CN106289037A - A kind of continuous casting steel billet shell thickness eddy current detection method - Google Patents
A kind of continuous casting steel billet shell thickness eddy current detection method Download PDFInfo
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- CN106289037A CN106289037A CN201610577344.8A CN201610577344A CN106289037A CN 106289037 A CN106289037 A CN 106289037A CN 201610577344 A CN201610577344 A CN 201610577344A CN 106289037 A CN106289037 A CN 106289037A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
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Abstract
The invention discloses a kind of continuous casting steel billet shell thickness eddy current detection method, belong to continuous casting steel billet detection technique field.Purpose be in order to solve prior art measure continuous casting and solidifying shell thickness deficiency, it is provided that a kind of by inside steel billet according to corresponding to temperature electrical conductivity be layered, the method recording continuous casting steel billet shell thickness by multifrequency electric eddy current measurement method.The method is particularly as follows: the casting billet surface in continuous cast mold exit places current vortex sensor, sensor is mutual inductance differential type, current vortex sensor carries out mixing by digital frequency synthesizer and excites, the multiple different frequency signal excited is mixed by adder, measure the signal amplification through signal conditioning circuit, filtering, reference signal with different frequency carries out computing cross-correlation the most respectively, by Signal separator and carry out the width of eddy current impedance signal and be separated, the signal separated is acquired and changes, it is transferred to computer and carries out the process of data, obtain the thickness of continuous casting steel billet green shell.
Description
Technical field
Present invention relates particularly to a kind of continuous casting steel billet shell thickness eddy current detection method, belong to continuous casting steel billet detection technique
Field.
Background technology
In continuous casting of iron and steel production process, measured by the online Non-Destructive Testing of the thickness of solidified slab shell in secondary in crystallizer exit and
Controlling, the uniformity for the bleed-out in continuous casting production process and shell thickness has carried out the most efficient detection, to improve continuous casting
The quality of production of steel billet, improves continuous casting automatization level, is embodied in following two aspect: detect crystallizer exit in real time
Shell thickness bears the static pressure ability of molten steel, in prevention casting process, bleed-out production accident occurs；Online Non-Destructive Testing solidification base
Thickness of the shell variation tendency, with the intensity of cooling of on-line control secondary cooling water, closed loop control secondary cooling water cooling water inflow.
The site environment produced due to continuous casting is severe, the impact of high temperature heat radiation, cooling water spray, dust etc., Er Qie
The green shell in crystallizer exit also exists solid phase area, two-phase section, liquid phase region.These factors determine the online nothing of thickness of continuous casting shell
Damaging testing requirement can long-term operation in high temperature, high water smoke environment.
At present, in casting process, thickness of solidified slab shell in secondary detection method mainly has experiment measurement method, numerical model method, strain to pass
Three classes such as sense detection method.Experiment measurement method mainly uses method of powder actuated shot, in two cold-zones, the steel nail of sulfur-bearing tracer is injected continuous casting
Base, uses sufur printing analysis, low power detection nailing pattern in strand solid phase, liquid phase region to determine thickness of solidified slab shell in secondary and liquid phase
Acupuncture point is put, this experimental technique technology maturation, and precision is high, and visual result is reliable, but is belonging to off-line and damages detection, measures work
Amount is big.Puncture green shell measurement method, pierce through solidified shell in secondary cooling area for continuous casting, make not solidified liquid steel water flow out, then to solidification
Shell thickness carries out on-line checking, and this detection method belongs to destructive detection, and execute-in-place difficulty is the biggest.Bulge method is to pass through
The position of detection continuous casting billet bulge determines wick-containing position, and this measuring method is directly perceived, and device is simple, but can only rough estimate wick-containing
Terminal position.Radiation method mainly bores radiographic source, by geiger counter detection radiographic source through ray after continuous casting billet according to using
The change of intensity detects the thickness of solidified shell, and the method technical thought is feasible, but the radioactive pollution of radioactive source is to human body
Affect with environment.Numerical model method is based on one-dimensional or two dimensional unsteady heat transfer governing equation, uses finite element
Difference Calculation method calculates inner temperature of continuous casting stock field, and then determines continuous casting billet internal morphology, this method low cost, but model is asked
Solve precision and depend on boundary condition accurately, but astable continuous casting produces to determine and is difficult to determine boundary condition accurately, with
Time model to calculate convergence time long, it is difficult to the change of online real-time estimate thickness of solidified slab shell in secondary.Stain measuring technology is by continuous casting
Base is correlated with in fan-shaped section and is installed foil resistance foil gauge, determines that continuous casting billet solidifies by on-line monitoring dependent variable change catastrophe point
The position of end, this method reliability, sensitivity are poor, but by on-the-spot hyperthermia radiation, two cold-zone water smokes, fan-shaped section or working roll
The impacts such as stress is complicated, test result repeatability is poor, cannot popularization and application at industrial site.
