CN103234989A - Method for determining Laves phase content in steel - Google Patents
Method for determining Laves phase content in steel Download PDFInfo
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- CN103234989A CN103234989A CN2013101349693A CN201310134969A CN103234989A CN 103234989 A CN103234989 A CN 103234989A CN 2013101349693 A CN2013101349693 A CN 2013101349693A CN 201310134969 A CN201310134969 A CN 201310134969A CN 103234989 A CN103234989 A CN 103234989A
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Abstract
The invention relates to a method for determining Laves phase content in steel. In a Mossbauer spectroscopy instrument, with a transmission mode, a sample is determined, such that a relationship between sample count and Doppler velocity is obtained; the obtained experiment data is placed in Recoil; possible peak spectrum number and corresponding possible phases are determined according to spectral line shape and iron-containing phase; the influence value of the element in spectral line possible corresponding phase upon the hyperfine field value iron element is introduced into the software, and automatic fitting is carried out; when peak spectral shapes are consistent and error value is low, fitting is finished; the fitting result is exported, and the proportion of the corresponding phase is viewed. With the method provided by the invention, a sample preparation technology is simple, the proportion value of iron-containing phase in steel can be obtained, and the result is accurate.
Description
Technical field
The present invention relates to a kind of method of measuring laves phase content in the steel, belong to metallurgical technology field.
Background technology
For solving energy shortage and the problem of environmental pollution that becomes increasingly conspicuous, high efficiency super (surpassing) critical pressure generating becomes hot issue in the world in recent years.Countries in the world thermal power generation unit parameter just by subcritical parameter (16.77MPa, 540 ℃) to supercritical parameter (25.0MP, 540 ℃～566 ℃; 24.0～30.0MPa, 580 ℃～610 ℃) development, the thermal efficiency can improve 6～7% like this.Improving the thermal efficiency mainly is the heat power problem, by improving steam parameter, namely improves vapor pressure and temperature, can obviously improve power plant thermal efficiency.When the steam parameter of unit reaches 22MPa, in the time of more than 570 ℃, under such temperature and ambient stress, the boiler steam pipe parts are subjected to baptism.The real case of boiler tubing shows, have in addition only several ten thousand hours working time, the early stage booster of part jet chimney frequently occurs, and causes and shuts down maintenance in unplanned, and power plant and electrical network are brought very big influence.Novel high chromium heat-resisting steel is the main use material of this class boiler reheater, superheater.Thereby the tissue variation of studying after this class steel military service is significant.
The staff of power plant recognizes after the existence of this class problem that this class problem of deep research obtains some achievements.Be example with T91 heat-resisting steel, a large amount of practical applications and simulation experiment study show that the early stage performance degradation of such steel and the main cause of inefficacy have following two aspects:
1, the answer of substructure.After Long-term Service under High Temperature, substructure is replied, and dislocation desity significantly descends, a large amount of dislocations or cancel out each other, or absorbed by crystal boundary and sub boundary, or be entangled with into dislocation wall mutually and further be converted into sub boundary, promoted the fragmentation of lath martensite and the recovery and recrystallization of crystal grain.A large amount of lath martensites are divided, and fragmentation in original crystal grain inside, the Nucleation Mechanism recrystallization by bending, and reduce the creep strength of material, cause the generation of creep phase III.
2, original precipitated phase alligatoring, cenotype generates.Under high temperature long-term creep effect, can separate out a kind of laves phase of being formed by Fe, Mo in the T91 type heat-resisting steel, this phenomenon will make Alloy Elements Mo, W more evenly spread in carbonide by distributing in the solid solution, makes that matrix lacks the solution strengthening element and reduced the solution strengthening effect in the steel.Have document to point out that the regional area of low Mo just becomes the place that creep is concentrated, thereby reduced activation energy of creep, tertiary creep is carried out.The initial stage particle is less an invigoration effect to Laves separating out in addition, can promote the mechanical property of heat-resisting steel to a certain extent, but should be mutually very easy alligatoring under the environment under arms.Through after the Long-term Service under High Temperature, elemental diffusion in the steel, the invigoration effect of other precipitated phases that weakened.On the other hand, according to Ostalwald alligatoring theory, the precipitated phase concentration of element that diameter is more big is more low, thereby impel alloying element to shift from the minor diameter precipitated phase to the major diameter precipitated phase, studies show that the precipitated phase alligatoring is after certain diameter, be easy to cracking, become formation of crack, significantly reduce the serviceable life of steel.
