阅读说明：本技术 一种含ε马氏体的低碳中锰钢中厚板及其制备方法 (Low-carbon medium manganese steel medium plate containing epsilon martensite and preparation method thereof ) 是由 苏冠侨 侯晓东 高秀华 初铭强 张书彦 王瑶 向明 于 2019-07-25 设计创作，主要内容包括：本发明公开了一种含ε马氏体的低碳中锰钢中厚板,其合金坯料的百分组成为：C：0.03-0.07％,Mn：3.50-7.50％,Si：0.10-0.40％,S：＜0.01％,P：＜0.01％,Al：0.003-0.015％,Cu：0.05-0.30％,Ni：0.05-0.30％,Mo：0.05-0.30％,Cr：0.70-1.00％,余量为Fe和不可避免的杂质。本发明还公开了其制备方法,通过将Cr的含量控制在0.70-1.00％、Al的含量控制在0.003-0.015％,同时控制两相区回火条件,可在组织中生成六方密排的ε马氏体组织,有效提高了该中厚板的力学性能。(The invention discloses a low-carbon medium manganese steel medium plate containing epsilon martensite, which comprises the following alloy blanks in percentage: c: 0.03 to 0.07%, Mn: 3.50-7.50%, Si: 0.10-0.40%, S: < 0.01%, P: < 0.01%, Al: 0.003-0.015%, Cu: 0.05-0.30%, Ni: 0.05 to 0.30%, Mo: 0.05-0.30%, Cr: 0.70-1.00%, and the balance of Fe and inevitable impurities. The invention also discloses a preparation method thereof, wherein the content of Cr is controlled to be 0.70-1.00%, the content of Al is controlled to be 0.003-0.015%, and the tempering condition of a two-phase region is controlled, so that a hexagonal close-packed epsilon martensite structure can be generated in the structure, and the mechanical property of the medium plate is effectively improved.)

1. The low-carbon medium manganese steel medium plate containing the epsilon martensite is characterized in that the alloy blank for preparing the low-carbon medium manganese steel medium plate containing the epsilon martensite comprises the following components in percentage: c: 0.03 to 0.07%, Mn: 3.50-7.50%, Si: 0.10-0.40%, S: < 0.01%, P: < 0.01%, Al: 0.003-0.015%, Cu: 0.05-0.30%, Ni: 0.05 to 0.30%, Mo: 0.05-0.30%, Cr: 0.70-1.00%, and the balance of Fe and inevitable impurities.

2. The low carbon medium manganese steel medium plate containing epsilon martensite according to claim 1, wherein the structure of the low carbon medium manganese steel medium plate containing epsilon martensite is tempered martensite, reversed austenite and epsilon martensite.

3. The low-carbon medium manganese steel medium plate containing epsilon martensite according to claim 1, wherein the alloy blank comprises the following components in percentage by weight: c: 0.04-0.05%, Mn: 5.4-5.6%, Si: 0.15-0.25%, S: 0.001-0.003%, P: 0.001-0.006%, Al: 003-0.015%, Cu: 0.25-0.30%, Ni: 0.25-0.30%, Mo: 0.18-0.20%, Cr: 0.79-0.91%, and the balance of Fe and inevitable impurities.

4. The epsilon martensite-containing low and medium carbon manganese steel medium plate of claim 1, wherein the epsilon martensite-containing low and medium carbon manganese steel medium plate has a thickness of 20-50 mm.

5. A method for manufacturing a low carbon medium manganese steel medium plate containing epsilon martensite according to any one of claims 1 to 4, comprising:

s1: heating the alloy blank to 1000-1200 ℃, and preserving heat for 2-5 h;

s2: hot rolling into a hot rolled plate with the thickness of 20-50mm, wherein the initial rolling temperature is 940-990 ℃, and the final rolling temperature is 880-930 ℃;

s3: cooling to room temperature at a cooling rate of 10-20 ℃/s to obtain a quenched medium plate;

s4: after the heating furnace is heated to 650-710 ℃, putting the quenched medium plate obtained from S3 into the heating furnace and preserving the heat for 50-70 min; cooling to room temperature at the air cooling speed of 0.1-0.2 ℃/s to obtain the low-carbon medium manganese steel medium plate containing the epsilon martensite.

6. The method of claim 5, wherein the alloy ingot is heated with a heating furnace in S1.

7. The method according to claim 5, wherein in S2, the initial rolling temperature is 940-970 ℃, and the final rolling temperature is 800-900 ℃.

8. The method of claim 7, wherein the start rolling temperature is 45 to 80 ℃ higher than the finish rolling temperature in S2.

