高品质机床铸件的稳定生产

Stable Production of High-Quality Castings Used for Machine Tools

叙述了用于高品质机床的铸件应当具备的条件：铸件材料为HT250、HT300、HT350等高牌号铸铁；尺寸精度要求较高，内应力必须较小；导轨面不得有任何缺陷，机加工面不得采用电弧焊。介绍了稳定生产高牌号高品质灰铸铁件的关键措施：（1）原铁液的温度控制在1500～1550℃，HT250牌号铸铁废钢加入量提高到53％，HT300牌号铸铁废钢加入量提高到60％；（2）型砂、芯砂的配制要采用合理的原砂、树脂及固化剂配比参数，涂料也要采用合理的配比参数，控制再生砂的质量，以及控制型砂（芯砂）的性能；（3）浇注系统按照大孔出流理论设计，浇注温度控制在1380～1420℃；（4）造型操作及铸型装配操作要正确。通过以上措施，铸件的表面粗糙度达到Ra12．5～50μm，批量生产的铸件尺寸精度达到CTl1级，铸件缺陷废品率降低至3％。

The conditions that the high-quality machine tools castings should obtained were described:casting material should be high grade gray cast iron including HT250,HT300 and HT350;dimension precision requirement should be higher;internal stress must be lower;no any defect allowed to be existing on the guide face, and using arc welding process was prohibited on machining face. The measures to stably produce high-grade and high quality gray iron castings were introduced as follows :( 1) The temperature of the base iron was controlled in the range of 1 500~1 550 ℃;the steel scrap charging amount for the HT250 grade cast iron was increased to 53%,and increased to 60% for the HT300 grade.( 2) Using rational mixture ratios of raw sand,furan resin and hardening agent for preparation of the molding sand and core sand,and the mixture ratio for coating preparation also should be rational;the quality of reclaimed sand must be controlled,the properties of molding sand and core sand must be controlled.( 3) The gating system was designed according to the theory flowing out from big hole;the pouring temperature was controlled in the range of 1 380 ~1 420 ℃.( 4) Molding operation and mold assembling operation must be correct. By implementing above mentioned measures,the casting surface roughness reached Ra 12.5 ~50 μm,the dimension precision of the casting produced in batch reached CT11 grade,the casting rejection rate reduced to 3%.