i am not partial to spring steels (ie 4140, 5160) because they move well under the hammer and relitivey forgiveing of some heat and lack there of and for me are relitively good water quench steels
car leaf spring can be 1045 5160 or some other thing the mill makes
a just do not recomend most exotic steels untill you do a fair bit of forgeing (A-32 is not recomended if cooled wrong lots of flying sharp things its not fun)
be safe happy forgeing