Title of Invention	"A METHOD TO DETERMINE THE GRAIN STRUCTURE AND CASTING DEFECT IN CAST STEEL BILLET BY ULTRASONIC IMMERSION C-SCAN IMAGING"
Abstract	The invention relates to a novel ultrasonic method by 5 MHZ focused beam probe and a multi-axis scan (x, y and z axes) in ultrasonic immersion system through image analysis, evaluating the effect of electro-magnetic stirring on soundness of high carbon as well as low carbon grade continuously cast steel billets.

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2 TITLE: A METHOD TO EVALUATE THE EFFECT OF ELECTRO-MAGNETIC STIRRING ON CONTINUOUSLY CAST STEEL BILLETS BY ULTRASONIC IMMERSION C-SCAN IMAGING. FIELD OF THE INVENTION The invention relates to ultrasonic immersion c-scan imaging technique to evaluate the effect of electromagnetic stirring on continuously cast steel billets for soundness by optimization of various parameters i.e. current, frequency, position etc. BACKGROUND OF THE INVENTION Usually evaluation of the effect of electro-magnetic stirring on soundness of continuously cast steel billets and slabs are assessed by the following methods: 1. Visual inspection of macro-etch 2. Sulphur print evaluation But ultrasonic assessment provides through thickness information of the test samples, whereas, macro-etching and sulphur print methods provide information in one plane only. For more realistic assessment these methods requires large number of test samples and hot acids which is hazardous and pollute the atmosphere also. Ultrasonic method is pollution free and eco-friendly method and may require less number of samples also. To overcome the problems faced during the evaluation of cleanliness level of steel, by above mentioned methods, a lot of interest has been shown to detect, 3 measure and analyze macro-level inclusions in steel using specialized ultrasonic techniques. It is preferred ultrasonic method in comparison to other methods as inspection could be done with a larger sample volume. While evaluating the macro-inclusion distribution and detection, in comparison to other methods, ultrasonic method was found to be more effective. Attenuation measurements were found to give very low numerical values. With this background, a high gain pulse echo ultrasonic technique was used for inclusion detection in forgings in a quantitative manner. Macro-etching and sulphur print methods provide information in one plane only. For more realistic assessment these methods requires large number of test samples and hot acids which is hazardous and pollute the atmosphere also. OBJECT OF THE INVENTION • The object of the invention is to evaluate the effect of electro-magnetic stirring on soundness of high and low carbon continuously cast steel billets. • Another object of the invention is to reduce the use of hazardous hot acids/chemicals for control of environment and industrial pollution. • Other object of the invention is to reduce the running cost of repetitive tests for quality check. 4 • Also the object of the invention is to make the process accessible to the demanding industries and reduce human error. BRIEF DESCRIPTION OF THE ACCOMPANYING TABLES, SCANNED IMAGES & GRAPHS • Figure 1 shows the schematic diagram of billet samples collected from Billet Caster. • Figure 2 shows ultrasonic C-Scan image of transverse section of non-EMS CC billet sample of HC Grade-A. • Figure 3 shows ultrasonic C-Scan image of transverse section of CC billet sample of HC Grade-A EMS Current 240A and Frequency 3.5 Hz. • Figure 4 shows ultrasonic C-Scan image of transverse section of CC billet samples of HC Grade-A at EMS Current 260A and Frequency 3.5 Hz. • Figure 5 shows ultrasonic C-Scan image of transverse section of CC billet sample of HC Grade-A at EMS Current 280A and Frequency 3.5 Hz. • Figure 6 shows ultrasonic C-Scan image of transverse section of CC billet samples of HC Grade-A at EMS Current 300A and Frequency 3.5 Hz. • Figure 7 shows effect of EMS current on the % equiaxed zone and % defective area of HC Grade-A as well as LC Grade-A billet samples. 5 • Figure 8 shows ultrasonic C-Scan image of transverse section of non-EMS CC billet sample of LC Grade-A. • Figure 9 shows ultrasonic C-Scan image of transverse section of CC billet sample of LC Grade-A at EMS Current 240A and Frequency 3.5 Hz. • Figure 10 shows ultrasonic C-Scan image of transverse section of CC billet of LC Grade-A at EMS Current 260A and Frequency 3.5 Hz. • Figure 11 shows ultrasonic C-Scan image of transverse section of CC billet sample of LC Grade-A at EMS Current 280A and Frequency 3.5 Hz. • Figure 12 shows ultrasonic C-Scan image of transverse section of CC billet sample of HC Grade-A at EMS Current 300A and Frequency 3.5 Hz. • Figure 13 shows ultrasonic C-Scan image of transverse section of CC billet sample of HC Grade-A at EMS Current 280A and Frequency 3 Hz. • Figure 14 shows ultrasonic C-Scan image of transverse section of CC billet of HC Grade-A at EMS Current 280A and Frequency 4 Hz. • Figure 15 shows ultrasonic C-Scan image of transverse section of CC billet sample of LC Grade-A at EMS Current 280A and Frequency 3 Hz. • Figure 16 shows ultrasonic C-Scan image of transverse section of CC billet sample of LC Grade-A at EMS Current 280A and Frequency 4 Hz. 6 • Figure 17 shows effect of EMS frequency on the % equiaxed zone and the % defective area of HC Grade-A as well