperature and aged for a short time is called artificial aging, and an aging phenomenon in which the workpiece is left at room temperature or in a natural condition for a long time is called natural aging. The third mode is that the vibration aging treatment gradually enters a practical stage from the beginning of the 80 s, and the vibration of a certain frequency is applied to work under the condition that the vibration aging treatment does not need heating and is not time-consuming like natural aging treatment, so that the internal stress is released, and the aging purpose is achieved. The purpose of aging treatment is to eliminate the internal stress of the workpiece, stabilize the structure and the size, improve the mechanical property and the like.

In mechanical production, in order to stabilize the size of a casting, the casting is often left at room temperature for a long time before being subjected to cutting. This measure is also referred to as aging. However, this aging is not a metal heat treatment process.

And (3) turning the end cap: and (4) turning the aged 13 × 25mm material to obtain the end cap with the required size.

The invention has the technical effects that: the anti-vibration strip assembly of the steam generator of the AP1000 unit is simple in structure, the product quality meets the precision requirement of the steam generator in a nuclear power station on the anti-vibration strip, and the anti-vibration strip assembly is safer to use. The preparation method of the vibration-proof strip ensures the process requirements of the nuclear power station on the vibration-proof strip assembly of the steam generator through strict preparation procedures, ensures the quality and improves the safety. The end cap is fixed on the anti-vibration strip in an upsetting mode, and the end cap is prevented from being pulled off in the assembling and welding processes of the anti-vibration strip assembly and the U-shaped pipe. In practice, the center of the end cap, and the portions of the anti-vibration strip adjacent the ends of the end cap, are flattened.

Drawings

Fig. 1 is a schematic structural diagram of a vibration-proof bar assembly of an AP1000 unit steam generator according to the present invention, and the reference numerals are: 1-anti-vibration strip, 2-end cap.

Detailed Description

Example 1

Referring to fig. 1, the anti-vibration bar assembly of the AP1000 steam generator set of the present embodiment includes: the anti-vibration bar 1 of V style of calligraphy structure and fix the two end caps 2 of locating anti-vibration bar both ends respectively.

The vibration-proof strip 1 is made of 405 stainless steel (SA-479 TYPE 405); the end cap 2 is made of 690 nickel-based alloy material (SB-166 UNSN 06690).

The center of the end cap 2 and the four places on the anti-vibration strip 1 adjacent to the two ends of the end cap are flattened. The two squashes at the end of the end cap are symmetrically distributed on the anti-vibration strip 1.

The preparation method of the vibration-proof strip assembly comprises the following steps: the manufacturing method comprises the following steps of manufacturing the anti-vibration bar, manufacturing the end cap, bending and forming the anti-vibration bar, assembling the end cap, upsetting, inspecting, cleaning, packaging and the like.

The anti-vibration bar and rod material is bent and formed: cutting the anti-vibration bar material by adding 50mm allowance according to the required size, bending the anti-vibration bar material at a set angle, placing the bent anti-vibration bar material on a plane grinding machine, and grinding the bent angle thickening area to meet the drawing requirements.

The end cap assembly: the surface of the end cap and an inner hole formed by linear cutting are lightly scrubbed by alcohol, and meanwhile, the stainless steel bar is cleaned by alcohol, and after the stainless steel bar is cleaned, burrs, bites, protruding metals or sharp corners are removed; and then the stainless steel rod is inserted into the cap end and is assembled by aligning with the angle.

The upsetting comprises the following steps: (1) and (3) tensile force process evaluation: evaluating the pull-out force of the assembled and upset end cap, so that the position of the sleeve cap does not move under the tension of 4448N minimum; recording the end pulling-out force under different pressures, and selecting the most appropriate pressure as a pressure process parameter in the upsetting procedure; (2) upsetting: and placing the cap end into an upsetting die, upsetting the central position of the end cap and the positions of the two ends of the adjacent end cap on the anti-vibration strip respectively by using a hydraulic machine, holding the pressure for 10 seconds after pressing down and positioning, and unloading to ensure that the requirements of the drawing are met after the cap end is upset. The upsetting positions on the anti-vibration strips are arranged at four positions, two positions are adjacent to the end cap end part respectively, and the upsetting positions are used for limiting the cap end and preventing the end cap from displacing on the anti-vibration strips.

