How many greads of steels can be used for making coil springs & what are their properties ?

Hi, wagh1965!

If you click on the following searches, it's likely that you'll find some information on sites that you'll be able to read and study to come up with an answer for your questions.

Types of Coil Springs - Google Search

Types of Coil Springs Grades - Google Search

Of particular interest might be the information that can be found on the following sites.

Coil spring - Wikipedia, the free encyclopedia

Spring (device - Wikipedia, the free encyclopedia)

By the way, I use a flat, blued and tempered type of spring steel when I make a certain type of musical instrument. So, you're question caught my eye because I already have an interest in certain types of spring steel.

Thanks!

Another great source of information on steels, their uses, and their properties is the multi-volume set of ASM Metals Handbooks. You'd almost certainly have to go to a university library to find them; it is unlikely that municipal libraries would carry something this specialized.