Komatsu Undercarriage Parts,Undercarriage Parts For Excavators,Komatsu Excavator Parts,Caterpillar Undercarriage Parts JINING SHANTE SONGZHENG CONSTRUCTION MACHINERY CO.LTD , https://www.sdkomatsudozerparts.com
1 Overview
The cylinder head is one of the key components of the diesel engine. It integrates lubrication, cooling, and intake and exhaust. Therefore, the quality of the casting is very strict. After the product is put into production, the scrap rate caused by the pressure leak of the cylinder head is very high, reaching about 70%, which becomes a problem affecting the quality of the cylinder head. In order to solve the problem of pressure test of the cylinder head as soon as possible, from all aspects of the production process, Detailed analysis, a series of experiments, and finally achieved good results, reducing the scrap rate, this article will be analyzed and solved from the casting process and material applications.
The location of the defect is very regular, that is, most of the leaking parts are in the oil hole of the cylinder head and the hole of the pipe. These places are the hot joints of the castings, and the shrinkage defects are easy to occur. Through the anatomical analysis of the leaking part of the cylinder head, the presence of defects can not be found with the naked eye. The position and size of the defect are found through the non-destructive detection of coloring, but a lot of manpower and material resources have been wasted. Therefore, the shrinkage defect constitutes a great deal for product quality. influences.
The shrinkage defect of the cylinder head belongs to microscopic shrinkage, so the cooling rate is slow, and the structure is not replenished by the molten iron to cause shrinkage defects. The original process is analyzed. In the casting process, furan resin self-hardening sand is used, the sand strength is 1.0MPa, and it is smelted by 2t/h induction furnace, w C = 2.9%~3.2%, w Si =1.7%~2.0%, w Mn =0.75% ~1.0%, w P <0.05%, w S <0.08%, casting temperature 1380-1390 °C. The slanted oil hole was brushed with chilled paint and placed with a 0.3mm thick tinplate. Above it was a riser with a diameter of 200mm and a height of 460mm. The hole in the conduit was brushed with chill paint and wrapped in a tin foil with a height of 150mm. From the perspective of the layout of the inner runner, the runner is thin near the hot section, and it can be said that the problem of eliminating the hot knot shrinkage defect has been considered in the process.
2. Analysis of the causes of shrinkage defects
(1) The pouring temperature of molten iron is too high. The pouring temperature of molten iron is high, which will cause shrinkage defects in the solidification and shrinkage period of the casting, especially thick parts. The cylinder head weighs 550kg, and the diameter of the hot joint reaches 70mm, which is easy to produce. Shrink the defect.
(2) The thickness of the chilling coating is not enough. The chilling coating should increase the thickness of the coating with the size of the thermal section. The operator generally applies a coating thickness of 0.3 mm and is thin.
(3) The effect of the feeder feeding is not ideal. Although the riser is used, it is very likely that the feeding of the hot section is insufficient.
(4) The height of the tinplate is not enough. From the position of the water leakage, the water leakage position is 35mm below the plane above the cylinder head, which is above the tinplate.
3. Solution
(1) Brush thickness 碲 碲 碲 碲 碲 碲 碲 is a kind of element that strongly increases the degree of subcooling of the metal liquid. The use of enamel paint can quickly solidify the iron in this part, make the structure here dense, prevent water leakage during pressure test, and strengthen with the increase of thickness, the coating brush thickness can reach 1mm, thus maximizing Quenching effect.
(2) Cold iron chilling in the middle hole to the inclined oil hole to add cold iron, the thickness is 15mm. The use of cold iron can change the distribution of the temperature field. With the chilling of cold iron, the solidification process of the casting is accelerated. During the process of casting into the graphitization expansion, the self-feeding effect can be improved, and the cold iron can be added at the hot joint to eliminate the overheating of the molten iron at the hot section. The resulting shrinkage and shrinkage defects. The riser is added above the hot section of the casting, and the cold iron is placed below to form the temperature field distribution of the hot and cold, which is favorable for the feeding during the sequential solidification process.
(3) Increase the size of the riser by using a heat-insulating riser, and change it into a heat-insulated riser with a diameter of 240 mm and a height of 500 mm (see attached drawing), and add an appropriate amount of heat-generating agent. According to the principle of equilibrium solidification, the riser does not have to be solidified later than the casting. The riser comes at the freezing point of the casting, and the shrinkage passage is closed in time, and the self-feeding is realized by the graphitized expansion of the casting. In the process of improvement, after summarizing the previous production experience, the root of the riser is designed to have a diameter of 100mm, which can reduce the thermal influence of the riser on the casting, provide the supplementary molten iron in time for the heat shrinkage of the casting, and solidify the graphitization in the casting. When expanding, the feeder's feeding passage has been blocked, which enhances the self-feeding ability of the casting and improves the quality of the casting. Moreover, this process achieves the sequential solidification of the connecting wall-hot section-riser, which completely eliminates the thermal contraction.
(4) Controlling the phosphorus content From the chemical component test data, it can be seen that there are some cylinder heads with w P >0.05%, and most of these cylinder heads are leaking. According to the relevant data, the extremely low phosphorus content is critical for the compactness of the cylinder block and the cylinder head. The quality of the recycled material and the scrap steel are strictly controlled while using high-quality pig iron.
(5) Strengthening the inoculation treatment and controlling excessive gestation will also cause leakage of castings. Inoculation can increase the degree of graphite nucleation during solidification of iron, which will increase the number of eutectic groups. An increase in the number of eutectic groups leads to an increase in the eutectic expansion force on the mold during solidification, with the result that non-dense castings occur. The uncompact forms are internal shrinkage and external shrinkage. Internal shrinkage causes the casting to appear leaking during pressure testing. Therefore, we strive to be accurate in weighing and ensure that it is added at 2/3 of the amount of molten iron.
(6) Raising the sand box Considering that the expansion of the cast iron piece itself has an important influence on the shrinkage defect, we raise the upper box of the cylinder head to 640mm, which greatly increases the rigidity of the sand box and blocks the casting during the solidification process. Expansion.
4. Conclusion
After a period of pressure test on the cylinder head, the improved cylinder head has a total of 30 pieces of pressure, one leak, and the water leakage rate has dropped from 70% to 3.3% now. It has reached the expected target and gained valuable from it. experience.
About the author: Li Zhaojun, Wang Peng, Yang Chengyan, Jia Zhiming, Sang Wei, Han Xiaowei, Cao Yu, Zibo Diesel Engine Corporation.