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PubMed2006

The integrity of welded interfaces in ultra-high molecular weight polyethylene: Part 2--interface toughness.

In Part 2 of a study of welding of ultra-high molecular weight polyethylene (UHMWPE), experiments were conducted to measure the interfacial fracture energy of butt welds, for various welding times and temperatures above the melting point. Their toughness was investigated at 37 degrees C in terms of their fracture energy, obtained by adapting the essential work of fracture (EWF) method. However, a proportion of the welded samples (generally decreasing with increasing welding time or temperature) failed in dual ductile/brittle mode, hence invalidating the EWF test. Even those failing in purely ductile mode showed a measurable interface work of fracture only for the highest weld temperature and time: 188 degrees C and 90 min. Results from the model presented in Part 1 show that this corresponds to the maximum reptated molecular weight reaching close to the peak in the molar mass distribution. Hence this work provides the first experimental evidence that the slow rate of self-diffusion in UHMWPE leads to welded interfaces acting as low-toughness crack paths. Since such interfaces exist around every powder particle in processed UHMWPE this problem cannot be avoided, and it must be accommodated in design of hip and knee bearing surfaces made from this polymer.

Adhesiveness↗

PubMed1989

Pulmonary functional impairment from years of arc welding.

PURPOSE: The adverse effects of arc welding on pulmonary function have been previously documented. However, in many of these studies, the effects of welding exposure and smoking were not separated. Also, some studies did not adjust for or ignored the effects of asbestosis on pulmonary function. We assessed the long-term effects of welding on pulmonary function in welders who had no evidence of asbestosis on chest radiographs, and adjusted each individual value for height, age, and years of cigarette smoking. PATIENTS AND METHODS: The study consisted of 226 male construction welders who had never worked in shipyards. Forced vital capacity (FVC) and flows were measured by spirometry, chest radiographs were obtained and examined for evidence of asbestosis using International Labor Office (ILO) criteria, and thoracic gas volume (TGV) was determined by planimetry. The subjects were also administered an occupational and respiratory questionnaire. Data on workers with asbestosis (ILO profusion 1/0 or greater) and pleural abnormalities were excluded. The mean age for the 226 subjects without asbestosis was 45 years, mean height was 175.7 cm, and mean duration of welding was 21.3 years. Pulmonary function measurements are presented as mean percentage of predicted (pop) and adjusted for height, age, and years of smoking. RESULTS: In 151 current cigarette smokers, mean midflows and terminal flows were decreased, FEF25-75 to 93.2 pop and FEF75-85 to 91.2 pop, but FVC, forced expiratory volume in one second (FEV1) and TGV were normal. The 43 nonsmokers also had reductions in flows but normal FVC and TGV. Flows in both groups were significantly (p less than 0.05) below those of the referent group. The regression coefficient was -0.0031 for years of welding and FVC pop, -0.0035 for FEV1 pop, and -0.0080 for midflow pop (FEF25-75) (all significant at p less than 0.05), but the coefficient for FEF75-85 pop was not significant. As calculated from regression equations, 40 years of welding would reduce FVC to 95.2 pop, FEV1 to 92.2 pop, midflow to 79.2 pop, and FEF75-85 to 81.7 pop. CONCLUSION: Long-term exposure to welding gases and fumes reduced flows in small airways of welders without asbestosis.

Adult↗

PubMed1981

Welding processes and ocular hazards and protection.

There are approximately 60 different forms of welding, but only six of these are commonly used. Shielded metal-arc or stick welding, gas metal-arc welding, and oxyacetylene welding are the most frequently used. All produce ultraviolet, visible, and infrared radiation at damaging levels. Conventional glass welding shields contain ultraviolet, visible, and infrared absorbers. Infrared absorbers, however, cause heating and secondary re-radiation. New polycarbonate lenses offer greater impact resistance, and have less tendency to welding spatter. Early abrasion-resistant and reflective coatings on plastics were ineffective. Thin layers of gold with proprietary coatings provide cool reflection and surface resistance. Thermal monitoring of welding indicated that these new shields reduce temperature rises above the ambient by 150% to 175% compared to green glass filter plates without interfering with the welder's vision.

