Title of Invention

A METHOD OF ASSESSMENT OF CLEANLINESS LEVEL OF CONTINUOUSLY CAST STEEL BY AN AUTOMATIC ULTRASONIC IMMERSION C-SCAN IMAGE ANALYSIS

Abstract

This invention relates to a method of assessment of cleanliness level of continuously cast steel by an automatic ultrasonic immersion C-scan image analysis in pixel for ensuring physical and mechanical properties of finished macro inclusion free clean steel products comprising the steps of preparing cylindrical cast sampler by a sampler device on plunging it deeper into the liquid steel from Laddie Furnace as well as from Tundish, cutting and grounding the samples to mirror finish with appropriate thickness and parallel faces; employing ultrasonic scanning in immersion tank with water specimen and the scanner using 5 megahertz (a unit of frequency which is equal to one million hertz) (MHz) and 10 megahertz (a unit of frequency which is equal to one million hertz) (MHz) focused beam probe on the mirror finish face of the samples with incremental distances small increment in x axis and y-axis respectively (Ax + Ay = 0.2 mm through C - scan data acquisition and analysis software developed for the purpose; finding out correlation between total oxygen in parts per million (ppm) and ultrasonic counts, a combination of ferrous oxide and manganese oxide (FeO + MnO) in slag and ultrasonic counts, number of heats in Tundish and ultrasonic counts, sequence number of heats in tundish and ultrasonic counts of various backscattered signal amplitudes of 0.4 - 05 (a.u) on arbitrary scale and various pixel sizes of the C-scan images using 5 megahertz (a unit of frequency which is equal to one million hertz)(MHz), 15 mm dia samples from caster and RH degasser sample, finding out correlation between total oxygen in parts per million (ppm) and ultrasonic counts in arbitrarily scale and various pixel sizes of the C-scan image using 5 megahertz (a unit of frequency which is equal to one million hertz) (MHz), 15 mm dia samples from caster and RS degasser sample; finding out correlation between total oxygen in parts per million (ppm) and ultrasonic counts in categorized 3 levels, using 10 megahertz (a unit of frequency which is equal to one million hertz) (MHz), 15 mm dia samples from tundish; preparing bar chart in ultrasonic counts with varying total oxygen in parts per million (ppm) in samples of 3 levels from both caster and RH degasser; categorizing inclusion severity levels into 8 levels according to 8 levels of backscattered signal amplitudes on preparing ultrasonic counts related with cleanliness severity level for RH degassed and caster samples to find out in various pixel sizes inclusion size groups and thus determining inclusion removal of steel in RH degasser and caster samples from correlated total oxygen, ultrasonic counts, backscattered amplitude, number of heats in tundish and sequence number in tundish.

