The bars are not stacked, they placed in a tray with at least an inch of separation between other parts.
All bars within the load are the same.
All sides, but seems to be slightly concentrated on one end, the end near heat source which could result from overheating as previously mentioned.
The furnace is gas powered, it's a brick oven, the heat is blown in through the base and distributed upwards and out the stack.
We only heat treat the same material in each batch so we don't mix the 4340 with the 4140.
The parts are machined to size prior to heat treating with CNC milling...
The furnace is open atmosphere (uncontrolled), we can't temper the parts for more than 30min at 1000F as the resulting hardness will be too low, we could lower the temperature but I don't see the advantage. How would I check the pre-heat treated steel for "decarb"? The steel is 4140 Annealed...
Thanks for the replies. Yes the features are only present after heat treating, the parts are machined from round bar.
Parts are usually quenched and tempered in one day, tempering is likely not an issue since the features are present after quenching.
I've tried a longer soak time and gotten...
Hi all, we've recently switched to 4140A from 4340A for some of the parts we manufacture. The 4140 is simply easier to come by and significantly cheaper in our location.
For the 4140 we soak the parts for 30min once the oven returns to it's set temperature of 1580F. The parts are 1" square...
