| 摘要 |
PURPOSE:To prevent the intercrystalline cracking and internal cracking in the surface layer part of an ingot by rolling a rolled stock at a prescribed number of passes at specific thickness reduction ratios, then subjecting the stock to high-draft rolling in which the depth of the compressive stress region to be acted in the rolling direction is set at specific % or above of the sheet thickness. CONSTITUTION:The rolled stock which is a thick plate consisting of a copper-Ni alloy is first subjected to 3-10 passes of rolling at the thickness reduction ratio per pass set at 1-5% at the time of hot rolling said stock. The stock is thereafter subjected to >=4 passes of high-draft rolling in which the depth hc of the compressive stress to be acted on the rolled stock in the rolling direction thereof is >=85% of the thickness h0. Since the initial draft and the number of passes of the rolling are limited, the recrystallized grains in the surface layer part are formed and the intercrystalline cracking is prevented. The compressive stress region and the number of passes of the rolling are limited in the ensuing high-draft rolling and, therefore, the internal cracking is satisfactorily prevented. The generation of the intercrystalline cracking and internal cracking in the surface layer part of the ingot are thereby prevented.
|
