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CN-121976113-A - High-strength hot rolled steel and preparation method thereof

CN121976113ACN 121976113 ACN121976113 ACN 121976113ACN-121976113-A

Abstract

The invention discloses a high-strength hot rolled steel and a preparation method thereof, wherein the high-strength hot rolled steel comprises the following components ：C：0.06%-0.09%,Si：0.05%-0.15%,Mn：1.8%-2.0%,P≤0.015%,S≤0.002%,Ti：0.11%-0.145%,Cr：0.1%-0.2%,Nb：0.04%-0.05%,V：0.01%-0.02%,N≤0.005%. by mass percent, wherein the preparation method comprises the steps of smelting and casting raw materials to obtain a plate blank, and heating, rolling, cooling, coiling and slow cooling the plate blank. Under the condition of completely containing no molybdenum, the high-strength hot rolled steel plate with the thickness of 9mm-14mm, the yield strength of more than or equal to 700MPa, the tensile strength of more than or equal to 770MPa, the elongation after fracture of more than or equal to 16 percent and the transverse impact energy of more than or equal to 70J at minus 20 ℃ is successfully produced.

Inventors

  • GUO QINGXIAN
  • Tan Dajin
  • LIANG LIANG
  • WANG HONGBING
  • LIANG WEN
  • XU BO
  • ZHANG HEXIONG
  • ZHOU JIANFENG
  • HUANG XIAOFENG
  • CHEN MINGRUI

Assignees

  • 湖南华菱涟源钢铁有限公司
  • 湖南华菱涟钢特种新材料有限公司

Dates

Publication Date
20260505
Application Date
20260210

Claims (10)

  1. 1. The preparation method of the high-strength hot rolled steel is characterized by comprising the following steps: Providing raw materials, and sequentially carrying out converter smelting, LF refining treatment and vacuum degassing to obtain refined molten steel, wherein the refined molten steel comprises the following components in percentage by mass: C：0.06%-0.09%,Si：0.05%-0.15%,Mn：1.8%-2.0%,P≤0.015%,S≤0.002%,Ti：0.11%-0.145%,Cr：0.1%-0.2%,Nb：0.04%-0.05%,V：0.01%-0.02%,N≤0.005% The balance of Fe and unavoidable impurity elements Casting the refined molten steel to obtain an alloy plate blank; And the alloy slab is subjected to heating treatment, rolling treatment, cooling treatment, coiling treatment and slow cooling treatment in sequence to obtain the high-strength hot rolled steel.
  2. 2. The preparation method of the high-strength hot rolled steel according to claim 1, wherein the vacuum degassing comprises the steps of ensuring that the minimum vacuum degree of a vacuum degassing furnace before treatment is less than or equal to 133Pa, blowing argon into 12 small pipes for 18-30min, prohibiting oxygen blowing in the treatment process, prohibiting adding alloy and slag in 6min before the vacuum degassing furnace breaks, and ensuring that the sedation time after molten steel breaking is more than or equal to 15min.
  3. 3. The method for preparing the high-strength hot-rolled steel according to claim 1, wherein the converter smelting comprises the steps of removing easily-oxidized elements including at least one of carbon, silicon and manganese by one-time oxygen blowing, adding 200-2000Kg of active lime for slag washing, and deoxidizing and alloying by adopting alloy or aluminum iron and the like, wherein the argon station temperature is more than or equal to 1534 ℃; the LF refining treatment comprises the steps of making yellow slag or yellow white slag, adding lime in an amount of more than or equal to 1000kg, keeping the time from the formation of the yellow white slag to the calcium treatment for more than or equal to 15min, prohibiting aluminum addition within 5min before the calcium treatment, and carrying out soft blowing for more than or equal to 6min after the calcium treatment.
  4. 4. The method for producing high-strength hot-rolled steel according to claim 1, wherein the casting treatment comprises a pulling rate control range of not less than 0.8/min, a tundish molten steel level of 1000.+ -.100 mm, a dynamic soft reduction, a casting blank center segregation of not more than 1.0 level, a center porosity of not more than 1.0 level, and a middle crack of not more than 1.5 level.
  5. 5. The method for producing a high-strength hot-rolled steel according to claim 1, wherein the rolling treatment comprises rough rolling and finish rolling performed in sequence; The rough rolling comprises the steps of adopting 5-7 times of rolling, wherein the rolling reduction rate of the first time is more than or equal to 18%, the rolling reduction rate of the last time is more than or equal to 24%, the initial rolling temperature is 1230-1260 ℃, and the final cooling temperature is 1030-1080 ℃; the finishing rolling comprises the steps of adopting 7 frames for continuous rolling, wherein the descaling pressure of a finishing rolling inlet is more than or equal to 18MPa, the inlet temperature of the initial rolling is less than or equal to 990 ℃, the reduction rate of the final pass is more than or equal to 10%, and the final cooling temperature is 825-855 ℃.
  6. 6. The method for producing high-strength hot-rolled steel according to claim 1, wherein the cooling treatment comprises an ultrafast cooling treatment and a layer cooling treatment which are sequentially performed, the cooling rate of the ultrafast cooling treatment is 80 ℃ to 200 ℃ per second, the cooling rate of the layer cooling treatment is not less than 15 ℃ per second, and the end temperature of the cooling treatment is 560 ℃ to 600 ℃.
  7. 7. The method according to claim 1, wherein the target coiling temperature of the coiling treatment is 560 ℃ to 600 ℃, and the coiling temperature of the head region and the tail region formed by extending the two ends of the steel material 10m toward the middle of the steel material respectively is controlled to be 20 ℃ to 30 ℃ higher than the target coiling temperature during the coiling treatment.
  8. 8. The method for producing high-strength hot-rolled steel according to claim 1, wherein the slow cooling treatment is performed by means of a concentrated stack cooling in a pit.
  9. 9. The method for producing high-strength hot-rolled steel according to claim 1, wherein the heating treatment is performed in a heating furnace having a holding temperature of 1230 ℃ to 1300 ℃ and a holding time of 20min to 100min, and the total in-furnace time of the alloy slab is 170min to 400min and a tapping temperature of 1230 ℃ to 1260 ℃.
  10. 10. A high strength hot rolled steel, characterized by being produced by the production method of the high strength hot rolled steel according to any one of claims 1 to 9.

