But why? The question of ASTM A312-TP321

Dear all experts,
In the Standard of ASTM A312, I have a doubt about the material TP321. As the Standard described, The Tensile Requirement of this material, t<3/8 in, is 75ksi; t>3/8in, is 70ksi. But in the Old Edition, there is no these differences.
Who can give me a explain.
Thanks for your any coments.

regards,

ChenYueshuang Received on Tue Mar 16 19:39:00 2004