CN101162171B - Method for measuring surface temperature of high-temperature casting billet within water fog medium - Google Patents

Abstract

The present invention discloses a method for measuring the surface temperature of a high-temperature casting blank in water-fog medium; the water-fog concentration of the surface of the high-temperature casting blank is measured and transmitted to a remote computer through an air water-fog concentration sensor; the attenuation coefficient K lambda of water-fog medium to radiant energy in the water-fog concentration is gained by the remote computer through the relation curve between the attenuation coefficients of the water-fog medium and the radiant energy; temperature data tested by a thermodetector are modified by the attenuation coefficient K lambda and the emissivity of filam on the surface of the casting blank and the real temperature of the surface of the casting blank in the water-fog medium can be measured in real-time; the gain of accurate temperature has an important support on the application of continuous casting front-edge technology such as electromagnetic mixing, secondary cooling dynamic control and so on in dynamic slight press and has very important significance on improving the quality of casting blank and the whole level of continuous casting.

Description

The measuring method of surface temperature of high-temperature casting billet within water fog medium

Technical field

The present invention relates to a kind of temp measuring method, the measuring method that specifically refers to a kind of surface temperature of high-temperature casting billet within water fog medium, be mainly used in the on-line measurement of the continuous casting secondary cooling process casting blank surface temperature of steel, to realizing that dynamic control, secondary cooling that the continuous casting secondary cools off are dynamically gently depressed, electromagnetic agitation, significant to the quality that improves strand.

Background technology

In recent years, the development of China's steel and iron industry is very rapid, and its steel product output ranked first in the world in continuous ten years.The continuous casting technology of China's steel also obtains to develop on a large scale very much, and the cast of present nearly all steel can both realize continuous casting steel machine, and the continuous casting ratio of China has surpassed 95% at present.Along with society requires to improve day by day to the cost performance of the final products of steel, to the kind and the higher requirement of quality proposition of continuous casting steel machine.

In the casting process, the molten steel of certain degree of superheat successively injects crystallizer by tundish through the mouth of a river and once cools off.In crystallizer, only solidified about 20% molten steel amount, 80% the molten steel amount ot-yet-hardened of also having an appointment.The casting blank solidification that pulls out from crystallizer becomes a thin shell, and (8～15mm), and the center remains high-temperature molten steel, solidifies while moving, the result forms a very long liquid core.For making strand continue to solidify, export to this strand operation area of The drawing straightener from crystallizer and be provided with water spray cooling zone (abbreviation secondary cooling zone), the water of atomizing is directly injected on the surface of high temperature strand, has quickened the transmission of heat, strand is solidified rapidly.The distribution of casting billet surface longitudinal and transverse temperature is even as far as possible, avoids temperature to change suddenly.

Secondary cooling area for continuous casting is the key link of direct and final decision strand internal soundness.The water supply intensity of each section of secondary cooling zone has determined the behavior of solidifying of cooling effect and strand.Intensity of cooling increases, and can quicken solidifying of strand, but the crack sensitivity of intensity of cooling and steel is closely related, and is subjected to the constraint of slab quality, so must adopts rational secondary cooling system to obtain suitable intensity of cooling.Secondary cooling mainly shows the influence of slab quality: (1) inhomogeneous cooling is even, will cause base shell temperature recovery too fast too high, and strand easily cracks or subcrack; (2) intensity of cooling is excessive, and surface temperature low excessively (as less than 900 ℃) when making the strand aligning easily produces surface transverse cracks, and intensity of cooling is crossed senior general and made flourishing transcrystalline or the bridging phenomenon of easily forming of column crystal simultaneously, makes center porosity and segregation aggravation; (3) intensity of cooling is not enough, and strand band liquid core aligning easily produces the aligning crackle; (4) two cold-zone casting blank surface temperatures are too high, and strand easily produces bulge deformation and center segregation is increased the weight of.From the thermal conduction study analysis, the heat radiation of strand comprises convection current, radiation and three kinds of modes of conduction.The advection heat flux depends on the temperature difference and the heat transfer coefficient of casting billet surface and environment, and radiation heat flux depends primarily on casting blank surface temperature, and the conduction thermoflux is directly related with casting blank surface temperature.The more important thing is that casting blank surface temperature has directly reflected the distribution of strand temperature inside and solidified situation.Therefore, casting blank surface temperature just becomes the key parameter of continuous casting secondary cooling control, and the solidification process information of strand inside needs to obtain by surface temperature, and this has more increased and obtains the importance of this key parameter of casting blank surface temperature accurately.

