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The Influence of Different Assist Gases on Ductile Cast Iron Cutting by CO2 Laser

Meško J., Nigrovič R., Zrak A.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 4

109--114

EN

This article deals with the technology and principles of the laser cutting of ductile cast iron. The properties of the CO2 laser beam, input parameters of the laser cutting, assist gases, the interaction of cut material and the stability of cutting process are described. The commonly used material (nodular cast iron - share of about 25% of all castings on the market) and the method of the laser cutting of that material, including the technological parameters that influence the cutting edge, are characterized. Next, the application and use of this method in mechanical engineering practice is described, focusing on fixing and renovation of mechanical components such as removing the inflow gate from castings with the desired quality of the cut, without the further using of the chip machining technology. Experimental samples from the nodular cast iron were created by using different technological parameters of laser cutting. The heat affected zone (HAZ), its width, microstructure and roughness parameter Pt was monitored on the experimental samples (of thickness t = 13 mm). The technological parameters that were varied during the experiments included the type of assist gases (N2 and O2), to be more specific the ratio of gases, and the cutting speed, which ranged from 1.6 m/min to 0.32 m/min. Both parameters were changed until the desired properties were achieved.

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The Effect of Refining and the Cooling Rate on Microstructure and Mechanical Properties of AlSi7Mg Alloy

Tupaj M., Orłowicz A. W., Mróz M., Trytek A.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 3 spec.

83--86

EN

The paper presents results of research on the effect of conventional refining with hexachloroethane and the cooling rate vcool. ranging within the solidification temperature regime from 12.5°C/min to 94.5°C/min on compactness of the material, values of microstructure parameters λ2D, λE, lmaxSi, and mechanical properties Rm, R0,2, A5 of unmodified AlSi7Mg alloy after heat treatment (solution treatment 540°C/6 h/water 20°C and aging 175°C/8 h/air). It has been found that as a result of refining and increased cooling rate, an improvement of material compactness occurred (reduction of the density index by 0.4%) accompanied by a decrease of values of parameters characterizing the microstructure: λ2D by 54.4 μm; λE by 4,6 μm; and lmaxSi by 50 μm. As a result of these changes, the value of Rm increased by about 40 MPa and R0.2 improved by about 36 MPa, while the value of A5 decreased by 1.3%.

3

Fatigue Properties of AlSi7Mg Alloy with Diversified Microstructure

Tupaj M., Orłowicz A. W., Mróz M., Trytek A.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 3 spec.

87--90

EN

The paper discusses the effect of microstructure on the fatigue strength of AlSi7Mg casting alloy refined conventionally with hexachloroethane without modifying and modified with TiB and Na. Castings made of both alloy variants were subjected to T6 heat treatment. It turned out that the applied refining secured satisfactory compactness of the material. In view of absence of gas and shrinkage porosity in the castings, short cracks nucleated on largest silicon precipitates and largest intermetallic phase precipitations as these were the locations where stress concentrations reached their highest values. Comprehensive modification of the alloy resulted in reduction of the value of SDAS parameter characterizing α(Al) phase dendrites, a decrease of the distance between silicone precipitates in the eutectic λE, and a decrease of the maximum size of silicone precipitates lmaxSi. The ultimate effect of these changes was an increase of the fatigue strength.

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The effect of microalloying on formation of microstructure parameters and thermal concentration state of solidifying melt

Bykovskykh S., Tischenko V., Bykovskykh P.

Krzepnięcie Metali i Stopów

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2000

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R. 2, nr 43

75--80

EN

The problem of improving reliability and casting of fast wearing machine parts, which were manufactured from steel cast, has been required of creation and using practice of various materials. One of most rational ways to cast quality increasing is the using of middle-carbon microalloyed in return for expensive high alloyed steels. For this, the microalloyed steels must possess good casting properties and enough high density of metal and surface quality of cast. [...]