CN112831724A

CN112831724A - S420 high-strength low-temperature structural steel and normalizing rolling preparation method thereof

Info

Publication number: CN112831724A
Application number: CN202110002572.3A
Authority: CN
Inventors: 潘中德; 袁睿; 武会宾; 吴俊平; 张鹏程; 胡其龙; 靳星; 张淼; 曹余良
Original assignee: University of Science and Technology Beijing USTB; Nanjing Iron and Steel Co Ltd
Current assignee: University of Science and Technology Beijing USTB; Nanjing Iron and Steel Co Ltd
Priority date: 2021-01-04
Filing date: 2021-01-04
Publication date: 2021-05-25

Abstract

The invention discloses S420 high-strength low-temperature structural steel and a normalizing rolling preparation method thereof, relating to the technical field of steel production, wherein the steel comprises the following chemical components in percentage by mass: 0.14 to 0.16 percent of C, 1.25 to 1.50 percent of Mn, 0.2 to 0.3 percent of Si, 0.04 to 0.05 percent of Nb, 0.06 to 0.09 percent of V, 0.008 to 0.015 percent of Ti, 0.25 to 0.35 percent of Ni, 0.015 to 0.040 percent of Alt, less than or equal to 0.1 percent of Cu, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.006 percent of N, less than or equal to 0.30 percent of Cr, less than or equal to 0.10 percent of Mo, and the balance of Fe and inevitable impurities. The high-strength low-temperature structural steel with the thickness of 60-80 mm is produced, the structural performance of a thick steel plate is improved through reasonable component design and rolling process, the yield strength is higher than 420MPa, the tensile strength is 520-680 MPa, the elongation is larger than 19%, and the-50 ℃ low-temperature impact energy is higher than 50J.

Description

S420 high-strength low-temperature structural steel and normalizing rolling preparation method thereof

Technical Field

The invention relates to the technical field of steel production, in particular to S420 high-strength low-temperature structural steel and a normalizing rolling preparation method thereof.

Background

The high-strength low-temperature structural steel is a resource-saving product with high technical content and high added value, and the normalized hot-rolled structural steel plate is widely applied to the fields of large-scale engineering machinery, buildings, offshore engineering platforms, extra-high voltage transmission components, frame structures of vehicles, pressure vessels and the like, and particularly in some welded structures, some components must be manufactured by using structural steel with excellent performance in a normalized state. The traditional normalizing process is to heat the rolled steel plate to the normalizing temperature and keep the temperature for a certain time and then air-cool the steel plate, thereby increasing the production cost and energy consumption and prolonging the production and delivery period. Compared with the prior art, the normalizing rolling process is simple, is convenient for tissue production and has more popularization significance.

The Chinese patent application with the publication number of CN103540848A discloses 'a 420 MPa-grade normalized super-thick steel plate for a structural use and a manufacturing method thereof', the invention content is that a super-thick Q420E steel plate is produced by a normalizing and rapid cooling process, the production process is complex, the alloy cost is high, the Ceq is high, meanwhile, the method can not get rid of the limitation of a compression ratio, and only products with the maximum thickness of 120mm can be produced by utilizing a continuous casting billet with the thickness of 400 mm.

The Chinese patent application with the publication number of CN104018071A discloses a production method of a Q420E steel plate with low carbon equivalent and high toughness, and the method adopts the traditional TMCP process to produce the Q420E steel plate, can not get rid of the limitation of a compression ratio, is only suitable for producing the steel plate with the thickness of less than 30mm, and is not suitable for producing the super-thick steel plate.

Disclosure of Invention

Aiming at the technical problems, the invention overcomes the defects of the prior art and provides S420 high-strength low-temperature structural steel which comprises the following chemical components in percentage by mass: 0.14 to 0.16 percent of C, 1.25 to 1.50 percent of Mn, 0.2 to 0.3 percent of Si, 0.04 to 0.05 percent of Nb, 0.06 to 0.09 percent of V, 0.008 to 0.015 percent of Ti, 0.25 to 0.35 percent of Ni, 0.015 to 0.040 percent of Alt, less than or equal to 0.1 percent of Cu, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.006 percent of N, less than or equal to 0.30 percent of Cr, less than or equal to 0.10 percent of Mo, and the balance of Fe and inevitable impurities.

The technical scheme of the invention is further defined as follows:

the S420 high-strength low-temperature structural steel comprises the following chemical components in percentage by mass: 0.147% of C, 1.27% of Mn, 0.21% of Si, 0.05% of Nb, 0.062% of V, 0.013% of Ti, 0.27% of Ni, 0.038% of Alt, 0.016% of Cu, 0.012% of P, 0.001% of S, 0.004% of N, 0.04% of Cr, 0.004% of Mo and the balance of Fe and inevitable impurities.

The S420 high-strength low-temperature structural steel comprises the following chemical components in percentage by mass: 0.156% of C, 1.31% of Mn, 0.22% of Si, 0.04% of Nb, 0.065% of V, 0.013% of Ti, 0.28% of Ni, 0.036% of Alt, 0.017% of Cu, 0.012% of P, 0.001% of S, 0.005% of N, 0.03% of Cr, 0.003% of Mo and the balance of Fe and inevitable impurities.

