| 摘要 |
<p>A process for the production of fine-grain, weldable sheet steel stock for large diameter pipes from microalloyed steel by thermomeohanical welding. A steel consisting of 0.05 to 0.07% carbon, 1.5 to 2.0% manganese, 0.01 to 0.04% titanium, 0.001 to 0.003% sulfur, 0.005 to 0.008% nitrogen, 0.25 to 0.40% silicon, 0.03 to 0.05% aluminum, and up to 0.08% niobium, with the remainder of iron and the usual impurities is produced The titanium content is adjusted to the nitrogen content. continuously cast slabs are heated to 1120 to 1160 deg.C. The niobium precipitations are dissolved thereby and during subsequent cooling during deformation precipitated mainly as strength-enhancing niobium oarbide. A coarsening of the titanium nitride precipitations that takes place during this heating has not proved to be detrimental. Deformation amounts to at least 55%. This is followed by thermomechanical rolling at a temperature of at most 850 deg.C, and finish rolling at a temperature above 650 deg.C. lntensified cooling at temperatures of between 550 and 500 deg.C can follow. :</p> |