Full Text

FIELD OF INVENTION The present invention relates to a method to assess cleanliness level of continuously cast steel by an automatic ultrasonic immersion c - scan image analysis. More specifically the present invention relates to assessment of non-metallic inclusions / pores, pinholes / blow holes, segregation etc. in continuously cast steel. BACKGROUND OF THE INVENTION In recent years, there has been a tremendous increase in the production of continuously cast steel, since the process of continuous casting is a faster method of steel casting from liquid steel at reduced production cost when compared with the conventional ingot route of casting. However, at the same time, more attention has been paid to improve product quality with respect to overall cleanliness level in order to improve reliability of the finished products, which has led to production of continuously cast product of high quality. A clean steel greatly affect many physical and mechanical properties like fatigue life, machinability and corrosion resistance. Superclean steel with respect to macroscopic oxide inclusions are a prerequisite for improved surface finish and prolonged lifetime of components as well as for the application of increasingly stringent forming processes. Presence of macro-inclusions can generate sliver defects during cold rolling for thinner gauge steel strips and can also become the reason for wire breakage during wire drawing for very thin sections. Traditional methods of measuring cleanliness level of steel is to measure its total oxygen which does not provide information about the size, location and distribution of more harmful macro-inclusions. Without the complete knowledge of such inclusions, quality control and process improvements can hardly be achieved. In order to achieve clean steel, steel producers have invested their major capital into metallurgical facilities. The process improvements made" due to installation of such facilities must be backed up by a reliable steel cleanliness evaluation technique. It is a common practice in most of the steel plants to measure Total Oxygen in steel samples as an indicator of cleanliness level in steel. However, in this technique very small quantity of sample is required which is not sufficient to assure the whole lot of heat. At the same time, sample preparation also takes a lot of time and corrective actions are delayed. Most of the total oxygen content in steel as measured by chemical methods is present in the form of non-metallic inclusions. The backscattered signals from these inclusions can be quantified in numbers and can be correlated with Total Oxygen content of steel. The present invention relates to correlations found using an ultrasonic technique using X' scan automatic immersion system with image analysis software to assess cleanliness level in continuously cast steel samples taken by a special sampler from liquid steel containers like ladles/tundishes/moulds etc. This technique provides larger volume inspection (compared with total oxygen and optical microscopic measurements to assess cleanliness in steel samples) and information about the steel defects like non-metallic inclusions/pores etc. in cast solidified samples taken from containers holding liquid steel using specific sampler. The back-scattered signals from non-metallic inclusions/pores etc. are displayed as echoes in 'A' scan with different amplitudes depending on their sizes and locations. A large number of 'A' scan data produces 'C scan display when the sample is scanned in both X and Y directions with specific incremental distances in these directions for capturing and storing them for further amplitude/image analysis with the help of an image analysis software. Good correlations were found between the counts of ultrasonic back scattered signals from non-metallic inclusions/pores etc of amplitudes beyond a threshold value and Total Oxygen content of steel during scanning the sample with specific incremental distances AX and AX equal to 0.2 mm. Using 15 mm diameter focused beam probe of frequencies 5 and 10 MHz, these correlations were developed. The correlations between ultrasonic counts and Total Oxygen were found to be better in case of 10 MHz frequency when compared with that of 5 MHz frequency. These ultrasonic counts were found to be well correlated with the number of heats cast through BOF vessels, Sequence No. of heats poured into the Tundish and Feo+MnO content of the LF slag using 5 MHz focused beam probe. Presence of non-metallic inclusions / cracks, pin holes/blow holes, segregation etc. makes the continuously cast product inferior in quality. The sources of non- metallic inclusions in continuously cast steels are listed below : A. Exogeneous Inclusions originate owing to the following reasons: • Entrapment of slag • Entrapment of mould powder • Wear of ladle refractories etc. B. Endogeneous Inclusions originate owing to the following reasons: • Entrapment of deoxidation products • Oxidation of metal stream if it is not shrouded Steel producers are making efforts continuously to improve the steel making processes in order to reduce these inclusions. The following processes are being adopted to achieve this objective in continuous casting of steel slabs. 