CN110747322A - A kind of 1180MPa nanoparticle reinforced ferritic steel and preparation method thereof - Google Patents

Abstract

The invention relates to a 1180MPa nanoparticle-strengthened ferritic steel. The main chemical mass percentages are as follows: C: 0.12-0.15%, Si: 0.20-0.30%, Mn: 1.0-2.0%, P≤0.001%, S≤0.001% , N: 0.010% ~ 0.030%, Ti: 0.12 ~ 0.30%, Mo: 0.20 ~ 0.60%, V: 0.10 ~ 0.15%, the balance is Fe and inevitable impurities, the present invention also relates to preparation as in claim 1 The method for strengthening ferritic steel with 1180MPa nano-particles comprises the following steps: smelting, casting and rough forging the mass percentage of the above-mentioned elements into billets; heating the billets at 1250-1300° C. It is rolled at about 100°C, the final rolling temperature is 900°C, and then rapidly water-cooled, the cooling rate is 40-50°C/s, cooled to 600°C for coiling, and the nanoparticle-strengthened ferritic steel prepared by the invention has good hole expansion performance. , good toughness, excellent welding performance, excellent mechanical properties, can be widely used in automobile side pillars, side reinforcements, suspension arms and anti-collision beams and other structural parts and steel structure engineering, the prospect is promising.

Description

A kind of 1180MPa nanoparticle reinforced ferritic steel and preparation method thereof

technical field

The invention relates to the technical field of steel structures and metal materials for power transmission and transformation projects, in particular to a 1180MPa nanoparticle-strengthened ferritic steel and a preparation method thereof.

Background technique

In recent years, with the development of nanotechnology, nanomaterials exhibit unique advantages such as high strength, high hardness and high toughness in terms of mechanical properties, which have attracted extensive attention of researchers. The development of nanotechnology has also opened up new ways for the design of new high-strength ferritic steels. The application of nanomaterials and nanotechnology to the design of steel materials, the use of nanoscale precipitation to strengthen and prevent grain growth technology, is expected to greatly increase. Improve the strength and toughness of structural steel.

In addition to the extremely high tensile strength (780-1000MPa), the new nanoparticle-strengthened high-strength ferritic steel (C is 0.05-0.1wt%) also requires certain plasticity and toughness (total elongation ≥ 20%), full Possibly reduced notch sensitivity, high fatigue strength, certain corrosion resistance, good manufacturability, low price and environmental friendliness. In 2016, Huang Yao et al. successfully developed 1000MPa nanoparticle ferritic steel, nano Particle ferritic steel uses the precipitation strengthening effect of nanoparticles to improve the tensile strength of the material and minimize the loss of toughness, so it has a high hole expansion rate and has been widely used in bridges, construction refractory steel, car seats, etc. on suspension, crash arms and fasteners.

Nanoparticle high-strength ferritic steel is not only an important direction of steel material research, but also has broad application and development prospects, and it is of great significance to improve the research level of nano-phase-strengthened steel in my country and develop new types of high-strength and high-toughness steel. There is no technical report on rolled nanoparticle ferritic steel and its preparation method.

In view of this, the present invention is proposed.

SUMMARY OF THE INVENTION

In order to solve the above deficiencies in the prior art, the present invention provides a 1180MPa nanoparticle-strengthened ferritic steel and a preparation method thereof.

The technical scheme provided by the present invention is:

A 1180MPa nanoparticle reinforced ferritic steel, characterized in that: the main chemical mass percentage of the 1180MPa nanoparticle reinforced ferritic steel is as follows:

C: 0.12～0.15%, Si: 0.20～0.30%, Mn: 1.0～2.0%, P≤0.001%, S≤0.001%, N: 0.010%～0.030%, Ti: 0.12～0.30%, Mo: 0.20～ 0.60%, V: 0.10-0.15%, and the balance is Fe and inevitable impurities.

