CN113308643B

CN113308643B - Production method of ultrahigh-strength Q1100E steel plate with good formability

Info

Publication number: CN113308643B
Application number: CN202110443351.XA
Authority: CN
Inventors: 成慧梅; 韩健; 李玉谦; 孙电强; 张瑞超; 冯俊鹏; 徐晓; 李宏鹏
Original assignee: Handan Iron and Steel Group Co Ltd; HBIS Co Ltd Handan Branch
Current assignee: Hangang Nengjia Steel Co ltd; Handan Iron and Steel Group Co Ltd; HBIS Co Ltd Handan Branch
Priority date: 2021-04-23
Filing date: 2021-04-23
Publication date: 2022-10-28
Anticipated expiration: 2041-04-23
Also published as: CN113308643A

Abstract

The invention relates to a production method of an ultrahigh-strength Q1100E steel plate with good formability, wherein a tempering procedure adopts a two-stage heating process, a tempering furnace is uniformly divided into 10 zones according to the total length, the zones 1-6 in the first stage are gradient heating stages, the heating mode is gradient heating from low to high, and the heating temperature is heated from room temperature to 200-250 ℃; in the second stage, a 7-10 area is a heat preservation section, and the heat preservation temperature of the steel plate is 200-250 ℃; the microstructure of the steel plate produced by the invention is a stable tempered martensite structure, the yield strength is more than or equal to 1100MPa, the tensile strength is more than or equal to 1350MPa, the elongation is more than or equal to 12%, the impact energy of a V-shaped standard sample at the low temperature of 40 ℃ below zero is more than or equal to 130J, the ductile-brittle transition temperature is lower than 100 ℃ below zero, no crack exists under bending angles of 45 degrees, 90 degrees, 135 degrees, 180 degrees and the like under the bending center diameter of 3 times of the plate thickness, and meanwhile, the steel plate has uniform structure, uniform performance, small residual stress and excellent whole plate forming capability.

Description

Production method of ultrahigh-strength Q1100E steel plate with good formability

Technical Field

The invention belongs to the technical field of metallurgical rolling, and particularly relates to a production method of an ultrahigh-strength Q1100E steel plate with good formability.

Background

The ultra-high strength steel with the yield strength of 1100MPa is the steel with the highest strength level in the field of the current domestic engineering machinery, and is mainly used for key structural members of concrete pump trucks in the engineering machinery industry, telescopic crane arms of automobile cranes, crawler crane bases and pull plates, large-tonnage hydraulic supports and the like. At present, only a few manufacturers at home can produce the ultrahigh-strength steel with the grade of 1100MPa for engineering machinery. In recent years, with the demand for lightweight design of various large construction machine manufacturers, the demand for ultra-high strength steel of 1100MPa class has also increased year by year.

Chinese patent CN104513936A introduces a quenched and tempered high-strength steel with yield strength of 1100MPa and a production method thereof, the invention adopts controlled rolling and controlled cooling, off-line quenching and tempering processes, and controls the chemical composition design, the base metal structure, the quenching heating temperature, the tempering heating temperature and other angles, thereby ensuring that the elongation, the low-temperature impact toughness and other properties of the steel are good while realizing the ultrahigh strength; but the forming performance is not controlled by the technology of the invention, and the strength and toughness control of the steel plate in a low-temperature service environment is not considered. Chinese patent CN109207858A introduces a production method of a low-alloy ultrahigh-strength steel Q1100E sheet, the Q1100E steel plate is obtained by adopting a two-fire finished-material rolling method and a direct tempering process, and the production method does not adopt a tempering process, has poor stability of the overall performance of the steel plate, is complex in process and long in production period, and is not beneficial to industrial batch production. The forming performance of the Q1100E steel plate is very important, and bending cracking in the forming process is the most easily occurred problem of the Q1100E steel plate in the using and processing process, so that a production method of the Q1100E steel plate with good forming performance is needed.

