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Showing papers on "Shielded metal arc welding published in 1994"


Book
24 Jan 1994
TL;DR: Control of Microstructures and Properties in Steel Arc Welds as discussed by the authors provides an overview of the most recent developments in welding metallurgy and illustrates how modern theories are capable of predicting the microstructure and properties of these joints.
Abstract: Control of Microstructures and Properties in Steel Arc Welds provides an overview of the most recent developments in welding metallurgy. Topics discussed include common welding processes, the thermal cycle during welding, defects that may occur during the welding process, the metallurgy of the material, metallurgical processes in the heat-affected zone and the fused metal, and the relationship between microstructures and mechanical properties. The book's final chapter presents examples of welded joints, illustrating how modern theories are capable of predicting the microstructure and properties of these joints. This book is an excellent resource for welding engineers, metallurgists, materials scientists, and others interested in the subject.

89 citations


Patent
16 Aug 1994
TL;DR: In this article, a shielding gas is proposed which in addition to argon and/or helium comprises a carbon dioxide fraction or an oxygen fraction or a fraction of a mixture of these gases of from 0.01 to 0.7 % by volume.
Abstract: The invention relates to a shielding gas arc welding method for non-ferrous materials, in particular aluminium materials and aluminium alloys, for example AlSi, which method comprises the continuous supply, during welding operation, of a shielding gas containing argon and/or helium to the weld spot (welding point) adjacent to the electrode. According to the invention, a shielding gas is proposed which in addition to argon and/or helium comprises a carbon dioxide fraction or an oxygen fraction or a fraction of a mixture of these gases of from 0.01 to 0.7 % by volume, preferably from 0.01 to 0.1 % by volume (from 100 to 7000 or 1000 ppm, respectively).

24 citations


Journal ArticleDOI
TL;DR: In this article, the air concentrations of total solid aerosols were determined gravimetrically, and total amounts of metal compounds (i.e., nickel (Ni), chromium (Cr), iron, and manganese) and water-soluble hexavalent chromium were determined.
Abstract: Tests of air concentrations of solid aerosols during manual metal arc (MMA) welding on stainless steel were carried out at three working sites. In addition to a detailed description of the work situation, samples of welding fume were collected from both the breathing zone and the general air. Air concentrations of total solid aerosols were determined gravimetrically. Total amounts of metal compounds (i.e., nickel (Ni), chromium (Cr), iron, and manganese) and water-soluble hexavalent chromium (CrVI), were determined. The mean fume concentrations during MMA welding were 5.4 mg/m3 inside a ship section, 3.0 mg/m3 at an offshore module, and 2.0 mg/m3in welding shops. The highest concentrations of CrVI were found during MMA welding inside the ship section, with a mean concentration of 140 µg/m3 (range 4–640 µg/m3). CrVIcomprised about 50% of the total Cr by weight. Though the base material contained approximately 20% Cr and 10% Ni, the Cr and Ni contents (µg/mg welding fumes) varied greatly among the different...

19 citations


Journal ArticleDOI
TL;DR: In this paper, an ultrasonic vibration source used has eight 15-kHz bolt-clamped Langevin-type lead-zircon-titanate (PZT) transducers of 60 mm diameter and is driven by a 50kW static induction thyristor power amplifier.
Abstract: Characteristics of ultrasonic butt welding of the same and of different metal plates are studied. The ultrasonic vibration source used has eight 15-kHz bolt-clamped Langevin-type lead-zircon-titanate (PZT) transducers of 60 mm diameter and is driven by a 50-kW static induction thyristor power amplifier. Welding specimens of aluminum, copper and steel plates of 6 mm thickness are successfully joined end-to-end with weld strength almost equal to that of an aluminum specimen. The input power required for aluminum, aluminum and copper, and aluminum and steel plates are about 5 kW/cm2, 5.5 kW/cm2 and 3.5 kW/cm2, respectively. The measured temperature rise at the specimen side surface and elongation of the welded specimen during a tensile test correspond to weld strength. The hardness distributions along the weldment of welded specimens are measured and the maximum temperature rise in an aluminum welding specimen is estimated to be over 480°C from the reduction of hardness at a welding specimen surface.