The checking: (1) detecting flatness, namely measuring the flatness on a detection platform by using a feeler gauge; (2) detecting the size, namely measuring the product by using a digital display micrometer; (3) detecting an angle, and measuring by using a digital display angle measuring instrument; (4) visual inspection, namely performing visual inspection on the workpieces one by one to ensure that the surface is free of defects, and performing crawling measurement on the surface roughness by using a roughness measuring instrument; (5) measuring the surface roughness by using a roughness detector or a comparison sample block; all the dimension detection results meet the requirements of drawings.

Cleaning: cleaning the bar according to relevant regulations to ensure that the surface of a finished product is free from rusty spots, dust and other pollutants, (1) sulfur, lead, mercury, cadmium and other low-melting-point metals, alloys and compounds thereof, and halogen-containing substances are prohibited from being used in the processes of preparation, testing, inspection, packaging and the like of the anti-vibration bar; (2) the lubricant, the cutting fluid and the cleaning agent do not contain the above substances; molybdenum disulfide lubricants, polytetrafluoroethylenes and other polyfluorinated materials have also been banned from use.

Example 2

The method for preparing the vibration-proof bar material in the embodiment 1 sequentially comprises the following steps: the method comprises the following steps of smelting in an induction furnace, smelting analysis, forging, hot rolling, first heat treatment, performance test (tensile and hardness) and metallographic phase inspection, product analysis, cold drawing, second heat treatment, finished product processing, performance test (tensile and hardness) and grain size inspection, marking and cleaning.

The induction furnace smelting comprises the following steps: when the alloy material is smelted, a nickel plate, pure iron and metal chromium are placed at the bottom of the induction furnace, mixed and densely loaded, after 70% of the alloy material is melted, slag accounting for 2% of the total feeding weight is added for steelmaking, after the temperature of molten steel reaches the tapping temperature, the molten steel is poured into a steel ladle, and after the temperature is kept for 1-2 minutes, the molten steel is cast into a steel ingot bar. The weight of each steel ingot is 40-50kg, the diameter of the steel ingot is 140mm at the small end, and the diameter of the steel ingot is 155mm at the large end.

The smelting analysis comprises the following steps: (1) sampling: turning or planing chemical analysis samples within 20mm of the ingot head and the ingot tail; (2) and taking a chemical analysis sample for each furnace number to measure the chemical components of the steel of each furnace, and screening according to content standard data. The smelting chemical composition meets the following requirements:

forging, namely forging the qualified steel ingot into a billet with the size of 50 x 50mm at 1150-1220 ℃;

(1) forging heating thermometer:

(2) forging: the forging compression ratio is 4-6; forging size: 50 x 50 mm; cutting off the big end of the square billet by more than 100mm and cutting off the small end by more than 50 mm; surface treatment of the forging stock: and (4) peeling and polishing the surface of the forging stock, and removing surface defects such as surface wrinkle, crack, heavy skin and the like.

The hot rolling: the steel billet is placed at 1050-;

(1) the billet heating temperature is as follows:

(2) rolling: adjusting the appearance of the rolled product to be straight, and rolling into a wire with the diameter of 16 mm; after cooling, the rolled product is inspected one by one for cracks, folds, scabs and impurities on the surface quality and is thoroughly polished; rolling ratio: not less than 5.

The first heat treatment: carrying out vacuum annealing treatment on the bar after hot rolling, and keeping the temperature at 800 +/-10 ℃;

the performance test comprises the following steps: (1) taking a group of samples from each furnace batch number of the hot rolled bar after heat treatment; (2) respectively performing a tensile test, a hardness test, a metallographic analysis and a product analysis on the sample, and removing unqualified products;

1. the tensile test results should meet the following requirements:

when the bar is less than or equal to 25mm, the longitudinal axis of the sample is consistent with the center of the bar, and the distance from the useful part of the sample to the heat treatment end of the bar is not less than the diameter of the bar.

