CN115433882A - High-tensile-strength low-density cold-rolled thin steel strip based on sub-rapid solidification and rolling process and manufacturing method thereof - Google Patents

Abstract

The invention discloses a high tensile strength low density cold rolling thin steel strip based on a sub-rapid solidification and rolling process and a manufacturing method thereof, wherein the low density cold rolling thin steel strip comprises the following chemical components in percentage by mass: c: 0.6-1.5%, mn 16-25%, al:6% -12%, V is 0.01% -0.2%, zr: 0.01-0.5%, si 0.01-0.5%, cu:0.01% -2%, ni:0.05 to 2 percent, and the balance of Fe and impurity elements. According to the manufacturing method, complex processes such as slab heating, multi-pass repeated hot rolling and the like are omitted in the hot rolling stage, the production flow is shorter, the process cost is low, and the energy consumption and carbon emission of production are greatly reduced; the low-density cold-rolled thin steel strip manufactured by the method has the yield strength of more than 1550MPa, the tensile strength of more than 1800MPa and the elongation of more than 10 percent.

Description

A low-density cold rolling with high tensile strength based on sub-rapid solidification + rolling process Thin steel strip and manufacturing method thereof

technical field

The invention belongs to the technical field of iron and steel production, and in particular relates to a low-density cold-rolled thin steel strip with high tensile strength based on a sub-rapid solidification + rolling process and a manufacturing method thereof.

Background technique

Compared with traditional ordinary high-strength steel, the biggest advantage of advanced high-strength steel is to reduce the thickness and weight of plate construction while ensuring mechanical properties, and also has good formability, anti-collision concave, fatigue resistance, and high work hardening rate, showing good application prospects in all walks of life. Fe-Mn-C-Al series low-density steel appeared in the last century. With the deepening of research, the particularity of low-density steel was gradually discovered. First of all, the density of this steel is lower than that of other steels. Studies have shown that for every 1% increase in Al, the density of the steel can be reduced by 1.3%, and at the same time, the stacking fault energy can be significantly increased. For every 1wt% Al increase, the stacking fault energy increases by 9 ~11 mJ/m ² . The work hardening mechanism of low-density steel is not limited to the transformation-induced plasticity and twinning-induced plastic strengthening of high-manganese steel. At the same time, the dispersed distribution of nano-scale second phase κ' carbides can pin the fine grains and the microalloying of Nb, V, Ti can further strengthen its comprehensive mechanical properties, including yield strength, Tensile strength, elongation after fracture, etc. In view of the above characteristics, low-density steel is widely used in automobiles, shipbuilding industries and other fields. By reducing weight, energy consumption and exhaust emissions can be reduced.

So far, people have been seeking the balance of the three major indicators of "lightweight, strength, and toughness" of metal materials. However, strength and toughness are always mutually exclusive, and it is difficult to obtain high strength while still ensuring good plasticity. Therefore, a low-density steel plate with high strength and high plasticity is urgently needed. At present, the research on Fe-Mn-C-Al series low-density, high-strength, high-plasticity steel is mainly prepared through the traditional production process of hot rolling, annealing after hot rolling, pickling, cold rolling, and annealing after cold rolling. The process is complicated. The energy consumption and environmental pollution are relatively high, the cost is high, and the development is difficult.

Existing patent document CN111235484B discloses a kind of preparation method of high-strength high-hardness low-density steel at present, it is characterized in that the chemical composition and weight percentage of this alloy steel are C: 0.7-1.8%, Mn: 25-34%, Al: 8-12%, Si: 0.3%-0.9%, Cr: 0.3%-1.2%, V: 0.1-0.7%, Ti: 0.1%-0.8%, Mo: 0.7%-1.3%, after hot forging, After water toughening, hot rolling and solution treatment, then cold rolling and aging treatment, the tensile strength can reach 950-1127MPa, and the hardness can reach 62-68HRC. Patent document CN104711494A discloses a high-strength and high-plastic NiAl reinforced low-density steel, which is characterized in that the chemical composition of the alloy steel is C: 0.5-1.5%, Mn: 10-30%, Al: 5-12 %, Ni: 5-15%, the tensile strength reaches above 1350MPa, and the elongation reaches above 10%. Patent document CN108779528B discloses a high-ductility, low-density, high-strength austenitic steel strip, which is characterized in that the chemical composition weight percent of the alloy steel is C: 0.65-0.9%, Mn: 5.0-20%, Al: 5.5 -11%, 0<Si≤0.15%, 0<Cu≤0.34%, 0<Cr≤0.14%, while adding one or more microalloying elements such as V, Ti, Nb, V, Zr, the steel The tensile strength is ≥800MPa, the elongation is ≥25%, and the density is ≤7.3kg/m ³ .

