KR100611498B1 - Cu added High manganese austenitic stainless steel - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to austenitic stainless steels, wherein, in weight%, C: 0.15% or less, Si: 1.0% or less, Mn: 7-10%, S: 0.01% or less, Ni: 4.0% or less, Cr: 14.0 ~ Consists of 20.0%, N: 0.30% or less, Cu: 3.0% or less, B: 0.005% or less, Ca: 0.005% or less and other Fe and inevitable elements, in the range of 52.9933 + 1.37513 XB + 0.298097 X Ca + 1.51623 X Cu-0.0187413 XBXB-4.98177 It is characterized by having a good hot workability by the composition so that the cross-sectional area reduction rate calculated by the formula of X Cu X Cu is 60% or more at 900 ℃.

Stainless steel, high manganese, hot workability

Description

Copper added high manganese austenitic stainless steel             

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing a comparison between actual values and predicted values of a cross-sectional area reduction rate at 900 ° C.

The present invention relates to a stainless steel that is used in general for automotive steel plates, architectural decoration, kitchenware, etc. More specifically, even when Cu is added to stabilize the austenite phase and improve cold workability, high hot workability is ensured. A manganese austenitic stainless steel.

The most widely used austenitic stainless steel is 304 steel, which has excellent workability and corrosion resistance. However, the 304 steel is expensive because it contains more than 8% Ni. In order to solve this disadvantage, an attempt has been made to replace expensive Ni with an inexpensive alloy element, and has been standardized to steel grades, such as 201 steel, 202 steel, and 204 steel, in which a part of Ni is replaced with Mn or N. These steels have the advantage of being nonmagnetic and easy to obtain high strength by replacing Ni with Mn or N. However, Mn has a deterioration in formability and corrosion resistance compared to Ni, and also deteriorates formability by N. There is a problem limited to. The addition of Cu improves the formability of the austenitic stainless steel having a high Mn and N content, but the addition of Cu lowers the hot workability and causes defects in hot rolling operations.

An object of the present invention is to provide a Cu-added high manganese austenitic stainless steel having excellent hot and cold workability as proposed to solve the conventional problems as described above.

Therefore, in order to achieve the object of the present invention by weight% C: 0.15% or less, Si: 1.0% or less, Mn: 7-10%, S: 0.01% or less, Ni: 4.0% or less, Cr: 14.0-20.0%, N: 0.30% or less, Cu: 3.0% or less, B: 0.005% or less, Ca: 0.005% or less and consist of other Fe and unavoidable elements, in the range of 52.9933 + 1.37513 XB + 0.298097 X Ca + 1.51623 X Cu -0.0187413 XBXB-4.98177 X Cu X It is characterized by providing a copper-added high manganese austenitic stainless steel, characterized in that the cross-sectional area reduction rate is calculated to be 60% or more at 900 ℃.

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Hereinafter, the present invention will be described in more detail.

The present inventors studied the effect of the alloying component of Cu-added high manganese austenitic stainless steel on hot workability, and derived a correlation between the reduction of the cross-sectional area at 900 ° C. and Cu, B, and Ca, which is a representative index of hot workability. Therefore, it was found that the hot workability and the moldability can be improved by appropriately adjusting the addition amounts of B and Ca which improve the hot workability according to the Cu content which improves the formability but lowers the hot workability.

Hereinafter, the features of the present invention will be described together with the functions. First, the reason for limiting the essential components in the present invention will be described.

C: It is an austenite phase forming element. When excessively added, it reacts with Cr to form chromium carbide, which lowers corrosion resistance, and reduces moldability and elongation. Therefore, it is preferable to maintain it at 0.15% or less of the standard range of 200 stainless steel.

Si: Since it is an element that inhibits hot workability while promoting the formation of a ferrite phase, it is preferable to limit it to a small amount as much as possible, and in the present invention, it is limited to 1% or less, which is a standard range of 200-based stainless steel.

Mn: An austenite-phase stabilizing element that replaces Ni as an element to replace the austenite phase to add 7% or more, when added in excess of 10% deterioration of corrosion resistance and cold workability.

S: It is an element that is inevitably contained in the main element alloy, and segregates at the grain boundaries and causes processing cracks during hot rolling.

Ni: Stabilizes the austenite phase as well as manganese. However, nickel is very expensive among the alloying elements, and when added too much, it lowers the solubility of nitrogen in the liquid phase to generate pores, so the content is limited to 4% or less.

Cr: It is an element that promotes the formation of passivation film and at the same time increases the solubility of nitrogen. It is required to add more than 14% to secure the overall corrosion resistance. However, in the case of excessive chromium, excessive ferrite phase remains after solidification, thereby degrading hot workability. Therefore, the amount of Cr added is limited to 14-18%.

N: Element that replaces Ni by stabilizing austenite phase. There is an advantage in improving strength and pitting resistance, but if the amount exceeds 0.3%, the amount of nitrogen is limited to 0.30% or less because pores by nitrogen may be generated when passing through the ferrite phase during casting.

Cu: Ni is an alternative element to stabilize the austenite phase and to soften steels such as Ni, or corrosion resistance and hot workability when excessive addition is limited to 3.0% or less.

B: It is a powerful trace additive element that improves hot workability, but when it is added excessively, the effect is saturated or the segregation decreases hot workability. Therefore, the content is made 0.005% or less.

