Manish Raj - Academia.edu (original) (raw)

Papers by Manish Raj

Research paper thumbnail of A Novel Method to Measure Cleanliness in Steel Using Ultrasonic C-Scan Image Analysis

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2008

The traditional method of measuring the cleanliness level of steel is to measure its total oxygen... more The traditional method of measuring the cleanliness level of steel is to measure its total oxygen (TO), which does not provide information about the size, location, and distribution of more harmful macroinclusions. The present article highlights a novel method for cleanliness assessment in steel samples using ultrasonic C-scan image analysis. The method provides quick and large volume inspection and ability to catch macroinclusions that possess difficulty during further processing of the thin gage steel products, particularly for auto grades such as interstitial-free (IF) steel. This method deals with a multiscan, immersion ultrasonic system using high-frequency focused beam and image analysis software. A good correlation was found between ultrasonic parameter counts and TO in steel samples taken from tundish during the continuous casting of slab. The ultrasonic counts were also found to be correlated with some steelmaking parameters.

Research paper thumbnail of Study of Inclusion Bands in Continuously Cast Steel Billets for Rolling Thermomechanically Treated Rebars

Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2008

The article presents the investigation results of inclusion bands generally formed toward the loo... more The article presents the investigation results of inclusion bands generally formed toward the loose end/inner radius of continuously cast (CC) strands of thermomechanically treated (TMT) rebar grade cast through curved molds. The main analytical tool used for this purpose was an ultrasonic C-scan image analysis system to reveal this band, and the defects detected in this band using the preceding technique were further measured and analyzed in an optical microscope and a scanning electron microscope (SEM) using energy-dispersive system (EDS). The investigation results revealed the presence of macrolevel globular macroinclusions in the size range 50 to 711 μm. The main constituents of the globular inclusions were found to be SiO2 and MnO. Impact test results revealed reduction in ductility in these bands when compared with the billet material without inclusion band toward the opposite face from the inner radius face. In Charpy testing, reduction in the impact energy in these bands was found to be 0.2 kg m. It is important to monitor the severity of macroinclusions present in these bands to avoid the cracking of TMT rebars during hot rolling.

Research paper thumbnail of Study of Inclusion Bands in Continuously Cast Steel Billets for Rolling Thermomechanically Treated Rebars

Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2008

The article presents the investigation results of inclusion bands generally formed toward the loo... more The article presents the investigation results of inclusion bands generally formed toward the loose end/inner radius of continuously cast (CC) strands of thermomechanically treated (TMT) rebar grade cast through curved molds. The main analytical tool used for this purpose was an ultrasonic C-scan image analysis system to reveal this band, and the defects detected in this band using the preceding technique were further measured and analyzed in an optical microscope and a scanning electron microscope (SEM) using energy-dispersive system (EDS). The investigation results revealed the presence of macrolevel globular macroinclusions in the size range 50 to 711 μm. The main constituents of the globular inclusions were found to be SiO2 and MnO. Impact test results revealed reduction in ductility in these bands when compared with the billet material without inclusion band toward the opposite face from the inner radius face. In Charpy testing, reduction in the impact energy in these bands was found to be 0.2 kg m. It is important to monitor the severity of macroinclusions present in these bands to avoid the cracking of TMT rebars during hot rolling.

Research paper thumbnail of Evaluation of the Effect of ElectroMagnetic Stirring on Soundness of Continuously Cast Billets Using Ultrasonic Technique

Effect of electro-magnetic stirring on soundness of continuously cast billets and slabs can be as... more Effect of electro-magnetic stirring on soundness of continuously cast billets and slabs can be assessed by many methods like visual inspection of macro-etch & sulphur print evaluation. Ultrasonic assessment provides through thickness information of the test samples, whereas, macro-etching and sulphur print methods provide information in one plane only. An attempt has been made to evaluate the soundness (inhomogeneities / flaws as well as effect of columnar / equiaxed grains) of continuously cast low carbon and high carbon continuously cast billets by ultrasonic attenuation as well as high gain pulse-echo technique in transverse cut slices. One low carbon grade (Grade -LC) and one high carbon grades (Grade -HC) were selected for this purpose.

