Casting technology of a diesel engine case

In recent years, with the development of diesel engine to the direction of high power, high strengthening, low noise, low emission and high reliability, the functional chambers of a single casting tend to be integrated, and the structure of some key parts becomes more and more complex, which puts forward higher requirements for the quality of castings. Therefore, in the casting process design, it is necessary to integrate multiple factor analysis, and apply the integrated coupling simulation technology in the process design to more accurately analyze and predict the casting defects, guide the casting process design, improve the guarantee of the casting process, shorten the research and development cycle, and improve the stability of the casting production quality.

This type of diesel engine case is a cuboid thin-wall cavity structure, and its outer dimension is about 4000 mm × 500 mm × The main wall thickness between the chambers and the outer wall is 12mm, and the wall thickness of the upper and lower flange is 50mm respectively. The overall wall thickness of the part is uniform, but some parts are thick and large, and the shape and structure are complex. The weight of the box part is about 1600kg, and the schematic diagram of the box is shown in Figure.

Box material: qt400-18ar; Metallographic structure: the matrix structure is ferrite, its content is more than 90%, spheroidizing grade is 1-2 (spheroidizing rate is more than 90%), graphite type I and II are not allowed, graphite size is 5-7; Sealing requirements: 1.0MPa water pressure test shall be carried out for water chamber and air chamber for 30min without leakage and sweating; Ultrasonic flaw detection: according to en 12680.3-2011, the important areas meet the requirements of level 2, and other areas meet the requirements of level 2-3.

  1. High internal quality requirements

According to en 12680.3-2011, the box is subject to ultrasonic flaw detection, and the important areas meet the level 2 requirements. Although the overall wall thickness of the casting seems to be more uniform, the overall wall thickness is thin, the main wall thickness is only 12mm, and there are many isolated hot spots in some parts. It belongs to complex thin-walled cavity casting, which is prone to shrinkage defects.

  1. The casting is easy to deform

The overall length of the box casting is 3700 mm, and it is easy to produce deformation due to uneven temperature field during solidification.

In the casting process design of complex diesel engine box, the application of balanced solidification limited feeding and ductile iron self feeding, combined with the reasonable design of gating system and the comprehensive design and application of riser chill, can effectively improve the process guarantee of large body casting. At the same time, the casting process is simulated and verified by casting simulation software to ensure the rationality of casting process design, It provides a theoretical basis for the subsequent casting process design of diesel case.