Eye Burns↗

PubMed2001

Electromyographic and discomfort analysis of confined-space shipyard welding processes.

This study examined muscle fatigue and discomfort in a confined-space welding operation at a shipyard. Surface electromyography (SEMG) was recorded from seven upper extremity and torso muscles of welders welding in a mock-up of the work environment. Following spectral transform of the SEMG data the percentage of the total signal power in the 10-30 Hz frequency band was compared over time during welding. For the conventional stick electrode welding process (SMAW) several muscles exhibited an increase in the percent of the total signal power in the low-frequency band. Fewer muscles exhibited this fatigue-related spectral density shift with a wire welding process (FCAW) the shipyard has considered adopting. This finding suggests that localized muscle fatigue may be reduced by a change to the wire welding process. Subjectively reported discomfort was generally low for both processes, but confirmed the finding that discomfort in the low back and shoulder regions is experienced in this welding operation.

Adult↗

PubMed2001

Corrosion behavior of a welded stainless-steel orthopedic implant.

The corrosion behavior of combinations of materials used in an orthopedic implant: the spherical part (forged or forged and annealed) constituting the head, the weld (tungsten inert gas (TIG) or electron beam (EB) techniques), and the cylindrical part (annealed) constituting the shaft of a femoral prosthesis - has been investigated. Open-circuit potentials, potentiodynamic curves, Tafel slope, mixed potential theory and susceptibility to intergranular attack are electrochemical and chemical procedures selected for this work. Electrochemical measurements using a microelectrode have been made in the following zones: spherical part, cylindrical part, weld, and weld/sphere, and weld/shaft interfaces. To detect intergranular attack, the Strauss test has been used. At the interfaces, corrosion currents, measured (Icorr) and predicted (Icouple) are low, in the order of the pico- to nanoampere. The electrochemical behavior of the electron beam (EB) weld is better than that of the tungsten inert gas (TIG). Welds at interfaces can behave either anodically or cathodically. It is better if welds, which are sensitive parts of the femoral prosthesis, behave cathodically. In this way, the risk of starting localized corrosion (pitting, crevice or intergranular corrosion) from a galvanic couple, remains low. From this point of view, the sample with the EB weld offers the best behavior. All the other samples containing a TIG type of weld exhibit a less favorable behavior. The mechanical treatments (forged, and forged and annealed) of the steel sphere did not show any difference in the corrosion behavior. No intergranular corrosion has been observed at the weld/steel interface for unsensitized samples. With sensitized samples, however, a TIG sample has exhibited some localized intergranular corrosion at a distance of 500 microm along the weld/stainless steel (sphere) interface.

Biocompatible Materials↗

PubMed2000

Assessment of exposure to manganese in welding operations during the assembly of heavy excavation machinery accessories.

Welder exposure to metals in various industrial sectors is poorly characterized. We had the opportunity to carry out an exploratory study to characterize manganese exposure in welding operations in a recently established Quebec factory that assembled accessories for heavy excavation machinery. Ten workers were sampled for total manganese for at least two consecutive days out of three followed by two consecutive days for respirable manganese (with a size selective sampler with a median cut-off of 4 microns), during a typical week in the summer of 1998. Parts being welded were characterized as large or small. Small parts were those being welded on tables during subassembly. Workers were divided into two groups according to the parts they were welding. Seventy-eight percent of the total manganese exposure levels of welding operations during the assembly of large accessories of heavy excavation machinery exceeded the manganese American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) of 0.20 mg/m3 (GM 0.24 mg/m3, n = 14) while none exceeded the TLV during the assembly of small pieces (GM 0.06 mg/m3, n = 8). Welding operations during the assembly of large heavy excavation machinery accessories may pose a significant health hazard. Considering the importance of task-related variables affecting exposure among workers, further studies are needed to better characterize exposure determinants of welding operations during the assembly of heavy excavation machinery accessories.

