CN113355582A

CN113355582A - Production method of low-carbon hot-rolled thin steel plate with multi-layer structure

Info

Publication number: CN113355582A
Application number: CN202110566674.8A
Authority: CN
Inventors: 朱国明; 梁晓慧; 田鹏; 康永林
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2021-05-24
Filing date: 2021-05-24
Publication date: 2021-09-07
Anticipated expiration: 2041-05-24
Also published as: CN113355582B

Abstract

A method for producing a low-carbon hot-rolled thin steel plate with a multi-layered structure belongs to the technical field of metallurgy. The production process of the method is as follows: continuous casting into billets → soaking in the 1# heating furnace → rough rolling in the rough rolling group → heating in the 2# heating furnace → high-pressure water dephosphorization → finishing rolling in the finishing rolling group → cooling by the layer cooling device → coiling machine coil Pick. The low-carbon hot-rolled thin steel sheet with multi-layer structure obtained by this method is different from the composite steel sheet obtained by the composite process such as explosion or hot rolling, and also different from the homogeneous steel sheet obtained by the ordinary hot rolling process or cold rolling process. The low-carbon hot-rolled thin steel sheet produced by this method has very high edge ductility, low risk of edge cracking, and excellent performance, which can well meet the needs of downstream users. The method omits the composite process of the composite steel plate, avoids the complex preparation process of the gradient material and the cracking of the homogeneous steel plate, and has the advantages of simplifying the process, reducing carbon emissions, high production efficiency, green environmental protection and low cost.

Description

Production method of low-carbon hot-rolled thin steel plate with multi-layer structure

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a production method of a low-carbon hot-rolled thin steel plate with a multi-layer structure.

Background

The low-carbon hot-rolled thin steel plate has high strength, good plasticity and toughness, easy processing and forming, good weldability and other excellent performances, is mainly used as a cold-rolled base material, a pickled plate base material, a tinned/zinc plate base material and the like, and is widely applied to the industries of ships, automobiles, highway bridges, buildings, mechanical equipment, oil pipelines, high-pressure containers and the like. At present, the production of the low-carbon hot-rolled steel plate mainly adopts austenite region rolling (the finishing rolling temperature is more than or equal to A)₃+50 deg.C, rolling in ferrite region (final rolling temperature)<A_GP) And recrystallizing and refining austenite or ferrite and controlling growth of the austenite or ferrite to obtain a homogeneous low-carbon hot-rolled steel plate with uniform grains and a single structure, and strictly forbidding rolling in a two-phase region or a non-recrystallization region to obtain a mixed crystal structure with non-uniform grains. And 2.0mm or less, particularly 1.2mm or less, is a homogeneous cold-rolled sheet or annealed sheet obtained by subjecting a hot-rolled sheet to multi-pass cold rolling and annealing. However, when the homogeneous steel plate with the single structure is subjected to cold working such as bending, stamping, hole expanding, flanging and cold rolling, the deformation borne by different positions is different, so that the homogeneous plate has bending surface cracks,Corner cracks, edge cracks, large resilience, cracks in a welding zone and the like, namely the edge ductility is poor, repair welding, preheating in advance, annealing after forming and the like are required; if the steel plate is selected according to the maximum deformation condition, the performance is wasted and the cost is high. In order to save cost and improve edge ductility, a steel sheet having a multi-layer structure is required to meet the above-described forming requirements. At present, in order to obtain a multilayer structure, composite plates are mainly produced by a plurality of steel plates with single structures through composite processes such as explosion, hot rolling, welding and the like, or gradient materials are obtained by continuously changing the composition and the structure of a plurality of materials through a chemical vapor deposition method, a physical evaporation method, a spraying method, 3D printing and the like. For example, the hot-rolled stainless steel composite plate is formed by rolling a carbon steel substrate and a stainless steel clad plate which are in a physically pure state under a high vacuum condition, has the corrosion resistance of stainless steel, and has good mechanical strength and processability of carbon steel, and realizes the perfect combination of low cost and high performance. And the combustion chamber wall of the supersonic combustion ramjet engine is made of a gradient heterogeneous gradient material which is obtained by 3D printing of low-temperature-resistant metal and high-temperature-resistant ceramic, and has a new function of better heat stress strength and mechanical strength. These materials, which integrate the excellent properties of various materials, are more and more emphasized by researchers in the materials field, but the preparation method is complex, the required raw materials are limited, the cost is higher, and the production efficiency is lower. In this regard, the development of a low-carbon hot-rolled steel sheet having a multi-layer structure is a key to solve the above problems.

