CN110952040B

CN110952040B - Production method of EH460 grade 150-inch thick steel plate with thickness of 200mm

Info

Publication number: CN110952040B
Application number: CN201911165542.3A
Authority: CN
Inventors: 邱保文; 赵晋斌; 车马俊; 张晓雪; 李恒坤; 伯飞虎
Original assignee: Nanjing Iron and Steel Co Ltd
Current assignee: Nanjing Iron and Steel Co Ltd
Priority date: 2019-11-25
Filing date: 2019-11-25
Publication date: 2021-06-15
Anticipated expiration: 2039-11-25
Also published as: CN110952040A

Abstract

The invention discloses a production method of an EH460 grade 150-one 200mm super-thick steel plate, which relates to the technical field of ocean engineering steel and comprises the following chemical components in percentage by mass: c: 0.08-0.11%, Si: 0.20-0.50%, Mn: 1.15-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.030-0.080%, V: 0.001-0.050%, Al: 0.01 to 0.05 percent of Ti: 0.005% -0.020%, Mo: 0.00-0.08%, Cr: 0.15-0.35%, Cu: 0.10% -0.50%, Ni: 0.01 to 0.80 percent of the total weight of the alloy, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities.

Description

Production method of EH460 grade 150-inch thick steel plate with thickness of 200mm

Technical Field

The invention relates to the technical field of steel for ocean engineering, in particular to a production method of an EH460 grade 150-one 200mm super-thick steel plate.

Background

Along with the gradual implementation of the national ocean economic strategy, the ocean engineering steel develops towards the direction of ultrahigh strength and extra thickness, and increasingly higher requirements are put forward on the performance and quality of the extra-thick steel plate.

The larger the thickness of the super-thick steel plate is, the more the adverse effect of the performance caused by the segregation of the central components of the plate blank is. The difference of the organization is large due to the difference of the cooling speed in the thickness direction, the core performance is difficult to meet the certification standard of classification society, and the product is unqualified. The deformation is not uniform in the rolling process, various defects caused by blanks are difficult to eliminate, and the low-temperature impact toughness of the steel plate, especially the low-temperature toughness of the core part, is seriously influenced.

In order to ensure the low-temperature toughness of the core, the conventional process requires that the thickness of the blank is more than 3 times of that of the finished steel plate, and the thickness of the continuous casting blank limits the thickness of the finished steel plate and is difficult to reach more than 150 mm.

CN108149137A discloses a method for manufacturing an EH460 extra thick steel plate with the thickness of 100-250 mm, wherein 800-900mm die casting blanks are used for rolling, and normalizing treatment is performed, so that the method is difficult to realize on continuous casting billets and the manufacturing process is complex.

CN109972033A discloses a method for manufacturing an EH460 extra thick steel plate with the maximum thickness of 150mm, which has strict requirements on the quality of a continuous casting billet, needs to control the center segregation C class of the casting billet to be less than or equal to 0.5 grade, and the center porosity to be less than or equal to 0.5 grade, is difficult to meet the requirements of mass production, has low qualification rate and high cost.

CN103160734B discloses a P460NL1(L2) extra-thick steel plate with the thickness of 250mm for performance protection and flaw detection pressure containers, which adopts die-cast steel ingot rolling, does not get rid of the limitation of conventional compression ratio, and needs normalizing treatment, and the chemical design alloying elements (V ten Nb + Ti ten Cr ten Ni) of the patent are less than or equal to 2.0, and the cost is high.

Disclosure of Invention

In order to solve the technical problems, the invention provides a production method of an EH460 grade 150-one 200mm super-thick steel plate, which comprises the following chemical components in percentage by mass: c: 0.08-0.12%, Si: 0.20-0.50%, Mn: 1.15-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.030-0.080%, V: 0.001-0.050%, Al: 0.01 to 0.05 percent of Ti: 0.005% -0.020%, Mo: 0.00-0.08%, Cr: 0.15-0.35%, Cu: 0.10% -0.50%, Ni: 0.01 to 0.80 percent of the total weight of the alloy, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities;

heating a continuous casting billet with the thickness of 320mm at 1160-1200 ℃, adopting one-stage rolling, carrying out laminar cooling before the last rolling, and then rolling to obtain the thickness of a finished product; after the red color is returned, the temperature is controlled to be accelerated and cooled to be below 420 ℃, and finally, the air cooling is carried out to the room temperature.

