CN112226677A

CN112226677A - Steel for 540 MPa-grade LPG fuel tank and manufacturing method thereof

Info

Publication number: CN112226677A
Application number: CN202010951101.2A
Authority: CN
Inventors: 张晓雪; 陈林恒; 赵晋斌; 车马俊; 邱保文; 李恒坤; 伯飞虎; 黄建华
Original assignee: Nanjing Iron and Steel Co Ltd
Current assignee: Nanjing Iron and Steel Co Ltd
Priority date: 2020-09-11
Filing date: 2020-09-11
Publication date: 2021-01-15

Abstract

The invention discloses a 540MPa grade LPG fuel tank steel and a manufacturing method thereof, relating to the technical field of steel production, and comprising the following chemical components in percentage by mass: c: 0.07 to 0.10 percent of Si: 0.20-0.40%, Mn: 1.40-1.60%, P is less than or equal to 0.012%, S is less than or equal to 0.002%, Als: 0.040% -0.060%, N is less than or equal to 0.0040%, Nb: 0.005-0.040%, Ti: 0.005-0.020%, Cr is less than or equal to 0.20%, Ni is less than or equal to 0.25%, Cu is less than or equal to 0.20%, Cu + Cr + Ni is less than or equal to 0.50%, and the balance is Fe and inevitable impurities. Compared with the delivery in the normalizing and quenching and tempering states, the alloy has the advantages of low alloy cost, low production cost and short delivery time.

Description

Steel for 540 MPa-grade LPG fuel tank and manufacturing method thereof

Technical Field

The invention relates to the technical field of steel production, in particular to steel for a 540 MPa-grade LPG fuel tank and a manufacturing method thereof.

Background

With the importance and dependence on clean energy at home and abroad, LPG has become an indispensable gas clean fuel in developed countries, and the national strategy reserves substances. The marine industry has come to bear with the marine industry striving to reduce atmospheric emissions and meet the International Maritime Organization (IMO) greenhouse gas emission reduction strategy to replace fuel. LPG fuels can reduce atmospheric emissions from ships, including greenhouse gases and other pollutants.

The TMCP steel sheet is not suitable for use as steel for fuel tanks because of the reduced strength and toughness after stress relief treatment, and is usually delivered in a normalized or quenched and tempered state. The steel plates in the normalized state and the quenched and tempered state need to be added with a large amount of alloy elements to ensure the low-temperature impact property, so that the welding property is reduced, and the steel plates are simultaneously limited by high alloy cost and long production period.

CN104831181A patent "a steel plate for LPG ship storage tank and its manufacturing method", the steel plate for storage tank has low welding crack sensitivity and excellent welding performance, and is produced by quenching and tempering process, which increases the two heat treatments to the steel plate, resulting in prolonged delivery time and increased manufacturing cost.

CN104674110 patent "a low temperature steel plate for pressure vessel", adds high content of Ni element to improve toughness, which increases alloy cost and is not suitable for mass production.

Disclosure of Invention

Aiming at the technical problems, the invention overcomes the defects of the prior art and provides the steel for the LPG fuel tank with the 540MPa grade, which has the advantages of low alloy cost, low production cost and short delivery date compared with normalized and quenched and tempered delivery.

In order to solve the technical problems, the invention provides a 540MPa grade LPG fuel tank steel which comprises the following chemical components in percentage by mass: c: 0.07 to 0.10 percent of Si: 0.20-0.40%, Mn: 1.40-1.60%, P is less than or equal to 0.012%, S is less than or equal to 0.002%, Als: 0.040% -0.060%, N is less than or equal to 0.0040%, Nb: 0.005-0.040%, Ti: 0.005-0.020%, Cr is less than or equal to 0.20%, Ni is less than or equal to 0.25%, Cu is less than or equal to 0.20%, Cu + Cr + Ni is less than or equal to 0.50%, and the balance is Fe and inevitable impurities.

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

the steel for the 540 MPa-grade LPG fuel tank comprises the following chemical components in percentage by mass: c: 0.07%, Si: 0.40%, Mn: 1.60%, P: 0.008%, S: 0.002%, Alt: 0.058%, N: 0.0038%, Nb: 0.025%, Ti: 0.014%, Cr: 0.20%, Ni: 0.20%, and the balance of Fe and inevitable impurities.

The steel for the 540 MPa-grade LPG fuel tank comprises the following chemical components in percentage by mass: c: 0.09%, Si: 0.40%, Mn: 1.55%, P: 0.008%, S: 0.002%, Alt: 0.040%, N: 0.0040%, Nb: 0.005%, Ti: 0.010%, Cr: 0.10%, Ni: 0.25%, Cu: 0.10%, and the balance of Fe and inevitable impurities.

