High cold formability austenitic stainless steel cold rolled sheet and method of production thereof

Abstract

The application discloses a high cold formability austenitic stainless steel cold-rolled plate and a production method thereof, and solves the technical problem of poor cold formability of the austenitic stainless steel cold-rolled plate. The high cold formability austenitic stainless steel cold-rolled plate comprises the following components in percentage by mass: C: 0.035-0.045%, Si: 0.25-0.3%, Mn: 2-3%, Cr: 14-14.5%, Ni: 9-9.5%, N: 0.17-0.20%, Cu: 1.3-1.6%, Mo: 0.5-0.7%, and the rest is Fe and inevitable impurity elements. The production method of the high cold formability austenitic stainless steel cold-rolled plate comprises smelting, refining, slab continuous casting, cold rolling, heat treatment and coiling. The application can improve the cold forming performance of the cold-rolled plate, and meanwhile, guarantees that the microstructure performance of the cold-rolled plate is stable after forming.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of stainless steel production and processing, and particularly relates to a high cold formability austenitic stainless steel cold-rolled plate and a production method thereof. BACKGROUND

[0002] Traditional fossil energy has played an indispensable role in promoting the development of the world economy, but it has also caused increasingly serious environmental pollution problems. In response to global climate deterioration and sustainable development issues, research, development and utilization of new energy are rapidly heating up worldwide, and countries are accelerating the popularization of green and low-carbon energy technologies. Compared with traditional fossil energy, natural gas and hydrogen energy have the technical advantages of being clean, efficient and sustainable, and are an important path to achieve the "double carbon" goal.

[0003] In the natural gas and hydrogen energy industry chain, storage and transportation are the most critical links, and among all storage and transportation methods, low-temperature liquefied gas storage and transportation is the most efficient way. The future advanced storage and transportation direction of LNG and liquid hydrogen storage tanks is thin film type tanks, and the inner layer of this type of storage tank needs to use austenitic stainless steel cold-rolled plates after complex forming processing. Due to the complex forming process, multiple pressing passes, large and multiple deformation zones in the forming process, the stainless steel is required to have excellent deformation capacity, and the deformation zone requires the stainless steel to have excellent metal fluidity.

[0004] The austenitic stainless steel cold-rolled plate using traditional components and traditional processes has the following problems in product design, production preparation and forming processing:

[0005] (1) The component design is unreasonable, it is difficult to realize good matching of product cold formability, hot workability and service performance, the forming process is prone to cracking, and the microstructure and performance of the formed steel plate are unstable during use;

[0006] (2) The production process control is difficult, it is difficult to accurately control the microstructure such as grain size and deformation texture, and the product formability is unstable. SUMMARY

[0007] In order to solve all or part of the above problems, the purpose of the present application is to provide a high cold formability austenitic stainless steel cold-rolled plate and a production method thereof, by reasonably designing the composition of the cold-rolled plate, and controlling the key process points of cold rolling, heat treatment and other processes, the cold forming performance of the cold-rolled plate is effectively improved, and the microstructure and performance of the cold-rolled plate after forming are stable.

[0008] In a first aspect, the present invention provides a high cold formability austenitic stainless steel cold-rolled plate, wherein the composition of the high cold formability austenitic stainless steel cold-rolled plate includes, by mass percentage, C: 0.035-0.045%, Si: 0.25-0.3%, Mn: 2-3%, Cr: 14-14.5%, Ni: 9-9.5%, N: 0.17-0.20%, Cu: 1.3-1.6%, Mo: 0.5-0.7%, and the rest is Fe and unavoidable impurity elements.

[0009] Optionally, the microstructural properties of the high cold formability austenitic stainless steel cold-rolled sheet are:

[0010] Grain size 8-9;

[0011] The extreme grain size is less than level 2;

[0012] Fully austenitic structure, no precipitates.

[0013] Optionally, the room temperature mechanical properties of the high cold formability austenitic stainless steel cold-rolled sheet are:

[0014] Tensile strength R m : 535~565MPa;

[0015] Yield strength R p2.0 : 220~250MPa;

[0016] Elongation A≥50%.

[0017] In a second aspect, the present invention provides a method for producing a high cold formability austenitic stainless steel cold-rolled sheet, comprising the following steps:

[0018] S1, through smelting, refining and slab continuous casting to obtain continuous casting billets;

[0019] S2, cold rolling the continuous casting slab to obtain a strip;

[0020] S3, heat treating the strip to obtain a steel strip;

[0021] S4, the steel strip is coiled by a coiler.

