Second, the bearing industry heat treatment energy-saving measures
As we all know, bearing heat treatment is a large energy consumer, more than 90% of bearing heat treatment equipment uses electric heating, commonly known as "electric tiger", its power consumption accounts for 25-30% of the bearing manufacturing power consumption. At the same time, heat radiant energy, waste flue gas, dust and noise are continuously generated during the heat treatment process, which causes a certain degree of pollution to the environment. Therefore, the development of energy-saving, environmentally-friendly heat treatment technology and equipment is an urgent problem to be solved in the bearing industry.
In recent years, China's bearing industry has adopted measures from the following aspects to improve the energy-saving and environmental protection effects of bearing heat treatment.
1. Optimize process energy saving
After a large number of process tests, under the premise of ensuring the improvement of heat treatment quality, the heat treatment process is optimized and simplified, and then the length of each section of the furnace and the processing cycle are rationally designed, and the thermal efficiency is fully utilized to produce significant energy saving effect. The most prominent in this respect is the multi-functional roller bottom controlled atmosphere heat treatment production line jointly developed by Beijing Tianma Bearing Co., Ltd. and Beijing Jiantong Yingdong Industrial Furnace Company.
2. Using waste heat to save energy
The Ministry of Finance recently released information that the central government will reward the top ten key energy-saving projects. The top ten energy-saving projects include the “Residual Heat and Pressure Utilization Projectâ€.
Bearing steel annealing is one of the most energy-intensive processes in the bearing industry. For many years, bearing manufacturers have made a lot of efforts to reduce the annealing energy consumption of bearing steel. Bearing steel forging waste heat annealing has been popular for a while. However, although this energy-saving process is theoretically feasible, there are many problems that are difficult to solve in practical operation. In the end, they all ended in failure.
In recent years, some bearing heat treatment equipment manufacturing enterprises, such as Hangzhou Jinzhou Electric Furnace Co., Ltd. and Suzhou Industrial Park Shenglong Electric Furnace Manufacturing Co., Ltd., have made a fuss about using heat treatment waste heat to develop a "heat recovery continuous isothermal annealing furnace". "Double-roller-type protective atmosphere spheroidizing annealing furnace" has achieved high efficiency and energy saving effect.
3. Intelligent control of energy saving
The bearing intelligent annealing control system developed by the Materials College of Hebei University of Technology, in the case of making full use of the original annealing furnace body of the enterprise, can be configured according to the thermal characteristics, temperature field distribution and furnace loading of the annealing furnace obtained through feedback during the operation. With equal parameters, intelligently adjust the heating temperature and cooling rate of each zone, and automatically complete the whole process of annealing, eliminating the human factors in operation and achieving remarkable energy saving effects.
4. Reduce heat loss and save energy
Bearing manufacturers and bearing heat treatment manufacturing companies have joined forces to reduce heat loss during heat treatment of bearing heat treatment.
One is to replace the pusher (plate) furnace with a roller hearth furnace, which avoids the heat loss of the tray. (One kilogram of steel is raised from room temperature to 800 ° C, which requires an absorption of 1.03 kcal).
The second is to optimize the design of the furnace, and at the same time reasonably select high-strength lightweight anti-carburizing bricks, high-quality ceramic fiber products and other thermal insulation materials to reduce the heat storage loss of the lining material and the heat loss on the surface of the furnace wall.
Third, the advantageous heat treatment manufacturers, such as Jinzhou Electric Furnace Co., Ltd., use large-scale numerical control equipment to process the heat treatment furnace components, improve the processing precision, improve the horizontal precision of the drive roller, improve the rigidity and sealing of the furnace shell, and reduce the weld seam. , thereby reducing heat loss and loss of atmosphere.
Third, bearing energy-saving heat treatment technology and equipment typical case
1. Multifunctional roller bottom controlled atmosphere heat treatment production line
The multi-functional roller-bottom controlled atmosphere heat treatment production line jointly developed by Beijing Tianma Bearing Co., Ltd. and Beijing Jiantong Yingdong Industrial Furnace Co., Ltd. is a high-quality, high-efficiency, energy-saving and environment-friendly heat treatment equipment at the leading level in China.