9 citations


Patent
30 Jun 1994
TL;DR: In this paper, a carbon dioxide laser beam welding of aluminium alloys using a shielding gas (mixt.) directed through shielding and working gas nozzles for plasma control at the welding point at the workpiece surface is described.
Abstract: In the carbon dioxide laser beam welding of aluminium alloys using a shielding gas (mixt.) directed through shielding and working gas nozzles for plasma control at the welding point at the workpiece surface, the novelty is that the shielding gas consists of pure Ne or a gas mixt. of Ar, He, N2, CO2, H2 and O2 with more than 25 vol.% pure Ne.The laser is a longitudinal flow, h.f. excited, high power carbon dioxide laser, the welding beam of which is focussed by a cooled parabolic mirror.

9 citations



Patent
11 Apr 1994
TL;DR: In this article, a method and apparatus for preventing catastrophic melting of the contact be in continuously-fed consumable electrode arc welding due to wire feed interruptions by monitoring the movement of the wire electrode with a high frequency sensor such as all optical encoder having a resolution on the order of <0.1 second was proposed.
Abstract: A method and apparatus for preventing catastrophic melting of the contact be in continuously-fed consumable electrode arc welding due to wire feed interruptions by monitoring the movement of the wire electrode with a high frequency sensor such as all optical encoder having a resolution on the order of <0.1 second and switching off the power to the welding apparatus if the wire electrode speed falls below a predetermined threshold.

8 citations


Patent
18 Aug 1994
TL;DR: In this paper, an electric arc is formed between the electrode and the workpiece, and a constant voltage is applied to form the arc, which is screened with a protective gas contg.
Abstract: Protective gas welding uses an electric arc formed between electrode and workpiece. A constant voltage is applied to form an electric arc. The electrode is inserted through a contact tube into the electric arc and a required distance between contact tube and workpiece is maintained. The novelty is that a smaller contact tube space (compared to the usual distance on welding with a rotating electric arc) of around 10-30%, and a lower voltage (compared to the usual voltage on welding with a rotating electric arc) of around 20-40% are used. The rotation electric arc produced is screened with a protective gas contg. 1-5 (vol.%) O2, 14-34 He and 65-85 Ar or 1-5 O2, 14-34 CO2 and 65-85 Ar.

7 citations


Patent
02 Jun 1994
TL;DR: A shielding gas mixture for electric arc welding includes at least 40% by volume of neon which acts as an ozone suppressor as discussed by the authors, which is the minimum required by the International Organization for Standardization.
Abstract: of EP0604014A shielding gas mixture for electric arc welding includes at least 40% by volume of neon which acts as an ozone suppressor.

4 citations


Journal ArticleDOI
TL;DR: In this article, the influence of extremely low levels of oxygen and nitrogen partial pressure, Po2 and PN2 in TIG welding atmospheres on the welding phenomenon and properties of welds of zirconium alloy tubing was investigated.
Abstract: The purpose of this study is to investigate the influence of extremely low levels of oxygen and nitrogen partial pressure, Po2 and PN2 in TIG welding atmospheres on the welding phenomenon and properties of welds of zirconium alloy tubing.In TIG welding of Zircaloy-2 tubing in welding atmospheres with various Po2 and PN2, the arc voltages were measured and the properties of welds (surface discoloration, oxygen and nitrogen contents) were examined.Although definite arc voltage change is not observed at welding in ≤ 4.1 Pa of Po2, a significant arc voltage drop with increase of PN2 is observed at welding in 0.4-16.9 Pa of PN2, and oxygen appears to inhibit this arc voltage drop.The surface of weld metal and heat affected zone (HAZ) in the atmosphere of 0.1 Pa of Po2 and 0.4 Pa of PN2 remains bright.The surface discoloration is observable slightly on weld metal and HAZ in the atmosphere of 1.1 Pa of Po2, and with increase of Po2 the initial straw color becomes darker until it gets partially blue.No surface discoloration is observable on weld metals and HAZ in the atmospheres of PN2 - 16.9 Pa with 0.1 Pa of Po2.The nitrogen content [N] in the weld metal increases linearly with increase of √PN2 and the increasing rate of [N] in inner part of weld metal is lower than that of [N] in outer part.The oxygen content [O] in the weld metal increases linearly with increase of √Po2 and shows same relations as [N], although the values of [0] in the weld metals fluctuate more than [N].