To the control mode of each section water supply intensity of secondary cooling, mainly be divided into static control and dynamically two kinds of controls.Because there is great limitation in the uncertainty of static control and empirical in actual production process.Development along with continuous casting technology, because consider the influence of variation (history) cumulative effect that cooling brings to secondary of pulling rate to casting blank surface temperature, secondary cools off dynamic control and can obviously improve slab quality, promotes continuous casting variety steel production range, improve conticaster throughput rate.In this sense, dynamically the temperature of continuous acquisition casting billet surface is to realizing dynamically control of secondary cooling, and the output and the slab quality that improve conticaster have extremely important realistic meaning and practical value.

At present continuous casting steel machine forefront technology (the liquid core is depressed technology, electromagnetic agitating technology etc.) all needs to know accurately the liquid core position of continuous casting billet, to determine depressing operation and electromagnetic agitation where.How to determine the position of liquid core of continuous casting billet, behind the coagulation factor of a certain steel grade of nailing experimental test that present generally employing is on-the-spot, binding isotherm calculates the liquid core position of strand.Yet a nailing test only can obtain the coagulation factor of a steel grade, and when the change of operating mode and casting steel grade, the corresponding change will be taken place in the liquid core position of continuous casting billet, can not be presented at the liquid core position under the different operating modes dynamically; And adopt solidification theory seldom in actual production, to obtain application in conjunction with the bigger difference of the resulting result of the method for numerical evaluation and produced on-site physical presence.Because casting blank surface temperature has directly reflected the strand temperature inside and has distributed and liquid core position, accurately obtained casting blank surface temperature and will play vital impetus to the application of cutting edge technology.

To obtain the casting blank surface temperature not a duck soup of secondary cooling area for continuous casting exemplary position dynamically, continuously, accurately.Since continuous casting production be a high temperature, continuously, the process of motion, this makes traditional contact temperature-measuring instrument such as very difficult realization temperature surveys such as thermopairs, and contactless Radiation Temperature Measurement Instrument table can solve the thermometric to moving target.The measuring method of casting blank surface temperature mostly adopts the contactless temperature-measuring based on photoelectric effect or heat radiation relative theory at present, as infrared three look Radiation Temperature Measurement Instrument, AGA780 thermal imaging system, CIT-M type infrared measurement of temperature linearization sensor, HWSG-II infrared double color temperature measurer, the intelligent temperature measurer of dichotomous fiber ratio color, SW-1 type colorimetric high temperature temperature measurer, infrared thermovision system, HWG-1 radiation temperature measurement view, line array CCD temperature measurer etc.Sharply evaporation has formed hot and humid water fog medium around strand because chilled water is ejected on the high temperature casting billet surface; Simultaneously, the oxidation of high temperature casting billet surface will produce more iron scale; Because water fog medium and iron scale to the absorption of radiation energy, make the true temperature of measured temperature and strand have very big error.How to determine the black body coefficient of moving object, be a difficult problem on engineering is used always, and states such as America and Europe, Japan do not have good solution yet, and this will directly influence temperature measurement accuracy.