The production line consists of roller-type heating furnace, lifting type quenching nitrate salt tank, oil tank, roller bottom cleaning furnace, dryer and double-layer roller bottom isothermal tempering furnace.
By programming the process parameters, four different heat treatment processes can be completed on this line: common martensite quenching, tempering, martensite quenching, tempering, bainite austempering, bainite quenching, etc. .
This production line is the result of introducing digestion, absorption, innovation and integrated innovation. It is at the leading level in the following aspects in China: it has four different functions in one production line, which can not only perform ordinary ordinary martensite quenching but also carry out horses. Quenching quenching and bainite quenching; replacing the oil quenching medium with nitrate salt quenching medium; replacing the nitrate tank with air tempering furnace for bainite isothermal treatment; quenching using computer-controlled lifting mechanism; the entire production line is highly sealed ,zero emission.
Under the premise of ensuring that the strength, hardness, metallographic structure and retained austenite amount reach the standard, the bainite fractional quenching is 26.6% higher than the ordinary martensite quenching impact toughness GCr15, and the GCr18Mo is increased by 36.8%. Bearings in many applications, such as rolling mills, wind turbines, railway passenger cars, etc., need to withstand a large impact load, and therefore need to improve the impact toughness, ordinary martensite quenching can not meet this requirement. The successful development of this production line has provided heat treatment equipment for the manufacture of bearings adapted to high impact loads.
This heat treatment production line can not only ensure the quality of heat treatment, hardness, metallographic structure, deformation and surface depletion of carbon can meet the national and industry standards, and has greatly improved compared with the previous, and, due to the optimization of heat treatment process and equipment sealing performance The improvement and energy saving effect are obvious. The average heat consumption of heat treatment in the national bearing industry is 730KWh/ton, and the power consumption index of this production line has reached 550KWh/ton. If it is applied in the whole industry, it will produce great economic benefits. At the same time, due to the lifting type of bathing method, the quenching deformation is greatly reduced, so that the processing allowance can be reduced and the effect of material saving can be achieved.
2. Double-layer roller bottom protection atmosphere spheroidizing annealing furnace
It is well known that the spheroidized annealed workpiece can be cooled to a temperature below 650 ° C, and a large amount of annealing residual heat is not utilized. In order to achieve the best effect of energy saving and consumption reduction, in May 2007, Hangzhou Jinzhou Electric Furnace Co., Ltd. innovated and developed the “double-layer roller bottom protection atmosphere spheroidizing annealing furnaceâ€. According to the characteristics of the spheroidizing annealing process, the furnace body is designed as a double-layered roller hearth furnace, and the upper layer is fed, and the feeding platform, the waste heat utilization room, the heating section, the heat preservation section, the quick cooling compartment, and the lower layer are the discharge table. Waste heat utilization room, slow cooling section, isothermal section, and quick cooling compartment. The waste heat utilization chamber of the upper and lower layers is a through chamber, without isolation, a heat cycle fan is installed to enhance the cyclic heat transfer, and the cold workpiece is preheated into the furnace by annealing residual heat, so that the workpiece is heated from room temperature to 300-350 ° C; The quick cooling chamber is a lifting passage with an elevator to move the workpiece from the upper layer to the lower layer. The structure of the double-conducting furnace ensures the energy-saving annealing process that makes full use of waste heat: into the furnace → heat recovery by heating → heating → heat preservation → rapid cooling → isothermal → slow cooling → (remaining heat utilization) strong cold → tapping.
The waste heat utilizes energy-saving double-layer annealing furnace, and the power consumption is reduced by 150~220KWh/ton steel. Compared with the spheroidizing annealing power consumption of China's bearing industry, 240～290KWh/ton steel, the power saving is nearly 90KWh/ton steel, and the power saving rate is over 30%. . And the annealing quality is excellent: no oxidation, decarburization layer depth ≤0.10mm, steel utilization rate increased by more than 3%, especially suitable for annealing of cold heading ferrule. The spheroidizing annealed microstructure is a uniform, fine, diffuse, rounded spherical (granular) spheroid, which can be stably controlled in the range of 2 to 2.5 (corresponding to SKF standard CG 2.1 to 2.3) . After spheroidizing annealing, the hardness is 185-202HBW, the hardness difference of one piece is ±5HBW, and the hardness difference of the whole batch is <15HBW.
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