Research paper thumbnail of A Novel Method to Measure Cleanliness in Steel Using Ultrasonic C-Scan Image Analysis

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2008

The traditional method of measuring the cleanliness level of steel is to measure its total oxygen... more The traditional method of measuring the cleanliness level of steel is to measure its total oxygen (TO), which does not provide information about the size, location, and distribution of more harmful macroinclusions. The present article highlights a novel method for cleanliness assessment in steel samples using ultrasonic C-scan image analysis. The method provides quick and large volume inspection and ability to catch macroinclusions that possess difficulty during further processing of the thin gage steel products, particularly for auto grades such as interstitial-free (IF) steel. This method deals with a multiscan, immersion ultrasonic system using high-frequency focused beam and image analysis software. A good correlation was found between ultrasonic parameter counts and TO in steel samples taken from tundish during the continuous casting of slab. The ultrasonic counts were also found to be correlated with some steelmaking parameters.

Research paper thumbnail of Failure of Nickel Coating on a Copper Mold of a Slab Caster

Journal of Failure Analysis and Prevention, 2008

Copper molds are critical components in the continuous casting of steel. Surface condition of the... more Copper molds are critical components in the continuous casting of steel. Surface condition of the mold directly affects product quality, and premature failure/low wear life affects the output of the continuous casting plant. This paper presents the failure analysis of a nickel coating on a copper plate during a plant trial using in situ ultrasonic testing for coating thickness evaluation and in situ testing to confirm the loss of coating. The failure analysis indicated maximum coating wear near the bottom corners of the mold. More wear was found on the wide end face compared with that observed on the narrow face. On top portion of the mold, wear was almost negligible. Based on the wear profile obtained during trial, it was recommended that the coating on the bottom portion of the mold have a higher hardness to improve mold life.

Research paper thumbnail of Determination of Condition of Recrystallised Grains After Annealing of Cold Rolled IF Grade Steel Sheets Based on Ultrasonic Measurements

The Interstitial Free (IF) grade steel sheets are used for auto body applications where these she... more The Interstitial Free (IF) grade steel sheets are used for auto body applications where these sheets require good formability/drawability property. To achieve this property the cold rolled sheets are annealed to obtain desirable texture in the recrystallised grains to avoid material failure during forming operation. The paper deals with an ultrasonic technique to determine the condition of the recrystallised grains after annealing operation. 79 % cold rolled IF grade steel sheets were annealed at 650 deg. C for different times. After annealing the scale was completely eliminated from the surface by pickling to make the surface conducive for transmission of ultrasonic surface waves. Ultrasonic transit time for a fixed distance in µs was measured in rolling as well as 45 0 to rolling direction using 4 MHz transmitting and receiving transducers. Unrecrystallised, partially recrystallised and fully recrystallised regions in this case were determined by measuring hardness in Rockwell B scale. In fully recrystallised grains the above transit time difference was found to be more than 2.20 µs in partially recrystallised grains it was within 1.52-2.20 whereas that for unrecrystallised grains, it was less than 1.52 µs.

Research paper thumbnail of Split Ends and Cracking Problem During Hot Rolling of Continuously Cast Steel Billets

Journal of Failure Analysis and Prevention, 2009

The paper presents a detailed analysis of split end and cracking problems that occurred during ho... more The paper presents a detailed analysis of split end and cracking problems that occurred during hot rolling of thermomechanically treated (TMT) grade steel bars. The major analytical tool was a multiscan computer-controlled ultrasonic image analysis system for analysis of the defects observed on transverse cut slices of the billets under investigation. The possible reasons for billet cracking during hot rolling such as a low Mn/S ratio, high casting speed, high degree of superheat, and high inclusion content in steel were analyzed. Additionally in the process parameters such as low roll diameter, high friction, and low reduction ratio were also analyzed. The cracking appeared to be associated with large surface/internal defects, axial porosity, off-centered cavities/porosities, off-centered cracks, and inclusion bands. The analysis results suggested methods to prevent such defects in continuously cast steel billets and to reduce/eliminate split end problems. The casting parameters should include: (a) Mn/S ratio >35, (b) degree of superheat <60 °C, and (c) casting speed: <3.0 m/min, where roll radius and initial thickness of the workpiece should be optimized.

