CN104197858A - Method for quantitatively describing topographic characteristics of solidification structures of variety steel continuous casting billet - Google Patents
Method for quantitatively describing topographic characteristics of solidification structures of variety steel continuous casting billet Download PDFInfo
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- CN104197858A CN104197858A CN201410457276.2A CN201410457276A CN104197858A CN 104197858 A CN104197858 A CN 104197858A CN 201410457276 A CN201410457276 A CN 201410457276A CN 104197858 A CN104197858 A CN 104197858A
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Abstract
The invention discloses a method for quantitatively describing topographic characteristics of solidification structures of a variety steel continuous casting billet. According to the method, the cross section of the variety steel continuous casting billet is subjected to hot pickling, with hydrochloric acid solution having a 1:0.5-1.5 volume ratio at the temperature of 60 DEG C to 80 DEG C for 5-35 minutes; a high-definition digital camera is used for taking a picture of overall appearance; more than one measurement point is selected from the picture of overall appearance to obtain typical solidification structure of each point; fractal dimension of each of different types of solidification structures is calculated by a box-counting method or/and a perimeter-area method in the fractal theory so as to quantitatively describe the topographic characteristics of the variety steel continuous casting billet. The method has the advantages that the topographic characteristics of the solidification structures of the continuous casting billet are more elaborately indicated, and the higher the fractal dimension, the higher the complexity of the appearance of grains and the higher self-similarity level of the grains; the topographic characteristics of the solidification structures in different areas of the continuous casting billet can be comprehensively compared; better correlation with internal quality and defects of the continuous casting billet can be achieved.
Description
Technical field
The present invention relates to metallurgical engineering technical field, relate in particular to a kind of new method of describing variety steel continuous casting billet Solidification Microstructure Morphology feature.
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Background technology
The solidified structure of variety steel continuous casting billet has reflected the architectural feature that it is overall, and therefore it has relation closely with the quality of continuous casting billet and final products.According to the pattern feature of crystal grain, the solidified structure of continuous casting billet is divided into these three regions of chill, columnar zone and equiax crystal district conventionally.How the feature of accurate description zones of different solidified structure just becomes research, controls and optimizes their basis.Forefathers are mainly the ratio by equiax crystal to this, and intercrystalline distance and subgrain spacing reflect the architectural feature of solidified structure.Meanwhile, also represent the different quality of continuous casting billet by the size of these indexs.For example, think that proportion of equiaxed grain is larger, intercrystalline is apart from less, and the quality of continuous casting billet is more even, and segregation is lower with the degree of defects such as loosening.But practice finds that this relation there will be deviation often.The quality of product is not that proportion of equiaxed grain is the bigger the better, and defect level is not with all present negative correlativing relation between intercrystalline distance always yet, and the intercrystalline of dissimilar solidified structure is apart from also often can not directly contrasting.Meanwhile, although equiax crystal has isotropic feature, the size of its overall ratio might not just reflect the pattern feature of this each crystal grain of region, also just can not effectively reflect its degree of uniformity and compactness extent.The inner segregation of strand is relevant with intercrystalline distance to the degree of defects such as loosening, but intercrystalline is apart from just from the compactness extent apart from this angle reflection intergranule, can not comprise the shape characteristic of crystal grain.In fact, segregation is all to form on the basis of solidified structure with the defect such as loose, and therefore the each side pattern of crystal grain has direct impact for the defect rank of strand.In addition, (the two inner crystal grain is all equiax crystal for the pattern relative equiax crystal district of columnar zone crystal grain and chill, but pattern difference) be anisotropic, if do not rely on actual die pattern feature and random to its spacing contrast be also certain to lose biased.Therefore, be just necessary very much to adopt a kind of more careful with comprehensively, more representational method describes the shape characteristic of continuous casting billet solidified structure.The present invention introduces this new method of fractal dimension to realize better the quantitative description to variety steel continuous casting billet Solidification Microstructure Morphology.
