Pit Type Furnace
Usual Temperature - 450* 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 :
Zero Distortion
Since there is no phase change (austenite to
martensite) and no rapid quenching, the parts do not warp or crack.
Extreme Hardness
Nitrided surfaces can be significantly harder than
carburized surfaces (up to 70 HRC equivalent).
Heat Resistance
The hardened case remains stable even if the part
operates at high temperatures (up to 500°C) during its working life.
No Post-Grinding
Because the process is so stable, parts are often
finished to their final size before nitriding.
Vertical Efficiency
The pit design allows long, slender parts to be treated without bending.
Application :
Precision Tooling
Injection molding screws, extrusion dies, and high
speed drill bits.
Engine Components
Crankshafts, camshafts, and valve stems for high performance racing or heavy diesel engines.
Gears & Spindles
High-precision gears where grinding after hardening
is too expensive or difficult.
Hydraulics
Piston rods and cylinders that require smooth, hard, and
rust-resistant surfaces.
Firearms
Barrels and bolts for increased longevity and environmental
resistance.
Process in short
Cleaning: Parts must be pristine; any oil or residue will block nitrogen
diffusion.
Loading: Parts are placed in the pit furnace and sealed.
Heating: The furnace is heated to a sub-critical range, typically 500°C to
590°C.
Nitrogen Injection: Anhydrous ammonia gas is introduced. At these
temperatures, the ammonia cracks into nascent nitrogen and hydrogen.
Diffusion (The Soak): Nitrogen atoms migrate into the steel surface,
reacting with alloying elements (like Cr, Al, and Mo) to form hard
nitrides.
Cooling: Parts are usually slow-cooled within the furnace or in a
specialized cooling pit. No quenching is required.
Post Oxidation (Optional): Many parts need oxidation at the end for that
steam should introduce which results in Black Metal finish surface.
Purpose :
The goal is to create an extremely hard, wear-resistant surface layer (the
“White Layer” and “Diffusion Zone”) while:
Preventing Distortion: Avoiding the high heat of carburizing so the part
stays perfectly straight.
Improving Fatigue Life: Creating compressive stresses on the surface to
prevent cracks.
Corrosion Resistance: Enhancing the metal's ability to resist rusting and
chemical attack.
