DEVELOPMENT OF NEW HIGH STRENGTH LOW ALLOY (HSLA) STEEL SHEETS-BEML E 500amp; BEML E 550

摘要

Pontoon bridge set (PMS) is a floating type pontoon bridge equipment used to transport military. vehicles, equipments and personnel across the water obstacles and marshy grounds. The design calculations for bouncy of the pontoon and the application for the Pontoon bridge prompted that steel used for pontoon fabrication to be of high strength structural steel sheets with yield stre;ngth of 500 -550 MPa and thickness of 2 mm & 3 mm. Also, the application demanded the steel to possess very good formability, weldability, low temperature toughness and atmospheric corrosion resistance. Such high strength steel sheets with all the above properties are not covered by any of the existing HSLA (High Strength Low Alloy) steel standards. Hence, there was a need to develop a new HSLA steel sheet.The alloy design was carried out keeping in view the design parameters and application needs. A Niobium Micro-alloyed Weathering steels with low Carbon and with low Sulphur and Phosphorus were designed. The steels were designated as BEML E 500 and BEML E550. Sample heats of the designed compositions were produced at a steel plant. The steel was processed at a steel hot rolling mill by thermo-mechanical processing.The end properties of the steel sheets were tested for chemistry and found to be meeting all the end properties, which are required for such a critical and special application. Since the development of such high strength steel for special application has been done for the first time, there is a need to protect the Intellectual Property Rights of this invention through a patent.Hence we are submitting our application for patenting of this invention.