and, thus, the process variables affecting the contraction model have been identified and evaluated. Amongst all of them, the most significant ones have been selected and they have been assessed in terms of contraction (Fig. 4). Te most relevant process variables are:
• Solidification rate • Riser sleeves and feeding system designs • Metal superheating
RESULTS AND DISCUSSION Te feeding elements that have been developed in the
frame of this R&D project and the validation tools that have been employed take into account the multiple factors affect- ing the contraction model of the studied alloys. It is then necessary to remark on the following key points. From the industrial practice point of view, the contraction due to the liquid- solid interval is considered a property of each alloy and it is not possible to act upon its behavior. Te analyses that have been performed with virtual tools
have outlined that as the cooling rate increases, the shrinkage associated to the liquid-solid interval is reduced. In order to experimentally verify this behavior, a specimen based test has been designed and carried out. Utilizing the very same molding and feeding system, with three differ- ent mini risers KMV 1650, KMV 780 and KMV 590 with modulus of 5.7, 4.2 and 3.9cm respectively are molded, one of them having a chill at the bottom while the two others do not. In this condition, metal from the same ladle is poured in both molds and, after they are cooled down, the shrinkage cavities are evaluated. It is verified that the shrinkage defects related to the pri-
mary and secondary contraction are bigger in the case of the specimen without chills. Te increase of cooling rate by the means of using a chill changes the thermal modulus, which is evident, but it also changes the contraction model. Te sleeves and the feeding systems that have been devel-
oped combine, in a balanced way, their insulating-exothermic capacity, their geometry, and their composition. With the target of optimizing their thermal performance, the main variables driving their functional response have been modi- fied so that the character is reinforced.
چ热过ً金 ș ৈ果Њ讨ખ ۱Иҿչপҫঢ়੭ङӟՇ开ӄ架框ङऩ项Շूથ֨ ङ式模ঢ়收金合९ू۱ր影дӱਖ਼ৰ֮Ӏ工ચ验ङ用҅ છ番一ҁপ֜键ҼЈљث要必有ћ我，此֨。প֜重ך ખ。 य़每йًঢ়收ङ生ф时隔间ब液֡，र来૪实Џ工ђ 合金ङ特性，ЉՕਈ改Պҿ性ਈ。通过ਗ਼拟工Ӏӣ析Շ ѫ孔ঢ়ङҼब隔间ब液֡Њ，升提ङ率速却Ӓव随，现 。صӗ
Од通过实验验ચથ性ਈ，ગઋ并进੧д一次样 ўડ验。实验҅用完Ҷबգङ造型չ੭ঢ়系统，采用І य़模数ӣӰО 、 չ ङЉգ微型ӈՍ13< 、13< չ13< ӣӰ进੧造型，ҿИ一Зङ底部 铁З一գر，Јӑەय़这֨。有өЗДѿҿ，铁Ӓ有没 。孔ঢ়ѳછե却Ӓҿ待，ИӀ模ҵҖً金ङИ包水 有没֨陷缺孔ঢ়ङҼबঢ়收次иչ次初Њ，明ચ验实
Ӓ激ङ样ўИ更加明显。显然，通过҅用Ӓ激增加Ӓ却 速率改Պд热模数，৲գ时，Э改Պд收ঢ়模式。 ֮य़一љ统系ঢ়੭ङӟՇ开չ套Սӈ热Շ ӈՍґ温 ੫ङ方式ৈ合д՟ਘङґ温 Շ热ਈ力、әѾৈ构Ճҿ 构成。Оѩ化ҿ热性ਈ，我ћલ整д促进ҿ功ਈՆ应ङ П要Հ数҅ґ温 Շ热特性得љ加强。 配。方配ङգЉдડغ৲ਈ性热Շչ温ґ化ѩОӣ成 并通过Ӓਯढ 统系温ґङॅׂО） ֣（珠漂љ用҅方 技术ৈ合一य़Շ热化合物。 ґ温（/4）չՇ热（+>5）ਈ力љӈՍ本૯ङґ温 ॅׂОਈ性热Շչ力ਈ
Fig. 10. This yield optimization example is in stainless steel.
ӟս率ѩ化实҆ Љ锈 ֣ 钢
March 2016
FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION | 61
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