1. Secondary Metallurgy • Tapping technique and ladle treatment • RH (Ruhrsthat Heraeus) degassing and Ca treatment • Titanium deoxidation 2. Tundish Metallurgy • Tundish size, steel level and mode of operation • Flow control devices in Tundish • Start of casting and ladle change 3. Submerged Entry Nozzles (SEN) and Mould • Flow of metal in mould • SEN variants • Electro Magnetic Breaks (EMBR) • Sequence length 4. Geometry of Continuous Slab Casters • Influence of the vertical segment. The effectiveness of these process changes in order to improve the steel cleanliness should be measured very carefully. The following methods have been used to assess non-metallic inclusions and other flaws in CC steel: 1. Visual Inspection of Macro-etch 2. Sulphur Print Evaluation 3. Magnetic Particle Inspection 4. Dye Penetration Test 5. Total Oxygen Measurement 6. Insoluble Aluminium Analysis 7. Microscopic Evaluation 8. Radioactive labeling 9. Eddy Current 10. Ultrasonic Testing The methods 1 and 2 are the most common methods which are followed by many steel producers. These methods require consumption of chemicals (acids) which pollutes the environment with more hazardous fumes. Visual interpretations of the results are prone to human errors. Sulphur print evaluation and etching has problems with low sulphur heats. Moreover, the results of these two methods are confined to the XY plane only and through thickness volumetric information is missing. Methods 3, 4 and 9 are conventional NDT (Non Destructive Testing) methods which are again confined to surface/subsurface only. In method 8 hazardous radioactive elements need to be handled. The information generated through this process is limited to the surface. Methods 5 and 6 involve chemical analysis methods in which small size samples are taken from liquid steel. However, this method does not provide accurate information in the solidified steel (distribution and location wise). Microscopic evaluation methods examine a very small spot on the sample surface. This method is time consuming, tedious and requires a large number of samples for accurate judgment. Moreover, chances of missing macro-inclusions are high. These are more detrimental than micro-inclusions. The inclusions generally detected in this case are in micro levels. Many steel plants follow Mannesman Inclusion Detection 'MIDAS' method for quantifying macro-inclusions using ultrasonic 'C scan immersion technique. This method needs special cross hot rolling of the samples cut from the cast slabs. Sample preparation takes a lot of time and the results are delayed. The present invention is mainly focused on developing a method using ultrasonic "C scan image analysis for correlating counts of ultrasonic back scattered signals from non-metallic inclusions/pores etc having amplitudes beyond a threshold value with Total Oxygen content of steel. Unlike 'MIDAS' method, steel samples are the cast samples taken from the Ladles/Tundishes/Moulds containing liquid steel. These samples need not require rolling or forging and can be prepared within short time; only cutting, grinding or polishing is required with both flat surfaces parallel. Some good correlations have also been shown between ultrasonic counts and (Feo+Mno) in slag; ultrasonic counts and Seq. No. of Heats in Tundish etc. OBJECTIVE OF THE INVENTION Objective of the invention are: • To develop an improved method of assessing cleanliness level in steel (particularly macro-inclusions) using Ultrasonic 'C scan image analysis software. • To find correlation between the ultrasonic parameter (ultrasonic counts) using computer controlled Automatic 'C' Scan Immersion and Image Analysis System and Total Oxygen content of steel, thus replacing Total Oxygen measurement in steel samples as a measure of steel cleanliness on obtaining good correlation between ultrasonic counts. • To develop an improved method of assessing cleanliness level in steel (particularly macro-inclusions) using 'Ultrasonic 'C' scan image analysis software. • To find correlation between the ultrasonic parameter (ultrasonic counts) using computer controlled Automatic 'C' Scan Immersion and Image Analysis System and the factors responsible for making steel dirty like, Seq.no. of heats in tundish, No. of heats poured in Tundish and FeO+MnO in slag etc. so that corrective actions can be taken to improve cleanliness level in steel. • To ensure cleanliness level in larger volume of steel at faster speed with quick corrective actions. • To replace Slime Extraction method of macro-inclusion detection and measurement in steel, followed in some steel plants which is a very long time taking process. • To help operational people to reduce non-metallic inclusions in "steel and hence reduction in some of the rolling defects like slivers in auto grade of steels like IF grade and wire breakages during wire drawing to very thin cross sections due to presence of macro-inclusions. • To ensure the products sent to the customers free from harmful macroinclusions which may cause further processing problems at their