- Jan 04, 2018 -
To solve the problem of shrinkage casting defects, the most fundamental point is "heat balance." The method is:
(1) The rapid solidification at the thick place and the hot section formed by the structure of the machine tool castings results in the basic balance of the temperature field around the casting of the machine tool artificially. The use of internal and external chill iron, local use of large heat storage zircon sand, chromite sand or special paint.
(2) a reasonable process design. The runner is located in the relative Pu Pu machine tool casting wall, the number of more and dispersed. The earliest access to thick-walled liquid metal at the first solidification, thin-wall at the post-solidification, so that the basic achieve a balanced everywhere. For machine tool castings with uniform wall thickness, multiple runners and vents are used. Within the runner, scattered and uniform, so that the overall heat balance. Fine and more vents, that is, smooth exhaust and heat from the role.
(3) change the location of the gate
(4) Selection of large heat storage material, which is the production of anti-wear products with lost foam is extremely important! Chromite replaced quartz sand and other small heat storage of other sand species, will achieve good results, the completion of micro-earthquake is better!
(5) low temperature fast burning, open pouring system. Make liquid metal quickly, smoothly, evenly filled mold. This should be due to conditions.
(6) ductile iron mold machine strength, surface hardness ≧ 90, sand box rigidity, beneficial to eliminate shrinkage.
(7) Need riser, when the first move to heat riser, and leave the heat section. If the riser will be placed on the festival, will increase the feeder size, the formation of "heat on the heat." Get bad, not only shrinkage difficult to shrink, but also produce a centralized shrinkage, but also reduces the craft yield.
(8) casting tilt and alloying, all benefit. Elimination of machine tool casting shrinkage defects is a complex understanding and implementation process. Should be based on the principle of "heat balance", to make scientific analysis of castings, to develop a reasonable process plan, relocation of suitable modeling materials, tooling and correct operation and standardization. Then any shrinkage of machine tool castings can be solved.
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