# Calculation results and Analysis and discussion of Sand casting

It is necessary to know the input of all kinds of energy, materials and so on when calculating carbon emissions. In this process, the mechanical equipment and related processes should be considered. Among them, the carbon emission coefficient of energy and materials. The carbon emission coefficient of steel and pig iron comes from China Iron and Steel Yearbook, the carbon emission coefficient of standard coal, coke and water comes from the general principle of comprehensive energy consumption calculation, and the other carbon emission coefficients come from literature research. The main energy sources calculated in this case are electricity, coke and alcohol. Electricity is the power consumption of all kinds of equipment, coke is the energy material for cupola ironmaking, and alcohol is the energy material for flow coating process. According to the formula, all kinds of carbon emissions of the three process schemes can be calculated directly.

The material consumption of the three process plans. Pig iron and scrap are smelting materials, depending on the amount of castings, gating systems and risers. The amount of moulding sand and paint is increased or decreased according to the gating system and riser of different schemes. Smelting gray cast iron per kilogram requires pig iron 0.146kg, return charge 0.457kg, scrap 0.498kg, coke 0.021kg. Self-hardening resin sand is used as molding sand with a density of 1.48 g/cm3. The recovery rate of used sand treated by sand treatment line of sand casting enterprises is 96%.

The pouring temperature varies with different process plans, and the average energy consumption per ton of molten iron in a foundry in recent months is shown in figure 1. As can be seen from the picture, the higher the temperature is, the more energy is consumed in smelting hot metal.

The process carbon emission of sand casting production system mainly comes from the smelting process. Among them, the process carbon emission mainly comes from the carbon dioxide produced by the chemical change of limestone in the slagging reaction. According to the calculation, the process carbon emissions of the three processes are 1.233kg and 1.128kg, respectively, and the carbon emissions of the three processes are 1.128kg and 1.126kg, respectively. Calculate all kinds of carbon emissions according to the formula.

It can be seen from figure 2 that the carbon emissions of FE2 are significantly higher than those of FE1 and FE3. Among the three process schemes, medium pig iron, scrap and total electric power carbon emissions account for a large proportion. From the point of view of subsequent carbon emission optimization, we can start from these three aspects to optimize the parameters related to the characteristics of process design. The carbon emissions of pig iron and scrap steel can be reduced by reducing the quality of the pouring system or riser to reduce the carbon emissions of smelting materials. Compared with FE2,FE3, FE3 optimizes the riser size and pouring temperature. For example, figure 3 shows the comparison of electric power carbon emissions of each process in the total power emission in the process plan, from which we can see that the melting energy of the optimized process plan (FE3) is significantly lower than that of FE2 and FE2.

It can also be seen from figure 3 that the electricity consumed by pouring accounts for a small proportion of carbon emissions. In the actual production, among the process parameters related to the pouring characteristics, the pouring time has a great influence on the quality. The casting quality can be optimized by changing the pouring time by changing the pouring speed. Reasonable pouring time plays an important role in the quality of castings. Therefore, the defect can be eliminated or the position of the defect can be changed by this method, so that the quality of the gating system can be further reduced without using risers, and the new process plan can be improved from these aspects, in the case of meeting the quality requirements, reduce the amount of smelted scrap, and finally achieve the purpose of reducing the overall carbon emission and improving the carbon efficiency of the process plan.

The comparison of material carbon emissions, energy carbon emissions and process carbon emissions of the three process schemes is shown in figure 4. The carbon emissions of this part can intuitively express the comparison of the emissions of the three types of carbon sources and the overall carbon emissions. FE2 has the most carbon emissions, and the defects can be eliminated by adding risers, but at the same time, it increases a certain amount of carbon emissions. Adding edge-pressing riser is one of the methods to eliminate defects, and there are many process parameters related to pouring characteristics. The carbon emission of FE3 is 0.981% lower than that of FE2. Compared with FE2, FE3 uses a necking riser with less quality, and at the same time optimizes the area of the gate associated with the pouring characteristics, resulting in a reduction of overall carbon emissions by FE3, and the process plan has been optimized.

Figure 5 is a comparison of the production time of the process plan, in which the castings in the cleaning department are naturally cooled for 24 hours. Although the production time of FE2 is longer than that of FE1, FE2 solves the defects preliminarily, while the production time of FE3 is the least. The optimization scheme (FE3) improves the production efficiency by optimizing the process parameters associated with pouring characteristics.

Figure 6 shows the cost of various resources in the process plan. The material cost and energy cost in the resource cost can be obtained according to the quality of material consumption and energy consumption multiplied by the corresponding price. Among them, the price of labor is calculated according to 20 yuan per hour. Figure 4 shows the process staffing of the three process schemes. The remaining cost mainly calculates the cost of the self-made wood mold. As can be seen from the figure, the resource cost of FE3 is 1.384% less than that of FE2. The cost of FE3 is less than that of FE1 and FE2, and the optimized scheme is obviously economical.

Finally, the carbon benefits of the three process schemes are calculated according to the formula, and according to the weighting factor, the carbon benefit of FE1 is 314.498, the carbon benefit of FE2 is 317.500, and the carbon benefit of FE3 is 313.211. The carbon benefit value of FE3 is the lowest, so the carbon benefit of FE3 is the highest, and the process parameters of the third process design scheme produce the best carbon benefit.

Taking the pouring characteristics affecting product quality in sand casting process design as the object, the application effect of process design feature carbon benefit model in traditional manufacturing industry is explored, and the following conclusions are obtained.

The main contents are as follows: 1) the casting process scheme of a base casting was studied by establishing the carbon benefit model of carbon emission, production time and resource cost under the influence of process design characteristics. After the process plan without defects (FE2) is improved by the process plan (FE1), the process plan that meets the quality requirements is obtained, and then by optimizing the process parameters related to the pouring characteristics, such as the pouring temperature, the cross-sectional area of the gate and the quality of the riser, the process plan (FE3) not only improves the defects, but also obtains the highest benefit.

2) through the case study of pouring characteristics, the proposed process design feature carbon benefit and its parameter optimization method can evaluate and optimize the carbon benefit of the subsequent casting process in the design stage. in the face of the process parameters associated with different pouring characteristics, some targeted optimization schemes are selected to improve the resource level and production efficiency of the sand casting industry. The method of characteristic carbon benefit of sand casting process design can provide new design ideas for the process plan design and optimization of the existing foundry industry, and provide a theoretical basis for the development of process design in the foundry industry and other manufacturing-related fields in the future.

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