Very Little Diffusion Occurs Across The Bond Interface

These observations support the hypothesis that says that wave formation is a result of extreme metal deformation and that bonding is a result of solid-state processes with very little diffusion. However, Hammerschmidt and Kreye (Ref 33) have presented an alternative mechanism for bonding based on the formation of a submicroscopic layer of molten metal, rather than solid-state bonding. Their investigation revealed that in bonds between copper and aluminum, a layer up to 5 m (200 in.) wide was...

R V Cos f COS f f EQ

Where R is the growth rate in the preferred direction required to maintain a constant weld pool shape and f ' is the angle between R and V, and ( f ' - f ) is the angle between the local preferred growth direction and R, which is normal to the solid-liquid interface. FIG. 12 SCHEMATIC SHOWING MOVEMENT OF A CURVED SOLID-LIQUID INTERFACE FOR SEVERAL GRAINS (A AND B), AND THE CHANGE IN THE RAPID GROWTH DIRECTION RELATIVE TO THE INTERFACE POSITION. FIG. 12 SCHEMATIC SHOWING MOVEMENT OF A CURVED...

Alternating Current Is Rectified To Dc

The inverter supplies can be switched from constant current to constant voltage for GMAW, resulting in a very versatile piece of equipment. The inverter-controlled power supplies are more stable and have faster response times than conventional silicon-controlled rectifier (SCR) power supplies. Figure 2 compares the response of an inverter-controlled arc welding machine and a thyristor-controlled welding machine. FIG. 2 STARTING CURRENT WAVEFORMS OF TWO POWER SOURCES TO SHOW RELATIVE RESPONSE...

Ripple Vmax VminEQ

Two terms are commonly used to define the characteristics of a power source for welding static output and dynamic response. Static characteristics are set forth by the manufacturer as a series of V-A curves (Fig. 4). The slope of the static V-A curve is the ratio of load voltage change to the change in load current, expressed in V 100 A. It indicates the achievable envelope of output limits, including the highest voltage the machine will support at a given current, and the...

What Are The Mechanical Properties Of The Weld Metal

In addition, a number of very application-specific corrosion and elevated-temperature tests were performed on the dissimilar metal welds. In contrast with the pipe weld of the first example, the primary tools used in this characterization were macrostructural examination, compositional mapping, x-ray diffraction, tension testing of all weld metal specimens, and microhardness traverses. FIG. 14 MICROHARDNESS READINGS (LOCATION IN MULTI-PASS WELD INDICATED BY DOTS) BELOW 240 HV INDICATING THAT NO...

Bonding Practice

Figure 1 shows the arrangement used in the parallel gap explosive bonding process. The explosive charge is placed in contact with the top plate, hereafter called the flyer plate. The explosive detonation is initiated from one end to generate a linear detonation front, which runs along the flyer plate length. Pressure generated by the expansion of the explosive products accelerates the flyer plate downward at the point where the explosive is reacting and results in the desired impact on the...

10j Qu And Q Li Interfacial Dislocation And Its Applications To Interface Cracks In Anisotropic Bimaterials J Elast Vol

STROH, DISLOCATIONS AND CRACKS IN ANISOTROPIC ELASTICITY, PHILOS. MAG., VOL 7, 1958, P 625-646 12. Q.Q. LI AND T.C.T. TING, LINE INCLUSION IN ANISOTROPIC ELASTIC SOLIDS, J. APPL. MECH., VOL 56, 1989, P 556-563 13. T.C.T. TING, EXPLICIT SOLUTION AND INVARIANCE OF THE SINGULARITIES AT AN INTERFACE CRACK IN ANISOTROPIC COMPOSITES, INT. J. SOLIDS STRUCT., VOL 22, 1986, P 965-983 14. M.D. PASHLEY AND D. TABOR, ADHESION AND DEFORMATION PROPERTIES OF CLEAN AND CHARACTERIZED METAL...

Class Iii Rated Output At 20 Duty Cycle

Duty cycle is the ratio of arc time to total time based on a 10 min averaging period. A 60 machine will deliver 6 min of arc time and 4 min off time without overheating. In Fig. 1, curve A shows a NEMA class I (60 ) 300 A rated machine that is capable of a maximum 375 A at reduced duty cycle (38 ) and 232 A at 100 (continuous). Curve B represents a NEMA class II (50 ) 250 A machine with a continuous duty of 176 A. Curve C represents an engine-driven machine rated at 225 A and 20 duty. It does...

Power Supply Output

Short-circuiting transfer encompasses the lowest range of welding currents and electrode diameters associated with the GMAW process. This type of transfer produces a small, fast-freezing weld pool that is generally suited for joining thin sections, for out-of-position welding, and for bridging of large root openings. Metal is transferred from the electrode to the workpiece only during a period when the electrode is in contact with the weld pool, and there is no metal transfer across the arc gap...

Nondestructive Characterization Techniques

Externally Observed Macroscopic Features. Several factors associated with the production and performance of welds are macroscopic and easily observed. The most obvious of these are the size, shape, and general appearance of the weld. To a large extent, these parameters depend on the geometry of the weld joint and the welding process selected. Figure 1 shows schematic representations of fillet, lap, butt, and groove welds, in which a number of features (defined in Table 1) are labeled. TABLE 1...

Total pressure M Pa

FIG. 5 EFFECT OF PRESSURE ON THE PRODUCT M C O FOR HYPERBARIC WELDING WITH A BASIC ELECTRODE. SOURCE REF 12 In Fig. 5, two lines are indicated. The solid line plots the product of the weld metal oxygen and carbon as a function of total pressure when the analytical weld metal oxygen concentration, O anal, was used. The broken line indicates a similar relationship however, in this case, the weld metal oxygen concentration has been corrected for the displacement of oxygen because of the formation...

Environmentally Induced Failure of Interlayers

The interlayer base-metal interfaces of some soft-interlayer welds appear particularly vulnerable to failure when exposed to external (corrosive) environments. For example, it is known that brazed silver interlayers between stainless steel are subject to galvanic corrosion in aqueous NaCl media (Ref 64, 65). When dissimilar base materials are joined, the potential for stress-corrosion cracking (SCC) exists if the joints are exposed simultaneously to some external (corrosive) environments and...

