Lasersko reparaturno zavarivanje alata s različitim oblicima impulsa

Repair welding of cold-work tool steels with conventional methods is very difficult due to cracking during remelting or cladding and is generally performed with preheating. As an alternative, repair welding with laser technology has recently been used. This paper presents the influence of different pulse shapes on welding of such tools with the pulsed Nd:YAG laser. Repair welding tests were carried out on AISI D2 tool steel, quenched and tempered to hardness of 56 HRc, followed by microstructural analysis and investigation of defects with scanning electron microscopy. Test results suggest that it is possible to obtain sound welds without preheating, with the right selection of welding parameters and appropriate pulse shape.Reparaturno zavarivanje alatnih čelika za rad na hladno konvencionalnim metodama je vrlo teško zbog pukotina nastalih tokom pretaljivanja i navarivanja i općenito vrši se uz predgrijavanje. U posljednje vrijeme se kao alternativna metoda koristi reparaturno zavarivanje upotrebom laserske tehnologije. Ovaj rad predstavlja utjecaj različitih oblika impulsa na zavarivanje alatnih čelika s pulsnim laserom Nd:YAG. Reparaturno zavarivanje testirano je na alatnom čeliku AISI D2, termički obrađenim na tvrdoću 56 HRc, poslije čega je provedena analiza mikrostrukture i traženje defekata skeniranjem elektronskim mikroskopom. Rezultati testiranja sugeriraju da je moguće izvesti dobre zavare bez predgrijavanja pravilnim izborom parametara zavarivanja i odgovarajućeg oblika impulsa

Lasersko reparaturno zavarivanje alata s različitim oblicima impulsa

Repair welding of cold-work tool steels with conventional methods is very difficult due to cracking during remelting or cladding and is generally performed with preheating. As an alternative, repair welding with laser technology has recently been used. This paper presents the influence of different pulse shapes on welding of such tools with the pulsed Nd:YAG laser. Repair welding tests were carried out on AISI D2 tool steel, quenched and tempered to hardness of 56 HRc, followed by microstructural analysis and investigation of defects with scanning electron microscopy. Test results suggest that it is possible to obtain sound welds without preheating, with the right selection of welding parameters and appropriate pulse shape.Reparaturno zavarivanje alatnih čelika za rad na hladno konvencionalnim metodama je vrlo teško zbog pukotina nastalih tokom pretaljivanja i navarivanja i općenito vrši se uz predgrijavanje. U posljednje vrijeme se kao alternativna metoda koristi reparaturno zavarivanje upotrebom laserske tehnologije. Ovaj rad predstavlja utjecaj različitih oblika impulsa na zavarivanje alatnih čelika s pulsnim laserom Nd:YAG. Reparaturno zavarivanje testirano je na alatnom čeliku AISI D2, termički obrađenim na tvrdoću 56 HRc, poslije čega je provedena analiza mikrostrukture i traženje defekata skeniranjem elektronskim mikroskopom. Rezultati testiranja sugeriraju da je moguće izvesti dobre zavare bez predgrijavanja pravilnim izborom parametara zavarivanja i odgovarajućeg oblika impulsa

Electrospark deposition for die repair

The electrospark deposition is a process for surfacing of hard metal alloys, e.g. carbides and stellites, on the surfaces of new or old machine elements. In this process, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. In the paper, the process is described and the thickness of deposited layer, chemical composition, dilution rate and the layer roughness are determined

Nanošenje električnom iskrom za popravak alata

The electrospark deposition is a process for surfacing of hard metal alloys, e.g. carbides and stellites, on the surfaces of new or old machine elements. In this process, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. In the paper, the process is described and the thickness of deposited layer, chemical composition, dilution rate and the layer roughness are determined.Nanošenje električnom iskrom postupak je za navarivanje tvrdih metalnih slitina, npr. karbida i stelita, na površinu novih ili starih elemenata strojeva. U tom postupku visoka struja provodi se kroz oscilirajuću elektrodu i supstrat na vrlo kratko vrijeme. U članku opisan je postupak i određeni su debljina nanesenog sloja, kemijski sastav, stupanj miješanja i hrapavost sloja

Procjena mikrostrukture alatnog čelika za hladni rad nakon pretaljivanja pulsirajućim laserom

The aim of this study is the investigation of micro-structural behaviour of a Mat. No. 1.2379 (EN-X160CrMoV121; AISI D2) cold work tool steel after remelting with a precise pulsed Nd:YAG laser. The investigated steel is one of the most hard to weld tool steels, due to large amount of alloying elements. The analysis was done on single spots remelted with specific laser pulse shape and parameters, assuring crack-less solidification. Re-solidifi ed areas were investigated with microscopy, hardness measurements, X-ray spectroscopy and diffraction method. Laser treatment causes rapid solidification leading into a formation of a fine dendritic microstructures containing high amount of retained austenite causing a significant decrease of hardness.Namjena ove studije je ispitivanje ponašanja mikro strukture alatnoga čelika za rad na hladno Mat. No.1.2379 (ENX160CrMoV121; AISI D2) po pretaljivanju s preciznim pulsiranim Nd:YAG laserom. Zbog velike količine legirnih elemenata istraživani materijal spada u grupu vrlo teško zavarljivih alatnih čelika. Analiza je provedena na pojedinim pretaljenim točkama korištenjem specifi čnog oblika i parametara laserskog impulsa koji osiguravaju skrućivanje bez pukotina. Pretaljena područja su ispitivana mikroskopom, mjerenjem mikro tvrdoće, rendgenskom spektroskopijom i defrakcijskom metodom. Tretman laserom uzrokvao je brzo skrućivanje koja dovodi do formiranja fi ne dendritičke strukture s velikim udjelom zaostalog austenita što uzrokuje bitno smanjivanje tvrdoće

