CN102560039A - After-forging preheat treatment process of large turbine low-pressure rotor forging piece - Google Patents
After-forging preheat treatment process of large turbine low-pressure rotor forging piece Download PDFInfo
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- CN102560039A CN102560039A CN 201010575276 CN201010575276A CN102560039A CN 102560039 A CN102560039 A CN 102560039A CN 201010575276 CN201010575276 CN 201010575276 CN 201010575276 A CN201010575276 A CN 201010575276A CN 102560039 A CN102560039 A CN 102560039A
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Abstract
The invention discloses an after-forging preheat treatment process of a large turbine low-pressure rotor forging piece, and provides an after-forging preheat treatment process solving the problem of structural heredity of 26Cr2Ni4MoV steel or 30Cr2Ni4MoV steel used by the large turbine low-pressure rotor forging piece. The after-forging preheat treatment process comprises the steps of: firstly, carrying out 1250DEG C*1.5h roughening and 350DEG C*10h bainite treatment on an experimental material to ensure that rough austenite grains and needle-shaped bainite structures are obtained; and then carrying out high-temperature pre-tempering (660DEG C*20h) and critical region normalizing treatment (770 DEG C*3h) and normal normalizing treatment (950 DEG C*1h) on a test sample treated by the step. After the after-forging preheat treatment process is adopted, the refining effect of the grains is remarkable, the thermal treatment period is shortened, the heating temperature is reduced, the final use performance requirement is ensured, the problem of the structural heredity is solved in the practical production on the premise of ensuring the quality of a rotor, the process is simplified, and the reference basis is provided. The process can be applied in practical production.
Description
Technical field
The present invention relates to conditioning heat treatment technology after a kind of forging of large-size steam turbine low pressure rotor forging.
Background technology
The large-size steam turbine low pressure rotor is the vital part of generating set; The shaping manufacturing of high quality low pressure rotor forging comprises production links such as smelting, ingot casting, forging and thermal treatment; The selection of thermal treatment process is the key of decision low pressure rotor inner quality and final performance, directly influences serviceability.
The present used material of large-size steam turbine low pressure rotor forging is generally 26Cr2Ni4MoV steel or 30Cr2Ni4MoV steel.This steel has good hardening capacity, obdurability and comprehensive mechanical performance, but this steel grade is essential coarse-grained steel, contains alloying elements such as higher Ni, Cr in the steel and makes it have the stronger genetic phenomenon of organizing.After rotor forging forge to be accomplished, before thermal treatment, its inner more crystal grain was thick, and whole roots rotor is in the mixed crystal state, and these thick austenite crystals are difficult to refinement, thereby the impact toughness of steel was obviously reduced, ductile-brittle transition temperature improves greatly.The normal multiple high temp normalizing process refine austenite crystal grain that adopts on the engineering; But repeatedly the normalizing process production cycle is long, power consumption is big; Can reduce the normalizing number of times guaranteeing to simplify technology under the prerequisite of rotor quality, will forge the post-heat-treated cycle shortens and is paid close attention to by people always.
For the explanation of the crystal grain of 26Cr2Ni4MoV steel or 30Cr2Ni4MoV steel heredity mechanism, it is generally acknowledged that open grain structure heredity is that the overheated steel of non-equilibrium microstructure is when slowly being heated to austenitizing, at Ac
1Near the austenite that forms the temperature is laminar and parent phase keeps the K-S orientation relationship, thereby causes the heredity of original texture of coarse crystal.Forging post-heat-treated and obtain the ferrite-pearlite tissue as far as possible, to upsetting, is the most effectively way of eliminating crystal grain heredity with the position in the original grain.But crystal grain heredity mainly appears in the high quality steel, and the austenite of high quality steel is very stable, and for example the isothermal transformation of 26Cr2Ni4MoV steel becomes to reach pearlitic incubation period 7h, is difficult in the production realize.Recent research shows, adopts and reduces austenitizing temperature, and reducing austenitic alloying level, thereby the way that stabilization of austenite is reduced can obtain perlitic transformation effectively.
The present invention is from suppressing austenitic formation of aciculiform and expansion, cutting off the hereditary approach of tissue; Thick austenite crystal carries out refinement after adopting the preparatory tempering of high temperature+critical zone normalizing+normal normalizing process to 26Cr2Ni4MoV steel and 30Cr2Ni4MoV steel large-size steam turbine low pressure rotor forging, organizes genetic problem that more reasonable technology is provided for solving in the actual production.
Summary of the invention
Task of the present invention is for conditioning heat treatment after the forging of 26Cr2Ni4MoV steel or 30Cr2Ni4MoV steel large-size steam turbine low pressure rotor forging a kind of advanced person to be provided feasible technology.
