CN113388774A - Hot-rolled air-cooled bainite high-toughness high-strength steel plate with tensile strength of more than or equal to 1300MPa and manufacturing method thereof - Google Patents

Abstract

The invention belongs to the technical field of steel making, and particularly provides a hot-rolled air-cooled bainite high-toughness high-strength steel plate with the tensile strength of more than or equal to 1300MPa and a manufacturing method thereof. The process flow is as follows: steel making → heating → 2300mm hot continuous rolling → hot plate shaping and cutting → air cooling → sampling → function inspection → packaging and warehousing → delivery; in the heating step, the heating temperature is 1200-1250 ℃; in the step of 2300mm hot continuous rolling, the final rolling temperature is 860-880 ℃, and the hot continuous rolling is air-cooled to room temperature after shaping and plate cutting. The method can obtain high strength and high toughness only by the air cooling process after hot rolling, and can keep good plate shape by controlling the cooling mode. The invention successfully prepares the non-quenched and tempered 1300MPa high-strength hot rolled steel plate which meets the technical requirements, the production process of the method is simplified, quenching and tempering are not needed, the energy consumption of quenching and tempering is avoided, and the defects of poor plate shape and difficult shaping after quenching and tempering are improved. The non-quenched and tempered 1300MPa high-strength hot rolled steel plate is successfully developed, can replace imported products, fills the blank of products and reduces the application cost.

Description

Hot-rolled air-cooled bainite high-toughness high-strength steel plate with tensile strength of more than or equal to 1300MPa and manufacturing method thereof

Technical Field

The invention belongs to the technical field of steel making, and particularly provides a hot-rolled air-cooled bainite high-toughness high-strength steel plate with the tensile strength of more than or equal to 1300MPa and a manufacturing method thereof.

Background

At present, great attention is paid to the use of high-strength structural steel in terms of steel structure steel in economically developed foreign countries, the strength grade of the steel is 275MPa at the lowest, and steel grades of 420, 460, 490, 550 and 590MPa are used in large quantities and are matched with corresponding standard standards, and respective steel series for engineering machinery are developed in major industrial countries in the world. Such as SSAB in sweden and JFE in japan, high strength steel sheets with a strength grade of 1100MPa have been developed through rational microalloying composition design and advanced production processes. The steel plate with 960MPa or above required by the engineering machinery industry in China is imported and used with the brand, and the price is very expensive.

In recent years, research on ultra-high-strength steel is also carried out in China, and a steel research institute has developed a brand-new microstructure control technology through deep research on a microalloying technology and development of a novel heat treatment technology, and is carrying out research and development on steel for Q960MPa, Q1100MPa and Q1300MPa engineering machinery.

Based on the above situation, it is very important to develop more advanced 1300MPa grade non-quenched and tempered advanced ultrahigh-strength steel in China, once the development is successful, on one hand, the requirement of domestic markets for the grade advanced ultrahigh-strength material can be met, the localization is realized, and on the other hand, the method has important guiding significance for developing higher grade steel in the future in China.

Disclosure of Invention

In order to overcome the problems in the related technology, the invention provides a hot-rolled air-cooled bainite high-toughness high-strength steel plate with the tensile strength of more than or equal to 1300MPa and a manufacturing method thereof, high strength and high toughness can be obtained only through the air-cooled process treatment after hot rolling, and good plate shape is kept through the control of a cooling mode. The invention successfully prepares the non-quenched and tempered 1300MPa high-strength hot rolled steel plate which meets the technical requirements, the production process of the method is simplified, quenching and tempering are not needed, the energy consumption of quenching and tempering is avoided, and the defects of poor plate shape and difficult shaping after quenching and tempering are improved. The non-quenched and tempered 1300MPa high-strength hot rolled steel plate is successfully developed, can replace imported products, fills the blank of products and reduces the application cost.

The technical scheme of the invention is as follows:

a manufacturing method of a hot-rolled air-cooled bainite high-toughness high-strength steel plate with tensile strength of more than or equal to 1300MPa comprises the following process flows: steel making → heating → 2300mm hot continuous rolling → hot plate shaping and cutting → air cooling → sampling → function inspection → packaging and warehousing → delivery; the method is characterized in that:

in the heating step, the heating temperature is 1200-1250 ℃;

in the step of 2300mm hot continuous rolling, the final rolling temperature is 860-880 ℃, and the hot continuous rolling is air-cooled to room temperature after shaping and plate cutting.

