Rom a nia – Republic of Serbia IPA Cross-border Cooperation Programme

1. NATIONAL RESEARCH AND DEVELOPMENT INSTITUTE FOR WELDING AND MATERIAL TESTING - ISIM TIMIŞOARA, ROMANIA Project: Promoting new ecologic filler alloys for soldering, based on the non-ferrous ore of the Romanian-Serbian cross-border area Project Reference: MIS ETC Code 1409 WORKSHOP #1 21st of February 2014 Innovative soldering processes with ecological materials Dr. Eng. Victor Verbitchi (ISIM Timisoara): Experiments for dissimilar joining by weld– brazing of aluminium and titanium parts Romania – Republic of SerbiaIPA Cross-border Cooperation Programme

2. Technical requirements • Several parts for the automotive industry require protective and decorating coatings. Electroplating and eloxation are some of the applied processes for this target. The process needs some electro-conductive supports for the parts to be electroplated or eloxated, in an electrolyte. • A technical solution consists of a rectangular aluminium frame having the approximated sizes: height of 1000…1200 mm and width 600…800 mm, made of an aluminium beam with the cross section of 40 mm x 20 mm. Profiled hooks, manufactured by bending Φ8 mm wire of titanium are welded into holes, with the diameter Φ8±ΔΦ, of the beam. The aluminium beam, titanium hooks and weld metal of the dissimilar joints undertake severe corrosion in the chemical aggressive environment of the electrolyte of the electro-plating installation.

3. Technical requirements (continued) • The present technology of welding the hooks to the frame has the disadvantage that the welds undertake decay by corrosion and the electric contact is affected. This causes nonconformities in quality tests and breaks in production of the electroplated parts. • In order to increase productivity, repeatability, joint quality and structural reliability, some tests on a weld-brazing process were performed, for joining the titanium hooks to the aluminium frame. This process is recommended under special conditions and requirements [1]. • The experimental work was carried out on dissimilar joints of hooks inserted into holes of an aluminium beam, prepared according to the specification. Various types of filler alloys and selected process parameters were used.

4. Base metals • Weld-brazing tests were performed on a beam of aluminium EN AW 1200, according to EN 573 [2], having a rectangular profile, with the sizes 40 mm x 20mm. Various products of aluminium and aluminium alloys are available for this purpose [3-5]. • In this beam, holes with the diameter of 8 mm were drilled. Hooks made of 8 mm diameter wire of titanium TiGr.1, according to ISO 5832-2 [6] are inserted into these holes and dissimilar joints are performed between the aluminium beam and the titanium hooks. Other grades of titanium wire or bars can be also applied [7]. • This is the original geometry of a frame used for placing various metal parts to be coated with a protective and decorating layer by an electro-chemical process. • In the fig.2.1 and fig.2.2, the work-piece prepared for the joining test is illustrated.

5. Fig.1. The work-piece prepared for the joining test. The upper side.Fig.2. The work-piece prepared for the joining test. The bottom side.

6. Chemical composition and mechanical characteristics of the aluminium part

7. Chemical composition and mechanical characteristicsof titanium TiGr.1

8. Filler Alloys

9. Fig.3. The MasterTig 2500W welding equipment. Experimental Procedure • The test joints were executed with a MasterTig 2500W welding equipment, for the WIG process, generating current in a wide range, 30... 350 A. • It is an inverter-based source that has an efficiency of 85%. • It can operate with very low energy input.

10. Fig.4. The workplace with the positioned work-piece • The weld-brazing tests have been carried out with the manual process, based on previous own research and experiments [19]. It is still possible to automate this process, provided that the welding torch with the nozzle for the shielding gas can get into the gap between the neighbouring hooks, taking into account the difficult accessibility caused by the geometrical configuration of the aluminium frame with the plenty of hooks on it.

11. The first bottom joint. • For the joint configuration, special care is to be taken with the maximum allowable openings between the parts, in order to reduce porosity formation, caused by the gas kept in the gap that expands and gets out of the gap, through the molten filler alloy, during the weld-brazing process. • The filler metal is a 1.6 mm AlMg5 rod, EN ISO 18273.

12. Fig.5. The current and voltage by weld-brazing by the first joint

13. Fig.6. Shielding gas flow, corgon 12.5 litres/min, by weld-brazing the first bottom joint • The flow of 12.5 litres/min of the shielding gas, corgon (mixture of argon with 18% carbon dioxide) is presented, as measured by the flow gauge with pressure reducer of the gas cylinder, by weld-brazing the first bottom joint.

14. Fig.7. Parameters by the fourth weld-brazed bottom joint.

15. Fig.8. Current and voltage during the weld-brazing process, by the first upper joint • The filler metal is a 1.6 mm AlMg5 rod, by the first and second upper joints. • Other filler metal were also applied in these experiments.

16. Fig.10. Weld-brazing parameters by the second upper joint • Fig.9. Weld-brazing process of the second upper joint, with a 1.6 mm AlMg5 rod

17. Fig.11. Weld-brazed assembly of the aluminium beam with the five titanium hooks. Bottom side.

18. Fig.12. Assembly of the aluminium beam with titanium hooks. Side view.

19. Non-destructive examination • Visual examination of the weld-brazed joints was applied according to SR EN ISO 17637: 2003. "Non-destructive testing of welds. Visual testing of fusion-welded joints" [20] and • EN 12799:2000 Brazing - Non-destructive examination of brazed joints (& A1:2003) [21]. • The visual examination was based on the following criteria: stability of the welding parameters, width of the weld bead at the top surface (measured value), penetration (total/partial), clear burned-edges (yes/no), general shape of the bead at the top surface (convex / plan / concave), and spatter (many/few/none). • By the visual examination, no defects were detected.

20. Conclusions • 1. The precise machining preparation of the beam hole for the joint, as well as finishing the hook surface, can allow a weld-brazing process with higher velocities and lower heat input, while keeping a proper penetration of both titanium hook and aluminium beam. • 2. A single weld-brazed joint at the bottom of the hook is requested in the specification of the frame with hooks. Another weld-brazed joint on the upper side of the beam improves the mechanical strength and corrosion withstand of the hook-beam assembly. • 3. Surface finishing of the parts has an important influence on avoiding the porosity of the weld-brazed joints. With improved surface preparation, this phenomenon did not occur.

21. Conclusions (continued) • 4. Higher welding speeds have produced a thinner weld bead, with an adequate appearance, without porosity. • 5. Hydrogen-induced porosity was avoided due to careful finishing of the surface that reduced the hydroxide layer, as a hydrogen source. • 6. The plastic deformation of the hooks subjected to the bending test must be kept under 0.5 mm, so that it should not be limited by the mechanical strength of the joint. • Failure by deformation of the base metal due to an uneven stress distribution in the hook- beam assembly is unlikely to occur, due to the high cross section of the aluminium beam.

22. CONTACT PERSON • Name: Dr. Eng. Victor Verbiţchi • Phone: +40256-491828-143 • Mobile: +40728-576630 • Fax: +40256-492797 • E-mail: vverbitchi@isim.ro • Web: www.isim.ro

23. Thank you for you attention !