01 adopts energy-efficient heat treatment process
1) If the carburizing temperature is increased from 930 ° C to 1050 ° C, the process cycle can be reduced by 40%, such as low pressure carburizing in a vacuum furnace, and carburizing at 1050 ° C.
2) Nitrocarburizing or the like instead of nitriding and carbonitriding can reduce the process temperature from 850 to 930 °C to 550 to 580 °C; instead of general gas nitriding, the nitriding time can be reduced from 30 to 70h. 2 ~ 3h.
3) Substituting carbonitriding for thin layer carburization. The treatment temperature can be reduced from 930 ° C to 850 ° C; when the depth of the layer is less than 1 mm, the carbonitriding time can be shortened by 30%; and because the heating temperature is low and the time is short, the deformation of the workpiece after quenching is small.
4) Acetylene low-pressure carburizing technology, high carburizing speed, energy saving; low consumption of raw material gas, low emission, high temperature carburizing, shortening process cycle and energy saving.
02 Shortening the heating time process
1) Zero heat preservation quenching According to the traditional heat treatment process, the holding time ≥ 1/2 or 1/3 of the total heating time. For carbon steel and low alloy structural steels that reach the thin part size, the zero heat holding quenching process can be used when the heating temperature is above Ac1 or Ac3. Practice has proved that the quenched and tempered steels such as 35Cr, 45Cr and 42CrMo adopt zero-intensity quenching process, which can all meet the installation and service conditions. Compared with the traditional heat preservation quenching process, the time required for the workpiece to be sterilized and the austenite homogenization is eliminated, and the energy consumption can be reduced by 20% to 30%.
For example, a drive shaft material 45 steel, the traditional heat treatment process is: 840 ° C × 60min quenching, 600 ° C × 120min tempering, hardness 215 ~ 245HBW. On the basis of the test, it is determined that the transmission shaft adopts (870±10) °C×0min quenching and “680±10†°C×0min tempering “zero insulation†quenching and tempering process. After testing, the fine lath martensite structure is obtained after quenching. After tempering, the microstructure is fine tempered sorbite, and the hardness is 215-235HBW, which fully meets the technical requirements and has good effect.
2) Uneven austenite is heated and quenched. When the steel is heated to the austenite state, it takes a long time for the carbide to fully dissolve the austenite to homogenize, but the austenite does not reach homogenization, that is, quenching does not affect the performance after quenching and tempering.
03 using surface, local heating instead of the overall heating method
The surface heating and quenching method is to heat the surface of the workpiece by induction, flame, laser, etc., and then harden the steel by spraying, immersing liquid and self-cooling. The quenching of the local surface of the workpiece can also be achieved by these methods. Replacing the overall heating and quenching with induction heating can save 33% to 50%, and replace it with carburizing and quenching energy by 90%. For example, low-hardenability structural steels 55Ti, 60Ti and 70Ti are used to manufacture automobile and tractor gears instead of carburized and hardened gears.
04 Accelerated chemical heat treatment process technology
Accelerated chemical heat treatment using a direct atmosphere, ion bombardment (ion carburizing, ion nitriding and ionic carbonitriding), chemical infiltration technology (rare earth infiltration technology and BH infiltration technology), can improve the carburizing speed About 20%, or lower the temperature by about 40 °C.
05 lower heating temperature method
Steel in the two-phase zone (sub-temperature) heating method, confirmed by production practice, the steel is heated and quenched in the two-phase region of A+F lower than AC3, and often can also obtain excellent performance, especially the sub-temperature quenching of low-carbon alloy steel. The obtained F+M mixed structure can achieve a good fit for strengthening and toughening.
06 Simplify or cancel the heat treatment process
For example, after high-pressure gas quenching after carburizing, steel parts are subjected to high-pressure (6×105～2×106Pa) H2, He and N2 gas quenching after vacuum carburizing or general gas carburizing, which can reach the cooling rate of static oil. The cooling is uniform and the deformation of the workpiece is small; the air-cooling quenching instead of the oil can avoid the pollution of the oil smoke; the intermediate cleaning process can be cancelled, and the electricity can be saved and saved.
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