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CN-122013044-A - TMCP (thermal mechanical control process) DH36 thick plate for low-manganese micro-niobium offshore wind power and manufacturing method thereof

CN122013044ACN 122013044 ACN122013044 ACN 122013044ACN-122013044-A

Abstract

The invention discloses a TMCP state DH36 thick plate for low-manganese micro-niobium offshore wind power and a manufacturing method thereof, wherein ,C：0.13-0.17%,Si：0.2-0.4%,Mn：1.1-1.4%,P≤0.018%,S≤0.003%,N≤0.006%,Nb：0.01-0.03%,Ti：0.005-0.02%,Al：0.02-0.04%,Ca：0.001-0.003%, is Fe and impurity elements, and simultaneously the following relations are satisfied that Ceq is more than or equal to 0.34% and less than or equal to 0.38%, ti/N is more than or equal to 2 and less than or equal to 3, ca is treated and is more than or equal to 1.0 and less than or equal to 2.5, and (% Ca) x (% S) is more than or equal to 5x 10 ‑6 . The thick plate manufacturing method adopts low manganese micro niobium components, combines TMCP technology to obtain fine and uniform ferrite and pearlite tissues, obtains the toughness required by DH36 by means of the comprehensive strength and toughness effects of solid solution strengthening, precipitation strengthening and fine crystal strengthening, improves the weldability of the steel plate by precipitation of carbonitride and grain refinement, can support 50KJ/cm of large heat input welding on the premise of no preheating before welding and no heat treatment after welding, greatly improves the welding efficiency, is particularly suitable for manufacturing TMCP DH36 offshore wind power towers, and can realize low-cost stable batch industrial production.

Inventors

  • LUO LONGFEI
  • Tu Zikang
  • LIU WEIHANG

Assignees

  • 宝钢湛江钢铁有限公司

Dates

Publication Date
20260512
Application Date
20260302

Claims (5)

  1. 1.A TMCP state DH36 thick plate for low-manganese micro-niobium offshore wind power is characterized by comprising the following components ：C：0.13-0.17%,Si：0.2-0.4%,Mn：1.1-1.4%,P≤0.018%,S≤0.003%,N≤0.006%,Nb：0.01-0.03%,Ti：0.005-0.02%,Al：0.02-0.04%,Ca：0.001-0.003%, in percentage by mass and the balance of Fe and impurity elements, wherein the following relations are satisfied, namely Ceq is more than or equal to 0.34% and less than or equal to 0.38%, ti/N is more than or equal to 2 and less than or equal to 3, ca is treated, ca/S is more than or equal to 1.0 and less than or equal to 2.5, and (% Ca) × (% S) is more than or equal to 5×10 -6 .
  2. 2. The TMCP state DH36 thick plate for low-manganese micro-niobium offshore wind power according to claim 1, wherein the microstructure of the thick plate product is fine ferrite + pearlite, and the average grain size is 30 μm or less.
  3. 3. The TMCP state DH36 thick plate for low-manganese micro-niobium offshore wind power according to claim 1, wherein said thick plate can support 50KJ/cm of high heat input welding without preheating before welding and without heat preservation after welding.
  4. 4. The method for manufacturing the TMCP state DH36 thick plate for low-manganese micro-niobium offshore wind power according to claim 1, comprising the steps of: 1) Preparing materials, namely preparing all the components according to the proportion; 2) In the steelmaking process, molten iron is processed by KR to remove S to below 0.005 percent, then enters the converter for smelting, is removed to below 0.01 percent, is refined by an LF furnace to remove S to below 0.002 percent, and then is sent into RH refining and degassing, O, H, N is respectively removed to below 0.003 percent, 0.0002 percent and 0.004 percent, the superheat degree is controlled to be 18-30 ℃ in the casting process, the components are uniformly stirred by adopting ‌ electromagnetic waves, and the segregation degree of the slab is reduced by adopting dynamic light pressure; 3) Heating, namely controlling the time of a plate blank in a furnace to be 0.8-1.20min/mm, and controlling the tapping temperature to be 1100-1150 ℃; 4) Rolling, namely rolling a plate blank in two stages, wherein the initial rolling temperature of a rough rolling stage is above 1050 ℃, the rolling reduction rate of the last 3 passes is above 10%, the plate blank is rolled to the middle thickness and then is heated on a roller way, the rolling is controlled between 750-900 ℃ in an austenite non-recrystallization region in a finish rolling stage, and the rolling reduction rate of the last pass is more than 8mm; 5) Cooling, namely conveying the rolled steel plate to MULPIC equipment for accelerated cooling, wherein the cooling rate is between 10 and 40 ℃ per second according to different thicknesses of the steel plate, and the final cooling temperature is between 400 and 700 ℃; 6) Stacking and slowly cooling, namely after cooling the steel plate with the thickness of more than or equal to 30mm by MULPIC equipment, discharging the steel plate to a stacking position within 20 minutes, and slowly cooling the steel plate at the stacking temperature of more than 300 ℃ for more than 24 hours; The steel plate with the thickness of less than 30mm is directly subjected to the step 7) without being subjected to slow cooling; 7) Flaw detection, namely after cooling or slow cooling is finished, flaw detection is carried out on the steel plate through online or manual flaw detection equipment; 8) Cutting: the steel plate is cut with a line or fire cutting to size, and storing in a finished product warehouse.
  5. 5. The method of claim 4, wherein the thick plate produced by the method is capable of supporting 50KJ/cm of high heat input welding without preheating prior to welding and without maintaining heat after welding.

