ASTM A334 Gr6 Seamless Carbon Alloy Steel Low Fin Tubes For Low Temperature Service ASTM A334 This specification covers several grades of minimum-wall-thickness, seamless and welded, carbon and alloy-steel tubes intended for use at low temperatures. Some product sizes may not be available under this specification because heavier wall thicknesses have an adverse affect on low-temperature impact properties. The advantages of ASTM A334 Grade 6 Tubes in low-temperature service are