In this two reason, second reason and mechanism are considered to the main cause that such steel lost efficacy always, have enough knowledge for this mechanism.For instructing practice operation, power plant need make mensuration by the new phase content of the Laves to separating out in the steel after heat-resisting steel moves a period of time.
At present the sign that changes the particularly variation of precipitated phase for such heat-resisting steel microstructure mainly adopts the method for metallography or X-ray diffraction (XRD).
The metallographic method is the most traditional way.The material that this method intercepting is used is made after the needed metallographic specimen, utilize optics or electron microscopic equipment, the internal microstructure that shows sample, can utilize simultaneously some utility appliance such as X ray single crystal diffraction, energy spectrometer to wait microstructure in the qualitative discriminating material, realize the particle size statistics.
Another is the method for XRD, and this method sample mainly is the carbonide after directly test or the extraction.Direct when test because tissue is complicated in the steel, and carbonide proportion is less relatively therein, it is numerous and diverse to record signal noise, seldom can reflect needed carbonide information simultaneously, so generally can take the second class sample to test.Sample can provide many detailed carbonide information after the extraction, comprises the category of carbides that comprises in the powder, the position of growth to, simultaneously can calculate the massfraction of carbonide in all extracts, and the lattice constant that has recorded phase in this sample.
M.Mattestrand etc. (2001) adopt the energy filter transmission electron microscope to distinguish the Laves phase, realize real accurately qualitative discriminating clearly, but transmission electron microscope sample making course complexity, and the field range of test is less, makes test have randomness.Wang Xue etc. (2012) adopt the backward scattering flying-spot microscope, distinguish the Laves phase according to contrast difference, and to particle implementation statistics, this method relative visual field is broad, the mensuration process is comparatively simple, yet in distinguishing, the figure image contrast is subjected to the influence of many factors, and the mensuration of this method is inaccurate as can be known.And in the XRD determining method, carbonide extraction and experimentation are cumbersome equally, and the experimental result instability.
Summary of the invention
Technical matters to be solved by this invention is to provide a kind of method of measuring Laves phase content in the steel simply, exactly.This method is utilized Mo﹠4﹠ssbauer spectrum equipment, has that equipment is simply common, sample preparation is convenient fast, measure characteristic of accurate.
The existing way of alloying element in steel has only two kinds, and the one, in matrix, form solid solution with Fe, perhaps be exactly in steel, to form compound together with C, N.So just can instead push away content in the chemical combination attitude if detect the variation of alloying element in the middle of matrix.In addition before the precipitated phase test of doing steel, the main precipitated phase in the general known steel, and the essential element in the steel.So at some elements in the steel, when only having a kind of chemical combination attitude structure precipitated phase, if can detect the ratio of this element in matrix, utilize the composition of steel can instead push away its ratio in precipitated phase.And the Mo﹠4﹠ssbauer spectrum effect can sensitivity record various solute atomss to ferrous alloy
57The isomer shift of Fe and the influence of hyperfine field.The solute atoms of each solid solution around the iron atom will make and the isomer shift of iron atom the iron atom hyperfine field be changed that each atom is fixing in the change value that ad-hoc location produces.