4 citations


Journal ArticleDOI
TL;DR: In this article, the importance of weld discontinuities in strain controlled low cycle fatigue (LCF) behavior of 304 stainless steel (SS) welds was evaluated in the presence of porosity and slag inclusions.
Abstract: Detailed investigations have been performed for assessing the importance of weld discontinuities in strain controlled low cycle fatigue (LCF) behavior of 308 stainless steel (SS) welds. The LCF behavior of 308 SS welds containing defects was compared with that of type 304 SS base material and 308 SS sound weld metal. Weld pads were prepared by shielded metal arc welding process. Porosity and slag inclusions were introduced deliberately into the weld metal by grossly exaggerating the conditions normally causing such defects. Total axial strain controlled LCF tests have been conducted in air at 823 K on type 304 SS base and 308 SS sound weld metal employing strain amplitudes in the range from ±0.25 to ±0.8 percent. A single strain amplitude of ±0.25 percent was used for all the tests conducted on weld samples containing defects. The results indicated that the base material undergoes cyclic hardening whereas sound and defective welds experience cyclic softening. Base metal showed higher fatigue life than sound weld metal at all strain amplitudes. The presence of porosity and slag inclusions in the weld metal led to significant reduction in life. Porosity on the specimen surface has been found to be particularly harmful and caused a reduction in life by a factor of seven relative to sound weld metal. Defect combination of porosity and slag inclusions was found to be more deleterious than the case when either the slag inclusions or porosity was present alone. Discontinuties acted as crack initiation sites and also enhanced crack propagation. The LCF properties of weld samples containing discontinuities have been correlated with the damage and fracture behavior.

Patent
06 Jul 1994
TL;DR: In this article, the air blow adapter was used to make the air for removing spatter to hardly leak from a torch when welding, and the welding wire was fed continuously with a welding wire.
Abstract: PURPOSE:To make the air for removing spatter to hardly leak from a torch when welding. CONSTITUTION:A torch nozzle 21 is used to execute the arc welding in a shield gas atmosphere with a welding wire 24 fed continuously, and it is provided mainly with a wire supporting part 23, a nozzle body 23, a gas feeding part and an air blow adapter 24. The wire supporting part 23 extends in one direction and supports the welding wire 26. The nozzle body 22 is arranged on the circumference of the wire supporting body 23 in an interval. The gas feeding part feeds a gas for removing spatter between the wire supporting part 23 and the nozzle body 22. The air blow adapter 24 feeds the shield gas between the wire supporting part 23 and the nozzle body 22 from the outer circumferential side of the nozzle body 22 when welding and after removing spatter.

Journal ArticleDOI
TL;DR: In this paper, the insertion metal of a 6061 aluminum alloy to a S45C carbon steel was used for friction welding, where the insert metal turned into a thin (20-30μm) and homogeneous layer at the weld interface, the maximum joint efficiency of tensile strength was obtained and was about 95%.
Abstract: Friction welding of a 6061 aluminum alloy to a S45C carbon steel was carried out using the insert metal of a 1050 aluminum. Optimum thickness of the insert metal, friction pressure, forge pressure, friction time and rotational speed of welding conditions were determined as 4mm, 90MPa, 300MPa, 1.2s and 2250rpm, respectively. When the insert metal turned into a thin (20-30μm) and homogeneous layer at the weld interface, the maximum joint efficiency of tensile strength was obtained and was about 95%. Successful welds were obtained by taking each optimum welding condition even if the thickness of the insert metal was varied from 2 to 6mm.

Journal ArticleDOI
TL;DR: In this paper, a narrow-gap AC-MIG welding process has been developed to ensure high efficiency in processing and metallurgically high-quality welds in welding of 980 MPa high-strength steels for penstocks (pressure shafts) in hydroelectric power stations.
Abstract: Summary Previous papers have shown the high‐current AC‐MIG welding process to be superior to the conventional DC‐MIG process in terms of welding efficiency and welded joint performance. The authors have used the AC‐MIG process to weld heavy‐gauge steel plates at a tensile strength level of 980 MPa. Weld metal with a very low hydrogen content is obtained by the newly developed process, resulting in a reduced preheating temperature during welding of high‐strength steels. The AC‐MIG process also produces an arc climbing effect with electrode negative polarity ‐ a desirable effect in narrow‐gap welding. AC‐MIG weld metal further contains low oxygen, conferring high toughness. As a result, a narrow‐gap AC‐MIG welding process has been developed to ensure high efficiency in processing and metallurgically high‐quality welds in welding of 980 MPa high‐strength steels for penstocks (pressure shafts) in hydroelectric power stations. Welding wires with chemical compositions satisfying suitable strength and toughness ...

