Method for improving the yield of a tmcp type low temperature high strength steel sheet

Abstract

The application discloses a production method for improving the yield of TMCP type low-temperature high-strength steel plate, which comprises a casting billet smelting process, a TMCP rolling process and a post-rolling water cooling process; the chemical composition of the casting billet obtained through the casting billet smelting process and the mass percentage of the chemical composition are as follows: C 0.15%-0.20%, Si 0.20%-0.30%, Mn 0.90%-1.40%, P≤0.025%, S≤0.010%, Cr 0.18%-0.25%, Nb 0.010%-0.020%, Alt≥0.020%, the balance of Fe and inevitable impurities, and carbon equivalent CEV 0.40%-0.46%; the TMCP rolling process is characterized in that the finishing rolling opening temperature is 840-860 DEG C, and the finish rolling temperature is 800-820 DEG C; the post-rolling water cooling process is characterized in that the water inlet temperature is 790-810 DEG C, the post-rolling water cooling system is divided into four zones A / B / C / D, the upper and lower distribution headers of each zone are controlled, and the flow rate water ratio of the middle and the edge of the header satisfies (1.2-1.4):1. The method improves the same plate uniformity, reduces the cutting edge amount of the head and tail and the width, and saves the cost under the premise of guaranteeing the excellent comprehensive performance of the steel plate.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular to a production method for improving the yield rate of TMCP type low-temperature high-strength steel plates. Background Art

[0002] Improving the yield rate not only increases the yield of finished steel, reduces waste, and lowers production costs, but also enhances a company's process technology and management level. The factors affecting the yield rate of steel plates are complex, primarily including the plate's specifications and structure, heat loss, plate shape, thickness dimensional deviation, and shear allowance. Among these, the shear allowance at the head, tail, and width of the plate have a significant impact on the yield rate. This is especially true for high-tech steel plates, which require strict production processes and require greater trimming. For example, for 460MPa-grade TMCP steel plates, the head and tail trimming is often over 500mm, and the width trimming is often over 150mm. Furthermore, the thinner the plate, the greater the trimming amount. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a production method for improving the yield rate of TMCP type low temperature high strength steel plate

[0004] To solve the above technical problems, the present invention adopts a technical solution comprising a slab smelting, TMCP rolling, and post-rolling water cooling process; the slab obtained from the slab smelting process has the following chemical composition and mass percentage: C 0.15% to 0.20%, Si 0.20% to 0.30%, Mn 0.90% to 1.40%, P ≤ 0.025%, S ≤ 0.010%, Cr 0.18% to 0.25%, Nb 0.010% to 0.020%, Alt ≥ 0.020%, the balance being Fe and unavoidable impurities, and a carbon equivalent (CEV) of 0.40% to 0.46%.

[0005] The TMCP rolling process: the finishing rolling start temperature is 840-860°C, and the final rolling temperature is 800-820°C;

[0006] The post-rolling water cooling process has an inlet water temperature of 790-810°C. The post-rolling water cooling system is divided into four zones, A / B / C / D. Manifolds are distributed above and below each zone. The flow rate ratio between the middle and edge of the manifold is controlled to meet (1.2-1.4):1 to ensure uniform cooling of the steel plate along the width direction.

[0007] Furthermore, during the post-rolling water cooling process, the water flow rate in the A / B zone is 20-50 m³ / hr, the water flow rate in the C / D zone is 100-120 m³ / hr, and the water outlet temperature of the steel plate is 600-700°C.

[0008] Furthermore, the ingot smelting process adopts converter primary smelting + LF refining + VD degassing + continuous casting steps; the ingots are cut and stacked immediately after they come off the line, and can be destackered only after they have cooled.

[0009] Furthermore, the thickness of the ingot is 200 to 300 mm, and the width of the ingot satisfies a width ratio of 1.3 to 1.5.

[0010] The beneficial effects of the above technical solution are as follows: the invention utilizes a high-carbon design to ensure steel plate strength; it also provides space for subsequent water cooling control; and it tightens the stacking of the ingots to increase the proportion of equiaxed grains. A two-stage controlled rolling process precisely controls the rolling temperature during both stages. Furthermore, an innovative post-rolling water cooling process achieves uniform cooling of the steel plate through the distribution of the water cooling area, resulting in a target microstructure of proeutectoid ferrite + pearlite + acicular ferrite. This microstructure has a wide cooling zone, facilitates homogenization during the cooling process, and achieves a high formation temperature with minimal head-to-tail blackheads. In particular, the use of a pure steel smelting mode produces high-quality ingots.

[0011] The present invention discloses a method for producing a high yield of TMCP low-temperature high-strength steel plates, which innovates component design and improves production technology. While ensuring excellent comprehensive performance of the steel plates, the method improves uniformity within the same plate, reduces the amount of trimming at the head, tail, and width, and saves costs. The resulting steel plates not only have excellent comprehensive performance, but also have high uniformity within the same plate, with blackheads at the head and tail ≤200 mm and width trimming of 50 mm to 80 mm, thereby increasing the yield of the steel plates by 3% to 5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0013] Figure 1 500 times the metallographic structure of the steel plate obtained in the embodiment of the present invention. DETAILED DESCRIPTION

[0014] The production method for improving the yield rate of TMCP type low temperature high strength steel plate includes the processes of billet smelting, TMCP rolling and post-rolling water cooling; the processes are as follows:

