KR101460279B1 - STAINLESS STEEL BASED ON Cr-Mn - Google Patents

Abstract

The present invention relates to a Cr-Mn-based stainless steel, which comprises 0.25% or less of carbon (C), 0.5% or less of nitrogen (N), 1.0 to 5.0% of silicon (Si) (P): 0.045% or less, S: not more than 0.03%, Cr: 16.0 to 19.0%, and nickel (Ni): not more than 1.0% And a content of Si and Mn satisfies the following formula (1): " (1) "
0.13? Si / Mn? 0.63 (1)

Description

Cr-Mn-based stainless steel {STAINLESS STEEL BASED ON Cr-Mn}

The present invention relates to a Cr-Mn-based stainless steel, and more particularly, to a Cr-Mn-based stainless steel which can simultaneously improve pitting corrosion resistance and critical corrosion potential in a low cost Cr-Mn austenitic stainless steel, It is about the river.

Generally, instability such as demand balance and price based on lack of Ni resources is one of the problems always encountered in industrial production of Cr-Ni austenitic stainless steel. For this reason, studies for replacing Ni with Mn have been studied for a long time.

In Japan, there is an example of studying Cr-Mn heat-resistant steel following the US and Germany and registered in aviation specification. Since the adoption of low Ni-Cr-Mn-N stainless steels 201 and 202 in the American Iron and Steel Institute (AISI) Various Mn-based austenitic stainless steels have been commercialized.

The above steel type is a favorable work in terms of Ni resource countermeasure and lower cost by replacing Ni of Cr-Ni austenitic steel with Mn and N. [ However, Cr-Mn-N type steels have many problems in manufacturing and characteristics to be solved. For example, Mn has a problem in that the corrosion resistance of the refractory is lowered due to easy erosion of the refractory during melting, the resistance to cold deformation is high due to the high resistance to cold deformation, and the property that the corrosion resistance is essentially not equal to that of the Cr-Ni system have.

In particular, the development of Cr-Mn austenitic stainless steels has been proceeding in the direction of designing steel grades to cope with corrosion resistance by adjusting Ni content.

That is, the austenitic stainless steel containing a large amount of Mn has been problematic in that the corrosion resistance is poor, and Ni is added to supplement the corrosion resistance. However, a product containing a large amount of expensive Ni has a problem in that the product price is increased.

Therefore, it is necessary to develop a low-cost Cr-Mn high corrosion resistant steel material with improved corrosion resistance and critical corrosion potential in Cr-Mn system.

In order to solve the above problems, the present invention provides a Cr-Mn-based stainless steel in which corrosion resistance is improved by adding Si, Sn and Cu to Cr-Mn austenitic stainless steels containing not more than 1% .

(C): not more than 0.25%, nitrogen (N): not more than 0.5%, silicon (Si): 1.0 to 5.0%, manganese (Mn): 8.0 to 16.0 (P): not more than 0.045%, sulfur (S): not more than 0.03%, chromium (Cr): 16.0 to 19.0%, nickel (Ni): not more than 1.0% , And a Cr-Mn-based stainless steel in which the content of Si and Mn satisfies the following formula (1).

0.13? Si / Mn? 0.63 (1)

In the stainless steel, the content of Sn and Cu may satisfy the following formulas (2) and (3).

0.2? (Sn + Cu / 10)? 0.45 (2)

0.1? Sn? 0.3 - (3)

Further, the corrosion area ratio after 9 times of spraying a 5% NaCl solution at 35 占 폚 for 2 hours, drying at 60 占 폚 for 4 hours, and wetting at 50 占 폚 for 9 times is less than 10%.

According to the embodiment of the present invention, the corrosion resistance of Cr-Mn-based stainless steel can be improved by adding low-cost Si to an appropriate range, and the critical current density of the Cr-Mn-based stainless steel can be lowered by optimizing the appropriate ratio of Cu and Sn have.