The importance of solidified shell based on crystallizer exit, its thickness of accurate characterization and uniformity, for optimizing even
Casting crystallizer technique and equipment, improve continuous casting billet quality and continuous casting production efficiency is most important.The most both at home and abroad for solidification base
Thickness of the shell detection method the most fundamentally solves industrial site application problem.
Summary of the invention
Therefore, measure the above-mentioned deficiency of continuous casting and solidifying shell thickness for prior art, connect it is desirable to provide a kind of
Cast steel base shell thickness eddy current detection method.The present invention can effectively overcome the surface high-temp of continuous casting production scene to radiate, water smoke
The impact of the adverse circumstances such as bad border, is suitable for measuring strand different surfaces temperature, the thin sheet continuous casting requirement of different cast steel grade respectively.
The principle of this method is according to continuous casting steel billet surface temperature on curie point, and the resistivity of billet material is with temperature
Degree change, and when steel is molten into liquid, its resistivity its resistivity of generation transition is 2-3 times during solid-state, therefore can be by steel
Base is divided into three layers according to resistivity, solidification layer, solid-liquid layer and layer liquid, and then uses current vortex technology, measures solidification layer
Thickness.
The purpose of this programme is realized by below scheme:
Casting billet surface in continuous cast mold exit places current vortex sensor, and sensor is mutual inductance differential type.Electricity whirlpool
Flow sensor carries out mixing by digital frequency synthesizer and excites, and three the different frequency signals excited are carried out by adder
Mixing, measures signal through the amplification of signal conditioning circuit, filtering, in three correlators respectively with the ginseng of three different frequencies
Examine signal and carry out computing cross-correlation, by Signal separator and carry out the width of eddy current impedance signal and be separated, the signal warp separated
Gather and conversion, be transferred to computer and carry out the process of data.The data procedures of computer disposal is as follows: work as timing signal, first
By utilizing temperature field that finite element emulation software pre-builds and electromagnetic field couples measurement model to carry out analogue simulation demarcation, obtain
Obtain measurement data and layer thickness relation curve.Replacing solidification layer with the hot steel plate of Varying-thickness again, another kind of hot steel plate replaces solid-liquid
Layer, molten steel is layer liquid, and measured data pass through least-squares algorithm, complete solidified layer thickness and solid-liquid layer measurement data
The correction of matching, it is thus achieved that measure inverting mathematical model.During measurement, it is the most available that measurement data brings measurement inverting mathematical model into
The thickness of continuous casting steel billet green shell.
Further, the casting billet surface being placed on distance continuous cast mold exit of current vortex sensor in described method
2mm position.
Further, in described method, digital frequency synthesizer is AD9959 digital frequency synthesizer.
Further, during parameter in the eddy-current coils of current vortex sensor is arranged in described method, it is actuated to 700HZ
To 12KHZ, inside radius is 12mm, and outer radius is 17mm to 19mm, and height is 4mm, and the former secondary number of turn is 60 circles.