2. The hardness test should be in accordance with:

the hardness test should examine the hardness of the bar in the middle of the distance from the center of the bar to the surface.

3. Metallographic analysis should be in accordance with:

4. product analysis: sampling at two ends of the tensile sample for material product analysis, wherein the analysis result is in accordance with:

5. re-test and re-heat treatment:

5.1 if the tensile test result of the bar does not meet the requirement, cutting two additional samples at the adjacent parts of the unqualified samples to perform the tensile test, and only if the test results of the two additional samples meet the requirement, checking and accepting;

5.2 if any batch of bars are improperly treated and the mechanical properties are unqualified, the batch of bars can be thermally treated again, but the number of times of the thermal treatment should not exceed two; after the heat treatment is carried out again, all tests (except the tests of chemical compositions and nonmetallic inclusions) specified by technical conditions are carried out on the batch of materials; all tests should meet the requirements of the technical conditions.

The cold drawing comprises the following steps: (1) firstly, softening annealing treatment is carried out, and the temperature is kept at the temperature of 720-750 ℃ for 40 minutes; (2) and (4) sequentially drawing by using a polycrystalline die according to the deformation requirement, polishing the surface microcracks, and performing next drawing after polishing until no defect exists.

The amount of drawing deformation at the time of cold drawing is φ 16 → φ 14 → φ 12.5 → φ 11 → 4.8 × 12.8 → 4.4 × 12.5 → 4.028 × 12.19.

The softening annealing treatment system is as follows:

the second heat treatment: the finished product material is spread in a bell jar type heat treatment furnace and is subjected to heat treatment under the protection of hydrogen, the annealing heat preservation temperature is 788-:

and (3) processing of the finished product: and (3) carrying out cold processing procedures such as straightening, polishing and the like on the bar subjected to heat treatment, wherein the processed thickness, width, torsion resistance, straightness and other dimensions meet the following requirements:

the performance test comprises the following steps: and (3) performing mechanical property test, hardness test and grain size test on the bar, and excluding the bar which does not meet the requirements of technical conditions.

1. The mechanical property test is in accordance with:

2. the hardness test should be in accordance with:

3. grain size inspection:

if the mechanical property of the bar does not meet the technical requirements, double sampling can be carried out on the adjacent part of the sample for retesting, and retesting results all meet the technical condition requirements.

The dimension inspection comprises the following steps: (1) visual inspection: carrying out visual inspection on the surface of each material one by one, wherein the defects of cracks, scratches and the like are required to be avoided, the bar is not allowed to be subjected to any welding repair, the surface roughness of the bar is inspected one by one, the inspection needs to be added to a suspicious area, and the measured result Ra is less than or equal to 1.6 mu m; (2) and (4) checking the size: a dimensional check was performed on 5% of the material to ensure that the material dimensions met the tolerance requirements of 4.028 ± 0.013 × (12.19).

The marking is as follows: marking or tying a label on each material accurately, and writing the name of a manufacturing factory, the brand and the specification of the material; smelting furnace number, batch number and part number; contract number or order number.

The cleaning comprises the following steps: cleaning the bar according to relevant regulations to ensure that the surface of the finished bar is free from rusty spots, dust and other pollutants; the steel bar cannot come into contact with materials that are harmful to it and integrity. Major metallic incompatible materials are lead, zinc, copper, aluminium, cadmium, tin, mercury, sulphur, arsenic, boron and generally low melting point alloys and their compounds, besides which fluorides, sulphates, chlorides and acid chlorides due to the degradation of chlorine-containing plastics are a potential hazard and tapes, markers, couplers, penetrants and coatings should be chosen with care; if an abrading tool is to be used, it is first ensured that the abrading tool is not contaminated.

