Atmosphere Furnace

What is Atmosphere Furnace

An atmosphere furnace is a specialized heating device designed to heat materials under controlled atmospheric conditions, using various gases or gas mixtures to prevent oxidation, decarburization, or other unwanted reactions. The primary function of the furnace atmosphere is to either act as a carrier for key elements in the heat treatment process or to protect the material from exposure to harmful elements in the air during high-temperature processing.Atmosphere furnace is used for various types of heat treatment at temperatures of up to 1100℃, such as gas carburizing, bright annealing, brazing, etc. Temperature, atmosphere, and transport are automatically controlled. These tightly sealed furnaces offer excellent, stable atmospheric conditions.

Advantages of Atmosphere Furnace

Metallurgical Processes
Atmosphere furnaces are extensively used in metallurgy for processes like annealing, tempering, and hardening. These processes require specific atmospheres to either protect the material from surface reactions or to facilitate surface changes. For instance, during annealing, the furnace might use an inert gas to prevent oxidation, ensuring the metal softens without any surface impurities.

Control of Atmosphere
The furnace's ability to control the atmosphere is crucial. It can be adjusted to purge oxygen, control surface chemistry to prevent or allow oxidation and reduction, and even introduce specific chemical species like carbon or nitrogen. This precision is vital in processes like carburizing or nitriding, where the surface chemistry is intentionally altered to enhance properties like hardness or wear resistance.

Furnace Design and Operation
Atmosphere furnaces are designed with features like air inlets and outlets, and seals that allow for the creation of a vacuum or specific atmospheres. The seal welding, including a high-temperature-resistant silica gel seal ring, ensures excellent sealing, which is necessary for maintaining the integrity of the controlled atmosphere.

Safety and Specific Applications
For applications involving gases like hydrogen, which can be explosive, furnaces are equipped with safety provisions such as explosion-proof features. This ensures that the furnace can be used safely even in high-risk applications.

Wire Heat Treatment Furnace

The Wire Heat Treatment Furnace is suitable for spheroidizing annealing, softening annealing,

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Efficient Methanol Cracking Furnace

The main technical parameters: 1. Splitting reaction equation: CH3OH→CO+2H2 Decomposition

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Short Time Cycle Furnaces

The STC furnace is suitable for spheroidizing annealing, softening annealing, complete annealing,

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How to Choose Atmosphere Furnace

Process requirements: Firstly, it is necessary to clarify your process requirements, including the required maximum temperature, temperature control accuracy, heating rate, type of atmosphere gas, etc. Different processes require different atmosphere furnaces to meet the requirements.

Temperature range: Determine the required temperature range based on process requirements. Ensure that the selected atmosphere furnace can reach and stably control the required temperature range.

Atmosphere gas: Consider the type of atmosphere gas required for the process, common atmosphere gases include nitrogen, hydrogen, argon, oxygen, etc. Choose a suitable atmosphere furnace to ensure that it can provide the required atmosphere gas.

Atmosphere control system: The atmosphere control system is of great significance for the accuracy of experimental results and the safety of equipment. Therefore, an atmosphere control system with high-precision control and safety protection functions should be selected.

Furnace material: The furnace material of an atmosphere furnace has a significant impact on the performance and durability of the equipment. Common furnace body materials include silicon carbide, aluminum oxide, high-temperature ceramics, etc. Select the appropriate furnace material according to the temperature and atmosphere requirements.

Heating element: The selection of heating element directly affects the heating speed and temperature uniformity of the atmosphere furnace. Common heating elements include resistance wire heating, silicon molybdenum rod heating, silicon carbon rod heating, etc. Suitable heating elements should be selected based on the usage temperature and heating power requirements.

Furnace cavity size and capacity: Select the appropriate furnace cavity size and capacity based on the size and quantity of the sample to be processed. Ensure that the furnace chamber is large enough to accommodate all the samples to be processed, and that there is sufficient space between the samples to ensure the uniformity of heat treatment.

Temperature control accuracy: Choose a stable and reliable temperature control system that can accurately control the furnace chamber temperature and achieve the required temperature gradient. The accuracy of temperature control directly affects the quality and stability of the heat treatment process.

Control system and software: Select devices with easy to operate and fully functional control systems and software interfaces. A good control system and software can improve operational efficiency, reduce operational errors, and provide data recording and analysis functions, which helps optimize the process flow.