Ysv Ysl Ylv COS

If the solder droplet forms an angle, 9, of less than 90 , then the solder is said to wet the metal. If the angle is greater than 90 , the solder is nonwetting. This is one method used to qualitatively assess solderability. The formation of intermetallic compounds can affect Young's equation because it alters the value of ysl. The influence of this term has been recognized (Ref 6), but the magnitude has not yet been calculated quantitatively. Surfaces of a metal crystal have...

References

ADAMS, JR., DYNAMICS OF WETTING IN BRAZING AND SOLDERING, TECHNICAL REPORT WAL TR 650 1, ARMY MATERIALS RESEARCH AGENCY, WATERTOWN ARSENAL, JULY 1962 2. S. WEISS AND C.M. ADAMS, JR., THE PROMOTION OF WETTING, WELD. J., VOL 46 (NO. 2), FEB 1967, P 49S-57S 3. W.D. HARKINS, PHYSICAL CHEMISTRY OF SURFACE FILMS, REINHOLD, 1952 4. M M. SCHWARTZ, MODERN METAL JOINING TECHNIQUES, WILEY, 1969 5. A. BONDI, SPREADING OF LIQUID METALS ON SOLID SURFACE CHEMISTRY OF HIGH ENERGY SUBSTANCES, CHEM. REV.,...

Introduction

FLUXES are added to the welding environment to improve arc stability, to provide a slag, to add alloying elements, and to refine the weld pool (Ref 1, 2). Different ingredients in the flux system will provide the process with different pyrometallurgical characteristics and thus different weld metal properties (Ref 3, 4). The slag that forms during welding covers the hot weld metal and protects it from the atmosphere. Welding slag consists of the glass-forming components of the flux, as well as...

Consumables

The two consumable, but essential, elements of the GMAW process are the electrode and the shielding gas, each of which is described below. The chemical composition of the electrode must be selected to achieve the desired properties in the weld metal. The composition is designed with extra deoxidizers or other scavenging agents to compensate for reactions with the atmosphere and the base metal. The deoxidizers most commonly used in steel electrodes are silicon and manganese. Silicon can also be...

Soldering

Like brazing and other joining processes, soldering involves several fields of science, including mechanics, chemistry, and metallurgy. Soldering is a simple operation (Ref 2), consisting of the relative placement of the parts to be joined, wetting the surfaces with molten solder, and allowing the solder to cool until it has solidified. Soldering in the field of electronics is in many respects different from soldering in other branches of industry. Although the physical principles of all...

Principles of Operation

Figure 1 shows a typical setup for automatic SAW. A continuous electrode is being fed into the joint by mechanically powered drive rolls. A layer of granular flux, just deep enough to prevent flash through, is being deposited in front of the arc. Electrical current, which produces the arc, is supplied to the electrode through the contact tube. The current can be direct current (dc) with electrode positive (reverse polarity), with electrode negative (straight polarity), or alternating current...

Shielding Gas and Fume Generation

The shielding gas used in solid and flux-cored wire welding affects the rate at which fumes are produced during welding, as well as the composition of the fumes. The type of shielding gas also affects the composition of the pollutant gases in the welding area. The fumes and gases generated in some welding applications impact on health and safety therefore, it is important for the user to review the Material Safety Data Sheets and precautionary labeling provided by the manufacturers and...

Stainless Steels

It has long been known that solidification cracking can be avoided in austenitic stainless steel welds by having a small concentration of ferrite in them. Recent work has shown, however, that residual ferrite content at room temperature is no more than a symptom and that it is really the solidification mode (whether the weld metal solidifies as primary austenite or ferrite) that is the deciding criterion (Ref 43). It has been found that susceptibility to solidification cracking is least for a...

Characteristics of the Components of a Shielding Gas Blend

To obtain a shielding gas that is suited to a specific application, a mix of gases is generally needed. Each basic gas contributes certain characteristics to the performance of the overall mix. Some gas blends have relatively specific areas of application and limited operating ranges others can be used on many materials under a variety of welding conditions. Each component of the blend brings with it properties that are supplemented by the others to produce an enhanced level of performance....

First bead

FIG. 31 SCHEMATIC SHOWING THAT THE HAZ ISOTHERMS AND THE SIZE AND LOCATION OF THE COARSEGRAINED REGION (CGR) CAN BE CONTROLLED IN A TANDEM THREE-WIRE HIGH CURRENT GAS-METAL ARC WELDING PROCEDURE. GRAIN REFINEMENT OF COARSE-GRAINED REGIONS INITIALLY FORMED IS OBTAINED BY OPTIMIZING THE DISTANCES BETWEEN THE THREE ARCS. SOURCE REF 41 FIG. 31 SCHEMATIC SHOWING THAT THE HAZ ISOTHERMS AND THE SIZE AND LOCATION OF THE COARSEGRAINED REGION (CGR) CAN BE CONTROLLED IN A TANDEM THREE-WIRE HIGH CURRENT...

N

The shape constant, C, can be obtained in terms of the core diameter, D, and the concentration factor, F. The concentration factor is defined as the ratio of the concentrated heat to the net energy reaching the weldment. The core diameter can be assumed to be the diameter of the plasma column in the arc welding process. The concentration factor and welding heat efficiency are not fully understood and have been subjected to manipulation during the mathematical analyses in order to obtain a...

K [Ke V AoDl [1 VAoDlEQ

Where Ke is the equilibrium distribution coefficient (K in Eq 8 and 12), and a0 is a distance that is related to the interatomic spacing. Different models use different definitions for a0 and different functional relationships, but give similar results. When V > D a0, K will approach 1. For D 5 x 10-5 cm2 s, or 5 x 10-8 ft2 s (a typical value for liquid diffusion), and a0 5 x 10-8 cm, or 2.0 x 10-8 in., K will approach 1 for V > 103 cm s, or 4 x 102 in. s. With K 1, there is no partition of...

V 09785 x 106V2

Sensors monitor the beam potential generated by the high-voltage (HV) supply and correct the control signal to the magnetic device power supply. Thus, the action of the device can be held constant as beam potential changes. This correction can be achieved by using computer software or an analog circuit. Such correction is often called square root compensation, because of the relationship indicated in Eq 13. Alignment coils are used for slight corrections to the x and y positions of the beam as...