The manufacturing methods of steel products published in the above patent documents all adopt the traditional continuous rolling process, which has long process flow, high energy consumption, many unit equipment, high infrastructure cost, high overall production cost, and segregation is easy to occur in the casting process due to high alloying elements , The rolling force in the rolling process is large, hot rolling and cold rolling are easy to form cracks, the development is difficult, and the development of thin steel strips with high tensile strength and high elongation is even more difficult.

Contents of the invention

The purpose of the present invention is to overcome the defects in the prior art, and provide a low-density cold-rolled thin steel strip with high tensile strength based on sub-rapid solidification+rolling process and its manufacturing method. The manufacturing method of the present invention, thermal In the rolling stage, complex processes such as slab heating and multi-pass repeated hot rolling are omitted, and only sub-rapid solidification + 20-50% reduction in a single pass is followed by cold rolling. The production process is shorter and the process cost is lower. Low, the energy consumption and carbon emissions of production are greatly reduced; in the casting stage, due to the thinner cast strip thickness and faster solidification speed, there is no obvious central P segregation zone and long strip MnS inclusion zone in the thin strip steel , showing higher toughness, which is conducive to subsequent cold deformation processing; the low-density cold-rolled thin steel strip manufactured by the method of the present invention has a yield strength of more than 1550 MPa, a tensile strength of more than 1800 MPa, and an elongation of more than 10%.

In order to achieve the above object, the technical solution of the present invention is to design a low-density cold-rolled thin steel strip with high tensile strength based on sub-rapid solidification+rolling process, and its chemical composition and mass percentage are: C: 0.6%-1.5 %, Mn: 16%-25%, Al: 6%-12%, V: 0.01%-0.2%, Zr: 0.01%-0.5%, Si: 0.01%-0.5%, Cu: 0.01%-2%, Ni: 0.05%-2%, the balance is Fe and impurity elements.

The preferred technical solution is that the chemical composition and mass percentage of the impurity elements meet the requirements of P≤0.06%, S≤0.002%, and N≤0.003%.

Correspondingly, the present invention also discloses a method for manufacturing a high-tensile-strength low-density cold-rolled thin steel strip based on a sub-rapid solidification+rolling process, comprising the following steps:

S1: Prepare molten steel by smelting according to the above chemical composition and mass percentage;

S2: preparing the molten steel prepared in step S1 into a cast strip through sub-rapid solidification;

S3: preparing the cast strip prepared in step S2 into a thin steel strip through one pass of hot rolling;

S4: cooling the thin steel strip prepared in step S3 to 600° C. to 800° C. through an air mist cooling system;

S5: solution-treating the thin steel strip prepared in step S4 at a temperature of 900°C to 1150°C for 1 to 3 hours, then performing cold rolling with a reduction of 20% to 50%, and aging at a temperature of 650°C to 850°C Cool in air after 10-12 hours of treatment;

Wherein, the yield strength of the low-density cold-rolled thin steel strip manufactured by the manufacturing method is above 1550 MPa, and the tensile strength is above 1800 MPa.

The preferred technical solution is that in the step S2, the specific operation is as follows: the molten steel prepared in the step S1 is solidified into a casting belt through a single-roll melt rotation method, and the thickness of the casting belt is 1.4-2.5 mm.

The preferred technical solution is also that in the step S3, in the step S3, the hot rolling reduction in one pass is 20%-50%, the thickness of the thin steel strip is 0.8-1.9mm, and the width is 60mm- 150mm.

In a preferred technical solution, in the step S3, the temperature at the exit of the hot rolling is 850°C to 1050°C.

