Mausumi Kar - Academia.edu (original) (raw)
Graduate Metallurgical Engineer and IRCA certified Lead Auditor for ISO 9001 and ISO 14001, certified Lead Auditor for Laboratory Management System ISO 17025 and certified Lead Auditor for AS9100 Aerospace Quality Management System having 33 years experience in Research
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In recent years the Steel Rolling Mills have undergone a significant change regarding quality req... more In recent years the Steel Rolling Mills have undergone a significant change regarding quality requirements, productivity and the thickness of the products being rolled. The Hot Strip Mills have emerged with higher productivity, excellent surface finish of coils with thinner gauge rolling. Stringent dimensional tolerance, strip finish and profile flatness requirements and higher mill productivity have called for improved wear resistance and fatigue crack resistance of the rolls used in the finishing stands. For the finishing stands of hot strip mills Duplex ICDP and ICDP-EC rolls are nowadays produced through either Vertical Centrifugal Casting (VCC) or Horizontal Centrifugal Casting (HCC) process. These duplex rolls generally consist of a Shell made of alloy cast iron and the Core made of spheroidal graphitic Iron. It has been observed that the Performance of the imported ICDP-EC Rolls manufactured by the Market leaders far superseded the Performance of the indigenous rolls due to higher wear and fatigue crack resistance of the imported rolls. Use of the imported rolls also improved the surface quality of products rolled and improved the campaign life of the rolls. A study of few Imported and Indigenous rolls was carried out to find out the deficiencies of the Indigenous Rolls in comparison to the Imported Rolls manufactured by the market leaders. In this paper the chemical compositions and microstructure of the imported rolls have been benchmarked with those of the indigenous rolls. The morphology and content of
The Rolling Mill rolls should resist major incidents in the mill like strip breaks and cobbles th... more The Rolling Mill rolls should resist major incidents in the mill like strip breaks and cobbles that generally lead to superficial cracks and subsequent spallings. Ideally a roll should have very low internal stress and high resistance to mechanical and thermal cracks. Superior performance relates to extended mill campaigns for greater uptime of mill and quality of the rolled sheet. For Cold Rolling applications the following properties are required: excellent mark resistance, good surface appearance of the sheet and increasing roughness retention to avoid slippage on the stands. The elimination of rehardening of the rolls (constant hardness throughout the life of the roll), the ability to be used in all stands of the mill, and the reduction of stock removal during grinding between campaigns, contribute to improved cost effectiveness. Various Improvement initiatives have been taken up by GPIL to improve Performance of the Forged Rolls. The paper discusses the major factors which adversely affect the Service Life of Forged rolls such as Fire Cracks, Soft Spots and Spalling. Reasons for soft spot occurrence were identified and the problem was mitigated. Measures have been taken to enhance resistance to crack propagation and reduce spalling. In this paper ways and means adopted by GPIL to improve Life of the Rolls have been discussed in detail.
In recent years the Steel Rolling Mills have undergone a significant change regarding quality req... more In recent years the Steel Rolling Mills have undergone a significant change regarding quality requirements, productivity and the thickness of the products being rolled. The Hot Strip Mills have emerged with higher productivity, excellent surface finish of coils with thinner gauge rolling. Stringent dimensional tolerance, strip finish and profile flatness requirements and higher mill productivity have called for improved wear resistance and fatigue crack resistance of the rolls used in the finishing stands. For the finishing stands of hot strip mills Duplex ICDP and ICDP-EC rolls are nowadays produced through either Vertical Centrifugal Casting (VCC) or Horizontal Centrifugal Casting (HCC) process. These duplex rolls generally consist of a Shell made of alloy cast iron and the Core made of spheroidal graphitic Iron. It has been observed that the Performance of the imported ICDP-EC Rolls manufactured by the Market leaders far superseded the Performance of the indigenous rolls due to higher wear and fatigue crack resistance of the imported rolls. Use of the imported rolls also improved the surface quality of products rolled and improved the campaign life of the rolls. A study of few Imported and Indigenous rolls was carried out to find out the deficiencies of the Indigenous Rolls in comparison to the Imported Rolls manufactured by the market leaders. In this paper the chemical compositions and microstructure of the imported rolls have been benchmarked with those of the indigenous rolls. The morphology and content of
The Rolling Mill rolls should resist major incidents in the mill like strip breaks and cobbles th... more The Rolling Mill rolls should resist major incidents in the mill like strip breaks and cobbles that generally lead to superficial cracks and subsequent spallings. Ideally a roll should have very low internal stress and high resistance to mechanical and thermal cracks. Superior performance relates to extended mill campaigns for greater uptime of mill and quality of the rolled sheet. For Cold Rolling applications the following properties are required: excellent mark resistance, good surface appearance of the sheet and increasing roughness retention to avoid slippage on the stands. The elimination of rehardening of the rolls (constant hardness throughout the life of the roll), the ability to be used in all stands of the mill, and the reduction of stock removal during grinding between campaigns, contribute to improved cost effectiveness. Various Improvement initiatives have been taken up by GPIL to improve Performance of the Forged Rolls. The paper discusses the major factors which adversely affect the Service Life of Forged rolls such as Fire Cracks, Soft Spots and Spalling. Reasons for soft spot occurrence were identified and the problem was mitigated. Measures have been taken to enhance resistance to crack propagation and reduce spalling. In this paper ways and means adopted by GPIL to improve Life of the Rolls have been discussed in detail.