The steel for the 540 MPa-grade LPG fuel tank comprises the following chemical components in percentage by mass: c: 0.10%, Si: 0.20%, Mn: 1.60%, P: 0.012%, S: 0.001%, Alt: 0.060%, N: 0.0025%, Nb: 0.040%, Ti: 0.005%, Cr: 0.25%, Ni: 0.10%, and the balance of Fe and inevitable impurities.

The steel for the 540 MPa-grade LPG fuel tank has the steel plate thickness of 8-50 mm.

The steel for the 540 MPa-grade LPG fuel tank has a steel plate microstructure comprising ferrite, bainite and a small amount of pearlite, wherein the ferrite grain size is 9-11.5 grade, the bainite is 10-30%, and the pearlite content is less than or equal to 10%.

The invention also aims to provide a method for manufacturing the steel for the 540 MPa-grade LPG fuel tank, which comprises the steps of molten iron desulphurization pretreatment, converter smelting, LF refining, RH vacuum treatment, continuous casting, casting blank heating, controlled rolling and controlled cooling after rolling, and specifically comprises the following steps:

the heating temperature of the casting blank is 1120-1150 ℃, two-stage controlled rolling is adopted, the two-stage controlled rolling comprises recrystallization zone rolling and non-recrystallization zone rolling, the cumulative reduction rate of rough rolling is more than or equal to 50%, the single-pass reduction rate of finish rolling is more than or equal to 10%, and the final rolling temperature is Ar₃+10 ℃; after rolling, the water cooling speed is 5-10 ℃/s, and the temperature of red return is 540 +/-20 ℃; and the steel plate is subjected to accelerated cooling and then air-cooled to room temperature.

The invention has the beneficial effects that:

(1) the invention optimizes the proportion of components and tissues, adopts TMCP process to produce the steel plate for the LPG fuel tank, has high strength and excellent low-temperature toughness, does not reduce the strength and the toughness after stress relief treatment, can replace normalizing and quenching and tempering steel plates, and is suitable for low-cost batch manufacturing;

(2) the limiting function of each chemical element in the invention is as follows:

c is the most common alloy element in steel and is the most economical and effective solid solution strengthening and precipitation strengthening element, but the toughness and plasticity are damaged and the performance of a welded joint is reduced due to the over-high content of C, and particularly when the content of the alloy element in normalized steel and quenched and tempered steel is high, the content of C needs to be strictly controlled in order to improve the welding performance of the steel;

si is mainly used for deoxidation and is added together with Al, so that oxygen in steel is better eliminated, and meanwhile, Si is a non-carbide forming element, so that the precipitation of carbide in super-cooled austenite can be delayed, and the super-cooled austenite is stabilized;

mn is the most important solid solution strengthening element in steel, can effectively improve the strength of the steel plate, can enlarge a gamma phase region, reduce the phase transition temperature, is beneficial to refining the phase transition structure, improves the toughness, reduces the ductile-brittle transition temperature and the like;

al is a deoxidizing element in steel, is also the most important grain refining element, and is a strong nitride forming element, so that the low-temperature toughness of a matrix and a welding joint is effectively improved;

nb is the most important grain refining element in steel, effectively improves austenite recrystallization temperature, is matched with controlled rolling and controlled cooling process to refine original austenite grains, is also an important solid solution strengthening element, and can effectively improve the strength of the steel;

ti is the most important grain refining element in steel, and has strong nitrogen fixation capacity, so that the growth of grains can be inhibited, and the low-temperature toughness of parent metal and weld metal is improved;

cr is a common alloy element in steel, a strong carbide forming element is beneficial to improving the strength, the wear resistance, the corrosion resistance, the high-temperature performance and the like, and the hardenability is effectively improved due to the Cr, so that the weldability is not facilitated;

cu is a common alloy element in steel, is beneficial to improving the strength and the corrosion resistance, effectively improves the hardenability and is easy to cause cracking in the continuous casting process;

ni is a common alloy element in steel, effectively improves the low-temperature impact toughness of a steel plate and a welding joint, but is high in price and not beneficial to low-cost manufacture, and Cr, Cu and Ni can be considered to be added in a composite mode, so that the alloy cost is reduced.

Drawings

FIG. 1 is a metallographic microstructure of example 1 of the present invention.

Detailed Description

Example 1

The steel for the 540 MPa-grade LPG fuel tank provided by the embodiment comprises the following chemical components in percentage by mass: c: 0.07%, Si: 0.40%, Mn: 1.60%, P: 0.008%, S: 0.002%, Alt: 0.058%, N: 0.0038%, Nb: 0.025%, Ti: 0.014%, Cr: 0.20%, Ni: 0.20%, and the balance of Fe and inevitable impurities.