1 is a view showing a corrosion area ratio according to the ratio of [Si / Mn] to [Sn + Cu / 10] according to an embodiment of the present invention.
2 is a graph showing the results of evaluation of corrosion resistance and moldability according to the relationship between Si and Si / Mn ratio according to an embodiment of the present invention.
3 is a graph showing the relationship between Sn and Cu contents and current density according to an embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described in detail below. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims.

The Cr-Mn type austenitic stainless steel according to the embodiment of the present invention contains 0.25% or less of carbon (C), 0.5% or less of nitrogen (N), 1.0 to 5.0% of silicon (Si) (P): 0.045% or less, S: not more than 0.03%, Cr: 16.0 to 19.0%, and nickel (Ni): not more than 1.0% Is made of iron and impurities.

First, the reason for limiting the numerical value of the component content in the examples according to the present invention will be described. Unless otherwise stated, the unit of the content is% by weight.

Carbon (C): not more than 0.25% by weight

Carbon is an element that causes work hardening of the austenitic stainless steel together with nitrogen, and when it exceeds 0.25% by weight, the cold rolling resistance is increased to lower the productivity of the cold rolled steel, so that the carbon content in the examples according to the present invention is limited to the above range .

Nitrogen (N): not more than 0.5% by weight

Nitrogen causes work hardening of the austenitic stainless steel together with the carbon, and in the Cr-Mn austenitic system, the stability of the austenitic phase is usually increased, and the austenite phase can be obtained in the entire temperature range. However, since the casting defects such as nitrogen pores can be generated in a large amount, the amount of nitrogen is controlled to 0.5 wt% or less.

Silicon (Si): 1.0 to 5.0 wt%

Silicon is effective for improving the pitting resistance and oxidation resistance. However, when it is contained in an amount exceeding 5.0% by weight, it is liable to cause surface defects such as moldability during hot forming and sticking during hot working. In addition, when the content of silicon is less than 1%, the oxidation resistance and the effect of improving the internal formula sharply decrease. Therefore, the content of silicon in the examples according to the present invention is controlled within the above range.

Manganese (Mn): 8.0 to 16.0 wt%

Manganese is added instead of expensive Ni to enhance the stabilization of the austenite phase. However, it is necessary to supplement with other elements because the more the addition, the lower the corrosion resistance. If the Mn content is less than 8%, the degree of austenite reduction may fall and the ferrite-type austenite-based two-phase type steel may be formed, resulting in a reduction in formability. When the Mn content exceeds 16%, a large amount of inclusions such as MnS The content of manganese is limited to the above range in the examples according to the present invention.

Phosphorus (P): 0.045% by weight or less

Phosphorus (P) is an unavoidable impurity contained in steel, which causes intergranular corrosion during pickling or inhibits hot workability, so the content is limited to the above range.

Sulfur (S): 0.03 wt% or less

Sulfur (S) is an unavoidable impurity contained in steel and is segregated in crystal grain boundaries to inhibit hot workability. Therefore, in the examples according to the present invention, the content of sulfur is limited to the above range.

Cr (Cr): 16.0 to 19.0 wt%

Chromium (Cr) is an alloy element added to improve the corrosion resistance of steel, and the critical content of chromium is 11% by weight. When the Cr content is less than 16%, the corrosion resistance is deteriorated. When the Cr content exceeds 19%, the delta ferrite phase is precipitated at the time of solidification, resulting in a two-phase system. 16.0 to 19.0% by weight.

Nickel (Ni): 1.0 wt% or less

Nickel is an austenitic element used to maintain phase balance and acts as a more austenite former than Mn. However, since nickel is high cost, the content of nickel in the embodiment according to the present invention is limited to the above range.

In addition, the high corrosion resistant austenitic stainless steel according to the embodiment of the present invention satisfies the following expression (1).

0.13? Si / Mn? 0.63 (1)

The reason why the Si / Mn ratio is set to 0.63 or less in the above formula (1) is that the steel sheet is kept from being transformed into a two-phase region (ferrite phase + austenite phase) at room temperature and high temperature, To ensure moldability. The reason for keeping the Si / Mn ratio at 0.13 or more is to secure the corrosion resistance by adding Si within the austenite single phase region.