For avoiding the influence of water smoke and steam to radiation wavelength, common way is that the method that adopts high velocity air to purge light path weakens the absorption to radiation wavelength of water smoke and steam, and consider the requirement of light path, air-flow is vertically to spray to casting billet surface, purging is not common convection heat transfer like this, but compulsory heat exchange---injection heat transfer, the temperature generation reduction by a relatively large margin that this makes the strand test point increases thermometric error greatly.The employing that has purges the method that light path and artificial intelligence combine, and obtains the temperature of casting billet surface by correction factor; Behind the usual optical pathway sweeping method, on light path, still have small amount of steam, at this moment the method correction temperature measurement error that adopts the artificial neural network to learn, owing to be subjected to the defective of sample number quantitative limitation and artificial intelligence study itself, this method has been difficult to wide practical value in actual production.The employing three look radiation thermometer contactless temperature-measurings that have, this method need not known the emissivity of casting billet surface, the absorption of the electromagnetic wave energy of infrared wavelength is improved the accuracy of thermometric by the absorption peak of avoiding selective gas, because the stability of this instrument is subject to the spectrum stability of optical filter, detector and the limitation that wavelength (wavelength period) is selected, the while complex structure, cost an arm and a leg, also be not widely used industrial at present.

Name is called " accurate measuring method of casted blank surface temperature of continuous casting secondary cold region ", application number discloses a kind of measuring method for the Chinese invention patent of " 01141418 ", this patent by adopting the method for contactless temperature-measuring, is got maximum as casting blank surface temperature by adopting with some measurement multi-group data in certain hour step-length scope to two cold-zone casting blank surface temperatures measurements.The deficiency of this patent is: one, at the secondary cooling section, because chilled water is ejected into sharply evaporation of back on the high temperature casting billet surface, around strand, formed hot and humid water fog medium, water fog medium makes that to a large amount of absorptions of radiation energy based on heat radiation correlation theory and photoelectric effect be that the result that basic non-contact type temperature measurement instrument is tested produces sizable deviation;

Two, for guaranteeing the even cooling of strand, in the spray district, casting billet surface is all awash, is not having water-covered areas, and the high temperature strand contacts with air oxidation reaction will take place, and produces a large amount of iron scales.The water droplet of iron scale and atomizing also will absorb a large amount of radiation energy in a large number, make the error of measuring further enlarge; Three, in the conticaster normal productive process, under the condition that each phase correlated condition tends towards stability substantially, the distribution of two cold-zone casting billet surface water fog mediums is in steady state (SS) substantially, if obtain approximate maximum temperature by the lengthening time step, do not reach the purpose of dynamically continuous acquisition casting blank surface temperature.By the analysis of also going up as can be known, adopt this method, can not get the accurate temperature of strand at all, casted blank surface temperature of continuous casting secondary cold region is measured do not had tangible practical value in each exemplary position of secondary cooling zone.

Name is called " continuous casting aligning target temperature Monitoring and Controlling and analytic system ", application number discloses a kind of temperature monitoring control and analytic system for the Chinese invention patent of " 03153364 ", in order to avoid the interference of medium, select for use the contactless infrared probe of 1-1.1 micron wave length to measure strand aligning point temperature.Its deficiency is: one, this patent is only measured the temperature in aligning district, does not relate to the secondary cooling zone of situation complexity.Aligning district strand is in radiation area simultaneously, the high temperature strand contacts with air, and oxidation reaction will take place, and will form a large amount of iron scales at casting billet surface, and will form the thin oxide film of one deck on the surface of strand, well-known, the blackness of most of metal oxides is all much larger than simple metal.But because technology limitation does not also have the relevant report about oxide film blackness under different temperatures now.Even, still can accurately not measure the temperature of strand aligning point so adopt infrared temperature probe; Two, because strand is 900 ℃-1200 ℃ in aligning point surface temperature, according to the relation curve of wavelength under the condition of different temperatures and spectral energy as can be known, the corresponding peaks wavelength is the 0.7-1.0 micron, when 1-1.1 micron wave length section, the spectrum ability also tends towards stability with the change of temperature, is unfavorable for the raising of measuring accuracy; Three, distinguish because the cooling of strand self and the cooling of strand backing roll at the continuous casting billet aligning, a large amount of water fog mediums is still arranged, this patent does not consider that water fog medium and casting billet surface iron scale to the influence of radiation energy, can not be used for the measurement of whole two cold-zone casting blank surface temperatures.