A further preferred technical solution is that the metallographic structure of the low-density cold-rolled thin steel strip produced by the manufacturing method is austenite and precipitated phases, the thickness of the cold-rolled thin steel strip is 0.5-1.0mm, and the elongation is More than 10%, the density is 6.5-7.2g/cm ³ .

Advantage and beneficial effect of the present invention are:

1. The process of developing low-density steel using traditional production techniques is complex and extremely difficult. The manufacturing method of the present invention produces hot-rolled steel strips through a sub-rapid solidification + one-pass hot-rolling process and then cold-rolls to reduce the production difficulty of low-density steel. No relevant production process reports have been seen before.

2. In the hot rolling stage of the manufacturing method of the present invention, complex processes such as slab heating and multi-pass repeated hot rolling are omitted, and cold rolling is carried out only through sub-rapid solidification + hot rolling with a reduction of 20-50% in a single pass. Rolling, the production process is shorter, the process cost is low, and the energy consumption and carbon emissions of production are greatly reduced.

3. In the casting stage of the low-density cold-rolled thin steel strip of the present invention, since the thickness of the cast strip is relatively thin and the solidification speed is fast, there is no obvious central P segregation zone and strip-shaped MnS inclusion zone in the thin strip steel, showing Higher toughness, which is beneficial to subsequent cold deformation processing.

4. In the traditional hot rolling process, alloying elements are precipitated during the cooling process of the slab. When the slab is reheated, the utilization rate of the alloying elements is often reduced due to insufficient remelting of the alloying elements; in the sub-rapid solidification process of the manufacturing method of the present invention, casting With direct hot rolling, the added alloy elements mainly exist in solid solution state, which can improve the utilization rate of the alloy.

5. The low-density cold-rolled thin steel strip of the present invention has a metallographic structure of austenite and precipitated phases, and has excellent high tensile properties: the yield strength is above 1550MPa, the tensile strength is above 1800MPa, and the elongation is 10% above.

detailed description

The specific implementation of the present invention will be further described below in conjunction with the examples. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

Example 1

Adopt the inventive method to manufacture a kind of high tensile strength low-density cold-rolled thin steel strip based on sub-rapid solidification+rolling process, comprising the steps:

S1: According to chemical composition and mass percentage: C: 1.1%, Mn: 21%, Al: 9.8%, V: 0.15%, Si: 0.5%, Ni: 1.5%, Zr: 0.15%, Cu: 1.5%, P: 0.06%, S: 0.002%, N: 0.003%, the balance is Fe and unavoidable impurity elements, smelting and preparing molten steel with qualified components;

S2: cast the molten steel qualified in step S1 into a cast strip with a thickness of 1.9mm by rotating a single-roller melt, and the temperature of the molten steel is about 1500°C;

S3: the cast strip prepared in step S2 is prepared into a thin steel strip through one hot rolling with a reduction of 40%, and the temperature of the thin steel strip after hot rolling is 950° C.;

S4: cooling the thin steel strip prepared in step S3 to 730° C. through air mist;

S5: solution-treating the thin steel strip prepared in step S4 at a temperature of 1000° C. for 1.5 hours, then performing cold rolling with a reduction of 40%, aging at a temperature of 650° C. for 10 hours, and then air-cooling;

The low-density cold-rolled thin steel strip produced by the manufacturing method has a width of 60 mm, a thickness of 0.75 mm, a density of 6.8 g/cm ³ , a yield strength of 1570 MPa, a tensile strength of 1800 MPa and an elongation of 16%.

Example 2

Adopt the inventive method to manufacture a kind of high tensile strength low-density cold-rolled thin steel strip based on sub-rapid solidification+rolling process, comprising the steps:

S1: According to chemical composition and mass percentage: C: 1.2%, Mn: 22%, Al: 10.2%, V: 0.15%, Zr: 0.15%, Cu: 1.5%, Si: 0.3%, Ni: 1.5%, P: 0.06%, S: 0.002%, N: 0.003%, the balance is Fe and unavoidable impurity elements, smelting and preparing molten steel with qualified components;

S2: cast the molten steel qualified in step S1 into a cast strip with a thickness of 1.9mm by rotating a single-roller melt, and the temperature of the molten steel is about 1540°C;