Technical scheme of the present invention is:
(1) workpiece for measurement is got fritter, behind the cleaning greasy dirt, utilize the coil file cutter that sample is made powdered sample under room temperature;
(2) get the granule of frustrating as in the instrument sample chamber, Mossbauer, the Mossbauer instrument adopts aero modes such as transmission, measure the gamma ray counting that sees through absorber and modulation energy namely with the relation of doppler velocity;
(3) Mo﹠4﹠ssbauer spectrum is imported in the Recoil software, read spectral line, differentiate the quantity of the solid solution that influences iron hyperfine field value according to spectral line;
(4) in conjunction with common phase in the alloying element in the workpiece for measurement and the steel, judge in the workpiece for measurement the influential element of hyperfine field value to iron, checked in their influence value to the hyperfine field value of iron by reference book;
(5) with in the influence value substitution Recoil software dialogue box that inquires, carry out match, repeatedly minimum one group of Select Error value after the match;
(6) according to the relative scale of the general area of each thing phase line in the fitting result,, multiply by then and detect abundance 2.2% divided by belongings phase line area under spectrum summation with Laves phase line spectrum area occupied, the iron that obtains forming the Laves phase accounts for the ratio of all ferro elements; Laves mutually in ferro element and Mo element ratio to close be 2:1, in conjunction with the top ratio that forms the iron of Laves phase, can obtain constituting the ratio of the Mo of Laves phase.
Step (2) is got the 10mg powdered sample and is put in the Mo﹠4﹠ssbauer spectrum instrument.
In the step (2), the access speed scope is-10 to 10mm/s, uses 1024 road multichannel analyzer image data, and step-length is 10/1024.
In the step (2), use the Co that is fixed in the Rh lattice
57As radioactive source, wherein energy is that the gamma-rays of 14.4Kev causes the nuclear resonance scattering of Fe in the material.
Major part is that Mo﹠4﹠ssbauer spectrum is measured and analyzed in the above technical scheme, and wherein Mo﹠4﹠ssbauer spectrum measuring principle and process are as follows:
Mossbauer effect is gamma-ray resonance fluorescence phenomenon, also claims ray non-recoil emission and resonant absorption effects, or claims, zero-phonon emission and the resonant absorption effects of ray.Because it is very responsive to the slight change of energy of, therefore can be used to survey owing to resonance atomic nucleus neighbouring physics and chemical environment change the trickle change of the resonance energy of that causes, thereby obtain the details of many structures of matter.For obtaining stronger gamma-rays resonance absorption, gamma-rays is launched under recoilless condition.In the experiment of Mossbauer, these resonant nucleus are all inserted among the lattice, because the constraint of lattice, part of atoms nuclear is realized the non-recoil process when emission and absorption.The basic reason that the Mossbauer makes a breakthrough experimentally is to launch nuclear or absorbs nuclear and all is subjected to the constraint of crystal lattice, thereby may realize non-recoil resonance absorption or reflection.The essential characteristic of non-recoil atomic nucleus resonance absorption is, obtains similar emission atomic nucleus and absorbs complete energy resonance between the atomic nucleus.When the principle of mossbauer effect changes whenever nuclear surrounding environment, variation on corresponding movement, division and the intensity etc. also can take place in resonance line, mossbauer effect utilizes the lattice implantation to realize gamma-rays non-recoil resonance absorption exactly, thereby surveys the information of atomic nucleus micro effectively.
Mossbauer spectrometer is mainly by (1) speed drive, and gamma-ray radiation isotope material can be launched in (2) Mossbauer source-also claim Mossbauer nuclear.Usually select the high metal of coordination symmetry as the matrix of radioactive source, annotate people, Coulomb excitation or nuclear reaction induce one matrix the inside (3) absorber-in most cases of parent nucleus isotope with diffusion, ion, absorber is the material of required research, (4) ray detector, (5) nuclear impulse circuit, the storage of (6) data, (7) Cryo Equipment and high temperature service, (8) externally-applied magnetic field device, (9) high-tension unit speed, systems such as (10) calibrating installation form.
Measuring process: the atomic nucleus divergent-ray in (1) Mossbauer source transits to ground state by the nuclear excitation attitude.The Mossbauer source is different from general radioactive source, and it is bound by radionuclide in the solid lattice and makes.(2) by the Doppler effect of relative motion between source and the absorber, make gamma-ray energy that a small modulation △ E be arranged
D(3) after the modulation, gamma-rays Mossbauer of the same race atomic nucleus in absorber causes resonance absorption, and (4) measure to see through absorber, gamma ray counting and modulation energy namely with the relation of doppler velocity, be exactly that transmission Mo﹠4﹠ssbauer spectrum Mossbauer absorbs.
