High-performance low-carbon bainite / martensite steel sheet and method for producing the same

Abstract

The application discloses a kind of high-performance low-carbon bainite / martensite steel plate and its production method, the steel plate chemical composition composition and mass percentage are as follows: C:0.10~0.14%, Si:0.20~0.30%, Mn:1.0~1.4%, P≤0.010%, S≤0.0020%, Ni:0.5~1.0%, Cr:0.6~0.8%, Mo:0.3~0.4%, Ti:0.012~0.016%, V:0.03~0.05%, Nb:0.020~0.030%, Al:0.02~0.05%, B:0.0012~0.0016%, La:0.02~0.04%, Ce:0.03~0.05%, the balance is Fe and inevitable impurities.Production method includes heating, rolling, quenching and tempering water cooling process.The application adds rare earth element, cooperates two-stage controlled rolling and water cooling process after tempering, and obtains the low-carbon bainite / martensite steel plate with excellent comprehensive mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of steel material smelting and processing technology, specifically relating to a high-performance low-carbon bainitic / martensitic steel plate and its production method. Background Technology

[0002] Rare earth elements combine with other elements in steel, especially harmful elements (S, O, etc.), which causes harmful substances to float and be removed, and regulates the microstructure, thereby improving the cleanliness of the molten steel. Adding rare earth elements to steel can also remove oxygen and sulfur from inclusions such as MnS and Al2O3, forming rare earth inclusions or rare earth composite inclusions, thus acting as modifiers and improving the overall performance of the steel.

[0003] Low-carbon bainitic / martensitic steel plates are widely used in industries such as pressure vessels and engineering machinery. The microstructure of these steels typically consists mainly of martensite, granular bainite, lath bainite, acicular ferrite, and second phases such as M / A islands. Due to the addition of a large number of alloying elements, controlling the content of elements such as O, N, S, and P in the steel is difficult, and inclusions such as MnS easily form in the steel, adversely affecting the overall properties of the steel plate, especially its impact toughness. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-performance low-carbon bainitic / martensitic steel plate and a method for producing the same.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a high-performance low-carbon bainitic / martensitic steel plate, wherein the chemical composition and mass percentage of the high-performance low-carbon bainitic / martensitic steel plate are as follows: C: 0.10-0.14%, Si: 0.20-0.30%, Mn: 1.0-1.4%, P≤0.010%, S≤0.0020%, Ni: 0.5-1.0%, Cr: 0.6-0. 0.8%, Mo: 0.3-0.4%, Ti: 0.012-0.016%, V: 0.03-0.05%, Nb: 0.020-0.030%, Al: 0.02-0.05%, B: 0.0012-0.0016%, La: 0.02-0.04%, Ce: 0.03-0.05%, with the balance being Fe and unavoidable impurities, of which La+Ce: ≤0.07%.

[0006] The high-performance low-carbon bainitic / martensitic steel plate of the present invention has a thickness of 20-35 mm and a microstructure of bainitic + martensitic.

[0007] The high-performance low-carbon bainitic / martensitic steel plate of this invention has a yield strength of 924-938 MPa, a tensile strength of 985-1000 MPa, an elongation of ≥13.6%, good low-temperature impact toughness, and a transverse impact energy of ≥62 J at -40℃.

[0008] The present invention also provides a method for producing high-performance low-carbon bainitic / martensitic steel plates, characterized in that the production method includes heating, rolling, quenching and tempering water cooling processes; the rolling process adopts a two-stage controlled rolling process, wherein the first stage rolling has a first pass reduction of ≥35mm and a first stage rolling final rolling temperature of ≥1000℃, the second stage has an initial rolling temperature of 930~960℃ and a final rolling temperature of 830~860℃, and is air-cooled to room temperature after rolling.

[0009] The heating process described in this invention has a heating rate of 300-400℃ / h, a heating temperature of 1210-1230℃, and a heat soaking time of ≥40min.

[0010] The quenching process described in this invention involves heating at a temperature of 890–900°C, with a heating coefficient of 2.5–3 min / mm, followed by water cooling after removal from the furnace.

[0011] The tempering and water cooling process described in this invention involves heating at a temperature of 580–610°C with a heating coefficient of 4.5–5 min / mm, followed by water cooling to room temperature at a rate of ≥10°C / s after exiting the furnace.

[0012] The beneficial effects of adopting the above technical solution are as follows: 1. This invention utilizes the composite addition of La and Ce rare earth elements. Rare earth elements can interact with elements such as O, S, and P in steel, thereby purifying the molten steel and modifying inclusions such as MnS, effectively reducing the content of inclusions such as MnS in the steel and improving the mechanical properties of the steel. 2. This invention adopts a first-stage rolling process with a first-pass reduction of ≥35mm, which is beneficial for rolling penetration and improves the internal quality of the steel plate. 3. This invention uses a rapid water cooling process after tempering to prevent the precipitation of large carbide particles during tempering, suppress temper brittleness, and ensure its performance requirements. 4. The addition of rare earth elements in this invention can obtain low-carbon bainitic / martensitic steel plates with excellent comprehensive mechanical properties and good low-temperature impact toughness, and the production process is simple. Attached Figure Description

[0013] Figure 1 The image shows the metallographic structure of the high-performance low-carbon bainitic / martensitic steel plate in Example 1. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to specific embodiments.

