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：将带点偏缺陷的nd钢管改锻成Φ210mm，取Φ210mm×200mm样坯车削成4级等长台阶（一级Φ150mm，二级Φ130mm，三级Φ110mm，四级Φ90mm），做酸浸塔形检测，在锻材Φ110mm、Φ90mm两级台阶上发现明显的类似于垫片的纵向暗条，而Φ150mm，Φ130mm两级台阶上纵向暗条纹则不明显。
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.
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.
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.
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
标签:   环氧地坪 地坪 环氧地坪施工 nd钢管