DEVELOPMENT OF HIGH PERFORMANCE CAST ALLOYS ALLOY 31 and ALLOY 59 for the CHEMICAL PROCESS INDUSTRY

摘要

Within the last decades great efforts were made by the producers of wrought corrosion resistant products to develop new alloys. The materials of construction for modern chemical process industry (CPI) plants, petrochemical and other industries not only have to resist uniform corrosion. New alloys must also have sufficient resistance against localized corrosion and stress corrosion cracking. These industries have to cope with both the technical and commercial challenges of rigid environmental regulations, the need to increase production efficiency, and at the same time possess the necessary versatility to handle varied feed stock and upset conditions.(1) Due to the production routes in all these companies, they concentrated on their standard products like plate, bar, wire and tube. All plants in the chemical process industries however also need castings for pumps and valves in the piping systems, connecting reactors and heat exchangers. In the past, only few foundries copied the analysis of the new materials, aiming at the production of castings similar in corrosion resistance to the wrought alloys. Prominent examples of highly corrosion resistant materials are Alloy 59 (UNS 06059) and Alloy 31 (UNS 08031) developed in wrought product forms, e. g. sheet, plate, strip and forging, in Germany. Some years ago, a German foundry obtained a license to produce cast versions of these alloys with the obligation to execute extensive testing of corrosion resistance and mechanical properties in direct comparison with the wrought materials. This paper reports the results of these efforts in some very corrosive media which are used in chemical plants. The tests were executed in the corrosion laboratories of an internationally acknowledged chemical enterprise.