The Heat treatment furnace is mainly composed of steel structure of the furnace body, insulation material system, furnace door, furnace top insulation air curtain, furnace door insulation air curtain, resistance band, and electrical control system. The insulation material system is mainly composed of insulation layers such as furnace wall, furnace top, furnace door, and furnace bottom. When the furnace is in operation, according to the requirements of the heat treatment process curve, the workpiece is heated and insulated in the furnace. When the requirements are met, the furnace door at the discharge end is opened, and the workpiece is driven out by the accumulation type chain transmission device at the top of the furnace. Then, the furnace door is closed, and a new round of heating and insulation operation is carried out repeatedly.
When the Heat treatment furnace is in operation, the temperature inside the furnace is relatively high, such as in the quenching furnace at around 1000 ℃. The structural characteristics of the furnace are that furnace doors are set up at the front and back, and the furnace doors open and close frequently. The top of the furnace is a stacked chain transmission device and a long open chain is reserved for lifting tools. The bottom of the furnace spans the cable trench for laying cables. During the operation of the Heat treatment furnace, the outer surface of the furnace wall should meet the temperature standard requirements to avoid high-temperature radiation to on-site operators when the furnace door is opened and closed, to avoid the impact of overheating of the furnace top temperature on the bearings, lubrication devices, and other components of the accumulation type chain transmission device, and to avoid the impact of overheating of the furnace bottom temperature. Based on the structural characteristics of the furnace and the above working conditions and requirements, strict requirements have been put forward for the insulation performance of the Heat treatment furnace.
1 Design requirements for insulation layer of furnace wall, furnace top, furnace door, and furnace bottom
The furnace walls, furnace tops, and furnace doors are all insulated with aluminum silicate fiber materials, and the furnace bottom is insulated with lightweight insulation bricks (as shown in the figure below). The insulation materials for the furnace walls, furnace tops, and furnace doors are distributed in layers. The insulation materials for the furnace walls are installed on the inner walls of the steel structure of the furnace body. After the anchoring nail welding arrangement is completed, two layers of 30mm ordinary aluminum silicate fiber blankets are first laid, and the joints of each layer of fiber blankets are staggered by 500mm to form an overall insulation layer of aluminum silicate fiber blankets, To more effectively prevent heat conduction, a high-purity aluminum silicate fiber module with a thickness of 450mm is used to fix it with anchors. Finally, a layer of high-density 50mm thick aluminum silicate fiber hard board is laid to achieve good flatness of the furnace wall and facilitate the layout of the resistance band. Due to the lack of resistance strip arrangement on the top and door of the furnace, only ordinary aluminum silicate fiber blankets with high-purity aluminum silicate fiber blocks need to be installed. Through the above measures, achieve continuous, dense, mutually compensating, and flat layout of insulation materials.
The bottom of the furnace is mainly made of lightweight refractory brick material, which consists of four levels from bottom to top: ordinary aluminum silicate fiber blanket, diatomaceous earth brick, general density lightweight refractory brick, and lower density lightweight refractory brick. According to the temperature conduction distribution, the insulation performance shows a stepwise increasing trend, while the material price from top to bottom shows a stepwise increasing trend, reflecting good economic efficiency, thus making the equipment have a good cost-effectiveness. A 50mm expansion joint is set every 5 meters during the laying of each layer of furnace bricks, filled with aluminum silicate material to prevent the furnace bottom from expanding and bulging at high temperatures.
2 Design points of furnace door opening and closing mechanism
The opening and closing mechanism of the furnace door adopts a cylinder as the power source. In order to minimize the opening and closing time while ensuring the smooth entry and exit of the workpiece, and avoid the rapid overflow of hot air inside the furnace that is not conducive to insulation, the opening and closing action of the furnace door is set as a double stroke, that is, the opening and closing action is divided into two steps; The first step is the rapid formation of blocks; The second step is to slowly form into place. In order to achieve smooth and slow travel and reduce the impact of the furnace door closing on the furnace body, a gas-liquid damping cylinder is used to complete the action, which plays a role in the second step of action, avoiding the impact of fast travel and achieving smooth and accurate closure of the furnace door.
3 Design requirements for insulation air curtains on furnace tops and end walls
In order to reduce the heat leakage from the furnace top strip gap during continuous operation of the furnace, as well as to reduce the radiation heat impact of the furnace temperature on the bearings, lubrication structures, and other components of the lifting device and accumulation chain transmission device, in addition to setting up overlapping cast iron cover plates that move together with the lifting device, an insulation air curtain is set up on the furnace top, which is collected by the fan to the furnace top air chamber and sprayed out through the nozzle to form two layers of continuous and dense air curtains, It can effectively prevent the heat inside the furnace from overflowing from the top cracks, thereby achieving the purpose of insulation and cooling the moving parts of the furnace top.
To reduce the escape of hot air inside the furnace during the opening and closing process of the furnace door, two sets of air curtains are installed on both sides of the slits at the inlet and outlet of the furnace at both ends. Before the furnace door opens, it starts to work to effectively prevent heat from overflowing from the top of the furnace door. When the furnace door is completely closed, it stops working. Considering the high temperature in this area during door opening and closing, all air curtains are made of stainless steel shells.
4 Design points for insulation at the furnace wall pipe penetration
Due to the arrangement of a large number of resistance bands inside the furnace, each group of resistance bands requires two wiring terminals to be led out to the outside of the furnace wall, and each heating zone is equipped with three thermocouples in the upper, middle, and lower parts. There are a large number of pipes passing through the furnace wall. In order to avoid the contact between the wiring terminals and the steel structure of the furnace body forming a heat bridge and short circuit, each wiring terminal is equipped with an insulation base and ceramic tube, as well as effective insulation and heat insulation, which is conducive to insulation and ensuring safety.
5 Analysis of usage effects
As the core equipment of the production line, the Heat treatment furnace significantly improves the quality of workpiece heat treatment and production efficiency. Through careful and reasonable insulation performance design, the temperature of the outer wall of the furnace meets the standard requirements, avoiding the high-temperature radiation to the on-site operator when the furnace door is opened and closed, avoiding the overheating effect of the furnace top on the components of the stacked chain transmission device, and also avoiding the overheating effect of the furnace bottom on the thermal radiation of the cable, preventing the phenomenon of cable insulation skin softening due to heat. The furnace has been put into production and application, and the overall insulation effect is good, ensuring the orderly and safe operation of equipment and operators.