Leakage refers to the leakage phenomenon of the cylinder block (cylinder head) during the pressure test (water pressure / air pressure), which mostly occurs in the water jacket cavity or oil passage cavity of the cylinder block (or cylinder head).
There are two main causes of leakage: inclusion and looseness (the leakage of crankcase caused by mechanical damage or casting crack is rare, which will not be discussed here).
1 leakage caused by inclusion
(1) During the core repair, the flash and burr were not removed, or the sand particles and agglomerates of different sizes with loose adhesion were not removed, which resulted in being washed down by molten iron and floating and enriched on the wall of water jacket or oil channel during the pouring, forming sand inclusion (sand hole). Make cavity wall through leakage.
(2) If the combined sand core is polluted by dust or sand particles or falls into loose sand in the mold cavity carelessly, if it is not cleaned up, sand holes will also be formed to make the cavity wall through and leak.
(3) The molten iron is not pure, and there is no filtering measure or poor slag blocking effect in the sprue, so that the slag inclusion in the molten iron enters the mold cavity, and the cavity wall of the water cavity or oil cavity forms a through slag hole and leaks.
(1) Carefully remove the flash burr of the sand core, and remove the sand agglomerates attached to the clay core to avoid the possible formation of sand holes on the wall of the water cavity / oil cavity.
(2) Blow out the sand core group with good combination of sand particles and dust pollution, and clean up the sand particles falling into the mold cavity.
(3) High efficiency filter shall be set in the sprue, and the cross sprue shall have good slag blocking function, and the molten iron purification work (slag making and slag removal) shall be done well to prevent slag holes on the cavity wall.
2 leakage caused by shrinkage
This kind of leakage often occurs in the water cavity (oil cavity) or nozzle and other hot spots.
(1) The composition of the molten iron is not appropriate. The Si / C is too high, the graphite flakes are coarse and the structure is loose.
(2) Too much inoculation results in too many eutectic clusters and the microcrystalline gap is difficult to be filled and compacted.
(1) On the premise that the specified carbon equivalent remains unchanged, the Si / C is limited between 0.5 and 0.6.
(2) The more effective measure is to use sisR (containing strontium) inoculant, which has strong graphitization ability. When the dosage is only 50% of FeSi inoculant, the cross-section sensitivity can be fully inoculated and eliminated, so as to avoid too many eutectic clusters
(3) It is reported that if the content of Pb is up to 0.0008%, the shrinkage leakage can be caused. It is necessary to pay attention to whether the Pb material is plated in the furnace charge or to remove the coating first. In addition, the trace elements affecting the shrinkage leakage are Ti, Al, etc., which will increase the shrinkage tendency of the molten iron Lattice control.