Vacuum system: The vacuum system is an important component of a vacuum atmosphere furnace, which directly affects the heating performance of the equipment and the accuracy of experimental results. Therefore, a vacuum system with high pumping speed and low reflux characteristics should be selected.

Energy consumption and environmental performance: Consider the energy consumption and environmental performance of the equipment. Choosing an energy-saving and environmentally friendly atmosphere furnace can reduce production costs and meet environmental requirements.

Why Atmosphere Furnace Is Desirable In Sintering

Firstly, the sintering atmosphere plays a crucial role in the sintering process. It aids in the removal of lubricants from the green compact and reduces residual surface oxides, which promotes bonding between adjacent powder particles. By controlling the atmosphere, the sintering process can be optimized for better results.

Secondly, atmosphere furnace helps protect the compacts from oxidation during the sintering process. Oxidation can negatively affect the properties of the sintered material, such as its strength and durability. By creating atmosphere, the furnace can prevent oxidation and ensure the desired properties of the final product.

Thirdly, atmosphere furnace allows for the use of different gases to control the sintering process. Different gases, such as nitrogen-hydrogen atmosphere, hydrogen, vacuum, dissociated ammonia, and endothermic gas atmosphere, can be used in different stages of the sintering process. This flexibility allows for precise control over the sintering conditions and can result in improved product quality.

Additionally, atmosphere furnace, particularly a vacuum sintering furnace, offers several advantages. Vacuum sintering reduces the contamination of harmful substances in the atmosphere, such as water, oxygen, nitrogen, and impurities, which can negatively affect the sintering process. It also removes the oxide film before the liquid phase appears, improving the wettability of the liquid and carbide phases, enhancing the microstructure of the alloy, and increasing the density of the material. Vacuum sintering also results in materials with higher wear resistance and strength, reducing product costs.

In summary, atmosphere furnace is desirable in sintering because it allows for the removal of lubricants, reduces residual surface oxides, protects the compacts from oxidation, and offers flexibility in controlling the sintering process. Additionally, a vacuum sintering furnace provides further advantages in terms of reducing contamination, improving alloy properties, and increasing material density.

Some Common Faults and Troubleshooting Methods of Atmosphere Furnace

In the high temperature test of the atmosphere furnace, if the temperature change does not reach the test temperature value, you can check the electrical system and eliminate the faults one by one. If the temperature rises very slowly, check the air circulation system to see if the adjustment baffle of the air circulation is opened normally, otherwise, check if the motor of the air circulation is operating normally. If the temperature overshoot is severe, then you need to tune the PID setting parameters. If the temperature rises directly, some common over-temperature protection of the atmosphere furnace, then, the controller fails and the control instrument must be replaced.

When the equipment suddenly fails during the test operation, the corresponding failure display prompt and audible alarm prompt will appear on the control instrument. The operator can quickly check which type of fault belongs to in the chapter of troubleshooting during the operation of the equipment, and can ask professionals to quickly troubleshoot the fault to ensure the normal progress of the test. There will be other phenomena in the use of other environmental test equipment, so specific phenomena should be analyzed and eliminated. Then you have to observe the temperature change, whether the temperature drops slowly, or the temperature tends to rise after the temperature reaches a certain value, the former should be checked, whether the studio is dried before the low temperature test in the vacuum atmosphere furnace to make it work After the chamber is kept dry, put the test samples in the working chamber and do the test again. Whether the test samples in the working chamber are placed too much so that the wind in the working chamber cannot be fully circulated. After the above reasons are eliminated, it is necessary to consider whether it is in the refrigeration system The fault, the fault and the troubleshooting method: In this case, please ask the manufacturer's professional for maintenance.

The Importance of Atmosphere in Atmosphere Furnace

Atmospheric controls are not often integral for atmosphere furnaces that are used to treat materials where the impact of process oxidation or gas integration is negligible, or where oxidation is the purpose of the process. Few special considerations need to be accounted for in these instances, as the materials can be processed at high temperatures in air with minimal risk of off-gassing and no requisite catalytic gases to encourage thermodynamic change.

