Study on the effect of technological parameters on mechanical properties of deep drawn steel melted from sponge iron serving the National Defense Industry

1. Since the end of the 20th century, the development of metallurgical technology has led to the creation of an advanced high-strength steel group - AHSS including dual phase steel which is superior in both strength and ductility and has been applied by a number of countries in the military. Dual phase steel billets have been initially studied in the country by melting from sponge iron and refining in vacuum furnace, which can be applied in manufacturing of some highly durable components in the military such as: artillery shells, rocket shells, etc. Due to the effect of technological parameters, deformation and heat treatment in the technology is crucial to the microstructure and mechanical properties of steel; thus, it is really urgent to specify the laws of their effect on steel in the country, thereby solving today's technology problems; bringing this material to be used in the National Defense production, ensuring the self-control of a part of essential supplies for the Army; contributing to the implementation of the Resolution No. 06 by the Politburo on the development of the National Defense Industry until 2020 and subsequent years.
2. The thesis studies the laws and technological parameters, effect of the degree of deformation and heat treatment used to make long thin-walled high-pressure tubular components in the military with steel grade surveyed as low-carbon dual phase steel. These laws are also applied to make high-strength thin steel plates that can be used in national defense and civil engineering.
Research methodology: Combining theoretical and empirical research. Using experimental planning method to design experiments and experimentally identify necessary data sets needed to formulate the laws; regression functions are evaluated according to statistical standards, ensuring accuracy and reliability of the relationship between the degree of deformation and heat treatment with the microstructure and mechanical properties of steel.