Research paper thumbnail of Non - Destructive Evaluation of Rolls of Hot Strip Mill of Tata Steel

Performance of rolls in an Integrated Steel Plant like Tata Steel affects many plant performance ... more Performance of rolls in an Integrated Steel Plant like Tata Steel affects many plant performance measures i.e. mills down time (which affects plant productivity), rejection of rolled products, roll dressing time, consumption of rolls / ton of steel rolled etc. In order to ensure the supply of the rolls without harmful flaws, NDT techniques, particularly Ultrasonic and Eddy Current, were developed and implemented on the shop floor to improve the plant performance by reducing their failure in the mill. Indefinite Chilled Cast Iron Double Poured Work Rolls of finishing stands, High Chrome Iron as well as Chrome Steel Work Rolls of early finishing and roughing stand were evaluated for their shell / core disbond as well as surface cracks using these techniques. High Speed Steel rolls under trial in the finishing stand F2 were also evaluated for their surface cracks using an eddy current inspection method developed at R&D Division of Tata Steel..

Research paper thumbnail of Development of an Ultrasonic Technique to Optimize the Scarfing Depth and Length of First and Last CC Slabs of a Sequence of IF Grade at Tata Steel

Presence of non-metallic inclusions & macro-flaws (cracks, pin holes/blow holes, segregation ... more Presence of non-metallic inclusions & macro-flaws (cracks, pin holes/blow holes, segregation etc.), in a large number, in first and last continuously cast (CC) slabs of a sequence of casting, makes the CC slabs inferior in quality. Due to this problem these slabs were being downgraded and a huge loss in net realization was observed due to the difference in the prices of downgraded and prime grade CC slabs of IF grade. A need was, therefore, felt to determine the optimum scarfing depth and optimum length of these slabs to upgrade them into prime quality. The paper highlights the effectiveness of ultrasonic techniques in detecting, measuring and analyzing macro- flaws in these slabs. 6 MHz twin crystal (T/R) along with 2 MHz single crystal probes were used to study the number of high gain internally reflected signals (flaw echoes) to assess overall flaws / inhomogeneities. The study revealed that the optimum scarfing depth was 7 mm from both top as well as bottom in case of both first and last IF grade slabs of the sequence casting. This helped in converting the inferior slabs into the prime grade. The optimum useful slab length in first and last slabs of IF grade, that can be converted to prime grade, in 11 meters long slabs, will be 8 meters and 9 meters respectively.

Research paper thumbnail of A Novel Method to Measure Cleanliness in Steel Using Ultrasonic C-Scan Image Analysis

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2008

The traditional method of measuring the cleanliness level of steel is to measure its total oxygen... more The traditional method of measuring the cleanliness level of steel is to measure its total oxygen (TO), which does not provide information about the size, location, and distribution of more harmful macroinclusions. The present article highlights a novel method for cleanliness assessment in steel samples using ultrasonic C-scan image analysis. The method provides quick and large volume inspection and ability to catch macroinclusions that possess difficulty during further processing of the thin gage steel products, particularly for auto grades such as interstitial-free (IF) steel. This method deals with a multiscan, immersion ultrasonic system using high-frequency focused beam and image analysis software. A good correlation was found between ultrasonic parameter counts and TO in steel samples taken from tundish during the continuous casting of slab. The ultrasonic counts were also found to be correlated with some steelmaking parameters.

Research paper thumbnail of Study of Inclusion Bands in Continuously Cast Steel Billets for Rolling Thermomechanically Treated Rebars

Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2008

The article presents the investigation results of inclusion bands generally formed toward the loo... more The article presents the investigation results of inclusion bands generally formed toward the loose end/inner radius of continuously cast (CC) strands of thermomechanically treated (TMT) rebar grade cast through curved molds. The main analytical tool used for this purpose was an ultrasonic C-scan image analysis system to reveal this band, and the defects detected in this band using the preceding technique were further measured and analyzed in an optical microscope and a scanning electron microscope (SEM) using energy-dispersive system (EDS). The investigation results revealed the presence of macrolevel globular macroinclusions in the size range 50 to 711 μm. The main constituents of the globular inclusions were found to be SiO2 and MnO. Impact test results revealed reduction in ductility in these bands when compared with the billet material without inclusion band toward the opposite face from the inner radius face. In Charpy testing, reduction in the impact energy in these bands was found to be 0.2 kg m. It is important to monitor the severity of macroinclusions present in these bands to avoid the cracking of TMT rebars during hot rolling.

