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High-grade duplex stainless steel with much suppressed formation of intermetallic phases and having an excellent corrosion resistance , embrittlement resistance, castability and hot workability

A technology of duplex stainless steel and intermetallic phase, applied in the field of duplex stainless steel, can solve the problem of reducing the formation speed of θ phase, reducing the proportion of austenite phase, and cannot completely suppress the θ equalization of high-quality duplex stainless steel

Inactive Publication Date: 2005-07-20
朴庸秀
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, alloying elements (e.g., Al or Zr) are ferrite formers, which reduce the austenite phase ratio and form various N-containing intermetallic compounds, thereby deteriorating corrosion resistance and mechanical properties (M.B. Cotrie et al., Metallurgical and Materials Transaction 28A (1997) 2477)
[0007] 3) When Sn is added to ferritic stainless steel containing 43 to 46% Cr, Sn precipitates in the nucleation region of θ phase (for example, grain boundary or grain boundary triple point), thereby reducing the θ phase forming speed
[0014] However, the above methods for adding a third alloying element or controlling the cooling process during heat treatment cannot completely suppress theta phase in high-quality duplex stainless steel

Method used

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  • High-grade duplex stainless steel with much suppressed formation of intermetallic phases and having an excellent corrosion resistance , embrittlement resistance, castability and hot workability
  • High-grade duplex stainless steel with much suppressed formation of intermetallic phases and having an excellent corrosion resistance , embrittlement resistance, castability and hot workability
  • High-grade duplex stainless steel with much suppressed formation of intermetallic phases and having an excellent corrosion resistance , embrittlement resistance, castability and hot workability

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Experimental program
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Effect test

example 1

[0105] Example 1: Method for making and testing steel of the invention

[0106] Now, the method of designing and manufacturing the optimal alloy according to the present invention will be described. By incorporating the alloy design factors (e.g., PREW in equation ①, [PREW(γ)-PREW[α]] for the corrosion resistance measure of each phase, Cr in equation ② 当量 and Ni of equation ③ 当量 ) are optimally combined to obtain a method for designing the alloy, and the resulting values ​​are shown in Table 2.

[0107] Cr is calculated by equations ② and ③ 当量 and Ni 当量 To determine this composition, use industrial purity grades Fe, Cr, Mo, Ni, W, Cu, Si, Mn and Fe-Cr-N as described in the claims of the present invention and combine these alloying elements at high frequency were melted in an induction furnace and deoxidized according to common methods (e.g. deoxidation of Ti, Mg, Al, Ca or Al+Ca components), sampling castings melted in air, and castings melted in vacuum and nitrogen atmosp...

example 2

[0116] Example 2: Comparison of Microstructure of Aging Products

[0117] Figures 1A to 1F It is a photograph of the microstructure, showing steel 4 of the present invention subjected to aging heat treatment for 30 minutes at 850°C ( Figure 1A ), steel 10 of the present invention ( Figure 1B ) and steel 36 of the present invention ( Figure 1C), comparative steel 47 ( Figure 1D ) and commercial high-quality duplex stainless steel UR 52N+ ( Figure 1E ) and SAF 2507 ( Figure 1F ), the precipitation of brittle intermetallic phases (e.g., θ and χ phases) that impair corrosion resistance and mechanical properties. The bright part shows the austenite phase, while the dark part shows the ferrite phase decomposed into the θ phase + austenite phase during the aging heat treatment. The degree of precipitation of intermetallic phases is "steel of the present invention 4 = steel of the present invention 10 = steel of the present invention 36 "commercial steel UR52 + "commercial...

example 3

[0118] Example 3: X-ray Diffraction Analysis Test

[0119] Figures 2A to 2D It is a graph of the X-ray diffraction analysis test results, showing the steel 4 ( Figure 2A ), comparative steel 47 ( Figure 2B ) and commercial high-quality duplex stainless steel UR 52N+ ( Figure 2C ) and SAF 2507 ( Figure 2D ), the precipitation of brittle intermetallic phases (e.g., θ and χ phases) that impair corrosion resistance and mechanical properties. Compared with comparative steel 47 and commercial steels UR 52N+ and SAF 2507, inventive steel 4 has no θ phase precipitated and very little χ phase precipitated, thereby significantly improving embrittlement resistance.

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Abstract

Formation of intermetallic phases such as sigma (sigma) and khi (chi) shows detrimental effects on the corrosion and mechanical properties of high-grade duplex stainless steel. The present invention provides high-grade duplex stainless steel with much suppressed formation of intermetallic phases, of which the chemical composition consists essentially, on a weight basis, of : Cr : 21.0% ~ 38.0%, Ni : 3.0% ~ 12.0%, Mo : 1.5% ~.6.5%, W : 6.5% or less, Si : 3.0% or less, Mn : 8.0% or less, N : 0.2% ~ 0.7%, C :0.1% or less, at least one element selected from the group consisting of Ba : 0.0001 ~ 0.6% and one or more elements of Mischmetal (MM) and Y : 0.0001 ~ 1.0% in total, and a balance of Fe and incidental impurities. The pitting resistance equivalent has a value of 40 <= PREW<= 67 defined by the following formula (1) : PREW = wt.%Cr + 3.3(wt.%Mo + 0.5wt.%W) + 30wt.%N(1) The present high-grade duplex stainless steel exhibits an excellent corrosion resistance, embrittlement resistance, castability and hot workability.

Description

technical field [0001] The present invention relates to duplex stainless steels with excellent corrosion resistance, and more particularly to duplex stainless steels with excellent corrosion resistance formed by inhibiting the formation of intermetallic phases (e.g., θ and χ phases) during production (casting, hot rolling or welding). High-quality duplex stainless steel with excellent corrosion resistance, embrittlement resistance, castability and hot workability. Background technique [0002] Among them, duplex stainless steel with austenitic (γ) phase that provides high machinability and ferrite (α) phase that provides high corrosion resistance is finely combined, and its strength is at least 1.7 higher than that of austenitic stainless steel. times, and exhibits high resistance to pitting corrosion and high resistance to stress corrosion cracking (SCC). Commercial high-quality duplex stainless steel with a pitting resistance equivalent weight (PREW=wt%Cr+3.3(wt%Mo+0.5wt%...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C22C38/42C22C38/44C22C38/58
CPCC22C38/42C22C38/002C22C38/44C22C38/005C21D2211/005C22C38/58C21D2211/001C22C38/001
Inventor 朴庸秀金淳太李仁诚
Owner 朴庸秀
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