Investigators: Roger Clough, Richard Fields, Donald Harne, George Hicho, and David Pitchure

Technical Description:

In 1993, the Copper Development Association (CDA) approached NIST with a problem. Lead-free solders will be required for plumbing in new building construction, but no one knows if these solders will perform as well as traditional lead-containing alloys. Because there is little data on the fracture and creep resistance of joints soldered with these new alloys, the maximum safe operating pressure for plumbing systems using these new solders cannot be determined and put into building procedures and codes. Working with CDA, NIST designed and is conducting tests that will provide the information required to establish safe plumbing codes for these new solders.

Technical Objectives:

• To determine the shear strength at room temperature and creep properties in shear at mildly elevated temperatures (38 ¯C - 139 ¯C) in air of copper tubing whose ends are joined by sleeves using lead-free solders.

• To assist industry, through the CDA, in establishing pressure ratings for the new lead- free solder joints in copper tube planning.

• To develop a better understanding of the mechanisms of delayed shear fracture of copper/solder joints.

Anticipated Outcome:

• Allow cost savings to the multi-billion dollar building construction industry by using maximum safe pressure ratings for the new solders.

• Prevent environmental degradation by enabling the use of lead-free solders.

• Development of new copper pipe plumbing codes.

Accomplishments for FY95:

• Creep equipment has been purchased, installed, and instrumented for computerized test monitoring.

• Approximately half of the proposed tests have been completed and analysis of these fractures indicates that the percentage of the joint wetted and joined with solder is a critical variable in determining actual performance of joints.

• Three test methods have been implemented and are being evaluated to determine:
  - Pre-test acoustic power transmission
  - Pre-test sample load compliance
  - Post-mortem optical fractography

Impacts and Technical Highlights:

• Millions of plumbing joints are made each year in the construction of houses, office buildings and high-rise apartments. In terms of shear volume of solder, the building industry's use of solder is substantial compared to that of the electronics industry. Cost savings can be appreciable if the required introduction of the new lead-free solders does not require the use of more expensive soldering techniques or the use of more expensive plumbing materials by the multi-billion dollar building construction industry. These test results will permit this industry and its regulators to optimize performance and safety.

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Last modified: Mon Jan 06 09:46:15 1997 Metallurgy Webmeister