Adult↗

PubMed2002

Exposure to cyclic anhydrides in welding: a new allergen-chlorendic anhydride.

Respiratory effects associated with welding fumes have been manifested in welders as occupational asthma. Previous studies have concerned mainly the effects of metal fume exposure, although it has also been suggested that asthma may develop as a result of exposure to contaminants generated from painted metals. To determine whether welding fumes contain irritating and sensitizing anhydrides, air samples were collected during the repair welding of forest harvesters, which were painted with chlorinated polyester paint. Samples were collected with an assembly of a spiral glass trap inserted between a filter holder with a Teflon filter and a Tenax sampling tube. Sample analyses were with GC-MS and GC-ECD. Sensitizing anhydrides released from the paint into the air were primarily chlorendic anhydride (<2-44 microg/m(3)) and phthalic anhydride (11-21 microg/m(3)). Hydrogen chloride (HCl) and hexachlorocyclopentadiene were also found. Airborne HCl was measured with Dräger tubes. Since paint films are electrical insulators, the film around the welding seam was removed before arc welding. Removal of paint with an abrasive wheel caused the least exposure to HCl (<0.5 ppm) in contrast to burning with a gas fuel torch, (HCl approximately 5 ppm). HCl exposure was the highest (<0.5-20 ppm) during welding. It is recommended that dry paint coating be removed from an area around the seam with an abrasive wheel, not by burning, before welding.

Acetic Anhydrides↗

PubMed2003

Emission of dust and gases in tubular cored wire welding of steel.

The emission of dusts and gases, which are generated during tubular cored wire welding and which are hazardous to health and the environment, were studied. Tests included various kinds of tubular electrode wires used for welding steel, that is, rutile flux cored wires, basic flux cored wires, and metal cored wires for welding unalloyed, low-alloy, and high-alloy steels as well as self-shielded flux cored wires used for welding low-alloy steels. The research results make it possible to assess the influence of the type of wire and welding conditions on the emission volume and to compare chemical hazards generated during tubular cored wire welding with those typical for other arc welding processes.

Air Pollutants, Occupational↗

PubMed1983

Retention and clearance of stainless steel shieldgas welding fumes in rat lungs.

The use of metal inert gas (MIG) stainless steel (SS) welding techniques is rapidly increasing. The possible health hazards of MIG/SS welding fumes are not known; more attention has been paid to manual metal arc (MMA) welding. In this study, 52 male Wistar rats were exposed to MIG/SS welding fumes generated by an automatic welding device for "nose only" exposure. For the retention study, the duration of exposure was one hour per workday for 1,2,3, and 4 weeks. For the clearance study, the duration was 4 weeks, and the follow-up period was 106 days. The retention and clearance of the alloyed metals of SS (chromium (Cr), manganese (Mn), nickel (Ni] and iron were studied in the rats' lungs, and the results were compared with the corresponding results of MMA/SS welding. The multielement chemical analysis was made using instrumental neutron activation analysis (INAA); the concentration of exogeneous iron (Feex) was determined by a magnetic measuring method. Feex and Cr were retained in the ratio expected; Mn, Ni and total Fe were retained slower than expected. The total Fe did not clear at all even though Feex cleared with the half-time of 50 d which corresponded well with that of pure magnetite. The accumulation of Cr in the lungs was very high: it cleared with the half-time of 240 d. The clearance patterns of Mn and Ni were very similar. They followed a double exponential model with half-times of 2 d and 125 d for Mn, and 3 d and 85 d for Ni. The results indicated that even though the retention patterns for MMA and MIG welding fumes were very similar, the clearances differed very much.

Animals↗

PubMed2003

Health effects of welding.