Disclosure of Invention

The invention aims to provide a production method of an ultrahigh-strength Q1100E steel plate with good formability, and solve the problem that the steel plate cracks in the process of machining and forming.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a production method of an ultrahigh-strength Q1100E steel plate with good formability comprises the working procedures of steel making, continuous casting, heating, controlled rolling, controlled cooling, quenching and tempering; the tempering procedure adopts a two-stage heating process, the tempering furnace is uniformly divided into 10 areas according to the total length, the areas 1-6 in the first stage are gradient heating stages, the heating mode is gradient heating from low to high, and the heating temperature is heated from room temperature to 200-250 ℃; the second stage has heat insulating section in 7-10 area and steel plate temperature 200-250 deg.c.

The production method of the ultrahigh-strength Q1100E steel plate with good formability comprises a tempering process, wherein the tempering process adopts a two-stage heating process, a first stage 1-6 area is a gradient heating stage, the heating temperature is heated from room temperature to 200-250 ℃, the heating speed is 4.0-8.5 ℃/min, and the heating time coefficient is 4.0-5.0min/mm; and in the second stage, a 7-10 area is a heat preservation section, the heat preservation temperature of the steel plate is 200-250 ℃, the steel plate moves back and forth in the heat preservation section through a conveying roller way, so that the steel plate is subjected to heat preservation in a swinging mode, the swinging speed is 2.5-4.0 m/min, the swinging amplitude is 16-30m, the heat preservation time coefficient is 2.5-3.0min/mm, and the heating uniformity of the steel plate and the sufficient release of residual stress in the steel plate are ensured.

In the tempering process, the quenched steel plate enters a tempering furnace for tempering, and a symmetrical ordered flow field is formed on the upper surface and the lower surface of the steel plate by adopting a mixed heating mode of open fire heating and a hot air circulating heat supplementing system, so that heat is transferred to the plate, the furnace gas is distributed more uniformly, and the local overheating of the steel plate is avoided; and naturally cooling the steel plate to room temperature after tempering.

The carbon atoms dissolved in the martensite in the quenching state are in a supersaturated state and are thermodynamically shown to be in an unstable state, after the swing type low-temperature tempering treatment, the mobility of the carbon atoms is enhanced, the carbon atoms are continuously diffused and exist in the form of iron carbide in combination with iron atoms in a matrix, the number of precipitated carbides is increased, the effect of hindering the dislocation movement is greatly weakened, the structure stress is released, the toughness is increased, and a tempered martensite stable structure is obtained, so that on one hand, part of residual stress can be eliminated, and on the other hand, the forming capability of a steel plate is also favorably improved;

according to the production method of the ultrahigh-strength Q1100E steel plate with good formability, the steel plate is transversely cut after the controlled cooling process is finished, the quenching process is that the transversely cut steel plate is put into a quenching furnace and heated to 870-890 ℃, the heating time coefficient is 2.2-3.2min/mm, the internal temperature uniformity of the steel plate tends to be consistent, so that the internal and external properties of the heat-treated steel plate are consistent, and fine and uniform austenite grains are formed; and (4) after the steel plate is taken out of the quenching furnace, the steel plate enters a quenching machine, and quenching treatment is carried out to room temperature by adopting water cooling.

In the above production method of the ultrahigh-strength Q1100E steel plate with good formability, the controlled cooling process comprises the steps of cooling the steel plate after controlled rolling in an intensive type laminar flow cooling device, adopting a front section 1/4 cooling mode, confirming that no blockage or water leakage exists in a cooling water nozzle, and preventing thermal stress of the steel plate caused by uneven cooling; the curling temperature is controlled to be 650-680 ℃, and then the steel plate enters the incubator to be naturally cooled to room temperature, so that hydrogen induced cracks are prevented, and the bending performance of the steel plate is ensured.

According to the production method of the ultrahigh-strength Q1100E steel plate with good formability, the rolling process is controlled, the head and tail temperature uniformity of the strip steel is guaranteed by putting a heat preservation cover before finish rolling, and the finish rolling temperature is controlled to be 860-880 ℃.