[0022] Optionally, in S2, during the cold rolling of the continuous casting slab, the deformation amount of the first pass is controlled to be 30-35%, the deformation amount of the last pass is controlled to be 5-6%, and the total deformation amount is controlled to be 75-80%, so as to ensure that the grains of the steel plate are fully broken.

[0023] Optionally, in S3, heat treating the strip includes:

[0024] In the first stage, the strip temperature is controlled at 920-940°C and the holding time is 9-10 min / mm;

[0025] In the second stage, the strip temperature is controlled at 1050-1070°C and the holding time is 4-5 min / mm;

[0026] In the third stage, the strip temperature is controlled at 1150-1170°C and the holding time is 0.5-1 min / mm;

[0027] In the fourth stage, the strip temperature is controlled at 1100-1120°C and the holding time is 1-2 min / mm.

[0028] As can be seen from the above technical solution, the high cold formability austenitic stainless steel cold-rolled sheet and the production method thereof provided by the present invention have the following advantages:

[0029] By rationally designing the composition of cold-rolled sheets and controlling the key process points of cold rolling, heat treatment and other processes, the cold forming performance of cold-rolled sheets can be effectively improved, ensuring the stability of the organizational performance of cold-rolled sheets after forming.

[0030] Other features and advantages of the present invention will be set forth in the description that follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation to the technical solution of the present invention.

[0032] Figure 1 Flowchart of the method for producing austenitic stainless steel cold-rolled sheet with high cold formability in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other in any manner.

[0034] like Figure 1 An embodiment of the present invention is shown, which discloses a high cold formability austenitic stainless steel cold-rolled plate. The composition of the high cold formability austenitic stainless steel cold-rolled plate includes, by mass percentage: C: 0.035-0.045%, Si: 0.25-0.3%, Mn: 2-3%, Cr: 14-14.5%, Ni: 9-9.5%, N: 0.17-0.20%, Cu: 1.3-1.6%, Mo: 0.5-0.7%, and the rest is Fe and unavoidable impurity elements.

[0035] The reasons for limiting the chemical elements in this embodiment are as follows:

[0036] It has been found in practice that C is an austenite stabilizing element. Properly increasing the C content can improve the stability of the cold forming process and prevent the processing cracking caused by martensite transformation. 23 C6 carbide affects the corrosion resistance of the material, so the C content is limited to 0.035-0.045%.

[0037] It has been found in practice that Si is added as a deoxidizer in smelting, but too high Si content will reduce the stability of the austenite structure during the processing process. Therefore, the Si content is limited to 0.25-0.3%.

[0038] Practice has shown that the primary function of Mn is to stabilize the austenite phase and to increase the solubility of N in steel. However, excessive Mn addition can easily form MnS inclusions, severely impacting product processing performance. Therefore, the Mn content is limited to 2-3%.

[0039] It has been found in practice that Cr is the most important alloying element in forming the passivation film of stainless steel. In order to improve the stability of the structure, the Cr content is appropriately reduced. Therefore, the Cr content is limited to 14-14.5%.

[0040] It has been found in practice that Ni is the main element for improving the stability of austenite in stainless steel, but excessive addition of Ni will lead to excessively high costs. Therefore, the Ni content is limited to 9-9.5%.

[0041] In practice, it has been found that nitrogen stabilizes austenite, inhibits the formation of intermetallic phases, and can also improve low-temperature strength and pitting corrosion resistance. In this application, the nitrogen content is increased to above 0.17%. However, excessive nitrogen will reduce toughness, so the nitrogen content is limited to 0.17-0.20%.

[0042] Cu has been found in practice to reduce the cold work hardening tendency of austenitic stainless steel, improve its deep drawing and formability, and enhance its corrosion resistance in reducing media. This application incorporates more than 1.3% Cu, but excessively high Cu content can severely degrade the material's hot workability. Therefore, the Cu content is limited to 1.3-1.6%.

[0043] It has been found in practice that Mo can improve pitting corrosion resistance. In order to compensate for the loss of corrosion resistance caused by the reduction of Cr content, 0.5-0.7% Mo is added to the steel of the present invention.

[0044] In this embodiment, the microstructural properties of the high cold formability austenitic stainless steel cold rolled sheet are: grain size 8-9, grain size range <2, full austenitic structure, no precipitation phase. The room temperature mechanical properties of the high cold formability austenitic stainless steel cold rolled sheet are: tensile strength R m : 535~565MPa, yield strength R p2.0: 220~250MPa, elongation A≥50%.

[0045] like Figure 1 The embodiment of the present invention is shown in FIG. 1 , which also discloses a method for producing a cold-rolled austenitic stainless steel sheet with high cold formability, comprising the following steps:

[0046] S1, through smelting, refining and slab continuous casting to obtain continuous casting billets;

[0047] S2, cold rolling the continuous casting slab to obtain a strip;

[0048] S3, heat treating the strip to obtain a steel strip;

[0049] S4, the steel strip is coiled by a coiler.

