AWS C3.2M/C3.2

The purpose of this standard is to describe the test method used to obtain reliable data on the strength of metal-to-metal, metal-to-nonmetal, and nonmetal-to-nonmetal brazed joints. Test specimens should be prepared using consistent and proper fabrication and brazing practices. Interpretation of the test results is the responsibility of the user.

It should be recognized that if the production practices for the brazed product do not follow the test specimen brazing practice, the joint strengths of the test specimen might not be the same as the product's joint strengths.

It is important that the user of this test maintain sufficient documentation of the materials, brazing parameters, and test conditions. This documentation will be required when comparing the results to the joint strengths obtained by others using this standard method. General use of this standard method may permit a compilation of brazed joint strengths and brazing design criteria at some future time.

The mechanical performance of a braze joint is necessarily an integration of the filler metal, the base metal, the geometry of the brazement, and the brazing procedure. Moreover, the properties of the base metal may be sensitive to the process parameters and joint overlap. As the overlap is increased, the failure location shifts from failure in the braze joint to failure in the base metal. Joints made with an overlap greater than this transition value will behave as being stronger than the materials being joined together. Material thicknesses (T) other than 3.0 mm (0.125 in.) may be used for test specimens. Overlaps should be adjusted accordingly.

When testing for long-term shear data such as stress rupture and creep properties, the double-lap shear specimen is required to achieve uniform test conditions. Shear strength versus overlap properties for the double-lap specimen show results similar to those obtained for the single-lap specimen.

The butt tensile specimen provides the tensile strength of the base metal-filler metal combinations when tested in tension. This specimen is not suitable for all filler metals such as those that produce butt tensile strengths far below the properties of the base metal. Filler metal-base-metal combinations of higher strength are often diffusion brazed to develop mechanical properties equal to those of the base metal. These tests provide excellent data for design purposes. The butt brazed tensile specimen can also be used to obtain stress rupture and creep design data. Moreover, impact and fatigue specimens can be cut from the butt brazed specimens.

The four-point bend specimen is specifically designed to obtain the butt tensile strength data of a brazed specimen that has very limited or no ductility. Typical of these materials are ceramics, graphite, cermets, and other similar materials.

Units of Measure and Rounding-Off Procedure. This specification makes use of both the International System of Units (SI) and inch-pound units. The standard sizes and dimensions in the two systems are not identical. For this reason, a conversion from a standard size or dimension in one system will not always coincide with a standard size or dimension in the other. However, if appropriate tolerances are applied in each case, suitable conversions encompassing the standard sizes of both systems of units can be made.