What is a Pit-Type Carbonitriding Furnace
May. 08, 2025
A pit-type carbonitriding furnace is a composite heat treatment equipment that integrates both carburizing and nitriding functions. Below is an analysis from three perspectives: its technical principles, process capabilities, and structural design:
1. Technical Principle: Composite Characteristics of Carbonitriding
Dual-Element Synergistic Diffusion
The well-type carbonitriding furnace introduces both carburizing media (e.g., methanol, kerosene) and nitriding media (e.g., ammonia gas) into the chamber simultaneously. Under high temperatures, the workpiece surface absorbs both carbon and nitrogen atoms, forming a composite diffusion layer enriched with carbon and nitrogen. This process integrates the strengthening effects of carburizing with the corrosion resistance of nitriding, transcending the functional limitations of single-element carburizing or nitriding.
Dynamic Control of Process Parameters
The furnace is equipped with a triple-head stainless steel dripping system and an ammonia gas inlet pipe, enabling independent regulation of carbon and nitrogen source supply rates. This facilitates precise control over the carbon-to-nitrogen ratio within the diffusion layer. For instance, by adjusting the methanol dripping rate and ammonia gas flow, gradient-distributed carbonitride layers can be achieved, meeting the performance requirements of diverse workpieces.
2. Process Capabilities: Addressing Diverse Heat Treatment Requirements
Multi-Process Compatibility
This equipment supports a wide range of thermal treatment processes, including carbonitriding, nitriding, carburizing, vacuum bright quenching, and bright annealing. For instance, when treating gears, carbonitriding can be applied first to enhance surface hardness and wear resistance, followed by vacuum bright quenching to eliminate internal stresses. This enables an efficient "one-furnace-for-multiple-processes" production model, maximizing equipment utilization.
Broad Material Applicability
The equipment is suitable for processing various workpieces, such as mechanical components, gears, bearings, hydraulic parts, standard fasteners, stamping dies, and cutting tools. It excels in handling specialty steels, including tool steel, bearing steel, and stainless steel, enabling optimized performance through adjustable process parameters. For example, after carbonitriding high-speed steel cutting tools, their surface hardness can exceed HRC 62 while maintaining core toughness, balancing hardness and ductility for enhanced cutting performance.
3. Structural Design: Ensuring Stability of Composite Thermal Processes
Core Components Synergistic Integration
1) Muffle Pot:
Constructed from heat-resistant steel, it stabilizes internal furnace pressure, ensuring uniform diffusion of carbonitriding atmospheres to prevent localized over- or under-penetration of workpieces.
2) Vacuum-Sealed Blower with Integrated Cooling:
Adopts a water-cooled sealing system to elevate furnace pressure to a micro-positive state, preventing air ingress and resultant atmosphere contamination. This design simultaneously accelerates the diffusion of carbon and nitrogen atoms into the workpiece matrix, enhancing treatment efficiency.
3) Multi-Pipeline System:
The furnace cover integrates dedicated pipelines for drip-feed tubes (carbon source), ammonia gas (nitrogen source), sampling ports, and exhaust vents. Each pipeline operates independently and is equipped with water-cooled jackets to enable rapid cooling of process gases and precise pressure regulation.
4) Process Monitoring & Control
Atmosphere Sampling & Analysis:
The sampling pipe connects to a U-tube glass manometer and CO₂ infrared analyzer for real-time monitoring of furnace atmosphere composition and pressure. This ensures dynamic equilibrium of carbon potential (Cp) and nitrogen potential (Np), guaranteeing consistent treatment quality.
Exhaust Regulation & Emission Control:
The exhaust vent features an adjustable pressure-release valve to control gas discharge rates, maintaining stable furnace pressure. Emitted waste gases are ignited prior to release, mitigating environmental pollution by eliminating unburned ammonia and hydrocarbons.
