The subject of this article is the study of influence of sintering time and sintering additives on mechanical properties and wear resistance. Si3N4 with Al2O3+Y2O3 additives (YAG) and Si3N4 with MgO additives was used as an experimental materials. Compositions sintered for 30 min achieved optimal combination the hardness and fracture toughness -15.05 GPa and 6.87 MPa.m 1/2 for Si3N4-MgO and 14.65 GPa and 5.71 MPa.m 1/2 for Si3N4 -YAG. Wear was mostly influenced by the hardness of ceramic materials. The specimen with the highest hardness achieved the highest wear resistance. Wear resistance of ceramics decreased with the grain growth and with the transformation progress of narrow α-Si3N4 phase to prismatic β-Si3N4 phase. The wear resistance of the studied ceramics can be described by model V ~ HV -1 . Si3N4 -YAG in comparison to Si3N4-MgO has several times greater wear resistance.

This article is focused on an analysis of factors negatively affecting the tube production process of tubes made from austenitic stainless steel with a very small diameter of ϕ 0.34 mm. The analysis was concentrated on factors that affect the drawing process stability of the seam tubes where the desired final dimensions—a diameter of ϕ 0.34 mm and a wall thickness of 0.057 mm—are limiting factors. Seam tubes made from steel 1.4306 and 1.4301, from producers KT and EW with a longitudinal weld line made by tungsten inert gas (TIG) welding, were used as blanks for constituent drawing operations. It is desirable to provide sufficient inert gas flow and cooling during the formation of a weld joint in a protective atmosphere chamber. A significant temperature gradient prevents the formation of undesirable Cr23C6 carbides in the heat-affected zone (HAZ) which negatively affects the plasticity and formability of the steel and is the cause of technological fractures.

In this paper, innovative resistance element welding (REW) technology for joining galvanized steel sheets to thermoplastics (PMMA) is introduced. The essence of the innovation is in the use of a special bimetallic joining element consisting of the core made of a Sn60Pb solder, and the sleeve made of a Cu tube. During resistance heating, the solder melts, thus allowing the formation of a metallurgical joint with galvanized steel sheet. Since Sn60Pb solder melting occurs at temperatures (from 183 to 190 °C) below the thermal decomposition temperature of most thermoplastics (for PMMA above 300 °C), there is no thermal destruction of the PMMA material around the joint. The mechanical fixation of the thermoplastic material at the overlap joint is provided by the sleeve made of Cu tube which has a substantially higher strength than a Sn60Pb solder.

The high-strength steels and tailor welded blanks (TWB) are applied in construction of cars parts to reduction of cars weight [1, 2]. The application of these materials brings possible complicatons during the forming when it proves the considerable influence of stress-strain characteristics differences of of the individual parts of TWB what result in non-constant material flow and consequently a negative movement of the weld interface [3, 4]. One of the ways of elimination of this negative effect is to choose a suitable blankholder system with optimal distribution of blankholder forces by using elastic blankholder with adjustable distribution of blankholder forces. Within the bounds of study the experimental blankholder system with elastic blankholder with adjustable distribution of blankholder forces was used [5, 6]. Finite element methods (FEM) simulation has unsubstitutable role n the study of formability of TWB whereby it is possible to determine the values and points of application of the blankholder forces [7, 8]. The FEM simulations results carried out in simulative LS-Dyna software are presented in this article which is focused on achieving weld interface movement minimalization of tailor welded blanks from DP600 and BH220 materials by optimization of blankholder forces [9, 10].

The main trend in the automotive industry today is the reduction in vehicle weight. The problem is addressed first and foremost by the use of different types of light and high strength materials in the production of the car body. Although galvanized steel sheet is still the basic construction material, nowadays aluminium alloy sheets are increasingly used in the production of vehicles. This paper is focused on the optimization of process parameters by resistance spot welding dissimilar materials: galvanized steel sheet and sheet made of aluminium.K e y w o r d s : resistance spot welding, steel/aluminium joints, weld nugget, properties