Non-corrosive Flux Research Articles

Microstructures and mechanical properties of brazed 6063 aluminum alloy joint with Al-Cu-Si-Ni filler metal

In this study, brazing experiments were carried out on 6063 aluminum alloy using Al-20Cu-5Si-2Ni filler alloy. Microstructure, mechanical property, and removing behavior of oxide film of the brazed joints were analyzed. The results revealed that the 3% (CsF-AlF3) + 97% (KF-AlF3) non-corrosive flux showed high activity, especially effective removal of oxide films during the brazing process. For the brazing condition of 580 °C/10 min, the brazing seam contained less CuAl2 intermetallic compared with that of 570 °C/20 min and presented a higher shear strength of 126.1 MPa at room temperature. After heat treatment the joint strength was increased to 156.5 MPa. Furthermore, the heat-treated joints subjected to a salt spray test still retained a shear strength of 150.2 MPa.

Development of Metal Composite Powder Non-corrosive Flux for Low Temperature Forming of the Aluminum Brazing Filler Material

Development of Metal Composite Powder Non-corrosive Flux for Low Temperature Forming of the Aluminum Brazing Filler Material

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.

Interfacial microstructure and mechanical properties of brazed aluminum / stainless steel - joints

Due to the demand of mass and cost reduction, joints based on dissimilar metals become more and more interesting. Especially there is a high interest for joints between stainless steel and aluminum, often necessary for example for automotive heat exchangers. Brazing offers the possibilities to manufacture several joints in one step at, in comparison to fusion welding, lower temperatures. In the recent work, aluminum / stainless steel - joints are produced by induction brazing using an AlSi10 filler and a non-corrosive flux. The mechanical properties are determined by tensile shear tests as well as fatigue tests at ambient and elevated temperatures. The microstructure of the brazed joints and the fracture surfaces of the tested samples are investigated by SEM.

Mechanical and microstructural behavior of brazed aluminum / stainless steel mixed joints

There is a requirement to combine different materials such as aluminum and stainless steel in industrial applications like automotive heat exchangers. Brazing offers the possibility to reduce the joining temperature in comparison to welding due to the lower liquidus temperature of the fillers. In the present work, the mechanical and microstructural behavior of aluminum / stainless steel mixed joints is investigated. The specimens are produced by induction brazing using an AlSi10filler and a non-corrosive flux. To evaluate the mechanical properties of the joints, tensile tests at elevated temperatures are carried out. Additionally, long-term thermal exposure experiments are done in order to investigate the changes in the microstructure.

Application of Induction Heating for Brazing Parts of Solar Collectors

This paper reports on the application of induction heating for brazing parts of solar collectors made of Al alloys. The tube-flange joint is a part of the collecting pipe of a solar collector. The main task was to design an induction coil for this type of joint, and to select the optimum brazing parameters. Brazing was performed with AlSi12 brazing alloy, and corrosive and non-corrosive flux types were also applied. The optimum brazing parameters were determined on the basis of testing the fabricated brazed joints by visual inspection, by leakage tests, and by macro- and micro-analysis of the joint boundary. The following conditions can be considered to be the best for brazing Al materials: power 2.69 kW,brazing time 24 s, flux BrazeTec F32/80.

Improving arc joining of Al to steel and Al to stainless steel

Gas-tungsten arc welding (GTAW) with controlled heat input could avoid the formation of massive brittle Al–Fe intermetallics during solidification in dissimilar-metal joining of aluminum to steel. In the first part of the present study an Al–Mg alloy was joined to galvanized steel by GTAW with an Al–Si filler metal. The weld solidification microstructure was explained based on the Al–Mg–Si phase diagram. Ultrasonic vibration during GTAW increased the joint strength by 27%. Grain refinement, decreased Fe–Al intermetallics, and increased microhardness in both the heat-affected zone and the weld were observed, thus explaining the improved joint strength. In the second part, an Al–Mg alloy was joined to 304 stainless steel using a Zn-15Al filler metal with a noncorrosive flux core. The weld solidification microstructure was explained based on the Al–Zn–Mg phase diagram. Postweld heat treatment (PWHT) at 280 °C for 30 min doubled or even tripled the joint strength depending on the Al-sheet thickness. Dissolution of coarse Zn-rich particles at the weld/steel interface was observed after PWHT, thus eliminating these weak particles from the interface. The formation of Zn-rich particles near the interface and their dissolution by PWHT were explained based on the Al–Fe–Zn phase diagram.

Brazability of dissimilar metals tungsten inert gas butt welding–brazing between aluminum alloy and stainless steel with Al–Cu filler metal

Dissimilar metals tungsten inert gas butt welding–brazing between 5A06 aluminum alloy and SUS321 stainless steel was carried out using Al–Cu6 filler metal and non-corrosive flux. A thin intermetallic compound layer has formed in welded seam/steel interface and the average thickness of the whole layer is 3–5 μm, which is less than the limited value of 10 μm. The intermetallic compound layer consists of Fe 4Al 13 phase and at the bottom Sn deposits in the molten flux layer and diffuses into steel matrix to form the grain boundary filter layer, which is the weak zone of the butt joint. The average microhardness of the layer is 644.7 HV, compared with 104.5 HV in welded seam and 200 HV in steel matrix. The tensile strength of butt joint reaches 172.5 MPa and the crack initiates from the IMC layer at the bottom of the joint and derives into welded seam at the upper part of the joint. The present joint in this study has higher level than those with coated layer.

