Lan85:
Because the modulus of elasticity is material dependant property, and API Stds. cover many different materials, which change from time to time. You should go to the particular material specs. and stds. for these kinds of mechanical properties.
dhengr:
API 5L standard incorporates manufacturing processes, chemical compositions, testing etc of different pipeline materials. There are no separate standard for the pipeline materials such as X56 and X65.
Modulus is a very structure-insensitive property that can't be changed appreciably via heat treatment, cold-working, etc. in steels. Any difference you see from testing different grades of X-grade pipe or from different sources is likely due to measurement error of the very small strains associated with the elastic region of the material. This is why API 5L doesn't list modulus, as there are many sources that list this for carbon steel. It also doesn't list physical properties or poisson's ratio, as these are widely available from various sources.