Description

TMCP (thermal mechanical control process) DH36 thick plate for low-manganese micro-niobium offshore wind power and manufacturing method thereof Technical Field The invention belongs to the field of niobium microalloying and thermo-mechanical rolling (TMCP) reinforced steel, and particularly relates to a TMCP state DH36 thick plate for low-manganese micro-niobium offshore wind power and a manufacturing method thereof. Background Wind power is a new energy industry which is developed faster in recent years, a thick plate for a wind power tower is used as a mechanism for supporting a fan, and service stability, manufacturing cost and the like of the thick plate have important effects on the development of the wind power industry. DH36 is the main variety of current offshore wind power steel, delivery states comprise normalizing state, TMCP state and the like, and the execution standard is GB/T712-2022 steel for ships and ocean engineering. The normalized DH36 is usually designed with high carbon equivalent and high alloy, and has poorer welding performance than TMCP DH36, which is unfavorable for long-term safe and stable service of offshore wind power towers, while TMCP DH36 is usually produced by combining lower C (generally about 0.1% or even lower), middle Mn (generally about 1.5%) and microalloy strengthening elements such as Nb, ti and the like with TMCP process, and because of lower C content and carbon equivalent, higher Nb is required to be added to improve toughness through precipitation strengthening, and the overall alloy and manufacturing cost are higher, thereby limiting the application of the alloy in the wind power field. For example, chinese patent CN 111155028a discloses a normalized DH36 wind power steel plate with a thickness of 60-100mm, the rest of component ：C：0.13-0.16%,Si：0.18-0.26%,Mn：1.4-1.5%,A1：0.02-0.05%,Nb：0.03-0.04%,Ti：0.01-0.02%,P：0.015%,S≤0.005%,N≤0.006%, is iron and unavoidable impurity elements, and carbon equivalent ceq=c+mn/6+ (cr+mo+v)/5+ (cu+ni)/15 is less than or equal to 0.43% by weight, and the normalized steel plate is produced by adopting a normalizing process. The technology adopts high carbon equivalent and high alloy components, has poorer weldability than TMCP process steel plates and higher alloy cost, and is not beneficial to low-cost commercial application and long-term service safety of wind power towers. Chinese patent CN 113462958A discloses a DH36 marine wind power steel plate, which comprises, by weight, 0.07-0.11% of C, less than or equal to 0.25% of Si, less than 1.60% of Mn, 0.010-0.030% of Nb, 0.01-0.02% of Ti, and less than or equal to 0.37% of carbon equivalent, wherein the thickness of the steel plate is below 36mm, a steel plate with a larger thickness cannot be produced, the steel plate is not suitable for the development direction of a large-thickness wind power tower, and the total alloy cost is higher. Chinese patent CN 112176248A discloses a low-carbon equivalent extra-thick specification offshore wind power steel DH36 steel plate and a production method thereof, wherein the steel comprises the following components in percentage by mass of 0.14-0.15% of C, 0.43-0.46% of Si, 1.35-1.45% of Mn and 0.38-0.40% of Ceq, and can be used for manufacturing extra-thick specification offshore wind power steel of 50-100 mm for TMCP delivery. The carbon equivalent exceeds the upper limit of 0.38% of TMCP DH36 standard requirement of less than or equal to 50mm, TMCP DH36 wind power steel of less than or equal to 50mm cannot be produced, the welding performance of the steel plate is not disclosed and developed in the patent, elements such as Nb, ti and the like which improve the welding performance are not contained in the steel plate, and Ca elements are not added to improve the inclusion morphology, so that the welding performance and long-term service stability are doubtful. Disclosure of Invention In order to overcome the defects of the prior art, the invention aims to provide a TMCP state DH36 thick plate for low-manganese micro-niobium offshore wind power and a manufacturing method thereof. The invention ensures the toughness of the steel plate through reasonable component matching and proper slab heating, rolling and cooling processes, realizes that the Mn content and the micro-niobium alloying content are lower than those of TMCP state DH36 for conventional offshore wind power, not only reduces the manufacturing cost, but also well solves the problems of high DH36 cost and long manufacturing period produced by the normalizing process, and in addition, improves the weldability of the product through means of separating out carbonitride, modifying inclusion, refining grains and the like, and is suitable for manufacturing offshore wind power towers. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: On the one hand, the TMCP state DH36 thick plate for the low-manganese micro-niobium offshore wind power ha