Showing papers on "Heat-affected zone published in 1982"

Heat generation and heat flow in the filler metal in GMA welding

Abstract: The physical processes governing the generation and the flow of heat in a consumable mild steel wire were investigated to determine the influence of the welding parameters on melting rate and drop temperature. The work is limited to processes where the wire is at positive polarity. The analysis of the heat balance is based on measurements of the melting rate as a function of the electric current and the extension length, at a given wire diameter. The ohmic power developed in the wire was calculated from the measured data. It was found that it is, in general, not sufficient to account for the observed melting rate. Consequently, there must be a flow of heat from the anode surface on the molten tip, through the liquid metal, to the solid part of the wire. The corresponding heat flow rate was derived from the experimental data; it was found to depend on current and melting rate. Simple physical models are presented that describe the transport of heat through the liquid and account for the experimental results. In the model for globular drop transfer, the dominant mechanism is fluid flow, which is caused by the Lorentz force. In the case of spray transfer, the heat flow is ascribed to thermal conduction through the liquid metal that is flowing down the pointed wire tip. The models yield expressions for melting rate and drop temperature as functions of current, extension length, and wire diameter. An analysis was made of data reported by Lesnewich on the critical current for the transition from globular to spray transfer. This transition occurs in a current range where the downward force on a drop is mainly due to the impact of the incoming liquid, and to electromagnetic effects. It was found that the total downward force is roughly equal to the sustaining force by the surface tension, at the critical current. Introduction This paper describes an investigation of the flow of heat and mass from a consumable wire to the weld pool. This subject is of interest, because the influx of drops of hot metal supplies a major part of the total power supplied to the weld pool (Ref. 1, 2). The work is limited to gas metal arc (GMA) and to stationary processes where the electric current I, the electrode or wire velocity, vw , and the length of the electrode or wire extension, L, are constant in time. We define the extension length as the distance between the melting front and the point, where the current enters the wire within the contact tube —Fig. 1. The flow processes mentioned above are described by the melting rate rh, and the drop temperature, Tdr. The latter two quantities are determined by the heat generated in the wire, and the heat flow through it. The work presented here deals with these processes. It leads to expressions for rh and T^r as functions of I, L, and the wire diameter, d w . Furthermore, an analysis is given of the mechanism which governs the transition from globular to spray transfer. The work presented here is limited to processes where the wire is positive with respect to the workpiece. A power I ip is then generated at the surface of the liquid tip by electron absorption, where

Process for the production of a composite metal part and products thus obtained

Abstract: The present invention relates to the production of metal parts whose core and surface must have different characteristics. Its subject comprises firstly a process for the production of a composite metal part by coating or hard-surfacing a metal core of low-alloy structural steel with a harder metal layer composed of a high-speed chromium-tungsten or chromium-molybdenum steel or a high-speed steel containing chromium associated at the same time with a plurality of elements such as tungsten, molybdenum, vanadium, and cobalt, this process being at the same time characterized in that this high-speed steel has a hardness higher than 57 Rockwell C, in that the low-alloy steel which constitutes the metal core is selected to be compatible with the said high-speed steel, in that the said high-speed steel is applied exclusively in the form of a prealloyed powder, and in that the coating or hard-surfacing of the core with this powder is effected with the aid of one of the welding processes of the follow-group: welding by means of a transferred or semi-transferred arc plasma torch, or welding by means of a laser torch, the operation of coating or hard-surfacing by welding being followed by heat treatment. Another subject of the invention comprises the products obtained by the abovedescribed process. It is particularly applicable to the production of rolls for cold rolling mills, rolling or forming rollers, shear blades, wear plates, and armor plates.

Spark plug for internal combustion engines having an alloy layer between the electrodes and tip ends

Abstract: A spark plug for an internal combustion engine including a center electrode, an earth electrode, a metal tip joined by welding to an ignition section of at least one of the center electrode and the earth electrode, and an alloy layer located at a welding portion between the metal tip and the at least one electrode. The metal tip is formed of material highly resistant to heat and wear which is distinct in the coefficient of thermal expansion from the material of the electrodes. The alloy layer is formed to have a thickness of at least about 10μ, so as to avoid the rupture of the metal tip along the surface thereof adjacent to the welding portion.