Interface Pae A SaejbAEQ

Where AE(A) (AE (B) is the extra energy of atom i of A (B) type, compared to its bulk state of A (B) materials. The interfacial energy between similar metals tends to be small. For dissimilar materials, however, interfacial energies tend toward large positive values if they do not form compounds and large negative values if they do form compounds. The ideal adhesion energy is similar to grain boundary cohesion and is the difference between the two surfaces and the interfacial energies radhesion...

Protection By An Atmosphere Or Flux

As mentioned previously, wetting is only one important facet of the brazing process. A low contact angle, which implies wetting, is also necessary, but is not a sufficient condition itself for flow. Viscosity is also important. Brazing filler metals with narrow melting ranges that are close to the eutectic composition generally have lower viscosities than those with wide melting ranges. Thus, a high surface tension of liquid filler metal, a low contact angle, and low...

Bmanufacturer Must Identify The Type And Nominal Content Of The Rareearth Oxide Addition

Wire feed systems are made from a number of components and vary from simple to complex. The basic system consists of a means of gripping the wire sufficiently to pull it from the spool and push it through the guide tube to the point of welding. Electronic switches and controls are necessary for the electric drive motor. The wire will be fed into the leading edge for cold wire feeds and into the trailing edge for hot wire feeds. Cables, hoses, and gas regulators are necessary to deliver the...

Mass Transfer

Although the International Institute of Welding (IIW) lists eight distinct metal transfer modes (Ref 3), the modes commonly used in U.S. welding practice are globular, spray, streaming, rotating, and short circuiting. The mode terms drop and repelled used by the IIW are often referred to as globular, and the mode term projected is generally referred to as spray. The globular, spray, streaming, and short-circuiting transfer modes are shown in Fig. 3, FIG. 3 GLOBULAR...

Heat AffectedZone Cracks

Microfissures are cracks that occur in the area of partial melting and the HAZ adjacent to the fusion line. Because no material can be purified to the state where it solidifies truly as an invariant, all materials have a temperature region of stable two-phase coexistence of solid and liquid. In fusion welding, this manifests itself in the formation of a zone of partial melting at temperatures below the alloy liquidus. The extent of this zone may be enlarged by the presence of chemical...

Decreased Thermal Expansion Coefficient

These aggregate characteristics constitute the strengthened solder materials that are able to withstand harsher application conditions. The reduced thermal expansion coefficient of these new solders is expected to be more compatible with that of state-of-the-art electronic components and with ceramic substrates. With respect to quality, solder joints have historically been judged by visual criteria. However, due to the nature of solder materials and the effect of the solder joint-forming...

Composition of a Weld

The composition of a weld will have a significant effect on its performance, contributing to both the mechanical and corrosion properties of the weld. In some instances, the effects can be drastic, such as sensitization of stainless steel or changing the ductile-to-brittle transition temperature of ferritic steels by an amount sufficient to cause brittle failure under normal use. In a number of cases, particular elements will govern the propensity toward certain defects or behavior. For...

Nonequilibrium Effects High Rate Weld Solidification and Composition Banding

As has been noted, while the constitutional supercooling model (described in previous sections of this article) gives valuable insights into the establishment of nonplanar structures, it does not necessarily give an exact depiction of the composition gradient develop within the dendrites or cells that may form and within the interdendritic or intercellular regions. This has been shown by Brooks and Baskes (Ref 16) in their study of gas-tungsten arc and electron-beam aluminum-copper and...

Shielding Gas Selection for GTAW

The most commonly used gas for GTAW, argon exhibits low thermal conductivity, which produces a narrow, constricted arc column this allows greater variations in arc length with minimal influence on arc power or weld bead shape. Its low ionization potential provides good arc starting characteristics and good arc stability using the direct current electrode negative (DCEN) power connection plus superior arc cleaning action and bead appearance when ac power is used. Argon is the most...

N X V 0 q R Ra

Another is represented by the conditions at the solid-liquid interface n.(lV0)s - n(lV6)1 psL (EQ 18) where + indicates the melting process and - indicates the solidification process. The subscripts s and l indicate the temperature and the properties in a solid and liquid, respectively. The n is a normal vector on the boundary surface or interface, ra is the radius of the heat-input area, L is the latent heat of the base material, and the subscript m represents the melting temperature of the...

Fundamentals of Soldering

Pure metals have a crystalline state and a well-defined melting temperature. They also possess reasonable ductility and strength. Metals are excellent electrical conductors, when compared with ceramics or plastic polymer materials. Thermal conductivity generally follows electrical conductivity (that is, a good electrical conductor also is a good thermal conductor). Melting and Solidification of Pure Metals. The melting behavior of pure lead is plotted in Fig. 1. From point A, which is room...

Procedures

Welding parameters, such as welding current, arc voltage, travel speed (for mechanized automatic operation), and plasma and shielding gas flow rates, are set by the procedure and implemented by the welder. Torch parameters include the correct electrode vertex angle and set-back distance, as well as the correct orifice diameter for the welding current level. The operating sequence for the PAW process was described in the section Principles of Operation at the...

Electrodes

The electrodes used in the SMAW process have many different compositions of core wire and a wide variety of flux- covering types and weights. Standard electrode diameters of the core wire range from 1.6 to 8 mm ( to in.). Electrode length usually ranges from 230 to 455 mm (9 to 18 in.) the shorter lengths are associated with the smaller-diameter electrodes. A bare, uncoated end of the electrode (the grip end) is provided for making electrical contact in the electrode holder. The coating on the...

Brazing

Many products are assembled from two or more individual components that are often permanently joined to produce structurally sound assemblies. Joining methods include various fasteners, interference-type joints, adhesives, and, for the highest-integrity joints, the many techniques classified under welding. Brazing, although fundamentally indifferent from welding, is one such technique. Early metalworkers, stimulated by a desire to produce structures that were difficult or impossible to build...

Shielding Gas Selection for FCAW

The majority of large-diameter (> 1.6 mm, or in.) wires that use a shielding gas use carbon dioxide. Some smaller diameter wires are formulated to operate in 100 CO2. The arcs are generally stable and provide a globular transfer over the usable operating range. Good performance over rust and mill scale on the plate surface is obtained with these large-diameter wires and CO2 shielding. Argon Carbon Dioxide. A significant number of small-diameter (< 1.6 mm, or in.) cored wires...

