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                    廠家對nd鋼管一般斑點狀偏析成因解決方法

                    發布時間:2019-05-20人氣:186

                    對ND鋼管一般斑點狀偏析的成因分析:根據試驗分析,結合nd鋼管鍛造生產情況,在排除一般疏松、氣體過飽和、鋼液純凈度太差等因素后,通過金相及能譜分析,發現點偏處組織有別于基體組織,如晶粒細化,硬度偏高(達310~340HV),組織也非珠光體正常組織,從而認為現有的點偏缺陷實質是受合金成分偏析導致的組織偏析。
                    Analysis of the causes of the general speckle segregation of ND steel pipes: According to the experimental analysis and combined with the forging production of ND steel pipes, after excluding the factors such as general porosity, gas supersaturation and poor purity of molten steel, metallographic and energy spectrum analysis showed that the structure at the point deviation was different from the matrix structure, such as grain refinement, high hardness (310-340HV), and the structure was not normal pearlite structure. It is believed that the existing point segregation defect is essentially the segregation of the structure caused by the segregation of the alloy composition. 酸浸塔形分析:將帶點偏缺陷的nd鋼管改鍛成Φ210mm,取Φ210mm×200mm樣坯車削成4級等長臺階(一級Φ150mm,二級Φ130mm,三級Φ110mm,四級Φ90mm),做酸浸塔形檢測,在鍛材Φ110mm、Φ90mm兩級臺階上發現明顯的類似于墊片的縱向暗條,而Φ150mm,Φ130mm兩級臺階上縱向暗條紋則不明顯。
                    Acid leaching tower shape analysis: the ND steel pipe with point deviation defect was forged into 210 mm, and the sample blank of 210 mm * 200 mm was turned into four equal-length steps (first 150 mm, second 130mm, third 110 mm, fourth 90 mm). The acid leaching tower shape detection was carried out. The vertical dark stripes similar to gaskets were found on the forged steel 110 mm and 90 mm steps, while the vertical dark stripes on the two steps of 150 mm and 90 mm were found. It is not obvious.

                    氣體檢測:根據所收集的5爐鋼相關氣體的檢測數據發現,點偏的出現及級別與nd鋼管中氣體含量并無直接關系。
                    Gas Detection: According to the collected data of gas related to 5 stoves of steel, it is found that the occurrence and grade of point deviation is not directly related to the gas content in ND steel pipe.

                    金相分析:在酸洗過的低倍試樣上點偏缺陷密集部位切取金相試樣進行高倍分析;對nd鋼管試樣進行拋光、高倍輕腐蝕后觀察宏觀形貌;將試樣偏析部位標識后再次進行低倍酸浸重腐蝕試驗。上述金相分析結果表明,偏析區組織類似于貝氏體組織,基體為珠光體+鐵素體;掃描電鏡下觀察,組織明顯存在不均勻,進一步放大倍數觀察,通過對點偏缺陷位置處能譜分析,發現了以MnS為代表的夾雜物的偏聚。
                    Metallographic analysis: metallographic specimens were cut at the point defect-intensive part of pickled low-power specimens for high-power analysis; ND steel tube specimens were polished and observed after high-power light corrosion; the segregation parts of the specimens were marked and the heavy corrosion test of low-power acid leaching was carried out again. The metallographic analysis results show that the segregation zone is similar to bainite structure, and the matrix is pearlite + ferrite. The structure is obviously inhomogeneous under scanning electron microscopy, and further magnification observation. The segregation of inclusions represented by MnS is found by energy spectrum analysis at the location of the point deviation defect.

                    結合上述分析結果,排除了點偏為一般疏松誤判的可能,也排除了由于氣體過飽和所引起的nd鋼管點狀偏析的可能,還排除了鋼液純凈度太差,夾雜物偏聚所致形成點狀偏析的可能。
                    Combined with the above analysis results, the possibility of misjudgement of point deviation for general looseness is excluded, the possibility of point segregation for ND steel tube caused by gas supersaturation is also excluded, and the possibility of point segregation caused by poor purity of molten steel and inclusion segregation is also excluded.


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