I Technical Characteristics

1.1. The furnace lining [1] adopts a steel-frame compressed fiber block fixation method, which prevents thermal bridge short circuits. The fibers are laid in a staggered manner, with both layered and stacked paving. The furnace lining has a low thermal conductivity, good thermal insulation performance, and high energy-saving benefits.

1.2. The concave-framed furnace door, with a layered installation of fibers, ensures that the electric heating elements do not protrude beyond the inner surface of the door, thus preventing damage to the electric heating elements and fibers during the lifting and lowering of the door due to collision.

1.3. The sealing between the furnace door and furnace opening, as well as between the trolley and furnace body, employs a soft fiber contact, and is equipped with a mechanical clamping device to ensure complete sealing of the furnace structure.

1.4. The new resistance belt suspension structure (fixed on the fiber lining with high-alumina ceramic screws) is safe, reliable, and fast and convenient for installation and maintenance.

1.5. Install an operation box on one side of the electric furnace mouth, enabling easy operation of the trolley's entry and exit, furnace door lifting, and sealing device from a close distance. This reduces the labor intensity of the operators, thereby lowering the equipment failure rate and ensuring safe use of the equipment.

II Purpose

Applied to: quenching and annealing of mechanical parts such as high manganese steel castings, stainless steel, high chromium castings, carbon steel, ductile iron, rollers, steel balls, etc.

III structural characteristics

1. Furnace body and sealing device

1.1. The furnace frame is constructed using high-quality national standard steel sections welded with Q235 steel plates, ensuring a sturdy and reliable structure. All weld seams are uniform and smooth, free from defects such as porosity, inclusions, and lack of fusion. The overall strength is good, making it resistant to deformation, and the exterior is flat and smooth. Outside the furnace shell, there is a centralized distribution of bakelite holders for the outgoing rods of electric heating elements, and the thermocouple holders are fixed on the left and right side walls.

1.2. The furnace lining is a full-fiber structure with a total fiber thickness of 260mm. It adopts standard refractory fibers produced by Shandong Luyang Co., Ltd. using the vacuum spinning method, with a compressed bulk density of ≥220Kg/m³. By adopting a scientific and reasonable inlaying method, this structure rarely experiences thermal bridge short-circuiting. It is also made by combining flat stacking and other methods, providing good air tightness. It has the advantages of being sturdy and reliable, easy to maintain, long service life, good energy-saving effect, light weight of the furnace body, and small temperature rise of the furnace shell.

2. Trolley and trolley traction mechanism

2.1. The trolley consists of a frame, trolley lining, trolley traction mechanism, etc.

2.2. The steel structure frame of the trolley is assembled from multiple longitudinal beams and cross beams, with the bottom plate made of thick Q235 steel plate, ensuring its rigidity and preventing deformation under full load conditions. The trolley frame structure not only possesses overall stability but also guarantees local stability, taking into full account the heavy load and wide width of the trolley itself in the design. Adequate consideration has been given to the uniform distribution of forces and thermal deformation throughout the entire trolley.

2.3. Construction of trolley furnace lining: A layer of 5mm-thick asbestos board is laid flat at the bottom of the trolley body, followed by two layers of diatomaceous earth bricks and heavy-duty bricks laid flat. The middle layer is made of (NG-1.3) straight bricks laid flat. The refractory layer is constructed using heavy-duty load-bearing bricks. When laying the refractory bricks, high-temperature binder is added to the mortar to improve structural strength, and the load-bearing plane of the refractory layer is kept flat. Special-shaped bricks are used around the trolley to prevent direct contact between the furnace gas and the side plates of the trolley. The refractory layer of the trolley where the heating elements are placed is constructed into a strip-shaped groove, which also serves as a place to rest the furnace bottom plate.

2.4. A heat-resistant steel floor plate made of ZG3Cr18Mn12Si2N is laid flat above the trolley furnace lining. A novel fastening method is adopted to prevent oxide scale from falling onto the heating elements. The heat-resistant steel floor plate is made in strip-groove shape and fabricated in blocks to reduce deformation and cracking at high temperatures. The load-bearing surface of the trolley is made flat, and workpieces can be placed arbitrarily in the length direction on the trolley surface with sizing blocks (provided by the user).

