Successful Pin Brazing

The key to successful Pin Brazing as with traditional Brazing techniques relies upon many key factors and there are several main factors, but when it comes to Pin Brazing there are just five areas on which I primarily focus when providing training classes or presentations. These are Power Supply, Surface Preparation for your connection, Surface Preparation for your Earth Device, having the correct Adjustment Setup and finally Operator Proficiency. The above factors can often be overlooked individually, often creating inadequate results and expensive delays so it is important that both operators and companies ensure that they have either received or made provision for training and certification by a qualified, experienced Instructor.

Not wanting to make this article into an 'instruction manual' it is my intention to focus on in more detail why some of the above factors are imperative considerations in both Pin Brazing product design and development and the consideration that must be given when taking the responsibility to develop and pioneer these innovative processes.

Connection Design.

Brazed joints using Silver based Filler metals should always have a capillary gap into which the molten filler metal can flow. Joint strength will vary with the joint gap and the degree of overlap between Connection type and parent metal, joint clearances of 0.03 to 0.08 mm (0.0012 to 0.0031 in) are recommended for the best capillary action and joint strength.During the Pin Brazing process, brazing material is drawn into the joint which is caused by the attraction between the molecules of the brazing material and the molecules of the metal surface to be joined. This will only work if: The surface of the metal is clean, the clearance between the metal surfaces is correct and the metal at the joint area is hot enough to allow the Pin Brazing material to evenly flow. Connection methods such as Crimp Terminals should be precision manufactured to ensure optimum capillary gap for joint strength and integrity, whilst also allowing excess heat created during initiation of the Pin Brazing Arc to flow freely away from the Substrate material in order reducing and unnecessary damage or increased Heat Affected Zone (HAZ).

Brazing Pins and their respective Alloys should be selected on their suitability for a particular application. Consideration should be given to the substrate design, the parent metal, the brazing process and the ergonomics of the operation. The use of Cadmium free, high Silver, free flowing filler Alloys with low melting ranges are essential in the development of Brazing Pins, which aid in the shielding of the Parent material during the Arc process and allow for an increased flow maximizing in the available surface area, which in turn allows for a more substantial electrical and mechanical connection.

In the Manufacture of Brazing Pins the choice of flux is as important as the choice of filler metal. The working range of the flux must be compatible with the brazing temperature, must have suitable life at temperature and should be suitable for both the heating method (in the case of Pin Brazing, Arc temperature could be in excess of 2000 Degrees Celsius) and the parent metals and become active below the melting point of the brazing alloy. It must stay active right through the brazing cycle removing any oxides formed on the parent metal. Observations should be made if the flux residues appear blackened and glassy as the flux has probably been exhausted during heating. This could be the result of contaminated flux (from very old or incorrectly stored Brazing Pins) or more likely the components have been overheated, possibly due to an incorrect adjustment setting on the Brazing Gun or an un-charged Battery Pack.

Pre-cleaning.

To promote good bonding the connection substrate should be free from grease and any surface oxide prior to brazing. Grease and oil are best removed using a degreasing solvent. Prior to this Pin Brazing Ancillaries can be used which will often include Surface Preparation Equipment such as Die Grinders and Angle Grinders fitted with Carbide Burrs, Mounted Points or abrasive Flap Discs. These mechanical surface preparation devices are intended to be utilized sparingly in order to not cause disruption to the substrate thickness or create uneven pits or troughs which may interfere with Capillary action or Arc length. Surface oxide can also be removed with a medium grade abrasive cloth. Consideration should also to be given to Consumable quality, as with Substrate material, components which have been exposed to moisture or grease can be the cause of defective brazes results. Care should be taken at all times to ensure that Consumables remain sealed in their original containers until required for use and should be inspected for surface oxidization or grease prior to being used.

Battery Status.

Most standard Pin Brazing Systems operate using a 36-42volt Battery Pack or Welding Generator set up to mirror the characteristics of the Battery pack. Careful consideration and testing has gone in to find batteries that are suitable for the extreme operational demands of the Pin Brazing Process and the equally extreme environments in which the process is utilised. Therefore only pre-approved batteries must be used, these battery types or their details will only be obtainable from your Pin Brazing Supplier or equipment manufacturer and it is important to note that different Pin Brazing Equipment Manufacturers do utilise different Battery types, which are attuned for use with only their respective tools and consumables. As a user batteries must be cared for in accordance with your user manual, and even under heavy usage could last for many years.