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1.
P. Martin, D. Franzen, B. Pustal, A. Buhrig-Polaczek
Foundry Institute RWTH Aachen University (Germany)
MODIFICATION OF MECHANICAL PROPERTIES OF HIGH SILICON DUCTILE IRON BY INFLUENCING SILICON MICRO SEGREGATION VIA ALUMINUM AND NICKEL
Abstract
By producing spheroidal graphite cast iron (SGI) with silicon (Si) contents of 3.2 to 4.3 mas. %, a higher ductility can be achieved while maintaining the same strength compared to ferritic- pearlitic grades. The resulting property range of the silicon solid solution hardened SGI materials represents an improvement to conventional grades and offers the potential to replace steel forged parts with the same material requirements by more cost-effective cast structures. However, the strengthening effect of silicon is only of limited use. If the Si content exceeds 4.3 mas. %, the elongation at fracture drops rapidly. The reason for this is the formation of superstructures in the crystal lattice, which strongly impede dislocation movement and embrittle the material. This embrittlement can also be detected at lower contents of 3.8 mas. % Si. Due to its segregation behavior, silicon tends to build up in the primary austenite and depletes with progressive solidification in the direction of the grain boundaries. As a result of locally higher Si content in the vicinity of the graphite spheres, superstructures are formed there. Previous investigations at the Foundry Institute have shown that the micro segregation profile of silicon can be levelled by the addition of aluminum. The aim of this work is to adjust the segregation profile of silicon by alloying aluminum (Al) and nickel (Ni) in a targeted manner, thus preventing the formation of FeSi superstructures. For this purpose, different contents of aluminum and nickel as well as a combination of both were tested. The segregation profile was qualitatively represented by Klemm etching and quantitatively evaluated by EDX measurement. A final evaluation of the results is carried out by means of an impact test. Here it is examined whether embrittlement could be positively counteracted.
2.
Xie Jingpei (1), Wang Aiqin (1), Wang Wenyan (1), Ma Douqin (1), Yang Bin (1), Mao Zhiping (1), Wang Zhenghui (2)
School of Material Science and Engineering, Henan University of Science and Technology, Luoyang, Kitajska / China (1)
Luoyang Luobei Heavy Industry Machinery Co., Ltd , Luoyang, Henan, Kitajska / China (2)
THE COMPUTER SIMULATION OF SOLIDIFICATION AND MODIFICATION OF THE INCLUSIONS IN LARGE-SCALE RUDDER HORN STEEL CASTING
Abstract
The solidification simulation for the large-scale rudder horn steel casting has been made by means of solidification simulation in computer. The order of solidification and efficient feeding were maintained through technological optimization, design of insulated risers, iron chill and yield, therefore the perfect castings are produced. The effects of rare earth (RE) on shape, size and distribution condition of inclusions were investigated. It was proved that the shape and distribution of inclusions could be improved and the plastic and toughness of the steel can be increased obviously by the rare earth modification.
Keywords: Casting; Numerical simulation; Stress distribution; Inclusions
3.
M. Drobne, U. Klančnik, A. Stergar, S. Novak, B. Košec
Valji d.o.o., Železarska cesta 3, 3220 Štore, Slovenija / Slovenia
ULTRASONIC INVESTIGATION OF METALLURGICAL BONDING IN COMPLEX CASTINGS
Abstract
Cast rolls for hot strip rolling are multilayered castings, composed of a harder, more wear resistant outer layer made of alloyed cast iron, a tough core made of nodular cast iron and in some cases also of an intermediate layer made of grey cast iron. As such, they can be considered as complex castings, since the differences between individual alloys comprising such ingots can be significant.
Ultrasonic inspection is one of the most fundamental nondestructive methods for inspecting casts ingots. It is often used for detection of abnormalities such as porosity or large non-metallic inclusions. In the case of multilayered cast rolls, ultrasound can also be used for detection and quality inspection of metallurgical bonding between respective alloys or layers.
The presented paper is focused on the use of ultrasound for centrifugally casted rolls, not only for the detection of casting abnormalities but also on the detection of layer depth and influence of specific microstructural constituents present at the bond on the reflected ultrasound signal.
Key words: ultrasound, microstructure, rolls, centrifugal casting
4.
J. Šporin (1), P. Mrvar (2), Ž. Vukelić (1)
University of Ljubljana, Faculty of Natural Science and Engineering, Department of Geotechnology, mining and environment, Slovenia (1)
University of Ljubljana, Faculty of Natural Science and Engineering, Department of Materials and Metallurgy, Slovenia (2)
ROLLER CONE WEAR MECHANISM
Abstract
Roller cone drill bits are widely used for drilling the hydro geological, oil, gas and other wells, for which the acquisition of the core is not essential. The breakdown of the drill bit or rapidly decreasing of rate of penetration during the drilling process results in a reduction in the progress of the drilling, which makes it necessary to remove the damaged or worn roller cone bit from the well. Due to this fact, scientists and engineers are increasingly focusing on research, the results of which would lead to an extension of the effective time of the drill bit and to increase the rate of penetration.
In our work, was monitored “in situ” drilling parameters during the drilling process with the Smith SB117PS 215.9 mm diameter roller cone drill bit, intended for drilling in soft rock materials. After drilling, the bit was thoroughly examined to determine the damage and wear that occurred during drilling.
The following modern and standardized investigative methods were used: analysis of the micro and macrostructure of rock materials and materials of roller cone bits carried out by optical and electronic microscopy, simultaneous thermal analysis of materials of drill bits, analysis of the chemical composition of rock materials and materials of drill bits, and determination of geomechanical parameters of rock materials. The resulting wear, local bursts and cracks were quantitatively and qualitatively defined and linked to the drilling regime and the mineralogical composition of the rock material.
Based on the metallographic examination of materials of drill bits and geophysical properties of rocks, the structural changes in the material of the drill bits and the manner and course of their wear have been identified.
Keywords: drilling, roller cone bit, mechanism of drill bit wear, carbide coating, HV hardness, high temperature