In the fastener industry, “high strength” typically refers to any medium carbon or medium carbon alloy steel that is quenched and tempered (heat treated). The heat treating process increases the strength of the raw material to the parameters defined by the ASTM or AASHTO specification in question. In the case of highway barrier pins, this most commonly comes into play in the case of headed connection pins called out to ASTM A449 or AASHTO M-164.
According to the American Institute of Steel Construction, quenched and tempered bolting material cannot be welded or heated. Applying heat to steel that has already been quenched and tempered will alter the mechanical properties of the steel in the area that has been heated. This compromises the integrity of the product and exposes both the supplier and the end user to potential liability due to these pins failing in the field. To avoid this problem, the correct way to manufacture a high strength barrier pin with a welded plate and/or nut would be to take “as rolled” medium carbon or medium carbon alloy steel round bar, cut it, weld the washer, and then send the entire assembly out for heat treating after performing the welding operation. The pin would then need to be tested in a finished condition to ensure that the mechanical properties are within the parameters of the applicable ASTM/AASHTO specification. If not manufactured and tested properly in this way, the manufacturer, as well as the contractor using the barrier pins, could be exposing themselves to a tremendous amount of liability.
Due to this potential for improper manufacturing, several states have approved headed pins that are heat-treated after forging as an acceptable alternative to designs that required welding to high strength steel. This option helps to avoid some of the potential pitfalls surrounding welding to high strength steel. If you have doubts about which type of barrier pin is required or approved for your particular job, please contact me and I may be able to help you sort out the correct barrier pins that are needed for your project and avoid any potential liability issues.