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本文介绍生产过程中或实弹打靶考核中与冶铸缺陷有关的失效分析三例。例一为杆状晶断口严重,导致整炉炮塔报废。分析认为因A1N沿铸造晶界析出,提高了低温脆性转变温度,降低延性、韧性指标,造成材料的脆性增加所致。冶炼上控制终脱氧时的加铝量,使残铝量<0.04%,可有效地避免平炉钢的杆状断口。例二为大量的MnS夹杂及严重的技晶偏析导致炮塔打靶报废。分析认为MnS与AlN相似,都使材料的脆性增加,同时,大量的MnS夹杂物破坏了金属的连续性,在夹杂物处因应力集中,易形成裂纹源,高的浇注温度会带来枝晶偏析、显微缩孔(疏松)等弊病,使炮塔内外表面性能差别较大,导致打靶时背强值降低而报废。控制硫含量及选择合适的脱氧制度是减少硫化锰夹杂的关键,避免高温浇注是铸钢生产中不可忽视的问题。例三为齿轮轴渗碳和高温回火后发现纵向大裂纹。主要因浇注时操作不当,造成大面积碳偏析,热处理后由于组织应力而引起纵向裂纹,注意操作规程,此类缺陷可避免。
This article describes three cases of failure analysis related to the defects of smelting during the production process or the actual shooting test. A case of severe rod shaped fracture, leading to the entire turret scrapped. It is considered that the precipitation of A1N along the grain boundaries of the cast increases the low temperature brittle transition temperature, decreases the ductility and toughness, and increases the brittleness of the material. Smelting control of the total amount of aluminum during deoxidation, the residual aluminum content of <0.04%, can be effectively avoided flat steel rod fracture. Example II for a large number of MnS inclusions and severe crystal segregation led to turret target scrapping. The analysis shows that MnS is similar to AlN, which makes the brittleness of the material increase. Meanwhile, a large number of MnS inclusions destroy the continuity of the metal. Due to the stress concentration in the inclusions, cracks easily form and the high pouring temperature will bring dendrites Segregation, micro-shrinkage (loose) and other ills, the turret inside and outside the surface of the larger differences in performance, leading to reduce the value of the back when the target and scrapped. Control of sulfur content and select the appropriate deoxidation system is to reduce the inclusions of manganese sulfide key to avoid high temperature casting is cast steel production can not be ignored problem. Example 3 for the gear shaft carburizing and tempering after the discovery of longitudinal cracks. Mainly due to improper operation of pouring, resulting in large areas of carbon segregation, heat treatment due to stress caused by longitudinal cracks, pay attention to operating procedures, such defects can be avoided.