304L in the European specifcations is Steel No 1.4306 or 1.4307 (which has a higher nickel content). For general purpose duties, the appropriate specification for plate is EN10088-2 but for pressure vessel plate you should use EN10028-7
Indeed, 1.4306 is equivalent to SS304L. This indication is an old but common used German indication called "Werkstoff number" (WN)
The indication as used in EN 10088-2 is: X2CrNi19-11
Jlu - you are right that 1.4306 is an old DIN designation but DIN designations were chosen for the new European standards that came out in the late 1990s. These new standards designate each grade by a name AND steel number.
The 304L grade was split in two to take into account different nickel contents:
Steel number 1.4306 has the name X2CrNi19-11 (as you pointed out) and the lower nickel variant (which is preferred by suppliers because its lower nickel content means it is cheaper)is Steel number 1.4307 and has the name X2CrNi18-9. 1.4306 has a slightly higher chromium content too.
From the name you can tell its nominal composition. The number following X is roughly the mid-point of the carbon content range times 100; the 18-9 is the respective nominal content of the chromium and nickel. The steel number is usually quoted rather the name because, as the number of the elements in the steel increases, the name becomes unwieldy.