Research paper thumbnail of Study of Inclusion Bands in Continuously Cast Steel Billets for Rolling Thermomechanically Treated Rebars

Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2008

The article presents the investigation results of inclusion bands generally formed toward the loo... more The article presents the investigation results of inclusion bands generally formed toward the loose end/inner radius of continuously cast (CC) strands of thermomechanically treated (TMT) rebar grade cast through curved molds. The main analytical tool used for this purpose was an ultrasonic C-scan image analysis system to reveal this band, and the defects detected in this band using the preceding technique were further measured and analyzed in an optical microscope and a scanning electron microscope (SEM) using energy-dispersive system (EDS). The investigation results revealed the presence of macrolevel globular macroinclusions in the size range 50 to 711 μm. The main constituents of the globular inclusions were found to be SiO2 and MnO. Impact test results revealed reduction in ductility in these bands when compared with the billet material without inclusion band toward the opposite face from the inner radius face. In Charpy testing, reduction in the impact energy in these bands was found to be 0.2 kg m. It is important to monitor the severity of macroinclusions present in these bands to avoid the cracking of TMT rebars during hot rolling.

Research paper thumbnail of Evaluation of the Effect of ElectroMagnetic Stirring on Soundness of Continuously Cast Billets Using Ultrasonic Technique

Effect of electro-magnetic stirring on soundness of continuously cast billets and slabs can be as... more Effect of electro-magnetic stirring on soundness of continuously cast billets and slabs can be assessed by many methods like visual inspection of macro-etch & sulphur print evaluation. Ultrasonic assessment provides through thickness information of the test samples, whereas, macro-etching and sulphur print methods provide information in one plane only. An attempt has been made to evaluate the soundness (inhomogeneities / flaws as well as effect of columnar / equiaxed grains) of continuously cast low carbon and high carbon continuously cast billets by ultrasonic attenuation as well as high gain pulse-echo technique in transverse cut slices. One low carbon grade (Grade -LC) and one high carbon grades (Grade -HC) were selected for this purpose.

Research paper thumbnail of A Novel Method to Measure Cleanliness in Steel Using Ultrasonic C-Scan Image Analysis

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2008

The traditional method of measuring the cleanliness level of steel is to measure its total oxygen... more The traditional method of measuring the cleanliness level of steel is to measure its total oxygen (TO), which does not provide information about the size, location, and distribution of more harmful macroinclusions. The present article highlights a novel method for cleanliness assessment in steel samples using ultrasonic C-scan image analysis. The method provides quick and large volume inspection and ability to catch macroinclusions that possess difficulty during further processing of the thin gage steel products, particularly for auto grades such as interstitial-free (IF) steel. This method deals with a multiscan, immersion ultrasonic system using high-frequency focused beam and image analysis software. A good correlation was found between ultrasonic parameter counts and TO in steel samples taken from tundish during the continuous casting of slab. The ultrasonic counts were also found to be correlated with some steelmaking parameters.

Research paper thumbnail of Failure of Nickel Coating on a Copper Mold of a Slab Caster

Journal of Failure Analysis and Prevention, 2008

Copper molds are critical components in the continuous casting of steel. Surface condition of the... more Copper molds are critical components in the continuous casting of steel. Surface condition of the mold directly affects product quality, and premature failure/low wear life affects the output of the continuous casting plant. This paper presents the failure analysis of a nickel coating on a copper plate during a plant trial using in situ ultrasonic testing for coating thickness evaluation and in situ testing to confirm the loss of coating. The failure analysis indicated maximum coating wear near the bottom corners of the mold. More wear was found on the wide end face compared with that observed on the narrow face. On top portion of the mold, wear was almost negligible. Based on the wear profile obtained during trial, it was recommended that the coating on the bottom portion of the mold have a higher hardness to improve mold life.