Based on the same inventive concept, the present invention also provides a method for preparing a 1180MPa nanoparticle-strengthened ferritic steel as claimed in claim 1, the method comprising the following steps:

1) The chemical mass percentage of 1180MPa nanoparticle-strengthened ferritic steel: C: 0.12-0.15%, Si: 0.20-0.30%, Mn: 1.0-2.0%, P≤0.001%, S≤0.001%, N: 0.010%～0.030%, Ti: 0.12～0.30%, Mo: 0.20～0.60%, V: 0.10～0.15%, the balance is Fe and inevitable impurities, smelted, cast and rough forged into billets according to the above components;

2), heating the steel billet in the step 1) at 1250-1300°C, soaking in vacuum for 4-24h, then rolling at about 1150°C, rolling for 1-6 passes, and then rapidly cooling with water at a cooling rate. At 40～50℃/s, cool to 600℃, keep for 1～2h, then cool to room temperature with the furnace;

3), rolling the high temperature heat preservation cast slab obtained in the step 2), the hot rolling reduction ratio is between 85% and 95%, the rolling temperature is 1150°C, and the rolling temperature range of 2 passes is 1080-1120℃, 3-pass rolling temperature range is 1020-1060℃, 4-pass rolling temperature range is 980-1020℃, 5-pass rolling temperature range is 940-960℃, final pass The rolling temperature is 900°C, and after water cooling to 600°C, it is coiled and cooled with the furnace to obtain ultra-high-strength ferritic steel with a tensile strength of more than 1180MP and a total elongation after fracture of more than 18%.

Preferably, the steel billet in the step 2) is heated at a high temperature of 1250°C, and after soaking for 10 hours, the high-temperature final rolling temperature is 900°C, and the coiling temperature is 600°C.

Compared with the prior art, the beneficial effects of the present invention are:

1. The present invention provides a 1180MPa nano-particle-strengthened ferritic steel, which is not only an important direction of steel material research, but also has broad application and development prospects, and is useful for improving the research level of nano-phase-strengthened steel in my country and developing new types of high-strength and high-strength steels. Tough steel grades are of great significance. The ultra-high-strength ferritic steel prepared by the present invention, while possessing ultra-high strength, has good hole-expanding performance, good toughness and excellent weldability, and can be widely used in the side center pillars of automobiles. In structural parts and steel structure projects such as edge reinforcements, suspension arms and anti-collision beams, the prospects are promising.

2. The present invention provides a preparation method of 1180MPa nanoparticle-strengthened ferritic steel. The method is simple and convenient to prepare and has strong feasibility. The present invention adopts conventional smelting and rolling equipment, and the hot rolling process is simple and feasible. Some industrial production lines can be produced on existing equipment. High-strength steel with a strength of 1180 MPa is usually prepared by multiphase structure strengthening or cold rolling process, and the present invention can be realized by alloying design + hot rolling process.

3. The present invention provides a 1180MPa nanoparticle-strengthened ferritic steel. The structure of this steel is an all-ferrite structure. Compared with martensite and bainite, ferrite is a soft phase, so all ferrite The body steel has excellent hole-expanding performance, and the steel type involved in the invention has a tensile strength of 990-1200MPa, an elongation rate of 17%-20%, and a hole-expansion rate of over 42%. Since the mass fraction of C is 0.10% to 0.15%, Si is not deliberately added, and the C element is mainly precipitated in the form of nano-particle carbides, so the welding performance is good and the mechanical properties are excellent.

Description of drawings

In order to illustrate the technical solutions of the present invention more clearly, the following briefly introduces the accompanying drawings that are used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, which are very important in the art. For those of ordinary skill, other drawings can also be obtained from these drawings without any creative effort.

Fig. 1 is the schematic diagram of heat treatment process of the present invention;

Fig. 2 is a schematic diagram of the precipitation morphology distribution of nano-sized carbides of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

Nanoparticle high-strength ferritic steel is not only an important direction of steel material research, but also has broad application and development prospects.

High-strength steels with a strength level of 1180MPa are usually prepared by multiphase structure strengthening or cold rolling process, while the highest strength of hot-rolled steels with full ferrite structure is about 1000MPa. On the other hand, by adding V element, the strength of nano-particle ferritic steel is further improved by utilizing the low-temperature precipitation strengthening effect of VC in the ferrite region, thereby preparing an ultra-high-strength nano-particle precipitation full ferritic steel.

To achieve the above object, the technical scheme of the present invention is:

A 1180MPa nanoparticle reinforced ferritic steel, characterized in that the main chemical mass percentage of the 1180MPa nanoparticle reinforced ferritic steel is as follows:

C: 0.12～0.15%, Si: 0.20～0.30%, Mn: 1.0～2.0%, P≤0.001%, S≤0.001%, N: 0.010%～0.030%, Ti: 0.12～0.30%, Mo: 0.20～ 0.60%, V: 0.10-0.15%, and the balance is Fe and inevitable impurities.