Disclosure of Invention

The invention provides a production method of a low-carbon hot-rolled thin steel plate with a multilayer structure, aiming at the problems that the homogeneous steel plate has poor edge ductility, cracks are easy to appear after punching forming, the cost is high, the production process of a composite plate or a gradient material is complex and the like.

In order to achieve the purpose, the invention adopts the following technical scheme;

the low-carbon hot-rolled steel sheet comprises the following chemical components in percentage by mass: c is less than or equal to 0.05 percent, Si is less than or equal to 0.03 percent, Mn: 0.07-0.15%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, Als: 0.025-0.050%, B is less than or equal to 0.003%, Nb + V + Ti + Cr is less than or equal to 0.10%, and the balance is Fe and unavoidable impurities. The preparation method comprises the following specific steps: continuous casting and billet forming → 1# heating furnace soaking → rough rolling of rough rolling mill group → 2# heating furnace heating → high-pressure water dephosphorization → finishing rolling of finishing rolling mill group → layer cooling device cooling → coiling of coiling machine.

And further, continuously casting the blank by using a continuous casting machine to obtain the casting blank with the thickness of 80-110 mm.

Further, the No. 1 heating furnace adopts a stepping roller bottom type heating furnace, and the No. 1 heating furnace heats the casting blank to A₃The temperature difference of the casting blank along the thickness direction is not more than 15 ℃, the casting blank is in complete austenitization, the soaking is realized, and the uniform tissue structure and temperature of the casting blank before rough rolling are ensured.

Furthermore, in the rough rolling procedure, 2-4 passes of rolling are adopted, and the single-pass reduction rate is more than or equal to 25%. The rough rolling and final rolling temperature is A₃+110 ℃, and the thickness of the obtained intermediate blank is 9-35 mm.

Further, the 2# heating furnace adopts a roller hearth type or induction heating furnace, and the outlet temperature of the 2# heating furnace is A₃+(90—280)℃。

Furthermore, the finish rolling procedure adopts 5-7 passes of rolling, high-pressure water dephosphorization is carried out before the first pass of finish rolling, and the finish rolling temperature is A₃- (60 ℃ to 140 ℃), ensuring that the subsequent steps in finish rolling realize partial recrystallization rolling and deformation induced ferrite rolling, and creating temperature conditions and deformation conditions for obtaining a multilayer structure.

Further, the cooling control adopts manual control cooling, wherein the quantity of laminar cooling water is 4200-4350 m³The water pressure is 0.06 MPa.

Further, the coiling temperature is A1- (40-110) DEG C, and completion of pearlite transformation and ferrite transformation before coiling is ensured, so that a low-carbon hot-rolled steel sheet having a 3-5-layer structure and a thickness of 0.7-3.2 mm is obtained.

The invention provides a method for producing a low-carbon hot-rolled thin steel plate with a multi-layer structure, which controls the temperature and the deformation of a plate blank in the process of finish rolling₃The partial recrystallization rolling and the strain-induced ferrite rolling are performed in a temperature range around the temperature rangeThe layer organization structure is critical. The method specifically comprises the following steps: partially recrystallized fine austenite grains and uncrystallized coarse austenite are obtained through partial recrystallization rolling, the phase of the recrystallized fine austenite grains is changed into fine ferrite grains in the layer cooling stage, and the phase of the uncrystallized coarse austenite is changed into coarse ferrite; fine ferrite grains and prolate untransformed austenite are obtained by deformation-induced ferrite rolling, and the prolate untransformed austenite is transformed into coarse ferrite in the layer cooling stage. In order to ensure that the lamellar structure is not damaged, the transformation is required to take place in a later pass in the finish rolling in order to control the extent of growth of fine austenite grains and fine ferrite grains and avoid the formation of a uniform single-layer structure. The outer layer has good plastic toughness than the thick ferrite structure of the crystal grains, high edge ductility and lower strength, and can ensure that the defects such as cracks are not easy to appear in the process of forming after punching, and meanwhile, the fine ferrite structure of the crystal grains in the inner layer has good plastic toughness and higher strength, and the combined action of the two can ensure that the integral material has better plastic toughness and strength, thereby meeting the deformation requirements of users on different positions in the forming processes such as bending, stamping, reaming, flanging, cold rolling and the like. The low-carbon hot-rolled thin steel plate with a multilayer structure produced by the method has high edge ductility, low edge cracking risk and excellent performance, can well meet the use requirements of downstream users, and also has the advantages of simplified working procedures, reduced carbon emission, high production efficiency, environmental protection, low cost and the like.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a microscopic view of a multi-layer structure of a low-carbon hot-rolled steel sheet according to an example of the present invention in the thickness direction;

