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| Formation analysis of white spot imperfections on
cold rolling 1Cr18Ni9Ti stainless steel pipes |
| YU Lei1,YANG Chun1,2,LIU Ming1,2,XIE Jinpeng1,2,ZHONG Zhenqian1,2,ZHANG Zhuo2 |
| 1. NCS Testing Technology Co., Ltd., Beijing 100081, China;
2. Central Iron & Steel Research Institute, Beijing 100081, China |
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| Guide |
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Abstract Many white spot imperfections were observed on the inner surface of 1Cr18Ni9Ti stainless-steel pipes produced by cold rolling process, so that the products could not be delivered normally. In order to confirm the reasons for the formation of white spots, the surface morphology, metallographic structure, grain size and micro area composition of this batch of steel pipes were analyzed and detected using scanning electron microscopy + energy disperse spectroscopy, metallographic microscope, and laser-induced breakdown spectroscopy. The results showed that the surface carburization occurred on both inner and outer surface of the pipe, and the carburization in white spot imperfection was much more serious than other areas. The severe intergranular corrosion was caused during pickling and passivating. Many grains on the surface were dropped off, deteriorating the roughness on partial surface, and forming white spot imperfections. The inadequate degreasing on pipe surface caused carburization in heat treatment process, which was the major reason for white spot imperfections.
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Received: 06 May 2021
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2022, Vol. 40 
