Low-Silver Brazing Alloy for Hard Metals
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Solution Overview
Problem
Existing brazing alloys face challenges in achieving low silver content while maintaining mechanical properties and avoiding embrittlement when soldering hard metals and cermets at temperatures around 710°C to 730°C, which can lead to undesirable hardening and embrittlement due to exceeding the AC1 temperature from the iron-carbon phase diagram.
Innovation Solution
A solder alloy composition free of silicon, alkali, and alkaline earth metals, phosphorus, and cadmium, with specific weight percentages of silver, copper, zinc, manganese, indium, nickel, and optional additions of tin, gallium, cobalt, and germanium, optimized to achieve a melting range of 710°C to 730°C and high shear strength without compromising ductility and formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the silver content is reduced in Ag-Cu-Zn solder alloys, then the cost is reduced and the melting point is lowered, but the mechanical properties such as ductility and formability deteriorate and the melting temperature increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ranges of multiple alloying elements (Cu: 38-48 wt.%, Zn: 18-28 wt.%, Mn: 8-12 wt.%, Ni: 0.5-2 wt.%, In: 1-3 wt.%, Ga: 0.5-2 wt.%, Sn: 0.5-2 wt.%, Co: 0.1-1 wt.%, Ge: 0.1-0.5 wt.%) to achieve the optimal balance between low melting point (710-730°C) and good mechanical properties, resolving the contradiction between silver content reduction and mechanical property maintenance
Solution Approach 2:
The patent creates a composite alloy system by combining Ag-Cu-Zn base alloy with multiple additional elements (Mn, Ni, In, Ga, Sn, Co, Ge) that work synergistically to achieve the desired properties. This composite approach allows the alloy to simultaneously exhibit low melting point, high ductility, good formability, and high shear strength without requiring high silver content
2Temperature
If the soldering temperature exceeds the AC1 temperature from the iron-carbon phase diagram, then the brazing process is completed, but austenite forms and subsequently leads to hard, brittle phases upon cooling, causing undesirable hardening and embrittlement
Solution Approach 1:
The patent applies parameter changes by precisely controlling the soldering temperature within the narrow range of 710-730°C, which is strategically selected to complete the brazing process while remaining below the AC1 transformation temperature of the steel workpiece. This temperature control prevents austenite formation and subsequent embrittlement, resolving the contradiction between completing the brazing process and avoiding harmful phase transformations
3Strength
If nickel is added to strengthen solder joints and improve wetting on tool steels, then the joint strength is improved, but the melting range of the alloys increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the nickel content within a narrow range of 0.5-2 wt.%. This controlled addition of nickel provides sufficient joint strength improvement and wetting enhancement on tool steels while limiting the increase in melting range, as nickel is added in small, controlled amounts that balance its beneficial effects against its tendency to raise the melting point
4Temperature
If elements like tin, gallium, indium, or manganese are added to lower the melting point, then the melting temperature is reduced, but the mechanical properties such as ductility and formability deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the content ranges of melting point lowering elements (In: 1-3 wt.%, Ga: 0.5-2 wt.%, Sn: 0.5-2 wt.%) in combination with other alloying elements. This controlled composition achieves the desired low melting point (710-730°C) while maintaining good mechanical properties through the synergistic effect of multiple elements working together in optimized proportions
Solution Approach 2:
The patent creates a composite alloy system where multiple elements (In, Ga, Sn, Mn, Ni) work synergistically to achieve the desired properties. The combination of these elements in specific proportions creates a composite material that simultaneously exhibits low melting point and good mechanical properties, overcoming the limitations of individual element additions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The alloy provides high shear strengths comparable to standard alloys, maintains ductility and formability, and is environmentally harmless, ensuring strong and flexible solder joints suitable for hard metals and cermets without the drawbacks of higher silver content or cadmium toxicity.
Implementation Method 1
The melting temperature of the brazing solder is lower than the melting temperature of the metal parts to be soldered. Both are wetted by the melted solder without melting themselves.
Implementation Method 2
Both are wetted by the melted solder without melting themselves.
Data Source
Figure 1~2
AI summary
The invention relates to novel brazing alloys containing copper, silver, zinc, manganese and indium, and to a method for producing same and the use thereof.