1、Analysis of the structural defects of the traditional group core casting process
Xinyuanzhu Group takes a common impeller as an example.
Impeller body casting size: 660×202 mm
Casting weight is 105 kg
Casting center wall thickness 202 mm
Blade wall thickness 21 mm
In the casting process, the casting center there is a large hot section, the casting has six blades is twisted surface, each blade needs at least two sand core assembly, the whole casting needs at least 12 sand core, and assembly sand core casting after casting gap produces a lot of flying edge, polishing difficulties, and very easy to polish too much caused by the blade surface shape transition is not smooth, thus affecting the impeller parts performance. Casting material is tentatively set at QT500-7, casting wall thickness difference is larger need for fast pouring, internal easy to produce shrinkage holes, shrinkage casting defects.
2、Impeller casting quality is improved through the design of pouring system
Xinyuanzhu Group takes into account the structural characteristics of impeller body castings, material characteristics, the need for fast pouring, and the need to make up for the shrinkage of thick and large hot joints, etc., and designs the process scheme of pouring and making up for the shrinkage by two top collets and setting the cold iron at the bottom of the hot joints in the center to achieve sequential solidification. The center of the casting has a thick and large cylindrical structure with a thickness of 180 mm, and the simulation verification of the design plan with a single top riser is found that the riser body is very large and the diameter of the riser neck is almost close to the center cylinder before shrinkage holes and shrinkage pine can be introduced into the riser, so that the large riser is directly set on the large hot section, resulting in a larger artificial hot section and local overheating in the center, and the large riser causes coarse metallographic organization at the root of the riser and subsequent removal of the riser. Difficult to remove. Considering the fast casting requirements, if in each blade design inside gate, firstly set inside gate cause blade shape irregularity, secondly the iron liquid into the cavity turbulent flow is serious, and the subsequent cleaning will cause blade grinding problems.
Based on these unfavorable factors, through many casting experiments, in the center of the top surface of the cylinder design two small gates, that is, as a complementary shrinkage gates, two gates are not in the center of the cylinder, can reduce the artificial heat section, the subsequent removal becomes easier, at the same time in the center of the bottom surface of the cylinder set cold iron for cooling, to achieve the thick part of the sequential solidification; Secondly, these two small gates set foam ceramic filter block as the upper part of the sprue, the use of foam Considering that the filtering block may be washed out when pouring the iron liquid in one riser, the filtering block is set in the two top risers, and the other riser is used after pouring in one riser for a period of time. Figure 2 shows the impeller body casting scheme. Figure 3 shows the solidification simulation of the casting scheme. The simulation verifies that the shrinkage holes and shrinkage pine are transferred into the riser, although there are some shrinkage pine and shrinkage holes at the root of the riser neck, according to the previous experience as the riser is overheated due to the direct pouring from the riser, these shrinkage holes and shrinkage pine can be introduced into the riser completely.
Xinyuanzhu Group specializes in the production of Ductile iron castings, Pig iron gray iron casting, Steel casting, Brass Casting, Malleable Iron Casting, and undertakes batch casting processing of castings. Welcome guests to cooperate with pictures or samples.