Dcep Dc Electrode Positive Dcen Dc Electrode Negative

Changes in Flux Composition With Delta Quantity. Figure 3 shows a transfer of manganese for welds made with SiO2-TiO2-CaO-1Na2O flux at constant SiO2 content in the flux. These values vary widely, depending on other alloy concentrations. The data imply that manganese is almost always lost to the slag, and that the activity of manganese varies considerably with changes in the amount of titania in the flux. Manganese is very important to weld metal hardenability and must be closely controlled to...

Mechanical Testing

A number of mechanical properties are used to characterize welds, including strength, ductility, hardness, and toughness. In general, the same samples and procedures are used in other areas of metallurgy (Ref 17). However, a prominent concern regarding the mechanical performance of welds is the direct comparison with base material. The goal is to ensure that the weld is not the weakest component of a structure, or if it is, to compensate for this in the design. Strength. Yield and tensile...

Basic Properties of a Shielding

The controlled electrical discharge known as the welding arc is formed and sustained by the establishment of a conductive medium called the arc plasma. This plasma consists of ionized gas, molten metals, slags, vapors, and gaseous atoms and molecules. The formation and structure of the arc plasma is dependent on the properties of the shielding gases used for welding. Table 1 lists the basic properties of gases used for welding (Ref 1). TABLE 1 PROPERTIES OF SHIELDING GASES USED FOR WELDING...

Solid

FIG. 5 LIQUID SOLDER DROPLETS ON A SOLID SURFACE UNDER TWO CONDITIONS. (A) WETTING. (B) NONWETTING. ARROWS INDICATE SURFACE TENSION. The physics of wetting is the governed by Young's equation (also known as Young-Depre equation because Young described the problem quantitatively in 1805 and Depre put it in mathematical terms in 1869) where ysv, ysl, and ylv refer to the solid-vapor, solid-liquid, and liquid-vapor surface tensions, respectively. Relative to each other, these parameters can be...

C iDlEQ

Where larc is the length of the arc plasma column. where E is the welding arc voltage and I is the welding current. For practical purposes, the welding heat source can be considered to be restricted within a circle of radius ra, where the heat flux drops to 1 100 of the center flux q 0. The radius of the significant heat input area can be written as

Titanium Alloys

Titanium alloys find use in aerospace applications, pressure vessels, and so on because of their high strength-to-weight ratio, high corrosion resistance, and high fracture toughness. Pure titanium has two allotropic forms low-temperature hexagonal close-packed (hcp) a-phase and elevated-temperature body-centered cubic (bcc) P-phase. Various alloying elements tend to preferentially stabilize one or the other of these phases. As a result, titanium alloys are generally classified as a, a+ P,...

Explosive Parameters and Shock Effects

Although many different types of explosives have been used for explosive bonding, those that have a broad range of low-detonation velocities are the most appropriate, because fo the deleterious effects of shock rarefaction. Shock fronts are described by a sharp discontinuity in pressure on one side of the transmitting medium where the violent motion that is due to high pressure is separated from a near-quiescent state in the unaffected material (Ref 1). This condition can produce tensile...

Dynamic Bend Angle and Material Properties

Attempts to correlate bonding success to starting material properties have been extremely difficult, because most material property compilations are determined at ambient conditions and do not account for the high strain rates associated with explosive conditions. Rules of thumb often dominate. Carpenter et al. (Ref 10) indicated that materials exhibiting tensile ductilities greater than 5 will survive the bending associated with the flyer plate acceleration. It is also generally recognized...

Formation Of Intermetallic Compounds

In practice, interactions are usually minimized by selecting the proper brazing filler metal keeping the brazing temperature as low as possible, but high enough to produce flow and keeping the time of brazing temperature short and cooling the brazed joint as quickly as possible without causing cracking or distortion. When diffusion brazing is desired, higher brazing temperatures and longer times at brazing temperatures are employed. Base-Metal Characteristics. The base metal has a prime effect...

Si02 yAliO TiO ZrOj

The basicity index is an estimate of the oxygen content in the weld metal and is therefore used to predict weld metal properties. Basic fluxes tend to have lower weld metal oxygen content with good weld metal toughness, while acidic fluxes tend to produce higher weld metal oxygen content and coarser microstructure with a lower resistance to cleavage. Fluxes with a basicity index greater than 1.5 are considered basic fluxes below 1.0 are considered acidic. Acid fluxes are typically preferred for...

Mcl 000087at 0015eq 6

The incomplete statistical correlation (R2 0.86) suggests that other factors are necessarily involved. Equilibrium melting ternperaUiJ'e range, F Equilibrium melting ternperaUiJ'e range, F Equilibrium melting le m per al Lire range, C FIG. 5 RELATIONSHIP BETWEEN MAXIMUM CRACK LENGTH AND EQUILIBRIUM MELTING TEMPERATURE RANGE IN ALLOY 625 WELDABILITY STUDY The solidification behavior of fusion welds is nonequilibrium in nature and may result in an extension of the solidification temperature range...

Solidstate Power Supplies Variable Hz

The frequency of the power source determines the type of heat that will be induced in the part high-frequency sources produce skin heating, whereas lower-frequency sources provide heating in thicker areas. The brazing heat usually develops within 10 to 60 s. Induction brazing is well suited for mass production. Mechanized brazing lines for moving assemblies to and from the coils are very common. Brazing filler metals is normally preplaced in the joint, and the brazing can be done in air with...

Process Overview

Soldering is defined as a joining process by which two substrates are bonded together using a filler metal (solder) with a liquidus temperature that does not exceed 450 C (840 F). The substrate materials remain solid during the bonding process. The solder is usually distributed between the properly fitted surfaces of the joint by capillary attraction. The bond between solder and base metal is more than adhesion or mechanical attachment, although these do contribute to bond strength. Rather, the...

Aluminum Alloys

The main problems in the welding of heat-treatable aluminum alloys are liquation cracking in the partially melted zone (see the section Unmixed and Partially Melted Zones in a Weldment in this article) and softening in the HAZ (Ref 14, 47). The latter means that the weld joint strength can be reduced. Reasons for the softening can be understood by referring to Fig. 36. The parent material is assumed to be a 2000- or 6000-series aluminum alloy, artificially aged to contain the metastable phase...