9. The method according to claim 7, wherein in S3, water is cooled to room temperature at a cooling rate of 20 ℃/S.

10. The method according to claim 7, wherein the cooling in S4 is performed at an air cooling rate of 0.1 ℃/S to room temperature.

Technical Field

The invention relates to the technical field of steel plate manufacturing and processing, in particular to a low-carbon medium manganese steel medium plate containing epsilon martensite and a preparation method thereof.

Background

According to the statistics of the world energy agency, the global energy demand is estimated to increase by 36% in 2035, and in 2010, 81.1% of energy supply sources are petroleum, coal and natural gas. The ever-increasing energy demand has far exceeded the limits of the exploitation capacity of land, and oceans covering 70% of the earth's surface have become a new energy exploitation direction to solve the energy crisis in various countries. In the process of developing ocean oil and gas resources, the construction of an offshore platform structure cannot be separated. Because the marine environments in China have larger difference in different regions, a great deal of high-quality steel for the marine platform in a specific service environment needs to be met urgently, and particularly, higher requirements on the strength, the toughness, the yield ratio and the like of steel materials are provided under polar environments (low temperature, random impact of marine ice blocks and the like).

In recent years, researches show that the low-carbon medium manganese steel can obtain a microstructure consisting of metastable austenite and tempered martensite by a process method combining hot rolling on-line quenching and critical zone tempering, and shows excellent toughness. However, the low-carbon medium manganese steel medium plate product prepared by the process still shows a high yield ratio (0.75-0.85). The tissue heterogenization can become a new development direction for regulating and controlling the yield ratio of the low-carbon medium manganese steel. The alloy components and tempering process parameters of the low-carbon medium manganese steel are optimized, so that the strength, low-temperature toughness and the like of a medium plate product can be obviously regulated and controlled, and a micro-metastable austenite, epsilon martensite and tempered martensite multiphase product can be obtained. During the deformation process, the two transformation processes of metastable austenite and epsilon martensite to martensite (TRIP effect and epsilon-TRIP effect) can greatly optimize the control range of the yield ratio. Therefore, the development of novel multi-phase low-carbon medium manganese steel plate products can bring important practical application value to the development of steel for ocean platforms in China.

Epsilon-martensite is a close-packed hexagonal structure form discovered by Schmidt in 1929, is usually easily found in high manganese steel, and is an important structure in steel. The ultra-low carbon medium manganese steel medium plate with high strength and toughness as described in patent CN201510241664.1, wherein the structure of the medium manganese steel medium plate is tempered martensite and fine stable reverse transformed austenite.

Disclosure of Invention

In order to overcome the defects of the prior art, one of the purposes of the invention is to provide a low-carbon medium manganese steel medium plate containing epsilon martensite, the yield ratio of the steel plate can be effectively regulated, the yield strength of the prepared low-carbon medium manganese steel medium plate is 750MPa, the tensile strength is 790 MPa and 1000MPa, the elongation is 16-22%, and the impact energy at-40 ℃ is more than 60J.

The invention also aims to provide a preparation method of the epsilon-martensite low-carbon medium-manganese steel medium plate, which adopts a two-phase region tempering process to form a metastable inversion into an austenite low body, and forms epsilon-martensite by controlling the air cooling rate, thereby obtaining the low-carbon medium-manganese steel medium plate with better mechanical property.

One of the purposes of the invention is realized by adopting the following technical scheme:

the low-carbon medium manganese steel medium plate containing the epsilon martensite comprises the following alloy blanks in percentage: c: 0.03 to 0.07%, Mn: 3.50-7.50%, Si: 0.10-0.40%, S: < 0.01%, P: < 0.01%, Al: 0.003-0.015%, Cu: 0.05-0.30%, Ni: 0.05 to 0.30%, Mo: 0.05-0.30%, Cr: 0.70-1.00%, and the balance of Fe and inevitable impurities.

Furthermore, the structure of the low-carbon medium manganese steel medium plate containing the epsilon martensite is tempered martensite, reversed austenite and epsilon martensite.

Further, the alloy blank comprises the following components in percentage: c: 0.04-0.05%, Mn: 5.4-5.6%, Si: 0.15-0.25%, S: 0.001-0.003%, P: 0.001-0.006%, Al: 003-0.015%, Cu: 0.25-0.30%, Ni: 0.25-0.30%, Mo: 0.18-0.20%, Cr: 0.79-0.91%, and the balance of Fe and inevitable impurities.

Further, the thickness of the low-carbon medium manganese steel medium plate containing the epsilon martensite is 20-50 mm.