In sum, the continuous casting secondary but the cold-zone be directly and the key link of final decision strand internal soundness.The water supply intensity of two each sections of cold-zone has determined the behavior of solidifying of cooling effect and strand, and the solidification process information of strand inside needs to obtain by surface temperature, and promptly casting blank surface temperature has directly reflected the distribution of strand temperature inside and solidified situation.Yet the present present situation of continuous casting technology is the determination techniques (this also is one of key issue of restriction continuous casting technology development) that does not also have ripe casting blank surface temperature.Especially to the mensuration of the casting blank surface temperature of water smoke cooling section, no matter be that contact or contactless method are all owing to the existence of water fog medium is difficult to obtain real casting blank surface temperature at present.The a large amount of water fog mediums of secondary cooling area for continuous casting high temperature casting billet surface are that continuous casting billet skin temperature can not be by the accurate restricted link of measuring of contactless mode to the absorption of radiation energy, how to solve the attenuation problem of casting billet surface water fog medium to the casting billet surface radiation energy, be that those skilled in the art wish the problem that solves always, in case solved this problem, just be expected accurately to obtain the temperature on high temperature continuous casting billet surface by contactless mode.

Summary of the invention

At the prior art above shortcomings, the measuring method that the purpose of this invention is to provide a kind of surface temperature of high-temperature casting billet within water fog medium, this method can be revised the influence of thermometric the water fog medium absorbed radiation energy, thereby obtains casting blank surface temperature accurately.

The object of the present invention is achieved like this:

The measuring method of surface temperature of high-temperature casting billet within water fog medium, it comprises the steps:

1., set up the physical model of testing, water smoke concentration c and decay coefficient K when simulating radiation energy in the laboratory by water fog medium _λBetween relation curve;

2., according to water smoke concentration c and decay coefficient K _λBetween relation curve set up decay coefficient K _λFuntcional relationship with the water smoke concentration c;

3., in the two chill casting base surface temperature test processs of production scene, record the probe temperature T of high temperature casting billet surface respectively by contactless temperature-measuring instrument and water smoke concentration sensor _SurveyWith the water smoke concentration c;

4., on the water smoke concentration c basis that 3. step obtains, the decay coefficient K that 2. obtains by step _λCan try to achieve decay coefficient K with the funtcional relationship of water smoke concentration c _λ

5., utilize this decay coefficient K _λTo the above-mentioned probe temperature T that obtains _SurveyThereby revise the true temperature that obtains casting billet surface under the water fog medium.

Further, described 1. go on foot water smoke concentration c and decay coefficient K _λBetween relation curve set up by the following method: the physical model of setting up test in the laboratory, detect the size distribution of water fog medium concentration and water mist particle by three-dimensional laser particle kinetic analyzer, in conjunction with the true temperature of sample and the probe temperature of employing contactless temperature-measuring instrument, water smoke concentration c and decay coefficient K when simulating the sample radiation energy by water fog medium _λBetween relation curve.

Utilize above-mentioned decay coefficient K _λTo probe temperature T _SurveyWhen revising in conjunction with the emissivity of casting billet surface oxide film to probe temperature T _SurveyRevise jointly.

This method is because can to obtain water fog medium exactly (be decay coefficient K to the absorption of radiation energy _λ, this also is that prior art wishes to obtain and the parameter that casting blank surface temperature is had a direct impact that can not accurately obtain), utilize this decay coefficient K _λThe casting blank surface temperature that can obtain non-contact measurement is exactly revised, thereby is implemented in the true temperature that whole two cold-zones of continuous casting continuously, dynamically obtain casting billet surface.Owing to obtain accurate, real casting blank surface temperature, to dynamically gently depress, the cooling of electromagnetic agitation, secondary dynamically the application of continuous casting cutting edge technology such as control play extremely important support, the integral level of raising slab quality and continuous casting is all had crucial meaning.

Description of drawings

Fig. 1-continuous casting secondary cooling zone contactless temperature-measuring system schematic.