[0015] Examples 1-6 and Comparative Examples 1-2

[0016] A method for producing high-performance low-carbon bainitic / martensitic steel plates, the main processes including heating, rolling, quenching, tempering and water cooling, are described below:

[0017] (1) Heating process: heating rate 300~400℃ / h, heating temperature 1210~1230℃, heat soaking time ≥40min.

[0018] (2) Rolling process: A two-stage controlled rolling process is adopted. The first stage rolling reduction is ≥35mm, the first stage rolling final rolling temperature is ≥1000℃, the second stage starting rolling temperature is 930~960℃, the final rolling temperature is 830~860℃, and after rolling, it is air-cooled to room temperature.

[0019] (3) Quenching process: heating temperature 890~900℃, heating coefficient 2.5~3min / mm, water cooling after taking out of the furnace.

[0020] (4) Tempering and water cooling process: heating temperature 580~610℃, heating coefficient 4.5~5min / mm, and water cooling to room temperature at a cooling rate of ≥10℃ / s after exiting the furnace.

[0021] Appendix Figure 1 The image shows the metallographic structure of the high-performance low-carbon bainitic / martensitic steel plate in Example 1 (the figures for other examples are similar and omitted). It can be seen that the metallographic structure of the steel plate in Example 1 is a multiphase structure of martensite and bainite.

[0022] All embodiments and comparative examples used 200mm cast billets. The production process parameters are shown in Table 1, the chemical composition and mass percentage of the steel plate are shown in Table 2, and the specifications and properties of the steel plate are shown in Table 3.

[0023] Table 1 Production process parameters for each embodiment and comparative example

[0024]

[0025] Table 2. Chemical composition and mass percentage (%) of steel plates in each embodiment and comparative example.

[0026]

[0027] The remaining components in Table 2 are Fe and unavoidable impurities.

[0028] Table 3 Specifications and mechanical properties of steel plates from various embodiments and comparative examples

[0029]

[0030] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-performance low-carbon bainite / martensite steel sheet, characterized by, The high-performance low-carbon bainite / martensite steel plate has a chemical composition and mass percentage as follows: C: 0.10-0.14%, Si: 0.20-0.30%, Mn: 1.0-1.4%, P≤0.010%, S≤0.0020%, Ni: 0.5-1.0%, Cr: 0.6-0.8%, Mo: 0.3-0.4%, Ti: 0.012-0.016%, V: 0.03-0.05%, Nb: 0.020-0.030%, Al: 0.02-0.05%, B: 0.0012-0.0016%, La: 0.02-0.04%, Ce: 0.03-0.05%, and the balance of Fe and inevitable impurities, wherein La+Ce≤0.07%. The production method of the high-performance low-carbon bainite / martensite steel plate comprises heating, rolling, quenching and tempering water cooling processes; the rolling process adopts a two-stage controlled rolling process, the first-stage rolling has a first pass reduction of ≥35 mm, the first-stage rolling has a final rolling temperature of ≥1000℃, the second-stage rolling has a starting rolling temperature of 930-960℃ and a final rolling temperature of 830-860℃, and the rolled product is air-cooled to room temperature. The quenching process has a heating temperature of 890-900℃ and a heating coefficient of 2.5-3 min / mm, and the quenched product is water-cooled after being discharged. The tempering water cooling process has a heating temperature of 580-610℃ and a heating coefficient of 4.5-5 min / mm, and the tempered product is water-cooled to room temperature at a cooling rate of ≥10℃ / s after being discharged.

2. The high-performance low-carbon bainite / martensite steel sheet according to claim 1, characterized in that, The high-performance low-carbon bainite / martensite steel plate has a thickness of 20-35 mm and a bainite+martensite structure.

3. The high-performance low-carbon bainite / martensite steel sheet according to claim 1, characterized in that, The high-performance low-carbon bainite / martensite steel plate has a yield strength of 924-938 MPa, a tensile strength of 985-1000 MPa, an elongation of ≥13.6%, and good low-temperature impact toughness with a transverse impact energy at -40℃ of ≥62 J.

4. A method of producing a high-performance low-carbon bainite / martensite steel sheet according to any one of claims 1 to 3, characterized by, The production method comprises heating, rolling, quenching and tempering water cooling processes; the rolling process adopts a two-stage controlled rolling process, the first-stage rolling has a first pass reduction of ≥35 mm, the first-stage rolling has a final rolling temperature of ≥1000℃, the second-stage rolling has a starting rolling temperature of 930-960℃ and a final rolling temperature of 830-860℃, and the rolled product is air-cooled to room temperature.

5. The method of producing a high-performance low-carbon bainite / martensite steel sheet according to claim 4, characterized by, The heating process has a heating rate of 300-400℃ / h, a heating temperature of 1210-1230℃, and a soaking time of ≥40 min.

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