A 13MnNiMoR thick steel plate for boiler drums and its production method

Abstract

This invention discloses a 13MnNiMoR thick steel plate for boiler drums, characterized in that its composition, by weight percentage, is: C 0.12-0.15%, Mn 1.30-1.50%, Si 0.20-0.40%, P≤0.015%, S≤0.005%, Nb 0.010-0.020%, V 0.020-0.040%, Cr 0.20-0.40%, Mo 0.20-0.40%, Ni 0.80-1.00%, Alt 0.020-0.050%, simultaneously satisfying Nb+V The content is 0.030-0.050%, with the remainder being Fe and impurities. The production method includes steelmaking, billet heating, rolling, and tempering heat treatment. This invention employs a rolling reduction technology that ensures a rolling compression ratio of 3 times or more for thick continuous casting billets, Nb+V micro-alloying, and a reduction of ≥38mm in three passes during one-stage rolling. This technology enables the production of 13MnNiMoR thick steel plates for boiler drums with a thickness >100-150mm from continuous casting billets. The steel plates exhibit excellent performance, with a 0℃ impact strength of ≥200J at 1 / 4 of the thickness and ≥150J at the core. The production process is simple and cost-effective, enabling economical and efficient production of the steel plates.

Description

Technical Field

[0001] This invention relates to a 13MnNiMoR thick steel plate for boiler drums and its production method. Background Technology

[0002] 13MnNiMoR is a low-alloy high-strength steel specifically designed for medium-low temperature and high-pressure environments. It is widely used in the boiler and pressure vessel manufacturing industry, primarily for applications requiring high internal pressure and specific temperature conditions. These applications demand not only high strength but also stringent requirements for low-temperature impact resistance, high-temperature tensile properties, simulated post-weld heat treatment performance, and internal quality. With the increasing size of boiler and pressure vessel equipment, the demand for 13MnNiMoR boiler drum steel plates with a thickness greater than 100-150mm is growing.

[0003] To achieve optimal mechanical properties, particularly high strength, low-temperature toughness, and high-temperature performance, of 13MnNiMoR boiler drum steel plates with a thickness greater than 100-150mm, the general production process involves rolling from ingot casting, electroslag remelting, and composite billets. This is accompanied by tempering, normalizing, accelerated cooling, and tempering heat treatment processes, increasing the complexity and cost of the manufacturing process. However, with advancements in continuous casting technology, especially the construction and use of 400-460mm thick continuously cast billets, sufficient compression ratios can be guaranteed, enabling the rolling production of 13MnNiMoR thick plates from continuously cast billets.

[0004] Application No. 201210492603.9 discloses a low-alloy high-strength steel plate for thick boiler drums and its manufacturing method. This invention uses steel ingots to roll steel plates, resulting in a low yield. It also requires warm charging and initial rolling, leading to high raw material and rolling costs. The invention adds 0.004-0.010% Ti, which is detrimental to the impact performance, especially the core impact performance of thick plates rolled from continuously cast billets. The invention uses a normalizing accelerated cooling + tempering heat treatment process, which involves many production steps and high production costs.

[0005] Application No. 201310736922.4 discloses a 13MnNiMoR steel plate for pressure vessels and its production method. This invention uses steel ingots to roll steel plates, resulting in low yield and high raw material and rolling costs. This invention adds 0.08-0.18% Nb, resulting in high alloy content. This invention uses a quenching and tempering heat treatment process, which involves multiple production steps and high production costs.

[0006] Application No. 201210223523.3 discloses a boiler drum steel with a thickness ≥80 mm and its production method. This invention uses a low-frequency bipolar series electroslag furnace for electroslag remelting, ingot drawing, and feeding. The production process is complex and the production cost is high. Application No. 201410709954.X discloses a production method for high-strength extra-thick boiler drum steel plates. This invention uses surface cleaning of cast billets, vacuum sealing of combined billets, and rolling of welded composite billets. The production process is complex and the production cost is high. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a production process for eliminating the magnetism of the end face of round steel, thereby solving the problem of magnetism of the steel end face, controlling the magnetism of the steel end face to <5GS, ensuring uniform flow of the welding liquid during welding, and guaranteeing welding quality.