Metallurgical and mechanical investigations of aluminium-steel butt joint made by tungsten inert gas welding–brazing

Dissimilar metals of 5A06 aluminium alloy and SUS321 stainless steel were butt joined by tungsten inert gas welding–brazing with BJ380A filler metal and modified non-corrosive flux. The interface in seam/steel is made up of two kinds of intermetallic phase layers, τ5-Al7Fe2Si phase in the seam side and θ-FeAl3 phase in the steel side. The granular phase in welded seam is CuAl2, and the lath shaped phase is τ6-Al5FeSi. In the fusion area, the chainlike phase is Al–Si eutectic structure, and the block-like phase is Al6(Fe,Mn). The tensile strength of the butt joint reaches 125 MPa, and fracture occurs at τ5-layer, with highest hardness value of 950 HV. The present joint without coated layer can reach the same level to those with coated layer.

Spreading behavior and microstructure characteristics of dissimilar metals TIG welding–brazing of aluminum alloy to stainless steel

Dissimilar metals TIG welding–brazing of 5A06 aluminum alloy to SUS321 stainless steel had been conducted using 4047 Al–Si eutectic filler metal and modified non-corrosive flux. And spreading behavior of filler metal on the groove surface and microstructure characteristics of the butt joint were investigated. The spreading behavior of liquid filler metal consisted of two parts: one was to spread on the back face to pack the steel; the other was to uphill spread on the front face of the groove to form a sound brazed seam. The interfacial layer, unequal in thickness at different position, ranged from 5 μm to 35 μm. And it was made up of three different kinds of IMC layers: from the welded seam to stainless steel, the first was τ 5-Al 7.2Fe 2Si and α-Al phases, the second was η-Fe 2Al 5 phase, and the third was FeSi 2 and η-Fe 2Al 5 phases. Average tensile strength of the butt joint reached 120.0 MPa and fracture occurred at the interfacial layer. Cracks derived from the top part of brittle η-Fe 2Al 5 interfacial layer when its thickness exceeded 10 μm.

Tailored hybrid blank production—New joining concepts using different solders

A consistent lightweight concept necessitates the combination of different lightweight materials. Because of the significant weight reduction, multimaterial design is becoming more and more interesting for the transportation industry. Mixed material concepts are partially limited because of the insufficient deformation behavior of the joining seams. To overcome this limitation, a brazing process has been developed in which aluminium and steel can be joined, with an enhanced deformation behaviour. Tailored hybrid blanks with deep drawing ratios of 1.9 are possible. Process studies, metallographic analyses, and tensile tests were carried out for AA6016 sheets in combination with DX56D. The AA6016 surface has to be activated using a noncorrosive flux. Although it is possible to avoid melting of the aluminium base metal, intermetallic FeAl compounds occur and were characterized using energy dispersive x-ray analysis. It was proven that the intermetallic compounds affect the mechanical characteristics of the seam. During tensile tests, butt seams show approximately 70% of the strength of the weaker base metal. The results of cupping tests show the ultimate possibility of using tailored hybrid blanks in a various number of applications.

Development of fluxes for lead-free solders containing zinc

New lead-free solders based on the Sn-Zn eutectic (92 wt. pct Sn - 8 wt. pct Zn) are promising candidates to replace near-eutectic tin-lead solders because these solders are less expensive than alternatives such as Sn-Ag eutectic base solders and the melting point of the tin-zinc eutectic (198 C) is much closer to melting point of commonly used tin-lead eutectic (183 C) than the melting point of the Sn-Ag eutectic (221 C). Solders based on the Sn-Zn eutectic have been shown to have excellent mechanical properties. However, the Zn-bearing solders oxidize easily during soldering and for this and perhaps other reasons the contact angle on copper for Sn-Zn solders is rather high when utilized with fluxes used for Sn-Pb solders. Tin chloride containing fluxes give satisfactory wetting of Sn-Zn eutectic solders on Cu but tin chloride is corrosive and, therefore, unacceptable as a flux for electronic applications. Development of a non-corrosive flux that gives satisfactory wetting of copper surfaces by tin-zinc eutectic solders is thus needed. At the present time tin or tin-lead solders are used for pre-tinning. This procedure adds to the production cost. Also Sn-Pb coatings are unacceptable for a lead-free soldering system. As this paper demonstrates, amore » tin containing organic compound that decomposes at soldering temperatures to produce metallic tin on surfaces to be soldered can be added to the flux to improve wetting of Sn-Zn eutectic solder on Cu. It may also be used for general pretinning purposes done before soldering.« less

最近のアルミニウムろう付技術とその応用 非腐食性フラックスによるアルミニウム合金の新しいろう付法

最近のアルミニウムろう付技術とその応用 非腐食性フラックスによるアルミニウム合金の新しいろう付法

Ｍｇ含有アルミニウム合金の非腐食性フラックスとの反応およびろう付性

Ｍｇ含有アルミニウム合金の非腐食性フラックスとの反応およびろう付性

Chemical reaction of non-corrosive flux with magnesium containing aluminium alloys and the improvement of brazeability

Chemical reaction of non-corrosive flux with magnesium containing aluminium alloys and the improvement of brazeability

4831701 Method of making a corrosion resistant aluminum heat exchanger using a particulate flux

A method of treating a heat exchanger made of aluminum or an aluminum alloy comprising applying onto the surface of the aluminum heat exchanger a noncorrosive flux having a flux core with an outer coating of zinc or a zinc alloy formed by vacuum vapor deposition or ion plating, and then heating the resulting heat exchanger to effect brazing. A diffused zinc layer forms on the surface of the heat exchanger and protects it from corrosion, in particular, from electrolytic corrosion.