Example 3

The method for preparing the end cap of example 1 includes the following steps in sequence: induction furnace smelting, electroslag refining, smelting analysis, forging, ultrasonic inspection, hot rolling, heat treatment, performance test, product analysis, end cap turning, size inspection, marking and cleaning.

The induction furnace smelting comprises the following steps: when the alloy material is smelted, a nickel plate, pure iron and metal chromium are placed at the bottom of an induction furnace, mixed and densely loaded, after 70% of the alloy material is melted, slag accounting for 2% of the total feeding is added for steel making, after the temperature of molten steel reaches the tapping temperature, the molten steel is poured into a steel ladle, after the temperature is measured, the molten steel is kept for 1-2 minutes, and steel ingot bars are cast, wherein the weight of each steel ingot is 40-50kg, the diameter of the small end of the steel ingot is 140mm, and the diameter of the large end of the.

The electroslag refining: after the alloy material is smelted, electroslag refining is carried out to effectively improve the purity and the structural uniformity of the alloy steel, improve the surface and the internal quality of a steel ingot and improve the performance of the alloy steel. After electroslag refining is finished, feeding is carried out, and ingot stripping is carried out for more than or equal to 3 minutes after feeding is carried out for 3-5 minutes. Then carrying out electroslag ingot surface treatment: peeling and grinding the surface.

The smelting analysis comprises the following steps: (1) sampling: turning or planing chemical analysis samples within 20mm of the ingot head and the ingot tail; (2) taking a chemical analysis sample for each furnace number, carrying out chemical component analysis on the material according to a test method required by ASTME38 chemical analysis methods of nickel-chromium and nickel-chromium-iron alloy, and screening according to content standard data, wherein the smelting chemistry is in accordance with:

the forging: and forging the steel ingot qualified by analysis into a billet with the size of 50 x 50mm at the temperature of 1240-1260 ℃.

1. Annealing the steel ingot before forging, wherein the heat treatment temperature is as follows:

2. deformation process: the forging compression ratio is 4-6; cutting off the big end of the square billet by more than 100mm and cutting off the small end by more than 50 mm; the size of the forged square billet is 50 x 50 mm; surface treatment of the forging stock: and (4) peeling and polishing the surface of the forging stock, and removing surface defects such as surface wrinkle, crack, heavy skin and the like.

The ultrasonic inspection comprises the following steps: and (3) carrying out ultrasonic detection on the peeled and polished square rod according to a detection method and an acceptance standard specified in bar nondestructive testing technical conditions.

The hot rolling: the square billet is placed at about 1200 ℃ for hot rolling to be rolled into a material with 13 x 25mm, the hot rolling temperature deviation is not more than 10 ℃, the defects of cracks, folding, scabbing, inclusion and the like of the surface quality are inspected one by one after the hot rolling cooling, and the square billet is thoroughly polished;

1. the forged square billet is annealed before hot rolling, and the annealing temperature is as follows:

2. and (3) rolling control: rolling the end cap material to 13 x 25 mm; after cooling, the rolled product is inspected one by one for defects such as surface cracks, folding, scabbing, impurities and the like, and is cut off or thoroughly polished; the rolling ratio is more than or equal to 5.

The heat treatment comprises the following steps: 1. solution treatment: the hot rolled end cap material 13 × 25mm is laid in a bell jar type hydrogen protection furnace for solution treatment, and the heat treatment temperature is as follows:

wherein the deviation of the heat preservation temperature is not more than +/-10 ℃.

2. Aging treatment: the bar after the solution treatment needs to be subjected to aging treatment, and the aging treatment is also carried out in a hydrogen protective furnace, wherein the heat treatment temperature is as follows:

steel grade	Specification of	Heating temperature of	Incubation time (h)	Cooling method
					SB-166 UNS N06690	13*25mm	704～732℃	8-12h	Air cooling

Wherein the temperature deviation of the aging treatment in the heat preservation period should not exceed +/-10 ℃.

3. The record of the solid solution and aging heat treatment should be listed in the quality certification document, and the record of the heat treatment should include the heat preservation temperature and the deviation thereof, the heat preservation time, the heating rate, the heating atmosphere and the cooling mode.

