Cracking resistance of AlMg4.5Mn alloy TIG welded joints

In this paper the AlMg4.5Mn TIG welded joints have been tested in order to investigate their cracking resistance. Testing plates, size of 500×250×12 mm, are welded by TIG procedure in a horizontal-vertical position. Various mixtures of inert gases are prepared and supplied by MESSER TEHNOGAS AD, Smederevo (Serbia), including Ar, Ar + 0.015% N 2 , Ar + 15% He + 0.015% N 2 , Ar + 30% He + 0.015% N 2 , Ar + 50% He + 0.015% N 2 . Nondestructive testing is used to check joint defects, primarily porosity, as typical for this type of alloys. The Charpy specimens, with the notch positioned in different regions of the welded joint, are tested using instrumented pendulum to separate crack initiation and growth energy. Crack resistance is evaluated by using static (KIc) and dynamic testing (Paris law - fatigue crack growth)

Analysis of welding of the rear bridge semi-housing assembly of a firefighter truck by the semi-automatic procedure in gas protection

The problem considered in this paper is the welding technology of the steel assembly of a firefighter truck rear bridge semi-housing. Since in this procedure the welding is done of the two dissimilar steels, it is necessary to analyze effects of welding on mechanical properties and microstructure of individual joint's zones. The weldability of the base metal was considered first (semi-housing tube and flange), then the welding method and the filler metal were selected and, finally, the technological parameters of welding were calculated. The computational and experimental methods were used for the base metal weldability estimate, based on the hardness measurements in the joint's critical zones and analysis of their structures. Experimental investigations performed were aimed for verification and/or eventual correction of the proposed welding technology

The effect of shielding gas composition on the toughness and crack growth parameters of AlMg4,5Mn weld metals

The experiment have been performed using samples of welded joints of the three components aluminium alloy AlMg4,5Mn. The welding was performed with GTAW in the shielded atmosphere of Ar+0,015N2, mixture of the inert gases Ar+50%He+0,015N2 and Ar+70%He+0,015N2. After welding has been completed, the metallographic tests, the tensile test and the tests of the hardness were performed. Also, the weld metal toughness was estimated, using the instrumental Charpy impact testing system, followed by estimating the crack initiation energy, crack growth energy and the fracture mechanics parameters. The goal was to establish the effects of shielding atmosphere composition on the mechanical properties and fracture mechanics parameters of weld metal

Analysis of welding of the rear bridge semi-housing assembly of a firefighter truck by the semi-automatic procedure in gas protection

The problem considered in this paper is the welding technology of the steel assembly of a firefighter truck rear bridge semi-housing. Since in this procedure the welding is done of the two dissimilar steels, it is necessary to analyze effects of welding on mechanical properties and microstructure of individual joint's zones. The weldability of the base metal was considered first (semi-housing tube and flange), then the welding method and the filler metal were selected and, finally, the technological parameters of welding were calculated. The computational and experimental methods were used for the base metal weldability estimate, based on the hardness measurements in the joint's critical zones and analysis of their structures. Experimental investigations performed were aimed for verification and/or eventual correction of the proposed welding technology

The effects of dynamic load on behaviour of welded joint A-387 Gr. 11 alloyed steel

The in-service behaviour of alloyed steel A-387 Gr. 11 Class 1, for pressure vessels, used for high temperature applications, depends on the properties of its welded joint, with parent metal (BM), heat-affected-zone (HAZ) and weld metal (WM), as constituents. Charpy testing of BM, WM and HAZ, together with, determination of the parameters of fatigue-crack growth and fatigue threshold ΔKth was used, in order to understand, how heterogeneity of structure and different mechanical properties of welded joint constituents affect on crack initiation and propagation

Estimates of weldability and selection of the optimal procedure and technology for welding of high strength steels