As shown from the above technical solution the present invention utilize mossbauer spectrometer record gamma ray counting and modulation energy namely with the relation of doppler velocity, obtain the solid solution atom for the hyperfine interaction of Fe atom, be converted into the content of such solid solution.The present invention that hence one can see that has following advantage: the firstth, and experimental facilities is simple, and this experiment need not utilize the transmission electron microscope equipment of high price, the region restriction that has reduced experimentation cost and tested.The secondth, sample preparation of the present invention is simple, can adopt powdered samples or bulk sample, when adopting powdered samples, only needs to frustrate out the amount about 10mg from tested sample, avoids polluting just passable.Save the trouble of transmission sample preparation, save test period and improve the probability of success of the test simultaneously.The 3rd is the present invention quantitatively the time, and precision is higher with sensitivity, can working sample in the few thing phase ratio of content.
Description of drawings
Fig. 1, the Mo﹠4﹠ssbauer spectrum fitting result.
Embodiment
Embodiment
To composition such as following table 1, specification is to take a sample in the T91 pipeline of Ф 60mm*10mm, and sample is carried out accelerated aging test under 675 ℃, 70MPa, and the time is 900 hours, this sample is carried out the quantitative measurement of Laves phase content after aging.
Table 1 is T91 steel standard analysis in the examples of implementation
The assay method following steps:
Step 1: adopt the line cutting from pipeline, to take out sample, adopt after alcohol acetone cleans, dry up, utilize the coil file cutter that material is slowly frustrated into granule from small sample, will hurry in the process of frustrating, guarantee not can heating up too high.
Step 2: get the granule of frustrating as in the instrument sample chamber, Mossbauer, the Mossbauer instrument adopts aero modes such as transmission, measure the gamma ray counting that sees through absorber and modulation energy namely with the relation of doppler velocity; The access speed scope is-10 to 10mm/s, uses 1024 road multichannel analyzer image data, and step-length is 10/1024.
Step 3: Mo﹠4﹠ssbauer spectrum is imported in the Recoil software, read spectral line, distinguish that according to spectral line this spectral line should have 5 solid solution that influence iron hyperfine field value.
Step 4: in conjunction with common phase in the alloying element among the T91 and the steel as can be known, the influential element of hyperfine field value of iron is comprised Fe-Ni, Fe-Cr, Fe-C, Fe-Mo, Fe-Ni, checked in their influence value to the hyperfine field value of iron by reference book.
Step 5 is carried out match with in meticulous value of 5 of the selections of inquiry in the step 4 substitution software dialogue box, repeatedly minimum one group of Select Error value after the match.
Step 5 is determined to be fit to derive fitting result after the result.Fig. 1 is fitting result, table 2 be the parameter form after the match.H value after the match is respectively 338.4,317,304.0,286.6,264.9, corresponds to Fe-Ni, Fe-C-Ni, Fe-Cr, Fe-Mo, cementite respectively.Laves phase (Fe has appearred in the sample of explanation after aging
2Mo).
Sextet4 is corresponding Laves phase in the fitting parameter table, by sextet population, the iron that influences of Laves phase accounts for and detects 16.1% of Fe as can be known, and ferro element proportion in steel is 1-0.12-0.21-0.43-0.01-0.004-8.82-0.98-0.21-0.072-0.042-0 .16-0.011=88.931.And Mo﹠4﹠ssbauer spectrum is for Fe
57Detecting abundance mutually is 2.2%, calculates the Mo that forms the Laves phase to be: 2.2% * 0.88931 * 16.1% ÷ 2=0.0157%.By Laves mutually in Mo testing result as can be known in this style Laves phase mass ratio be 0.0157%.
