Found a video by Kevin Potter that was helpful to me concerning rebound vs contruction.

My question is on the 4140. It had the poorest rebound but would  increasing the mass help the rebound?It was the smallest anvil of the lot. And does hardening the face help with rebound or is hardening mostly done to protect the face of the anvil.

I am planning on getting a 100# piece of 5" dia 4140 from the salvage yard for a post anvil, and wondering if I should expect it to be a good anvil.  Thanks  Jeff

 

 

 

Harding the face will improve rebound faster than bulking up the base

4140 is a tough, flexible steel, rather than a hard steel. That is why it is used for race car frames, etc.  Much better strength to weight ratio than A36.

 

Typical with most steels, as it comes from the mill, it is in the dead soft annealed condition (RockwellC 13), so that it can be drilled, turned, sawn, etc.

If you are going to weld on it, it needs a preheat, and a post weld heat treatment. It can be heated and quenched to harden it somewhat, but may be susceptible to cracking. It will also work harden to a degree, but may deform under heavy use before that happens. 

Jeff: You might contact the outfits in the interior who heat treat and see what it'd cost to bring one end of that shaft to a RC 58-60. As our admitted knuckle dragging donut hound says 4140 as from the mill is as soft as it can be. 4140 is an amazing alloy that can take horrific stress and pressure without work hardening to an embrittled state. If you own a recently made high powered rifle take a look at the breach and consider that thin looking steel takes pressures I think in the 200,000psi range. (The guys who actually know will correct me I hope) Still it's outrageously high pressure and it happens fast.

 

Airframes are 4130 a lower carbon version of the same chromemolly alloy and if you've ever watched the wings of an airplane in flight you get an idea of the important properties of chrome molly steel. virtually any common steel subjected to the stress and flexing of an airframe would work harden become brittle and break and pretty quickly. What the chrome does I'm not sure but the mollebdenum is like rebar in concrete or straw in mud bricks. It has a long molecule and gives steel alloys a high flex rebound and doesn't work harden. More and it becomes air hardening steel like a chainsaw bar, it's not only really flex strong over heating it just makes it stronger. In the correct alloy and % that is. It's great stuff, I LOVE molly steel.

 

The difference between 4130 and 4140 is 0.1% carbon, bringing 4140 into the carbon range where it can be hardened appreciably. The molly % isn't high enough it's an air hardening alloy though. Heat treating a piece that thick isn't something a beginner is going to do well in a home shop. Heck, there are threads here about hardening 4140 and the pitfalls involved. If yo can have it done professionally for reasonable that's what I'd do.

 

Once heat treated it'll make a superb anvil.

 

Frosty The Lucky.

Thanks  Guys.