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As mentioned in last month’s article, there are many suppliers of brazing paste out there, many of whom will put their brazing-paste into small tubular cartridges from which the paste can be easily and quickly dispensed onto components that are to be brazed. As shown in Figure 1, proper dispensing of paste from a cartridge begins with an electronically-controlled source of pressurized air (which can be adjusted over a wide range), and may also contain optional timing mechanisms. All of this can be contained in a simple table-top unit, such as the one shown, but which also comes in different shapes and sizes, and with other options.

The air hose coming from the dispensing unit should have a connector that is able to attach to, and lock onto, the back end of the paste-cartridge in a leak-tight fashion, thus allowing the high-pressure air to push the piston in the paste-cartridge forward. The dispensing unit may also have digital or analog meters on their face to show what the air pressure is in the hose, and it may also contain controls to allow the operator to vary dispensing time (which could vary from a small fraction of a second all the way to continuous-flow) if it is desirable to automate, or semi-automate the paste dispensing process.

What kind of dispensing-tip should be used for brazing-paste cartridges?.

There are many suppliers of brazing paste out there, and many of them will put that paste into small tubular cartridges for you, from which that paste can be easily and quickly dispensed onto components that are about to be brazed. BUT, the choice of the actual type of cartridge-tip that you will use to extrude that brazing-paste from the cartridge is YOUR decision, NOT the decision of the paste-supplier, your customer, or some industry “tradition” you may be heard about, or perhaps observed being used at some brazing shop. by Dan Kay

Don’t Blame the Braze because Joint was Poorly Designed, and NO, larger fillets won’t compensate for that!.

Have you ever heard someone tell you something like this: “Well, brazing may be okay, but if you really want a strong joint, you should weld it!” Such comments are often made when someone sees what appears to be a cracked brazed-joint, such as that shown in Figure 1, and they then assume that (1) the crack they are looking at probably extends all the way through the brazed-joint, and that (2) if the joint had been welded it would not have cracked. by Dan Kay

A number of companies I’ve visited who conduct vacuum brazing operations have asked for assistance in understanding how to properly use a torch-brazing (flame braze) process to repair some of the assemblies that did not fully braze during their vacuum brazing operations.

The components were such that they did not want to send the entire assembly back through the vacuum brazing furnace, but merely needed to fix a small portion of the assembly where it did not fully braze. So let’s take a brief look at torch-brazing to see what it is, and how it can be used by brazing shops today to meet some of their production-repair needs. by Dan Kay

People sometimes ask me to help them determine if it is better for them to purchase a vacuum furnace or a continuous-belt furnace for their particular brazing needs. This important decision (for any brazing company) should not be a difficult question for them to answer for themselves, and involves understanding primarily three (3) key factors about their production: what is the quantity of brazed components that they need to produce, what is the sensitivity to oxygen of any of those base metals that they are planning to braze, and thirdly, do any of those base metals contain elements that will easily and readily outgas when heated. by Dan Kay

303 stainless steel is a machinable grade of 304-stainless steel. As mentioned in my earlier article (about 321-stainless), austenitic stainless steels are essentially iron-based alloys with at least 10.5% (or more) chromium added to it, as well as from 8-12% nickel, have inherent corrosion resistance, are usually very brazeable, are generally non-magnetic, and do not require (or effectively respond to) subsequent heat-treatment after brazing. They are primarily used in the “annealed” (soft) condition in end-use service.

303-Stainless is generally available in either of two chemistries, standard 303, or 303Se. The use of 303Se has apparently decreased significantly over the years, but it is still available. The standard grade of 303 contains a minimum of 0.15-percent sulfur added to its chemistry, the sulfur being added for machinability purposes. Notice in Table 1 that the other grades of austenitic stainless steels all are limited to no more than 0.030 sulfur maximum, which means that regular 303 stainless contains a minimum of six (6) times the usual amount of sulfur that is contained in all the other types of austenitic stainless steel. Remember, that’s a minimum amount; it can be higher! by Dan Kay

A number of companies who are currently using vacuum-furnaces for many of their brazing processes are also using induction-brazing equipment to join some of their other production parts. Let’s take a brief look at the induction-brazing process to see what it is, and how it can be effectively used by brazing shops today to meet some of their production needs.

This article is written without a lot of complex language in order to make this process as simple and easy to understand as possible, and to therefore encourage people to use it more. For a deeper, more thorough engineering-study of the principles and theory of induction heating, the reader is referred to other technical books and articles on the subject. This current article will give you a good, basic understanding of induction brazing, and how to apply it in your brazing shops. by Dan Kay