What is Brazing?
Brazing is the joining of metals through the use of heat and a filler metal one whose melting temperature is above 840F(450C) but below the melting point of the metals being joined. (A more exact name for the brazing process discussed in this book may be “silver brazing,” since in most cases the filler metal used is a silver alloy. To remain brief, we’ll use the term “brazing” throughout this book, with the understanding that we are referring to a torch brazing process with a silver-bearing filler metal. Where exceptions occur, it will be noted.) Brazing is probably the most versatile method of metal joining today, for a number of reasons. Brazed joints are strong. On non- ferrous metals and steels, the tensile strength of a properly made joint will often exceed that of the metals joined. On stainless steels, it is possible to develop a joint whose tensile strength is 130,000 pounds per square inch. ( 896.3 megapascal [MPa] ). Brazed joints are ductile, able to withstand considerable s
Brazing joins two pieces of base metal when a melted metallic filler flows across the joint and cools to form a solid bond. Similar to soldering, brazing creates an extremely strong joint, usually stronger than the base metal pieces themselves, without melting or deforming the components. Two different metals, or base metals such as silver and bronze, are perfect for brazing. Use this method to make a bond that is invisible, resilient in a wide range of temperatures, and can withstand jolting and twisting motion. The process of brazing is the same as soldering, although metals and temperatures differ. You can braze pipes, rods, flat metals, or any other shape as long as the pieces fit neatly against each other without large gaps. Brazing handles more unusual configurations with linear joints, whereas most welding makes spot welds on simpler shapes. First, you must clean the entire area to be joined or else the melted braze mixture will clump instead of flow, making an inconsistent join
Brazing, simply put, is joining metal to metal by filling the joint with a different, melted metal at temperatures over 840F. The melted metal filling the gap must be able to wet the pieces being joined so that it is drawn into the gap by capillary action. Below 840F, the equivalent process is called soldering. If the process is hot enough to melt the metals being joined, it becomes welding or braze-welding. The pieces being joined together are referred to as the base metal, while the melted metal that fills the gap between them is called the filler metal. Filler metal is also called brazing rod, spelter, or brazing alloy. The following discussion of brazing focuses on the techniques and materials used in brazing bicycle frames, but most of the information applies to any similar brazing of light-weight steel components.
Brazing is the joining of two base materials with a filler metal. As defined by the American Welding Society (AWS) brazing temperatures must be below the melting point of the two base materials, and the filler metal must have a liquidus above 450°C (840°F) to flow smoothly into joints. Mostly performed in a furnace with a controlled atmosphere of vacuum, hydrogen, nitrogen-hydrogen, etc., brazing is also done using torch or induction heating. Brazing does the work for you When a narrow space exists between two parallel surfaces, molten brazing filler metal is drawn into that space–even against gravity! This phenomenon is known as capillary action. Advantages of brazing Design flexibility: Assemblies of thin sheet materials, different thermal mass, or dissimilar metals are easily joined. Metallurgical integrity: Only the brazing filler metal is melted, not the base metal. Labor efficiency: Numerous joints and parts can be batched and brazed simultaneously; welding processes only one pa
