Influence of lack-of-fusion defects on load capacity of MAG welded joints
Pressure vessels operating at elevated temperatures and pressures are made of creep resisting plate and welded from individual components using the MAG welding process. The paper proposed focuses on the occurrence of lack-of-fusion defects in MAG welded plate components of pressure vessels. Lack of fusion, which is a planar defect and is, therefore, difficult to detect by common NDT methods, can result in catastrophic consequences since the latter do not only damage a pressure vessel but also jeopardize the environment and workers' health. The present paper deals with a research on the influence of a welding speed in welding of plate components made of S235JR steel of 8 mm in thickness, special care being taken to deliberately produce lack-of-fusion defects and possibly other weld defects. Test pieces prepared so as to contain various lack-of-fusion defects were subjected to destructive tensile testing. The force required for a weld failure was compared to actual weld defects. In the test pieces produced with lower welding speeds, a failure occurred in the welded joint and along a lack-of-fusion defect. In the test pieces produced with higher welding speeds, however, a fracture occurred outside a weld, although lack of fusion was present in the weld. Parallel to the tensile tests, radiographic examinations of lack-of-fusion defects were conducted and relevant micro sections were analysed. The aim of the study conducted was to elaborate a guideline for quality welding of plate components of pressure vessels.
Lack of Fusion Characterisation of Indications
For efficient testing of welded joints, it is indispensable to be acquainted with non-destructive testing methods, as well as to know as much as possible about the defects to be detected. In the welding literature there are comparatively few reports on lack of fusion defects, although the latter is of the most risky weld defects. For their detection, there are no efficient testing methods available. The present study focused on gathering as many as possible data on lack of fusion. It was found with which welding processes they were likely to occur, where they were located, and what their properties were. The indications of lack of fusion were studied using different non-destructive testing methods. Testing was carried out on butt-welded joints obtained in gas-shielded welding with a consumable electrode. In addition to non-destructive testing methods, metallographic and mechanical tests were used too. It was to be found why non-destructive testing methods were inefficient in lack of fusion detection.
HPLC determination of chlorhexidine gluconate and p-chloroaniline in topical ointment.
A novel fast isocratic reversed-phase HPLC method for simultaneous determination of chlorhexidine and its degradation product p-chloroaniline was developed. Zorbax SB Phenyl column (75 mm x 4.6 mm, 3.5 microm) was used for the separation. Mobile phase composed of acetonitrile and buffer solution of 0.08 M sodium phosphate monobasic containing 5 ml of triethylamine (0.5%) and adjust with 85% phosphoric acid to pH 3.0 in ratio 35:65 (v/v) pumped isocratically at flow rate 0.6 ml min(-1) was used. UV detection was performed at 239 nm, the total analysis time was about 10 min. The method is suitable for practical routine analysis of topical ointment in the quality control laboratory.