Q. How do I TIG weld alloy C91000?

A: For TIG welding, you can use our Phos Bronze A or our Silicon Bronze rod. Phos Bronze A gives better color match. Silicon Bronze gives stronger welds. The TIG welding temp. for both of these filler metals is a little higher than the melting point of the C91000 (1505 Solidus 1760 Liquidus). Because of this temperature question, and depending on the thickness of the welded part, you may want to consider brazing. To braze C91000, you may use our Phos Copper 0 alloy.

-top-

A: The number of rods per pound (or per kg.) varies with the alloy and with the
diameter.
Here are a few commonly used alloys and diameters.

-top-

Q. Brazing Concepts: Solidus, Liquidus and Brazing Range

A: When brazing, the terms melting point and freezing point are not properly used, unless you are dealing with an unalloyed metal.
Almost all brazing filler metals are alloys (combinations of elements). You cannot simply guess the melting point of an alloy by figuring the weighted average of the melting points of its elements. Usually, alloys are mixtures that melt little by little through a range of temperatures. A metallurgist makes a distinction between a pure metal’s melting point and a brazing filler metal’s melting range.

Solidus
The temperature at which an alloy begins to melt.

Liquidus
The temperature above which an alloy is completely molten.

Eutectic Point
An alloy is an “Eutectic composition” if it has a specific melting point like that of a pure metal. A Eutectic alloys melting range is small: solidus and liquidus are almost equal. The melting point in this case is called the “eutectic point”.

Brazing Range
To ensure a free flowing action, brazing usually requires temperatures above the liquidus. But, for example when brazing joints with a wide gap, you may need a more pasty, sluggish brazing filler metal that will not flow all over the joint. Sometimes, then, the low end of the brazing range for certain brazing filler metals is below the liquidus.

-top-

Q: I am experiencing a weld cracking problem on our TIG (GTAW) production line where we weld thinner sections of 6xxx series aluminum metal sheets using aufhauser 4043 filler material. Why do you think my welds are cracking? And why is it that not all of my welds, but only some of them are cracking?

A: The aluminum/magnesium/silicon base alloys (6xxx series) are highly crack sensitive because they contain approximately 1 % Magnesium Silicide (Mg₂Si), which falls close to the peak of the solidification crack sensitivity curve.

The Mg₂Si content of these materials is the primary reason that there are no 6xxx series filler alloys made. The cracking tendency of these alloys is lowered to acceptable levels during arc welding by the dilution of the weld pool with excess magnesium (by use of the 5xxx series Al-Mg filler alloys) or excess silicon (by use of the 4xxx series Al-Si filler alloys).

When we TIG (GTAW) weld on thin material, it is often possible to produce a weld, particularly on corner joints, by melting both edges of the base material together without adding filler material. In the majority of arc welding applications with this base material, we must add filler material if we want to have consistently crack free welds. A possible exception would be counteracting the cracking mechanism by maintaining a compressive force on the parts during the welding operation, which requires specialized fabrication techniques and considerations. This method is seldom used.

I suspect that the welds in question that are not cracking are those that have had filler material added during welding. My advice would be to ensure that filler alloy is added to all welds during welding in order to reduce crack sensitivity. Consideration should also be given when evaluating the cause of cracking to any differences in welds associated with weld size, and variations in tensile stresses introduced by shrinkage, joint expansion, or externally applied loads.

-top-

Q: What is the tensile strength of brazed joints

A: It all depends
No manufacturer lists the tensile strength of their brazing alloys.
This is not to make life difficult for the ultimate consumer. It's because people tend to place to much emphasis on any number that might be published. Design engineers sometimes base designs on a number that's not appropriate for the ultimate use.

In fact, the strength of a brazed joint depends more on the design and the brazing procedure then on the filler metal used.

Furthermore, tensile strength numbers thaw Aufhauser has measured apply to material in the wrought state. When the filler metal is used in brazing, it is effectively recast. Recast metal has different properties from the wrought metal.

Empirical testing of various brazed joints has shown that the PSI of the alloy does not correlate directly to the strength of the tested joint. We know some of the factors that influence this process. For example, if the alloy is overheated, the lower melting elements are burned off to a higher degree. This effectively changes the composition of the deposited metal. Thus our advice is to encourage customers to do their own testing of the brazed joint.

But there are some rules of thumb
If customers insist on a certain PSI number, we suggest a number ranging from 60,000-70,000 PSI when tested in the wrought state.

Another rough guideline is that joints properly brazed with Aufhauser Silver alloys have a shear strength that exceeds three times the shear strength of the thinner, joined metal.

-top-

Q: Joining aluminum to copper

A: It is difficult to braze or weld aluminum to copper, because of the low melting temperature (1018 F) of the aluminum-copper eutectic and its extreme brittleness. By heating and cooling rapidly, however, reasonably ductile joints are made for applications such as copper inserts in aluminum castings. The usual filler metals and fluxes for brazing aluminum to aluminum can be used, or the silver alloy filler metals BAg-1 and BAg-la can be used if heating and cooling are rapid (to minimize diffusion). Pretinning the copper surfaces with solder or silver alloy filler metal improves wetting and permits shorter time at brazing temperature. A more practical way to braze aluminum to copper is to braze one end of a short length of aluminum-coated steel tube to the aluminum, and then silver braze the other

-top-

Wire Gauge / Gage Conversion Chart

Wire Gauges / Gages Arranged In Columns As Follows:

AWG= American Wire Gauge

B&S= Brown & Sharpe

SWG= Imperial Standard Wire Gauge-(British legal standard)

Wire Gauge /Gage Comment:

Values are stated in approximate decimals of an inch excluding the metric numbers. As a number of gauges are in use for various shapes and metals, it is advisable to state the thickness in thousands when specifying in gauge number. Metric wire gauge is 10 times the diameter in millimeters.

-top-

-top-

-top-