JMTH-OPS-WRK-0329-00
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Braze Joint Visual Inspection
1. Purpose / Scope
1.1. This work instruction describes the criteria and process for visually inspecting aluminum dip brazed
and vacuum brazed joints produced by Collins Aerospace Mountainhome.
1.2. This work instruction applies for both dip brazed and vacuum brazed parts and should take place prior
to any sanding, deburring, emerying, and/or machining of the joints takes place.
1.3. This work instruction defines the typical criteria for visual inspection of brazed part. In the event of a
conflict between the job traveler and this document, the job traveler will take precedence.
1.4. Any job specific variables will be defined on the job traveler and other applicable engineering
documents called out in the job traveler, including the internal parts breakout drawing (IPB) and/or
process sheets.
2. Responsibility
2.1. It is the responsibility of employees such as inspectors and brazing operators who inspect braze joints to
understand and adhere to this document.
2.2. Manufacturing engineering is responsible for maintaining and updating this document.
3. References
4. Definitions
4.1. Braze Joint Proper – the total area, as defined by the engineering drawing, of the faying surfaces to be
joined by brazing, excluding any fillets that form at the edges of that area.
4.2. Faying Surface – a surface that is in contact with a joint.
4.3. Surface Porosity – A roughened or spongy appearance, or open pores, on the surface of the brazed fillet.
Such pores are not sharply linear or crack-like in shape. Surface porosity is confined to the fillet and
does not progress into the brazed joint proper.
4.4. Void – Any area of the braze joint proper that is not completely filled with brazing filler metal.
5. Safety Information
5.1. Parts may be hot when coming out of the brazing furnace or drying oven. Wait until the parts are cool
to the touch prior to inspecting.
5.2. Parts may also be very cold when coming out of a freezer. Thermal gloves are recommended when
inspecting these parts.
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6. Braze Joint Classifications
6.1. Class A joints are those joints subjected to high stresses, cyclic stresses, or both.
6.2. Class B joints are those joints subjected to low or moderate stresses, cyclic stresses, or both.
6.3. Class C joints are those joints subjected to low or moderate stresses, cyclic stresses, or both.
6.4. If no class is specified, Class A shall apply.
6.5. Braze joint classifications, when provided, will always be called out on the job traveler.
7. Inspection Process
7.1. Before inspecting for braze joint conformity, the part must be clean, dry, and free of FOD.
7.1.1. Dip brazed parts must be cleaned of all flux/salt and salt tested (if required) prior to inspection.
7.1.2. Vacuum brazed parts may be inspected directly after brazing.
7.2. Bring the part to a well-lit area, and place it on a workbench, table, or other work surface that is free of
FOD.
7.3. Inspect all visible braze joints in accordance with the criteria listed in Section 6.
7.3.1.1. Use magnification of 10X power and/or a flashlight wherever possible to identify defects.
0.001” – 0.005” feeler gauges or shim pieces, may also be used.
7.3.1.2. For braze joints where both side of the joint is visible, the easiest way to detect voids is to
shine the flashlight directly onto the joint and look for light to shine through on the other side
of the joint. See Figure 7.3.1.2.
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MTH-OPS-WRK-0329-00
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Figure 7.3.1.2
7.3.1.3. Use the mirror to view joints that are hard to see or are obstructed by part features. An
example of this would be a braze joint underneath a flange.
7.3.1.4. Any evidence of brazing salt or stop off residue is unacceptable.
7.3.1.5. Any pitting of the parent material due to salt erosion is unacceptable.
7.4. If visual inspection yields ambiguous or uninterpretable results, other inspections, such as ultrasonic
inspections, may be performed.
7.5. If there is any evidence of failure criteria as described in Section 8, non-conform the part in accordance
with WI-018-2.
8.1.1. Figures 8.1.1.a and 8.1.1.b below show ideal brazing joints.
8.1.2. Any part with obvious assembly errors shall be rejected immediately.
8.1.3. Any part containing fin stock that is clearly shifted shall be rejected immediately.
Shine a light on
one side of the
This is especially useful
for finding small voids.
exists in the joint.
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8.1.4. Frost or ice that is stuck on the part from the freezer may sometimes obstruct a clear view of a
braze joint. Address frost/ice as necessary.
Figure 8.1.1.a
parent material. Braze Joint
The braze joint exhibits
butt joint where two flat
plates are brazed
evidence of excess braze.
slightly below the parent
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Figure 8.1.1.b
8.2. Surface Porosity and Voids
8.2.1. Surface porosity, voids, or brazing filler metal skips are allowed, provided they meet the following
criteria:
8.2.1.1. Any discontinuity of 0.015” or less is uninterpretable and is not considered a defect. This
applies for braze joint classes.
8.2.1.2. Braze fillet voids, surface porosity, and brazing filler metal skips are acceptable as long as
they do not extend into the braze joint proper. Braze fillet condition shall not be cause for
rejection unless it compromises the quality of workmanship.
8.2.1.3. Any filler discontinuity that extends into the braze joint proper shall not exceed the limits
shown in Table 8.2.1.3 below.