[0050] In S2, during the cold rolling of the continuous casting slab, the deformation amount of the first pass is controlled to be 30-35%, the deformation amount of the last pass is controlled to be 5-6%, and the total deformation amount is controlled to be 75-80% to ensure that the grains of the steel plate are fully broken.

[0051] In S3, the strip is heat treated including:

[0052] In the first stage, the strip temperature is controlled at 920-940°C and the holding time is 9-10 min / mm;

[0053] In the second stage, the strip temperature is controlled at 1050-1070°C and the holding time is 4-5 min / mm;

[0054] In the third stage, the strip temperature is controlled at 1150-1170°C and the holding time is 0.5-1 min / mm;

[0055] In the fourth stage, the strip temperature is controlled at 1100-1120°C and the holding time is 1-2 min / mm.

[0056] The present invention is further illustrated below by way of examples, but the present invention is not limited to the scope of the embodiments. Experimental methods without specific conditions in the following examples can be carried out according to conventional methods and conditions.

[0057] Example 1: Finished product specification is 1.2*1219mm cold coil

[0058] The deformation of the first cold rolling pass is 33%, the deformation of the last cold rolling pass is 5.5%, and the total deformation is 78%.

[0059] The first stage of heat treatment: steel plate temperature 930℃, holding time 9.5min / mm.

[0060] The second stage of heat treatment: steel plate temperature 1050℃, holding time 4.5min / mm.

[0061] The third stage of heat treatment: steel plate temperature 1160℃, holding time 0.7min / mm.

[0062] The fourth stage of heat treatment: steel plate temperature 1100℃, holding time 1.5min / mm.

[0063] Example 2: Finished product specification is 1.2*1250mm cold coil

[0064] The deformation of the first cold rolling pass is 32%, the deformation of the last cold rolling pass is 6%, and the total deformation is 75%.

[0065] The first stage of heat treatment: steel plate temperature 920℃, holding time 10min / mm.

[0066] The second stage of heat treatment: steel plate temperature 1060℃, holding time 4.5min / mm.

[0067] The third stage of heat treatment: steel plate temperature 1150℃, holding time 1min / mm.

[0068] The fourth stage of heat treatment: steel plate temperature 1120℃, holding time 1min / mm.

[0069] Example 3: Finished product specification is 1.2*1300mm cold coil

[0070] The first cold rolling deformation is 35%, the last cold rolling deformation is 6%, and the total deformation is 80%. The first stage of heat treatment: steel plate temperature is 940℃, and the holding time is 9min / mm.

[0071] The second stage of heat treatment: steel plate temperature 1060℃, holding time 5min / mm.

[0072] The third stage of heat treatment: steel plate temperature 1160℃, holding time 0.8min / mm.

[0073] The fourth stage of heat treatment: steel plate temperature 1110℃, holding time 1.5min / mm.

[0074] Example 4: Finished product specification is 1.2*1800mm cold coil

[0075] The first cold rolling deformation is 33%, the last cold rolling deformation is 5%, and the total deformation is 78%. The first stage of heat treatment: steel plate temperature is 930℃, holding time is 10min / mm;

[0076] The second stage of heat treatment: steel plate temperature 1070℃, holding time 4min / mm;

[0077] The third stage of heat treatment: steel plate temperature 1170℃, holding time 0.5min / mm;

[0078] The fourth stage of heat treatment: steel plate temperature 1110℃, holding time 1min / mm.

[0079] Example 5: Finished product specification is 1.2*1500mm cold coil

[0080] The first cold rolling pass deformation is 32%, the last pass deformation is 6%, and the total deformation is 75%.The first stage of heat treatment: steel plate temperature is 940℃, holding time is 9min / mm.

[0081] The second stage of heat treatment: steel plate temperature 1050℃, holding time 5min / mm;

[0082] The third stage of heat treatment: steel plate temperature 1160℃, holding time 0.8min / mm.

[0083] The fourth stage of heat treatment: steel plate temperature 1120℃, holding time 1min / mm.

[0084] Comparative example: finished product specification is 1.2*1500mm cold coil

[0085] The first cold rolling deformation is 20%, the last cold rolling deformation is 10%, and the total deformation is 65%. Heat treatment stage: steel plate temperature is 1080℃, and the holding time is 6min / mm.

