Arc Brazing Research Articles

Microstructure and bonding strength of tin-based Babbitt alloy on ASTM 1045 steel by MIG arc brazing

The effect of composition of welding wires on the interfacial microstructure and the bonding strength of Babbitt alloys and steel substrate has been studied. A cladding of Sn-based Babbitt alloys was obtained on the surface of medium carbon steel by MIG arc brazing. The microstructure of Babbitt alloys and the interfacial microstructure of the interface between Babbitt alloys and steel substrate have been systematically investigated. The bonding strength of Babbitt and steel substrate has been collected according to the destructive testing method of the bimetallic bonding strength of sliding bearing. Among the three samples, the BW8-4 and steel substrate without no SnSb segregation had the highest bonding strength (83.07 MPa).The reason for the enhancement of the bonding strength was discussed. The IMC layers were harder than the α-Sn matrix so that they can effectively prevent the crack between generating and expanding at the joint part. Then, the bonding strength can be enhanced a lot. However, in samples obtained by BW11-6 and BW8-8, the segregated SnSb phase near the junction which was hard and fragile would result in the concentration of stress. And the SnSb would also lead to the occurrence of brittle fracture in the segregation. So that the bonding strength had been greatly reduced.

Arc Brazing of Aluminium, Aluminium Matrix Composites and Stainless Steel in Dissimilar Joints

The publication describes the approaches and results of the investigation of arc brazing processes to produce dissimilar joints of particle reinforced aluminium matrix composites (AMC) to aluminium alloys and steels. Arc brazing allows for low thermal energy input to the joint parts, and is hence suitable to be applied to AMC. In addition, a braze filler B-Al40Ag40Cu20 alloyed with Si with a liquidus temperature of below 500 °C is selected to further reduce the thermal energy input during joining. The microstructures of the joining zones were analysed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), and X-ray diffraction analysis (XRD), as well as their hardness profile characterised and discussed. Joint strengths were measured by tensile shear tests, and resulting areas of fracture were discussed in accordance to the joints’ microstructures and gained bond strength values.

Microstructure and tribological behavior of tungsten inert gas welding arc brazing tin-based babbit

The microstructure of the tin-based babbit obtained by the method of tungsten inert gas welding (TIG) arc brazing was studied by optical microscopy (OM) and X-ray diffraction (XRD). Tribological behavior was investigated by high-temperature friction and wear testing machine (HTFWT), laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS). It can be found that the higher welding current of the melting tin-based babbit makes it possible to form isomer structure with fine crystals of the cubic SnSb compounds and large star Cu6Sn5 compounds so that a higher hardness can be achieved, and a lower wear rate can be obtained over the entire distance of sliding friction. When the applied load is 2 N, the contact surface is oxidized due to the accumulation of friction heat and oxide, which plays a role of lubricated film. Also, the softer Sn-based solid solution forms obvious furrow under abrasive wear, and the harder SbSn and Cu6Sn5 intermetallic compounds shatter and leave a hole under friction.

Strength Improvement Through Grain Refinement of Intermetallic Compound at Al/Fe Dissimilar Joint Interface by the Addition of Alloying Elements

Dissimilar material joining between Al alloys and steel may be effective in decreasing the weight of automobile bodies. In this study, dissimilar lap joining of Al alloys containing certain alloying elements, such as Ni, Cr, Mn, Ti, or Si, to interstitial-free steel was performed by tungsten inert gas arc brazing, and the effect of the alloying element on the joint strength associated with the Al-Fe intermetallic compound layer at the dissimilar interface was examined. The addition of an appropriate amount of an alloying element to the alloy increased the joint strength; the addition of Ni exhibited the most effective improvement. The additions of some elements changed the grain structure of the η-Fe2Al5 layer but not its chemical composition. This is the first study to clarify that smaller grain size of η-Fe2Al5 correlated to greater strength of the Al/Fe dissimilar joint.

