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CN-118932254-B - Q690D high-strength steel and preparation method thereof

CN118932254BCN 118932254 BCN118932254 BCN 118932254BCN-118932254-B

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a Q690D high-strength steel plate and a preparation method thereof. According to the invention, by controlling the alkalinity of LF final slag and the CaO/Al 2 O 3 ratio, and formulating a reasonable argon blowing system, the adsorption efficiency of LF to inclusions is improved, meanwhile, the RH calcium treatment time and the calcium wire addition are controlled, the castability and the inclusion removal efficiency are both considered, the molten steel cleanliness is improved, the total amount of inclusions and large-size inclusions are reduced, the D-class inclusions and the Ds-class inclusions in rolled materials are all <1.0 level, and the flaw detection qualification rate of the steel plate is improved to more than 99.9%.

Inventors

  • LI PING
  • LI SIJUN
  • ZHOU HAO
  • LIU ZHIGUANG
  • WU XUPENG
  • HU BIN
  • ZOU CHUNFENG
  • FU CHANGWEI
  • HAO SHUAI
  • Du jinke

Assignees

  • 山东钢铁股份有限公司

Dates

Publication Date
20260512
Application Date
20240816

Claims (9)

  1. 1. The Q690D high-strength steel plate is characterized by comprising the following chemical components in percentage by weight, wherein the chemical components comprise ：C：0.14-0.2%、Si：0.2-0.4%、Mn：1.1-1.6%、P≤0.015%、S≤0.005%、Cr：0.1-0.4%、Nb：0.01-0.04%、Ti：0.01-0.03%、Mo：0.1-0.4%、Als:0.01-0.045%、B：0.001-0.003%、CEV≤0.62, parts of iron and unavoidable impurities in balance; the preparation method of the Q690D high-strength steel plate comprises the following steps: 1) Smelting in a converter: the content of C at the smelting end point is controlled to be 0.05-0.09%, the tapping temperature is controlled to be 1630-1650 ℃, and the alkalinity of the final slag is controlled to be 3.0-4.0; the molybdenum oxide briquette is arranged at the front part of the waste steel hopper and added together with the waste steel; 2) LF refining: The final slag alkalinity is controlled to be 5-6, the refined slag CaO/Al 2 O 3 is controlled to be 1.8-2.0, and the slag thickness is 110-120mm; 3) RH refining: After RH treatment, feeding a nano high-calcium wire 70-80 m/furnace, wherein the soft blowing time is 10-12min, the slag thickness is 100-120mm, and the T.Ca content in steel is controlled at 8-10 ppm; 4) Continuous casting: The crystallizer adopts non-sinusoidal vibration, the liquidus temperature is 1510-1520 ℃, the superheat degree of the tundish is controlled according to 20-30 ℃, and the pulling speed is 1.1-1.4m/min; 5) Rolling: heating the continuous casting blank, wherein the tapping temperature is 1180-1210 ℃, the heating rate is 8-10min/cm, and the furnace time is 210-230min; rough rolling, namely rough rolling initial rolling temperature is 1140-1170 ℃ and rough rolling final rolling temperature is 1050-1120 ℃; finish rolling, namely, finish rolling is carried out at a finish rolling start temperature of 890-950 ℃ and finish rolling finish temperature of 810-860 ℃; cooling, namely cooling the temperature of 770-820 ℃ at the inlet, 670-700 ℃ at the outlet and controlling the cooling speed at 5-10 ℃ per second; 6) And (3) heat treatment: the quenching heating temperature is 900-920 ℃, the heat preservation time is 7-13min, the tempering heating temperature is 510-530 ℃, and the heat preservation time is 15-25min.
  2. 2. The Q690D high strength steel sheet according to claim 1, wherein in step 1), alloying is performed using silicon manganese, high carbon ferromanganese, medium carbon ferrochromium, ferroniobium in amounts of 14.15-16.18kg/t steel, 2.65-4.65kg/t steel, 2.6-3.5kg/t steel, 0.23-0.31kg/t steel, and the alloy is added in alignment with the steel flow impact zone when the steel is put one fifth to three quarters.
  3. 3. The Q690D high-strength steel plate according to claim 1, wherein the weight ratio of the chemical components of the molybdenum oxide briquette is 48-55% of Mo, less than or equal to 0.1% of Si and less than or equal to 0.05% of P.
  4. 4. The Q690D high-strength steel plate according to claim 1, wherein in the step 2), the LF refining adopts full bottom blowing argon stirring, the argon flow in the early stage of strong stirring and shell breaking is 500-750L/min, the argon blowing stirring time is 2-3min, the argon flow in the electrified slag adding and white slag making stage is 100-200L/min, the argon flow in the white slag refining and fine-tuning component stage is 100-180L/min, the argon flow is 50-70L/min, and the soft blowing time is 5-7min.
  5. 5. The Q690D high strength steel sheet according to claim 1, wherein in step 3), RH is used in the present treatment mode, the dip tube is inserted to a depth of 400mm, the vacuum degree is 120 to 133Pa and the holding time is 15 to 20min, and the pure degassing time is 10 to 15min.
  6. 6. The Q690D high strength steel sheet according to claim 1, wherein in step 4), during the continuous casting, the whole process protection casting is adopted, the argon sealing flow of the ladle is 90-100L/min, the liquid surface of the tundish is covered with carbonized rice husk, and the adding amount is 1-1.5kg/t steel.
  7. 7. The Q690D high strength steel sheet according to claim 1, wherein in step 4), the continuous casting billet is cooled down slowly to 400 ℃ or below by stack cooling.
  8. 8. The Q690D high-strength steel sheet according to claim 1, wherein in step 5), the total rolling passes are 12 to 16 passes, the rough rolling total rolling passes are 5 to 7 passes, the finish rolling total rolling passes are 7 to 9 passes, and the rolling thickness is 24.7 to 25.05mm.
  9. 9. The Q690D high-strength steel sheet according to claim 1, wherein the steel sheet obtained has a yield strength of 720-790MPa, a tensile strength of 770-940MPa, an elongation after break of 14.5-19.5%, an impact energy of-20 ℃ of 114-252J, and both D-class and Ds-class inclusions in the rolled material <1.0 grade.