B.B. Mandelbrot has proposed the whole concept of fractal geometry first in 20 century 70s, and fractal dimension is one of them basic concept.These new ideas are mainly complexity and the self similarity degree for weighing complex figure.In general, fractal dimension is larger, and the complexity of figure and self similarity degree are also larger.At present, this thought has been applied to a lot of fields and has accomplished tangible results.The present invention is applied to the quantitative description to the dissimilar Solidification Microstructure Morphology of variety steel continuous casting billet by this concept and computing method first.
Summary of the invention
For existing methodical deficiency, object of the present invention is mainly to provide a kind of new method that not only can describe solidification morphology feature and can set up with slab quality relevance.
To achieve these goals, the present invention has adopted following technological means:
A new method of describing variety steel continuous casting billet Solidification Microstructure Morphology feature, comprises the following steps:
(1) wash the overall pattern of the solidified structure that obtains variety steel continuous casting billet by hot acid: hot acid is washed the aqueous hydrochloric acid solution (technical hydrochloric acid) that middle acid solution volumetric ratio is 1:0.5-1.5, and acid etching temperature is 60 DEG C to 80 DEG C, and etching time is 5-35min.After hot acid is washed, utilize high-definition digital camera to take pictures, obtain the overall pattern of continuous casting billet solidified structure;
(2) taking pictures on the overall shape appearance figure obtaining, in chill, column crystal and three regions of equiax crystal, respectively choose more than one measurement point, obtain typical solidified structure crystal grain; Choose the typical solidified structure of zones of different (chill, column crystal and equiax crystal): choose the typical solidified structure crystal grain of sufficient amount in zones of different from overall pattern, obtain the typical solidified structure of this point.
(3) utilize fractal dimension to be quantitatively described the pattern of dissimilar solidified structure: to utilize several box methods in fractal theory or/and girth area-method is calculated the fractal dimension of dissimilar solidified structure, and carry out the shape characteristic of the different solidified structures of quantitative description with this;
(4) described several box methods are calculated fractal dimension, use the pattern of the single solidified structure of square box sub-covering of these two kinds of different length of sides of S1 and S2, and calculate the wherein box number of " non-NULL " (N1 and N2) respectively.Then utilizing formula D=(lgN1-lgN2)/(lgS2-lgS1)+1 this equation obtains the fractal dimension D of Solidification Microstructure Morphology.
(5) described girth area-method is calculated fractal dimension, first measure respectively girth (P) and the area (A) of multiple similar Solidification Microstructure Morphologies, then taking lgA as horizontal ordinate, make scattergram taking lgP as ordinate, and by the linear fit of different pieces of information point in figure being obtained to its slope (S).Finally utilize this equation of formula D=2 × S+1 to obtain the fractal dimension D of the Solidification Microstructure Morphology in observed region.
Than existing method, the present invention has following beneficial effect:
(1) can be more careful and the pattern feature of quantitative response continuous casting billet solidified structure all sidedly.Fractal dimension is larger, and pattern complexity and the self similarity degree of crystal grain are higher.
(2) contrast that the pattern feature of continuous casting billet zones of different solidified structure can be combined.Because fractal dimension itself has just comprised the pattern feature of crystal grain self.
(3) can better be associated with internal soundness and the defect of continuous casting billet.Continuous casting billet defect is closely related with the pattern feature of solidified structure crystal grain.Due to fractal dimension can more careful and comprehensive reflection crystal grain pattern, therefore just can utilize this new method better to study the relation of continuous casting billet quality with solidified structure.Under condition of the same race, fractal dimension is larger, solidified structure more evenly, finer and close, defect occurrence degree is lower.
Brief description of the drawings
Fig. 1 is the solidified structure of actual variety steel continuous casting billet;
Fig. 2 is the fractal dimension of zones of different solidified structure in Fig. 1;
Fig. 3 is the graph of a relation of fractal dimension and defect rank.