[0086] The chemical composition and failure rate of the listed examples and comparative examples are shown in Tables 1 and 2:

[0087] Table 1 lists the chemical compositions of the examples and comparative examples (weight percentage)

[0088] C Si Mn Cr Ni N Fe Example 1 0.035 0.25 2.0 14.0 9.0 0.17 margin Example 2 0.037 0.27 2.2 14.3 9.2 0.18 margin Example 3 0.045 0.30 2.5 14.5 9.1 0.20 margin Example 4 0.040 0.28 2.8 14.2 9.3 0.17 margin Example 5 0.042 0.26 2.7 14.1 9.5 0.20 margin Comparative Example 0.020 0.25 1.1 17.3 8.3 0.06 margin

[0089] Table 2 shows the defective rates of the examples and comparative examples

[0090]

[0091] As shown in Tables 1 and 2, the cold formability of austenitic stainless steel cold-rolled sheets has been greatly improved, which can meet the processing requirements of thin-film low-temperature storage tanks. The proportion of cracking or unusable after cold forming is controlled below 1%.

[0092] As can be seen from the above, by designing an excellent alloy composition system and controlling the content of key elements, it is possible to ensure the material's basic cold formability while also maintaining hot workability and corrosion resistance. Furthermore, by optimizing the matching of cold rolling and heat treatment processes and precisely controlling microstructures such as grain size and deformation texture, cold formability can be improved.

[0093] It should be noted that, unless otherwise specified, the technical or scientific terms used in the present invention should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0094] In addition, the terms "first," "second," etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. In the description of the present invention, "plurality" means more than two, unless otherwise specifically defined.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A high cold formability austenitic stainless steel cold rolled sheet, characterized in that: The composition of the high cold formability austenitic stainless steel cold-rolled sheet includes, by mass percentage, C: 0.035-0.045%, Si: 0.25-0.3%, Mn: 2-3%, Cr: 14-14.5%, Ni: 9-9.5%, N: 0.17-0.20%, Cu: 1.3-1.6%, Mo: 0.5-0.7%, and the remainder is Fe and unavoidable impurity elements; The method for producing austenitic stainless steel cold-rolled sheet with high cold formability comprises the following steps: S1, through smelting, refining and slab continuous casting to obtain continuous casting billets; S2, cold rolling the continuous casting slab to obtain a strip; S3, heat treating the strip to obtain a steel strip; S4, coiling the steel strip through a coiler; In S2, during the cold rolling of the continuous casting billet, the deformation of the first pass is controlled to be 30-35%, the deformation of the last pass is controlled to be 5-6%, and the total deformation is controlled to be 75-80%, so as to ensure that the grains of the steel plate are fully broken; In S3, heat treating the strip includes: In the first stage, the strip temperature is controlled at 920-940°C and the holding time is 9-10 min / mm; In the second stage, the strip temperature is controlled at 1050-1070°C and the holding time is 4-5 min / mm; In the third stage, the strip temperature is controlled at 1150-1170°C and the holding time is 0.5-1 min / mm; In the fourth stage, the strip temperature is controlled at 1100-1120°C and the holding time is 1-2 min / mm.

2. The high cold formability austenitic stainless steel cold-rolled sheet according to claim 1, characterized in that: The microstructural properties of the high cold formability austenitic stainless steel cold rolled sheet are: Grain size 8-9; The extreme grain size is less than level 2; Fully austenitic structure, no precipitates.

3. The high cold formability austenitic stainless steel cold rolled sheet according to claim 2, characterized in that: The room temperature mechanical properties of the high cold formability austenitic stainless steel cold rolled sheet are: Tensile strength R m : 535~565MPa; Yield strength R p2.0 : 220~250MPa; Elongation A≥50%.

4. A method for producing austenitic stainless steel cold-rolled sheet with high cold formability according to any one of claims 1 to 3, characterized in that: The steps include: S1, through smelting, refining and slab continuous casting to obtain continuous casting billets; S2, cold rolling the continuous casting slab to obtain a strip; S3, heat treating the strip to obtain a steel strip; S4, coiling the steel strip through a coiler; In S2, during the cold rolling of the continuous casting slab, the deformation of the first pass is controlled to be 30-35%, the deformation of the last pass is controlled to be 5-6%, and the total deformation is controlled to be 75-80% to ensure that the grains of the steel plate are fully broken; In S3, the strip is heat treated including: In the first stage, the strip temperature is controlled at 920-940°C and the holding time is 9-10 min / mm; In the second stage, the strip temperature is controlled at 1050-1070°C and the holding time is 4-5 min / mm; In the third stage, the strip temperature is controlled at 1150-1170°C and the holding time is 0.5-1 min / mm; In the fourth stage, the strip temperature is controlled at 1100-1120°C and the holding time is 1-2 min / mm.

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