With high production efficiency, low environmental pollution and low production cost, epc is regarded as a new material processing technology in the 21st century. Grate is an important part of metallurgical equipment sintering machine, sintering machine with grate on the high temperature coke after combustion, ash slag plays a supporting role, the material requires its heat resistance, wear resistance, brand Cr20Mn14Si2N. The outline dimensions of the grate strip casting are 70 mm high, 40 mm wide and 800 mm long, and the casting blank mass is 19 kg. Casting technology requires full processing, no casting defects are allowed on the working surface, and high production efficiency is required. It can be seen that although the structure of grate strip casting is simple, it has high requirements for production technology and casting technology.
Production of grate strip by epc is an advanced and efficient process. Aiming at the problems of slag inclusion and sand inclusion in the original lost mode casting process, as well as the reasons for casting scrapping, this study optimized the casting process of grate bar castings on the basis of careful analysis of the original process, in order to effectively improve the casting production efficiency and reduce the production cost by optimizing the casting process.
Original process and production status
1.1 The original process parameters adopt the production method of lost mode casting. The group in the box is adopted in the modeling, and the cracks are filled with wet paint. The size of the sand box is 2 200 mm long, 1 200 mm wide and 800 mm high. Each box contains 1 cluster of castings, and each cluster produces 12 models. The pouring riser process is shown in FIG. 2. The casting temperature is 1 620 ℃, the negative pressure of casting is -0.055mpa, and the negative pressure is -0.02mpa during pressure holding, and the pressure holding time is 30 min.
1.2 Original process characteristics and casting quality
1.2.1 Characteristics of the original process
There are two risers in the casting in the original process. The metal liquid is poured into the casting from one riser. The riser at the far end is a cold riser, and the end near the sprue is a hot riser. The feeding distance of riser set in the original process is equal to 3 times of the wall thickness of the casting feeding part. Due to the poor feeding effect of cold riser at the far end, the middle part of the casting cannot be fed beyond the feeding distance, so this feeding process is unreasonable. The size of the sand box is relatively large, which can accommodate more castings. However, the process of producing 12 pieces of model cluster in one box and burying only one layer in the buried box is unreasonable. The space of the sand box is not effectively utilized, and the production efficiency is too low.
1.2.2 Casting quality
1) Castings with slag and sand inclusion defects are fully processed castings, requiring higher casting quality. But because of the use of the box group type, so the strength of the parts filled with wet paint is not enough, adhesion is not strong, belongs to the vulnerable parts of the problem. During pouring, these bonding parts will be broken by high temperature metal liquid, resulting in casting slag and sand inclusion defects; In addition, in the casting process, because the actual use of the casting is not taken into account, the actual working face of the casting is upward in the direction of the casting position, but the working face of the casting is not allowed to have defects, resulting in the casting scrap due to slag and sand. Defects of slag and sand inclusion after full processing are shown in Figure 3.
2) Folded pores appear on the surface of the castings. According to the shape of the defects, it is determined that the water vapor generated by the coating is not dry enough to cause the pores. As a result of production process, this is, the worker is in the drying of coating and check link to do not quite meticulous, cause coating to do not get complete drying. The shape of stomatal defects is shown in Figure 4.
2. Process optimization and application effect
2.1 Process optimization
According to the problems in actual production and the reason of casting scrap, the casting process of grate strip was optimized.
2.1.1 Improvement of pouring riser
In order to increase the stability of the process, the design of casting pouring riser is changed. The original two risers are moved closer to the middle of the casting length direction. According to the calculation of feeding distance, the center of the riser is 260 mm away from both ends of the casting, and the feeding can be achieved in place. There are three grate bars across one riser. In addition, the inner gate is directly connected with the two risers to realize the feeding of hot risers, increase the feeding efficiency, and make the temperature field of the casting more reasonable. After optimization, the sprue of the gating system is 60 mm×60 mm, the sprue is 60 mm×50 mm, and the inner sprue is 50 mm×40 mm. The model cluster has three layers, and the distance between each layer is 60 mm.
2.1.2 Defect control
1) For slag and sand inclusion, the working face of the casting shall be downward in the direction of the pouring position to ensure the quality of the working face; Using the group outside the box, to ensure the model airtight after coating, to prevent the weak parts of coating damage caused by dry joint coating slag, sand trap defects; The foam sprue cup is used. When coating, the sprue cup should be brushed again. When burying the box, resin sand is placed on the periphery of the sprue cup to ensure the strength of the sprue cup, so as to control the connection between the sprue cup and the sprue.
2) Stomata
It is necessary to control strictly from the aspects of management, process implementation and supervision and inspection to ensure the drying of coating and prevent the drying of coating. For the problem that the operation is not meticulous enough, the factory needs to train the workers and related management personnel, so that the responsibility is assigned to the person, the supervision is in place, and each production link is carefully handled to prevent low-level mistakes from affecting the overall benefit of the foundry.
2.2 Application Effect
The original arrangement of white mold leads to low utilization rate of sand box. Two more layers of castings can be placed in the direction of height to achieve the pouring of 36 castings in 3 layers of 2 model clusters. According to this idea, the form of the optimized casting process of the grate strip can be obtained, and the model cluster diagram is shown in Figure 5. As can be seen from Figure 5, after process optimization, more products can be poured from one gate, the production efficiency is increased by 3 times, and the cost is also reduced. In the process of small batch production, the defects of slag and sand inclusion of the casting are effectively controlled, and the rejection rate of the casting is less than 5%. At present, batch production has been realized, the process is stable, no shrinkage cavity, shrinkage porosity, slag, sand and other defects have been found after casting processing.
3 conclusion
1) By optimizing the casting process, the casting production efficiency is effectively improved and the production cost is reduced.
2) White drying and coating drying is very important, it must be dry, to avoid the defects caused by water vapor.
3) The molding outside the box can avoid the defect of the damage of the bonding place and the sand. The casting process can be more stable by adjusting the casting pouring position and rationally optimizing the casting pouring riser.
4) The optimized process has been adopted and promoted in the factory, and the mass production has proved that the process has stable performance and reliable product quality.
