The welding of alloy steels in practice is a difficult process in order to achieve mechanically or chemically resistant high-quality welds. In some cases, the weldability of many materials can be difficult or is not recommended because of poor and unsuitable properties of welded joints. In our research work, we investigate the selection of an appropriate welding method for welding the manganese steel HS 20 used at dynamically strained components in the car industry. The welding methods have been selected from accessible methods of the KARRER, s.r.o. Tovarníky industrial plant. Based on the comparable welding technologies MMA, MIG/ MAG and TIG, we tested and verified the quality of welds by means of selected weld tests. The quality of these welds, obtained by the abovementioned methods, was evaluated by weld tests in laboratory conditions of the Department of Quality and Engineering Technologies (Slovak University of Agriculture in Nitra) in cooperation with NDB, s.r.o. Bratislava and SES Tlmače, a.s. The aim of the research work is to set the most suitable and effective method of welding for given components from all the technologies available in the mentioned industrial plant. Based on relevant information, we also want to enrich the scope of knowledge about welding of manganese materials in order to make the welding process more effective.

Every car needs for operation, if possible, the highest quality fuel. Fossil fuels produced from crude oil by conventional technology are being increasingly replaced by alternative fuels. It is caused by new technologies that allow combustion of such fuels and, at the same time, provide economically more efficient operation of cars. From the perspective of ecology, they are also of great importance when it comes to meeting the strict emission standards of the European Union. The experiment compares two types of alternative propulsion with LPG and CNG at selected makes of Fiat cars with 1.4 litre engines. These engines can also utilize conventional fuels – petrol and are mass-produced directly from the factory. The measurements themselves were carried out during predetermined driving cycles such as urban, extra-urban and highway. All the three categories of measurements were carried out under normal driving conditions in a standard manner in compliance with all traffic regulations. Based on all measurements obtained from both engines with LPG and CNG propulsion, we found that the car with the LPG engine became economically more advantageous. The benefit was found in expenses return with this system as well as in measured consumption, prices and availability of filling stations.

As it is generally known, diesel engines operate with air excess, i.e. lean mixtures. Intake resistances in intake manifolds of diesel engines negatively influence their ecological parameters. Based on these facts, we may conclude that less air in the intake manifold causes increased production of exhaust fumes and fuel consumption. One of the reasons of increased intake resistance is a blocked air filter. In the experiment, we have simulated the increased intake resistance and wished to point out possible consequences of pressure drop at the end of the compression stroke. The choking effect was realized by means of a throttle and scale, which was mounted on the air filter position. By using the dynamic method and obtained results, we found that choking at the rotation angle of 90° and 45° caused the difference of 0.16 MPa of the measured quantity during the maximum revs set on 2000 min-1. The difference in pressure at the end of the compression stroke with the rotation angle of 30° and 90° was by 0.86 MPa higher. Pressure drop in manifold showed the value 0.15 MPa. Manufacturers recommend regular replacement of air cleaners of combustion engines in service intervals; however, we must also keep in mind the environment in which the engine operates. In excessively dusty and otherwise polluted areas, it is necessary to replace cleaners a bit earlier.

In engineering industry the production of components begins with separation of the base material and this technological operation can be time consuming, especially in large-scale production. Such production can be made more efficient by means of laser technology focusing on material cutting. Efficiency of cutting is determined not only by shortening of working time or energy saving, but also by the required cutting quality. In the paper we compare the impact of cutting speed changing and laser beam performance on the cutting edge quality. Based on requirements of dimensional accuracy and preset roughness of the cutting edge, we evaluated the cutting quality of laser in samples of different materials. Measured values of sample dimensions and roughness are compared in conclusions of the paper, where we estimate whether the samples meet specified requirements of dimensional accuracy and roughness of the cutting edge in order to make the production process more efficient.

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