PubMed · 2880365
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W Aichhorn. 1986. [Plasma welding, why?].. https://pubmed.ncbi.nlm.nih.gov/2880365/
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OBJECTIVE: The goal of this work was to improve the mechanical strength of laser-welded gold alloy with age-hardenability at intraoral temperature. METHODS: The gold alloy was cast conventionally in plate patterns (0.5 mm x 3.0 mm x 20 mm). After bench-cooling the mold to room temperature (as-cast state), transverse sections of the plate were made at mid-span. They were butted against one another and welded using Nd:YAG laser (current: 320 A; time: 10 ms; spot diameter: 1 mm). Three laser pulses were applied from both sides to cover the joint width (3.0 mm) of the specimens before or after solution heat treatment at 700 degrees C/5 min. Uncut control specimens (non-welded) were also prepared. After solution treatment, two different heat treatments were given the laser-welded specimens: high-temperature aging at 250 degrees C/15 min, or intraoral aging at 37 degrees C/3 days. Control specimens underwent all of the heat treatments after solution treatment. Tensile testing was conducted at a crosshead speed of 2 mm/min and a gauge length of 10 mm. RESULTS: Solution treatment of the gold alloy before laser-welding did not improve the mechanical strength of laser-welded gold alloy after high-temperature aging or intraoral aging. The joint strengths of laser-welded gold alloy were improved only by solution heat treatments after laser-welding and subsequent aging treatment at high or intraoral temperatures. SIGNIFICANCE: The results of this study indicated that laser-welded cast gold alloy prostheses aged at high or intraoral temperatures produce high strength when they are solution-treated after laser-welding.
The distortion of laser welded titanium plates was assessed for different operating conditions of the laser welding device, and with different welding parameters (in terms of weld point and prewelding). In this study, Nd : YAG laser welding device was used to join the titanium plates. The results showed that distortion increased stepwise after each welding point along the welding zone (one-side welding), but decreased consecutively as the welding proceeded on the second side of the weld (two-side welding). In the case of one-side welding, the dependence of distortion on current and spot diameter presented maxima--due to changes in the welding pool characteristics. For two-side weld the same parameters exercised little influence on its distortion recovery, due to the effect of solidified weld pools from the first side. Current and spot diameter determined the weld pool, which in turn regulated distortion based on shrinkage. Four-point prewelding significantly decreased the final distortion for both one- and two-side welds. Alternating two-side welding of prewelded assembly showed lower distortion than a classic two-side weld.
PURPOSE: To make an clinical implication for the use of laser welding pure titanium,this study investigate the effect of irradiation power on the mechanical properties of laser-welded joints. METHODS: The pure titanium tensile test and three-point bending test rods were laser-welded with different irradiation power. Then the tensile rods were tested for the ultimate tensile strength (UTS), and the bending rods for the ultimate bending strength (UBS). The tensile fracture surface was examined by scanning electron microscopy (SEM). Metallurgical analysis was also performed on polished longitudinal sectioned samples. RESULTS: A small portion of the central area in group 1.4 kW was not joined. ANOVA showed no significant difference of OTS and VBS between group 1.6 kW and group 1.8 kW at the 0.05 level. SEM examination and metallurgical analysis showed that there were defects such as pores and cracks in the welding zone; and as the irradiation power increased, there were more pores and cracks. CONCLUSION: The increase in laser irradiation power cannot increase melting depth significantly.