2. Engine cylinder head lost mold cast iron parts installed bench test through mechanical processing and installed machine bench test, bench test basis: 1 GB 1105 - 1987 "Internal Combustion Engine Bench Performance Test Method". 2GB/ T 9486 —1988 “Measurement method for steady-state exhaust smoke of diesel engines”. The results are shown in Table 4. FSN: 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在 在The exhaust gas temperature under the calibration conditions decreased by 19 °C, and the smoke decreased by 0.22 FN. Increasing the specific power of the engine (kW/displacement·L), reducing fuel consumption and reducing exhaust emissions are both internal requirements for the development of the automotive industry and an objective requirement for the external environment. According to the engine bench test results of the lost foam casting cylinder head, the use of the lost foam casting process to organize the production of the engine block and cylinder head will promote the development of the automotive industry.

V. Some experiences

The singularity of the castings in the horizontal direction and the vertical direction is about 1. 9 % ～ 2. 2 % 5 %至1. 5 %。 The vertical direction is about 1. 3 % ~ 1. 5 %. Before finalizing the shrinkage of the product mold, the same foam sample as the product foam model material should be used to cut the sample approximately the same as the product foam model. After several trials and a stable shrinkage value, the product mold is developed to avoid unnecessary losses.

(2) The machining allowance of castings usually refers to the small machining allowance of lost foam castings, which is close to the setting of precision casting (such as cylinder head castings with specifications of 480mm × 190mm × 90mm, 6 peripheral contours) 5毫米)。 The machining allowance of the surface is set to 2. 5mm). It should be noted that the premise of this setting is to ensure that the shrinkage of the casting is correct, otherwise the remaining amount should be appropriately increased.

(3) The wall thickness of the foam model usually requires a certain tolerance on the technical requirements of the wall thickness of the casting. For the lost foam casting process, it is best to take the upper limit of the wall thickness, and cannot simply pursue the reduction of the weight of the casting. Balance the overall effect. Especially in the intake and exhaust passages in the cylinder head products, when the wall thickness of the casting is < 5mm, water leakage defects are easily generated. The main reason is that when the pre-expansion of the bead in production is unstable, the wall thickness is thin. It is difficult to fuse the beads between the molds during the molding process, resulting in loose defects in the mold, which may cause the paint to infiltrate during the dipping, and the cast castings may have water leakage. It should be noted that the additional process wall thickness should be added to the side that does not affect the airway performance and the cooling water volume.

(4) Foam model hollowing process For partially thick foam models and deeper holes, a two-stage sealing and intermediate hollowing process can be used. In this way, the bead material can be saved, and the adverse effects of carbon inclusions and surface carbon enrichment on the casting can be reduced.

(5) After the foam model is glued, after the fully aging foam film is finished, the assembly of the product foam model is completed according to a certain glue process, and the casting molding work of the casting is realized within 7 working days. If the storage time of the foam model is too long, the foaming of the foamed film is prone to occur. If the depth of the degumming layer is within the machining allowance of the casting, it cannot affect the quality of the casting: If the depth of the debonding layer exceeds the machining allowance of the casting, the casting will occur due to the infiltration of the coating. The phenomenon of the coating phenomenon is generated inside, which leads to leakage defects of the casting during high pressure test.

5毫米。 The thickness of the coating is 0. 5mm. The thickness of the coating is 0. 5mm Just left and right. 5毫米左右左右的气层和液液。 If the dip coating process, that is, the first dipping and drying, and then the second dip coating and drying, even if the thickness of the coating is maintained at about 0. 5mm, the permeability of the coating layer and the liquid The adsorption of the phase foam is also greatly reduced, and it is easy to produce carbon inclusions, carbon rich surfaces and pores in the casting. This is mainly due to the fact that the second layer of coating covers the micropores on the first layer of coating. In order to ensure the success of the first dip coating process of the model cluster, it is necessary to pay attention to avoid the phenomenon that the right angle of the product structure or the transition of the interface is not smooth in the design of the foam die, otherwise a large amount of bubbles will be generated during the dip coating: Cracks are formed on the dip-coated coating, which in turn affects the dip coating effect.

(7) The comparison between lost foam casting and ordinary sand casting is the same in the classic casting principle. Some sand holes reserved for ordinary sand casting are still needed in the layout of the lost foam casting process, and even more Open some process holes. Because lost foam casting requires both sand and sand holes, as well as paint entry and exit holes, do not think that the lost foam casting process can reduce or even put out the process sand holes: ordinary sand casting is easy to shrink Insulation risers and overflow risers for loose and venting are also suitable for lost foam casting: In addition, ordinary sand casting and lost foam casting are also closely monitored for weather changes because of air humidity and atmospheric temperature casting. The quality of the product has a great impact.

(8) Impregnation of engine block and cylinder head castings When using the lost foam casting process to produce automobile engine block and cylinder head castings, whether it is made of aluminum alloy or iron alloy, it needs to be impregnated, which can improve product quality and The yield of castings has been verified in production practices at home and abroad.

(9) Heat treatment of engine block and cylinder head castings In order to reduce costs and speed up production, we have cancelled the heat treatment process of castings for a long time. At that time, the background was to produce single-cylinder diesel engine block and cylinder head castings from ordinary gray cast iron. After the heat treatment process was omitted, no obvious product quality fluctuations were found. With the development and production of multi-cylinder diesel engines and the improvement of energy-saving and environmental protection requirements in the automotive industry, the material requirements for engine block and cylinder head castings have also changed. High grades of cast iron, malleable cast iron and ductile iron are increasingly being used. In the production, we found that the casting sand cleaning is difficult to complete in one time, the hardness of the casting is too high, which makes the machining difficult. After the casting is installed, due to the large casting stress inside, it is easy to change the size and even crack and crack in normal work. Later, we carried out the stress-relieving low-temperature annealing heat treatment test for castings (for cast iron parts with a casting weight of less than 200kg, the furnace temperature is < 200 °C, the heating speed is < 100 °C / h, and the temperature is kept at 500 °C for 5h, then at 30 °C / The speed of h is cooled and cooled below 200 °C, and satisfactory results are obtained.

(10) Management of lost foam casting production In the initial stage of applying lost foam casting technology, people tend to focus only on specific technical links, while ignoring systematic and scientific management in the whole process of lost foam casting production. Benefits. Therefore, we must first accumulate a large number of process parameters suitable for the various processes of the company's production conditions, and then select some representative process parameters that can stabilize the quality, and then form the enterprise standard: Then develop a complete quality management system. And constantly improve and develop in production practice.

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