as LC Grade-A billet samples at EMS current 280A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Stirring intensity decreases with increasing frequency and it is related to the "skin effect" according to which eddy currents are more concentrated on the outer part of the conductor as the frequency increases. The following relationship describe the effect of EMS frequency on stirring intensity, F Fa B2M(f)f Where, BM = magnetic induction in the considered point inside the metal (in Gauss) f = Frequency of power supply, in Hz. The above formula shows that the stirring force is the product of B2M (f) (which decreases with increasing frequency) and f. At frequency zero the force is zero and at higher frequency the force approaches to zero again because the term B2M (f) becomes very small. In between, there is a specific frequency, the so- called optimum frequency, at which the stirring force is maximum. The current of EMS coil controls its performance, because the stirring force (F), acting on the liquid steel is proportional to the square of the magnetic flux (BM, 7 which is proportional to the current). Consequently, the current setting is the main operational parameter, which is to be chosen as function of the casting conditions. Generally, the current is kept constant during casting. Theoretically, the current setting depends on the chemical composition of each steel grade. An optimization is to be done for each individual case. Increased casting speed as well as increased superheat needs increased current settings. In practice however, the justification of different current setting as function of casting speed and superheat shall have to be ascertained for each specific case. During any metallurgical improvement obtained by EMS (such as reduction of surface and subsurface defects, increase of equiaxed zone, decrease of axial porosity or segregation etc.), too low current settings give insufficient improvements, too high current settings give practically no further improvements and spend electrical power for nothing. Moreover, too high current settings may give rise to negative effects. Consequently, the optimum current setting is the compromise of good results and reasonable power consumption. It needs many casts and analysis under reproducible conditions with and without stirring, to establish quantitatively the exact relation between improvement and current setting. The attempts have been made to determine the best combination of EMS current and frequency for ensuring good surface as well as subsurface quality of CC steel billets cast at Billets Casters. Two close casting grades, one of high carbon grade (HC Grade-A) and another of low carbon grade (LC Grade-A) of steel billet was considered. The chemical compositions of the above mentioned grades have been shown in Table 1 and Table 2 respectively. The experiments were 8 conducted on the above grades of CC billets with EMS currents 240, 260, 280 and 300 amperes (A), while frequency was kept constant to 3.5 Hz during casting. In some of the heats EMS frequencies were set at 3, 3, 5 and 4 hertz (Hz) while EMS current was kept constant during casting. In both the cases, the corresponding CC billet samples were collected and its effect on billet quality was assessed by using ultrasonic immersion C-Scan imaging technique. Each billet sample of cross section of 130 x 130 mm was sliced into transverse and longitudinal sections (approximately 20 mm thick) and ground to good surface finish. Figure-1 shows the schematic diagram of billet samples collected from Billet Caster. All the steel billet samples were examined using the ultrasonic immersion C-Scan imaging technique. All microstructural features observed, in each case, were recorded and analyzed subsequently. Finally, data of axial porosity, columnar/equiaxed zone, % defective area (which includes segregation, inclusions, pinhole, internal as well a subsurface cracks) of the total scanned area in each grades of steel were compared for determining the best combination of EMS parameters. A series of tests -were carried out with the billet specimens to evaluate and optimize the EMS current and frequency with respect to CC steel billet quality. These specimens were subsequently tested in a water tank using a 5 MHz ultrasonic focused beam probe. The C-scan images were obtained with the help of a computer controlled ultrasonic immersion C-scan system. The other details of the equipment and testing parameters are given below: 9 Name of the equipment - Multi-scan (X, Y, and Z) automatic ultrasonic Immersion C-scan inclusion detection system Probe - 5 MHz, 15 mm diameter., spherical focused single crystal normal probe, focal length 1.5" in water Media - Water Pulser Receiver Setting: Make and Model - Panametrics Computer Controlled Pulser Receiver Model 5800 Mode - Pulse Echo Pulse Repetition Frequency -100 Hz Energy - 50μJ Damping - 50 ohm High Pass Filter -1 kHz Low Pass Filter - 30 MHz Input Attenuation - 0 dB Output Attenuation - 7 dB Gain - 40 dB Scanning Setting: Water path - 25.68 mm Scan Length - In case of transverse billet sample 140 mm max. - In case of transverse billet sample 170 mm max. - In case of transverse billet sample 140 mm max. 10 - In case of transverse billet sample 170 mm max. Scan Resolution -0.4mm Index Resolution - 0.4 mm Scan Mode - Bi-Directional Calibration - In order to achieve reproducible result during ultrasonic evaluation of macro level flaw counts, the equipment was standardized with a 0.7 mm Flat Bottom Hole (FBH) in the same billet sample. 