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THESSCO LIMITED - Sheffield England

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Phosphorus Brazing Alloys - Self fluxing
 
THESSCO
grade

Nominal composition (%)

Ag
Cu
P
Others

Melting
Range C)
[1]

Standard Specifikations

B.S.
1845:1984
DIN
8513
General comments
Flux
Phos 15
Phos 6
Phos 5
Phos 2
14.5
81
4.5
-
6
87
7
-
5
89
6
-
2
91.5
6.5
-
645 -
800
[700]
645 -
720
[700]
645 -
815
[710]
645 -
825
[740]
CP1
(L-Ag15P)
   
CP4
L-Ag5P
CP2
(L-Ag2P)

Suitable for flux-free brazing of copper and high copper alloys in air, or in a protective atmosphere furnace. A flux will normally be required for parent metals with copper contents of less than 90%. Care must also be taken with joint design to ensure that clearances appropriate to these less fluid alloys are maintained.

Y
or
U
NOTE: WARNING:

Standard Specification designations enclosed in brackets are near equivalents which do not correspond over the whole compositional range.

1. The upper melting point figure is the true liquids of the alloy but in practice brazing may be carried out at temperature significantly lower than those listed, as indicated [ ] thus.

2. * Brittish Patent 1.237.791 made under license to manufacture agreement.

1. Health & Safety Data sheets covering phosphorus alloys are available on request.

2. Phosphorus containing alloys must not be used on ferrous or nickel based parent metals. Since they will result in brittle joints.

3. They must not be exposed to hot sulphur bearing atmospheres in service due to the danger of selective phase corrosion.

Phosphorus Brazing Alloys  

Brazing with silver copper - phosphorus is widely used for joining copper to copper, where the absence of a flux is a major benefit. The self - fluxing action of phosphorus ensures that flux entrapment problems are largely avoided and that high standards of joint soundness can be maintained.

High phosphorus levels give excellent capillary penetration, since the fluidity of the molten brazing alloy is controlled by the phosphorus content. An example of this may be seen in phos 6 which has the highest fluidity of this group of alloys, with only Phos 0 approaching its performance in this respect.

Alloys with high phosphorus levels are less ductile than the lower phosphorus grades, particulary those with significant silver contents. For applications where optimum mechanical strength or resistance to vibration is required the lower phosphorus alloys such as Phos 5, Phos 2 and Phos CP6 are preferred. The 15% silver alloy, Phos 15, is the only grade available in foil form and is generally restricted in use to electrical and high integrity applications.

The tin containing alloy, Phos OT, offers controlled fluidity, a low melting point and joints of good appearance.

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Silver Brazing Alloys
 
THESSCO
grade

Nominal composition (%)

Ag
Cu
Zn
Sn
Others
Melting
Range C)

Standard Specifikations

B.S.
1845:1984
DIN
8513
General comments
Flux
HO
M25T
M13
M10T
M8T
M0T
M0
L18
L13S
L7
60
26
14
-
-
55
21
22
2
-
43
37
20
-
-
40
30
28
2
-
38
32
28
2
-
30
36
32
2
-
30
38
32
-
-
25
41
34
-
-
20
43
36.8
-
Si 0.2
14
51
35
-
-
695 - 730
630 - 660
690 - 770
650 - 710
660 - 720
665 - 755
680 - 770
700 - 800
690 - 810
810 - 835
AG13
L-Ag60
AG14
AG5
AG20
AG21
L-Ag25
(L-Ag20)

The higher silver, tincon taining alloys in this group approach the level of properties exhibited by the cadmium-bearing grades.

Ag-Cu-Zn ternary grades are a little less fluid but have greater strength at temperatures above 200°C, than Cadmium bearing alloys.

Due to higher mean brazing temperatures, time cycles tend to be longer, leading to increased demands on the flux. This may result in premature flux exhaustion and a consequent increase in post-braze cleaning costs.

Y
or
U
--------
U
or
F
--------
F
or
B
NOTE: WARNING:
Standard Specification designations enclosed in brackets are near equivalents which do not correspond over the whole compositional range. 1. Whilst not requiring the use of local exhaust ventilation, these alloys should nevertheless, only be used under conditions of adequate ventilation.

2. Health & Safety Data sheets covering these alloys are available on request.
Silver Brazing Alloys  
Good levels of ventilation are advisable to prevent build up of fumes arising from the brazing process but the stringent precautions required for cadmium-bearing grades are not necessary. It is for this reason that the silver-copper-zinc together with the newer tin-containing grades have enjoyed a significant increase in usage. Whilst they lack the exceptional fluidity of the cadmium alloys, they will still offer the user the principal attributes of the silver brazing alloy family.
Brazing Flux
 

THESSCO
Grade

Operating
Range (°C)
Characteristics

Fluidity
Activity
Life
General Comments
Availability
General
Purpose
Y
550 - 750
Good
High
Moderate
Suitable for low temperature alloys and short time cycles
Suitable for lower temperature alloys and longer time cycles
Suitable for intermediate temperature alloys and long time cycles
For high temperature alloys and extended time cycles
Powder and Paste
Powder only
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