In the heating process, the temperature of a heating section is 1210-1250 ℃, the heating time is 180-240min, the temperature of a soaking section is 1190-1230 ℃, the soaking time is 30-50min, and enough soaking time ensures the uniformity of the internal temperature of a casting blank and prevents the strip shape problem in the subsequent rolling process caused by uneven temperature.

The production method of the ultrahigh-strength Q1100E steel plate with good formability comprises the following chemical components in percentage by mass: c:0.14 to 0.18%, si:0.10 to 0.30%, mn: 0.80-1.20%, P is less than or equal to 0.010%, S is less than or equal to 0.002%, nb: 0.015-0.035%, V:0.030 to 0.050%, ti: 0.010-0.020%, cr:0.35 to 0.55%, mo:0.50 to 0.70%, ni: 0.30-0.60%, B:0.0010 to 0.0020%, als: 0.015-0.040%, N is less than or equal to 0.0045%, H is less than or equal to 0.0002%, and the balance is Fe and other inevitable impurities.

According to the production method of the ultrahigh-strength Q1100E steel plate with good formability, the thickness of the steel plate is 6mm to 12mm, the microstructure is tempered martensite, the yield strength is more than or equal to 1100MPa, the tensile strength is more than or equal to 1350MPa, the elongation is more than or equal to 12%, the impact energy of a V-shaped standard sample at the low temperature of-40 ℃ is more than or equal to 130J, and the ductile-brittle transition temperature is lower than-100 ℃.

The tempering furnace is a roller-hearth heat treatment furnace, a mixed heating mode of open fire heating and hot air forced convection is adopted, the temperature of the atmosphere in the furnace is ensured to be uniform in a low-temperature state, and the heat exchange between the upper surface and the lower surface of a steel plate and furnace gas is mainly carried out in a convection mode. Domestic tempering furnaces are generally uniformly divided into heating zones with different numbers according to the designed total length, the heating method is to set the heating zones to be uniform in temperature, and the heating zones are accurately divided into two stages by the invention: the first stage gradient heating stage is in the area 1-6, and the second stage heat preservation stage is in the area 7-10. In the first stage of gradient heating, the steel plate is slowly heated to 200-250 ℃ at a low heating speed of 4.0-8.5 ℃/min. In the heating process of the steel plate, if the heating speed is too high, temperature difference is formed due to the inconsistency of the heating speed and the heating time of the surface layer and the core part, so that the volume expansion is uneven, thermal stress is generated, and the steel plate is deformed in the use forming process. In the second stage of heat preservation section, the heat preservation temperature of the steel plate is 200-250 ℃, and heat preservation is carried out in a steel plate swinging mode, so that the heating uniformity of the steel plate and the full release of the internal stress of the steel plate are ensured. The carbon atoms of the quenched martensite in solid solution are in a supersaturated state, when the tempering temperature reaches 200-250 ℃, the martensite is decomposed, the activity of the internal atoms is increased, the supersaturated carbon in the martensite begins to be gradually precipitated in the form of carbide, the supersaturation degree of the carbon in the martensite is continuously reduced, meanwhile, the lattice distortion degree is also weakened, and the internal stress is reduced. The tempered martensite structure consisting of martensite with a low supersaturation degree and extremely fine carbides is a stable structure, and can relieve internal stress on the one hand and also be beneficial to improving the forming capability of the steel plate on the other hand.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:

the microstructure of the steel plate produced by the invention is a stable tempered martensite structure, the yield strength is more than or equal to 1100MPa, the tensile strength is more than or equal to 1350MPa, the elongation is more than or equal to 12%, the impact energy of a V-shaped standard sample at the low temperature of 40 ℃ below zero is more than or equal to 130J, the ductile-brittle transition temperature is lower than 100 ℃ below zero, no crack exists under bending angles of 45 degrees, 90 degrees, 135 degrees, 180 degrees and the like under the bending center diameter of 3 times of the plate thickness, and meanwhile, the steel plate has uniform structure, uniform performance, small residual stress and excellent whole plate forming capability.