Many of the epidemiology studies performed are difficult to compare because of differences in worker populations, industrial settings, welding techniques, duration of exposure, and other occupational exposures besides welding fumes. Some studies were conducted in carefully controlled work environments, others during actual workplace conditions, and some in laboratories. Epidemiology studies have shown that a large number of welders experience some type of respiratory illness. Respiratory effects seen in full-time welders have included bronchitis, airway irritation, lung function changes, and a possible increase in the incidence of lung cancer. Pulmonary infections are increased in terms of severity, duration, and frequency among welders. Although epidemiological studies have demonstrated an increase in pulmonary illness after exposure to welding fumes, little information of the causality, dose-response, and possible underlying mechanisms regarding the inhalation of welding fumes exists. Even less information is available about the neurological, reproductive, and dermal effects after welding fume exposure. Moreover, carcinogenicity and short-term and long-term toxicology studies of welding fumes in animals are lacing or incomplete. Therefore, an understanding of possible adverse health effects of exposure to welding fumes is essential to risk assessment and the development of prevention strategies and will impact a large population of workers.

Air Pollutants, Occupational↗

PubMed1993

Relation between various chromium compounds and some other elements in fumes from manual metal arc stainless steel welding.

For the years 1987-1990 160 individual samples of manual metal arc stainless steel (MMA/SS) welding fumes from the breathing zone of welders in four industrial plants were collected. Concentrations of soluble and insoluble chromium (Cr) III and Cr VI compounds as well as of some other welding fume elements (Fe, Mn, Ni, F) were determined. Concentration of welding fumes in the breathing zone ranged from 0.2 to 23.4 mg/m3. Total Cr amounted to 0.005-0.991 mg/m3 (including 0.005-0.842 mg/m3 Cr VI). Total Cr content of fumes varied from 0.1 to 7.4%. The distribution of particular Cr compounds was: 52.6% soluble Cr (including 50.7% Cr VI), 65.5% total Cr VI, and 11.4% insoluble Cr VI. The results obtained indicate that MMA/SS welding is a process that could be highly hazardous to human health. Evaluation of occupational exposure has shown that MMA/SS welders may exceed the admissible concentrations of soluble and insoluble Cr VI forms as well as of Mn and Ni. In the plants investigated the sum of the ratios of concentrations of particular welding fumes in the breathing zone of welders exceeded corresponding maximum allowable concentration values by 24 times (including 17 times for total Cr VI). Due to the variety and changeability of particular parameters occurring in the working environment, the composition of MMA/SS welding fumes (in the welder's breathing zone) is so variable that it is not possible to assess the exposure by means of one universal exposure indicator (maximum additive hygienic limit value). The evaluation should be based on the results of measurements of concentrations of particular elements in welding fumes.

Air↗

PubMed2005

Occupational asthma due to manual metal-arc welding of special stainless steels.

Occupational asthma (OA) can be induced by fumes of manual metal-arc welding on stainless steel. In recent years, the use of special stainless steels (SSS) with high chromium content has increased. This study presents two cases of OA caused by manual metal-arc welding on SSS. In both cases, the diagnosis of OA was based on respiratory symptoms, occupational exposure and positive findings in the specific challenge tests. In the first case, a 46-yr-old welder had experienced severe dyspnoea while welding SSS (SMO steel), but not in other situations. Challenge tests with both mild steel and stainless steel using a common electrode were negative. Welding SSS with a special electrode caused a delayed 37% drop in forced expiratory volume in one second (FEV1). In the second case, a 34-yr-old male had started to experience dyspnoea during the past few years, while welding especially SSS (Duplex steel). The workplace peak expiratory flow monitoring was suggestive of OA. Challenge tests with both mild steel and stainless steel using a common electrode did not cause bronchial obstruction. Welding SSS with a special electrode caused a delayed 31% drop in FEV1. In conclusion, exposure to manual metal-arc welding fumes of special stainless steel should be considered as a new cause of occupational asthma.

Adult↗

PubMed2004

Gene-expression profiling using suppression-subtractive hybridization and cDNA microarray in rat mononuclear cells in response to welding-fume exposure.

