“Problem-Solver Alloy” for Fasteners

In addition to ultra-fine wires, cables, and stranded wires, 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,

 

Figure 1: Screw connections with fasteners made of ISA-CON®450 reduce contact resistance and heat development.

Figure 2 and 3: Measuring setup: Two bolts (silver plated ISA-CON®450 bolts), terminated to a shunt resistor, are used as a current-conducting joining element.

 

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.

 

 

Figure 4 and 5 (lateral view): 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.

 

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.

 

Figures 10 to 13 (top view): Steel bolt 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.

 

About the Author

Samuel Brockhaus worked as a Business Development Manager at  Isabellenhütte Heusler GmbH & Co. KG that develops electric resistor materials, thermoelectric materials for temperature measurement as well as electric components and sensors for precision measurement technology for the electrical and electronics industry. Then, later he worked as a project manager at Viessmann Group that is an international manufacturers of heating, cooling and climate control technology

 

This article originally appeared in the Bodo’s Power Systems magazine.