Having been educated by Jim in the science of mainsprings and spring rates etc I am still puzzling over what difference the various steels used to make springs can have.
I also have a vague memory of it being possible to calculate spring rate from the spring dimensions, albeit maybe only an approximation ... but maybe memory is fading.
But... to the original question: What steels are used to make springs and what are the differences between them? Which is best ? Is one steel inherently 'softer' than another? Is one likely to last longer?
I am also pretty sure I have heard the term 'Swedish steel' but always thought that is marketing hype similar to 'Jersey Potatoes' or 'Lincolnshire Potatoes' which just mean 'grown in wherever'.

Just Lockdown musings.
Cheers, Phil