2. Main Classification Methods

2.1 Classified by Heating Mode

1. Direct-fired Gas Roller Hearth Furnace

Low-NOx flat flame burners are arranged inside the hearth to heat workpieces directly by thermal radiation, featuring high thermal efficiency and fast temperature rise. It is mostly used for normalizing and quenching & tempering of carbon steel and ordinary pipes without protective atmosphere or simple atmosphere protection.

2. Indirect Gas Roller Hearth Furnace with Radiant Tubes

Flue gas is confined inside radiant tubes and completely isolated from the process atmosphere in the furnace. Nitrogen, nitrogen-hydrogen mixed gas or pure hydrogen can be introduced to realize oxidation-free heat treatment, suitable for bright annealing of precision alloys, stainless steel and bearing steel.

3. All-electric Heating Roller Hearth Furnace

Heated by resistance bands, silicon carbide rods or electric radiant tubes, it boasts ultra-high temperature control precision with zero flue gas emission. It is the preferred choice for working conditions with strict environmental supervision and high cleanliness requirements, such as aerospace aluminum alloys and lithium battery materials.

2.2 Classified by Atmosphere System

1. Atmospheric Roller Hearth Furnace: No protective atmosphere, resulting in oxidized workpiece surfaces, only for stress relief and high-temperature normalizing of ordinary forgings.

2. Nitrogen-based Protective Atmosphere Roller Hearth Furnace: Nitrogen mixed with trace hydrogen for low-cost bright annealing.

3. All-hydrogen Roller Hearth Furnace: Forced convection with high-purity hydrogen to achieve mirror-bright surface, specially used for stainless steel and precision strip materials.

4. Vacuum Airlock Roller Hearth Furnace: Front and rear vacuum chambers are equipped to isolate ambient air, achieving extremely low oxygen content and preventing decarburization and oxidation.

2.3 Classified by Hearth Structure

• Single-layer roller hearth furnace: The mainstream type in the industry, whose length can be customized on demand with easy maintenance.

• Multi-layer roller hearth furnace: Furnace rollers are stacked vertically, increasing production capacity by 2~4 times within the same workshop area, suitable for intensive processing of small parts.

• Segmented roller hearth production line: Integrated connecting line including preheating section, heating & soaking section, quenching section, tempering section and cooling section.

2.4 Classified by Working Temperature

• Low-temperature tempering furnace: 200~650℃

• Medium-temperature annealing & quenching-tempering furnace: 650~950℃

• High-temperature normalizing & solution furnace: 950~1150℃