The technical effects are as follows: the invention analyzes each component in the super-thick steel plate, optimizes the proportion of each component, thereby preparing the 150-inch and 200-inch EH 420-grade super-thick steel plate with the guaranteed performance and the guaranteed flaw detection thickness.

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

the production method of the EH460 grade 150-mm extra-thick steel plate comprises the following chemical components in percentage by mass: c: 0.08-0.095%, Si: 0.20-0.33%, Mn: 1.453-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.050% -0.065%, V: 0.02% -0.039%, Al: 0.02% -0.03%, Ti: 0.015% -0.020%, Mo: 0.00-0.03%, Cr: 0.15-0.20%, Cu: 0.21 to 0.31%, Ni: 0.01 to 0.30 percent of the total weight of the alloy, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities.

The production method of the EH460 grade 150-mm extra-thick steel plate comprises the following chemical components in percentage by mass: c: 0.095% -0.105%, Si: 0.35-0.41%, Mn: 1.302-1.45%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.060% -0.080%, V: 0.001% -0.022%, Al: 0.01 to 0.023 percent, Ti: 0.005% -0.010%, Mo: 0.06% -0.08%, Cr: 0.23-0.30%, Cu: 0.35-0.50%, Ni: 0.33 to 0.46 percent of the total weight of the alloy, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities.

The production method of the EH460 grade 150-mm extra-thick steel plate comprises the following chemical components in percentage by mass: c: 0.105 to 0.12 percent, Si: 0.40-0.50%, Mn: 1.15-1.30%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.030-0.046%, V: 0.040% -0.050%, Al: 0.043-0.05%, Ti: 0.007% -0.012%, Mo: 0.035-0.05%, Cr: 0.28% -0.35%, Cu: 0.10% -0.20%, Ni: 0.065-0.80 percent, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities.

EH460 stage 150 as previously describedA production method of a 200mm super-thick steel plate, wherein rolling is carried out in a recrystallization zone, and the reduction rate of each pass is more than 10 percent; before the last rolling, laminar cooling is carried out on the intermediate blank, so as to ensure that the temperature of the blank at a position 30mm away from the upper surface and the lower surface is analyzed and calculated and then is at the phase transition temperature Ar₁The last pass of rolling and the reduction ratio>15％。

The production method of the EH460 grade 150-mm extra-thick steel plate comprises the steps of controlling the cooling temperature to be below 400 ℃ when the surface temperature is 780-820 ℃ after the temperature is returned to be red, and controlling the accelerated cooling.

The invention has the beneficial effects that:

(1) c is the most economic and effective strengthening element in the steel, the strength of the steel is improved through solid solution strengthening and precipitation strengthening, but the improvement of the content of C has adverse effects on the plasticity, toughness and welding performance of the steel, particularly in high-strength ship plate steel, the content of various alloy elements is higher, so that the carbon equivalent and the weld sensitivity index are higher, and the content of C is reduced under the condition, so that the toughness and the plasticity of the steel are improved, and the welding performance of the steel is improved;

si has a proper solid solution strengthening effect, although Si is a ferrite stabilizing element which can increase the gamma-alpha transformation temperature and promote the formation of proeutectoid ferrite, which is contrary to other solid solution strengthening elements which can refine ferrite grains, after the Si is added into steel, the precipitation of carbides in super-cooled austenite can be delayed in dynamics and the promotion effect on stabilizing the super-cooled austenite is realized, the main effect of Si is deoxidation, and the Si is added together with Al and can eliminate oxygen in the steel during steel making and refining, thereby preventing shrinkage cavity in the solidification process caused by the generation of CO;

mn is an element that enhances the strength of steel by solid solution strengthening, is the most important element in steel to compensate for the strength loss caused by the decrease in C content, and is also an element that expands the γ phase region, contributing to obtaining a fine phase transition product, and can enhance the toughness of steel and lower the ductile-brittle transition temperature.

