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About ice forging!
I've heard the saying of ice forging before! That is, during heat treatment, cool the tool to MINUS two or three hundred degrees! For what? What molecular structure is tight! ! Now Zliren's kitchen knife is old when shopping in GS! ! I don't know if it is credible or not! !
Where is the ice forging? . . . . Some tool steels, especially powder steels, will undergo cryogenic treatment after quenching to improve their toughness without reducing their hardness. Generally, it is impossible to use liquid nitrogen-196℃ and absolute zero -273. 15℃, and it can only approach the temperature that can never be reached [this post was finally edited by Cliff on August 22, 2005].
I have no practical experience in cold treatment, but I have read some materials that cold treatment can improve the toughness of steel.
Just searched and found a paper:
Cryogenic treatment and effect of Cr 12MoV steel drawing punch
Hengyang Campus of Hunan University (42 1 10 1) Tang Minghua
The performance changes of Cr 12MoV steel drawing punch after different heat treatment processes were studied. The results show that cryogenic treatment can obviously improve the strength, toughness and wear resistance of steel, and can control the dimensional deformation of the drawing punch of Cr 12MoV steel after heat treatment. After cryogenic treatment, the service life of the die is greatly improved.
Die steel; Cryogenic treatment; performance
This increase or decrease in toughness may also be related to metal composition.
Cause analysis of improving material properties by cryogenic treatment;
① It transforms austenite with lower hardness into martensite with higher hardness, stability, wear resistance and heat resistance;
② Through ultra-low temperature treatment, carbide particles with higher hardness and finer particle size are more widely distributed in the crystal lattice of the treated material;
(3) It can produce more uniform, finer and denser microstructure in metal grains;
(4) Due to the addition of micro-carbide particles and finer crystal lattice, the molecular structure is denser, and the tiny holes in the material are greatly reduced;
⑤ After ultra-low temperature treatment, the internal thermal stress and mechanical stress of the material are greatly reduced, thus effectively reducing the possibility of cracks;
⑥ In the treated substance, the molecular structure will produce new combinations due to the decrease of its electronic kinetic energy.
Shuangliren Ice Forging Technology/View /2074547.htm Baidu Encyclopedia
Cold die forging, cold extrusion, cold upsetting and other plastic processing. Cold forging is a forming process below the recrystallization temperature of materials, and forging below the recovery temperature. In production, it is customary to call the forging of unheated blank cold forging. Cold forging materials are mostly aluminum and some alloys, copper and some alloys, low carbon steel, medium carbon steel and low alloy structural steel, which have low deformation resistance and good plasticity at room temperature. Cold forgings have good surface quality and high dimensional accuracy, which can replace some cutting processes. Cold forging can strengthen metal and improve the strength of parts.
The recrystallization is: /view/302 1994.htm Baidu encyclopedia.
When the annealing temperature is high enough and the annealing time is long enough, a new strain-free grain recrystallization core will be produced in the microstructure of deformed metal or alloy. The new grains keep growing until the original deformed structure disappears completely, and the properties of metals or alloys also change significantly. This process is called recrystallization.
Among them, the temperature at which new grains begin to form is called the start recrystallization temperature, and the temperature at which the microstructure is completely occupied by new grains is called the end recrystallization temperature or the complete recrystallization temperature. The temperature range of recrystallization process is affected by alloy composition, deformation degree, original grain size and annealing temperature. In practical application, the arithmetic average of the start recrystallization temperature and the end recrystallization temperature is often used as a parameter to measure the thermal stability level of metal or alloy properties, which is called recrystallization temperature.
The lowest recrystallization temperature =0.4Tm(K), where: TM- melting point of metal, k-k temperature.
The recrystallization temperature of steel is mostly high temperature, which is a multiple of melting point.
The landlord's question is puzzling and contradictory. Ice forging is a steel processing technology, which has nothing to do with MINUS 200 degrees. It is not clear how brittle steel will be at MINUS 200 degrees. Metals such as aluminum and mercury have superconductivity at MINUS 250 degrees. What does the landlord want to ask? What happens to an object at MINUS 200 degrees Celsius?