The goal pursued in the production of steel castings.
The second law of thermodynamics states that as long as there is a temperature difference, the heat is always spontaneously transmitted from the high temperature object to the low temperature object. Therefore, controlling and weakening the heat transfer of the riser and prolonging the liquid time of the riser can improve the feeding capacity of the riser. T71. The thermal energy loss of molten steel in the riser is mainly carried out in three ways: heat conduction, heat convection and heat radiation. The conduction heat dissipation of the thermal insulation riser is mainly related to the thermal conductivity of the thermal insulation riser material. Therefore, under the condition that the thermal insulation effect of the covering agent is ideal, the thermal conductivity of the thermal insulation riser sleeve can be reduced, and the heat preservation effect can be improved, thereby reducing the heat loss of the riser. Improve the feeding capacity of the riser to the casting.
Using Fourier's theorem, the heat loss of the riser wall conduction can be approximated: “the heat transfer capacity of the riser; k—the thermal conductivity of the riser material; AT—the temperature difference between the inner and outer surfaces of the riser; A—the surface area of ​​the riser; Mouth thickness.
The heat conduction mainly occurs on the side of the riser, and the heat transfer from the riser sleeve to the sand type is known from (1-1). Under the same conditions, the ATA/5 is relatively stable. Therefore, a material with a low thermal conductivity X is selected for heat preservation. The mouth sleeve can reduce the heat dissipation of the riser and prolong the solidification time of the riser. The heat insulation riser sleeve made of floating beads has a lower thermal conductivity X, and the dryness of the riser sleeve plays a decisive role in the heat preservation effect.
2 Insulation riser process research As mentioned above, as the output of castings increases, the amount of insulation riser sleeves also increases. The insulation riser sleeve originally produced by the natural drying process can not meet the production needs, and its heat preservation effect is very low, which seriously affects the feeding effect of the riser and the quality of the steel casting.
After careful analysis, it is found that there are three problems in the original formula of the insulation riser sleeve (溧ç +高模数水玻璃) and the process. First, the natural drying time is insufficient, the moisture can not be completely eliminated, and the whole process is broken during the pouring process. In the molten steel, the castings produce pores and inclusions; the second is to use floating beads as aggregates, and the riser sleeves are thickened and thickened under the high temperature and rolling pressure of the molten steel, which seriously affects the heat preservation effect; The insulation riser of the material is damaged and burst when it is kiln-dried, and the riser sleeve cannot be used.
In response to the above problems, the production process of the insulated riser sleeve was tested: firstly, starting from the raw materials, adjust the formula of the insulated riser sleeve, and change the formula of the original "deep beads + high modulus water glass" to "溧 + + refractory clay "HS modulus water glass please" refractory clay and beaded mixed mill to supplement the low refractoriness of the floating beads, low strength and other shortcomings, and the clay has a certain thermal insulation. After use, greatly The sturdiness of the insulated riser sleeve and the scouring resistance of the molten steel are increased, the shrinkage after contact with the molten steel is reduced, and the heat preservation effect of the insulated riser sleeve is improved.
The size of the test was first made during the test. Through the experimental research, analysis and improvement, the drying process of the insulated riser sleeve was determined: the heating rate S5i/h, the furnace temperature was increased to 1000, the heat preservation time was 35h, and the furnace was cooled to below 500. After adding clay, the problem of drying cracking was solved, and the problem of the rise of the riser sleeve after pouring was avoided. The pressure head of the riser during the feeding process was guaranteed, and the filling of the heat-insulated riser was effectively improved. Reduced efficiency, the riser height can be appropriately reduced in the process design process, and the process yield rate is increased accordingly.
"K's modulus water glass ST is a formula, the wet strength of the heat insulation riser sleeve is improved, and the difficulty of making the heat insulation riser sleeve is reduced; the application of the new technology of the heat insulation riser sleeve drying meets the fast-paced, large-scale production. At the same time, most of the moisture in the insulated riser sleeve can be removed due to drying, so the dry strength is high, there is no crack and block phenomenon, and the heat preservation effect is better than the natural drying type.
3 Application conditions After testing, comparing and analysing the riser sleeves of the same covering agent, the results show that the steel castings produced according to the original process have the anatomical results of the riser as shown, indicating the feeding effect. Good, while the casting process yield increased by 2.0%. The riser sleeve produced by this process has been successfully applied to the production of steel castings.
4 Conclusion The thermal energy loss of the riser of the steel castings mainly depends on the thermal properties of the thermal insulation material and the heat dissipation area. When the thermal insulation effect of the covering agent is ideal and the thermal insulation riser is slightly worse, the heat conduction is the main way to reduce the heat of the riser. .
The new insulated riser sleeve contains a certain amount of fire-fired clay, which has good strength and heat preservation performance after thorough drying.
High quality insulation riser sleeve + high quality covering agent
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