This steel is not only an important research direction of iron and steel materials, but also has broad application and development prospects, and is of great significance for improving the research level of nano-phase reinforced steel in my country and developing new types of high-strength and high-toughness steel. The ultra-high-strength iron prepared by the invention Element steel, while having ultra-high strength, has good hole expansion performance, good toughness and excellent weldability, and can be widely used in structural parts and steel such as side pillars, side reinforcements, suspension arms and anti-collision beams of automobiles. In structural engineering, the prospects are considerable;

In addition, the structure of this steel is an all-ferrite structure. Compared with martensite and bainite, ferrite is a soft phase, so all-ferritic steel has excellent hole-expanding performance. The tensile strength is 990-1200MPa, the elongation is 17%-20%, and the hole expansion rate is above 42%. Since the mass fraction of C is 0.10% to 0.15%, Si is not deliberately added, and the C element is mainly precipitated in the form of nano-particle carbides, so the welding performance is good and the mechanical properties are excellent.

Based on the same inventive concept, the present invention also provides a method for preparing 1180MPa nanoparticle-strengthened ferritic steel,

The method adopts high temperature soaking at 1250℃～1300℃, final rolling at 900℃ and low temperature coiling at 600℃, and the steps are as follows:

Step 1: Strengthen the chemical mass percentage of ferritic steel with 1180MPa nanoparticles: C: 0.12-0.15%, Si: 0.20-0.30%, Mn: 1.0-2.0%, P≤0.001%, S≤0.001%, N: 0.010%～0.030%, Ti: 0.12～0.30%, Mo: 0.20～0.60%, V: 0.10～0.15%, the balance is Fe and inevitable impurities, smelted, cast and rough forged into billets according to the above components;

Step 2: The steel billet in the step 1) is heated at 1250-1300°C, soaked in vacuum for 4-24 hours, rolled at about 1150°C, rolled for 1-6 passes, and then rapidly cooled with water at a cooling rate. At 40～50℃/s, cool to 600℃, keep for 1～2h, then cool to room temperature with the furnace;

Step 3: The high temperature heat preservation cast slab obtained in the step 2) is rolled, and the hot rolling reduction rate is between 85% and 95%. 1080-1120℃, 3-pass rolling temperature range is 1020-1060℃, 4-pass rolling temperature range is 980-1020℃, 5-pass rolling temperature range is 940-960℃, final pass The rolling temperature is 900℃;

After being water-cooled to 600°C, it is coiled and cooled with the furnace to obtain ultra-high-strength ferritic steel with a tensile strength of more than 1180MP and a total elongation after fracture of more than 18%.

Wherein, the steel billet in the step 2) is heated at a high temperature of 1250°C, and after soaking for 10 hours, the high-temperature finish rolling temperature is 900°C, and the coiling temperature is 600°C.

The preparation method of the method is simple and convenient, and the feasibility is strong. The present invention adopts conventional smelting and steel rolling equipment, and the hot rolling process is simple and feasible;

At present, most industrial production lines can be produced on existing equipment. High-strength steels with a strength of 1180 MPa are usually prepared by multiphase structure strengthening or cold rolling process, and the present invention can be realized by alloying design + hot rolling process.

Precipitation of a large number of nano-sized carbides by high-temperature coiling is the main feature of the present invention to improve the strength of the ferritic steel under the premise of ensuring the good formability of the ferritic steel itself.

The main function of each element in the present invention:

C: Strong carbide element, mainly precipitates with Ti and Mo in the form of (Ti, Mo)C in the austenite stage, the precipitated nanoparticles grow faster, while providing precipitation strengthening, it can effectively fine The austenitic grains have a great effect on the microstructure refinement of ferritic steels.

The content of carbon should not be too high. The main function of C is to precipitate in the form of nano-carbides of (Ti, Mo)C and VCN. If the content of C is too high, it is easy to form pearlite and reduce the formability of ferrite.

Si: Si is an effective solid solution strengthening element. When the Si content is too high, it will accelerate the precipitation of carbides, make the carbides coarser, and deteriorate the formability.

Mn: Mn is a solid solution strengthening element. Increasing the content can improve the strength of the steel, but when the Mn content is too high, there will be segregation or the formation of a hard phase, which will deteriorate the formability.

P: P is a solid solution strengthening element. When the content of P is too high, there will be segregation and the formability will be deteriorated.

S: S is a harmful element. The lower the S content, the better. When the S content is high, the toughness of the steel is deteriorated.