Table 8.2.1.3 – Discontinuity Acceptance Criteria
Class Discontinuity
A 0.090" 10%
B 0.090" 25%
C 0.120" 50% * There is no formal definition for “discontinuity size”. If the discontinuity is both longer and wider than the allowable size, then it shall be further evaluated.
In most cases, the width of the entire joint is less than 0.090”. In these instances, if the void is not a through void, it is considered to be acceptable (for class A and B
joints.)
the same color as the
parent material.
butt joint where the side
of a wall is brazed to a
flat surface. The wall is
perpendicular to the flat
evidence of excess braze.
This joint was NOT
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8.2.2. Cracks
8.2.3. Erosion
8.2.3.1. Any evidence of braze filler erosion of the exposed base metal is unacceptable if the erosion
of either member exceeds the criteria shown in Table 8.2.3.1 below.
Table 8.2.3.1 – Erosion Acceptance Criteria
Class
A 5%
B 15%
C 15%
* Erosion allowance applies to the thinnest component of the brazed joint
8.2.4. Lack of Brazing Filler Metal Melting
8.2.4.1. Any failure of the brazing filler metal to melt completely is unacceptable. This applies for all
joints.
8.2.4.2. Usually, when lack of brazing filler metal exists, the braze material will be much darker than
the parent material. Additionally, the material will feel flaky and/or very rough.
8.2.5. Through Voids
Table 8.2.5.1 – Through Void Criteria
Class Through Void Criteria
A Any void that can be seen at the edges and extend
through the full width of the joint is unacceptable. B
C
Any edge void that extends through the full joint is
acceptable provided that it does not compromise the
function of the part.
8.2.6. Flux Residue
8.2.6.1. Evidence of any leftover corrosive flux or flux residue, such as brazing salts, is
unacceptable.
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8.2.7. Quality of Workmanship
8.2.7.1. The quality of workmanship shall be such that the assemblies are suitable for the intended
purpose and that adjacent surfaces are free of excess brazing filler metal that could interfere
with subsequent operations or the function of the product.
8.2.7.2. A brazed part may be rejected if there is excess braze in areas where it is hard or impossible
to remove. Examples of this include:
8.2.7.2.1. Excess braze on sensitive areas, such as card guides, where removal poses a high risk
of a surface finish and/or dimensional out-of-tolerance condition.
8.2.7.2.2. Excess braze in fin stock that will cause functionality issues and cannot be removed
(e.g. excess braze in a cooling passage with lanced offset fin is almost always not
repairable and requires part rejection.)
9. Additional Information
9.1. Internal Discontinuities
9.1.1. The information provided in this section is for reference only and may not be necessarily used to
accept or reject braze joints during visual inspection.
9.1.2. When braze joints have nondestructive testing (NDT) performed on them, internal discontinuities
are visible. Table 9.1.2 below summarizes the allowable internal discontinuities for braze joints.
Table 9.1.2 – Internal Discontinuities Criteria
Class
A 15%
B 25%
C No requirement
9.2. Large-area Braze Joints
9.2.1. Most brazing joints bond the side of thin wall (generally ~0.035 – 0.090” thick) to another surface.
Internal discontinuities described in Section 9.1 do not normally appear in these types of braze
joints.
9.2.2. However, braze joints where both faying surfaces are large (many vacuum braze joints are like
this) may exhibit internal discontinuities. As long as all internal discontinuities conform to Section
9.1, they should not compromise the fit, form, or function of the braze joint or the part.
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9.3. Machining and Deburring of Braze Joint
9.3.1. Any machining or deburring that occurs on a braze joint may cause apparent voids to appear in the
braze joint. While not likely, this is most likely to occur when machining into a large-area braze
joint and removing a large amount of material.
9.3.2. Unless the machined or deburred joint shows a through void, cracking, other mechanical failure, or
will interfere with the intended fit, form, or function of the part, then the braze joint is acceptable.
9.3.3. See Figures 9.3.3.a and 9.3.3.b below for examples of what may occur after braze joint machining
or deburring.
Figure 9.3.3.a
braze joint.
brazing material and
not visible before this
surface was deburred. A
mechanical failure.
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Figure 9.3.3.b
processing. This opened
braze joint.
brazing material and
not visible before this
surface was deburred. A
mechanical failure.
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9.4. Additional Reference Figures
clear that the entire joint has bonded.
Additionally, there are no obvious issues
with the joint.
Braze Joint
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Figure 9.4.1.b
Braze Joint
brazed joint.
not normally a criteria for
braze quality.
there was a lot of braze filler
material available at this joint
during the brazing process.
braze material, the surface of
the fillet looks a little darker
and rougher. This is
failure criteria listed in
technically comprised of
form, or function.
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Revision Record
Reference/Remarks
00 06/15/2020
All This document replaces WI-010-4.16. Changes include the new numbering format (MTH-OPS) and the first 4 sections of this document to conform to Collins Aerospace requirements.
Document Control
06/15/2020
Revision:
00
Production Review & Date:
Quality Approval & Date: