Solid State Phenomena Vol. 212

Abstract: The paper demonstrates the potential of unconventional metal forming method that consists in introducing shear stress at the die/workpiece interface during compression. In practice it can be realized by induction of reciprocating, vertical motion of a punch that adheres strongly to a workpiece. To estimate an effect of the method on the material flow, a relevant finite element model has been developed and the selected results of numerical simulations are presented in the paper. In comparison to the conventional forging, forming aided by shear stress is able to provide a number of benefits such as significant increase of local strains, lower press loads and the opportunity to control the strain distribution in the workpiece volume. Perspectives for continuation of the studies as well as possible application areas of forging aided by shear stress are discussed in the summary.

Abstract: The paper presents results of tests of mechanical properties, hardness measurements, macro-and microstructures of welded joints austenitic and austenitic-ferritic steel with high manganese and aluminium content meant for automotive industry. Tests were conducted on flat sheets made of steel X20MnAl18-3 and X55MnAl25-5. Tested welded joints were ruptured in tensile strength test in all cases inside the weld which is connected with lower resistance to stretching of welded joints in comparison with resistance of joined steels. Resistance to stretching of tested samples, regardless of the method of welding, is on a similar level.

Abstract: Coatings obtained in Zn-Al-Mg baths on steel plates by using the continuous method provide effective protection against corrosion. They have greater corrosion resistance than traditional zinc coatings. Even though Zn-Al-Mg coatings have many advantages, they are not made on galvanized products by use of the batch hot dip method. For products galvanized by use of the batch hot dip method coating growth mainly depends on the content of silicon in the steel. An increase in coating thickness is particularly intense in the case of high-silicon steel. In the paper the results of tests on obtaining Zn-Al-Mg coatings on high-silicon steel by use of the batch hot dip method have been presented. The growth kinetics of coatings obtained in the Zn-31Al-3Mg bath on steel with Si content of 0.27% has been defined. The structure has been developed and the chemical composition of particular structural components of the coating has be established. It has been determined that coatings obtained in the Zn-31Al-3Mg bath are continuous and they have uniform thickness. The structure of the coating is compact and the chemical composition points to the presence of phases of the Fe-Al system. The presence of silicon in the steel limits steel reactivity in the tested bath. The course of growth kinetics of the coating is close to parabolic.

Abstract: The article presents investigation of steel subjected to external stress during hot-dip metallization. The results of experimental investigations of the LME phenomenon, reasons of its formation and influence of different parameters are described. Samples made of C70D steel subjected to various loads inducing tensile stress (400-800 MPa) during hot dip metallization ina zinc bath with 2% tin addition were investigated. The processes of hot dip metallization were carried out at 450°C temperature and immersion time of 180 s. It can be observed that the stress value can affect the behaviour of metal during the hot dip metallization process. Coated samples were analysed on a light microscope to specify the possibility of the occurrence of LME. These studies provided the basis for the selection of samples and areas for further quantitative andqualitative analysis on a scanning electron microscope (SEM) with a microanalysis system. The analysis of cracks in three microareas revealed that the tin content in the front of a fracture is twice as big as it is in other measuring points. It may be related to crack propagation due to the phenomenon of LME, by the accumulation of the initiating element atoms and those propagating the fracture.

Abstract: The main aim of this work was to determine the effect of nitriding process on the electrochemical properties of martensitic steel X39Cr13 used for surgical instruments treatments. The research was conducted on the samples of diameter d = 14 mm made of X39Cr13 martensitic steel in the annealed condition. The samples were subjected to heat-treatment: hardening and tempering processes. The way of surface preparation of the samples contained mechanical processing: barrel finishing, chemical passivation and nitriding using fluorescent methods. The nitriding process was carried out in an apparatus for machining a cooled anode glow type JON-600. Nitriding process was carried out at a temperature T = 470 °C. To evaluate the electrochemical properties the pitting corrosion resistance were studied. The corrosion resistance tests of samples were carried out by means of potentiodynamic method (registering anodic polarization curves). The measurements were conducted in physiological Tyrodes solution. On the basis of the results it was affirmed diverse corrosion resistance of the samples for different variants of the surface preparation. The highest corrosion resistance was observed for the barrel finished and nitriding process of the samples. The research revealed that the suggested variants of surface treatment influence the corrosion resistance of the X39Cr13 steel intended for surgical tools.

