KR20230037040A - Thick plate for high-strength container with excellent core toughness and manufacturing method - Google Patents

Abstract

A thick plate for a high-strength container having excellent core toughness and a manufacturing method relate to the field of steel production technology, and its chemical composition and mass percentage are as follows: C: 0.08% to 0.12%, and Si : 0.10% to 0.30%, Mn: 1.10% to 1.50%, Ni: 0.50% to 0.80%, Mo: 0.08% to 0.15%, V: 0.03% to 0.06%, P≤0.006%, S≤0.002%, the remainder being Fe and unavoidable impurities. The maximum thickness reaches 80mm to meet the demand for high-strength low-temperature container board used in -70℃ conditions, 1/4 thickness core part -70℃ KV ₂ value ≥ 150J, yield strength ≥ 420MPa, tensile strength With strength≥560MPa, it can be used to dry large low-temperature spherical tanks or storage tanks.

Description

Thick plate for high-strength container with excellent core toughness and manufacturing method

The present invention relates to the field of steel production technology, and in particular, to a high-strength container plate having excellent core toughness and a manufacturing method.

As facilities such as low-temperature spherical tanks in the chemical industry develop with large capacity, the demand for the thickness of steel plates for low-temperature containers is gradually increasing. In order to improve the safety of the equipment, it is usually required that the impact performance of the core part of thick steel plate also meet the technical index requirements. As the plate thickness increases, the rolling compression ratio decreases when producing blanks of the same thickness, and after using the normalizing + tempering treatment, it is very difficult to guarantee the impact performance of the core part and the toughness of the core part The stability of the toughness is also reduced, and when quenching + tempering is used, the cooling rate of the core part is improved and the toughness of the core part can be guaranteed by subdividing the structure of the core part.

Thick steel plates used in low-temperature spherical tanks in China are usually 09MnNiDR steel, and the working temperature can reach -70 ° C, but their yield strength and tensile strength are low, so thick plates of 60 mm or more are used. The values required to complete the production of thick plates with standardization are only 260MPa and 420MPa. If the strength of the steel sheet is greatly improved under the premise of ensuring the toughness of the low-temperature core, the volume of a container such as a low-temperature spherical tank can be greatly increased without increasing the thickness of the sheet or by slightly increasing it.

The steel sheet for low-temperature spherical tank containers and its production method created by Chinese invention patent Publication No. CN104911319B is a two-step control rolling using Nb trace alloying, quenching + tempering, or normalizing + quenching + tempering heat treatment, 1/2 Although the impact of the thickness can satisfy the use at -70 ° C, the thick plate thereof has a yield strength of about 400 MPa and a tensile strength of less than 560 MPa.

In summary, in the prior art, steel for low-temperature containers in which a steel sheet having a thickness of > 50 mm simultaneously satisfies a service temperature of -70 ° C, yield strength ≥ 420 MPa and tensile strength ≥ 560 MPa has not yet been reported.

In order to solve the above technical problem, the present invention provides a thick plate for a high-strength container having excellent core toughness and a manufacturing method.

In order to solve the above technical problem, the present invention provides a thick plate for a high-strength container having excellent toughness of the core part, and its chemical composition and mass percentage are as follows, C: 0.08% to 0.12% , Si: 0.10% to 0.30%, Mn: 1.10% to 1.50%, Ni: 0.50% to 0.80%, Mo: 0.08% to 0.15%, V: 0.03% to 0.06%, P≤0.006% , and S≤0.002%, the remainder being Fe and unavoidable impurities.

In terms of technical effect, the product of the present invention satisfies the use requirements of -70 ° C in low temperature impact toughness of the entire thickness, and significantly improves yield strength and tensile strength based on 0.5Ni low temperature steel according to the prior art. to improve material performance.

The technical solutions limited to the further steps of the present invention are as follows.

As described above, in the thick plate for a high-strength container having excellent core toughness, its chemical composition and mass percentage are as follows: C: 0.08% to 0.09%, Si: 0.10% to 0.21%, Mn: 1.10 % ~ 1.45%, Ni: 0.50% ~ 0.62%, Mo: 0.08% ~ 0.10%, V: 0.03% ~ 0.037%, P≤0.006%, S≤0.0005%, the rest is Fe and unavoidable is an impurity

As described above, in the thick plate for a high-strength container having excellent core toughness, its chemical composition and mass percentage are as follows: C: 0.10% to 0.11%, Si: 0.14% to 0.20%, Mn: 1.18 % ~ 1.37%, Ni: 0.50% ~ 0.74%, Mo: 0.096% ~ 0.12%, V: 0.039% ~ 0.047%, P≤0.005%, S≤0.001%, the rest is Fe and unavoidable is an impurity

As described above, in the thick plate for a high-strength container having excellent core toughness, the thickness of the steel plate is 50 to 80 mm.

