Stduy On The Performance Of DH Carbon-free Molding Sand

Green sand is one of the most important molding material in Sand Casting, which can be used in very broad area, and the amounts of sand consumption is very large. The coal sand, which is widely used at home and abroad. The coal sand has caused serious environmental pollution and health hazards. It is not fit for the needs of the scientific development of the foundry industry and the environmental protection policy of reducing consumption and reducing emissions. "Green casting" is the main line of industry development and structure adjustment in the future. This paper mainly focus on the production process of green casting.Donghua University has cooperated with some industry, they have developed a kind of green sand, called ’ DH carbon-free molding sand’. The sand is made up of some nontoxic and inorganic material, it does not produce toxic gases in casting process.Firstly,A series of experiments are carried out.The wet compressive strength, permeability, hot wet tensile strength, gas evolution, thermal expansion, hot pressing strength, high temperature form transformation, DSC-TG curve of YunXi Environment Friendly Molding Sand are systematically studied, which are compared with that of the conventional coal sand.This test helps to further understand the characteristics of YunXi Environment Friendly Molding Sand and the effects of molding sand performance on the casting defects and casting quality. The result shows that the wet compressive strength, permeability, thermal expansion of YunXi Environment Friendly Molding Sand are similar with coal sand, but the hot wet tensile strength, hot pressing strength, gas evolution of YunXi Environment Friendly Molding Sand are far superior to that of coal sand. These advantages can effectively reduce the casting defects, and ensure the quality of the casting.Secondly,A series of experiments are carried out, the wet compressive strength of Yunxi environmental sand are studied, which tested in burning condition of different temperature, and compared with that of the conventional coal sand to measure the recycling performance is good or bad. In addition, differential thermal analysis and thermal gravimetric analysis of Yunxi environment-friendly molding sand are carried out, and the form changes are observed when sand heated. The DSC-TG curve and high temperature form change are analyzed. Explained the changes of the wet compressive strength of sand in different burning temperature. Studies have shown that the descending trend of Yunxi environment-friendly molding sand are moderate than conventional coal sand with the rise of the burning temperature. which can adapt to the wider temperature range, and the recycling performance is better. Research work can helps to further improve the recycling performance of sand, control the cost of casting, and further promote the production process of green casting.Thirdly,By adding a small amount of inorganic and environmentally friendly additives I to the DH carbon-free sand, study on changes of the compressive strength, residual strength, permeability, collapsibility, gas evolution. In order to get a sand that have a better performance.The result shows that after adding a small amount of additives I to the DH carbon-free sand, the compressive strength of sand get greatly promotion, the residual strength is very low at every temperature,collapsibility is good. The permeability, gas evolution are essentially same as before. When the mass fraction of additives I in sand was 2%, the compressive strength and residual strength are reasonable. Not only can guarantee the mould strength, the final strength can meet the required strength of sand casting.Finally,In order to verify the affect of performance changes of sand on the quality of casting and casting defects when sand in casting process of high temperature.DH carbon-free molding sand and the other sand composed of DH carbon-free molding sand and additives I are prepared.This molding sand was used in the pouring experiment of iron casting sample and the used in factories.Then,The application performance of DH carbon-free molding sand are examined from two aspects of the burning-on condition and surface finishment.The experimental results show that the DH carbon-free molding sand adding some additives I, casting surface can still form a burning-on layer which was easily stripped, and the surface of the casting was smooth, casting quality was good.