Will Result In Desired Change If Current Levels Are Maintained By Adjustment Of Wire Feed Speed

Considerable skill and experience are necessary to select the optimal combination for each application. This selection is further complicated by the fact that the optimal settings for the variables are also affected by the type of base metal, the electrode composition, the welding position, quality requirements, and the number of completed weldments required. Thus, no single set of parameters provides optimal results in every case. Welding Current. As the electrode feed speed is varied, the...

16 Ws Steffan Nitrogenbased Atmosphere Furnace Brazing System Provides Strength And Leakproof Performance Of Newly

METALS HANDBOOK, 9TH ED., POWDER METALLURGY, VOL 7, 1984, P 358 18. METALS HANDBOOK 8TH ED., VOL 6, 1971, P 595 19. PRODUCT LITERATURE, SECO-WARWICK CORP. (SUNBEAM), SEPT 1977 20. A. SAKAMOTO, STUDY OF FURNACE ATMOSPHERE FOR VACUUM-INERT GAS PARTIAL-PRESSURE BRAZING, WELD. J., NOV 1991, P 311S-320S 21. NEW GENERATION OF VACUUM HEAT-TREATMENT FURNACES FEATURE HIGH GAS PRESSURE QUENCHING AND OIL QUENCH VACUUM FURNACE, METALLURGIA, MAY 1989, P 205 22. W.R. JONES, VACUUM--ANOTHER ATMOSPHERE ,...

The Substrate Can Be Rigid Or Flexible

There are many methods of applying the conductive patterns that make up the circuitry and each has its own specific soldering solutions. Many different materials are used for substrates. Substrates used for electrical electronic applications must be insulators to allow the conductive circuitry to function in the manner of a network made from separate insulated wires. Common substrate materials for this application include ceramics and organic laminates. Metals can also be used as substrates if...

References cited in this section

MYERS, WHY THE GROWING INTEREST IN GAS TUNGSTEN ARC WELDING THE FABRICATOR, VOL 22 (NO. 9), NOV 1992, P 38 -39 4. WELDING HANDBOOK, 8TH ED., VOL 2, AMERICAN WELDING SOCIETY, 1991, P 74-107 5. T. BYRD, INVERTER POWER SOURCES AN EFFICIENT ALTERNATIVE, WELD. J., VOL 72 (NO. 1), JAN 1993, P 37-40 6. A.A. SADEK, M. USHIO, AND F. MATSUDA, EFFECTS OF RARE EARTH METAL OXIDE ADDITIONS TO TUNGSTEN ELECTRODES, METALL. TRANS. A, VOL 21, 1990, P 3221-3234 7. JR. KEY, ANODE CATHODE GEOMETRY AND SHIELDING...

Process Features

Flux-cored arc welding has two major variations. The gas-shielded FCAW process (Fig. 1) uses an externally supplied gas to assist in shielding the arc from nitrogen and oxygen in the atmosphere. Generally, the core ingredients in gas-shielded electrodes are slag formers, deoxidizers, arc stabilizers, and alloying elements. FIG. 1 GAS-SHIELDED FLUX-CORED ARC WELDING. SOURCE REF 1 FIG. 1 GAS-SHIELDED FLUX-CORED ARC WELDING. SOURCE REF 1 In the self-shielded FCAW process, the core ingredients...

EQ

Using the chain rule, the cooling-rate equation is Because the temperature-distribution equations are a function of w and r, the cooling-rate equations can be obtained by differentiating the temperature-distribution equations with respect to w and multiplying by -v. The cooling rate is defined as the slope of a tangent line drawn on the temperature-time curve. Because the cooling rate changes with temperature, when one speaks of a cooling rate, the specific temperature, 0c, at which it occurs...

Pyrochemical Kinetics During Welding

The ability of a flux to refine as well as protect the weld pool is related to the mass transport processes in the flux. The flux should melt approximately 200 C (360 F) below that of the alloy for proper flux coverage and for protection of the weld deposit. One of the most important physical properties of a flux is its slag viscosity, which not only governs the way the slag flows and covers the molten weld pool but also strongly affects the transport processes involved in pore removal,...

Precleaning and Surface Preparation

An unclean surface will not permit the solder to flow, which makes soldering either difficult or impossible and contributes to the formation of a poor joint. Materials such as oil, grease, paint, pencil markings, drawing, and cutting lubricants, general atmospheric dirt, oxide, and rust films must be removed before soldering. The importance of cleanliness cannot be overemphasized in ensuring sound soldered joints. Fluxing alone cannot substitute for adequate precleaning (Ref 19). Because...

Weld Macrostructure

Figures 5(a) and 5(b) show transverse sections of two welds, a submerged arc weld made on a 25 mm (1 in.) thick ASTM A 36 steel and a flux-cored weld made on a 50 mm (2 in.) thick ASTM A 537 steel. Readily apparent features include the number of passes and number of layers, fusion zone area, weld aspect ratio, extent of penetration, face width, and the reinforcement and curvature of the top bead. A transverse macrosection will also show any gross porosity or large inclusions present in a weld...

Powerlaw Creep

FIG. 5 SCHEMATIC OF NUMEROUS PATHS OF MATERIAL TRANSFER GENERATED DURING DIFFUSION BONDING PROCESS. (A) SURFACE SOURCE MECHANISMS. (B) INTERFACE SOURCE MECHANISMS. (C) BULK DEFORMATION MECHANISMS. SEE TEXT FOR SPECIFIC MECHANISMS INDICATED BY NUMBERS SHOWN IN SCHEMATIC. FIG. 5 SCHEMATIC OF NUMEROUS PATHS OF MATERIAL TRANSFER GENERATED DURING DIFFUSION BONDING PROCESS. (A) SURFACE SOURCE MECHANISMS. (B) INTERFACE SOURCE MECHANISMS. (C) BULK DEFORMATION MECHANISMS. SEE TEXT FOR SPECIFIC...

The SMAW Process

The important features of the SMAW process are shown in Fig. 1. The arc is initiated by momentarily touching or scratching the electrode on the base metal. The resulting arc melts both the base metal and the tip of the welding electrode. The molten electrode metal flux is transferred across the arc (by arc forces) to the base-metal pool, where it becomes the weld deposit covered by the protective, less-dense slag from the electrode covering. Advantages and Limitations. The SMAW process is the...