end. The present invention has overcome the drawbacks of earlier methods for cleanliness assessment in steel samples. The special features of the proposed invention are quick and large volume inspection and ability to catch macro- inclusions which are really troublesome in further processing of the thin gauge products. BRIEF DESCRIPTION OF THE ACCOMPANYINGDRAWINGS Figure 1 shows photographs of Ultrasonic 'C' Scan Image Analysis System showing (a) Multi-axis (X,Y and Z) Scanner, (b) Pulser Receiver Model 5800, (c) Computer display of TV scan signals and X' scan coloured image. Figure 1(d) represents in schematic diagram showing experimental set up of immersion tank with specimen, transducer, scanner, pulser receiver and PC Data acquisition system. Figure 2 shows correlation between ultrasonic counts and total oxygen, ppm'at 5 MHz Figure3 shows correlation between ultrasonic counts and (FeO+MnO) % in slag at 5 MHz Figure 4 shows correlation between ultrasonic counts and no. of heats poured in tundish at 5 MHz Figure 5 shows correlation between ultrasonic counts and sequence no. of heats poured poured in tundish at 5 MHz Figure 6 shows correlation between ultrasonic counts and total oxygen, ppm at 10 MHz for the back scattered signals amplitudes 1.1-1.2 (a.u.) Figure 7 shows correlation between ultrasonic counts and total oxygen, ppm at 10 MHz for the back scattered signals amplitudes 0.55-0.65 (a.u) Figure 8 shows correlation between ultrasonic counts and total oxygen, ppm at 10 MHz for the back scattered signals amplitudes 0.40-0.50 (a.u.) Figures 9 to 12 shows the decreasing trend of ultrasonic counts with decrease in total oxygen, ppm in both RH and caster samples. Figure 13 shows the defects/macro-inclusions size distributions in terms of pixels as recorded in *C scan image or the caster as well as RH samples with different total oxygen content. Figures 14 to 19 shows the typical ultrasonic X' scan coloured images indicating increase in ultrasonic counts at 5 MHz with increase in no. of heats made in BOF vessel, sequence no. of heats in tundish, no of heats poured in tundish, FeO+MnO in slag and total oxygen in RH and caster samples. Figure 20 shows an example of cleanliness improvement in caster samples when compared with RH samples using present method of cleanliness assessment based on 8 different amplitude levels at 5 MHz ultrasonic frequency. Figure 21 shows an example of pick up of macro-inclusions in caster samples when compared with RH samples using present method of cleanliness assessment based on 8 different amplitude levels at 5 MHz ultrasonic frequency. Figure 22 shows an example of cleanliness improvement in caster samples when compared with RH samples using present method of cleanliness assessment based on inclusion sizes with area range (0.04-0.12 mm2) at 5 MHz ultrasonic frequency. Figure 23 shows an example of pick up of macro-inclusions in caster samples when compared with RH samples using present method of cleanliness assessment based on inclusion sizes with area range (0.04-0.12 mm2) at 5 MHz ultrasonic frequency. Figure 24 shows a typical ultrasonic 'C scan image of a RH degassed sample. Pink colour spots with amplitude 1.0-2.0 (a.u) indicates visible inclusions in the image. Figure 25 shows a typical ultrasonic XC scan image of a caster sample. Different amplitudes of the backscattered signals are displayed by different colours. DETAILED DESCRIPTION 25 mm diameter and 100 mm long cylindrical steel cast samples were taken by a special sampler device by plunging it deeper (approx. 300 mm below the liquid steel surface) into the liquid steel from Ladle Furnace as well as from Tundish. 25 mm dia. and 15.0 mm thick samples were cut from these samples and were ground with mirror finish to thickness 14.8 mm and parallel faces on which ultrasonic measurements were made. The ultrasonic scanning using 5 MHz & 10 MHz focused beam probe (with 38.1 mm focal length in water) was done on the mirror finish face with incremental distances AX = AY = 0.2 mm. Water path for testing the sample was calculated using relation: where, Sw = Water path, Sf = Focal distance in water, Sm = Sound path in test material, Cw = Sound velocity in water, Cm = Sound velocity in test material Figure 1 shows photographs of Ultrasonic yC Scan Image Analysis System showing (a) Immersion tank with water, specimen and scanner, (b) Pulser Receiver Model 5800 and (c) Computer display of 'A' scan signals and coloured yC scan image based on the signal amplitudes. Figure 1(d) shows a schematic diagram showing experimental set up. Experimental data analysis was done using a C-Scan Data Acquisition and Analysis Software developed using National Instrument's Labview. Results of 5 MHz, 15 mm dia. focused beam probe : Total ultrasonic counts in all the samples were measured considering the various backscattered signal amplitudes on arbitrary scale and various pixel sizes in grey mode presentation of the C- Scan image. 1. As shown in Fig.2, Ultrasonic counts of amplitudes 0.40-0.50 (a.u) Vs Total Oxygen graph plot reveals a second order polynomial equation y = - 1.0121x2 + 80.532x - 994.94 where x and y are Total Oxygen in ppm and ultrasonic counts respectively. Correlation coefficient was found to be R2 = 0.5705. 