真空低压消失模壳型铸造失模工艺优化研究.pdf

真空低压消失模壳型铸造失模工艺优化研究
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真空低压消失模売型铸造失模工艺优化研究
ptimization Study on Removing Pattern of Expendable Pattern
Shell Casting with Vacuum and Low Pressure
将文明,樊自田,廖德锋,赵忠,选普
(伴中科技大学材料科学与工程学院塑性成型模拟及模具技术国家重点实验空,武汉430074)
IANG Wen-ming, FAN Zi-tian, LIAO De-feng, ZHAO Zhong, DONG Xuan-pu
(State Key Laboratory of Plastic Simulation and Die Mold Technology
School of Materials Science and Engineering, Huazhong University of
Science and Technology, Wuhan 430074, China)
摘要:针对真空低压消失模壳刑铸造工艺中采用的海売在失模中易于开裂现象,对失模工艺进行系统研究,考察失模方
式、温度对薄壳失模的影响,并结合EPS泡沫材料热失重分析和泡沫模温度场分布规律,分析薄壳开製机制。结果表
明:随炉升温失模过程中,型売尖水收缩缓慢,强度逐漸提髙,型壳不易开裂;高温400℃以上肓接放入尖模,型売放人不
久均开裂,主要由于型売急速失水收缩受阻所致,而鈴长时间预烘型壳高温自接放人失模,型売不开裂;低250
300℃直接放人失模,暇壳收缩相对較慢,主要受釗泡沫模的膨胀力作用,膨胀力与失模温度,时间及泡沫模有关。得到
低温直接放入时模样厚度写失模混度关系式,模样战厚,所需失模温度越低
关键词:消失模売型铸造;尖模;丌裂;收缩;膨胀力
中图分类号:TG249
文献标识码:A文章编号:1001-4.381(2010)08-0061-06
bstract: Considering the thin-shell cracking phenomenon of removing pattern process during the ex
pendable pattern shell casting with vacuum and low pressure, some systemic studies were carried out.
The influence of removing method and temperature on removing pattern of thin shell was investigated
and the mechanism of shell cracking was analyzed using the thermogravimetric analysis(TGA) and
tcmpcrature field of the expanded polystyrene(EPS) foam pattcrn, The results indicated that shell
was not easy to crack due to slow shrinkage of shell dehydration and shell strength gradually increased
during removing process with furnace temperature. Bccause rapid shrinkage of thin shell was hin-
dered, shell rapidly was destroyed during high temperature above 400C directly entering furnace
howevcr, the shell preheated for long time did not crack when suffered above removing process. For
low temperature 250-300C directly entering furnace, the shell shrinkage was relatively slow, and
ell was suffered from expansion force of foam pattern. The expansion force is related 1o removing
temperature, tire and foam pattern. The relation formula of pattern thickness and removing tempera
ture was deduced for low temperature directly entering furnacc, and the more thick foam thickness is
the more low removing temperature
Key words: expendable pattern shell casting; removing pattern; cracking; shrinkage; expansion force
目前,航空航天、汽车工业对复杂薄壁的铝镁合现气孔、裂纹等缺陷;普通沙型铸造难以满足表面粗
金精密铸件的需求日益增多に。然而复杂薄壁铝糙度和尺寸精度要求。消失模铸造是一种生产复
镁合金铸件在重力下浇注成形难度大,金属液易于杂、高精度铸件的新方法い,但泡沫模样会在浇注
氧化燃烧,常出现浇不足、氧化夹杂等缺陷,铸件性过程中产生分解气体,铸件易产生气孔、夹杂等缺
能偏低。目前,铝镁合金铸件常釆用压力铸造、金属陷,模样分解的吸热通常还使浇注温度较高和液态
型铸造和砂型铸造等方法生产。压力铸造容易卷金属氧化瀠烧加剧
气,铸件通常不能进行热处理,且成本较高?;金属
真空低压消失模壳型铸造是将消失模锛造、熔模
铸型加工周期长,无退让性和透气性差,铸件易于出精密铸造及真空低压铸造相结合,是生产复杂精密铝