Problemi kod reparaturnog zavarivanja alatnog čelika sa duplex zaštitom

The present paper addresses problems in laser welding of die-cast tools used for aluminum pressure die-castings and plastic moulds. To extend life cycle of tools various surface improvements are used. These surface improvements significantly reduce weldability of the material. This paper presents development of defects in repair welding of duplex-treated tool steel. The procedure is aimed at reduction of defects by the newly developed repair laser welding techniques. Effects of different repair welding process parameters and techniques are considered. A microstructural analysis is conducted to detect defect formation and reveal the best laser welding method for duplex-treated tools.U radu su istraženi problemi kod laserskog zavarivanja alata za lijevanje u industriji tlačnog lijeva aluminija ili plastike. Za produženje života alata primjenjena su različita poboljšanja površine. Ovakva poboljšanja značajno smanjaju sposobnost materijala za zavarivanje. U radu se opisuje razvoj grešaka kod reparaturog zavarivanja alatnog čelika sa dupleks zaštitom. Nametnuta procedura nastoji smanjiti greške sa novom zavarivnom tehnikom. Proučeni su I efekti različitih parametra procesa i tehnika zavarivanja. Mikrostrukturnim istraživanjima nastoju se naći greške za odabir najboljeg postupka za lasersko zavarivanje alata za dupleks zaštitom

Procjena utjecaja operativnih parametara Nd:YAG pulsnog lasera na metalurška svojstva različitih alatnih čelika pomoću DOE softvera

To ensure the reliability of repair welded tool surfaces, clad quality should be improved. The relationships between metallurgical characteristics of cladding and laser input welding parameters were studied using the design of experiments software. The influence of laser power, welding speed, focal point position and diameter of welding wire on the weld-bead geometry (i.e. penetration, cladding zone width and heat-affected-zone width), microstructural homogeneity, dilution and bond strength was investigated on commonly used tool steels 1,2083, 1,2312 and 1,2343, using DOE software.Poboljšanje kvalitete navarenog sloja nužno je za osiguranje pouzdanosti površina alata, obrađenih postupkom reparaturnog navarivanja. Odnos između metalurških osobina navarenog sloja i ulaznih parametara laserskog zavarivanja istražen je pomoću softvera Design of experiments. Utjecaj snage lasera, brzine zavarivanja, položaja žarišta i promjera žice za zavarivanje na geometriju navara (t.j. na penetraciju, širinu navara i širinu zone utjecaja topline), mikrostrukturna homogenost, miješanje i snaga spoja istraženi su na uobičajenim alatnim čelicima 1,2083, 1,2312 i 1,2343 pomoću softvera DOE

Izrada dvoplastnog alata za ubrizgavanje termoplasta postupkom zavarivanja

The article presents the technology of deposit cladding different materials, using the injection molds for thermoplastic as a case study. The aim of the study is to surface weld to the working surface of the mold a different material with corresponding physical properties. Steel (1.1141) and a copper alloy were used as the base, onto which different materials were surface-welded. Tungsten inert gas (TIG) welding was employed to make molds inserts. An analysis of cross-sectioned specimens was made by optical microscopy, and chemical and hardness profiles were measured too. The thermal conductivity of base and cladded layer was also tested. Finally, a thermal fatigue test was employed to investigate the thermal fatigue properties of such surfaces.U članku predstavljena je tehnologija navarivanja različitih materijala na primjeru alata za ubrizgavanje termoplasta. Cilj istraživanja je navarivanje drukčijeg materijala s odgovarajućim fizikalnim svojstvima na radnu površinu alata. Ulošci alata izrađeni su postupkom zavarivanja volframovom elektrodom uz zaštitu inertnog plina (TIG). Kao osnova na koju su navareni različiti materijali korišteni su čelik (1.1141) i bakarna slitina. Poprečni presjek uzoraka analiziran je optičkim mikroskopom, izmjereni su i kemijski profil i profil tvrdoće. Testirana je i toplinska provodljivost osnovnog i navarenog materijala. Na kraju je izvršen i test termičkog zamora u svrhu istraživanja svojstava termičkog zamora takvih površina

The manufactoring of a two–layered injection mold by welding

The article presents the technology of deposit cladding different materials, using the injection molds for thermoplastic as a case study. The aim of the study is to surface weld to the working surface of the mold a different material with corresponding physical properties. Steel (1.1141) and a copper alloy were used as the base, onto which different materials were surface-welded. Tungsten inert gas (TIG) welding was employed to make molds inserts. An analysis of cross-sectioned specimens was made by optical microscopy, and chemical and hardness profiles were measured too. The thermal conductivity of base and cladded layer was also tested. Finally, a thermal fatigue test was employed to investigate the thermal fatigue properties of such surfaces

Problems in repair-welding of duplex-treated tool steels

The present paper addresses problems in laser welding of die-cast tools used for aluminum pressure die-castings and plastic moulds. To extend life cycle of tools various surface improvements are used. These surface improvements significantly reduce weldability of the material. This paper presents development of defects in repair welding of duplex-treated tool steel. The procedure is aimed at reduction of defects by the newly developed repair laser welding techniques. Effects of different repair welding process parameters and techniques are considered. A microstructural analysis is conducted to detect defect formation and reveal the best laser welding method for duplex-treated tools