MANUFACTURING OF CLAD JOINTS USING TEE TECHNIQUE OF LIQUID INTERFACE DIFFUSION BONDING (LIDB)

摘要

Over the past half decade, an alliance of metallurgists, engineers, and fabricator have developed seamless clad joints, of a corrosion resistant alloy metallically bonded inside of a carbon steel substrate, primarily aimed at down-hole threaded joints, steel catenary risers and line pipe for rigorous physical environments. Many of the same individuals were concurrently developing an excellent clad plate of similar materials for forming into seam welded pipe. The majority of the problems, data and solutions for the two products are identical and are given in this paper. One major problem was to match the temperature requirements of both the cladding corrosion resistant alloy (CRA) and the carbon steel (CS) substrate. This was achieved by two steps; raising the allowable maximum CS temperature to 2010 deg. F by the design of a new, unique chemistry and secondly, by invention of an activator material that provided metallic bonding in the required temperature range for co-extrusion of the product. The temperature is several hundred degrees F. below the usual forge bonding temperatures. When seamless clad hollows are reduced in wall thickness, and elongated in length by the extrusion process, all of these seamless products are clad with the CRA material having a true bonding between the CRA and the CS. The local bond line shear strength is 57000 psi or greater, higher even than either of the two primary materials. The carbon steel is very weld-able, with a carbon equivalent of 37.5. Ductile to brittle transition temperatures are below -40 deg. F. A special inerting technique was invented to eliminate oxygen and other detrimental contaminants from the bond line. This results in a bond line impact strength typically of 70 lb-ft with essentially no effects from fatigue phenomena. The new CS is sour service compatible and is suited for the slow strain rate of the extrusion process and merely requires spray quenching down from the extrusion temperatures. There is full retention of the corrosion resistant alloy properties after processing. The final step was the design of an effective threaded joint, one that allows the threads to exist in the CS only. This new configuration passes all laboratory testing, however rigorous.