The major norms for materials for hose clamps are the Swedish SS2298 and the German DIN3017.
By the right hand menu you can click for more detailed information about these norms and you will find as well a cross reference to national norms.
This will guide you to find the right material for certain applications, which is as important as to choose the right type of clamp.
Generally the material used has no bearing whatsoever on the mechanical function of the clamp, but certain materials in combination with a certain design of the clamps provides better clamping force.
Universal information about steel qualities you can find under the link "Stahlschluessel".