Further, the method for building up of measurement model is to crystallizer exit by finite element emulation software ANSYS
Strand carries out temperature field and is simulated calculating according to formula one and boundary condition, and calculating can show that strand internal temperature gradient divides
Cloth cloud atlas, in conjunction with chemical composition and the computing formula two of solid-liquid phase line temperature of steel grade, it can be deduced that the solidus temperature of steel grade
Value and liquidus, during calculating, strand parameter is:
Crystallizer wall thickness: 20mm, effective length: 1000mm, casting speed: 2 5.5m/min, pouring temperature: 1547 DEG C,
Slab thickness: 50mm.
The coefficient of heat conduction (w/m. DEG C) of λ material, C specific heat (J/Kg. DEG C), ρ density (Kg/m in formula3), τ casts
Base setting time (s), Lf-molten steel solidification latent heat (J/kg).
T l=Tf-∑ Δ T i% (formula two)
In formula: TlFor solid-liquid phase line temperature, TfIt is ferrum not to add 1% element i make fusing point reduce for steel grade fusing point, Δ T
Value.
According to simulation calculation, determine required measurement scope.Selecting measurand is thin plate strand, and slab thickness scope is
20-100 millimeter, shell thickness scope is 5-20 millimeter scope.Electromagnetic property according to metal varies with temperature, continuous cast mold
At lower exit port, base surface temperature is higher than Curie temperature, and when steel is molten into liquid, the characteristic of resistivity generation transition, by steel
Base is corresponding with material temperature according to resistivity, is layered by the strand in continuous cast mold exit.
The process that measurement model carries out in described method emulation demarcation specifically includes:
Step one: use phase place rotation to cut algorithm mutually in MATLAB and three groups of different resistance values are carried out data process；
Step 2: change the thickness of solidified shell layer, the thickness respective change of remaining two-layer, repeat many times of step one,
Multiple-plate nominal data is surveyed to multifrequency；Experiment curv corresponding to different frequency and mathematical model is obtained by method of least square.
Mathematical model such as formula three
Wherein ufiFor measuring the magnitude of voltage that signal phase is corresponding under different frequency.αi,βi,χiBy multi-group data and minimum
Square law obtains, diFor layer thickness.Then solving equations obtains thickness inverse model such as formula four
Step 3: measure substitute measurand with the hot steel plate of known thickness two-layer and molten steel composition shell thickness, only change
The thickness of two-layered steel plates, the thickness of molten steel keeps constant, obtains sensor measurement signal three not with measuring system described in scheme
Amplitude that same frequency is corresponding and phase place, be modified measurement model.
The beneficial effects of the present invention is: multifrequency current vortex technology is applied in continuous casting steel billet thickness measuring by the present invention, and it is excellent
Point be can high temperature, many water smoke continuous casting production environment under, the concreting thickness of non-contacting on-line measurement continuous casting billet, specifically
Be embodied in following some:
1, using high temperature resistant type platypelloid type excitation coil, coil is mutual inductance differential form, and texture of coil is tungsten, insulation
Using the ceramic paint mopping on one side of coiling on one side, the additional water collar of coil can effectively overcome the surface high-temp spoke of continuous casting production scene
Penetrate, the impact of the adverse circumstances such as water smoke environment, guarantee the eddy current coil reliable work in high-temperature metal surface more than 1000 DEG C simultaneously
Make.
2, it is layered according to the resistivity of material corresponding to temperature inside the strand in crystallizer exit first, utilizes
Current vortex multifrequency measurement method obtains shell thickness, makes inside strand more simple and clear, solidified shell thickness measuring can be made more smart
Accurate.
3, finite element emulation software is used, to temperature field analysis in continuous casting billet, it is thus achieved that below crystallizer, shell thickness is measured
Scope.Devise probe coil size, structure and driving frequency scope according to this measurement area requirement, more there is specific aim,
It makes to produce the measurement of high temperature bad border slab thickness at continuous casting, has had the most feasible scheme.
4, use multifrequency multi-layered conductive structure thickness measuring that continuous-cast blank thickness of the shell is measured for the first time so that multifrequency Eddy
Etection theory is applied and is verified in hot environment is put into practice.