S3: The cast strip prepared in step S2 is prepared into a thin steel strip through one hot rolling with a reduction of 40%, and the temperature of the thin steel strip after hot rolling is 1000° C.;

S4: cooling the thin steel strip prepared in step S3 to 710° C. through air mist;

S5: solution-treating the thin steel strip prepared in step S4 at a temperature of 1050° C. for 2 hours, then performing cold rolling with a reduction of 40%, aging at a temperature of 750° C. for 11 hours, and then air-cooling;

The low-density cold-rolled thin steel strip produced by the manufacturing method has a width of 80mm, a thickness of 0.70mm, a density of 6.8g/cm ³ , a yield strength of 1590MPa, a tensile strength of 1827Mpa and an elongation of 16%.

Example 3

Adopt the inventive method to manufacture a kind of high tensile strength low-density cold-rolled thin steel strip based on sub-rapid solidification+rolling process, comprising the steps:

S1: According to chemical composition and mass percentage: C: 1.2%, Mn: 22%, Al: 10.2%, V: 0.15%, Si: 0.5%, Ni: 2.0%, Zr: 0.15%, Cu: 1.5%, P: 0.06%, S: 0.002%, N: 0.003%, the balance is Fe and unavoidable impurity elements, smelting and preparing molten steel with qualified components;

S2: cast the molten steel qualified in step S1 into a cast strip with a thickness of 1.9mm by rotating a single-roller melt, the casting and rolling speed is 85m/min, and the temperature of the molten steel is about 1555°C;

S3: The cast strip prepared in step S2 is prepared into a thin steel strip through one hot rolling with a reduction of 45%, and the temperature of the thin steel strip after hot rolling is 870° C.;

S4: cooling the thin steel strip prepared in step S3 to 860° C. through air mist;

S5: solution-treating the thin steel strip prepared in step S4 at a temperature of 1050° C. for 2.0 hours, then performing cold rolling with a reduction of 40%, aging at a temperature of 700° C. for 11 hours, and then air-cooling;

The low-density cold-rolled thin steel strip manufactured by the manufacturing method has a width of 70mm, a thickness of 0.65mm, a density of 6.8g/cm ³ , a yield strength of 1610MPa, a tensile strength of 1842Mpa and an elongation of 15%.

Example 4

Adopt the inventive method to manufacture a kind of high tensile strength low-density cold-rolled thin steel strip based on sub-rapid solidification+rolling process, comprising the steps:

S1: According to chemical composition and mass percentage: C: 1.2%, Mn: 22%, Al: 10.2%, V: 0.15%, Si: 0.5%, Ni: 2.0%, Zr: 0.15%, Cu: 1.5%, P: 0.06%, S: 0.002%, N: 0.003%, the balance is Fe and unavoidable impurity elements, smelting and preparing molten steel with qualified components;

S2: cast the molten steel qualified in step S1 into a cast strip with a thickness of 1.9 mm by rotating a single-roller melt, the casting and rolling speed is 75 m/min, and the temperature of the molten steel is about 1550 ° C;

S3: The cast strip prepared in step S2 is processed into a thin steel strip by hot rolling with a reduction rate of 45% in one pass, and the temperature of the thin steel strip after hot rolling is 950° C.;

S4: cooling the thin steel strip prepared in step S3 to 750° C. through gas mist;

S5: solution-treating the thin steel strip prepared in step S4 at a temperature of 1100° C. for 2.0 hours, then performing cold rolling with a reduction of 45%, aging at a temperature of 700° C. for 11 hours, and then air-cooling;

The low-density cold-rolled thin steel strip manufactured by the manufacturing method has a width of 60mm, a thickness of 0.60mm, a density of 6.8g/cm ³ , a yield strength of 1620MPa, a tensile strength of 1860Mpa and an elongation of 15%.

