Milan Marônek

ANALYSIS OF WELD JOINT DEFORMATIONS BY OPTICAL 3D SCANNING

This paper presents an analysis of weld joint deformation using optical 3D scanning. The weld joints of bimetals were made by explosion welding (EXW). GOM ATOS II TripleScan SO MV320 equipment with measuring volume 320 × 240 × 240 mm, 5.0 MPix camera resolution and GOM ATOS I 350 with a measuring volume of 250 × 200 × 200 mm, 0.8 MPix camera resolution were used for experimental deformation measurements of weldments. The scanned samples were compared with reference specimens. The angular and transverse deformation were visualized by colour deviation maps. The maximum observed deformations of the weld joints ranged from −1.96 to +1.20 mm.

OPTIMIZING THE WELDING OF PLASTICS WITH THE USE OF DIFFERENTIAL SCANNING CALORIMETRY AND THERMOGRAVIMETRIC ANALYSIS

Plastics have different thermal stability, depending on the structure of the polymer chains. It is therefore very important to know their thermal properties, which influence the temperature regime of processing equipment. This paper presents examples of differential scanning analysis (DSC) and thermogravimetry analysis (TG) of selected plastics in an Ar protective atmosphere and also in an oxidative atmosphere of static air. These analyses can be used for proposing a welding temperature regime.

Electron Beam Welding of steel sheets treated by nitrooxidation

The paper describes the nitrooxidation process in a fluid environment applied to low-carbon steel sheets. The influence of this process on structural changes, weldability, mechanical properties and formability is also presented. Specimens welded by electron beam welding were examined by visual inspection, microstructure analysis and microhardness analysis. Visual inspection showed irregularities in weld bead formation, significant porosity and excessive spatter. In order to improve the appearance of the weld bead, it was necessary to use a triple welding pass and electron beam oscillation. The structural microanalysis of electron beam-welded specimens revealed a polygonal ferrite structure with the presence of upper bainite. The heat-affected zone was approximately three times wider in comparison to laser beam welding. No grain coarsing was observed in the high temperature heat-affected zone. In comparing electron beam welding and laser beam welding of nitrooxidation-treated materials, it can be claimed that electron beam welding is not a suitable welding method for this type of material.

Effect of Multiple Local Repairs on Microstructure and Mechanical Properties of T24 Steel Welded Joint

The effect of multiple local repairs on the microstructure and mechanical properties of the T24 steel welded joints was studied. T24 steel tubes were butt-welded by the GTAW method. Peripheral welded joints were made in four locations of the tube. In order to simulate the repair procedure, the welds were cut off from the root and the first local repair was performed. Other two local repairs were carried out in the same way. After each local repair, the microstructure and mechanical properties of the joints were evaluated. The results of the mechanical tests demonstrate that only two local repairs can be performed on the T24 steel peripheral welded joint. After the third local repair, impact energy of the welded joint was lower than required value, which is attributed to the coarser martensite and the coarser carbide precipitates formed in the heat-affected zone, compared with the weld metal.

The Influence of the Filler Material on Weld Joints Made of Duplex Stainless Steels

Application of beam welding methods for joining austenitic, duplex and other stainless steels is the right choice which not only lowers weld joint degradation but increases the production efficiency. There are many different demands on butt joints of duplex steels. One of them is equal ratio between austenite and ferrite of weld metal, because it can significantly influence the weld joints performance in real environment. The aim of this paper is to evaluate the influence of filler material on mechanical and technological properties of weld joints made from stainless steel SAF 2507.

Adhesive Bonding of Aluminium Alloy A5754 by Epoxy Resins

Joining thin sheets of aluminium and its alloys is a promising area in the field of joining materials. Nowadays, joining methods that do not melt the material itself are increasingly being utilised. This paper deals with adhesive bonding of aluminium alloy A5754 by two-component epoxy resins. Theresults show that joints bonded by Hysol 9466 have appropriate mechanical properties, but that joints bonded by Hysol 9492 have better thermal stability.

Comparison of the Laser and Electron Beam Welding of Steel Sheets Treated by Nitro-Oxidation

Nitro-oxidized steel specimens welded by a CO2 laser and an electron beam were examined for quality and integrity by visual inspection, microstructure, and microhardness analysis. Visual inspection of the specimens welded by laser revealed the lack of root penetration at maximal welding speed from the selected welding speed range (30 to 60 mm/s) and a neat weld at the welding speed of 40 mm/s. However, in comparison to laser beam welding, the electron beam welding (EBW) process produced the weld joints with a wider heat affected zone, while the weld joints were much more prone to porosity. The microstructure of the weld joints made by both the laser beam welding and EBW methods did not show any abnormalities in phase composition owing to the presence of nitrides in the surface layer of the materials welded after nitro-oxidation.