Fast responsive control of current and voltage waveforms for gas metal arc brazing of thin zinc-coated steel sheets

Thin zinc-coated steel sheets are brazed together using a copper-silicon filler alloy and employing a gas metal arc process with dynamic control of current and voltage transients. The actual heat inputs for different wire feed rates during brazing were estimated from the recorded current and voltage transients. Lowering of heat input was aimed at to reduce the thermal distortion and the thickness of the interface layer with intermetallic compounds while ensuring a sound, continuous bead profile. The influence of overall heat input on the thermal distortion, joint strength and interface layer thickness is examined using Fourier number that depicts a ratio of the rate of heat dissipation to accumulation. An increase in brazing speed and a decrease in the wire feed rate resulted in reduced heat input, higher Fourier number, thinner interfacial layer and improved joint strength. The brazing induced thermal distortion reduced with increase in Fourier number. Irrespective of the sheet thickness, a range of Fourier number in between 0.22–0.26 provided brazed joint strength up to 96 % of that of the base metals with minimum interface layer thickness and thermal distortion.

The effect of arc brazing process parameters on the microstructure and mechanical properties of high-strength steel HCT780XD using the copper-based filler metal CuAl8

The effect of undermatching, describing the joining of high-strength base materials with the use of lower strength filler materials, is one of the major common concerns resulting in the limited industrial application of arc brazing. A missing database of mechanical properties and in particular reachable joint strengths is a reason for not adopting the process in production. For this purpose, arc brazed joints of the high-strength steel, HCT780XD, with the copper-based filler-metal, CuAl8, were investigated. The objective of this work was to analyze quantitatively the influence of the CMT-SynchroPulse process and of the resulting intermetallic phase Fe3AlyCuz on the microstructure and mechanical properties of an overlap joint. Tensile strength tests and fatigue strength tests were conducted as well as metallurgical analyzation. The results showed that current industrial concerns about undermatching were not confirmed. For the CMT-SynchroPulse process and a defined amount of intermetallic phases a positive influence on the tensile strength could be determined. For an amount of approximately 8.5% of intermetallic phase within the brazing seam, samples failure occurred in the heat-affected zone of the base material. During the cyclic tests, a negative influence of a predefined gap between the lower and the upper sheet on the fatigue strength could be identified.

Effect of brazing current and speed on the bead characteristics, microstructure, and mechanical properties of the arc brazed galvanized steel sheets

Gas metal arc (GMA) brazing was employed to join hot-dip galvanized steel sheets (GI) in lap joint configuration using CuSi3 filler. The effects of brazing current and speed on the joint characteristics such as bead geometry, microstructure, weldability, microhardness and tensile shear strength were studied. The bead geometry was assessed by examining the bead shape, width, contact angle, penetration width and depth of the fused zone. The microstructural investigations were performed using scanning electron microscopy (SEM), and composition was determined using energy dispersive spectroscopy (EDS). The formation of Fe-Si phases was noticed in the bead which was found to increase with brazing current and brazing speed. The pores were nucleated in GI lap joint at highest current 80A and lower brazing speeds 60–70cm/min. The bead shape and size, joint strength, weldability were found best at a combination of 70A and 80cm/min which could be attributed to a uniform distribution of Fe5Si3(Cu) in the bead. It is suggested that for a pore-free bead structure, the heat input should lie in the range of 58.5–93.6J/mm for the arc brazing of GI sheets.

Alloyed Fluxes of Aluminum–Stainless Steel Arc Brazing

Alloyed fluxes consisting of the non-corrosive flux KAlF4 and alloyed elements Cu, Mn, Ni, and Zr were investigated, respectively, for aluminum–stainless steel TIG brazing. All the alloyed fluxes could both increase the spreading area and decrease the IMC thickness notably. Utilizing the unalloyed flux in the standard braze alloy as a control for comparison, the area increased from 55.3 to 98.5 mm2 with 30% Mn alloyed flux and the thickness was reduced from 15.1 to 4.1 μm with 10% Ni alloyed flux, in maximum. The variation tendencies of spreading area and IMC thickness with element content were obviously different. The change of wetting and spreading behavior was attributed to the combination effect of flux and alloyed elements. The IMC decreased with the alloyed elements was related to the change of dissolution rate of the stainless steel into the liquid aluminum.

