FAQ - Joining metals - A critical fusor construction element
Posted: Wed Feb 14, 2018 7:18 pm
The following is a quick rinse in what methods are sometimes used to join metals in fusor construction. The mere assembly and joining of components to a fusor is just part of the big picture here. However you assemble and attach items to a fusor, it must also be vacuum tight and vacuum friendly. This is a critical dual consideration here.
How do I put a fusor together from parts that will hold and work well?
1. Soft Soldering- A tin-lead or tin-silver based joining technique. Used extensively in electronics and plumbing. Flows and wets to fill small open areas and voids between joints. The weakest of all molten metal joins.
Disadvantages - Requires both join pieces to be heated to full solder melting point, (400 deg+). Typically, softens and fails structurally above 350 deg F.
2. Silver Soldering - A form of brazing using a special silver-copper alloy. Used almost exclusively by the Jewelry business or assembly of bright, white metals. The joint is very strong.
Disadvantages - Both pieces at the joint must be heated to near red heat! (900+ deg F). Will not flow to fill voids between joints. Surfaces to be joined must be close fitting or in contact. Weakens and fails near 800 deg F. A paste flux must be used and cleaned off the joint after brazing.
3. Classic Brazing - A brass/broze alloy. Used extensively where a good strong join is needed that is stronger than silver soldering. Used in some auto body work.
Disadvantages - Both pieces at the joint must be heated to near red heat! (1100+ deg F). Will not flow to fill voids between joints. Surfaces to be joined must be close fitting or in contact. Weakens and fails near 900 deg F. A paste flux must be used and cleaned off the joint after brazing.
4. True fusion welding - In this form of joining the two metals to be joined are fully melted and fused together. There are several forms of fusion welding. Fusion welding is the strongest of all metal-to-metal joints...
A. Gas Welding - Usually oxy-actyline torch welding, most often using a similar metal welding rod as filler.
Disadvantages - the welding must typically see both items to be welded heated to over 1500++ degrees F. Expensive welding setup required.
B. MIG Arc Welding - Metal Inert Gas welding. A reel of wire of the same metal to be welded is fed into a shielded gas electrical arc melting the two metals to be joined at the joint and filling the joint with molten wire metal. This typically heats to melting temperature only the joint area and only moderately heats the surrounding metal. Good for joining items where you don't want to over heat other parts of the metals to be joined.
Typically used on sheet metal joints and materials not much more than 1/8" thick. Automotive industry uses this form a lot.
Disadvanges - Expensive electrical/electronic welder demanded. Usually leaves a bulging bead of filler metal at the joint. (can be ground down)
C. TIG Arc Welding - Tungsten inert Gas welding. This is the cleanest form of welding solid joints. Typically, no feeder wire is used. The gas shielded arc literally puddles the two metals together in a smooth uniform joint. Well worked joints are prepared with excess metal lips that can melt into a smooth, non-bulging, non-concave joint that needs no cleaning or further attention. Typically used on pieces under 1/4 inch thick. Used extensively in the assembly of large medical items or scientific professional assemblies.
Disadvantages: Very expensive electronic controlled welder is the norm. Typically requires careful planning and preparation of pieces to be welded for excellent finished results expected of such TIG welds.
D. Resistance Welding - often called "spot welding". In this form form of welding two pointed electrodes of special alloy are mashed together, under pressure, between the thin pieces to be welded. Hundreds of amperes of current flow through the electrodes on opposite sides of the joint and force the two items to melt and fusion weld in a spot the size of the electrodes. The actual weld process takes a tiny fraction of a second. In the finest small item spot welders, the weld is an electronically controlled capacitive discharge. This is the lowest temperature fusion weld possible as the surrounding metal remains cool. This is the finest way to join two pieces of sheet metal or wire where other forms of fusion welding would melt the entire assembly.
Disadvantages - Rare and expensive welders are the norm in this form of welding.
