Optimalizacija parametara zavarivanja trenjem Al-Cu spojeva

master's thesis

• Title (english): Optimization of friction welding parameters of Al-Cu joints
• Author: Luka Stefanović
• Mentor: Zoran Kožuh (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2022-12-15, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Production Mechanical Engineering

Abstract

Zavarivanje trenjem je relativno nova i nedovoljno istražena tehnologija zavarivanja čija je svrha spajanje materijala unosom topline proizvedene trenjem. Konvencionalnim tehnologijama zavarivanja je unos topline ostvaren preko električnog luka pomoću kojeg se metali rastaljuju i formiraju međumolekulske veze koje nakon skrućivanja ostvaruju čvrst zavareni spoj. Takvim načinom zavarivanja je teško povezati dva različita metala odnosno metala koja imaju lošu metaluršku kompatibilnost koja ovisi o radijusu atoma, temperaturi tališta, rasporedu elektrona u vanjskoj ljusci, vrsti kristalne rešetke i sposobnosti stvaranja zajedničkih intermetalnih spojeva koji ojačavaju međusobne veze. Nadalje, unos topline kod zavarivanja električnim lukom je proporcionalan kvadratu jakosti struje koja se koristi pri zavarivanju što znači da unesena toplina može postići enormne vrijednosti. Prekomjeran unos topline dovodi do prekomjerno povećanih temperatura koje olakšavaju ostvarivanje nepoželjnih pojava korozije i vodikove krhkosti. Prilikom zavarivanja trenjem, kinetička energija međusobnog gibanja dijelova prelazi u toplinsku energiju i na taj način je unos topline manji. U procesu zavarivanja trenjem metali ne prelaze u tekuće agregacijsko stanje, već postižu viskozno-plastično stanje u kojem pri povišenoj temperaturi i pod utjecajem tlaka zadržavaju trajnu plastičnu deformaciju i ostvaruju trajnu vezu. Ovim postupkom moguće je zavarivati gotovo sve vrste čelika, titanove legure, magnezij, aluminij i bakar. Glavni nedostatak postupka jest što iziskuje visoka početna ulaganja i to što je uglavnom limitiran na sučeljene i kutne spojeve. U ovom diplomskom radu, navesti će se postupci zavarivanja trenjem i s njima povezani parametri te specificirati kako oni utječu na svojstva zavara. U radu će također biti navedene kombinacije materijala koje je moguće zavarivati trenjem te će se prikazati pregled industrijskih proizvoda kod kojih se koristi zavarivanje trenjem za njihovu izradu. Nadalje, utvrditi će se granični tlak sabijanja za izradu uzoraka promjera 14 mm te će se proučiti kako promjena tlaka sabijanja utječe na Al-Cu spojeve. Izrađeni uzorci će biti analizirani pomoću vlačnog testa i preko svjetlosnog mikroskopa pod uvećanjem od 200 puta. U konačnici će se prikazati rezultati ispitivanja iz kojih će biti izvučeni odgovarajući zaključci.

Abstract (english)

Friction welding is relatively new and insufficiently researched welding technology whose purpose is bonding of metals enabled through heat input created through friction. Heat input of conventional welding technologies is accomplished by electric arc which melts metals that create intermolecular bonds in liquid state. Thus, after solidification is completed, firm welded connection is formed. With arc welding it is hard to bond two different metals that have unfortunate metallurgical compatibility which depends on radii of atoms, layout of outer-shell electrons, crystal lattice, melting temperature and the ability to form intermetallic compunds that strengthen the bond between metals. Furthermore, heat input in arc welding processes is proportional with rate of charges in electric current used for welding squared, which means that excessive heat can be achieved. Overwhelming amount of heat leads to increased temperatures that in turn increase the chances of corrosion and hydrogen induced cracks occurrence. With friction welding, kinetic energy of mutual motion of parts is converted into heat. That way heat input is much lower. In friction welding process, metals do not reach liquid state, but achieve permanent bond through highly viscous-plastic state in which they permanently deform through conditions of increased temperatures and pressures. With this process it is possible to weld almost all types of steel, titanium alloys, magnesium, aluminium and copper. Main drawback of this process is that it requires high starting investment and its usage is mostly limited to angular and butt joints. In this master’s thesis, friction welding processes and their process parameters will be listed. It will also be analyzed how these process parameters affect the properties of the weld. In this thesis, combinations of materials that can be friction welded will also be adduced and industrial products that have friction welding as a part of their making will be showcased. Furthermore, marginal upsetting pressure for the making of samples with the diameter of 14 mm will be established as well as the effect that upsetting pressure has on Al-Cu welds. Samples will be analyzed by tensile test and welds will be studied under optical microscope under 200x magnification. In the end, results of the testing will be shown and appropriate conclusions will be brought.

• Keywords: Aluminij; bakar; unos topline; zavarivanje trenjem
• Keywords (english): Aluminium; copper; heat input; friction welding
• Language: croatian
• URN:NBN: urn:nbn:hr:235:657065
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2022-12-04 10:25:10