FIG. 2 is a thickness-wise microscopic view of a multi-layer structure of a low-carbon hot-rolled steel sheet according to an example of the present invention;

FIG. 3 is a thickness-wise microscopic view of a multi-layer structure of a low-carbon hot-rolled steel sheet according to an example of the present invention.

Detailed Description

Example 1:

a production method of a low-carbon hot-rolled thin steel plate with a multi-layer structure comprises the following chemical components in percentage by mass: c: 0.05%, Si: 0.03%, Mn: 0.12%, P: 0.010%, S: 0.003%, Als: 0.035%, the balance being Fe and unavoidable impurities.

The production method of the low-carbon hot-rolled steel sheet with the multilayer structure comprises the following steps:

continuous casting blank → 1# heating furnace soaking → rough rolling of rough rolling mill group → 2# heating furnace heating → high pressure water dephosphorization → finishing rolling of finishing rolling mill group → layer cooling device cooling → coiling of coiling machine;

and obtaining the qualified slab with the chemical components through converter smelting → LF refining → slab continuous casting, wherein the drawing speed is 5m/min, and the thickness of the casting blank is 95 mm. Uniformly heating in a No. 1 stepping roller bottom type heating furnace for 8min, wherein the temperature difference of the casting blank along the thickness direction is 10 ℃, and the outlet temperature of the casting blank is 1070 ℃. And (3) feeding the blank into a roughing mill group for 2-pass rolling, wherein the roughing rolling finishing temperature is 1000 ℃, the thickness of the intermediate blank after the roughing rolling is 35 mm, and then heating the intermediate blank to 1080 ℃ in a 2# roller hearth type heating furnace. After phosphorus removal by high-pressure water, the steel plate enters a finish rolling process, a finish rolling unit adopts 6 passes of rolling, and the rolling temperature of an F5 rack is ensured to be A₃And the finish rolling temperature is 830 ℃, and the thickness of the finished product is 3.0 mm. After finish rolling, the laminar cooling device is manually controlled, and the quantity of laminar cooling water is 4340m³The water pressure is 0.06 MPa. The coiling temperature was controlled at about 650 ℃ to obtain a low-carbon hot-rolled steel sheet having a 3-layer structure, and a microstructure of the multi-layer structure in the thickness direction thereof was as shown in FIG. 1.

Example 2:

a production method of a low-carbon hot-rolled thin steel plate with a multi-layer structure comprises the following chemical components in percentage by mass: c: 0.03%, Si: 0.01%, Mn: 0.15%, P: 0.012%, S: 0.001%, Als: 0.040 percent, less than or equal to 0.003 percent of B, less than or equal to 0.03 percent of Ti, and the balance of Fe and inevitable impurities.

and obtaining the qualified slab with the chemical components through converter smelting → LF refining → slab continuous casting, wherein the drawing speed is 6m/min, and the thickness of the casting blank is 80 mm. Uniformly heating in a No. 1 stepping roller bottom type heating furnace for 7min, wherein the temperature difference of a casting blank along the thickness direction is 12 ℃, and the outlet temperature of the casting blank is 1080 ℃. And (3) feeding the blank into a roughing mill group for 3-pass rolling, wherein the roughing rolling finishing temperature is 1010 ℃, the thickness of the intermediate blank after roughing rolling is 25 mm, and then heating the intermediate blank to 1100 ℃ in a 2# roller hearth type heating furnace. After phosphorus removal by high-pressure water, the steel plate enters a finish rolling process, a finish rolling unit adopts 5 passes of rolling, and the rolling temperature of the frames F3 and F4 is ensured to be A₃And the finish rolling temperature is about 800 ℃, and the thickness of the finished product is 1.5 mm. After finish rolling, the laminar cooling device is manually controlled, and the quantity of laminar cooling water is 4300m³The water pressure is 0.06 MPa. The coiling temperature was 630 ℃ to obtain a low-carbon hot-rolled steel sheet having a 5-layer structure, and a microstructure of the multi-layer structure in the thickness direction thereof is shown in FIG. 2.

