Physico-Chemical Aspects of Surface Activation during Fluxless Brazing in Shielding-Gas Furnaces

Bach, Friedrich Wilhelm; Möhwald, Kai; Holländer, Ulrich

doi:10.4028/www.scientific.net/kem.438.73

Cited by 11 publications

(9 citation statements)

References 4 publications

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“…The balanced application of conventional fluxes is sometimes difficult, this problem is thus avoided. Here, the results gained by Bach et al [9][10][11][12] are pointing to a high effectivity.…”

Section: Reisgen Et Almentioning

confidence: 50%

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Gaseous Shielding Gas Additives as Flux Substitute for TIG Arc Brazing

2015

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Brazing is one of the key technologies in the field of joining of metal components. To improve the wetting of brazing material and work-piece surface, it is often required to fall back on the use of flux. The application of these substances requires accuracy and is often connected with considerable expenditure and it is, just as the removal of flux residues, often an additional working step which has to be carried out manually. Within the framework of a DFG research project it has been investigated to which degree gaseous substances as addition to the shielding gas may replace conventional flux in TIG arc brazing. To this end, investigations have been carried out using different combinations of base and filler materials. Mainly monosilane as a gaseous flux substitute has been added in low concentrations to the shielding gas volume flow. The resulting brazed joints have been quantified with regard to their geometry, their fusion conditions and their chemical compositions. These qualities were then correlated and evaluated with the provided quantity of monosilane in order to identify dependencies.

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Section: Reisgen Et Almentioning

confidence: 50%

“…In furnace brazing, also gaseous agents such as monosilane (SiH4) [9][10][11][12][13][14] have of late been applied. These are easier to handle since they are dispensed directly into the furnace atmosphere.…”

Section: Reisgen Et Almentioning

confidence: 99%

Gaseous Shielding Gas Additives as Flux Substitute for TIG Arc Brazing

2015

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“…Flux-free brazing of steel components under shielding gas or in high vacuum furnaces are widely used industrial examples, where the absence of oxygen is essential for successful joining. Prerequisites are carefully controlled process atmospheres and elevated brazing temperatures, in order to initiate physico-chemical processes, which yield oxide-free metal surfaces suitable to be wetted with the braze metal [3]. Especially in absence of an oxide reducing agent like hydrogen the level of oxygen and water residue in the process gas has to be extremely low, in order to avoid re-oxidation of the surfaces.…”

Section: Mechanism Of Steel Deoxidation During High Temperature Brazimentioning

confidence: 99%

“…Oxygen activities of metal oxides (continuous lines) and those in hydrogen with different water content (dashed lines) as calculated from their free enthalpies of formation; thermodynamic data are from Ref [3]. …”

mentioning

confidence: 99%

Brazing in SiH4-Doped Inert Gases: A New Approach to an Environment Friendly Production Process

Holländer

Wulff

Langohr

et al. 2019

Int. J. of Precis. Eng. and Manuf.-Green Tech.

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Engineering under protective atmospheres or in vacuum allows the production of materials and components, where the absence of oxygen is an essential requirement for a successful processing. Ideally, joining or coating of (and with) metallic materials needs oxide free material surfaces, in order to achieve durable joints or coatings. Using the established technology of brazing in controlled atmosphere, fundamental physical mechanisms for deoxidation of metal surfaces are presented and the role of oxygen and water residue in the process atmosphere is analyzed. Furthermore, the doping of gases with monosilane for generating virtually oxygen-free process atmospheres is introduced and its advantages for an oxygen-free production are discussed.

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“…In principle different kinds of techniques can be applied for brazing stainless steel, e.g., induction brazing and furnace brazing in vacuum or protective gases. Generally, processing this kind of material is a demanding task, which requires a careful control of all parameters for a successful brazing process 12. In this context, a precise deposition of the filler metal at the joint plays a central role for accurate brazing results.…”

Section: Introductionmentioning

confidence: 99%

Processing and characterization of injection moldable polymer–particle composites applicable in brazing processes

Kirchberg

Holländer

Möhwald

et al. 2012

J of Applied Polymer Sci

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A novel method has been developed to process highly filled polymer-particle composites to test samples as braze metal preforms. Polypropylene (PP), low-density polyethylene (LD-PE) and high-density polyethylene (HD-PE) were used as polymer matrices. Two types of nickel-based braze metal microparticles (Ni 102 and EXP 152) were compounded to the polymer matrices at filler contents up to 65 vol %. With enhancing filler content, torque at kneading rotors, and injection molding parameter were significantly affected by increasing viscosity. Injection molded composites show well-distributed spherical microparticles and particle-particle interactions. Polymers decompose residue-free at temperatures above 550 C, even for their composites. Adding particles reduces polymer crystallinity, whereas defined cooling at 5 C/min significantly increases the crystallinity and melt peak temperature of polymers compared to undefined cooling prior injection molding. Storage modulus of polymers increases significantly by adding filler particles. LD-PE þ 65 vol % EXP 152 show the most suitable composite performance. HD-PE 65 133 76 132 HD-PE þ 50 vol % Ni 102 60 131 70 132 HD-PE þ 60 vol % Ni 102 63 130 73 132 HD-PE þ 50 vol % EXP 152 63 131 73 131 HD-PE þ 60 vol % EXP 152 63 129 72 130 Crystallinity K and melt peak temperature T m . a Calculated from eq. (2) and melting enthalpy DH m measured in DSC. ARTICLE 1674

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Physico-Chemical Aspects of Surface Activation during Fluxless Brazing in Shielding-Gas Furnaces

Cited by 11 publications

References 4 publications

Gaseous Shielding Gas Additives as Flux Substitute for TIG Arc Brazing

Gaseous Shielding Gas Additives as Flux Substitute for TIG Arc Brazing

Brazing in SiH4-Doped Inert Gases: A New Approach to an Environment Friendly Production Process

Processing and characterization of injection moldable polymer–particle composites applicable in brazing processes

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