薄壁缸体常见铸造缺陷浅析及对策

Analysis and Countermeasures of the Casting Defects on Common Thin Section Cylinder Blocks

介绍了生产典型薄壁缸体铸件的技术要求,针对生产过程中先后遇到的冷芯缸体内腔与外表铸造缺陷及防止措施进行了阐述。对于水套内腔局部断芯,可通过使用特种砂替代硅砂,改进水套砂芯涂料工艺,严格控制原砂需酸值,保证砂芯足够强度来防止;对于水套外壁夹砂缺陷,采用天然钠土,减少上箱水套外壁热辐射时间,减少砂芯发气量来防止;对于表面粘砂缺陷,通过细化型砂粒度,增加砂型孔隙阻力,增加砂型气体背压,阻止金属液侵入砂型孔隙,控制旧砂温度与水分,减少铸件热粘砂,调整型砂参数来防止;对于烧结缺陷,减少装配螺钉尺寸,使用特种混合砂,降低油道芯烘干温度,减少油道芯的圆角半径,更改涂料配方来防止。

Typical thin-wall cylinder castings and technical requirements were introduced. The foundry defects on cold core,inner and outer surfaces of cavity on the cylinder were elaborated. To prevent the inner cavity of water jacket from breaking,special sand was used instead of silica sand. Improved water jacket sand core coating process and acidity regimentation were also used to increase the sand core strength. To prevent sand inclusion defect on outer wall of water jacket,bentonite was used and thermal radiation time of outer wall on upper box water jacket was decreased. To prevent burnt-on sand defects,the sand grain size was refined and porosity resistance was increased. High air back pressures can keep melt from running into the sand gap. Adjustment of re-used sand temperature and moisture can reduce thermally bonded sand. These parameters also reduced the sand defects. To prevent sintering defects,small size of screws were used. And using special mixed sand,reducing the oil core drying temperature and round radius,improving paint formula are also helpful.