80mm=0.8dm,50mm=0.5dm,5mm=0.05dm,1m=10dm,钢的密度为7.85 kg/dm^3,10[0.80+2(0.50-0.05)]*0.05*7.85=6.67(kg/m)1米长国标80x50X5的槽钢重6.67kg