High strength steels belong into a group of high quality steels, with exceptional mechanical properties, especially in regards to tensile strength. At the same time, as their deficiency is emphasized the limited and difficult weldability. In other words, some of those steels are weldable only with application of special measures related to controlled heat input. In that way, the favorable mechanical properties can be kept within the heat affected zone, with condition that the optimal welding technology is selected. Existing, very scarce and often unclear and insufficient recommendations for selection of the optimal welding technology are one of the causes of large number of flaws in welded joints. Mentioned problems, as well as others, can be successfully solved by proper selection of the procedure, filler metal and technology of welding, verified by experiments conducted in laboratory or in real operating conditions. Those experiments can not be performed in arbitrary conditions. Thus, partially due to results reported in this paper, technologists will obtain the possibility to predict in advance, in a very short time period, the mechanical and metallurgical properties of joints of this class of high strength steels. This will be possible without conducting the large number of practical tests or relying on personal experience of a designer

Testing the toughness of polypropylene filled with glass powder Contemporary Materials, III1 (2012) Professional papers UDK

Abstract: The purpose of this paper is to show polymer waste as a raw material or otherwise usable material derived from a partial separation of communal waste. This paper describes the possibilities of polypropylene re-use through recycling with addition of glass powder, from the point of view of toughness caused by impact load. Standard test specimens, made of basic material -polypropylene, with addition of 0%, 5%, 10%, 15%, 20%, 25% and 30% of glass powder with granulation less than 0,5 mm, have been tested through six processing cycles. The measured values gave a possibility of forming patterns for changes of the observed material with different content of additives, through processing cycles, which can be helpful in further research and analysis

The effect of shielding gas on the toughness of ALMg4.5Mn weld metals made by GMAW

The effect of MIG/MAG shielding gas on the toughness of aluminium alloy AlMg4.5Mn weld metal has been analysed using the instrumented Charpy pendulum for standard toughness testing. The MIG/MAG welding was performed in the shielded atmosphere of Ar, as well as the mixtures of gases Ar + 0.0307 % O 2, Ar + 30 % He + 0.0317 %O 2 and Ar + 48 % He + 0.0290 % O 2. Metallographic tests have been performed in order to check the appearance and porosity of the weld metal, as well as its toughness testing at different temperatures (20, - 90, - 196 °C), using the instrumental Charpy pendulum, in order to separate the crack initiation and crack growth energy. In this way, a comprehensive insight of the effect of shielding gas on the weld metal toughness has been obtained

Microstructure in the joining zone during the friction welding of the two dissimilar steels

Purpose - The purpose of this paper is to point out the possibilities for friction welding of dissimilar steels which are used in various industries. In addition, friction welding is a welding method that is applied for executing the very responsible joints. This research is focused on friction and tribological processes in the friction plane of the two pieces during the welding. Design/methodology/approach - The present study research has been conducted based on the experimental testing of cylindrical specimens and results are analyzed. Findings - The austenite grain size is affected by several factors through the friction process phase and the compacting phase during the welding. The very fine grain is the consequence of the high degree of the plastic deformation of the near-the-contact layers even in the friction phase. The viscous layer, which is formed during the stable friction phase, is the area where the moving of matter occurs according to a very complex mechanism. Originality/value - The paper contains useful results from the area of conventional friction welding of dissimilar steels and it can be very useful to researchers and engineers who deal with similar problems

How to replace the original material for the welded structure manufacturing

Due to difficult pandemic situation with COVID-19 decease, as well as due to current geopolitical circumstances in the world, we are facing the shortage of steel and therefore the impossibility of delivering the contracted products within the agreed deadlines. It is thus necessary to find suitable steel for replacement. The procedure for selecting one such steel for substituting the deficit steel 25CrMo4, for the purposes of producing a responsible welded assembly, is described in this paper. After the careful analysis, the steel 42CrMo4 was taken into consideration as a possible substitute material. Prior to applying the new selected steel, it was necessary to perform the following tests: analyze its chemical composition, determine its most important mechanical properties and evaluate its weldability. Then, the optimal welding and heat treatment technologies were determined, so that the quality of the responsible welded structure would meet all the requirements, as the structure made of originally used steel. For the new steel, all the mentioned and some additional tests were conducted and the appropriate welding technology was prescribed. To verify the selected technology, appropriate tests were conducted on the model welded samples, the results of which are presented in this paper. Based on the analysis of the obtained results, it was concluded that the 25CrMo4 steel can be replaced by the 42CrMo4 steel, however, with the mandatory application of appropriate supplementary measures