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1

Review of the Hard-Facing Technology Application for Reparation of the Given Parts in Various Branches of Industry

Lazić V., Arsić D., Mutavdžić M., Nikolić R., Meško J., Radović L., Ilić N.

Multidisciplinary Aspects of Production Engineering

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2018

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Vol. 1, Iss. 1

279--285

EN

This paper deals with the problem of defining the optimal procedure for reparation of the machine parts of large dimensions and complex shapes. The procedure consists of establishing the causes of the part's damages, definition of the reparation technology, with selection of its parameters and ways of execution. The reparation is done by hard-facing, with heat treatment that consists of preheating, additional heating and the post hard-facing tempering. The process parameters' selection includes choosing the right filler metal(s), ways and order of depositing the hard-faced layers, ways of reaching and maintaining the preheating temperatures, checking of the base metal's chemical composition and mechanical properties and deciding on the post-process heat and mechanical processing of the executed hard-facing. The executed reparation of the forging hammer's mallet, presented in details, serves as an example how the reparation can successfully serve as a substitute for procuring the new part and thus producing the savings both directly in lower costs and indirectly in shortening the down-time of the damaged part operation.

2

Correlations of Mechanical Properties and Microstructure at Specific Zones of Welded Joint of High-Strength Low-Alloy Steels

Ivanović L., Marjanović V., Ilić A., Stojanović B., Lazić V.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

285--292

EN

This paper presents experimental testing of the mechanical characteristics and properties of samples made of high-strength low-alloy steel with two different multi pass V grove butt welded joint. Two sample groups are tested: the root pass is made by manual metal arc welding process for the former and metal inert gas welding process for the latter. Other passes of those multi passes welded joints are made by metal active gas welding process. Further, the research included analyses of the experimentally obtained mechanical properties and load response of the samples in correlations to microhardness distribution and microstructural state at specific zones of the welded joints. Since both the chemical composition and microstructural state of high-strength low-alloy steel originate from special production processes their nature must be fully understood. Accordingly, the nature of the steels should directly impact not only the selection and definition of welding but the design process of mechanical constructions, too. From the practical aspect, mechanical characteristics and properties as well as load response of welded joints are crucial. But, sensitivity of those steels to inadequate welding technology and improper parameters or filler metal is high. On the other side, design codes and recommendations are not yet fully developed and precise. Results obtained in this research implicate that even small changes of welding technology causes the change of characteristics itself. Consequently, the steels development must be accompanied with the improvement of the welding processes and design modifications.

3

Influence of welding time on quality of the friction welded joint of two dissimilar steels

Ratković N., Lazić V., Arsić D., Nikolić R., Hadzima B.

Zeszyty Naukowe. Quality. Production. Improvement

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2017

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No. 1 (6)

1--11

EN

There are several factors that influence the friction welding (FW) process, i.e. the quality of the welded joint, like the welding time, the contact pressure, the compacting pressure, the friction speed etc. The joining process is additionally complicated if the two different materials are to be welded to each other. The subject of research, presented in this paper, is the welding time of the FW process, since the level of axial and radial plastic deformation of the welded pieces and shortening of the welded part depend mainly on the welding time. The paper first presents some theoretical basics of the FW process and then, in the experimental part, the influence of the process duration is investigated. The two materials that the experimental samples were made of are the high-speed steel and the steel for tempering.

4

Selection of the optimum technology of the forging dies reparation from the aspect of tribological characteristics

Lazić V., Jovanović M., Adamović D., Ratković N.

Tribologia

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2005

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nr 2

11-30

EN

This paper presents a preceding procedure that should be conducted in order to successfully regenerate damaged forging dies by the hard facing process. After the tool damage types identification, as well as their causes, we have chosen the procedure and the parameters of hard facing that we further corrected by conducting the test hard facings on models. Thus, we were able to relate the output results with the repair technology, taking as a criterion the quality of the surface layers wear resistance, micro hardness, level of residual stresses and strains, etc. This enabled the selection of the optimum technology of hard facing for the adopted procedure and filler material, as well as the selected thermal-treating regime. Our tribological and other investigations have shown that the working life of the hard-faced tool can be longer than that of the new tool.

PL

W artykule przedstawiono procedurę, którą powinna poprzedzać regenerację uszkodzonych matryc kuźniczych metodą napawania. Po zidentyfikowaniu rodzajów zużycia matryc kuźniczych i jego przyczyn, autorzy wybrali procedurę i parametry napawania, a następni zweryfikowali je na próbkach modelowych. Badano wpływ technologii regeneracji na odporność na zużycie, mikrotwardość, poziom naprężeń szczątkowych, odkształceń itp. Pozwoliło to na wybór optymalnej technologii napawania oraz materiału elektrody, a także warunków obróbki cieplnej. Wykonane badania wykazały i potwierdziły, że trwałość narzędzi regenerowanych napawaniem może być wyższa niż narzędzi nowych.