A production method of high-toughness chromium-molybdenum steel plate

Abstract

The application discloses a production method of high-toughness chromium-molybdenum steel plate, which comprises the following steps: heating, rolling, accelerated water cooling, quenching and tempering water cooling; in the accelerated water cooling process, the steel plate is in-line water quenched to room temperature at a cooling speed of greater than or equal to 22 DEG C / s after rolling; in the tempering water cooling process, the heating temperature is 695-705 DEG C, the heating coefficient is 5-5.5 min / mm, and the water cooling speed is greater than or equal to 15 DEG C / s after discharging to room temperature. The application adopts the accelerated water cooling process after rolling and the water cooling process after tempering, refines the original grains of the steel plate, prevents large-grain carbides from being precipitated in the tempering cooling process, and improves the low-temperature toughness of the steel plate. The chromium-molybdenum steel plate with good low-temperature impact toughness can be obtained without multiple quenching, the transverse impact energy at-20 DEG C is greater than or equal to 330 J, and the production process is simple.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for producing high-toughness chromium-molybdenum steel plates. Background Technology

[0002] Chromium-molybdenum steel is widely used in the manufacture of large boilers and pressure vessels for hydrogen-containing equipment in the petrochemical industry. It is a commonly used heat-resistant and hydrogen-resistant steel, and its service conditions are harsh. Therefore, this steel grade is required not only to have high strength, good bending performance, high-temperature performance, and hydrogen resistance, but also excellent impact toughness. This steel grade is usually produced using conventional TMCP rolling process, normalizing (accelerated cooling), and tempering processes. Due to the coarse original grains after hot rolling, and the large precipitates generated after normalizing (accelerated cooling) and high-temperature tempering, the impact toughness of the steel plate decreases. Typically, the transverse low-temperature impact toughness of the steel plate at -20℃ does not exceed 300J. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for producing high-toughness chromium-molybdenum steel plates.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for producing high-toughness chromium-molybdenum steel plate includes heating, rolling, accelerated water cooling, quenching and tempering water cooling processes; in the accelerated water cooling process, after the steel plate is rolled, the steel plate is water quenched online to room temperature at a cooling rate of ≥22℃ / s.

[0005] Furthermore, in the heating process described in this invention, the steel billet is heated to 1180-1200°C at a rate of ≥280°C / h and then held at that temperature for 40-50 minutes.

[0006] Furthermore, the rolling process described in this invention adopts a two-stage controlled rolling process. In the first stage, the first pass reduction is ≥36mm and the final rolling temperature is ≥1030℃. In the second stage, the initial rolling temperature is 910~930℃ and the final rolling temperature is 810~830℃.

[0007] Furthermore, in the quenching process described in this invention, the heating temperature is 900-910℃, the heating coefficient is 3-3.5 min / mm, and the product is water-cooled after exiting the furnace.

[0008] Furthermore, in the tempering and water cooling process described in this invention, the heating temperature is 695-705℃, the heating coefficient is 5-5.5 min / mm, and after exiting the furnace, it is water cooled to room temperature at a cooling rate of ≥15℃ / s.

[0009] Furthermore, the chemical composition and mass percentage of the high-toughness chromium-molybdenum steel plate of the present invention are as follows: C: 0.11-0.15%, Si: 0.50-0.70%, Mn: 0.40-0.65%, P≤0.009%, S≤0.0014%, Cr: 1.15-1.50%, Al: 0.02-0.04%, Mo: 0.50-0.65%, with the balance being Fe and unavoidable impurities.

[0010] The steel plate of this invention has a thickness of 30-40 mm.

[0011] The chromium-molybdenum steel plate produced by the method of the present invention has good low-temperature impact toughness, with a transverse impact energy of ≥330J at -20℃, and the metallographic structure of the steel plate is tempered sorbite.

