What is bright annealing furnace?

Bright annealing furnace is a heat treatment device that heats and slowly cools metals in a sealed protective atmosphere; its primary function is to maintain a bright surface finish on the metal without decarburization. Compared to conventional annealing, it prevents the formation of scale, eliminating the need for subsequent acid pickling, and is commonly used for the treatment of materials such as stainless steel, copper, and steel pipes.

Working Principle and Key Features

‌Protective Atmosphere for Oxidation Prevention: A mixture of nitrogen and hydrogen is introduced into the furnace to isolate oxygen, preventing the metal surface from oxidizing or decarburizing at high temperatures and ensuring a mirror-like finish after treatment.

Precise Temperature Control: After heating to the set temperature, the system maintains the temperature before slowly cooling to below 500°C for natural cooling. This avoids deformation caused by rapid cooling while eliminating internal stresses in the material and restoring its plasticity.

Environmental and Energy-Saving Advantages: Post-treatment acid washing is unnecessary, reducing chemical pollution. Some equipment utilizes forced convection circulation to achieve a temperature uniformity of ±5°C, resulting in energy savings of over 10% compared to traditional equipment.‌‌

Common Types and Applications

‌Bell-Type‌: Suitable for coiled strips, coils, and wire rods. A sealed chamber is formed by raising and lowering the outer cover. The largest domestic capacity has reached 30 tons, with furnace temperature uniformity controlled within ±4°C.

‌Mesh Belt Type‌: Suitable for continuous steel pipe production. A mesh belt conveyor physically separates the pipes to prevent contact, ensuring uniform circumferential heating and improving the stability of heat treatment quality.

‌Bogie-Type‌: Suitable for large workpieces. The furnace body and bogie are integrated with a light rail system, requiring no foundation for installation. It offers excellent thermal insulation and is easy to operate.‌‌

Main Application Areas

Stainless Steel Materials:Used for solution treatment to improve corrosion resistance. The original rolled texture is retained on the surface, allowing for direct use without further processing. Typical products include tableware, kitchenware, and medical devices.

Copper and Aluminum Alloys:Used for processing coils and tubes to reduce hardness and improve machinability or formability. Widely used in industries such as wire and cable, and welding wire.

Precision Components:Used for processes such as stress relief of silicon steel sheets, fasteners, sintering of bearing steel balls, and high-end soft magnetic materials, which require high temperature uniformity and consistency. It can also be used for electronic packaging materials such as pure nickel strips and Kovar alloys.