Method for welding with the help of ion implantation

Abstract: The invention is a method for welding together two parts with the help of ion implantation. The method comprises weakening the chemical and atomic bonds of the surface and near surface atoms of at least one of the surfaces to be welded together by ion implantation techniques. The ion implanted surface may then be cold or diffusion welded to the surface of the other part using conventional methods. The method is particularly applicable to welding together parts of dissimilar metals normally difficult to affect a satisfactory weld.

Method and apparatus for controlling resistance welding

Abstract: Method of controlling resistance welding to obtain high quality welds in which the pressure between the electrodes (2a, 2b) holding the materials (1a, 1b) to be welded is controlled so that the resistance value between the two electrodes (2a, 2b) is a predetermined value, and the welding current is regulated so that the voltage between the electrodes is a predetermined value, and the time during which the welding current flows is controlled to a fixed period.

A new approach to the weldability of nickel-base As-cast and power metallurgy superalloys

Abstract: The repair of nickel-base superalloys such as those used in the first and second stages of the rotating sections of a gas turbine is examined. Welding is affected by stress and temperature levels of the blade, wall thickness, and material composition. Steps to achieve crack-free welds include preheating above 600C (1112F) for GTA and plasma arc welding and above 900C (1652F) for EB welding. It is concluded that crack formation can be prevented by controlling the cooling rate during welding; that hardness measurements provide useful results for crack-free welding using GTA, plasma, friction, and electron beams; and that small differences in chemical composition and homogeneity can have a decisive effect on weld behavior.

Method of welding titanium alloy parts with titanium insert

Abstract: A method of welding opposite end surfaces of two titanium alloy parts kept in alignment by a high energy-density welding process such as electron beam welding, laser beam welding or TIG arc welding, characterized by closely interposing an insert member of either practically pure titanium or Ti-Al binary alloy containing up to 3 Wt % of Al. Owing to thorough alloying of the inserted titanium with the constituents of the fused base metal, the weld metal in a weld joint obtained by this method is sufficiently high in both strength and toughness. By an optional postwelding heat treatment, the strength of the weld metal can further be enhanced.

Arc welding gun with gas diffuser and external cooling conduit

Abstract: A welding wire gun operable in the high temperature environment of a high current density welding system. The welding gun includes a tubular member through which welding wire and shielding gas are adapted to pass. A gas diffuser member is mounted upon one end of the tubular member and, in turn, supports a welding tip therein such that the end of the welding tip projects beyond the diffuser in the direction of the joint to be welded. Additionally, the welding gun is constructed to provide for flowing of a coolant material around the tubular member proximate the diffuser member for maintaining the welding tip below its melting or distortion temperature. A tubular nozzle member is supported at one end from the diffuser member and extends beyond both the diffuser member and the welding tip in such a way as to define an annular shielding gas chamber about the diffuser and welding tip. Gas passages formed through the diffuser communicate with the annular gas chamber and are angularly oriented with the central axis of the diffuser and welding tip so as to maximize the velocity and minimize turbulence of the gas flow through the gun to thereby maintain a high energy shielding gas envelope around the welding wire and weld puddle.

Apparatus for cutting and/or welding laminar thermoplastics material

Abstract: Laser apparatus for longitudinally slitting and welding a collapsed tube of polyethylene film comprises a laser having a guide (27) directing the laser beam at the film as it passes over a roller (13). The middle section of the roller is a hollow quartz cylinder (40) which absorbs laser energy passing through the film and enhances cutting and welding efficiency. A jet (80) of air is directed at the film immediately in front of the focus (60) of the laser to flatten the film on the cylinder (40) and disperse any smoke.

Consumable electrode type arc welding device

Abstract: PURPOSE:To provide a titled welding device which improves welding performance and the efficiency in welding work by the constitution wherein the waveform of welding current is pulsed to form a spray arc and a separate filler wire is fed under electrical heating into the arc. CONSTITUTION:Welding current is flowed from a power source 24 through a tip 16 to a consumable electrode 10, which is fed by a roll 12 driven by a motor 14, to generate an arc 20 between the electrode and a base material 60. The adequate pulse waveform corresponding to the feed speed of the electrode 10 is formed in the welding current by a frequency setter 46, a pulse width setter 48 and a switching element 34 to make the droplet from the electrode 10 into a spray. A filler wire 26 is at the same time fed into the arc 20 while it is heated by part of the welding current supplied from a power feeder 32 to adjust the penetration rate of the molten metal. The heating current for the wire 26 is controlled by a frequency setter 46, a pulse width setter 50, a current comparator 59, a switching element 36, etc. so that said current is kept at <=1/2 of the welding current and is made zero during the quiescent period of the pulse.