In order to lower the critical corrosion potential in Equation (1), the following equations (2) and (3) must be satisfied. More specifically, the content of Sn should satisfy 0.1 to 0.3% by weight, and the value of Sn + Cu / 10 should satisfy 0.2 to 0.45%.

0.1? Sn? 0.3 - (2)

0.2? (Sn + Cu / 10)? 0.45 (3)

Hereinafter, embodiments according to the present invention will be described.

In the above formula (2), Sn is contained in an amount of 0.1 to 0.3. Sn is an element having excellent corrosion resistance in an acidic atmosphere such as sulfuric acid, and is used as an element for improving corrosion resistance against general corrosion (corrosiveness in an acidic atmosphere) . The effect of improving corrosion resistance is excellent even when a trace amount of Sn is added in an amount of 0.1% or more. However, since Sn is equal to or higher than the Ni price, there is a problem in cost of the product when contained in a large amount. In addition, when added in an amount exceeding 0.3%, edge cracking can occur during hot rolling, which is due to the low melting point of Sn. Therefore, the content of Sn in the examples according to the present invention is limited to the above range.

In addition, in the equation (3), Cu is an element showing similar characteristics to Sn, and an edge crack can be generated in hot rolling when a large amount of elements are included. Therefore, the value of (Sn + Cu / 10) is limited to 0.45. On the other hand, in the case where (Sn + Cu / 10) is less than 0.2, the effect of containing Sn and Cu is small, so the value of (Sn + Cu / 10) is limited to the above range in the embodiment of the present invention.

[Example]

Table 1 below shows a composition system capable of controlling Si, Mn and [Si / Mn] in a Cr-Mn type austenitic steel to improve the corrosion resistance without inhibiting moldability while maintaining the stability of the austenite phase.

Table 2 also shows the range of [Sn + Cu / 10] which can reduce the edge crack during hot rolling while controlling the Sn and Cu contents to improve the general corrosion resistance (critical corrosion current). The qualitative characteristics (mV), critical current density (mA / cm 2) and elongation (%) of the quality characteristics shown in Tables 1 and 2 were evaluated on the basis of the thickness of 1 mm of cold rolled annealed material.

C Si Mn P S Ni Cr N Si / Mn Formula potential (mV) Elongation (%) Remarks 0.09 1.5 8.0 0.035 0.002 0.8 17.5 0.18 0.19 125 55 Honor 0.12 1.5 11.0 0.035 0.002 0.8 17.0 0.20 0.14 100 54 Honor 0.12 2.7 8.0 0.035 0.002 0.7 17.5 0.21 0.34 250 50 Honor 0.11 2.7 11.0 0.035 0.002 0.8 17.0 0.19 0.25 210 52 Honor 0.12 2.7 15.0 0.035 0.002 0.8 16.8 0.19 0.18 180 51 Honor 0.03 3.3 8.0 0.035 0.002 0.9 17.0 0.19 0.48 350 48 Honor 0.12 3.3 11.0 0.035 0.002 0.8 18.1 0.19 0.35 320 47 Honor 0.12 3.3 15.0 0.035 0.002 0.8 17.0 0.19 0.25 260 48 Honor 0.11 4.5 8.0 0.035 0.002 0.8 17.8 1.80 0.56 380 45 Honor 0.12 4.5 11.0 0.035 0.002 One 17.0 0.19 0.41 320 46 Honor 0.12 4.5 15.0 0.035 0.002 0.8 18.5 0.20 0.30 300 43 Honor 0.09 0.6 18.0 0.035 0.002 0.8 17.0 0.19 0.08 65 55 Comparative Example 0.12 0.6 11.0 0.035 0.002 0.8 17.0 0.19 0.05 50 57 Comparative Example 0.12 0.6 15.0 0.035 0.002 0.7 17.5 0.20 0.04 42 54 Comparative Example 0.11 1.5 15.0 0.035 0.002 0.8 17.0 0.19 0.10 55 49 Comparative Example 0.12 5 8.0 0.035 0.002 0.9 18.0 0.18 0.63 410 42 Comparative Example 0.12 6.2 15.0 0.035 0.002 0.8 17.0 0.19 0.41 480 39 Comparative Example