Special Factors Affecting Transformation Behavior in a Weldment

Several aspects of the weld thermal cycle and weld segregation should be considered because of their effect on the transformation upon cooling PEAK TEMPERATURES REACHED IN THE HEAT-AFFECTED ZONE (HAZ) CAN BE VERY MUCH HIGHER THAN THE AC3 TEMPERATURE (THAT IS, THE TEMPERATURE AT WHICH TRANSFORMATION OF FERRITE TO AUSTENITE IS COMPLETED DURING HEATING). THE HEATING RATES ARE VERY HIGH, AND THE TIMES SPENT AT HIGH TEMPERATURE ARE ONLY OF THE ORDER OF A FEW SECONDS. THE TEMPERATURE GRADIENT IN THE...

SiO 1 fAIO TiOj ZrO

Where the chemical components are given in wt . When the basicity index for a given flux is less than one, the flux is considered acidic. A flux with a BI between 1.0 and 1.2 can be classified as neutral. A flux with a BI greater than 1.2 is considered basic. In general, the higher the basicity, the cleaner the weld with respect to nonmetallic inclusions (that is, lower weld metal oxygen content) (Ref 23). Figure 7 illustrates the correlation between weld metal oxygen and the basicity index for...

Example 1 Multipass Weld in a 107 m 42 in Diameter X65 Pipe

This weld is a circumferential weld on a 12.7 mm (0.50 in.) thick, 1.07 m (42 in.) diameter X-65 pipe. The X-65 materials is designated by API as a pipe steel with at least 448 MPa (65 ksi) yield strength and 566 MPa (82 ksi) tensile strength. This type of weld is typical for a large oil or gas pipeline. However, for this example, procedures were deliberately selected to produce a weld with a range of defects. These procedures, given by Table 4, are not representative of standard practice....

Soldering Equipment

The proper application of heat is of paramount importance in any soldering operation. The solder should melt while the surface is heated to permit the molten solder to wet and flow over the surface. The best heating method is therefore another important consideration. Soldering Irons. The traditional soldering tool is the soldering iron, or bit, with a copper tip than can be heated electrically, by direct flame, or in an oven. Because soldering is a heat-transfer process, the maximum surface...

Diffusion Bonding Process

The DB process, that is, the application of pressure and temperature to an interface for a prescribed period of time, is generally considered complete when cavities fully close at the faying surfaces. Relative agreement is found for the mechanisms and sequence of events that lead to the collapse of interface voids, and the discussion below describes these metallurgical processes. Although this theoretical understanding of the DB process is universally applicable, it should be understood that...

Electrode Regions and Arc Column

The cathode and anode are similar in several respects. Both exhibit a voltage drop caused by a space charge that covers a very thin region over their surfaces, and the arc is significantly contracted on the surfaces. Figure 1 shows that the total arc voltage is partitioned between the electrode drops and arc column. The relative magnitude of these drops depends on welding parameters and electrode material. FIG. 1 PLOT OF RELATIVE ARC VOLTAGE DISTRIBUTION VERSUS RELATIVE ARC LENGTH BETWEEN...

Hydrogen Induced Cracking Cold Cracking

Cold cracks are defects that form as the result of the contamination of the weld microstructure by hydrogen. Whereas solidification cracking and HAZ cracking occur during or soon after the actual welding process, hydrogen-induced cracking is usually a delayed phenomenon, occurring possibly weeks or even months after the welding operation. The temperature at which these defects tend to form ranges from -50 to 150 C (-60 to 300 F) in steels. The fracture is either intergranular or transgranular...

Quality Control

Table 3 lists that are commonly used to evaluate the solderability properties of selected soldered components. TABLE 3 TEST STANDARDS USED TO EVALUATE SOLDERABILITY TABLE 3 TEST STANDARDS USED TO EVALUATE SOLDERABILITY Dip Test. The most useful test for assessing solderability is the dip test, because of its accuracy and simplicity. It is conducted with the additions of cams and timers so that standardized conditions are established. The dip test is a reasonable simulation of practical...

Dt5 Electrodes Are Classified Using Dcep However They Are Sometimes Used With Dcen In Practice

Indicates the minimum tensile strength ol the deposited weid metal in a test weld made with the electrode and m accordance with specified welding conditions Indicates the primary welding position lor which the electrode is < Jesigr> ed 0 llat and horizontal positions Indicates usability and performance capabilities Indicates a llux cored electrode FIG. 4 CLASSIFICATION SYSTEM FOR CARBON STEEL FLUX-CORED ELECTRODES. THE LETTER X AS USED IN THIS FIGURE AND IN ELECTRODE CLASSIFICATION...

Inclusion radius lin 440 400 4000

FIG. 17 EFFECT OF PARTICLE RADIUS ON ENERGY BARRIER TO FERRITE NUCLEATION AT INCLUSIONS, AG* (HETEROGENEOUS), NORMALIZED RELATIVE TO THE HOMOGENEOUS NUCLEATION BARRIER, AG*H (HOMOGENEOUS). CORRESPONDING ENERGY BARRIER TO NUCLEATION OF FERRITE AT AUSTENITE GRAIN BOUNDARIES IS INDICATED BY HORIZONTAL BROKEN LINE. SOURCE REF 6 Broadly, the major factors affecting transformation behavior in ferritic steel weld metals are alloy composition, weld heat input (by its effect on y grain size and Ai8.5),...

N 100 [asi Amneq

Where A Si is the change in the weight percent of silicon, and A Mn is the change in the weight percent of manganese. To determine the Wall neutrality number, two different weld deposit pads must be made. One weld pad is welded with the same parameters as those specified for the weld test plate for the flux and electrode being used. The other weld pad is welded with the same parameters except that the voltage is increased by 8 V. The A Si and A Mn quantities in Eq 1 are then determined by the...

Shielding Gas Selection for PAW

The physical configuration of the PAW system requires the use of two gases a plasma or orifice gas and a shielding gas. The primary role of the plasma gas, which exits the torch through the center orifice, is to control arc characteristics and shield the electrode. The shielding gas, introduced around the periphery of the arc, shields or protects the weld area. In many applications, the shielding gas is also partially ionized to enhance the performance of the plasma gas. Low-Current (< 100 A)...

