Introduction to Heat Treatment of Heat Resistant Steel Castings

Introduction to Heat Treatment of Heat Resistant Steel Castings
When it comes to heat-resistant steel castings, we have to mention the heat treatment industry; When it comes to heat treatment, we have to mention the four industrial processes: annealing, normalizing, quenching and tempering. Now let's talk about their differences.
1、 Annealing
It means slowly heating the metal to a certain temperature, holding it for a period of time, and then slowly cooling it to room temperature. Think about it. You cooked a bowl of noodles, but it was too hot. So you should put it aside and let it cool before eating. Annealing is the truth.

2、 Normalizing
It is a heat treatment process in which the metal is heated to 30~50 ℃ above the critical temperature and cooled in the air after holding for an appropriate time. It sounds like normalizing and annealing. However, the cooling rate of normalizing is slightly faster and the production cycle is shorter. For example, if you want to eat noodles, add a fan to blow, and you can often arrive later, that is, you can get the product faster. Therefore, when annealing and normalizing can also meet the performance requirements of parts, normalizing should be used as much as possible. If annealing and normalizing are brothers, quenching and tempering are good partners.
3、 Quenching
It is to heat the metal above the critical point. At this time, the internal structure and state of the metal will change - austenitizing. We need to keep the temperature for a certain time to allow the metal to undergo this change, and then cool it at a rate greater than the critical cooling rate to obtain the metastable martensite or lower bainite structure. This rapid cooling method is usually as follows: one is to put the metal into water for cooling, and the other is to put it into oil for cooling. After quenching, martensite structure is obtained, but the internal structure of this structure state is unbalanced. Although the hardness is high, the plasticity, toughness and brittleness are poor. Therefore, the quenched metal will not be delivered as a finished product. After all, the manufacturer is not stupid. After all, this kind of metal cannot be processed again. For example, the mobile phone screen is made of brittle metal, and no one will want it. Therefore, the role of tempering is reflected!
4、 Tempering
After the metal is hardened, it is heated to a temperature below the critical temperature. Heat preservation for a period of time, so that the internal structure of the metal can be evenly distributed and then cooled to room temperature, so that a finished product with certain strength, hardness, plasticity and toughness can be obtained. This is an example of 1+1 ＞ 2!