Antanas Ciuplys

Research on possibilities to replace industrial wear plates by surfaced coatings using waste materials

This research indicates the possibility to replace commercial materials and surfacing techniques by submerged arc welding under the flux and powder of industrial waste materials to obtain the chute with high abrasive wear resistance but for a lower price. Industrial waste of hard metal inserts, emery wheels, chips of case hardened stainless steels were grinded, granulated and blended. Prepared powder mixture served as alloying source increasing precipitation of hard particles during solidification of the weld. Abrasive wear resistance of coating six times exceeds wear resistance of industrial materials, while hardness exhibited very similar values. The results presented in this paper are based on micro-structural analysis of the surfaced and commercial coatings and are supported by analyses of the hardness and abrasive wear resistance. The complementary value of this research is a possibility to recycle industrial waste, which accumulates in huge quantities in the metals working industry.

Peculiarities of Fatigue Fracture of Steel Hardened by Various Surface Treatments

Fatigue strength is one of the most important mechanical properties. Durability and reliability of car parts is often defined by their fatigue strength, since most of them are loaded with dynamic, repeating or variable loads and the main type of failure is metal fatigue. Fatigue crack usually starts on the metal surface. The interrelationship of the surface layer together with the characteristics of internal metal volume determine the value of fatigue limit and the coefficient level of stresses’ intensity, which is required for the start of fatigue crack. Various hardening methods of surface have a huge impact on fatigue strength of structural materials. The choice of surface processing method is determined by properties and microstructure of a material, as well as the purpose and working conditions of part’s material. Very often the optimum processing is a combination of several methods, which enables to obtain the required properties (high fatigue strength, wear, etc.). Hardening with high-frequency electric current (HfEC) is widely used process for the surface hardening of steel. The components are heated by means of an alternating magnetic field to a temperature within or above the transformation range followed by immediate quenching. The core of the component remains unaffected by the treatment and its physical properties are those of the bar from which it was machined. Investigation of specific fatigue fracture properties enables to determine the kinetic of processes, related with fatigue crack initiation and propagation. Analysing fractures of machine parts and comparing them with the most specific “mode” fractures it is possible to determine the nature of affecting loads and the reason of part failure. The impact of several combined surfaces processing on the fatigue strength and fractures of carbon steel samples is investigated in the work. The surface was hardened using different processing combinations: by hardening with high frequency electricity currents, rolling by rollers, heating and cooling under different temperatures. Experimentally it was proved that thermal treatment of plastically deformed carbon steel significantly increases fatigue strength. After surface hardening with the given regimes, the microstructure and residual stresses are formed in such way that fatigue crack begins to grow under the hardened sample surface. Samples, in which the fatigue crack initiates inside the sample, have higher fatigue strength than the samples, the fatigue crack of which initiates on the surface.

Excavations of ironware of the third–fifth century from Marvele necropolis (Lithuania)

This study presents the overview of ironware excavations of the third–fifth century demolished tombs from Marvele necropolis. Three axes, four spearheads, two knives and a clasp were excavated in 2006. Afterwards, a metallographic and chemical analysis as well as mechanical properties of artefacts, also metallurgical slag, clinkers and iron concretions found in the surroundings of tombs were tested and presented in this article. General tests were executed in order to compare results with other archaeological and scientific researches. Metallographic analysis and hardness tests’ results revealed that axes were forged from two separate billets of iron, whilst spearheads and knives from one. The results of chemical analysis have affirmed earlier results of other Lithuanian archaeological sites. Although some differences in chemical composition were observed, this fact shows possible not local origin of some ironware.

Improvement of Cyclic Strength of Carbon Steel by Various Surface Treatments

Fatigue strength is one of the most important mechanical properties. Durability and reliability of car parts are often defined by their fatigue strength, since most of them are loaded with dynamic, repeating or variable loads and the main type of failure is metal fatigue. Various surface hardening methods have a huge impact on fatigue strength of structural materials. The choice of surface processing method is determined by properties and microstructure of a material, as well as the purpose and working conditions of part’s material. Very often the optimum processing is a combination of several methods, which enables to obtain the required properties (high fatigue strength, wear, etc.). The impact of several combined surfaces processing on the fatigue strength of carbon steel samples is investigated in the work. The surface was hardened using different processing combinations: by hardening with high frequency electricity currents, rolling by rollers, heating and cooling under different temperatures. Experimentally it is proved that thermal treatment of plastically deformed carbon steel significantly increases fatigue strength. Experiments showed that after surface hardening with the given regimes, the microstructure and residual stresses are formed in such way that fatigue crack begins to grow under the hardened sample surface.Copyright