Research paper thumbnail of Determination of Condition of Recrystallised Grains After Annealing of Cold Rolled IF Grade Steel Sheets Based on Ultrasonic Measurements

The Interstitial Free (IF) grade steel sheets are used for auto body applications where these she... more The Interstitial Free (IF) grade steel sheets are used for auto body applications where these sheets require good formability/drawability property. To achieve this property the cold rolled sheets are annealed to obtain desirable texture in the recrystallised grains to avoid material failure during forming operation. The paper deals with an ultrasonic technique to determine the condition of the recrystallised grains after annealing operation. 79 % cold rolled IF grade steel sheets were annealed at 650 deg. C for different times. After annealing the scale was completely eliminated from the surface by pickling to make the surface conducive for transmission of ultrasonic surface waves. Ultrasonic transit time for a fixed distance in µs was measured in rolling as well as 45 0 to rolling direction using 4 MHz transmitting and receiving transducers. Unrecrystallised, partially recrystallised and fully recrystallised regions in this case were determined by measuring hardness in Rockwell B scale. In fully recrystallised grains the above transit time difference was found to be more than 2.20 µs in partially recrystallised grains it was within 1.52-2.20 whereas that for unrecrystallised grains, it was less than 1.52 µs.

Research paper thumbnail of Split Ends and Cracking Problem During Hot Rolling of Continuously Cast Steel Billets

Journal of Failure Analysis and Prevention, 2009

The paper presents a detailed analysis of split end and cracking problems that occurred during ho... more The paper presents a detailed analysis of split end and cracking problems that occurred during hot rolling of thermomechanically treated (TMT) grade steel bars. The major analytical tool was a multiscan computer-controlled ultrasonic image analysis system for analysis of the defects observed on transverse cut slices of the billets under investigation. The possible reasons for billet cracking during hot rolling such as a low Mn/S ratio, high casting speed, high degree of superheat, and high inclusion content in steel were analyzed. Additionally in the process parameters such as low roll diameter, high friction, and low reduction ratio were also analyzed. The cracking appeared to be associated with large surface/internal defects, axial porosity, off-centered cavities/porosities, off-centered cracks, and inclusion bands. The analysis results suggested methods to prevent such defects in continuously cast steel billets and to reduce/eliminate split end problems. The casting parameters should include: (a) Mn/S ratio >35, (b) degree of superheat <60 °C, and (c) casting speed: <3.0 m/min, where roll radius and initial thickness of the workpiece should be optimized.

Research paper thumbnail of Non - Destructive Evaluation of Rolls of Hot Strip Mill of Tata Steel

Performance of rolls in an Integrated Steel Plant like Tata Steel affects many plant performance ... more Performance of rolls in an Integrated Steel Plant like Tata Steel affects many plant performance measures i.e. mills down time (which affects plant productivity), rejection of rolled products, roll dressing time, consumption of rolls / ton of steel rolled etc. In order to ensure the supply of the rolls without harmful flaws, NDT techniques, particularly Ultrasonic and Eddy Current, were developed and implemented on the shop floor to improve the plant performance by reducing their failure in the mill. Indefinite Chilled Cast Iron Double Poured Work Rolls of finishing stands, High Chrome Iron as well as Chrome Steel Work Rolls of early finishing and roughing stand were evaluated for their shell / core disbond as well as surface cracks using these techniques. High Speed Steel rolls under trial in the finishing stand F2 were also evaluated for their surface cracks using an eddy current inspection method developed at R&D Division of Tata Steel..

Research paper thumbnail of Development of an Ultrasonic Technique to Optimize the Scarfing Depth and Length of First and Last CC Slabs of a Sequence of IF Grade at Tata Steel

Presence of non-metallic inclusions & macro-flaws (cracks, pin holes/blow holes, segregation ... more Presence of non-metallic inclusions & macro-flaws (cracks, pin holes/blow holes, segregation etc.), in a large number, in first and last continuously cast (CC) slabs of a sequence of casting, makes the CC slabs inferior in quality. Due to this problem these slabs were being downgraded and a huge loss in net realization was observed due to the difference in the prices of downgraded and prime grade CC slabs of IF grade. A need was, therefore, felt to determine the optimum scarfing depth and optimum length of these slabs to upgrade them into prime quality. The paper highlights the effectiveness of ultrasonic techniques in detecting, measuring and analyzing macro- flaws in these slabs. 6 MHz twin crystal (T/R) along with 2 MHz single crystal probes were used to study the number of high gain internally reflected signals (flaw echoes) to assess overall flaws / inhomogeneities. The study revealed that the optimum scarfing depth was 7 mm from both top as well as bottom in case of both first and last IF grade slabs of the sequence casting. This helped in converting the inferior slabs into the prime grade. The optimum useful slab length in first and last slabs of IF grade, that can be converted to prime grade, in 11 meters long slabs, will be 8 meters and 9 meters respectively.