- Title
- Laser welding of thin-walled stainless steel tubing
- Creator
- Mabveka, Greystone Graham
- Subject
- Laser welding
- Subject
- Welding Mechanical engineering
- Date Issued
- 2019
- Date
- 2019
- Type
- Thesis
- Type
- Masters
- Type
- MTech
- Identifier
- http://hdl.handle.net/10948/40690
- Identifier
- vital:36223
- Description
- Longitudinal butt welds in the motor industry are increasingly being made by laser welding. One of the materials being welded is thin walled type 441 stainless steel tubing. The welding process parameters should however be optimised to give a weld that possesses acceptable properties. In this research, a Yb:YAG laser machine was used to weld a 1.2mm thick tubing. Laser power and welding speed were varied to achieve an optimum weld whose properties compare well with the parent metal. The two parameters were combined such that the heat input was in the range of 7.5 to 25kJ/m. The welds were characterised by the microstructure from the weld, intergranular attack and mechanical properties. It has been shown by microstructure study that grains originated from ‘weld metal/base metal’ interface and elongated towards the weld centreline. A defined line ran through the interface through the thickness of the plate. Smaller grains were noted around the interface in some welds. Susceptibility to intergranular attack tests showed random ditching in the weld metal microstructure which indicated that the weldments produced were acceptable. Mechanical tests of all welds showed a slight increase in micro-hardness in the weld metal. While the base metal had a micro-hardness range of 160 –199HV0.1, it increased to 187 – 242HV0.1 in the fusion zone. An ANOVA regression of tensile test results predicted an expected maximum of 471MPa to occur when a 1000W power is used at a welding speed of 0.06m/s. Fracture morphology of tensile test samples showed that all failures were by overload. This showed that the weld metal still exhibited similar ductility properties with the base metal.
- Format
- xx, 158 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Engineering Built Environment and Information Technology
- Language
- English
- Rights
- Nelson Mandela University
- Hits: 1515
- Visitors: 1711
- Downloads: 289
Collections
NMU School of Engineering
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Greystone Graham Mabveka.pdf | 6 MB | Adobe Acrobat PDF | View Details Download |