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Improvement of casting process of main body of testing machine
At present, the main body of the testing machine produced by our factory is prone to shrinkage hole defects, the yield is low, and some of the salvage costs are high. Based on this situation, the process is improved.
1. Technical requirements
The main body of 588B-8a belongs to medium and thick wall castings. The main wall thickness is 90mm, the partial thickness is 200mm, the material is QT600-3, the casting weight is 875kg, and the maximum contour size is 1335mm×540mm×400mm. There shall be no casting defects such as shrinkage, shrinkage, inclusions and porosity in the surface and inner cavity of the casting.
2. Analysis of problems in the original process
First, the original process (see Figure 1) is divided from the middle of the cross arm, symmetrical up and down, and the upper shape is high, which is not conducive to feeding.
Second, the original process uses the principle of sequential solidification, introducing molten iron from the thick parts at both ends, and using the dark riser to fill, so that the dark riser is required to be large, and the inner runner is overheated by the hot section here, resulting in Under the gate, shrinkage is formed, and the hot joints at both ends are finally solidified, which tends to cause shrinkage on the top surface of the hot section, and the yield is low, and the casting quality is unstable.
3. Process improvement measures
(1) Change the parting surface as shown in Fig. 2, from the top surface of the cross arm, the height of the sand box is fixed, the casting is basically in the lower box, and the indenter is enlarged to facilitate the feeding.
(2) The gating system improves the application of the simultaneous solidification principle, effectively utilizing the graphitized expansion of ductile iron to achieve no riser casting.
Specific measures: placing the runner in the middle of the two cross arms and introducing two thin and wide inner runners to the two cross arms, alleviating the overheating of the hot joints, thus eliminating the need to replenish the riser. It also overcomes the shrinkage and shrinkage defects of the castings, and also ensures the yield and improves the casting yield.
4. Conclusion
Through the improvement of technological measures, the castings have no riser casting, the quality of the products and similar products meet the requirements, the scrap rate is controlled within 1%, and the production rate is above 95%. Compared with before the improvement, the delivery time is guaranteed. And casting quality, and save production costs, reducing the labor intensity of workers.
About the author: Liu Zhifeng, Tianshui Xinghuo Machine Tool Co., Ltd. Casting Branch.