Gas carburizing furnace for steel

Types of Gas Carburizing Furnaces for Steel

A gas carburizing furnace for steel is a heat treatment furnace used for carburizing steel or any other products. Different types of gas carburizing furnaces are available, such as bell-ows, pit, entry-and-exit, vertical, retort, and controlled atmosphere gas carburizing furnaces.

• Bell-ows carburizing furnace:

This furnace has a bellows that acts as a protective cover, and it usually appears like an arch. The carriage is driven by a gearbox, which is connected to a motor. Bell gas carburizing furnaces also have heating elements in the side walls or roof. The furnace is generally used for large workpieces or high-production applications.

• Pit carburizing furnace:

As the name suggests, the pit carburizing furnace is in pit form. It is mainly used to create parts that need to carry out continuous heat treatment processes. The advantage of a pit carburizing furnace is that it usually has high productivity; therefore, most people prefer using it. Additionally, it is in the underground form, which allows it to save space.

• Entry-and-exit carburizing furnace:

The entry-and-exit carburizing furnace has horizontal heating chambers. This allows workpieces to enter and exit the furnace chambers easily. The atmosphere inside the carburizing furnace can be controlled to optimize surface hardening and minimize scale formation.

• Vertical carburizing furnace:

Vertical carburizing furnaces are usually used in high-volume production applications, for example, the automotive and aerospace industries. The vertical carburizing furnace allows quick and easy loading and unloading of workpieces. Also, it has automation capability, which allows easily integrated into production lines.

• Retort carburizing furnace:

In this type of furnace, a retort acts like a sealed container with a cylindrical shape. It carries out carburizing processes by exposing the steel to carbon gas. Many industries use the retort carburizing furnace because it is energy efficient and has high carbon penetration rates. Nonetheless, the carburizing process in this kind of furnace can take long hours or even overnight.

• Controlled atmosphere gas carburizing furnace:

The controlled atmosphere gas carburizing furnace provides a precise and consistent carbon content. It protects the workpieces from oxidation and decarburization. Also, the carburizing process in a controlled atmosphere is uniform. Therefore, the desired mechanical properties are achieved.

Specification and Maintenance

Specifications

• Capacity: The capacity is typically indicated by the amount, volume, or weight of steel that the gas carburizing furnace can process in a single batch.
• Temperature Range: Carburizing furnaces are designed to operate at specific temperature ranges. This range is critical because carburizing requires precise temperature control to ensure that the carbon diffusion process occurs effectively and uniformly throughout the steel workpieces.
  (a)Low-temperature Carburizing Furnaces: Low-temperature carburizing typically occurs at temperatures between 850 to 970 degrees Celsius (1,560 to 1,780 degrees Fahrenheit).
  (b)High-temperature Carburizing Furnaces: High-temperature carburizing is performed at temperatures ranging from 1,000 to 1,100 degrees Celsius (1,832 to 2,012 degrees Fahrenheit).
• Quenching Methods: Gas carburizing furnaces may use different quenching methods, including:
  (a)Liquid Quenching: This involves immersing the carburized steel parts in a liquid quenchant, typically oil or water, to rapidly cool them. Liquid quenching is common in carburizing furnaces that aim to achieve higher hardness levels in the steel.
  (b)Gas Quenching: In gas quenching, the steel workpieces are cooled using a high-velocity gas stream, often nitrogen. This method offers the advantage of reduced distortion and easier post-processing, making it suitable for delicate or precise components.
• Case Depth: The case depth refers to the depth of the hardened layer produced by the carburizing process. Different applications require specific case depths to achieve the desired balance of surface hardness and toughness in the underlying steel.
• Furnace Atmosphere: The atmosphere in the carburizing furnace is vital for the process's success. Common furnace atmospheres include:
  (a)Controlled Atmosphere: This involves regulating the levels of carbon, nitrogen, and hydrogen in the furnace to optimize carburizing and prevent unwanted reactions.
  (b)Vacuum: Vacuum carburizing uses a low-pressure environment to facilitate carbon infusion into the steel while minimizing oxidation and contamination.
• Dimensions: The dimensions of a carburizing furnace are significant overall sizes and shapes of the equipment. Typically, the furnace consists of a treatment chamber and a quencher. The exact size of the furnace is directly dependent on the capacity and volume it can handle.
• Temperature Uniformity: The temperature uniformity of the furnace is the ability to maintain a consistent temperature across the entire chamber during heating. This ensures that all parts of the workpiece are evenly heated, facilitating uniform carbon diffusion and consistent material properties throughout the entire workpiece.

