In automobile power system castings and powder metallurgy parts, the existence of micropores will lead to leakage and affect the dynamic performance of automobiles. The infiltration technology introduced in this paper can play a role in densification and non leakage of various pressure bearing castings, and plays an important role in improving the economic benefits of enterprises.

Microporosity and Infiltration of Castings

Generation and influence of micropores

Porosity is a phenomenon in materials, especially in the casting process of metal parts: shrinkage porosity caused by volume change in the process of changing from liquid to solid; Flow holes on the surface or inside caused by insufficient pressure state; Porosity caused by the interception of various gases in the mold. If some of the micro pores or defects that are difficult to be found by naked eyes are penetrated by gas or liquid, they will cause leakage or surface defects on the casting wall, make the parts lose their due functions in the use process, and affect the performance of the products; When machining, noise will be generated to accelerate tool wear; Shorten the service life of castings. In addition, the improvement of scrap rate has affected cost saving. Micropore phenomenon also exists in powder metallurgy manufacturing process.

Casting infiltration

Casting infiltration is to fill all micropores and interconnecting air gaps of the casting with stable and flexible sealing materials (infiltration can cover micropores with the size of one thousandth of a mm to 0.5mm), so that the infiltrated part can resist heat, oil, chemicals or other external influences (such as vibration), and obtain high-quality surface treatment. The infiltration process will not lead to the change of the overall dimensions of the parts that have undergone surface treatment and other processing procedures, or cause any pollution to them. It can also shorten the production time, improve the product quality, and reduce waste. It is a permanent solution to micro holes and the best solution to save costs. At present, infiltration technology has been widely used as an indispensable process in the casting process of automobile parts.

Typical infiltration castings of automobile power system, such as engine block, cylinder head, crankcase, intake manifold, oil pump, nozzle, water pump, valve cover, gearbox housing, compressor, etc. Infiltration treatment can cover micropores with diameters ranging from one thousandth of a millimeter to 0.5 mm, and the pressure bearing capacity of the treated castings can reach the breaking strength of the castings.

Infiltration technology

Infiltration technology mainly includes three elements: sealant, equipment and process flow.

Sealant

The performance of impregnating sealant directly affects the effect of impregnation. Traditional infiltrating sealants, such as sodium silicate (also known as water glass), are cheap, but have poor performance - they are easy to crack when the temperature changes, and they attach to the surface of components due to their high viscosity, causing serious waste. In addition, the production cycle is too long; Polyester, with good sealing effect and good chemical corrosion resistance, but containing toxins and harmful solvents, is not easy to produce. These two kinds of sealants have been gradually replaced by high-quality sealants that are more effective and environmentally friendly. Ultraseal International has more than 30 years of experience in providing complete infiltration technology, including high-quality sealants, modern infiltration equipment and unique and professional infiltration services. It took the lead in developing commercial methacrylate sealant, introduced PC504/66 sealant with higher quality in 1970, and developed recyclable sealant Ultraseal MX2 in 1987. The Sinterseal 100 developed by Ultraseal is particularly suitable for powder metallurgy parts.