Heat treat anvil top plate

[caotropheus]

Greetings

Covid 19 lockdown and long days at home. So I am building my 3rd anvil. The final estimate weight is around 45 kg. This time I am using the method of welding the top plate. I took a plough share 12 mm thick, I annealed it, cut to shape and I am welding it as top plate to a mild steel body.  The plough steel seems to attached firmly to 7018 welds and it was pre heated  before welding. I am approaching the part I have to heat treat the top plate. I am making a stake anvil.

I made a small experiment and hardened a bit of steel on water, it broke easily upon hammer impact. I also made some observations under the stereoscopic microscope of the interface between 7018 welds and different steels. The steels were at room temperature, about 20 C. I lay 3 beads on top of steels, cut a slice, polished the cuts and etched for about 1 hour on muriatic acid 32%. Then I made my observations.

7018 weld top / mild bottom

7018 weld top / leaf spring bottom, notice micro cracks in the interface

7018 weld top/ plough steel bottom

So, I know the plough top plate  steel is brittle if hardened in water, I still have to harden test the steel in oil and air hardening. I doubt in my home conditions I can harden a 12 mm top plate air hardening steel attached to 45 kg non magnetic hot steel. To harden this top plate in oil is completely out of the question for obvious reasons. So, I am left for water quenching and I am afraid the top plate will detach from the welds. Also the quenching method will be a garden hose and many buckets of water being pored on the anvil.

Do you guys have suggestions that can help me heat treat this top plate? thanks.