E. Common arc welding - Un-shielded Arc Welding. uses a filler rod as the electrode that is covered with a flux that goes molten and shields the metal weldment as it cools from oxidation. Used extensively in massive constructions such as huge mutli-ton vehicle assembly and repair, ship building, etc.. 1 inch thick plate is often welded this way with giant kiloamp arc welders.
Disadvatages - A nasty finished weldment with a huge bulging seam that always requires at least hammer and wire brush techniques to clean the ugly flux covered seam. Grinding with a power grinder is often employed to clean away spelter balls in and around the weldment.
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For fusor use
Method #1 is not used inside a fusor, ever!
If the fusor is not going to reach a shell temperature of over 200 deg F. method #1 can be used on the external shell and its external attachments. Still, its use around any item that is to be heated while in use is just not recommended.
Method #2 can be used internally, but not to attach or assemble a grid as the grid can glow red hot under power use, weakening and failing joints here. I have used this method successfully in demo fusor grids where a lot of power is not applied or allowed to heat the grid to red heat. Only high silver content, Jewelry alloys should be used. 60%++. https://www.riogrande.com/category/tool ... ing/solder
I recommend the "easy 650 paste" High melting point.
Method #3 is not recommended as many brazing alloys contain zinc that is not vacuum friendly. Stick with method #2 using silver if you must braze.
Method #4A is not recommended for fusor work. Too much heating of often delicate components is bad.
Method 4B is a viable method if you have a MIG welder. Post weld cleanup is usually demanded. Not recommended unless you are a near expert user of this method.
Method 4C is the ultimate and desired method for assembling a stainless steel fusor and all of its attachments. As close to professional assembly as possible for the amateur. TIG is the way to go.
Method 4D is the absolute best method for assembling a wire or thin metal grid. It is also used to weld the grid to a threaded bolt.
Method 4E is just too crude for fusor assembly. However, if you are extremely proficient in this form of welding and have the welder, it could be used. Definitely not recommended at all.
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I hope this settles this question, but due to the total lack of newbie FAQ reading I am sure this effort will rarely be used for this type of information.
Richard Hull
How do I put a fusor together from parts that will hold and work well?
1. Soft Soldering- A tin-lead or tin-silver based joining technique. Used extensively in electronics and plumbing. Flows and wets to fill small open areas and voids between joints. The weakest of all molten metal joins.
Disadvantages - Requires both join pieces to be heated to full solder melting point, (400 deg+). Typically, softens and fails structurally above 350 deg F.
2. Silver Soldering - A form of brazing using a special silver-copper alloy. Used almost exclusively by the Jewelry business or assembly of bright, white metals. The joint is very strong.
Disadvantages - Both pieces at the joint must be heated to near red heat! (900+ deg F). Will not flow to fill voids between joints. Surfaces to be joined must be close fitting or in contact. Weakens and fails near 800 deg F. A paste flux must be used and cleaned off the joint after brazing.
3. Classic Brazing - A brass/broze alloy. Used extensively where a good strong join is needed that is stronger than silver soldering. Used in some auto body work.
Disadvantages - Both pieces at the joint must be heated to near red heat! (1100+ deg F). Will not flow to fill voids between joints. Surfaces to be joined must be close fitting or in contact. Weakens and fails near 900 deg F. A paste flux must be used and cleaned off the joint after brazing.
4. True fusion welding - In this form of joining the two metals to be joined are fully melted and fused together. There are several forms of fusion welding. Fusion welding is the strongest of all metal-to-metal joints...
A. Gas Welding - Usually oxy-actyline torch welding, most often using a similar metal welding rod as filler.
Disadvantages - the welding must typically see both items to be welded heated to over 1500++ degrees F. Expensive welding setup required.
