Laser brazing of a dissimilar joint of austenitic stainless steel and pure copper

In many industries, there are applications that require the joining of stainless steel and copper components; therefore, the welding of dissimilar stainless steel/copper joints is a common process. For this investigation, the optimal brazing conditions and suitable filler metals for laser brazing of stainless steel/copper lap joints were studied. Tensile shear force increases with increases in the laser spot diameter or in the laser irradiation angle, which is associated with increased bonding width; however, as bonding width approaches 2 mm, tensile shear force reaches a saturated value due to fracturing at the HAZ of the Cu base plate. In order to obtain joints with high tensile shear strength, laser brazing was optimized by using Cu–Si-based filler metal under the following conditions: laser power, 4 kW; spot diameter, 3 mm; laser irradiation angle, 80°; irradiation position shift, 0.6 mm; brazing speed, 0.30 m/min; and filler metal feed speed, 0.30 min. Concerning filler metals, it was found that the Ni–Cu type showed relatively large tensile shear force even at high welding speeds in comparison with those of the Cu–Si, Cu, Cu–Ni, Ni–Cu and Ni types, respectively.     

Chemiluminescence detection of mono-, bis-, and tris-hydroperoxy triacylglycerols present in vegetable oils

A reliable method was needed to analyze molecular species of oxidized vegetable oils. In order to accomplish this goal, mono-, bis-, and tris-hydroperoxides (Mono-OOH, Bis-OOH, and Tris-OOH, respectively) of triacylglycerols formed during autoxidation and photosensitized oxidation of oils were determined by reversed-phase high-performance liquid chromatography in combination with chemiluminescence detection (CL-HPLC). Mono-OOH was the major species (96% of total hydroperoxides) in trioleoylglycerol [peroxide value (PV) 0.16 meg/kg], and Bis-OOH and Tris-OOH showed prolonged accumulation with photooxidation. This profile was confirmed in photooxidation of trilinoleoylglycerol and trilinoleoylglycerol. Soybean oil (PV 6 meq/kg) contained Mono-OOH oleoyl-linoleoylglycerol as the main peroxidic molecular species (50% of total hydroperoxides). Mono-OOH trilinoleoylglycerol was the principal species (61% of total hydroperoxides) in safflower oil (PV 5 meq/kg), and Mono-OOH oleoyl-oleoyl-linoleoylglycerol was the representative species (66% of total hydroperoxides) in olive oil (PV 3 meq/kg). The CL-HPLC method, which is specific for the detection of hydroperoxides, should prove useful in studies of triacylglycerol oxidation in foods and vegetable oils.     

Chemiluminescence detection of mono-, bis-, and tris-hydroperoxy triacylglycerols present in vegetable oils

A reliable method was needed to analyze molecular species of oxidized vegetable oils. In order to accomplish this goal, mono-, bis-, and tris-hydroperoxides (Mono-OOH, Bis-OOH, and Tris-OOH, respectively) of triacylglycerols formed during autoxidation and photosensitized oxidation of oils were determined by reversed-phase high-performance liquid chromatography in combination with chemiluminescence detection (CL-HPLC). Mono-OOH was the major species (96% of total hydroperoxides) in trioleoylglycerol [peroxide value (PV) 0.16 meq/kg], and Bis-OOH and Tris-OOH showed prolonged accumulation with photooxidation. This profile was confirmed in photooxidation of trilinoleoylglycerol and trilinolenoylglycerol. Soybean oil (PV 6 meq/kg) contained Mono-OOH oleoyl-linoleoyl-linoleoylglycerol as the main peroxidic molecular species (50% of total hydroperoxides). Mono-OOH trilinoleoylglycerol was the principal species (61% of total hydroperoxides) in safflower oil (PV 5 meq/kg), and Mono-OOH oleoyl-oleoyl-linoleoylglycerol was the representative species (66% of total hydroperoxides) in olive oil (PV 3 meq/kg). The CL-HPLC method, which is specific for the detection of hydroperoxides, should prove useful in studies of triacylglycerol oxidation in foods and vegetable oils.