Maintenance

• Regular Inspection: Periodically check the gas carburizing furnace for signs of damage, such as cracks, deformations, and loose connections. Particularly, inspect the furnace liner and sealing parts to ensure that the gas leakage is not occurring and that operational safety is hence guaranteed.
• Cleaning: Maintain a clean fuel/air combustion system and furnace interior. Remove the carbon deposition and ash from the combustion system and periodically clean the furnace interior so that the diffusion of carbon is not prevented by impurities.
• Equipment Lubrication: Keep the moving parts of the gas carburizing furnace, such as gears, bearings, and valves, lubricated adequately as prescribed. This helps to ensure that the equipment is operating well, hence reducing the abrasion and failure rate of the parts.
• Atmosphere Monitoring: Regularly monitor the carburizing atmosphere parameters in the furnace, such as temperature, pressure, carbon concentration, etc., ensuring that the process is stable and controllable. Adjust the relevant parameters promptly as per the atmospheric composition changes to ensure the quality of carburizing.
• Furnace Temperature Calibration: Periodically calibrate the temperature control system and corresponding sensors of the carburizing furnace to ensure that the furnace is carburizing at the correct temperature. This helps to maintain the consistent quality of carburizing and avoid overheating or underheating.
• Safety Checks: Regularly check the safety devices of the gas carburizing furnace, such as gas leakage detectors, pressure relief valves, etc. Ensure that these safety devices are working normally so as to avert potential risks and hazards.
• Equipment Repair: Timely repair and maintenance of parts of the carburizing furnace, such as the sealing components, heating elements, cooling system, etc. This way, the durability and reliability of the furnace will be ensured.

Usage scenarios of gas carburizing furnace for steel

Gas carburizing furnaces for steels are used in various industries where steel components require surface hardening. Some of the common usage scenarios are as follows.

• Automotive industry: The automotive industry uses gas carburizing furnaces to produce automobile parts like gears, axles, crankshafts, and drive shafts. Gear needs to have a tough outer surface to resist abrasions from friction when in use. Hence, it is usually gas carburized. The toughness can be achieved by hardening the surface of the steel gear through carburizing. Also, the lightweight of the drive shafts and axles does not have to compromise their strength because they are gas carburized for high strength and low weight.
• Aerospace industry: The aerospace industry carburizes steel components of aircraft and spacecraft to make them wear-resistant and able to endure high-stress levels. Examples of parts that undergo carburizing are landing gear, drive shafts, and turbine shafts.
• Machine tools industry: The machine tool industry uses gas carburizing furnaces to surface-harden cutting tools and gear boxes. Cutting tools, like drills and milling cutters, are made of steels that are gas carburized for increased hardness and improved abrasion resistance. Also, the gear boxes in the industry are carburized to enhance the strength of the gears and extend their service life.
• Oil and gas industry: Components of oil and gas wells, such as drill pipes and couplings, are gas carburized to increase their toughness and resistance to wear. The harsh and abrasive environment of oil and gas extraction requires the use of gas carburizing to enhance the longevity of equipment.

How to Choose Gas Carburizing Furnaces for Steel

When selecting a gas carburizing furnace, a number of factors need to be taken into consideration. These include furnace design, construction material, charge mechanism, temperature control and measuring devices, quenching system, sealing mechanism, and safety features.

• Furnace Design: Various types of carburizing furnaces with distinct designs are available to suit different industries. The most popular options are pit, mesh-belt, and pusher carburizing furnaces. Choose a furnace that will meet particular requirements in a given industrial setting.
• Construction Material: The life span of a carburizing furnace is largely dependent on the construction material. This is the material used to make the inner and outer furnace walls. Typical options include steel alloy and refractor ceramic. Usually, those materials that are corrosion-resistant and have a high melting point improve lifespan.
• Charge Mechanism: The gas carburizing furnace's charge mechanism refers to how the equipment adds carbon to metal. The two main options are immersion and gas treatment. Using a carburizing liquid has the benefit of lowering activation energy and boosting reaction speed. On the other hand, gas treatment is less expensive and more widely available.
• Temperature Control and Measuring Devices: Temperature control and measuring devices regulate and monitor temperature levels. Options include thermocouples, pyrometers, and PLC-based control systems. Choose a carburizing furnace with accurate measuring devices and reliable control systems for precise heat treatment.
• Quenching System: This system cools the carburized steel quickly, causing a change in its structure. It improves strength and hardness. Common quenching methods are oil, water, and air quenching. The carburizing furnace's quenching system should be suitable for the heat treatment and material used.
• Sealing Mechanism: Carburizing furnaces seal mechanisms efficiently to regulate gas flow while minimizing heat loss. The sealing options include labyrinth seals and flexible seals. Select the sealing mechanism that is not only user-friendly but also effective.
• Safety Features: Safety features such as explosion-proof designs, gas leak detection, and automatic shut-off systems protect operators and facilities in case of emergencies.

Gas carburizing furnace for steel Q and A

Q: What is the purpose of carburizing gas furnaces?

A: The purpose of a gas carburizing furnace is to increase the surface hardness of steel components by infusing carbon into their surfaces.

Q: Are gas carburizing furnaces economical?

A: Yes, gas carburizing furnaces are often more affordable than induction and salt bath methods for case hardening steel. Despite having higher initial costs, their operating expenses typically remain lower.

Q: Is the carburizing gas process environmentally friendly?

A: Yes, the gas carburizing process is considered environmentally friendly because it uses natural gas as the primary energy source, which produces minimal carbon dioxide when combusted compared to other fossil fuels. Moreover, carburizing furnaces often have waste heat recovery systems that recycle excess heat for various industrial applications, reducing the need for more natural gas.

Q: Are carburizing gas furnaces durable?

A: Carburizing gas furnaces are typically very durable and are designed to withstand high temperatures and harsh environments. The materials used in the construction of these furnaces are chosen for their strength and resistance to wear and damage. In addition, many carburizing gas furnaces are equipped with heat recovery systems that allow them to use waste heat from the carburizing process to preheat incoming gases and reduce the overall energy consumption of the furnace.