Another object of the present invention is to provide a method for manufacturing a thick plate for a high-strength container having excellent core toughness, which includes the following steps.

Steelmaking continuous casting stage: molten metal is pre-treated, smelting is performed by complex blowing at the top and bottom of the rotary furnace, LF+RH refining, component control is carried out according to the design requirements of the component, and the continuous casting process uses electromagnetic Stirring, the blank produced is 260mm thick;

Slab heating step: the slab is heated to 1150 to 1180 ° C, the total furnace smelting time of the slab is ≥ 240 min, the soaking section warming time is 30 to 60 min, and the total slab temperature uniformity ≤ 10 °C;

Rolling and cooling control step: After the slab is taken out of the furnace, descaling is performed using high-pressure water, the descaling water pressure is ≥ 18 MPa, and two-step controlled rolling is used, and the first step is austenite rolling in the recrystallization zone, the second step is precision rolling in the austenite non-recrystallization region, and controlling cooling after rolling;

Heat treatment step: Heat treatment is performed using an offline quenching + tempering process.

As described above, in the method of manufacturing a thick plate for a high-strength container having excellent core toughness,

Steelmaking continuous casting stage: The molten metal is pre-treated, the S content in the molten metal is <0.002wt%, the steelmaking is carried out using a rotary furnace, the LF furnace is subjected to deep deoxygenation and desulfurization, and the alloy composition is within the target range. , and the RH furnace proceeds with degassing, and the degree of vacuum ≤ 0.3 torr; Continuous casting is performed using the secondary cooling water weak cooling and low tensile speed method, the slab tensile speed is 0.8 to 1.2 m/min, the thickness of the continuously cast slab is 260 mm, and the casting blank is stack cooled. (stack cooling) treatment is carried out, and the stack cooling time is ≧48 hours.

As described above, the manufacturing method of a high-strength container thick plate having excellent core toughness is as follows, using two-step controlled rolling: the first step is rolling in an austenite recrystallization zone, and the total reduction is 30% to 50 %; The second step is precision rolling in the austenite non-recrystallization zone, the rolling start temperature is lower than 850°C, the rolling reduction is 45% to 65%, and the final rolling temperature is 780 to 820°C; Cooling is controlled after rolling, and the self tempering temperature is controlled between 580 and 620°C.

As described above, in the method for manufacturing a high-strength container thick plate having excellent core toughness, the off-line quenching step used for heat treatment: the quenching temperature is 870 to 890 ° C, the warming time is 30 to 60 min, and the After that, it is quenched directly to room temperature using the maximum cooling capacity of the equipment.

As described above, in the method of manufacturing a thick plate for a high-strength container having excellent core toughness, tempering step: heating the steel plate to be quenched to 605 to 625 ° C, tempering for 40 to 70 min, taking it out of the furnace and cooling in air to obtain a uniform and finely tempered sorbite structure.

Beneficial effects of the present invention are as follows.

(1) Chemical composition design of the present invention

C: As a strengthening element and austenite stable element in steel, as the carbon content in the steel increases, the yield point and tensile strength improve. Although the yield strength can be improved by 40 to 50 MPa, the plasticity and impact properties are poor and the ductile-brittle transition temperature is high, which is detrimental to the low-temperature toughness of HAZ. As low as possible under the premise;

Ni: Forms α and γ phase solid solutions with Fe to form infinite solid solution in the γ phase to expand the γ phase region, forms austenite and is a stable element, prevents screw dislocation from easily It can ensure the occurrence of cross slip and improve the plastic deformation performance of the material, and since Ni is also a noble metal element, it is added as little as possible under the premise of ensuring performance;

Mn: As an austenite stable element, it is also a base material strengthening element, and the hardenability of the material is clearly improved by improving the strength through solid solution strengthening and precipitation strengthening, and Mn element segregates the core part during the continuous casting process. ) easily occurs, so it is not good to have too high a content;

Si: As a deoxidizing element, it can suppress clustering of P at the crystal boundary, but when the content of Si is too high, it is disadvantageous to the low-temperature toughness of the weld heat affected zone (HAZ). and;

