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为解决钢厂高强度船板钢连铸坯经常出现的中间裂纹等内部缺陷问题,从该钢种连铸坯中间裂纹区域获取试样,并对其进行了高温力学性能测试。结果表明,低温脆性区(即第三脆性区)的温度范围为750～925℃,在900～950℃温度区断口处存在较多液膜。综合断口形貌、液膜存在的温度范围以及断口纵断面金相组织等方面进行分析,认为950℃时塑性开始下降的主要原因是由于断口处存在液膜,并推断液膜的形成原因为晶界处形成了(FeS+FeO)或(MnS+FeS+FeO)低熔点共晶相。同时,该试样在750～950℃区间内塑性下降的发生机制可以大致归结为:900～950℃区间内由于低熔点共晶相液膜作用导致塑性下降;850～900℃之间由于低熔点共晶相液膜与晶界铁素体膜复合作用导致塑性下降;850℃以下由于晶界铁素体膜作用导致塑性下降。
In order to solve the internal defects such as intermediate cracks often appearing in the high strength ship steel slabs of steel mills, the samples were obtained from the middle crack region of the steel slab and the high temperature mechanical properties were tested. The results show that the temperature range of the low temperature brittle zone (ie the third brittle zone) is 750-925 ℃, and there are many liquid films at the temperature of 900-950 ℃. Based on the analysis of the fracture surface, the temperature range of the liquid film and the metallographic structure of the fracture surface, the main reason that the plasticity begins to decrease at 950 ℃ is that the liquid film exists at the fracture surface and the formation reason of the liquid film is crystal Boundary formed (FeS + FeO) or (MnS + FeS + FeO) low melting point eutectic phase. At the same time, the mechanism of plastic decrease of the sample in the range of 750-950 ℃ can be summarized as follows: the plasticity decreases due to the low-melting eutectic phase liquid film in the range of 900-950 ℃; the low melting point The co-crystal phase liquid film and the grain boundary ferrite film composite lead to plasticity decrease; below 850 ℃ due to the grain boundary ferrite film plasticity decreased.