Welders with radiographic pneumoconiosis abnormalities have shown a gradual clearing of the X-ray identified effects following removal from exposure. In some cases, the pulmonary fibrosis associated with welding fumes appears in a more severe form in welders. Accordingly, for the early detection of welding-fume-exposure-induced pulmonary fibrosis, the gene expression profiles of peripheral mononuclear cells from rats exposed to welding fumes were studied using suppression-subtractive hybridization (SSH) and a cDNA microarray. As such, Sprague-Dawley rats were exposed to a stainless steel arc welding fume for 2 h/day in an inhalation chamber with a 1107.5 +/- 2.6 mg/m3 concentration of total suspended particulate (TSP) for 30 days. Thereafter, the total RNA was extracted from the peripheral blood mononuclear cells, the cDNA synthesized from the total RNA using the SMART PCR cDNA method, and SSH performed to select the welding-fume-exposure-regulated genes. The cDNAs identified by the SSH were then cloned into a plasmid miniprep, sequenced and the sequences analysed using the NCBI BLAST programme. In the SSH cloned cDNA microarray analysis, five genes were found to increase their expression by 1.9-fold or more, including Rgs 14, which plays an important function in cellular signal transduction pathways; meanwhile 36 genes remained the same and 30 genes decreased their expression by more than 59%, including genes associated with the immune response, transcription factors and tyrosine kinases. Among the 5200 genes analysed, 256 genes (5.1%) were found to increase their gene expression, while 742 genes (15%) decreased their gene expression in response to the welding-fume exposure when tested using a commercial 5.0k DNA microarray. Therefore, unlike exposure to other toxic substances, prolonged welding-fume exposure was found to substantially downregulate many genes.

Air Pollutants, Occupational↗

PubMedDate not supplied

Workplace exposure to submicron particle mass and number concentrations from manual arc welding of carbon steel.

Particle emissions from manual shielded metal arc welding of carbon steel were sampled in a typical industrial maintenance and metal fabrication workplace environment. Particle number measurements over the size range from 14 nm to 10 microm using a scanning mobility particle sizer and an optical particle counter showed that welding produced an approximately lognormal particle mode with a 120 nm count median and a geometric standard deviation of 2.07. This study produced welding particle number concentrations on the order of 2 x 10(5)/cm(3) in the building air 8.5 m away from the welding. Workplace exposure samples were below the current 8-hour American Conference of Governmental Industrial Hygienists mass concentration threshold limit value of 5 mg/m(3). Submicron particles comprised 80% of the total aerosol mass collected by a cascade impactor during welding. The concentration of larger particles was indistinguishable from indoor background. Microscopy showed that the welding emissions are dominated by clusters formed from <0.1 microm primary spheres. These data on the particles resulting from aerosol transformation by natural dilution inside an industrial building can be compared with laboratory-scale studies of welding particulate. The particle number characteristics observed in this study are significant because toxicological hypotheses suggest that number or surface area may be a better metric than mass when evaluating the health effects of fine particles.

Environmental Monitoring↗

PubMed2000

Construction of an exposure chamber for animals and its use for inhalation exposure to welding fumes and gases.

An inhalation exposure system, consisting of an inhalation chamber and an generating and feeding device for welding fumes and gases with a welding robot, was constructed and examined for its application to experimental toxicology for ventilatory responses of conscious rats to welding fumes and gases. The exposure system allowed an inhalation of fresh welding fumes and gases, and could supply airflow containing stable concentrations of fumes and ozone even the levels exceeding those corresponding occupational exposure limit values were supplied into the exposure chamber. The air temperature in the chamber was kept constant under rat's physiological conditions. Rats were exposed to fresh welding fumes and gases and examined for their ventilatory responses with a body plethysmograph in the chamber. A transient increase in breathing frequency with a concomitant decrease in the tidal volume was observed within several minutes immediately after the start of welding operation. The rapid, shallow breathing response disappears after repeated exposures, indicating rapid adaptation of this ventilatory response to inhalation of welding fumes and gases.

Adaptation, Physiological↗

PubMed2003

Metallurgical effects on titanium by laser welding on dental stone.

