Search

During EB welding of nickel-base superalloys flaws may occur under unfavorable conditions. In welds of Waspaloy “Cameron” flaws appeared in the heat-affected zone, while flaws in the weld seam were observed in the case of Inconel 713 “Nimocast.” The flaws in Waspaloy could not be detected by conventional NDT methods because of their position at the root of the weld. Therefore, for direct observation of flaw formation in these alloys, acoustic emission measurements were made during EB welding of these alloys. Two different types of acoustic emission were found. In nickel-base superalloys and in austenitic steel background noise occurs as so-called burst signals which follow one another at short time intervals; these signals correlate exactly with markings (grooves) on the surface of the weld seam. This type of acoustic emission depends on the local heat transfer (beam current per unit time and area). Apparently this background noise is caused by weld solidification. Flaw formation, on the other hand, is indicated by single burst signals having a much higher amplitude than those due to solidification. In the case of Waspaloy this second type of acoustic emission was observed only at fairly high speeds of welding (i.e., higher than 25 mm/sec). This result is consistent with evaluations of micrographs.

A quantitative study has been made of the effects of welding and material variables on porosity formation in the tungsten inert gas arc welding of copper. It has been confirmed that porosity can result from the occurrence of the steam reaction in the weldpool. The extent of this porosity is increased by increasing water vapour content of the arc atmosphere, increasing oxygen content of the base material, and decreasing welding speed. All three factors interact so that the threshold porosity levelfor eachfactor is strongly influenced by the value of the other two factors. The steam reaction has been investigated during arc melting by determining the oxygen and hydrogen contents of copper buttons which have reacted with argon–water vapour atmospheres. It is shown that hydrogen ispreferentially absorbed from the arc following dissociation of the water vapour. The final levels of the oxygen and hydrogen in the button correspond to the equilibrium for the steam reaction in a high-temperature zone under...

Describes measurements of the temperature distribution and the composition of the plasma-MIG arc system using optical spectroscopy. It is found that the central part of the arc contains the elements Fe, Mn, Cu, Ca and Ar at a temperature of about 7000K. The outer regions of the arc show only argon spectral lines and have much higher temperature value ( approximately=13000K). From these measurements a number of conclusions can be drawn about the physical properties of the plasma-MIG welding arc. The most important conclusion is that only a very small part of the wire current flows through the bright inner arc.

Heat content of the droplet detaching from the wire tip in MIG arc welding is measured calorimetrically under a special electrodes arrangement shown in Fig. 1, 2.Ozawa already reported on this problem and we tested further to understand the temperature characteristics for wires of low and high conductivities.Fig. 4 shows the results for copper and aluminum wires and Fig. 6 those for steel and stainless steel wires. For aluminum wire, the heat content Qm expressed in cal/g increases as the current is increased in globular transfer range and reaches a nearly constant high value. The temperature is estimated to be nearly equal to the boiling point for the spray transfer range.The characteristic curve of Qm-I under a constant wire extension for steel or stainless steel wire (Fig. 6) is shown in Fig. 7. Qm increases as the current I is increased for globular transfer range, AB, which is similar to that of aluminum shown in Fig. 8. After reaching a maximum value, Qm decreases for further current increase (curve BCD).The decrease of Qm is related to the pencil-like forming of the wire tip, which is the well-known characteristic for wires of low thermal and electric conductivities, and this suggests that the droplet can detach more easily when the wire tip takes the pencil-like form. Qm-I curves in Fig. 6(a) can be explained clearly from the above mentioned idea. Fig. 8 shows a Qm-I curve for aluminum wire for an extraordinarily long wire extension, and the curve shows the same tendency as that of steel wire.Now we understand that the droplet temperature decreases to as low as the melting point of the wire material when the wire is preheated sufficiently by joule's loss, and it rises to as high as the boiling point when the joule's heating is negligible and the wire is heated abruptly by arc of sufficiently large current density.Figs. 9, 11 show the equivalent melting voltage calculated from Qm and the specific melting rate m (mg/Amp⋅sec) shown in Figs. 4-8. From these figures we can clearly estimate the joule's heating and the anode heating.