Tig welding method of narrow groove

Abstract: PURPOSE:To make an arc oscillatable in the transverse direction of a groove and to perform stable penetration in the TIG welding stage of a narrow groove joint of extra thick plates, by forming an electrode and a filler metal respectively into a band shape, and applying an alternating magnetic field in the weld line direction to the arc. CONSTITUTION:A nonconsumable W electrode 4 screwed 3 to a copper electrode nozzle 2 is formed into a band shape and a filler metal 10 to be supplied to an arc 11 part by passing through the inside of a filler nozzle 8 of a gas shielded nozzle 6 is also formed into a band shape in TIG welding in the narrow groove between groove wall surfaces 19 and 19. A magnetic core 12 of which the forward end passes through a gas shielded nozzle 7 and extends to the part near the arc 11 is connected to the magnetic pole of an electromagnet coil 13. The arc 11 is oscillated in the transverse direction by the alternating magnetic field generated from the core 12 and the narrow groove of extra thick plates is welded in the joint part having high quality by using the bank-like filler metal.

Welding method of tempered type steel pipe

Abstract: PURPOSE:To obtain a welded steel pipe having high tensile strength and low temp. toughness, by tempering the same under limited conditions under submerged arc welding by a wire of the specific compsn. consisting of C, Si, Mn, Ni, Cu, P, S, Fe, etc. and a flux having specific basicity. CONSTITUTION:A steel pipe is welded by submerged arc welding by using a welding wire consisting of 0.05-0.15% C, =1.5, more preferably about 1.5-2.5 basicity B expressed by the equations. The welded steel pipe is quenched after heating to 900-1,100 deg.C and is then tempered for >=5min at 600-700 deg.C, whereby the welded steel pipe having the weld metal of high low temp. toughness wherein the Charpy transition temp. is about =50kg/mm. is obtd.

Development and Application of Dabber Gas Tungsten Arc Welding for Repair of Aircraft Engine, Seal Teeth

Abstract: Dabber TIG welding can be defined as a modification of an automatic TIG welding system. Modifications, both mechanical and electronic, combine to cause an intermittent filler wire feed to the molten weld puddle. This interrupted action allows for momentary cooling of the weld puddle. Energy input, as heat, for a given time span is reduced by this action. In addition the interruption allows solidification of the puddle with resultant narrow, uniform bead. This weld mode is characterized by shallow heat affected zones and precise weld build up configurations. This paper describes the application of this procedure to Gas Turbine Seals.Copyright © 1982 by ASME

Method of an apparatus for welding together metal components

Abstract: In having a method of welding together metal components (A,B) a high restraint geometry (as defined in the Specification) the components are urged into abutment and a high energy density weld is effected at a location in said abutment by means such as a focussed laser beam (L). In order to compensate for the high restraint geometry of the components which prevents them from deformation such as to accommodate welding stresses, an additional force (J) is applied, for example by a roller (K), to urge the components together adjacent to the position at which the weld is effected. The method is advantageously employed to form a continuous elongate weld between a plateform and web of a brake shoe.

Method for heat treating metal

Abstract: A method for relieving stress in the microstructure welds and the heat affected zone in the adjacent base metal in low alloy steel by induction heating in a second post-weld heat treatment. The heated area is monitored with a radiation pyrometer to ensure precise temperature control of the procedure.

