The improvement of cryogenic treatment for ferrous metals is mainly in the following aspects:
Improve the hardness and strength of the workpiece
Improve the wear resistance of workpiece
The mechanism of metal material cold treatment equipment is as follows:
- Improve the hardness and strength of the workpiece
In a sense, cryogenic treatment is the continuation of quenching, which makes the materials with lower MF point continue to complete the transformation from a to M. after conventional quenching, the retained austenite of some materials can reach 25%, or even higher. Through continuous transformation, the degree of * * rc1-3 can be increased, and sometimes even hrc5-6 can be achieved. The hardness of the workpiece is improved slightly by precipitation of nano sized ultrafine carbides in martensite matrix. Qian Shiqiang of Shanghai Jiaotong University has used 16Mn experiment. The hardness of the workpiece after several times of deep cooling is 1.5 degree higher than that of the non cryogenic one, which indicates that the dispersed ultrafine carbide plays a role of dispersion strengthening on the microstructure. According to the material manual, when the hardness of the material is above HRC50, we can see that the tensile strength of chromium steel, chromium vanadium steel and chromium molybdenum steel usually increases by about 30MPa every time the hardness is increased by hrc0.5 degrees.
- Improve the wear resistance of workpiece
With the increase of hardness, the wear resistance of martensite is more obvious than that of austenite. When the hardness of materials such as w18cr4vcr12 increases from hv600 to HV800, the relative wear resistance increases by about 15% to 20% respectively. A large number of ultrafine carbides precipitated and dispersed on the martensite dislocation lines and twin bands play a role in pinning and supporting the martensite matrix. Even though the deep cooling sometimes does not significantly improve the hardness of the workpiece, we can obviously see the improvement of its wear resistance. For high carbon and high alloy workpieces, it is more common to improve wear resistance by 50%.
Cryogenic treatment — function:
It can precipitate ultrafine carbides, improve the wear resistance of the workpiece, refine the grain size and improve the impact toughness of the workpiece.
It can change the residual austenite, improve the hardness and wear resistance of the workpiece, and stabilize the size of the workpiece.
It can increase the corrosion resistance of martensitic stainless steel and improve the polishing performance of workpiece.
It can improve the conductivity and corrosion resistance of nonferrous metals.
It can reduce the deformation and cracking of die. Improve the dimensional accuracy of the workpiece.
The working temperature is + 200 ℃ ~ – 150 ℃, the minimum temperature in the box is ≤ – 150 ℃, and the maximum cooling speed is ≥ 50 ℃ min,
The accuracy of temperature control is ± 0.1 ℃ for heating, cooling and constant temperature, and ± 0.1 ℃ for temperature field uniformity.
The controller can record the whole running curve completely.
Cryogenic treatment — application field
It is suitable for cutting tools, measuring tools, moulds, casting industry, hardware industry, auto parts, textile parts, precision stamping dies, nano materials, precision plastic molds, cutting tools, hobbing cutters, screw punches, knitting machine parts, precision springs, aluminum alloy materials, motor shafts and screws Screw tooth plate, powder metallurgy mold, packaging mold, tungsten carbide material, pneumatic tool parts, golf head, racing engine, aluminum alloy, copper alloy, cemented carbide, plastic, rubber, asphalt, glass, Kuangshan geological drill bit, nozzle, spring, gear, bearing, saw blade, turbine shaft of engine, roll, valve, high speed tool steel, cemented carbide cutting tool and other parts Drill bit, etc.