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5 Archives of Foundry Engineering

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Checking the metallurgy with the aid of inclusion analysis

100%

Senberger J. , Zadera A. , Cech J.

2011

tom Vol. 11, iss. 1

118-122

Results of studying the influence of inclusion morphology on properties of heavy casting are given. The inclusion morphology is dependent on content and kind of the deoxidizing element. Due to segregations the inclusions can be formed in heavy castings under different conditions (by concentration of deoxidizing elements) than in castings of common size. In heavy casting during deoxidation the inclusions of the IVth type occur more frequently. Deoxidation with zirconium shows to be for some heavy casting unsuitable one. Similarly in castings deoxidized with cerium and lanthanum the inclusions of greater sizes occur that can unfavourably influence the steel properties and increase the tendency to crack formation. The inclusion morphology after deoxidation with magnesium is also unsuitable for heavy castings.

Evaluation of Porosity in Al Alloy Die Castings

100%

Říhová M. , Cech J. , Havlíčková J.

Archives of Foundry Engineering

2012

nr 1

Influence of Compound Deoxidation of Steel with Al, Zr, Rare Earth Metals, and Ti on Properties of Heavy Castings

100%

Senberger J. , Cech J. , Zadera A.

Archives of Foundry Engineering

2012

nr 1

Influence of compound deoxidation of steel with Al, Zr, rare earth metals, and Ti on properties of heavy castings

100%

Senberger J. , Cech J. , Zadera A.

tom Vol. 12, iss. 1

99-104

Heavy steel castings deoxidized with aluminium are sometimes brittle intercrystalline failed during their service along primary grain boundaries what is initiated by aluminium nitrides and so called conchoidal fractures are formed. The tendency to forming the conchoidal fractures depends in particular on cooling rate (the casting modulus), aluminium and nitrogen contents in steel. During deoxidation, when manufacturing heavy castings, the elements with high affinity to nitrogen, zirconium or titanium, are added to steel that would decrease nitrogen activity by the bond on stable nitrides. The formation of stable nitrides should reduce the tendency of steel to the formation of conchoidal fractures. Deoxidation was thermodynamically analyzed at presence of the mentioned elements. For particular conditions a probable course of deoxidation was estimated at test castings. The deoxidation course was checked by microanalysis of deoxidation products (inclusions). For service and experimental castings the anticipated composition of inclusions was compared. It has been proved that in heavy castings with high aluminium contents in steel under studied conditions neither the addition of zirconium nor of titanium nor of rare earth metals will prevent the formation of conchoidal fractures.

Evaluation of porosity in Al alloy die castings

100%

Říhová M. , Cech J. , Havlíčková J.

tom Vol. 12, iss. 1

93-98

Mechanical properties of an Al-alloy die casting depend significantly on its structural properties. Porosity in Al-alloy castings is one of the most frequent causes of waste castings. Gas pores are responsible for impaired mechanical-technological properties of cast materials. On the basis of a complex evaluation of experiments conducted on AlSi9Cu3 alloy samples taken from the upper engine block which was die-cast with and without local squeeze casting it can be said that castings manufactured without squeeze casting exhibit maximum porosity in the longitudinal section. The area without local squeeze casting exhibits a certain reduction in mechanical properties and porosity increased to as much as 5%. However, this still meets the norms set by SKODA AUTO a.s.