[0008] The technical solution of this invention to solve the above technical problems is: a 13MnNiMoR thick steel plate for boiler drums, the composition of which by weight percentage is: C 0.12-0.15%, Mn 1.30-1.50%, Si 0.20-0.40%, P ≤0.015%, S ≤0.005%, Nb 0.010-0.020%, V 0.020-0.040%, Cr 0.20-0.40%, Mo 0.20-0.40%, Ni 0.80-1.00%, Alt 0.020-0.050%, while simultaneously satisfying Nb+V 0.030-0.050%, with the remainder being Fe and impurities.

[0009] The present invention further specifies the following:

[0010] Preferably, the composition of the 13MnNiMoR thick steel plate, by weight percentage, is: C 0.14%, Mn 1.42%, Si 0.28%, P 0.011%, S 0.002%, Nb 0.01%, V 0.028%, Cr 0.25%, Mo 0.26%, Ni 0.83%, Alt 0.029%, simultaneously satisfying Nb+V 0.038%, with the remainder being Fe and impurities.

[0011] Preferably, the composition of the 13MnNiMoR thick steel plate, by weight percentage, is: C 0.13%, Mn 1.36%, Si 0.23%, P 0.009%, S 0.001%, Nb 0.015%, V 0.032%, Cr 0.27%, Mo 0.25%, Ni 0.89%, Alt 0.038%, simultaneously satisfying Nb+V 0.047%, with the remainder being Fe and impurities.

[0012] Preferably, the composition of the 13MnNiMoR thick steel plate, by weight percentage, is: C 0.15%, Mn 1.35%, Si 0.22%, P 0.007%, S 0.001%, Nb 0.018%, V 0.031%, Cr 0.31%, Mo 0.33%, Ni 0.32%, Alt 0.042%, simultaneously satisfying Nb+V 0.049%, with the remainder being Fe and impurities.

[0013] This invention provides a method for producing 13MnNiMoR thick steel plates for boiler drums, specifically including the following steps:

[0014] (1) Steelmaking process: smelt steel according to the above chemical composition and continuously cast it into slabs, and require Ti < 0.004%, and the center segregation of the slabs is of type C and does not exceed grade 1.0;

[0015] (2) Heating process: The billet is heated in a heating furnace with a heating coefficient of 10.0-15.0 min / cm and a heating temperature of 1200-1240℃;

[0016] (3) Rolling process: A one-stage large reduction rolling process is adopted. The rolling reduction requires that the single-pass reduction of the last 3-5 passes be ≥38mm and the reduction rate be ≥18%; the last 1-2 passes have a small reduction of 5-15mm and a reduction rate of 2-7%, so as to better control the thickness and shape of the steel plate; the rolling end temperature is ≥1010℃, and the rolled steel plate is cooled in air;

[0017] (4) Tempering process: The tempering heat treatment temperature is 640-680℃, the holding time in the furnace is 2.5-4.0min / mm, and after tempering, it is air-cooled to room temperature.

[0018] The smelting process in (1) above specifically includes: converter smelting, LF refining, RH vacuum treatment followed by continuous casting, wherein the converter tapping temperature is 1620-1680℃, LF refining is used for alloying with Cr, Mo, Ni, etc., RH refining vacuum treatment time is ≥15 minutes, and the superheat of the continuously cast steel is 5-20℃.

[0019] The beneficial effects of this invention are as follows: This invention adopts Nb+V microalloying and a one-stage high-reduction rolling process, that is, the reduction in the first stage rolling is guaranteed to be ≥38mm in 3 passes, and the single-pass high reduction in the last 3-5 passes of the first stage high reduction is ≥38mm, which ensures the penetration deformation of rolling and improves the microstructure and properties of the core of the thick plate. The small reduction in the last 1-2 passes is 5-15mm, which can better control the thickness and shape of the steel plate. Nb+V microalloying further improves the strength and impact toughness of the steel plate after rolling and tempering. The absence of Ti avoids the deterioration of the impact performance of the core of the thick plate, and the thickness of the thick plate is ≥200J at 0℃ at 1 / 4 and the core is ≥150J at 0℃. This invention realizes the hot rolling + tempering process to replace the existing rolling and tempering, normalizing + tempering heat treatment process, and eliminates the normalizing heat treatment process. The production process is simple and the production cost is low, which can realize the economical and efficient production of steel plates and meet the manufacturing and service requirements of boilers and pressure vessels. Detailed Implementation

[0020] Example

[0021] This embodiment provides a 13MnNiMoR thick steel plate for boiler drums, with a thickness of 115mm. The composition by weight percentage is: C 0.14%, Mn 1.42%, Si 0.28%, P 0.011%, S 0.002%, Nb 0.01%, V 0.028%, Cr 0.25%, Mo 0.26%, Ni 0.83%, Alt 0.029%, while also satisfying Nb+V 0.038%, with the remainder being Fe and impurities.