Nb refines grains through two different ways, one is that the high temperature region improves the austenite complete recrystallization temperature through the solute dragging effect of Nb to the austenite grain boundary, prevents the recrystallized austenite grains from growing large, the other is that the lower temperature region disperses and separates out before the austenite is transformed to ferrite through Nb carbon and nitride to become the nucleation particles of ferrite, so that the ferrite is formed under a smaller supercooling degree and is not easy to grow, thereby refining the ferrite grains;

v is a strengthening element in steel, the strength of the steel can be obviously improved due to precipitation strengthening of VC and V (CN), but the ductile-brittle transition temperature is improved, the content of the V is generally controlled to be below 0.10 percent, the welding performance of the low-carbon alloy steel can be obviously improved by the vanadium, and under the condition of coexistence of V, Nb and Ti, the proper vanadium content has good effect of improving the toughness of a welding seam;

al element is a strong oxide forming element and a strong nitride forming element, has specific requirements in the ship plate steel standard, generally requires that Alt is more than or equal to 0.020%, and can ensure that the steel plate can obtain fine austenite grains when being reheated in the welding and heat treatment processes; ti is a strong nitride forming element, TiN is precipitated in molten steel when the solubility product is exceeded, the optimum Ti content is 0.008% -0.015% when 0.004% -0.008% of N in the steel, in the range, the toughness of the HAZ zone can be obviously improved, and transverse cracks in the continuous casting process can be substantially eliminated;

cr is beneficial to improving the strength, hardenability, wear resistance, corrosion resistance and high-temperature oxidation resistance, and is not beneficial to weldability;

cu can increase the strength of the steel plate, improve the corrosion resistance of the steel plate and improve the Hydrogen Induced Cracking (HIC) resistance of the steel plate;

ni is the only element capable of improving low temperature impact toughness (DWTT, NDT, CTOD and CVN); copper-induced surface cracking during continuous casting and hot rolling can also be effectively prevented.

The Cr, Cu and Ni are added in a composite way, so that the strength can be improved, the low-temperature toughness can be improved, and the alloy cost is reduced compared with that of the single addition of Ni;

(2) in the invention, a soft core sandwich structure with low surface temperature, high hardness and difficult deformation and high core temperature, low hardness and easy deformation can be formed by rolling in a recrystallization zone, the regions of the blank deformed in the previous period at 1/8 positions above and below the thickness center are still at the non-recrystallization temperature Tnr, the rolling deformation is concentrated in the high-temperature region, effectively permeates into the core and has multiplication effect, the grain refining effect of the region is obvious, and the blank thickness multiplication effect under the conventional rolling process is achieved;

(3) the invention breaks through the limitation of the compression ratio of the conventional process, does not need heat treatment, can produce 150-EH 460 extra-thick plates with the thickness of 200mm by utilizing the continuous casting billet with the thickness of 320mm, has the central yield strength of more than 390MPa and the central impact energy of-40 ℃ of more than 120J, is qualified in the flaw detection ASTM A578/A578M C grade, and has the Z-direction performance far exceeding the requirements of the Z35 grade.

Drawings

FIG. 1 is a metallographic structure diagram showing a steel plate 1/2 thick in example 1 of the present invention.

Detailed Description

A production method of an EH460 grade 150-one 200mm extra-thick steel plate comprises the following chemical components in percentage by mass: c: 0.08-0.12%, Si: 0.20-0.50%, Mn: 1.15-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.030-0.080%, V: 0.001-0.050%, Al: 0.01 to 0.05 percent of Ti: 0.005% -0.020%, Mo: 0.00-0.08%, Cr: 0.15-0.35%, Cu: 0.10% -0.50%, Ni: 0.01 to 0.80 percent of the total weight of the alloy, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities;

heating a continuous casting billet with the thickness of 320mm at 1160-1200 ℃, adopting one-stage rolling, carrying out laminar cooling before the last rolling, and then rolling to obtain the thickness of a finished product; and when the surface temperature is reduced to 760-820 ℃, controlling the accelerated cooling to ensure that the cooling temperature is reduced to below 400 ℃, and finally cooling to room temperature. Rolling in a recrystallization zone, wherein the reduction rate of each pass is more than 10 percent; before the last rolling, laminar cooling is carried out on the intermediate blank, so as to ensure that the temperature of the blank at a position 30mm away from the upper surface and the lower surface is analyzed and calculated and then is at the phase transition temperature Ar₁The final rolling is performed at a reduction ratio>15％。

The chemical compositions of examples 1 to 3 are shown in Table 1, the process parameters of the production process are shown in Table 2, and the tensile and impact properties and flaw detection results are shown in Table 3.

