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If you're in the market for a new steel bike frame, you may be wondering about the differences between tig and fillet brazed welding techniques. In this article, we'll explore the pros and cons of each method to help you make an informed decision.
What is Tig Welding?
Tig welding is a process that fuses metals together by melting them at high temperatures above 1450 °C. While this method is relatively easy and clean, it can weaken the metal and result in possible breaks, especially with very thin tubes.
What is Fillet Brazing?
Fillet brazing, on the other hand, "glues" metals together using a lower alloyed metal alloy. This method does not melt the metals to be joined, and as such, does not alter the balance of the tubes. However, it can be a slower and more expensive process.
Fillet Brazed Frame Types
Fillet brazed frames can be divided into two types: those with conjunctions and those without. Frames with conjunctions have a retro charm and are characterized by machined and chrome-plated joints, while frames without conjunctions are stiffer and can be designed with more freedom in terms of geometry.
Pros and Cons
Tig Welding
Pros : Ease of processing, cleanliness, lightness, freedom of geometry.
Cons : Possible breaks with very thin tubes.
Fillet Brazed Frame, Without Conjunctions
Pros : Stiffer than tig, it does not alter the balance of the tubes, pleasant to look at (looks like a monocoque), freedom of geometries like the tig.
Cons : Slow processing, more expensive, a few dozen grams heavier.
Fillet Brazed Frame, With Conjunctions
Pros : Undisputed retro charm with machined
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Ok After this quik list of differences that I hope nswered most of your questions let me explain better what I meant
Tig vs Fillet Silver Brazed: Differences between tig and fillet brazed
I will try to make some clarity on this subject that is too often underestimated and misunderstood: what is the difference between a racing bike frame or a mtb steel welded tig and the same welded in fillet brazed?
Without going into too much technical speeches that the "common mortal" like me would not understand, I will try to explain in the simplest way possible by putting myself in the shoes of a very common person who wants an answer as simple and comprehensive as possible. 
The difference is enormous and basically it is that the tig fuses the metals to be joined, while the fillet brazed "glues" them with the help of a lower alloyed metal alloy.
The latter is in turn divided into two types, a frame with conjunctions and a frame without conjunctions
After saying this, the passionate cyclist's question arises: What is the best method among the three?
Let's analyze the different methods and draw conclusions. Today the new steel alloys have exceptional breaking loads and therefore the companies that produce tubes for cycling can make tubes with very thin thicknesses, less than half a millimeter and through adequate heat treatments can withstand high stresses over a period of time very long (unthinkable with aluminum or carbon frames).
The tig as we have said must melt the metals to unite them so it brings the temperature above 1450 ° C and partly alters the balance of the metal and theoretically weakens it, in fact on all the frames welded with tig, regardless of the type of material (aluminum, steel, titanium) breaks occur just after the weld bead. 
frame breakage due to tig welding
The brazed fillet being a "bonding" does not melt the metals to be joined so it does not alter the balance or at least it does so to a much lesser extent, this depends on the type of alloy / material used to join the tubes.
The alloys commonly used are with silver percentages ranging from 5% (the most used) to 60% silver (the least used), therefore temperatures ranging from 850 ° C to 550 ° C approximately. The higher the silver percentage, the lower the "bonding" temperature, therefore less stress on the tubes but more stress on the pocket being very expensive.
Few artisans use 50-60% silver alloys and their method advertises it with the words "Silver Fillet Brazed".
I conclude with the pros and cons. 
Frame in tig
Pro : ease of processing, cleanliness, lightness, freedom of geometry.
Cons : possible breaks with very thin tubes.
Frame in brazed fillet, without conjunctions 
Pro : stiffer than the tig, it does not alter the balance of the tubes, pleasant to look at (looks like a monocoque), freedom of geometries like the tig .
Cons : slow processing, more expensive, a few dozen grams heavier.
Brazed fillet frame, with conjunctions 
Pro : undisputed retro charm with machined and chrome-plated joints
Cons : slow processing, more expensive, bound in the choice of angles.
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