[0022] This embodiment provides a method for producing 13MnNiMoR thick steel plates for boiler drums, specifically including the following steps:

[0023] (1) Steelmaking process: molten steel is smelted according to the above chemical composition and continuously cast into slabs, and Ti < 0.004% is required. The center segregation of the slab is of type C and does not exceed grade 1.0. The process includes converter smelting, LF refining, RH vacuum treatment and then continuous casting. The converter tapping temperature is 1620℃. LF refining is used for alloying with Cr, Mo, Ni and other alloys. RH refining vacuum treatment time is 18 minutes. The superheat of the continuously cast steel is 6℃. The continuous casting process adopts dynamic light reduction technology and the casting is 370mm continuous casting slab.

[0024] (2) Heating process: The billet is heated in a heating furnace with a heating coefficient of 11.5 min / cm and a heating temperature of 1207℃;

[0025] (3) Rolling process: A one-stage large reduction rolling process is adopted. The rolling reduction is required to be 38-42mm in the last 3-5 passes with a reduction rate of 18-22%; the last 1-2 passes have a small reduction of 6-10mm with a reduction rate of 3-5%, so as to better control the thickness and shape of the steel plate; the rolling end temperature is 1026℃, and the rolled steel plate is cooled in the air.

[0026] (4) Tempering process: The tempering heat treatment temperature is 672℃, the furnace holding time is 412min, and after tempering, it is air-cooled to room temperature. Example

[0027] A 13MnNiMoR thick steel plate for boiler drums, with a thickness of 130mm, has the following composition by weight percentage: C 0.13%, Mn 1.36%, Si 0.23%, P 0.009%, S 0.001%, Nb 0.015%, V 0.032%, Cr 0.27%, Mo 0.25%, Ni 0.89%, Alt 0.038%, while also satisfying Nb+V 0.047%, with the remainder being Fe and impurities.

[0028] This invention provides a method for producing 13MnNiMoR thick steel plates for boiler drums, specifically including the following steps:

[0029] (1) Steelmaking process: molten steel is smelted according to the above chemical composition and continuously cast into slabs, and Ti < 0.004% is required. The center segregation of the slab is of type C and does not exceed grade 1.0. The process includes converter smelting, LF refining, RH vacuum treatment and then continuous casting. The converter tapping temperature is 1640℃. LF refining is used for alloying with Cr, Mo, Ni and other alloys. RH refining vacuum treatment time is 20 minutes. The superheat of the continuously cast steel is 12℃. The continuous casting process adopts dynamic light reduction technology and the casting is 460mm continuous casting slab.

[0030] (2) Heating process: The billet is heated in a heating furnace with a heating coefficient of 11.9 min / cm and a heating temperature of 1213℃;

[0031] (3) Rolling process: A one-stage large reduction rolling process is adopted. The rolling reduction is required to be 38-42mm in the last 3-5 passes with a reduction rate of 18-20%; the last 1-2 passes have a small reduction of 7-11mm with a reduction rate of 2-4%, so as to better control the thickness and shape of the steel plate; the rolling end temperature is 1014℃, and the rolled steel plate is cooled in the air.

[0032] (4) Tempering process: The tempering heat treatment temperature is 658℃, the furnace holding time is 465min, and after tempering, it is air-cooled to room temperature. Example

[0033] A 13MnNiMoR thick steel plate for boiler drums, with a thickness of 150mm, has the following composition by weight percentage: C 0.15%, Mn 1.35%, Si 0.22%, P 0.007%, S 0.001%, Nb 0.018%, V 0.031%, Cr 0.31%, Mo 0.33%, Ni 0.32%, Alt 0.042%, simultaneously satisfying Nb+V 0.049%, with the remainder being Fe and impurities.