The second purpose of the invention is realized by adopting the following technical scheme:

the preparation method of the low-carbon medium manganese steel medium plate containing the epsilon martensite comprises the following steps:

s1: heating the alloy blank to 1000-1200 ℃, and preserving heat for 2-5 h;

s2: hot rolling into a hot rolled plate with the thickness of 20-50mm, wherein the initial rolling temperature is 940-990 ℃, and the final rolling temperature is 880-930 ℃;

s3: cooling to room temperature at a cooling rate of 10-20 ℃/s to obtain a quenched medium plate;

s4: after the heating furnace is heated to 650-710 ℃, putting the quenched medium plate obtained from S3 into the heating furnace and preserving the heat for 50-70 min; cooling to room temperature at the air cooling speed of 0.1-0.2 ℃/s to obtain the low-carbon medium manganese steel medium plate containing the epsilon martensite.

Further, in S1, the alloy ingot is heated with a heating furnace.

Further, in S2, the initial rolling temperature is 940-.

Further, in S2, the start rolling temperature is 45-80 ℃ higher than the finish rolling temperature.

Further, in S3, water was cooled to room temperature at a cooling rate of 20 ℃/S.

Further, in S4, the steel sheet was cooled to room temperature at an air cooling rate of 0.1 ℃/S.

Compared with the prior art, the invention has the beneficial effects that:

the low-carbon medium-manganese steel medium plate containing the epsilon martensite provided by the invention has the advantages that when the Cr content in an alloy blank is controlled to be 0.70-1.0% and the Al content is controlled to be 0.003-0.015%, a medium plate structure containing the epsilon martensite can be obtained through tempering and air cooling in a critical zone, the yield strength of the obtained low-carbon medium-manganese steel medium plate is 500-750MPa, the tensile strength is 790-1000MPa, the elongation is 16-22%, and the impact energy at minus 40 ℃ is more than 60J;

the preparation method of the low-carbon medium manganese steel medium plate containing the epsilon martensite provided by the invention has the advantages that the process conditions are controllable, the physical and mechanical properties of the structure of the obtained medium plate are stable, the repeatability is high, and the method can be widely applied to practical production.

Drawings

FIG. 1 is a schematic flow diagram of a production process of the present invention;

FIG. 2 is a composition diagram of the EBSD phase of the low-carbon medium-manganese steel medium plate containing epsilon martensite in example 1;

FIG. 3 is a composition diagram of the EBSD phase of the low-carbon medium-manganese steel medium plate containing epsilon martensite in example 3;

FIG. 4 is a phase composition analysis of low and medium manganese steel medium plates containing epsilon martensite according to examples 1 and 3.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and specific embodiments, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.

The following are specific examples of the present invention, and raw materials, equipments and the like used in the following examples can be obtained by purchasing them unless otherwise specified.

The hot rolling mill adopted in the implementation of the invention is a phi 450 hot rolling mill designed and manufactured by the rolling technology of the northeast university and the key laboratory of the continuous rolling automation country;

the heating furnace adopted by the hot rolling treatment is a high-temperature box type resistance furnace with the model number of RX 4-85-13B;

the heating furnace adopted for the tempering treatment is a box-type resistance furnace with the model number of RX-36-10.

The invention provides a low-carbon medium manganese steel medium plate containing epsilon martensite, which is prepared from the alloy blank according to the percentage composition: c: 0.03 to 0.07%, Mn: 3.50-7.50%, Si: 0.10-0.40%, S: < 0.01%, P: < 0.01%, Al: 0.003-0.015%, Cu: 0.05-0.30%, Ni: 0.05 to 0.30%, Mo: 0.05-0.30%, Cr: 0.70-1.00%, and the balance of Fe and inevitable impurities.

The flow chart of the preparation method of the low-carbon medium manganese steel medium plate containing the epsilon martensite is shown in figure 1, and the preparation method comprises the following steps:

s1: heating the alloy blank to 1000-1200 ℃, and preserving heat for 2-5 h;

s2: hot rolling into a hot rolled plate with the thickness of 20-50mm, wherein the initial rolling temperature is 940-990 ℃, and the final rolling temperature is 880-930 ℃;

s3: cooling to room temperature at a cooling rate of 10-20 ℃/s to obtain a quenched medium plate;

s4: after the heating furnace is heated to 650-710 ℃, putting the quenched medium plate obtained from S3 into the heating furnace and preserving the heat for 50-70 min; cooling to room temperature at the air cooling speed of 0.1-0.2 ℃/s to obtain the low-carbon medium manganese steel medium plate containing the epsilon martensite.