31 Dec 1994
TL;DR: In this paper, the effects of titanium and nitrogen contents on the C-Mn shielded metal arc weld (SMAW) metal properties have been studied and the results show that an optimum level of titanium (30 ppm) addition enhanced the formation of acicular ferrite and hence improved the Charpy-V impact and CTOD toughness values.
Abstract: A The effects of titanium and nitrogen contents on the C-Mn shielded metal arc weld (SMAW) metal properties have been studied. There are still uncertainties concerning the exact role of each element and interactions between these elements with respect to the weld metal microstructure and fracture toughness properties. Therefore, systematic additions of titanium (in the range of 5 to 450 ppm) and nitrogen (80, 160 and 240 ppm) were made to obtain various amounts of acicular ferrite and different microstructures which lead to varying fracture behaviors. The research program covers the determination of tensile properties, Charpy-V notch transition curves and crack tip opening displacement (CTOD) fracture toughness values of different weld deposits containing three different nitrogen contents. The results show that an optimum level of titanium (30 ppm) addition enhanced the formation of acicular ferrite and hence improved the Charpy-V impact and CTOD toughness values. An increase of nitrogen increased the strength but caused a drastic deterioration of both Charpy-V impact and CTOD toughness values at the upper shelf and transition regime.



Journal ArticleDOI
TL;DR: In this article, the authors examined the influence of the heat affected zone as well as load ratio on the fatigue crack growth rate and fatigue threshold in a structural steel weldment of ASTM grade A514.
Abstract: Fatigue crack growth behavior of a structural steel weldment was studied in room temperature ambient atmosphere. The investigation also examined the influence of the heat affected zone on the fatigue threshold and the fatigue crack growth rate. The influence of load ratio on the fatigue threshold and the fatigue crack growth rate was also studied. Micromechanism of crack growth process in the threshold region was also investigated. Compact tension specimens were prepared from ASTM grade A514 structural steel in such a way that the cracks propagated through the heat affected zone, base metal and weldment. Welding was done by the shielded metal arc welding (SMAW) process. The results of the present investigation indicate that the fatigue crack growth rate was lower at all load ratios in the linear region when the crack propagated through the base metal. The fatigue threshold was highest in these specimens. The threshold was found to decrease with an increase in load ratio and a non-linear power law relationship was found to exist between the load ratio and the fatigue threshold. The crack growth process was found to be predominantly by striations. Extensive crack branching and secondary cracking were observed in high ΔΚ regions whereas crack branching was not generally observed in the threshold region. INTRODUCTION In recent years there has been significant interest in crack propagation and in fatigue threshold /1,2/. Design of structural components against fatigue failure on the basis of fatigue threshold has nowadays become an accepted practice. Fatigue threshold, AKth, defines the stress intensity factor below which the pre-existing cracks or flaws present in a structural component will not propagate in cyclic loading situations (Fig. 1). Hence, structural components designed on the basis of fatigue threshold are expected to have infinite lives or at least last for a very long period of time. Numerous variables /3-9/ can influence the fatigue crack growth rate and threshold parameter. Among these the influence of microstructure and load ratio are most important from a practical point of view. Even though in the past many studies 710-21/ have examined the influence of load ratio and microstructure on fatigue crack growth rate and fatigue threshold in a wide variety of materials, relatively little information is available on the influence of load ratio and microstructure on fatigue crack growth rate and the fatigue threshold in the case of structural steel weldments. The present investigation examined the influence of the heat affected zone as well as load ratio on the fatigue crack growth rate and fatigue threshold in a structural steel weldment of ASTM grade A514. The welding was done using the shielded metal arc welding process (SMAW).




Journal ArticleDOI
TL;DR: In this article, the effects of electron beam welding cooling rate and PWHT conditions on weld metal toughness were investigated and the mechanism of toughness changes metallographically, and it was clarified that in order to increase the toughness of electronbeam weld metal for low alloy steel, the structure should be lower bainite by increasing welding cooling and a temper parameter of about 19 should be selected as the key for PWHT.
Abstract: Electron beam welding is featured in (1) capability of welding thick plates by a single pass, (2) less weld distortions, and it has been applied to welding of heavy section large structures.But, when a heavy section low alloy steel plate is welded, the weld metal toughness deteriorates. Therefore, it is very important to increase the weld metal toughness.Weld metal toughness is affected by weld metal structure and carbide precipitation.Then we have investigated the effects of the electron beam welding cooling rate and PWHT conditions on weld metal toughness and we have also studied the mechanism of toughness changes metallographically. Consequently, it has been clarified that in order to increase the toughness of electron beam weld metal for low alloy steel, the structure should be lower bainite by increasing welding cooling rate and a temper parameter of about 19 should be selected as the key for PWHT.