Air atmospheres are usually comprised of up to 78% nitrogen (N2) and 21% oxygen (O2). While oxygen reacts with many chemical elements at varying temperatures, nitrogen is considered the chemically inert carrier gas of air. It has been shown to react with such high strength metals as molybdenum (Mo) and titanium (Ti) at elevated temperatures but is routinely used as a reducing gas to prevent material oxidation in high temp furnaces. This blanketing process is accomplished using gas inlets such as nitrogen flowmeters and an exhaust port to expel spent gas from the chamber via a fume hood or an external manifold piping. Electronic monitoring systems may be required to maintain distinct composition levels relative to the temperature values of the chamber. Nitrogen blanketing can be used to prevent the oxidation of ferrous metals and to decarburize the surface of steel products.

The reactivity of hydrogen with select metals at high temperatures can be problematic for heating elements manufactured from silicon carbide (SiC) and molybdenum discilicide (MoSi2). Nitrogen gas compounds can degrade the surface composition of carbon-rich materials, resulting in significant mechanical instability over time and increased maintenance requirements. Forming gases comprised of part hydrogen also require additional safety requirements as they may be explosive in nature. Argon gas is often preferable for maintaining inert atmospheres in such high temp furnace grades and is often used for atmospheric purging. Where hydrogen is critical for the process yield, high temp furnaces often use a retort to safely protect the furnace elements from chemical attack and to contain potentially hazardous compounds.

Heat Treatment Processes That Atmosphere Furnace

Annealing: Used to soften a metal or change its microstructure.

Bright annealing: Performed in an inert atmosphere of nitrogen, hydrogen, or argon to limit oxidation; pure hydrogen is usually the preferred atmosphere.

Brazing: When done on copper and silver, an atmosphere of pure hydrogen or, in some cases, dissociated ammonia.

Carburizing: Adds carbon to the surface of steel to increase its hardenability and typically uses an endothermic atmosphere.

Carbonitriding: The diffusion of carbon and nitrogen atoms into the surface of a metal to increase hardness; nitrogen is usually added to the endothermic atmosphere.

Nitriding: Heating metal in the presence of nitrogen (usually in the form of ammonia) to increase both corrosion resistance and hardness.

Neutral hardening: Used to prevent oxidation and decarburization in tool steels by using an inert or protective atmosphere such as nitrogen or argon.

Sintering: Depending on the metallic compounds being sintered, uses either an inert/protective atmosphere or a hydrogen atmosphere.

Tempering: Used to increase grain size, ductility, and toughness of previously heat-treated metals.

Hot isostatic pressing: Similar to sintering, but performed at much higher pressures.

How to Install and Maintain the Atmosphere Furnace Correctly

The atmosphere furnace is a well-known high-temperature experimental equipment that can provide atmosphere protection and various atmosphere environments, and can also be used for production. However, users prefer to have a stable atmosphere environment. How to automatically stabilize the pressure in the furnace and replenish the gas in time has become a function that many users care about. One solenoid valve controls the air intake and the other solenoid valve controls the pressure relief. When the pressure gauge detects that the pressure is lower than a certain set pressure, it will give an electric signal to the solenoid valve. You know how the solenoid valve is turned on. At this time, the gas source will replenish gas in the atmosphere furnace, and when the pressure in the atmosphere furnace is restored When the set value is reached, the solenoid valve is closed and no more gas is supplied. The same principle can realize automatic pressure relief. This cycle of work ensures the stability and sufficient gas in the furnace.

Atmosphere furnace furnace has good airtightness: In order to control the furnace atmosphere and maintain a certain furnace pressure, the working space in the furnace should always be isolated from the outside air, and try to avoid air leakage and suction. Controllable Atmosphere Furnace Under controllable atmosphere, electric heating elements should be provided with high-carburizing materials or anti-carburizing coatings, and low-voltage power supplies should try to avoid carburizing short-circuit damage or carbon deposition on the furnace wall. In the process of filling, unloading, quenching and cooling, all need to be carried out under sealed conditions. Therefore, before or after unloading, a closed quenching mechanism and a controlled atmosphere cooling chamber are necessary. The door of the furnace, the structure that communicates with the outside must be strict, and the fire-proof sealing device should be opened.

The installation of atmosphere furnace is as follows
The electric furnace is installed to suit the physiological operating height of the human body, the effective load of the installation foundation should be greater than 500KG, and the installation ground should be flat to ensure the smooth and accurate movement of the inner tank into and out of the furnace.