Accompanying drawing explanation
Strand cross-section temperature isogram under Fig. 1 pulling rate V=4.5m/min
Fig. 2 is continuous cast mold exit of the present invention strand interior laminate layer schematic diagram.
Fig. 3 is continuous-cast blank multi-layer sheet vortex sensor measuring schematic diagram of the present invention.
Fig. 4 is that thickness of solidified slab shell in secondary electric eddy current measurement device of the present invention arranges schematic diagram.
Fig. 5 is medium frequency of the present invention under 4kHZ encourages, the length of penetration schematic diagram of current vortex.
Fig. 6 is high-temperature probe water collar outline drawing of the present invention.
Fig. 7 is the schematic diagram calculation that finite element emulation software of the present invention is simulated demarcating.
Fig. 8 is thickness and the graph of relation of voltage change under different frequency of the present invention.
Fig. 9 is the measurement system general principles block diagram of the inventive method.
Detailed description of the invention
Below in conjunction with the accompanying drawings the detailed description of the invention of the present invention is illustrated:
The thickness of on-line measurement continuous cast mold exit of the present invention solidified shell, the eddy current coil of the present invention is the company of measurement
The thickness of the solidification strand in casting crystallizer exit, due to the particularity of object, therefore carries out autonomous Design to eddy current coil.?
When strand just goes out continuous cast mold, strand is internal is solid-state district, solid-liquid two-phase region, liquid phase region, and the thickness in these intervals is to be difficult to
Measure.Firstly the need of knowing the scope of shell thickness, according to the scope of measurement design probe and the system of measurement.
By finite element emulation software ANSYS, the strand in crystallizer exit being carried out temperature field according to formula one and is
Row boundary condition is simulated calculating, and calculating can show that strand internal temperature gradient cloud charts is as it is shown in figure 1, combine steel grade
Chemical composition and the computing formula two of solid-liquid phase line temperature, it can be deduced that the solidus temperature values of steel grade and liquidus temperature
Value.During calculating, strand parameter is as shown in table 1.
Table 1
| Crystallizer wall thickness | Effective length | Casting speed | Pouring temperature | Slab thickness |
| 20mm | 1000mm | 2-5.5m/min | 1547℃ | 50mm |
The coefficient of heat conduction (w/m. DEG C) of λ material, C specific heat (J/Kg. DEG C), ρ density (Kg/m in formula3), τ casts
Base setting time (s), Lf-molten steel solidification latent heat (J/kg).
T l=Tf-∑ Δ T i% formula two
In formula: TlFor solid-liquid phase line temperature, TfIt is ferrum not to add 1% element i make fusing point reduce for steel grade fusing point, Δ T
Value.
According to simulation calculation, determine required measurement scope.Selecting measurand is thin plate strand, and slab thickness scope is
20-100 millimeter, shell thickness scope is 5-20 millimeter scope.
Electromagnetic property according to metal varies with temperature, and continuous cast mold lower exit port ejection surface temperature is higher than Curie's temperature
Degree, and when steel is molten into liquid, the characteristic of resistivity generation transition, by corresponding with material temperature according to resistivity for steel billet,
The strand that can make continuous cast mold exit is layered, and institute's established model is as in figure 2 it is shown, 4 be wherein solid-state district, and 5 is solid-liquid two
Phase region, 6 is liquid phase region.
Setting up sensor model on detection object model, institute's established model is as shown in Figure 3.Wherein, R1For coil inside radius,
R2For coil outer radius, D be eddy current coil height, H be lift-off distance, t1Flaggy thickness, t is removed for solid-state2For solid-liquid two-phase region
Thickness, t3Thickness for liquid phase region.Carry out sensor optimization calculating on the mold.
Result of calculation supports that in Fig. 4,1 is tundish by the placement location of current vortex sensor as shown in Figure 4, and 2 is crystallization
Device, 3 is current vortex sensor.Show that, when lift-off distance is for 2mm, vortex density can expire by finite element emulation software ANSYS
Foot measurement requirement.Therefore current vortex sensor 3 is placed on below at continuous cast mold 2 away from casting billet surface 2mm position.