B. MIG Arc Welding - Metal Inert Gas welding. A reel of wire of the same metal to be welded is fed into a shielded gas electrical arc melting the two metals to be joined at the joint and filling the joint with molten wire metal. This typically heats to melting temperature only the joint area and only moderately heats the surrounding metal. Good for joining items where you don't want to over heat other parts of the metals to be joined.
Typically used on sheet metal joints and materials not much more than 1/8" thick. Automotive industry uses this form a lot.
Disadvanges - Expensive electrical/electronic welder demanded. Usually leaves a bulging bead of filler metal at the joint. (can be ground down)
C. TIG Arc Welding - Tungsten inert Gas welding. This is the cleanest form of welding solid joints. Typically, no feeder wire is used. The gas shielded arc literally puddles the two metals together in a smooth uniform joint. Well worked joints are prepared with excess metal lips that can melt into a smooth, non-bulging, non-concave joint that needs no cleaning or further attention. Typically used on pieces under 1/4 inch thick. Used extensively in the assembly of large medical items or scientific professional assemblies.
Disadvantages: Very expensive electronic controlled welder is the norm. Typically requires careful planning and preparation of pieces to be welded for excellent finished results expected of such TIG welds.
D. Resistance Welding - often called "spot welding". In this form form of welding two pointed electrodes of special alloy are mashed together, under pressure, between the thin pieces to be welded. Hundreds of amperes of current flow through the electrodes on opposite sides of the joint and force the two items to melt and fusion weld in a spot the size of the electrodes. The actual weld process takes a tiny fraction of a second. In the finest small item spot welders, the weld is an electronically controlled capacitive discharge. This is the lowest temperature fusion weld possible as the surrounding metal remains cool. This is the finest way to join two pieces of sheet metal or wire where other forms of fusion welding would melt the entire assembly.
Disadvantages - Rare and expensive welders are the norm in this form of welding.
E. Common arc welding - Un-shielded Arc Welding. uses a filler rod as the electrode that is covered with a flux that goes molten and shields the metal weldment as it cools from oxidation. Used extensively in massive constructions such as huge mutli-ton vehicle assembly and repair, ship building, etc.. 1 inch thick plate is often welded this way with giant kiloamp arc welders.
Disadvatages - A nasty finished weldment with a huge bulging seam that always requires at least hammer and wire brush techniques to clean the ugly flux covered seam. Grinding with a power grinder is often employed to clean away spelter balls in and around the weldment.
*****************************************************************************************************************************************************************
For fusor use
Method #1 is not used inside a fusor, ever!
If the fusor is not going to reach a shell temperature of over 200 deg F. method #1 can be used on the external shell and its external attachments. Still, its use around any item that is to be heated while in use is just not recommended.
Method #2 can be used internally, but not to attach or assemble a grid as the grid can glow red hot under power use, weakening and failing joints here. I have used this method successfully in demo fusor grids where a lot of power is not applied or allowed to heat the grid to red heat. Only high silver content, Jewelry alloys should be used. 60%++. https://www.riogrande.com/category/tool ... ing/solder
I recommend the "easy 650 paste" High melting point.
Method #3 is not recommended as many brazing alloys contain zinc that is not vacuum friendly. Stick with method #2 using silver if you must braze.
Method #4A is not recommended for fusor work. Too much heating of often delicate components is bad.
Method 4B is a viable method if you have a MIG welder. Post weld cleanup is usually demanded. Not recommended unless you are a near expert user of this method.
Method 4C is the ultimate and desired method for assembling a stainless steel fusor and all of its attachments. As close to professional assembly as possible for the amateur. TIG is the way to go.
Method 4D is the absolute best method for assembling a wire or thin metal grid. It is also used to weld the grid to a threaded bolt.
Method 4E is just too crude for fusor assembly. However, if you are extremely proficient in this form of welding and have the welder, it could be used. Definitely not recommended at all.
*************************************************************************************************************************************
I hope this settles this question, but due to the total lack of newbie FAQ reading I am sure this effort will rarely be used for this type of information.
Richard Hull