Pit Type Furnace
Usual Temperature - 500* C to 650* C
Capacity – From 50 kg to 2500 kg, Size is customizable as per job sizes.
Heat Source – Electric, Gas & Oil
Energy Efficient structure + energy efficient control panel
Can also provide with Programmable operating through PlC, hmi, Scada.
Loading – Vertically Hanging
Why Pit Type?
- Zero Bending: By hanging a long shaft vertically, gravity acts as a stabilizing force, keeping the part perfectly straight.
- Uniform Quenching: When you lift a hanging job out of a Pit furnace and drop it into a quench tank, the fluid hits all sides simultaneously, reducing the risk of "banana" warping.
Advantages :
Speed
It is much faster than gas nitriding. A deep case that takes 24 hours in a gas furnace can often be achieved in 2 to 4 hours in a salt
bath.
Uniformity
Because the liquid salt surrounds the entire part, complex geometries, blind holes, and internal threads are treated perfectly
evenly.
Lower Temperature
Like gas nitriding, it stays below the transformation temperature, meaning minimal distortion or change in
core dimensions.
High Surface Hardness
It produces an extremely hard “Compound Layer” (White Layer) that is very resistant to abrasion.
Versatility
Works excellently on low-carbon steels, alloy steels, cast iron, and even stainless steel.
Application :
Automotive
Crankshafts, valves, rocker arms, and wiper motor gears.
Industrial Tools
Metal extrusion dies, plastic injection molds, and
stamping tools.
Hydraulics
Hydraulic cylinders, piston rods, and valve spools
(especially those requiring the black QPQ finish).
Firearms
Slides, barrels, and trigger components for superior scratch and rust resistance.
Textile Machinery
High-speed cams and needles that experience constant friction.
Process in short
Pre-heating : Parts are cleaned and pre-heated to approximately 400°C
to prevent thermal shock and moisture explosions.
Immersion : The parts are lowered into a molten salt bath (typically a
mixture of sodium and potassium cyanates) at 570°C to 580°C.
Chemical Reaction : The salt reacts with the steel surface, releasing
active nitrogen and carbon. Nitrogen diffuses into the metal, while
carbon helps stabilize the hardened layer.
Salt Recovery/Quench : Parts are moved to a cooling tank (water or oil)
to wash off the salt.
Oxidation (Optional) : Many parts then undergo an "AB1" or "QPQ"
(Quench-Polish-Quench) step in an oxidizing salt bath to create a black,
corrosion-resistant finish.
Purpose :
The goal is to improve the mechanical and chemical properties of the “skin” of
the metal:
Wear & Scuff Resistance : To prevent "galling" (metal-to-metal sticking)
in moving parts.
Fatigue Strength : To increase the part's ability to withstand repetitive
stress cycles by up to 100%.
Corrosion Protection : When followed by oxidation (blackening), it
provides better rust resistance than chrome plating.