According to particularity and the correlation theory of EDDY CURRENT of measured target, use finite element emulation software and impedance analysis
Eddy current coil is emulated by method, so that eddy current coil can be with the thickness of on-line checking solidified shell and the efficiency of eddy-current coils
Can reach optimum.
In formula, f is the master drive frequency of eddy current coil, and ρ is pcrmeability, and μ is relative permeability, and d is skin depth, and R is line
Circle inside radius.
Eddy-current coils master drive frequency and coil inside radius can be drawn, with above-mentioned two based on formula five, formula six
On the basis of factor, respectively outer radius, height and the number of turn of eddy current coil is carried out finite element stimulation, the knot obtained by calculating
During really data import to MATLAB, it is analyzed processing to it by MATLAB, has finally given being actuated to of eddy-current coils
700HZ to 12KHZ, inside radius is 12mm, and outer radius is 17mm to 19mm, and height is 4mm, and the former secondary number of turn is that 60 circles can obtain
Obtaining maximal efficiency, finite element simulation skin depth is as shown in Figure 5.
The present invention is in order to be applicable to the environment such as continuous casting scene high temperature, many water smokes, and excitation coil coiling used uses high temperature resistant
Tungsten filament and ceramic paint be wound with screw type, the probing shell of sensor uses the metal shell with water-cooled effect, visits
Head shell water-cooled designs as shown in Figure 6.
First use finite element emulation software to be simulated demarcating, then utilize hot steel plate and liquid molten steel that measurement model is entered
Row is revised.
In multi frequency detection, the current vortex sensor signal of three frequency Waveform composition encourages, owing to superposition is former
Winding wire sexual system ought to be used, so the impedance variation of probe is to hinder under each frequency independent drive under hybrid frequency encourages
The linear synthesis of resistance.Its effect controls same probe, then by the output of three instruments with the eddy-current instrument of three platform independent
Addition is the same, therefore when finite element simulation, uses three single frequencies to deactivate coil.
Step one: different driving frequencies can produce different resistance values, three groups of different driving frequencies will produce three
Organize different resistance values, use phase place rotation to cut algorithm mutually in MATLAB and three groups of different resistance values are carried out data process；
Step 2: change the thickness of solidified shell layer, the thickness respective change of remaining two-layer, repeat many times of step one,
Multiple-plate nominal data is surveyed to multifrequency；Experiment curv corresponding to different frequency and mathematical model is obtained by method of least square.
Mathematical model such as formula three
Wherein ufiFor measuring the magnitude of voltage that signal phase is corresponding under different frequency.αi,βi,χiBy multi-group data and minimum
Square law obtains, diFor layer thickness.Only need to obtain the thickness of upper two layers.Then solving equations obtains thickness inverse model as public
Formula four
Use the Computing Principle that finite element emulation software is simulated demarcating as it is shown in fig. 7, in figure, due to casting billet surface temperature
Degree is higher than curie point, relative permeability μiBeing 1, electrical conductivity is corresponding according to temperature, and coil is mutual inductance differential type.Probe coil is joined
Number: r1,r2-probe coil internal diameter and external diameter, (12-l1)-probe length；l1-lift-off；Material electric conductivity: σ1,σ2,…,σm,
σm+1,σm+2；Material relative permeability: μ1,μ2,…,μm,μm+1,μm+2Each layer intersection z direction is sat: z1,z2,…,zm,z1+m,zi
=-(dm+dm-1,…di+2+di+1), i=1,2,3 ... m-1, dm+dm-1,…di+2+di+1The thickness of-each layer.
Step 3: measure substitute measurand with the hot steel plate of known thickness two-layer and molten steel composition shell thickness, only change
The thickness of two-layered steel plates, the thickness of molten steel keeps constant, obtains sensor measurement signal three not with measuring system described in scheme
Amplitude that same frequency is corresponding and phase place, be modified measurement model, thickness and change in voltage under the different frequency finally given
The relation curve of value is as shown in Figure 8.
