When it comes to heat-resistant steel castings, you have to mention the heat treatment industry; when you mention heat treatment, you have to mention four industrial fires, annealing, normalizing, quenching, tempering. Let's talk about the difference between them.
It is to slowly heat the metal to a certain temperature, keep it warm for a period of time, then slowly cool to room temperature. Think about it, you boiled the bowl of noodles, but it is too hot, so you should put it aside, let it cool eat it again, annealing is the reason.
It is a heat treatment process that heats the metal to 30 ~ 50 ℃ above the critical temperature keeps it in the air for an appropriate period of time. It sounds like normalizing annealing. However, the normalizing cooling speed is slightly faster the production cycle is shorter. For example, if you want to eat noodles, add a fan to blow it, you will often be able to get to the noodles faster, that is, you can get the product faster. Therefore, when annealing normalization can also meet the performance requirements of parts, use normalizing as much as possible. If it is said that annealing normalizing are brothers, quenching tempering are good partners who will never leave.
It is heating the metal above the critical point. At this time, the internal structure state of the metal will change-austenitization. We need to keep the heat for a certain period of time to allow the metal to undergo this change, then cool it at a rate greater than the critical cooling rate to obtain the metastable martensite structure lower bainite structure. This rapid cooling method is usually like this: a One is to cool the metal in water the other is to cool it in oil. After quenching, the martensite structure is obtained, but the internal structure imbalance of this structure state. Although the hardness is high, the plasticity toughness are poor, the brittleness is also large. Therefore, the quenched metal will be shipped as a finished product. After all, the manufacturer is stupid. After all, this kind of secondary processing cannot be performed. For example, mobile phone screens are made of brittle metal, no one would want. Therefore, the effect of tempering is reflected!
After the metal is hardened, it is heated to a temperature below the critical temperature. Insulation for a period of time, so that the tissues in the metal can be evenly distributed then cooled to room temperature, you can get a finished product that has a certain strength, hardness, certain plasticity toughness. This is an example of 1 + 1> 2!
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