X－60钢中晶内铁素体片的形成及其对焊接热影响区的作用

用晶内铁素体片（ＩＦＰ）技术显著改善了Ｘ－６０钢熔焊热模拟后热影响区（ＨＡＺ）的韧性。试验发现：ＩＦＰ和冲击能密切相关,ＩＦＰ的体积分数＞６０％时,冲击能＞１５０Ｊ．光学金相和ＳＥＭ检验提示了ＩＦＰ的特征,它是原奥氏体晶粒内出现的大量微细的铁素体片,是在焊后的控冷过程中以“形核脱氧产物”为非自发形核核心而生成的．并非任何脱氧产物都有诱发ＩＦＰ的作用．有效的夹杂物是在较高初始氧位下,用ＲＥ,Ｚｒ,Ｔｉ脱氧所形成的细小、均布且具有较高硫容量的复合氧化物夹杂．

FORMATION OF INTRAGRANULAR FERRITE PLATES AND THEIR EFFECT ON HEAT AFFECTED ZONE OF STEEL X-60

The heat affected zone (HAZ) toughness of steel X-60 after simulation tests of molten welding was improved by means of the technology of intragranular ferrite plate (IFP).It was found that the absorbed energy during impect tests depends strongly on the quantity of IFP. If the volume fraction of IFP is larger than 60%, then the absorbed energy will go up to 150 J and more. The examination of optical microscopy and SEM exhibited that IFP consists of fine ferrite plates originating inside the initial austenite grains. These IFP forined by the so called "nucleating inclusions" as nuclei during the controlled cooling process after welding simulation. The nucleating inclusions are some fine and evenly distributed composite oxides with higher sulphur content, which result from the deoxidation by RE, Zr, Ti under a higher initial oxygen potential.