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中碳镍铬钼钢经穿管制成无缝钢管后,在纵向断口上有时出现长短不等的“小裂口”。试验结果证明:断口上的“小裂口”不是原来就存在于钢管内部的裂纹,而是钢管内的片状或片状分布的夹杂在打断口时裂纹沿夹杂物开裂的现象。这类夹杂的存在可能与冶炼、浇铸工艺有关,而夹杂的片状形态和同心圆分布却可能与轧制穿管工艺有关。这样的夹杂对在与其正交方向开预裂纹的断裂韧性没有明显降低的作用。
After the carbon-carbon, nickel-chromium-molybdenum steel is made into seamless steel tube through the tube, there are sometimes “small cracks” in the longitudinal fracture. The test results show that the “small rips” on the fracture are not the cracks originally existing in the steel pipe, but the cracks in the steel pipe are flaky or flake inclusions. The existence of such inclusions may be related to the smelting and casting process, while the inclusion flake shape and concentric distribution may be related to the rolling process. Such inclusions have no significant effect on the fracture toughness of the pre-crack in the direction perpendicular thereto.