Ca: A trace element that improves hot workability, but when it is added in an excessive amount, inclusions are generated in a large amount, so that the nozzle may be clogged or surface defects caused by inclusions are limited to 0.005% or less.

Hereinafter, embodiments of the present invention will be described.

Table 1 below shows the alloying components used to prepare Cr-Mn-N-Cu austenitic stainless steel. The steels of Table 1 were designed using the central complex design of response surface analysis to statistically analyze the effects of Cu, B and Ca. The molten stainless steel having the components shown in Table 1 below were cast into ingots, 10% of the diameter after the rolling in a conventional hot rolling process), and the minor components B and Ca were cast and the diameters of 10 mm were obtained through the usual hot rolling. After making high temperature tensile test specimen at 5 minutes at 1250 ℃ and cooling to 900 ℃ for 5 seconds, after 30 seconds, the rate of cross-sectional reduction after tensile failure (RA: Reduction of Area) was measured. It is shown in. The predicted value of RA calculated from the response surface analysis method (RA = 52.9933 + 1.37513 XB + 0.298097 X Ca + 1.51623 X Cu-0.0187413 XBXB-4.98177 X Cu X Cu) is calculated in Table 2 together. In summary. The predictive formula was statistically significant and the explanatory power was excellent with the corrected R ² value of 91.1%.

Table of Alloying Components of Inventive Materials and Comparative Materials (wt.%) Steel grade C Si Mn S Cr Ni N B Ca Cu Comparative Material 1 0.050 0.51 9.01 0.0027 15.01 1.00 0.21 0.0027 0.0021 3.11 Comparative Material 2 0.050 0.52 9.07 0.0024 14.99 1.00 0.21 0.0012 0.0009 2.54 Comparative Material 3 0.051 0.53 9.06 0.0030 14.97 1.00 0.21 0.0011 0.0028 2.52 Comparative Material 4 0.050 0.52 8.98 0.0020 14.97 1.00 0.20 0.0000 0.0016 1.61 Comparative Material 5 0.510 0.52 9.04 0.0025 14.99 1.00 0.20 0.0043 0.0008 2.52 Comparative Material 6 0.051 0.52 9.07 0.0031 15.01 0.99 0.21 0.0042 0.0030 2.50 Invention 1 0.050 0.52 8.95 0.0022 14.99 0.99 0.20 0.0026 0.0000 1.57 Invention 2 0.051 0.53 9.06 0.0027 15.03 0.99 0.21 0.0010 0.0009 0.63 Invention 3 0.050 0.53 9.02 0.0015 15.00 1.00 0.21 0.0025 0.0018 1.59 Invention 4 0.051 0.52 9.05 0.0018 15.00 1.00 0.20 0.0026 0.0017 1.59 Invention 5 0.050 0.52 9.00 0.0016 14.99 0.99 0.22 0.0025 0.0018 1.58 Invention 6 0.050 0.55 9.01 0.0030 15.04 1.00 0.20 0.0010 0.0021 0.65 Invention 7 0.050 0.51 9.05 0.0014 15.00 0.99 0.20 0.0046 0.0018 1.57 Invention Material 8 0.050 0.52 9.02 0.0026 14.87 0.99 0.20 0.0026 0.0031 1.60 Invention 9 0.049 0.52 8.96 0.0021 15.05 0.98 0.20 0.0040 0.0006 0.66 Invention 10 0.050 0.51 8.95 0.0032 15.00 0.98 0.20 0.0026 0.0012 0.00 Invention 11 0.050 0.54 8.95 0.0027 15.01 1.00 0.21 0.0042 0.0025 0.65

In Table 2, the measured RA and the RA predicted by the calculation are compared and summarized in FIG. 1.

Cross-sectional area reduction rate of invention and comparative material, measured value and calculated value Steel grade RA (actually measured) RA (calculation) Comparative Material 1 29.9 35.1 Comparative Material 2 40.6 38.7 Comparative Material 3 45.1 44.1 Comparative Material 4 40.7 47.4 Comparative Material 5 54.5 49.7 Comparative Material 6 62.5 57.0 Invention 1 65.3 65.0 Invention 2 70.0 67.1 Invention 3 67.3 69.8 Invention 4 67.2 69.9 Invention 5 71.3 69.9 Invention 6 79.9 70.6 Invention 7 68.3 71.7 Invention Material 8 72.9 74.0 Invention 9 78.7 78.9 Invention 10 77.0 80.2 Invention 11 82.4 84.5

       As described above, according to the present invention, in order to prevent the degradation of the hot rolled surface quality due to the surface cracks generated during hot rolling, the addition range of the trace alloy component for securing the RA of 60 or more, which must be normally secured at 900 ° C, is defined as Cu. It can be easily derived according to the content range of, so it can be used for alloy design of stainless steel that can secure cold workability and hot workability at the same time.

Claims (2)

By weight% C: 0.15% or less, Si: 1.0% or less, Mn: 7-10%, S: 0.01% or less, Ni: 4.0% or less, Cr: 14.0-20.0%, N: 0.30% or less, Cu: 3.0 % Or less, B: 0.005% or less, Ca: 0.005% or less and composed of other Fe and inevitable elements, in the above range 52.9933 + 1.37513 XB + 0.298097 X Ca + 1.51623 X Cu-0.0187413 XBXB-4.98177 X Cu X Cu Copper-added high manganese austenitic stainless steel, characterized in that the cross-sectional area reduction ratio is calculated to be 60% or more at 900 ℃. delete

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