Microstructure of weld heat-affected zone of 12Cr–Mo steel

Abstract: Detailed studies have been made of the transformations and microstructure of the weld heat-affected zone (HAZ) of a class 212Cr–Mo steel, particular attention being given to δ-ferrite. The investigation covered a wide range of welding heat inputs and involved real and simulated HAZ material. To obtain the phasetransformation data extensive use was made of a weld simulator and dilatometer. The weld H AZ consisted of three regions: secondary-hardened martensite, homogeneous martensite, and duplex δ-ferrite and martensite adjacent to the fusion line. The amount of δ-ferrite increased with increasing weld heat input. It was shown that δ-ferrite forms above 1320°–1360°C, depending on the heat rate and remains untransformed on cooling to room temperature for the normal range of weld cooling rates. Detailed metallography showed that δ-ferrite forms at austenite grain boundaries, involves redistribution of allo ying elements and is associated with interphase precipitation of carbides. However, in amounts ...

Welding process for applying a hardfacing to a nodular iron base metal

Abstract: A hardfacing 16 is applied to a nodular iron base metal 15 without preheating or postheating the base metal. Initially a gas tungsten arc welding torch is applied to the base metal (at ambient temperature) to form a puddle of the base metal. Then a filler metal, e.g. a high chromium iron. is fed into contact with the arc to form a melt of the filler metal on the base metal. The base metal is then allowed to cool to ambient temperature with postheating.

Electro-slag welding process for irregular sections

Abstract: An electro-slag welding method and apparatus has been developed for butt-joint welding of steel rails or other metallic pieces having irregular cross section, in which the head and the web of the rail is surrounded with a conventional water cooled copper mold and the flange area is surrounded by a ceramic lined crucible. In addition to the conventional single central welding electrode, two or more electrodes are inserted through the lids of the ceramic crucible adjacent the outer ends of the rail flange so as to reduce the total welding current required to produce a complete flange weld and spread the welding energy, thereby reducing excess power and overheating at the central electrode, resulting in better metallurgical quality welds.

Method and apparatus for shaping beads of welded steel section

Abstract: In manufacturing steel sections by high-frequency resistance welding, weld beads are produced along the weld line of the material. However, rolls disposed in the neighborhood of the welding end point squeeze the red-hot weld beads into a uniform shape.

T-joint welding method

Abstract: PURPOSE:To execute T-joint welding which forms stably and uniformly a penetration bed on the left and right, by making the end edge of the second member press-contact with the reverse side of a groove-like groove of the first member, generating an arc on the surface side of the groove, and also providing an alternating field CONSTITUTION:The end edge of the second member 3 is butted so as to be orthogonal to the reverse side of a groove of the first member 1 having a groove-like groove 2, a W electrode 4 and the first member 1 are electrified from a welding power source 5, an arc 6 is generated on the center line Y of the second member 3 on the surface side of the groove 2, and a molten metal 13 is formed by melting a filler rod (omitted in the figure) Also, at the same time, an alternating current is made to flow from a power source 9 to a coil 8 of an enameled copper wire, etc wound to a torch body 7, protecting a weld from the air by making shield gas 10 of inert gas flow, an alternating field being orthogonal to a welding current is formed, the molten metal 13 is rocked and stirred, and a T-joint weld having a uniform penetration bed is formed on the left and right leg parts by a solidified weld metal 14

Precise positioning for a welding electrode which follows a three dimensional weld path

Abstract: A welding apparatus which includes a welding electrode and a filler wire assembly. The welding electrode and the filler wire assembly are fixed together and are to move along a weld path on a workpiece. The weld path may either take a regular or an irregular shape. The welding electrode is mounted on a welding electrode bracket which is rotatably mounted on a rotational axis upon a housing. The rotational axis of the filler wire assembly in respect to the welding electrode is precisely controlled so that just the tip of the filler wire is continuously located just forward (along the weld path) of the tip of the welding electrode regardless of the direction of movement of the welding electrode along the weld path. Three dimensional, preprogrammed movement along an X-axis, a Y-axis and a Z-axis can occur between the welding electrode and the workpiece. The welding electrode is also permitted an additional amount of limited movement along the Z-axis which is not programmed. This limited movement is to maintain the electrode at a constant distance from the workpiece within the weld path. This is obtained through an automatic voltage control system which is to hold the arc voltage constant.

