Heat treatment of welded 13%Cr-4%Ni martensitic stainless steels for sour service
- TWI, Cambridge (United Kingdom). Materials Dept.
For many years, the petroleum industry has employed martensitic stainless steels for wellhead and valve applications, and increasing use has been made of 13%Cr-4%Ni alloys. This material type was originally developed as a cast alloy (e.g., ASTM A487/A487M-89a Grade CA6NM). The combination of a low-carbon content and the addition of 3.5 to 4.5% nickel produces a fine, lath martensite structure which, after a tempering heat treatment, can exhibit superior mechanical properties. Thus, CA6NM and its forged variant ASTM A182/A182M-91 F6NM find application for production fluids containing CO{sub 2} and H{sub 2}S environments, particularly when hardening occurs, as is the case with fusion welds. Sensitivity to sulfide SCC increases at high material hardness levels, and the NACE MR0175 standard limits 13%Cr-4%Ni alloys to HRC 23 maximum for sour service. Attainment of such a hardness level requires careful consideration of tempering procedure. In this paper, the roles of welding procedure, material composition and postweld heat treatment are examined in relation to producing the minimum hardness levels in the weld zone.
- OSTI ID:
- 89687
- Journal Information:
- Welding Journal, Vol. 74, Issue 7; Other Information: PBD: Jul 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Postweld heat treatment of 13%Cr 4%Ni steels for sour service
Investigation of the stress corrosion cracking of duplex stainless steel weldments in sour conditions