On-site phenomenon: After the same batch of workpieces is discharged from the furnace, the hardness of the upper, middle, and lower layers of the furnace chamber differs significantly, and the rework rate increases. During troubleshooting, first confirm whether the loading amount exceeds the rated load and whether material stacking obstructs hot air circulation. After confirming that loading is reasonable, the problem of poor furnace temperature uniformity often points to the layout of heating elements and the furnace chamber structure design.
The heating elements of box-type industrial electric heating furnaces are mostly distributed on both sides and at the bottom of the furnace chamber, with heat mainly transferred by radiation. Taking the SRX-30-12 pit-type industrial electric heating furnace as an example, the heating elements are arranged in layers along the circumference of the furnace retort, and together with a guide cylinder they form an airflow channel from bottom to top. The temperature uniformity in the furnace chamber can reach ±5°C (under empty furnace test conditions). Compared with box-type furnaces, the pit-type structure is more convenient for loading and unloading long shaft-type, slender rod-type, and workpieces that need to be suspended during heat treatment, while also reducing contact and shielding between workpieces and the furnace bottom.
Tube-type electric heating furnaces are suitable for small cross-section, continuous pass-through working conditions. When the weight of a single workpiece exceeds 5 kg or the external dimensions are irregular, the loading space of a tube-type furnace is limited, the gap between the workpiece and the tube wall is difficult to ensure, and the risk of overheating increases. The furnace chamber of a pit-type industrial electric heating furnace is a vertical cylinder with an effective loading diameter of 300 mm and a depth of 600 mm. It can accommodate larger shaft-type and disc-type parts and is suitable for heat treatment scenarios with multiple varieties and small batches.
Before use, a reasonable upper temperature limit and holding time should be set according to material characteristics to avoid overheating operation. The maximum working temperature of the SRX-30-12 is 1200°C, the rated power is 30 kW, the temperature control accuracy is ±1°C, and it supports multi-stage programmed heating. The furnace lining adopts a composite structure of alumina fiber and lightweight refractory bricks, with low heat storage. It takes about 60 minutes to heat the empty furnace to 1000°C. Thermocouples are arranged at the rear side of the furnace chamber and at the furnace cover, allowing real-time monitoring of temperature distribution. This equipment is mainly used for normalizing, tempering, and annealing of metal parts, as well as preheating processes before hot bending of glass products.
