阅读说明：本技术 一种高延展性的eh420级别船板钢及其生产方法 (High-ductility EH 420-grade ship plate steel and production method thereof ) 是由 杨浩 陈振业 赵燕青 魏浩 刘需 于 2019-10-13 设计创作，主要内容包括：本发明公开了一种高延展性的EH420级别船板钢及其生产方法,所述船板钢化学成分组成及其质量百分含量为：C：0.08～0.13%、Si：0.10～0.25%、Mn：1.0～1.4%、Nb：0.01～0.03%、Ti：0.02～0.04%、Als：0.02～0.04%、P≤0.02%、S≤0.01%,其余为铁和不可避免的杂质；所述生产方法包括连铸、加热、轧制、冷却工序。本发明EH420级船板钢不含Ni、Cu、V等金属元素,采用超快速冷却+层流冷却的两段式冷却方式,终轧温度较高,轧机负荷低,轧制效率高,生产成本低廉,船板钢的组织为软相铁素体和硬相贝氏体,具有高延展性。(The invention discloses a high-ductility EH 420-grade ship plate steel and a production method thereof, wherein the ship plate steel comprises the following chemical components in percentage by mass: c: 0.08-0.13%, Si: 0.10 to 0.25%, Mn: 1.0-1.4%, Nb: 0.01-0.03%, Ti: 0.02 to 0.04%, Als: 0.02-0.04%, P is less than or equal to 0.02%, S is less than or equal to 0.01%, and the balance is iron and inevitable impurities; the production method comprises the working procedures of continuous casting, heating, rolling and cooling. The EH 420-grade ship plate steel does not contain metal elements such as Ni, Cu, V and the like, adopts a two-stage cooling mode of ultra-fast cooling and laminar cooling, has higher finish rolling temperature, low rolling mill load, high rolling efficiency and low production cost, and has the structure of soft-phase ferrite and hard-phase bainite and high ductility.)

1. The high-ductility EH 420-grade ship plate steel is characterized by comprising the following chemical components in percentage by mass: c: 0.08-0.13%, Si: 0.10 to 0.25%, Mn: 1.0-1.4%, Nb: 0.01-0.03%, Ti: 0.02 to 0.04%, Als: 0.02-0.04%, P is less than or equal to 0.02%, S is less than or equal to 0.01%, and the balance is iron and inevitable impurities.

2. The high ductility EH420 grade ship plate steel according to claim 1, wherein the finished ship plate steel thickness is 16-25 mm.

3. The high ductility EH420 grade ship plate steel according to claim 1, wherein the ship plate steel structure is soft phase ferrite and hard phase bainite, the volume fraction of the soft phase ferrite is 70-80%, and the volume fraction of the hard phase bainite is 20-30%.

4. The high ductility EH420 grade ship plate steel according to claim 1, wherein the ship plate steel has a yield strength of 462-515 MPa, a tensile strength of 551-623 MPa, an impact energy at-40 ℃ of 243-295J, and an elongation after fracture of 28.4-31.8%.

5. The method for producing the high-ductility EH 420-grade ship plate steel according to any one of claims 1 to 4, wherein the production method comprises the steps of continuous casting, heating, rolling and cooling; in the cooling process, an ultra-fast cooling process is adopted for front-stage cooling, the cooling speed is 40-60 ℃/s, and the temperature is cooled to 690-720 ℃; and the back section is subjected to laminar cooling at the cooling speed of 15-20 ℃/s, the temperature of the red returning is controlled at 520-550 ℃, and then the air cooling is carried out to the room temperature.

6. The production method of the EH420 grade ship plate steel with high ductility according to claim 5, wherein the continuous casting process is characterized in that the thickness of a continuous casting slab is 140-200 mm, and the chemical composition and the mass percentage of the continuous casting slab are as follows: c: 0.08-0.13%, Si: 0.10 to 0.25%, Mn: 1.0-1.4%, Nb: 0.01-0.03%, Ti: 0.02 to 0.04%, Als: 0.02-0.04%, P is less than or equal to 0.02%, S is less than or equal to 0.01%, and the balance is iron and inevitable impurities.

7. The method for producing the EH420 grade ship plate steel with high ductility according to claim 5, wherein the heating process is carried out at 1180-1220 ℃ for 1.5-2.5 h.

8. The production method of the high-ductility EH 420-grade ship plate steel according to any one of claims 5 to 7, wherein the first stage of the rolling process is a rough rolling stage, the initial rolling temperature is 1050-1150 ℃, and the temperature is kept after the rolling is carried out to 45-75 mm; the second stage is a finish rolling stage, the initial rolling temperature is 950-970 ℃, and the final rolling temperature is 920-930 ℃.

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to high-ductility EH 420-grade ship plate steel and a production method thereof.

