Tempering spring steel has me scratching my head over color changes

I've been working on a project using old leaf springs to make some simple tools. When I temper the steel after quenching, the colors don't show up like they should. I set my oven to 400 degrees Fahrenheit, but the steel turns blue way too fast instead of that straw yellow I'm aiming for. I even bought a new oven thermometer to double check the heat, and it says it's right on. Maybe the steel has different stuff in it from being in a car for years? I tried lowering the temperature a bit, but then the steel stays too soft. Has anyone else had this happen with recycled spring steel? I'm really curious if there's a trick to getting the temper right on this kind of material. Any tips would be awesome.

2 comments

2 Comments

the_troy3d ago

Look at the surface of that recycled steel (it might have lost carbon from all those years on the road). That missing layer can make the colors show up way faster than you'd think.

wesley_foster443d ago

Wait, you're saying the carbon just wears off over time? That's crazy if a piece of metal getting rained on and driven for years changes how it takes color now. So the steel is basically pre-weathered and that's why the patina forms super fast?