Navarivanje pod prahom s višežičanom elektrodom

Submerged arc surfacing with a multiple-wire electrode is a new process variant which has been rarely used, in spite of its numerous advantages in comparison to other processes, in practical applications. The unit for surfacing with the multiple - electrode differs little from a classic unit for submerged arc welding with a single-wire electrode. The difference between them consists in that in our unit several wires travel through a joint contact tube simultaneously. All of the wires are fed with the same rate and have a joint regulation and power source. In welding with the multiple-wire electrode it is possible to weld with two, three, four or even more wires simultaneously. In the joint contact tube wires of different diameters and different chemical composition and solid or flux-cored wires may be used. Mechanical properties of surfacing welds depend on the type the parent metal and the filler material, welding parameters and the type of welding flux used.Navarivanje s višežičanom elektrodom pod prahom novi je postupak koji se, usprkos brojnim prednostima pred ostalim postupcima, još uvijek ne upotrebljava u praksi. Naprava za zavarivanje s višežičanom elektrodom suštinski se ne razlikuje od klasične naprave za zavarivanje sa samo jednom žicom. Razlika je samo da pri novoj napravi kroz kontaktnu mlaznicu istovremeno putuje više žica. Sve žice imaju istu brzinu, zajedničko podešavanje i samo jedan izvor električne struje. Pri zavarivanja sa višežičanom elektrodom moguće je upotrijebiti dvije, tri, četiri ili čak i više žica istodobnno. Kroz kontaktnu mlaznicu mogu prolaziti žice različitih promjera, kemijskog sastava, moguće je upotrijebiti masivne ili punjene žice. Mehanička svojstva navarenog sloja ovise od vrste osnovnog i dodatnog materiala, parametara zavarivanja i vrste zaštitnog praha

Elektrolučno zavarivanje pod prahom višestrukom žičanom elektrodom u uskom rasporu

The article treats a completely new variant of narrow gap welding. First, nine different welding heads for narrow gap welding are described and shown schematically. The core of the article is devoted to a description and schematic representation of a unit for welding with twin-wire and triple-wire electrodes respectively and a description of technology for narrow-gap submerged-arc welding of thick workpieces. A macrograph of the weld is shown too, and basic optimum welding parameters for attaining a quality weld are given. Finally, main advantages of multiple-wire narrow-gap submerged-arc welding are stated.U članku je prikazan potpuno novi način zavarivanja u uskom rasporu. Najprije je opisno i shematski prikazano devet različitih glava za zavarivanje u uskom rasporu. Glavni dio članka predstavlja opis i shematski prikaz uređaja za zavarivanje dvostrukom i trostrukom žičanom elektrodom, kao i opis tehnologije zavarivanja debelih radnih komada u uskom rasporu pod prahom. Isto tako prikazan je makro obrus vara i navedeni su osnovni optimalni parametri za postizanje kvalitetnog vara. Na kraju članka navedene su glavne prednosti zavarivanja u uskom rasporu sa višestrukom žičanom elektrodom pod prahom

Premoštenje zazora pri zavarivanju s višežičanom elektrodom

An investigation on bridging larger welding gaps between workpieces occurring in practice due to structural requirements or to defects in weld edge preparation is described. Some characteristic cases from practice where a larger root gap should be bridged or the space between two or three workpieces should be filled with a greater quantity of filler material are described. Submerged-arc welding with twin-wire and triple-wire electrodes was applied.Opisano je istraživanje premoštenja zazora između komada za zavarivanje, koji se u praksi pojavljuju zbog konstrukcijskih zahtijeva ili grešaka prilikom pripreme stranica šavova. Opisani su neki karakteristični primjeri iz prakse, gde je bilo potrebno širi zazor ili prostor između dva ili tri komada za zavarivanje premostiti pomoću veće količine dodatnog materiala. Upotrebljeno je zavarivanje pod prahom uz upotrebu dvostruke i trostruke žičane elektrode

Faktori koji utječu na oblik zavara kod elektrolučnog zavarivanja trostrukom žičanom elektrodom

The article describes the influences of welding parameters, modes of metal transfer through the arc and the number of wires applied on weld formation and final shape. Diagrams show the influence of current intensity and arc voltage while a figure shows the influence of streaming and rotating metal transfers on the final weld shape. Diagrams and macro specimens, however, show the influence of the number of wires used on the weld shape and weld formation in submerged arc welding with a triple-wire electrode.U članku je opisan utjecaj parametara zavarivanja, utjecaj načina prolaska materijala kroz električni luk i utjecaj broja žica na nastajanje zavara i njegov konačni oblik. Pomoću dijagrama su prikazani utjecaji jačine struje zavarivanja i napetosti električnog luka, a slika prikazuje utjecaj prelaska materijala tečenjem i utjecaj prelaska materijala okretanjem na završni oblik zavara. Dijagramima i pomoću makrobrušenih uzoraka prikazan je utjecaj broja žica na oblik i nastanak vara kod zavarivanja trostrukom žičanom elektrodom pod zaštitom praha

Oxy-Hydrogen Flame for Cutting of Steels

The paper deals with oxy-hydrogen cutting of steel plates. The first part deals with calculation of the combustion efficiency of an oxy-hydrogen flame. A device for supply of a hydrogen-oxygen mixture is described. The main part of the paper is focused on oxy-hydrogen cutting and its advantages. The main conclusions show that the cut surface is flat and very smooth, the heat-affected zone is very narrow, and the cutting speed is relatively high

Tungsten inert gas (TIG) welding of aluminum alloy EN AW-AlZn5.5MgCu

The paper presents the results of tungsten inert gas (TIG) welding of aluminium alloy 7075-T6 in the butt joint, with single-V edge preparation. The sample dimensions were 100 × 75 × 20 mm3. The TIG welding was done with 2 mm diameter filler wire made of 5183 (AlMg4,5Mn) at four preheating temperatures. During the welding a temperature was measured at six locations with thermocouples. For successfully welded samples tensile test were done and microstructure of base metal, heat affected zone and weld was analysed. The welds brake at heat affected zone between base metal and the weld. The optimal preheating temperature was at 200 °C

How to Extend the Life of Die-Casting Tools

The paper explores some possibilities of extending the life of die-casting tools for non-ferrous metals, particu-larly aluminium, magnesium, and their alloys. In the first part of the paper is shown theoretical background of the problem. The major part treats the tools: tool life, tool manufacture, tool certificate, tool operation and repair of tools by welding. Welding is the only technology fit for repair of tools and thus to extend their service life. In the paper is shown some welding processes, which are suitable for repair welding of tools

Laser grooving of surface cracks on hot work tool steel

The paper presents the analysis of laser grooving of 1.2343 tool steel hardened to 46 HRC. The effect of laser power and grooving speed on groove shape (i.e. depth and width), the material removal rate and the purity of produced groove as a measure of groove quality was investigated and analyzed using response surface methodology. Optimal parameters of laser grooving were found, which enables pure grooves suitable for laser welding

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

Problems in laser repair welding of polished surfaces

This paper presents problems in laser repair welding of the tools for injection moulding of plastics and light metals. Tools for injection moulding of the car headlamps are highly polished in order to get a desirable quality of the injected part. Different light metals, glasses, elastomers, thermoplastics and thermosetting polymers are injected into the die cavity under high pressures resulting in the surface damages of the tool. Laser welding is the only suitable repair welding technique due to the very limited sputtering during deposition of the filler metal. Overlapping of the welds results in inhomogeneous hardness of the remanufactured surface. Results have shown strong correlation between hardness and surface waviness after final polishing of the repair welded surface