Background

With the development of ocean shipping, the demand for steel for ship plates is increasing, and the strength of steel for ship hull structures is also gradually increasing. The EH420 grade ship plate steel has been widely used in the fields of ship and ocean engineering. Currently, people are concerned not only with the strength of the hull structure, but also with the collision safety of the ship. The collision of ships often causes catastrophic consequences such as structural damage, cargo leakage, environmental pollution, casualties and the like. The impact resistance of the hull is directly related to the deformability of the steel used for the hull. The better the ductility of the steel for a hull, the more energy is absorbed during deformation, and the safety of the hull at the time of collision can be improved. Therefore, the development of the EH420 hull steel having high ductility is of great significance in improving hull strength and ship collision safety.

Disclosure of Invention

The invention aims to provide high-ductility EH 420-grade ship plate steel and a production method thereof. The EH 420-grade ship plate steel does not contain metal elements such as Ni, Cu, V and the like, is alloy decrement type EH 420-grade high-strength ship plate steel, has higher ductility and can improve the collision safety of a ship body; the preparation process adopts a new generation TMCP process taking an ultra-fast cooling technology as a core, obtains the ship plate steel with higher strength and ductility on the basis of alloy reduction by controlling reasonable finish rolling temperature and cooling path, and can also reduce the load of a rolling mill, greatly improve the production efficiency and realize low-cost production.

In order to solve the technical problems, the invention adopts the technical scheme that: the high-ductility EH 420-grade ship plate steel comprises the following chemical components in percentage by mass: c: 0.08-0.13%, Si: 0.10 to 0.25%, Mn: 1.0-1.4%, Nb: 0.01-0.03%, Ti: 0.02 to 0.04%, Als: 0.02-0.04%, P is less than or equal to 0.02%, S is less than or equal to 0.01%, and the balance is iron and inevitable impurities.

The thickness of the ship plate steel finished product is 16-25 mm.

The ship plate steel structure comprises soft phase ferrite and hard phase bainite, wherein the volume fraction of the soft phase ferrite is 70-80%, and the volume fraction of the hard phase bainite is 20-30%.

The yield strength of the ship plate steel is 462-515 MPa, the tensile strength is 551-623 MPa, the impact energy at minus 40 ℃ is 243-295J, and the elongation after fracture is 28.4-31.8%.

The invention also provides a production method of the EH 420-grade ship plate steel with high ductility, which comprises the working procedures of continuous casting, heating, rolling and cooling; in the cooling process, an ultra-fast cooling process is adopted for front-stage cooling, the cooling speed is 40-60 ℃/s, and the temperature is cooled to 690-720 ℃; and the back section is subjected to laminar cooling at the cooling speed of 15-20 ℃/s, the temperature of the red returning is controlled at 520-550 ℃, and then the air cooling is carried out to the room temperature.

In the continuous casting process, the thickness of a continuous casting slab is 140-200 mm, and the continuous casting slab comprises the following chemical components in percentage by mass: c: 0.08-0.13%, Si: 0.10 to 0.25%, Mn: 1.0-1.4%, Nb: 0.01-0.03%, Ti: 0.02 to 0.04%, Als: 0.02-0.04%, P is less than or equal to 0.02%, S is less than or equal to 0.01%, and the balance is iron and inevitable impurities.

In the heating process, the heating temperature is 1180-1220 ℃, and the heat is preserved for 1.5-2.5 h.

In the rolling procedure, the first stage is a rough rolling stage, the initial rolling temperature is 1050-1150 ℃, and the temperature is kept after rolling to 45-75 mm; the second stage is a finish rolling stage, the initial rolling temperature is 950-970 ℃, and the final rolling temperature is 920-930 ℃.

The standard of the high-ductility EH 420-grade ship plate steel product and the standard of the performance detection method refer to 2018 edition material and welding specification published by China classification society.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: 1. the EH 420-grade ship plate steel does not contain metal elements such as Ni, Cu, V and the like, has low alloy content and low cost. 2. The EH 420-grade ship plate steel provided by the invention has the structure comprising soft phase ferrite and hard phase bainite, wherein the volume fraction of the soft phase ferrite is 70-80%, the volume fraction of the hard phase bainite is 20-30%, and the ship plate steel has high ductility. 3. The invention utilizes the ultra-fast cooling technology, can improve the finish rolling temperature, reduce the load of the rolling mill and improve the rolling efficiency. 4. The yield strength of the EH 420-grade ship plate steel is 462-515 MPa, the tensile strength is 551-623 MPa, the impact energy at minus 40 ℃ is 243-295J, and the elongation after fracture is 28.4-31.8%.

Drawings

FIG. 1 is a typical metallographic structure of a high ductility EH420 grade ship plate steel of example 1;

FIG. 2 shows the metallographic structure of the high ductility EH420 grade ship plate steel of example 1 at a distance of 5mm from the tensile fracture.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.