Description

Q690D high-strength steel and preparation method thereof Technical Field The invention belongs to the technical field of metallurgy, and particularly relates to Q690D high-strength steel and a preparation method thereof. Background Q690D steel is low alloy high strength steel with yield strength of 690MPa, is widely applied to various fields such as ocean engineering, oil and gas pipelines, buildings, bridges, energy sources, engineering machinery and the like, and is generally required to be delivered in a flaw detection or flaw detection and heat treatment state, but flaw detection failure often occurs, and steel plate delivery and subsequent product orders are affected. Most typical flaw detection is not suitable for abnormal nonmetallic inclusion in a steel plate, the inclusion has different properties from steel, the behavior is inconsistent in the processing stress process, stress concentration is generated around the inclusion, microcracks are easy to generate, and the flaw detection is not suitable. Chinese patent application CN 117187695A is a Q690D high-strength steel plate and a preparation method thereof. The Q690D high-strength steel plate comprises the following chemical components in percentage by weight, wherein the balance of ：C：0.06-0.2％、Si：0.1-0.6％、Mn：0.8-2.0％、P≤0.03％、S≤0.02％、Nb：0.01-0.05％、V：0.08-0.12％、N：0.01-0.02％、Ni：0.2-0.3％、Cr：0.3-0.5％, is iron and unavoidable impurities. The production process comprises converter smelting, LF refining, continuous casting, heating, rolling and cooling, wherein the steelmaking link does not need vacuum degassing refining, continuous casting blank heating adopts hot charging, heat treatment is not needed after rolling, energy consumption is reduced, and production cost is reduced. However, the patent application aims at short-process reduction production of Q690D high-strength steel, reduces energy consumption, and still has the phenomenon of failure in flaw detection. Disclosure of Invention In order to solve the problems, the invention provides Q690D high-strength steel and a preparation method thereof, which can reduce the number and the size of inclusions, improve the product quality and improve the flaw detection qualification rate of the steel plate to more than 99.9 percent. In order to achieve the above purpose, the present invention adopts the following technical scheme: the invention provides Q690D high-strength steel, which comprises the following chemical components in percentage by weight, wherein the balance of ：C：0.14-0.2％、Si：0.2-0.4％、Mn：1.1-1.6％、P≤0.015％、S≤0.005％、Cr：0.1-0.4％、Nb：0.01-0.04％、Ti：0.01-0.03％、Mo：0.1-0.4％、Als:0.01-0.045％、B：0.001-0.003％、CEV≤0.62, is iron and unavoidable impurities. The invention further provides a preparation method of the Q690D high-strength steel, which comprises the following steps: 1) Smelting in a converter: Smelting by adopting a top-bottom combined blown converter, wherein a ladle adopts a red clean ladle with good bottom blowing, and the baking temperature is more than or equal to 800 ℃. The molybdenum oxide briquette is placed in the front of the waste steel bucket and added together with the waste steel, and the adding amount of the molybdenum oxide briquette is 4.38-8.77kg/t steel. The molybdenum oxide briquette is prepared by adding 10% of reduction promoter, 7% of volatilization-inhibiting adhesive and 3% of hydraulic pressing into molybdenum oxide powder. The reduction promoter and the volatilization-inhibiting adhesive used in the invention are common raw materials in the field, and are obtained by purchasing. Molybdenum oxide briquette is composed of Mo (48-55 wt.%), si (less than or equal to 0.1) and P (less than or equal to 0.05). The content of C at the smelting end point is controlled to be 0.05-0.09%, the tapping temperature is controlled to be 1630-1650 ℃, and the alkalinity of the final slag is controlled to be 3.0-4.0. Alloying by adopting 14.15-16.18kg/t of silicon-manganese, 2.65-4.65kg/t of high-carbon ferromanganese, 2.6-3.5kg/t of medium-carbon ferrochromium, 0.23-0.31kg/t of ferroniobium, and finishing adding when placing one fifth to three quarters of steel, wherein the alloy is added in alignment with a steel flow impact zone. 60-70% Of Mn, 16.5-20% of Si, less than or equal to 1.8% of C, less than or equal to 0.25% of P and less than or equal to 0.04% of S; 65-72% of high-carbon ferromanganese, less than or equal to 2.5% of Si, less than or equal to 7% of C, less than or equal to 0.25% of P and less than or equal to 0.03% of S; medium carbon ferrochrome: cr is more than or equal to 52 percent, C is less than or equal to 2.0 percent, si is less than or equal to 3.0 percent, si is less than or equal to 3.0 percent; 50% -60% of Nb, less than or equal to 2.5% of Si, less than or equal to 2.0% of Al, less than or equal to 0.05% of C, less than or equal to 0.05% of P and less than or equal to 0.03% of S; deoxidizing by adopting aluminum ferromanganese, adding 2.0-2.5kg/t of aluminum ferr