As the alloys do not contain deoxidants, autogenous welding is not recommended because of porosity. Filler metal compositions contain typically 0.2 to 0.5% titanium, to prevent weld metal porosity. Argon shielding gas is normally used for both TIG and MIG (MIG welding) but in TIG welding, an argon-H2 mixture, with appropriate filler, improves weld pool fluidity and produces a cleaner weld bead. Gas backing (usually argon) is recommended, especially in pipe welding, to produce an oxide-free underbead.