1. Divided into two parts: different materials, differe […]
1. Divided into two parts: different materials, different equipment, different process parameters, and different microstructure and quality after heat treatment. Even if the material grade, equipment and process parameters are the same, the microstructure and quality after heat treatment will be different due to the upper and lower limits of the chemical composition, the upper and lower limits of the heat treatment temperature, and the upper and lower limits of the holding time. Even if the upper and lower limits of the chemical composition, the upper and lower limits of the heat treatment temperature, and the upper and lower limits of the holding time are the same, the structure and quality after heat treatment will also be different due to the difference in the process, quality, and structure of the hot and cold processing in the early stage of heat treatment. Therefore, after a problem arises, it is necessary to analyze the specific problem specifically, that is, to divide it into two.
2, two figures: Fe-C phase diagram, C curve. The Fe-C phase diagram is an essential knowledge for dealing with steel. The C curve is the tissue transition diagram of the steel after heating. These two figures are the basis of the heat treatment foundation. Only by grasping these two figures, it is possible to dry heat treatment after deep understanding of these two figures, and heat treatment can get started.
3. Three processes: 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. The three processes are well understood, and the heat treatment is getting started.
4, four fires: annealing, normalizing, quenching, tempering. These four fires are the most conventional heat treatments. The quality of these four fires reflects the heat treatment level to some extent. If the four fires are good, they are a heat treatment technician.
5. Five organizations: austenite, cementite, martensite, bainite, pearlite. A deep understanding of the characteristics, organization, precipitation (formation) conditions, performance, etc. of these five organizations can improve the level of heat treatment technology.
6, six major defects: namely oxidation, decarburization, overheating, over-burning, deformation, cracking six major defects, which in the work are most taboo to produce over-burning and cracking defects, because these two defects are irreparable defects, the other four It should also be avoided as much as possible, although it can make up for it, but it obviously increases the workload and production costs. The six major defects that can be avoided or mitigated by heat treatment are a qualified heat treatment engineer.
7. Seven phase transitions: pearlite transformation to austenite (P→A), austenite transformation to pearlite (A→P), austenite transformation to sorbite (A→S), austenite Transformation into yttrium (A→T) austenite transformation to martensite (A→M), austenite transformation to bainite (A→B), martensite transformation to tempering Markov Body (M→M back) grasping these seven phase change heat treatments is a high level.
8. Eight major processes: 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, PCD, CVD, ion plating, etc.).