It is not known for certain that dental stone components influence titanium welding. In this study, we investigated metallurgical problems caused by laser welding on dental stones using wrought commercial pure (CP) titanium. A pulsed Nd:YAG laser irradiated a number of specimens' surfaces which were fixed on either a dental hard stone or a titanium plate. The metallurgical properties of the weld were evaluated using the Vickers hardness test, microstructure observation, fractured surface observation and quantitative analysis of oxygen and hydrogen. In the weld formed on the dental stone there was an increase in hardness, the existence of an acicular structure and a brittle fractured surface, and an increase in the oxygen and hydrogen concentrations compared with base metal. In the weld formed on the titanium plate, these changes were not observed. Therefore, it was demonstrated that laser welding on dental stones made the welds brittle.

Analysis of Variance↗

PubMed2001

Strategies for risk assessment and control in welding: challenges for developing countries.

Metal arc welding ranges from primitive (manual) to increasingly complex automated welding processes. Welding occupies 1% of the labour force in some industrialised countries and increasing knowledge of health risks, necessitating improved assessment strategies and controls have been identified by the International Institute of Welding (IIW), ILO, WHO and other authoritative bodies. Challenges for developing countries need to be addressed. For small scale production and repair work, predominantly by manual metal arc on mild steel, the focus in developing economies has correctly been on control of obvious physical and acute health affects. Development introduces more sophisticated processes and hazards. Work pieces of stainless steel and consumables with chromium, nickel and manganese constituents are used with increasingly complex semi-manual or automated systems involving variety of fluxes or gasses. Uncritical adoption of new welding technologies by developing countries potentiates future health problems. Control should be integral at the design stage, otherwise substantive detriments and later costs can ensue. Developing countries need particular guidance on selection of the optimised welding consumables and processes to minimise such detriments. The role of the IIW and the MFRU are described. Applications of occupational hygiene principals of prevention and control of welding fume at source by process modification are presented.

Air Pollutants, Occupational↗

PubMed2000

[Stress-corrosion test of laser welded ceramic alloys].

OBJECTIVE: The corrosion properties of dental material are very critical. This study is to investigate the corrosion properties of laser welded basemetalalloys. METHODS: The precise stainless rod molds had been made in size of phi 3 mm x 4 mm, with which 20 wax patterns were made. They were invested with inner investment (Bellavest) and outer investment (phosphate and gypsum). Then they were casted with CW-PA (Ni-Cr-Nb) alloys. All casted alloy rods were ultra-sonic washed in distilled water. Every two rods were contacted longitudinally by a special welding jig. Laser welding machine (DL-2002) was used to weld them at 305 V, 20 ms. The specimens were divided into 2 groups as following: 1. The group of stress-corrosion: 5 laser welded samples were subjected to the stress-corrosion test under 261.44 MPa in the 37 degrees C artificial saliva for 3 months in a special stress-corrosion test jig. After that, the ultimate tensile strength (UTS) was tested, the surface microcrack at the fusion zone (FZ), the heat affecting zone (HAZ) and the interface zone was observed with SEM (ARMY-1845, USA), the elements were also analyzed with EPMA (ARMY-1845, USA) at the fusion zone (FZ), the parent metal zone and the interface zone. 2. The other 5 laser welded samples were made as the controlled group. No special treatment were done to them, and the UTS was also tested, the surface of the micro crack and the elements at the FZ, the HAZ, parent metal zone and the interface zone were observed and analyzed with SEM, EPMA as well. RESULTS: The study showed us that the UTS of the stress-corrosion group was 502.48 +/- 12.49 MPa, while that of the controlled group was 446.05 +/- 82.50 MPa, there was no significant difference (P > 0.05). There was no microcrack on any sample's surface at the FZ, the HAZ and the interface zone. The main elements of the FZ were Ni(56.63%), Cr(19.36%), Nb (6.57%), Si(6.01%), Al(0.32%) and Mo(11.11%), while the elements of the parent metal zone were Ni(60.77%), Cr (20.59%), Nb(5.03%), Si(3.95%), Al(0.37%) and Mo(9.29%) respectively. CONCLUSION: The results suggest that the corrosion properties of laser welded alloys are excellent.

Corrosion↗