The invention relates to a manufacturing method of a hot-rolled air-cooled bainite high-toughness high-strength steel plate with the tensile strength of more than or equal to 1300MPa, which is characterized by comprising the following concrete steps of steelmaking:

1) and a molten iron pretreatment step

Pretreating the slag in the furnace with S less than or equal to 0.0030 wt.%, P less than or equal to 0.01 wt.%, and completely removing the slag; adopting fine material scrap steel;

2) and a converter step

The converter draws carbon for one time, and avoids point blowing; argon purging is carried out on a steel ladle before tapping, a tapping hole is controlled, and free flow is avoided;

3) and a refining step

Adopting an LF + RH double-path process, wherein the N increasing amount of LF treatment is controlled to be less than or equal to 10 ppm; LF adopts active lime and fluorite to produce reducing slag; calcium treatment is carried out by adopting a calcium silicate wire, and 500 m CaSi wire is fed to lead inclusions to be fully spheroidized;

4) and a continuous casting step

Protective pouring is carried out in the whole process, argon is adopted to purge the tundish before pouring, no molten steel is exposed in the pouring process, N is strictly controlled to be absorbed at a water port, and the increase of N is controlled to be less than or equal to 5 ppm; the constant drawing speed is kept in the steel casting process; the control target of the superheat degree of continuous casting is not more than 25 ℃.

The hot-rolled air-cooled bainite high-toughness high-strength steel plate with the tensile strength of more than or equal to 1300MPa can be prepared by adopting the method.

The scheme of the invention has the following beneficial effects:

(1) in the aspect of component design, the alloy content is lower, and the cost is saved. In the component design, C in the medium carbon is less than or equal to 0.30 percent, Si: 1.2-1.6%, Mn: 1.5-1.8 percent of Ti, less than or equal to 0.1 percent of Cr, less than or equal to 1.0 percent of V, less than or equal to 0.15 percent of B, wherein the high silicon is mainly used for obtaining partial retained austenite and has martensite transformation in the deformation process to ensure the strength of the steel plate.

(2) On the aspect of mechanical property, each index of the hot rolled steel plate of the hot rolled air-cooled bainite high-toughness high-strength steel with the tensile strength of more than or equal to 1300MPa prepared by the method meets the requirement, the hot rolled steel plate has excellent mechanical property and good processing properties such as cutting, welding and the like, the aim of reducing the weight of a vehicle body is fulfilled by the actual use of a user, and the use requirement of the user is completely met.

(3) The invention does not need quenching and tempering treatment, reduces energy consumption, reduces cost, protects environment and reduces labor intensity of workers.

(4) The invention adopts the air cooling process after rolling to obtain stable bainite and residual austenite structures without annealing treatment.

(5) The reasonable plate thickness is 3.0-6.0 mm, and the light weight and corrosion resistance of the non-quenched 1300MPa high-strength hot-rolled steel plate can be realized.

(6) The non-quenched and tempered 1300MPa high-strength hot-rolled steel plate produced by the method fills the blank of domestic similar steel grades, can replace imported similar products, increases the steel varieties of enterprises, realizes higher finished product quality and yield, and has good economic benefit.

Drawings

FIG. 1 is a metallographic structure drawing (15 μm) of test steel prepared in example;

FIG. 2 is a metallographic structure chart (0.5 μm) of test steel prepared in example.

Detailed Description

Examples

The hot-rolled air-cooled bainite high-toughness high-strength steel plate with the tensile strength of more than or equal to 1300MPa is manufactured according to the method of the invention, and the chemical components and the mass percentage of the test steel are shown in Table 1 (the balance is iron and inevitable impurities):

TABLE 1 test Steel chemical composition

C

Mn

Si

P

S

Ti

Cr

V

B

0.25

1.69

1.50

≤0.010

≤0.003

0.05

0.79

0.13

0.0020

First, steel making

1. Molten iron pretreatment step

Pretreating the slag in the furnace with S less than or equal to 0.0030 wt.%, P less than or equal to 0.01 wt.%, and completely removing the slag; fine scrap steel is adopted.

2. Converter procedure

The converter draws carbon for one time, and avoids point blowing; before tapping, argon purging is carried out on a steel ladle, a tapping hole is controlled, and free flow is avoided.