This technology at first be after forging to forging carry out the long period the preparatory temper of high temperature (660 ℃ * 20h), the recovery and recrystallization of inner α tissue takes place, upset original α and organize orderly spatial orientation, reduce remained austenite content, cut off tissue heredity.But 26Cr2Ni4MoV Steel Alloy constituent content is high; And the disperse of indissoluble carbide distributes the ferritic recrystallization temperature is improved; Ferritic is not easy to occur in crystallization under the tempering temperature in advance, still keeps former martensitic lath characteristic after the preparatory tempering of high temperature, and the orientation of crystal grain is still very remarkable.This have identical bits to ferritic heating be higher than transformation temperature after, will change the strip austenite into, produce tissue heredity.Sheet (pin) the shape form of martensite, bainite but the preparatory tempering of high temperature can be degenerated, the dispersity of increase tempered structure is postponed the austenitic formation of sheet, therefore can alleviate the degree of crystal grain heredity.
Forging carries out critical zone normalizing treatment (Ac again after the preparatory temper of high temperature
1～Ac
3The critical zone high temperature side, 770 ℃ * 3h), can accomplish the recovery austenitic transformation under this temperature, and generate spherical austenite, crystal grain obtains refinement.Critical zone high temperature side normalizing temperature is lower than Ac slightly
3, this temperature is easy to spherical austenitic forming core and grows up, and the speed that forming core is grown up is exceedingly fast; The austenitic appearance of strongly inhibited sheet; Also can be annexed by spherical austenite and grow up even form part sheet austenite, tissue heredity has been eliminated in a large amount of granular austenitic existence, well refinement crystal grain.This temperature also is beneficial to the recovery and recrystallization of α tissue, and critical zone high temperature side normalizing meeting decomposes the part residual austenite, and the decomposition of residual austenite has reduced the austenitic forming core core of needle-like, has suppressed the austenitic formation of needle-like, has weakened tissue heredity.
Forging is through the preparatory tempering of high temperature+critical zone normalizing (Ac
1～Ac
3The critical zone high temperature side, 770 ℃ * 3h) handle after recover austenite and spherical austenite and deposit because forging is inner, the mixed crystal phenomenon generation is arranged.Reach the purpose of crystal grain thinning and homogeneous microstructureization, must on the basis of reducing tissue heredity, utilize the process of complete austenitizing to realize, therefore, carry out again on this basis normalizing treatment (950 ℃ * 1h).
Need to prove that the practical implementation of above-mentioned processing parameter depends on the smelting quality of large-scale steel ingot, purity control, component segregation, forging quality and steel ingot size etc., is to confirm according to analysis of lot of test data utility theory and numerical evaluation.
Accompanying drawing 1 is to use the 26Cr2Ni4MoV steel rotor forging centre hole sample metallographic microstructure photo after the preparatory tempering of above-mentioned high temperature+critical zone normalizing+normal normalizing process processing, can find out that grain fineness number reaches 7.5～8.0 grades.The preparatory tempering of high temperature+critical zone normalizing+normal normalizing process has not only shortened forging post-heat-treated process cycle, has reduced Heating temperature, has guaranteed the use properties requirement that rotor forging is final again.Simultaneously the preparatory tempering temperature of high temperature for the stove of joining in producing provides convenience, also has the effect of expansion hydrogen with to wait to expect temperature identical concurrently.
Description of drawings
Fig. 1 is the rotor forging centre hole sample metallographic microstructure after the preparatory tempering of employing high temperature+critical zone normalizing+normal normalizing process is handled.
Embodiment
To certain 26Cr2Ni4MoV steel 300MW steam turbine low-pressure rotor forging; Its roughing diameter is Φ 1850mm, and the forging diameter is Φ 1920mm, and test cuts from rotor forging centre hole plug with material; Be cut into the metallographic specimen of 15mm * 15mm * 20mm with line; At first sample is carried out 1250 ℃ * 1.5h roughening treatment and the processing of 350 ℃ * 10h bainite, make it to obtain thick austenite crystal and needle-like lower bainite tissue, handle back sample grain fineness number greater than 1 grade.
Then to the sample after the above-mentioned processing carry out the preparatory tempering of high temperature (660 ℃ * 20h)+the critical zone normalizing treatment (770 ℃ * 3h)+(950 ℃ * 1h) handle of normal normalizings.
Sample to after handling shows austenite grain boundary with supersaturation TNP+X 2073 solution heat erosion, and its grain fineness number reaches 7.5～8.0 grades.
Adopt the preparatory tempering of high temperature+critical zone normalizing+normal normalizing process, grain refining effect is obvious, has shortened heat treatment cycle; Reduced Heating temperature, guaranteed final use properties requirement again, for guaranteeing under the prerequisite of rotor quality in the actual production; Solve tissue heredity's problem; Simplify technology, reference frame is provided, this technology can be used for production application.
