Field notes
Notes from the tank side
What we learned about salt, oil and water — written for process engineers, not for search engines.
2026.09.18
2026.08.26
2026.07.30
Why a quench salt bath needs periodic filtration
Oxide scale, sludge and carbon black suspended in molten salt change the cooling rate — and the cooling rate decides hardness, distortion and cracking.
0.5% versus 1.5%: what the water in nitrate quenching actually does
Adding water to nitrate salt is one of the few deliberate water additions in heat treatment. How much, how, and how it is held decide the shape of the cooling curve.
Four things to watch when judging CHD under GB/T 9450-2025
The new standard is stricter about interpolation, spacing and reporting. The usual mistakes are not in the hardness tester but in sampling and indentation layout.
Tell us what your bath is doing.
We will tell you what to do next.
One call is enough to establish three things: where your bath stands today, which step comes first, and how long it takes.