0.7 mm Flat Bottom Hole (FBH) resulted in 5 V peak. This peak was indicated by yellow colour, kept as upper threshold. 1 V peak-to-peak (i.e. 20% of full screen height) was kept the lower threshold as indicated by green colour. This technique was applied to evaluate the quality of steel billet samples. Ultrasonic C-scan can image different five intermediate layers of the billet samples and plot in two dimensions of the final image. Therefore, all the internal defects appeared at the final image, where as in macro-etched structure revealed only top etched layer of the samples. One major advantage of ultrasonic C-scan over A-scan is that classification of different kinds of defects is possible by imaging of the defects by this method. This method also reveals three different regions in the samples such as chilled zone, equiaxed zone and columnar zone in different gray/colour scale. 11 A series of C-scan tests were carried out with varying parameter settings. The instrument variables for these tests were as follows: • Resolution : 0.4 mm x 0.4 mm • Voltage setting : 20V and • Gain : 33 dB Grey scale was used to differentiate the results from the gated area. Referring to ultrasonic C-scan images, and based on a grey scale that depicts attenuated signals darker, one may see clear identification of defects by the darker areas. Although not very sharp, each and every one of the areas is reproduced with a certain degree of dimensional accuracy. However the boundary of each defect is not well defined. Prior to this work, the Billet Caster used a setting of 260A EMS current and 3.5 Hz EMS frequency for all the close casting grades. In this work, it has been tried to find out the optimum combination of EMS current and frequency which will produce billet with good internal quality consistently. Initially EMS current was set to 240, 260 280, and 300A during casting and billet samples were collected and examined to find out the effect of change in current. Samples without EMS (non-EMS) condition were also collected. This is aluminium killed steel with carbon content 0.63%. The other details of the grade have been shown Table 1. 12 Figure 2 shows the ultrasonic C-Scan image of transverse section of non-EMS billet sample of HC Grade-A. It can be easily observed that there is a very small equiaxed zone with a large columnar zone and a huge defective area in non-EMS billet samples when compared with the EMS billet samples. After use of EMS, there was significant improvement in quality of CC billets in terms of larger% equiaxed zone, small axial porosity and low% defective areas, which is desirable. It is also evident from the Figures 3-6 which show the ultrasonic C-Scan images of transverse sections of CC billet sample of HC Grade-A, at EMS current 240, 260, 280 and 300A. Figure 7 demonstrates the quantitive values of the effect of EMS current on the quality of HC Grade-A billet samples in terms of % equiaxed zone and the % defective area of total area. It is clear that the equiaxed zone in non-EMS samples is only 15% whereas it is 35, 39, 47 and 45% in EMS billet samples at the EMS current 240, 260, 280 and 300A respectively. Similarly, the defective area in the non-EMS billet sample is as high a 19% of the total area of the billet sample, while it is 15, 13, 10 and 10% in EMS billet samples at the EMS current 240, 260, 280 and 300A respectively. In can be, therefore, concluded that the % of equiaxed zone increase sharply with the increase in EMS current. It is most significant at EMS current 280A after that it increases marginally. Similarly, the % total defective area in the billet sample, with respect to the total area of billet section, also decreases considerably with increase in EMS current up to 280A after that it does not decrease further. 13 LC Grade-A This is a cold heading quality grade and its application is for high tensile fasteners. The details of this grade have been shown in Table 2. Figure 8 shows the ultrasonic C-Scan image of transverse section of non-EMS billet sample LC Grade-A. It can be easily observed that there is a very small equiaxed zone with a large columnar zone and a huge defective area in non-EMS billet samples when compared with the EMS billet samples. When EMS was used, there was significant improvement in quality of CC billets in terms of larger % equiaxed zone, small axial porosity and low % defective areas, which is desirable. It is also evident from the Figures 9-12 which show the ultrasonic C- Scan images of transverse sections of billet sample of LC Grade-A at EMS current 240, 260, 280 and 300A. Figures 7 demonstrates the quantative values of the effect of EMS current on the quality of LC Grade-A billet samples in term % equiaxed zone and the % defective area of total area. It is clear that the equiaxed zone in non-EMS sample is only 12% whereas, in EMS billet samples, it is 33, 37, 39 and 37% at the EMS current 240, 260, 280 and 300A .respectively. Similarly, the defective area in the non-EMS billet sample is as high as 22% of the total area of the billet sample, while, in EMS billet samples, at the EMS current 240, 260, 280 and 300A, it is 19, 17, 13 and 