Table 1 examples 1-3 steel sheet chemistry

Table 2 examples 1-3 steel sheet production process parameters

Table 3 examples 1-3 steel sheets tensile, impact properties and flaw detection results

As is clear from fig. 1, the steel sheet obtained in example 1 of the present invention had a structure mainly composed of bainite and ferrite at a sheet thickness of 1/2.

In conclusion, the method gets rid of the limitation of the compression ratio of the conventional process, the produced steel plate reaches the EH460 grade, the yield strength is 393-429 MPa, the tensile strength is 521-561 MPa, the core impact toughness at the low temperature of-40 ℃ reaches more than 120J, the performance in the thickness direction is good, the requirement of the highest grade Z35 is far exceeded, and the flaw detection meets the requirement of the ASTM A578/A578M C grade.

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. A production method of EH460 grade 150-one 200mm extra thick steel plates is characterized in that: the chemical components and the mass percentage are as follows: c: 0.08-0.12%, Si: 0.20-0.50%, Mn: 1.15-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.030-0.080%, V: 0.001-0.050%, Al: 0.01 to 0.05 percent of Ti: 0.005% -0.020%, Mo: 0.00-0.08%, Cr: 0.15-0.35%, Cu: 0.10% -0.50%, Ni: 0.01 to 0.80 percent of the total weight of the alloy, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities;

heating a continuous casting billet with the thickness of 320mm at 1160-1200 ℃, and adopting one-stage rolling in a recrystallization zone, wherein the reduction rate of each pass is more than 10%; before the last rolling, the intermediate blank is cooled by laminar flow and then rolled to the thickness of a finished product, and the temperature of the blank at a position 30mm away from the upper surface and the lower surface is ensured to be analyzed and calculated at the phase transition temperature Ar₁The following; last pass rolling, reduction>15 percent; after the red color is returned, the temperature is controlled to be accelerated and cooled to be below 420 ℃, and finally, the air cooling is carried out to the room temperature.

2. The method for producing the EH460 grade 150-200mm extra thick steel plate as claimed in claim 1, wherein the chemical components and the mass percentages are as follows: c: 0.08-0.095%, Si: 0.20-0.33%, Mn: 1.453-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.050% -0.065%, V: 0.02% -0.039%, Al: 0.02% -0.03%, Ti: 0.015% -0.020%, Mo: 0.00-0.03%, Cr: 0.15-0.20%, Cu: 0.21 to 0.31%, Ni: 0.01 to 0.30 percent of the total weight of the alloy, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities.

3. The method for producing the EH460 grade 150-200mm extra thick steel plate as claimed in claim 1, wherein the chemical components and the mass percentages are as follows: c: 0.095% -0.105%, Si: 0.35-0.41%, Mn: 1.302-1.45%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.060% -0.080%, V: 0.001% -0.022%, Al: 0.01 to 0.023 percent, Ti: 0.005% -0.010%, Mo: 0.06% -0.08%, Cr: 0.23-0.30%, Cu: 0.35-0.50%, Ni: 0.33 to 0.46 percent of the total weight of the alloy, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities.

4. The method for producing the EH460 grade 150-200mm extra thick steel plate as claimed in claim 1, wherein the chemical components and the mass percentages are as follows: c: 0.105 to 0.12 percent, Si: 0.40-0.50%, Mn: 1.15-1.30%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Nb: 0.030-0.046%, V: 0.040% -0.050%, Al: 0.043-0.05%, Ti: 0.007% -0.012%, Mo: 0.035-0.05%, Cr: 0.28% -0.35%, Cu: 0.10% -0.20%, Ni: 0.065-0.80 percent, less than or equal to 1.30 percent of Cr, Ni, Mo and Cu, and the balance of Fe and inevitable impurities.

5. The method for producing the EH460 grade 150-200mm extra thick steel plate as claimed in claim 1, wherein: when the surface temperature is 780-820 ℃ after the re-reddening, the cooling re-reddening temperature is below 400 ℃ when the accelerated cooling is controlled.