The performance test comprises the following steps:

1. sampling: any sample of each batch number is taken for mechanical property test, and the longitudinal axis of the tensile sample is parallel to the axial direction of the bar. The useful part of the tensile sample separates the end of the bar and is at least one time of the diameter of the bar; the position of the longitudinal axis of the tensile sample is the center of the bar; the specimen is of sufficient length to intercept all of the test quantities of hardness, metallographic, etc. and the specimens needed for possible retesting.

2. The tensile test should be in accordance with:

wherein, the tensile test adopts a standard sample with the gauge length of 50mm and the diameter of 12.5 mm.

3. Metallographic analysis: sampling at the position adjacent to the sample of the tensile test to perform metallographic analysis, wherein the metallographic analysis detection standard is as follows:

4. macroscopic erosion test: and (3) taking one of the rods in each batch to carry out a macroscopic etching test, testing the cross section parts of the crop ends at the two ends of the rods, and evaluating by naked eyes or by using a magnifying glass with the magnification of less than 10 times without allowing the defects of shrinkage cavities, cracks, slag inclusion, pinholes and the like.

5. Intergranular corrosion test: a group of (two) samples are taken from any one rod after aging treatment for each batch of rods to carry out intercrystalline corrosion test, the samples are taken at a position near the stretching, the samples are sensitized firstly, the temperature is kept at 675 +/-5 ℃ for 1 hour, and the corrosion rate of the samples is less than 20mdd (milligram/square decimeter day).

6. Product analysis: and (3) taking any one sample in each furnace near the tensile sample as a product analysis of the material, wherein the product analysis result is in accordance with:

and (3) end cap turning: and (3) performing a performance test on the aged 13 × 25mm material, performing machining on the qualified material, and machining into an end cap product with the diameter of 22.86 +/-0.05 and the length of 50.8 +/-0.07 according to requirements.

The size inspection comprises the following steps: 1. visual inspection is carried out on the surface of each material one by one, and the end cap is not allowed to have nicks, burrs, longitudinal cracks and metal bulges. 2. The material is subjected to a size check, the check quantity of material per furnace should be more than 5%.

The marking is as follows: each material should be accurately marked or labeled, and the method should include: ordering number, material brand and specification, bar part number, smelting furnace number, heat treatment furnace number and bar manufacturing factory name.

And (3) cleaning the bar according to relevant regulations to ensure that the surface of the finished end cap is free from rusty spots, dust and other pollutants.

Claims

1. A preparation method of an end cap in an anti-vibration strip assembly of a nuclear power unit steam generator is characterized by sequentially comprising the following steps of: smelting in an induction furnace, forging, hot rolling, heat treatment and end cap turning;

wherein,

smelting in the induction furnace: when the alloy material is smelted, a nickel plate, pure iron and metal chromium are placed at the bottom of an induction furnace, after 70 percent of the alloy material is melted, slag accounting for 2 percent of the total feeding weight is added for steelmaking, after the temperature of molten steel reaches the tapping temperature, the molten steel is poured into a steel ladle, and after the temperature is kept for 1 to 2 minutes, the molten steel is cast into steel ingots;

forging, namely heating the steel ingot at 1150-1220 ℃, preserving heat and forging the steel ingot into a steel billet with the size of phi 50 multiplied by 50 mm;

hot rolling: heating the steel billet at 1200 +/-10 ℃, preserving heat, and then carrying out hot rolling to obtain a bar with the diameter of 13 mm by 25 mm;

the heat treatment comprises the following steps: (1) solution treatment: flatly paving a bar with the diameter of 13 mm multiplied by 25mm of the hot-rolled end cap material in a bell-type hydrogen protection furnace for solution treatment; (2) aging treatment: placing the bar subjected to the solution treatment in a hydrogen protection furnace for aging treatment;

and (3) turning the end cap: and (4) turning the aged bar with the diameter of 13 mm multiplied by 25mm to process the bar into an end cap with the required size.