Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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Effect of Manufacturing Process on the Corrosion Properties of 304L Stainless Steel Pipe with 8-inch Diameter

8인치 직경의 304L 스테인리스강관의 부식특성에 미치는 제작공정의 영향

  • Kim, K.T. (Research Center for Energy and Clean Technology, School of Materials Science and Engineering, Andong National University) ;
  • Hur, S.Y. (Research Center for Energy and Clean Technology, School of Materials Science and Engineering, Andong National University) ;
  • Chang, H.Y. (Power Engineering Research Institute, KEPCO Engineering & Construction Company) ;
  • Kim, Y.S. (Research Center for Energy and Clean Technology, School of Materials Science and Engineering, Andong National University)
  • 김기태 (안동대학교 신소재공학부, 청정에너지소재기술 연구센터) ;
  • 허승영 (안동대학교 신소재공학부, 청정에너지소재기술 연구센터) ;
  • 장현영 (KEPCO E&C, 미래전력기술연구소) ;
  • 김영식 (안동대학교 신소재공학부, 청정에너지소재기술 연구센터)
  • Received : 2018.10.19
  • Accepted : 2018.11.27
  • Published : 2018.12.31
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Abstract

Austenitic stainless steels used in nuclear power plants mainly use pipes made of seamless pipes, which depend on imports. The manufacturing process and high cost are some of the problems associated with seamless pipes. Therefore, in this study, the corrosion characteristics of the seamless pipe and the SAW pipe were assessed to determine the safety and reliability of the SAW pipe in a bid to replace the seamless pipe. Microstructure was analyzed using an optical microscope and the degree of hardness was measured using a Rockwell B scale. Intergranular corrosion resistance was evaluated by ASTM A262 Practice A, C, and E methods. The degree of sensitization was determined using a DL-EPR test. Anodic polarization test was performed in deaerated 1% NaCl solution at $30^{\circ}C$ and the U-bend method was used to evaluate the SCC resistance in 0.01 M $Na_2S_4O_6$ at $340^{\circ}C$ and 40% NaOH solution at $290^{\circ}C$. Weld metal of the SAW pipe specimen showed relatively high degree of sensitization and intergranular corrosion rate. However, annealing to SAW pipes improved the corrosion properties in comparison to that of the seamless pipe.

Keywords

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Fig. 1 Effect of manufacturing process and annealing on the microstructure of 304L stainless steel pipe; (a) SP8, (b) SAW8B, (c) SAW8W, (d) SAW8B-1010, (e) SAW8B-1060, (f) SAW8B-1110, (g) SAW8W-1010, (h) SAW8W-1060, (i) SAW8W-1110.

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Fig. 2 Effect of annealing on the surface hardness of 304L stainless steel pipe.

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Fig. 3 Effect of manufacturing process and annealing on the sensitization of 304L stainless steel pipe; (a) SP8, (b) SAW8B, (c) SAW8W, (d) SAW8B-1010, (e) SAW8B-1060, (f) SAW8B-1110, (g) SAW8W-1010, (h) SAW8W-1060, (i) SAW8W-1110.

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Fig. 4 Effect of annealing temperature on the intergranular corrosion rate of 304L stainless steel pipe by ASTM A262 Practice C method.

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Fig. 6 Surface appearance of 304L stainless steel pipe after the corrosion test in boiling 6% CuSO4 + 16% H2SO4 by ASTM A262 Practice E method.

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Fig. 5 Effect of annealing temperature on the degree of sensitization of 304L stainless steel pipe.

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Fig. 7 Effect of annealing temperature on the anodic polarization curves of 304L stainless steel pipe in deaerated 1% NaCl at 30 ℃.

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Fig. 8 Surface appearance after liquid penetration test on 304L stainless steel pipe after SCC test using U-bend test method; (a) 340 ℃, 0.01M Na2S4O6 for 500 hrs, (b) 290 ℃, 40% NaOH for 500 hrs.

Table 1 Specimen identification and heat treatment condition

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