The thickness schematic diagram of eddy current coil on-line measurement solidified shell of the present invention, as shown in Figure 9.It is encouraged by multiple-frequency signal
Source AD9959, eddy current probe coil, signal processing circuit, correlator, signals collecting and conversion and computer composition.
Current vortex sensor needs three different driving frequencies to encourage test coil of eddy current simultaneously.Therefore, by
The pumping signal of the three road different frequencies that AD9959 produces must be mixed by adder, thus meets multifrequency simultaneously to whirlpool
Stream detection coil encourages, and the design uses the circuit of summation operation in the same direction of principle of stacking to complete the mixed of different frequency signals
Frequently.
Measuring simple signal excitation for shell thickness cannot realize, traditional Impedance Analysis can only suppress one
Interference factor.Therefore, it is desirable to the information obtaining more examined workpiece needs to encourage current vortex sensor by multiple frequencies.
Three layers of conductive structure thickness measure are then needed the sinusoidal signal mixing frequency excitation mode of three different frequencies, and must assure that each
Pumping signal can pass through shell thickness, therefore uses three quadricorrelators the eddy current of frequency alias can be responded signal and is wrapped
The information contained separates, and obtains the direct current signal under single frequency excitation.
The thickness of on-line measurement solidified shell of the present invention is such being measured: in continuous cast mold exit distance
Placing above-mentioned current vortex sensor at casting billet surface 2mm, current vortex sensor carries out mixing by AD9959 and excites, and three are not
With frequency be mixed by adder, measurement end signal, through the amplification of signal conditioning circuit, filtering, enters in the correlator
The computing cross-correlation of row, it is achieved that the separation of different frequency signals and the width of eddy current impedance signal are separated, and separate
Signal is acquired and changes, and is finally transferred to computer and carries out the process of data.
Form shell thickness with the hot steel plate of known thickness two-layer and molten steel and measure replacement measurand, sense with described in Fig. 9
Device and measurement system obtained data.Carry out the data processed at computer, the measurement model that emulation is demarcated in advance be modified,
Obtain practical measurement model.
When measuring, the sensor and measurement system acquisition measured value are brought measurement model into and can be calculated solidified shell thickness
Degree.When steel grade changes, need to re-scale.
In order to improve certainty of measurement, in steel billet, layering can be segmented further, but measure frequency and need to add more multi-frequency, measures
Speed will reduce.This problem needs compromise to consider at timing signal.
The above is the preferred embodiment of the present invention, it is noted that for those skilled in the art
For, on the premise of without departing from principle of the present invention, it is also possible to make some improvements and modifications, these improvements and modifications are also
Should be regarded as protection scope of the present invention.
Claims (7)
1. a continuous casting steel billet shell thickness eddy current detection method, it is characterised in that described method is: go out at continuous cast mold
Casting billet surface at Kou places current vortex sensor, and sensor is mutual inductance differential type, and current vortex sensor is closed by numerical frequency
Growing up to be a useful person and carry out mixing and excite, three the different frequency signals excited are mixed by adder, measure signal through signal
The amplification of modulate circuit, filtering, in three correlators, reference signal with three different frequencies carries out computing cross-correlation respectively,
By Signal separator and carry out the width of eddy current impedance signal and be separated, the signal separated is acquired and conversion, is transferred to calculate
Machine carries out the process of data, and the data procedures of computer disposal is as follows: work as timing signal, first passes through and utilizes finite element emulation software
The temperature field and the electromagnetic field couples measurement model that pre-build carry out analogue simulation demarcation, it is thus achieved that measurement data and layer thickness relation
Curve, then replace solidification layer with the hot steel plate of Varying-thickness, another kind of hot steel plate replaces solid-liquid layer, and molten steel is layer liquid, measured
Data by least-squares algorithm, complete solidified layer thickness and the correction of the matching of solid-liquid layer measurement data, it is thus achieved that measure
Inverting mathematical model, during measurement, measurement data is brought measurement inverting mathematical model into and i.e. be can get the thickness of continuous casting steel billet green shell.
