| A martensitic stainless steel seamless pipe for
linepipe application, KL-HP12CR, has been developed with good weldability, mechanical
properties and corrosion
resistance. Weldability is improved by the reduction of both C and N content.
C reduction is also effective to the improvement of CO2 corrosion resistance
achieving the corrosion rate less than 0.127 mm/y under the CO2 environment at
160°C and 2.0 MPa. It can be applied under the H2S environment at pH4.0 and
0.001 MPa, since the resistance to sulfide stress cracking (SSC) is improved
by Mo addition. The pipe has X80-grade strength and sufficient low temperature
toughness for the practical use as a linepipe. Post weld heat treatment (PWHT)
in a few minutes, the reduction of C content and addition of Ti are effective
to prevent intergranular stress corrosion cracking (IGSCC) at the heat affected
zone. Further application of the pipe is expected for the transportation of product
fluid with corrosive gas such as CO2, as an economical material with low life
cycle cost. |
