CN104043833A

CN104043833A - Method for adopting powder metallurgy hot isostatic pressing near-net-shape forming technology for preparing motor protecting ring

Info

Publication number: CN104043833A
Application number: CN201410308698.3A
Authority: CN
Inventors: 祁进坤; 方玉城; 王雪欣; 任淑彬; 赵钢; 寇晓磊
Original assignee: YANTAI TAIHAI MANOIR NUCLEAR EQUIPMENT CO Ltd; Hebei Wuwei Aero & Power Technology Co ltd
Current assignee: YANTAI TAIHAI MANOIR NUCLEAR EQUIPMENT CO Ltd; Hebei Wuwei Aero & Power Technology Co ltd
Priority date: 2014-07-02
Filing date: 2014-07-02
Publication date: 2014-09-17
Anticipated expiration: 2034-07-02
Also published as: CN104043833B

Abstract

The invention provides a method for adopting a powder metallurgy hot isostatic pressing near-net-shape forming technology for preparing a motor protecting ring and belongs to the field of metal materials. The protecting ring is made of a protecting ring steel material with the nitrogen content of 0.4-1.0%, the process of combining a pressurizing induction melting of mother alloy and nitrogen atomization is adopted for preparing powder with the average granularity of 5 micrometers-100 micrometers, the powder is placed into a cylindrical or a circular-ring-shaped bag sleeve, then vacuumizing and seal welding are carried out, then the powder is placed in a hot isostatic pressing furnace for pressurization and heat preservation, compacting is carried out on the powder to obtain a protecting ring blank, the bag sleeve is turned off through a machining method, cold swelling formation and annealing stress relief are carried out on the blank, the processing temperature ranges from 330 DEG C to 350 DEG C, the speed of temperature rising is smaller than 40 DEG C per hour, the speed of temperature falling is smaller than 30 DEG C per hour, and time for heat preservation ranges from 10 minutes-12 minutes. According to the method, the texture performance is uniform, the crystal particles are small, the overall performance of products is high, the use reliability of the protecting ring and a whole machine can be improved greatly, surface cracks of the protecting ring in the manufacturing process can be effectively avoided, the protecting ring is treated in the mode of being free from solid solutions, the rate of finished products is effectively increased, and the manufacturing cost can be effectively lowered.

Description

Adopt powder metallurgy high temperature insostatic pressing (HIP) Near net Shaping Technology to prepare the method for motor retaining ring

Technical field

The invention belongs to metal material field, relate to a kind of method that adopts powder metallurgy high temperature insostatic pressing (HIP) Near net Shaping Technology to prepare motor retaining ring.

Background technology

Retaining ring is the heavy forging steel loop of compression fit at generator amature two ends, is one of large-scale vital part of thermoelectricity generating equipment.Retaining ring is stressed complexity in High Rotation Speed, not only will bear huge centrifugal force, the additional stress that erection stress simultaneously also will bear hot charging time, uneven load cause, the alternate stress being transmitted by rotor and due to the concentrated stress that requires in structure to cause.Therefore,, for ensureing the long-term safety operation of unit, require retaining ring to have enough intensity, good toughness, uniform mechanical property and minimum residual stress.Retaining ring is worked in the corrosive medium of high-intensity magnetic field, humidity, and therefore retaining ring adopts austenitic nonmagnetic steel manufacture conventionally.In addition due to the particularity of working environment, require shelling ring material to possess certain stress corrosion resistant ability.Therefore shelling ring material is required to have good metallurgical quality, chemical composition, institutional framework, grain size and uniform crystal particles degree all want reasonable.In existing material, P900 (18Cr-18Mn-0.6N), P900-N (18Cr-18Mn-0.9N) and P2000 (16Cr-14Mn-3Mo-0.9N), P900NMo (18Cr-18Mn-2Mo-0.9N) different materials have good fracture toughness in air, splitting resistance in various environment is also fine, is the widely used steel grade of the above high-rating generator retaining ring of current 300MW.

