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Medium Cr ferrite stainless steel with ultra low content of C and N and manufacturing method thereof

A manufacturing method and a ferritic technology, applied in the field of stainless steel, can solve the problems of difficulty in avoiding the sigma phase brittle temperature zone, difficulties in industrial production of ferritic stainless steel, etc., and achieve good room temperature toughness, excellent resistance to pitting corrosion, and reduce production costs. Effect

Active Publication Date: 2014-12-24
CENT IRON & STEEL RES INST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The existence of three brittle temperature zones has brought great difficulties to the industrial production of ferritic stainless steel
However, the crimping temperature of general stainless steel is difficult to avoid the brittle temperature zone of the σ phase.

Method used

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  • Medium Cr ferrite stainless steel with ultra low content of C and N and manufacturing method thereof
  • Medium Cr ferrite stainless steel with ultra low content of C and N and manufacturing method thereof
  • Medium Cr ferrite stainless steel with ultra low content of C and N and manufacturing method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0061] Example 1: Pitting corrosion resistance of medium-Cr ferritic stainless steel samples with ultra-low C and N content

[0062] The pitting potential of the medium-Cr ferritic stainless steel 3# sample with ultra-low C and N content and the comparison materials 316 and 304 austenitic stainless steel were tested by potentiodynamic method according to the national standard GB4334.9-84 ( figure 1 ). The results show that the 3# sample (Table 3) with higher pitting equivalent (PRE) has the highest pitting potential, about 832mV, about 200mV higher than 304 austenitic stainless steel, and about 100mV higher than 316 austenitic stainless steel, indicating that Mo element The increase of the content has a significant effect on improving the pitting corrosion resistance.

[0063] Table 3 Differences in main components and pitting equivalents between medium-Cr ferritic stainless steel with ultra-low C and N content and 304 / 316 stainless steel

[0064]

Embodiment 2

[0065] Example 2: Depassivation acidity (Depassivation pH, pH d )

[0066] According to the ASTM-G48 method of the American Society for Testing and Materials, the medium-Cr ferritic stainless steel 1# and 3# samples with ultra-low C and N content and the comparison materials 444 ferritic stainless steel and 316 austenitic stainless steel were removed. Passivation acidity test ( figure 2 ). The depassivation acidity value is a measured value, and its meaning refers to the ability of the material to resist the occurrence and expansion of crevice corrosion by electrochemical methods. The lower the value, the stronger the crevice corrosion resistance. It can be seen from Table 4 that the pHd value of the 1# sample with a Mo content of 1.12% is 1.83, and the pH of the 3# sample with a Mo content of 1.97% d The value reached 1.47, much smaller than the two comparative materials 316 austenitic stainless steel and 444 ferritic stainless steel, indicating that only when the acidity...

Embodiment 3

[0069] Example 3: Crevice corrosion resistance of medium-Cr ferritic stainless steel samples with ultra-low C and N content

[0070] According to the ASTM-G48 method of the American Society for Testing and Materials, the 3# sample of medium Cr ferritic stainless steel with ultra-low C and N content and the comparison materials 304 austenitic stainless steel and 316 austenitic stainless steel were tested in different media. Corrosion performance ( Figure 3-5 ). The test results show that the weight loss of 304 austenitic stainless steel has reached 1.9845g, far exceeding the critical value of 1g for judging the occurrence of crevice corrosion, and Figure 5 It shows that there are many obvious crevice corrosion pits on the surface of the sample; although 316 austenitic stainless steel does not produce obvious corrosion pits after the test, its weight loss is still as high as 1.6548g. In contrast, the Cr ferritic stainless steel 3# sample with a Mo content of 1.97% and an ult...

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Abstract

The invention provides a medium Cr ferrite stainless steel with ultra low content of C and N and a manufacturing method thereof, belonging to the technical field of stainless steel. The stainless steel comprises, on the basis of weight percentage, no less than 19.0 but no more than 21.5 of Cr, no less than 1.0 but no more than 4.0 of Mo, no more than 0.0040 of C, no more than 0.01 of N, no less than 0.20 but no more than 0.40 of Nb, no less than 0.10 but no more than 0.20 of Ti, no more than 0.35 of Mn and no more than 0.05 of Si, with the balance being Fe, and it is guaranteed that Cr (wt. %) + 3.3 Mo (wt. %) are no less than 23.3. The manufacturing method comprises the following steps: melting; continuous casting or die casting; hot coping; hot rolling and crimping; continuous annealing; removal of scales; cold rolling and annealing; pickling and flattening; and welding. The medium Cr ferrite stainless steel with ultra low content of C and N provided by the invention has the advantages of good ductility at room temperature, resistance to pitting and crevice corrosion and weldability.

Description

technical field [0001] The invention belongs to the technical field of stainless steel, in particular to a medium-Cr ferritic stainless steel with ultra-low C and N content and a manufacturing method thereof. Background technique [0002] The Cr content of medium-Cr ferritic stainless steel with ultra-low C and N content is about 20%, and its corrosion resistance is further improved by adding a certain amount of Mo, Nb, and Ti to stabilize it; at the same time, its C+N content is ≤250ppm, This ensures that this type of steel not only has excellent corrosion resistance, but also has certain toughness and processing performance. Compared with austenitic stainless steel, medium chromium ferritic stainless steel usually does not contain precious Ni element, and is cheap and has strong market competitiveness. Compared with high-Cr ferritic stainless steel, medium-Cr ferritic stainless steel has lower Cr and Mo content, which further reduces production cost and technical difficul...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/28C21D8/02
Inventor 屈华鹏郎宇平陈海涛荣凡康喜范杨长强秦海斌
Owner CENT IRON & STEEL RES INST
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