Radomir Jovičić

Welding and testing of welded joints made of HARDOX 400

Rad primljen / Paper received: Januar 2018. Adresa autora / Authors address: 1 i 3 Inovacioni centar Mašinskog fakulteta u Beogradu, Beograd, Srbija. Innovation Center of Faculty of Mechanical Engineering, Belgrade, Serbia MFGO, Fabrika građevinske opreme, Mladenovac, Srbija MFGO, Construction equipment manufacturer, Mladenovac, Serbia KonMat, Beograd, Srbija. KonMat, Belgrade, Serbia Tehnološko metalurški fakultet Univerziteta u Beogradu, Beograd, Srbija. Faculty of Technology and Metallurgy, University of Belgrade, Serbia Stetter GmbH, Memmingen, Nemačka. Stetter GmbH, Memmingen, Germany

Uticaj zaštitne atmosfere i brzine dovođenja žice na stabilnost mig/mag postupka zavarivanja

Rezime: Stabilnost procesa zavarivanja ima značajan uticaj na postizanje propisanog nivoa kvaliteta zavarenog spoja. Povećanje stabilnosti utiče na smanjenje mogućnosti pojave nesavršenosti, odnosno grešaka u samom spoju. Stabilnost procesa zavarivanja se ogleda u stabilnosti električnog luka. Promene dužine luka tokom zavarivanja utiču na varijaciju parametara zavarivanja, tačnije na jačinu struje i napon. Na osnovu praćenja parametara zavarivanja u realnom vremenu može se izvršiti statistička analiza dobijenih rezultata. U radu je prikazan uticaj brzine dovođenja žice i vrste zaštitne atmosfere na stabilnost MIG/MAG postupka zavarivanja pri upotrebi metalne punjene elektrodne žice.

Obim ispitivanja zavarenog spoja prema SRPS EN 13445-5

Pressure vessels are, according to the degree of risk that present for humans and the environment, divided into the vessels of high and low level of hazard. One of the most important aspects of the conformity assessment of the new pressure equipment and for the evaluation of their safety for work, are nondestructive testing of welded joints. Given the importance and responsibility carried by these tests, the extents of nondestructive testings are recomanded by the standards depending on the type of welded joint and testing group of materials. However, the recomanded extent of tests are the result of analysis and experience, and are subject to change over the years. In this paper, the changes in the extent of nondestructive testing of welded joints in relation to the EN 13445-5: 2009 and EN 13445-5: 2015 are analysed depending on the groups of materials and the type of welded joint of pressure vessels, with reference to the practical examples.

Methods for calculating the preheat temperature welding the high strength steels

With preheating of steel the cooling speed of a heat affected zone decreases, which prevents appearance of structure prone to cold cracks. On the other hand, too small cooling speed, in this area, results with growth the metal grains which, also, leads as to the higher prone to cracks. Common used method for calculation of preheating temperature for high strength steels ar Itto - Bessyo method, and method by standard SRPS EN 1011-2. This paper presents the methods for calculating the preheating temperature of micro aloyed steel P460 NL1. Analysis of the results obtained from both methods shows significant differences in the amounts calculated preheat temperature. It was concluded that both methods have limitations that must be taken into account in their application in practice.

Influence of gas shielding atmosphere on weldability of AIMg4.5Mn alloy

In this paper is shown the influence of gas shielding atmosphere on the weldability of AlMg4.5Mn alloy. Prepared plates were welded using tungsten inert gas (TIG) with four different shielding atmospheres. Metallographic testing, tensile testing and hardness testing of welded joints were carried out. It has been shown that composition of shielding atmosphere has effect on the weld appearance, depth of penetration, overflowing of filler material, porosity in the weld metal, as well as on values of tensile strength and hardness. Weldments obtained by welding in a shielding atmosphere Ar + 50% He + 0.015% N2 have the best appearance of the weld metal, good overflowing of filler material and satisfactory width to hight ratio. It was also established that these welds have the lowest weld metal porosity.

Definition of welding parameters by cooling time in temperature range 800-500ºC

Cooling time in the temperature range 800 - 500°C has a great effect on the structures that arrise in the heat affected zone of welds steel. Data on optimal cooling time t8/5 for the certain steels can be found in the literature. The period of the cooling time t8/5, during the welding of the particular joints, in addition to the thickness and physical properties of welded steel, depends on shape of the weld, the welding process and welding parameters as well. In this work, the procedure for the selection of welding parameters for a butt joint welded to the microalloyed steel P 460 NL1 is presented. The microstructure in the heat affected zone and the results of measurement of their hardness are showed and analysed. It is concluded that the welding parameters selected with the help of cooling time t8/5 provide the satisfactory structure and hardness of welds.

Welded Joints Behaviour in Service with Special Reference to Pressure Equipment

Quality and structural integrity of welded pressure equipment are defined by The Pressure Equipment Directive (97/23/EC). The problem is complex, due to welded joint imperfections, matching effect, heterogeneity of microstructure and material properties. Equipment can be fit for service with defects unacceptable by codes, what should be proved by fracture mechanics approach, especially for cracks in the heat-affected-zone.