Electric conveyor furnaces

Purpose and application

The conveyor electric furnace is a heated tunnel along the bottom of which the supporting part of the conveyor passes. Furnaces in which the supporting surface is moving are called continuous furnaces and can be used for various heat treatment processes in a continuous (continuous) mode. Various processes can be carried out in conveyor ovens depending on the design and operating temperatures. The most popular processes are drying of bulk or molded materials, tempering or annealing of small metal products, heating for hardening, and many other thermal processes. Special designs of conveyor ovens are available for heating in a protective atmosphere. Conveyor ovens are successfully integrated in the heat treatment line, for example, after the heating chamber, a cooling or quenching module is attached to the furnace. Mainly, conveyor ovens are used in batch or mass production when large performance and stable quality. Conveyor ovens are generally modular when required the length of the furnace is formed by modules of several heating blocks.

Description of construction

The heated part of the furnace has the form of a pass-through or dead-end tunnel; in this case, the support for the blanks is the conveyor belt. Opony surface of the conveyor is placed in the heating chamber and wrapped in the opposite direction already in the cold zone. There are furnace designs when the tape is wrapped back in the heating chamber without cooling. This design is recommended for high temperature processes such as hardening.

Electric furnace frame made of steel profiles, which are framed by casings, forming a through tunnel. Outside, the frame and protruding drums of the conveyor are protected by decorative screens. The lining of electric furnaces is mainly produced made of ceramic fiber materials, various brands and thermal insulation boards. Assembly line, can be in the form of a braided wire mesh or stamped links. Conveyor, working surface, passes through a heated chamber. In the heating chamber, the belt rests on silicon carbide plates or rollers. The conveyor belt is driven from the drive drum with elements for pressing the net to the pulling drum or by means of traction chains. High temperature zone, on both sides partially overlap, heat-insulated dampers. The exit of hot gas from the furnace is reduced by curtains made of heat-resistant fabric or silicone tapes. Heating in SKO furnaces up to a temperature of 700 ° C is carried out using fans and flow screens. In furnaces with a higher temperature, for example, SKO 8.70.2 / 9, heat exchange is carried out mainly by radiation.

Gas circulation allows you to accelerate the heating of workpieces and equalize the temperature across the cross section of the products. On the frame of the vaulted part, stands are installed with fans brought into the furnace space. The fan circulates air from heaters to the charge, transferring heat to the workpiece. Thus, convection heating from the heated air flow. Purging the heating chamber. (option) For the possibility of removing vapors, fumes or smoke in the roof section can be installed gate valve branch.

The belt is driven by a drive drum, which rotates from an electromechanical drive through a chain transmission with asterisks. Smooth regulation of the belt movement speed is ensured by means of a frequency converter.

Conveyor electric furnaces have electronic heating control with digital temperature display. Temperature control is performed through powerful thyristor units with PWM function. To register a heat treatment schedule mode in the control cabinet there is a registering device "Termodat", current indicators, with the function of an electricity meter, and other devices. In order to increase the safety of work, all electric furnaces are equipped with interlock switches for removing voltage (heating shutdown) when the damper is opened. When the thermocouple breaks and the temperature is exceeded the protection is triggered, which cuts off the supply voltage of the furnace heaters. The necessary power and control equipment is mounted in the control cabinet.

Main technical characteristics of electric carburizing furnaces