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Embodiment
Embodiment:
1) utilize hydrochloric acid water (technical hydrochloric acid) solution that acid solution volumetric ratio is 1:0.5-1.5 to carry out hot acid to the transversal section of variety steel continuous casting billet and wash experiment, acid etching temperature is the scope of 60 DEG C to 80 DEG C, and etching time is 5-35min; After hot acid is washed, utilize high-definition digital camera to take pictures, obtain the overall pattern of this transversal section continuous casting billet solidified structure; As shown in Figure 1.Because the different compositions of continuous casting billet differ to the extent of reaction of acid etching solution, therefore after pickling, the Solidification Microstructure Morphology of continuous casting billet transversal section will be presented; Be convenient to the photo of shooting clear and choose afterwards measurement point.
2) solidified structure in Fig. 1 is made up of three different regions of chill, column crystal and equiax crystal, and outside is chill region, when cooling, contact with continuous cast mold madial wall, and quick heat radiating, cooling, and form chill; Chill inner side is column crystal region, and column crystal inner side (nucleus that mediates belongs to last cooling region) forms equiax crystal region.Taking pictures on the overall shape appearance figure obtaining, in chill, column crystal and three regions of equiax crystal, respectively choose more than one measurement point, obtain the typical solidified structure crystal grain of these measurement points, obtain the typical solidified structure of this measurement point.In figure, in these three regions, select altogether eight different location points (as shown in Figure 2).(1) wherein number belongs to chill region with (8) number, and (2) belong to column crystal region with (7), and (3) to (6) belong to equiax crystal region.Then, choose respectively the typical solidified structure crystal grain of sufficient amount from these eight location points.
3) utilize respectively the several box methods in fractal theory or/and eight diverse locations of girth area-method calculating are put the fractal dimension of typical solidified structure crystal grain, calculate respectively corresponding fractal dimension; If adopt number box method and girth area-method to calculate, the calculated value of two kinds of methods averaged simultaneously.By the overall shape appearance figure obtaining of taking pictures is processed, utilize computer program just can identify each typical solidified structure crystal grain (measurement point) of choosing according to the step and method of setting, then obtain the correlation parameter of this typical case's solidified structure crystal grain, and correlation parameter can be brought into several box methods or/and girth area-method, thereby calculate the fractal dimension of each typical solidified structure crystal grain.The computer program that the method is used in conjunction with, is not innovative point of the present invention, and those skilled in the art can work out this program as required, therefore be not described further at this.Finally as calculated average result as shown in Figure 3, the fractal dimension D of equiax crystal is in 2.6 to 2.9 scope in chill, in equiax crystal region, the fractal dimension of equiax crystal is larger in 2.1 to 2.7 scope and fluctuation, and in column crystal region, the fractal dimension of crystal grain is in 2.8 to 3.0 scope.
4) Fig. 3 is the relation of eight diverse location point defect grades and fractal dimension.Visible, the two becomes good negative correlation.
Several box method of the present invention, it calculates fractal dimension, covers the pattern of single solidified structure with the box (square) of these two kinds of different length of sides of S1 and S2, and calculates the wherein box number of " non-NULL " (N1 and N2) respectively.Then utilizing formula D=(lgN1-lgN2)/(lgS2-lgS1)+1 this equation obtains the fractal dimension D of Solidification Microstructure Morphology.
Described girth area-method of the present invention, it calculates fractal dimension, first measure respectively girth (P) and the area (A) of multiple similar Solidification Microstructure Morphologies, then taking lgA as horizontal ordinate, make scattergram taking lgP as ordinate, and by the linear fit of different pieces of information point in figure being obtained to its slope (S).Finally utilize this equation of formula D=2 × S+1 to obtain the fractal dimension D of the Solidification Microstructure Morphology in observed region.
The present invention, utilizes this new quantitative description to weigh complexity and the self similarity degree of Solidification Microstructure Morphology.Can better be associated with internal soundness and the defect of continuous casting billet.Continuous casting billet defect is closely related with the pattern feature of solidified structure crystal grain.Due to fractal dimension can more careful, more representational reflection crystal grain pattern, therefore just can utilize this new method better to study the relation of continuous casting billet quality with solidified structure.Under condition of the same race, fractal dimension is larger, solidified structure more evenly, finer and close, defect occurrence degree is lower.