Embodiment

Introduce the present invention in detail below in conjunction with embodiment and understand this method with further.

The casting billet surface water fog medium is to the absorption of radiation energy, the maximum constraints link of the contactless temperature-measuring instrument temperature survey accuracy that to be influence invent based on photoelectric effect or heat radiation correlation theory; Simultaneously, the emissivity of casting billet surface also is a key factor that influences the radiation temperature measurement accuracy.Therefore, the purpose of patent and requirement according to the present invention need solve two problems: the decay coefficient K when 1, finding out radiation energy by water fog medium _λ2, determine the emissivity of casting billet surface oxide film oxide film under different temperatures.After these two parameters obtain, just can revise and obtain the real temperature of casting billet surface the temperature that the contactless temperature-measuring instrument is measured.

Mensuration for the emissivity of casting billet surface oxide film, pass through simulated field continuous casting production actual conditions in the laboratory, use the standard items of testing sample and known emissivity to compare measurement, simulating the testing sample oxide film is the temperature variant relation curve of emissivity in 900-1200 ℃ in temperature range.

Water fog medium is the key problem that patent of the present invention need solve to the absorption of radiation energy.When radiation energy passed thickness and is the water fog medium layer of ds, owing to absorb and scattering, radiation intensity will be from I _λWeaken and be I _λ+ dI _λ, introduce decay coefficient K _λ(K _λ=α+γ, wherein α, γ are respectively the absorption coefficient and the scattering coefficient of water fog medium), then have

dI _λ＝-K _λI _λds

"-" number expression radiation intensity weakens on the way in the formula.

With the following formula s integration of adjusting the distance, then can get:

$I_{\mathrm{\λ}}\left(s\right)=I_{\mathrm{\λ}}\left(0\right)\exp [-{\∫}_0^s{K}_{\mathrm{\λ}}\left(s^{*}\right){\mathrm{ds}}^{*}]$

In the following formula, s ^*Dummy variable for integration; I _λ(0) be apart from the s=0 place, i.e. the radiation intensity of casting billet surface.Decay coefficient K _λRelevant with concentration c of incident wavelength λ, water fog medium temperature T, water fog medium etc., that is:

K _λ＝K _λ(λ，T，c)

Though decay coefficient K _λWith three relating to parameters of concentration c of incident wavelength λ, water fog medium temperature T, water fog medium, but the present invention only finds out decay coefficient K by experiment _λWith the relation of water fog medium concentration c, will influence decay coefficient K _λA plurality of parameter predigestings be one of them parameter.The present invention sets up the physical model of test in the laboratory, detect the size distribution of water fog medium concentration and water mist particle by three-dimensional laser particle kinetic analyzer (3D-PDA), in conjunction with the true temperature (adopting the contact temperature-measuring instrument to obtain) of sample and the probe temperature of employing contactless temperature-measuring instrument, can obtain radiation intensity thus from I _λWeaken and be I _λ+ dI _λThe time radiation energy damping capacity, measure simultaneously true temperature loca (casting billet surface) and probe temperature loca apart from ds, utilize formula dI _λ=-K _λI _λDs can calculate decay coefficient K _λSo, water smoke concentration c and decay coefficient K in the time of can simulating the sample radiation energy by water fog medium _λBetween relation curve.

Relation curve between water smoke concentration and the attenuation coefficient has been arranged, utilized the method for numerical evaluation just can obtain decay coefficient K by computer programming _λWith the funtcional relationship of water smoke concentration c, therefore know the moisture concentration of two cold-zone each section water fog mediums, just can calculate decay coefficient K _λMeasure the corresponding sensor of accurately measuring water in air part concentration under the water fog medium of exploitation for the moisture concentration under the high temperature.Because there are corresponding relation in moisture concentration and humidity, therefore also can obtain decay coefficient K by humidity (utilizing humidity measuring apparatus) _λ

