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New laser welding technology extends the use of advanced high-strength steel alloys

Krypton learned that a Brazilian researcher, Milton de Lima, has developed an innovative method of laser welding at high temperatures that enhances the performance of advanced high-strength steels (AHSS) for use in the automotive and aerospace industries.

In recent years, there has been an increased demand for high performance advanced high strength alloys in the automotive industry due to the increasingly stringent requirements on passenger safety, vehicle performance and fuel economy. High-strength steels offer better formability and crash resilience than traditional steels and can be used in critical safety locations in body structures to withstand vehicle collisions. However, certain high-strength alloys tend to become brittle due to welding and may fracture when subjected to the hot stamping and forming required for many manufacturing processes.

Developers developed techniques that include induction heating 22MnB5 steel and heating it to approximately 450 ° C 10 minutes before laser welding to equalize the temperature. 22MnB5 is used in automotive construction and safety components. The high mechanical strength of the final part reduces the weight by 30% to 50% compared to conventional cold forming. After welding, the sheet is held at an elevated temperature for 10 minutes to produce a bainitic structure. Metallurgists have found that bainite is a plate-like microstructure formed in steel under certain conditions and is the best candidate for making rugged, reliable welded joints, with particular emphasis on high compressive and tensile strength .

Analysis shows that the sheet welded at this high temperature contains bainite and is much harder than the sheet welded at room temperature, which contains martensite, a microstructure with lower tensile strength.

The researchers said the technology is easy to apply to manufacturing to enhance laser welding of high-strength and ultra-high-strength steels. The automotive industry uses laser welding to connect billet and stamped structural parts such as columns, beams, reinforcing bars, etc. faster and more reliably than traditional welding methods.

Although research is still in its infancy, bainitic steels are expected to be a good barrier and armor material because of their high mechanical energy absorption.

Milton de Lima is currently working on a project supported by FAPESP to demonstrate the viability of its technology in Brazil and to use it for laser welding of maraging steel, which is a Brazilian rocket and The basic components of missile engines.