[0012] The beneficial effects of the above technical solution are as follows: (1) After the steel plate is rolled, the accelerated water cooling process is adopted to refine the original grains of the steel plate. Due to the hereditary effect of grain refinement, a good basic structure is provided for subsequent heat treatment, which improves the impact toughness. (2) The water cooling process is adopted after tempering in this invention to prevent the precipitation of large carbides during the tempering cooling process, suppress temper brittleness, and ensure its low-temperature toughness. (3) This invention can obtain chromium-molybdenum steel plate with good low-temperature impact toughness without multiple quenchings, and the production process is simple. Attached Figure Description

[0013] Figure 1 The image shows the metallographic structure of the high-toughness chromium-molybdenum steel plate from Example 1. Detailed Implementation

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

[0015] This invention provides a method for producing high-toughness chromium-molybdenum steel plates, including heating, rolling, accelerated water cooling, quenching, and tempering water cooling processes; specifically as follows: (1) Heating: Heat the billet to 1180~1200℃ at a rate of ≥280℃ / h and then hold it for 40~50min.

[0016] (2) Rolling: A two-stage controlled rolling process is adopted. The first stage rolling reduction is ≥36mm and the first stage rolling final temperature is ≥1030℃. The second stage starting rolling temperature is 910~930℃ and the final rolling temperature is 810~830℃.

[0017] (3) Accelerated water cooling: After the steel plate is rolled, it is water quenched online to room temperature at a cooling rate of ≥22℃ / s.

[0018] (4) Quenching: Heating temperature is 900~910℃, heating coefficient is 3~3.5min / mm, and water cooling is performed after taking it out of the furnace.

[0019] (5) Tempering and water cooling: The heating temperature is 695~705℃, the heating coefficient is 5~5.5min / mm, and after taking it out of the furnace, it is water cooled to room temperature at a cooling rate of ≥15℃ / s.

[0020] Examples 1-8

[0021] The production process parameters for each embodiment 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. The metallographic structure of the steel plate in Example 1 is shown in Table 3. Figure 1 The metallographic structures of the other embodiments are the same, so they are omitted.

[0022]

[0023]

[0024] The remaining components in Table 2 are Fe and unavoidable impurities.

[0025]

[0026] pass Figure 1 It can be seen that the steel plate provided by the present invention has a tempered sorbitic structure. As shown in Table 1, the chromium-molybdenum steel plate prepared by the method provided by the present invention has good low-temperature impact toughness, with a transverse impact energy of ≥330J at -20℃.

[0027] 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 method for producing high-toughness chromium-molybdenum steel plate, characterized in that, The production method includes heating, rolling, accelerated water cooling, quenching, and tempering water cooling processes; The rolling process adopts a two-stage controlled rolling process. In the first stage, the first pass reduction is ≥36mm and the final rolling temperature is ≥1030℃. In the second stage, the initial rolling temperature is 910~930℃ and the final rolling temperature is 810~830℃. In the accelerated water cooling process, after the steel plate is rolled, it is water quenched online to room temperature at a cooling rate of ≥22℃ / s. The quenching process involves heating at a temperature of 900–910℃, with a heating coefficient of 3–3.5 min / mm, followed by water cooling after removal from the furnace. The tempering and water cooling process involves heating at a temperature of 695–705°C with a heating coefficient of 5–5.5 min / mm, followed by water cooling to room temperature at a rate of ≥15°C / s after exiting the furnace. The steel plate produced by the method has good low-temperature impact toughness, with a transverse impact energy of ≥330J at -20℃. The chemical composition and mass percentage of the steel plate are as follows: C: 0.11-0.15%, Si: 0.50-0.70%, Mn: 0.40-0.65%, P≤0.009%, S≤0.0014%, Cr: 1.15-1.50%, Al: 0.02-0.04%, Mo: 0.50-0.65%, with the balance being Fe and unavoidable impurities.

2. The method for producing a high-toughness chromium-molybdenum steel plate according to claim 1, characterized in that, The heating process involves heating the steel billet to 1180–1200°C at a rate of ≥280°C / h and then holding it at that temperature for 40–50 minutes.

3. The method for producing a high-toughness chromium-molybdenum steel plate according to claim 1, characterized in that, The thickness of the steel plate is 30-40mm.

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