提高机床铸件精度及精度保持性的试验研究

Experimental Study on Improving Precision and Precision Retention of Machine Tool Castings

在不同碳当量和合金化下,浇注薄、厚两种不同结构尺寸的灰铸铁和球墨铸铁T型床身导轨试样,研究碳当量、残余应力、材质刚度、结构刚度等对床身精度及精度保持性的影响。结果表明：高碳当量下结合复合合金化和＂阶梯式升温降温法＂热时效可获得同时具有高抗拉强度、高弹性模量、低应力的铸铁件;相同结构下,低碳当量、未经合金化和热时效的1~#薄导轨与高碳当量、经复合合金化和热时效的2#薄导轨试样经三个月后,直线度分别增加了31.5μm和18.1μm,后者因具有高的材质刚度和低的残余应力,其直线度比前者变化缓慢且变化幅度小、精度保持性好;相同材质下,灰铸铁1~#、2~#薄导轨与3~#、4~#厚导轨试样的直线度分别为355.8、383.1μm和37.7、27.9μm,后者因其高的结构刚度,直线度比前者小约十倍;球墨铸铁5~#、6~#厚导轨试样具有高的材质刚度和结构刚度,其直线度分别为19.5、17.4μm,均小于其他试样,且后者略小于前者。

Under the different carbon equivalent（CE） and alloying, two different structure sizes of T-type lathe bedway samples of gray cast iron and ductile iron were poured. The effects of CE, residual stress, material rigidity and structural rigidity on the precision and precision retention of lathe bedway castings were studied. The results show that compounded alloying and ＂multistep rising/falling temperature ＂ hot aging under higher CE condition can help to get iron castings with high tensile strength, high elastic modulus and low residual stress. Under the same structure, the straightness of 1~# thin bedway sample that has lower CE but no alloying as well as hot aging and 2~# thin bedway sample that has higher CE and compounded alloying as well as hot aging respectively increases 31.5 and 18.1 μm after three months. Due to the higher material rigidity and lower residual stress, the straightness of the latter changes more slowly and its range is smaller, which means better precision retention. Under the same material, the straightness of gray cast iron 1~# and 2~# thin bedway samples and 3~# and 4~# thick bedway samples respectively is 355.8, 383.1 μm and 37.7, 27.9 μm. Due to the higher structural rigidity, the straightness of the latter is about 10 times less than the former. The straightness of ductile iron 5~# and 6~# thick bedway samples that have both high material rigidity and structural rigidity respectively is 19.5, 17.4 μm. Both of them are smaller than the other samples, and the latter is slightly smaller than the former.