The specific implementation step of this method is: A, set up the physical model of test in the laboratory, detect the size distribution of water fog medium concentration and water mist particle by three-dimensional laser particle kinetic analyzer (3D-PDA), in conjunction with the true temperature of sample and the probe temperature of employing contactless temperature-measuring instrument, water smoke concentration c and decay coefficient K when simulating the sample radiation energy by water fog medium _λBetween relation curve;

B, according to water smoke concentration c and decay coefficient K _λBetween relation curve set up water smoke concentration c and decay coefficient K _λFuntcional relationship;

C, in the two chill casting base surface temperature test processs of production scene, record the probe temperature T of high temperature casting billet surface respectively by contactless temperature-measuring instrument and water smoke concentration sensor _SurveyWith the water smoke concentration c;

On D, the water smoke concentration c basis that obtains in C step, the decay coefficient K that obtains by step B _λCan try to achieve decay coefficient K with the funtcional relationship of water smoke concentration c _λ

E, utilize this decay coefficient K _λWith the emissivity of oxide film jointly to the above-mentioned probe temperature T that obtains _SurveyThereby revise the true temperature that obtains casting billet surface under the water fog medium.

Above-mentioned data processing is to finish by the Automatic Program of computer-internal.During concrete operations, the present invention is transferred to remote computer 1 by the water smoke concentration that air water mistiness degree sensor 2 records the high temperature casting billet surface, obtains under this concentration water fog medium to the decay coefficient K of radiation energy by remote computer 1 by the relation curve between the attenuation coefficient of water fog medium concentration and radiation energy (this curve in advance chamber obtain and place in the computing machine) by experiment _λ, utilize this decay coefficient K _λWith the emissivity of casting billet surface oxide film the temperature data of temperature measurer 3 tests is revised and recorded the true temperature of the casting billet surface under the water fog medium in real time.

Fig. 1 is a continuous casting secondary cooling zone contactless temperature-measuring system schematic of the present invention, it is divided into three parts: one, (temperature measurer and moisture content concentration sensor have many covers for contactless temperature-measuring instrument 3 and moisture content concentration sensor 2, be 3 covers on the figure, be located at different positions respectively) with dynamic, continuous temperature measurement; Two, software platform; Three, terminal computer control system.Label 1 is software platform and terminal computer control system.

Adopt the non-contact type temperature measurement instrument directly to measure to the measurement of casting blank surface temperature, need not purge light path.Owing to considered decay and the strand oxide film temperature variant relation of water fog medium, so measured temperature is the true temperature of strand to radiation energy.

The present invention proves fully feasible through project team a large amount of theory and experimental study, this patent of invention can be widely used on the slab caster and billet caster of various sections, by obtaining the surface temperature of strand accurately, dynamically, directly direct impetus is played in the lifting of whole continuous casting level.

Claims (1)

1. the measuring method of surface temperature of high-temperature casting billet within water fog medium, it is characterized in that: it comprises the steps:

1., set up the physical model of test in the laboratory, detect the size distribution of water fog medium concentration and water mist particle by three-dimensional laser particle kinetic analyzer, in conjunction with the true temperature of sample and the probe temperature of employing contactless temperature-measuring instrument, water smoke concentration c and decay coefficient K when simulating the sample radiation energy by water fog medium _λBetween relation curve;

2., according to water smoke concentration c and decay coefficient K _λBetween relation curve set up decay coefficient K _λFuntcional relationship with the water smoke concentration c;

3., in the two chill casting base surface temperature test processs of production scene, record the probe temperature T of high temperature casting billet surface respectively by contactless temperature-measuring instrument and water smoke concentration sensor _SurveyWith the water smoke concentration c;

4., on the water smoke concentration c basis that 3. step obtains, the decay coefficient K that 2. obtains by step _λCan try to achieve decay coefficient K with the funtcional relationship of water smoke concentration c _λ

5., utilize this decay coefficient K _λSimultaneously in conjunction with the emissivity of casting billet surface oxide film to the above-mentioned probe temperature T that obtains _SurveyThereby revise the true temperature that obtains casting billet surface under the water fog medium.

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