The casting method of machine tool castings
is commonly sand casting, followed by special casting methods. The machine tool castings are made of fine gray cast iron HT200-HT300, with accurate proportions and higher tensile and bending strength.
1. The machine tool castings are made of resin sand and lost foam solid mold casting, the single piece reaches more than 40 tons, and the annual output is about 8,500 tons; including the machine bed, table, column, beam, and gantry top connecting beam.
2. The machine tool castings are made of fine gray cast iron HT200-HT300, with accurate ratio and higher tensile and bending strength.
采用流行的热处理工艺，使铸件的应力变形减少到小度,长久使用更趋于稳定。 3. The machine tool casting
adopts popular heat treatment technology, which reduces the stress and deformation of the casting to a small degree, and it is more stable for long-term use.
Standard for gray cast iron: GB9439—88
Features of gray cast iron parts:
(1) Good abrasion resistance and shock absorption. Since graphite in cast iron is good for lubrication and oil storage, it has good wear resistance. Also, due to the presence of graphite, gray cast iron has better shock absorption than steel.
(2) Good process performance. Gray cast iron has a high carbon content, which is close to the eutectic composition, so it has a relatively low melting point, good fluidity, and small shrinkage, so it is suitable for casting complex structures or thin-walled castings. In addition, graphite makes chip formation easier during cutting, so the machinability of gray cast iron is better than that of steel.
The relationship between hardness and tensile strength: There is a corresponding relationship between the hardness and tensile strength of gray cast iron, and its empirical relationship is:
a. When O≥196N / mm 2
HB = RH (Fly 00 + 0 4380b) (B1)
b. When 0≥796N / mm2
HB = RH (44 + O 7240b) (B2)
The relative hardness (RH) value in the formula is mainly determined by the raw material, melting process, processing process and cooling rate of the casting.
Use of the advantages of resin sand casting machine bed castings Large machine tools such as machine bed castings have great advantages over traditional sand molds. It not only saves expensive wood mold costs, but also facilitates operation, shortens the production cycle and improves production efficiency. , Has the advantages of high dimensional accuracy, small machining allowance, good surface quality and so on.
Resin sand mold has good rigidity and high sand mold strength at the beginning of pouring. This condition can make use of the graphitization expansion of the solidification process of cast iron to effectively eliminate the defects of shrinkage and shrinkage, and achieve less and no riser casting of gray cast iron and ductile iron.
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