3. Refining procedure

And an LF and RH double-path process is adopted, and the requirement on the gas content is strictly controlled. The LF treatment process is required to keep micro-positive pressure, the increase of N in LF is strictly controlled, and the increase of N is required to be less than or equal to 10 ppm; the LF adopts active lime and fluorite to produce reducing slag with good fluidity, and strictly controls the argon blowing strength to avoid the exposure of molten steel as much as possible; calcium treatment with calcium silicate wire and feeding CaSi wire 500 m to spheroidize the inclusion fully and improve the product performance.

4. Continuous casting procedure

And carrying out protective pouring in the whole process. Argon is adopted to purge the tundish before casting, no molten steel is exposed in the casting process, the water mouth is strictly controlled to suck N, and the increase of N is controlled to be less than or equal to 5 ppm; high-alkalinity slag inclusion is adopted to facilitate the removal of inclusions in steel; the soft reduction function is put into the steel casting process; the constant drawing speed is kept in the steel casting process; the control target of the superheat degree of continuous casting is not more than 25 ℃. The slab is hot-charged and the rest slabs are placed in a slow cooling area in the warehouse.

Second, hot rolling

1. Heating furnace section

The heating temperature is 1150-1250 ℃, and the target tapping temperature is 1200-1250 ℃. The furnace atmosphere of the heating furnace is controlled, the generation of the casting blank iron scale is reduced, and the uniform heating temperature is ensured.

2. Rolling and cooling section

Selecting a 3+3 mode for control in the rough rolling pass; load distribution of a finish rolling model is well done, and rolling stability is guaranteed; the finishing temperature is as follows: 860 to 880 ℃; water spraying cooling is not needed after final rolling, and direct air cooling is carried out after shaping and cutting of the hot plate, so that water spraying and wind blowing are avoided.

TABLE 2 partial process parameters for rolling of sample steels

Austenitizing temperature/. degree.C	1200～1250
		Thickness of the blank/mm	60
Number of tracks	7
		Target thickness/mm	6
Final Rolling temperature/. degree.C	860～880
		Cooling Rate/(. degree. C/s)	Air cooling after rolling

TABLE 3 partial process parameters for rolling of sample steels

TABLE 4 sample Steel Properties

The WELDOX1300 high strength steel performance level is equivalent to that of the Swedish SSAB steel.

TABLE 5 comparison of properties of the sample steels of this example with SSAB steels

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It is to be understood that the present invention is not limited to what has been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims (3)

1. A manufacturing method of a hot-rolled air-cooled bainite high-toughness high-strength steel plate with tensile strength of more than or equal to 1300MPa comprises the following process flows: steel making → heating → 2300mm hot continuous rolling → hot plate shaping and cutting → air cooling → sampling → function inspection → packaging and warehousing → delivery; the method is characterized in that:

in the heating step, the heating temperature is 1200-1250 ℃;

in the step of 2300mm hot continuous rolling, the final rolling temperature is 860-880 ℃, and the hot continuous rolling is air-cooled to room temperature after shaping and plate cutting.

2. The method for manufacturing the hot-rolled air-cooled bainite high-toughness and high-strength steel plate with the tensile strength of more than or equal to 1300MPa according to claim 1, wherein the steel making comprises the following specific steps:

1) and a molten iron pretreatment step

Pretreating the slag in the furnace with S less than or equal to 0.0030 wt.%, P less than or equal to 0.01 wt.%, and completely removing the slag; adopting fine material scrap steel;

2) and a converter step

The converter draws carbon for one time, and avoids point blowing; argon purging is carried out on a steel ladle before tapping, a tapping hole is controlled, and free flow is avoided;

3) and a refining step

Adopting an LF + RH double-path process, wherein the N increasing amount of LF treatment is controlled to be less than or equal to 10 ppm; LF adopts active lime and fluorite to produce reducing slag; calcium treatment is carried out by adopting a calcium silicate wire, and 500 m CaSi wire is fed to lead inclusions to be fully spheroidized;

4) and a continuous casting step

Protective pouring is carried out in the whole process, argon is adopted to purge the tundish before pouring, no molten steel is exposed in the pouring process, N is strictly controlled to be absorbed at a water port, and the increase of N is controlled to be less than or equal to 5 ppm; the constant drawing speed is kept in the steel casting process; the control target of the superheat degree of continuous casting is not more than 25 ℃.

3. The hot-rolled air-cooled bainite high-toughness high-strength steel plate with the tensile strength of more than or equal to 1300MPa, prepared by the method of claim 1 or 2.

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