The preparation of retaining ring is at present that time heating of many fire, multiple operation distortion are shaped, this process will be passed through multiple forging work steps such as ingot smelting, electroslag remelting and pulling, blanking, pier are thick, free piercing, core bar drawing, plug reaming conventionally, and it is more than 8 times conventionally adding showing tremendous enthusiasm time.Because this technique process is long, cause that the production cycle is long, process costs is higher, forming process controllability is poor simultaneously, forging face crack serious, coarse grains and inhomogeneous, and heat forging technology is seriously not suitable with current demand for development.In addition, the problem such as coarse-grain, mixed crystal occurring in manufacture process has more and more caused the attention of power station heavy forging manufacturing firm, becomes one of important step of controlling product quality, raising technological level.Therefore, how the thin above-mentioned several Retaining Ring Steel austenite structures of homogenize are also the key issues that current retaining ring is produced.

Summary of the invention

The complex process, the retaining ring surface that the present invention seeks in order to solve how fiery Forging Technology existence easily go out crackle, the inhomogeneous technical problem of interior tissue performance.

A kind of method that adopts powder metallurgy high temperature insostatic pressing (HIP) Near net Shaping Technology to prepare motor retaining ring, adopt powder metallurgy heat and other static pressuring processes to be prepared, there is technique: first according to existing several alloys as P900 (18Cr-18Mn-0.6N), P900-N (18Cr-18Mn-0.9N) and P2000 (16Cr-14Mn-3Mo-0.9N), the composition requirement of P900NMo (18Cr-18Mn-2Mo-0.9N), adopt pressurized Induction Melting and nitrogen atomization technique prepared composition to meet the demands, particle mean size is the powder of 5～100 μ m powder, then according to final products size and sintering shrinkage rule design jacket, conventionally jacket is of a size of on the front size of final products cold expanding distortion basis and amplifies 15-20%, jacket shape is determined according to final products shape, be generally cylindrical or annular, powder is packed in cylindrical or annular jacket and vacuumized and solder up, then be placed in high temperature insostatic pressing (HIP) stove in 1150-1300 DEG C, pressure 70～120MPa, insulation 60-120min carries out densification and obtains retaining ring blank, again jacket is adopted machined way car to fall and rear blank is carried out to cold expanding shaping and annealing destressing processing, treatment temperature is 330-350 DEG C, heating rate is less than 40 DEG C/h, rate of temperature fall is less than 30 DEG C/h, temperature retention time is 10-12 hour, finally require to carry out fine finishining according to product size and roughness.

The present invention's prepared retaining ring under above-mentioned process conditions, owing to adopting powder metallurgical technique, the structure property of retaining ring is more even, crystal grain is more tiny, therefore every mechanical performance index of retaining ring is apparently higher than traditional forging and forming technology, as (95～105 DEG C of P900 strength of alloy, before cold expanding distortion) reach 1290～1300MPa, undulating value is less than 15MPa, yield strength reaches 1280～1295MPa, undulating value is less than 15MPa, percentage elongation is greater than 20%, the contraction percentage of area is greater than 60%, ballistic work is greater than 130J, even grain size, average grain size is 40-45 μ m, the performance level that combination property reaches far above common process.In addition this technique process is simple, can effectively avoid the face crack of retaining ring in forging process, and retaining ring is exempted from solution treatment, effectively improves yield rate, and reduces manufacturing cost.

Brief description of the drawings:

Fig. 1 is process chart of the present invention:

Detailed description of the invention:

(1) preparation size is Φ 600mm (external diameter) × 50mm (wall thickness) × 400mm (height) P900 (18Cr-18Mn-0.6N) retaining ring (note: be of a size of the front size of cold expanding distortion)