The steel plate with good comprehensive performance produced by the process has excellent overall stability, the low-temperature impact power value far exceeds 27J required by the standard, the bending performance is good, and the excellent whole plate forming capability is shown. The production process is simple, the mass production is facilitated, the problems that the steel for the large-scale engineering machinery suspension arm is bent and cracked in the processing and using processes are solved, and the market popularization significance is great.

Drawings

FIG. 1 is a schematic view of the zones of a tempering furnace;

FIG. 2 is a 200X microstructure of a 6mm thick gauge steel plate in example 1;

FIG. 3 is a 200X microstructure of a 7mm thick gauge steel plate of example 2;

FIG. 4 is a 200X microstructure of an 8mm thick gauge steel plate of example 3;

FIG. 5 is a 200X microstructure of a 10mm thick gauge steel plate of example 4;

FIG. 6 is a 200X microstructure of a 12mm thick gauge steel plate of example 5;

FIG. 7 is a 200X microstructure of an 8mm thick gauge steel plate of example 6.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In order to better illustrate the invention, the following examples are given by way of further illustration.

Examples 1 to 6

The chemical compositions and the mass percentages of the steel sheets of examples 1 to 6 are shown in table 1. The production process comprises the working procedures of steel making, continuous casting, heating, controlled rolling, controlled cooling, quenching and tempering, and the heating section temperature, the soaking section temperature, the total heating time of the heating furnace and the soaking section time of the heating furnace in the heating working procedures of the embodiments 1 to 6 are shown in a table 2. The rolling specification and the finish rolling temperature of the steel plate in the rolling process are controlled in examples 1 to 6, the cooling mode and the coiling temperature in the cooling process are controlled in table 3, the temperature uniformity of the head and the tail of the steel plate is guaranteed by putting a heat preservation cover before the finish rolling in the rolling process in examples 1 to 6, and the steel plate enters a heat preservation box for natural cooling to the room temperature after being coiled in the cooling control process in examples 1 to 6, so that hydrogen induced cracks are prevented, and the bending performance of the steel plate is guaranteed. The heating temperature and the time coefficient of the heating section of the steel plate in the quenching procedures of examples 1 to 6 are shown in a table 4, the purpose of heat preservation is that the uniformity of the internal temperature of the steel plate tends to be consistent, so that the internal and external properties of the heat-treated steel plate are consistent, fine and uniform austenite grains are formed, and the steel plate in the quenching procedures of examples 1 to 6 is taken out of the heating furnace and then is quenched to room temperature. Examples 1-6 tempering procedure, shown in fig. 1, the heating zone is divided exactly into two stages: the gradient heating stage of the first stage is 1-6 areas, the heat preservation stage of the second stage is 7-10 areas, each heating area is heated by an upper burner and a lower burner, the heating temperature, the heating speed, the heating time coefficient, the heat preservation mode of the heat preservation section and the swing speed of each area of the tempering furnace are shown in a table 5, the heating uniformity of the steel plate and the sufficient release of the residual stress in the steel plate are ensured, and the steel plate is naturally cooled to the room temperature after being tempered in the examples 1-6.

TABLE 1

TABLE 2

TABLE 3

TABLE 4

TABLE 5

The steel plates after being tempered in the examples 1 to 6 are subjected to tension detection, 180-degree bending detection and impact detection, and the detection results are shown in Table 6, the yield strength of the steel plates in the examples of the invention is more than 1100MPa, the tensile strength of the steel plates is more than 1350MPa, the elongation of the steel plates is more than 12%, the low-temperature impact toughness values at minus 40 ℃ are more than 130J (standard samples), the requirements that the standard is more than or equal to 27J are greatly exceeded, no crack exists under the bending angles of 45 degrees, 90 degrees, 135 degrees and 180 degrees under the bending center diameter of 3 times of the plate thickness, and the steel plates show excellent whole plate forming capability. FIGS. 2 to 7 show that the microstructures of the steel sheets produced in examples 1 to 6 were stable tempered martensite structures.