2. As shown in Fig.3, Ultrasonic counts Vs (FeO+MnO) in slag graph plot reveals a trend line equation y = 2 E - 06 X 6752 where x and y are (FeO+MnO) in slag and ultrasonic counts respectively. Correlation coefficient was found to be R2 =0.7103. Ultrasonic counts were the numbers of backscattered signals from the inclusions with areas 0.04-0.44 mm2 (as measured from the pixels). 3. As shown in Fig.4, Ultrasonic counts Vs No. of heats poured in tundish graph plot reveals a second order polynomial equation y = -11.8 X2+ 111.98x - 69.408, where x and y are No. of heats in tundish and ultrasonic counts respectively. Correlation coefficient was found to be R2 =0.8769. Ultrasonic counts were measured in the same manner as mentioned in point 2. 4. As shown in Fig.5, Ultrasonic counts Vs Sequence no. of heats in tundish graph plot reveals a trend line equation y = 2E-32 X 20-768, where x and y are No. of heats in tundish and ultrasonic counts respectively. Correlation coefficient was found to be R2 = 0.903. Ultrasonic counts were measured in the same manner as mentioned in point 2 Results of 10 MHz, 15 mm dia. Focused beam probe : The same samples were tested with 10 MHz focused beam probe. In this case, ultrasonic backscattered signal amplitudes were arbitrarily cateqorized in 3 levels; 1.1-1.2 level-1, 0.55-0.65 level-2 and 0.40-0.50 level-3. The results are as given below: 1. As shown in Fig.6, Ultrasonic counts level-1 Vs Total Oxygen graph plot reveals a second order polynomial y = -0.6763 X2 + 59.624 X - 671.91 where x and y are Total Oxygen in ppm and ultrasonic counts level-1 respectively. Correlation coefficient was found to be R2 =0.9464. 2. As shown in Fig.7, Ultrasonic counts level-2 Vs Total Oxygen graph plot reveals a second order polynomial y = -1.8228 X2 + 156.88 x - 2702 where x and y are Total Oxygen in ppm and ultrasonic counts level-2 respectively. Correlation coefficient was found to be R2 =0.8568. 3. As shown in Fig.8, Ultrasonic counts level-3 Vs Total Oxygen graph plot reveals a second order polynomial y = -1.1333 X2 + 87.791 x - 1239.1, where x and y are Total Oxygen in ppm and ultrasonic counts level-3 respectively. Correlation coefficient was found to be R2= 0.2768. 4. As shown in Fig.9, Ultrasonic total counts (level-l+ level-2+ level-3) Vs Total Oxygen graph plot reveals a second order polynomial y = -3.6325 X 2 + 304.29 x - 4613 where x and y are Total Oxygen in ppm and ultrasonic total counts respectively. Correlation coefficient was found to be R2 = 0.8932. 5. As shown in Fig. 10 -12, the bar chart shows decrease in ultrasonic counts with decrease in total oxygen content of the samples 8075, 8074 and 8073. The trend was same for both samples taken at RH as well as at caster. 6. Fig. 13 shows the variation in defect/inclusion size distribution in caster samples as well as RH degassed samples. On arbitrary scale coarse, medium and fine size defects/inclusions were of 1-3, 3-5 and 5-7 pixel sizes respectively in ultrasonic C scan image plot. 7. Fig.14-19 illustrates ultrasonic C scan images indicating increase in ultrasonic counts with increase in no. of Heats made in BOF Vessel, Seq. No. in tundish, No. of Heats poured in tundish, FeO+MnO in slag and Total Oxygen in LF and Caster samples. Inclusion severity levels and size analysis results using 5 MHz focused beam probe: Inclusion severity levels were categorized into 8 levels according to the amplitudes of the backscattered signals e.g. Level-1( 0.2-0.4), Level-2 (0.4-0.5), Level-3 (0.55-0.65), Level-4 (0.75-0.85), Level-5 (0.85-0.95), Level-6 (1.0-1.2), Level-7 (1.2-1.4) and Level-8 (1.4-1.6). Inclusion size analysis was based on the pixel (1 Pixel = 0.2X0.2= 0.04 mm2) size as recorded in ultrasonic 'C scanning. Inclusion size groups were categorized as 1-3 Pixel (0.04-0.12 mm2), 3-5 Pixel (0.12 -0.20 mm2), 5-7 Pixel (0.20 -0.28 mm2), 7-9 Pixel (0.28 -0.36 mm2), 9-11 Pixel (0.36 -0.44 mm2), 1. Fig.20 shows Ultrasonic Counts Vs Cleanliness severity level plot (a) showing good example of inclusion removal in steel. There is drastic decrease in ultrasonic counts of level 3-6 in caster samples when compared with RH samples.(b) a fair inclusion removal in caster samples when compared with RH samples. 2. Fig.21 shows Ultrasonic Counts Vs Cleanliness severity level plot (a) showing good example of inclusion pick up in steel. There is drastic increase in ultrasonic counts of level 3-6 in caster samples when compared with RH samples (b) a fair inclusion pick up in caster samples when compared with RH samples. This is due to re-oxidation of steel. 3. Fig.22 shows Ultrasonic Counts Vs Inclusion size (area wise) plot in RH degassed and caster samples (a) showing good example of inclusion removal in steel. There is drastic decrease in ultrasonic counts of inclusion size range (0.04-0.12 mm2) in caster samples when compared with RH samples.(b) The similar observation as in (a). Inclusions with area >(0.04- 0.12 mm2) were absent in both RH as well as caster samples. 