Editor’s note: Alloys can be very interesting in replacing such metals as Copper and Stainless Steel. Copper is soft, but has high electrical and thermal conductivity and Stainless Steel is strong, but has low thermal conductivity.
Thermal conductivity of metals and alloys
“Problem-solver alloy” ISA-CON®450 for fasteners
In addition to ultra-fine wires, cables and stranded wires made of ISA-CON®414, Isabellenhütte is now also manufacturing semi-finished products/preliminary materials for fasteners, such as screws and bolts, made of ISA-CON®450, another version of the copper-based alloy. This reduces electrical resistance and thus heat development in the system. In addition, undesired heat can be dissipated better.
Both types of material, ISA-CON®414 and ISA-CON®450, are characterized by a high strength (similar to that of stainless steel) and high conductivity (similar to that of copper). With ISA-CON®450, the tensile strength is between 450 and 550 megapascals and the conductivity is 80 percent ACS (International Annealed Copper Standard). This combination makes the material ideal as a conductive fastener, for example as a bolt, screw, spring contact, plug connector or bus bar.
Problem solving with ISA-CON®450
When problems occur by using fasteners made of steel, for example, due to excessively high performance loss and heat development, or due to space problems or too high of a weight, using the ISA-CON®450 alloy is a worthwhile alternative. With current-carrying components, the electrical resistance, both in the material as well as at the contact transition, is reduced compared to steel. This reduces the loss in performance significantly and the weight and diameter of components can be reduced too. The direct connection, for example as a bridging of a distance between two bus bars with a supporting function instead of a steel bolt or pin for a plug contact, is a promising application.
Heat reduction by 50 percent
The requirements for the bolt application were a significantly reduced electrical resistance and thus a significantly reduced heat development of the bolt itself. Direct use here means that the entire current is conducted directly via the ISA-CON®450 bolt, which connects a shunt resistor with a plug. Thanks to the high conductivity of the alloy, there is only low electrical resistance with correspondingly reduced heat development in the contact bolt. In addition, the heat development, which usually occurs in the shunt resistor, is dissipated better and is thus overall reduced by 50 percent compared to a component with a steel contact.
Another plus: ISA-CON®450, like ISA-CON®414, is also heat-resistant, which means the bolt retains its mechanical strength in applications with higher ambient temperatures.
Current-carrying components made of steel that take quite a bit of effort to cool or that have to be significantly oversized to ensure sufficient conductivity can simply be replaced with ISA-CON®450. Mechanically-supportive fasteners made of copper also often have to be oversized in order to comply with mechanical loads. Cross-sections can be reduced while maintaining the same level of safety due to the increased strength of ISA-CON®. This allows for a reduction in weight and space, which is, for example, usually very relevant in the automotive sector.
Screws for indirect use
An indirect connection replaces a previously non-current-carrying component, such as a steel screw, which presses a contact onto a bus bar. The pressed contact surface here and thus the component surface can be reduced, since part of the current can flow through the screw. The screw offers additional safety due to its high conductivity.
The customer feedback at Isabellenhütte has been very positive so far. The direct use of ISA-CON®450 bolts in particular has a very good cost-benefit ratio. Mr. Brockhaus, Business Development manager at Isabellenhütte, says the following about this: “If heat development, electric conductivity and contact resistances are insignificant in application, steel or simple copper alloys, such as bronze or brass, may be sufficient. However, if the aforementioned problems occur, ISA-CON®450 is an ideal problem-solving alloy.” The alloy is of interest for all types of mechanically-stressed plug connectors, which require high conductivity and a high level of reliability.
Screw connections with fasteners made of ISA-CON®450 reduce contact resistance and heat development. (Image with permission: ©Isabellenhütte Heusler GmbH & Co. KG)
Measuring setup: Two bolts (silver plated ISA-CON®450 bolts), terminated to a shunt resistor, are used as a current conducting joining element. (Image with permission: ©Isabellenhütte Heusler GmbH & Co. KG)
Comparison of heat generation in a resistor by using ISA-CON®450 bolts (picture 4) and steel bolts (picture 5) with load of 300 A as infrared image. (Image with permission: ©Isabellenhütte Heusler GmbH & Co. KG)
ISA-CON450 bolt (top view)
To analyse the heat generation in the resistor four different loading increments are used: 150 A, 200 A, 250 A, 300 A. The load time always takes 30 sec. During load time an infrared video is recorded. At the end of the video the above shown pictures are made for temperature reporting. (Image with permission: ©Isabellenhütte Heusler GmbH & Co. KG)