| High silicon austenitic stainless steel is one kind of the acid corrosion resistance material, it is widely used in the sulfuric acid industry. But the cooling rate is slow during the solidification process, the flow capacity of the alloy is low, and crystalline structure is thick, the castings have local porosity and micro cracks. In the hydraulic pressure test, leakage occurs, which causes the product to discard, and affects the production efficiency and cost. This paper utilizes the analysis of product failure to develop a scheme of thinning agent and cooling treatment of copper plate, to control the solidification process of products, to study the effects of related process parameters on the microstructure and properties of the samples, and to find an optimized scheme of the production of high silicon austenitic stainless steel.The analysis of the actual corrosion failure of products finds that the main causes of failure are shrinkage porosity and precipitates in the microstructure of castings. The existence of defects accelerates the corrosion of the castings, and galvanic corrosion occurred on the anode protection system. The phenomenon of the failure of the product is promoted by the double electrolytic corrosion. Because of the defects of castings is occurred during the solidification process, therefore, according to the actual production conditions of the product we formulated the specific iron powder refining agent and copper base plate quenching process.Effect of refinement on microstructure and properties of high silicon stainless steel was found by iron powder that the changing of particle size and pouring temperature affects the solidification process of the casting. Iron powder particles can be used as cold mass, cause the melt to produce hot and cold components, then form more crystal nuclei, thus the nucleation rate of the whole casting is greatly increased. When the pouring temperature is relatively high, the mechanical property is decreased with the increasing of grain refiner. Low temperature casting showed the opposite characteristics. When the particle size is 40 mesh, the grain size is decreased with the increasing of pouring temperature and the mechanical property is improved. When the thinning agent is 120 mesh, the changing law is opposite. In the middle of the pouring temperature, the performance of the sample does not increase or decrease with the increasing of the particle size. The property of the samples made by 80 mesh refinement agent does not change with the changing of pouring temperature.The copper base plate has good heat dissipating capacity, which promotes the casting sequence solidification, ensures the positive temperature gradient and reduces the casting defects. Through the studying of copper plate quenching process, with the decreasing of pouring temperature, the microstructure of the sample is gradually refined. The microstructure of the low temperature of the thermal insulation shell is smaller than that at high temperature. The microstructure of the sample which is used in the ventilation cooling is much smaller than that of natural cooling. At the high mold shell temperature, the mechanical properties of the samples are increased with the decreasing of the pouring temperature. When the mold shell temperature is low, there are defects in the organization, and the casting temperature is too low to reduce the mechanical properties. With the same degree of refinement of the microstructure, the mechanical properties of the materials in low temperature shell temperature and ventilation cooling mode are higher than that in the corresponding temperature and natural cooling methods.Compared with the actual production of castings, refinement of iron powder and cold treatment of copper plate have refined the microstructure of samples and controlled the defects and improved the mechanical properties. Therefore, in the actual production, this test scheme can make the qualified rate of products greatly enhance, and promote the maximization of enterprise benefits. |
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