The microstructure and properties of high strength gray cast iron produced by sand casting were improved; The effect of hard inclusions in gray cast iron on its structure and properties was studied; The quality of molten iron was controlled by changing the proportion of raw materials, and the mechanical and technological properties of high-strength gray cast iron cylinder were improved; The main defects in grey cast iron are analyzed and improved to improve the yield of castings and stabilize the production process. The main contents include:
1.Formation mechanism of hard inclusion phase in gray iron castings
Through the observation and analysis of the microstructure of the samples, the morphology, size and distribution of MNS, tin, carbides and other inclusions in gray iron castings are determined, their formation mechanism is discussed, and the influence of the formation of the second phase inclusions on the microstructure, mechanical properties and machinability of gray iron is studied.
2.Quality control of cast iron liquid
On the premise of ensuring that the composition change of molten iron meets the requirements, increase the proportion of scrap steel, test the formability, microstructure and mechanical properties of castings through production tests, adjust the proportion of raw materials, control the content of miscellaneous cemented carbide and inclusions in the alloy, and improve the refinement and uniformity of matrix structure, Finally determine the best material ratio.
3.Cause analysis and elimination measures of main defects in grey cast iron
The engine cylinder block is a very complex part. In the process of sand casting production, various defects will appear, mainly including white mouth, air hole and slag hole, which have a great impact on the yield and performance of high-strength gray iron castings. Therefore, this paper studies and analyzes the causes of the main defects of castings, and puts forward a stable and reasonable casting process plan by improving the casting process parameters to reduce or avoid these defects.
For the high-strength gray cast iron automobile engine block castings, from the perspective of technology and production, strictly control and optimize the composition of cast iron, reasonably adopt the inoculation and casting process, and strengthen the management in various links such as raw material preparation, branding equipment, process, chemical composition inspection, microscopic texture, defect inspection, etc, It can greatly improve the yield and casting quality of high-strength iron castings. This paper aims to carry out scientific and technological research on key problems and key processes in the process of R & D and production of thin-wall and high-strength automobile engine cylinder block castings by the project cooperation unit, and carry out fruitful research work from the aspects of casting process optimization, casting microstructure control, and discussion and elimination of the causes of casting defects, It provides strong support for promoting its product upgrading and technological progress, which is of great significance and value.