Topic for this video is a category of alloy steels that achieve very high strength levels with a simple heat treatment after the manufacture of the part. For the full transcript, click here: https://www.michlinmetals.com/maraging-steels-maraging-200-maraging-250-maraging-300/ These alloys are called "Maraging" steels. MAR from martensite and AGEING for how they develop  strength.   Conventional steel alloys  like 4340 ,that can achieve comparable strength levels have a minimum carbon content of point 4 % and require a high temperature austenitizing step followed by rapid quenching and then a final tempering to develop their strength. Needless to say, this process can be very troublesome in many part configurations. With these carbon levels any welding requirement can be very problematic.