N: Generally speaking, N is a harmful element in steel, but in this patent, N is a beneficial element, mainly for precipitation strengthening with V in the form of nano-particles of VCN, which is most conducive to precipitation in the ferrite stage. When the N content is too high, the nitrides are coarsened and the formability is deteriorated.

Ti: The combination of Ti and C can form fine carbide TiC, which plays a strong role in precipitation strengthening. At the same time, at the high temperature stage of austenite, it can combine with N to form TiN, refine the austenite grains, and greatly improve the The strength of the steel will not affect the formability of the steel.

Mo: When Mo is precipitated together with Ti and C to form carbides, it can inhibit the growth and coarsening process of (Ti, Mo)C, making the precipitated carbide particles finer and making the effect of precipitation strengthening more significant.

V: and C are precipitated in the form of VCN nano-carbide, and the volume fraction of the nanoparticles is high, and the size of the nanoparticles is small, which can provide a strong precipitation effect.

Example 2

According to the chemical composition given in Table 1, an electromagnetic induction furnace is used for vacuum smelting, and the cast billet is forged into a billet for subsequent processes:

Table 1 is the mass percentage of each component

The hot rolling process is to heat the forging billet to 1250°C for 10 hours under vacuum, then hot-roll it on a 350mm two-roll hot rolling mill for 6 passes to obtain a hot-rolled sheet with a thickness of about 3 to 5 mm, with a total deformation of 93 ~95%, and the starting and finishing temperatures are 1150°C and 900°C, respectively.

After finishing rolling, it is coiled by water cooling to 600°C at a cooling rate of 40-50°C/s, and after coiling in a heating furnace at an isothermal temperature for 1-2 hours, then cooling with the furnace.

The final mechanical properties corresponding to different components are shown in Table 2:

Table 2 shows the final mechanical properties corresponding to different components

Finally, it should be noted that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention for which the application is pending.

Claims (3)

1. 1180MPa nanoparticle reinforced ferritic steel is characterized in that the 1180MPa nanoparticle reinforced ferritic steel has the following main chemical mass percentages:

c: 0.12-0.15%, Si: 0.20 to 0.30%, Mn: 1.0-2.0%, P is less than or equal to 0.001%, S is less than or equal to 0.001%, N: 0.010% -0.030%, Ti: 0.12-0.30%, Mo: 0.20-0.60%, V: 0.10 to 0.15%, and the balance of Fe and inevitable impurities.

2. The method of making a 1180MPa nano-particle strengthened ferritic steel of claim 1, wherein the method comprises the steps of:

1) the chemical mass percentage of 1180MPa nano particle reinforced ferrite steel is as follows: c: 0.12-0.15%, Si: 0.20 to 0.30%, Mn: 1.0-2.0%, P is less than or equal to 0.001%, S is less than or equal to 0.001%, N: 0.010% -0.030%, Ti: 0.12-0.30%, Mo: 0.20-0.60%, V: 0.10-0.15% of Fe and inevitable impurities in balance, and smelting, casting and rough forging the components to obtain a billet;

2) heating the steel billet in the step 1) at 1250-1300 ℃, carrying out vacuum heat preservation for 4-24 h, then carrying out rolling at about 1150 ℃, carrying out 1-6 times of rolling, then carrying out rapid water cooling at a cooling speed of 40-50 ℃/s, cooling to 600 ℃, carrying out heat preservation for 1-2 h, and then carrying out furnace cooling to room temperature;

3) and rolling the high-temperature heat-preservation casting blank obtained in the step 2), wherein the hot rolling reduction rate is 85-95%, the rolling temperature is 1150 ℃, the rolling temperature interval of 2 passes is 1080-1120 ℃, the rolling temperature interval of 3 passes is 1020-1060 ℃, the rolling temperature interval of 4 passes is 980-1020 ℃, the rolling temperature interval of 5 passes is 940-960 ℃, the rolling temperature of the final pass is 900 ℃, the steel is cooled to 600 ℃ by water and coiled, the steel is cooled along with the furnace to obtain the ultra-high-strength ferritic steel, the tensile strength of the steel is more than 1180MP, and the total elongation after fracture is more than 18%.

3. The method for preparing 1180MPa nanoparticle reinforced ferritic steel according to claim 2, wherein the billet in step 2) is heated at 1250 ℃ and soaked for 10 hours at 900 ℃ and 600 ℃ after finishing rolling.

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