S and P: S easily forms Mn and precipitate MnS to reduce low-temperature toughness; P easily clusters at the grain boundary, reducing the crack expansion resistance of the grain boundary and deteriorating low-temperature toughness;

Mo: Strength and tempering stability of steel can be improved by improving hardenability, and when coexisting with chromium or manganese, tempering brittleness caused by other elements can be reduced or suppressed;

V: can improve hardenability, and as a strong carbonitride forming element, can improve the strength of the material through solid solution and precipitation, and when V exists simultaneously with Cr and Mo, complex carbides are formed in the tempering process Forming and reducing the plasticity and toughness of the welded joint, designing to ensure plasticity and toughness, the amount of V must be controlled, and the role of subdivision of V on crystal grains and the beneficial role of V on strength must be reviewed;

(2) The low-temperature high-strength container plate manufactured according to the present invention has a thickness of 50 to 80 mm, a 1/4 thickness core KV ₂ value ≥ 150 J under -70 ° C condition, and a yield strength ≥ 420 MPa, tensile strength ≥ 560 MPa;

(3) The product of the present invention replaces domestic and foreign 0.5Ni steel brands such as 09MnNiDR and is used for drying containers such as propane, butane, ethane and ethylene to upgrade material performance and enlarge the container It can provide material guarantee for power generation.

1 is a photograph of the structure of a 1/4 thickness tempered state of an 80 mm steel sheet corroded with a 4% nitric acid alcohol solution in Example 1;
Figure 2 is a photograph of the structure of the 1/2 thickness tempered state of the 80mm steel sheet corroded with 4% nitric acid alcohol solution in Example 1.

In the thick plates and manufacturing methods for high-strength containers having excellent core toughness provided in the following examples, the chemical components are as shown in Table 1, and the parameters of the smelting and rolling process are shown in Table 2. As described, the parameters of the heat treatment process are as shown in Table 3, and the specific steps are as follows.

Steelmaking continuous casting stage: molten metal is pre-treated, S content in molten metal is <0.002wt%, steel is made using a rotary furnace, LF furnace is used for deep deoxygenation and desulfurization, and alloy components are within the target range , and the RH furnace proceeds with degassing, and the degree of vacuum ≤ 0.3 torr; Continuous casting is performed using the secondary cooling water weak cooling and low tensile speed method, the slab tensile speed is 0.8 to 1.2 m/min, the thickness of the continuous casting slab is 260 mm, and the casting blank is subjected to stack cooling treatment, and the stack cooling time is ≥ 48 hours;

Slab heating step: the slab is heated to 1150 to 1180 ° C, the total furnace smelting time of the slab is ≥ 240 min, the soaking section warming time is 30 to 60 min, and the total slab temperature uniformity ≤ 10 °C;

Step using two-step controlled rolling: the first step is rolling in an austenite recrystallization zone, and the total reduction is 30% to 50%; In the second step, precision rolling is performed in the austenite non-recrystallization region, the rolling start temperature is lower than 850 ° C, the rolling reduction is 45% to 65%, and the final rolling temperature is 780 to 820 ° C. is; Cooling is controlled after rolling, and the self tempering temperature is controlled between 580 and 620°C;

Off-line quenching step used for heat treatment: the quenching temperature is 870-890 ° C, the holding time is 30-60 min, and after being taken out of the furnace, it is directly quenched to room temperature using the maximum cooling capacity of the equipment;

Tempering step: the steel sheet to be quenched is heated to 605 to 625° C., tempered for 40 to 70 min, taken out of the furnace and air-cooled to obtain a uniform and finely tempered sorbite structure.

Table 1

Table 2

Table 3

The mechanical performance of the products according to the examples is as shown in Table 4.

Table 4

At the same time, as can be seen from Figs. 1 and 2, the tissue obtained by the product of the present invention is a tempered sorbite tissue, which can obtain good overall mechanical performance. The maximum thickness reaches 80mm to meet the requirements of high-strength low-temperature container board used in -70℃ conditions, and the 1/4 thickness core part -70℃ KV ₂ value ≥ 150J, yield strength ≥ 420MPa, tensile strength ≥ 560MPa. , Significantly improve yield strength and tensile strength based on 0.5Ni low-temperature steel according to the prior art, and replace propane, butane, ethane and ethylene by replacing Chinese and foreign 0.5Ni steel brands such as 09MnNiDR It can be used for drying containers to upgrade material performance and provide material guarantee for the development of larger containers.