Description

High-strength hot rolled steel and preparation method thereof Technical Field The invention belongs to the technical field of metallurgy, and particularly relates to a high-strength hot rolled steel and a preparation method thereof. Background The steel material is a key basic material in the fields of engineering machinery, heavy transportation equipment, large building structures and the like. With the increasing demands of light equipment, severe service environment and full life cycle cost control, the market has raised requirements on high-strength hot rolled steel plates, namely, not only the yield strength of 700MPa level is required to be achieved, but also excellent plasticity, excellent low-temperature impact toughness (especially transverse toughness), good welding performance and engineering applicability are required to be achieved. At present, the hot rolled steel with the strength of 700MPa and above is realized, and the conventional technical route adopted generally mainly depends on adding noble alloy elements such as carbon (C), molybdenum (Mo), vanadium (V) and the like with higher content. Although increasing the carbon content can effectively improve the strength, the weldability, formability and low-temperature toughness of the steel are often impaired. While the molybdenum element has obvious contribution to improving hardenability and strength, the alloy cost can be greatly increased, and the large-scale popularization and application of materials are not facilitated. In addition, for steel sheets having a large thickness (for example, 8mm or more), it has been a major challenge in the production process to ensure the refinement of the core structure, to suppress center segregation, and to ensure uniformity of mechanical properties (particularly, low-temperature toughness) in the thickness direction and the width direction during rolling and cooling. Therefore, the prior art scheme has a prominent contradiction that how to develop a hot rolled steel plate suitable for thicker specifications (such as 9mm-14 mm) on the premise of obviously reducing the alloy cost (especially completely discarding expensive molybdenum element) and strictly controlling the carbon content, so that the comprehensive performance of the hot rolled steel plate simultaneously meets the performance requirements of high strength (the yield strength is more than or equal to 700 MPa), high elongation (the elongation after fracture is more than or equal to 16%) and excellent low-temperature toughness (-20 ℃ transverse impact power KV2 is more than or equal to 70J), and becomes a key problem to be broken through in the industry. Disclosure of Invention Aiming at solving the technical problems that the high-strength hot rolled steel in the common technology is difficult to achieve low alloy cost, carbon content control, thicker specification, high strength, high elongation and excellent low-temperature toughness, the invention provides a preparation method of the high-strength hot rolled steel, which comprises the following steps: Providing raw materials, and sequentially carrying out converter smelting, LF refining treatment and vacuum degassing to obtain refined molten steel, wherein the refined molten steel comprises the following components in percentage by mass: C：0.06%-0.09%,Si：0.05%-0.15%,Mn：1.8%-2.0%,P≤0.015%,S≤0.002%,Ti：0.11%-0.145%,Cr：0.1%-0.2%,Nb：0.04%-0.05%,V：0.01%-0.02%,N≤0.005% And the balance of Fe and unavoidable impurity elements. Casting the refined molten steel to obtain an alloy plate blank; And the alloy slab is subjected to heating treatment, rolling treatment, cooling treatment, coiling treatment and slow cooling treatment in sequence to obtain the high-strength hot rolled steel. Further, the vacuum degassing comprises the steps that the minimum vacuum degree of the vacuum degassing furnace before treatment is less than or equal to 133Pa, the number of argon blowing small pipes is more than 12, the circulation time is 18-30min, oxygen blowing is forbidden in the treatment process, alloy and slag charge are forbidden to be added in 6min before the vacuum degassing furnace breaks, and the sedation time after molten steel breaks the air is more than or equal to 15min. Further, the converter smelting comprises the steps of removing easily-oxidized elements including at least one of carbon, silicon and manganese by one-time oxygen blowing, adding 200-2000Kg of active lime for slag washing, and deoxidizing and alloying by adopting alloy or aluminum iron and the like, wherein the argon station temperature is more than or equal to 1534 ℃; the LF refining treatment comprises the steps of making yellow slag or yellow white slag, adding lime in an amount of more than or equal to 1000kg, keeping the time from the formation of the yellow white slag to the calcium treatment for more than or equal to 15min, prohibiting aluminum addition within 5min before the calcium treatment, and carrying out soft blowing f