Pit type nitriding furnace is equipment used for nitriding treatment, which consists of a furnace shell, furnace lining, furnace cover lifting mechanism, furnace sealing fan, muffle tank, heating element, and electric control system.
The furnace shell is usually welded from steel plates and steel sections, while the furnace lining is an energy-saving composite structure made of high-strength ultra lightweight energy-saving refractory bricks, aluminum silicate fibers, diatomaceous earth insulation bricks, and asbestos boards.
This type of furnace is a periodic operation electric furnace, with a maximum working temperature of 950 ℃. The furnace of the well type nitriding furnace is a vertical shaft type, with stainless steel furnace tanks and material baskets inside, and workpieces are placed in the material baskets.
The atmosphere control adopts a drip type, which drips into the furnace through a flow meter and dropper. The fan is installed on the furnace cover, which can perform forced circulation of temperature and atmosphere inside the furnace.
Pit type nitriding furnace is mainly used for gas nitriding of carbon steel parts, quenching of molds, and other heat treatments. It can also be used for gas nitrogen carbon co diffusion (soft nitriding) treatment, and is a widely used heat treatment equipment in industrial production.
*The benefits of nitriding treatment
The nitriding process is a chemical surface heat treatment process that involves infiltrating nitrogen or carbon atoms into the surface of steel parts at a temperature of 500-580 ℃. This process mainly involves nitriding and can also incorporate a small amount of carbon, aiming to improve the wear resistance, fatigue resistance, corrosion resistance, and high-temperature resistance of steel.
The nitriding process of carbon steel can be divided into three categories according to the co-diffusion medium state: solid, liquid, and gas. Among them, the gas method is suitable for large-scale production due to its ease of mechanization and automation, stable processing quality, but relatively complex equipment.
During the nitriding process, by controlling the specific gas ratio in the nitriding atmosphere, such as adjusting the ratio of endothermic transformation gases, a thin layer of cementite can be generated on the surface of the steel, thereby improving the hardness and wear resistance of the steel. This treatment not only improves the surface hardness of the steel, but also provides it with excellent wear resistance, fatigue resistance, corrosion resistance, and high temperature resistance.
In general, nitriding treatment is the last process in the production of workpieces, but for workpieces that require high precision, precision grinding or ultra precision grinding can be performed after nitriding to further improve surface quality. Among them, the nitriding depth of carbon steel can be controlled by adjusting several key parameters during the nitriding process, including nitriding temperature, holding time, uniformity of nitriding atmosphere, and microstructure before nitriding treatment.
*Features of pit type nitriding furnace
1. Energy saving and efficient: Adopting a new type of energy-saving furnace lining, fast heating, low heat loss, and good furnace temperature uniformity, especially suitable for heat treatment of shaft workpieces.
2. Uniform temperature: The pit type nitriding furnace is designed with a hot air circulation device, which can make the atmosphere and temperature inside the furnace uniform. This is very important for the heat treatment process and can ensure the heat treatment quality of the workpiece.
3. Intelligent control: Using microcomputer intelligent instruments, the furnace temperature can be set according to process requirements and automatically tracked and displayed. In addition, through PLC program control, it is possible to achieve the networking of upper and lower level microcomputers for various temperatures and atmospheres. With the cooperation of robotic arms, automatic control, recording, and workshop group control of the entire process can be achieved, achieving less or no human operation.
4. Good environmental benefits: The exhaust gas from the positive pressure gas nitriding furnace is discharged after combustion, which has good environmental benefits.
5. Long service life: The muffle tank, loading basket, fan, etc. of the nitriding furnace are made of heat-resistant alloy steel, which has a long service life.
6. Fully functional: Equipped with nitrogen, ammonia, pressure monitoring, and alarm functions for high furnace temperature, circulating water interruption, circulating fan failure, cold air fan failure, and lifting motor failure.
*Why Choose COOLDO
COOLDO is a company with over 20 years of experience specializing in metal melting, casting, and heat treatment furnaces. We are committed to providing high-quality equipment and the most suitable turnkey solutions based on customer needs.
COOLDO Pit type nitriding furnace is mainly composed of several parts, including the furnace body, furnace lining, furnace liner, furnace cover and its transmission system, heating elements, hot air circulation system, and control system:
1. Furnace body: The furnace body frame is welded with high-quality national standard profile steel and Q235 steel plate, with a firm and reliable structure, and all welds are uniform and smooth, without defects such as pores, inclusions, and lack of fusion. The overall strength is high, not easy to deform, and the appearance is flat and smooth.
2. Furnace lining: Made of Japan ISOLITE high temperature white cotton structure: fire resistance ≥ 1350 ℃, low thermal conductivity: 0.3 Gcal/mh ℃, low heat storage: 172616 KJ/M2. Reinforced anchors and scientific and reasonable installation methods are used. Precompression treatment shall be conducted again before installation of the fiber folding block (compression unit weight: ≥ 245g/M3). The structure is fixed to a folded block with anchors, and has low thermal conductivity, excellent chemical stability, thermal stability, thermal vibration resistance, excellent strength and corrosion resistance.
3. Muffle tank process: Made of SUS316 stainless steel with a thickness of 8mm. A corrugated molding machine is used to press it into a corrugated shape to improve the strength and expansion performance of the muffle tank.
The inner layer of the muffle tank is welded by argon arc welding, and the weld seam is dense and free of pores. After welding, use a polishing machine for polishing treatment. After polishing, use 402A heat resistant steel welding rod for welding.
After welding, use a polishing machine to polish the spot welding slag attached to its inner and outer surfaces. Operating according to this welding operation process greatly extends the service life of the muffle tank.
4. Furnace lid: The furnace lid is made of heat resistant steel SUS316, δ 8mm. The bottom adopts a head-type structure, and the butterfly shaped head is formed by back pressure.
6. Heating element: The heating elements are arranged in two zones. Reasonably distribute the power of each zone according to the uniformity of furnace temperature.
Due to the large furnace body, heating elements are arranged around the furnace wall. The heating element is wound with high-temperature resistance tape 0Cr26AL6BN to form a corrugated type, with a long-term service temperature of 1000 ° (Shougang).
7. Fixation of heating element: New ceramic screws are used to hang on the furnace lining fiber. The suspension method using this new type of porcelain screw will not produce short circuits, which can make replacement and maintenance more convenient.
8. Hot air circulation system: Composed of a sealed motor, fan blades, windshield, and wind deflector etc.
9. Fan blade: Fan blade φ350, air volume: 2400 — 3200M3/H, material: SUS316.
10. Windshield: Made of SUS316 material with a thickness of 3MM. The bottom adopts a head-type structure, which has high strength and strong deformation resistance.
11. New nitrogen potential control system: Equipped with nitrogen, ammonia, and pressure monitoring, and has alarm functions for abnormal gas flow rate, decomposition rate exceeding the limit, furnace temperature exceeding the limit, circulating water interruption, circulating fan failure, cold air fan failure, and lifting motor failure.
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