The effect of TIG arc brazing current on interfacial structure and bonding strength of tin-based babbit

The interfacial structure of the tin-based babbit obtained by TIG arc brazing was studied through the OM, XRD, SEM and EDS and the bonding strength was investigated by the Electronic Universal Testing Machine. It can be found that interfacial layers, unequal in thickness, ranged from 10.26 to 34.27 μm and IMCs layers formed at the interface, ranged from 1.5 to 4 μm as the welding current increased from 50 to 90 A. Also, the bonding strength apparently increased from 73 to 155 Mpa and shear fractures which occurred at the interface near iron substrate side were mainly brittle cleavage fracture. On the brazed interface, the higher element concentration of Fe was helpful to promote the metallurgical reaction and ensured the bonding property. The phase constituents of IMCs were FeSn, FeSn2 and Fe3Sn2. Moreover, the FeSn layer was plate shape, FeSn2 layer and Fe3Sn2 layer were branched shape which staggered with the plastic Sn-based solid solution so that the bonding strength was improved. Physical model of the Fe–Sn IMC layers formation mechanism was proposed, the experimental results further showed that the model was scientific and effective.

Wetting length in gas metal arc brazing of galvanised steel

Appropriate substrate surface wetting by a molten filler ensures a sound bead profile during brazing. A theory to estimate the wetting length considering gradual cooling of liquid filler and loss in its ability to spread is currently unavailable. We present here a methodology to estimate wetting length based on the minimisation of energy for spreading of a liquid filler considering its gradual cooling and tested the computed results in gas metal arc brazing of galvanised sheets for a wide range of conditions. The computed wetting lengths are used further to estimate bead height and toe angle of joint profile.

Wetting behavior of AlAgCu brazing filler on aluminum matrix composites and stainless steel

Suitable joining technologies are necessary for the application of aluminum matrix composites (AMC). Especially dissimilar joints between AMC and stainless steel are of enhanced interest. In this work, the approach of arc brazing source of this material combination is investigated. Therefore, basic examinations like the wetting behavior of a developed filler on the base metals is realized. The used filler of the system Al-Ag-Cu show a ternary eutectic of the phases Ag2Al, Al2Cu, and solid solution of Al. Sessile drop technique is applied for the wetting tests. To generate the arc, a TIG welding unit is used. The results of these wetting tests, like the wetting angles and the microstructure of the interfaces, are described and discussed. The wetting angle measured on cross sections show that the wetting on AMC is good (< 30°) while the wetting on stainless steel (~ 90 °) has to be improved. That demonstrates the excellent wettability of the AMC and the suitability of that approach. The wettability of stainless steel can be improved by pretreating, like preheating and polishing, which results in a wetting angle of approx. 35°. The influence of these pretreatments on the microstructure due to a various diffusion behavior of, for example, Al at the interface of the combined materials are described. Different phases in comparison to the filler can be seen at the interfaces of braze metal and the base metals by using SEM, due to a strong diffusion of Al. Analyze by energy-dispersive x-ray spectroscopy (EDXS) and x-ray diffraction (XRD) at the interface of braze metal to stainless steel indicate intermetallic layers of the system Fe-Al, like AlFe3, Al2Fe and Al13Fe4. In the case of the AMC, a solid solution of Al in shape of a not compact layer occurs and no formation of Al4C3 can be detected.

Joining of material compounds of aluminium matrix composites (AMC) by arc brazing using Al-Ag-Cu system filler alloy

Aluminium matrix composites (AMC) are in the focus of recent research. In the field of lightweight design, dissimilar joints with AMC are of current interest. To ensure the positive properties of AMC—like high specific strength, increased wear resistance, and low coefficient of thermal expansion (CTE)—a suitable joining technique is necessary. This work shows the state of the art of arc brazing using a filler material of the alloying system Al-Ag-Cu. Joints of AMC/stainless steel and AMC/aluminium alloy are investigated. The formation of brittle Al-Fe intermetallic phases in AMC/stainless steel joints must be reduced to obtain a sufficient joint strength. Therefore, an adapted alloying concept is used for the filler material. The filler (40 wt% Al, 40 wt% Ag, and 20 wt% Cu) is alloyed with various contents of Si (1.2, 1.3, and 1.4 wt%). Primarily solidified Si can be seen above 1.3 wt% Si in the microstructure. The melting temperature could be reduced about 10 K by additional Si. The microstructure analyzed by SEM, EDXS, and XRD, as well as the hardness profile of the joining zone, are characterized and discussed. In case of the interface braze metal/aluminium material, the formation of a thin (approx. 5 μm) phase layer, consisting of solid solution of Al, can be seen. Compared with that insights, the phase layer at the interface braze metal/stainless steel consists of intermetallics of the system Fe-Al. The results of the hardness measurements at the interface and XRD patterns prove the presence of Fe3Al, FeAl, and FeAl3. Cracks can occur between the brittle phases FeAl and FeAl3, due to their high hardness of approx. 600 HV0.005 (rep. FeAl) and 1020 HV0.005 (rep. FeAl3) and in combination of internal stress formation during cooling.