In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed using equivalent substitution or equivalent transformation are included in the scope of the claimed protection of the present invention.

Claims (9)

In the thick plate for a high-strength container having excellent core toughness,
Its chemical composition and mass percentage are as follows:
C: 0.08% to 0.12%, Si: 0.10% to 0.30%, Mn: 1.10% to 1.50%, Ni: 0.50% to 0.80%, Mo: 0.08% to 0.15%, V: 0.03% to 0.06%, P≤0.006%, S≤0.002%, and the rest is Fe and unavoidable impurities. According to claim 1,
Its chemical composition and mass percentage are as follows:
C: 0.08% to 0.09%, Si: 0.10% to 0.21%, Mn: 1.10% to 1.45%, Ni: 0.50% to 0.62%, Mo: 0.08% to 0.10%, V: 0.03% to 0.03% 0.037%, P≤0.006%, S≤0.0005%, and the rest is Fe and unavoidable impurities. According to claim 1,
Its chemical composition and mass percentage are as follows:
C: 0.10% to 0.11%, Si: 0.14% to 0.20%, Mn: 1.18% to 1.37%, Ni: 0.50% to 0.74%, Mo: 0.096% to 0.12%, V: 0.039% to 0.039% 0.047%, P≤0.005%, S≤0.001%, and the rest is Fe and unavoidable impurities. According to claim 1,
A thick plate for a high-strength container having excellent core toughness, characterized in that the thickness of the steel plate is 50 to 80 mm. In the method of manufacturing a thick plate for a high-strength container having excellent core toughness according to any one of claims 1 to 4,
Steelmaking continuous casting stage: molten metal is pre-treated, smelting is performed by complex blowing at the top and bottom of the rotary furnace, LF+RH refining, component control is carried out according to the design requirements of the component, and the continuous casting process uses electromagnetic stirring, and the produced blank material has a thickness of 260 mm;
Slab heating step: the slab is heated to 1150 to 1180 ° C, the total furnace smelting time of the slab is ≥ 240 min, the soaking section warming time is 30 to 60 min, and the total slab temperature uniformity ≤ 10 ℃ step;
Rolling and cooling control step: After the slab is taken out of the furnace, descaling is performed using high-pressure water, the descaling water pressure is ≥ 18 MPa, and two-step controlled rolling is used, and the first step is austenite rolling in the recrystallization region, and the second step is precision rolling in the austenite non-recrystallization region, and controlling cooling after rolling;
Heat treatment step: a step of performing heat treatment using an offline quenching + tempering process. According to claim 5,
In steelmaking continuous casting, the molten metal is pre-treated, the S content in the molten metal is <0.002wt%, the steelmaking is performed using a rotary furnace, the LF furnace is subjected to deep deoxygenation and desulfurization, and the alloy components are within the target range. adjusted to reach, the RH furnace proceeds with degassing, the degree of vacuum ≤ 0.3torr; Continuous casting is performed using the secondary cooling water weak cooling and low tensile speed method, the slab tensile speed is 0.8 to 1.2 m/min, the thickness of the continuously cast slab is 260 mm, and the casting blank is stack cooled. A method of manufacturing a thick plate for a high-strength container having excellent core toughness, characterized in that the stack cooling treatment is performed and the stack cooling time is ≥ 48 hours. According to claim 5,
In the step of using two-step controlled rolling, the first step is rolling in the austenite recrystallization zone, and the total reduction is 30% to 50%; The second step is precision rolling in the austenite non-recrystallization zone, the rolling start temperature is lower than 850°C, the rolling reduction is 45% to 65%, and the final rolling temperature is 780 to 820°C; A method of manufacturing a thick plate for a high-strength container having excellent core toughness, characterized in that cooling is controlled after rolling, and the self-tempering temperature is controlled between 580 and 620 ° C. According to claim 5,
The offline quenching step used for heat treatment has excellent core toughness, characterized by a quenching temperature of 870 to 890 ° C, a holding time of 30 to 60 min, and quenching directly to room temperature using the maximum cooling capacity of the equipment after taking out of the furnace. Method for manufacturing a thick plate for a high-strength container having a. According to claim 5,
In the tempering step, the steel sheet to be quenched is heated to 605 to 625 ° C, tempered for 40 to 70 min, taken out of the furnace and air-cooled to obtain a uniform and finely tempered sorbite structure. A method of manufacturing a thick plate for a high-strength container having excellent core toughness.

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