Researching On Heat Treatment Of High-Power Laser To Mould Steel

Laser quenching is one of the important field of using laser technology in industry, which is closely connected with several subjects, i.e. laser physics theory, laser processing technology, metal physics et, al. The history, application and present processing situation of laser are introduced at first.We studied the effect of laser quenching (harden by phase transformation) on some representative mould steels. Through measuring the rigidity on the surface of samples treated by laser heat treatment , and through photographing microstructures of the steel surface , we find many reasons attribute to high hardness. These reasons include ultra-fine grains, high density dislocation and more content of carbon in martensite. Moreover, laser overlapping treatment is another actual problem in many places. By a lot of experiments, as be showed in many theses, we find the hardness of mould steels were lowered because of tempering. And we also discovered there is no decreasing of the hardness on the surface of Cr12 steel. It is due to Dispersion harden by plentiful of alloy carbide and decreasing of residual austcnitc .These research work should provide some useful references for technicians in practice. At last, the program was also introduced.Five chapters were divided as follows:In Chapter One characteristics of laser was described. Laser technology has also been introduced.In Chapter Two, varieties of laser technology and laser processing system have been described. Next, the laser processing in our lab was introduced particularly.In Chapter Three, the principle of laser quenching was introduced. Subsequently, the math model based on heat conducting principle has also been constructed.In Chapter Four, in our experiments, we selected four representative mould steels as samples. After laser heat treatment, the hardness of samples was measured by special instrument, microstructure was also photographed to be analyzed carefully. Through these experiments, we also debated on the theories which explain the new phenomenon occurring in laser overlapping treatment.In Chapter Five, our research and this thesis were summarized, and the future work was also predicted.In this thesis, we studied the effect of laser heat treatment and overlapping treatment on mould steel, debated on the principle of laser heat treatment, and explained the new phenomenon observed in this experiment. To some degree, maybe our research is beneficial to the development of laser heat treatment technology in practice.