2. continuous casting steel billet shell thickness eddy current detection method as claimed in claim 1, it is characterised in that electricity in described method
The casting billet surface 2mm position being placed on distance continuous cast mold exit of eddy current sensor.
3. continuous casting steel billet shell thickness eddy current detection method as claimed in claim 1, it is characterised in that number in described method
Word frequency synthesizer is AD9959 digital frequency synthesizer.
4. continuous casting steel billet shell thickness eddy current detection method as claimed in claim 1, it is characterised in that in described method
The parameter of the eddy-current coils of current vortex sensor is set to, and is actuated to 700HZ to 12KHZ, and inside radius is 12mm, and outer radius is
17mm to 19mm, height is 4mm, and the former secondary number of turn is 60 circles.
5. continuous casting steel billet shell thickness eddy current detection method as claimed in claim 1, it is characterised in that survey in described method
The method for building up of amount model is, by finite element emulation software ANSYS, the strand in crystallizer exit is carried out temperature field according to public affairs
Formula one and boundary condition are simulated calculating, and calculating can draw strand internal temperature gradient cloud charts, in conjunction with the change of steel grade
Study point and the computing formula two of solid-liquid phase line temperature, it can be deduced that the solidus temperature values of steel grade and liquidus, meter
During calculation, strand parameter is:
Crystallizer wall thickness: 20mm, effective length: 1000mm, casting speed: 2 5.5m/min, pouring temperature: 1547 DEG C, strand
Thickness: 50mm,
The coefficient of heat conduction of λ material in formula, unit: w/m. DEG C, C is than heat unit: J/Kg. DEG C, ρ density unit: Kg/m3,
τ casting blank solidification unit of time: s, Lf-molten steel solidification latent heat unit: J/kg,
Tl=Tf-∑ Δ T i% formula two
In formula: TlFor solid-liquid phase line temperature, TfIt is ferrum not to add 1% element i make fusing point decreasing value for steel grade fusing point, Δ T,
According to simulation calculation, determining required measurement scope, selecting measurand is thin plate strand, and slab thickness scope is 20-
100 millimeters, shell thickness scope is 5-20 millimeter scope, varies with temperature according to the electromagnetic property of metal, under continuous cast mold
Side's exit base surface temperature is higher than Curie temperature, and when steel is molten into liquid, the characteristic of resistivity generation transition, by steel billet
Corresponding with material temperature according to resistivity, the strand in continuous cast mold exit is layered.
6. continuous casting steel billet shell thickness eddy current detection method as claimed in claim 5, it is characterised in that right in described method
Measurement model carries out the process of emulation demarcation and specifically includes:
Step one: use phase place to rotate the three groups of different resistance values to corresponding three frequencies that cut algorithm mutually in MATLAB and carry out
Data process,
Step 2: changing casting speed, the thickness of solidified shell changes therewith, and the thickness of remaining two-layer consequently also becomes, repeats step
Rapid one, obtain multifrequency and survey multiple-plate calibration curve.
7. continuous casting steel billet shell thickness eddy current detection method as claimed in claim 6, it is characterised in that use in described method
The hot steel plate of known thickness and molten steel composition shell thickness are measured and are substituted measurand, only change the thickness of steel plate, the thickness of molten steel
Keep constant, measurement model is modified.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107063142A (en) * | 2017-05-04 | 2017-08-18 | 盐城工学院 | A kind of sheet billet continuous casting thickness of solidified slab shell in secondary detecting system |
| CN112179261A (en) * | 2020-09-24 | 2021-01-05 | 桂林理工大学 | Method for detecting thickness of steel rail decarburized layer based on electromagnetic response |
| JPWO2022034864A1 (en) * | 2020-08-12 | 2022-02-17 | ||
| CN115994461A (en) * | 2022-11-29 | 2023-04-21 | 北华航天工业学院 | Finite element simulation method for influence of defects on impedance in magnetic leakage-vortex composite detection |
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