Powder-cutting method is currently in wide use with success for cutting stainless steel quickly. The use of this method, however, presents some difficulty with cutting and welding operation of 18-8 stainless steel where the heat affected zone within the temperature range of about 500 to 800°C. develops carbide precipitation which is liable to intergranular corrosion. On this account it become essential in manufacturing work to know the extent of influence exerted by heat on the power-cut stainless steel or whether additive heat effect would exist due to subsequent welding operation. Since the powder-cut edge has uneven surface and thick covering of oxide films, it also become necessary to determine to what extent the surface should be treated before welding.Research from which the results reported here were obtained was undertaken to get information in respect to the effect of heat in powder-cutting and welding on 18-8 stainless steel of 12 mm thickness and effect of surface treatment after cutting on its weldability. The followings summarize the results of the writer's tests and observations.(1) Heat-affected areas from powder-cutting is relatively very small as compared with that of welding.(2) When welding is done following the powder-cutting, the heat effect from the powder-cutting was not added to that produced by welding.(3) In The case of manual arc welding and submerged arc welding, the surface tseatment after powdercutting will have almost negligible effect on mechanical properties of the welded joint. Consequently, light grinding or shotblasting of the surface after hammering slugs is all that is necessary before welding.(4) In the case of inert gas metal arc welding, the slug at the joint will have considerable influence. In this case, the powder-cut surface should be cleaned with special attention, and preferably with machining.

The objective of this investigation was to establish the factors governing weldability and to determine their effects with sufficient quantitativeness to be able to predict cracking. A test was developed that permits variation of three factors deduced to be important—strain, maximum temperature, and cooling rate—so that welding conditions can be duplicated on a parent-metal specimen. Predictions of cracking during cooling of aluminum alloy panels containing 4.5 and 8 weight percent copper were made from results of this test and observed to be very accurate.

The plasma arc welding has a feature of giving deep penetrated weld bead, as reported on the welding of austenitic stainless steel plate. This feature is somewhat different from the conventional TIG arc welding.In the plasma arc welding of titanium plates (thickness 7-11 mm), sound welds are obtained with a careful shielding of weldments from the open air atmosphere. Metallurgical and mechanical tests are made with almost satisfactory results.From the view point of welding heat source, plasma arc has a property, resembles to linear heat source. Deformation and shrinkage of weldment by the plasma arc welding are thus far smaller than those by ordinary arc welding.These experimental results are described briefly in this article.

In this report, effects of rod-diameter, nozzle-diameter, acetylene-condition and.flame-type on usability of gas welding rod and mechanical properties of gas weld steels were investigated, using the welding rod III containing 1.37 % Mn.and 0.13 % Si and by the same way as the report 1.The results obtained are as follows:1. In case of thicker base plates, excellent welds were obtained by adopting comparatively large diameters of rod and nozzle.2. Bend test results of welded joints obtained by the use of genetator acetylene were little different from those by by the use of dissolved acetylene.3. When an extreme carburizing flame or an oxidizing flame, whose core-length was below about 8 mm in case of the nozzle number "500", was adopted, the bend test result of welded joint was bad.

This study was undertaken to assess the weld crack sensitivity of "R74S", which is a weldable Al-Zn-Mg alloy of medium strength.The experiments were conducted using an automatic MIG welding machine. 12mm thick sheet specimens of R74S in the T4 temper were welded with A5356WY, A5556WY and an Al-4%/Mg-1.5%Zn alloy as filler metals. 5083 sheet specimens in the O temper were used as control material.The assessment of weld crack sensitivity was made by Gapped-T-joint weld cracking test, in which the sensitivity was numerically expressed by the width of gap at crack tip. The data were statistically analyzed with repetitions, because scatter of the data was considerable.The results obtained are summarized as follows:(1) The data of the sensitivity followed the normal distribution when the tests were conducted with repetitions under the same conditions. The assessment, therefore, must be made by statistical analysis with repetitions because of the wide scatter of the data.(2) The sensitivity of R74S was approximately the same as that of 5083, though the former was very slightly higher than the latter. When 5083 and R74S as base metals were welded together with A5556WY as filler metal, the sensitivity was intermediate between the sensitivity of 5083-5083 welds and that of R74S-R74S welds.(3) The weld crack sensitivity was affected by the composition of the filler alloys. An Al-Mg-Zn alloy when used as filler metal to weld R74S resulted in higher sensitivity than A5556WY or A5356WY.It was concluded that Al-Mg alloys such as A5556WY and A5356WY were more desirable as filler metals to weld R74S than Al-Mg-Zn alloys due to lower sensitivity and easier welding operation.