C Si Mn P S Ni Cr N Sn +
Cu / 10 electric current
density
(mA / cm ² ) Presence or absence of edge crack Remarks 0.12 3.8 11.0 0.035 0.002 0.8 18.1 0.19 0.24 0.01 Not occurring Honor 0.12 3.8 15.0 0.035 0.002 0.8 17.0 0.19 0.35 0.007 Not occurring Honor 0.11 4.5 8.0 0.035 0.002 0.8 17.8 1.80 0.4 0.003 Not occurring Honor 0.12 4.5 11.0 0.035 0.002 One 17.0 0.19 0.45 0.001 Not occurring Honor 0.09 1.5 8.0 0.035 0.002 0.8 17.5 0.18 0.05 0.2 Not occurring Comparative Example 0.12 1.5 11.0 0.035 0.002 0.8 17.0 0.20 0.03 0.25 Not occurring Comparative Example 0.12 2.7 8.0 0.035 0.002 0.7 17.5 0.21 0.01 0.3 Not occurring Comparative Example 0.11 2.7 11.0 0.035 0.002 0.8 17.0 0.19 0.07 0.15 Not occurring Comparative Example 0.12 2.7 15.0 0.035 0.002 0.8 16.8 0.19 0.13 0.07 Not occurring Comparative Example 0.12 4.5 15.0 0.035 0.002 0.8 18.5 0.20 0.67 0.0005 Occur Comparative Example 0.12 3.8 11.0 0.035 0.002 0.8 18.1 0.19 0.85 0.0003 Occur Comparative Example

FIG. 1 is a graph showing the results of a Cyclic Corrosion Test (CCT) in which a 5% NaCl solution at 35 ° C. according to an embodiment of the present invention is sprayed for 2 hours, dried at 60 ° C. for 4 hours, FIG. 1 is a photograph showing the corrosion area ratio according to the ratio of [Si / Mn] and [Sn + Cu / 10] after 9 cycles, wherein the corrosion area ratio is less than 10%.

2 is a graph showing the relationship between the Si content, the Si content, and the Si content in the Cr-Mn system, while maintaining the stability of the austenite phase by controlling the Si, Mn and Si / Mn ratios according to the embodiment of the present invention, 2 is a graph showing the range of the embodiment according to the present invention of the parameters of [Mn] and [Si / Mn], wherein the value of Si / Mn is in the range of 0.13 to 0.63, And the moldability was excellent.

FIG. 3 is a graph showing the relationship between Sn and Cu content in the range of [Sn + Cu / 10], which can reduce edge cracks during hot rolling while improving the general corrosion resistance (critical corrosion current) FIG. Referring to FIG. 3, it can be seen that the range of [Sn + Cu / 10], which is excellent in corrosion resistance and hot workability, is 0.2 to 0.45.

While the present invention has been described in connection with certain exemplary embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (4)

(C): not more than 0.25% (excluding 0%), nitrogen (N): not more than 0.5% (excluding 0%), silicon (Si): 1.0 to 5.0%, manganese (Mn): 8.0 to 16.0 (P): not more than 0.045% (excluding 0%), sulfur (S): not more than 0.03% (excluding 0%), chromium (Cr): 16.0 to 19.0%, nickel (Ni): not more than 1.0% %), The remainder being composed of iron and impurities,
Wherein the content of Si and Mn satisfies the following formula (1)
And a content of Sn and Cu satisfies the following formula (2).
0.13? Si / Mn? 0.63 (1)
0.2? (Sn + Cu / 10)? 0.45 (2) delete The method according to claim 1,
Wherein said stainless steel is a Cr-Mn-based austenitic stainless steel having a Sn content satisfying the following formula (3)
0.1? Sn? 0.3 - (3) 4. The method according to claim 1 or 3,
Wherein the corrosion area ratio after 9 cycles of spraying 5% NaCl solution at 35 ° C for 2 hours, drying at 60 ° C for 4 hours and wetting at 50 ° C is less than 10% Austenitic stainless steel.

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