[0034] This invention provides a method for producing 13MnNiMoR thick steel plates for boiler drums, specifically including the following steps:

[0035] (1) Steelmaking process: molten steel is smelted according to the above chemical composition and continuously cast into slabs, and Ti < 0.004% is required. The center segregation of the slab is of type C and does not exceed grade 1.0. The process includes converter smelting, LF refining, RH vacuum treatment and then continuous casting. The converter tapping temperature is 1680℃. LF refining is used for alloying with Cr, Mo, Ni and other alloys. RH refining vacuum treatment time is 25 minutes. The superheat of the continuously cast steel is 15℃. The continuous casting process adopts dynamic light reduction technology and the casting is 460mm continuous casting slab.

[0036] (2) Heating process: The billet is heated in a heating furnace with a heating coefficient of 12.6 and a heating temperature of 1225℃;

[0037] (3) Rolling process: A one-stage large reduction rolling process is adopted. The rolling reduction is required to be 38-40 mm in the last 3-5 passes with a reduction rate of 18-19%; the last 1-2 passes have a small reduction of 8-13 mm with a reduction rate of 2-7%, so as to better control the thickness and shape of the steel plate; the rolling end temperature is 1013℃, and the rolled steel plate is cooled in the air.

[0038] (4) Tempering process: The tempering heat treatment temperature is 655℃, the furnace holding time is 536, and after tempering, it is air-cooled to room temperature.

[0039] The boiler drum of this invention uses 13MnNiMoR thick steel plate with a thickness of 100-150mm, a yield strength of 509-546MPa, a tensile strength of 620-655MPa, an elongation after fracture of 20%-22.5%, an average transverse 0℃ impact energy at 1 / 4 of the thickness ≥200J, and an average transverse 0℃ impact energy at 1 / 2 of the thickness ≥150J.

[0040] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A 13MnNiMoR thick steel plate for boiler drums, the composition of which, by weight percentage, is: C 0.12-0.15%, Mn 1.30-1.50%, Si 0.20-0.40%, P ≤0.015%, S ≤0.005%, Nb 0.010-0.020%, V 0.020-0.040%, Cr 0.20-0.40%, Mo 0.20-0.40%, Ni 0.80-1.00%, Alt 0.020-0.050%, simultaneously satisfying Nb+V 0.030-0.050%, with the remainder being Fe and impurities; The production method of the above-mentioned 13MnNiMoR thick steel plate specifically includes the following steps: (1) Steelmaking process: According to the above chemical composition, after converter smelting, LF refining, and RH vacuum treatment, it is continuously cast into slabs, and Ti < 0.004% is required. The center segregation of the slab is of type C and does not exceed grade 1.

0. The converter tapping temperature is 1620-1680℃, LF refining is used for Cr, Mo and Ni alloying, RH refining vacuum treatment time is ≥ 15 minutes, and the superheat of the continuously cast steel is 5-20℃. (2) Heating process: The billet is heated in a heating furnace with a heating coefficient of 10.0-15.0 min / cm and a heating temperature of 1200-1240℃; (3) Rolling process: A one-stage large reduction rolling process is adopted. The rolling reduction requires that the single-pass reduction of the last 3-5 passes be ≥38mm and the reduction rate be ≥18%; the last 1-2 passes have a small reduction of 5-15mm and a reduction rate of 2-7%, so as to better control the thickness and shape of the steel plate; the rolling end temperature is ≥1010℃, and the rolled steel plate is cooled in air; (4) Tempering process: The tempering heat treatment temperature is 640-680℃, the holding time in the furnace is 2.5-4.0min / mm, and after tempering, it is air-cooled to room temperature.

2. The 13MnNiMoR thick steel plate for boiler drums according to claim 1, characterized in that, The composition of the 13MnNiMoR thick steel plate, by weight percentage, is: C 0.14%, Mn 1.42%, Si 0.28%, P 0.011%, S 0.002%, Nb 0.01%, V 0.028%, Cr 0.25%, Mo 0.26%, Ni 0.83%, Alt 0.029%, simultaneously satisfying Nb+V 0.038%, with the remainder being Fe and impurities.

3. The 13MnNiMoR thick steel plate for boiler drums according to claim 1, characterized in that: The composition of the 13MnNiMoR thick steel plate, by weight percentage, is: C 0.13%, Mn 1.36%, Si 0.23%, P 0.009%, S 0.001%, Nb 0.015%, V 0.032%, Cr 0.27%, Mo 0.25%, Ni 0.89%, Alt 0.038%, simultaneously satisfying Nb+V 0.047%, with the remainder being Fe and impurities.