(1952). Use of Thoriated Tungsten Electrodes in Inert Gas Shielded Arc Welding—Investigation of Potential Hazard. American Industrial Hygiene Association Quarterly: Vol. 13, No. 4, pp. 191-195.

In order to stabilize the arc in the automatic metallic arc welding, we manufactured a new apparatus to control the arc length.In this paper we report the function of this apparatus and some results obtained from its application to practice.

This paper discusses the butt welding of steel sheets by the carbon arc process. It explains first that autogenous welding is divided into two main classes, viz., gas and electric; that electric arc welding is divided into two classes, viz., metallic and carbon arc. Gas and metallic arc welding in general require beveling of plates for butt welds while carbon arc welding does not. The controlling variables in carbon arc welding are (1) amperes in the arc, (2) voltage across the arc, (3) magnetic field about the arc, (4) atmosphere about the arc, (5) speed of feed, and (6) filling-in material. Discussion is given of the effect of each of these variables of the resulting weld with special reference to the action of a magnetic field parallel to the direction of the arc upon the current in the arc and the effect of the atmosphere about the arc on the ductility of the resulting weld.

PERCUSSION welding is not new. Early work goes back beyond the beginning of the century, but little application has been made of it and only a meager amount of literature is available. However, this method has a real field of usefulness as the application described in this paper will show. The original Vang process wherein a capacitor charged to a high potential, often to several thousand volts, is discharged across the gap between parts as they approach each other under a propelling force, is a good general description of the method used. The arc so produced heats the abutting surfaces before they collide so that a very thin layer of metal is brought to welding temperature. The propelling force, while continuing to act, brings the parts together percussively and the weld is made. Little metal is heated and little heat penetrates the adjoining metal; therefore, the heat balance problem is greatly minimized and different metals weld together with little trouble. There is, however, the problem of protecting personnel from high voltage. Also, the two surfaces being welded must be insulated electrically from each other. This excludes the use of this process for joining the ends of the same piece of metal, as in making a ring.

We studied the shape of bead-i.e. penetration, width, hight of reinforcement, reinforced area, penetrated area and fused area-obtained by C. S. arc welding process. And this process was compared with various welding processes, i.e. argon arc, submerged arc and manual arc with two types of coated electrodes, about the items mentioned above and penetration ratio : penetration/width of bead.Moreover the electric energy needed to deposit unit length of bead was calculated, and the ratios of penetration, width of bead and fused area to the energy were compared.Next authors investigated the effects of oxygen added in the supplied gas in case of C. S. arc welding on the porosity of weld metal and the shape of bead.The results obtained are as follows.i) Penetration in case of C. S. arc welding is largest compared with those by other welding processes. It is 1.7 times of that by argon arc welding, 1.6 times of that by submerged arc welding and 2.2-3.8 times of those by manual arc weldings.ii) Penetration ratio in case of C. S. arc welding is largest among others, too.iii) In spite of the same proceeding rate of bead, width of bead by submerged arc welding is largest compared with C. S. and argon arc welding processes.iv) The electric energy needed to make the same length and penetration of bead is smallest in case of C. S. arc welding compared with others.v) With increase of oxygen content of supplied gas in case of C. S. arc welding, the penetration increases and width of bead decreases.vi) The limit of permissible addition of oxygen in supplied gas, below which the blow hole does not occur in bead, depends upon the degree of deoxidation of base metal and contents of deoxidizers of filler wire.

To understand the effect of surface materials on metallic arc welding electrodes, something must be known as regards the fundamental theory of arc heat distribution, arc vapor resistance, and similar matters which are modified by the presence of surface materials. The character of the arc may be changed by chemical and structural variations in the surface materials. Stability is one such arc characteristic. Two types of stability are recognized,?chemical and electrical. Surface materials have a significant influence on the brittleness or ductility of weld metal. They also can be used to control the arc type, four such types being recognized. The influence of surface materials on the heating of electrodes is another phase of the matter of practical significance. Surface materials may be employed to control both the operating characteristics of the electrode and the resultant weld properties. Among the operating characteristics might be mentioned stability and rate of melting. Among the weld properties are included freedomf rom blow-holes and tensile strength. These and other practical applications of a comprehensive knowledge of surface materials are cited in this paper.