Abstract: In this paper the current knowledge about the influence of alloy additions used in galvanizing baths has been analysed. The optimum concentration of Al, Ni and Pb addition has been established. Tests have been conducted to determine the synergistic influence of the addition of AlNiPb in a zinc bath upon the structure and growth kinetics of coatings. The structure and the chemical composition of coatings obtained on steel with low silicon contents and on Sandelin steel have been developed. It has been determined that the synergistic influence of the AlNiPb addition effectively lowers the reactivity of Sandelin steel and it improves zincs flowing off the product surface which results in decreased zinc consumption and better appearance of the coating. The structure of coatings obtained in a Zn-AlNiPb bath on Sandelin steel is similar to the structure of coatings obtained on low-silicon steel.

Abstract: In this work tests on the course of zinc coating formation on model iron alloys with diversified silicon additions in molten zinc, with short times of contact at the solid-liquid border have been presented. The experiments were carried out at the temperature of 440°C. The assumed time of contact between solid and liquid phases was: 1, 4, 9, 14, 29, 59 seconds. The test stand was designed. The structure and thickness of coatings obtained on steel without silicon, on Sandelin steel and on high-silicon steel was defined. Based on the results we may ascertain that in the first stadium of the galvanizing process the impact of silicon upon the intensity of coating growth is small. Increased reactivity of silicon is already observed after about 29-59 seconds of the process.

Abstract: In the paper the author presents the results of tests defining the characteristics of behaviour of Sandelin steel in the high-temperature galvanizing process. The growth kinetics of hot-dip zinc coatings on the substrate of 0.05% Si steel in the temperature range of 540-580°C has been established. The structure of the coatings and their phase composition have been developed and the chemical composition of structural components of the coating has be defined. It has been determined that the coating is composed of a compact layer δ₁ and an area of a two-phase mixture of δ₁ and Zn. The conducted tests confirmed the presence of phase Γ₁ , which does not form a continuous layer but it forms individual precipitates which are irregular in shape. The growth kinetics of the coating indicates that an increase in temperature causes a decrease in the coating thickness, which might prove that dissolving processes prevailed over the processes of diffuse coating growth.

Abstract: The corrosion resistance of ZnAl40Cu3 alloy are presented in the paper. Base alloy, alloy with silicon and alloy with silicon and rare earth elements were tested. The scope of the examination included: potentiodynamic and potentiostatic examinations, studies of the alloy surface condition after corrosion tests. The studies have shown, that the addition of rare earth elements improves the corrosion resistance of the ZnAl40Cu3 alloy in 3% NaCl environment. The presence of the silicon precipitates does not decrease the corrosion resistance of the ZnAl40Cu3 alloy in the 3% NaCl environment

Abstract: The aim of this paper was to determine the resistance to high-temperature corrosion in atmosphere of air for alloy Fe-40Al-5Cr-0.2Ti-0.2B. Corrosion tests were conducted in temperatures from 600 to 900°C in time from 2 to 64 hours. Conducted tests have shown a slight increase of weight of samples in periods of time which followed. Increase of weight is connected with corrosion products in the form of passive oxides which form on the surface of the alloy. Kinetics of corrosion processes has parabolic course in tested temperature range which proves the formation of passive layers of corrosion products on the surface of samples. Heat resistance of the alloy on intermetallic phase matrix FeAl brings about potential possibilities to apply this alloy as a material meant for work in elevated and high temperatures in the environment which includes oxygen.