Journal ArticleDOI
TL;DR: In this paper, the authors performed creep rupture tests under uniaxial loading condition on 2.25Cr-1Mo steel and its welded joints, namely Induction Pressure Welded (IPW) and Manual Metal Arc Welded(MMAW) joints, at test temperatures of 550 and 600°C and stresses of 110-180 MPa.

Patent
21 Jun 1994
TL;DR: In this article, the welding operation without misoperation through correct generation and extinction of arc by operating a coated electrode by judging the welding condition based on the current and the voltage values of the main circuit.
Abstract: PURPOSE:To execute the welding operation without misoperation through correct generation and extinction of arc by operating a coated electrode by judging the welding condition based on the current and the voltage values of the main circuit. CONSTITUTION:When an automatic switching device 1 is started, the voltage between an electrode 44 in contact with a contact rod 40 and a base metal 42 reaches the arc voltage, and the arc current runs. The voltage and the current are detected by a voltage/current sensor 17, an arc extinction detection switching circuit 25 stores the changes of the voltage and the current, and the welding condition is monitored. When the arc of the electrode 44 on the weld seam is extinguished, the voltage of the welding circuit 7 reaches the no-load voltage of a welding machine 37, and the current becomes zero. A contact switching motor 29 is driven by the signal from the sensor 17, and a first welding circuit contact 34a is switched to a second welding circuit contact 34b. In this case, a trigger pulse circuit 20 is operated, and the main circuit switch 19 is operated to evergize the welding circuit 7 and a new electrode 44 for arc generation.

Journal ArticleDOI
TL;DR: In this article, the effects of extremely low oxygen and nitrogen partial pressures, PO2 and PN2, in TIG welding atmospheres on the welding phenomena and properties of welds in zirconium alloy tubing were investigated.
Abstract: Summary The purpose of this study is to investigate the effects of extremely low oxygen and nitrogen partial pressures, PO2 and PN2, in TIG welding atmospheres on the welding phenomena and properties of welds in zirconium alloy tubing. During TIG welding of Zircaloy‐2 tubing in welding atmospheres with various PO2 and PN2, the arc voltages were measured, and the properties of the welds (surface discoloration, oxygen and nitrogen contents) were examined. Although no definite arc change is found at PO2 < 4.1 Pa, a significant arc voltage drop occurs with an increasing PN2 during welding at PN2 = 0.4–16.9 Pa, so that oxygen appears to inhibit this arc voltage drop. The weld metal surface and heat affected zone (HAZ) in the PO2 = 0.1 Pa and PN2 = 0.4 Pa welding atmospheres remains bright. Some surface discoloration is found on the weld metal and HAZ in the Po2 = 1.1 Pa welding atmosphere, the initial straw colour becoming darker to a partially blue colour with an increasing PO2. No surface discoloration is fo...


Patent
02 Sep 1994
TL;DR: In this paper, an electric soldering device (10) uses a welding filler supplied in a wet environment (12), and the welding filler may be supplied to the welding site (13) in a water-free environment that extends up to the site.
Abstract: An electric soldering device (10) uses a welding filler (11) supplied in a wet environment (12). The welding filler (11) may be supplied to the welding site (13) in a water-free environment that extends up to the welding site (13).

Patent
11 May 1994
TL;DR: A non-alloyed basic cored wire for electric arc welding with gas shielding, comprising an internally hollow filiform metal support filled with a mixture containing weld material, slagging agents and deoxidants, characterised in that said mixture has the following chemical specification by weight: Mntot 15-19 %; Sitot 11,5-14,5 %; Fetot 34-40 %; CaO 18-22 %; MgO 6-8 %; Al2O3 5-7 %.
Abstract: not available for EP0666786Abstract of corresponding document: WO9409941A non-alloyed basic cored wire for electric arc welding with gas shielding, comprising an internally hollow filiform metal support filled with a mixture containing weld material, slagging agents and deoxidants, characterised in that said mixture has the following chemical specification by weight: Mntot 15-19 %; Sitot 11,5-14,5 %; Fetot 34-40 %; CaO 18-22 %; MgO 6-8 %; Al2O3 5-7 %.