Example 5

Adopt the inventive method to manufacture a kind of high tensile strength low-density cold-rolled thin steel strip based on sub-rapid solidification+rolling process, comprising the steps:

S1: According to chemical composition and mass percentage: C: 1.0%, Mn: 21%, Al: 10.5%, V: 0.2%, Si: 0.5%, Ni: 1.5%, Zr: 0.20%, Cu: 1.5%, P: 0.06%, S: 0.002%, N: 0.003%, the balance is Fe and unavoidable impurity elements, smelting and preparing molten steel with qualified components;

S2: cast the molten steel qualified in step S1 into a cast strip with a thickness of 1.9mm by rotating a single-roller melt, the casting and rolling speed is 75m/min, and the temperature of the molten steel is about 1500°C;

S3: The cast strip prepared in step S2 is processed into a thin steel strip by hot rolling with a reduction rate of 45% in one pass, and the temperature of the thin steel strip after hot rolling is 950° C.;

S4: cooling the thin steel strip prepared in step S3 to 730° C. through air mist;

S5: solution-treating the thin steel strip prepared in step S4 at a temperature of 1100° C. for 3.0 hours, then performing cold rolling with a reduction of 50%, aging at a temperature of 800° C. for 10 hours, and then air-cooling;

The low-density cold-rolled thin steel strip produced by the manufacturing method has a width of 80mm, a thickness of 0.55mm, a density of 6.8g/cm ³ , a yield strength of 1650MPa, a tensile strength of 1878Mpa and an elongation of 14%.

The metallographic structures of the low-density cold-rolled thin steel strips prepared in Examples 1-5 are all austenite and precipitated phases.

In the manufacturing method of the present invention, complex processes such as slab heating and multi-pass repeated hot rolling are omitted in the hot rolling stage, and only sub-rapid solidification + 20-50% reduction in a single pass is followed by cold rolling to produce The process is shorter, the process cost is low, and the energy consumption and carbon emissions of production are greatly reduced; in the casting stage, due to the thinner cast strip thickness and faster solidification speed, there is no obvious central P segregation zone and long The strip-shaped MnS inclusion belt shows higher toughness, which is beneficial to subsequent cold deformation processing; the low-density cold-rolled thin steel strip manufactured by the method of the present invention has a yield strength of more than 1550MPa, a tensile strength of more than 1800MPa, and an elongation more than 10%.

The role of each element in high strength, high plasticity and low density steel is as follows:

C: The role of C element is mainly to form κ'-carbides with Mn and Al elements, forming precipitation strengthening and dispersion strengthening, and improving the strength of steel. C is an austenite forming element, which can promote the formation of austenite and at the same time Reduce the density of steel, but too much C content will form too many κ'-carbides, which will adversely affect the elongation of the alloy.

Mn: Mn element is an austenite forming element, which can promote the formation of austenite, which is very beneficial to the strong plasticity of steel, and Mn element can form κ'-carbide with C and Al elements, through precipitation strengthening and dispersion The strengthening effect further improves the strong plasticity of the steel. The density of the Mn element is slightly lower than that of the Fe element, which will not increase the density of the steel. At the same time, the Mn element is relatively cheap. However, excessive addition of the Mn element will cause the steel to precipitate a large amount of β during the aging process. -Mn phase, which is a hard phase, will greatly reduce the plasticity of steel, therefore, the content of Mn is controlled within a range, and the content of the present invention is 16%-25%.

Al: Al element will greatly reduce the density of steel, form κ'-carbide with C and Mn elements, and further improve the strong plasticity of steel through precipitation strengthening and dispersion strengthening, but too high Al content will increase the cost of steel, therefore, The control of Al content is within a range, and the content of the present invention is 6%-12%.

V: The V element can effectively improve the strength and toughness of the steel by forming carbonitrides in the steel grade, and can dissolve more V elements under sub-rapid solidification conditions, which is beneficial to better precipitation in the later stage and better precipitation. The effect of strengthening, on the one hand, adding V will increase the cost, on the other hand, V will precipitate on the grain boundary and cause cracks on the steel strip. Therefore, the concentration of V is controlled at 0.01%-0.2%.

Zr: The Zr element can remove the N element in the steel and inhibit the formation of AlN. Under sub-rapid solidification conditions, Zr can better play a role in refining grains. However, Zr element is relatively expensive and increases the cost of steel. Therefore, the content of Zr element is controlled at 0.01%-0.5%.