TABLE 6

。

Claims

1. A production method of an ultra-high strength Q1100E steel plate with good formability comprises the working procedures of steel making, continuous casting, heating, controlled rolling, controlled cooling, quenching and tempering; the method is characterized in that: the tempering process is that the quenched steel plate enters a tempering furnace for tempering, a mixed heating mode of open fire heating and a hot air circulation heat supplementing system is adopted, symmetrical ordered flow fields are formed on the upper surface and the lower surface of the steel plate, and the steel plate is naturally cooled to room temperature after being tempered; the tempering procedure adopts a two-stage heating process, the tempering furnace is uniformly divided into 10 areas according to the total length, the areas 1-6 in the first stage are gradient heating stages, the heating temperature is increased from room temperature to 200-250 ℃, the heating speed is 4.0-8.5 ℃/min, and the heating time coefficient is 4.0-5.0min/mm; in the second stage, a 7-10 area is a heat preservation section, the heat preservation temperature of the steel plate is 200-250 ℃, the steel plate moves back and forth in the heat preservation section through a conveying roller way, so that the steel plate is subjected to heat preservation in a swinging mode, the swinging speed is 2.5-4.0 m/min, the swinging amplitude is 16-30m, and the heat preservation time coefficient is 2.5-3.0min/mm;

the steel plate comprises the following chemical components in percentage by mass: c:0.14 to 0.18%, si:0.10 to 0.30%, mn: 0.80-1.20%, P is less than or equal to 0.010%, S is less than or equal to 0.002%, nb: 0.015-0.035%, V:0.030 to 0.050%, ti: 0.010-0.020%, cr:0.35 to 0.55%, mo:0.50 to 0.70%, ni: 0.30-0.60%, B:0.0010 to 0.0020 percent, als: 0.015-0.040%, N is less than or equal to 0.0045%, H is less than or equal to 0.0002%, and the balance is Fe and other inevitable impurities; the thickness of the Q1100E steel plate is 6-12 mm, the microstructure is tempered martensite, the yield strength is more than or equal to 1100MPa, the tensile strength is more than or equal to 1350MPa, the elongation is more than or equal to 12%, the low-temperature-40 ℃ impact energy of a V-shaped standard sample is more than or equal to 130J, the ductile-brittle transition temperature is lower than-100 ℃, and no crack exists at bending angles of 45 degrees, 90 degrees, 135 degrees and 180 degrees under the bending center diameter of 3 times of the plate thickness.

2. The method for producing an ultra-high strength Q1100E steel sheet with good formability according to claim 1, wherein the steel sheet is transversely cut after the controlled cooling process is finished, and the method comprises the following steps: the quenching process is that the transversely cut steel plate is put into a quenching furnace and heated to 870-890 ℃, the heating time coefficient is 2.2-3.2min/mm, the steel plate is put into a quenching machine after being taken out of the quenching furnace and is cooled by water

Quenching to room temperature.

3. A method for producing an ultra high strength Q1100E steel sheet excellent in formability according to claim 1, wherein: and the controlled cooling process comprises the steps of cooling the steel plate after controlled rolling in an intensive laminar flow cooling device, controlling the curling temperature to 650-680 ℃ by adopting a front section 1/4 cooling mode, and then naturally cooling the steel plate in an incubator to room temperature.

4. A method for producing an ultra high strength Q1100E steel sheet excellent in formability according to claim 1, wherein: the rolling procedure is controlled, the heat preservation cover is put into use before finish rolling to ensure the head and tail temperature uniformity of the strip steel, and the finish rolling temperature is controlled to be 860-880 ℃.

5. A method for producing an ultra high strength Q1100E steel sheet excellent in formability according to claim 1, wherein: in the heating process, the temperature of the heating section is 1210-1250 ℃, the heating time is 180-240min, and the temperature of the soaking section is 1190-1230

Soaking at 30-50min.