4. Fig.23 shows a typical ultrasonic 'C scan image of RH degassed sample from heat no. V 05706 with Total oxygen 29.5 ppm. Pink colour spots with amplitude 1.0-2.0 indicates visible inclusions in the image. 5. Fig.24 shows a typical display of ultrasonic XC scan image analysis of the sample from Tundish of same heat no. V 05706 with Total oxygen 30.5 ppm. A drastic reduction in ultrasonic counts 11 was observed indicating good example of inclusion removal by floatation. 6. Fig.25 shows a typical colour display of ultrasonic 'C scan image of the sample no. 8074 from Tundish at 5 MHz frequency. Different amplitudes of the backscattered signals are displayed by different colours. WE CLAIM: 1. A method of assessment of cleanliness level of continuously cast steel by an automatic ultrasonic immersion C-scan image analysis in pixel for ensuring physical and mechanical properties of finished macro inclusion free clean steel products comprising the steps of preparing cylindrical cast sampler by a sampler device on plunging it deeper into the liquid steel from Laddie Furnace as well as from Tundish, cutting and grounding the samples to mirror finish with appropriate thickness and parallel faces; employing ultrasonic scanning in immersion tank with water specimen and the scanner using 5 megahertz (MHz) and 10 megahertz (MHz) focused beam probe on the mirror finish face of the samples with incremental distances small increment in x axis and y-axis respectively (Ax + Ay = 0.2 mm through C-scan data acquisition and analysis software developed for the purpose; finding out correlation between total oxygen in parts per million (ppm) and ultrasonic counts, a combination of ferrous oxide and manganese oxide (Feo + MnO) in slag and ultrasonic counts, number of heats in Tundish and ultrasonic counts, sequence number of heats in tundish and ultrasonic counts of various backscattered signal amplitudes of 0.4 - 05 (a.u) on arbitrary- scale and various pixel sizes of the C-scan images using 5 megahertz (MHz), 15 mm dia samples from caster and RH degasser sample, finding out correlation between total oxygen in parts per million (ppm) and ultrasonic counts in arbitrarily scale and various pixel sizes of the C- scan image using 5 megahertz (MHz), 15 mm dia samples from caster and RS degasser sample; finding out correlation between total oxygen in parts per million (ppm) and ultrasonic counts in categorized 3 levels, using 10 megahertz (MHz), 15 mm dia samples from tundish; preparing bar chart in ultrasonic counts with varying total oxygen in parts per million (ppm) in samples of 3 levels from both caster and RH degasser; categorizing inclusion severity levels into 8 levels according to 8 levels of backscattered signal amplitudes on preparing ultrasonic counts related with cleanliness severity level for RH degassed and caster samples to find out in various pixel sizes inclusion size groups and thus determining inclusion removal of steel in RH degasser and caster samples from correlated total oxygen, ultrasonic counts, backscattered amplitude, number of heats in tundish and sequence number in tundish. 2. A method of assessment of cleanliness level as claimed in claim 1, wherein samples from ladle furnace as well as from tundish were taken as 25 mm dia and 15 mm thick samples were cut from the said samples and were ground with mirror finish to 14.8 mm thickness and focused beam probe with 38.1 mm focal length in water was done on the mirror finish with increment distance AX = AY = 0.2 mm. 3. A method of assessment as claimed in claim 1, wherein water path for testing the sample was calculated using relation Where Sw = water path, Sf = Focal distance in water, Sm = Sound path in test material, Cw = Sound velocity in water and Cm = Sound velocity in test material. 4. A method of assessment as claimed in claim 1, wherein using 5 megahertz (MHz) focused beam probe a second order polynomial equation Y =-1 .0121 X2+ 80.532 X - 994.94 were formulated where X and Y are total oxygen in ppm and ultrasonic counts respectively, with correlation coefficient R2 = 0.5705. 5. A method of assessment as claimed in claim 1, wherein using 5 megahertz (MHz) focused beam probe a trend line equation Y = 2E - 06 X6.752 were formulated, where X and Y are a combination of ferrous oxide and manganese oxide (FeO + MnO) in slag and ultrasonic counts respectively with correlation coefficient R2 = 0.7103. 6. A method of assessment as claimed in claim 1, wherein using 5 megahertz (MHz) focused beam probe a second order polynomial equation Y = -11.8 X2 +111.98 X - 69.408 is formulated where X and Y are number of heats in tundish and ultrasonic counts respectively with correlation coefficient R2 =0.8769. 7. A method of assessment as claimed in claim 1, wherein using 5 megahertz (MHz) focused beam probe a trend line equation Y = 2E - 32 x20.768 was formulated where X and Y are number of heats in tundish and ultrasonic counts respectively with correlation coefficient R2 = 0.903. 