On 2018-08-08 14:48:54
Eight knowledge that metal heat treatment experts must master
1. Split in two
Different materials, different equipment and different process parameters result in different microstructure and quality after heat treatment.
Even if the material brand, equipment and process parameters are the same, the structure and quality will be different after heat treatment due to the difference in the upper and lower limits of chemical composition content, heat treatment temperature and holding time.
Even if the upper and lower limits of chemical composition content, heat treatment temperature and holding time are the same, the structure and quality after heat treatment will also be different due to different cold and hot processing technology, quality and structure in the early stage of heat treatment.
Therefore, when problems arise, they should be analyzed in detail, that is, they should be divided into two parts.
2. Two figures
Fe-C phase diagram and C curve.
Fe-C phase diagram is a necessary knowledge in dealing with iron and steel, and it is the basis of heat treatment process.
C-curve is the transformation diagram of steel structure after heating and cooling. These two diagrams are the basis of heat treatment. Only by grasping these two diagrams and understanding them in depth, can dry heat treatment be possible and heat treatment be introduced.
3. Three processes
That is, heating, heat preservation and cooling.
These three processes run through all the heat treatment processes, and the quality of these three processes determines the quality of the final heat treatment. These three processes are well understood, and heat treatment is just the beginning.
4. Four fires
Namely annealing, normalizing, quenching and tempering.
These four fires are the most conventional heat treatment. The quality of these four fires reflects the level of heat treatment to a certain extent. If these four fires burn well, you are a heat treatment technician.
5. Six organizations
They are austenite, cementite, ferrite, martensite, bainite and pearlite.
Only with a deep understanding of the characteristics, morphology, precipitation (formation) conditions and properties of these six structures can the level of heat treatment technology be improved.
6. Six defects
The six defects are oxidation, decarburization, overheating, overburning, deformation and cracking.
Among them, overburning and cracking defects are the most taboo in the work, because these two defects are irreparable defects, and the other four should be avoided as far as possible. Although they can be made up, they obviously increase the workload and production cost.
Those who engage in heat treatment can avoid or alleviate these six defects, and they are qualified heat treatment engineers.
7. Seven phase transitions
(1) Pearlite transforms into austenite (P → a);
(2) The transformation of austenite to pearlite (a → P);
(3) Austenite transforms into sorbite (a → s);
(4) Austenite transforms into troostite (a → T);
(5) Transformation of austenite to martensite (a → m);
(6) Austenite transforms into bainite (a → b);
(7) The transformation of martensite into tempered martensite (m → m).
Holding these seven phases, heat treatment is a high level.
8. Eight processes
Namely: annealing process, normalizing process, quenching process, tempering process, surface quenching process, chemical heat treatment process, vacuum heat treatment process, special heat treatment process (laser, ion nitriding, PVD, CVD, ion plating, etc.).
Can accurately grasp the eight processes, heat treatment you are an expert!!!