The S420 high-strength low-temperature structural steel comprises the following chemical components in percentage by mass: 0.158% of C, 1.40% of Mn, 0.21% of Si, 0.04% of Nb, 0.063% of V, 0.013% of Ti, 0.28% of Ni, 0.037% of Alt, 0.018% of Cu, 0.012% of P, 0.001% of S, 0.004% of N, 0.03% of Cr, 0.003% of Mo and the balance of Fe and inevitable impurities.

The thickness of the S420 high-strength low-temperature structural steel is 60-80 mm.

The invention also aims to provide a normalizing rolling preparation method of the S420 high-strength low-temperature structural steel, which comprises the following steps:

smelting raw materials are sequentially subjected to molten iron pretreatment, converter smelting, LF refining, RH vacuum refining and continuous casting to produce a continuous casting billet which meets the requirement of chemical components and has the thickness of 320mm, and the central segregation C class of the casting billet is controlled to be less than or equal to 1.0 level;

the heating temperature is controlled to be 1210 +/-20 ℃, the tapping temperature is controlled to be 1184-1201 ℃, and the furnace time is 321-378 min; after the steel plate is taken out of the furnace, two-stage rolling is carried out, the temperature of the first-stage rough rolling and the final rolling is more than or equal to 980 ℃, and the reduction rate of the last 2 passes of rough rolling is more than 20%; the second stage of finish rolling is carried out at the initial rolling temperature of 900-950 ℃ and the final rolling temperature of 880-910 ℃;

and then the steel plate is air-cooled to 600-650 ℃ for stacking and slow cooling, and the slow cooling time is more than or equal to 48 h.

The invention has the beneficial effects that:

(1) the high-strength low-temperature structural steel with the thickness of 60-80 mm is produced by using a continuous casting billet through a normalizing rolling method, the structural performance of a thick steel plate is improved through reasonable component design and a rolling process, the high-strength low-temperature structural steel has mechanical properties equivalent to those of a steel plate subjected to normalizing heat treatment, the yield strength is higher than 420MPa, the tensile strength is 520-680 MPa, the elongation is greater than 19%, and the-50 ℃ low-temperature impact energy is higher than 50J;

(2) the production process adopted by the invention is simple, the alloy and production cost is reduced, the product can meet the performance requirement of European standard EN10025 on the steel plate in the normalized delivery state, and the method can be widely applied to the manufacture of thick plates in a plurality of fields such as shipbuilding, maritime work, wind power, bridges, buildings, engineering machinery and the like;

(3) the chemical composition design of the invention adopts the design concept of low carbon and high manganese, and in order to improve the strength without influencing the impact toughness, alloy elements such as Nb, Ti, Ni, Cr, Cu, Mo and the like are added in a compounding way on the basis of C-Mn steel solid solution strengthening, and the effects of grain refinement, precipitation strengthening, phase change strengthening and the like are fully exerted to achieve the purposes of high strength, high toughness and excellent welding performance, and the specific principle is as follows:

the increase of the content of C can improve the strength and reduce the Ar3 temperature, but can deteriorate the low-temperature toughness and the welding performance of the steel, and the low-C component can inhibit the formation of pearlite during the transformation of high-temperature ferrite and promote the transformation of bainite and is very beneficial to the structure regulation, so the content of C is controlled to be 0.14-0.16 percent;

mn is a weak carbide forming element, can reduce the austenite transformation temperature, refines ferrite grains and is beneficial to improving the strength and toughness of the steel plate, and meanwhile, Mn can also strengthen the ferrite in a solid solution mode, increase the hardenability of the steel plate and promote the formation of bainite, but when the Mn content is too high, segregation is easily formed, and the steel plate is hardened and the ductility is deteriorated, so that the Mn content is designed to be 1.25-1.40%;

nb can also improve hardenability, the transformation temperature is reduced in low-carbon steel to promote the formation of a bainite structure, the tendency of forming bainite is increased along with the increase of the content of solid-solution niobium in the steel, and Nb (C, N) precipitated by deformation induction has a pinning effect on austenite grain boundaries, so that the recrystallization of deformed austenite can be effectively inhibited, but because the compression ratio in the rolling process of the invention is smaller, the effect of inhibiting recrystallization is weakened, therefore, considering cost saving, the addition of Nb is not suitable, and the range of 0.04-0.05 percent is controlled; ti is a nitrogen-fixing element, the nitride particles of the titanium can prevent the growth of crystal grains of a billet in the heating, rolling and welding processes and improve the toughness of a base metal and a welding heat affected zone, and for the titanium-based alloy, the addition of the Ti is necessary because the compression ratio is smaller and the structure regulation effect during later phase transformation can be affected by overlarge size of the original crystal grains, but the excessive titanium content can cause the coarsening of the nitride of the titanium and is unfavorable for the low-temperature toughness, so the titanium content in the invention is determined to be 0.008% -0.015%;

ni is particularly key to improving the toughness of the steel plate, can effectively disperse the aggregation of carbides, stabilize super-cooled austenite, inhibit the growth of ferrite and bainite grains and improve low-temperature toughness, but Ni is expensive, and the manufacturing cost is increased by adding too much Ni, so that the Ni is set to be 0.25-0.35%;

the addition of Cr and Cu is to increase the precipitation strengthening effect, belongs to a strength enhancing element, and the content is controlled below 0.30% and 0.10% respectively.