Civil Engineering Advantage Of Filler Welds

GAS-METAL ARC WELDING (GMAW) is an arc welding process that joins metals together by heating them with an electric arc that is established between a consumable electrode (wire) and the workpiece. An externally supplied gas or gas mixture acts to shield the arc and molten weld pool. Although the basic GMAW concept was introduced in the 1920s, it was not commercially available until 1948. At first, it was considered to be fundamentally a high-current-density, small-diameter, bare-metal electrode...

6 M C Noland Hm Gadberry Jb Loser And E C Sneegas High Velocity Metal

WORKING A SURVEY, NASA REPORT N67-26560, SP 5062, NASA, 1967 7. A.A. EZRA, PRINCIPLES AND PRACTICE OF EXPLOSIVE METAL WORKING, INDUSTRIAL NEWSPAPERS LIMITED, JOHN ADAMS HOUSE, LONDON, 1973 9. R.W. GURNEY, THE INITIAL VELOCITIES OF FRAGMENTS FROM BOMBS, SHELLS, AND GRENADES, REPORT 405, BALLISTIC RESEARCH LABORATORY, 1943 10. S. CARPENTER, RH. WITTMAN, AND R.J. CARLSON, RELATIONSHIPS OF EXPLOSIVE WELDING PARAMETERS TO MATERIAL PROPERTIES AND GEOMETRY FACTORS, PROC. FIRST INT. CONF. OF THE CENTER...

Mechanism of Diffusion Bonding

In diffusion bonding, the nature of the joining process is essentially the coalescence of two atomically clean solid surfaces. Complete coalescence comes about through a three-stage metallurgical sequence of events. Each stage, as shown in Fig. 2, is associated with a particular metallurgical mechanism that makes the dominant contribution to the bonding process. Consequently, the stages are not discretely defined, but begin and end gradually, because the metallurgical mechanisms overlap in...

H

FIG. 4 SPRAY TRANSFER MODE IN GAS-METAL ARC WELDING OF STEEL. (A) SCHEMATIC SHOWING TRANSFER OF ELECTRODE MATERIAL DROPLETS ONTO CATHODE BASE METAL. (B) HIGH-SPEED PHOTOGRAPH OF SPRAY METAL TRANSFER MODE FIG. 5 HIGH-SPEED PHOTOGRAPH OF STREAMING TRANSFER MODE IN GAS-METAL ARC WELDING OF STEEL FIG. 6 SHORT-CIRCUITING TRANSFER MODE IN GAS-METAL ARC WELDING OF STEEL. (A) SCHEMATIC SHOWING TRANSFER OF ELECTRODE MATERIAL BY SURFACE TENSION OF WELD POOL ONTO CATHODE BASE METAL. (B) HIGH-SPEED...

R r

0.00441-I (550- 25) 32.2 (EQ 65) resulting in R being equal to 2n(0.028)32.2, which is equal to 5.7 C s (10.3 F s). This value is the maximum safe cooling rate for this steel and the actual cooling rate cannot exceed this value. Preheating Temperature Requirement. Although the critical cooling rate cannot be exceeded, in the actual welding operation a preheat can be used to reduce the cooling rate to 5.7 C s (10.3 F s). Assume that the welding condition is 25(250)0.9 aniT. Hnet - 804J mm (EQ...

3sp Chen Theoretical Studies Of Metallic Interfaces Mater Sci Eng B Vol 6 1990p 113121

MCMAHON, JR., A MICROSCOPIC THEORY OF BRITTLE FRACTURE IN DEFORMABLE SOLIDS A RELATION BETWEEN IDEAL WORK TO FRACTURE AND PLASTIC WORK, ACTA METALL., VOL 28, 1980, P 1479-1488 5. ML. JOKL, V. VITEK, AND C.J. MCMAHON, JR., ON THE MICROMECHANICS OF BRITTLE FRACTURE EXISTING VS INJECTED CRACKS, ACTA METALL., VOL 37, 1989, P 87-97 6. J. HACK, S.P. CHEN, AND D. SROLOVITZ, A KINETIC CRITERION FOR QUASI-BRITTLE FRACTURE, ACTA METALL., VOL 37, 1989, P 1957-1970 7. A. KELLY...

GTAW Process Variations

Manual welding refers to the GTAW process in which the welder manipulates the welding torch by hand. If a motorized wire feeder is attached to the torch, the process is classified as semiautomatic welding. Products generated by skilled manual welders account for a large proportion of GTAW applications. The equipment can be quite inexpensive, and properly trained welders can join a wide variety of materials. Manual welding is used extensively in stainless steel piping as well as for the root...

The Material Has Poor Ductility In The Z Direction

FIG. 16 TYPICAL LOCATION FOR LAMELLAR TEARING IN A T-JOINT FIG. 16 TYPICAL LOCATION FOR LAMELLAR TEARING IN A T-JOINT Lamellar tearing can occur during flame cutting and cold shearing operations. Low material strength in the z direction is the primary cause, with stress in that direction initiating the tearing. Thermal heating and stresses from weld shrinking create the fracture. Lamellar tearing can take place shortly after welding or occasionally months later. Thicker, higher-strength...

Development of Weld Microstructures

Solidification Metals

Nonplanar solidification develops when a protrusion moves ahead of the rest of the solid-liquid interface and continues to grow in a stable manner. This increases the surface area. The stable radius is given by Eq 4, which shows that the protrusion must move into a supercooled region in order to be stable. This is possible in a casting, because a negative temperature gradient is developed (that is, the temperature decreases from the solid-liquid interface into the liquid). In a pure material...

Process Parameters

Pretty Silicon Bronze Bead Welding

Current is one of the most important operating conditions to control in any welding operation, because it is related to the depth of penetration, welding speed, deposition rate, and quality of the weld. Fundamentally, there are but three choices of welding current DIRECT CURRENT ELECTRODE NEGATIVE (DCEN) DIRECT CURRENT ELECTRODE POSITIVE (DCEP) Figures 5 and 6 show the effect of dc and ac on weld shape. Table 2 gives the recommended current relative to workpiece material. TABLE...

Diffusion Bonding with Interface Aids

Additional layers of material in the form of coatings or foils are often used as bonding aids for a variety of reasons. For example, an intermediate material can be used when joining dissimilar materials where a brittle intermetallic would otherwise form. In this case, the interfacial material would be selected for its compatibility with each of the materials to be joined and for its ability to prevent the creation of a brittle reaction layer. To promote diffusion in materials that contain...

