Pit-Type Spheroidizing Annealing Furnace

Core Applications
Spheroidizing Annealing (Primary Process)
High-carbon steel and medium-carbon alloy wire rods (for nail-making, bolts, and bearings) undergo high-temperature soaking to transform internal cementite into spherical carbides. This reduces hardness and improves plasticity, preventing breakage during subsequent wire drawing or cold heading.
Softening and Stress-Relief Annealing
Eliminates internal processing stresses in cold-drawn wire to improve toughness; enables bright, oxidation-free annealing for stainless steel wire.

Applicable Materials
Nail-making wire rods, cold-heading screw wire, spring steel wire, stainless steel wire, and welding wire base material.
III. Core Equipment Advantages
Bright Finish without Decarburization
The sealed muffle tank combined with a protective atmosphere ensures the wire surface remains free of oxidation or black scale after annealing, eliminating the need for subsequent pickling-thereby saving processing steps and benefiting the environment.
Uniform Temperature Field and High Product Consistency
Equipped with a high-power top circulation fan, the furnace maintains a vertical temperature difference of ≤±5°C. This ensures uniform spheroidization hardness across the entire wire load, stabilizing wire drawing quality.
Energy-Saving Insulation Design
Features an all-fiber lightweight furnace lining; compared to older furnaces using refractory bricks, heat loss is reduced by over 20%, resulting in significant electricity savings during long-term production.
High-Capacity Batch Production
Utilizes a vertical deep-well structure capable of loading several tons of wire coils per batch, making it ideal for large-scale, continuous industrial heat treatment. Automated Temperature Control
Features intelligent PID-based multi-stage temperature control that automatically executes the complete spheroidizing process-including heating, soaking, and controlled cooling-eliminating the need for continuous manual monitoring.

Complete Operational Workflow
An overhead crane lifts the furnace lid and loads the stacked coils of wire into the furnace retort;
The lid is closed and secured with multiple soft seals; nitrogen is introduced to purge the air and provide a protective atmosphere;
The control system automatically raises the temperature to the spheroidizing setpoint, while a circulation fan continuously agitates the hot air to maintain uniform temperature during the soaking phase;
Upon completion of the spheroidizing soak, an external water-cooling circuit is activated to facilitate slow cooling;
Once cooled to ambient temperature, the system is depressurized and the furnace opened; the softened wire is then removed and proceeds directly to the wire drawing or nail-making stage.