Study On Heating Process Of Wide Band Beam By Polygon Mirror In Laser Materials Processing

Laser processing on material surface is a transient, un-balanced, disproportioned complex physical chemistry process, which creates temperature field and corresponding temperature grads field that have significant effect on processing quality. Till now, there isn't any method which can monitor heat progress during laser processing on-line at home and abroad. The main reason is that during the processing progress, the temperature of the inner part of material cannot be measured. So simulate analyzing through establishing mathematic physics model is the main method to study the heat progress of laser processing on material surface.Ths essential problem of the heat progress of laser processing on material surface is the complex heat transfer created during the material-laser beam interaction. Mode of laser beam, shape of facula and form of the affect of laser beam to the material are key factors that influence the temperature field. Facula can be divided into static state beam facula and dynamic state beam facula according to the way of formation. Focused beam scanning superposing forms dynamic state beam facula, which creates the more complex temperature field than static state beam facula does. In the study before, temperature field of static state beam facula that has the same average power with dynamic state facula was used to manifest as dynamic state facula temperature field, neglecting the particularity of the high energy density at the action spot of the dynamic state facula and the cycle process of heating and cooling of every bit of the. facula. Laser rotating mirror scans the focused laser beam into lineation facula. This work takes facula scanned by laser rotating mirror as an example, puts forward the mathematical physics model according with the forming process of facula scanned, studies the relationship between parameter and temperature distribution, and simulates static state facula temperature fields with the same average power under different parameter by computer. In the zone of action of laser, the surface layer temperature of facula scanned by laserrotating mirror is higher than that of static state facula; and the bottom layer temperature is lower than that of static state facula, having obvious "skin effect".On the basis of laser rotating mirror facula temperature field and its character adequately discussed and studied, mathematics model of laser rotating mirror scanning wideband temperature field is built, and the relationship between parameter and temperature distribution is studied. The computer simulates the temperature curve and three dimensional temperature distributions under different parameter, and simulates the appearance of (chilling band heat treated by laser rotating mirror wideband). The method of using temperature curve to calculate the time of heating of austenization and the cooling velocity of martensite transforming is put forward. Mathematic expression of temperature and rate of change of temperature to time at the point (xO, yO, zO) at any time of laser rotating mirror scanning wideband temperature field is developed and "traveling-wave method of temperature wave line" is put forward.In this work, part of the theory conclusions mentioned above is verified by experiments, and quite ideal results are acquired. The research work above provides theory basic for exactly modeling and quality controlling of laser processing temperature field having the character of scanning and superposing process.