Fusion Zone of a Single Pass Weld

Transformations in Single-Pass Weld Metal. It is usually not necessary to select a filler metal that has exactly the same composition as the base metal it is more important that the weld metal has the same strength and other properties (such as toughness or corrosion resistance). Because these properties are governed by the microstructure, it is important to understand the influence of different factors on phase transformations in the weld metal. But first, for a meaningful communication of the...

50 Ew Collings Introduction To Titanium Alloy Design Alloying Jl Walter

SIMS, ED., ASM INTERNATIONAL, 1988, P 267 51. C R. THOMAS AND F.P.A. ROBINSON, KINETICS AND MECHANISM OF GRAIN GROWTH DURING WELDING IN NIOBIUM STABILISED 17 CHROMIUM STAINLESS STEELS, MET. TECHNOL, APRIL 1978, P 133-138 52. J.C. WILLIAMS AND E.A. STARKE, JR., THE ROLE OF THERMOMECHANICAL PROCESSING IN TAILORING THE PROPERTIES OF ALUMINUM AND TITANIUM ALLOYS, DEFORMATION, PROCESSING AND STRUCTURE, G. KRAUSS, ED., AMERICAN SOCIETY FOR METALS, 1984, P 279-354 53. W.A....

Dynamic Bend Angle And The Physical And Mechanical Properties Of The Metal Constituents

FIG. 1 SCHEMATIC SHOWING KEY COMPONENTS USED IN THE PARALLEL GAP EXPLOSIVE WELDING PROCESS Flyer Plate Acceleration FIG. 1 SCHEMATIC SHOWING KEY COMPONENTS USED IN THE PARALLEL GAP EXPLOSIVE WELDING PROCESS Flyer Plate Acceleration Figure 2, an intermediate view of the explosive bonding process, shows an idealization of the metal deformation that results after explosive detonation. Flash radiography performed during the bonding process has been used to develop this pictorial representation (Ref...

Joint Design

Butt Joint Civil Engineering

Joints should be designed to fulfill the requirements of the finished assembly, as well as to permit the application of the flux and solder. Joint design should maintain proper clearance during heating and upon solidification of the filler metal. Special fixtures may be necessary or the units can be crimped, clinched, wrapped, or otherwise held together. The selection of a joint design for a specific application will primarily depend on the service requirements of the assembly. It may also...

Inclusions Due To Entrapped Slag Tungsten Electrode Pieces Or Defects Present In The Starting Material

A number of techniques are widely used to assess the presence of surface and subsurface defects in welds. The most common of these are liquid penetrant inspection for surface cracks, magnetic particle inspection, x-ray radiography, and ultrasonic inspection. Penetrant inspection involves the application of an indicator fluid that has a surface tension sufficiently low to be drawn into surface cracks too small to be detected visually. The excess dye or fluorescent material is then removed from...

The Aspiration Of Atmosphere Air Into The

Shielding gas may contain oxidizing reagents a common gas is 75Ar-25CO2 or 100 CO2. As a 100 to 1000 ppm, depending on the type of welding consumable used. The weld metal oxygen measured directly at the molten electrode tip has been reported to be as high as 1400 ppm. Individual droplets have been found to contain as much as 2000 ppm O2. There are two views concerning the genesis of the high oxygen content. One suggests that pyrochemical or electrochemical reactions (or both) provide oxygen to...

Special Applications of the SMAW Process

Underwater welding began during World War I when the British naval force used it to make temporary repairs of leaking rivets on ship hulls. The introduction of covered electrodes enabled succesful underwater welding and the production of welds having approximately 80 of the strength and 40 of the ductility of similar welds made in air. Because of the somewhat diminished weld properties, this SMAW application is generally restricted to salvage operations or underwater repair work. Underwater...

Bringing The Workpiece Joint Area To The Soldering Temperature

Soldering Dip Bath Method

The angle at which the copper tip is applied to the work is important in terms of delivering maximum heat. The flat side of the tip should be applied to the work to obtain the maximum area of contact. Flux-cored solders should not be melted on the soldering tip, because this destroys the effectiveness of the flux. The cored solder should be touched to the soldering tip to initiate good heat transfer, and then the solder should be melted on the work parts to complete the solder joint (Ref 11)....

Inertia Drive Welding

The inertia-drive FRW method uses a similar type of machine except that the spindle holding the rotating piece is attached to a flywheel. The flywheel controls the energy input to the weld. The moment of inertia of the flywheel is an important variable that is adjusted by adding or removing flywheels. The amount of energy stored in the flywheel is controlled by its speed. Once the spindle is at the correct speed, the drive system is disengaged, leaving a rotating flywheel mass. Axial pressure...

Shielding Gases for GMAW

By far, the largest number of gas blends have been developed for GMAW, especially for joining carbon steel. These can be roughly divided into four categories pure gases, argon-oxygen mixes, argon carbon dioxide mixes, and three-part gas blends composed of either argon, helium, oxygen, carbon dioxide, or hydrogen. Table 3 contains suggestions for shielding gas selection based on material type, thickness, and mode of metal transfer. TABLE 3 RECOMMENDED SHIELDING GAS SELECTION FOR GMAW TABLE 3...

Friction Welding Process Parameters

Steps Friction Welding

FRICTION WELDING (FRW) is a solid-state welding process in which the heat for welding is produced by the relative motion of the two interfaces being joined. This method relies on the direct conversion of mechanical energy to thermal energy to form the weld, without the application of heat from any other source. Under normal conditions no melting occurs at the interface. Figure 1 shows a typical friction weld, in which a nonrotating workpiece is held in contract with a rotating workpiece under...

Unaltered Graincoarsened Uagc Zone The Zone That Is Not Reheated Above About 200 C 390 F Or The Zone That Is Again

Figure 30 shows how the crack tip opening displacement (CTOD) value of simulated specimens varies with the peak temperature of the second thermal cycle, Tp2 (Tp1 1400 C, or 2550 F). It is seen that the ICGC, UAGC, and SCGC regions have CTOD values less than about 0.1 mm (0.004 in.). Similar low values have been obtained by locating the crack tip in the CTOD tests at corresponding locations in the HAZ of actual multipass weldments. These low toughness regions are commonly known as local brittle...