Example 3:

a production method of a low-carbon hot-rolled thin steel plate with a multi-layer structure comprises the following chemical components in percentage by mass: c: 0.01%, Si: 0.02%, Mn: 0.09%, P: 0.012%, S: 0.001%, Als: 0.040 percent, less than or equal to 0.10 percent of Nb, V, Ti and Cr, and the balance of Fe and inevitable impurities.

through converter smelting → LFAnd (4) refining → continuously casting the slab to obtain the qualified slab with the chemical components, wherein the drawing speed is 7m/min, and the thickness of the casting blank is 110 mm. Uniformly heating in a No. 1 stepping roller bottom type heating furnace for 6min, wherein the temperature difference of a casting blank along the thickness direction is 14 ℃, and the temperature of the casting blank is increased to 1110 ℃. And (3) feeding the blank into a roughing mill group for 4-pass rolling, wherein the finishing temperature of the roughing rolling is 1030 ℃, the thickness of the intermediate blank after the roughing rolling is 15 mm, and then feeding the intermediate blank into a 2# induction heating furnace to be heated to 1150 ℃. High-pressure water dephosphorization is carried out before the intermediate billet enters the finish rolling procedure, the finish rolling unit adopts 7-pass rolling, and the rolling temperature of the F5 and F6 racks is ensured to be A₃And the finish rolling temperature is 760 ℃, and the thickness of the finished product is 0.8 mm. After finish rolling, the laminar cooling device is manually controlled, and the quantity of laminar cooling water is 4210m³The water pressure is 0.06 MPa. The coiling temperature was 620 ℃ to obtain a low-carbon hot-rolled steel sheet having a 5-layer structure, and a microstructure of the multi-layer structure in the thickness direction thereof is shown in FIG. 3.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A method for producing a low-carbon hot-rolled steel sheet with a multi-layer structure, characterized in that: the chemical composition and mass percentage of the low-carbon hot-rolled steel sheet: C≤0.05%, Si≤0.03%, Mn: 0.07～0.15%, P≤0.015%, S≤0.010%, Als: 0.025～0.050%, B≤0.003%, Nb+V+Ti+Cr≤0.10%, the balance is Fe and inevitable impurities; specific preparation steps As follows: continuous casting into billet → soaking in the 1# heating furnace → rough rolling in the rough rolling unit → heating in the 2# heating furnace → high-pressure water dephosphorization → finishing rolling in the finishing rolling group → cooling by the layer cooling device → coiling by the coiler.

2 . The method for producing a low-carbon hot-rolled thin steel sheet with a multi-layer structure according to claim 1 , wherein the thickness of the slab obtained after continuous casting is 80-110 mm. 3 .

3. a kind of low-carbon hot-rolled thin steel sheet production method with multi-layer structure according to claim 1, is characterized in that: 1# soaking furnace or 2# heating furnace are stepping roller hearth type heating furnace or induction heating furnace , the outlet temperature of the 1# soaking furnace is A ₃ +180℃, and the temperature difference of the slab along the thickness direction is ≤15℃; the outlet temperature of the 2# heating furnace is A ₃ +(90-280)℃.

4. The method for producing a low-carbon hot-rolled thin steel sheet with a multi-layer structure according to claim 1, wherein the rough rolling process adopts 2-4 passes of continuous rolling, and the rough rolling finishing temperature is A ₃ +110℃, the thickness of the obtained intermediate blank is 9-35mm.

5. The method for producing a low-carbon hot-rolled thin steel sheet with a multi-layer structure according to claim 1, characterized in that: the finishing rolling process adopts 5-7 passes of rolling, and the finishing rolling temperature is A ₃ -(60-140)℃.

6. The method for producing a low-carbon hot-rolled thin steel sheet with a multi-layer structure according to claim 1, wherein the cooling control adopts a manual cooling mode, wherein the amount of cold water in the layer is 4200-4350 m ³ /h, and the water The pressure is 0.06MPa.

7 . The method for producing a low-carbon hot-rolled thin steel sheet with a multi-layered structure according to claim 1 , wherein the coiling temperature is A ₁ -(40-110)° C. to obtain 3-5 layers of Low carbon hot-rolled steel sheet with microstructure and thickness of 0.7-3.2mm.