13% respectively. Hence, it can be concluded that the % equiaxed zone increases sharply with the increasing EMS current. It is most significant at EMS current 280A after that it 14 increases marginally. Similarly, the % total defective area in the billet sample, with respect to the total are of billet section, also decreases considerably with increase in EMS current up to 280A and after that it does not decrease further. Optimization of EMS frequency After optimization of EMS current, EMS frequency was, then, set to 3, 3, 5 (existing practice) and 4 Hz, keeping EMS current constant at 280 during casting and billet samples were collected. These billet samples were also ultrasonically analyzed and evaluated. Figures 13 and 14 shows the ultrasonic C-Scan image of transverse section of billet samples of HC Grade-A at EMS current 280 A and EMS frequency 3 Hz and 4 Hz respectively whereas Figures 15 and 16 show the ultrasonic C-Scan image of transverse section of billet samples of LC Grade-A at EMS current 280A and EMS frequency 3 and 4 Hz respectively. In both the grades, it was found that quality of the billet samples appears sounder, in terms of the % equiaxed zone, axial porosity and the % defective areas, when the EMS frequency was 3.5 Hz, when compared to the same with the EMS frequency 3 Hz and 4 Hz. Figure 13 demonstrate the quantitative values of the effect of EMS frequency on the quality of billet samples of both the grades in term of the % equiaxed zone and the % defective area of total area. It is obvious that the equiaxed zone in non-EMS HC Grade-A samples is only 15% whereas, in EMS billet samples, it is 33, 47 and 48% at the EMS frequency 15 3, 3.5 and 4 Hz respectively. Similarly, the defective area in the non-EMS billet sample is as high as 19% of the total area of the billet sample, while, in EMS billet samples, at the EMS frequency 3, 3.5 and 4 Hz, it is 18, 10 and 11% respectively. Hence, it can be concluded that, in this case, the % equiaxed zone increases sharply with the increasing EMS frequency. It is most significant at EMS frequency 3.5 Hz after that it increases marginally. Similarly, the % total defective area in the billet sample, with the respect to the total area of billet section, also decreases considerably with increase in EMS frequency up to 3.5 Hz and after that it starts increasing. In case of LC Grade-A, in non-EMS samples it is 12% only whereas, in EMS billet samples, it is 28, 39 and 37% at the EMS frequency 3, 3.5 and 4 Hz respectively. Similarly, the defective area in the non-EMS billet sample is as high as 22% of the total area of the billet sample, while, in EMS billet samples, at the EMS frequency 3, 3.5 and 4 Hz, it is 21, 13 and 16% respectively. Hence, it can be concluded that, in this case also, the % equiaxed zone increases with the increase in EMS frequency. It is most significant at EMS frequency 3.5 Hz and after that it increases marginally. The % total defective area in the billet sample, with respect to the total area of billet section, also decreases considerably with increase in EMS frequency up to 3.5 Hz and after that it starts increasing further. It was observed that billet samples contain large axial porousity with lot of subsurface defects also. Therefore EMS frequency should not be increased further. 16 WE CLAIM 1. A novel ultrasonic method by 5 MHZ focused beam probe and a multi-axis scan (x, y and z axes) in ultrasonic immersion system through image analysis, evaluating the effect of electro-magnetic stirring on soundness of high carbon-as well as low'carbon grade continuously cast steel billets, 2. The method as claimed in claim (1), wherein determination of soundness of high carbon as well as low carbon grade continuously cast steel billets samples through ultrasonic immersion C-Scan image plot. 3. The method as claimed in claim (1) and (2), wherein observation, record and analysis of all macro structural features i.e. axial porosity, columnar/equiaxed zone, % defective area including segregation, inclusions, pinhole, internal as well as subsurface cracks of the total scanned area in each grades of steel. 4. The method as claimed in claim (1), (2) and (3) wherein comparison and evaluation of the effect of electro-magnetic stirring evaluation of the effect of electro-magnetic stirring on soundness at high carbon as well as low carbon grade continuously cast steel billets. 5. The method as claimed in claims (1), (2), (3) and (4) wherein determination of the best combination of electro-magnetic stirring parameters for producing sound high carbon as well as low carbon grade continuously cast steel billets. 17 6. The method as claimed in claims (1), (2), (3), (4) and (5) wherein identification, location and sizing of all macro structural features axial porosity, columnar/equiaxed zone, % defective area including segregation, inclusions, pinhole,, internal as well as subsurface cracks of the total scanned area in high and low carbon continuously cast steel billets on C-Scan image plot. Dated this 5th Day of FEBRUARY 2008 The invention relates to a novel ultrasonic method by 5 MHZ focused beam probe and a multi-axis scan (x, y and z axes) in ultrasonic immersion system through image analysis, evaluating the effect of electro-magnetic stirring on soundness of high carbon as well as low carbon grade continuously cast steel billets.