Electrical installation, under the premise of ensuring personal safety, in order to achieve a suitable application environment, the specific requirements are as follows: the experimental atmosphere furnace and the control cabinet are grounded as a whole, and the grounding resistance of the grounding wire should be less than 4Ω. Power configuration: 3-phase 380V. The user's electrical control cabinet configuration power should be greater than 20Kw.

The thermocouple is inserted into the furnace with a depth of 25mm, and is connected with the temperature control instrument by the compensation wire of the N graduation number. When installing the resistance wire, do not use force to prevent breakage.

Atmosphere furnace maintenance work
The rated power should not be exceeded during use, can it be installed and maintained correctly, and the temperature of the atmosphere furnace should not exceed the maximum operating temperature. It is forbidden to put wet workpieces into the furnace. Heated workpieces containing excessive moisture should be dried in advance.
Keep the furnace clean, and remove metal oxides, slag and impurities in the furnace in time. Care should be taken when loading and unloading the workpiece to prevent damage to the silicon molybdenum rod.
Silicon molybdenum rod alkali, alkali metals, silicic acid and boron compounds can corrode it at high temperature. Water vapor has a strong oxidizing effect on it. Hydrogen and gas containing a large amount of hydrogen will decompose silicon molybdenum rod at high temperature. Attention must be paid strictly.
The workshop must be equipped with 1/2 pipe with a water source back force of 0.2MPa.
Connect the gas filling port to fill CO2 and other protective gases. When the pressure gauge of the atmosphere furnace indicates 0.02～0.04MPa, stop filling.
By investigating the flow rate and controlling the outlet temperature at 40℃cgh.
Regularly check whether the contact of each terminal is good.

FAQ

Q: What are furnace cycle rates?

A: On average, furnaces should kick on and turn off anywhere from three to eight times per hour. However, if your furnace turns on and off more frequently, don't assume the furnace is short cycling just yet.

Q: What is the best cycle rate for heat?

A: A Cycle rate is the maximum number of times a system will run, in an hour, when using 50% of its capacity to maintain a given temperature. For a high efficiency (90%+) gas or oil forced air systems would have a recommended cycle rate of 3. This means the heating system will cycle a maximum of 3 times in an hour.

Q: What is a furnace cycle?

A: A furnace doesn't run continuously when it's powered on. It works in a process called “cycling” in order to be effective as well as energy efficient. It kicks on when the thermostat detects that the indoor temperature is lower than desired, then turns off when it has reached the right level.

Q: What is an atmosphere furnace?

A: The "furnace atmosphere" means a gas to be filled and heated in the furnace by which the. product (workpiece) is indirectly heat-treated. The atmosphere gases include air, inert gases, hydrogen (reducing gas), and others, which are heated up to 1000 - 2500℃

Q: How do the different furnaces differ in their structures?

A: These furnaces are uniquely designed, depending on each furnace's intended function, heating manner, type of fuel and method of air combustion, but they all have common features, namely mechanisms that, when working together, produce heat. Typically, fuel is fed into a burner.

Q: What is the atmosphere of a heat treatment furnace?

A: THE ATMOSPHERE within a furnace chamber is a basic factor in achieving the desired chemical reactions with metals during heat treating. For example, prevention of surface oxidation or scaling may be one important task of the furnace atmosphere when metals are exposed to elevated temperatures.

Q: What is heating atmosphere?

A: Convection: Vertical heating of the atmosphere is known as convection. The air in contact with the earth upsurges vertically on heating in the form of currents and transfers the heat of the atmosphere. Advection: The transfer of heat through the horizontal movement of air is called advection.

Q: What is the dew point of a furnace atmosphere?

A: Dew point (DP) is a measure of the moisture composition in a furnace atmosphere. In the various zones of a sintering furnace, the atmosphere can vary widely from a relatively wet, oxidizing atmosphere in the pre-heat zone to a dry, reducing atmosphere in the hot and cooling zones.

Q: How do you create a reducing atmosphere in a furnace?

A: Typically, this is achieved through using the combustion products of fuels and tailoring the ratio of CO:CO2. However, other common reducing atmospheres in the metal processing industries consist of dissociated ammonia, vacuum, and/or direct mixing of appropriately pure gases of N2, Ar, and H2.

Q: How do I control the temperature of my furnace?

A: By changing the circuit configuration, the temperature of the resistance furnace can be controlled. In case of three-phase circuits, the heating element will give less heat when it is connected in star configuration whereas it will give more heat when in delta configuration.

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