8. A method of assessment as claimed in claim 1, wherein arbitrarily categorized 3 levels of signal amplitudes using 10 megahertz (MHz) focused beam probe are l.l-1.2(a.u) level - 1,0.55 - 0.65 (a.u) level -2 and 0.40 - 50 (a.u) level - 3 and 8 levels of backscattered signal amplitudes for inclusion severity levels are 0.2 - 0.4 (a.u) - level - 1, 0.4 - 0.5 (a.u) - level 2, 0.55 - 0.65 (a.u) - level 3, 0.75 - 0.85 (a.u.) - level 4, 0.85 - 0.95 (a.u) - level 5, 1.0 - 1.2 (a.u) - level 6, 1.2 - 1.4 (a.u) - level 7 and 1.4-1.6 (a.u) level 8. 9. A method of assessment as claimed in claims 1 and 8, wherein using 10 MHz focused beam probe a second order polynomial equation Y = - 0.6763 X2 + 59.624 X - 671.91 was formulated where X and Y are total oxygen in parts per million (ppm) and ultrasonic counts level -1 respectively with correlation coefficient R2 = 0.9464. 10. A method of assessment as claimed in claims 1 and 8, wherein using 10 megahertz (MHz) focused beam probe a second order polynomial equation Y = -1.8228 X2 + 156.88 X - 2702 was formulated where X and Y are total oxygen in parts per million (ppm) and ultrasonic counts level 2 respectively with correlation coefficient R2 = 0.8568. 11. A method of assessment as claimed in claims 1 and 8, wherein using 10 megahertz (MHz) focused beam probe a second order polynomial equation Y = -1.8228 X2 + 156.88 X - 2702 was formulated where X and Y are total oxygen in parts per million (ppm) and ultrasonic counts level 3 respectively with correlation coefficient R2 = 0.2768. 12. A method of assessment as claimed in claims 1 and 8 wherein using 10 megahertz (MHz) focused beam probe a second order polynomial equation Y = -3.6325 X2 + 304.29 X - 4 613 was generated where X and Y are total oxygen in parts per million (ppm) and total ultrasonic counts levels 1, 2 and 3 with correlation coefficient R2 = 0.8932. 13. A method of assessment as claimed in claim 1 wherein using 5 or 10 megahertz (MHz) focused beam probe fine, medium and coarse size defects/inclusions of 1-3 pixel (0.04 - 0.12 mm2), 3-5 pixel (0.12 - 20 mm2) and 5 -7 pixel (0.20 - 0.28 mm2) respectively were assessed in the recorded ultrasonic C- scan image analysis. 14. A method of assessment as claimed in claims 1, 8 and 13 wherein using 5 or 10 megahertz (MHz) focused beam probe the removal of coarser defects/ inclusions of size range 0.04 - 0.44 mm2 are made effective through correlated total oxygen, ultrasonic consists, backscattered amplitudes, number of heats in tundish and sequence number in tundish, recorded in the ultrasonic C-scan image analysis. ABSTRACT TITLE: A METHOD OF ASSESSMENT OF CLEANLINESS LEVEL OF CONTINUOUSLY CAST STEEL This invention relates to a method of assessment of cleanliness level of continuously cast steel by an automatic ultrasonic immersion C-scan image analysis in pixel for ensuring physical and mechanical properties of finished macro inclusion free clean steel products comprising the steps of preparing cylindrical cast sampler by a sampler device on plunging it deeper into the liquid steel from Laddie Furnace as well as from Tundish, cutting and grounding the samples to mirror finish with appropriate thickness and parallel faces; employing ultrasonic scanning in immersion tank with water specimen and the scanner using 5 megahertz (a unit of frequency which is equal to one million hertz) (MHz) and 10 megahertz (a unit of frequency which is equal to one million hertz) (MHz) focused beam probe on the mirror finish face of the samples with incremental distances small increment in x axis and y-axis respectively (Ax + Ay = 0.2 mm through C - scan data acquisition and analysis software developed for the purpose; finding out correlation between total oxygen in parts per million (ppm) and ultrasonic counts, a combination of ferrous oxide and manganese oxide (FeO + MnO) in slag and ultrasonic counts, number of heats in Tundish and ultrasonic counts, sequence number of heats in tundish and ultrasonic counts of various backscattered signal amplitudes of 0.4 - 05 (a.u) on arbitrary scale and various pixel sizes of the C-scan images using 5 megahertz (a unit of frequency which is equal to one million hertz)(MHz), 15 mm dia samples from caster and RH degasser sample, finding out correlation between total oxygen in parts per million (ppm) and ultrasonic counts in arbitrarily scale and various pixel sizes of the C-scan image using 5 megahertz (a unit of frequency which is equal to one million hertz) (MHz), 15 mm dia samples from caster and RS degasser sample; finding out correlation between total oxygen in parts per million (ppm) and ultrasonic counts in categorized 3 levels, using 10 megahertz (a unit of frequency which is equal to one million hertz) (MHz), 15 mm dia samples from tundish; preparing bar chart in ultrasonic counts with varying total oxygen in parts per million (ppm) in samples of 3 levels from both caster and RH degasser; categorizing inclusion severity levels into 8 levels according to 8 levels of backscattered signal amplitudes on preparing ultrasonic counts related with cleanliness severity level for RH degassed and caster samples to find out in various pixel sizes inclusion size groups and thus determining inclusion removal of steel in RH degasser and caster samples from correlated total oxygen, ultrasonic counts, backscattered amplitude, number of heats in tundish and sequence number in tundish.