Documents:

00206-kol-2008-abstract.pdf

00206-kol-2008-claims.pdf

00206-kol-2008-correspondence others.pdf

00206-kol-2008-description complete.pdf

00206-kol-2008-drawings.pdf

00206-kol-2008-form 1.pdf

00206-kol-2008-form 2.pdf

00206-kol-2008-form 3.pdf

00206-kol-2008-gpa.pdf

206-KOL-2008-(01-08-2012)-CORRESPONDENCE.pdf

206-KOL-2008-(23-02-2012)-ABSTRACT.pdf

206-KOL-2008-(23-02-2012)-AMANDED CLAIMS.pdf

206-KOL-2008-(23-02-2012)-DESCRIPTION (COMPLETE).pdf

206-KOL-2008-(23-02-2012)-DRAWINGS.pdf

206-KOL-2008-(23-02-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

206-KOL-2008-(23-02-2012)-FORM-1.pdf

206-KOL-2008-(23-02-2012)-FORM-2.pdf

206-KOL-2008-(23-02-2012)-FORM-3.pdf

206-KOL-2008-(23-02-2012)-FORM-5.pdf

206-KOL-2008-(23-02-2012)-OTHERS.pdf

206-KOL-2008-(23-02-2012)-PETITION UNDER RULE 137.pdf

206-kol-2008-form 18.pdf

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