Quartz glass is widely used in aerospace, energy, optoelectronics, chemical industry and other fields because of its high purity, good stability, high temperature resistance, radiation resistance and heat shock resistance. The precision and ultra precision machining technology of quartz glass components has become an important research direction in the field of advanced manufacturing technology. Quartz glass is a hard and brittle material with poor machinability. It is mainly processed by grinding, grinding, polishing and other methods. The traditional grinding method for the material removal of quartz glass is mainly brittle removal, which is easy to produce microcracks and difficult to form nano-scale optical surface. In order to obtain high-quality and low damage machined surface of quartz glass, it is theoretically required that the grinding process should be carried out in the ductile mode as far as possible, which requires that the cutting depth of abrasive particles should be less than the critical cutting depth of brittle ductile transformation to realize the removal of micron or even nano materials. Therefore, it is difficult to realize ductile domain grinding of quartz glass under the condition of ordinary processing equipment, and the processing cost is high.
From the perspective of material removal energy, in order to realize the material removal of quartz glass, at least the energy that can destroy the Si-O binding potential energy needs to be applied to the material. Therefore, if the Si-O binding potential energy can be weakened in the grinding process and the mechanical removal energy can be reduced, the microcracks caused by material brittle removal can be reduced and the processing quality of quartz glass can be improved. One of the main methods to weaken the binding potential energy of Si-O is the chemical modification method, that is, in the grinding process, through the chemical action of grinding fluid or grinding wheel binder on quartz glass, break the micro network structure of quartz glass and reduce the bond energy of bonding bond, so as to realize the ductile domain grinding of quartz glass. In order to achieve this dynamic balance, the composition of grinding fluid plays an important role in the chemical modification of quartz glass surface.
The proportion of China's photovoltaic glass output in the world has increased year by year. In 2019, the global photovoltaic glass output was 5.52 million square meters, of which China's output accounted for more than 90%, reaching 4.971 million square meters. In the production of photovoltaic glass, China has been in an absolute monopoly position. By the end of 2019, there were 20 enterprises in production in China's photovoltaic glass industry, with a production capacity of 98 kilns, a total of 244 lines, and a production capacity of 35860 tons / day. Among them, five enterprises such as Xinyi solar energy, fulette, rainbow, Jinxin and CSG account for about 80% of the overall production capacity of the industry.
The quality of photovoltaic glass directly determines the product performance, efficiency and service life of photovoltaic modules. Therefore, the technical certification of photovoltaic glass is more strict and complex. Due to the complex certification, long cycle and high cost, photovoltaic glass enterprises are generally stable once they have established a purchase and sales relationship with module manufacturers.
The supply chains of photovoltaic glass and float glass are highly overlapped. The upstream is also raw materials such as soda ash, dolomite and limestone and fuels and equipment such as natural gas and heavy oil, while the downstream is only for the photovoltaic module industry.
The production cost of photovoltaic glass is relatively rigid. In the production of raw glass, heavy soda ash and quartz sand are the main raw materials. The concentration of soda ash industry is high, and large soda ash suppliers have a strong voice. Due to the relatively small volume of photovoltaic glass, the bargaining power is relatively weak. In order to ensure the high transmittance of the original glass, the iron content of the glass is lower than that of ordinary glass, which is generally controlled at about 0.015% - 0.02%. Therefore, the quartz sand with high transmittance and low iron content needs to be used in the production of the original glass, and its quality is determined by the content of silica and iron in the quartz sand.