Claims (3)
1. conditioning heat treatment technology after the forging of a large-size steam turbine low pressure rotor forging; It is characterized in that: said forging material is the 26Cr2Ni4MoV rotor steel; At first experiment material is carried out 1250 ℃ * 1.5h roughening treatment and the processing of 350 ℃ * 10h bainite; Make it to obtain thick austenite crystal and needle-like lower bainite tissue, handle the back grain fineness number greater than 1 grade; Then to the material after the above-mentioned processing carry out the preparatory tempering of high temperature (660 ℃ * 20h)+the critical zone normalizing treatment (770 ℃ * 3h)+(950 ℃ * 1h) handle of normal normalizings.
2. conditioning heat treatment technology after the forging of steam turbine low-pressure rotor forging as claimed in claim 1 is characterized in that: test materials is at first carried out the preparatory temper of high temperature.
3. conditioning heat treatment technology after the forging of steam turbine low-pressure rotor forging as claimed in claim 1 is characterized in that: carry out the critical zone normalizing treatment after the preparatory temper of high temperature again.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201010575276 CN102560039A (en) | 2010-12-07 | 2010-12-07 | After-forging preheat treatment process of large turbine low-pressure rotor forging piece |
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| CN 201010575276 CN102560039A (en) | 2010-12-07 | 2010-12-07 | After-forging preheat treatment process of large turbine low-pressure rotor forging piece |
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| CN102560039A true CN102560039A (en) | 2012-07-11 |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103131934A (en) * | 2013-03-26 | 2013-06-05 | 上海交通大学 | Method for improving uniformity of 30Cr2Ni4MoV steel casting structure |
| CN104630443A (en) * | 2015-01-22 | 2015-05-20 | 燕山大学 | Large-scale cylindrical shell section heat treatment method |
| CN104946870A (en) * | 2015-07-02 | 2015-09-30 | 杭州汽轮动力集团有限公司 | Heat treatment method for strength of 28CrMoNiV steel capable of improving industrial steam turbine rotor forge piece |
| CN105969949A (en) * | 2016-06-02 | 2016-09-28 | 溧阳市金昆锻压有限公司 | 18CrNiMo7-6 gear shaft forging preheating isothermal annealing process |
| CN106086360A (en) * | 2016-07-25 | 2016-11-09 | 杭州汽轮动力集团有限公司 | A kind of heat treatment method of Industrial Steam Turbine Rotors Aided forging |
| CN107099649A (en) * | 2017-04-24 | 2017-08-29 | 湖北东舟重工科技股份有限公司 | A kind of heat treatment method of the sub- warm normalizing thinning microstructure of Medium Carbon Steel Containing Manganese two-phase section |
| CN108441617A (en) * | 2018-04-19 | 2018-08-24 | 二重（德阳）重型装备有限公司 | A kind of conditioning treatment method of 30Cr2Ni4MoV steel low pressure rotor |
| CN114875214A (en) * | 2022-06-01 | 2022-08-09 | 东北大学 | Heat treatment method of COST-FB2 steel large forging |
-
2010
- 2010-12-07 CN CN 201010575276 patent/CN102560039A/en active Pending
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103131934A (en) * | 2013-03-26 | 2013-06-05 | 上海交通大学 | Method for improving uniformity of 30Cr2Ni4MoV steel casting structure |
| CN103131934B (en) * | 2013-03-26 | 2015-01-14 | 上海交通大学 | Method for improving uniformity of 30Cr2Ni4MoV steel casting structure |
| CN104630443A (en) * | 2015-01-22 | 2015-05-20 | 燕山大学 | Large-scale cylindrical shell section heat treatment method |
| CN104946870A (en) * | 2015-07-02 | 2015-09-30 | 杭州汽轮动力集团有限公司 | Heat treatment method for strength of 28CrMoNiV steel capable of improving industrial steam turbine rotor forge piece |
| CN105969949A (en) * | 2016-06-02 | 2016-09-28 | 溧阳市金昆锻压有限公司 | 18CrNiMo7-6 gear shaft forging preheating isothermal annealing process |
| CN106086360A (en) * | 2016-07-25 | 2016-11-09 | 杭州汽轮动力集团有限公司 | A kind of heat treatment method of Industrial Steam Turbine Rotors Aided forging |
| CN107099649A (en) * | 2017-04-24 | 2017-08-29 | 湖北东舟重工科技股份有限公司 | A kind of heat treatment method of the sub- warm normalizing thinning microstructure of Medium Carbon Steel Containing Manganese two-phase section |
| CN108441617A (en) * | 2018-04-19 | 2018-08-24 | 二重（德阳）重型装备有限公司 | A kind of conditioning treatment method of 30Cr2Ni4MoV steel low pressure rotor |
| CN114875214A (en) * | 2022-06-01 | 2022-08-09 | 东北大学 | Heat treatment method of COST-FB2 steel large forging |
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Application publication date: 20120711 |