First require to carry out alloy melting according to P900 (18Cr-18Mn-0.6N) alloying component, adopt nitrogen atomization technique to carry out powder process, powder mean particle sizes is controlled at 10 μ m; Then adopt mild steel welding jacket, according to final products dimensional requirement, and consider sintering shrinkage impact, jacket size Φ 720mm (external diameter) × 60mm (wall thickness) × 480mm (height); Pack powder in jacket ram-jolt, and be evacuated to 10 ^-1after Pa, carry out sealing, after sealing, carry out HIP sintering densified, 1220 DEG C of sintering temperatures, pressure 100MPa, insulation 60min, sintering densification processing obtains retaining ring blank, jacket is removed again, carry out cold expanding shaping, deformation rate is 40%, then the destressing processing of annealing, treatment temperature is 330 DEG C, 30 DEG C/h of heating rate, and temperature retention time is 10 hours, 20 DEG C/h of rate of temperature fall, finally requires to carry out fine finishining processing according to product size and roughness and reaches retaining ring finished product.Adopt above-mentioned technique, the tensile strength (95～105 DEG C, before cold expanding distortion) of retaining ring reaches 1295MPa, undulating value 10MPa, yield strength reaches 1290MPa, undulating value 10MPa, percentage elongation 22%, the contraction percentage of area 62%, ballistic work 130J, average grain size is 42 μ m.

(2) preparation size is Φ 500mm (external diameter) × 40mm (wall thickness) × 400mm (height) P900NMo (18Cr-18Mn-2Mo-0.9N) retaining ring (note: be of a size of the front size of cold expanding distortion)

First require to carry out alloy melting according to P900NMo (18Cr-18Mn-2Mo-0.9N) alloying component, adopt nitrogen atomization technique to carry out powder process, powder mean particle sizes is controlled at 80 μ m; Then adopt mild steel welding jacket, according to final products dimensional requirement, and consider sintering shrinkage impact, jacket size Φ 580mm (external diameter) × 46.4mm (wall thickness) × 464mm (height); Pack powder in jacket ram-jolt, and be evacuated to 10 ^-1after Pa, carry out sealing, after sealing, carry out HIP sintering densified, 1250 DEG C of sintering temperatures, pressure 120MPa, insulation 90min, sintering densification processing obtains retaining ring blank, jacket is removed and carry out cold expanding distortion again, deformation rate is 45%, the destressing processing of then annealing, and treatment temperature is 350 DEG C, 40 DEG C/h of heating rate, temperature retention time is 10 hours, and 30 DEG C/h of rate of temperature fall finally requires to carry out fine finishining processing according to product size and roughness and reaches retaining ring finished product.Adopt above-mentioned technique, the tensile strength (95～105 DEG C, before cold expanding distortion) of retaining ring reaches 1380MPa, undulating value 8MPa, yield strength reaches 1350MPa, undulating value 8MPa, percentage elongation 24%, the contraction percentage of area 62%, ballistic work 135J, average grain size is 40 μ m.

Claims

1. a method that adopts powder metallurgy high temperature insostatic pressing (HIP) Near net Shaping Technology to prepare motor retaining ring, it is characterized in that adopting powder metallurgy heat and other static pressuring processes to substitute traditional forging deformation technique and carry out the shaping of motor retaining ring, retaining ring material contains P900:18Cr-18Mn-0.6N, P900-N:18Cr-18Mn-0.9N and P2000:16Cr-14Mn-3Mo-0.9N, P900NMo:18Cr-18Mn-2Mo-0.9N meets different capacity motor requirements, nitrogen content is 0.4～1.0% Retaining Ring Steel material, adopt pressurized Induction Melting foundry alloy and meet the demands in conjunction with nitrogen atomization technique prepared composition, particle mean size is 5～100 μ m powder, powder is packed in cylindrical or annular jacket and vacuumized and solder up, then be placed in high temperature insostatic pressing (HIP) stove in 1150-1300 DEG C, pressure 70～120MPa, insulation 60-120min carries out densification and obtains retaining ring blank, again jacket is adopted machined way car to fall and rear blank is carried out to cold expanding shaping and annealing destressing processing, treatment temperature is 300-350 DEG C, heating rate is less than 40 DEG C/h, rate of temperature fall is less than 30 DEG C/h, temperature retention time is 10-15 hour, finally require to carry out fine finishining according to product size and roughness.