Originally posted by c55m8o
It's a form or "annealing" (read the Wiki article). Excerpt: Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing damage to its properties such as strength and hardness. It is a process that produces conditions by heating and maintaining at a suitable temperature, and then cooling very slowly. It is used to induce softness, relieve internal stresses, refine the structure and improve cold working properties.

If the spring was heated and not immersed in a solution but cooled slowly in air, it is the "normalizing" heat treatment form of annealing. (The former method actually 'hardens' the exterior of metals.)

I don't think my springs need to be soften and reduce the strength and harness of them. But what the reader might realize when reading all this is, if the action wasn't done in a furnace to provide uniform heat over the entire surface and heat the volume of the material equally, but just hit with a torch in spots, the annealing will be 'spotty' as there's just no way each and every part of that spring was heated uniformly. I surmise that would definitely lead to shearing forces occuring -within- the spring coils existing between the boundries of the spring that were softened through annealing an not softened as much by not having received as high a heat treatment. ...could break.

You may 'want' a softer spring though. And controlled annealing in a furnace would be the way to do it. (you just really don't know what spring rate you'll be getting in any case). I personally just think taking a torch to a spring would be a very inferior way to do it vs. doing it in a furnace. It definitely would result in a non-uniformly altered spring having soft and hard spots throughout both the surface and volume, with additional sheering stresses produced at those boundaries vs. the lower stresses throughout the material annealing is supposed to produce.
okay, as far as i know the guys who compressed my springs for me (Snell Springs) have heat treating equipment, they actually make springs. they heat the spring up, then they are able to move the spring carefully without damaging it and thus compressing the spring. Then going through another process which hardens them again. in this case the springs properties havent been slightly modified. i was talking to the guy just before and he tells me that tourching the spring is softing the spring, what he's done to my spring is that he hasnt soften'd it hes just lowered my springs with the same hardness of the spring.
i couldnt catch everything he said..but yeah phew..it was a real handful.
btw, how'd you know so much about properties of metal? and spring rates? its good that you know, and pass you knowledge on..:P