1. High-alloyed porous steel can be welded by means of argon-arc welding, using infusible electrodes, and by means of arc welding in carbon dioxide, using fusible electrodes. Argon-arc welding of steel with a porosity exceeding 30–35% must be performed with an addition. Automatic or semiautomatic welding can be used in dependence on the configuration of the joints and the number of articles to be produced. 2. Austenite wire which secures an austenite-ferrite or a ferrite-austenite (nor more than 60% ferrite) microstructure in the seam metal (standard Sv-08Kh20N9G7T, Sv-08Kh20N10G6, Sv-10Kh20N15, or Sv-06Khl9N9T wire) can be used as the additional material in argon-arc welding and welding in carbon dioxide of porous ferrite and martensite steels. 3. The mechanical properties and the intercrystallite corrosion resistance of welded joints of porous steel Kh17N2 are satisfactory. High-temperature annealing (1200°C, 1 h) in a hydrogen medium with subsequent normalization promotes the reduction of oxide films and improves the intercrystallite corrosion resistance of the metal in the zone near the seam in welded joints.

Effect of the nitrogen partial pressures in the welding atmospheres of several gas mixtures and welding conditions on the nitrogen content and porosity of stainless steel weld metals were studied by using an arc atmosphere controlled chamber.The results were summarized as follows1. The nitrogen contents of weld metals decrease with increasing welding current.2. The anomalous nitrogen absorption into weld metal is observed at low arc atmospheric pressures.3. The existence of oxidizing gas in arc atmosphere such as oxygen or carbondioxide contributes greatly to the nitrogen absorption into weld metals.4. In reducing gas atmospheres such as nitrogen-hydrogen mixtures, the nitrogen contents in weld metals show a tendency to obey the square root law.5. Although some calculations for the nitrogen absorption into weld metals were made using thermo-dynamic data obtained by an equilibrium study, a great difference between the calculated values and experimental values was generally observed.

As to the consumption of tungsten electrode the following phenomena are observed.The consumption of pure and thoriated tungsten shows a remarkable difference at arc starting as shown in Fig. 2. The explosive expansion of gas in intercrystal zone of sintered electrode is presumed as the main cause of the consumption at arc starting. Experiment shows the minimum consumption at 1.5% ThO2 content. Thoria acts to decrease the arc starting period of cold cathode state and at the same time acts to increase the number of sintered defects as shown in Fig. 3.It is observed that the metal vapour in arc atmosphere little affects the consumption in stationary period, while iron particle spattered on the electrode acts to increase the consumption of electrode. Photo 5 shows a remarkable change of electrode shape when the electrode is contaminated by carbon vapour.Oxygen and nitrogen affect also the consumption; the former decreases the surface tension and the latter produces gas holes in the molten electrode tip. See Photo XI .

Effect of nitrogen partial pressures in the welding atmospheres of several gas mixtures on the nitrogen content of aluminum weld metals was systematically studied.The important conclusions are as follows;1. Aluminum weld metals absorb a large quantity of nitrogen in the welding atmospheres containing nitrogen.2. The nitrogen contents of weld metals increase with increasing arc voltage and decrease with increasing welding current.3. Anomalous nitrogen absorption by weld metal is observed at low atmospheric pressures.4. The existence of an oxidizing gas in arc atmospheres does not contribute to the enhancement of nitrogen absorption by aluminum weld metals.

EXTENSIVE experimental and analytical studies have provided a basic understanding of the manifestation of arc cathode instability relative to fluctuations of arc voltage as influenced by electrical, chemical, and geometrical parameters. These studies have contributed significantly to the development of controlled cathode stabilization systems of the argon-shielded consumable electrode arcs as applied to the welding of mild steel.