Method and device of welding

Abstract: PURPOSE:To apply defect-free welding upon materials to be welded which differ in welding conditions according to welding positions by controlling heat input in such a way that the temp. near the succeeding end of the molten pool of the materials to be welded coincides with preset temps. CONSTITUTION:In a TIG welding method which generates an arc 20 with a nonconsumable electrode 12 of a welding head 14 rotating around a fixed circular pipe 10 which is an object to be welded, the IR light radiated from the temp. measuring point P near the succeeding end of a molten pool 22 formed by the arc 20 is conducted through an IR light condensing part 24, an optical fiber 28, etc. to an IR temp. detector 30. Here, the IR light past an interference filter 34 is converted to an electric signal with a detecting element 36. Said signal is inputted through an amplifier 38 to a control device 42 which compares the same with the temps. preset at each of sections AB, BC, CD, DA and regulates a pulse welding power source 44 in such a way that said signal coincides with said temps., thereby controlling the heat input to the object 10 by the arc 20.

Hot wire type arc welding system

Abstract: In a welding apparatus employing a switching element between a power source and a filler wire, a protection circuit operates to discontinue the function of the switching element when a short-circuit is detected between, for example, the filler wire and a welding electrode, so that the switching element is protected from damage due to an overcurrent.

Butt welding method of high purity ferritic stainless clad steel

Abstract: PURPOSE:To obtain a welded joint part which is excellent in both corrosion resistance and a mechanical property, by welding a base metal part of clad steel with a same metal, subsequently, performing butt-welding on a cladding member by a build up welding according to a low dilution welding method by use of a welding rod having the same composition as a cladding material. CONSTITUTION:In case of welding of clad steel whose cladding material is high purity ferritic stainless steel containing 16-21wt% Cr and 0.75-3.5wt% Mo, the same metal welding of a base metal part is completed, and thereafter, a cladding member is butt-welded by building up to >=2 layers in accordance with a low dilution welding method by use of a welding rod having the same composition as the cladding material. As for welding of said cladding material, if necessary, the first layer is welded by a ferritic stainless steel welding rod containing 25-33wt% Cr and 0.75-3.5wt% Mo, and the residual part is welded with a same material or the first layer is welded by a welding rod having the same component as the cladding material, and therefore, said welding can be executed, as well.

The fatigue crack growth behavior of electron-beam welded a286 superalloy

Abstract: Fatigue crack growth curves(Δa/ΔN =f(K max )) were measured with 2.5 mm thick sheets of electron beam welded iron base superalloy A286. Fatigue testing frequency was 21 kHz,R = −1 (mean stress zero) and the environment was noncorrosive silicone oil at 20 °C. Two series of samples with different welding conditions were tested. One series was welded perfectly, whereas the second contained microcracks within the weld and the heat affected zone. It was shown that the crack growth rate in the base metal is slower than in the weld. The threshold stress intensity factorK th of the base metal is 14 MNm-3/2 and that of the weld, 10 MNm -3/2 . However, at higherK max values, the crack grows more rapidly in the weld than in the base metal; for example, the crack growth rate is 16 times higher at Kmax = 20 MNm -3/2 . Microcracks introduced by an imperfect welding process do not influence the fatigue cracking behavior in the threshold regime; atK max = 15 MNm-3/2, however, the crack growth rates differ by an order of magnitude. Fractographic examination shows considerable differences in the fracture appearance of weld, heat affected zone, and base material. Weld and base metal display ductile fracture surfaces and the heat affected zone is characterized by crystallographic fracture facets.

Flux cored wire for submerged arc welding

Abstract: PURPOSE:To perform welding with easy start of arc and high stability of arcs at a high rate of deposition by using a flux cored wire of a specific compsn. contg. stainless steel powder in submerged arc welding of stainless steel. CONSTITUTION:A flux of the following compsn. is packed in a stainless steel hollow wire of the same material as the stainless steel to be welded as a flux cored wire to be used in submerged arc welding of stainless steel: A flux which contains 0.5-20% 1 or >=2 kinds among rutile, ilmenite and zircon sand by weight of the wire, 0.05-3% 1 or >=2 kinds among potash feldspar, silica and wollastonite, 0.2-5% 1 or >=2 kinds among calcium carbonate, lithium carbonate and barium carbonate, 0.3-2% fluorides such as CaF2 and wherein stainless steel powder is so mixed at <=25% ratio that weld metal and the materials to be welded have the same compsn.