API TR 6MET

This document examines mechanical properties of metallic materials used for API 6A and 17D wellhead equipment for service above 250 °F. A total of eleven different alloys meeting API 6A, PSL 3 conditions were supplied “in condition” by a variety of suppliers. Materials in this test program included alloys common to the oil and gas industry. The alloys tested included low alloy steels, martensitic, precipitation hardened and duplex stainless steels, and nickel alloys. Yield strength reduction ratios at temperatures of 300, 350, 400, and 450 °F are reported. As a result of testing, yield strength reduction ratios at 300 °F to 450 °F ranged from 92 % to 87 % for the low alloy steels, 92 % to 88 % for the martensitic stainless steels 81 % to 73 % for super duplex, 99 % to 89 % for the precipitation hardened stainless steel and 94 % to 89 % for the nickel alloys. The reported results represent an average over the different heats for each type of material. These results are intended to expand the data shown in API 6A for design and rating of equipment for use at elevated temperatures.

This document includes the results of additional testing to review the accuracy of the derating factors for the precipitation-hardened stainless steel values first published.