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Next,
Car and truck springs, especially recent ones, are almost surely not any specific grade of steel. The charts and posts stating that they are all 1090, 5160, etc. are pure guess work. Unless you were able to contact the manufacturer with the lot number of the springs you used, there is no way they could tell you what they are....and even then they might not know. I believe all US auto springs are made overseas, mainly from Chinese steel, and the alloy used changes as the supply changes. You could have two different alloy springs on the same truck.
That said, the steel types used for automotive springs will normally make an OK knife. The HT is a bit of guesswork, though.
Last,
Getting a known steel from a source that deals in knife steel is the way to assure the best edge retention and blade hardness. Aldo (new jersey steel barron), and the major knife suppliers get steel that is already in the right condition and have had the alloy assayed to assure the quality. A four foot bar of good 1084 ( or 5160) will cost about $15. That way you know the exact HT regimen needed, and can nail the edge down right.
http://newjerseysteelbaron.com/