The manufacturing method comprises the steps of molten iron desulphurization pretreatment, converter smelting, LF refining, RH vacuum treatment, continuous casting, casting blank heating, controlled rolling and controlled cooling after rolling, and specifically comprises the following steps: heating a 260mm casting blank to 1150 ℃, preserving heat for 300min, and performing two-stage controlled rolling, wherein the rolling temperature of a recrystallization zone is 1050 ℃; and (3) when the thickness of the warm blank is 80mm, the pass deformation is 32mm, the initial rolling temperature of rolling in a non-recrystallization region is 785 ℃, the final rolling temperature is 770 ℃, the rolled steel plate is 30mm, after rolling, weak cooling is adopted, the cooling speed is 8 ℃/s, the temperature of red returning is 530 ℃, and then air cooling is carried out to the room temperature.

Example 2

The present embodiment provides a 500MPa grade steel for LPG fuel tank, which is different from embodiment 1 in that:

the chemical components and the mass percentage are as follows: c: 0.09%, Si: 0.40%, Mn: 1.55%, P: 0.008%, S: 0.002%, Alt: 0.040%, N: 0.0040%, Nb: 0.005%, Ti: 0.010%, Cr: 0.10%, Ni: 0.25%, Cu: 0.10%, and the balance of Fe and inevitable impurities.

Heating a 320mm casting blank to 1130 ℃, preserving heat for 300min, and performing two-stage controlled rolling, wherein the rolling temperature of a recrystallization zone is 1050 ℃; and (3) cooling the blank to be 150mm in thickness and 32-40 mm in pass deformation, wherein the initial rolling temperature of rolling in a non-recrystallization region is 765 ℃, the final rolling temperature is 760 ℃, the rolled steel plate is 50mm, water cooling is adopted after rolling, the cooling speed is 10 ℃/s, the re-reddening temperature is 540 ℃, and then air cooling is carried out to the room temperature.

As shown in the figure 1, the microstructure of the steel plate comprises ferrite, bainite and a small amount of pearlite, the grain size of the ferrite is 9-11.5 grades, the bainite is 10-30 percent, and the pearlite content is less than or equal to 10 percent.

The mechanical properties of the steel sheets prepared in the examples are shown in table 1,

TABLE 1 mechanical Properties of cryogenic Steel for LPG fuel tank

As can be seen from Table 1, the steel plate for LPG fuel tanks produced by the TMCP process has high strength, excellent low-temperature toughness and no reduction in strength and toughness after stress relief treatment.

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. A540 MPa grade LPG fuel tank steel is characterized in that: the chemical components and the mass percentage are as follows: c: 0.07 to 0.10 percent of Si: 0.20-0.40%, Mn: 1.40-1.60%, P is less than or equal to 0.012%, S is less than or equal to 0.002%, Als: 0.040% -0.060%, N is less than or equal to 0.0040%, Nb: 0.005-0.040%, Ti: 0.005-0.020%, Cr is less than or equal to 0.20%, Ni is less than or equal to 0.25%, Cu is less than or equal to 0.20%, Cu + Cr + Ni is less than or equal to 0.50%, and the balance is Fe and inevitable impurities.

2. The steel for a 540MPa grade LPG fuel tank according to claim 1, characterized in that: the chemical components and the mass percentage are as follows: c: 0.07%, Si: 0.40%, Mn: 1.60%, P: 0.008%, S: 0.002%, Alt: 0.058%, N: 0.0038%, Nb: 0.025%, Ti: 0.014%, Cr: 0.20%, Ni: 0.20%, and the balance of Fe and inevitable impurities.

3. The steel for a 540MPa grade LPG fuel tank according to claim 1, characterized in that: the chemical components and the mass percentage are as follows: c: 0.09%, Si: 0.40%, Mn: 1.55%, P: 0.008%, S: 0.002%, Alt: 0.040%, N: 0.0040%, Nb: 0.005%, Ti: 0.010%, Cr: 0.10%, Ni: 0.25%, Cu: 0.10%, and the balance of Fe and inevitable impurities.

4. The steel for a 540MPa grade LPG fuel tank according to claim 1, characterized in that: the chemical components and the mass percentage are as follows: c: 0.10%, Si: 0.20%, Mn: 1.60%, P: 0.012%, S: 0.001%, Alt: 0.060%, N: 0.0025%, Nb: 0.040%, Ti: 0.005%, Cr: 0.25%, Ni: 0.10%, and the balance of Fe and inevitable impurities.

5. The steel for a 540MPa grade LPG fuel tank according to claim 1, characterized in that: the thickness of the steel plate is 8-50 mm.

6. The steel for a 540MPa grade LPG fuel tank according to claim 1, characterized in that: the microstructure of the steel plate is ferrite, bainite and a small amount of pearlite, the grain size of the ferrite is 9-11.5 grades, the bainite is 10-30 percent, and the pearlite content is less than or equal to 10 percent.

7. A manufacturing method of 540MPa grade LPG fuel tank steel comprises molten iron desulphurization pretreatment, converter smelting, LF refining, RH vacuum treatment, continuous casting, casting blank heating, controlled rolling and controlled cooling after rolling, and is characterized in that: the method is applied to any one of claims 1 to 6, and specifically comprises the following steps: