中文版Steel heat treatment knowledge
Heats up the steel to certain temperature and keeps warm period of time, then causes it to cool slowly, is called the annealing. The steel annealing is heats up the steel to occurs changes the temperature which or the part changes, after undergoing the heat preservation, slow cooling heat treatment method. The annealing goal, is to eliminate the organization flaw, the improvement organization causes the ingredient uniformization as well as the refined grain, enhances the steel the mechanical properties, reduces the residual stress; Simultaneously may reduce degree of hardness, enhances the plasticity and toughness, the improvement machining performance. Therefore annealing both to eliminate before the improvement the working procedure carry-over organization flaw and the internal stress, and finishes the preparation for the subsequent handling, therefore the annealing belongs to the half-finished product heat treatment, also calls in advance the heat treatment.
2. steel normalizing
The normalizing is heats up the steel to the critical temperature above, causes the steel to transform completely into the even austenite, then in air natural cooling heat treatment method. It can eliminate the hyper-eutectoid steel the netted iron carbide, regarding the hypo-eutectoid steel hot may the refinement crystal lattice, enhances the comprehensive mechanical properties, to requests not the high components with to replace the annealing craft is hot quite economical.
3. steel quenching
Quenching is heats up the steel to the critical temperature above, keeps warm period of time, then puts in very quickly the hardening agent, causes its temperature to reduce suddenly, is bigger than the critical cooling rate the speed to cool rapidly, but obtains the heat treatment method which primarily is not balanced by the martensite organizes. Quenching can increase the steel the intensity and degree of hardness, but must reduce its plasticity. In quenching the commonly used hardening agent includes: Water, oil, lye and salts solution and so on.
4. steel tempering
Will quench already the steel heats up to certain temperature, uses certain method cooling to be called the tempering again. Its goal eliminates the internal stress which quenching produces, reduces degree of hardness and brittleness, obtains the anticipated mechanical properties. The tempering is divided the high tempering, the average tempering and the low tempering three kinds. The tempering are many and quenching, hot coordinate use.
⑴Quenching and retempering treatment: After the quenching, high tempering's heat treatment method is called the quenching and retempering treatment. The high tempering is refers to 500-650℃ between carries on the tempering. The quenching and tempering may enable the steel the performance, the material quality to obtain the very great degree adjustment, its intensity, the plasticity and toughness are good, have the good synthesis mechanical property.
⑵Aging treatment of metal: In order to eliminate the precision measuring instrument or the mold, the components in the long-term use the size, the shape changes, often before low tempering (low tempering temperature 150-250℃) the precision work, heats up the work piece 100-150℃, maintains 5-20 hours, this kind for stable precision workpiece quality's processing, is called the effectiveness. To the low temperature or moves under the load condition the steel products component to carry on the aging treatment of metal, eliminates the residual stress, stable steel products organization and size, especially important.
5. steel superficial heat treatment
⑴Case hardening: Is the steel stock surface through the flash heat to the critical temperature above, but before the quantity of heat has not passed to the core, with enough time rapid cooling, like this may quench the surface layer in the martensite organization, but the core has not occurred changes, this realized the surface to be hard, but core invariable goal. Is suitable in the medium carbon steel.
⑵Thermochemical treatment: Is refers to the chemical element atom, with the aid of high temperature when atomic diffusion's ability, permeates it the work piece the surface layer to go, changes the work piece surface layer the chemical composition and the structure, thus achieves enables the steel the surface layer to have the specific request organization and the performance one kind of heat treatment craft. Is different according to the permeating element's type, the thermochemical treatment may divide into the cementation, azotize, the cyaniding and the metallic cementation and so on four kinds.
Cementation: The cementation is incites the carbon atom to permeate the steel surface layer the process. Is also enables the low-carbon steel the work piece to have the high-carbon steel surface layer, again after quenching and the low tempering, enables the work piece the surface layer to have the high degree of hardness and the resistance to wear, but the work piece center section was still maintaining low-carbon steel toughness and the plasticity.
Azotize: Also calls the nitriding, is aims at the steel the surface layer permeating nitrogen atom process. Its goal is enhances the surface layer degree of hardness and the resistance to wear as well as enhances the fatigue strength, corrosion resistivity and so on. At present produces uses the gas nitration.
Cyaniding: Also calls the carbonitriding, is refers to the steel simultaneously permeates the carbon atom and the nitrogen atom process. It enables the steel surface to have the cementation and the azotize characteristic.
Infiltrates the metal: Is refers to by the metal atom permeates the steel the surface layer process. It is causes the steel the surface layer alloy, enables the work piece surface to have certain alloy steel, the special steel characteristic, like heat-resisting, wear-resisting, oxidation resistance, anti-corrosive and so on. In the production commonly used has aluminizes, the chromizing, the boronization, to infiltrate the silicon and so on.