Si: Si element can deoxidize, Si element can also reduce the specific gravity of steel, and more Si element can be dissolved under sub-rapid solidification conditions, which can better achieve the effect of solid solution strengthening and improve the strength of steel, but the silicon content Too high will reduce the weldability of steel, therefore, allow the maximum content of Si to be 0.5%.

Cu: Cu elements can stabilize austenite, and Cu elements are cheaper than Ni elements, and more Cu elements can be dissolved under sub-rapid solidification conditions, reducing the segregation of Cu elements, reducing the tendency of cracking, and better achieving solid solution strengthening However, if the Cu content is too high, the cost will increase and the rolling process will be more prone to cracking. Therefore, the Cu concentration must be within 0.01%-2%.

Ni: Ni element can stabilize austenite and increase stacking fault energy. Ni concentrated on the surface of steel can also improve the corrosion resistance and oxidation resistance of steel, and can inhibit the absorption of H in the corrosion process. Under sub-rapid solidification conditions Under this condition, more Ni elements can be dissolved, and the effect of solid solution strengthening can be better achieved. Therefore, the added content of Ni is within 0.05%-2%.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (7)

1. A low-density cold-rolled thin steel strip with high tensile strength based on sub-rapid solidification+rolling process, characterized in that its chemical composition and mass percentages are: C: 0.6%-1.5%, Mn: 16% -25%, Al: 6%-12%, V: 0.01%-0.2%, Zr: 0.01%-0.5%, Si: 0.01%-0.5%, Cu: 0.01%-2%, Ni: 0.05%-2 %, the balance is Fe and impurity elements. 2. The low-density cold-rolled thin steel strip with high tensile strength based on sub-rapid solidification+rolling process as claimed in claim 1, characterized in that, the chemical composition and mass percentage of impurity elements meet P≤0.06%, S ≤0.002%, N≤0.003%. 3. a kind of manufacturing method of the low-density cold-rolled thin strip of high tensile strength based on sub-rapid solidification+rolling process as claimed in claim 1 or 2, is characterized in that, comprises the steps: S1: preparing molten steel by smelting according to the chemical composition and mass percentage described in claim 1 or 2; S2: preparing the molten steel prepared in step S1 into a cast strip through sub-rapid solidification; S3: preparing the cast strip prepared in step S2 into a thin steel strip through one pass of hot rolling; S4: cooling the thin steel strip prepared in step S3 to 600° C. to 800° C. through an air mist cooling system; S5: solution-treating the thin steel strip prepared in step S4 at a temperature of 900°C to 1150°C for 1 to 3 hours, then performing cold rolling with a reduction of 20% to 50%, and aging at a temperature of 650°C to 850°C Cool in air after 10-12 hours of treatment; Wherein, the yield strength of the low-density cold-rolled thin steel strip manufactured by the manufacturing method is above 1550 MPa, and the tensile strength is above 1800 MPa. 4. the manufacturing method of the high tensile strength low-density cold-rolled thin steel strip based on sub-rapid solidification+rolling process as claimed in claim 3, is characterized in that, in described step S2, specific operation is: The molten steel prepared in step S1 is solidified into a cast strip through the method of rotating a single-roll melt, and the thickness of the cast strip is 1.4-2.5 mm. 5. the manufacturing method of the high tensile strength low-density cold-rolled thin steel strip based on sub-rapid solidification+rolling process as claimed in claim 3, it is characterized in that, in described step S3, one hot rolling press The lower amount is 20%-50%, the thickness of the thin steel strip is 0.8-1.9mm, and the width is 60mm-150mm. 6. the manufacturing method of the low-density cold-rolled thin strip of high tensile strength based on sub-rapid solidification+rolling process as claimed in claim 3, it is characterized in that, in described step S3, hot-rolling finishing rolling temperature It is 850°C to 1050°C. 7. the method for manufacturing the low-density cold-rolled thin steel strip based on sub-rapid solidification+rolling process as described in any one of claims 3 to 6, characterized in that, the The metallographic structure of the low-density cold-rolled thin steel strip is austenite and precipitated phases. The thickness of the cold-rolled thin steel strip is 0.5-1.0mm, the elongation is over 10%, and the density is 6.5-7.2g/cm ³ .