An experimental study was made of the properties of the high current dc electric arc in argon, helium, and their mixtures at atmospheric pressure. Tungsten‐rod electrodes were used over a current range from 10 to 100 amperes. Measurements of the voltage‐current and the voltage‐electrode separation characteristics were made along with the plasma voltage gradients in both the pure gases and in the mixtures.It was found that this type of arc was very stable when the system was free from oxide impurities and that the cathodic processes played a major role in the arc mechanism. The results obtained suggest that the value of the anode voltage drop for the inert gas arc over the current range studied is negligibly small. At the higher currents or with smaller diameter cathodes, tungsten was able to evaporate from the cathode in sufficient quantities to influence the character of the discharge. It was observed that the properties of the arc in mixtures of gases were in between the properties observed in the pure ...

It is well known that the effect of longitudinal magnetic field on weld zone causes a turning of arc column and a turbulance of mloten pool. That is to say, magnetic stirring is generated. The influence of the magnetic stirring on the weld zone in the case of TIG or MIG welding has already been reported. According to the reports number of blowholes decreases, and reduction of grain to small size and improvement of welding speed can be expected. But the result in the case of Submerged-arc Welding has not been reported yet. This report investigates the influence of magnetic stirrig on the weld zone by Submerged-arc Welder with magnetic equipment. The results obtained from these studies are as follows:1) The bead becomes wider up to a certain strength of magnetic field, but it becomes narrower again when the magnetic field strength exceeds a certain limit.2) The depth of penetration also shows the same tendency as the bead width. It becomes shallower up to a certain limit.3) The heihgt of reinforcement increases in proportion to the degree of magnetic field strenght.4) The average sectional area of bead does not change so much.5) Magnetic stirring minimizes the primary crystals of weld metal. But their minimization has a certain limit. It cannot be minimized beyond the limit.

In this papea, we report the effect of IR drop in electrode and net arc energy on the so-called self requlating characteristics of MIG Welding. The radiant heat from molten pool of base metal is too small to explain the phenomena, as shown in the previous paper (Japanease W.J. Vol. 25 No. 2 1956).It must be noticed that, when we ajusted arc length shorter, the part of electrode from feeding contact point to, the arc becomes longer, in ordinary adjustment (Fig. 1-B). To separate the causes of the phenomena, we measured the melting speed when the arc length and wire length from the feeding contact point to the arc are changed respectively as shown Fig.1.According to our expeaiment, about 15% of the increase of the melting speed when the arc length is ajusted shorter, (which is the characteristics of the so-called self regulation), is due to the increase of the joule's heat above mentioned. See Table 1 & 2. Fig. 3 show the variation of the dorp along the wire of 100mm length when the same current is flowed. IR drop in Table 1 & 2 are estimated from those occillograms.The increase of electrode drop of arc when the arc is ajusted shorter, which is discussed in the previous paper, may explain to remainder.

The object of this research is to clarify a relation between porosity of weld and volume percentage of nitrogen in the mixed gas supplied for shielding of arc and its neighborhood. Three kinds of mixed gas ; C02-N2, A-N2 and 02-N2, were supplied.The results of experiments showed the following facts1. In the case of CO2-N2 arc welding, the weld metal becomes very porous regardless of content of deoxidizers in the base metal, when the volume percentage of nitrogen in supplied gas is over the limit value, 4.5%.2. Also in the case of A-N2 arc welding this limit value is nearly the same. But the weld metal by A-N2 arc welding has generally higher content of total nitrogen, including nitride, than that by C02-N2 arc welding with the same mixed percentage of nitrogen.3. The true partial pressure of nitrogen in arc atmosphere is deduced to be over about 0.1 atm., when a weld metal becomes porous.And the difference between the above "true" value, about 10%, and the "supplied" value, 4.5%, was discussed.

MOST MEN associated with resistance welding machines are conscious of the fact that the introduction of magnetic material into the throat of such equipment causes a reduction of the welding current. The degree of reduction and simple mathematical tools for estimating it are contained in this paper.

1. A radically new process has been developed for producing relief pictures by vacuum diffusion welding, which combines the operations of powder compaction, sintering, and weld-bonding. 2. The optimum process parameters have been established experimentally for welding steel 15 to sintered PNE nickel and sintered PZh2M2 iron.