Corrosion Behavior of Brazed Zinc-Coated Structured Sheet Metal

Arc brazing has, in comparison to arc welding, the advantage of less heat input while joining galvanized sheet metals. The evaporation of zinc is reduced in the areas adjacent to the joint and improved corrosion protection is achieved. In the automotive industry, lightweight design is a key technology against the background of the weight and environment protection. Structured sheet metals have higher stiffness compared to typical automobile sheet metals and therefore they can play an important role in lightweight structures. In the present paper, three arc brazing variants of galvanized structured sheet metals were validated in terms of the corrosion behavior. The standard gas metal arc brazing, the pulsed arc brazing, and the cold metal transfer (CMT®) in combination with a pulsed cycle were investigated. In experimental climate change tests, the influence of the brazing processes on the corrosion behavior of galvanized structured sheet metals was investigated. After that, the corrosion behavior of brazed structured and flat sheet metals was compared. Because of the selected lap joint, the valuation of damage between sheet metals was conducted. The pulsed CMT brazing has been derived from the results as the best brazing method for the joining process of galvanized structured sheet metals.

Effects of Alloyed Fluxes on Spreading Behavior and Microstructures of Aluminum–Titanium TIG Brazing Interface

Alloyed fluxes consisting of the non-corrosive aluminum brazing potassium fluoroaluminate flux and alloyed elements Cu, Zr and Ni were firstly developed and studied for aluminum–titanium TIG arc brazing. Not only the alloyed fluxes can promote wetting of molten aluminum filler on the titanium, but suppress the formation of the intermetallic compound (IMC) layer as well. Results indicated that the alloyed fluxes exerted different influences on spreading areas. Comparing with the unalloyed flux, the spreading area of aluminum on titanium with Cu alloyed flux increased significantly, from 116 to 143 mm2. Moreover, evident differences in IMC thickness were observed corresponding to various fluxes. The IMC thickness rose dramatically at first and then declined with the increasing concentration of alloying element. The IMC can be reduced effectively by employing the fluxes with 50% Cu or Ni. The root cause is attributed to the Cu and Ni distribution in the aluminum brazing joint.

Welding process characteristics of pulse on pulse MIG arc brazing of aluminum alloy to stainless steel

While the MIG arc brazing method provides significant potential for joining aluminum alloy to stainless steel, the welding process is still hard to examine and control quantitatively. In this work, pulse on pulse was applied to improve the stability of conventional pulse gas metal arc brazing (P-GMAB) process, which was determined by measurement of welding current and voltage signals. The results based on time domain and frequency domain analysis demonstrate that the welding process stability of pulse on pulse gas metal arc brazing (PP-GMAB) far outweighs that of P-GMAB. These quantitative results are tested and validated with experimental results. The metal transfer mode of P-GMAB was the blend of one drop per pulse (ODPP) and multiple drops per pulse (MDPP). However, for high energy pulse of PP-GMAB, the droplet transfer mode is primarily ODPP with a few number of two drop per pulse (TDPP); for low energy pulse, the metal transfer maintains ODPP through the whole welding process. The improved weld formation by employing the pulse on pulse mode is due to its stabler welding process.

