對(duì)ND鋼管一般斑點(diǎn)狀偏析的成因分析：根據(jù)試驗(yàn)分析，結(jié)合nd鋼管鍛造生產(chǎn)情況，在排除一般疏松、氣體過(guò)飽和、鋼液純凈度太差等因素后，通過(guò)金相及能譜分析，發(fā)現(xiàn)點(diǎn)偏處組織有別于基體組織，如晶粒細(xì)化，硬度偏高(達(dá)310～340HV），組織也非珠光體正常組織，從而認(rèn)為現(xiàn)有的點(diǎn)偏缺陷實(shí)質(zhì)是受合金成分偏析導(dǎo)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(diǎn)偏缺陷的nd鋼管改鍛成Φ210mm，取Φ210mm×200mm樣坯車削成4級(jí)等長(zhǎng)臺(tái)階（一級(jí)Φ150mm，二級(jí)Φ130mm，三級(jí)Φ110mm，四級(jí)Φ90mm），做酸浸塔形檢測(cè)，在鍛材Φ110mm、Φ90mm兩級(jí)臺(tái)階上發(fā)現(xiàn)明顯的類似于墊片的縱向暗條，而Φ150mm，Φ130mm兩級(jí)臺(tái)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(cè)：根據(jù)所收集的5爐鋼相關(guān)氣體的檢測(cè)數(shù)據(jù)發(fā)現(xiàn)，點(diǎn)偏的出現(xiàn)及級(jí)別與nd鋼管中氣體含量并無(wú)直接關(guān)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(guò)的低倍試樣上點(diǎn)偏缺陷密集部位切取金相試樣進(jìn)行高倍分析；對(duì)nd鋼管試樣進(jìn)行拋光、高倍輕腐蝕后觀察宏觀形貌；將試樣偏析部位標(biāo)識(shí)后再次進(jìn)行低倍酸浸重腐蝕試驗(yàn)。上述金相分析結(jié)果表明，偏析區(qū)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(jìn)一步放大倍數(shù)觀察，通過(guò)對(duì)點(diǎn)偏缺陷位置處能譜分析，發(fā)現(xiàn)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(jié)合上述分析結(jié)果，排除了點(diǎn)偏為一般疏松誤判的可能，也排除了由于氣體過(guò)飽和所引起的nd鋼管點(diǎn)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(diǎn)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.