Several box methods (BOX-COUNTING METHOD) that the present invention adopts are a kind of practical approaches of conventional calculating fractal graph point dimension; Get the etui that the length of side is r and (can be understood as the etui that topological dimension is d, cover fractal, because there are various levels of cavity and gap in fractal inside, therefore some etui is empty, some etui has covered a fractal part, and it is not empty calculating how many etuis, and " non-NULL " of gained (non-empty) box number scale is N(r), then dwindle the size r of box, gained N(r) naturally increase; When, r → 0 o'clock, obtains the fractal dimensionality dependence that several box methods define.The present invention adopts girth area-method (PERIMETER-AREA METHOD), is a kind of practical approach of conventional calculating fractal graph point dimension, and it just can calculate after obtaining the girth of different solidified structures and area.For several box methods and girth area-method, be a kind of prior art, be also a kind of ripe theoretical, specifically can consult " fractal geometry ", Earthquake Press publishes for 2005, and old Yong, Chen Ling write.
Finally explanation is, above embodiment is only unrestricted in order to technical scheme of the present invention to be described, although the present invention is had been described in detail with reference to preferred embodiment, those of ordinary skill in the art is to be understood that, can modify or be equal to replacement technical scheme of the present invention, and not departing from aim and the scope of technical solution of the present invention, it all should be encompassed in the middle of claim scope of the present invention.
Claims (1)
1. a method for quantitative description variety steel continuous casting billet Solidification Microstructure Morphology feature, is characterized in that, comprises the following steps:
(1) wash the overall pattern of the solidified structure that obtains variety steel continuous casting billet by hot acid: it is that the aqueous hydrochloric acid solution of 1:0.5-1.5 carries out hot acid to the transversal section of variety steel continuous casting billet and washes that hot acid is washed middle volumetric ratio, acid etching temperature is the scope of 60 DEG C to 80 DEG C, and etching time is 5-35min; After hot acid is washed, utilize high-definition digital camera to take pictures, obtain the overall pattern of continuous casting billet solidified structure;
(2) taking pictures on the overall shape appearance figure obtaining, in chill, column crystal and three regions of equiax crystal, respectively choose more than one measurement point, obtain the typical solidified structure of this point: by choose the typical solidified structure crystal grain of sufficient amount in three regions from overall pattern, obtain the typical solidified structure of this point;
(3) utilize fractal dimension to be quantitatively described the pattern of dissimilar solidified structure: to utilize several box methods in fractal theory or/and girth area-method is calculated the fractal dimension of dissimilar solidified structure, and carry out its shape characteristic of quantitative description with this;
Described several box methods, it calculates fractal dimension, uses the pattern of the single solidified structure of square box sub-covering of these two kinds of different length of sides of S1 and S2, and calculates the wherein box number of " non-NULL " respectively, obtains N1 and N2 numerical value;
Then utilizing formula D=(lgN1-lgN2)/(lgS2-lgS1)+1 this equation obtains the fractal dimension D of Solidification Microstructure Morphology;
Described girth area-method, it calculates fractal dimension, measures first respectively girth (P) and the area (A) of multiple similar Solidification Microstructure Morphologies, then taking lgA as horizontal ordinate, make scattergram taking lgP as ordinate, and by the linear fit of different pieces of information point in figure being obtained to its slope (S); Finally utilize this equation of formula D=2 × S+1 to obtain the fractal dimension D of the Solidification Microstructure Morphology in observed region.
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Cited By (2)
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| CN109425319A (en) * | 2017-08-25 | 2019-03-05 | 宝山钢铁股份有限公司 | A method of detection acid cleaning process is to lateral section influence degree |
| US10782244B2 (en) | 2016-09-22 | 2020-09-22 | SSAB Enterprises, LLC | Methods and systems for the quantitative measurement of internal defects in as-cast steel products |
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