Technology improvement for manufacturing and repair of collapsible pipelines

Application of arc brazing technology for manufacturing and repair of collapsible pipelines to replace arc MIG/MAG welding was proposed. The use of this technology to connect galvanized elements of collapsible pipelines preserving the protective coating in the joints was analyzed and justified. Strength of samples of welded and brazed joints, galvanized pipes, collapsible field pipelines by tear test was investigated and strength characteristics of joints defined by measuring the hardness of a section connections was defined. It was found that joints made by arc brazing by CuAl8 filler rod have the strength level of the welded joints. Due to the small thermal effects, with arc brazing, there is no destruction of the protective zinc coating at the joint place. Research results allow recommending arc brazing technology by CuAl8 filler for manufacturing and repair of collapsible pipelines, preserving strength joints without destruction of the protective zinc coating at the joint place.

Development of the zinc coating pipe connection technology with arc soldering method using

The application of the arc brazing method for zinc-coated pipes joining with using the copper-based additives is suggested in this publication. This method is an alternative of the arc welding with minimal destruction of coating at the adjacent to the weld area, and it application has been analyzed and substantiated. The microstructure and microhardness research of the zinc-coated low-carbon steel pipes with the diameter of 150 mm and wall thickness of 3.2 mm was made and research results are presented. The research results have shown that joint formation takes place due to a diffusive layer at the alloy line, and the connection strength depends on its sizes. It is revealed that magnification of the intermetallic phases volume concentration in the weld metal increases its strength. It is found that the strength of the arc-welded pipe joints is affected by bevel edges. The connection with bevel edges has a greater strength with straight edges, as well as the contact area is increased with the base metal weld. The arc brazing method can be recommended for zinc-coated pipes joining with using the CuAl8 wire and the bevel edge has to be made before arc brazing via research results. This method will provide the sufficient joints strength without the considerable zinc cover damage.

최신의 고능률 브레이징 기술개발 동향

Recent developing tendency for technologies of high efficient brazing are studied by searching of NDSL, Science Direct, KIPRIS, PCT and so on. Active metal brazing, arc brazing, fluxless brazing, brazing with low melting point, reactive air brazing, laser brazing, laser droplet brazing are investigated. By optimal selecting of the above mentioned technologies, it needs to investigate an economical metallurgical design and the advanced brazing methods. To improve the embrittlement of intermetallic compound at brazing interface, it must be studied the inexpensive variant metals including nonmetals and the heat sources(MIG, TIG, Laser) by hybrid techniques. Key words: Brazing, fluxless brazing, Laser brazing, Active metal, Laser droplet, Intermetallic compound

Microstructure and Mechanical Properties of Plasma Arc Brazed AISI 304L Stainless Steel and Galvanized Steel Plates

Plasma arc brazing is used to join the AISI 304L stainless steel and galvanized steel plate butt joints with the CuSi3Mn1 filler wire. The effect of parameters on weld surface appearance, interfacial microstructure, and composition distribution in the joint was studied. The microhardness and mechanical tests were conducted to determine the mechanical properties of the welded specimens. The results indicated that good appearance, bead shape, and sufficient metallurgical bonding could be obtained when the brazing process was performed with a wire feeding speed of 0.8 m/min, plasma gas flow rate of 3.0 l/min, welding current of 100 A, and welding speed of 27 cm/min. During plasma arc brazing process, the top corner of the stainless steel and galvanized steel plate were heated and melted, and the melted quantity of stainless steel was much more than that of the galvanized steel due to the thermal conductivity coefficient difference between the dissimilar materials. The microhardness test results shows that the microhardness value gradually increased from the side of the galvanized steel to the stainless steel in the joint, and it is good for improving the mechanical properties of joint. The tensile strength was a little higher than that of the brazing filler, and the fracture position of weld joint was at the base metal of galvanized steel plate.

Microstructure of arc brazed and diffusion bonded joints of stainless steel and SiC reinforced aluminum matrix composite

Joint interfaces of aluminum and stainless steel often exhibit intermetallics of Al-Fe, which limit the joint strength. In order to reduce these brittle phases in joints of aluminum matrix composites (AMC) and stainless steel, diffusion bonding and arc brazing are used. Due to the absence of a liquid phase, diffusion welding can reduce the formation of these critical in- termetallics. For this joining technique, the influence of surface treatments and adjusted time- temperature-surface-pressure-regimes is investigated. On the other hand, arc brazing offers the advantage to combine a localized heat input with the application of a low melting filler and was conducted using the system Al-Ag-Cu. Results of the joining tests using both approaches are described and discussed with regard to the microstructure of the joints and the interfaces.