Drawings

FIG. 1 is a metallographic structure diagram of a steel sheet according to example 1;

FIG. 2 is a metallographic structure diagram of a steel sheet according to example 2;

FIG. 3 is a metallographic structure chart of a steel sheet according to example 3.

Detailed Description

The chemical components of the steel plate are shown in table 1, the normalizing rolling process of the steel plate is shown in table 2, and the normalized rolling state performance of the steel plate is shown in table 3.

TABLE 1 chemical composition (wt%) of steel sheet of examples

TABLE 2 normalizing Rolling Process of Steel sheets of examples

TABLE 3 mechanical properties of normalized rolled steel sheets of examples

From the above examples, it can be seen that after normalized rolling, the steel plate produced by the invention has yield strength of 430-450 MPa, elongation of 22-30%, tensile strength of 580-620 MPa, impact energy at-50 ℃ of not less than 88J, and good comprehensive performance and performance uniformity.

In conclusion, on the basis of industrial production experience, on the basis of fully considering the characteristics of reinforced elements in the microalloy steel and the interaction among the elements, the invention provides a brand-new normalizing rolling process for the alloying idea of the microalloy steel thick plate and the complex-phase reinforcement design based on composite precipitation reinforcement, can effectively solve the problem of uneven performance of a normalized ultra-thick steel plate, has obvious effects on improving the performance stability of products, improving the production efficiency, greatly reducing the raw material cost and the production cost of a hot-rolled structural steel plate, and can also keep the mechanical property of the thick plate prepared by the normalizing rolling process even after normalizing. Wide process window, simple and feasible production process and stable performance.

In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.

Claims

1. The S420 high-strength low-temperature structural steel is characterized in that: the chemical components and the mass percentage are as follows: 0.14 to 0.16 percent of C, 1.25 to 1.50 percent of Mn, 0.2 to 0.3 percent of Si, 0.04 to 0.05 percent of Nb, 0.06 to 0.09 percent of V, 0.008 to 0.015 percent of Ti, 0.25 to 0.35 percent of Ni, 0.015 to 0.040 percent of Alt, less than or equal to 0.1 percent of Cu, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.006 percent of N, less than or equal to 0.30 percent of Cr, less than or equal to 0.10 percent of Mo, and the balance of Fe and inevitable impurities.

2. The S420 high-strength low-temperature structural steel as claimed in claim 1, wherein: the chemical components and the mass percentage are as follows: 0.147% of C, 1.27% of Mn, 0.21% of Si, 0.05% of Nb, 0.062% of V, 0.013% of Ti, 0.27% of Ni, 0.038% of Alt, 0.016% of Cu, 0.012% of P, 0.001% of S, 0.004% of N, 0.04% of Cr, 0.004% of Mo and the balance of Fe and inevitable impurities.

3. The S420 high-strength low-temperature structural steel as claimed in claim 1, wherein: the chemical components and the mass percentage are as follows: 0.156% of C, 1.31% of Mn, 0.22% of Si, 0.04% of Nb, 0.065% of V, 0.013% of Ti, 0.28% of Ni, 0.036% of Alt, 0.017% of Cu, 0.012% of P, 0.001% of S, 0.005% of N, 0.03% of Cr, 0.003% of Mo and the balance of Fe and inevitable impurities.

4. The S420 high-strength low-temperature structural steel as claimed in claim 1, wherein: the chemical components and the mass percentage are as follows: 0.158% of C, 1.40% of Mn, 0.21% of Si, 0.04% of Nb, 0.063% of V, 0.013% of Ti, 0.28% of Ni, 0.037% of Alt, 0.018% of Cu, 0.012% of P, 0.001% of S, 0.004% of N, 0.03% of Cr, 0.003% of Mo and the balance of Fe and inevitable impurities.

5. The S420 high-strength low-temperature structural steel as claimed in claim 1, wherein: the thickness of the steel plate is 60-80 mm.

6. A normalizing rolling preparation method of S420 high-strength low-temperature structural steel is characterized by comprising the following steps: application to any of claims 1 to 5, in particular comprising the following steps:

the heating temperature is controlled to be 1210 +/-20 ℃, the tapping temperature is controlled to be 1184-1201 ℃, and the furnace time is 321-378 min;

after the steel plate is taken out of the furnace, two-stage rolling is carried out, the temperature of the first-stage rough rolling and the final rolling is more than or equal to 980 ℃, and the reduction rate of the last 2 passes of rough rolling is more than 20%; the second stage of finish rolling is carried out at the initial rolling temperature of 900-950 ℃ and the final rolling temperature of 880-910 ℃;