200mw laser pointer is the ideal tool and assistant for the teacher

Which abc curve for the isothermal transformation of austenite to the pearl breaks and Bayesian start line, Ms is the martensite transformation start line a 'b' c 'is the austenite to pearl size bainite isothermal transformation End of line. Abc line above the left and Ms line for supercooled austenite region (breeding area), austenite above the A1 temperature rapidly cooled to below the Ms temperature, rather than meet with the abc line is not transformed into pearlite or bainite, can only be transformed into martensite. Under continuous cooling conditions due to the undercooling, which makes the incubation period of growth of undercooled austenite, C curve to the right and the shape change. The safety situation of green laser pointer workshop can be improved further.
Part of the isothermal transformation disappear, such as the curve updw below (known as CCT curves), Therefore, the actual quenching, cooling rate and updw curves meet, the austenite can be transformed into martensite, the cooling rate curve coincides with updw tangent line, this cooling rate is called the critical cooling rate of the martensitic transformation. To get the full martensite, the cooling rate must be greater than the critical speed of the martensitic transformation. Conventional quenching water quenching cooling rate of about 600 ° C / S. Laser Hardening, due to the high power density, the heating time is short, according to the calculations, the cooling rate of the laser hardening up to thousands of degrees per second, higher than the maximum cooling rate of the conventional heat treatment an order of magnitude. Therefore, the laser heating workpiece is very easy to achieve self-quenching. 200mw laser pointer is the ideal tool and assistant for the teacher, lecturer, business man and so on.
Laser hardening the surface preparation. Metal surface on the laser radiation energy absorption capacity depends primarily on the surface state. General metal surface after machining, surface roughness is small, the reflection rate of up to 80 ~ 90%, the metal surface to absorb light energy efficiency. In order to improve the efficiency of absorption of the metal surface of the laser in front of the laser hardening of surface preparation. Surface preparation methods, including phosphide France, to improve the surface roughness, oxidation, spray coating method, coating method, one of the most commonly used are the following: black paint method. Coated on the surface of the part with carbon ink or graphite - binder mixture, the formation of the absorbing film, the absorption rate of up to about 90%, increase carbon materials. The better quality of green laser pointer will make the price of green laser pointer higher.
This method can be used for any material can also be a partial coating, the coating thickness is difficult to control, the laser will produce a dazzling light and smoke effects are not very stable. With black paint applied to the part surface coating absorption rate similar to the carbon coating, the coating adhesion. Ease of coating and uniform thickness. But the laser will produce smoke and odor, difficult to clear. In recent years, the United States with more than a grade Krylonl602 black lacquer, the main ingredients of the graphite powder and sodium silicate or potassium silicate, spray method, the thickness of 10 ~ 20μm. Domestic-ray machine developed by a 86-l black lacquer, has been supplying the domestic market. The phosphating sub-phosphide high temperature (90 ~ 98 ° C) temperature phosphating (55 ~ 70 ° C) and room temperature phosphating (about 25 ° C). It is the 3rd generation of green laser pointer.
In the laser processing of different materials, laser processing, surface preparation layer of the three phosphating process (phosphating film) on the laser absorption rate, is generally believed that the effect of the high school temperature phosphating better. Disadvantages: The process is complex, large investment in equipment, the high cost of wastewater treatment (pollution), laser treatment, the roughness increases. Phosphating formed in the surface layer of phosphate: phosphoric acid, manganese, zinc phosphate, including manganese phosphate. Later found that the phosphate film after laser treatment the surface intergranular micro-pattern, and manganese phosphate film after laser treatment to generate a low melting point compounds will drill into several grain depth along the iron-based alloy grain boundaries, as shown in Figure 5 in recent years phosphating pretreatment for other methods instead. The management personnel of green laser pointer should take great responsibility.