Documents:

01446-kol-2007-abstract.pdf

01446-kol-2007-claims.pdf

01446-kol-2007-correspondence others 1.1.pdf

01446-kol-2007-correspondence others.pdf

01446-kol-2007-description complete.pdf

01446-kol-2007-drawings.pdf

01446-kol-2007-form 1.pdf

01446-kol-2007-form 18.pdf

01446-kol-2007-form 2.pdf

01446-kol-2007-form 3.pdf

01446-kol-2007-gpa.pdf

1446-KOL-2007-(06-11-2013)-CORRESPONDENCE.pdf

1446-KOL-2007-(06-11-2013)-FORM-1.pdf

1446-KOL-2007-(10-06-2013)-ABSTRACT.pdf

1446-KOL-2007-(10-06-2013)-CLAIMS.pdf

1446-KOL-2007-(10-06-2013)-CORRESPONDENCE.pdf

1446-KOL-2007-(10-06-2013)-DRAWINGS.pdf

1446-KOL-2007-(10-06-2013)-FORM-2.pdf

1446-KOL-2007-CORRESPONDENCE 1.1.pdf

1446-KOL-2007-CORRESPONDENCE.pdf

1446-KOL-2007-EXAMINATION REPORT.pdf

1446-KOL-2007-FORM 18.pdf

1446-KOL-2007-GPA.pdf

1446-KOL-2007-GRANTED-ABSTRACT.pdf

1446-KOL-2007-GRANTED-CLAIMS.pdf

1446-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

1446-KOL-2007-GRANTED-DRAWINGS.pdf

1446-KOL-2007-GRANTED-FORM 1.pdf

1446-KOL-2007-GRANTED-FORM 2.pdf

1446-KOL-2007-GRANTED-FORM 3.pdf

1446-KOL-2007-GRANTED-SPECIFICATION-COMPLETE.pdf

1446-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-01446-kol-2007.jpg