Table 2 be the parameter form after the match
Claims (4)
1. method of measuring laves phase content in the steel is characterized in that step is as follows:
(1) workpiece for measurement is got fritter, behind the cleaning greasy dirt, utilize the coil file cutter that sample is made powdered sample under room temperature;
(2) get the granule of frustrating as in the instrument sample chamber, Mossbauer, the Mossbauer instrument adopts aero modes such as transmission, measure the gamma ray counting that sees through absorber and modulation energy namely with the relation of doppler velocity;
(3) Mo﹠4﹠ssbauer spectrum is imported in the Recoil software, read spectral line, differentiate the quantity of the solid solution that influences iron hyperfine field value according to spectral line;
(4) in conjunction with common phase in the alloying element in the workpiece for measurement and the steel, judge in the workpiece for measurement the influential element of hyperfine field value to iron, checked in their influence value to the hyperfine field value of iron by reference book;
In the influence value substitution Recoil software dialogue box that inquires, carry out match, repeatedly minimum one group of Select Error value after the match;
(6) according to the relative scale of the general area of each thing phase line in the fitting result,, multiply by then and detect abundance 2.2% divided by belongings phase line area under spectrum summation with Laves phase line spectrum area occupied, the iron that obtains forming the Laves phase accounts for the ratio of all ferro elements; Laves mutually in ferro element and Mo element ratio to close be 2:1, in conjunction with the top ratio that forms the iron of Laves phase, can obtain constituting the ratio of the Mo of Laves phase.
2. method according to claim 1 is characterized in that, step (2) is got the 10mg powdered sample and is put in the Mo﹠4﹠ssbauer spectrum instrument.
3. method according to claim 1 is characterized in that, in the step (2), the access speed scope is-10 to 10mm/s, uses 1024 road multichannel analyzer image data, and step-length is 10/1024.
4. method according to claim 1 is characterized in that, in the step (2), uses the Co that is fixed in the Rh lattice
57As radioactive source.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104677925A (en) * | 2015-03-23 | 2015-06-03 | 贵州电力试验研究院 | Method for measuring ratio of each iron oxide in mixture |
| CN108268027A (en) * | 2016-12-30 | 2018-07-10 | 乐视汽车（北京）有限公司 | Driving locus optimization method and optimization system |
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| US4640722A (en) * | 1983-12-12 | 1987-02-03 | Armco Inc. | High temperature ferritic steel |
| JP2000073147A (en) * | 1998-08-27 | 2000-03-07 | Kawasaki Steel Corp | Chromium-containing steel excellent in high temperature strength workability and surface property |
| CN101311277A (en) * | 2007-05-25 | 2008-11-26 | 丹阳市精密合金厂 | Homogenization treatment process for high-temperature alloyed steel ingot |
| CN101915773A (en) * | 2010-08-30 | 2010-12-15 | 河北省电力研究院 | Method for nondestructively testing 9 percent Cr steel Laves phase |
| CN102866172A (en) * | 2012-08-31 | 2013-01-09 | 广东电网公司电力科学研究院 | Measuring method of Laves phase content of T/P 92 steel |
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- 2013-04-18 CN CN201310134969.3A patent/CN103234989B/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4640722A (en) * | 1983-12-12 | 1987-02-03 | Armco Inc. | High temperature ferritic steel |
| JP2000073147A (en) * | 1998-08-27 | 2000-03-07 | Kawasaki Steel Corp | Chromium-containing steel excellent in high temperature strength workability and surface property |
| CN101311277A (en) * | 2007-05-25 | 2008-11-26 | 丹阳市精密合金厂 | Homogenization treatment process for high-temperature alloyed steel ingot |
| CN101915773A (en) * | 2010-08-30 | 2010-12-15 | 河北省电力研究院 | Method for nondestructively testing 9 percent Cr steel Laves phase |
| CN102866172A (en) * | 2012-08-31 | 2013-01-09 | 广东电网公司电力科学研究院 | Measuring method of Laves phase content of T/P 92 steel |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104677925A (en) * | 2015-03-23 | 2015-06-03 | 贵州电力试验研究院 | Method for measuring ratio of each iron oxide in mixture |
| CN108268027A (en) * | 2016-12-30 | 2018-07-10 | 乐视汽车（北京）有限公司 | Driving locus optimization method and optimization system |
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