[0015] (1) Ingot smelting: adopt converter primary smelting + LF refining + VD degassing + continuous casting process; ingots are cut and stacked immediately after leaving the production line, and can be destackered after cooling; steel plate reverse material extraction, that is, the size of the required ingot is calculated in reverse according to the order size of the steel plate, especially the thickness and width of the continuous casting ingot. The ingot thickness is 200-300mm, and the ingot width meets the width ratio of 1.3-1.5, which is the ratio of the width of the steel plate to the ingot;

[0016] The chemical composition and mass percentage of the ingot obtained by the ingot smelting process are as follows: C 0.15%-0.20%, Si 0.20%-0.30%, Mn 0.90%-1.40%, P≤0.025%, S≤0.010%, Cr 0.18%-0.25%, Nb 0.010%-0.020%, Alt≥0.020%, the balance being Fe and unavoidable impurities, and carbon equivalent (CEV) 0.40%-0.46%.

[0017] (2) TMCP rolling: rough rolling + finishing rolling process is adopted; the steel thickness after rough rolling is 60mm~80mm, the finishing rolling start temperature is 840℃~860℃, and the final rolling temperature is 800℃~820℃; the steel plate thickness is 10~30mm.

[0018] (3) Post-rolling water cooling process: water inlet temperature 790-810℃; the post-rolling water cooling system is divided into 4 zones A / B / C / D according to the running direction of the steel plate. Each zone has upper and lower distribution headers. The water flow in the middle of the header is controlled to be greater than the water flow on both sides. The flow ratio between the middle and the edge meets (1.2-1.4):1, so as to ensure the cooling uniformity of the steel plate along the width direction; the water flow in the A / B zone is 20-50m³ / hr, and the water flow in the C / D zone is 100-120m³ / hr, forming a cooling method that is slow first and then fast; the water outlet temperature of the steel plate is 600-700℃.

[0019] (4) The steel plate is 460MPa grade low temperature steel, and the mechanical properties of the obtained steel plate meet the following requirements: ReH ≥ 460MPa under room temperature tensile test, Rm 570~690MPa, A ≥ 22.0%, average transverse impact energy at -40℃ ≥ 100J, and the performance testing method refers to ASTM A20 / A20M; the uniformity of the steel plate is high, the blackhead at the head and tail is ≤ 200mm, the width of the trimming is 50mm~80mm, and the yield rate of the steel plate is increased by 3%~5%; Figure 1 It can be seen that its metallographic structure is: proeutectoid ferrite + pearlite + acicular ferrite.

[0020] Example 1-8: The production method for improving the yield rate of TMCP type low-temperature high-strength steel plate is specifically described as follows.

[0021] The thickness and chemical composition of the steel plates of each embodiment are shown in Table 1; the process parameters of each embodiment are shown in Table 2; the properties, trimming amount and yield rate of the steel plates obtained in each embodiment are shown in Table 3.

[0022] Table 1: Thickness and chemical composition of steel plates in various examples

[0023]

[0024] Table 2: Steel plate production process of each embodiment

[0025]

[0026] Table 3: Steel plate properties, trimming amount and yield rate of each example

[0027] .

Claims

1. A production method for improving the yield rate of TMCP type low-temperature high-strength steel plate, characterized by: The method includes the processes of slab smelting, TMCP rolling and post-rolling water cooling; the chemical composition and mass percentage of the slab obtained in the slab smelting process are as follows: C 0.15%-0.20%, Si 0.20%-0.30%, Mn 0.90%-1.40%, P≤0.025%, S≤0.010%, Cr0.18%-0.25%, Nb 0.010%-0.020%, Alt≥0.020%, the balance being Fe and unavoidable impurities, and carbon equivalent CEV 0.40%-0.46%; The TMCP rolling process adopts a rough rolling + finishing rolling process; the steel thickness after rough rolling is 60mm-80mm, the finishing rolling start temperature is 840℃-860℃, and the final rolling temperature is 800℃-820℃; the steel plate thickness is 10-30mm; The post-rolling water cooling process: the water inlet temperature is 790-810°C, the post-rolling water cooling system is divided into four zones (A / B / C / D), each zone has a header distributed above and below, and the flow rate ratio between the middle and edge of the header is controlled to meet (1.2-1.4):1; the water flow rate in the A / B zone is 20-50m³ / hr, the water flow rate in the C / D zone is 100-120m³ / hr, and the steel plate outlet water temperature is 600-700°C; The steel plate is 460MPa grade low-temperature steel, and the obtained steel plate has the following mechanical properties: room temperature tensile ReH ≥ 460MPa, Rm 570-690MPa, A ≥ 22.0%, average transverse impact energy at -40°C ≥ 100J, and the performance testing method refers to ASTM A20 / A20M; head and tail blackhead ≤ 200mm, and the width of the trimming is 50mm-80mm; its metallographic structure is: proeutectoid ferrite + pearlite + acicular ferrite.

2. The method for improving the yield rate of TMCP type low temperature high strength steel plate according to claim 1, characterized in that: The ingot smelting process adopts converter primary smelting + LF refining + VD degassing + continuous casting process; the ingots are cut and stacked immediately after leaving the production line, and can be destackered only after cooling.

3. The method for improving the yield rate of TMCP type low temperature high strength steel plate according to claim 1 or 2, characterized in that: The thickness of the ingot is 200 to 300 mm, and the width of the ingot satisfies a width ratio of 1.3 to 1.5.

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