2.5. The trolley traveling mechanism adopts a self-propelled wheel-type mode. A total of 12 wheels are installed in 6 rows beneath the trolley body. Two reducers are installed inside the trolley head box, which transmit the traveling power to the trolley's driving wheels through sprockets and chains, driving the trolley to move. The trolley is equipped with a built-in braking device to ensure accurate and timely stopping of the trolley and prevent inaccurate positioning due to inertia. The composition of the driving wheels is as follows: one row of driving wheels, two rows of driven wheels, and three rows of passive wheels.

2.6. A safety limit switch is installed at the extreme limit of the trolley's travel, and a dead stop block is set at the terminal position of the trolley entering the furnace chamber to prevent the trolley from exceeding its travel range and causing damage to both the trolley and the furnace body, thus avoiding accidents.

2. 7.  The sealing between the trolley and the furnace body adopts a knife-inserting type seal. This structural form is characterized by ease of operation, safety, and good sealing performance.

2. The transmission control cable of the trolley utilizes a cable reel to facilitate the retraction and extension of the cable when the trolley enters and exits the furnace body. The tail of the trolley is equipped with spring-loaded moving and stationary contacts for power connection, which completes the power on/off of the heating elements on the trolley. This contact method features a large and sufficient contact surface, ensuring good contact and preventing electric sparks and overheating over prolonged use.

3. Furnace door and clamping device

3.1. Due to the large size of the furnace door, the outer frame of the furnace door is made of large-sized channel steel, which enhances the structural strength and makes it less prone to deformation and warping.

3.2. The furnace door lining is a full-fiber structure, with the fiber compression blocks designed in a concave frame style. This design prevents the electric heating elements from protruding beyond the inner surface, ensuring that the electric heating elements and fibers are not damaged by collision during the lifting and lowering of the furnace door.

3.3. The lifting and lowering of the furnace door utilizes an electric hoist as the driving force, equipped with a built-in braking device to ensure smooth lifting and lowering. The use of an electric hoist results in low equipment and operational costs, simple maintenance, and safe operation. Enclosed gantry columns are installed on both sides of the furnace door, welded from steel sections and steel plates, providing sufficient lifting strength.

3.4. The cable chain support for the furnace door is made of stainless steel heat-resistant material, which increases structural strength and effectively prevents heat radiation.

3.5. The pressing (sealing) of the furnace door and furnace mouth is achieved by using an electric push rod for pressing and sealing

4. Heating element and fixing device

4.1. The heating elements are arranged in 6 zones, with power distribution in each zone optimized based on the uniformity of furnace temperature. Due to the large size of the electric furnace, the heating elements are arranged on five surfaces, including the left and right side walls, furnace door, rear wall, and trolley; the heating elements are made of 0Cr25Al5 alloy strips wound into a corrugated shape.

4.2. The left and right side walls, rear wall, and furnace door are hung on the furnace lining fibers using new ceramic screws, respectively. The heating elements on the trolley are laid flat in the strip grooves built with refractory bricks, and their surface load is smaller than that of heating elements in other parts. The hanging method using new ceramic screws will not cause short circuits, and replacement and maintenance are relatively convenient.

5. Electrical control system

5.1. The dimensions, structure, and paint film (color code to be determined by the buyer) of the cabinet shall comply with the industry's general standards, and the installation of components, wiring, and various identifications shall all comply with relevant standards.

5.2. Main control components and operation and display devices such as thyristors, AC contactors, fast-acting fuses, intermediate relays, circuit breakers, limit switches, buttons, and signal indicator lights shall be sourced from renowned brands. Current and voltage indicating instruments shall be sensitive, accurate, reliable, and have a long lifespan. The incoming power supply of the control cabinet shall be connected using copper busbar connections, achieving both safety and aesthetic effects.

6. Automatic temperature control system

6.1. The temperature control system is controlled by six independent temperature control devices, utilizing PID zero-crossing triggered thyristors and Shanghai Guolong high-precision intelligent digital display instruments for temperature control. The furnace temperature is recorded by a Hangzhou Pangu six-point paperless recorder (as shown in the lower right figure), which ensures high temperature control accuracy, stable furnace temperature, small temperature fluctuations, and features an audible and visual overtemperature alarm function.